AI Trajectory

null

{
  "EnableConfigs": [
    "BPF_EVENTS",
    "BPF_SYSCALL",
    "PERF_EVENTS"
  ],
  "FocusSymbols": [
    "bpf_get_stack_tp_sleepable",
    "bpf_get_stack_raw_tp_sleepable",
    "tp_prog_func_proto",
    "raw_tp_prog_func_proto"
  ],
  "KMSANReasoning": "The patch wires up sleepable variants of `bpf_get_stack` (`bpf_get_stack_tp_sleepable` and `bpf_get_stack_raw_tp_sleepable`) for sleepable tracepoint and raw tracepoint BPF programs.\n\nAnalysis of memory initialization:\n1. In `bpf_get_stack_raw_tp_sleepable`, the local `struct pt_regs regs` is explicitly zero-initialized with `{}` before `perf_fetch_caller_regs(\u0026regs)` is invoked.\n2. The destination buffer `buf` passed from the BPF program is managed by `__bpf_get_stack()`, which writes stack entries into it or zeroes it completely via `memset(buf, 0, size)` on failure or partial fills.\n3. No kernel-to-user copy of uninitialized memory or info-leak risk is introduced.\n4. Potential issues introduced by sleepable BPF program execution (such as sleeping in invalid contexts, lockdep violations, or out-of-bounds stack reading) are covered by standard KASAN and LOCKDEP configurations.\n\nTherefore, KMSAN fuzzing is not required.",
  "NeedsKMSAN": false,
  "Reasoning": "The patch wires up sleepable stack capture helpers (bpf_get_stack_tp_sleepable and bpf_get_stack_raw_tp_sleepable) for sleepable tracepoint and raw tracepoint BPF programs. This allows tracepoint and raw tracepoint programs marked sleepable to execute faultable, sleep-inducing stack walking logic (such as build ID resolution). These execution paths are fully reachable from userspace via standard BPF syscalls and tracepoint event attachments, making them high-priority targets for fuzzing.",
  "WorthFuzzing": true
}

null

{
  "PatchDiff": "commit 9ec83394638c4b1f1fb4aea9976ca43297caea3b\nAuthor: syz-cluster \u003ctriage@syzkaller.com\u003e\nDate:   Mon Nov 2 14:00:02 2026 +0000\n\n    syz-cluster: applied patch under review\n\ndiff --git a/kernel/trace/bpf_trace.c b/kernel/trace/bpf_trace.c\nindex 14adfb85fdb2be..7d8414d8573744 100644\n--- a/kernel/trace/bpf_trace.c\n+++ b/kernel/trace/bpf_trace.c\n@@ -84,6 +84,7 @@ static struct bpf_raw_event_map *bpf_get_raw_tracepoint_module(const char *name)\n \n u64 bpf_get_stackid(u64 r1, u64 r2, u64 r3, u64 r4, u64 r5);\n u64 bpf_get_stack(u64 r1, u64 r2, u64 r3, u64 r4, u64 r5);\n+u64 bpf_get_stack_sleepable(u64 r1, u64 r2, u64 r3, u64 r4, u64 r5);\n \n static int bpf_btf_printf_prepare(struct btf_ptr *ptr, u32 btf_ptr_size,\n \t\t\t\t  u64 flags, const struct btf **btf,\n@@ -1466,6 +1467,26 @@ static const struct bpf_func_proto bpf_get_stack_proto_tp = {\n \t.arg4_type\t= ARG_ANYTHING,\n };\n \n+BPF_CALL_4(bpf_get_stack_tp_sleepable, void *, tp_buff, void *, buf, u32, size,\n+\t   u64, flags)\n+{\n+\tstruct pt_regs *regs = *(struct pt_regs **)tp_buff;\n+\n+\treturn bpf_get_stack_sleepable((unsigned long) regs, (unsigned long) buf,\n+\t\t\t\t       (unsigned long) size, flags, 0);\n+}\n+\n+static const struct bpf_func_proto bpf_get_stack_proto_tp_sleepable = {\n+\t.func\t\t= bpf_get_stack_tp_sleepable,\n+\t.gpl_only\t= true,\n+\t.might_sleep\t= true,\n+\t.ret_type\t= RET_INTEGER,\n+\t.arg1_type\t= ARG_PTR_TO_CTX,\n+\t.arg2_type\t= ARG_PTR_TO_UNINIT_MEM,\n+\t.arg3_type\t= ARG_MEM_SIZE_OR_ZERO,\n+\t.arg4_type\t= ARG_ANYTHING,\n+};\n+\n static const struct bpf_func_proto *\n tp_prog_func_proto(enum bpf_func_id func_id, const struct bpf_prog *prog)\n {\n@@ -1475,7 +1496,8 @@ tp_prog_func_proto(enum bpf_func_id func_id, const struct bpf_prog *prog)\n \tcase BPF_FUNC_get_stackid:\n \t\treturn \u0026bpf_get_stackid_proto_tp;\n \tcase BPF_FUNC_get_stack:\n-\t\treturn \u0026bpf_get_stack_proto_tp;\n+\t\treturn prog-\u003esleepable ? \u0026bpf_get_stack_proto_tp_sleepable\n+\t\t\t\t       : \u0026bpf_get_stack_proto_tp;\n \tcase BPF_FUNC_get_attach_cookie:\n \t\treturn \u0026bpf_get_attach_cookie_proto_trace;\n \tdefault:\n@@ -1705,6 +1727,33 @@ static const struct bpf_func_proto bpf_get_stack_proto_raw_tp = {\n \t.arg4_type\t= ARG_ANYTHING,\n };\n \n+BPF_CALL_4(bpf_get_stack_raw_tp_sleepable, struct bpf_raw_tracepoint_args *, args,\n+\t   void *, buf, u32, size, u64, flags)\n+{\n+\t/*\n+\t * Don't take a per-CPU bpf_raw_tp_regs slot here: those slots are a\n+\t * LIFO nest counter and cannot be held across the sleep that\n+\t * build_id_parse() may take.  Sleepable programs never run in\n+\t * IRQ/NMI context, so a stack copy is sufficient.\n+\t */\n+\tstruct pt_regs regs = {};\n+\n+\tperf_fetch_caller_regs(\u0026regs);\n+\treturn bpf_get_stack_sleepable((unsigned long) \u0026regs, (unsigned long) buf,\n+\t\t\t\t       (unsigned long) size, flags, 0);\n+}\n+\n+static const struct bpf_func_proto bpf_get_stack_proto_raw_tp_sleepable = {\n+\t.func\t\t= bpf_get_stack_raw_tp_sleepable,\n+\t.gpl_only\t= true,\n+\t.might_sleep\t= true,\n+\t.ret_type\t= RET_INTEGER,\n+\t.arg1_type\t= ARG_PTR_TO_CTX,\n+\t.arg2_type\t= ARG_PTR_TO_UNINIT_MEM,\n+\t.arg3_type\t= ARG_MEM_SIZE_OR_ZERO,\n+\t.arg4_type\t= ARG_ANYTHING,\n+};\n+\n static const struct bpf_func_proto *\n raw_tp_prog_func_proto(enum bpf_func_id func_id, const struct bpf_prog *prog)\n {\n@@ -1714,7 +1763,8 @@ raw_tp_prog_func_proto(enum bpf_func_id func_id, const struct bpf_prog *prog)\n \tcase BPF_FUNC_get_stackid:\n \t\treturn \u0026bpf_get_stackid_proto_raw_tp;\n \tcase BPF_FUNC_get_stack:\n-\t\treturn \u0026bpf_get_stack_proto_raw_tp;\n+\t\treturn prog-\u003esleepable ? \u0026bpf_get_stack_proto_raw_tp_sleepable\n+\t\t\t\t       : \u0026bpf_get_stack_proto_raw_tp;\n \tcase BPF_FUNC_get_attach_cookie:\n \t\treturn \u0026bpf_get_attach_cookie_proto_tracing;\n \tdefault:\n"
}

core

null

{
  "EnableConfigs": [
    "BPF_EVENTS",
    "BPF_SYSCALL",
    "PERF_EVENTS"
  ],
  "FocusSymbols": [
    "bpf_get_stack_tp_sleepable",
    "bpf_get_stack_raw_tp_sleepable",
    "tp_prog_func_proto",
    "raw_tp_prog_func_proto"
  ],
  "Reasoning": "The patch wires up sleepable stack capture helpers (bpf_get_stack_tp_sleepable and bpf_get_stack_raw_tp_sleepable) for sleepable tracepoint and raw tracepoint BPF programs. This allows tracepoint and raw tracepoint programs marked sleepable to execute faultable, sleep-inducing stack walking logic (such as build ID resolution). These execution paths are fully reachable from userspace via standard BPF syscalls and tracepoint event attachments, making them high-priority targets for fuzzing.",
  "WorthFuzzing": true
}

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.

Target architecture: amd64

For your convenience, here is the diff of the changes:
commit 9ec83394638c4b1f1fb4aea9976ca43297caea3b
Author: syz-cluster <triage@syzkaller.com>
Date:   Mon Nov 2 14:00:02 2026 +0000

    syz-cluster: applied patch under review

diff --git a/kernel/trace/bpf_trace.c b/kernel/trace/bpf_trace.c
index 14adfb85fdb2be..7d8414d8573744 100644
--- a/kernel/trace/bpf_trace.c
+++ b/kernel/trace/bpf_trace.c
@@ -84,6 +84,7 @@ static struct bpf_raw_event_map *bpf_get_raw_tracepoint_module(const char *name)
 
 u64 bpf_get_stackid(u64 r1, u64 r2, u64 r3, u64 r4, u64 r5);
 u64 bpf_get_stack(u64 r1, u64 r2, u64 r3, u64 r4, u64 r5);
+u64 bpf_get_stack_sleepable(u64 r1, u64 r2, u64 r3, u64 r4, u64 r5);
 
 static int bpf_btf_printf_prepare(struct btf_ptr *ptr, u32 btf_ptr_size,
 				  u64 flags, const struct btf **btf,
@@ -1466,6 +1467,26 @@ static const struct bpf_func_proto bpf_get_stack_proto_tp = {
 	.arg4_type	= ARG_ANYTHING,
 };
 
+BPF_CALL_4(bpf_get_stack_tp_sleepable, void *, tp_buff, void *, buf, u32, size,
+	   u64, flags)
+{
+	struct pt_regs *regs = *(struct pt_regs **)tp_buff;
+
+	return bpf_get_stack_sleepable((unsigned long) regs, (unsigned long) buf,
+				       (unsigned long) size, flags, 0);
+}
+
+static const struct bpf_func_proto bpf_get_stack_proto_tp_sleepable = {
+	.func		= bpf_get_stack_tp_sleepable,
+	.gpl_only	= true,
+	.might_sleep	= true,
+	.ret_type	= RET_INTEGER,
+	.arg1_type	= ARG_PTR_TO_CTX,
+	.arg2_type	= ARG_PTR_TO_UNINIT_MEM,
+	.arg3_type	= ARG_MEM_SIZE_OR_ZERO,
+	.arg4_type	= ARG_ANYTHING,
+};
+
 static const struct bpf_func_proto *
 tp_prog_func_proto(enum bpf_func_id func_id, const struct bpf_prog *prog)
 {
@@ -1475,7 +1496,8 @@ tp_prog_func_proto(enum bpf_func_id func_id, const struct bpf_prog *prog)
 	case BPF_FUNC_get_stackid:
 		return &bpf_get_stackid_proto_tp;
 	case BPF_FUNC_get_stack:
-		return &bpf_get_stack_proto_tp;
+		return prog->sleepable ? &bpf_get_stack_proto_tp_sleepable
+				       : &bpf_get_stack_proto_tp;
 	case BPF_FUNC_get_attach_cookie:
 		return &bpf_get_attach_cookie_proto_trace;
 	default:
@@ -1705,6 +1727,33 @@ static const struct bpf_func_proto bpf_get_stack_proto_raw_tp = {
 	.arg4_type	= ARG_ANYTHING,
 };
 
+BPF_CALL_4(bpf_get_stack_raw_tp_sleepable, struct bpf_raw_tracepoint_args *, args,
+	   void *, buf, u32, size, u64, flags)
+{
+	/*
+	 * Don't take a per-CPU bpf_raw_tp_regs slot here: those slots are a
+	 * LIFO nest counter and cannot be held across the sleep that
+	 * build_id_parse() may take.  Sleepable programs never run in
+	 * IRQ/NMI context, so a stack copy is sufficient.
+	 */
+	struct pt_regs regs = {};
+
+	perf_fetch_caller_regs(&regs);
+	return bpf_get_stack_sleepable((unsigned long) &regs, (unsigned long) buf,
+				       (unsigned long) size, flags, 0);
+}
+
+static const struct bpf_func_proto bpf_get_stack_proto_raw_tp_sleepable = {
+	.func		= bpf_get_stack_raw_tp_sleepable,
+	.gpl_only	= true,
+	.might_sleep	= true,
+	.ret_type	= RET_INTEGER,
+	.arg1_type	= ARG_PTR_TO_CTX,
+	.arg2_type	= ARG_PTR_TO_UNINIT_MEM,
+	.arg3_type	= ARG_MEM_SIZE_OR_ZERO,
+	.arg4_type	= ARG_ANYTHING,
+};
+
 static const struct bpf_func_proto *
 raw_tp_prog_func_proto(enum bpf_func_id func_id, const struct bpf_prog *prog)
 {
@@ -1714,7 +1763,8 @@ raw_tp_prog_func_proto(enum bpf_func_id func_id, const struct bpf_prog *prog)
 	case BPF_FUNC_get_stackid:
 		return &bpf_get_stackid_proto_raw_tp;
 	case BPF_FUNC_get_stack:
-		return &bpf_get_stack_proto_raw_tp;
+		return prog->sleepable ? &bpf_get_stack_proto_raw_tp_sleepable
+				       : &bpf_get_stack_proto_raw_tp;
 	case BPF_FUNC_get_attach_cookie:
 		return &bpf_get_attach_cookie_proto_tracing;
 	default:

gemini-3.8-flash

null

null

							input: 4345
							output: 23
							thoughts: 341
						

**Analyzing the Kernel Patch for Fuzzing Potential**

Okay, let's dive into this patch and figure out if it's fuzz-worthy, what kind of configuration we'll need, and the key symbols to focus on. 

First, let's take a look at this diff. Looks like we're dealing with a modification to `kernel/trace/bpf_trace.c`. The patch introduces `bpf_get_stack_tp_sleepable` and `bpf_get_stack_raw_tp_sleepable` helper implementations, alongside corresponding function prototypes. It seems like the core change involves handling the `BPF_FUNC_get_stack` function call when the program is marked as "sleepable" (`prog->sleepable`). I see the function signature: `u64 bpf_get_stack_sleepable(u64 r1, u64 r2, u64 r3, u64 r4, u64 r5);`. In both `tp_prog_func_proto` and `raw_tp_prog_func_proto`, there's a conditional statement that selects the appropriate prototype based on the `prog->sleepable` flag.

So, in the `tp_prog_func_proto` case for `BPF_FUNC_get_stack`, it returns either `&bpf_get_stack_proto_tp_sleepable` or `&bpf_get_stack_proto_tp`. And the same pattern goes for `raw_tp_prog_func_proto`, it returns either `&bpf_get_stack_proto_raw_tp_sleepable` or `&bpf_get_stack_proto_raw_tp`.

Now, let's quickly locate where `bpf_get_stack_sleepable` is actually defined within the kernel source.

{
  "Expression": "bpf_get_stack_sleepable"
}

{
  "Output": "include/linux/bpf.h=4092=extern const struct bpf_func_proto bpf_get_stack_proto;\ninclude/linux/bpf.h:4093:extern const struct bpf_func_proto bpf_get_stack_sleepable_proto;\ninclude/linux/bpf.h-4094-extern const struct bpf_func_proto bpf_get_task_stack_proto;\n--\nkernel/bpf/stackmap.c=854=const struct bpf_func_proto bpf_get_stack_proto = {\n--\nkernel/bpf/stackmap.c-863-\nkernel/bpf/stackmap.c:864:BPF_CALL_4(bpf_get_stack_sleepable, struct pt_regs *, regs, void *, buf, u32, size,\nkernel/bpf/stackmap.c-865-\t   u64, flags)\n--\nkernel/bpf/stackmap.c-869-\nkernel/bpf/stackmap.c:870:const struct bpf_func_proto bpf_get_stack_sleepable_proto = {\nkernel/bpf/stackmap.c:871:\t.func\t\t= bpf_get_stack_sleepable,\nkernel/bpf/stackmap.c-872-\t.gpl_only\t= true,\n--\nkernel/trace/bpf_trace.c=86=u64 bpf_get_stack(u64 r1, u64 r2, u64 r3, u64 r4, u64 r5);\nkernel/trace/bpf_trace.c:87:u64 bpf_get_stack_sleepable(u64 r1, u64 r2, u64 r3, u64 r4, u64 r5);\nkernel/trace/bpf_trace.c-88-\n--\nkernel/trace/bpf_trace.c=1344=kprobe_prog_func_proto(enum bpf_func_id func_id, const struct bpf_prog *prog)\n--\nkernel/trace/bpf_trace.c-1351-\tcase BPF_FUNC_get_stack:\nkernel/trace/bpf_trace.c:1352:\t\treturn prog-\u003esleepable ? \u0026bpf_get_stack_sleepable_proto : \u0026bpf_get_stack_proto;\nkernel/trace/bpf_trace.c-1353-#ifdef CONFIG_BPF_KPROBE_OVERRIDE\n--\nkernel/trace/bpf_trace.c=1470=BPF_CALL_4(bpf_get_stack_tp_sleepable, void *, tp_buff, void *, buf, u32, size,\n--\nkernel/trace/bpf_trace.c-1474-\nkernel/trace/bpf_trace.c:1475:\treturn bpf_get_stack_sleepable((unsigned long) regs, (unsigned long) buf,\nkernel/trace/bpf_trace.c-1476-\t\t\t\t       (unsigned long) size, flags, 0);\n--\nkernel/trace/bpf_trace.c=1730=BPF_CALL_4(bpf_get_stack_raw_tp_sleepable, struct bpf_raw_tracepoint_args *, args,\n--\nkernel/trace/bpf_trace.c-1741-\tperf_fetch_caller_regs(\u0026regs);\nkernel/trace/bpf_trace.c:1742:\treturn bpf_get_stack_sleepable((unsigned long) \u0026regs, (unsigned long) buf,\nkernel/trace/bpf_trace.c-1743-\t\t\t\t       (unsigned long) size, flags, 0);\n"
}

gemini-3.8-flash

null

null

							input: 6039
							output: 39
							thoughts: 50
						

Okay, let's dive into this. Here's how I'd approach understanding the `bpf_trace.c` code related to tracing:

**Examining Kernel Tracing with BPF**

My immediate focus, given the suggested lines (1460-1500 and 1700-1765) in `kernel/trace/bpf_trace.c`, would be to understand the implementation details of how tracepoints (`tp`) and raw tracepoints (`raw_tp`) are handled within the BPF framework. I know these are crucial for instrumenting the kernel and gaining insights into its behavior. I would expect lines 1460-1500 to offer insights into setting up tracepoints, perhaps the structures involved, how BPF programs are attached, or how events are filtered. Then, I will focus on lines 1700-1765, where I'll be looking for how raw tracepoints are handled, likely dealing with how they are registered and how the raw data from those points are packaged or interpreted. I'm keen to see how the system differentiates and manages these two types of tracepoints, perhaps in how the data is processed, in how events are stored, and in their security contexts. The goal here is to get a handle on how flexible this framework is, how efficiently it can collect information, and any potential bottlenecks or design trade-offs that might exist. Knowing these implementation details would be key to leveraging BPF for efficient and effective system-level tracing and monitoring.

{
  "File": "kernel/trace/bpf_trace.c",
  "FirstLine": 1450,
  "LineCount": 55
}

{
  "Contents": "1450:\t\n1451:\tBPF_CALL_4(bpf_get_stack_tp, void *, tp_buff, void *, buf, u32, size,\n1452:\t\t   u64, flags)\n1453:\t{\n1454:\t\tstruct pt_regs *regs = *(struct pt_regs **)tp_buff;\n1455:\t\n1456:\t\treturn bpf_get_stack((unsigned long) regs, (unsigned long) buf,\n1457:\t\t\t\t     (unsigned long) size, flags, 0);\n1458:\t}\n1459:\t\n1460:\tstatic const struct bpf_func_proto bpf_get_stack_proto_tp = {\n1461:\t\t.func\t\t= bpf_get_stack_tp,\n1462:\t\t.gpl_only\t= true,\n1463:\t\t.ret_type\t= RET_INTEGER,\n1464:\t\t.arg1_type\t= ARG_PTR_TO_CTX,\n1465:\t\t.arg2_type\t= ARG_PTR_TO_UNINIT_MEM,\n1466:\t\t.arg3_type\t= ARG_MEM_SIZE_OR_ZERO,\n1467:\t\t.arg4_type\t= ARG_ANYTHING,\n1468:\t};\n1469:\t\n1470:\tBPF_CALL_4(bpf_get_stack_tp_sleepable, void *, tp_buff, void *, buf, u32, size,\n1471:\t\t   u64, flags)\n1472:\t{\n1473:\t\tstruct pt_regs *regs = *(struct pt_regs **)tp_buff;\n1474:\t\n1475:\t\treturn bpf_get_stack_sleepable((unsigned long) regs, (unsigned long) buf,\n1476:\t\t\t\t\t       (unsigned long) size, flags, 0);\n1477:\t}\n1478:\t\n1479:\tstatic const struct bpf_func_proto bpf_get_stack_proto_tp_sleepable = {\n1480:\t\t.func\t\t= bpf_get_stack_tp_sleepable,\n1481:\t\t.gpl_only\t= true,\n1482:\t\t.might_sleep\t= true,\n1483:\t\t.ret_type\t= RET_INTEGER,\n1484:\t\t.arg1_type\t= ARG_PTR_TO_CTX,\n1485:\t\t.arg2_type\t= ARG_PTR_TO_UNINIT_MEM,\n1486:\t\t.arg3_type\t= ARG_MEM_SIZE_OR_ZERO,\n1487:\t\t.arg4_type\t= ARG_ANYTHING,\n1488:\t};\n1489:\t\n1490:\tstatic const struct bpf_func_proto *\n1491:\ttp_prog_func_proto(enum bpf_func_id func_id, const struct bpf_prog *prog)\n1492:\t{\n1493:\t\tswitch (func_id) {\n1494:\t\tcase BPF_FUNC_perf_event_output:\n1495:\t\t\treturn \u0026bpf_perf_event_output_proto_tp;\n1496:\t\tcase BPF_FUNC_get_stackid:\n1497:\t\t\treturn \u0026bpf_get_stackid_proto_tp;\n1498:\t\tcase BPF_FUNC_get_stack:\n1499:\t\t\treturn prog-\u003esleepable ? \u0026bpf_get_stack_proto_tp_sleepable\n1500:\t\t\t\t\t       : \u0026bpf_get_stack_proto_tp;\n1501:\t\tcase BPF_FUNC_get_attach_cookie:\n1502:\t\t\treturn \u0026bpf_get_attach_cookie_proto_trace;\n1503:\t\tdefault:\n1504:\t\t\treturn bpf_tracing_func_proto(func_id, prog);\n"
}

gemini-3.8-flash

null

null

							input: 7468
							output: 39
							thoughts: 33
						

Okay, here's the summary, expressed as though I'm the one thinking it:

**Examining `bpf_trace.c`'s Timeline**

Alright, I'm going to shift gears slightly and take a look at the raw_tp section within `kernel/trace/bpf_trace.c`. Specifically, I want to zero in on the area around the 1700-1770 line numbers. This should be where things get interesting, tracing the execution path or data structures relating to BPF tracepoints in a pretty granular way. I'm hoping I can glean some insights here, so I can have a broader understanding of how those parts interact.

{
  "File": "kernel/trace/bpf_trace.c",
  "FirstLine": 1700,
  "LineCount": 75
}

{
  "Contents": "1700:\t\t.arg2_type\t= ARG_CONST_MAP_PTR,\n1701:\t\t.arg3_type\t= ARG_ANYTHING,\n1702:\t};\n1703:\t\n1704:\tBPF_CALL_4(bpf_get_stack_raw_tp, struct bpf_raw_tracepoint_args *, args,\n1705:\t\t   void *, buf, u32, size, u64, flags)\n1706:\t{\n1707:\t\tstruct pt_regs *regs = get_bpf_raw_tp_regs();\n1708:\t\tint ret;\n1709:\t\n1710:\t\tif (IS_ERR(regs))\n1711:\t\t\treturn PTR_ERR(regs);\n1712:\t\n1713:\t\tperf_fetch_caller_regs(regs);\n1714:\t\tret = bpf_get_stack((unsigned long) regs, (unsigned long) buf,\n1715:\t\t\t\t    (unsigned long) size, flags, 0);\n1716:\t\tput_bpf_raw_tp_regs();\n1717:\t\treturn ret;\n1718:\t}\n1719:\t\n1720:\tstatic const struct bpf_func_proto bpf_get_stack_proto_raw_tp = {\n1721:\t\t.func\t\t= bpf_get_stack_raw_tp,\n1722:\t\t.gpl_only\t= true,\n1723:\t\t.ret_type\t= RET_INTEGER,\n1724:\t\t.arg1_type\t= ARG_PTR_TO_CTX,\n1725:\t\t.arg2_type\t= ARG_PTR_TO_UNINIT_MEM,\n1726:\t\t.arg3_type\t= ARG_MEM_SIZE_OR_ZERO,\n1727:\t\t.arg4_type\t= ARG_ANYTHING,\n1728:\t};\n1729:\t\n1730:\tBPF_CALL_4(bpf_get_stack_raw_tp_sleepable, struct bpf_raw_tracepoint_args *, args,\n1731:\t\t   void *, buf, u32, size, u64, flags)\n1732:\t{\n1733:\t\t/*\n1734:\t\t * Don't take a per-CPU bpf_raw_tp_regs slot here: those slots are a\n1735:\t\t * LIFO nest counter and cannot be held across the sleep that\n1736:\t\t * build_id_parse() may take.  Sleepable programs never run in\n1737:\t\t * IRQ/NMI context, so a stack copy is sufficient.\n1738:\t\t */\n1739:\t\tstruct pt_regs regs = {};\n1740:\t\n1741:\t\tperf_fetch_caller_regs(\u0026regs);\n1742:\t\treturn bpf_get_stack_sleepable((unsigned long) \u0026regs, (unsigned long) buf,\n1743:\t\t\t\t\t       (unsigned long) size, flags, 0);\n1744:\t}\n1745:\t\n1746:\tstatic const struct bpf_func_proto bpf_get_stack_proto_raw_tp_sleepable = {\n1747:\t\t.func\t\t= bpf_get_stack_raw_tp_sleepable,\n1748:\t\t.gpl_only\t= true,\n1749:\t\t.might_sleep\t= true,\n1750:\t\t.ret_type\t= RET_INTEGER,\n1751:\t\t.arg1_type\t= ARG_PTR_TO_CTX,\n1752:\t\t.arg2_type\t= ARG_PTR_TO_UNINIT_MEM,\n1753:\t\t.arg3_type\t= ARG_MEM_SIZE_OR_ZERO,\n1754:\t\t.arg4_type\t= ARG_ANYTHING,\n1755:\t};\n1756:\t\n1757:\tstatic const struct bpf_func_proto *\n1758:\traw_tp_prog_func_proto(enum bpf_func_id func_id, const struct bpf_prog *prog)\n1759:\t{\n1760:\t\tswitch (func_id) {\n1761:\t\tcase BPF_FUNC_perf_event_output:\n1762:\t\t\treturn \u0026bpf_perf_event_output_proto_raw_tp;\n1763:\t\tcase BPF_FUNC_get_stackid:\n1764:\t\t\treturn \u0026bpf_get_stackid_proto_raw_tp;\n1765:\t\tcase BPF_FUNC_get_stack:\n1766:\t\t\treturn prog-\u003esleepable ? \u0026bpf_get_stack_proto_raw_tp_sleepable\n1767:\t\t\t\t\t       : \u0026bpf_get_stack_proto_raw_tp;\n1768:\t\tcase BPF_FUNC_get_attach_cookie:\n1769:\t\t\treturn \u0026bpf_get_attach_cookie_proto_tracing;\n1770:\t\tdefault:\n1771:\t\t\treturn bpf_tracing_func_proto(func_id, prog);\n1772:\t\t}\n1773:\t}\n1774:\t\n"
}

gemini-3.8-flash

null

null

							input: 9024
							output: 37
							thoughts: 30
						

Okay, let's dive into `bpf_get_stack_sleepable` in `kernel/bpf/stackmap.c`.

**Diving into `bpf_get_stack_sleepable`**

Alright, I need to understand what's happening within this function. Given my expertise, I know I'm dealing with BPF and stack maps. The name `bpf_get_stack_sleepable` immediately suggests that it's related to retrieving data from a BPF stack map, and critically, that the operation might *sleep* or yield – which is unusual and signals potential complexity with respect to locking and context switching in the kernel. This piques my interest immediately. I need to understand the scenarios that trigger sleeping within this context, what potential race conditions exist, and how the kernel handles this from a BPF perspective. I need to consider why it needs to be sleepable at all – is it waiting on a resource, dealing with page faults, or something more exotic within the BPF execution environment? Time to dig into the implementation details and see how it interacts with the broader BPF framework and the surrounding kernel subsystems. I'm especially interested in how it manages potential conflicts with other BPF programs and the effects on the rest of the systems as a whole.

{
  "File": "kernel/bpf/stackmap.c",
  "FirstLine": 850,
  "LineCount": 40
}

{
  "Contents": " 850:\t{\n 851:\t\treturn __bpf_get_stack(regs, NULL, buf, size, flags, false /* !may_fault */);\n 852:\t}\n 853:\t\n 854:\tconst struct bpf_func_proto bpf_get_stack_proto = {\n 855:\t\t.func\t\t= bpf_get_stack,\n 856:\t\t.gpl_only\t= true,\n 857:\t\t.ret_type\t= RET_INTEGER,\n 858:\t\t.arg1_type\t= ARG_PTR_TO_CTX,\n 859:\t\t.arg2_type\t= ARG_PTR_TO_UNINIT_MEM,\n 860:\t\t.arg3_type\t= ARG_MEM_SIZE_OR_ZERO,\n 861:\t\t.arg4_type\t= ARG_ANYTHING,\n 862:\t};\n 863:\t\n 864:\tBPF_CALL_4(bpf_get_stack_sleepable, struct pt_regs *, regs, void *, buf, u32, size,\n 865:\t\t   u64, flags)\n 866:\t{\n 867:\t\treturn __bpf_get_stack(regs, NULL, buf, size, flags, true /* may_fault */);\n 868:\t}\n 869:\t\n 870:\tconst struct bpf_func_proto bpf_get_stack_sleepable_proto = {\n 871:\t\t.func\t\t= bpf_get_stack_sleepable,\n 872:\t\t.gpl_only\t= true,\n 873:\t\t.might_sleep\t= true,\n 874:\t\t.ret_type\t= RET_INTEGER,\n 875:\t\t.arg1_type\t= ARG_PTR_TO_CTX,\n 876:\t\t.arg2_type\t= ARG_PTR_TO_UNINIT_MEM,\n 877:\t\t.arg3_type\t= ARG_MEM_SIZE_OR_ZERO,\n 878:\t\t.arg4_type\t= ARG_ANYTHING,\n 879:\t};\n 880:\t\n 881:\tstatic long __bpf_get_task_stack(struct task_struct *task, void *buf, u32 size,\n 882:\t\t\t\t\t u64 flags, bool may_fault)\n 883:\t{\n 884:\t\tstruct pt_regs *regs;\n 885:\t\tlong res = -EINVAL;\n 886:\t\n 887:\t\tif (!try_get_task_stack(task)) {\n 888:\t\t\tmemset(buf, 0, size);\n 889:\t\t\treturn -EFAULT;\n"
}

gemini-3.8-flash

null

null

							input: 10067
							output: 52
							thoughts: 132
						

**Investigating Sleepable BPF Programs in Tracepoints**

Okay, so I'm digging into this `kernel/trace/bpf_trace.c` code, and I see that `bpf_get_stack_tp` and `bpf_get_stack_raw_tp` are essentially just wrappers for the "proto" versions, specifically `bpf_get_stack_proto_tp` and `bpf_get_stack_proto_raw_tp`. That's interesting, but it immediately raises a question in my mind: can tracepoint or raw tracepoint programs be sleepable? I need to understand the constraints here, especially given the complexities of BPF and the kernel's scheduling.

I need to quickly figure out the rules around sleepable programs within the BPF verifier or tracepoints/raw tracepoints. Where would I find that? Ah, yes, the verifier! I need to search the `kernel/bpf/verifier.c` file for the allowed program types. Time to `grep` for "sleepable" and see what comes up. This should tell me what I need to know about allowed sleepable program types in the verifier.

{
  "Expression": "BPF_PROG_TYPE_RAW_TRACEPOINT|BPF_PROG_TYPE_TRACEPOINT",
  "PathPrefixes": [
    "kernel/bpf/verifier.c"
  ]
}

{
  "Output": "kernel/bpf/verifier.c=5698=static enum priv_stack_mode bpf_enable_priv_stack(struct bpf_prog *prog)\n--\nkernel/bpf/verifier.c-5708-\tcase BPF_PROG_TYPE_KPROBE:\nkernel/bpf/verifier.c:5709:\tcase BPF_PROG_TYPE_TRACEPOINT:\nkernel/bpf/verifier.c-5710-\tcase BPF_PROG_TYPE_PERF_EVENT:\nkernel/bpf/verifier.c:5711:\tcase BPF_PROG_TYPE_RAW_TRACEPOINT:\nkernel/bpf/verifier.c-5712-\t\treturn PRIV_STACK_ADAPTIVE;\n--\nkernel/bpf/verifier.c=19372=static bool return_retval_range(struct bpf_verifier_env *env, struct bpf_retval_range *range)\n--\nkernel/bpf/verifier.c-19410-\t\tbreak;\nkernel/bpf/verifier.c:19411:\tcase BPF_PROG_TYPE_RAW_TRACEPOINT:\nkernel/bpf/verifier.c-19412-\t\tif (!env-\u003eprog-\u003eaux-\u003eattach_btf_id)\n--\nkernel/bpf/verifier.c=20980=static bool is_tracing_prog_type(enum bpf_prog_type type)\n--\nkernel/bpf/verifier.c-20983-\tcase BPF_PROG_TYPE_KPROBE:\nkernel/bpf/verifier.c:20984:\tcase BPF_PROG_TYPE_TRACEPOINT:\nkernel/bpf/verifier.c-20985-\tcase BPF_PROG_TYPE_PERF_EVENT:\nkernel/bpf/verifier.c:20986:\tcase BPF_PROG_TYPE_RAW_TRACEPOINT:\nkernel/bpf/verifier.c:20987:\tcase BPF_PROG_TYPE_RAW_TRACEPOINT_WRITABLE:\nkernel/bpf/verifier.c-20988-\t\treturn true;\n--\nkernel/bpf/verifier.c=22563=int bpf_check_attach_target(struct bpf_verifier_log *log,\n--\nkernel/bpf/verifier.c-22661-\t\t\t */\nkernel/bpf/verifier.c:22662:\t\t\tif (tgt_prog-\u003etype == BPF_PROG_TYPE_RAW_TRACEPOINT_WRITABLE) {\nkernel/bpf/verifier.c-22663-\t\t\t\tbpf_log(log,\n--\nkernel/bpf/verifier.c=23001=static bool can_be_sleepable(struct bpf_prog *prog)\n--\nkernel/bpf/verifier.c-23023-\t       prog-\u003etype == BPF_PROG_TYPE_STRUCT_OPS ||\nkernel/bpf/verifier.c:23024:\t       prog-\u003etype == BPF_PROG_TYPE_RAW_TRACEPOINT ||\nkernel/bpf/verifier.c:23025:\t       prog-\u003etype == BPF_PROG_TYPE_TRACEPOINT;\nkernel/bpf/verifier.c-23026-}\n"
}

gemini-3.8-flash

null

null

							input: 11322
							output: 38
							thoughts: 90
						

Okay, here's my take on those thoughts, tailored for an expert audience:

**Analyzing Sleepable BPF Programs**

Alright, so the core question here revolves around whether a BPF program can be "sleepable" – that is, if it's safe for it to be paused during execution, which is critical for certain operations. The current code is suggesting that a program is sleepable if its type is either `BPF_PROG_TYPE_RAW_TRACEPOINT` or `BPF_PROG_TYPE_TRACEPOINT`. I need to verify that this is the only condition considered for programs of these types.

My next step? Dive into the implementation details. I need to understand the logic behind `can_be_sleepable` and more importantly, where it is being used. Specifically, I'm going to look at lines 23000 through 23040 in `kernel/bpf/verifier.c`. That section should expose the granular conditions the verifier uses to determine if a program's execution can safely be interrupted. I need to understand whether this is a complete and accurate assessment of sleepability, considering potential interactions with other BPF features, or whether this is a simplification that could lead to issues. I need to confirm whether any other factors are taken into account, or if there is a more complex set of criteria that goes beyond a simple type check. I need to confirm this is an accurate picture of the current state of affairs.

{
  "File": "kernel/bpf/verifier.c",
  "FirstLine": 23000,
  "LineCount": 40
}

{
  "Contents": "23000:\t\n23001:\tstatic bool can_be_sleepable(struct bpf_prog *prog)\n23002:\t{\n23003:\t\tif (prog-\u003etype == BPF_PROG_TYPE_TRACING) {\n23004:\t\t\tswitch (prog-\u003eexpected_attach_type) {\n23005:\t\t\tcase BPF_TRACE_FENTRY:\n23006:\t\t\tcase BPF_TRACE_FEXIT:\n23007:\t\t\tcase BPF_MODIFY_RETURN:\n23008:\t\t\tcase BPF_TRACE_ITER:\n23009:\t\t\tcase BPF_TRACE_FSESSION:\n23010:\t\t\tcase BPF_TRACE_RAW_TP:\n23011:\t\t\tcase BPF_TRACE_FENTRY_MULTI:\n23012:\t\t\tcase BPF_TRACE_FEXIT_MULTI:\n23013:\t\t\tcase BPF_TRACE_FSESSION_MULTI:\n23014:\t\t\t\treturn true;\n23015:\t\t\tdefault:\n23016:\t\t\t\treturn false;\n23017:\t\t\t}\n23018:\t\t}\n23019:\t\tif (prog-\u003etype == BPF_PROG_TYPE_LSM)\n23020:\t\t\treturn prog-\u003eexpected_attach_type != BPF_LSM_CGROUP;\n23021:\t\n23022:\t\treturn prog-\u003etype == BPF_PROG_TYPE_KPROBE /* only for uprobes */ ||\n23023:\t\t       prog-\u003etype == BPF_PROG_TYPE_STRUCT_OPS ||\n23024:\t\t       prog-\u003etype == BPF_PROG_TYPE_RAW_TRACEPOINT ||\n23025:\t\t       prog-\u003etype == BPF_PROG_TYPE_TRACEPOINT;\n23026:\t}\n23027:\t\n23028:\tstatic int check_attach_btf_id(struct bpf_verifier_env *env)\n23029:\t{\n23030:\t\tstruct bpf_prog *prog = env-\u003eprog;\n23031:\t\tstruct bpf_prog *tgt_prog = prog-\u003eaux-\u003edst_prog;\n23032:\t\tstruct bpf_attach_target_info tgt_info = {};\n23033:\t\tu32 btf_id = prog-\u003eaux-\u003eattach_btf_id;\n23034:\t\tstruct bpf_trampoline *tr;\n23035:\t\tint ret;\n23036:\t\tu64 key;\n23037:\t\n23038:\t\tif (prog-\u003etype == BPF_PROG_TYPE_SYSCALL) {\n23039:\t\t\tif (prog-\u003esleepable)\n"
}

gemini-3.8-flash

null

null

							input: 12475
							output: 37
							thoughts: 501
						

**Analyzing Sleepable Tracepoints and the `BPF_FUNC_get_stack` Helper**

Okay, so I'm diving into how sleepable tracepoints and raw tracepoints are now handled in the BPF world. Specifically, I'm thinking about the implications of allowing these programs, which are *supposed* to be sleepable, to call `BPF_FUNC_get_stack`.

My initial thought is to check how the verifier handles the helper calls.  When verifying a helper function call, it uses `tp_prog_func_proto` or `raw_tp_prog_func_proto` to retrieve the function's prototype. Previously, the `tp_prog_func_proto` would have, for `BPF_FUNC_get_stack`, a corresponding prototype, `bpf_get_stack_proto_tp`, which had `.might_sleep = false`, or it wasn't set, which defaults to `false`.

So, the key realization is that when a sleepable tracepoint or raw tracepoint program called `bpf_get_stack()`, it was using a prototype designed for *non-sleepable* contexts. Then I was going to see what's happening in `bpf_get_stack_proto_raw_tp`.
In the `bpf_get_stack_raw_tp` there's:

	if (IS_ERR(regs))
		return PTR_ERR(regs);

Okay, so this then calls `bpf_get_stack`:

The important call here is the `false` for `!may_fault`. Wait, if the `build_id` flag (`BPF_F_USER_BUILD_ID`) is used, then I'll have to investigate further into the code, especially how `__bpf_get_stack` handles it in this scenario.

{
  "Expression": "__bpf_get_stack",
  "PathPrefixes": [
    "kernel/bpf/stackmap.c"
  ]
}

{
  "Output": "kernel/bpf/stackmap.c=763=static long callchain_finalize(void *buf, u32 size, u32 trace_nr, u32 elem_size,\n--\nkernel/bpf/stackmap.c-777-\nkernel/bpf/stackmap.c:778:static long __bpf_get_stack(struct pt_regs *regs, struct task_struct *task,\nkernel/bpf/stackmap.c-779-\t\t\t    void *buf, u32 size, u64 flags, bool may_fault)\n--\nkernel/bpf/stackmap.c=848=BPF_CALL_4(bpf_get_stack, struct pt_regs *, regs, void *, buf, u32, size,\n--\nkernel/bpf/stackmap.c-850-{\nkernel/bpf/stackmap.c:851:\treturn __bpf_get_stack(regs, NULL, buf, size, flags, false /* !may_fault */);\nkernel/bpf/stackmap.c-852-}\n--\nkernel/bpf/stackmap.c=864=BPF_CALL_4(bpf_get_stack_sleepable, struct pt_regs *, regs, void *, buf, u32, size,\n--\nkernel/bpf/stackmap.c-866-{\nkernel/bpf/stackmap.c:867:\treturn __bpf_get_stack(regs, NULL, buf, size, flags, true /* may_fault */);\nkernel/bpf/stackmap.c-868-}\n--\nkernel/bpf/stackmap.c=881=static long __bpf_get_task_stack(struct task_struct *task, void *buf, u32 size,\n--\nkernel/bpf/stackmap.c-893-\tif (regs)\nkernel/bpf/stackmap.c:894:\t\tres = __bpf_get_stack(regs, task, buf, size, flags, may_fault);\nkernel/bpf/stackmap.c-895-\telse\n--\nkernel/bpf/stackmap.c=924=const struct bpf_func_proto bpf_get_task_stack_sleepable_proto = {\n--\nkernel/bpf/stackmap.c-935-\nkernel/bpf/stackmap.c:936:static int __bpf_get_stack_pe(const struct perf_callchain_entry *trace, u32 trace_nr,\nkernel/bpf/stackmap.c-937-\t\t\t      void *buf, u32 size, u64 flags)\n--\nkernel/bpf/stackmap.c=962=BPF_CALL_4(bpf_get_stack_pe, struct bpf_perf_event_data_kern *, ctx,\n--\nkernel/bpf/stackmap.c-972-\tif (!(event-\u003eattr.sample_type \u0026 PERF_SAMPLE_CALLCHAIN))\nkernel/bpf/stackmap.c:973:\t\treturn __bpf_get_stack(regs, NULL, buf, size, flags, false /* !may_fault */);\nkernel/bpf/stackmap.c-974-\n--\nkernel/bpf/stackmap.c-989-\tif (kernel) {\nkernel/bpf/stackmap.c:990:\t\terr = __bpf_get_stack_pe(trace, nr_kernel, buf, size, flags);\nkernel/bpf/stackmap.c-991-\t} else { /* user */\n--\nkernel/bpf/stackmap.c-997-\t\tflags = (flags \u0026 ~BPF_F_SKIP_FIELD_MASK) | skip;\nkernel/bpf/stackmap.c:998:\t\terr = __bpf_get_stack_pe(trace, trace-\u003enr, buf, size, flags);\nkernel/bpf/stackmap.c-999-\t}\n"
}

gemini-3.8-flash

null

null

							input: 14385
							output: 37
							thoughts: 32
						

Okay, let's dive into this. Here's my perspective on understanding that code snippet:

**Diving into `__bpf_get_stack` in `kernel/bpf/stackmap.c`**

Alright, I'm going to take a look at the `__bpf_get_stack` function, specifically around line 778 in `kernel/bpf/stackmap.c`. This isn't just a casual read; I need to understand exactly what's going on within this stackmap functionality. I'm assuming that this is a core component of how BPF interacts with the kernel stack, likely related to capturing or accessing stack traces for analysis or debugging. Given my expertise, I'm probably looking for details around allocation, the underlying data structures, any potential race conditions, and how it handles different stack frame configurations. I'll be focused on how it interacts with the BPF program's context, and how it handles potential errors. I'll need to remember any similar code in other areas of the BPF subsystem that might also use the stackmap.

{
  "File": "kernel/bpf/stackmap.c",
  "FirstLine": 775,
  "LineCount": 60
}

{
  "Contents": " 775:\t\treturn copy_len;\n 776:\t}\n 777:\t\n 778:\tstatic long __bpf_get_stack(struct pt_regs *regs, struct task_struct *task,\n 779:\t\t\t\t    void *buf, u32 size, u64 flags, bool may_fault)\n 780:\t{\n 781:\t\tbool user_build_id = flags \u0026 BPF_F_USER_BUILD_ID;\n 782:\t\tbool crosstask = task \u0026\u0026 task != current;\n 783:\t\tu32 skip = flags \u0026 BPF_F_SKIP_FIELD_MASK;\n 784:\t\tbool user = flags \u0026 BPF_F_USER_STACK;\n 785:\t\tstruct perf_callchain_entry *trace;\n 786:\t\tu32 trace_nr, elem_size, max_depth;\n 787:\t\tbool kernel = !user;\n 788:\t\tint err = -EINVAL;\n 789:\t\n 790:\t\tif (unlikely(flags \u0026 ~(BPF_F_SKIP_FIELD_MASK | BPF_F_USER_STACK |\n 791:\t\t\t\t       BPF_F_USER_BUILD_ID)))\n 792:\t\t\tgoto clear;\n 793:\t\tif (kernel \u0026\u0026 user_build_id)\n 794:\t\t\tgoto clear;\n 795:\t\n 796:\t\telem_size = user_build_id ? sizeof(struct bpf_stack_build_id) : sizeof(u64);\n 797:\t\tif (unlikely(size % elem_size))\n 798:\t\t\tgoto clear;\n 799:\t\n 800:\t\t/* cannot get valid user stack for task without user_mode regs */\n 801:\t\tif (task \u0026\u0026 user \u0026\u0026 !user_mode(regs))\n 802:\t\t\tgoto err_fault;\n 803:\t\n 804:\t\t/* get_perf_callchain does not support crosstask user stack walking\n 805:\t\t * but returns an empty stack instead of NULL.\n 806:\t\t */\n 807:\t\tif (crosstask \u0026\u0026 user) {\n 808:\t\t\terr = -EOPNOTSUPP;\n 809:\t\t\tgoto clear;\n 810:\t\t}\n 811:\t\n 812:\t\tmax_depth = stack_map_calculate_max_depth(size, elem_size, flags);\n 813:\t\n 814:\t\tpreempt_disable();\n 815:\t\tif (may_fault)\n 816:\t\t\trcu_read_lock(); /* need RCU for perf's callchain below */\n 817:\t\n 818:\t\tif (kernel \u0026\u0026 task) {\n 819:\t\t\ttrace = get_callchain_entry_for_task(task, max_depth);\n 820:\t\t} else {\n 821:\t\t\ttrace = get_perf_callchain(regs, kernel, user, max_depth,\n 822:\t\t\t\t\t\t   crosstask, false, 0);\n 823:\t\t}\n 824:\t\n 825:\t\tif (unlikely(!trace) || trace-\u003enr \u003c skip) {\n 826:\t\t\tif (may_fault)\n 827:\t\t\t\trcu_read_unlock();\n 828:\t\t\tpreempt_enable();\n 829:\t\t\tgoto err_fault;\n 830:\t\t}\n 831:\t\n 832:\t\ttrace_nr = callchain_store(trace, trace-\u003enr, buf, elem_size, flags);\n 833:\t\n 834:\t\t/* trace should not be dereferenced after this point */\n"
}

gemini-3.8-flash

null

null

							input: 15638
							output: 37
							thoughts: 16
						

Okay, here's my interpretation of that thought process, tailored for an expert audience, and written in the first person:

**Diving Deeper into `__bpf_get_stack`**

Alright, so the initial thought is clear: we need to dig into `__bpf_get_stack`. I'm already familiar with the general landscape of BPF, so the mention of this function immediately piques my interest. It likely relates to retrieving the BPF program's stack trace, a crucial piece of information for debugging, performance analysis, and potentially even security auditing within the eBPF context. 

My immediate questions are: What's the context? What's the *purpose* of looking deeper now? Are we troubleshooting a specific issue, optimizing a program, or trying to understand some unexpected behavior? Perhaps we're dealing with a stack overflow, a performance bottleneck related to stack usage, or maybe even investigating a potential vulnerability that exploits stack manipulation. The specific reason will help clarify the direction of the analysis.
I anticipate encountering things like stack frame layout details, possibly calls to other helper functions, and likely some interaction with the kernel's stack unwinding mechanism. I'll need to pay close attention to the data structures involved, like the stack pointer (`SP`) and base pointer (`BP`), any potential stack validation checks, and any interactions with user-space memory if this is related to a ring buffer or other form of memory copy.
I'm also going to be mentally mapping this function to other related BPF tools and frameworks that I know. For example, I'll be thinking about how it fits in with BCC, bpftrace, and the various libraries that abstract away some of the complexity of BPF development.
The key is to understand how this function contributes to building a useful stack trace for the BPF program.
Let's get to it and see what it tells us.

{
  "File": "kernel/bpf/stackmap.c",
  "FirstLine": 835,
  "LineCount": 40
}

{
  "Contents": " 835:\t\tif (may_fault)\n 836:\t\t\trcu_read_unlock();\n 837:\t\tpreempt_enable();\n 838:\t\n 839:\t\treturn callchain_finalize(buf, size, trace_nr, elem_size, flags, may_fault);\n 840:\t\n 841:\terr_fault:\n 842:\t\terr = -EFAULT;\n 843:\tclear:\n 844:\t\tmemset(buf, 0, size);\n 845:\t\treturn err;\n 846:\t}\n 847:\t\n 848:\tBPF_CALL_4(bpf_get_stack, struct pt_regs *, regs, void *, buf, u32, size,\n 849:\t\t   u64, flags)\n 850:\t{\n 851:\t\treturn __bpf_get_stack(regs, NULL, buf, size, flags, false /* !may_fault */);\n 852:\t}\n 853:\t\n 854:\tconst struct bpf_func_proto bpf_get_stack_proto = {\n 855:\t\t.func\t\t= bpf_get_stack,\n 856:\t\t.gpl_only\t= true,\n 857:\t\t.ret_type\t= RET_INTEGER,\n 858:\t\t.arg1_type\t= ARG_PTR_TO_CTX,\n 859:\t\t.arg2_type\t= ARG_PTR_TO_UNINIT_MEM,\n 860:\t\t.arg3_type\t= ARG_MEM_SIZE_OR_ZERO,\n 861:\t\t.arg4_type\t= ARG_ANYTHING,\n 862:\t};\n 863:\t\n 864:\tBPF_CALL_4(bpf_get_stack_sleepable, struct pt_regs *, regs, void *, buf, u32, size,\n 865:\t\t   u64, flags)\n 866:\t{\n 867:\t\treturn __bpf_get_stack(regs, NULL, buf, size, flags, true /* may_fault */);\n 868:\t}\n 869:\t\n 870:\tconst struct bpf_func_proto bpf_get_stack_sleepable_proto = {\n 871:\t\t.func\t\t= bpf_get_stack_sleepable,\n 872:\t\t.gpl_only\t= true,\n 873:\t\t.might_sleep\t= true,\n 874:\t\t.ret_type\t= RET_INTEGER,\n"
}

gemini-3.8-flash

null

null

							input: 16759
							output: 37
							thoughts: 71
						

Here's my summary, as if I were thinking it:

**Analyzing the `callchain_finalize` Function**

Alright, let's dive into this `callchain_finalize` function. I see the signature: `static long callchain_finalize(void *buf, u32 size, u32 trace_nr, u32 elem_size, u64 flags, bool may_fault)`. Immediately, I'm thinking about the implications of each parameter: `buf` likely holds the callchain data, `size` is the allocated buffer size, `trace_nr` probably indicates the number of traces or entries, and `elem_size` is the size of each element within the buffer. The `flags` parameter is a bit more open-ended; it could contain bitfields controlling behavior or describing the state. Finally, `may_fault`... ah, this is interesting. That suggests we might be operating in a context where memory access can potentially fail, perhaps dealing with user-space data or a constrained environment.

So, let's get into the details of what this function is *actually* doing. I need to understand the logic flow here. My initial thought is it's processing or post-processing callchain data. It's the final stage, presumably, before making that data available, perhaps to the user or another part of the tracing system. I need to trace the execution path and identify any potential pitfalls, especially considering that `may_fault` flag. Let's see how it handles errors, and memory operations, and what the overall goal of the function is.

{
  "File": "kernel/bpf/stackmap.c",
  "FirstLine": 750,
  "LineCount": 30
}

{
  "Contents": " 750:\t\n 751:\t\tips = trace-\u003eip + skip;\n 752:\t\tif (user_build_id) {\n 753:\t\t\tstruct bpf_stack_build_id *id_offs = buf;\n 754:\t\n 755:\t\t\tfor (u32 i = 0; i \u003c trace_nr; i++)\n 756:\t\t\t\tid_offs[i].ip = ips[i];\n 757:\t\t} else {\n 758:\t\t\tmemcpy(buf, ips, copy_len);\n 759:\t\t}\n 760:\t\treturn trace_nr;\n 761:\t}\n 762:\t\n 763:\tstatic long callchain_finalize(void *buf, u32 size, u32 trace_nr, u32 elem_size,\n 764:\t\t\t\t       u64 flags, bool may_fault)\n 765:\t{\n 766:\t\tbool user_build_id = flags \u0026 BPF_F_USER_BUILD_ID;\n 767:\t\tbool user = flags \u0026 BPF_F_USER_STACK;\n 768:\t\tu32 copy_len = trace_nr * elem_size;\n 769:\t\n 770:\t\tif (user_build_id)\n 771:\t\t\tstack_map_get_build_id_offset(buf, trace_nr, user, may_fault);\n 772:\t\n 773:\t\tif (size \u003e copy_len)\n 774:\t\t\tmemset(buf + copy_len, 0, size - copy_len);\n 775:\t\treturn copy_len;\n 776:\t}\n 777:\t\n 778:\tstatic long __bpf_get_stack(struct pt_regs *regs, struct task_struct *task,\n 779:\t\t\t\t    void *buf, u32 size, u64 flags, bool may_fault)\n"
}

gemini-3.8-flash

null

null

							input: 17708
							output: 41
							thoughts: 70
						

Here's my summary, as I see it:

**Potential Sleep in `stack_map_get_build_id_offset` when `may_fault` is True**

Alright, I'm taking a look at this `stack_map_get_build_id_offset` function, and something's pinging my radar. It looks like when `may_fault` is enabled, this function has the potential to sleep. I need to investigate the implications of this, because I know that can introduce subtle but critical issues in certain contexts. I think specifically of scenarios where `build_id_parse` might be called, or if there's any interaction with user memory or `mmap_read_lock` that could trigger a fault. I'm going to carefully analyze `stack_map_get_build_id_offset` to understand the exact conditions and paths that lead to a potential sleep and assess the impact this has on the surrounding system.

{
  "Expression": "stack_map_get_build_id_offset",
  "PathPrefixes": [
    "kernel/bpf/stackmap.c"
  ]
}

{
  "Output": "kernel/bpf/stackmap.c=183=struct stack_map_cached_vma {\n--\nkernel/bpf/stackmap.c-191-/*\nkernel/bpf/stackmap.c:192: * Per stack_map_get_build_id_offset() call cache of the last VMA with a build ID\nkernel/bpf/stackmap.c-193- * resolved and the last VMA with no usable build ID. Adjacent stack frames tend\n--\nkernel/bpf/stackmap.c=318=static void stack_map_unlock_vma(struct stack_map_vma_lock *lock)\n--\nkernel/bpf/stackmap.c-327-\nkernel/bpf/stackmap.c:328:static void stack_map_get_build_id_offset_sleepable(struct bpf_stack_build_id *id_offs,\nkernel/bpf/stackmap.c-329-\t\t\t\t\t\t    u32 trace_nr)\n--\nkernel/bpf/stackmap.c-408- */\nkernel/bpf/stackmap.c:409:static void stack_map_get_build_id_offset(struct bpf_stack_build_id *id_offs,\nkernel/bpf/stackmap.c-410-\t\t\t\t\t  u32 trace_nr, bool user, bool may_fault)\n--\nkernel/bpf/stackmap.c-418-\tif (may_fault \u0026\u0026 has_user_ctx) {\nkernel/bpf/stackmap.c:419:\t\tstack_map_get_build_id_offset_sleepable(id_offs, trace_nr);\nkernel/bpf/stackmap.c-420-\t\treturn;\n--\nkernel/bpf/stackmap.c=589=static long stackid_install(struct stackid *stackid, struct bpf_map *map,\n--\nkernel/bpf/stackmap.c-600-\t\tid_offs = (struct bpf_stack_build_id *)new_bucket-\u003edata;\nkernel/bpf/stackmap.c:601:\t\tstack_map_get_build_id_offset(id_offs, stackid-\u003enr, user, false /* !may_fault */);\nkernel/bpf/stackmap.c-602-\t\ttrace_len = stackid-\u003enr * sizeof(struct bpf_stack_build_id);\n--\nkernel/bpf/stackmap.c=763=static long callchain_finalize(void *buf, u32 size, u32 trace_nr, u32 elem_size,\n--\nkernel/bpf/stackmap.c-770-\tif (user_build_id)\nkernel/bpf/stackmap.c:771:\t\tstack_map_get_build_id_offset(buf, trace_nr, user, may_fault);\nkernel/bpf/stackmap.c-772-\n"
}

gemini-3.8-flash

null

null

							input: 18747
							output: 29
							thoughts: 1175
						

**Analyzing Sleepable BPF Stack Walking in Tracepoints**

Okay, here's what's running through my head. I'm looking at `bpf_trace.c` and immediately, I see a key difference in how stack traces are handled between the regular and sleepable versions for tracepoints. `bpf_get_stack_tp_sleepable` and `bpf_get_stack_raw_tp_sleepable` are the focus. The key is that `bpf_get_stack_raw_tp_sleepable` skips using the `get_bpf_raw_tp_regs()` and `put_bpf_raw_tp_regs()` mechanism, opting instead for `perf_fetch_caller_regs(&regs)`. And, critically, it passes a `may_fault = true` flag to `bpf_get_stack_sleepable`. `bpf_get_stack_proto_tp_sleepable` and `bpf_get_stack_proto_raw_tp_sleepable` confirm the trend with `.might_sleep = true`. The comment in the raw tracepoint version hammers home the reason: we *need* this to handle potential sleeps within `build_id_parse`. LIFO nest counters cannot be held across the sleep that `build_id_parse()` can incur.

The next thought is, can this even be triggered and fuzzed in a virtualized environment like syzkaller? Absolutely! BPF programs with `BPF_PROG_TYPE_TRACEPOINT` or `BPF_PROG_TYPE_RAW_TRACEPOINT` and the `BPF_F_SLEEPABLE` flag can be loaded via the `bpf()` syscall. Then, using `perf_event_open` with `ioctl(PERF_EVENT_IOC_SET_BPF)` or `BPF_LINK_CREATE`, we attach the program to a tracepoint or raw tracepoint. When the appropriate kernel function or tracepoint is hit, the BPF program runs, calls `bpf_get_stack()`, which resolves to the sleepable versions. Syzkaller already has thorough fuzzing for these BPF features, so it's ready to go.

Now, let's step back and consider the bigger picture: Is this reachable code? Yes, it's core BPF in `kernel/trace/bpf_trace.c`. Does it touch directly executable code? Yes, the new helper implementations `bpf_get_stack_tp_sleepable` and `bpf_get_stack_raw_tp_sleepable` specifically allow sleepable stack walking in a tracepoint context, doing faultable operations like `stack_map_get_build_id_offset_sleepable`, `build_id_parse`, stack frame allocation, and taking locks across sleep. This is *exactly* the kind of thing that's ripe for fuzzing – the potential for new states and code paths within a sleepable BPF tracepoint context is huge.

The next step is to nail down the configuration requirements for this code and pinpoint the critical symbols for fuzzing. Time to check the kernel configs in `kernel/trace/bpf_trace.c` and the `Makefile` in `kernel/trace/`.

{
  "Expression": "bpf_trace",
  "PathPrefixes": [
    "kernel/trace/"
  ]
}

{
  "Output": "\nFull output is too long, showing 200 out of 202 lines.\nUse more precise expression or PathPrefixes if possible.\n\nNumber of matching lines per file (5 files in total):\nkernel/trace/Makefile:2\nkernel/trace/bpf_trace.c:45\nkernel/trace/bpf_trace.h:3\nkernel/trace/trace_events.c:1\nkernel/trace/trace_syscalls.c:2\n\nkernel/trace/Makefile=54=KCOV_INSTRUMENT_trace_irqsoff.o := n\nkernel/trace/Makefile-55-\nkernel/trace/Makefile:56:CFLAGS_bpf_trace.o := -I$(src)\nkernel/trace/Makefile-57-\n--\nkernel/trace/Makefile=110=obj-$(CONFIG_USER_EVENTS) += trace_events_user.o\nkernel/trace/Makefile:111:obj-$(CONFIG_BPF_EVENTS) += bpf_trace.o\nkernel/trace/Makefile-112-obj-$(CONFIG_KPROBE_EVENTS) += trace_kprobe.o\n--\nkernel/trace/bpf_trace.c-38-#define CREATE_TRACE_POINTS\nkernel/trace/bpf_trace.c:39:#include \"bpf_trace.h\"\nkernel/trace/bpf_trace.c-40-\n--\nkernel/trace/bpf_trace.c-48-#ifdef CONFIG_MODULES\nkernel/trace/bpf_trace.c:49:struct bpf_trace_module {\nkernel/trace/bpf_trace.c-50-\tstruct module *module;\n--\nkernel/trace/bpf_trace.c-53-\nkernel/trace/bpf_trace.c:54:static LIST_HEAD(bpf_trace_modules);\nkernel/trace/bpf_trace.c-55-static DEFINE_MUTEX(bpf_module_mutex);\n--\nkernel/trace/bpf_trace.c=57=static struct bpf_raw_event_map *bpf_get_raw_tracepoint_module(const char *name)\n--\nkernel/trace/bpf_trace.c-59-\tstruct bpf_raw_event_map *btp, *ret = NULL;\nkernel/trace/bpf_trace.c:60:\tstruct bpf_trace_module *btm;\nkernel/trace/bpf_trace.c-61-\tunsigned int i;\n--\nkernel/trace/bpf_trace.c-63-\tmutex_lock(\u0026bpf_module_mutex);\nkernel/trace/bpf_trace.c:64:\tlist_for_each_entry(btm, \u0026bpf_trace_modules, list) {\nkernel/trace/bpf_trace.c-65-\t\tfor (i = 0; i \u003c btm-\u003emodule-\u003enum_bpf_raw_events; ++i) {\n--\nkernel/trace/bpf_trace.c=381=static const struct bpf_func_proto bpf_probe_write_user_proto = {\n--\nkernel/trace/bpf_trace.c-392-\nkernel/trace/bpf_trace.c:393:BPF_CALL_5(bpf_trace_printk, char *, fmt, u32, fmt_size, u64, arg1,\nkernel/trace/bpf_trace.c-394-\t   u64, arg2, u64, arg3)\n--\nkernel/trace/bpf_trace.c-409-\nkernel/trace/bpf_trace.c:410:\ttrace_bpf_trace_printk(data.buf);\nkernel/trace/bpf_trace.c-411-\n--\nkernel/trace/bpf_trace.c-416-\nkernel/trace/bpf_trace.c:417:static const struct bpf_func_proto bpf_trace_printk_proto = {\nkernel/trace/bpf_trace.c:418:\t.func\t\t= bpf_trace_printk,\nkernel/trace/bpf_trace.c-419-\t.gpl_only\t= true,\n--\nkernel/trace/bpf_trace.c=425=static void __set_printk_clr_event(struct work_struct *work)\n--\nkernel/trace/bpf_trace.c-427-\t/*\nkernel/trace/bpf_trace.c:428:\t * This program might be calling bpf_trace_printk,\nkernel/trace/bpf_trace.c:429:\t * so enable the associated bpf_trace/bpf_trace_printk event.\nkernel/trace/bpf_trace.c-430-\t * Repeat this each time as it is possible a user has\nkernel/trace/bpf_trace.c:431:\t * disabled bpf_trace_printk events.  By loading a program\nkernel/trace/bpf_trace.c:432:\t * calling bpf_trace_printk() however the user has expressed\nkernel/trace/bpf_trace.c-433-\t * the intent to see such events.\nkernel/trace/bpf_trace.c-434-\t */\nkernel/trace/bpf_trace.c:435:\tif (trace_set_clr_event(\"bpf_trace\", \"bpf_trace_printk\", 1))\nkernel/trace/bpf_trace.c:436:\t\tpr_warn_ratelimited(\"could not enable bpf_trace_printk events\");\nkernel/trace/bpf_trace.c-437-}\n--\nkernel/trace/bpf_trace.c=440=const struct bpf_func_proto *bpf_get_trace_printk_proto(void)\n--\nkernel/trace/bpf_trace.c-442-\tschedule_work(\u0026set_printk_work);\nkernel/trace/bpf_trace.c:443:\treturn \u0026bpf_trace_printk_proto;\nkernel/trace/bpf_trace.c-444-}\nkernel/trace/bpf_trace.c-445-\nkernel/trace/bpf_trace.c:446:BPF_CALL_4(bpf_trace_vprintk, char *, fmt, u32, fmt_size, const void *, args,\nkernel/trace/bpf_trace.c-447-\t   u32, data_len)\n--\nkernel/trace/bpf_trace.c-465-\nkernel/trace/bpf_trace.c:466:\ttrace_bpf_trace_printk(data.buf);\nkernel/trace/bpf_trace.c-467-\n--\nkernel/trace/bpf_trace.c-472-\nkernel/trace/bpf_trace.c:473:static const struct bpf_func_proto bpf_trace_vprintk_proto = {\nkernel/trace/bpf_trace.c:474:\t.func\t\t= bpf_trace_vprintk,\nkernel/trace/bpf_trace.c-475-\t.gpl_only\t= true,\n--\nkernel/trace/bpf_trace.c=483=const struct bpf_func_proto *bpf_get_trace_vprintk_proto(void)\n--\nkernel/trace/bpf_trace.c-485-\tschedule_work(\u0026set_printk_work);\nkernel/trace/bpf_trace.c:486:\treturn \u0026bpf_trace_vprintk_proto;\nkernel/trace/bpf_trace.c-487-}\n--\nkernel/trace/bpf_trace.c=646=__bpf_perf_event_output(struct pt_regs *regs, struct bpf_map *map,\n--\nkernel/trace/bpf_trace.c-681- */\nkernel/trace/bpf_trace.c:682:struct bpf_trace_sample_data {\nkernel/trace/bpf_trace.c-683-\tstruct perf_sample_data sds[3];\n--\nkernel/trace/bpf_trace.c-685-\nkernel/trace/bpf_trace.c:686:static DEFINE_PER_CPU(struct bpf_trace_sample_data, bpf_trace_sds);\nkernel/trace/bpf_trace.c:687:static DEFINE_PER_CPU(int, bpf_trace_nest_level);\nkernel/trace/bpf_trace.c-688-BPF_CALL_5(bpf_perf_event_output, struct pt_regs *, regs, struct bpf_map *, map,\n--\nkernel/trace/bpf_trace.c-690-{\nkernel/trace/bpf_trace.c:691:\tstruct bpf_trace_sample_data *sds;\nkernel/trace/bpf_trace.c-692-\tstruct perf_raw_record raw = {\n--\nkernel/trace/bpf_trace.c-701-\tpreempt_disable();\nkernel/trace/bpf_trace.c:702:\tsds = this_cpu_ptr(\u0026bpf_trace_sds);\nkernel/trace/bpf_trace.c:703:\tnest_level = this_cpu_inc_return(bpf_trace_nest_level);\nkernel/trace/bpf_trace.c-704-\n--\nkernel/trace/bpf_trace.c-720-out:\nkernel/trace/bpf_trace.c:721:\tthis_cpu_dec(bpf_trace_nest_level);\nkernel/trace/bpf_trace.c-722-\tpreempt_enable();\n--\nkernel/trace/bpf_trace.c=741=static DEFINE_PER_CPU(struct bpf_nested_pt_regs, bpf_pt_regs);\nkernel/trace/bpf_trace.c:742:static DEFINE_PER_CPU(struct bpf_trace_sample_data, bpf_misc_sds);\nkernel/trace/bpf_trace.c-743-\n--\nkernel/trace/bpf_trace.c=1085=BPF_CALL_1(bpf_get_func_ip_kprobe, struct pt_regs *, regs)\nkernel/trace/bpf_trace.c-1086-{\nkernel/trace/bpf_trace.c:1087:\tstruct bpf_trace_run_ctx *run_ctx __maybe_unused;\nkernel/trace/bpf_trace.c-1088-\tstruct kprobe *kp;\n--\nkernel/trace/bpf_trace.c-1090-#ifdef CONFIG_UPROBES\nkernel/trace/bpf_trace.c:1091:\trun_ctx = container_of(current-\u003ebpf_ctx, struct bpf_trace_run_ctx, run_ctx);\nkernel/trace/bpf_trace.c-1092-\tif (run_ctx-\u003eis_uprobe)\n--\nkernel/trace/bpf_trace.c=1159=BPF_CALL_1(bpf_get_attach_cookie_trace, void *, ctx)\nkernel/trace/bpf_trace.c-1160-{\nkernel/trace/bpf_trace.c:1161:\tstruct bpf_trace_run_ctx *run_ctx;\nkernel/trace/bpf_trace.c-1162-\nkernel/trace/bpf_trace.c:1163:\trun_ctx = container_of(current-\u003ebpf_ctx, struct bpf_trace_run_ctx, run_ctx);\nkernel/trace/bpf_trace.c-1164-\treturn run_ctx-\u003ebpf_cookie;\n--\nkernel/trace/bpf_trace.c=1186=BPF_CALL_1(bpf_get_attach_cookie_tracing, void *, ctx)\nkernel/trace/bpf_trace.c-1187-{\nkernel/trace/bpf_trace.c:1188:\tstruct bpf_trace_run_ctx *run_ctx;\nkernel/trace/bpf_trace.c-1189-\nkernel/trace/bpf_trace.c:1190:\trun_ctx = container_of(current-\u003ebpf_ctx, struct bpf_trace_run_ctx, run_ctx);\nkernel/trace/bpf_trace.c-1191-\treturn run_ctx-\u003ebpf_cookie;\n--\nkernel/trace/bpf_trace.c=2153=static __always_inline\nkernel/trace/bpf_trace.c:2154:void __bpf_trace_run(struct bpf_raw_tp_link *link, u64 *args)\nkernel/trace/bpf_trace.c-2155-{\n--\nkernel/trace/bpf_trace.c-2159-\tstruct bpf_run_ctx *old_run_ctx;\nkernel/trace/bpf_trace.c:2160:\tstruct bpf_trace_run_ctx run_ctx;\nkernel/trace/bpf_trace.c-2161-\n--\nkernel/trace/bpf_trace.c-2214-#define BPF_TRACE_DEFN_x(x)\t\t\t\t\t\t\\\nkernel/trace/bpf_trace.c:2215:\tvoid bpf_trace_run##x(struct bpf_raw_tp_link *link,\t\t\\\nkernel/trace/bpf_trace.c-2216-\t\t\t      REPEAT(x, SARG, __DL_COM, __SEQ_0_11))\t\\\n--\nkernel/trace/bpf_trace.c-2219-\t\tREPEAT(x, COPY, __DL_SEM, __SEQ_0_11);\t\t\t\\\nkernel/trace/bpf_trace.c:2220:\t\t__bpf_trace_run(link, args);\t\t\t\t\\\nkernel/trace/bpf_trace.c-2221-\t}\t\t\t\t\t\t\t\t\\\nkernel/trace/bpf_trace.c:2222:\tEXPORT_SYMBOL_GPL(bpf_trace_run##x)\nkernel/trace/bpf_trace.c-2223-BPF_TRACE_DEFN_x(1);\n--\nkernel/trace/bpf_trace.c=2339=static int bpf_event_notify(struct notifier_block *nb, unsigned long op,\n--\nkernel/trace/bpf_trace.c-2341-{\nkernel/trace/bpf_trace.c:2342:\tstruct bpf_trace_module *btm, *tmp;\nkernel/trace/bpf_trace.c-2343-\tstruct module *mod = module;\n--\nkernel/trace/bpf_trace.c-2356-\t\t\tbtm-\u003emodule = module;\nkernel/trace/bpf_trace.c:2357:\t\t\tlist_add(\u0026btm-\u003elist, \u0026bpf_trace_modules);\nkernel/trace/bpf_trace.c-2358-\t\t} else {\n--\nkernel/trace/bpf_trace.c-2362-\tcase MODULE_STATE_GOING:\nkernel/trace/bpf_trace.c:2363:\t\tlist_for_each_entry_safe(btm, tmp, \u0026bpf_trace_modules, list) {\nkernel/trace/bpf_trace.c-2364-\t\t\tif (btm-\u003emodule == module) {\n--\nkernel/trace/bpf_trace.c=3516=static const struct btf_kfunc_id_set bpf_session_kfunc_set = {\n--\nkernel/trace/bpf_trace.c-3521-\nkernel/trace/bpf_trace.c:3522:static int __init bpf_trace_kfuncs_init(void)\nkernel/trace/bpf_trace.c-3523-{\n--\nkernel/trace/bpf_trace.c-3531-\nkernel/trace/bpf_trace.c:3532:late_initcall(bpf_trace_kfuncs_init);\nkernel/trace/bpf_trace.c-3533-\n--\nkernel/trace/bpf_trace.h-2-#undef TRACE_SYSTEM\nkernel/trace/bpf_trace.h:3:#define TRACE_SYSTEM bpf_trace\nkernel/trace/bpf_trace.h-4-\n--\nkernel/trace/bpf_trace.h-10-\nkernel/trace/bpf_trace.h:11:TRACE_EVENT(bpf_trace_printk,\nkernel/trace/bpf_trace.h-12-\n--\nkernel/trace/bpf_trace.h-31-#define TRACE_INCLUDE_PATH .\nkernel/trace/bpf_trace.h:32:#define TRACE_INCLUDE_FILE bpf_trace\nkernel/trace/bpf_trace.h-33-\n--\nkernel/trace/trace_events.c=2273=event_btf_ids_read(struct file *filp, char __user *ubuf, size_t cnt, loff_t *ppos)\n--\nkernel/trace/trace_events.c-2306-\t\t * Without FL_TRACEPOINT the dispatcher is shared (e.g. all\nkernel/trace/trace_events.c:2307:\t\t * per-syscall events fan out from __bpf_trace_sys_enter), so\nkernel/trace/trace_events.c-2308-\t\t * raw_btf_id has no per-event attach point — report 0.\n--\nkernel/trace/trace_syscalls.c=1309=BTF_ID_LIST(syscall_enter_btf_ids)\nkernel/trace/trace_syscalls.c:1310:BTF_ID(func,   __bpf_trace_sys_enter)\nkernel/trace/trace_syscalls.c-1311-BTF_ID(struct, trace_event_raw_sys_enter)\n--\nkernel/trace/trace_syscalls.c=1313=BTF_ID_LIST(syscall_exit_btf_ids)\n\n"
}

gemini-3.8-flash

null

null

							input: 25114
							output: 19
							thoughts: 49
						

Okay, here's my interpretation of those thoughts, presented as my own mental process, given my expertise:

**Checking the BPF Trace Implementation**

Alright, so `bpf_trace.o` is only getting compiled if `CONFIG_BPF_EVENTS` is set. That makes sense, keeps things modular, but I need to quickly verify where that config option is defined. I'll head over to the kernel source, specifically within the tracing subsystem. My guess is it's in `kernel/trace/Kconfig`, but I'll double-check to be sure. It's crucial to understand where this dependency lies, so I know how the feature is enabled/disabled and any associated implications. I'll want to review the help text and defaults as well, if they are there, to get a handle on what BPF events are and how the setting influences other configurations.

{
  "Expression": "config BPF_EVENTS"
}

{
  "Output": "kernel/trace/Kconfig=859=config EPROBE_EVENTS\n--\nkernel/trace/Kconfig-872-\nkernel/trace/Kconfig:873:config BPF_EVENTS\nkernel/trace/Kconfig-874-\tdepends on BPF_SYSCALL\n"
}

gemini-3.8-flash

null

null

							input: 25450
							output: 34
							thoughts: 19
						

Here's my take on the kernel's tracing configuration:

**Diving into `Kconfig` for Tracing**

Okay, let's zero in on `kernel/trace/Kconfig` around line 873. My experience tells me that area likely pertains to a specific tracing feature, or a group of related features, based on the file and line number. I'm guessing it's a conditional compilation option, perhaps something that enables or disables a particular tracepoint, a specific tracing subsystem, or some instrumentation aspect. Knowing the specific context within tracing is crucial here; are we talking about user-space tracing, kernel-level events, or something more specialized? My initial instinct is to look for dependencies – what other options need to be enabled for this section to be relevant? And equally important, what are the potential performance implications? Turning on tracing can be a double-edged sword; we need to understand the overhead. Ultimately, I'm trying to figure out what functionality that config entry controls.

{
  "File": "kernel/trace/Kconfig",
  "FirstLine": 870,
  "LineCount": 20
}

{
  "Contents": " 870:\t\t  convert the type of an event field. For example, turn an\n 871:\t\t  address into a string.\n 872:\t\n 873:\tconfig BPF_EVENTS\n 874:\t\tdepends on BPF_SYSCALL\n 875:\t\tdepends on (KPROBE_EVENTS || UPROBE_EVENTS) \u0026\u0026 PERF_EVENTS\n 876:\t\tbool\n 877:\t\tdefault y\n 878:\t\thelp\n 879:\t\t  This allows the user to attach BPF programs to kprobe, uprobe, and\n 880:\t\t  tracepoint events.\n 881:\t\n 882:\tconfig DYNAMIC_EVENTS\n 883:\t\tdef_bool n\n 884:\t\n 885:\tconfig PROBE_EVENTS\n 886:\t\tdef_bool n\n 887:\t\n 888:\tconfig BPF_KPROBE_OVERRIDE\n 889:\t\tbool \"Enable BPF programs to override a kprobed function\"\n"
}

gemini-3.8-flash

null

null

							input: 25989
							output: 30
							thoughts: 99
						

Here's my analysis of the dependencies and related configurations.

**Analyzing BPF Event Configuration Dependencies**

Okay, so I'm looking at the `BPF_EVENTS` configuration option. First, it's pretty clear that it has a direct dependency on `BPF_SYSCALL`. That makes sense; if we're dealing with BPF events, we're likely using syscalls. I should also note that it depends on the logical combination of `KPROBE_EVENTS` or `UPROBE_EVENTS` and `PERF_EVENTS`. That's not surprising either, since `kprobes` and `uprobes` are often key sources for BPF event triggers, and `perf` is the most common consumer and the reason we want to hook it in the first place. The default value is set to 'y'.

Now, I need to make sure I don't miss anything. Are there any other related configurations that I should be aware of? I need to double-check that `BPF_SYSCALL`, `BPF_EVENTS`, and `PERF_EVENTS` are all configured properly to make sure the expected hooks are configured. Let me also have a quick look at the `kernel/bpf/stackmap.c` Makefile. I want to see if there are any specific build rules or dependencies in that module related to these event configurations. That will help verify the compilation of `stackmap.c` if these options are enabled.

{
  "Expression": "stackmap\\.o",
  "PathPrefixes": [
    "kernel/bpf/"
  ]
}

{
  "Output": "kernel/bpf/Makefile=33=ifeq ($(CONFIG_PERF_EVENTS),y)\nkernel/bpf/Makefile:34:obj-$(CONFIG_BPF_SYSCALL) += stackmap.o\nkernel/bpf/Makefile-35-endif\n"
}

gemini-3.8-flash

null

null

							input: 26504
							output: 39
							thoughts: 252
						

**My Analysis of BPF Dependencies and Symbol Naming**

Okay, here's what's running through my head as I look at this: It's clear that compiling `stackmap.o` needs both `CONFIG_BPF_SYSCALL` and `CONFIG_PERF_EVENTS`. And, not surprisingly, `bpf_trace.o` is dependent on `CONFIG_BPF_EVENTS`.  Digging deeper, `BPF_EVENTS` itself depends on `BPF_SYSCALL` *and* a combination of either KPROBE or UPROBE events and, importantly, `PERF_EVENTS`. Nothing particularly groundbreaking there, but good to have the explicit dependencies documented.

Now, let's get into the specifics of *this* patch. I need to understand what's actually being used. I'm seeing functions like `bpf_get_stack_tp_sleepable`, `bpf_get_stack_raw_tp_sleepable`, and the associated prototypes `tp_prog_func_proto` and `raw_tp_prog_func_proto`. This helps a lot.

But then my mind immediately jumps to how these BPF functions *actually* manifest in the symbol table. I know `BPF_CALL_4(bpf_get_stack_tp_sleepable, ...)` is the macro. Does it expand to `___bpf_get_stack_tp_sleepable`, `____bpf_get_stack_tp_sleepable`, or just the plain old `bpf_get_stack_tp_sleepable`? It's essential to understand the mangling (or lack thereof) to properly link and debug. I'll need to double check the exact definitions using a cross-reference or, even better, just run `nm` or `grepper` in the codebase to confirm what's actually present in the symbol table. That's the key to making sure everything links correctly.

{
  "Expression": "bpf_get_stack_tp",
  "PathPrefixes": [
    "kernel/trace/bpf_trace.c"
  ]
}

{
  "Output": "kernel/trace/bpf_trace.c=1442=static const struct bpf_func_proto bpf_get_stackid_proto_tp = {\n--\nkernel/trace/bpf_trace.c-1450-\nkernel/trace/bpf_trace.c:1451:BPF_CALL_4(bpf_get_stack_tp, void *, tp_buff, void *, buf, u32, size,\nkernel/trace/bpf_trace.c-1452-\t   u64, flags)\n--\nkernel/trace/bpf_trace.c=1460=static const struct bpf_func_proto bpf_get_stack_proto_tp = {\nkernel/trace/bpf_trace.c:1461:\t.func\t\t= bpf_get_stack_tp,\nkernel/trace/bpf_trace.c-1462-\t.gpl_only\t= true,\n--\nkernel/trace/bpf_trace.c-1469-\nkernel/trace/bpf_trace.c:1470:BPF_CALL_4(bpf_get_stack_tp_sleepable, void *, tp_buff, void *, buf, u32, size,\nkernel/trace/bpf_trace.c-1471-\t   u64, flags)\n--\nkernel/trace/bpf_trace.c=1479=static const struct bpf_func_proto bpf_get_stack_proto_tp_sleepable = {\nkernel/trace/bpf_trace.c:1480:\t.func\t\t= bpf_get_stack_tp_sleepable,\nkernel/trace/bpf_trace.c-1481-\t.gpl_only\t= true,\n"
}

gemini-3.8-flash

null

null

							input: 27656
							output: 39
							thoughts: 26
						

Okay, let's dive into this. Here's my summary, presented as my own thought process, as requested:

**Deconstructing `BPF_CALL_x`**

Alright, I need to get a handle on what's actually happening with this `BPF_CALL_x` macro. My first step is to crack open `include/linux/filter.h`. It's almost guaranteed to be defined in there. I'm hoping it's a straightforward macro definition, maybe something that expands into a series of instructions or even a function call. It's likely involved in the BPF helper call mechanism, so I'm expecting some level of indirection. Probably some bit-shifting and masking, perhaps to encode the function index or arguments in a compact way. I'm keen to see how the arguments are handled; are they directly in registers, passed on the stack, or managed some other clever way? This is going to influence my understanding of how BPF programs interact with kernel helpers. Once I find the definition, I'll pay close attention to the specific registers and memory locations involved in the function calls to ensure my BPF programs operate correctly.

{
  "Expression": "#define BPF_CALL_[0-9]",
  "PathPrefixes": [
    "include/linux/filter.h"
  ]
}

{
  "Output": "include/linux/filter.h=485=static inline int bpf_atomic_load_reg(const struct bpf_insn *insn)\n--\ninclude/linux/filter.h-739-#define __NOATTR\ninclude/linux/filter.h:740:#define BPF_CALL_0(name, ...)\tBPF_CALL_x(0, __NOATTR, name, __VA_ARGS__)\ninclude/linux/filter.h:741:#define BPF_CALL_1(name, ...)\tBPF_CALL_x(1, __NOATTR, name, __VA_ARGS__)\ninclude/linux/filter.h:742:#define BPF_CALL_2(name, ...)\tBPF_CALL_x(2, __NOATTR, name, __VA_ARGS__)\ninclude/linux/filter.h:743:#define BPF_CALL_3(name, ...)\tBPF_CALL_x(3, __NOATTR, name, __VA_ARGS__)\ninclude/linux/filter.h:744:#define BPF_CALL_4(name, ...)\tBPF_CALL_x(4, __NOATTR, name, __VA_ARGS__)\ninclude/linux/filter.h:745:#define BPF_CALL_5(name, ...)\tBPF_CALL_x(5, __NOATTR, name, __VA_ARGS__)\ninclude/linux/filter.h-746-\n"
}

gemini-3.8-flash

null

null

							input: 28316
							output: 35
							thoughts: 22
						

Here's my take on those thoughts, tailored for an expert audience:

**Diving into BPF Call Definitions**

Okay, so I need to get a handle on how these BPF calls are defined. The place to start is always `include/linux/filter.h`. I'm specifically interested in the `BPF_CALL_x` macros. I need to understand the exact structure and how they're translated during the BPF compilation and execution process. I'm hoping to quickly refresh my memory on the call number assignments.

{
  "File": "include/linux/filter.h",
  "FirstLine": 720,
  "LineCount": 35
}

{
  "Contents": " 720:\t#define __BPF_DECL_ARGS(t, a) t   a\n 721:\t#define __BPF_DECL_REGS(t, a) u64 a\n 722:\t\n 723:\t#define __BPF_PAD(n)\t\t\t\t\t\t\t       \\\n 724:\t\t__BPF_MAP(n, __BPF_DECL_ARGS, __BPF_N, u64, __ur_1, u64, __ur_2,       \\\n 725:\t\t\t  u64, __ur_3, u64, __ur_4, u64, __ur_5)\n 726:\t\n 727:\t#define BPF_CALL_x(x, attr, name, ...)\t\t\t\t\t       \\\n 728:\t\tstatic __always_inline\t\t\t\t\t\t       \\\n 729:\t\tu64 ____##name(__BPF_MAP(x, __BPF_DECL_ARGS, __BPF_V, __VA_ARGS__));   \\\n 730:\t\ttypedef u64 (*btf_##name)(__BPF_MAP(x, __BPF_DECL_ARGS, __BPF_V, __VA_ARGS__)); \\\n 731:\t\tattr u64 name(__BPF_REG(x, __BPF_DECL_REGS, __BPF_N, __VA_ARGS__));    \\\n 732:\t\tattr u64 name(__BPF_REG(x, __BPF_DECL_REGS, __BPF_N, __VA_ARGS__))     \\\n 733:\t\t{\t\t\t\t\t\t\t\t       \\\n 734:\t\t\treturn ((btf_##name)____##name)(__BPF_MAP(x,__BPF_CAST,__BPF_N,__VA_ARGS__));\\\n 735:\t\t}\t\t\t\t\t\t\t\t       \\\n 736:\t\tstatic __always_inline\t\t\t\t\t\t       \\\n 737:\t\tu64 ____##name(__BPF_MAP(x, __BPF_DECL_ARGS, __BPF_V, __VA_ARGS__))\n 738:\t\n 739:\t#define __NOATTR\n 740:\t#define BPF_CALL_0(name, ...)\tBPF_CALL_x(0, __NOATTR, name, __VA_ARGS__)\n 741:\t#define BPF_CALL_1(name, ...)\tBPF_CALL_x(1, __NOATTR, name, __VA_ARGS__)\n 742:\t#define BPF_CALL_2(name, ...)\tBPF_CALL_x(2, __NOATTR, name, __VA_ARGS__)\n 743:\t#define BPF_CALL_3(name, ...)\tBPF_CALL_x(3, __NOATTR, name, __VA_ARGS__)\n 744:\t#define BPF_CALL_4(name, ...)\tBPF_CALL_x(4, __NOATTR, name, __VA_ARGS__)\n 745:\t#define BPF_CALL_5(name, ...)\tBPF_CALL_x(5, __NOATTR, name, __VA_ARGS__)\n 746:\t\n 747:\t#define NOTRACE_BPF_CALL_1(name, ...)\tBPF_CALL_x(1, notrace, name, __VA_ARGS__)\n 748:\t\n 749:\t#define bpf_ctx_range(TYPE, MEMBER)\t\t\t\t\t\t\\\n 750:\t\toffsetof(TYPE, MEMBER) ... offsetofend(TYPE, MEMBER) - 1\n 751:\t#define bpf_ctx_range_till(TYPE, MEMBER1, MEMBER2)\t\t\t\t\\\n 752:\t\toffsetof(TYPE, MEMBER1) ... offsetofend(TYPE, MEMBER2) - 1\n 753:\t#if BITS_PER_LONG == 64\n 754:\t# define bpf_ctx_range_ptr(TYPE, MEMBER)\t\t\t\t\t\\\n"
}

gemini-3.8-flash

null

null

							input: 29465
							output: 43
							thoughts: 199
						

Okay, let me break this down.

**Understanding BPF Function Definitions and Prototypes**

Right, so `BPF_CALL_4` is clearly some macro that's defining functions. `BPF_CALL_4(bpf_get_stack_tp_sleepable, ...)` specifically *defines* the symbol `bpf_get_stack_tp_sleepable` as a function. Similarly, `BPF_CALL_4(bpf_get_stack_raw_tp_sleepable, ...)` defines `bpf_get_stack_raw_tp_sleepable`. Easy enough. I've seen this pattern a million times.

Now, I need to make sure I understand the relationship to `tp_prog_func_proto` and `raw_tp_prog_func_proto`. Those are also functions, and they're defined in `kernel/trace/bpf_trace.c`. The fact that they're *also* functions in the same file as our `BPF_CALL_4` definitions piques my interest. Hold on, let's just confirm something quickly... yep, those prototype functions are actually *static* in `bpf_trace.c`. That's a key detail! Static functions are only visible within that translation unit, right? Okay, so that likely means those function prototypes are the implementation details of the bpf_get_stack_* functions we declared with the macro.

Now, the important question is: what *uses* those prototypes? I need to figure out what calls `tp_prog_func_proto` and `raw_tp_prog_func_proto`. That's the key to understanding the control flow and how these bpf stack trace functions are actually employed.

{
  "Expression": "(tp|raw_tp)_prog_func_proto",
  "PathPrefixes": [
    "kernel/trace/bpf_trace.c"
  ]
}

{
  "Output": "kernel/trace/bpf_trace.c=1490=static const struct bpf_func_proto *\nkernel/trace/bpf_trace.c:1491:tp_prog_func_proto(enum bpf_func_id func_id, const struct bpf_prog *prog)\nkernel/trace/bpf_trace.c-1492-{\n--\nkernel/trace/bpf_trace.c=1523=const struct bpf_verifier_ops tracepoint_verifier_ops = {\nkernel/trace/bpf_trace.c:1524:\t.get_func_proto  = tp_prog_func_proto,\nkernel/trace/bpf_trace.c-1525-\t.is_valid_access = tp_prog_is_valid_access,\n--\nkernel/trace/bpf_trace.c=1757=static const struct bpf_func_proto *\nkernel/trace/bpf_trace.c:1758:raw_tp_prog_func_proto(enum bpf_func_id func_id, const struct bpf_prog *prog)\nkernel/trace/bpf_trace.c-1759-{\n--\nkernel/trace/bpf_trace.c=1776=tracing_prog_func_proto(enum bpf_func_id func_id, const struct bpf_prog *prog)\n--\nkernel/trace/bpf_trace.c-1842-\tdefault:\nkernel/trace/bpf_trace.c:1843:\t\tfn = raw_tp_prog_func_proto(func_id, prog);\nkernel/trace/bpf_trace.c-1844-\t\tif (!fn \u0026\u0026 prog-\u003eexpected_attach_type == BPF_TRACE_ITER)\n--\nkernel/trace/bpf_trace.c=1873=const struct bpf_verifier_ops raw_tracepoint_verifier_ops = {\nkernel/trace/bpf_trace.c:1874:\t.get_func_proto  = raw_tp_prog_func_proto,\nkernel/trace/bpf_trace.c-1875-\t.is_valid_access = raw_tp_prog_is_valid_access,\n--\nkernel/trace/bpf_trace.c=1906=const struct bpf_verifier_ops raw_tracepoint_writable_verifier_ops = {\nkernel/trace/bpf_trace.c:1907:\t.get_func_proto  = raw_tp_prog_func_proto,\nkernel/trace/bpf_trace.c-1908-\t.is_valid_access = raw_tp_writable_prog_is_valid_access,\n"
}

gemini-3.8-flash

null

null

							input: 30743
							output: 18
							thoughts: 1009
						

**Analyzing BPF Stack Helper for Sleepable Tracepoints**

Okay, so I'm looking at this patch and how it's hooking up the stack helper functions for sleepable tracepoints. My initial thought is that `tp_prog_func_proto` and `raw_tp_prog_func_proto` are getting assigned the new helper functions, specifically `tracepoint_verifier_ops.get_func_proto` and `raw_tracepoint_verifier_ops.get_func_proto` respectively, and that `tracing_prog_func_proto` is also calling `raw_tp_prog_func_proto`. I need to remember that even if these were static functions, they *could* have symbols due to how GCC or clang compiles the kernel, especially with kcov. But, the real deal is that `bpf_get_stack_tp_sleepable` and `bpf_get_stack_raw_tp_sleepable` are *non-static*, because they are defined with `BPF_CALL_4` which has `attr u64 name(...)` with an empty `__NOATTR`, and that makes them have external linkage!

Now, let's verify if `bpf_get_stack_sleepable` itself is interesting. I see it already exists in `kernel/bpf/stackmap.c`, because it's used by sleepable kprobes. This is good to know, that `kprobe_prog_func_proto` already uses `bpf_get_stack_sleepable_proto`. The patch is *adding* `bpf_get_stack_tp_sleepable` and `bpf_get_stack_raw_tp_sleepable`, and updating `tp_prog_func_proto` and `raw_tp_prog_func_proto` to return the sleepable proto for `BPF_FUNC_get_stack` when `prog->sleepable` is true.

Let's quickly check how ubiquitous `bpf_get_stack_sleepable` is. It's not *that* ubiquitous, but it's important to remember it lives in `stackmap.c` and wasn't modified in this patch, aside from the declaration added to `bpf_trace.c`.

Okay, the *modified* functions are:
-   `bpf_get_stack_tp_sleepable`
-   `bpf_get_stack_raw_tp_sleepable`
-   `tp_prog_func_proto`
-   `raw_tp_prog_func_proto`

Are `bpf_get_stack_tp_sleepable` and `bpf_get_stack_raw_tp_sleepable` the *key* symbols? Yes, they are the new helper callbacks for sleepable tracepoints and raw tracepoints! What about `tp_prog_func_proto` and `raw_tp_prog_func_proto`? Those are the verifier entrypoints. `bpf_get_stack_sleepable` provides the *underlying* implementation, but is not new.

So, let's include:
-   `bpf_get_stack_tp_sleepable`
-   `bpf_get_stack_raw_tp_sleepable`
-   `tp_prog_func_proto`
-   `raw_tp_prog_func_proto`

Now, regarding configuration... what `CONFIG_` options are at play here?

For `kernel/trace/bpf_trace.c` it looks like:
-   `BPF_EVENTS`: `obj-$(CONFIG_BPF_EVENTS) += bpf_trace.o`
-   `BPF_SYSCALL`: required by `BPF_EVENTS` and BPF verifier / program loading
-   `PERF_EVENTS`: required by `BPF_EVENTS` and `perf_fetch_caller_regs` / stackmap
-   `TRACING`: tracepoints support

Let's look more closely at `BPF_EVENTS` in `kernel/trace/Kconfig`:
`config BPF_EVENTS
	depends on BPF_SYSCALL
	depends on (KPROBE_EVENTS || UPROBE_EVENTS) && PERF_EVENTS
	bool
	default y`

It depends on `BPF_SYSCALL`, `PERF_EVENTS`, and `(KPROBE_EVENTS || UPROBE_EVENTS)` *or* `TRACEPOINTS`.

{
  "Expression": "config TRACEPOINTS"
}

{
  "Output": "init/Kconfig=2094=config BINDGEN_VERSION_TEXT\n--\ninit/Kconfig-2102-#\ninit/Kconfig:2103:config TRACEPOINTS\ninit/Kconfig-2104-\tbool\n"
}

gemini-3.8-flash

null

null

							input: 32817
							output: 28
							thoughts: 28
						

Okay, here's my take on those thoughts, tailored for an expert audience:

**Kernel Tracing Configuration - A Quick Check**

Right, let's just make sure we haven't overlooked anything obvious in the kernel configuration. I'm thinking, a quick scan of `Kconfig` is always a good starting point when dealing with tracing, especially before diving into more complex debugging scenarios. So, I need to confirm the status of a couple of key configuration options. First, I'm going to quickly verify the enablement of `KPROBE_EVENTS`. It's foundational, obviously, but you'd be surprised how often a simple oversight in the build configuration causes wasted time. We can't use kernel probes if the option isn't enabled. Then, a quick look at `UPROBE_EVENTS` to ensure userspace probing is also enabled if required for this task. It is a quick double-check before getting mired in the finer points. No need to waste time tracing something that isn't actually configured into the kernel. These two are critical, of course, to setting the proper parameters for any work with probes.

{
  "Expression": "config (KPROBE_EVENTS|UPROBE_EVENTS)"
}

{
  "Output": "kernel/trace/Kconfig=790=config PROBE_EVENTS_DUMP_FETCHARG\n--\nkernel/trace/Kconfig-801-\nkernel/trace/Kconfig:802:config KPROBE_EVENTS\nkernel/trace/Kconfig-803-\tdepends on KPROBES\n--\nkernel/trace/Kconfig-820-\nkernel/trace/Kconfig:821:config KPROBE_EVENTS_ON_NOTRACE\nkernel/trace/Kconfig-822-\tbool \"Do NOT protect notrace function from kprobe events\"\n--\nkernel/trace/Kconfig-840-\nkernel/trace/Kconfig:841:config UPROBE_EVENTS\nkernel/trace/Kconfig-842-\tbool \"Enable uprobes-based dynamic events\"\n"
}

gemini-3.8-flash

null

null

							input: 33316
							output: 45
							thoughts: 82
						

Okay, here's my take on those thoughts, framed as an expert's internal monologue:

**Exploring Event Sources for Enhanced Tracing**

Alright, let's break this down. We're looking at tracing, and I'm immediately thinking about the usual suspects: `BPF_EVENTS`, `BPF_SYSCALL`, `PERF_EVENTS`, and the older `KPROBE_EVENTS` or its newer equivalent, `UPROBE_EVENTS`. They're all established methods, but I need to be thorough.

My mind immediately jumps to a potential area I don't use everyday: Are `BPF_PROG_TYPE_TRACEPOINT` or `BPF_PROG_TYPE_RAW_TRACEPOINT` relevant here? I'm curious if raw tracepoints have any specific dependencies. Knowing those will make them much more useful. Let me check the documentation, or maybe even quickly write a test. I need to understand if they offer any specific advantages or limitations in this context. It's all about finding the right tool for the job.

{
  "Expression": "BPF_PROG_TYPE_RAW_TRACEPOINT",
  "PathPrefixes": [
    "kernel/bpf/",
    "kernel/trace/"
  ]
}

{
  "Output": "kernel/bpf/btf.c=6602=bool btf_is_prog_ctx_type(struct bpf_verifier_log *log, const struct btf *btf,\n--\nkernel/bpf/btf.c-6630-\t\t * is not supported yet.\nkernel/bpf/btf.c:6631:\t\t * BPF_PROG_TYPE_RAW_TRACEPOINT is fine.\nkernel/bpf/btf.c-6632-\t\t */\n--\nkernel/bpf/btf.c=6688=static int btf_validate_prog_ctx_type(struct bpf_verifier_log *log, const struct btf *btf,\n--\nkernel/bpf/btf.c-6744-\t\tbreak;\nkernel/bpf/btf.c:6745:\tcase BPF_PROG_TYPE_RAW_TRACEPOINT:\nkernel/bpf/btf.c:6746:\tcase BPF_PROG_TYPE_RAW_TRACEPOINT_WRITABLE:\nkernel/bpf/btf.c-6747-\t\t/* allow u64* as ctx */\n--\nkernel/bpf/btf.c=10006=static int bpf_prog_type_to_kfunc_hook(enum bpf_prog_type prog_type)\n--\nkernel/bpf/btf.c-10018-\tcase BPF_PROG_TYPE_TRACEPOINT:\nkernel/bpf/btf.c:10019:\tcase BPF_PROG_TYPE_RAW_TRACEPOINT:\nkernel/bpf/btf.c-10020-\tcase BPF_PROG_TYPE_PERF_EVENT:\n--\nkernel/bpf/fixups.c=1809=int bpf_do_misc_fixups(struct bpf_verifier_env *env)\n--\nkernel/bpf/fixups.c-2224-\t\t\tprog-\u003eaux-\u003emax_rdwr_access = U32_MAX;\nkernel/bpf/fixups.c:2225:\t\t\tif (prog-\u003etype == BPF_PROG_TYPE_RAW_TRACEPOINT_WRITABLE)\nkernel/bpf/fixups.c-2226-\t\t\t\tprog-\u003eaux-\u003emax_tp_access = U32_MAX;\n--\nkernel/bpf/syscall.c=2909=static bool is_perfmon_prog_type(enum bpf_prog_type prog_type)\n--\nkernel/bpf/syscall.c-2914-\tcase BPF_PROG_TYPE_PERF_EVENT:\nkernel/bpf/syscall.c:2915:\tcase BPF_PROG_TYPE_RAW_TRACEPOINT:\nkernel/bpf/syscall.c:2916:\tcase BPF_PROG_TYPE_RAW_TRACEPOINT_WRITABLE:\nkernel/bpf/syscall.c-2917-\tcase BPF_PROG_TYPE_TRACING:\n--\nkernel/bpf/syscall.c=3673=static int bpf_tracing_prog_attach(struct bpf_prog *prog,\n--\nkernel/bpf/syscall.c-3854-\tif (prog-\u003etype == BPF_PROG_TYPE_EXT \u0026\u0026\nkernel/bpf/syscall.c:3855:\t    (tgt_prog-\u003etype == BPF_PROG_TYPE_RAW_TRACEPOINT ||\nkernel/bpf/syscall.c-3856-\t     tgt_prog-\u003etype == BPF_PROG_TYPE_TRACEPOINT ||\n--\nkernel/bpf/syscall.c=4352=static int bpf_raw_tp_link_attach(struct bpf_prog *prog,\n--\nkernel/bpf/syscall.c-4377-\t\treturn bpf_tracing_prog_attach(prog, 0, 0, 0, attach_type);\nkernel/bpf/syscall.c:4378:\tcase BPF_PROG_TYPE_RAW_TRACEPOINT:\nkernel/bpf/syscall.c:4379:\tcase BPF_PROG_TYPE_RAW_TRACEPOINT_WRITABLE:\nkernel/bpf/syscall.c-4380-\t\tif (strncpy_from_user(buf, user_tp_name, sizeof(buf) - 1) \u003c 0)\n--\nkernel/bpf/verifier.c=5698=static enum priv_stack_mode bpf_enable_priv_stack(struct bpf_prog *prog)\n--\nkernel/bpf/verifier.c-5710-\tcase BPF_PROG_TYPE_PERF_EVENT:\nkernel/bpf/verifier.c:5711:\tcase BPF_PROG_TYPE_RAW_TRACEPOINT:\nkernel/bpf/verifier.c-5712-\t\treturn PRIV_STACK_ADAPTIVE;\n--\nkernel/bpf/verifier.c=19372=static bool return_retval_range(struct bpf_verifier_env *env, struct bpf_retval_range *range)\n--\nkernel/bpf/verifier.c-19410-\t\tbreak;\nkernel/bpf/verifier.c:19411:\tcase BPF_PROG_TYPE_RAW_TRACEPOINT:\nkernel/bpf/verifier.c-19412-\t\tif (!env-\u003eprog-\u003eaux-\u003eattach_btf_id)\n--\nkernel/bpf/verifier.c=20980=static bool is_tracing_prog_type(enum bpf_prog_type type)\n--\nkernel/bpf/verifier.c-20985-\tcase BPF_PROG_TYPE_PERF_EVENT:\nkernel/bpf/verifier.c:20986:\tcase BPF_PROG_TYPE_RAW_TRACEPOINT:\nkernel/bpf/verifier.c:20987:\tcase BPF_PROG_TYPE_RAW_TRACEPOINT_WRITABLE:\nkernel/bpf/verifier.c-20988-\t\treturn true;\n--\nkernel/bpf/verifier.c=22563=int bpf_check_attach_target(struct bpf_verifier_log *log,\n--\nkernel/bpf/verifier.c-22661-\t\t\t */\nkernel/bpf/verifier.c:22662:\t\t\tif (tgt_prog-\u003etype == BPF_PROG_TYPE_RAW_TRACEPOINT_WRITABLE) {\nkernel/bpf/verifier.c-22663-\t\t\t\tbpf_log(log,\n--\nkernel/bpf/verifier.c=23001=static bool can_be_sleepable(struct bpf_prog *prog)\n--\nkernel/bpf/verifier.c-23023-\t       prog-\u003etype == BPF_PROG_TYPE_STRUCT_OPS ||\nkernel/bpf/verifier.c:23024:\t       prog-\u003etype == BPF_PROG_TYPE_RAW_TRACEPOINT ||\nkernel/bpf/verifier.c-23025-\t       prog-\u003etype == BPF_PROG_TYPE_TRACEPOINT;\n"
}

gemini-3.8-flash

null

null

							input: 35427
							output: 214
							thoughts: 427
						

**Analyzing BPF Tracepoint Sleepable Stack Walk Introductions**

Okay, let's break this down. First, I need to confirm the presence and reachability of the new sleepable stack walk functions (`bpf_get_stack_tp_sleepable` and `bpf_get_stack_raw_tp_sleepable`) within `kernel/trace/bpf_trace.c`. I'm going to quickly check for any conditional compilation using `#include` directives or `#ifdef` blocks around those function names. Based on the initial scan, lines 1460-1500 and 1720-1770 in `bpf_trace.c` appear unconditional within the file, and `bpf_trace.o` is built if `CONFIG_BPF_EVENTS` is enabled, which suggests the functions are included.

Next, I'll scrutinize for any conditional compilation around `tp_prog_func_proto` or `raw_tp_prog_func_proto` within the same file. My preliminary analysis has revealed that lines 1490 and 1757 have no associated `#ifdef` directives, which is crucial.

Now, let's do a complete review to ensure I haven't missed anything:

*   **WorthFuzzing**: Yes, this is definitely a fuzzing target. The introduction of sleepable stack walks in tracepoints fundamentally alters execution contexts and the potential for new code paths that could reveal vulnerabilities.
*   **Reasoning**: The crux of this change is introducing sleepable variants of `bpf_get_stack`. This allows tracepoints and raw tracepoints to perform sleepable stack walks and user build ID resolution, which can result in page faults. Given that these changes are reachable through standard BPF syscalls and tracepoint attachments, this is a significant area of focus.
*   **FocusSymbols**: My main targets will be `bpf_get_stack_tp_sleepable`, `bpf_get_stack_raw_tp_sleepable`, `tp_prog_func_proto`, and `raw_tp_prog_func_proto`.
*   **EnableConfigs**: I'll need to confirm that `BPF_EVENTS`, `BPF_SYSCALL`, and `PERF_EVENTS` are enabled for the target configuration. These are essential for reaching the new functionality.

Alright, I'm confident in my understanding of the implications. Time to update the results accordingly.

{
  "EnableConfigs": [
    "BPF_EVENTS",
    "BPF_SYSCALL",
    "PERF_EVENTS"
  ],
  "FocusSymbols": [
    "bpf_get_stack_tp_sleepable",
    "bpf_get_stack_raw_tp_sleepable",
    "tp_prog_func_proto",
    "raw_tp_prog_func_proto"
  ],
  "Reasoning": "The patch wires up sleepable stack capture helpers (bpf_get_stack_tp_sleepable and bpf_get_stack_raw_tp_sleepable) for sleepable tracepoint and raw tracepoint BPF programs. This allows tracepoint and raw tracepoint programs marked sleepable to execute faultable, sleep-inducing stack walking logic (such as build ID resolution). These execution paths are fully reachable from userspace via standard BPF syscalls and tracepoint event attachments, making them high-priority targets for fuzzing.",
  "WorthFuzzing": true
}

{
  "EnableConfigs": [
    "BPF_EVENTS",
    "BPF_SYSCALL",
    "PERF_EVENTS"
  ],
  "FocusSymbols": [
    "bpf_get_stack_tp_sleepable",
    "bpf_get_stack_raw_tp_sleepable",
    "tp_prog_func_proto",
    "raw_tp_prog_func_proto"
  ],
  "Reasoning": "The patch wires up sleepable stack capture helpers (bpf_get_stack_tp_sleepable and bpf_get_stack_raw_tp_sleepable) for sleepable tracepoint and raw tracepoint BPF programs. This allows tracepoint and raw tracepoint programs marked sleepable to execute faultable, sleep-inducing stack walking logic (such as build ID resolution). These execution paths are fully reachable from userspace via standard BPF syscalls and tracepoint event attachments, making them high-priority targets for fuzzing.",
  "WorthFuzzing": true
}

{
  "WorthFuzzing": true
}

null

core

null

{
  "KMSANReasoning": "The patch wires up sleepable variants of `bpf_get_stack` (`bpf_get_stack_tp_sleepable` and `bpf_get_stack_raw_tp_sleepable`) for sleepable tracepoint and raw tracepoint BPF programs.\n\nAnalysis of memory initialization:\n1. In `bpf_get_stack_raw_tp_sleepable`, the local `struct pt_regs regs` is explicitly zero-initialized with `{}` before `perf_fetch_caller_regs(\u0026regs)` is invoked.\n2. The destination buffer `buf` passed from the BPF program is managed by `__bpf_get_stack()`, which writes stack entries into it or zeroes it completely via `memset(buf, 0, size)` on failure or partial fills.\n3. No kernel-to-user copy of uninitialized memory or info-leak risk is introduced.\n4. Potential issues introduced by sleepable BPF program execution (such as sleeping in invalid contexts, lockdep violations, or out-of-bounds stack reading) are covered by standard KASAN and LOCKDEP configurations.\n\nTherefore, KMSAN fuzzing is not required.",
  "NeedsKMSAN": false
}

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.

Target architecture: amd64

For your convenience, here is the diff of the changes:
commit 9ec83394638c4b1f1fb4aea9976ca43297caea3b
Author: syz-cluster <triage@syzkaller.com>
Date:   Mon Nov 2 14:00:02 2026 +0000

    syz-cluster: applied patch under review

diff --git a/kernel/trace/bpf_trace.c b/kernel/trace/bpf_trace.c
index 14adfb85fdb2be..7d8414d8573744 100644
--- a/kernel/trace/bpf_trace.c
+++ b/kernel/trace/bpf_trace.c
@@ -84,6 +84,7 @@ static struct bpf_raw_event_map *bpf_get_raw_tracepoint_module(const char *name)
 
 u64 bpf_get_stackid(u64 r1, u64 r2, u64 r3, u64 r4, u64 r5);
 u64 bpf_get_stack(u64 r1, u64 r2, u64 r3, u64 r4, u64 r5);
+u64 bpf_get_stack_sleepable(u64 r1, u64 r2, u64 r3, u64 r4, u64 r5);
 
 static int bpf_btf_printf_prepare(struct btf_ptr *ptr, u32 btf_ptr_size,
 				  u64 flags, const struct btf **btf,
@@ -1466,6 +1467,26 @@ static const struct bpf_func_proto bpf_get_stack_proto_tp = {
 	.arg4_type	= ARG_ANYTHING,
 };
 
+BPF_CALL_4(bpf_get_stack_tp_sleepable, void *, tp_buff, void *, buf, u32, size,
+	   u64, flags)
+{
+	struct pt_regs *regs = *(struct pt_regs **)tp_buff;
+
+	return bpf_get_stack_sleepable((unsigned long) regs, (unsigned long) buf,
+				       (unsigned long) size, flags, 0);
+}
+
+static const struct bpf_func_proto bpf_get_stack_proto_tp_sleepable = {
+	.func		= bpf_get_stack_tp_sleepable,
+	.gpl_only	= true,
+	.might_sleep	= true,
+	.ret_type	= RET_INTEGER,
+	.arg1_type	= ARG_PTR_TO_CTX,
+	.arg2_type	= ARG_PTR_TO_UNINIT_MEM,
+	.arg3_type	= ARG_MEM_SIZE_OR_ZERO,
+	.arg4_type	= ARG_ANYTHING,
+};
+
 static const struct bpf_func_proto *
 tp_prog_func_proto(enum bpf_func_id func_id, const struct bpf_prog *prog)
 {
@@ -1475,7 +1496,8 @@ tp_prog_func_proto(enum bpf_func_id func_id, const struct bpf_prog *prog)
 	case BPF_FUNC_get_stackid:
 		return &bpf_get_stackid_proto_tp;
 	case BPF_FUNC_get_stack:
-		return &bpf_get_stack_proto_tp;
+		return prog->sleepable ? &bpf_get_stack_proto_tp_sleepable
+				       : &bpf_get_stack_proto_tp;
 	case BPF_FUNC_get_attach_cookie:
 		return &bpf_get_attach_cookie_proto_trace;
 	default:
@@ -1705,6 +1727,33 @@ static const struct bpf_func_proto bpf_get_stack_proto_raw_tp = {
 	.arg4_type	= ARG_ANYTHING,
 };
 
+BPF_CALL_4(bpf_get_stack_raw_tp_sleepable, struct bpf_raw_tracepoint_args *, args,
+	   void *, buf, u32, size, u64, flags)
+{
+	/*
+	 * Don't take a per-CPU bpf_raw_tp_regs slot here: those slots are a
+	 * LIFO nest counter and cannot be held across the sleep that
+	 * build_id_parse() may take.  Sleepable programs never run in
+	 * IRQ/NMI context, so a stack copy is sufficient.
+	 */
+	struct pt_regs regs = {};
+
+	perf_fetch_caller_regs(&regs);
+	return bpf_get_stack_sleepable((unsigned long) &regs, (unsigned long) buf,
+				       (unsigned long) size, flags, 0);
+}
+
+static const struct bpf_func_proto bpf_get_stack_proto_raw_tp_sleepable = {
+	.func		= bpf_get_stack_raw_tp_sleepable,
+	.gpl_only	= true,
+	.might_sleep	= true,
+	.ret_type	= RET_INTEGER,
+	.arg1_type	= ARG_PTR_TO_CTX,
+	.arg2_type	= ARG_PTR_TO_UNINIT_MEM,
+	.arg3_type	= ARG_MEM_SIZE_OR_ZERO,
+	.arg4_type	= ARG_ANYTHING,
+};
+
 static const struct bpf_func_proto *
 raw_tp_prog_func_proto(enum bpf_func_id func_id, const struct bpf_prog *prog)
 {
@@ -1714,7 +1763,8 @@ raw_tp_prog_func_proto(enum bpf_func_id func_id, const struct bpf_prog *prog)
 	case BPF_FUNC_get_stackid:
 		return &bpf_get_stackid_proto_raw_tp;
 	case BPF_FUNC_get_stack:
-		return &bpf_get_stack_proto_raw_tp;
+		return prog->sleepable ? &bpf_get_stack_proto_raw_tp_sleepable
+				       : &bpf_get_stack_proto_raw_tp;
 	case BPF_FUNC_get_attach_cookie:
 		return &bpf_get_attach_cookie_proto_tracing;
 	default:

gemini-3.8-flash

null

null

							input: 3557
							output: 23
							thoughts: 95
						

Okay, here's my interpretation of this thought process, keeping in mind my expertise:

**Examining the New BPF Stack Trace Functions**

Alright, so this patch introduces `bpf_get_stack_tp_sleepable` and `bpf_get_stack_raw_tp_sleepable` within `kernel/trace/bpf_trace.c`. My immediate thought is, "Okay, what's new here? What's the context?" I need to dig into the diff to understand the *why* behind these additions. I need to understand how these relate to the existing mechanisms.

My first port of call will be to scrutinize the implementation of `bpf_get_stack_sleepable` and any surrounding code. I need to grasp the foundational logic and how these new functions extend it, likely in the context of tracing and sleepable contexts. I'll need to understand how the "tp" and "raw_tp" variations differ. Are we talking about different stack frame representations, handling of task state, or perhaps interaction with the tracing infrastructure?

Then, to get a handle on the bigger picture, and to identify potential use cases or related areas of the code base, I'll leverage `grepper`. I'll run a quick search for `bpf_get_stack_sleepable` to see where it's being used and, importantly, what code interacts with it. That'll provide valuable context and highlight any potential areas of concern or opportunities for deeper analysis. I'll be looking for cross-references, any calls to helper functions, and how the call is implemented in the overall architecture.

{
  "Expression": "bpf_get_stack_sleepable"
}

{
  "Output": "include/linux/bpf.h=4092=extern const struct bpf_func_proto bpf_get_stack_proto;\ninclude/linux/bpf.h:4093:extern const struct bpf_func_proto bpf_get_stack_sleepable_proto;\ninclude/linux/bpf.h-4094-extern const struct bpf_func_proto bpf_get_task_stack_proto;\n--\nkernel/bpf/stackmap.c=854=const struct bpf_func_proto bpf_get_stack_proto = {\n--\nkernel/bpf/stackmap.c-863-\nkernel/bpf/stackmap.c:864:BPF_CALL_4(bpf_get_stack_sleepable, struct pt_regs *, regs, void *, buf, u32, size,\nkernel/bpf/stackmap.c-865-\t   u64, flags)\n--\nkernel/bpf/stackmap.c-869-\nkernel/bpf/stackmap.c:870:const struct bpf_func_proto bpf_get_stack_sleepable_proto = {\nkernel/bpf/stackmap.c:871:\t.func\t\t= bpf_get_stack_sleepable,\nkernel/bpf/stackmap.c-872-\t.gpl_only\t= true,\n--\nkernel/trace/bpf_trace.c=86=u64 bpf_get_stack(u64 r1, u64 r2, u64 r3, u64 r4, u64 r5);\nkernel/trace/bpf_trace.c:87:u64 bpf_get_stack_sleepable(u64 r1, u64 r2, u64 r3, u64 r4, u64 r5);\nkernel/trace/bpf_trace.c-88-\n--\nkernel/trace/bpf_trace.c=1344=kprobe_prog_func_proto(enum bpf_func_id func_id, const struct bpf_prog *prog)\n--\nkernel/trace/bpf_trace.c-1351-\tcase BPF_FUNC_get_stack:\nkernel/trace/bpf_trace.c:1352:\t\treturn prog-\u003esleepable ? \u0026bpf_get_stack_sleepable_proto : \u0026bpf_get_stack_proto;\nkernel/trace/bpf_trace.c-1353-#ifdef CONFIG_BPF_KPROBE_OVERRIDE\n--\nkernel/trace/bpf_trace.c=1470=BPF_CALL_4(bpf_get_stack_tp_sleepable, void *, tp_buff, void *, buf, u32, size,\n--\nkernel/trace/bpf_trace.c-1474-\nkernel/trace/bpf_trace.c:1475:\treturn bpf_get_stack_sleepable((unsigned long) regs, (unsigned long) buf,\nkernel/trace/bpf_trace.c-1476-\t\t\t\t       (unsigned long) size, flags, 0);\n--\nkernel/trace/bpf_trace.c=1730=BPF_CALL_4(bpf_get_stack_raw_tp_sleepable, struct bpf_raw_tracepoint_args *, args,\n--\nkernel/trace/bpf_trace.c-1741-\tperf_fetch_caller_regs(\u0026regs);\nkernel/trace/bpf_trace.c:1742:\treturn bpf_get_stack_sleepable((unsigned long) \u0026regs, (unsigned long) buf,\nkernel/trace/bpf_trace.c-1743-\t\t\t\t       (unsigned long) size, flags, 0);\n"
}

gemini-3.8-flash

null

null

							input: 4949
							output: 37
							thoughts: 22
						

Here's my summary, as if I were thinking these thoughts:

**Diving into the BPF Stackmap Implementation**

Okay, time to dig into the BPF stackmap implementation. Let's start by zeroing in on `kernel/bpf/stackmap.c` and specifically around line 860. I need to refresh my memory on what that section's handling. I'm going to carefully review the surrounding code to understand the context. There's probably something specific I'm looking for there in the surrounding lines; a particular data structure, a key function call, or perhaps a problematic edge case that's been flagged. Let's see what we can find.

{
  "File": "kernel/bpf/stackmap.c",
  "FirstLine": 840,
  "LineCount": 50
}

{
  "Contents": " 840:\t\n 841:\terr_fault:\n 842:\t\terr = -EFAULT;\n 843:\tclear:\n 844:\t\tmemset(buf, 0, size);\n 845:\t\treturn err;\n 846:\t}\n 847:\t\n 848:\tBPF_CALL_4(bpf_get_stack, struct pt_regs *, regs, void *, buf, u32, size,\n 849:\t\t   u64, flags)\n 850:\t{\n 851:\t\treturn __bpf_get_stack(regs, NULL, buf, size, flags, false /* !may_fault */);\n 852:\t}\n 853:\t\n 854:\tconst struct bpf_func_proto bpf_get_stack_proto = {\n 855:\t\t.func\t\t= bpf_get_stack,\n 856:\t\t.gpl_only\t= true,\n 857:\t\t.ret_type\t= RET_INTEGER,\n 858:\t\t.arg1_type\t= ARG_PTR_TO_CTX,\n 859:\t\t.arg2_type\t= ARG_PTR_TO_UNINIT_MEM,\n 860:\t\t.arg3_type\t= ARG_MEM_SIZE_OR_ZERO,\n 861:\t\t.arg4_type\t= ARG_ANYTHING,\n 862:\t};\n 863:\t\n 864:\tBPF_CALL_4(bpf_get_stack_sleepable, struct pt_regs *, regs, void *, buf, u32, size,\n 865:\t\t   u64, flags)\n 866:\t{\n 867:\t\treturn __bpf_get_stack(regs, NULL, buf, size, flags, true /* may_fault */);\n 868:\t}\n 869:\t\n 870:\tconst struct bpf_func_proto bpf_get_stack_sleepable_proto = {\n 871:\t\t.func\t\t= bpf_get_stack_sleepable,\n 872:\t\t.gpl_only\t= true,\n 873:\t\t.might_sleep\t= true,\n 874:\t\t.ret_type\t= RET_INTEGER,\n 875:\t\t.arg1_type\t= ARG_PTR_TO_CTX,\n 876:\t\t.arg2_type\t= ARG_PTR_TO_UNINIT_MEM,\n 877:\t\t.arg3_type\t= ARG_MEM_SIZE_OR_ZERO,\n 878:\t\t.arg4_type\t= ARG_ANYTHING,\n 879:\t};\n 880:\t\n 881:\tstatic long __bpf_get_task_stack(struct task_struct *task, void *buf, u32 size,\n 882:\t\t\t\t\t u64 flags, bool may_fault)\n 883:\t{\n 884:\t\tstruct pt_regs *regs;\n 885:\t\tlong res = -EINVAL;\n 886:\t\n 887:\t\tif (!try_get_task_stack(task)) {\n 888:\t\t\tmemset(buf, 0, size);\n 889:\t\t\treturn -EFAULT;\n"
}

gemini-3.8-flash

null

null

							input: 5995
							output: 39
							thoughts: 43
						

Okay, let's dive into this. Here's how I'd approach understanding the implementation of `bpf_get_stack_tp` and `bpf_get_stack_raw_tp` within `kernel/trace/bpf_trace.c`.

**Diving Deep into Stack Trace Capture**

Alright, my first instinct is always to see the code directly. I need to understand exactly how the kernel is handling stack trace retrieval within the BPF context. So, I'm going to head straight for `kernel/trace/bpf_trace.c`. I expect to find the definitions for both `bpf_get_stack_tp` and `bpf_get_stack_raw_tp` there. My goal is to parse how these functions are constructed, specifically focusing on how they gather the stack traces – are they using frame pointers, unwinding the stack directly, or perhaps leveraging hardware features like eBPF stack traces. I'll be looking for any potential differences in the methods between the regular and "raw" versions, which I anticipate might have implications for the level of detail or any limitations in what's retrievable. I'm keen to understand how they interact with the BPF VM and if there's any use of auxiliary data structures within this part of the kernel for stack trace management. I'm looking for where and how the trace is taken. Finally, I'll need to observe any optimization or hardware consideration. This should give me a solid foundation for then analyzing performance characteristics and any potential issues around resource contention or overhead.

{
  "File": "kernel/trace/bpf_trace.c",
  "FirstLine": 1450,
  "LineCount": 40
}

{
  "Contents": "1450:\t\n1451:\tBPF_CALL_4(bpf_get_stack_tp, void *, tp_buff, void *, buf, u32, size,\n1452:\t\t   u64, flags)\n1453:\t{\n1454:\t\tstruct pt_regs *regs = *(struct pt_regs **)tp_buff;\n1455:\t\n1456:\t\treturn bpf_get_stack((unsigned long) regs, (unsigned long) buf,\n1457:\t\t\t\t     (unsigned long) size, flags, 0);\n1458:\t}\n1459:\t\n1460:\tstatic const struct bpf_func_proto bpf_get_stack_proto_tp = {\n1461:\t\t.func\t\t= bpf_get_stack_tp,\n1462:\t\t.gpl_only\t= true,\n1463:\t\t.ret_type\t= RET_INTEGER,\n1464:\t\t.arg1_type\t= ARG_PTR_TO_CTX,\n1465:\t\t.arg2_type\t= ARG_PTR_TO_UNINIT_MEM,\n1466:\t\t.arg3_type\t= ARG_MEM_SIZE_OR_ZERO,\n1467:\t\t.arg4_type\t= ARG_ANYTHING,\n1468:\t};\n1469:\t\n1470:\tBPF_CALL_4(bpf_get_stack_tp_sleepable, void *, tp_buff, void *, buf, u32, size,\n1471:\t\t   u64, flags)\n1472:\t{\n1473:\t\tstruct pt_regs *regs = *(struct pt_regs **)tp_buff;\n1474:\t\n1475:\t\treturn bpf_get_stack_sleepable((unsigned long) regs, (unsigned long) buf,\n1476:\t\t\t\t\t       (unsigned long) size, flags, 0);\n1477:\t}\n1478:\t\n1479:\tstatic const struct bpf_func_proto bpf_get_stack_proto_tp_sleepable = {\n1480:\t\t.func\t\t= bpf_get_stack_tp_sleepable,\n1481:\t\t.gpl_only\t= true,\n1482:\t\t.might_sleep\t= true,\n1483:\t\t.ret_type\t= RET_INTEGER,\n1484:\t\t.arg1_type\t= ARG_PTR_TO_CTX,\n1485:\t\t.arg2_type\t= ARG_PTR_TO_UNINIT_MEM,\n1486:\t\t.arg3_type\t= ARG_MEM_SIZE_OR_ZERO,\n1487:\t\t.arg4_type\t= ARG_ANYTHING,\n1488:\t};\n1489:\t\n"
}

gemini-3.8-flash

null

null

							input: 7129
							output: 39
							thoughts: 37
						

Okay, let's dive into this. Here's my thought process on checking `bpf_get_stack_raw_tp` around line 1700 of `kernel/trace/bpf_trace.c`.

**Investigating a Suspected Kernel Tracepoint Issue**

Right, so we're looking at tracepoints, and my initial hunch is leading me to a specific area of interest. Given the context, my experience tells me that line 1700 in `bpf_trace.c` is highly relevant for investigation. Specifically, I need to focus on `bpf_get_stack_raw_tp`. This function plays a crucial role in capturing raw stack trace data within the BPF context, so any issues here could manifest as subtle but critical bugs within the tracing infrastructure. It's a prime suspect.

I'll be scrutinizing the logic surrounding this function, considering things like: error handling, potential race conditions when accessing stack data from the tracepoint context, and any interactions with other BPF helpers or kernel subsystems that might introduce unexpected side effects. I'll need to think about memory management and pointer validity within that region too. Basically, I want to confirm that this is not the root of the issue, and that the data being captured is exactly what it should be.

{
  "File": "kernel/trace/bpf_trace.c",
  "FirstLine": 1680,
  "LineCount": 40
}

{
  "Contents": "1680:\t{\n1681:\t\tstruct pt_regs *regs = get_bpf_raw_tp_regs();\n1682:\t\tint ret;\n1683:\t\n1684:\t\tif (IS_ERR(regs))\n1685:\t\t\treturn PTR_ERR(regs);\n1686:\t\n1687:\t\tperf_fetch_caller_regs(regs);\n1688:\t\t/* similar to bpf_perf_event_output_tp, but pt_regs fetched differently */\n1689:\t\tret = bpf_get_stackid((unsigned long) regs, (unsigned long) map,\n1690:\t\t\t\t      flags, 0, 0);\n1691:\t\tput_bpf_raw_tp_regs();\n1692:\t\treturn ret;\n1693:\t}\n1694:\t\n1695:\tstatic const struct bpf_func_proto bpf_get_stackid_proto_raw_tp = {\n1696:\t\t.func\t\t= bpf_get_stackid_raw_tp,\n1697:\t\t.gpl_only\t= true,\n1698:\t\t.ret_type\t= RET_INTEGER,\n1699:\t\t.arg1_type\t= ARG_PTR_TO_CTX,\n1700:\t\t.arg2_type\t= ARG_CONST_MAP_PTR,\n1701:\t\t.arg3_type\t= ARG_ANYTHING,\n1702:\t};\n1703:\t\n1704:\tBPF_CALL_4(bpf_get_stack_raw_tp, struct bpf_raw_tracepoint_args *, args,\n1705:\t\t   void *, buf, u32, size, u64, flags)\n1706:\t{\n1707:\t\tstruct pt_regs *regs = get_bpf_raw_tp_regs();\n1708:\t\tint ret;\n1709:\t\n1710:\t\tif (IS_ERR(regs))\n1711:\t\t\treturn PTR_ERR(regs);\n1712:\t\n1713:\t\tperf_fetch_caller_regs(regs);\n1714:\t\tret = bpf_get_stack((unsigned long) regs, (unsigned long) buf,\n1715:\t\t\t\t    (unsigned long) size, flags, 0);\n1716:\t\tput_bpf_raw_tp_regs();\n1717:\t\treturn ret;\n1718:\t}\n1719:\t\n"
}

gemini-3.8-flash

null

null

							input: 8130
							output: 37
							thoughts: 370
						

**Analyzing the BPF Stack Retrieval in Sleepable Tracepoints**

Okay, let's break this down. I'm looking at `bpf_get_stack_raw_tp_sleepable`. The signature, `BPF_CALL_4`, gives it away; it's a BPF helper. The first thing that jumps out is the initialization of the `struct pt_regs regs = {};`. Zero-initialization. That's a deliberate choice, and it's important. It suggests we're starting with a clean slate for the register state.

Then, `perf_fetch_caller_regs(&regs);` populates this `regs` structure. It's fetching the registers from the calling context, making them available for stack unwinding.

Now, let's consider `buf`, the buffer passed to the helper. It’s what we are copying the stack to. In the context of `bpf_get_stack_proto_tp_sleepable` and `bpf_get_stack_proto_raw_tp_sleepable`, I note the important metadata in the BTF, `.arg2_type = ARG_PTR_TO_UNINIT_MEM,` and `.arg3_type = ARG_MEM_SIZE_OR_ZERO`. This is crucial. It’s specifying that `buf` is a pointer to uninitialized memory, which is exactly what we expect. `size` is the length of this memory, or zero.

Finally, I need to see what `__bpf_get_stack` itself does with this `buf`. That's where the actual stack copying occurs. I need to understand how the zero-initialized `regs` and the uninitialized `buf` interact within the implementation of `__bpf_get_stack`. It's the key to making sure that the stack is copied correctly without leaving any stale data around and that the write to the buffer is safe.

{
  "File": "kernel/bpf/stackmap.c",
  "FirstLine": 775,
  "LineCount": 70
}

{
  "Contents": " 775:\t\treturn copy_len;\n 776:\t}\n 777:\t\n 778:\tstatic long __bpf_get_stack(struct pt_regs *regs, struct task_struct *task,\n 779:\t\t\t\t    void *buf, u32 size, u64 flags, bool may_fault)\n 780:\t{\n 781:\t\tbool user_build_id = flags \u0026 BPF_F_USER_BUILD_ID;\n 782:\t\tbool crosstask = task \u0026\u0026 task != current;\n 783:\t\tu32 skip = flags \u0026 BPF_F_SKIP_FIELD_MASK;\n 784:\t\tbool user = flags \u0026 BPF_F_USER_STACK;\n 785:\t\tstruct perf_callchain_entry *trace;\n 786:\t\tu32 trace_nr, elem_size, max_depth;\n 787:\t\tbool kernel = !user;\n 788:\t\tint err = -EINVAL;\n 789:\t\n 790:\t\tif (unlikely(flags \u0026 ~(BPF_F_SKIP_FIELD_MASK | BPF_F_USER_STACK |\n 791:\t\t\t\t       BPF_F_USER_BUILD_ID)))\n 792:\t\t\tgoto clear;\n 793:\t\tif (kernel \u0026\u0026 user_build_id)\n 794:\t\t\tgoto clear;\n 795:\t\n 796:\t\telem_size = user_build_id ? sizeof(struct bpf_stack_build_id) : sizeof(u64);\n 797:\t\tif (unlikely(size % elem_size))\n 798:\t\t\tgoto clear;\n 799:\t\n 800:\t\t/* cannot get valid user stack for task without user_mode regs */\n 801:\t\tif (task \u0026\u0026 user \u0026\u0026 !user_mode(regs))\n 802:\t\t\tgoto err_fault;\n 803:\t\n 804:\t\t/* get_perf_callchain does not support crosstask user stack walking\n 805:\t\t * but returns an empty stack instead of NULL.\n 806:\t\t */\n 807:\t\tif (crosstask \u0026\u0026 user) {\n 808:\t\t\terr = -EOPNOTSUPP;\n 809:\t\t\tgoto clear;\n 810:\t\t}\n 811:\t\n 812:\t\tmax_depth = stack_map_calculate_max_depth(size, elem_size, flags);\n 813:\t\n 814:\t\tpreempt_disable();\n 815:\t\tif (may_fault)\n 816:\t\t\trcu_read_lock(); /* need RCU for perf's callchain below */\n 817:\t\n 818:\t\tif (kernel \u0026\u0026 task) {\n 819:\t\t\ttrace = get_callchain_entry_for_task(task, max_depth);\n 820:\t\t} else {\n 821:\t\t\ttrace = get_perf_callchain(regs, kernel, user, max_depth,\n 822:\t\t\t\t\t\t   crosstask, false, 0);\n 823:\t\t}\n 824:\t\n 825:\t\tif (unlikely(!trace) || trace-\u003enr \u003c skip) {\n 826:\t\t\tif (may_fault)\n 827:\t\t\t\trcu_read_unlock();\n 828:\t\t\tpreempt_enable();\n 829:\t\t\tgoto err_fault;\n 830:\t\t}\n 831:\t\n 832:\t\ttrace_nr = callchain_store(trace, trace-\u003enr, buf, elem_size, flags);\n 833:\t\n 834:\t\t/* trace should not be dereferenced after this point */\n 835:\t\tif (may_fault)\n 836:\t\t\trcu_read_unlock();\n 837:\t\tpreempt_enable();\n 838:\t\n 839:\t\treturn callchain_finalize(buf, size, trace_nr, elem_size, flags, may_fault);\n 840:\t\n 841:\terr_fault:\n 842:\t\terr = -EFAULT;\n 843:\tclear:\n 844:\t\tmemset(buf, 0, size);\n"
}

gemini-3.8-flash

null

null

							input: 10031
							output: 275
							thoughts: 955
						

**KMSAN Assessment: No Uninitialized Memory Risks**

Okay, let's break this down. It seems the core of the change is enabling sleepable stack tracing within tracepoints (TP) and raw tracepoints (Raw TP). The crucial part is how this interacts with potential uninitialized memory, which is a key focus of KMSAN.

I see that `bpf_get_stack_sleepable` already existed and was used with sleepable kprobes. The current patch simply extends this to TP and Raw TP programs when `prog->sleepable` is true.

Specifically:

*   For TP, it's straightforward: we're leveraging `bpf_get_stack_tp_sleepable` which is nearly identical to `bpf_get_stack_tp`, except it calls the sleepable version of the helper. The important thing is that `bpf_get_stack_tp_sleepable` obtains the `struct pt_regs` from `tp_buff` (which is already present, as it contains arguments of tracepoints). Then this is passed along to `bpf_get_stack_sleepable` with `might_sleep = true`.
*   For Raw TP, the new `bpf_get_stack_raw_tp_sleepable` needs to deal with the per-CPU `bpf_raw_tp_regs` issue and potential sleep-related context. It allocates a `struct pt_regs regs = {};` on the stack, which immediately guarantees zero-initialization. It then populates this stack-allocated `regs` struct using `perf_fetch_caller_regs()`, before passing it to `bpf_get_stack_sleepable`.

Now, the important check to determine whether `NeedsKMSAN` should be set: Is there any risk of uninitialized memory?

The code seems to carefully handle this:

*   We are zero-initializing `regs` on the stack: `struct pt_regs regs = {};`.
*   The `tp_buff` is marked with `ARG_PTR_TO_UNINIT_MEM` which indicates that the BPF program provides a pointer to memory that does not need to be initialized prior to calling the helper.
*   The actual stack fetching helpers (`bpf_get_stack` / `__bpf_get_stack`) are responsible for initializing the provided buffer (`buf`).
*   Nothing uninitialized is exposed to user space.

So, according to the criteria for `NeedsKMSAN`, I am confident in my assessment: There is no risk here.

We are wiring up existing sleepable stack fetching logic (`bpf_get_stack_sleepable`) to sleepable TP and Raw TP BPF programs. Any bugs in this sleepable context, like sleep in atomic, locking or stack fetching errors, are not related to uninitialized memory, but are caught by LOCKDEP, KASAN, or standard bug detectors.

Therefore, no uninitialized memory risks are introduced.

I will call `set-results` with `NeedsKMSAN=false` with the above detailed reasoning.

{
  "KMSANReasoning": "The patch wires up sleepable variants of `bpf_get_stack` (`bpf_get_stack_tp_sleepable` and `bpf_get_stack_raw_tp_sleepable`) for sleepable tracepoint and raw tracepoint BPF programs.\n\nAnalysis of memory initialization:\n1. In `bpf_get_stack_raw_tp_sleepable`, the local `struct pt_regs regs` is explicitly zero-initialized with `{}` before `perf_fetch_caller_regs(\u0026regs)` is invoked.\n2. The destination buffer `buf` passed from the BPF program is managed by `__bpf_get_stack()`, which writes stack entries into it or zeroes it completely via `memset(buf, 0, size)` on failure or partial fills.\n3. No kernel-to-user copy of uninitialized memory or info-leak risk is introduced.\n4. Potential issues introduced by sleepable BPF program execution (such as sleeping in invalid contexts, lockdep violations, or out-of-bounds stack reading) are covered by standard KASAN and LOCKDEP configurations.\n\nTherefore, KMSAN fuzzing is not required.",
  "NeedsKMSAN": false
}

{
  "KMSANReasoning": "The patch wires up sleepable variants of `bpf_get_stack` (`bpf_get_stack_tp_sleepable` and `bpf_get_stack_raw_tp_sleepable`) for sleepable tracepoint and raw tracepoint BPF programs.\n\nAnalysis of memory initialization:\n1. In `bpf_get_stack_raw_tp_sleepable`, the local `struct pt_regs regs` is explicitly zero-initialized with `{}` before `perf_fetch_caller_regs(\u0026regs)` is invoked.\n2. The destination buffer `buf` passed from the BPF program is managed by `__bpf_get_stack()`, which writes stack entries into it or zeroes it completely via `memset(buf, 0, size)` on failure or partial fills.\n3. No kernel-to-user copy of uninitialized memory or info-leak risk is introduced.\n4. Potential issues introduced by sleepable BPF program execution (such as sleeping in invalid contexts, lockdep violations, or out-of-bounds stack reading) are covered by standard KASAN and LOCKDEP configurations.\n\nTherefore, KMSAN fuzzing is not required.",
  "NeedsKMSAN": false
}