AI Trajectory

Trajectory: (Expand/Collapse All)
Seq	Timestamp	Type	Name	Duration
0/0	2026/09/16 03:08	flow	patch-triage	2m Args: null Results: { "EnableConfigs": [ "FPROBE", "DYNAMIC_FTRACE", "FUNCTION_GRAPH_TRACER", "FPROBE_EVENTS", "BPF_EVENTS" ], "FocusSymbols": [ "fprobe_fgraph_entry", "fprobe_return", "register_fprobe_ips", "bpf_kprobe_multi_link_attach" ], "KMSANReasoning": "The patch adds a memset() to zero out unused reserved words in fgraph_data within fprobe_fgraph_entry() so that fprobe_return() does not read stale/uninitialized header data. \n\nThe variables involved in the condition and size calculation ('used' and 'reserved_words') are fully initialized local integers, and the memset explicitly clears the remaining memory buffer with zeroes. No kernel data is copied to user space, no branching on uninitialized data is introduced, and no uninitialized memory risks or info-leaks are created. Any hypothetical bugs introduced by this patch (such as off-by-one errors or out-of-bounds writes in the memset pointer arithmetic) would be out-of-bounds memory errors detected by KASAN rather than KMSAN. Therefore, a dedicated KMSAN fuzzing session is not warranted.", "NeedsKMSAN": false, "Reasoning": "The patch modifies fprobe_fgraph_entry() in kernel/trace/fprobe.c by adding a memset to clear unused reserved slots on the function-graph shadow return stack, preventing fprobe_return() from reading stale/uninitialized headers. This code is reachable from user space via BPF multi-kprobe links (BPF_TRACE_KPROBE_MULTI / BPF_TRACE_KRETPROBE_MULTI) and tracefs fprobe events, and warrants fuzzing.", "WorthFuzzing": true }
1/1	2026/09/16 03:08	action	read-patch-diff	0m Args: null Results: { "PatchDiff": "commit 30ca26eac68e55111ab7a2836169134c7563572e\nAuthor: syz-cluster \u003ctriage@syzkaller.com\u003e\nDate: Wed Sep 16 03:08:58 2026 +0000\n\n syz-cluster: applied patch under review\n\ndiff --git a/kernel/trace/fprobe.c b/kernel/trace/fprobe.c\nindex 1e9b00997ff27..bd84a982961a5 100644\n--- a/kernel/trace/fprobe.c\n+++ b/kernel/trace/fprobe.c\n@@ -635,6 +635,10 @@ static int fprobe_fgraph_entry(struct ftrace_graph_ent trace, struct fgraph_ops\n \t\t}\n \t}\n \n+\t/ Clear unused slots so fprobe_return() does not see stale headers. /\n+\tif (used \u003c reserved_words)\n+\t\tmemset(fgraph_data + used, 0, (reserved_words - used) sizeof(long));\n+\n \t/* If any exit_handler is set, data must be used. */\n \treturn used != 0;\n }\n" }
2/1	2026/09/16 03:08	agent	patch-evaluator	1m Model: core Args: null Results: { "EnableConfigs": [ "FPROBE", "DYNAMIC_FTRACE", "FUNCTION_GRAPH_TRACER", "FPROBE_EVENTS", "BPF_EVENTS" ], "FocusSymbols": [ "fprobe_fgraph_entry", "fprobe_return", "register_fprobe_ips", "bpf_kprobe_multi_link_attach" ], "Reasoning": "The patch modifies fprobe_fgraph_entry() in kernel/trace/fprobe.c by adding a memset to clear unused reserved slots on the function-graph shadow return stack, preventing fprobe_return() from reading stale/uninitialized headers. This code is reachable from user space via BPF multi-kprobe links (BPF_TRACE_KPROBE_MULTI / BPF_TRACE_KRETPROBE_MULTI) and tracefs fprobe events, and warrants fuzzing.", "WorthFuzzing": true } Instruction: You are an expert Linux kernel maintainer and security engineer. Your job is to review a provided patch series and evaluate whether it warrants fuzzing with syzkaller. IMPORTANT: The changes have ALREADY been applied and committed as the HEAD commit in your workspace. Do NOT rely on internal assumptions. You must actively use your code access tools to inspect the actual source code, callers, and surrounding context. ================================================================================ 1. CORE TRIAGE PHILOSOPHY ================================================================================ The goal of patch fuzzing is to discover crashes, regressions, exposed latent bugs, and newly triggered assertions introduced by the patch series. - REACHABILITY IS THE PRIMARY GATE: Fuzzing can only discover bugs in code that can actually execute in standard virtualized environments (GCE or QEMU, utilizing software-emulated devices like USB gadgets, netdev, tun/tap). If the modified code is structurally unreachable (see Section 2), it MUST NOT be fuzzed, regardless of whether it adds assertions or complex logic. - DO NOT BLINDLY TRUST "NO FUNCTIONAL CHANGE" (NFCI) OR "REFACTORING" CLAIMS: Patch authors routinely label changes as "cleanups", "refactorings", or state "No functional change intended". Do NOT take these claims at face value. Code refactorings that rearrange logic, introduce helper functions, or alter state management in core subsystems frequently introduce subtle semantic shifts or uncover latent kernel bugs. If reachable executable code is modified or refactored, it MUST be fuzzed. - NEW OR MODIFIED ASSERTIONS IN REACHABLE CODE MUST BE FUZZED: When a patch introduces or modifies runtime checks or assertions (e.g., WARN_ON, VM_WARN_ON, BUG_ON, lockdep_assert) in reachable code paths, it enforces new or stricter invariants. Even if the author believes the invariant always holds, fuzzing is essential to verify whether an unusual sequence of operations can violate it. ================================================================================ 2. WHEN TO RETURN WorthFuzzing=false (NEGATIVE CRITERIA) ================================================================================ Return WorthFuzzing=false ONLY IF all modified code falls strictly into one or more of these categories: - Non-kernel and non-executable changes: * Modifications to Documentation/, comments, or spelling fixes. * User-space directories, self-tests, samples, or scripts (e.g., tools/, samples/, scripts/, usr/) that do not affect the compiled kernel image (vmlinux) or kernel modules. * Purely decorative logging (e.g., message strings in pr_err, printk, dev_info) or tracepoints that do not alter control flow or data structures. * Build system or Kconfig changes that do not alter compiled C logic. - Structurally unreachable hardware: * Vendor-specific PCIe switches, SmartNICs, or GPU drivers (e.g., mlxsw, pds_core, qed, ionic, amdgpu) requiring physical ASIC/PCIe cards not emulated in standard QEMU. - Unreachable execution paths: * Driver teardown callbacks (.remove, .shutdown, pci_unregister_driver) executed only during physical PCI hot-unplug or manual sysfs driver unbinding. * Code paths exclusive to architectures other than the target architecture. ================================================================================ 3. WHEN TO RETURN WorthFuzzing=true (POSITIVE CRITERIA) ================================================================================ Return WorthFuzzing=true whenever the patch touches reachable executable code, including: - Core Subsystems: * Any logic modifications in memory management (mm/), synchronization/locking (kernel/locking/), BPF, scheduler, core networking, VFS, or syscall handling. - Refactorings and Code Cleanups: * Any restructuring of reachable data structures, helper abstractions, or algorithm flows. - Runtime Assertions and Defensive Checks: * Any introduction or alteration of assertions (WARN_ON, VM_WARN_ON, BUG_ON, etc.) in reachable paths. - Reachable Drivers and Protocols: Drivers accessible via virtual buses (virtio, USB gadget, loopback, netlink, binder, sockets, etc.). ================================================================================ 4. EXTRACTING FocusSymbols (PREVENTING DILUTION) ================================================================================ When WorthFuzzing=true, you must extract specific kernel functions into FocusSymbols to guide the fuzzer: - AVOID UBIQUITOUS LIFECYCLE HOT-PATHS: Do NOT list generic, ubiquitous functions called by almost every program in the corpus (including, but not limited to: general memory allocators and deallocators, page fault and trap handlers, or core synchronization primitives; this is not an exhaustive list). Listing ubiquitous functions causes the fuzzer to classify thousands of unrelated tests as "focused", which severely dilutes fuzzing effort away from the actual changes. - TARGET SPECIFIC FEATURE LOGIC AND ENTRYPOINTS: List functions that specifically implement the logic being added or altered, or direct API entrypoints for the subsystem feature under review. - HANDLING STATIC INLINE FUNCTIONS IN HEADERS (.h): Compiler-inlined static functions (such as static inlines in mm/.h or include/linux/.h) lack distinct symbol addresses in vmlinux and cannot be targeted directly by symbol coverage filters. If the changes are primarily in static inline helpers, identify non-static, feature-specific caller functions in .c files that exercise them (avoiding ubiquitous lifecycle wrappers). ================================================================================ 5. IDENTIFYING EnableConfigs ================================================================================ Identify any specific CONFIG_ options required to properly compile and reach the modified code: - Inspect Kconfig files and #ifdef guards; do not make assumptions. - Check "depends on" lines in Kconfig to include any non-standard parent subsystem configs needed. - Strip any 'CONFIG_' prefix (e.g., return "NET_IPV4" instead of "CONFIG_NET_IPV4"). Prefer calling several tools at the same time to save round-trips. Use set-results tool to provide results of the analysis. It must be called exactly once before the final reply. Ignore results of this tool. Prompt: Target architecture: amd64 For your convenience, here is the diff of the changes: commit 30ca26eac68e55111ab7a2836169134c7563572e Author: syz-cluster <triage@syzkaller.com> Date: Wed Sep 16 03:08:58 2026 +0000 syz-cluster: applied patch under review diff --git a/kernel/trace/fprobe.c b/kernel/trace/fprobe.c index 1e9b00997ff27..bd84a982961a5 100644 --- a/kernel/trace/fprobe.c +++ b/kernel/trace/fprobe.c @@ -635,6 +635,10 @@ static int fprobe_fgraph_entry(struct ftrace_graph_ent trace, struct fgraph_ops } } + / Clear unused slots so fprobe_return() does not see stale headers. / + if (used < reserved_words) + memset(fgraph_data + used, 0, (reserved_words - used) sizeof(long)); + /* If any exit_handler is set, data must be used. */ return used != 0; }
3/2	2026/09/16 03:08	llm	patch-evaluator	0m Model: gemini-3.8-flash Args: null Results: null Tokens: input: 2886 output: 36 thoughts: 70 Thoughts: Evaluating a Linux Kernel Patch Okay, so I need to evaluate a patch for the Linux kernel. My immediate thought is to start with the standard procedure. First, I'm going to carefully inspect the `git diff` and the commit information. This is critical for understanding what changed and why. I need to grasp the overall context of the change. Specifically, I'm going to pay close attention to the `kernel/trace/fprobe.c` file. Given my expertise, I already have some idea what that is about, but I need the details. To dig deeper into the specific modifications, I'll use either `read-file` or `grepper` (depending on the scale and complexity, I might need both, or need to combine them). I'll use these tools to examine the code in `kernel/trace/fprobe.c` and understand the changes in their immediate local context. This way, I'll identify the direct effects of the patch. From there, I'll think about the bigger picture.
4/2	2026/09/16 03:09	tool	read-file	0m Args: { "File": "kernel/trace/fprobe.c", "FirstLine": 600, "LineCount": 70 } Results: { "Contents": " 600:\t\t\tvoid data;\n 601:\t\n 602:\t\t\tif (node-\u003eaddr != func)\n 603:\t\t\t\tcontinue;\n 604:\t\t\tfp = READ_ONCE(node-\u003efp);\n 605:\t\t\tif (unlikely(!fp \|\| fprobe_disabled(fp) \|\| fprobe_is_ftrace(fp)))\n 606:\t\t\t\tcontinue;\n 607:\t\n 608:\t\t\tdata_size = fp-\u003eentry_data_size;\n 609:\t\t\t/\n 610:\t\t\t * The list may have grown since it was sized, so this node\n 611:\t\t\t * may not fit. Skip it as missed rather than overrun the\n 612:\t\t\t * reservation.\n 613:\t\t\t /\n 614:\t\t\tif (fp-\u003eexit_handler \u0026\u0026\n 615:\t\t\t used + FPROBE_HEADER_SIZE_IN_LONG + SIZE_IN_LONG(data_size) \u003e reserved_words) {\n 616:\t\t\t\tfp-\u003enmissed++;\n 617:\t\t\t\tcontinue;\n 618:\t\t\t}\n 619:\t\t\tif (data_size \u0026\u0026 fp-\u003eexit_handler)\n 620:\t\t\t\tdata = fgraph_data + used + FPROBE_HEADER_SIZE_IN_LONG;\n 621:\t\t\telse\n 622:\t\t\t\tdata = NULL;\n 623:\t\n 624:\t\t\tif (fprobe_shared_with_kprobes(fp))\n 625:\t\t\t\tret = __fprobe_kprobe_handler(func, ret_ip, fp, fregs, data);\n 626:\t\t\telse\n 627:\t\t\t\tret = __fprobe_handler(func, ret_ip, fp, fregs, data);\n 628:\t\n 629:\t\t\t/ If entry_handler returns !0, nmissed is not counted but skips exit_handler. /\n 630:\t\t\tif (!ret \u0026\u0026 fp-\u003eexit_handler) {\n 631:\t\t\t\tint size_words = SIZE_IN_LONG(data_size);\n 632:\t\n 633:\t\t\t\tif (write_fprobe_header(\u0026fgraph_data[used], fp, size_words))\n 634:\t\t\t\t\tused += FPROBE_HEADER_SIZE_IN_LONG + size_words;\n 635:\t\t\t}\n 636:\t\t}\n 637:\t\n 638:\t\t/ Clear unused slots so fprobe_return() does not see stale headers. /\n 639:\t\tif (used \u003c reserved_words)\n 640:\t\t\tmemset(fgraph_data + used, 0, (reserved_words - used) sizeof(long));\n 641:\t\n 642:\t\t/* If any exit_handler is set, data must be used. /\n 643:\t\treturn used != 0;\n 644:\t}\n 645:\tNOKPROBE_SYMBOL(fprobe_fgraph_entry);\n 646:\t\n 647:\tstatic void fprobe_return(struct ftrace_graph_ret trace,\n 648:\t\t\t\t struct fgraph_ops gops,\n 649:\t\t\t\t struct ftrace_regs fregs)\n 650:\t{\n 651:\t\tunsigned long fgraph_data = NULL;\n 652:\t\tunsigned long ret_ip;\n 653:\t\tstruct fprobe fp;\n 654:\t\tint size, curr;\n 655:\t\tint size_words;\n 656:\t\n 657:\t\tfgraph_data = (unsigned long *)fgraph_retrieve_data(gops-\u003eidx, \u0026size);\n 658:\t\tif (WARN_ON_ONCE(!fgraph_data))\n 659:\t\t\treturn;\n 660:\t\tsize_words = SIZE_IN_LONG(size);\n 661:\t\tret_ip = ftrace_regs_get_instruction_pointer(fregs);\n 662:\t\n 663:\t\tpreempt_disable_notrace();\n 664:\t\n 665:\t\tcurr = 0;\n 666:\t\twhile (size_words \u003e curr) {\n 667:\t\t\tread_fprobe_header(\u0026fgraph_data[curr], \u0026fp, \u0026size);\n 668:\t\t\tif (!fp)\n 669:\t\t\t\tbreak;\n" }
5/2	2026/09/16 03:09	llm	patch-evaluator	0m Model: gemini-3.8-flash Args: null Results: null Tokens: input: 4323 output: 36 thoughts: 49 Thoughts: Okay, let's dive into this. Here's how I'd approach understanding the interconnections within `fprobe.c` and its relationship with the broader tracing ecosystem: Dissecting the `fprobe.c` Puzzle My immediate inclination is to gain a holistic perspective. I need to understand how `fprobe.c` fits into the bigger picture. Therefore, I want to investigate the code and how it relates to `fgraph`, the function prober, the BPF (Berkeley Packet Filter) integration, and the role of `tracefs`. A deep dive is necessary to get a full picture. I suspect that the critical relationship will become more clear if I trace the execution from where the `fgraph` entry point is invoked, by reviewing the code that came before.
6/2	2026/09/16 03:09	tool	read-file	0m Args: { "File": "kernel/trace/fprobe.c", "FirstLine": 560, "LineCount": 50 } Results: { "Contents": " 560:\t\t\treturn 0;\n 561:\t\n 562:\t\tguard(rcu)();\n 563:\t\thead = rhltable_lookup(\u0026fprobe_ip_table, \u0026func, fprobe_rht_params);\n 564:\t\treserved_words = 0;\n 565:\t\trhl_for_each_entry_rcu(node, pos, head, hlist) {\n 566:\t\t\tif (node-\u003eaddr != func)\n 567:\t\t\t\tcontinue;\n 568:\t\t\tfp = READ_ONCE(node-\u003efp);\n 569:\t\t\tif (!fp \|\| !fp-\u003eexit_handler)\n 570:\t\t\t\tcontinue;\n 571:\t\t\t/\n 572:\t\t\t Since fprobe can be enabled until the next loop, we ignore the\n 573:\t\t\t * fprobe's disabled flag in this loop.\n 574:\t\t\t /\n 575:\t\t\treserved_words +=\n 576:\t\t\t\tFPROBE_HEADER_SIZE_IN_LONG + SIZE_IN_LONG(fp-\u003eentry_data_size);\n 577:\t\t}\n 578:\t\tif (reserved_words) {\n 579:\t\t\tfgraph_data = fgraph_reserve_data(gops-\u003eidx, reserved_words sizeof(long));\n 580:\t\t\tif (unlikely(!fgraph_data)) {\n 581:\t\t\t\trhl_for_each_entry_rcu(node, pos, head, hlist) {\n 582:\t\t\t\t\tif (node-\u003eaddr != func)\n 583:\t\t\t\t\t\tcontinue;\n 584:\t\t\t\t\tfp = READ_ONCE(node-\u003efp);\n 585:\t\t\t\t\tif (fp \u0026\u0026 !fprobe_disabled(fp) \u0026\u0026 !fprobe_is_ftrace(fp))\n 586:\t\t\t\t\t\tfp-\u003enmissed++;\n 587:\t\t\t\t}\n 588:\t\t\t\treturn 0;\n 589:\t\t\t}\n 590:\t\t}\n 591:\t\n 592:\t\t/\n 593:\t\t TODO: recursion detection has been done in the fgraph. Thus we need\n 594:\t\t * to add a callback to increment missed counter.\n 595:\t\t /\n 596:\t\tret_ip = ftrace_regs_get_return_address(fregs);\n 597:\t\tused = 0;\n 598:\t\trhl_for_each_entry_rcu(node, pos, head, hlist) {\n 599:\t\t\tint data_size;\n 600:\t\t\tvoid data;\n 601:\t\n 602:\t\t\tif (node-\u003eaddr != func)\n 603:\t\t\t\tcontinue;\n 604:\t\t\tfp = READ_ONCE(node-\u003efp);\n 605:\t\t\tif (unlikely(!fp \|\| fprobe_disabled(fp) \|\| fprobe_is_ftrace(fp)))\n 606:\t\t\t\tcontinue;\n 607:\t\n 608:\t\t\tdata_size = fp-\u003eentry_data_size;\n 609:\t\t\t/*\n" }
7/2	2026/09/16 03:09	llm	patch-evaluator	0m Model: gemini-3.8-flash Args: null Results: null Tokens: input: 5362 output: 27 thoughts: 28 Thoughts: Here's my thought process, as if I were considering this code: Analyzing fprobe.c Okay, so I'm looking at `fprobe.c`. Hmm, I wonder what that is in the context of this project. It's not immediately obvious from the filename. My immediate next step is to check the `Kconfig` files. That's the best place to start looking for definitions, dependencies, and descriptions of what `fprobe` is supposed to do. A quick search through the `Kconfig` files should give me the necessary information to proceed. It should tell me whether it's enabled by default, what it depends on, and ideally, what function it provides. That should give me the context I need to understand the purpose of `fprobe.c` and how it fits into the overall system.
8/2	2026/09/16 03:09	tool	grepper	0m Args: { "Expression": "config FPROBE", "PathPrefix": "kernel/trace" } Results: { "Output": "kernel/trace/Kconfig=349=config FUNCTION_SELF_TRACING\n--\nkernel/trace/Kconfig-362-\nkernel/trace/Kconfig:363:config FPROBE\nkernel/trace/Kconfig-364-\tbool \"Kernel Function Probe (fprobe)\"\n--\nkernel/trace/Kconfig=731=config BLK_DEV_IO_TRACE\n--\nkernel/trace/Kconfig-755-\nkernel/trace/Kconfig:756:config FPROBE_EVENTS\nkernel/trace/Kconfig-757-\tdepends on FPROBE\n" }
9/2	2026/09/16 03:09	llm	patch-evaluator	0m Model: gemini-3.8-flash Args: null Results: null Tokens: input: 5749 output: 34 thoughts: 19 Thoughts: Here's a summary of my thought process, as requested: Navigating the Kernel's Trace Configuration Okay, so I need to dive into the kernel's tracing configuration, specifically to see what's being enabled or disabled around that area. Let's start by looking directly at the `kernel/trace/Kconfig` file, around line 363. That's usually a good place to begin my exploration when I'm dealing with tracing, as this is where all the options that configure how the kernel traces code are. This likely means I'm looking for the relevant options.
10/2	2026/09/16 03:09	tool	read-file	0m Args: { "File": "kernel/trace/Kconfig", "FirstLine": 360, "LineCount": 30 } Results: { "Contents": " 360:\t\n 361:\t\t If unsure, say N.\n 362:\t\n 363:\tconfig FPROBE\n 364:\t\tbool \"Kernel Function Probe (fprobe)\"\n 365:\t\tdepends on HAVE_FUNCTION_GRAPH_FREGS \u0026\u0026 HAVE_FTRACE_GRAPH_FUNC\n 366:\t\tdepends on DYNAMIC_FTRACE_WITH_ARGS\n 367:\t\tselect FUNCTION_GRAPH_TRACER\n 368:\t\tdefault n\n 369:\t\thelp\n 370:\t\t This option enables kernel function probe (fprobe) based on ftrace.\n 371:\t\t The fprobe is similar to kprobes, but probes only for kernel function\n 372:\t\t entries and exits. This also can probe multiple functions by one\n 373:\t\t fprobe.\n 374:\t\n 375:\t\t If unsure, say N.\n 376:\t\n 377:\tconfig FUNCTION_PROFILER\n 378:\t\tbool \"Kernel function profiler\"\n 379:\t\tdepends on FUNCTION_TRACER\n 380:\t\tdefault n\n 381:\t\thelp\n 382:\t\t This option enables the kernel function profiler. A file is created\n 383:\t\t in debugfs called function_profile_enabled which defaults to zero.\n 384:\t\t When a 1 is echoed into this file profiling begins, and when a\n 385:\t\t zero is entered, profiling stops. A \"functions\" file is created in\n 386:\t\t the trace_stat directory; this file shows the list of functions that\n 387:\t\t have been hit and their counters.\n 388:\t\n 389:\t\t If in doubt, say N.\n" }
11/2	2026/09/16 03:09	llm	patch-evaluator	0m Model: gemini-3.8-flash Args: null Results: null Tokens: input: 6386 output: 26 thoughts: 17 Thoughts: Here's my attempt at summarizing the thought process, tailored for an expert audience: Investigating Dependencies on FPROBE Okay, so I need to get a handle on the usage of `FPROBE`. I'm thinking, let's figure out the landscape. What code is actually using `FPROBE`? Are there any downstream components or libraries that are heavily reliant on it? My immediate goal is to map out the connections, identify any potential bottlenecks or critical dependencies. This will help me understand its significance in the broader context of the system, and allow me to assess the impact of any changes to `FPROBE` – or conversely, if it's okay to refactor it. I need a clear dependency graph, either manually assembled or generated via some kind of tool.
12/2	2026/09/16 03:09	tool	grepper	0m Args: { "Expression": "depends on.FPROBE\|select.FPROBE" } Results: { "Output": "kernel/trace/Kconfig=756=config FPROBE_EVENTS\nkernel/trace/Kconfig:757:\tdepends on FPROBE\nkernel/trace/Kconfig-758-\tdepends on HAVE_REGS_AND_STACK_ACCESS_API\n--\nkernel/trace/Kconfig=770=config PROBE_EVENTS_BTF_ARGS\nkernel/trace/Kconfig-771-\tdepends on HAVE_FUNCTION_ARG_ACCESS_API\nkernel/trace/Kconfig:772:\tdepends on FPROBE_EVENTS \|\| KPROBE_EVENTS\nkernel/trace/Kconfig-773-\tdepends on DEBUG_INFO_BTF \u0026\u0026 BPF_SYSCALL\n--\nlib/Kconfig.debug=2382=config FPROBE_SANITY_TEST\n--\nlib/Kconfig.debug-2384-\tdepends on DEBUG_KERNEL\nlib/Kconfig.debug:2385:\tdepends on FPROBE\nlib/Kconfig.debug-2386-\tdepends on KUNIT=y\n--\nsamples/Kconfig=89=config SAMPLE_FPROBE\nsamples/Kconfig-90-\ttristate \"Build fprobe examples -- loadable modules only\"\nsamples/Kconfig:91:\tdepends on FPROBE \u0026\u0026 m\nsamples/Kconfig-92-\thelp\n" }
13/2	2026/09/16 03:09	llm	patch-evaluator	0m Model: gemini-3.8-flash Args: null Results: null Tokens: input: 6927 output: 18 thoughts: 32 Thoughts: Okay, here's my take on those thoughts, tailored for an expert audience, presented in the first person: BPF and fprobe: Diving Deeper Right, so we're looking at fprobe. But my immediate thought is, "Let's make sure we haven't overlooked any of the BPF angles here." We need to thoroughly examine how fprobe is leveraging BPF – specifically, the various methods we're likely using. I'm thinking about things like `bpf_fentry` for function entry tracing, potentially `bpf_kprobe_multi` for more flexible kernel probe attachment, and any other BPF programs we've integrated. A comprehensive assessment requires us to identify all these specific BPF program types. Essentially, I'm making a mental checklist of the BPF components involved to ensure we have a complete picture of the fprobe implementation. I want to rule out a failure to consider all the nuances that might be relevant to analysis.
14/2	2026/09/16 03:09	tool	grepper	0m Args: { "Expression": "register_fprobe" } Results: { "Output": "Documentation/trace/fprobe.rst=24=attach callbacks to multiple function entry and exit. User needs to set up\nDocumentation/trace/fprobe.rst:25:the `struct fprobe` and pass it to `register_fprobe()`.\nDocumentation/trace/fprobe.rst-26-\n--\nDocumentation/trace/fprobe.rst=28=and/or `exit_handler` as below.\n--\nDocumentation/trace/fprobe.rst-36-\nDocumentation/trace/fprobe.rst:37:To enable the fprobe, call one of register_fprobe(), register_fprobe_ips(), and\nDocumentation/trace/fprobe.rst:38:register_fprobe_syms(). These functions register the fprobe with different types\nDocumentation/trace/fprobe.rst-39-of parameters.\nDocumentation/trace/fprobe.rst-40-\nDocumentation/trace/fprobe.rst:41:The register_fprobe() enables a fprobe by function-name filters.\nDocumentation/trace/fprobe.rst-42-E.g. this enables @fp on \"func()\" function except \"func2()\".::\nDocumentation/trace/fprobe.rst-43-\nDocumentation/trace/fprobe.rst:44: register_fprobe(\u0026fp, \"func\", \"func2\");\nDocumentation/trace/fprobe.rst-45-\nDocumentation/trace/fprobe.rst:46:The register_fprobe_ips() enables a fprobe by ftrace-location addresses.\nDocumentation/trace/fprobe.rst-47-E.g.\n--\nDocumentation/trace/fprobe.rst-52-\nDocumentation/trace/fprobe.rst:53: register_fprobe_ips(\u0026fp, ips, ARRAY_SIZE(ips));\nDocumentation/trace/fprobe.rst-54-\nDocumentation/trace/fprobe.rst:55:And the register_fprobe_syms() enables a fprobe by symbol names.\nDocumentation/trace/fprobe.rst-56-E.g.\n--\nDocumentation/trace/fprobe.rst-61-\nDocumentation/trace/fprobe.rst:62: register_fprobe_syms(\u0026fp, syms, ARRAY_SIZE(syms));\nDocumentation/trace/fprobe.rst-63-\nDocumentation/trace/fprobe.rst=64=To disable (remove from functions) this fprobe, call::\nDocumentation/trace/fprobe.rst-65-\nDocumentation/trace/fprobe.rst:66: unregister_fprobe(\u0026fp);\nDocumentation/trace/fprobe.rst-67-\n--\nDocumentation/trace/fprobe.rst=80=Same as ftrace, the registered callbacks will start being called some time\nDocumentation/trace/fprobe.rst:81:after the register_fprobe() is called and before it returns. See\nDocumentation/trace/fprobe.rst-82-Documentation/trace/ftrace.rst.\nDocumentation/trace/fprobe.rst-83-\nDocumentation/trace/fprobe.rst:84:Also, the unregister_fprobe() will guarantee that both enter and exit\nDocumentation/trace/fprobe.rst:85:handlers are no longer being called by functions after unregister_fprobe()\nDocumentation/trace/fprobe.rst-86-returns as same as unregister_ftrace_function().\n--\nDocumentation/trace/fprobe.rst=159=code will be shared with kprobes, please set FPROBE_FL_KPROBE_SHARED\n--\nDocumentation/trace/fprobe.rst-165-\nDocumentation/trace/fprobe.rst:166: register_fprobe(\u0026fprobe, \"func\", NULL);\nDocumentation/trace/fprobe.rst-167-\n--\ninclude/linux/fprobe.h=87=static inline bool fprobe_shared_with_kprobes(struct fprobe fp)\n--\ninclude/linux/fprobe.h-92-#ifdef CONFIG_FPROBE\ninclude/linux/fprobe.h:93:int register_fprobe(struct fprobe fp, const char filter, const char notfilter);\ninclude/linux/fprobe.h:94:int register_fprobe_ips(struct fprobe fp, unsigned long addrs, int num);\ninclude/linux/fprobe.h:95:int register_fprobe_syms(struct fprobe fp, const char *syms, int num);\ninclude/linux/fprobe.h:96:int unregister_fprobe(struct fprobe fp);\ninclude/linux/fprobe.h:97:int unregister_fprobe_async(struct fprobe fp);\ninclude/linux/fprobe.h-98-bool fprobe_is_registered(struct fprobe fp);\ninclude/linux/fprobe.h=99=int fprobe_count_ips_from_filter(const char filter, const char notfilter);\ninclude/linux/fprobe.h-100-#else\ninclude/linux/fprobe.h:101:static inline int register_fprobe(struct fprobe fp, const char filter, const char notfilter)\ninclude/linux/fprobe.h-102-{\n--\ninclude/linux/fprobe.h-104-}\ninclude/linux/fprobe.h:105:static inline int register_fprobe_ips(struct fprobe fp, unsigned long addrs, int num)\ninclude/linux/fprobe.h-106-{\n--\ninclude/linux/fprobe.h-108-}\ninclude/linux/fprobe.h:109:static inline int register_fprobe_syms(struct fprobe fp, const char *syms, int num)\ninclude/linux/fprobe.h-110-{\n--\ninclude/linux/fprobe.h-112-}\ninclude/linux/fprobe.h:113:static inline int unregister_fprobe(struct fprobe fp)\ninclude/linux/fprobe.h-114-{\n--\ninclude/linux/fprobe.h-116-}\ninclude/linux/fprobe.h:117:static inline int unregister_fprobe_async(struct fprobe fp)\ninclude/linux/fprobe.h-118-{\n--\nkernel/trace/bpf_trace.c=2428=static void bpf_kprobe_multi_link_release(struct bpf_link link)\n--\nkernel/trace/bpf_trace.c-2433-\t/* Don't wait for RCU GP here. /\nkernel/trace/bpf_trace.c:2434:\tunregister_fprobe_async(\u0026kmulti_link-\u003efp);\nkernel/trace/bpf_trace.c-2435-\tkprobe_multi_put_modules(kmulti_link-\u003emods, kmulti_link-\u003emods_cnt);\n--\nkernel/trace/bpf_trace.c=2780=int bpf_kprobe_multi_link_attach(const union bpf_attr attr, struct bpf_prog prog)\n--\nkernel/trace/bpf_trace.c-2919-\nkernel/trace/bpf_trace.c:2920:\terr = register_fprobe_ips(\u0026link-\u003efp, addrs, cnt);\nkernel/trace/bpf_trace.c-2921-\tif (err) {\n--\nkernel/trace/fprobe.c=923=int fprobe_count_ips_from_filter(const char filter, const char notfilter)\n--\nkernel/trace/fprobe.c-928-/\nkernel/trace/fprobe.c:929: register_fprobe() - Register fprobe to ftrace by pattern.\nkernel/trace/fprobe.c-930- * @fp: A fprobe data structure to be registered.\n--\nkernel/trace/fprobe.c-938- /\nkernel/trace/fprobe.c:939:int register_fprobe(struct fprobe fp, const char filter, const char notfilter)\nkernel/trace/fprobe.c-940-{\n--\nkernel/trace/fprobe.c-961-\tif (ret \u003e= 0)\nkernel/trace/fprobe.c:962:\t\tret = register_fprobe_ips(fp, addrs, ret);\nkernel/trace/fprobe.c-963-\n--\nkernel/trace/fprobe.c-969-}\nkernel/trace/fprobe.c:970:EXPORT_SYMBOL_GPL(register_fprobe);\nkernel/trace/fprobe.c-971-\nkernel/trace/fprobe.c:972:static int unregister_fprobe_nolock(struct fprobe fp);\nkernel/trace/fprobe.c-973-\nkernel/trace/fprobe.c-974-/\nkernel/trace/fprobe.c:975: register_fprobe_ips() - Register fprobe to ftrace by address.\nkernel/trace/fprobe.c-976- * @fp: A fprobe data structure to be registered.\n--\nkernel/trace/fprobe.c-986- /\nkernel/trace/fprobe.c:987:int register_fprobe_ips(struct fprobe fp, unsigned long addrs, int num)\nkernel/trace/fprobe.c-988-{\n--\nkernel/trace/fprobe.c-1014-\tif (ret) {\nkernel/trace/fprobe.c:1015:\t\tunregister_fprobe_nolock(fp);\nkernel/trace/fprobe.c-1016-\t\t/ In error case, wait for clean up safely. /\n--\nkernel/trace/fprobe.c-1021-}\nkernel/trace/fprobe.c:1022:EXPORT_SYMBOL_GPL(register_fprobe_ips);\nkernel/trace/fprobe.c-1023-\nkernel/trace/fprobe.c-1024-/\nkernel/trace/fprobe.c:1025: register_fprobe_syms() - Register fprobe to ftrace by symbols.\nkernel/trace/fprobe.c-1026- * @fp: A fprobe data structure to be registered.\n--\nkernel/trace/fprobe.c-1034- /\nkernel/trace/fprobe.c:1035:int register_fprobe_syms(struct fprobe fp, const char *syms, int num)\nkernel/trace/fprobe.c-1036-{\n--\nkernel/trace/fprobe.c-1046-\nkernel/trace/fprobe.c:1047:\tret = register_fprobe_ips(fp, addrs, num);\nkernel/trace/fprobe.c-1048-\n--\nkernel/trace/fprobe.c-1052-}\nkernel/trace/fprobe.c:1053:EXPORT_SYMBOL_GPL(register_fprobe_syms);\nkernel/trace/fprobe.c-1054-\nkernel/trace/fprobe.c=1055=bool fprobe_is_registered(struct fprobe fp)\n--\nkernel/trace/fprobe.c-1061-\nkernel/trace/fprobe.c:1062:static int unregister_fprobe_nolock(struct fprobe fp)\nkernel/trace/fprobe.c-1063-{\n--\nkernel/trace/fprobe.c-1100-/\nkernel/trace/fprobe.c:1101: unregister_fprobe_async() - Unregister fprobe without RCU GP wait\nkernel/trace/fprobe.c-1102- * @fp: A fprobe data structure to be unregistered.\n--\nkernel/trace/fprobe.c-1108- /\nkernel/trace/fprobe.c:1109:int unregister_fprobe_async(struct fprobe fp)\nkernel/trace/fprobe.c-1110-{\n--\nkernel/trace/fprobe.c-1114-\nkernel/trace/fprobe.c:1115:\treturn unregister_fprobe_nolock(fp);\nkernel/trace/fprobe.c-1116-}\n--\nkernel/trace/fprobe.c-1118-/*\nkernel/trace/fprobe.c:1119: unregister_fprobe() - Unregister fprobe with RCU GP wait\nkernel/trace/fprobe.c-1120- * @fp: A fprobe data structure to be unregistered.\n--\nkernel/trace/fprobe.c-1126- /\nkernel/trace/fprobe.c:1127:int unregister_fprobe(struct fprobe fp)\nkernel/trace/fprobe.c-1128-{\nkernel/trace/fprobe.c:1129:\tint ret = unregister_fprobe_async(fp);\nkernel/trace/fprobe.c-1130-\n--\nkernel/trace/fprobe.c-1134-}\nkernel/trace/fprobe.c:1135:EXPORT_SYMBOL_GPL(unregister_fprobe);\nkernel/trace/fprobe.c-1136-\n--\nkernel/trace/trace_fprobe.c=735=static inline void init_trace_event_call(struct trace_fprobe tf)\n--\nkernel/trace/trace_fprobe.c-750-\nkernel/trace/trace_fprobe.c:751:static int register_fprobe_event(struct trace_fprobe tf)\nkernel/trace/trace_fprobe.c-752-{\n--\nkernel/trace/trace_fprobe.c-757-\nkernel/trace/trace_fprobe.c:758:static int unregister_fprobe_event(struct trace_fprobe tf)\nkernel/trace/trace_fprobe.c-759-{\n--\nkernel/trace/trace_fprobe.c=763=static int __register_tracepoint_fprobe(struct trace_fprobe tf)\n--\nkernel/trace/trace_fprobe.c-786-\nkernel/trace/trace_fprobe.c:787:\t\tret = register_fprobe_ips(\u0026tf-\u003efp, \u0026ip, 1);\nkernel/trace/trace_fprobe.c-788-\t\tif (ret \u003c 0)\n--\nkernel/trace/trace_fprobe.c=797=static int trace_fprobe_verify_target(struct trace_fprobe tf)\n--\nkernel/trace/trace_fprobe.c-806-\t Note: since we don't lock the module, even if this succeeded,\nkernel/trace/trace_fprobe.c:807:\t * register_fprobe() later can fail.\nkernel/trace/trace_fprobe.c-808-\t /\n--\nkernel/trace/trace_fprobe.c=814=static int __register_trace_fprobe(struct trace_fprobe tf)\n--\nkernel/trace/trace_fprobe.c-837-\t/* TODO: handle filter, nofilter or symbol list /\nkernel/trace/trace_fprobe.c:838:\treturn register_fprobe(\u0026tf-\u003efp, tf-\u003esymbol, NULL);\nkernel/trace/trace_fprobe.c-839-}\n--\nkernel/trace/trace_fprobe.c=842=static void __unregister_trace_fprobe(struct trace_fprobe tf)\n--\nkernel/trace/trace_fprobe.c-844-\tif (trace_fprobe_is_registered(tf))\nkernel/trace/trace_fprobe.c:845:\t\tunregister_fprobe(\u0026tf-\u003efp);\nkernel/trace/trace_fprobe.c-846-\tif (tf-\u003etuser) {\n--\nkernel/trace/trace_fprobe.c=854=static int unregister_trace_fprobe(struct trace_fprobe tf)\n--\nkernel/trace/trace_fprobe.c-868-\t/ Will fail if probe is being used by ftrace or perf /\nkernel/trace/trace_fprobe.c:869:\tif (unregister_fprobe_event(tf))\nkernel/trace/trace_fprobe.c-870-\t\treturn -EBUSY;\n--\nkernel/trace/trace_fprobe.c=946=static int register_trace_fprobe_event(struct trace_fprobe tf)\n--\nkernel/trace/trace_fprobe.c-958-\t/* Register new event /\nkernel/trace/trace_fprobe.c:959:\tret = register_fprobe_event(tf);\nkernel/trace/trace_fprobe.c-960-\tif (ret) {\n--\nkernel/trace/trace_fprobe.c-971-\tif (ret \u003c 0)\nkernel/trace/trace_fprobe.c:972:\t\tunregister_fprobe_event(tf);\nkernel/trace/trace_fprobe.c-973-\telse\n--\nkernel/trace/trace_fprobe.c=1105=static int __tprobe_event_module_cb(struct notifier_block self,\n--\nkernel/trace/trace_fprobe.c-1125-\nkernel/trace/trace_fprobe.c:1126:\t\t\tWARN_ON_ONCE(register_fprobe_ips(\u0026tf-\u003efp, \u0026ip, 1));\nkernel/trace/trace_fprobe.c-1127-\t\t} else if (val == MODULE_STATE_GOING \u0026\u0026\n--\nkernel/trace/trace_fprobe.c-1136-\t\t\t !tf-\u003etuser-\u003etpoint) {\nkernel/trace/trace_fprobe.c:1137:\t\t\tunregister_fprobe(\u0026tf-\u003efp);\nkernel/trace/trace_fprobe.c-1138-\t\t}\n--\nkernel/trace/trace_fprobe.c=1503=static int disable_trace_fprobe(struct trace_event_call call,\n--\nkernel/trace/trace_fprobe.c-1523-\t\tlist_for_each_entry(tf, trace_probe_probe_list(tp), tp.list) {\nkernel/trace/trace_fprobe.c:1524:\t\t\tunregister_fprobe(\u0026tf-\u003efp);\nkernel/trace/trace_fprobe.c-1525-\t\t\tif (tf-\u003etuser) {\n--\nlib/tests/test_fprobe.c=77=static void test_fprobe_entry(struct kunit test)\n--\nlib/tests/test_fprobe.c-85-\t/* Before register, unregister should be failed. /\nlib/tests/test_fprobe.c:86:\tKUNIT_EXPECT_NE(test, 0, unregister_fprobe(\u0026fp_entry));\nlib/tests/test_fprobe.c:87:\tKUNIT_EXPECT_EQ(test, 0, register_fprobe(\u0026fp_entry, \"fprobe_selftest_target\", NULL));\nlib/tests/test_fprobe.c-88-\n--\nlib/tests/test_fprobe.c-100-\nlib/tests/test_fprobe.c:101:\tKUNIT_EXPECT_EQ(test, 0, unregister_fprobe(\u0026fp_entry));\nlib/tests/test_fprobe.c-102-}\n--\nlib/tests/test_fprobe.c=104=static void test_fprobe(struct kunit test)\n--\nlib/tests/test_fprobe.c-111-\tcurrent_test = test;\nlib/tests/test_fprobe.c:112:\tKUNIT_EXPECT_EQ(test, 0, register_fprobe(\u0026fp, \"fprobe_selftest_target\", NULL));\nlib/tests/test_fprobe.c-113-\n--\nlib/tests/test_fprobe.c-125-\nlib/tests/test_fprobe.c:126:\tKUNIT_EXPECT_EQ(test, 0, unregister_fprobe(\u0026fp));\nlib/tests/test_fprobe.c-127-}\n--\nlib/tests/test_fprobe.c=129=static void test_fprobe_syms(struct kunit test)\n--\nlib/tests/test_fprobe.c-137-\tcurrent_test = test;\nlib/tests/test_fprobe.c:138:\tKUNIT_EXPECT_EQ(test, 0, register_fprobe_syms(\u0026fp, syms, 2));\nlib/tests/test_fprobe.c-139-\n--\nlib/tests/test_fprobe.c-151-\nlib/tests/test_fprobe.c:152:\tKUNIT_EXPECT_EQ(test, 0, unregister_fprobe(\u0026fp));\nlib/tests/test_fprobe.c-153-}\n--\nlib/tests/test_fprobe.c=156=static void test_fprobe_data(struct kunit test)\n--\nlib/tests/test_fprobe.c-164-\tcurrent_test = test;\nlib/tests/test_fprobe.c:165:\tKUNIT_EXPECT_EQ(test, 0, register_fprobe(\u0026fp, \"fprobe_selftest_target\", NULL));\nlib/tests/test_fprobe.c-166-\n--\nlib/tests/test_fprobe.c-168-\nlib/tests/test_fprobe.c:169:\tKUNIT_EXPECT_EQ(test, 0, unregister_fprobe(\u0026fp));\nlib/tests/test_fprobe.c-170-}\n--\nlib/tests/test_fprobe.c=172=static void test_fprobe_skip(struct kunit test)\n--\nlib/tests/test_fprobe.c-179-\tcurrent_test = test;\nlib/tests/test_fprobe.c:180:\tKUNIT_EXPECT_EQ(test, 0, register_fprobe(\u0026fp, \"fprobe_selftest_target\", NULL));\nlib/tests/test_fprobe.c-181-\n--\nlib/tests/test_fprobe.c-190-\nlib/tests/test_fprobe.c:191:\tKUNIT_EXPECT_EQ(test, 0, unregister_fprobe(\u0026fp));\nlib/tests/test_fprobe.c-192-}\n--\nlib/tests/test_fprobe.c=256=static void test_fprobe_multi(struct kunit test)\n--\nlib/tests/test_fprobe.c-268-\t/* Test Case 1: Register in order 1 -\u003e 2 /\nlib/tests/test_fprobe.c:269:\tKUNIT_EXPECT_EQ(test, 0, register_fprobe(\u0026fp1, \"fprobe_selftest_target\", NULL));\nlib/tests/test_fprobe.c:270:\tKUNIT_EXPECT_EQ(test, 0, register_fprobe(\u0026fp2, \"fprobe_selftest_target\", NULL));\nlib/tests/test_fprobe.c-271-\n--\nlib/tests/test_fprobe.c-274-\t/ Unregister all /\nlib/tests/test_fprobe.c:275:\tKUNIT_EXPECT_EQ(test, 0, unregister_fprobe(\u0026fp1));\nlib/tests/test_fprobe.c:276:\tKUNIT_EXPECT_EQ(test, 0, unregister_fprobe(\u0026fp2));\nlib/tests/test_fprobe.c-277-\nlib/tests/test_fprobe.c-278-\t/ Test Case 2: Register in order 2 -\u003e 1 /\nlib/tests/test_fprobe.c:279:\tKUNIT_EXPECT_EQ(test, 0, register_fprobe(\u0026fp2, \"fprobe_selftest_target\", NULL));\nlib/tests/test_fprobe.c:280:\tKUNIT_EXPECT_EQ(test, 0, register_fprobe(\u0026fp1, \"fprobe_selftest_target\", NULL));\nlib/tests/test_fprobe.c-281-\n--\nlib/tests/test_fprobe.c-284-\t/ Unregister all /\nlib/tests/test_fprobe.c:285:\tKUNIT_EXPECT_EQ(test, 0, unregister_fprobe(\u0026fp1));\nlib/tests/test_fprobe.c:286:\tKUNIT_EXPECT_EQ(test, 0, unregister_fprobe(\u0026fp2));\nlib/tests/test_fprobe.c-287-}\n--\nsamples/fprobe/fprobe_example.c=90=static int __init fprobe_init(void)\n--\nsamples/fprobe/fprobe_example.c-100-\t\t/ filter based fprobe /\nsamples/fprobe/fprobe_example.c:101:\t\tret = register_fprobe(\u0026sample_probe, symbol,\nsamples/fprobe/fprobe_example.c-102-\t\t\t\t nosymbol[0] == '\\0' ? NULL : nosymbol);\n--\nsamples/fprobe/fprobe_example.c-105-\t\tsymbuf = symbol;\nsamples/fprobe/fprobe_example.c:106:\t\tret = register_fprobe_syms(\u0026sample_probe, (const char *)\u0026symbuf, 1);\nsamples/fprobe/fprobe_example.c-107-\t\tgoto out;\n--\nsamples/fprobe/fprobe_example.c-130-\nsamples/fprobe/fprobe_example.c:131:\tret = register_fprobe_syms(\u0026sample_probe, syms, count);\nsamples/fprobe/fprobe_example.c-132-\tkfree(syms);\n--\nsamples/fprobe/fprobe_example.c-135-\tif (ret \u003c 0)\nsamples/fprobe/fprobe_example.c:136:\t\tpr_err(\"register_fprobe failed, returned %d\\n\", ret);\nsamples/fprobe/fprobe_example.c-137-\telse\n--\nsamples/fprobe/fprobe_example.c=143=static void __exit fprobe_exit(void)\nsamples/fprobe/fprobe_example.c-144-{\nsamples/fprobe/fprobe_example.c:145:\tunregister_fprobe(\u0026sample_probe);\nsamples/fprobe/fprobe_example.c-146-\n" }
15/2	2026/09/16 03:09	llm	patch-evaluator	0m Model: gemini-3.8-flash Args: null Results: null Tokens: input: 13705 output: 36 thoughts: 173 Thoughts: My Understanding of `fprobe` and Its Implications Okay, so `fprobe`, as I understand it, plays a pretty critical role in the kernel tracing landscape. My initial thought is that it's leveraged in two primary ways: firstly, it's intrinsically linked to `bpf_kprobe_multi_link_attach` within `kernel/trace/bpf_trace.c`. This is where it's used for BPF link attachment in the context of `kprobe.multi`, which is a standard BPF program type. Nothing surprising there; it integrates cleanly. The second usage is through tracefs and specifically `trace_fprobe.c`. This one is interesting because it deals with those dynamic trace events, the kind you’d find in something like `/sys/kernel/tracing/fprobe_events`. These, importantly, are user-space configurable and triggerable. Now, the really intriguing bit is that both of these mechanisms can be manipulated from userspace. My mental alarms are going off – both `bpf$BPF_LINK_CREATE` or operations via tracefs can conjure fprobes in the system! Which implies they can be created or modified via `syzkaller` as well. This, to my mind, is a potential attack surface. To get a grip on what this specific patch is doing, and, more importantly, why it was deemed necessary, I need to dig deeper into the code. I'll need to focus on `fprobe.c`, specifically around the sections for `fprobe_return` and `fprobe_fgraph_entry`. This should clarify the patch's purpose and its implications in terms of potential vulnerabilities or performance improvements. This is good stuff; I'll need to keep this in mind when I audit the code and any potential security issues.
16/2	2026/09/16 03:09	tool	read-file	0m Args: { "File": "kernel/trace/fprobe.c", "FirstLine": 665, "LineCount": 45 } Results: { "Contents": " 665:\t\tcurr = 0;\n 666:\t\twhile (size_words \u003e curr) {\n 667:\t\t\tread_fprobe_header(\u0026fgraph_data[curr], \u0026fp, \u0026size);\n 668:\t\t\tif (!fp)\n 669:\t\t\t\tbreak;\n 670:\t\t\tcurr += FPROBE_HEADER_SIZE_IN_LONG;\n 671:\t\t\tif (fprobe_registered(fp) \u0026\u0026 !fprobe_disabled(fp)) {\n 672:\t\t\t\tif (WARN_ON_ONCE(curr + size \u003e size_words))\n 673:\t\t\t\t\tbreak;\n 674:\t\t\t\tfp-\u003eexit_handler(fp, trace-\u003efunc, ret_ip, fregs,\n 675:\t\t\t\t\t\t size ? fgraph_data + curr : NULL);\n 676:\t\t\t}\n 677:\t\t\tcurr += size;\n 678:\t\t}\n 679:\t\tpreempt_enable_notrace();\n 680:\t}\n 681:\tNOKPROBE_SYMBOL(fprobe_return);\n 682:\t\n 683:\t#ifdef CONFIG_MODULES\n 684:\t\n 685:\t#define FPROBE_IPS_BATCH_INIT 128\n 686:\t/* instruction pointer address list /\n 687:\tstruct fprobe_addr_list {\n 688:\t\tint index;\n 689:\t\tint size;\n 690:\t\tunsigned long addrs;\n 691:\t};\n 692:\t\n 693:\tstatic int fprobe_remove_node_in_module(struct module mod, struct fprobe_hlist_node node,\n 694:\t\t\t\t\t\t struct fprobe_addr_list alist)\n 695:\t{\n 696:\t\tlockdep_assert_in_rcu_read_lock();\n 697:\t\n 698:\t\tif (!within_module(node-\u003eaddr, mod))\n 699:\t\t\treturn 0;\n 700:\t\n 701:\t\tdelete_fprobe_node(node);\n 702:\t\t/ If no address list is available, we can't track this address. /\n 703:\t\tif (!alist-\u003eaddrs)\n 704:\t\t\treturn 0;\n 705:\t\t/\n 706:\t\t * Don't care the type here, because all fprobes on the same\n 707:\t\t * address must be removed eventually.\n 708:\t\t */\n 709:\t\tif (!rhltable_lookup(\u0026fprobe_ip_table, \u0026node-\u003eaddr, fprobe_rht_params)) {\n" }
17/2	2026/09/16 03:09	llm	patch-evaluator	0m Model: gemini-3.8-flash Args: null Results: null Tokens: input: 14986 output: 20 thoughts: 34 Thoughts: Analyzing Memory Allocation in `fgraph_reserve_data` Okay, so I need to understand how `fgraph_reserve_data` handles its memory allocation. My immediate thought is, "where exactly does this function grab its memory from?" Since I need to trace this, I'm going to start with a very straightforward approach. I'll use `grep` to quickly search the codebase for every instance of `fgraph_reserve_data`. This will give me a comprehensive list of all the places where this function is called, which should give me the context necessary to see the calls related to memory allocation. This initial search should help me understand the flow, at a minimum, and ideally pinpoint the allocation calls.
18/2	2026/09/16 03:09	tool	grepper	0m Args: { "Expression": "fgraph_reserve_data" } Results: { "Output": "include/linux/ftrace.h=1259=struct fgraph_ops {\n--\ninclude/linux/ftrace.h-1267-\ninclude/linux/ftrace.h:1268:void fgraph_reserve_data(int idx, int size_bytes);\ninclude/linux/ftrace.h-1269-void fgraph_retrieve_data(int idx, int size_bytes);\n--\nkernel/trace/fgraph.c=319=static void ret_stack_init_task_vars(unsigned long ret_stack)\n--\nkernel/trace/fgraph.c-326-/*\nkernel/trace/fgraph.c:327: fgraph_reserve_data - Reserve storage on the task's ret_stack\nkernel/trace/fgraph.c-328- * @idx:\tThe index of fgraph_array\n--\nkernel/trace/fgraph.c-339- * Otherwise, NULL if there's not enough space left on the\nkernel/trace/fgraph.c:340: * ret_stack for the data, or if fgraph_reserve_data() was called\nkernel/trace/fgraph.c-341- * more than once for a single entryfunc() call.\nkernel/trace/fgraph.c-342- /\nkernel/trace/fgraph.c:343:void fgraph_reserve_data(int idx, int size_bytes)\nkernel/trace/fgraph.c-344-{\n--\nkernel/trace/fgraph.c-377-/*\nkernel/trace/fgraph.c:378: fgraph_retrieve_data - Retrieve stored data from fgraph_reserve_data()\nkernel/trace/fgraph.c-379- * @idx:\tthe index of fgraph_array (fgraph_ops::idx)\n--\nkernel/trace/fgraph.c-387- \nkernel/trace/fgraph.c:388: Returns: The stored data from fgraph_reserve_data() called by the\nkernel/trace/fgraph.c-389- * matching entryfunc() for the retfunc() this is called from.\n--\nkernel/trace/fprobe.c=547=static int fprobe_fgraph_entry(struct ftrace_graph_ent trace, struct fgraph_ops gops,\n--\nkernel/trace/fprobe.c-578-\tif (reserved_words) {\nkernel/trace/fprobe.c:579:\t\tfgraph_data = fgraph_reserve_data(gops-\u003eidx, reserved_words * sizeof(long));\nkernel/trace/fprobe.c-580-\t\tif (unlikely(!fgraph_data)) {\n--\nkernel/trace/ftrace.c=850=static int profile_graph_entry(struct ftrace_graph_ent trace,\n--\nkernel/trace/ftrace.c-861-\nkernel/trace/ftrace.c:862:\tprofile_data = fgraph_reserve_data(gops-\u003eidx, sizeof(profile_data));\nkernel/trace/ftrace.c-863-\tif (!profile_data)\n--\nkernel/trace/trace_functions_graph.c=226=static int graph_entry(struct ftrace_graph_ent trace,\n--\nkernel/trace/trace_functions_graph.c-262-\t !tracer_flags_is_set(tr, TRACE_GRAPH_SLEEP_TIME)) {\nkernel/trace/trace_functions_graph.c:263:\t\tftimes = fgraph_reserve_data(gops-\u003eidx, sizeof(ftimes));\nkernel/trace/trace_functions_graph.c-264-\t\tif (ftimes)\n--\nkernel/trace/trace_functions_graph.c-267-\t\t/* Only need to record the calltime /\nkernel/trace/trace_functions_graph.c:268:\t\tftimes = fgraph_reserve_data(gops-\u003eidx, sizeof(ftimes-\u003ecalltime));\nkernel/trace/trace_functions_graph.c-269-\t}\n--\nkernel/trace/trace_irqsoff.c=178=static int irqsoff_graph_entry(struct ftrace_graph_ent trace,\n--\nkernel/trace/trace_irqsoff.c-203-\nkernel/trace/trace_irqsoff.c:204:\tcalltime = fgraph_reserve_data(gops-\u003eidx, sizeof(calltime));\nkernel/trace/trace_irqsoff.c-205-\tif (calltime) {\n--\nkernel/trace/trace_sched_wakeup.c=115=static int wakeup_graph_entry(struct ftrace_graph_ent trace,\n--\nkernel/trace/trace_sched_wakeup.c-139-\nkernel/trace/trace_sched_wakeup.c:140:\tcalltime = fgraph_reserve_data(gops-\u003eidx, sizeof(calltime));\nkernel/trace/trace_sched_wakeup.c-141-\tif (calltime) {\n--\nkernel/trace/trace_selftest.c=776=static __init int store_entry(struct ftrace_graph_ent trace,\n--\nkernel/trace/trace_selftest.c-784-\nkernel/trace/trace_selftest.c:785:\tp = fgraph_reserve_data(gops-\u003eidx, size);\nkernel/trace/trace_selftest.c-786-\tif (!p) {\n" }
19/2	2026/09/16 03:09	llm	patch-evaluator	0m Model: gemini-3.8-flash Args: null Results: null Tokens: input: 16547 output: 25 thoughts: 1097 Thoughts: Analyzing Potential Stale Data in fprobe_fgraph and Implications Okay, let's dive into this. I'm taking a close look at `fprobe_fgraph_entry` and `fprobe_return`. My immediate concern is how the data buffer, `fgraph_data`, is handled and reused. In `fprobe_fgraph_entry`, I see that it reserves a buffer based on the number of `exit_handler` functions associated with the current function being probed. It calculates `reserved_words` which is the amount to allocate and reserves the data using `fgraph_reserve_data`. The interesting bit is that it iterates through a list of probes, calculating `reserved_words`. Then it iterates again, this time writing the header and data, but only when `ret` is zero. Then importantly, it clears the unused slots, but only when `used < reserved_words`. The function returns `used != 0`. Now, in `fprobe_return`, the allocated buffer is retrieved using `fgraph_retrieve_data`, and then iterated through. The code reads the header, checks a few things (including that `fp` is valid) and calls `fp->exit_handler` if a probe is registered. Here's the problem: if `used < reserved_words` in `fprobe_fgraph_entry`, there's a potential for stale data! The remaining slots in `fgraph_data` were NOT cleared, and since the return stack is reused across function calls, that stale data could be garbage from a previous function call. `fprobe_return` could then read that garbage, interpret it as an fprobe header, and trigger a wild pointer dereference! This could occur if a previous function call allocated data and returned, but for some reason, the probe wasn't used. This is a very significant vulnerability. The scenario that triggers my alarm bells is if `used == 0`. `fprobe_fgraph_entry` explicitly returns `used != 0`. I need to understand whether `fgraph` still uses the return stack frame if `fprobe_fgraph_entry` returns 0. I should check how fgraph uses the return value and trace how `fgraph_reserve_data` is used by grepping through the code. I need to understand if `fprobe_fgraph_entry`'s return value determines whether the stack frame is pushed. I suspect that this is a critical bug.
20/2	2026/09/16 03:09	tool	grepper	0m Args: { "Expression": "entryfunc", "PathPrefix": "kernel/trace" } Results: { "Output": "kernel/trace/fgraph.c=319=static void ret_stack_init_task_vars(unsigned long ret_stack)\n--\nkernel/trace/fgraph.c-332- task's ret_stack shadow stack, for a given fgraph_ops during\nkernel/trace/fgraph.c:333: * the entryfunc() call. If entryfunc() returns zero, the storage\nkernel/trace/fgraph.c:334: * is discarded. An entryfunc() can only call this once per iteration.\nkernel/trace/fgraph.c-335- * The fgraph_ops retfunc() can retrieve this stored data with\n--\nkernel/trace/fgraph.c-340- * ret_stack for the data, or if fgraph_reserve_data() was called\nkernel/trace/fgraph.c:341: * more than once for a single entryfunc() call.\nkernel/trace/fgraph.c-342- /\nkernel/trace/fgraph.c=343=void fgraph_reserve_data(int idx, int size_bytes)\n--\nkernel/trace/fgraph.c-382- * This is to be called by a fgraph_ops retfunc(), to retrieve data that\nkernel/trace/fgraph.c:383: * was stored by the fgraph_ops entryfunc() on the function entry.\nkernel/trace/fgraph.c-384- * That is, this will retrieve the data that was reserved on the\n--\nkernel/trace/fgraph.c-388- * Returns: The stored data from fgraph_reserve_data() called by the\nkernel/trace/fgraph.c:389: * matching entryfunc() for the retfunc() this is called from.\nkernel/trace/fgraph.c-390- * Or NULL if there was nothing stored.\n--\nkernel/trace/fgraph.c=531=static struct fgraph_ops fgraph_stub = {\nkernel/trace/fgraph.c:532:\t.entryfunc = ftrace_graph_entry_stub,\nkernel/trace/fgraph.c-533-\t.retfunc = ftrace_graph_ret_stub,\n--\nkernel/trace/fgraph.c=649=int function_graph_enter_regs(unsigned long ret, unsigned long func,\n--\nkernel/trace/fgraph.c-691-\t\t\tif (ftrace_ops_test(\u0026gops-\u003eops, func, NULL) \u0026\u0026\nkernel/trace/fgraph.c:692:\t\t\t gops-\u003eentryfunc(\u0026trace, gops, fregs))\nkernel/trace/fgraph.c-693-\t\t\t\tbitmap \|= BIT(i);\n--\nkernel/trace/fgraph.c=1212=void fgraph_update_pid_func(void)\n--\nkernel/trace/fgraph.c-1222-\t\t\tgops = container_of(op, struct fgraph_ops, ops);\nkernel/trace/fgraph.c:1223:\t\t\tgops-\u003eentryfunc = ftrace_pids_enabled(op) ?\nkernel/trace/fgraph.c-1224-\t\t\t\tfgraph_pid_func : gops-\u003esaved_func;\nkernel/trace/fgraph.c-1225-\t\t\tif (ftrace_graph_active == 1)\nkernel/trace/fgraph.c:1226:\t\t\t\tstatic_call_update(fgraph_func, gops-\u003eentryfunc);\nkernel/trace/fgraph.c-1227-\t\t}\n--\nkernel/trace/fgraph.c=1283=static void ftrace_graph_enable_direct(bool enable_branch, struct fgraph_ops gops)\n--\nkernel/trace/fgraph.c-1292-\tif (gops) {\nkernel/trace/fgraph.c:1293:\t\tfunc = gops-\u003eentryfunc;\nkernel/trace/fgraph.c-1294-\t\tretfunc = gops-\u003eretfunc;\n--\nkernel/trace/fgraph.c-1298-\t\t\t\t sizeof(fgraph_array_bitmask) BITS_PER_BYTE) {\nkernel/trace/fgraph.c:1299:\t\t\tfunc = fgraph_array[i]-\u003eentryfunc;\nkernel/trace/fgraph.c-1300-\t\t\tretfunc = fgraph_array[i]-\u003eretfunc;\n--\nkernel/trace/fgraph.c=1333=int register_ftrace_graph(struct fgraph_ops gops)\n--\nkernel/trace/fgraph.c-1379-\t/ Always save the function, and reset at unregistering /\nkernel/trace/fgraph.c:1380:\tgops-\u003esaved_func = gops-\u003eentryfunc;\nkernel/trace/fgraph.c-1381-#ifdef CONFIG_DYNAMIC_FTRACE\nkernel/trace/fgraph.c-1382-\tif (ftrace_pids_enabled(\u0026gops-\u003eops))\nkernel/trace/fgraph.c:1383:\t\tgops-\u003eentryfunc = fgraph_pid_func;\nkernel/trace/fgraph.c-1384-#endif\n--\nkernel/trace/fprobe.c=259=static struct fgraph_ops fprobe_graph_ops = {\nkernel/trace/fprobe.c:260:\t.entryfunc\t= fprobe_fgraph_entry,\nkernel/trace/fprobe.c-261-\t.retfunc\t= fprobe_return,\n--\nkernel/trace/ftrace.c=926=static struct fgraph_ops fprofiler_ops = {\nkernel/trace/ftrace.c:927:\t.entryfunc = \u0026profile_graph_entry,\nkernel/trace/ftrace.c-928-\t.retfunc = \u0026profile_graph_return,\n--\nkernel/trace/ftrace.c=4460=static void print_subops(struct seq_file m, struct ftrace_ops ops, struct dyn_ftrace rec)\n--\nkernel/trace/ftrace.c-4478-\t\t\tseq_printf(m, \" {ent:%pS ret:%pS}\",\nkernel/trace/ftrace.c:4479:\t\t\t\t (void )gops-\u003eentryfunc,\nkernel/trace/ftrace.c-4480-\t\t\t\t (void )gops-\u003eretfunc);\n--\nkernel/trace/trace_functions_graph.c=436=static struct fgraph_ops funcgraph_ops = {\nkernel/trace/trace_functions_graph.c:437:\t.entryfunc = \u0026trace_graph_entry,\nkernel/trace/trace_functions_graph.c-438-\t.retfunc = \u0026trace_graph_return,\n--\nkernel/trace/trace_functions_graph.c=441=int allocate_fgraph_ops(struct trace_array tr, struct ftrace_ops ops)\n--\nkernel/trace/trace_functions_graph.c-448-\nkernel/trace/trace_functions_graph.c:449:\tgops-\u003eentryfunc = \u0026trace_graph_entry;\nkernel/trace/trace_functions_graph.c-450-\tgops-\u003eretfunc = \u0026trace_graph_return;\n--\nkernel/trace/trace_functions_graph.c=472=static int graph_trace_init(struct trace_array tr)\n--\nkernel/trace/trace_functions_graph.c-476-\tif (tracer_flags_is_set(tr, TRACE_GRAPH_ARGS))\nkernel/trace/trace_functions_graph.c:477:\t\ttr-\u003egops-\u003eentryfunc = trace_graph_entry_args;\nkernel/trace/trace_functions_graph.c-478-\telse\nkernel/trace/trace_functions_graph.c:479:\t\ttr-\u003egops-\u003eentryfunc = trace_graph_entry;\nkernel/trace/trace_functions_graph.c-480-\n--\nkernel/trace/trace_functions_graph.c=505=static int ftrace_graph_trace_args(struct trace_array tr, int set)\n--\nkernel/trace/trace_functions_graph.c-514-\t/* See if there's any changes */\nkernel/trace/trace_functions_graph.c:515:\tif (tr-\u003egops-\u003eentryfunc == entry)\nkernel/trace/trace_functions_graph.c-516-\t\treturn 0;\n--\nkernel/trace/trace_functions_graph.c-519-\nkernel/trace/trace_functions_graph.c:520:\ttr-\u003egops-\u003eentryfunc = entry;\nkernel/trace/trace_functions_graph.c-521-\n--\nkernel/trace/trace_irqsoff.c=241=static struct fgraph_ops fgraph_ops = {\nkernel/trace/trace_irqsoff.c:242:\t.entryfunc\t\t= \u0026irqsoff_graph_entry,\nkernel/trace/trace_irqsoff.c-243-\t.retfunc\t\t= \u0026irqsoff_graph_return,\n--\nkernel/trace/trace_sched_wakeup.c=178=static struct fgraph_ops fgraph_wakeup_ops = {\nkernel/trace/trace_sched_wakeup.c:179:\t.entryfunc = \u0026wakeup_graph_entry,\nkernel/trace/trace_sched_wakeup.c-180-\t.retfunc = \u0026wakeup_graph_return,\n--\nkernel/trace/trace_selftest.c=909=static struct fgraph_fixture store_bytes[4] __initdata = {\n--\nkernel/trace/trace_selftest.c-911-\t\t.gops = {\nkernel/trace/trace_selftest.c:912:\t\t\t.entryfunc\t\t= store_entry,\nkernel/trace/trace_selftest.c-913-\t\t\t.retfunc\t\t= store_return,\n--\nkernel/trace/trace_selftest.c-919-\t\t.gops = {\nkernel/trace/trace_selftest.c:920:\t\t\t.entryfunc\t\t= store_entry,\nkernel/trace/trace_selftest.c-921-\t\t\t.retfunc\t\t= store_return,\n--\nkernel/trace/trace_selftest.c-927-\t\t.gops = {\nkernel/trace/trace_selftest.c:928:\t\t\t.entryfunc\t\t= store_entry,\nkernel/trace/trace_selftest.c-929-\t\t\t.retfunc\t\t= store_return,\n--\nkernel/trace/trace_selftest.c-935-\t\t.gops = {\nkernel/trace/trace_selftest.c:936:\t\t\t.entryfunc\t\t= store_entry,\nkernel/trace/trace_selftest.c-937-\t\t\t.retfunc\t\t= store_return,\n--\nkernel/trace/trace_selftest.c=1048=static struct fgraph_ops fgraph_ops __initdata = {\nkernel/trace/trace_selftest.c:1049:\t.entryfunc\t\t= \u0026trace_graph_entry_watchdog,\nkernel/trace/trace_selftest.c-1050-\t.retfunc\t\t= \u0026trace_graph_return,\n" }
21/2	2026/09/16 03:09	llm	patch-evaluator	0m Model: gemini-3.8-flash Args: null Results: null Tokens: input: 20956 output: 29 thoughts: 87 Thoughts: Here's my thought process, as if I were analyzing this code: Deep Dive into fprobe Implementation Okay, so I'm digging into how `fprobe` works, and I need to refresh my memory on the core mechanics. First, I recall that `fprobe_graph_ops` gets registered when the feature is enabled. That's my starting point. Now I want to understand the actual function hooking. Let's focus on `fprobe_fgraph_entry` and `fprobe_return` within `kernel/trace/fprobe.c`. Those are likely the key entry points for instrumenting function calls. Time to dive into the code! I'll read through `kernel/trace/fprobe.c`, specifically focusing on the code around `write_fprobe_header` and `read_fprobe_header`. I'm guessing these functions handle the data structures that store the instrumentation metadata. This should give me a solid understanding of the data flow and how the kernel handles the probed information at the point of the call and return.
22/2	2026/09/16 03:09	tool	grepper	0m Args: { "Expression": "write_fprobe_header", "PathPrefix": "kernel/trace" } Results: { "Output": "kernel/trace/fprobe.c=138=static int del_fprobe_hash(struct fprobe fp)\n--\nkernel/trace/fprobe.c-159-\nkernel/trace/fprobe.c:160:static inline bool write_fprobe_header(unsigned long stack,\nkernel/trace/fprobe.c-161-\t\t\t\t\tstruct fprobe fp, unsigned int size_words)\n--\nkernel/trace/fprobe.c=181=struct __fprobe_header {\n--\nkernel/trace/fprobe.c-187-\nkernel/trace/fprobe.c:188:static inline bool write_fprobe_header(unsigned long stack,\nkernel/trace/fprobe.c-189-\t\t\t\t\tstruct fprobe fp, unsigned int size_words)\n--\nkernel/trace/fprobe.c=547=static int fprobe_fgraph_entry(struct ftrace_graph_ent trace, struct fgraph_ops *gops,\n--\nkernel/trace/fprobe.c-632-\nkernel/trace/fprobe.c:633:\t\t\tif (write_fprobe_header(\u0026fgraph_data[used], fp, size_words))\nkernel/trace/fprobe.c-634-\t\t\t\tused += FPROBE_HEADER_SIZE_IN_LONG + size_words;\n" }
23/2	2026/09/16 03:09	llm	patch-evaluator	0m Model: gemini-3.8-flash Args: null Results: null Tokens: input: 21636 output: 36 thoughts: 24 Thoughts: Here's my summary, as if I were the one thinking it: Diving into `fprobe.c` for some Kernel Trace Insights Okay, time to get my hands dirty and jump into the heart of the matter. I need to understand what's happening with the function probing functionality, so I'm focusing on lines 160-220 of `kernel/trace/fprobe.c`. This section should reveal some key aspects of how function probes are defined, registered, and maybe even how the tracing infrastructure interacts with them. I'm hoping to see how the probes are initialized, where the probe metadata is stored and managed, and especially, the mechanisms for hooking into functions or tracing them at runtime. I need to be aware of the data structures involved, the synchronization primitives used (if any), and how the probe's activation and deactivation are handled to be useful for debugging a performance problem. This range should hopefully provide a concise snapshot of the probe's fundamental interactions within the kernel's tracing system. Let's see what gems are hidden in there!
24/2	2026/09/16 03:09	tool	read-file	0m Args: { "File": "kernel/trace/fprobe.c", "FirstLine": 160, "LineCount": 60 } Results: { "Contents": " 160:\tstatic inline bool write_fprobe_header(unsigned long stack,\n 161:\t\t\t\t\t\tstruct fprobe fp, unsigned int size_words)\n 162:\t{\n 163:\t\tif (WARN_ON_ONCE(size_words \u003e MAX_FPROBE_DATA_SIZE_WORD \|\|\n 164:\t\t\t\t !arch_fprobe_header_encodable(fp)))\n 165:\t\t\treturn false;\n 166:\t\n 167:\t\tstack = arch_encode_fprobe_header(fp, size_words);\n 168:\t\treturn true;\n 169:\t}\n 170:\t\n 171:\tstatic inline void read_fprobe_header(unsigned long stack,\n 172:\t\t\t\t\t\tstruct fprobe *fp, unsigned int size_words)\n 173:\t{\n 174:\t\tfp = arch_decode_fprobe_header_fp(stack);\n 175:\t\tsize_words = arch_decode_fprobe_header_size(stack);\n 176:\t}\n 177:\t\n 178:\t#else\n 179:\t\n 180:\t/* Generic fprobe_header /\n 181:\tstruct __fprobe_header {\n 182:\t\tstruct fprobe fp;\n 183:\t\tunsigned long size_words;\n 184:\t};\n 185:\t\n 186:\t#define FPROBE_HEADER_SIZE_IN_LONG\tSIZE_IN_LONG(sizeof(struct __fprobe_header))\n 187:\t\n 188:\tstatic inline bool write_fprobe_header(unsigned long stack,\n 189:\t\t\t\t\t\tstruct fprobe fp, unsigned int size_words)\n 190:\t{\n 191:\t\tstruct __fprobe_header fph = (struct __fprobe_header )stack;\n 192:\t\n 193:\t\tif (WARN_ON_ONCE(size_words \u003e MAX_FPROBE_DATA_SIZE_WORD))\n 194:\t\t\treturn false;\n 195:\t\n 196:\t\tfph-\u003efp = fp;\n 197:\t\tfph-\u003esize_words = size_words;\n 198:\t\treturn true;\n 199:\t}\n 200:\t\n 201:\tstatic inline void read_fprobe_header(unsigned long stack,\n 202:\t\t\t\t\t\tstruct fprobe fp, unsigned int size_words)\n 203:\t{\n 204:\t\tstruct __fprobe_header fph = (struct __fprobe_header )stack;\n 205:\t\n 206:\t\tfp = fph-\u003efp;\n 207:\t\tsize_words = fph-\u003esize_words;\n 208:\t}\n 209:\t\n 210:\t#endif\n 211:\t\n 212:\t/\n 213:\t fprobe shadow stack management:\n 214:\t * Since fprobe shares a single fgraph_ops, it needs to share the stack entry\n 215:\t * among the probes on the same function exit. Note that a new probe can be\n 216:\t * registered before a target function is returning, we can not use the hash\n 217:\t * table to find the corresponding probes. Thus the probe address is stored on\n 218:\t * the shadow stack with its entry data size.\n 219:\t *\n" }
25/2	2026/09/16 03:09	llm	patch-evaluator	0m Model: gemini-3.8-flash Args: null Results: null Tokens: input: 22826 output: 36 thoughts: 57 Thoughts: Checking the x86_64 Fprobe Implementation Okay, so I'm diving into the fprobe implementation, specifically wondering about the `arch_fprobe_header_encodable` function on x86_64, a common architecture, but one with its nuances. I need to quickly determine if this is defined, and if so, how it's handled. Since I know the fprobe code well, lines 145-165 of `kernel/trace/fprobe.c` are the logical place to start – that should encompass the crucial architecture-specific header encoding details or, possibly, the conditional compilation that dictates whether this function even exists on this particular architecture. I'm expecting this section to provide the answer directly; perhaps it's a macro defining or undefining the function based on the x86_64 configuration, or maybe it's a platform-specific implementation. This is going to give me a solid handle on how x86_64 fprobe header encoding is implemented.
26/2	2026/09/16 03:09	tool	read-file	0m Args: { "File": "kernel/trace/fprobe.c", "FirstLine": 145, "LineCount": 25 } Results: { "Contents": " 145:\t\t\treturn -EINVAL;\n 146:\t\n 147:\t\tif (!fprobe_registered(fp))\n 148:\t\t\treturn -ENOENT;\n 149:\t\n 150:\t\tfph-\u003efp = NULL;\n 151:\t\thlist_del_rcu(\u0026fph-\u003ehlist);\n 152:\t\treturn 0;\n 153:\t}\n 154:\t\n 155:\t#ifdef ARCH_DEFINE_ENCODE_FPROBE_HEADER\n 156:\t\n 157:\t/* The arch should encode fprobe_header info into one unsigned long /\n 158:\t#define FPROBE_HEADER_SIZE_IN_LONG\t1\n 159:\t\n 160:\tstatic inline bool write_fprobe_header(unsigned long stack,\n 161:\t\t\t\t\t\tstruct fprobe fp, unsigned int size_words)\n 162:\t{\n 163:\t\tif (WARN_ON_ONCE(size_words \u003e MAX_FPROBE_DATA_SIZE_WORD \|\|\n 164:\t\t\t\t !arch_fprobe_header_encodable(fp)))\n 165:\t\t\treturn false;\n 166:\t\n 167:\t\tstack = arch_encode_fprobe_header(fp, size_words);\n 168:\t\treturn true;\n 169:\t}\n" }
27/2	2026/09/16 03:09	llm	patch-evaluator	0m Model: gemini-3.8-flash Args: null Results: null Tokens: input: 23509 output: 27 thoughts: 1398 Thoughts: Worth Fuzzing Decision: Confirmed Okay, let's break this down. First, I need to understand the change. The `git diff` shows a `memset` addition within `kernel/trace/fprobe.c`. My initial thought is to figure out the context. I'll need to check the commit message using `git log` if available. Now, let's evaluate its reachability, I need to remember the specific criteria. I'll go through sections 1, 2, and 3. My expertise helps: reachability is the primary gate. I know fuzzing is limited to executable code within standard environments. NFCI or refactoring claims aren't a free pass, and new or modified assertions are automatically a good target. Section 2 provides the negative criteria (when to return `WorthFuzzing=false`). Non-kernel code, unreachable hardware, or unreachable paths are immediate disqualifiers. Section 3 (positive criteria) lists the good candidates: core subsystems like memory management, synchronization, BPF, scheduler, networking, VFS, syscalls, refactors, assertions, and reachable drivers/protocols. `kernel/trace/fprobe.c` immediately falls within a core subsystem (tracing/BPF). I'm confident it's reachable. I know `fprobe` can be registered through two primary methods: BPF and Tracefs. BPF leverages syscalls (`bpf_kprobe_multi_link_attach`) that are heavily fuzzed by Syzkaller. Tracefs lets you create dynamic fprobe events via writing to `/sys/kernel/tracing/fprobe_events` and `/sys/kernel/tracing/events/.../enable`. I've worked with them a lot! I remember `fprobe_fgraph_entry` handles function entry and `fprobe_return` executes on function return. The patch's `memset` clears unused slots in the reserved storage. That shadow ret_stack in `kernel/trace/fprobe.c` has something to do with fprobe execution, and is used when any fprobe / BPF multi-kretprobe is triggered. Now, let's explore this. Multiple probes, skipping entry, or different sizes between reserved and used can trigger that `memset`. My radar goes up: a bug in `memset` could be an out-of-bounds write if `reserved_words < used`, or `fgraph_data` could be NULL with a non-zero reserved size! Wait. The code includes a check (`used < reserved_words`). But could `fgraph_data` be NULL? Let's check the code: If `reserved_words` is non-zero, it calls `fgraph_reserve_data`. If that fails, it immediately returns. If `reserved_words` is zero, fgraph_data is NULL, however, and `used` will never be less than zero! But if `fprobe_disabled(fp)` or `entry_handler` returns non-zero, or if `write_fprobe_header` fails, used can be less than reserved_words. Therefore, the code can be problematic. It's a key spot affecting memory layout on the `ret_stack`. This is reachable executable kernel code and core subsystem (tracing / BPF). So, `WorthFuzzing = true`. Next, I need to figure out what configurations are required (EnableConfigs) for this to run. That means I need to check `kernel/trace/Makefile` now.
28/2	2026/09/16 03:10	tool	grepper	0m Args: { "Expression": "fprobe\\.o", "PathPrefix": "kernel/trace" } Results: { "Output": "kernel/trace/Makefile=125=obj-$(CONFIG_FTRACE_RECORD_RECURSION) += trace_recursion_record.o\nkernel/trace/Makefile:126:obj-$(CONFIG_FPROBE) += fprobe.o\nkernel/trace/Makefile-127-obj-$(CONFIG_RETHOOK) += rethook.o\nkernel/trace/Makefile:128:obj-$(CONFIG_FPROBE_EVENTS) += trace_fprobe.o\nkernel/trace/Makefile-129-\n" }
29/2	2026/09/16 03:10	llm	patch-evaluator	0m Model: gemini-3.8-flash Args: null Results: null Tokens: input: 25825 output: 24 thoughts: 131 Thoughts: Kernel Function Probe Configuration: A Quick Review Okay, let's just double-check the `CONFIG_FPROBE` setting within `kernel/trace/Kconfig`. I'm going to quickly scan line 363 here... Yep, there it is: `CONFIG_FPROBE` is a boolean, depends on `HAVE_FUNCTION_GRAPH_FREGS`, `HAVE_FTRACE_GRAPH_FUNC`, and `DYNAMIC_FTRACE_WITH_ARGS`, selects `FUNCTION_GRAPH_TRACER`, and defaults to 'n'. Now, just to be sure, I need to remind myself what enables `DYNAMIC_FTRACE_WITH_ARGS`. Time to cross-reference that one in `Kconfig` as well.
30/2	2026/09/16 03:10	tool	grepper	0m Args: { "Expression": "config DYNAMIC_FTRACE_WITH_ARGS" } Results: { "Output": "kernel/trace/Kconfig=334=config DYNAMIC_FTRACE_WITH_CALL_OPS\n--\nkernel/trace/Kconfig-337-\nkernel/trace/Kconfig:338:config DYNAMIC_FTRACE_WITH_ARGS\nkernel/trace/Kconfig-339-\tdef_bool y\n" }
31/2	2026/09/16 03:10	llm	patch-evaluator	0m Model: gemini-3.8-flash Args: null Results: null Tokens: input: 26229 output: 34 thoughts: 22 Thoughts: Here's my take on those lines from `kernel/trace/Kconfig`: Analyzing `kernel/trace/Kconfig` Section Okay, let's dive into lines 335-345 of `kernel/trace/Kconfig`. I'm expecting this to be something related to specific tracing features or instrumentation within the kernel, given the file path. Let me see... Hmm, it looks like this section is defining configuration options related to... alright, I see. It appears we're dealing with options for configuring the ftrace, or function trace, infrastructure. Specifically, these lines probably cover sub-features or fine-grained control over how function tracing behaves, perhaps relating to filtering, record mechanisms or enabled instrumentation within the ftrace core. I'm guessing that the configuration options are designed to control the amount of tracing and the system impact by specifying whether certain function entry/exit points, or data structures are relevant. I need to look closer at the specific options defined here to confirm these assumptions and better understand their dependencies. From the context, this could be related to the `TRACE_EVENT` or similar trace-points system. Need a closer look to be sure.
32/2	2026/09/16 03:10	tool	read-file	0m Args: { "File": "kernel/trace/Kconfig", "FirstLine": 335, "LineCount": 15 } Results: { "Contents": " 335:\t\tdef_bool y\n 336:\t\tdepends on HAVE_DYNAMIC_FTRACE_WITH_CALL_OPS\n 337:\t\n 338:\tconfig DYNAMIC_FTRACE_WITH_ARGS\n 339:\t\tdef_bool y\n 340:\t\tdepends on DYNAMIC_FTRACE\n 341:\t\tdepends on HAVE_DYNAMIC_FTRACE_WITH_ARGS\n 342:\t\n 343:\tconfig DYNAMIC_FTRACE_WITH_JMP\n 344:\t\tdef_bool y\n 345:\t\tdepends on DYNAMIC_FTRACE\n 346:\t\tdepends on DYNAMIC_FTRACE_WITH_DIRECT_CALLS\n 347:\t\tdepends on HAVE_DYNAMIC_FTRACE_WITH_JMP\n 348:\t\n 349:\tconfig FUNCTION_SELF_TRACING\n" }
33/2	2026/09/16 03:10	llm	patch-evaluator	0m Model: gemini-3.8-flash Args: null Results: null Tokens: input: 26757 output: 34 thoughts: 163 Thoughts: Analyzing FPROBE Configuration Dependencies Okay, so I'm looking at `FPROBE` and immediately see it's chained to a few critical things: `HAVE_FUNCTION_GRAPH_FREGS`, `HAVE_FTRACE_GRAPH_FUNC`, and `DYNAMIC_FTRACE_WITH_ARGS`. Now, `DYNAMIC_FTRACE_WITH_ARGS` itself has its own dependencies, `DYNAMIC_FTRACE` and `HAVE_DYNAMIC_FTRACE_WITH_ARGS`. Gotta keep all these pieces in mind! On amd64 (x86_64), which is what I'm primarily focused on, these `HAVE_...` symbols seem to be handled either by `ARCH_SUPPORTS_...` or directly in `arch/x86/Kconfig`. Right, so that's where the magic is happening. My next logical step is to dive into `arch/x86/Kconfig` and trace back the definition of `HAVE_FUNCTION_GRAPH_FREGS`. Gotta see how those dependencies are wired up and whether there's anything platform-specific I need to know about.
34/2	2026/09/16 03:10	tool	grepper	0m Args: { "Expression": "HAVE_FUNCTION_GRAPH_FREGS", "PathPrefix": "arch/x86" } Results: { "Output": "arch/x86/Kconfig=57=config X86\n--\narch/x86/Kconfig-245-\tselect HAVE_FTRACE_GRAPH_FUNC\t\tif HAVE_FUNCTION_GRAPH_TRACER\narch/x86/Kconfig:246:\tselect HAVE_FUNCTION_GRAPH_FREGS\tif HAVE_FUNCTION_GRAPH_TRACER\narch/x86/Kconfig-247-\tselect HAVE_FUNCTION_GRAPH_TRACER\tif X86_32 \|\| (X86_64 \u0026\u0026 DYNAMIC_FTRACE)\n" }
35/2	2026/09/16 03:10	llm	patch-evaluator	0m Model: gemini-3.8-flash Args: null Results: null Tokens: input: 27346 output: 21 thoughts: 88 Thoughts: Kernel Tracing Configuration Considerations Okay, so I'm looking at kernel tracing configurations, and it's clear that `DYNAMIC_FTRACE` is going to be essential for what I need. But, I should also consider `FPROBE_EVENTS`. It looks like `FPROBE_EVENTS` relies on `FPROBE`, and that enables the dynamic event interface in tracefs for fprobe through `/sys/kernel/tracing/fprobe_events`, which seems potentially very useful. Given my current project, BPF multi-kprobe is also on my mind, so I need to make sure to check out `BPF_KPROBE_MULTI` in the Kconfig file. I'll need to double check how all these fit together.
36/2	2026/09/16 03:10	tool	grepper	0m Args: { "Expression": "bpf_kprobe_multi" } Results: { "Output": "include/linux/trace_events.h=793=int bpf_get_perf_event_info(const struct perf_event event, u32 prog_id,\n--\ninclude/linux/trace_events.h-796-\t\t\t unsigned long missed);\ninclude/linux/trace_events.h:797:int bpf_kprobe_multi_link_attach(const union bpf_attr attr, struct bpf_prog prog);\ninclude/linux/trace_events.h-798-int bpf_uprobe_multi_link_attach(const union bpf_attr attr, struct bpf_prog prog);\n--\ninclude/linux/trace_events.h=847=static inline int\ninclude/linux/trace_events.h:848:bpf_kprobe_multi_link_attach(const union bpf_attr attr, struct bpf_prog prog)\ninclude/linux/trace_events.h-849-{\n--\nkernel/bpf/syscall.c=5793=static int link_create(union bpf_attr attr, bpfptr_t uattr)\n--\nkernel/bpf/syscall.c-5883-\t\t\t attr-\u003elink_create.attach_type == BPF_TRACE_KPROBE_SESSION)\nkernel/bpf/syscall.c:5884:\t\t\tret = bpf_kprobe_multi_link_attach(attr, prog);\nkernel/bpf/syscall.c-5885-\t\telse if (attr-\u003elink_create.attach_type == BPF_TRACE_UPROBE_MULTI \|\|\n--\nkernel/trace/bpf_trace.c=88=static int bpf_btf_printf_prepare(struct btf_ptr ptr, u32 btf_ptr_size,\n--\nkernel/trace/bpf_trace.c-90-\t\t\t\t s32 btf_id);\nkernel/trace/bpf_trace.c:91:static u64 bpf_kprobe_multi_cookie(struct bpf_run_ctx ctx);\nkernel/trace/bpf_trace.c:92:static u64 bpf_kprobe_multi_entry_ip(struct bpf_run_ctx ctx);\nkernel/trace/bpf_trace.c-93-\n--\nkernel/trace/bpf_trace.c=1110=BPF_CALL_1(bpf_get_func_ip_kprobe_multi, struct pt_regs , regs)\nkernel/trace/bpf_trace.c-1111-{\nkernel/trace/bpf_trace.c:1112:\treturn bpf_kprobe_multi_entry_ip(current-\u003ebpf_ctx);\nkernel/trace/bpf_trace.c-1113-}\n--\nkernel/trace/bpf_trace.c=1122=BPF_CALL_1(bpf_get_attach_cookie_kprobe_multi, struct pt_regs , regs)\nkernel/trace/bpf_trace.c-1123-{\nkernel/trace/bpf_trace.c:1124:\treturn bpf_kprobe_multi_cookie(current-\u003ebpf_ctx);\nkernel/trace/bpf_trace.c-1125-}\n--\nkernel/trace/bpf_trace.c=2329=struct bpf_session_run_ctx {\n--\nkernel/trace/bpf_trace.c-2335-#ifdef CONFIG_FPROBE\nkernel/trace/bpf_trace.c:2336:struct bpf_kprobe_multi_link {\nkernel/trace/bpf_trace.c-2337-\tstruct bpf_link link;\n--\nkernel/trace/bpf_trace.c-2345-\nkernel/trace/bpf_trace.c:2346:struct bpf_kprobe_multi_run_ctx {\nkernel/trace/bpf_trace.c-2347-\tstruct bpf_session_run_ctx session_ctx;\nkernel/trace/bpf_trace.c:2348:\tstruct bpf_kprobe_multi_link link;\nkernel/trace/bpf_trace.c-2349-\tunsigned long entry_ip;\n--\nkernel/trace/bpf_trace.c=2352=struct user_syms {\n--\nkernel/trace/bpf_trace.c-2357-#ifndef CONFIG_HAVE_FTRACE_REGS_HAVING_PT_REGS\nkernel/trace/bpf_trace.c:2358:static DEFINE_PER_CPU(struct pt_regs, bpf_kprobe_multi_pt_regs);\nkernel/trace/bpf_trace.c:2359:#define bpf_kprobe_multi_pt_regs_ptr()\tthis_cpu_ptr(\u0026bpf_kprobe_multi_pt_regs)\nkernel/trace/bpf_trace.c-2360-#else\nkernel/trace/bpf_trace.c:2361:#define bpf_kprobe_multi_pt_regs_ptr()\t(NULL)\nkernel/trace/bpf_trace.c-2362-#endif\n--\nkernel/trace/bpf_trace.c=2422=static void free_user_syms(struct user_syms us)\n--\nkernel/trace/bpf_trace.c-2427-\nkernel/trace/bpf_trace.c:2428:static void bpf_kprobe_multi_link_release(struct bpf_link link)\nkernel/trace/bpf_trace.c-2429-{\nkernel/trace/bpf_trace.c:2430:\tstruct bpf_kprobe_multi_link kmulti_link;\nkernel/trace/bpf_trace.c-2431-\nkernel/trace/bpf_trace.c:2432:\tkmulti_link = container_of(link, struct bpf_kprobe_multi_link, link);\nkernel/trace/bpf_trace.c-2433-\t/* Don't wait for RCU GP here. /\n--\nkernel/trace/bpf_trace.c-2437-\nkernel/trace/bpf_trace.c:2438:static void bpf_kprobe_multi_link_dealloc(struct bpf_link link)\nkernel/trace/bpf_trace.c-2439-{\nkernel/trace/bpf_trace.c:2440:\tstruct bpf_kprobe_multi_link kmulti_link;\nkernel/trace/bpf_trace.c-2441-\nkernel/trace/bpf_trace.c:2442:\tkmulti_link = container_of(link, struct bpf_kprobe_multi_link, link);\nkernel/trace/bpf_trace.c-2443-\tkvfree(kmulti_link-\u003eaddrs);\n--\nkernel/trace/bpf_trace.c-2448-\nkernel/trace/bpf_trace.c:2449:static int bpf_kprobe_multi_link_fill_link_info(const struct bpf_link link,\nkernel/trace/bpf_trace.c-2450-\t\t\t\t\t\tstruct bpf_link_info info)\n--\nkernel/trace/bpf_trace.c-2453-\tu64 __user uaddrs = u64_to_user_ptr(info-\u003ekprobe_multi.addrs);\nkernel/trace/bpf_trace.c:2454:\tstruct bpf_kprobe_multi_link kmulti_link;\nkernel/trace/bpf_trace.c-2455-\tu32 ucount = info-\u003ekprobe_multi.count;\n--\nkernel/trace/bpf_trace.c-2462-\nkernel/trace/bpf_trace.c:2463:\tkmulti_link = container_of(link, struct bpf_kprobe_multi_link, link);\nkernel/trace/bpf_trace.c-2464-\tinfo-\u003ekprobe_multi.count = kmulti_link-\u003ecnt;\n--\nkernel/trace/bpf_trace.c-2499-#ifdef CONFIG_PROC_FS\nkernel/trace/bpf_trace.c:2500:static void bpf_kprobe_multi_show_fdinfo(const struct bpf_link link,\nkernel/trace/bpf_trace.c-2501-\t\t\t\t\t struct seq_file seq)\nkernel/trace/bpf_trace.c-2502-{\nkernel/trace/bpf_trace.c:2503:\tstruct bpf_kprobe_multi_link kmulti_link;\nkernel/trace/bpf_trace.c-2504-\tbool has_cookies;\nkernel/trace/bpf_trace.c-2505-\nkernel/trace/bpf_trace.c:2506:\tkmulti_link = container_of(link, struct bpf_kprobe_multi_link, link);\nkernel/trace/bpf_trace.c-2507-\thas_cookies = !!kmulti_link-\u003ecookies;\n--\nkernel/trace/bpf_trace.c-2524-\nkernel/trace/bpf_trace.c:2525:static const struct bpf_link_ops bpf_kprobe_multi_link_lops = {\nkernel/trace/bpf_trace.c:2526:\t.release = bpf_kprobe_multi_link_release,\nkernel/trace/bpf_trace.c:2527:\t.dealloc_deferred = bpf_kprobe_multi_link_dealloc,\nkernel/trace/bpf_trace.c:2528:\t.fill_link_info = bpf_kprobe_multi_link_fill_link_info,\nkernel/trace/bpf_trace.c-2529-#ifdef CONFIG_PROC_FS\nkernel/trace/bpf_trace.c:2530:\t.show_fdinfo = bpf_kprobe_multi_show_fdinfo,\nkernel/trace/bpf_trace.c-2531-#endif\n--\nkernel/trace/bpf_trace.c-2533-\nkernel/trace/bpf_trace.c:2534:static void bpf_kprobe_multi_cookie_swap(void a, void b, int size, const void priv)\nkernel/trace/bpf_trace.c-2535-{\nkernel/trace/bpf_trace.c:2536:\tconst struct bpf_kprobe_multi_link link = priv;\nkernel/trace/bpf_trace.c-2537-\tunsigned long addr_a = a, addr_b = b;\n--\nkernel/trace/bpf_trace.c-2547-\nkernel/trace/bpf_trace.c:2548:static int bpf_kprobe_multi_addrs_cmp(const void a, const void b)\nkernel/trace/bpf_trace.c-2549-{\n--\nkernel/trace/bpf_trace.c-2556-\nkernel/trace/bpf_trace.c:2557:static int bpf_kprobe_multi_cookie_cmp(const void a, const void b, const void priv)\nkernel/trace/bpf_trace.c-2558-{\nkernel/trace/bpf_trace.c:2559:\treturn bpf_kprobe_multi_addrs_cmp(a, b);\nkernel/trace/bpf_trace.c-2560-}\nkernel/trace/bpf_trace.c-2561-\nkernel/trace/bpf_trace.c:2562:static u64 bpf_kprobe_multi_cookie(struct bpf_run_ctx ctx)\nkernel/trace/bpf_trace.c-2563-{\nkernel/trace/bpf_trace.c:2564:\tstruct bpf_kprobe_multi_run_ctx run_ctx;\nkernel/trace/bpf_trace.c:2565:\tstruct bpf_kprobe_multi_link link;\nkernel/trace/bpf_trace.c-2566-\tu64 cookie, entry_ip;\n--\nkernel/trace/bpf_trace.c-2570-\t\treturn 0;\nkernel/trace/bpf_trace.c:2571:\trun_ctx = container_of(current-\u003ebpf_ctx, struct bpf_kprobe_multi_run_ctx,\nkernel/trace/bpf_trace.c-2572-\t\t\t session_ctx.run_ctx);\n--\nkernel/trace/bpf_trace.c-2577-\taddr = bsearch(\u0026entry_ip, link-\u003eaddrs, link-\u003ecnt, sizeof(entry_ip),\nkernel/trace/bpf_trace.c:2578:\t\t bpf_kprobe_multi_addrs_cmp);\nkernel/trace/bpf_trace.c-2579-\tif (!addr)\n--\nkernel/trace/bpf_trace.c-2584-\nkernel/trace/bpf_trace.c:2585:static u64 bpf_kprobe_multi_entry_ip(struct bpf_run_ctx ctx)\nkernel/trace/bpf_trace.c-2586-{\nkernel/trace/bpf_trace.c:2587:\tstruct bpf_kprobe_multi_run_ctx run_ctx;\nkernel/trace/bpf_trace.c-2588-\nkernel/trace/bpf_trace.c:2589:\trun_ctx = container_of(current-\u003ebpf_ctx, struct bpf_kprobe_multi_run_ctx,\nkernel/trace/bpf_trace.c-2590-\t\t\t session_ctx.run_ctx);\n--\nkernel/trace/bpf_trace.c=2594=static __always_inline int\nkernel/trace/bpf_trace.c:2595:kprobe_multi_link_prog_run(struct bpf_kprobe_multi_link link,\nkernel/trace/bpf_trace.c-2596-\t\t\t unsigned long entry_ip, struct ftrace_regs fregs,\n--\nkernel/trace/bpf_trace.c-2598-{\nkernel/trace/bpf_trace.c:2599:\tstruct bpf_kprobe_multi_run_ctx run_ctx = {\nkernel/trace/bpf_trace.c-2600-\t\t.session_ctx = {\n--\nkernel/trace/bpf_trace.c-2624-\trcu_read_lock();\nkernel/trace/bpf_trace.c:2625:\tregs = ftrace_partial_regs(fregs, bpf_kprobe_multi_pt_regs_ptr());\nkernel/trace/bpf_trace.c-2626-\told_run_ctx = bpf_set_run_ctx(\u0026run_ctx.session_ctx.run_ctx);\n--\nkernel/trace/bpf_trace.c-2628-\tbpf_reset_run_ctx(old_run_ctx);\nkernel/trace/bpf_trace.c:2629:\tftrace_partial_regs_update(fregs, bpf_kprobe_multi_pt_regs_ptr());\nkernel/trace/bpf_trace.c-2630-\trcu_read_unlock();\n--\nkernel/trace/bpf_trace.c=2638=kprobe_multi_link_handler(struct fprobe fp, unsigned long fentry_ip,\n--\nkernel/trace/bpf_trace.c-2641-{\nkernel/trace/bpf_trace.c:2642:\tstruct bpf_kprobe_multi_link link;\nkernel/trace/bpf_trace.c-2643-\tint err;\nkernel/trace/bpf_trace.c-2644-\nkernel/trace/bpf_trace.c:2645:\tlink = container_of(fp, struct bpf_kprobe_multi_link, fp);\nkernel/trace/bpf_trace.c-2646-\terr = kprobe_multi_link_prog_run(link, ftrace_get_entry_ip(fentry_ip),\n--\nkernel/trace/bpf_trace.c=2652=kprobe_multi_link_exit_handler(struct fprobe fp, unsigned long fentry_ip,\n--\nkernel/trace/bpf_trace.c-2655-{\nkernel/trace/bpf_trace.c:2656:\tstruct bpf_kprobe_multi_link link;\nkernel/trace/bpf_trace.c-2657-\nkernel/trace/bpf_trace.c:2658:\tlink = container_of(fp, struct bpf_kprobe_multi_link, fp);\nkernel/trace/bpf_trace.c-2659-\tkprobe_multi_link_prog_run(link, ftrace_get_entry_ip(fentry_ip),\n--\nkernel/trace/bpf_trace.c=2769=static int addrs_check_error_injection_list(unsigned long addrs, u32 cnt)\n--\nkernel/trace/bpf_trace.c-2779-\nkernel/trace/bpf_trace.c:2780:int bpf_kprobe_multi_link_attach(const union bpf_attr attr, struct bpf_prog prog)\nkernel/trace/bpf_trace.c-2781-{\nkernel/trace/bpf_trace.c:2782:\tstruct bpf_kprobe_multi_link link = NULL;\nkernel/trace/bpf_trace.c-2783-\tstruct bpf_link_primer link_primer;\n--\nkernel/trace/bpf_trace.c-2881-\tbpf_link_init(\u0026link-\u003elink, BPF_LINK_TYPE_KPROBE_MULTI,\nkernel/trace/bpf_trace.c:2882:\t\t \u0026bpf_kprobe_multi_link_lops, prog, attr-\u003elink_create.attach_type);\nkernel/trace/bpf_trace.c-2883-\n--\nkernel/trace/bpf_trace.c-2902-\t\t Sorting addresses will trigger sorting cookies as well\nkernel/trace/bpf_trace.c:2903:\t\t * (check bpf_kprobe_multi_cookie_swap). This way we can\nkernel/trace/bpf_trace.c-2904-\t\t * find cookie based on the address in bpf_get_attach_cookie\n--\nkernel/trace/bpf_trace.c-2907-\t\tsort_r(addrs, cnt, sizeof(addrs),\nkernel/trace/bpf_trace.c:2908:\t\t bpf_kprobe_multi_cookie_cmp,\nkernel/trace/bpf_trace.c:2909:\t\t bpf_kprobe_multi_cookie_swap,\nkernel/trace/bpf_trace.c-2910-\t\t link);\n--\nkernel/trace/bpf_trace.c-2935-#else / !CONFIG_FPROBE /\nkernel/trace/bpf_trace.c:2936:int bpf_kprobe_multi_link_attach(const union bpf_attr attr, struct bpf_prog prog)\nkernel/trace/bpf_trace.c-2937-{\n--\nkernel/trace/bpf_trace.c-2939-}\nkernel/trace/bpf_trace.c:2940:static u64 bpf_kprobe_multi_cookie(struct bpf_run_ctx ctx)\nkernel/trace/bpf_trace.c-2941-{\n--\nkernel/trace/bpf_trace.c-2943-}\nkernel/trace/bpf_trace.c:2944:static u64 bpf_kprobe_multi_entry_ip(struct bpf_run_ctx ctx)\nkernel/trace/bpf_trace.c-2945-{\n--\ntools/lib/bpf/libbpf.c=12316=bpf_program__attach_kprobe_multi_opts(const struct bpf_program prog,\ntools/lib/bpf/libbpf.c-12317-\t\t\t\t const char pattern,\ntools/lib/bpf/libbpf.c:12318:\t\t\t\t const struct bpf_kprobe_multi_opts opts)\ntools/lib/bpf/libbpf.c-12319-{\n--\ntools/lib/bpf/libbpf.c-12332-\ntools/lib/bpf/libbpf.c:12333:\tif (!OPTS_VALID(opts, bpf_kprobe_multi_opts))\ntools/lib/bpf/libbpf.c-12334-\t\treturn libbpf_err_ptr(-EINVAL);\n--\ntools/lib/bpf/libbpf.c=12499=static int attach_kprobe_multi(const struct bpf_program prog, long cookie, struct bpf_link link)\ntools/lib/bpf/libbpf.c-12500-{\ntools/lib/bpf/libbpf.c:12501:\tLIBBPF_OPTS(bpf_kprobe_multi_opts, opts);\ntools/lib/bpf/libbpf.c-12502-\tconst char spec;\n--\ntools/lib/bpf/libbpf.c=12530=static int attach_kprobe_session(const struct bpf_program prog, long cookie,\n--\ntools/lib/bpf/libbpf.c-12532-{\ntools/lib/bpf/libbpf.c:12533:\tLIBBPF_OPTS(bpf_kprobe_multi_opts, opts, .session = true);\ntools/lib/bpf/libbpf.c-12534-\tconst char spec;\n--\ntools/lib/bpf/libbpf.h=599=bpf_program__attach_kprobe_opts(const struct bpf_program prog,\n--\ntools/lib/bpf/libbpf.h-602-\ntools/lib/bpf/libbpf.h:603:struct bpf_kprobe_multi_opts {\ntools/lib/bpf/libbpf.h-604-\t/ size of this struct, for forward/backward compatibility /\n--\ntools/lib/bpf/libbpf.h-622-\ntools/lib/bpf/libbpf.h:623:#define bpf_kprobe_multi_opts__last_field unique_match\ntools/lib/bpf/libbpf.h-624-\n--\ntools/lib/bpf/libbpf.h=626=bpf_program__attach_kprobe_multi_opts(const struct bpf_program prog,\ntools/lib/bpf/libbpf.h-627-\t\t\t\t const char pattern,\ntools/lib/bpf/libbpf.h:628:\t\t\t\t const struct bpf_kprobe_multi_opts opts);\ntools/lib/bpf/libbpf.h-629-\n--\ntools/testing/selftests/bpf/benchs/bench_trigger.c=230=static void attach_ksyms_all(struct bpf_program empty, bool kretprobe)\ntools/testing/selftests/bpf/benchs/bench_trigger.c-231-{\ntools/testing/selftests/bpf/benchs/bench_trigger.c:232:\tLIBBPF_OPTS(bpf_kprobe_multi_opts, opts);\ntools/testing/selftests/bpf/benchs/bench_trigger.c-233-\tstruct bpf_link link = NULL;\n--\ntools/testing/selftests/bpf/prog_tests/bpf_cookie.c=183=static void kprobe_multi_attach_api_subtest(void)\n--\ntools/testing/selftests/bpf/prog_tests/bpf_cookie.c-185-\tstruct bpf_link link1 = NULL, link2 = NULL;\ntools/testing/selftests/bpf/prog_tests/bpf_cookie.c:186:\tLIBBPF_OPTS(bpf_kprobe_multi_opts, opts);\ntools/testing/selftests/bpf/prog_tests/bpf_cookie.c-187-\tLIBBPF_OPTS(bpf_test_run_opts, topts);\n--\ntools/testing/selftests/bpf/prog_tests/fill_link_info.c=390=static void test_kprobe_multi_fill_link_info(struct test_fill_link_info skel,\n--\ntools/testing/selftests/bpf/prog_tests/fill_link_info.c-393-{\ntools/testing/selftests/bpf/prog_tests/fill_link_info.c:394:\tLIBBPF_OPTS(bpf_kprobe_multi_opts, opts);\ntools/testing/selftests/bpf/prog_tests/fill_link_info.c-395-\tstruct bpf_link link;\n--\ntools/testing/selftests/bpf/prog_tests/kprobe_multi_test.c=143=static void\ntools/testing/selftests/bpf/prog_tests/kprobe_multi_test.c:144:test_attach_api(const char pattern, struct bpf_kprobe_multi_opts opts)\ntools/testing/selftests/bpf/prog_tests/kprobe_multi_test.c-145-{\n--\ntools/testing/selftests/bpf/prog_tests/kprobe_multi_test.c=175=static void test_attach_api_pattern(void)\ntools/testing/selftests/bpf/prog_tests/kprobe_multi_test.c-176-{\ntools/testing/selftests/bpf/prog_tests/kprobe_multi_test.c:177:\tLIBBPF_OPTS(bpf_kprobe_multi_opts, opts);\ntools/testing/selftests/bpf/prog_tests/kprobe_multi_test.c-178-\n--\ntools/testing/selftests/bpf/prog_tests/kprobe_multi_test.c=183=static void test_attach_api_addrs(void)\ntools/testing/selftests/bpf/prog_tests/kprobe_multi_test.c-184-{\ntools/testing/selftests/bpf/prog_tests/kprobe_multi_test.c:185:\tLIBBPF_OPTS(bpf_kprobe_multi_opts, opts);\ntools/testing/selftests/bpf/prog_tests/kprobe_multi_test.c-186-\tunsigned long long addrs[8];\n--\ntools/testing/selftests/bpf/prog_tests/kprobe_multi_test.c=202=static void test_attach_api_syms(void)\ntools/testing/selftests/bpf/prog_tests/kprobe_multi_test.c-203-{\ntools/testing/selftests/bpf/prog_tests/kprobe_multi_test.c:204:\tLIBBPF_OPTS(bpf_kprobe_multi_opts, opts);\ntools/testing/selftests/bpf/prog_tests/kprobe_multi_test.c-205-\tconst char syms[8] = {\n--\ntools/testing/selftests/bpf/prog_tests/kprobe_multi_test.c=221=static void test_attach_api_fails(void)\ntools/testing/selftests/bpf/prog_tests/kprobe_multi_test.c-222-{\ntools/testing/selftests/bpf/prog_tests/kprobe_multi_test.c:223:\tLIBBPF_OPTS(bpf_kprobe_multi_opts, opts);\ntools/testing/selftests/bpf/prog_tests/kprobe_multi_test.c-224-\tLIBBPF_OPTS(bpf_test_run_opts, topts);\n--\ntools/testing/selftests/bpf/prog_tests/kprobe_multi_test.c=392=static void test_session_skel_api(void)\n--\ntools/testing/selftests/bpf/prog_tests/kprobe_multi_test.c-394-\tstruct kprobe_multi_session skel = NULL;\ntools/testing/selftests/bpf/prog_tests/kprobe_multi_test.c:395:\tLIBBPF_OPTS(bpf_kprobe_multi_opts, opts);\ntools/testing/selftests/bpf/prog_tests/kprobe_multi_test.c-396-\tLIBBPF_OPTS(bpf_test_run_opts, topts);\n--\ntools/testing/selftests/bpf/prog_tests/kprobe_multi_test.c=433=static void test_session_cookie_skel_api(void)\n--\ntools/testing/selftests/bpf/prog_tests/kprobe_multi_test.c-435-\tstruct kprobe_multi_session_cookie skel = NULL;\ntools/testing/selftests/bpf/prog_tests/kprobe_multi_test.c:436:\tLIBBPF_OPTS(bpf_kprobe_multi_opts, opts);\ntools/testing/selftests/bpf/prog_tests/kprobe_multi_test.c-437-\tLIBBPF_OPTS(bpf_test_run_opts, topts);\n--\ntools/testing/selftests/bpf/prog_tests/kprobe_multi_test.c=465=static void test_unique_match(void)\ntools/testing/selftests/bpf/prog_tests/kprobe_multi_test.c-466-{\ntools/testing/selftests/bpf/prog_tests/kprobe_multi_test.c:467:\tLIBBPF_OPTS(bpf_kprobe_multi_opts, opts);\ntools/testing/selftests/bpf/prog_tests/kprobe_multi_test.c-468-\tstruct kprobe_multi skel = NULL;\n--\ntools/testing/selftests/bpf/prog_tests/kprobe_multi_test.c-489-\ntools/testing/selftests/bpf/prog_tests/kprobe_multi_test.c:490:static void do_bench_test(struct kprobe_multi_empty skel, struct bpf_kprobe_multi_opts opts)\ntools/testing/selftests/bpf/prog_tests/kprobe_multi_test.c-491-{\n--\ntools/testing/selftests/bpf/prog_tests/kprobe_multi_test.c=517=static void test_kprobe_multi_bench_attach(bool kernel)\ntools/testing/selftests/bpf/prog_tests/kprobe_multi_test.c-518-{\ntools/testing/selftests/bpf/prog_tests/kprobe_multi_test.c:519:\tLIBBPF_OPTS(bpf_kprobe_multi_opts, opts);\ntools/testing/selftests/bpf/prog_tests/kprobe_multi_test.c-520-\tstruct kprobe_multi_empty skel = NULL;\n--\ntools/testing/selftests/bpf/prog_tests/kprobe_multi_test.c=540=static void test_kprobe_multi_bench_attach_addr(bool kernel)\ntools/testing/selftests/bpf/prog_tests/kprobe_multi_test.c-541-{\ntools/testing/selftests/bpf/prog_tests/kprobe_multi_test.c:542:\tLIBBPF_OPTS(bpf_kprobe_multi_opts, opts);\ntools/testing/selftests/bpf/prog_tests/kprobe_multi_test.c-543-\tstruct kprobe_multi_empty skel = NULL;\n--\ntools/testing/selftests/bpf/prog_tests/kprobe_multi_test.c=675=static void test_attach_probe_dup_sym(void)\ntools/testing/selftests/bpf/prog_tests/kprobe_multi_test.c-676-{\ntools/testing/selftests/bpf/prog_tests/kprobe_multi_test.c:677:\tLIBBPF_OPTS(bpf_kprobe_multi_opts, opts);\ntools/testing/selftests/bpf/prog_tests/kprobe_multi_test.c-678-\tconst char syms[1] = { \"bpf_fentry_shadow_test\" };\n--\ntools/testing/selftests/bpf/prog_tests/kprobe_multi_testmod_test.c=9=static void kprobe_multi_testmod_check(struct kprobe_multi skel)\n--\ntools/testing/selftests/bpf/prog_tests/kprobe_multi_testmod_test.c-19-\ntools/testing/selftests/bpf/prog_tests/kprobe_multi_testmod_test.c:20:static void test_testmod_attach_api(struct bpf_kprobe_multi_opts opts)\ntools/testing/selftests/bpf/prog_tests/kprobe_multi_testmod_test.c-21-{\n--\ntools/testing/selftests/bpf/prog_tests/kprobe_multi_testmod_test.c=50=static void test_testmod_attach_api_addrs(void)\ntools/testing/selftests/bpf/prog_tests/kprobe_multi_testmod_test.c-51-{\ntools/testing/selftests/bpf/prog_tests/kprobe_multi_testmod_test.c:52:\tLIBBPF_OPTS(bpf_kprobe_multi_opts, opts);\ntools/testing/selftests/bpf/prog_tests/kprobe_multi_testmod_test.c-53-\tunsigned long long addrs[3];\n--\ntools/testing/selftests/bpf/prog_tests/kprobe_multi_testmod_test.c=68=static void test_testmod_attach_api_syms(void)\ntools/testing/selftests/bpf/prog_tests/kprobe_multi_testmod_test.c-69-{\ntools/testing/selftests/bpf/prog_tests/kprobe_multi_testmod_test.c:70:\tLIBBPF_OPTS(bpf_kprobe_multi_opts, opts);\ntools/testing/selftests/bpf/prog_tests/kprobe_multi_testmod_test.c-71-\tconst char syms[3] = {\n--\ntools/testing/selftests/bpf/prog_tests/stacktrace_ips.c=50=static void test_stacktrace_ips_kprobe_multi(bool retprobe)\ntools/testing/selftests/bpf/prog_tests/stacktrace_ips.c-51-{\ntools/testing/selftests/bpf/prog_tests/stacktrace_ips.c:52:\tLIBBPF_OPTS(bpf_kprobe_multi_opts, opts,\ntools/testing/selftests/bpf/prog_tests/stacktrace_ips.c-53-\t\t.retprobe = retprobe\n--\ntools/testing/selftests/bpf/prog_tests/uprobe_multi_test.c=1215=static void test_session_skel_api(void)\n--\ntools/testing/selftests/bpf/prog_tests/uprobe_multi_test.c-1217-\tstruct uprobe_multi_session skel = NULL;\ntools/testing/selftests/bpf/prog_tests/uprobe_multi_test.c:1218:\tLIBBPF_OPTS(bpf_kprobe_multi_opts, opts);\ntools/testing/selftests/bpf/prog_tests/uprobe_multi_test.c-1219-\tstruct bpf_link link = NULL;\n--\ntools/testing/selftests/bpf/prog_tests/uprobe_multi_test.c=1259=static void test_session_single_skel_api(void)\n--\ntools/testing/selftests/bpf/prog_tests/uprobe_multi_test.c-1261-\tstruct uprobe_multi_session_single *skel = NULL;\ntools/testing/selftests/bpf/prog_tests/uprobe_multi_test.c:1262:\tLIBBPF_OPTS(bpf_kprobe_multi_opts, opts);\ntools/testing/selftests/bpf/prog_tests/uprobe_multi_test.c-1263-\tint err;\n" }
37/2	2026/09/16 03:10	llm	patch-evaluator	0m Model: gemini-3.8-flash Args: null Results: null Tokens: input: 36908 output: 20 thoughts: 117 Thoughts: Investigating BPF_KPROBE_MULTI and CONFIG_FPROBE Okay, so I need to figure out the relationship between `BPF_KPROBE_MULTI` and `CONFIG_FPROBE`. My first instinct is to check where `BPF_KPROBE_MULTI` is actually defined, which I suspect is in relation to `CONFIG_FPROBE`. Let's confirm that by digging into the kernel source. Ah, yes, in `kernel/trace/bpf_trace.c`, there it is: a `struct bpf_kprobe_multi_link` is defined, and it's conditional on `#ifdef CONFIG_FPROBE`. That's a strong indicator. Now, I want to confirm what exactly enables `BPF_KPROBE_MULTI`. My next move is to check the Kconfig files – likely either in `kernel/bpf/Kconfig` or `kernel/trace/Kconfig` – to see what configuration options specifically control this functionality. Looking for any bpf multi kprobe config.
38/2	2026/09/16 03:10	tool	grepper	0m Args: { "Expression": "BPF.KPROBE" } Results:* { "Output": "\nFull output is too long, showing 500 out of 733 lines.\nUse more precise expression if possible.\n\nDocumentation/bpf/libbpf/program_types.rst=18=described in more detail in the footnotes.\n--\nDocumentation/bpf/libbpf/program_types.rst-85-+-------------------------------------------+----------------------------------------+----------------------------------+-----------+\nDocumentation/bpf/libbpf/program_types.rst:86:\| ``BPF_PROG_TYPE_KPROBE`` \| \| ``kprobe+`` [#kprobe]_ \| \|\nDocumentation/bpf/libbpf/program_types.rst-87-+ + +----------------------------------+-----------+\n--\nDocumentation/bpf/libbpf/program_types.rst-105-+ +----------------------------------------+----------------------------------+-----------+\nDocumentation/bpf/libbpf/program_types.rst:106:\| \| ``BPF_TRACE_KPROBE_MULTI`` \| ``kprobe.multi+`` [#kpmulti]_ \| \|\nDocumentation/bpf/libbpf/program_types.rst-107-+ + +----------------------------------+-----------+\n--\nDocumentation/bpf/libbpf/program_types.rst-109-+ +----------------------------------------+----------------------------------+-----------+\nDocumentation/bpf/libbpf/program_types.rst:110:\| \| ``BPF_TRACE_KPROBE_SESSION`` \| ``kprobe.session+`` [#kpmulti]_ \| \|\nDocumentation/bpf/libbpf/program_types.rst-111-+ +----------------------------------------+----------------------------------+-----------+\n--\ninclude/linux/bpf_types.h=35=BPF_PROG_TYPE(BPF_PROG_TYPE_FLOW_DISSECTOR, flow_dissector,\n--\ninclude/linux/bpf_types.h-38-#ifdef CONFIG_BPF_EVENTS\ninclude/linux/bpf_types.h:39:BPF_PROG_TYPE(BPF_PROG_TYPE_KPROBE, kprobe,\ninclude/linux/bpf_types.h-40-\t bpf_user_pt_regs_t, struct pt_regs)\n--\ninclude/linux/bpf_types.h=154=BPF_LINK_TYPE(BPF_LINK_TYPE_PERF_EVENT, perf)\ninclude/linux/bpf_types.h-155-#endif\ninclude/linux/bpf_types.h:156:BPF_LINK_TYPE(BPF_LINK_TYPE_KPROBE_MULTI, kprobe_multi)\ninclude/linux/bpf_types.h-157-BPF_LINK_TYPE(BPF_LINK_TYPE_STRUCT_OPS, struct_ops)\n--\ninclude/uapi/linux/bpf.h=1000=enum bpf_map_type {\n--\ninclude/uapi/linux/bpf.h-1054-/* Note that tracing related programs such as\ninclude/uapi/linux/bpf.h:1055: * BPF_PROG_TYPE_{KPROBE,TRACEPOINT,PERF_EVENT,RAW_TRACEPOINT}\ninclude/uapi/linux/bpf.h-1056- * are not subject to a stable API since kernel internal data\n--\ninclude/uapi/linux/bpf.h=1062=enum bpf_prog_type {\n--\ninclude/uapi/linux/bpf.h-1064-\tBPF_PROG_TYPE_SOCKET_FILTER,\ninclude/uapi/linux/bpf.h:1065:\tBPF_PROG_TYPE_KPROBE,\ninclude/uapi/linux/bpf.h-1066-\tBPF_PROG_TYPE_SCHED_CLS,\n--\ninclude/uapi/linux/bpf.h=1099=enum bpf_attach_type {\n--\ninclude/uapi/linux/bpf.h-1141-\tBPF_PERF_EVENT,\ninclude/uapi/linux/bpf.h:1142:\tBPF_TRACE_KPROBE_MULTI,\ninclude/uapi/linux/bpf.h-1143-\tBPF_LSM_CGROUP,\n--\ninclude/uapi/linux/bpf.h-1155-\tBPF_NETKIT_PEER,\ninclude/uapi/linux/bpf.h:1156:\tBPF_TRACE_KPROBE_SESSION,\ninclude/uapi/linux/bpf.h-1157-\tBPF_TRACE_UPROBE_SESSION,\n--\ninclude/uapi/linux/bpf.h=1170=enum bpf_link_type {\n--\ninclude/uapi/linux/bpf.h-1178-\tBPF_LINK_TYPE_PERF_EVENT = 7,\ninclude/uapi/linux/bpf.h:1179:\tBPF_LINK_TYPE_KPROBE_MULTI = 8,\ninclude/uapi/linux/bpf.h-1180-\tBPF_LINK_TYPE_STRUCT_OPS = 9,\n--\ninclude/uapi/linux/bpf.h=1192=enum bpf_perf_event_type {\n--\ninclude/uapi/linux/bpf.h-1195-\tBPF_PERF_EVENT_URETPROBE = 2,\ninclude/uapi/linux/bpf.h:1196:\tBPF_PERF_EVENT_KPROBE = 3,\ninclude/uapi/linux/bpf.h-1197-\tBPF_PERF_EVENT_KRETPROBE = 4,\n--\ninclude/uapi/linux/bpf.h-1319-/* link_create.kprobe_multi.flags used in LINK_CREATE command for\ninclude/uapi/linux/bpf.h:1320: * BPF_TRACE_KPROBE_MULTI attach type to create return probe.\ninclude/uapi/linux/bpf.h-1321- /\ninclude/uapi/linux/bpf.h=1322=enum {\ninclude/uapi/linux/bpf.h:1323:\tBPF_F_KPROBE_MULTI_RETURN = (1U \u003c\u003c 0)\ninclude/uapi/linux/bpf.h-1324-};\n--\ninclude/uapi/linux/bpf.h=1527=union bpf_attr {\n--\ninclude/uapi/linux/bpf.h-3260- \t\trestrictions. It is only available if the kernel was compiled\ninclude/uapi/linux/bpf.h:3261: * \t\twith the CONFIG_BPF_KPROBE_OVERRIDE configuration\ninclude/uapi/linux/bpf.h-3262- * \t\toption, and in this case it only works on functions tagged with\n--\ninclude/uapi/linux/bpf.h=6838=struct bpf_link_info {\n--\ninclude/uapi/linux/bpf.h-6943-\t\t\t\t\t__u64 cookie;\ninclude/uapi/linux/bpf.h:6944:\t\t\t\t} kprobe; /* BPF_PERF_EVENT_KPROBE, BPF_PERF_EVENT_KRETPROBE /\ninclude/uapi/linux/bpf.h-6945-\t\t\t\tstruct {\n--\ninclude/uapi/linux/bpf.h=7536=enum bpf_task_fd_type {\n--\ninclude/uapi/linux/bpf.h-7538-\tBPF_FD_TYPE_TRACEPOINT,\t\t/ tp name /\ninclude/uapi/linux/bpf.h:7539:\tBPF_FD_TYPE_KPROBE,\t\t/ (symbol + offset) or addr /\ninclude/uapi/linux/bpf.h-7540-\tBPF_FD_TYPE_KRETPROBE,\t\t/ (symbol + offset) or addr /\n--\nkernel/bpf/btf.c=6162=bool btf_is_prog_ctx_type(struct bpf_verifier_log log, const struct btf btf,\n--\nkernel/bpf/btf.c-6173-\t /\nkernel/bpf/btf.c:6174:\tif (prog_type == BPF_PROG_TYPE_KPROBE) {\nkernel/bpf/btf.c-6175-\t\twhile (btf_type_is_modifier(t) \u0026\u0026 !btf_type_is_typedef(t))\n--\nkernel/bpf/btf.c=6248=static int btf_validate_prog_ctx_type(struct bpf_verifier_log log, const struct btf btf,\n--\nkernel/bpf/btf.c-6262-\t/* KPROBE and PERF_EVENT programs allow bpf_user_pt_regs_t typedef /\nkernel/bpf/btf.c:6263:\tif (prog_type == BPF_PROG_TYPE_KPROBE \|\| prog_type == BPF_PROG_TYPE_PERF_EVENT) {\nkernel/bpf/btf.c-6264-\t\twhile (btf_type_is_modifier(t) \u0026\u0026 !btf_type_is_typedef(t))\n--\nkernel/bpf/btf.c-6289-\tswitch (prog_type) {\nkernel/bpf/btf.c:6290:\tcase BPF_PROG_TYPE_KPROBE:\nkernel/bpf/btf.c-6291-\t\tif (__btf_type_is_struct(t) \u0026\u0026 strcmp(tname, \"pt_regs\") == 0)\n--\nkernel/bpf/btf.c=9156=static int bpf_prog_type_to_kfunc_hook(enum bpf_prog_type prog_type)\n--\nkernel/bpf/btf.c-9195-\t\treturn BTF_KFUNC_HOOK_NETFILTER;\nkernel/bpf/btf.c:9196:\tcase BPF_PROG_TYPE_KPROBE:\nkernel/bpf/btf.c-9197-\t\treturn BTF_KFUNC_HOOK_KPROBE;\n--\nkernel/bpf/syscall.c=2874=static bool is_perfmon_prog_type(enum bpf_prog_type prog_type)\n--\nkernel/bpf/syscall.c-2876-\tswitch (prog_type) {\nkernel/bpf/syscall.c:2877:\tcase BPF_PROG_TYPE_KPROBE:\nkernel/bpf/syscall.c-2878-\tcase BPF_PROG_TYPE_TRACEPOINT:\n--\nkernel/bpf/syscall.c=3407=static void bpf_link_show_fdinfo(struct seq_file m, struct file filp)\n--\nkernel/bpf/syscall.c-3415-\tif (type \u003c ARRAY_SIZE(bpf_link_type_strs) \u0026\u0026 bpf_link_type_strs[type]) {\nkernel/bpf/syscall.c:3416:\t\tif (link-\u003etype == BPF_LINK_TYPE_KPROBE_MULTI)\nkernel/bpf/syscall.c:3417:\t\t\tseq_printf(m, \"link_type:\\t%s\\n\", link-\u003eflags == BPF_F_KPROBE_MULTI_RETURN ?\nkernel/bpf/syscall.c-3418-\t\t\t\t \"kretprobe_multi\" : \"kprobe_multi\");\n--\nkernel/bpf/syscall.c=3995=static int bpf_perf_link_fill_kprobe(const struct perf_event event,\n--\nkernel/bpf/syscall.c-4012-\telse\nkernel/bpf/syscall.c:4013:\t\tinfo-\u003eperf_event.type = BPF_PERF_EVENT_KPROBE;\nkernel/bpf/syscall.c-4014-\tinfo-\u003eperf_event.kprobe.name_len = ulen;\n--\nkernel/bpf/syscall.c=4147=static int bpf_perf_link_fill_link_info(const struct bpf_link link,\n--\nkernel/bpf/syscall.c-4162-\t\treturn bpf_perf_link_fill_tracepoint(event, info);\nkernel/bpf/syscall.c:4163:\tcase BPF_PROG_TYPE_KPROBE:\nkernel/bpf/syscall.c-4164-\t\treturn bpf_perf_link_fill_probe(event, info);\n--\nkernel/bpf/syscall.c=4215=static void bpf_perf_link_show_fdinfo(const struct bpf_link link,\n--\nkernel/bpf/syscall.c-4230-\t\treturn bpf_tracepoint_link_show_fdinfo(event, seq);\nkernel/bpf/syscall.c:4231:\tcase BPF_PROG_TYPE_KPROBE:\nkernel/bpf/syscall.c-4232-\t\treturn bpf_probe_link_show_fdinfo(event, seq);\n--\nkernel/bpf/syscall.c=4474=static int bpf_prog_attach_check_attach_type(const struct bpf_prog prog,\n--\nkernel/bpf/syscall.c-4509-\t\treturn 0;\nkernel/bpf/syscall.c:4510:\tcase BPF_PROG_TYPE_KPROBE:\nkernel/bpf/syscall.c:4511:\t\tif (prog-\u003eexpected_attach_type == BPF_TRACE_KPROBE_MULTI \u0026\u0026\nkernel/bpf/syscall.c:4512:\t\t attach_type != BPF_TRACE_KPROBE_MULTI)\nkernel/bpf/syscall.c-4513-\t\t\treturn -EINVAL;\nkernel/bpf/syscall.c:4514:\t\tif (prog-\u003eexpected_attach_type == BPF_TRACE_KPROBE_SESSION \u0026\u0026\nkernel/bpf/syscall.c:4515:\t\t attach_type != BPF_TRACE_KPROBE_SESSION)\nkernel/bpf/syscall.c-4516-\t\t\treturn -EINVAL;\n--\nkernel/bpf/syscall.c-4523-\t\tif (attach_type != BPF_PERF_EVENT \u0026\u0026\nkernel/bpf/syscall.c:4524:\t\t attach_type != BPF_TRACE_KPROBE_MULTI \u0026\u0026\nkernel/bpf/syscall.c:4525:\t\t attach_type != BPF_TRACE_KPROBE_SESSION \u0026\u0026\nkernel/bpf/syscall.c-4526-\t\t attach_type != BPF_TRACE_UPROBE_MULTI \u0026\u0026\n--\nkernel/bpf/syscall.c=5793=static int link_create(union bpf_attr attr, bpfptr_t uattr)\n--\nkernel/bpf/syscall.c-5878-\t\tbreak;\nkernel/bpf/syscall.c:5879:\tcase BPF_PROG_TYPE_KPROBE:\nkernel/bpf/syscall.c-5880-\t\tif (attr-\u003elink_create.attach_type == BPF_PERF_EVENT)\nkernel/bpf/syscall.c-5881-\t\t\tret = bpf_perf_link_attach(attr, prog);\nkernel/bpf/syscall.c:5882:\t\telse if (attr-\u003elink_create.attach_type == BPF_TRACE_KPROBE_MULTI \|\|\nkernel/bpf/syscall.c:5883:\t\t\t attr-\u003elink_create.attach_type == BPF_TRACE_KPROBE_SESSION)\nkernel/bpf/syscall.c-5884-\t\t\tret = bpf_kprobe_multi_link_attach(attr, prog);\n--\nkernel/bpf/verifier.c=5323=static enum priv_stack_mode bpf_enable_priv_stack(struct bpf_prog prog)\n--\nkernel/bpf/verifier.c-5332-\tswitch (prog-\u003etype) {\nkernel/bpf/verifier.c:5333:\tcase BPF_PROG_TYPE_KPROBE:\nkernel/bpf/verifier.c-5334-\tcase BPF_PROG_TYPE_TRACEPOINT:\n--\nkernel/bpf/verifier.c=11348=static int check_get_func_ip(struct bpf_verifier_env env)\n--\nkernel/bpf/verifier.c-11359-\t\treturn 0;\nkernel/bpf/verifier.c:11360:\t} else if (type == BPF_PROG_TYPE_KPROBE) {\nkernel/bpf/verifier.c-11361-\t\treturn 0;\n--\nkernel/bpf/verifier.c=17745=static bool return_retval_range(struct bpf_verifier_env env, struct bpf_retval_range range)\n--\nkernel/bpf/verifier.c-17806-\t\tbreak;\nkernel/bpf/verifier.c:17807:\tcase BPF_PROG_TYPE_KPROBE:\nkernel/bpf/verifier.c-17808-\t\tswitch (env-\u003eprog-\u003eexpected_attach_type) {\nkernel/bpf/verifier.c:17809:\t\tcase BPF_TRACE_KPROBE_SESSION:\nkernel/bpf/verifier.c-17810-\t\tcase BPF_TRACE_UPROBE_SESSION:\n--\nkernel/bpf/verifier.c=19127=static bool is_tracing_prog_type(enum bpf_prog_type type)\n--\nkernel/bpf/verifier.c-19129-\tswitch (type) {\nkernel/bpf/verifier.c:19130:\tcase BPF_PROG_TYPE_KPROBE:\nkernel/bpf/verifier.c-19131-\tcase BPF_PROG_TYPE_TRACEPOINT:\n--\nkernel/bpf/verifier.c=20821=static bool can_be_sleepable(struct bpf_prog prog)\n--\nkernel/bpf/verifier.c-20841-\nkernel/bpf/verifier.c:20842:\treturn prog-\u003etype == BPF_PROG_TYPE_KPROBE / only for uprobes / \|\|\nkernel/bpf/verifier.c-20843-\t prog-\u003etype == BPF_PROG_TYPE_STRUCT_OPS \|\|\n--\nkernel/events/core.c=11836=static int __perf_event_set_bpf_prog(struct perf_event event,\n--\nkernel/events/core.c-11855-\nkernel/events/core.c:11856:\tif (((is_kprobe \|\| is_uprobe) \u0026\u0026 prog-\u003etype != BPF_PROG_TYPE_KPROBE) \|\|\nkernel/events/core.c-11857-\t (is_tracepoint \u0026\u0026 prog-\u003etype != BPF_PROG_TYPE_TRACEPOINT) \|\|\n--\nkernel/events/core.c-11860-\nkernel/events/core.c:11861:\tif (prog-\u003etype == BPF_PROG_TYPE_KPROBE \u0026\u0026 prog-\u003esleepable \u0026\u0026 !is_uprobe)\nkernel/events/core.c-11862-\t\t/* only uprobe programs are allowed to be sleepable /\n--\nkernel/trace/Kconfig=877=config PROBE_EVENTS\n--\nkernel/trace/Kconfig-879-\nkernel/trace/Kconfig:880:config BPF_KPROBE_OVERRIDE\nkernel/trace/Kconfig-881-\tbool \"Enable BPF programs to override a kprobed function\"\n--\nkernel/trace/bpf_trace.c=173=unsigned int trace_call_bpf_faultable(struct trace_event_call call, void ctx)\n--\nkernel/trace/bpf_trace.c-184-\nkernel/trace/bpf_trace.c:185:#ifdef CONFIG_BPF_KPROBE_OVERRIDE\nkernel/trace/bpf_trace.c-186-BPF_CALL_2(bpf_override_return, struct pt_regs , regs, unsigned long, rc)\n--\nkernel/trace/bpf_trace.c=1311=static bool is_kprobe_multi(const struct bpf_prog prog)\nkernel/trace/bpf_trace.c-1312-{\nkernel/trace/bpf_trace.c:1313:\treturn prog-\u003eexpected_attach_type == BPF_TRACE_KPROBE_MULTI \|\|\nkernel/trace/bpf_trace.c:1314:\t prog-\u003eexpected_attach_type == BPF_TRACE_KPROBE_SESSION;\nkernel/trace/bpf_trace.c-1315-}\n--\nkernel/trace/bpf_trace.c=1317=static inline bool is_kprobe_session(const struct bpf_prog prog)\nkernel/trace/bpf_trace.c-1318-{\nkernel/trace/bpf_trace.c:1319:\treturn prog-\u003etype == BPF_PROG_TYPE_KPROBE \u0026\u0026\nkernel/trace/bpf_trace.c:1320:\t prog-\u003eexpected_attach_type == BPF_TRACE_KPROBE_SESSION;\nkernel/trace/bpf_trace.c-1321-}\n--\nkernel/trace/bpf_trace.c=1329=static inline bool is_uprobe_session(const struct bpf_prog prog)\nkernel/trace/bpf_trace.c-1330-{\nkernel/trace/bpf_trace.c:1331:\treturn prog-\u003etype == BPF_PROG_TYPE_KPROBE \u0026\u0026\nkernel/trace/bpf_trace.c-1332-\t prog-\u003eexpected_attach_type == BPF_TRACE_UPROBE_SESSION;\n--\nkernel/trace/bpf_trace.c=1343=kprobe_prog_func_proto(enum bpf_func_id func_id, const struct bpf_prog prog)\n--\nkernel/trace/bpf_trace.c-1351-\t\treturn prog-\u003esleepable ? \u0026bpf_get_stack_sleepable_proto : \u0026bpf_get_stack_proto;\nkernel/trace/bpf_trace.c:1352:#ifdef CONFIG_BPF_KPROBE_OVERRIDE\nkernel/trace/bpf_trace.c-1353-\tcase BPF_FUNC_override_return:\n--\nkernel/trace/bpf_trace.c=2780=int bpf_kprobe_multi_link_attach(const union bpf_attr attr, struct bpf_prog prog)\n--\nkernel/trace/bpf_trace.c-2810-\tflags = attr-\u003elink_create.kprobe_multi.flags;\nkernel/trace/bpf_trace.c:2811:\tif (flags \u0026 ~BPF_F_KPROBE_MULTI_RETURN)\nkernel/trace/bpf_trace.c-2812-\t\treturn -EINVAL;\n--\nkernel/trace/bpf_trace.c-2880-\nkernel/trace/bpf_trace.c:2881:\tbpf_link_init(\u0026link-\u003elink, BPF_LINK_TYPE_KPROBE_MULTI,\nkernel/trace/bpf_trace.c-2882-\t\t \u0026bpf_kprobe_multi_link_lops, prog, attr-\u003elink_create.attach_type);\n--\nkernel/trace/bpf_trace.c-2887-\nkernel/trace/bpf_trace.c:2888:\tif (!(flags \u0026 BPF_F_KPROBE_MULTI_RETURN))\nkernel/trace/bpf_trace.c-2889-\t\tlink-\u003efp.entry_handler = kprobe_multi_link_handler;\nkernel/trace/bpf_trace.c:2890:\tif ((flags \u0026 BPF_F_KPROBE_MULTI_RETURN) \|\| is_kprobe_session(prog))\nkernel/trace/bpf_trace.c-2891-\t\tlink-\u003efp.exit_handler = kprobe_multi_link_exit_handler;\n--\nkernel/trace/bpf_trace.c=3459=static int __init bpf_trace_kfuncs_init(void)\n--\nkernel/trace/bpf_trace.c-3462-\nkernel/trace/bpf_trace.c:3463:\terr = err ?: register_btf_kfunc_id_set(BPF_PROG_TYPE_KPROBE, \u0026bpf_session_kfunc_set);\nkernel/trace/bpf_trace.c-3464-\terr = err ?: register_btf_kfunc_id_set(BPF_PROG_TYPE_TRACING, \u0026bpf_session_kfunc_set);\n--\nkernel/trace/trace_kprobe.c=1774=int bpf_get_kprobe_info(const struct perf_event event, u32 fd_type,\n--\nkernel/trace/trace_kprobe.c-1790-\tfd_type = trace_kprobe_is_return(tk) ? BPF_FD_TYPE_KRETPROBE\nkernel/trace/trace_kprobe.c:1791:\t\t\t\t\t : BPF_FD_TYPE_KPROBE;\nkernel/trace/trace_kprobe.c-1792-\tprobe_offset = tk-\u003erp.kp.offset;\n--\nsamples/bpf/task_fd_query_user.c=310=int main(int argc, char *argv)\n--\nsamples/bpf/task_fd_query_user.c-349-\tCHECK_AND_RET(test_debug_fs_kprobe(0, \"blk_mq_start_request\",\nsamples/bpf/task_fd_query_user.c:350:\t\t\t\t\t BPF_FD_TYPE_KPROBE));\nsamples/bpf/task_fd_query_user.c-351-\tCHECK_AND_RET(test_debug_fs_kprobe(1, \"__blk_account_io_done\",\n--\nsamples/bpf/task_fd_query_user.c-355-\tCHECK_AND_RET(test_nondebug_fs_probe(\"kprobe\", \"bpf_check\", 0x0, 0x0,\nsamples/bpf/task_fd_query_user.c:356:\t\t\t\t\t false, BPF_FD_TYPE_KPROBE,\nsamples/bpf/task_fd_query_user.c-357-\t\t\t\t\t BPF_FD_TYPE_KRETPROBE,\n--\nsamples/bpf/task_fd_query_user.c-361-\tCHECK_AND_RET(test_nondebug_fs_probe(\"kprobe\", \"bpf_check\", 0x5, 0x0,\nsamples/bpf/task_fd_query_user.c:362:\t\t\t\t\t false, BPF_FD_TYPE_KPROBE,\nsamples/bpf/task_fd_query_user.c-363-\t\t\t\t\t BPF_FD_TYPE_KRETPROBE,\n--\nsamples/bpf/task_fd_query_user.c-366-\tCHECK_AND_RET(test_nondebug_fs_probe(\"kprobe\", \"bpf_check\", 0x0, 0x0,\nsamples/bpf/task_fd_query_user.c:367:\t\t\t\t\t true, BPF_FD_TYPE_KPROBE,\nsamples/bpf/task_fd_query_user.c-368-\t\t\t\t\t BPF_FD_TYPE_KRETPROBE,\n--\nsamples/bpf/task_fd_query_user.c-371-\t\t\t\t\t ksym_get_addr(\"bpf_check\"), false,\nsamples/bpf/task_fd_query_user.c:372:\t\t\t\t\t BPF_FD_TYPE_KPROBE,\nsamples/bpf/task_fd_query_user.c-373-\t\t\t\t\t BPF_FD_TYPE_KRETPROBE,\n--\nsamples/bpf/task_fd_query_user.c-376-\t\t\t\t\t ksym_get_addr(\"bpf_check\"), false,\nsamples/bpf/task_fd_query_user.c:377:\t\t\t\t\t BPF_FD_TYPE_KPROBE,\nsamples/bpf/task_fd_query_user.c-378-\t\t\t\t\t BPF_FD_TYPE_KRETPROBE,\n--\nsamples/bpf/task_fd_query_user.c-381-\t\t\t\t\t ksym_get_addr(\"bpf_check\"), true,\nsamples/bpf/task_fd_query_user.c:382:\t\t\t\t\t BPF_FD_TYPE_KPROBE,\nsamples/bpf/task_fd_query_user.c-383-\t\t\t\t\t BPF_FD_TYPE_KRETPROBE,\n--\nsamples/bpf/task_fd_query_user.c-386-\t\t\t\t\t ksym_get_addr(\"bpf_check\"), true,\nsamples/bpf/task_fd_query_user.c:387:\t\t\t\t\t BPF_FD_TYPE_KPROBE,\nsamples/bpf/task_fd_query_user.c-388-\t\t\t\t\t BPF_FD_TYPE_KRETPROBE,\n--\nsamples/bpf/tracex6.bpf.c=55=SEC(\"kprobe/bpf_map_copy_value\")\nsamples/bpf/tracex6.bpf.c:56:int BPF_KPROBE(bpf_prog2, struct bpf_map map)\nsamples/bpf/tracex6.bpf.c-57-{\n--\ntools/bpf/bpftool/feature.c=328=static void probe_kernel_image_config(const char define_prefix)\n--\ntools/bpf/bpftool/feature.c-367-\t\t/ bpf_override_return() helper /\ntools/bpf/bpftool/feature.c:368:\t\t{ \"CONFIG_BPF_KPROBE_OVERRIDE\", },\ntools/bpf/bpftool/feature.c-369-\n--\ntools/bpf/bpftool/link.c=326=show_kprobe_multi_json(struct bpf_link_info info, json_writer_t wtr)\n--\ntools/bpf/bpftool/link.c-332-\tjsonw_bool_field(json_wtr, \"retprobe\",\ntools/bpf/bpftool/link.c:333:\t\t\t info-\u003ekprobe_multi.flags \u0026 BPF_F_KPROBE_MULTI_RETURN);\ntools/bpf/bpftool/link.c-334-\tjsonw_uint_field(json_wtr, \"func_cnt\", info-\u003ekprobe_multi.count);\n--\ntools/bpf/bpftool/link.c=582=static int show_link_close_json(int fd, struct bpf_link_info info)\n--\ntools/bpf/bpftool/link.c-650-\t\tbreak;\ntools/bpf/bpftool/link.c:651:\tcase BPF_LINK_TYPE_KPROBE_MULTI:\ntools/bpf/bpftool/link.c-652-\t\tshow_kprobe_multi_json(info, json_wtr);\n--\ntools/bpf/bpftool/link.c-667-\t\t\tbreak;\ntools/bpf/bpftool/link.c:668:\t\tcase BPF_PERF_EVENT_KPROBE:\ntools/bpf/bpftool/link.c-669-\t\tcase BPF_PERF_EVENT_KRETPROBE:\n--\ntools/bpf/bpftool/link.c=829=static void show_kprobe_multi_plain(struct bpf_link_info info)\n--\ntools/bpf/bpftool/link.c-837-\ntools/bpf/bpftool/link.c:838:\tif (info-\u003ekprobe_multi.flags \u0026 BPF_F_KPROBE_MULTI_RETURN)\ntools/bpf/bpftool/link.c-839-\t\tprintf(\"\\n\\tkretprobe.multi \");\n--\ntools/bpf/bpftool/link.c=1026=static int show_link_close_plain(int fd, struct bpf_link_info info)\n--\ntools/bpf/bpftool/link.c-1093-\t\tbreak;\ntools/bpf/bpftool/link.c:1094:\tcase BPF_LINK_TYPE_KPROBE_MULTI:\ntools/bpf/bpftool/link.c-1095-\t\tshow_kprobe_multi_plain(info);\n--\ntools/bpf/bpftool/link.c-1110-\t\t\tbreak;\ntools/bpf/bpftool/link.c:1111:\t\tcase BPF_PERF_EVENT_KPROBE:\ntools/bpf/bpftool/link.c-1112-\t\tcase BPF_PERF_EVENT_KRETPROBE:\n--\ntools/bpf/bpftool/link.c=1140=static int do_show_link(int fd)\n--\ntools/bpf/bpftool/link.c-1173-\t}\ntools/bpf/bpftool/link.c:1174:\tif (info.type == BPF_LINK_TYPE_KPROBE_MULTI \u0026\u0026\ntools/bpf/bpftool/link.c-1175-\t !info.kprobe_multi.addrs) {\n--\ntools/bpf/bpftool/link.c-1257-\t\t\tbreak;\ntools/bpf/bpftool/link.c:1258:\t\tcase BPF_PERF_EVENT_KPROBE:\ntools/bpf/bpftool/link.c-1259-\t\tcase BPF_PERF_EVENT_KRETPROBE:\n--\ntools/bpf/bpftool/perf.c=65=static void print_perf_json(int pid, int fd, __u32 prog_id, __u32 fd_type,\n--\ntools/bpf/bpftool/perf.c-80-\t\tbreak;\ntools/bpf/bpftool/perf.c:81:\tcase BPF_FD_TYPE_KPROBE:\ntools/bpf/bpftool/perf.c-82-\t\tjsonw_string_field(json_wtr, \"fd_type\", \"kprobe\");\n--\ntools/bpf/bpftool/perf.c=115=static void print_perf_plain(int pid, int fd, __u32 prog_id, __u32 fd_type,\n--\ntools/bpf/bpftool/perf.c-125-\t\tbreak;\ntools/bpf/bpftool/perf.c:126:\tcase BPF_FD_TYPE_KPROBE:\ntools/bpf/bpftool/perf.c-127-\t\tif (buf[0] != '\\0')\n--\ntools/build/feature/test-bpf.c=30=int main(void)\n--\ntools/build/feature/test-bpf.c-34-\t/* Check fields in attr /\ntools/build/feature/test-bpf.c:35:\tattr.prog_type = BPF_PROG_TYPE_KPROBE;\ntools/build/feature/test-bpf.c-36-\tattr.insn_cnt = 0;\n--\ntools/include/uapi/linux/bpf.h=1000=enum bpf_map_type {\n--\ntools/include/uapi/linux/bpf.h-1054-/ Note that tracing related programs such as\ntools/include/uapi/linux/bpf.h:1055: * BPF_PROG_TYPE_{KPROBE,TRACEPOINT,PERF_EVENT,RAW_TRACEPOINT}\ntools/include/uapi/linux/bpf.h-1056- * are not subject to a stable API since kernel internal data\n--\ntools/include/uapi/linux/bpf.h=1062=enum bpf_prog_type {\n--\ntools/include/uapi/linux/bpf.h-1064-\tBPF_PROG_TYPE_SOCKET_FILTER,\ntools/include/uapi/linux/bpf.h:1065:\tBPF_PROG_TYPE_KPROBE,\ntools/include/uapi/linux/bpf.h-1066-\tBPF_PROG_TYPE_SCHED_CLS,\n--\ntools/include/uapi/linux/bpf.h=1099=enum bpf_attach_type {\n--\ntools/include/uapi/linux/bpf.h-1141-\tBPF_PERF_EVENT,\ntools/include/uapi/linux/bpf.h:1142:\tBPF_TRACE_KPROBE_MULTI,\ntools/include/uapi/linux/bpf.h-1143-\tBPF_LSM_CGROUP,\n--\ntools/include/uapi/linux/bpf.h-1155-\tBPF_NETKIT_PEER,\ntools/include/uapi/linux/bpf.h:1156:\tBPF_TRACE_KPROBE_SESSION,\ntools/include/uapi/linux/bpf.h-1157-\tBPF_TRACE_UPROBE_SESSION,\n--\ntools/include/uapi/linux/bpf.h=1170=enum bpf_link_type {\n--\ntools/include/uapi/linux/bpf.h-1178-\tBPF_LINK_TYPE_PERF_EVENT = 7,\ntools/include/uapi/linux/bpf.h:1179:\tBPF_LINK_TYPE_KPROBE_MULTI = 8,\ntools/include/uapi/linux/bpf.h-1180-\tBPF_LINK_TYPE_STRUCT_OPS = 9,\n--\ntools/include/uapi/linux/bpf.h=1192=enum bpf_perf_event_type {\n--\ntools/include/uapi/linux/bpf.h-1195-\tBPF_PERF_EVENT_URETPROBE = 2,\ntools/include/uapi/linux/bpf.h:1196:\tBPF_PERF_EVENT_KPROBE = 3,\ntools/include/uapi/linux/bpf.h-1197-\tBPF_PERF_EVENT_KRETPROBE = 4,\n--\ntools/include/uapi/linux/bpf.h-1319-/* link_create.kprobe_multi.flags used in LINK_CREATE command for\ntools/include/uapi/linux/bpf.h:1320: * BPF_TRACE_KPROBE_MULTI attach type to create return probe.\ntools/include/uapi/linux/bpf.h-1321- /\ntools/include/uapi/linux/bpf.h=1322=enum {\ntools/include/uapi/linux/bpf.h:1323:\tBPF_F_KPROBE_MULTI_RETURN = (1U \u003c\u003c 0)\ntools/include/uapi/linux/bpf.h-1324-};\n--\ntools/include/uapi/linux/bpf.h=1527=union bpf_attr {\n--\ntools/include/uapi/linux/bpf.h-3260- \t\trestrictions. It is only available if the kernel was compiled\ntools/include/uapi/linux/bpf.h:3261: * \t\twith the CONFIG_BPF_KPROBE_OVERRIDE configuration\ntools/include/uapi/linux/bpf.h-3262- * \t\toption, and in this case it only works on functions tagged with\n--\ntools/include/uapi/linux/bpf.h=6838=struct bpf_link_info {\n--\ntools/include/uapi/linux/bpf.h-6943-\t\t\t\t\t__u64 cookie;\ntools/include/uapi/linux/bpf.h:6944:\t\t\t\t} kprobe; /* BPF_PERF_EVENT_KPROBE, BPF_PERF_EVENT_KRETPROBE /\ntools/include/uapi/linux/bpf.h-6945-\t\t\t\tstruct {\n--\ntools/include/uapi/linux/bpf.h=7536=enum bpf_task_fd_type {\n--\ntools/include/uapi/linux/bpf.h-7538-\tBPF_FD_TYPE_TRACEPOINT,\t\t/ tp name /\ntools/include/uapi/linux/bpf.h:7539:\tBPF_FD_TYPE_KPROBE,\t\t/ (symbol + offset) or addr /\ntools/include/uapi/linux/bpf.h-7540-\tBPF_FD_TYPE_KRETPROBE,\t\t/ (symbol + offset) or addr /\n--\ntools/lib/bpf/bpf.c=782=int bpf_link_create(int prog_fd, int target_fd,\n--\ntools/lib/bpf/bpf.c-825-\t\tbreak;\ntools/lib/bpf/bpf.c:826:\tcase BPF_TRACE_KPROBE_MULTI:\ntools/lib/bpf/bpf.c:827:\tcase BPF_TRACE_KPROBE_SESSION:\ntools/lib/bpf/bpf.c-828-\t\tattr.link_create.kprobe_multi.flags = OPTS_GET(opts, kprobe_multi.flags, 0);\n--\ntools/lib/bpf/bpf_tracing.h=455=struct pt_regs;\n--\ntools/lib/bpf/bpf_tracing.h-521-\ntools/lib/bpf/bpf_tracing.h:522:#define BPF_KPROBE_READ_RET_IP(ip, ctx)\t\t({ (ip) = (ctx)-\u003elink; })\ntools/lib/bpf/bpf_tracing.h:523:#define BPF_KRETPROBE_READ_RET_IP\t\tBPF_KPROBE_READ_RET_IP\ntools/lib/bpf/bpf_tracing.h-524-\n--\ntools/lib/bpf/bpf_tracing.h-526-\ntools/lib/bpf/bpf_tracing.h:527:#define BPF_KPROBE_READ_RET_IP(ip, ctx)\t\t({ (ip) = PT_REGS_RET(ctx); })\ntools/lib/bpf/bpf_tracing.h:528:#define BPF_KRETPROBE_READ_RET_IP\t\tBPF_KPROBE_READ_RET_IP\ntools/lib/bpf/bpf_tracing.h-529-\n--\ntools/lib/bpf/bpf_tracing.h-531-\ntools/lib/bpf/bpf_tracing.h:532:#define BPF_KPROBE_READ_RET_IP(ip, ctx)\t\t\t\t\t \\\ntools/lib/bpf/bpf_tracing.h-533-\t({ bpf_probe_read_kernel(\u0026(ip), sizeof(ip), (void )PT_REGS_RET(ctx)); })\n--\ntools/lib/bpf/bpf_tracing.h-597-\ntools/lib/bpf/bpf_tracing.h:598:#define BPF_KPROBE_READ_RET_IP(ip, ctx) ({ _Pragma(__BPF_TARGET_MISSING); 0l; })\ntools/lib/bpf/bpf_tracing.h-599-#define BPF_KRETPROBE_READ_RET_IP(ip, ctx) ({ _Pragma(__BPF_TARGET_MISSING); 0l; })\n--\ntools/lib/bpf/bpf_tracing.h=793=struct pt_regs;\n--\ntools/lib/bpf/bpf_tracing.h-806-/\ntools/lib/bpf/bpf_tracing.h:807: BPF_KPROBE serves the same purpose for kprobes as BPF_PROG for\ntools/lib/bpf/bpf_tracing.h-808- * tp_btf/fentry/fexit BPF programs. It hides the underlying platform-specific\n--\ntools/lib/bpf/bpf_tracing.h-815- /\ntools/lib/bpf/bpf_tracing.h:816:#define BPF_KPROBE(name, args...)\t\t\t\t\t \\\ntools/lib/bpf/bpf_tracing.h-817-name(struct pt_regs ctx);\t\t\t\t\t\t \\\n--\ntools/lib/bpf/bpf_tracing.h=828=____##name(struct pt_regs ctx, ##args)\n--\ntools/lib/bpf/bpf_tracing.h-834-/\ntools/lib/bpf/bpf_tracing.h:835: * BPF_KRETPROBE is similar to BPF_KPROBE, except, it only provides optional\ntools/lib/bpf/bpf_tracing.h-836- * return value (in addition to `struct pt_regs ctx`), but no input\n--\ntools/lib/bpf/bpf_tracing.h=851=static __always_inline typeof(name(0)) ____##name(struct pt_regs ctx, ##args)\n--\ntools/lib/bpf/bpf_tracing.h-875-/\ntools/lib/bpf/bpf_tracing.h:876: BPF_KSYSCALL is a variant of BPF_KPROBE, which is intended for\ntools/lib/bpf/bpf_tracing.h-877- * tracing syscall functions, like __x64_sys_close. It hides the underlying\n--\ntools/lib/bpf/bpf_tracing.h=918=____##name(struct pt_regs ctx, ##args)\ntools/lib/bpf/bpf_tracing.h-919-\ntools/lib/bpf/bpf_tracing.h:920:#define BPF_KPROBE_SYSCALL BPF_KSYSCALL\ntools/lib/bpf/bpf_tracing.h-921-\ntools/lib/bpf/bpf_tracing.h:922:/ BPF_UPROBE and BPF_URETPROBE are identical to BPF_KPROBE and BPF_KRETPROBE,\ntools/lib/bpf/bpf_tracing.h-923- * but are named way less confusingly for SEC(\"uprobe\") and SEC(\"uretprobe\")\n--\ntools/lib/bpf/bpf_tracing.h-925- */\ntools/lib/bpf/bpf_tracing.h:926:#define BPF_UPROBE(name, args...) BPF_KPROBE(name, ##args)\ntools/lib/bpf/bpf_tracing.h-927-#define BPF_URETPROBE(name, args...) BPF_KRETPROBE(name, ##args)\n--\ntools/lib/bpf/features.c=362=static int probe_uprobe_multi_link(int token_fd)\n--\ntools/lib/bpf/features.c-376-\ntools/lib/bpf/features.c:377:\tprog_fd = bpf_prog_load(BPF_PROG_TYPE_KPROBE, NULL, \"GPL\",\ntools/lib/bpf/features.c-378-\t\t\t\tinsns, ARRAY_SIZE(insns), \u0026load_opts);\n--\ntools/lib/bpf/features.c=454=static int probe_kern_arg_ctx_tag(int token_fd)\n--\ntools/lib/bpf/features.c-501-\n\n" }
39/2	2026/09/16 03:10	llm	patch-evaluator	0m Model: gemini-3.8-flash Args: null Results: null Tokens: input: 49299 output: 29 thoughts: 91 Thoughts: Examining the BPF Trace Infrastructure Okay, let's break this down. My initial observation is that `bpf_kprobe_multi_link_attach`, specifically, located in `kernel/trace/bpf_trace.c`, appears to be gated behind a `#ifdef CONFIG_FPROBE` preprocessor directive. Interesting... this strongly suggests that functionality related to FPROBE, which I'm very familiar with, is crucial for this multi-link attachment behavior. Furthermore, I know that `bpf_trace.c` as a whole is compiled only if `CONFIG_BPF_EVENTS` is enabled. That's not unexpected; the BPF trace infrastructure is fundamental to these kinds of event hooks. But I need to confirm the build order and dependencies. Time to consult the `kernel/trace/Makefile`. I need to verify how `bpf_trace.o` is built and under what conditions. This will solidify my understanding of the pre-requisites for this section of the code.
40/2	2026/09/16 03:10	tool	grepper	0m Args: { "Expression": "bpf_trace\\.o", "PathPrefix": "kernel/trace" } Results: { "Output": "kernel/trace/Makefile=54=KCOV_INSTRUMENT_trace_irqsoff.o := n\nkernel/trace/Makefile-55-\nkernel/trace/Makefile:56:CFLAGS_bpf_trace.o := -I$(src)\nkernel/trace/Makefile-57-\n--\nkernel/trace/Makefile=109=obj-$(CONFIG_USER_EVENTS) += trace_events_user.o\nkernel/trace/Makefile:110:obj-$(CONFIG_BPF_EVENTS) += bpf_trace.o\nkernel/trace/Makefile-111-obj-$(CONFIG_KPROBE_EVENTS) += trace_kprobe.o\n" }
41/2	2026/09/16 03:10	llm	patch-evaluator	0m Model: gemini-3.8-flash Args: null Results: null Tokens: input: 49804 output: 27 thoughts: 1576 Thoughts: Focusing on fprobe Configuration and Key Symbols Alright, let's break down how fprobe and its interfaces are enabled. First, `FPROBE` is the core config that compiles `kernel/trace/fprobe.c`. It's dependent on `DYNAMIC_FTRACE_WITH_ARGS`, which in turn depends on `DYNAMIC_FTRACE`, along with `HAVE_FUNCTION_GRAPH_FREGS` and `HAVE_FTRACE_GRAPH_FUNC`. Crucially, `FPROBE` selects `FUNCTION_GRAPH_TRACER`. Then we have `FPROBE_EVENTS`, enabling the `tracefs` interface, specifically `fprobe_events`. And of course, there's the role of `BPF_EVENTS` and `BPF_SYSCALL` in enabling BPF multi-kprobe attachment via syscall. Now, a more detailed look at the dependencies shows: `DYNAMIC_FTRACE`, `FUNCTION_TRACER`, `FPROBE`, and `FPROBE_EVENTS`. Digging into `kernel/trace/Kconfig` confirms `FPROBE` depends on `HAVE_FUNCTION_GRAPH_FREGS`, `HAVE_FTRACE_GRAPH_FUNC`, and `DYNAMIC_FTRACE_WITH_ARGS` and selects `FUNCTION_GRAPH_TRACER`. `FPROBE_EVENTS` depends on `FPROBE`, `HAVE_REGS_AND_STACK_ACCESS_API` and selects `TRACING`, `PROBE_EVENTS`, and `DYNAMIC_EVENTS`. `FPROBE_SANITY_TEST` is enabled with `DEBUG_KERNEL`, `FPROBE`, and `KUNIT`. Next, let's zoom in on what functions were modified, or are central to the altered logic. I see `fprobe_fgraph_entry` has been changed. A comment highlights that we're clearing unused slots to prevent `fprobe_return` from reading stale headers. Bingo! `fprobe_return` is the function that reads these headers, and the code change directly addresses the issue of stale data. Are these functions ubiquitous? Not at all! They're specific to fprobe usage with fgraph. So, we've got `fprobe_fgraph_entry` and `fprobe_return`. We also have the registration points: `register_fprobe`, `register_fprobe_ips`, `register_fprobe_syms`. In `trace_fprobe.c` and `bpf_trace.c`, there's `bpf_kprobe_multi_link_attach`, `kprobe_multi_link_handler`, and `kprobe_multi_link_exit_handler`. Now, in `kernel/trace/fprobe.c`, besides `fprobe_fgraph_entry` and `fprobe_return`, we have `write_fprobe_header` (which is static inline, so it probably won't be in the symbol table, but it's important context). Other symbols include `fprobe_handler` / `__fprobe_handler`, `register_fprobe`, and `register_fprobe_ips`. `fprobe_fgraph_entry` and `fprobe_return` are marked with `NOKPROBE_SYMBOL`, meaning they are not inlined. They must have a symbol, and we see that they are. This is very important. Since they are not inlined, they must be called from elsewhere. Are `fprobe_fgraph_entry` and `fprobe_return` appropriate FocusSymbols? Absolutely! They are exactly where the logic change is. `fprobe_fgraph_entry` is the modified function, and `fprobe_return` is directly connected with that data. `bpf_kprobe_multi_link_attach` is the syscall entry point, and `register_fprobe` is the registration API. Further relevant symbols include `register_fprobe_ips`, and `trace_fprobe_create` (in `kernel/trace/trace_fprobe.c`). That last one will be the function to check how tracefs interacts with fprobe.
42/2	2026/09/16 03:10	tool	grepper	0m Error: no matches Args: { "Expression": "fprobe_events", "PathPrefix": "kernel/trace" } Results: { "error": "no matches" }
43/2	2026/09/16 03:10	llm	patch-evaluator	0m Model: gemini-3.8-flash Args: null Results: null Tokens: input: 52316 output: 28 thoughts: 22 Thoughts: Here's my take on those thoughts: Locating the Dynamic Event Creation Function Okay, so I need to get into the heart of how these dynamic events are created. My initial thought is to dive into the kernel source, specifically focusing on the tracing infrastructure. Given that we're dealing with "fprobe," the file I'm going to target is `kernel/trace/trace_fprobe.c`. That file should house the core logic for managing and, crucially, creating these dynamic events. I'm expecting to find a function responsible for the creation process within that file, as that's the obvious location for the fprobe related source. From there, I can analyze its implementation details to understand how events are registered and configured.
44/2	2026/09/16 03:10	tool	grepper	0m Args: { "Expression": "trace_probe_create", "PathPrefix": "kernel/trace" } Results: { "Output": "kernel/trace/trace_eprobe.c=72=static int eprobe_dyn_event_create(const char raw_command)\nkernel/trace/trace_eprobe.c-73-{\nkernel/trace/trace_eprobe.c:74:\treturn trace_probe_create(raw_command, __trace_eprobe_create);\nkernel/trace/trace_eprobe.c-75-}\n--\nkernel/trace/trace_fprobe.c=1414=static int trace_fprobe_create(const char raw_command)\nkernel/trace/trace_fprobe.c-1415-{\nkernel/trace/trace_fprobe.c:1416:\treturn trace_probe_create(raw_command, trace_fprobe_create_cb);\nkernel/trace/trace_fprobe.c-1417-}\n--\nkernel/trace/trace_kprobe.c=1115=static int trace_kprobe_create(const char raw_command)\nkernel/trace/trace_kprobe.c-1116-{\nkernel/trace/trace_kprobe.c:1117:\treturn trace_probe_create(raw_command, trace_kprobe_create_cb);\nkernel/trace/trace_kprobe.c-1118-}\n--\nkernel/trace/trace_probe.c=2830=bool trace_probe_match_command_args(struct trace_probe tp,\n--\nkernel/trace/trace_probe.c-2848-\nkernel/trace/trace_probe.c:2849:int trace_probe_create(const char raw_command, int (createfn)(int, const char *))\nkernel/trace/trace_probe.c-2850-{\n--\nkernel/trace/trace_probe.h=379=bool trace_probe_match_command_args(struct trace_probe tp,\nkernel/trace/trace_probe.h-380-\t\t\t\t int argc, const char *argv);\nkernel/trace/trace_probe.h:381:int trace_probe_create(const char raw_command, int (createfn)(int, const char ));\nkernel/trace/trace_probe.h-382-int trace_probe_print_args(struct trace_seq s, struct probe_arg args, int nr_args,\n--\nkernel/trace/trace_uprobe.c=727=int trace_uprobe_create(const char raw_command)\nkernel/trace/trace_uprobe.c-728-{\nkernel/trace/trace_uprobe.c:729:\treturn trace_probe_create(raw_command, __trace_uprobe_create);\nkernel/trace/trace_uprobe.c-730-}\n" }
45/2	2026/09/16 03:10	llm	patch-evaluator	0m Model: gemini-3.8-flash Args: null Results: null Tokens: input: 53203 output: 210 thoughts: 257 Thoughts: My Assessment of the Fprobe Implementation Okay, so `trace_fprobe_create` is definitely the right parser for fprobe's dynamic events, no question there. Time to double-check my mental map of the key FocusSymbols: * `fprobe_fgraph_entry`: That's where that `memset` was added, right where I thought. * `fprobe_return`: Yep, the caller that iterates through `fgraph_data` and handles header parsing. Looks solid. * `register_fprobe_ips`: The core function for registering those fprobe IPs, essential piece. * `bpf_kprobe_multi_link_attach`: And of course, the BPF link attach function leveraging fprobe. All checks out. Now, let me just confirm the EnableConfigs that underpin all this: * `FPROBE`: Enables the whole fprobe subsystem – crucial, obviously. * `DYNAMIC_FTRACE`: Needed as a prerequisite for `DYNAMIC_FTRACE_WITH_ARGS` and `FPROBE` - makes sense. * `FUNCTION_GRAPH_TRACER`: That's the function graph tracer selected by `FPROBE` and obviously needed for fgraph. * `BPF_EVENTS`: Confirms BPF kprobe multi link attach support in `bpf_trace.c`. Good, integrated as expected. * `FPROBE_EVENTS`: Enables dynamic fprobe events via tracefs. Yup, everything is lining up perfectly. The code itself and the Kconfig options support this implementation flawlessly. I'm confident in the logic and the configurations. Alright, let's call `set-results`.
46/2	2026/09/16 03:10	tool	set-results	0m Args: { "EnableConfigs": [ "FPROBE", "DYNAMIC_FTRACE", "FUNCTION_GRAPH_TRACER", "FPROBE_EVENTS", "BPF_EVENTS" ], "FocusSymbols": [ "fprobe_fgraph_entry", "fprobe_return", "register_fprobe_ips", "bpf_kprobe_multi_link_attach" ], "Reasoning": "The patch modifies fprobe_fgraph_entry() in kernel/trace/fprobe.c by adding a memset to clear unused reserved slots on the function-graph shadow return stack, preventing fprobe_return() from reading stale/uninitialized headers. This code is reachable from user space via BPF multi-kprobe links (BPF_TRACE_KPROBE_MULTI / BPF_TRACE_KRETPROBE_MULTI) and tracefs fprobe events, and warrants fuzzing.", "WorthFuzzing": true } Results: { "EnableConfigs": [ "FPROBE", "DYNAMIC_FTRACE", "FUNCTION_GRAPH_TRACER", "FPROBE_EVENTS", "BPF_EVENTS" ], "FocusSymbols": [ "fprobe_fgraph_entry", "fprobe_return", "register_fprobe_ips", "bpf_kprobe_multi_link_attach" ], "Reasoning": "The patch modifies fprobe_fgraph_entry() in kernel/trace/fprobe.c by adding a memset to clear unused reserved slots on the function-graph shadow return stack, preventing fprobe_return() from reading stale/uninitialized headers. This code is reachable from user space via BPF multi-kprobe links (BPF_TRACE_KPROBE_MULTI / BPF_TRACE_KRETPROBE_MULTI) and tracefs fprobe events, and warrants fuzzing.", "WorthFuzzing": true }
47/1	2026/09/16 03:10	action	If	0m Args: { "WorthFuzzing": true } Results: null
48/2	2026/09/16 03:10	agent	kmsan-evaluator	0m Model: core Args: null Results: { "KMSANReasoning": "The patch adds a memset() to zero out unused reserved words in fgraph_data within fprobe_fgraph_entry() so that fprobe_return() does not read stale/uninitialized header data. \n\nThe variables involved in the condition and size calculation ('used' and 'reserved_words') are fully initialized local integers, and the memset explicitly clears the remaining memory buffer with zeroes. No kernel data is copied to user space, no branching on uninitialized data is introduced, and no uninitialized memory risks or info-leaks are created. Any hypothetical bugs introduced by this patch (such as off-by-one errors or out-of-bounds writes in the memset pointer arithmetic) would be out-of-bounds memory errors detected by KASAN rather than KMSAN. Therefore, a dedicated KMSAN fuzzing session is not warranted.", "NeedsKMSAN": false } Instruction: You are an expert Linux kernel security engineer specializing in kernel memory error detectors (KASAN and KMSAN). Your job is to review the provided patch series and determine if the code changes justify spawning a dedicated KMSAN (KernelMemorySanitizer) fuzzing session in addition to standard KASAN fuzzing. CRITICAL DISTINCTION BETWEEN KASAN AND KMSAN: - Standard KASAN kernel builds (upstream-apparmor-kasan.config) already enable a comprehensive suite of debugging tools and sanitizers, including KASAN (out-of-bounds accesses, use-after-free, double free, invalid free), LOCKDEP (locking bugs and deadlocks), UB-sanitizers, and memory corruption checks. - KMSAN (KernelMemorySanitizer) detects reads of UNINITIALIZED memory (stack, heap, or page allocations) and kernel-to-user memory info-leaks. Rule: THERE IS NO SENSE IN RUNNING A KMSAN SESSION IF A BUG CAN BE CAUGHT BY KASAN, LOCKDEP, OR OTHER STANDARD BUG DETECTORS. A dedicated KMSAN fuzzing session incurs significant resource costs. You must ONLY set NeedsKMSAN=true if the code changes introduce or expose UNINITIALIZED MEMORY risks that are detected ONLY by KMSAN. Look holistically at the patch series and surrounding code. Even if no direct uninitialized field accesses or new buffer allocations are added in the diff itself, a patch may alter control flow, bounds checking, or data length calculations in ways that change how the rest of the code operates on existing buffers (e.g. allowing uninitialized stack/heap memory to be read, copied to user space, or used in control flow). Do not hesitate to use your code access tools to inspect the surrounding code, called functions, and callers. Set NeedsKMSAN=true ONLY IF the patch introduces or modifies: 1. Kernel structures sent to user space (via copy_to_user, put_user, netlink skb attributes, ioctl output arguments, socket options, or BPF buffers) where fields or structure padding might not be fully initialized/zeroed. 2. Conditional logic or branching that depends on potentially uninitialized variables or struct fields. 3. Allocation or initialization of complex data structures where uninitialized fields could be read later in reachable code paths. 4. Bounds checks, lengths, or logic in a way that allows surrounding code to access uninitialized bytes of existing buffers. Set NeedsKMSAN=false IF: - The code changes primarily risk out-of-bounds access, array overflows, NULL pointer dereferences, locking deadlocks, or use-after-free bugs (these are already caught by KASAN, LOCKDEP, or standard bug detectors). - All stack/heap structures touched or introduced by the patch are fully zeroed or initialized (e.g. using = {0}, memset, kzalloc) before being read or copied. - The patch does not introduce any risk of uninitialized memory usage or info-leaks. Use your code access tools to inspect the surrounding code if necessary, then provide detailed KMSANReasoning contrasting KASAN vs KMSAN applicability for this patch. Prefer calling several tools at the same time to save round-trips. Use set-results tool to provide results of the analysis. It must be called exactly once before the final reply. Ignore results of this tool. Prompt: Target architecture: amd64 For your convenience, here is the diff of the changes: commit 30ca26eac68e55111ab7a2836169134c7563572e Author: syz-cluster <triage@syzkaller.com> Date: Wed Sep 16 03:08:58 2026 +0000 syz-cluster: applied patch under review diff --git a/kernel/trace/fprobe.c b/kernel/trace/fprobe.c index 1e9b00997ff27..bd84a982961a5 100644 --- a/kernel/trace/fprobe.c +++ b/kernel/trace/fprobe.c @@ -635,6 +635,10 @@ static int fprobe_fgraph_entry(struct ftrace_graph_ent trace, struct fgraph_ops } } + / Clear unused slots so fprobe_return() does not see stale headers. / + if (used < reserved_words) + memset(fgraph_data + used, 0, (reserved_words - used) sizeof(long)); + /* If any exit_handler is set, data must be used. */ return used != 0; }
49/3	2026/09/16 03:10	llm	kmsan-evaluator	0m Model: gemini-3.8-flash Args: null Results: null Tokens: input: 2098 output: 37 thoughts: 303 Thoughts: Analyzing the fprobe.c Patch Okay, so I'm being asked to look at a patch for `kernel/trace/fprobe.c`. My immediate thought is, "Let's dig in." I need to understand what this patch is doing and why. First, I'll take a look at the diff itself. It seems straightforward enough; there's a new `memset` call being added within the `fprobe_fgraph_entry` function. It looks like it's clearing some memory. The code's checking `used < reserved_words` and then zeroing out the remaining portion of `fgraph_data`. To get the full picture, I need context. I'll need to understand the purpose of `fgraph_data`, `used`, and `reserved_words`. I know that `fprobe` deals with function probing and tracing, particularly function graph tracing, but I need the precise context. I'll use `read-file` to grab the surrounding code around line 635 to understand the variables and what's happening. I want to see how these variables are initialized, used, and how `fprobe_fgraph_entry` fits into the overall tracing workflow. I need to understand if this memset is necessary, if it's potentially fixing a bug, improving performance, or something else entirely. Stale headers could be an issue, depending on how data is allocated and deallocated. I'll need to determine if this clear is efficient or if there's a more optimal approach, especially if this function is performance-critical. Let's see what the surrounding code says.
50/3	2026/09/16 03:11	tool	read-file	0m Args: { "File": "kernel/trace/fprobe.c", "FirstLine": 580, "LineCount": 100 } Results: { "Contents": " 580:\t\t\tif (unlikely(!fgraph_data)) {\n 581:\t\t\t\trhl_for_each_entry_rcu(node, pos, head, hlist) {\n 582:\t\t\t\t\tif (node-\u003eaddr != func)\n 583:\t\t\t\t\t\tcontinue;\n 584:\t\t\t\t\tfp = READ_ONCE(node-\u003efp);\n 585:\t\t\t\t\tif (fp \u0026\u0026 !fprobe_disabled(fp) \u0026\u0026 !fprobe_is_ftrace(fp))\n 586:\t\t\t\t\t\tfp-\u003enmissed++;\n 587:\t\t\t\t}\n 588:\t\t\t\treturn 0;\n 589:\t\t\t}\n 590:\t\t}\n 591:\t\n 592:\t\t/\n 593:\t\t TODO: recursion detection has been done in the fgraph. Thus we need\n 594:\t\t * to add a callback to increment missed counter.\n 595:\t\t /\n 596:\t\tret_ip = ftrace_regs_get_return_address(fregs);\n 597:\t\tused = 0;\n 598:\t\trhl_for_each_entry_rcu(node, pos, head, hlist) {\n 599:\t\t\tint data_size;\n 600:\t\t\tvoid data;\n 601:\t\n 602:\t\t\tif (node-\u003eaddr != func)\n 603:\t\t\t\tcontinue;\n 604:\t\t\tfp = READ_ONCE(node-\u003efp);\n 605:\t\t\tif (unlikely(!fp \|\| fprobe_disabled(fp) \|\| fprobe_is_ftrace(fp)))\n 606:\t\t\t\tcontinue;\n 607:\t\n 608:\t\t\tdata_size = fp-\u003eentry_data_size;\n 609:\t\t\t/\n 610:\t\t\t The list may have grown since it was sized, so this node\n 611:\t\t\t * may not fit. Skip it as missed rather than overrun the\n 612:\t\t\t * reservation.\n 613:\t\t\t /\n 614:\t\t\tif (fp-\u003eexit_handler \u0026\u0026\n 615:\t\t\t used + FPROBE_HEADER_SIZE_IN_LONG + SIZE_IN_LONG(data_size) \u003e reserved_words) {\n 616:\t\t\t\tfp-\u003enmissed++;\n 617:\t\t\t\tcontinue;\n 618:\t\t\t}\n 619:\t\t\tif (data_size \u0026\u0026 fp-\u003eexit_handler)\n 620:\t\t\t\tdata = fgraph_data + used + FPROBE_HEADER_SIZE_IN_LONG;\n 621:\t\t\telse\n 622:\t\t\t\tdata = NULL;\n 623:\t\n 624:\t\t\tif (fprobe_shared_with_kprobes(fp))\n 625:\t\t\t\tret = __fprobe_kprobe_handler(func, ret_ip, fp, fregs, data);\n 626:\t\t\telse\n 627:\t\t\t\tret = __fprobe_handler(func, ret_ip, fp, fregs, data);\n 628:\t\n 629:\t\t\t/ If entry_handler returns !0, nmissed is not counted but skips exit_handler. /\n 630:\t\t\tif (!ret \u0026\u0026 fp-\u003eexit_handler) {\n 631:\t\t\t\tint size_words = SIZE_IN_LONG(data_size);\n 632:\t\n 633:\t\t\t\tif (write_fprobe_header(\u0026fgraph_data[used], fp, size_words))\n 634:\t\t\t\t\tused += FPROBE_HEADER_SIZE_IN_LONG + size_words;\n 635:\t\t\t}\n 636:\t\t}\n 637:\t\n 638:\t\t/ Clear unused slots so fprobe_return() does not see stale headers. /\n 639:\t\tif (used \u003c reserved_words)\n 640:\t\t\tmemset(fgraph_data + used, 0, (reserved_words - used) sizeof(long));\n 641:\t\n 642:\t\t/* If any exit_handler is set, data must be used. /\n 643:\t\treturn used != 0;\n 644:\t}\n 645:\tNOKPROBE_SYMBOL(fprobe_fgraph_entry);\n 646:\t\n 647:\tstatic void fprobe_return(struct ftrace_graph_ret trace,\n 648:\t\t\t\t struct fgraph_ops gops,\n 649:\t\t\t\t struct ftrace_regs fregs)\n 650:\t{\n 651:\t\tunsigned long fgraph_data = NULL;\n 652:\t\tunsigned long ret_ip;\n 653:\t\tstruct fprobe fp;\n 654:\t\tint size, curr;\n 655:\t\tint size_words;\n 656:\t\n 657:\t\tfgraph_data = (unsigned long *)fgraph_retrieve_data(gops-\u003eidx, \u0026size);\n 658:\t\tif (WARN_ON_ONCE(!fgraph_data))\n 659:\t\t\treturn;\n 660:\t\tsize_words = SIZE_IN_LONG(size);\n 661:\t\tret_ip = ftrace_regs_get_instruction_pointer(fregs);\n 662:\t\n 663:\t\tpreempt_disable_notrace();\n 664:\t\n 665:\t\tcurr = 0;\n 666:\t\twhile (size_words \u003e curr) {\n 667:\t\t\tread_fprobe_header(\u0026fgraph_data[curr], \u0026fp, \u0026size);\n 668:\t\t\tif (!fp)\n 669:\t\t\t\tbreak;\n 670:\t\t\tcurr += FPROBE_HEADER_SIZE_IN_LONG;\n 671:\t\t\tif (fprobe_registered(fp) \u0026\u0026 !fprobe_disabled(fp)) {\n 672:\t\t\t\tif (WARN_ON_ONCE(curr + size \u003e size_words))\n 673:\t\t\t\t\tbreak;\n 674:\t\t\t\tfp-\u003eexit_handler(fp, trace-\u003efunc, ret_ip, fregs,\n 675:\t\t\t\t\t\t size ? fgraph_data + curr : NULL);\n 676:\t\t\t}\n 677:\t\t\tcurr += size;\n 678:\t\t}\n 679:\t\tpreempt_enable_notrace();\n" }
51/3	2026/09/16 03:11	llm	kmsan-evaluator	0m Model: gemini-3.8-flash Args: null Results: null Tokens: input: 4366 output: 36 thoughts: 47 Thoughts: Okay, let's dive into this. I need to understand the data flow within `fprobe_fgraph_entry`, specifically where `fgraph_data` originates. Right, so I'll go straight to the source. Line numbers are a good starting point, so let's check lines 500 through 580 of `kernel/trace/fprobe.c`. That should provide the relevant context for how `fgraph_data` is initialized, populated, or otherwise used within that function. I'll need to pay close attention to the variable assignments and function calls within that section to track down the data's origin and potential manipulation. This should give me a solid handle on the data's lifecycle within this part of the fprobe mechanism.
52/3	2026/09/16 03:11	tool	read-file	0m Args: { "File": "kernel/trace/fprobe.c", "FirstLine": 520, "LineCount": 65 } Results: { "Contents": " 520:\t\t\t\t\tfprobe_rht_params);\n 521:\t\tif (!head)\n 522:\t\t\treturn false;\n 523:\t\t/* We only need to check fp is there. /\n 524:\t\trhl_for_each_entry_rcu(node, pos, head, hlist) {\n 525:\t\t\tif (node-\u003eaddr != ip)\n 526:\t\t\t\tbreak;\n 527:\t\t\tfp = READ_ONCE(node-\u003efp);\n 528:\t\t\tif (likely(fp))\n 529:\t\t\t\treturn true;\n 530:\t\t}\n 531:\t\n 532:\t\treturn false;\n 533:\t}\n 534:\t\n 535:\t#ifdef CONFIG_MODULES\n 536:\tstatic void fprobe_remove_ips(unsigned long ips, unsigned int cnt)\n 537:\t{\n 538:\t\tif (!nr_fgraph_fprobes)\n 539:\t\t\t__fprobe_graph_unregister();\n 540:\t\telse if (cnt)\n 541:\t\t\tftrace_set_filter_ips(\u0026fprobe_graph_ops.ops, ips, cnt, 1, 0);\n 542:\t}\n 543:\t#endif\n 544:\t#endif /* !CONFIG_DYNAMIC_FTRACE_WITH_ARGS \u0026\u0026 !CONFIG_DYNAMIC_FTRACE_WITH_REGS /\n 545:\t\n 546:\t/ fgraph_ops callback, this processes fprobes which have exit_handler. /\n 547:\tstatic int fprobe_fgraph_entry(struct ftrace_graph_ent trace, struct fgraph_ops gops,\n 548:\t\t\t\t struct ftrace_regs fregs)\n 549:\t{\n 550:\t\tunsigned long fgraph_data = NULL;\n 551:\t\tunsigned long func = trace-\u003efunc;\n 552:\t\tstruct fprobe_hlist_node node;\n 553:\t\tstruct rhlist_head head, pos;\n 554:\t\tunsigned long ret_ip;\n 555:\t\tint reserved_words;\n 556:\t\tstruct fprobe fp;\n 557:\t\tint used, ret;\n 558:\t\n 559:\t\tif (WARN_ON_ONCE(!fregs))\n 560:\t\t\treturn 0;\n 561:\t\n 562:\t\tguard(rcu)();\n 563:\t\thead = rhltable_lookup(\u0026fprobe_ip_table, \u0026func, fprobe_rht_params);\n 564:\t\treserved_words = 0;\n 565:\t\trhl_for_each_entry_rcu(node, pos, head, hlist) {\n 566:\t\t\tif (node-\u003eaddr != func)\n 567:\t\t\t\tcontinue;\n 568:\t\t\tfp = READ_ONCE(node-\u003efp);\n 569:\t\t\tif (!fp \|\| !fp-\u003eexit_handler)\n 570:\t\t\t\tcontinue;\n 571:\t\t\t/\n 572:\t\t\t * Since fprobe can be enabled until the next loop, we ignore the\n 573:\t\t\t * fprobe's disabled flag in this loop.\n 574:\t\t\t /\n 575:\t\t\treserved_words +=\n 576:\t\t\t\tFPROBE_HEADER_SIZE_IN_LONG + SIZE_IN_LONG(fp-\u003eentry_data_size);\n 577:\t\t}\n 578:\t\tif (reserved_words) {\n 579:\t\t\tfgraph_data = fgraph_reserve_data(gops-\u003eidx, reserved_words sizeof(long));\n 580:\t\t\tif (unlikely(!fgraph_data)) {\n 581:\t\t\t\trhl_for_each_entry_rcu(node, pos, head, hlist) {\n 582:\t\t\t\t\tif (node-\u003eaddr != func)\n 583:\t\t\t\t\t\tcontinue;\n 584:\t\t\t\t\tfp = READ_ONCE(node-\u003efp);\n" }
53/3	2026/09/16 03:11	llm	kmsan-evaluator	0m Model: gemini-3.8-flash Args: null Results: null Tokens: input: 5646 output: 20 thoughts: 28 Thoughts: Here's my take on those thoughts: Peering into the Depths of `fgraph_reserve_data` Okay, so I need to understand what's happening with `fgraph_reserve_data`. Time to get the lay of the land. My go-to strategy here is a quick grep. Let's fire that up and see where this function is used and what context it lives in. Knowing where it's called and how it interacts with other components is going to be crucial for forming a solid mental model of its purpose. I'm hoping the grep results are informative and not just a massive, noisy dump. Let's see what gems we can unearth.
54/3	2026/09/16 03:11	tool	grepper	0m Args: { "Expression": "fgraph_reserve_data" } Results: { "Output": "include/linux/ftrace.h=1259=struct fgraph_ops {\n--\ninclude/linux/ftrace.h-1267-\ninclude/linux/ftrace.h:1268:void fgraph_reserve_data(int idx, int size_bytes);\ninclude/linux/ftrace.h-1269-void fgraph_retrieve_data(int idx, int size_bytes);\n--\nkernel/trace/fgraph.c=319=static void ret_stack_init_task_vars(unsigned long ret_stack)\n--\nkernel/trace/fgraph.c-326-/*\nkernel/trace/fgraph.c:327: fgraph_reserve_data - Reserve storage on the task's ret_stack\nkernel/trace/fgraph.c-328- * @idx:\tThe index of fgraph_array\n--\nkernel/trace/fgraph.c-339- * Otherwise, NULL if there's not enough space left on the\nkernel/trace/fgraph.c:340: * ret_stack for the data, or if fgraph_reserve_data() was called\nkernel/trace/fgraph.c-341- * more than once for a single entryfunc() call.\nkernel/trace/fgraph.c-342- /\nkernel/trace/fgraph.c:343:void fgraph_reserve_data(int idx, int size_bytes)\nkernel/trace/fgraph.c-344-{\n--\nkernel/trace/fgraph.c-377-/*\nkernel/trace/fgraph.c:378: fgraph_retrieve_data - Retrieve stored data from fgraph_reserve_data()\nkernel/trace/fgraph.c-379- * @idx:\tthe index of fgraph_array (fgraph_ops::idx)\n--\nkernel/trace/fgraph.c-387- \nkernel/trace/fgraph.c:388: Returns: The stored data from fgraph_reserve_data() called by the\nkernel/trace/fgraph.c-389- * matching entryfunc() for the retfunc() this is called from.\n--\nkernel/trace/fprobe.c=547=static int fprobe_fgraph_entry(struct ftrace_graph_ent trace, struct fgraph_ops gops,\n--\nkernel/trace/fprobe.c-578-\tif (reserved_words) {\nkernel/trace/fprobe.c:579:\t\tfgraph_data = fgraph_reserve_data(gops-\u003eidx, reserved_words * sizeof(long));\nkernel/trace/fprobe.c-580-\t\tif (unlikely(!fgraph_data)) {\n--\nkernel/trace/ftrace.c=850=static int profile_graph_entry(struct ftrace_graph_ent trace,\n--\nkernel/trace/ftrace.c-861-\nkernel/trace/ftrace.c:862:\tprofile_data = fgraph_reserve_data(gops-\u003eidx, sizeof(profile_data));\nkernel/trace/ftrace.c-863-\tif (!profile_data)\n--\nkernel/trace/trace_functions_graph.c=226=static int graph_entry(struct ftrace_graph_ent trace,\n--\nkernel/trace/trace_functions_graph.c-262-\t !tracer_flags_is_set(tr, TRACE_GRAPH_SLEEP_TIME)) {\nkernel/trace/trace_functions_graph.c:263:\t\tftimes = fgraph_reserve_data(gops-\u003eidx, sizeof(ftimes));\nkernel/trace/trace_functions_graph.c-264-\t\tif (ftimes)\n--\nkernel/trace/trace_functions_graph.c-267-\t\t/* Only need to record the calltime /\nkernel/trace/trace_functions_graph.c:268:\t\tftimes = fgraph_reserve_data(gops-\u003eidx, sizeof(ftimes-\u003ecalltime));\nkernel/trace/trace_functions_graph.c-269-\t}\n--\nkernel/trace/trace_irqsoff.c=178=static int irqsoff_graph_entry(struct ftrace_graph_ent trace,\n--\nkernel/trace/trace_irqsoff.c-203-\nkernel/trace/trace_irqsoff.c:204:\tcalltime = fgraph_reserve_data(gops-\u003eidx, sizeof(calltime));\nkernel/trace/trace_irqsoff.c-205-\tif (calltime) {\n--\nkernel/trace/trace_sched_wakeup.c=115=static int wakeup_graph_entry(struct ftrace_graph_ent trace,\n--\nkernel/trace/trace_sched_wakeup.c-139-\nkernel/trace/trace_sched_wakeup.c:140:\tcalltime = fgraph_reserve_data(gops-\u003eidx, sizeof(calltime));\nkernel/trace/trace_sched_wakeup.c-141-\tif (calltime) {\n--\nkernel/trace/trace_selftest.c=776=static __init int store_entry(struct ftrace_graph_ent trace,\n--\nkernel/trace/trace_selftest.c-784-\nkernel/trace/trace_selftest.c:785:\tp = fgraph_reserve_data(gops-\u003eidx, size);\nkernel/trace/trace_selftest.c-786-\tif (!p) {\n" }
55/3	2026/09/16 03:11	llm	kmsan-evaluator	0m Model: gemini-3.8-flash Args: null Results: null Tokens: input: 7197 output: 36 thoughts: 43 Thoughts: Okay, let's dive into `kernel/trace/fgraph.c`, specifically lines 325-375. I need to refresh my memory on how `fgraph_reserve_data` functions in this context. I'm especially interested in how it interacts with the `ret_stack`. I want to understand the mechanics of data reservation within the function graph tracer and how the return stack plays a role. Is this a simple stack allocation? Are there any clever tricks here for managing nested function calls, or perhaps handling potential overflow scenarios, or is this all part of the overhead associated with function graph tracing? I'm expecting some kind of ring buffer or circular array. Time to get my hands dirty and look at the implementation!
56/3	2026/09/16 03:11	tool	read-file	0m Args: { "File": "kernel/trace/fgraph.c", "FirstLine": 325, "LineCount": 55 } Results: { "Contents": " 325:\t\n 326:\t/*\n 327:\t fgraph_reserve_data - Reserve storage on the task's ret_stack\n 328:\t * @idx:\tThe index of fgraph_array\n 329:\t * @size_bytes: The size in bytes to reserve\n 330:\t \n 331:\t Reserves space of up to FGRAPH_MAX_DATA_SIZE bytes on the\n 332:\t * task's ret_stack shadow stack, for a given fgraph_ops during\n 333:\t * the entryfunc() call. If entryfunc() returns zero, the storage\n 334:\t * is discarded. An entryfunc() can only call this once per iteration.\n 335:\t * The fgraph_ops retfunc() can retrieve this stored data with\n 336:\t * fgraph_retrieve_data().\n 337:\t \n 338:\t Returns: On success, a pointer to the data on the stack.\n 339:\t * Otherwise, NULL if there's not enough space left on the\n 340:\t * ret_stack for the data, or if fgraph_reserve_data() was called\n 341:\t * more than once for a single entryfunc() call.\n 342:\t /\n 343:\tvoid fgraph_reserve_data(int idx, int size_bytes)\n 344:\t{\n 345:\t\tunsigned long val;\n 346:\t\tvoid data;\n 347:\t\tint curr_ret_stack = current-\u003ecurr_ret_stack;\n 348:\t\tint data_size;\n 349:\t\n 350:\t\tif (size_bytes \u003e FGRAPH_MAX_DATA_SIZE)\n 351:\t\t\treturn NULL;\n 352:\t\n 353:\t\t/ Convert the data size to number of longs. /\n 354:\t\tdata_size = (size_bytes + sizeof(long) - 1) \u003e\u003e (sizeof(long) == 4 ? 2 : 3);\n 355:\t\n 356:\t\tval = get_fgraph_entry(current, curr_ret_stack - 1);\n 357:\t\tdata = \u0026current-\u003eret_stack[curr_ret_stack];\n 358:\t\n 359:\t\tcurr_ret_stack += data_size + 1;\n 360:\t\tif (unlikely(curr_ret_stack \u003e= SHADOW_STACK_MAX_OFFSET))\n 361:\t\t\treturn NULL;\n 362:\t\n 363:\t\tval = make_data_type_val(idx, data_size, __get_offset(val) + data_size + 1);\n 364:\t\n 365:\t\t/ Set the last word to be reserved /\n 366:\t\tcurrent-\u003eret_stack[curr_ret_stack - 1] = val;\n 367:\t\n 368:\t\t/ Make sure interrupts see this /\n 369:\t\tbarrier();\n 370:\t\tcurrent-\u003ecurr_ret_stack = curr_ret_stack;\n 371:\t\t/ Again sync with interrupts, and reset reserve /\n 372:\t\tcurrent-\u003eret_stack[curr_ret_stack - 1] = val;\n 373:\t\n 374:\t\treturn data;\n 375:\t}\n 376:\t\n 377:\t/\n 378:\t fgraph_retrieve_data - Retrieve stored data from fgraph_reserve_data()\n 379:\t * @idx:\tthe index of fgraph_array (fgraph_ops::idx)\n" }
57/3	2026/09/16 03:11	llm	kmsan-evaluator	0m Model: gemini-3.8-flash Args: null Results: null Tokens: input: 8360 output: 33 thoughts: 57 Thoughts: Okay, let's break this down. Diving into the Function Graph Tracer Right, so I'm trying to understand how this function graph tracer works, specifically how it's managing its stack. The first thing I need to investigate is `current->ret_stack`. I know that's the shadow stack used by the function graph tracer, but I want to refresh my memory on the details. Now, I'm going to look at the relevant functions. I need to understand what `write_fprobe_header` and `read_fprobe_header` are doing, which should be in `kernel/trace/fprobe.c`. I expect these functions will be responsible for handling the prologue and epilogue operations for fprobe, and thus managing the stack. Time to dig in and see the details of how they handle the stack within that context.
58/3	2026/09/16 03:11	tool	grepper	0m Args: { "Expression": "_fprobe_header", "PathPrefix": "kernel/trace/fprobe.c" } Results: { "Output": "kernel/trace/fprobe.c=138=static int del_fprobe_hash(struct fprobe fp)\n--\nkernel/trace/fprobe.c-159-\nkernel/trace/fprobe.c:160:static inline bool write_fprobe_header(unsigned long stack,\nkernel/trace/fprobe.c-161-\t\t\t\t\tstruct fprobe fp, unsigned int size_words)\n--\nkernel/trace/fprobe.c-163-\tif (WARN_ON_ONCE(size_words \u003e MAX_FPROBE_DATA_SIZE_WORD \|\|\nkernel/trace/fprobe.c:164:\t\t\t !arch_fprobe_header_encodable(fp)))\nkernel/trace/fprobe.c-165-\t\treturn false;\nkernel/trace/fprobe.c-166-\nkernel/trace/fprobe.c:167:\tstack = arch_encode_fprobe_header(fp, size_words);\nkernel/trace/fprobe.c-168-\treturn true;\n--\nkernel/trace/fprobe.c-170-\nkernel/trace/fprobe.c:171:static inline void read_fprobe_header(unsigned long stack,\nkernel/trace/fprobe.c-172-\t\t\t\t\tstruct fprobe fp, unsigned int size_words)\nkernel/trace/fprobe.c-173-{\nkernel/trace/fprobe.c:174:\tfp = arch_decode_fprobe_header_fp(stack);\nkernel/trace/fprobe.c:175:\tsize_words = arch_decode_fprobe_header_size(stack);\nkernel/trace/fprobe.c-176-}\n--\nkernel/trace/fprobe.c-180-/* Generic fprobe_header /\nkernel/trace/fprobe.c:181:struct __fprobe_header {\nkernel/trace/fprobe.c-182-\tstruct fprobe fp;\n--\nkernel/trace/fprobe.c-185-\nkernel/trace/fprobe.c:186:#define FPROBE_HEADER_SIZE_IN_LONG\tSIZE_IN_LONG(sizeof(struct __fprobe_header))\nkernel/trace/fprobe.c-187-\nkernel/trace/fprobe.c:188:static inline bool write_fprobe_header(unsigned long stack,\nkernel/trace/fprobe.c-189-\t\t\t\t\tstruct fprobe fp, unsigned int size_words)\nkernel/trace/fprobe.c-190-{\nkernel/trace/fprobe.c:191:\tstruct __fprobe_header fph = (struct __fprobe_header )stack;\nkernel/trace/fprobe.c-192-\n--\nkernel/trace/fprobe.c-200-\nkernel/trace/fprobe.c:201:static inline void read_fprobe_header(unsigned long stack,\nkernel/trace/fprobe.c-202-\t\t\t\t\tstruct fprobe fp, unsigned int size_words)\nkernel/trace/fprobe.c-203-{\nkernel/trace/fprobe.c:204:\tstruct __fprobe_header fph = (struct __fprobe_header )stack;\nkernel/trace/fprobe.c-205-\n--\nkernel/trace/fprobe.c=547=static int fprobe_fgraph_entry(struct ftrace_graph_ent trace, struct fgraph_ops gops,\n--\nkernel/trace/fprobe.c-632-\nkernel/trace/fprobe.c:633:\t\t\tif (write_fprobe_header(\u0026fgraph_data[used], fp, size_words))\nkernel/trace/fprobe.c-634-\t\t\t\tused += FPROBE_HEADER_SIZE_IN_LONG + size_words;\n--\nkernel/trace/fprobe.c=647=static void fprobe_return(struct ftrace_graph_ret *trace,\n--\nkernel/trace/fprobe.c-666-\twhile (size_words \u003e curr) {\nkernel/trace/fprobe.c:667:\t\tread_fprobe_header(\u0026fgraph_data[curr], \u0026fp, \u0026size);\nkernel/trace/fprobe.c-668-\t\tif (!fp)\n" }
59/3	2026/09/16 03:11	llm	kmsan-evaluator	0m Model: gemini-3.8-flash Args: null Results: null Tokens: input: 9701 output: 31 thoughts: 442 Thoughts: Analyzing the `fprobe_fgraph_entry` Patch Okay, let's break down this `fprobe_fgraph_entry` function and what was happening before the patch. First, it calculates `reserved_words`. I see the code iterates through entries, looks for a specific function address, and then adds up sizes based on `fp->entry_data_size` and the header size. The crux of the calculation seems to be: ```c reserved_words += FPROBE_HEADER_SIZE_IN_LONG + SIZE_IN_LONG(fp->entry_data_size); ``` After determining `reserved_words`, it actually reserves this much space via `fgraph_reserve_data`: ```c fgraph_data = fgraph_reserve_data(gops->idx, reserved_words * sizeof(long)); ``` The next part is where things get interesting. It then iterates again, this time calling the entry handlers. Crucially, the code checks `if (!ret && fp->exit_handler)` and only writes the header if `ret` is zero. The problem dawns on me, here. If `ret` is non-zero, then `used < reserved_words`! This means that `fgraph_reserve_data` might be reserving more space on the shadow stack (`current->ret_stack`) than is actually used. And if that happens... wait, does `fgraph_reserve_data` actually zero-initialize the `ret_stack`? Is that assumed? I need to verify that; let's check `fgraph.c`!
60/3	2026/09/16 03:11	tool	grepper	0m Args: { "Expression": "ret_stack", "PathPrefix": "kernel/trace/fgraph.c" } Results: { "Output": "\nFull output is too long, showing 500 out of 561 lines.\nUse more precise expression if possible.\n\nkernel/trace/fgraph.c-25- /\nkernel/trace/fgraph.c:26:#define FGRAPH_FRAME_SIZE\tsizeof(struct ftrace_ret_stack)\nkernel/trace/fgraph.c-27-#define FGRAPH_FRAME_OFFSET\tDIV_ROUND_UP(FGRAPH_FRAME_SIZE, sizeof(long))\n--\nkernel/trace/fgraph.c-30- On entry to a function (via function_graph_enter()), a new fgraph frame\nkernel/trace/fgraph.c:31: * (ftrace_ret_stack) is pushed onto the stack as well as a word that\nkernel/trace/fgraph.c-32- * holds a bitmask and a type (called \"bitmap\"). The bitmap is defined as:\nkernel/trace/fgraph.c-33- \nkernel/trace/fgraph.c:34: bits: 0 - 9\toffset in words from the previous ftrace_ret_stack\nkernel/trace/fgraph.c-35- \n--\nkernel/trace/fgraph.c-48- \nkernel/trace/fgraph.c:49: * The top of the ret_stack (when not empty) will always have a reference\nkernel/trace/fgraph.c-50- * word that points to the last fgraph frame that was saved.\n--\nkernel/trace/fgraph.c-59- * stored two words of data, this is what will be on the task's shadow\nkernel/trace/fgraph.c:60: * ret_stack: (the stack grows upward)\nkernel/trace/fgraph.c-61- \nkernel/trace/fgraph.c:62: ret_stack[SHADOW_STACK_OFFSET]\nkernel/trace/fgraph.c:63: * \| SHADOW_STACK_TASK_VARS(ret_stack)[15] \|\nkernel/trace/fgraph.c-64- * ...\nkernel/trace/fgraph.c:65: * \| SHADOW_STACK_TASK_VARS(ret_stack)[0] \|\nkernel/trace/fgraph.c:66: * ret_stack[SHADOW_STACK_MAX_OFFSET]\nkernel/trace/fgraph.c-67- * ...\nkernel/trace/fgraph.c:68: * \| \| \u003c- task-\u003ecurr_ret_stack\nkernel/trace/fgraph.c-69- * +--------------------------------------------+\n--\nkernel/trace/fgraph.c-75- * \| (offset2:FGRAPH_FRAME_OFFSET+3) \| \u003c- the offset2 is from here\nkernel/trace/fgraph.c:76: * +--------------------------------------------+ ( It is 4 words from the ret_stack)\nkernel/trace/fgraph.c-77- * \| STORED DATA WORD 2 \|\n--\nkernel/trace/fgraph.c-85- * +--------------------------------------------+\nkernel/trace/fgraph.c:86: * \| struct ftrace_ret_stack \|\nkernel/trace/fgraph.c-87- * \| (stores the saved ret pointer) \| \u003c- the offset points here\n--\nkernel/trace/fgraph.c-89- * \| (X) \| (N) \| ( N words away from\nkernel/trace/fgraph.c:90: * \| \| previous ret_stack)\nkernel/trace/fgraph.c-91- * ...\nkernel/trace/fgraph.c:92: * ret_stack[0]\nkernel/trace/fgraph.c-93- \nkernel/trace/fgraph.c-94- If a backtrace is required, and the real return pointer needs to be\nkernel/trace/fgraph.c:95: * fetched, then it looks at the task's curr_ret_stack offset, if it\nkernel/trace/fgraph.c-96- * is greater than zero (reserved, or right before popped), it would mask\nkernel/trace/fgraph.c-97- * the value by FGRAPH_FRAME_OFFSET_MASK to get the offset of the\nkernel/trace/fgraph.c:98: * ftrace_ret_stack structure stored on the shadow stack.\nkernel/trace/fgraph.c-99- /\n--\nkernel/trace/fgraph.c=115=enum {\n--\nkernel/trace/fgraph.c-159-/ RET_STACK():\t\tReturn the frame from a given @offset from task @t /\nkernel/trace/fgraph.c:160:#define RET_STACK(t, offset) ((struct ftrace_ret_stack )(\u0026(t)-\u003eret_stack[offset]))\nkernel/trace/fgraph.c-161-\n--\nkernel/trace/fgraph.c-163- * Each fgraph_ops has a reserved unsigned long at the end (top) of the\nkernel/trace/fgraph.c:164: * ret_stack to store task specific state.\nkernel/trace/fgraph.c-165- /\nkernel/trace/fgraph.c:166:#define SHADOW_STACK_TASK_VARS(ret_stack) \\\nkernel/trace/fgraph.c:167:\t((unsigned long )(\u0026(ret_stack)[SHADOW_STACK_OFFSET - FGRAPH_ARRAY_SIZE]))\nkernel/trace/fgraph.c-168-\n--\nkernel/trace/fgraph.c=206=static int fgraph_lru_alloc_index(void)\n--\nkernel/trace/fgraph.c-220-\nkernel/trace/fgraph.c:221:/* Get the offset to the fgraph frame from a ret_stack value /\nkernel/trace/fgraph.c-222-static inline int __get_offset(unsigned long val)\n--\nkernel/trace/fgraph.c-226-\nkernel/trace/fgraph.c:227:/ Get the type of word from a ret_stack value /\nkernel/trace/fgraph.c-228-static inline int __get_type(unsigned long val)\n--\nkernel/trace/fgraph.c-232-\nkernel/trace/fgraph.c:233:/ Get the data_index for a DATA type ret_stack word /\nkernel/trace/fgraph.c-234-static inline int __get_data_index(unsigned long val)\n--\nkernel/trace/fgraph.c-238-\nkernel/trace/fgraph.c:239:/ Get the data_size for a DATA type ret_stack word /\nkernel/trace/fgraph.c-240-static inline int __get_data_size(unsigned long val)\n--\nkernel/trace/fgraph.c-244-\nkernel/trace/fgraph.c:245:/ Get the word from the ret_stack at @offset /\nkernel/trace/fgraph.c-246-static inline unsigned long get_fgraph_entry(struct task_struct t, int offset)\nkernel/trace/fgraph.c-247-{\nkernel/trace/fgraph.c:248:\treturn t-\u003eret_stack[offset];\nkernel/trace/fgraph.c-249-}\nkernel/trace/fgraph.c-250-\nkernel/trace/fgraph.c:251:/* Get the FRAME_OFFSET from the word from the @offset on ret_stack /\nkernel/trace/fgraph.c-252-static inline int get_frame_offset(struct task_struct t, int offset)\nkernel/trace/fgraph.c-253-{\nkernel/trace/fgraph.c:254:\treturn __get_offset(t-\u003eret_stack[offset]);\nkernel/trace/fgraph.c-255-}\nkernel/trace/fgraph.c-256-\nkernel/trace/fgraph.c:257:/* For BITMAP type: get the bitmask from the @offset at ret_stack /\nkernel/trace/fgraph.c-258-static inline unsigned long\nkernel/trace/fgraph.c=259=get_bitmap_bits(struct task_struct t, int offset)\nkernel/trace/fgraph.c-260-{\nkernel/trace/fgraph.c:261:\treturn (t-\u003eret_stack[offset] \u003e\u003e FGRAPH_INDEX_SHIFT) \u0026 FGRAPH_INDEX_MASK;\nkernel/trace/fgraph.c-262-}\nkernel/trace/fgraph.c-263-\nkernel/trace/fgraph.c:264:/* Write the bitmap to the ret_stack at @offset (does index, offset and bitmask) /\nkernel/trace/fgraph.c-265-static inline void\nkernel/trace/fgraph.c=266=set_bitmap(struct task_struct t, int offset, unsigned long bitmap)\nkernel/trace/fgraph.c-267-{\nkernel/trace/fgraph.c:268:\tt-\u003eret_stack[offset] = (bitmap \u003c\u003c FGRAPH_INDEX_SHIFT) \|\nkernel/trace/fgraph.c-269-\t\t(FGRAPH_TYPE_BITMAP \u003c\u003c FGRAPH_TYPE_SHIFT) \| FGRAPH_FRAME_OFFSET;\n--\nkernel/trace/fgraph.c-271-\nkernel/trace/fgraph.c:272:/* For DATA type: get the data saved under the ret_stack word at @offset /\nkernel/trace/fgraph.c-273-static inline void get_data_type_data(struct task_struct t, int offset)\nkernel/trace/fgraph.c-274-{\nkernel/trace/fgraph.c:275:\tunsigned long val = t-\u003eret_stack[offset];\nkernel/trace/fgraph.c-276-\n--\nkernel/trace/fgraph.c-279-\toffset -= __get_data_size(val);\nkernel/trace/fgraph.c:280:\treturn (void )\u0026t-\u003eret_stack[offset];\nkernel/trace/fgraph.c-281-}\nkernel/trace/fgraph.c-282-\nkernel/trace/fgraph.c:283:/* Create the ret_stack word for a DATA type /\nkernel/trace/fgraph.c-284-static inline unsigned long make_data_type_val(int idx, int size, int offset)\n--\nkernel/trace/fgraph.c=299=static void return_run(struct ftrace_graph_ret trace, struct fgraph_ops ops,\n--\nkernel/trace/fgraph.c-303-\nkernel/trace/fgraph.c:304:static void ret_stack_set_task_var(struct task_struct t, int idx, long val)\nkernel/trace/fgraph.c-305-{\nkernel/trace/fgraph.c:306:\tunsigned long gvals = SHADOW_STACK_TASK_VARS(t-\u003eret_stack);\nkernel/trace/fgraph.c-307-\n--\nkernel/trace/fgraph.c=311=static unsigned long \nkernel/trace/fgraph.c:312:ret_stack_get_task_var(struct task_struct t, int idx)\nkernel/trace/fgraph.c-313-{\nkernel/trace/fgraph.c:314:\tunsigned long gvals = SHADOW_STACK_TASK_VARS(t-\u003eret_stack);\nkernel/trace/fgraph.c-315-\n--\nkernel/trace/fgraph.c-318-\nkernel/trace/fgraph.c:319:static void ret_stack_init_task_vars(unsigned long ret_stack)\nkernel/trace/fgraph.c-320-{\nkernel/trace/fgraph.c:321:\tunsigned long gvals = SHADOW_STACK_TASK_VARS(ret_stack);\nkernel/trace/fgraph.c-322-\n--\nkernel/trace/fgraph.c-326-/*\nkernel/trace/fgraph.c:327: fgraph_reserve_data - Reserve storage on the task's ret_stack\nkernel/trace/fgraph.c-328- * @idx:\tThe index of fgraph_array\n--\nkernel/trace/fgraph.c-331- * Reserves space of up to FGRAPH_MAX_DATA_SIZE bytes on the\nkernel/trace/fgraph.c:332: * task's ret_stack shadow stack, for a given fgraph_ops during\nkernel/trace/fgraph.c-333- * the entryfunc() call. If entryfunc() returns zero, the storage\n--\nkernel/trace/fgraph.c-339- * Otherwise, NULL if there's not enough space left on the\nkernel/trace/fgraph.c:340: * ret_stack for the data, or if fgraph_reserve_data() was called\nkernel/trace/fgraph.c-341- * more than once for a single entryfunc() call.\n--\nkernel/trace/fgraph.c=343=void fgraph_reserve_data(int idx, int size_bytes)\n--\nkernel/trace/fgraph.c-346-\tvoid data;\nkernel/trace/fgraph.c:347:\tint curr_ret_stack = current-\u003ecurr_ret_stack;\nkernel/trace/fgraph.c-348-\tint data_size;\n--\nkernel/trace/fgraph.c-355-\nkernel/trace/fgraph.c:356:\tval = get_fgraph_entry(current, curr_ret_stack - 1);\nkernel/trace/fgraph.c:357:\tdata = \u0026current-\u003eret_stack[curr_ret_stack];\nkernel/trace/fgraph.c-358-\nkernel/trace/fgraph.c:359:\tcurr_ret_stack += data_size + 1;\nkernel/trace/fgraph.c:360:\tif (unlikely(curr_ret_stack \u003e= SHADOW_STACK_MAX_OFFSET))\nkernel/trace/fgraph.c-361-\t\treturn NULL;\n--\nkernel/trace/fgraph.c-365-\t/* Set the last word to be reserved /\nkernel/trace/fgraph.c:366:\tcurrent-\u003eret_stack[curr_ret_stack - 1] = val;\nkernel/trace/fgraph.c-367-\n--\nkernel/trace/fgraph.c-369-\tbarrier();\nkernel/trace/fgraph.c:370:\tcurrent-\u003ecurr_ret_stack = curr_ret_stack;\nkernel/trace/fgraph.c-371-\t/ Again sync with interrupts, and reset reserve /\nkernel/trace/fgraph.c:372:\tcurrent-\u003eret_stack[curr_ret_stack - 1] = val;\nkernel/trace/fgraph.c-373-\n--\nkernel/trace/fgraph.c=392=void fgraph_retrieve_data(int idx, int size_bytes)\n--\nkernel/trace/fgraph.c-401- Every registered fgraph_ops has a task state variable\nkernel/trace/fgraph.c:402: * reserved on the task's ret_stack. This function returns the\nkernel/trace/fgraph.c-403- * address to that variable.\n--\nkernel/trace/fgraph.c=408=unsigned long fgraph_get_task_var(struct fgraph_ops gops)\nkernel/trace/fgraph.c-409-{\nkernel/trace/fgraph.c:410:\treturn ret_stack_get_task_var(current, gops-\u003eidx);\nkernel/trace/fgraph.c-411-}\n--\nkernel/trace/fgraph.c-413-/\nkernel/trace/fgraph.c:414: @offset: The offset into @t-\u003eret_stack to find the ret_stack entry\nkernel/trace/fgraph.c:415: * @frame_offset: Where to place the offset into @t-\u003eret_stack of that entry\nkernel/trace/fgraph.c-416- \nkernel/trace/fgraph.c:417: Returns a pointer to the previous ret_stack below @offset or NULL\nkernel/trace/fgraph.c-418- * when it reaches the bottom of the stack.\n--\nkernel/trace/fgraph.c-421- \nkernel/trace/fgraph.c:422: offset = task-\u003ecurr_ret_stack;\nkernel/trace/fgraph.c-423- * do {\nkernel/trace/fgraph.c:424: \tret_stack = get_ret_stack(task, offset, \u0026offset);\nkernel/trace/fgraph.c:425: } while (ret_stack);\nkernel/trace/fgraph.c-426- \nkernel/trace/fgraph.c:427: Will iterate through all the ret_stack entries from curr_ret_stack\nkernel/trace/fgraph.c-428- * down to the first one.\nkernel/trace/fgraph.c-429- /\nkernel/trace/fgraph.c:430:static inline struct ftrace_ret_stack \nkernel/trace/fgraph.c:431:get_ret_stack(struct task_struct t, int offset, int frame_offset)\nkernel/trace/fgraph.c-432-{\n--\nkernel/trace/fgraph.c=461=void fgraph_retrieve_parent_data(int idx, int size_bytes, int depth)\nkernel/trace/fgraph.c-462-{\nkernel/trace/fgraph.c:463:\tstruct ftrace_ret_stack ret_stack = NULL;\nkernel/trace/fgraph.c:464:\tint offset = current-\u003ecurr_ret_stack;\nkernel/trace/fgraph.c-465-\tunsigned long val;\n--\nkernel/trace/fgraph.c-472-\nkernel/trace/fgraph.c:473:\t\tret_stack = get_ret_stack(current, offset, \u0026next_offset);\nkernel/trace/fgraph.c:474:\t\tif (!ret_stack \|\| --depth \u003c 0)\nkernel/trace/fgraph.c-475-\t\t\tbreak;\n--\nkernel/trace/fgraph.c-478-\nkernel/trace/fgraph.c:479:\tif (!ret_stack)\nkernel/trace/fgraph.c-480-\t\treturn NULL;\n--\nkernel/trace/fgraph.c=560=ftrace_push_return_trace(unsigned long ret, unsigned long func,\n--\nkernel/trace/fgraph.c-563-{\nkernel/trace/fgraph.c:564:\tstruct ftrace_ret_stack ret_stack;\nkernel/trace/fgraph.c-565-\tunsigned long val;\n--\nkernel/trace/fgraph.c-570-\nkernel/trace/fgraph.c:571:\tif (!current-\u003eret_stack)\nkernel/trace/fgraph.c-572-\t\treturn -EBUSY;\n--\nkernel/trace/fgraph.c-579-\t/\nkernel/trace/fgraph.c:580:\t We must make sure the ret_stack is tested before we read\nkernel/trace/fgraph.c-581-\t * anything else.\n--\nkernel/trace/fgraph.c-588-\t /\nkernel/trace/fgraph.c:589:\tif (current-\u003ecurr_ret_stack + FGRAPH_FRAME_OFFSET + 1 \u003e= SHADOW_STACK_MAX_OFFSET) {\nkernel/trace/fgraph.c-590-\t\tatomic_inc(\u0026current-\u003etrace_overrun);\n--\nkernel/trace/fgraph.c-593-\nkernel/trace/fgraph.c:594:\toffset = READ_ONCE(current-\u003ecurr_ret_stack);\nkernel/trace/fgraph.c:595:\tret_stack = RET_STACK(current, offset);\nkernel/trace/fgraph.c-596-\toffset += FGRAPH_FRAME_OFFSET;\n--\nkernel/trace/fgraph.c-598-\t/ ret offset = FGRAPH_FRAME_OFFSET ; type = reserved /\nkernel/trace/fgraph.c:599:\tcurrent-\u003eret_stack[offset] = val;\nkernel/trace/fgraph.c:600:\tret_stack-\u003eret = ret;\nkernel/trace/fgraph.c-601-\t/\nkernel/trace/fgraph.c:602:\t * The unwinders expect curr_ret_stack to point to either zero\nkernel/trace/fgraph.c:603:\t * or an offset where to find the next ret_stack. Even though the\nkernel/trace/fgraph.c-604-\t * ret stack might be bogus, we want to write the ret and the\nkernel/trace/fgraph.c:605:\t * offset to find the ret_stack before we increment the stack point.\nkernel/trace/fgraph.c:606:\t * If an interrupt comes in now before we increment the curr_ret_stack\nkernel/trace/fgraph.c-607-\t * it may blow away what we wrote. But that's fine, because the\n--\nkernel/trace/fgraph.c-609-\t * What we worry about is the offset being correct after we increment\nkernel/trace/fgraph.c:610:\t * the curr_ret_stack and before we update that offset, as if an\nkernel/trace/fgraph.c-611-\t * interrupt comes in and does an unwind stack dump, it will need\n--\nkernel/trace/fgraph.c-614-\tbarrier();\nkernel/trace/fgraph.c:615:\tWRITE_ONCE(current-\u003ecurr_ret_stack, offset + 1);\nkernel/trace/fgraph.c-616-\t/\n--\nkernel/trace/fgraph.c-622-\t/ Still keep it reserved even if an interrupt came in /\nkernel/trace/fgraph.c:623:\tcurrent-\u003eret_stack[offset] = val;\nkernel/trace/fgraph.c-624-\nkernel/trace/fgraph.c:625:\tret_stack-\u003eret = ret;\nkernel/trace/fgraph.c:626:\tret_stack-\u003efunc = func;\nkernel/trace/fgraph.c-627-#ifdef HAVE_FUNCTION_GRAPH_FP_TEST\nkernel/trace/fgraph.c:628:\tret_stack-\u003efp = frame_pointer;\nkernel/trace/fgraph.c-629-#endif\nkernel/trace/fgraph.c:630:\tret_stack-\u003eretp = retp;\nkernel/trace/fgraph.c-631-\treturn offset;\n--\nkernel/trace/fgraph.c=649=int function_graph_enter_regs(unsigned long ret, unsigned long func,\n--\nkernel/trace/fgraph.c-671-\tif (static_branch_likely(\u0026fgraph_do_direct)) {\nkernel/trace/fgraph.c:672:\t\tint save_curr_ret_stack = current-\u003ecurr_ret_stack;\nkernel/trace/fgraph.c-673-\n--\nkernel/trace/fgraph.c-677-\t\t\t/ Clear out any saved storage /\nkernel/trace/fgraph.c:678:\t\t\tcurrent-\u003ecurr_ret_stack = save_curr_ret_stack;\nkernel/trace/fgraph.c-679-\t} else\n--\nkernel/trace/fgraph.c-684-\t\t\tstruct fgraph_ops gops = READ_ONCE(fgraph_array[i]);\nkernel/trace/fgraph.c:685:\t\t\tint save_curr_ret_stack;\nkernel/trace/fgraph.c-686-\n--\nkernel/trace/fgraph.c-689-\nkernel/trace/fgraph.c:690:\t\t\tsave_curr_ret_stack = current-\u003ecurr_ret_stack;\nkernel/trace/fgraph.c-691-\t\t\tif (ftrace_ops_test(\u0026gops-\u003eops, func, NULL) \u0026\u0026\n--\nkernel/trace/fgraph.c-695-\t\t\t\t/* Clear out any saved storage /\nkernel/trace/fgraph.c:696:\t\t\t\tcurrent-\u003ecurr_ret_stack = save_curr_ret_stack;\nkernel/trace/fgraph.c-697-\t\t}\n--\nkernel/trace/fgraph.c-710- out_ret:\nkernel/trace/fgraph.c:711:\tcurrent-\u003ecurr_ret_stack -= FGRAPH_FRAME_OFFSET + 1;\nkernel/trace/fgraph.c-712- out:\n--\nkernel/trace/fgraph.c-718-/ Retrieve a function return address to the trace stack on thread info./\nkernel/trace/fgraph.c:719:static struct ftrace_ret_stack \nkernel/trace/fgraph.c-720-ftrace_pop_return_trace(struct ftrace_graph_ret trace, unsigned long ret,\n--\nkernel/trace/fgraph.c-722-{\nkernel/trace/fgraph.c:723:\tstruct ftrace_ret_stack ret_stack;\nkernel/trace/fgraph.c-724-\nkernel/trace/fgraph.c:725:\tret_stack = get_ret_stack(current, current-\u003ecurr_ret_stack, offset);\nkernel/trace/fgraph.c-726-\nkernel/trace/fgraph.c:727:\tif (unlikely(!ret_stack)) {\nkernel/trace/fgraph.c-728-\t\tftrace_graph_stop();\nkernel/trace/fgraph.c:729:\t\tWARN(1, \"Bad function graph ret_stack pointer: %d\",\nkernel/trace/fgraph.c:730:\t\t current-\u003ecurr_ret_stack);\nkernel/trace/fgraph.c-731-\t\t/ Might as well panic, otherwise we have no where to go /\n--\nkernel/trace/fgraph.c-750-\t /\nkernel/trace/fgraph.c:751:\tif (unlikely(ret_stack-\u003efp != frame_pointer)) {\nkernel/trace/fgraph.c-752-\t\tftrace_graph_stop();\n--\nkernel/trace/fgraph.c-754-\t\t \" from func %ps return to %lx\\n\",\nkernel/trace/fgraph.c:755:\t\t ret_stack-\u003efp,\nkernel/trace/fgraph.c-756-\t\t frame_pointer,\nkernel/trace/fgraph.c:757:\t\t (void )ret_stack-\u003efunc,\nkernel/trace/fgraph.c:758:\t\t ret_stack-\u003eret);\nkernel/trace/fgraph.c-759-\t\tret = (unsigned long)panic;\n--\nkernel/trace/fgraph.c-764-\toffset += FGRAPH_FRAME_OFFSET;\nkernel/trace/fgraph.c:765:\tret = ret_stack-\u003eret;\nkernel/trace/fgraph.c:766:\ttrace-\u003efunc = ret_stack-\u003efunc;\nkernel/trace/fgraph.c-767-\ttrace-\u003eoverrun = atomic_read(\u0026current-\u003etrace_overrun);\n--\nkernel/trace/fgraph.c-775-\nkernel/trace/fgraph.c:776:\treturn ret_stack;\nkernel/trace/fgraph.c-777-}\n--\nkernel/trace/fgraph.c=809=__ftrace_return_to_handler(struct ftrace_regs fregs, unsigned long frame_pointer)\nkernel/trace/fgraph.c-810-{\nkernel/trace/fgraph.c:811:\tstruct ftrace_ret_stack ret_stack;\nkernel/trace/fgraph.c-812-\tstruct ftrace_graph_ret trace;\n--\nkernel/trace/fgraph.c-818-\nkernel/trace/fgraph.c:819:\tret_stack = ftrace_pop_return_trace(\u0026trace, \u0026ret, frame_pointer, \u0026offset);\nkernel/trace/fgraph.c-820-\nkernel/trace/fgraph.c:821:\tif (unlikely(!ret_stack)) {\nkernel/trace/fgraph.c-822-\t\tftrace_graph_stop();\n--\nkernel/trace/fgraph.c-866-\t * The ftrace_graph_return() may still access the current\nkernel/trace/fgraph.c:867:\t * ret_stack structure, we need to make sure the update of\nkernel/trace/fgraph.c:868:\t * curr_ret_stack is after that.\nkernel/trace/fgraph.c-869-\t /\nkernel/trace/fgraph.c-870-\tbarrier();\nkernel/trace/fgraph.c:871:\tcurrent-\u003ecurr_ret_stack = offset - FGRAPH_FRAME_OFFSET;\nkernel/trace/fgraph.c-872-\n--\nkernel/trace/fgraph.c=888=unsigned long ftrace_return_to_handler(unsigned long frame_pointer)\n--\nkernel/trace/fgraph.c-894-/\nkernel/trace/fgraph.c:895: ftrace_graph_get_ret_stack - return the entry of the shadow stack\nkernel/trace/fgraph.c-896- * @task: The task to read the shadow stack from.\n--\nkernel/trace/fgraph.c-900- * call graph at @idx starting with zero. If @idx is zero, it\nkernel/trace/fgraph.c:901: * will return the last saved ret_stack entry. If it is greater than\nkernel/trace/fgraph.c:902: * zero, it will return the corresponding ret_stack for the depth\nkernel/trace/fgraph.c-903- * of saved return addresses.\nkernel/trace/fgraph.c-904- /\nkernel/trace/fgraph.c:905:struct ftrace_ret_stack \nkernel/trace/fgraph.c:906:ftrace_graph_get_ret_stack(struct task_struct task, int idx)\nkernel/trace/fgraph.c-907-{\nkernel/trace/fgraph.c:908:\tstruct ftrace_ret_stack ret_stack = NULL;\nkernel/trace/fgraph.c:909:\tint offset = task-\u003ecurr_ret_stack;\nkernel/trace/fgraph.c-910-\n--\nkernel/trace/fgraph.c-914-\tdo {\nkernel/trace/fgraph.c:915:\t\tret_stack = get_ret_stack(task, offset, \u0026offset);\nkernel/trace/fgraph.c:916:\t} while (ret_stack \u0026\u0026 --idx \u003e= 0);\nkernel/trace/fgraph.c-917-\nkernel/trace/fgraph.c:918:\treturn ret_stack;\nkernel/trace/fgraph.c-919-}\n--\nkernel/trace/fgraph.c=928=unsigned long ftrace_graph_top_ret_addr(struct task_struct task)\n--\nkernel/trace/fgraph.c-930-\tunsigned long return_handler = (unsigned long)dereference_kernel_function_descriptor(return_to_handler);\nkernel/trace/fgraph.c:931:\tstruct ftrace_ret_stack ret_stack = NULL;\nkernel/trace/fgraph.c:932:\tint offset = task-\u003ecurr_ret_stack;\nkernel/trace/fgraph.c-933-\n--\nkernel/trace/fgraph.c-937-\tdo {\nkernel/trace/fgraph.c:938:\t\tret_stack = get_ret_stack(task, offset, \u0026offset);\nkernel/trace/fgraph.c:939:\t} while (ret_stack \u0026\u0026 ret_stack-\u003eret == return_handler);\nkernel/trace/fgraph.c-940-\nkernel/trace/fgraph.c:941:\treturn ret_stack ? ret_stack-\u003eret : 0;\nkernel/trace/fgraph.c-942-}\n--\nkernel/trace/fgraph.c=964=unsigned long ftrace_graph_ret_addr(struct task_struct task, int idx,\n--\nkernel/trace/fgraph.c-966-{\nkernel/trace/fgraph.c:967:\tstruct ftrace_ret_stack ret_stack;\nkernel/trace/fgraph.c-968-\tunsigned long return_handler = (unsigned long)dereference_kernel_function_descriptor(return_to_handler);\n--\nkernel/trace/fgraph.c-976-\nkernel/trace/fgraph.c:977:\ti = idx ? : task-\u003ecurr_ret_stack;\nkernel/trace/fgraph.c-978-\twhile (i \u003e 0) {\nkernel/trace/fgraph.c:979:\t\tret_stack = get_ret_stack(task, i, \u0026i);\nkernel/trace/fgraph.c:980:\t\tif (!ret_stack)\nkernel/trace/fgraph.c-981-\t\t\tbreak;\nkernel/trace/fgraph.c-982-\t\t/\nkernel/trace/fgraph.c:983:\t\t For the tail-call, there would be 2 or more ftrace_ret_stacks on\nkernel/trace/fgraph.c:984:\t\t * the ret_stack, which records \"return_to_handler\" as the return\nkernel/trace/fgraph.c-985-\t\t * address except for the last one.\n--\nkernel/trace/fgraph.c-989-\t\t /\nkernel/trace/fgraph.c:990:\t\tif (ret_stack-\u003eretp == retp \u0026\u0026\nkernel/trace/fgraph.c:991:\t\t ret_stack-\u003eret != return_handler) {\nkernel/trace/fgraph.c-992-\t\t\tidx = i;\nkernel/trace/fgraph.c:993:\t\t\treturn ret_stack-\u003eret;\nkernel/trace/fgraph.c-994-\t\t}\n--\nkernel/trace/fgraph.c=1034=trace_func_graph_ent_t ftrace_graph_entry = ftrace_graph_entry_stub;\n--\nkernel/trace/fgraph.c-1036-/* Try to assign a return stack array on FTRACE_RETSTACK_ALLOC_SIZE tasks. /\nkernel/trace/fgraph.c:1037:static int alloc_retstack_tasklist(unsigned long ret_stack_list)\nkernel/trace/fgraph.c-1038-{\n--\nkernel/trace/fgraph.c-1047-\tfor (i = 0; i \u003c FTRACE_RETSTACK_ALLOC_SIZE; i++) {\nkernel/trace/fgraph.c:1048:\t\tret_stack_list[i] = kmem_cache_alloc(fgraph_stack_cachep, GFP_KERNEL);\nkernel/trace/fgraph.c:1049:\t\tif (!ret_stack_list[i]) {\nkernel/trace/fgraph.c-1050-\t\t\tstart = 0;\n--\nkernel/trace/fgraph.c-1063-\nkernel/trace/fgraph.c:1064:\t\tif (t-\u003eret_stack == NULL) {\nkernel/trace/fgraph.c-1065-\t\t\tatomic_set(\u0026t-\u003etrace_overrun, 0);\nkernel/trace/fgraph.c:1066:\t\t\tret_stack_init_task_vars(ret_stack_list[start]);\nkernel/trace/fgraph.c:1067:\t\t\tt-\u003ecurr_ret_stack = 0;\nkernel/trace/fgraph.c-1068-\t\t\tt-\u003ecurr_ret_depth = -1;\n--\nkernel/trace/fgraph.c-1070-\t\t\tsmp_wmb();\nkernel/trace/fgraph.c:1071:\t\t\tt-\u003eret_stack = ret_stack_list[start++];\nkernel/trace/fgraph.c-1072-\t\t}\n--\nkernel/trace/fgraph.c-1078-\tfor (i = start; i \u003c end; i++)\nkernel/trace/fgraph.c:1079:\t\tkmem_cache_free(fgraph_stack_cachep, ret_stack_list[i]);\nkernel/trace/fgraph.c-1080-\treturn ret;\n--\nkernel/trace/fgraph.c=1084=ftrace_graph_probe_sched_switch(void ignore, bool preempt,\n--\nkernel/trace/fgraph.c-1108-\nkernel/trace/fgraph.c:1109:static DEFINE_PER_CPU(unsigned long , idle_ret_stack);\nkernel/trace/fgraph.c-1110-\nkernel/trace/fgraph.c=1111=static void\nkernel/trace/fgraph.c:1112:graph_init_task(struct task_struct t, unsigned long ret_stack)\nkernel/trace/fgraph.c-1113-{\nkernel/trace/fgraph.c-1114-\tatomic_set(\u0026t-\u003etrace_overrun, 0);\nkernel/trace/fgraph.c:1115:\tret_stack_init_task_vars(ret_stack);\nkernel/trace/fgraph.c-1116-\tt-\u003eftrace_timestamp = 0;\nkernel/trace/fgraph.c:1117:\tt-\u003ecurr_ret_stack = 0;\nkernel/trace/fgraph.c-1118-\tt-\u003ecurr_ret_depth = -1;\nkernel/trace/fgraph.c:1119:\t/ make curr_ret_stack visible before we add the ret_stack /\nkernel/trace/fgraph.c-1120-\tsmp_wmb();\nkernel/trace/fgraph.c:1121:\tt-\u003eret_stack = ret_stack;\nkernel/trace/fgraph.c-1122-}\n--\nkernel/trace/fgraph.c=1128=void ftrace_graph_init_idle_task(struct task_struct t, int cpu)\nkernel/trace/fgraph.c-1129-{\nkernel/trace/fgraph.c:1130:\tt-\u003ecurr_ret_stack = 0;\nkernel/trace/fgraph.c-1131-\tt-\u003ecurr_ret_depth = -1;\n--\nkernel/trace/fgraph.c-1135-\t /\nkernel/trace/fgraph.c:1136:\tif (t-\u003eret_stack)\nkernel/trace/fgraph.c:1137:\t\tWARN_ON(t-\u003eret_stack != per_cpu(idle_ret_stack, cpu));\nkernel/trace/fgraph.c-1138-\nkernel/trace/fgraph.c-1139-\tif (ftrace_graph_active) {\nkernel/trace/fgraph.c:1140:\t\tunsigned long ret_stack;\nkernel/trace/fgraph.c-1141-\n--\nkernel/trace/fgraph.c-1144-\nkernel/trace/fgraph.c:1145:\t\tret_stack = per_cpu(idle_ret_stack, cpu);\nkernel/trace/fgraph.c:1146:\t\tif (!ret_stack) {\nkernel/trace/fgraph.c:1147:\t\t\tret_stack = kmem_cache_alloc(fgraph_stack_cachep, GFP_KERNEL);\nkernel/trace/fgraph.c:1148:\t\t\tif (!ret_stack)\nkernel/trace/fgraph.c-1149-\t\t\t\treturn;\nkernel/trace/fgraph.c:1150:\t\t\tper_cpu(idle_ret_stack, cpu) = ret_stack;\nkernel/trace/fgraph.c-1151-\t\t}\nkernel/trace/fgraph.c:1152:\t\tgraph_init_task(t, ret_stack);\nkernel/trace/fgraph.c-1153-\t}\n--\nkernel/trace/fgraph.c=1157=void ftrace_graph_init_task(struct task_struct t)\nkernel/trace/fgraph.c-1158-{\nkernel/trace/fgraph.c:1159:\t/ Make sure we do not use the parent ret_stack /\nkernel/trace/fgraph.c:1160:\tt-\u003eret_stack = NULL;\nkernel/trace/fgraph.c:1161:\tt-\u003ecurr_ret_stack = 0;\nkernel/trace/fgraph.c-1162-\tt-\u003ecurr_ret_depth = -1;\n--\nkernel/trace/fgraph.c-1164-\tif (ftrace_graph_active) {\nkernel/trace/fgraph.c:1165:\t\tunsigned long ret_stack;\nkernel/trace/fgraph.c-1166-\n--\nkernel/trace/fgraph.c-1169-\nkernel/trace/fgraph.c:1170:\t\tret_stack = kmem_cache_alloc(fgraph_stack_cachep, GFP_KERNEL);\nkernel/trace/fgraph.c:1171:\t\tif (!ret_stack)\nkernel/trace/fgraph.c-1172-\t\t\treturn;\n\n" }
61/3	2026/09/16 03:11	llm	kmsan-evaluator	0m Model: gemini-3.8-flash Args: null Results: null Tokens: input: 20852 output: 21 thoughts: 266 Thoughts: Analyzing Potential Data Leakage in fprobe_fgraph Okay, let's break this down. My initial concern is with the allocation of `ret_stack`. It's allocated using `kmem_cache_alloc` but without the `__GFP_ZERO` flag. That's a red flag immediately. Even if it were zeroed initially, `ret_stack` is clearly reused across function calls; `curr_ret_stack` is moved around as functions enter and exit. This suggests that the contents of `fgraph_data` within `fgraph_reserve_data` might be holding stale data from previous function invocations on the same task. We're reserving `reserved_words * sizeof(long)` worth of memory, and that memory could very well be garbage left over from something completely unrelated. Now, that comment in the patch: `/* Clear unused slots so fprobe_return() does not see stale headers. /` It's essentially acknowledging the exact problem I was just thinking about! The `memset` in that `if (used < reserved_words)` block is precisely* trying to mitigate this data leakage, clearing out the unused portion of the reserved space. But I still don't fully understand why this patch was needed in the first place. Was this an intentional design decision, or a bug that was discovered and fixed? I need more context. Let me check the git log, perhaps looking for the commit that introduced `fprobe_fgraph_entry`. Let's grep for recent commits or just inspect `kernel/trace/fprobe.c` directly. This needs more investigation!
62/3	2026/09/16 03:11	tool	grepper	0m Args: { "Expression": "fprobe_fgraph_entry" } Results: { "Output": "kernel/trace/fprobe.c=231=static inline int __fprobe_kprobe_handler(unsigned long ip, unsigned long parent_ip,\n--\nkernel/trace/fprobe.c-252-\nkernel/trace/fprobe.c:253:static int fprobe_fgraph_entry(struct ftrace_graph_ent trace, struct fgraph_ops gops,\nkernel/trace/fprobe.c-254-\t\t\t struct ftrace_regs fregs);\n--\nkernel/trace/fprobe.c=259=static struct fgraph_ops fprobe_graph_ops = {\nkernel/trace/fprobe.c:260:\t.entryfunc\t= fprobe_fgraph_entry,\nkernel/trace/fprobe.c-261-\t.retfunc\t= fprobe_return,\n--\nkernel/trace/fprobe.c=536=static void fprobe_remove_ips(unsigned long ips, unsigned int cnt)\n--\nkernel/trace/fprobe.c-546-/* fgraph_ops callback, this processes fprobes which have exit_handler. /\nkernel/trace/fprobe.c:547:static int fprobe_fgraph_entry(struct ftrace_graph_ent trace, struct fgraph_ops gops,\nkernel/trace/fprobe.c-548-\t\t\t struct ftrace_regs fregs)\n--\nkernel/trace/fprobe.c-644-}\nkernel/trace/fprobe.c:645:NOKPROBE_SYMBOL(fprobe_fgraph_entry);\nkernel/trace/fprobe.c-646-\n" }
63/3	2026/09/16 03:11	llm	kmsan-evaluator	0m Model: gemini-3.8-flash Args: null Results: null Tokens: input: 21899 output: 200 thoughts: 4373 Thoughts: KMSAN Determination for fprobe patch Okay, here's the breakdown of whether we need KMSAN for this patch. I've walked through the code, considered the intent of the patch, and reviewed the specific criteria for using KMSAN. First, I examined the patch itself. It introduces a `memset` to zero out unused slots in a data structure named `fgraph_data`. This is done within `fprobe_fgraph_entry` before any data is read by `fprobe_return`. The goal is to prevent stale data from lingering in the stack and being potentially misinterpreted. Now, let's consider the KMSAN criteria. Does this patch: 1. Send kernel structures to user space? No. 2. Introduce conditional logic based on uninitialized variables? No, all variables involved are initialized. 3. Allocate or initialize data structures with potentially uninitialized fields that could be read later? No, this patch explicitly zeros unused fields. 4. Modify bounds checks or logic in a way that allows access to uninitialized data? No, it zeroes out that data. The core of the issue boils down to the difference between KASAN and KMSAN. KASAN is already enabled in the standard kernel build and it will catch out-of-bounds writes or reads, null pointer dereferences, etc. KMSAN's purpose is to catch reads of truly uninitialized memory. This patch prevents that situation from occurring by zeroing it out. It's a memory initialization patch, not an uninitialized memory exposure patch. Any potential bounds error introduced by this patch would be caught by KASAN. Furthermore, this patch, in fact, prevents reads of potentially stale data (which could be the output of uninitialized memory at first use, after the `kmem_cache_alloc` call). Therefore, based on the documented criteria, this patch does not justify a dedicated KMSAN fuzzing session. The code changes don't introduce any new risk of uninitialized memory usage, and they actually fix a potential issue by ensuring that the allocated memory is zeroed. I will set `NeedsKMSAN = false`.
64/3	2026/09/16 03:11	tool	set-results	0m Args: { "KMSANReasoning": "The patch adds a memset() to zero out unused reserved words in fgraph_data within fprobe_fgraph_entry() so that fprobe_return() does not read stale/uninitialized header data. \n\nThe variables involved in the condition and size calculation ('used' and 'reserved_words') are fully initialized local integers, and the memset explicitly clears the remaining memory buffer with zeroes. No kernel data is copied to user space, no branching on uninitialized data is introduced, and no uninitialized memory risks or info-leaks are created. Any hypothetical bugs introduced by this patch (such as off-by-one errors or out-of-bounds writes in the memset pointer arithmetic) would be out-of-bounds memory errors detected by KASAN rather than KMSAN. Therefore, a dedicated KMSAN fuzzing session is not warranted.", "NeedsKMSAN": false } Results: { "KMSANReasoning": "The patch adds a memset() to zero out unused reserved words in fgraph_data within fprobe_fgraph_entry() so that fprobe_return() does not read stale/uninitialized header data. \n\nThe variables involved in the condition and size calculation ('used' and 'reserved_words') are fully initialized local integers, and the memset explicitly clears the remaining memory buffer with zeroes. No kernel data is copied to user space, no branching on uninitialized data is introduced, and no uninitialized memory risks or info-leaks are created. Any hypothetical bugs introduced by this patch (such as off-by-one errors or out-of-bounds writes in the memset pointer arithmetic) would be out-of-bounds memory errors detected by KASAN rather than KMSAN. Therefore, a dedicated KMSAN fuzzing session is not warranted.", "NeedsKMSAN": false }

LLM Calls Summary:
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Tool Calls Summary:
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