AI Trajectory

null

{
  "EnableConfigs": [
    "BPF_SYSCALL",
    "BPF_EVENTS",
    "DEBUG_INFO_BTF",
    "NET"
  ],
  "FocusSymbols": [
    "tracing_prog_func_proto",
    "bpf_skb_event_output"
  ],
  "KMSANReasoning": "The patch modifies `tracing_prog_func_proto` to forbid `bpf_skb_output` in tracing programs that run after the target function finishes execution (`BPF_TRACE_FEXIT`, `BPF_TRACE_FEXIT_MULTI`, `BPF_TRACE_FSESSION`, `BPF_TRACE_FSESSION_MULTI`). This prevents potential use-after-free (UAF) accesses where a target function consumes or frees the `skb` argument before the exit/session tracing program executes.\n\nUse-after-free conditions on freed kernel objects are tracked and detected by KASAN. The patch adds a verifier check and does not allocate memory, initialize kernel structures, alter buffer bounds, or expose any uninitialized stack or heap data to userspace or control flow. Since there is no risk of uninitialized memory reads or information disclosure, a dedicated KMSAN fuzzing session is not warranted.",
  "NeedsKMSAN": false,
  "Reasoning": "The patch updates BPF tracing verifier helper validation by introducing tracing_prog_may_run_after_target() to disallow bpf_skb_output in tracing programs that run after the target function (such as BPF_TRACE_FEXIT and BPF_TRACE_FSESSION), where skb pointer arguments may have already been consumed/freed. This modifies reachable logic in the core BPF subsystem exercised via the bpf() syscall during program verification and execution.",
  "WorthFuzzing": true
}

null

{
  "PatchDiff": "commit a038671b729c160aefbc07025a4e09ed56b52568\nAuthor: syz-cluster \u003ctriage@syzkaller.com\u003e\nDate:   Thu Sep 24 03:40:25 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 29260951aa871..29c83e2938cd0 100644\n--- a/kernel/trace/bpf_trace.c\n+++ b/kernel/trace/bpf_trace.c\n@@ -1339,6 +1339,20 @@ static inline bool is_trace_fsession(const struct bpf_prog *prog)\n \t\tprog-\u003eexpected_attach_type == BPF_TRACE_FSESSION_MULTI);\n }\n \n+static inline bool tracing_prog_may_run_after_target(const struct bpf_prog *prog)\n+{\n+\t/* The target may consume pointer arguments before these programs run. */\n+\tswitch (prog-\u003eexpected_attach_type) {\n+\tcase BPF_TRACE_FEXIT:\n+\tcase BPF_TRACE_FEXIT_MULTI:\n+\tcase BPF_TRACE_FSESSION:\n+\tcase BPF_TRACE_FSESSION_MULTI:\n+\t\treturn true;\n+\tdefault:\n+\t\treturn false;\n+\t}\n+}\n+\n static const struct bpf_func_proto *\n kprobe_prog_func_proto(enum bpf_func_id func_id, const struct bpf_prog *prog)\n {\n@@ -1730,6 +1744,8 @@ tracing_prog_func_proto(enum bpf_func_id func_id, const struct bpf_prog *prog)\n \tswitch (func_id) {\n #ifdef CONFIG_NET\n \tcase BPF_FUNC_skb_output:\n+\t\tif (tracing_prog_may_run_after_target(prog))\n+\t\t\treturn NULL;\n \t\treturn \u0026bpf_skb_output_proto;\n \tcase BPF_FUNC_xdp_output:\n \t\treturn \u0026bpf_xdp_output_proto;\ndiff --git a/tools/testing/selftests/bpf/progs/verifier_helper_restricted.c b/tools/testing/selftests/bpf/progs/verifier_helper_restricted.c\nindex 889c9b78b912e..058e71927cd5c 100644\n--- a/tools/testing/selftests/bpf/progs/verifier_helper_restricted.c\n+++ b/tools/testing/selftests/bpf/progs/verifier_helper_restricted.c\n@@ -3,6 +3,7 @@\n \n #include \u003clinux/bpf.h\u003e\n #include \u003cbpf/bpf_helpers.h\u003e\n+#include \u003cbpf/bpf_tracing.h\u003e\n #include \"bpf_misc.h\"\n \n struct val {\n@@ -17,6 +18,13 @@ struct {\n \t__type(value, struct val);\n } map_spin_lock SEC(\".maps\");\n \n+struct {\n+\t__uint(type, BPF_MAP_TYPE_PERF_EVENT_ARRAY);\n+\t__uint(max_entries, 1);\n+\t__type(key, __u32);\n+\t__type(value, __u32);\n+} perf_event_map SEC(\".maps\");\n+\n SEC(\"kprobe\")\n __description(\"bpf_ktime_get_coarse_ns is forbidden in BPF_PROG_TYPE_KPROBE\")\n __failure __msg(\"program of this type cannot use helper bpf_ktime_get_coarse_ns\")\n@@ -165,4 +173,28 @@ l0_%=:\texit;\t\t\t\t\t\t\\\n \t: __clobber_all);\n }\n \n+SEC(\"fentry/skb_tx_error\")\n+__description(\"bpf_skb_output is allowed in BPF_TRACE_FENTRY\")\n+__success\n+int BPF_PROG(skb_output_fentry, void *skb)\n+{\n+\t__u64 meta = 0;\n+\n+\tbpf_skb_output(skb, \u0026perf_event_map, BPF_F_CURRENT_CPU,\n+\t\t       \u0026meta, sizeof(meta));\n+\treturn 0;\n+}\n+\n+SEC(\"fexit/skb_tx_error\")\n+__description(\"bpf_skb_output is forbidden in BPF_TRACE_FEXIT\")\n+__failure __msg(\"program of this type cannot use helper bpf_skb_output\")\n+int BPF_PROG(skb_output_fexit, void *skb)\n+{\n+\t__u64 meta = 0;\n+\n+\tbpf_skb_output(skb, \u0026perf_event_map, BPF_F_CURRENT_CPU,\n+\t\t       \u0026meta, sizeof(meta));\n+\treturn 0;\n+}\n+\n char _license[] SEC(\"license\") = \"GPL\";\n"
}

core

null

{
  "EnableConfigs": [
    "BPF_SYSCALL",
    "BPF_EVENTS",
    "DEBUG_INFO_BTF",
    "NET"
  ],
  "FocusSymbols": [
    "tracing_prog_func_proto",
    "bpf_skb_event_output"
  ],
  "Reasoning": "The patch updates BPF tracing verifier helper validation by introducing tracing_prog_may_run_after_target() to disallow bpf_skb_output in tracing programs that run after the target function (such as BPF_TRACE_FEXIT and BPF_TRACE_FSESSION), where skb pointer arguments may have already been consumed/freed. This modifies reachable logic in the core BPF subsystem exercised via the bpf() syscall during program verification and execution.",
  "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 a038671b729c160aefbc07025a4e09ed56b52568
Author: syz-cluster <triage@syzkaller.com>
Date:   Thu Sep 24 03:40:25 2026 +0000

    syz-cluster: applied patch under review

diff --git a/kernel/trace/bpf_trace.c b/kernel/trace/bpf_trace.c
index 29260951aa871..29c83e2938cd0 100644
--- a/kernel/trace/bpf_trace.c
+++ b/kernel/trace/bpf_trace.c
@@ -1339,6 +1339,20 @@ static inline bool is_trace_fsession(const struct bpf_prog *prog)
 		prog->expected_attach_type == BPF_TRACE_FSESSION_MULTI);
 }
 
+static inline bool tracing_prog_may_run_after_target(const struct bpf_prog *prog)
+{
+	/* The target may consume pointer arguments before these programs run. */
+	switch (prog->expected_attach_type) {
+	case BPF_TRACE_FEXIT:
+	case BPF_TRACE_FEXIT_MULTI:
+	case BPF_TRACE_FSESSION:
+	case BPF_TRACE_FSESSION_MULTI:
+		return true;
+	default:
+		return false;
+	}
+}
+
 static const struct bpf_func_proto *
 kprobe_prog_func_proto(enum bpf_func_id func_id, const struct bpf_prog *prog)
 {
@@ -1730,6 +1744,8 @@ tracing_prog_func_proto(enum bpf_func_id func_id, const struct bpf_prog *prog)
 	switch (func_id) {
 #ifdef CONFIG_NET
 	case BPF_FUNC_skb_output:
+		if (tracing_prog_may_run_after_target(prog))
+			return NULL;
 		return &bpf_skb_output_proto;
 	case BPF_FUNC_xdp_output:
 		return &bpf_xdp_output_proto;
diff --git a/tools/testing/selftests/bpf/progs/verifier_helper_restricted.c b/tools/testing/selftests/bpf/progs/verifier_helper_restricted.c
index 889c9b78b912e..058e71927cd5c 100644
--- a/tools/testing/selftests/bpf/progs/verifier_helper_restricted.c
+++ b/tools/testing/selftests/bpf/progs/verifier_helper_restricted.c
@@ -3,6 +3,7 @@
 
 #include <linux/bpf.h>
 #include <bpf/bpf_helpers.h>
+#include <bpf/bpf_tracing.h>
 #include "bpf_misc.h"
 
 struct val {
@@ -17,6 +18,13 @@ struct {
 	__type(value, struct val);
 } map_spin_lock SEC(".maps");
 
+struct {
+	__uint(type, BPF_MAP_TYPE_PERF_EVENT_ARRAY);
+	__uint(max_entries, 1);
+	__type(key, __u32);
+	__type(value, __u32);
+} perf_event_map SEC(".maps");
+
 SEC("kprobe")
 __description("bpf_ktime_get_coarse_ns is forbidden in BPF_PROG_TYPE_KPROBE")
 __failure __msg("program of this type cannot use helper bpf_ktime_get_coarse_ns")
@@ -165,4 +173,28 @@ l0_%=:	exit;						\
 	: __clobber_all);
 }
 
+SEC("fentry/skb_tx_error")
+__description("bpf_skb_output is allowed in BPF_TRACE_FENTRY")
+__success
+int BPF_PROG(skb_output_fentry, void *skb)
+{
+	__u64 meta = 0;
+
+	bpf_skb_output(skb, &perf_event_map, BPF_F_CURRENT_CPU,
+		       &meta, sizeof(meta));
+	return 0;
+}
+
+SEC("fexit/skb_tx_error")
+__description("bpf_skb_output is forbidden in BPF_TRACE_FEXIT")
+__failure __msg("program of this type cannot use helper bpf_skb_output")
+int BPF_PROG(skb_output_fexit, void *skb)
+{
+	__u64 meta = 0;
+
+	bpf_skb_output(skb, &perf_event_map, BPF_F_CURRENT_CPU,
+		       &meta, sizeof(meta));
+	return 0;
+}
+
 char _license[] SEC("license") = "GPL";

gemini-3.8-flash

null

null

							input: 3858
							output: 39
							thoughts: 94
						

Okay, let's get down to it.

**Analyzing the Proposed Change**

Alright, I see the change focuses on `kernel/trace/bpf_trace.c` and adds new tests in `tools/testing/selftests/bpf/progs/verifier_helper_restricted.c`. That's the lay of the land, so let's dig into the details. I need to understand what's being modified within that trace file, specifically around lines 1339 and 1730. Time to pull up `kernel/trace/bpf_trace.c` and take a look, I'll use `read-file` or `grepper` to get a precise look at the surrounding code to grasp the context of the changes. This'll give me the information necessary to know if the changes are correct and if any testing gaps exist.

{
  "File": "kernel/trace/bpf_trace.c",
  "FirstLine": 1330,
  "LineCount": 40
}

{
  "Contents": "1330:\t{\n1331:\t\treturn prog-\u003etype == BPF_PROG_TYPE_KPROBE \u0026\u0026\n1332:\t\t       prog-\u003eexpected_attach_type == BPF_TRACE_UPROBE_SESSION;\n1333:\t}\n1334:\t\n1335:\tstatic inline bool is_trace_fsession(const struct bpf_prog *prog)\n1336:\t{\n1337:\t\treturn prog-\u003etype == BPF_PROG_TYPE_TRACING \u0026\u0026\n1338:\t\t       (prog-\u003eexpected_attach_type == BPF_TRACE_FSESSION ||\n1339:\t\t\tprog-\u003eexpected_attach_type == BPF_TRACE_FSESSION_MULTI);\n1340:\t}\n1341:\t\n1342:\tstatic inline bool tracing_prog_may_run_after_target(const struct bpf_prog *prog)\n1343:\t{\n1344:\t\t/* The target may consume pointer arguments before these programs run. */\n1345:\t\tswitch (prog-\u003eexpected_attach_type) {\n1346:\t\tcase BPF_TRACE_FEXIT:\n1347:\t\tcase BPF_TRACE_FEXIT_MULTI:\n1348:\t\tcase BPF_TRACE_FSESSION:\n1349:\t\tcase BPF_TRACE_FSESSION_MULTI:\n1350:\t\t\treturn true;\n1351:\t\tdefault:\n1352:\t\t\treturn false;\n1353:\t\t}\n1354:\t}\n1355:\t\n1356:\tstatic const struct bpf_func_proto *\n1357:\tkprobe_prog_func_proto(enum bpf_func_id func_id, const struct bpf_prog *prog)\n1358:\t{\n1359:\t\tswitch (func_id) {\n1360:\t\tcase BPF_FUNC_perf_event_output:\n1361:\t\t\treturn \u0026bpf_perf_event_output_proto;\n1362:\t\tcase BPF_FUNC_get_stackid:\n1363:\t\t\treturn \u0026bpf_get_stackid_proto;\n1364:\t\tcase BPF_FUNC_get_stack:\n1365:\t\t\treturn prog-\u003esleepable ? \u0026bpf_get_stack_sleepable_proto : \u0026bpf_get_stack_proto;\n1366:\t#ifdef CONFIG_BPF_KPROBE_OVERRIDE\n1367:\t\tcase BPF_FUNC_override_return:\n1368:\t\t\treturn \u0026bpf_override_return_proto;\n1369:\t#endif\n"
}

gemini-3.8-flash

null

null

							input: 4854
							output: 39
							thoughts: 13
						

Okay, I'm ready. Let's see what we're working with. I need to focus on understanding this passage as if it's *my* train of thought. Alright, let's dive in and pretend I'm the one who needs to unpack this idea.

***

**My Analytical Process at Line 1740**

Okay, so we're at line 1740. I know from my experience that a specific line number rarely exists in isolation; it's a marker within a larger context. I need to understand what this line signifies within the broader argument or narrative, whatever it may be. I'm immediately running through the potential types of information this could contain: is it data, a counterargument, a pivotal moment of change, or a concluding thought? I need to use clues from my field to help determine its significance and how it relates to everything else I know. I'm mentally tracing the preceding lines, trying to re-establish the logical flow. I'm focusing on keywords, key concepts, or any shifts in tone that might indicate a change in direction. I need to avoid preconceived notions and bias, and simply understand what's in front of me as the author intended. This is a crucial element in my work, since it is important to be able to understand the thoughts of others in a similar field. Only by being able to do this can I properly contribute.

{
  "File": "kernel/trace/bpf_trace.c",
  "FirstLine": 1730,
  "LineCount": 40
}

{
  "Contents": "1730:\t\tcase BPF_FUNC_get_stack:\n1731:\t\t\treturn \u0026bpf_get_stack_proto_raw_tp;\n1732:\t\tcase BPF_FUNC_get_attach_cookie:\n1733:\t\t\treturn \u0026bpf_get_attach_cookie_proto_tracing;\n1734:\t\tdefault:\n1735:\t\t\treturn bpf_tracing_func_proto(func_id, prog);\n1736:\t\t}\n1737:\t}\n1738:\t\n1739:\tconst struct bpf_func_proto *\n1740:\ttracing_prog_func_proto(enum bpf_func_id func_id, const struct bpf_prog *prog)\n1741:\t{\n1742:\t\tconst struct bpf_func_proto *fn;\n1743:\t\n1744:\t\tswitch (func_id) {\n1745:\t#ifdef CONFIG_NET\n1746:\t\tcase BPF_FUNC_skb_output:\n1747:\t\t\tif (tracing_prog_may_run_after_target(prog))\n1748:\t\t\t\treturn NULL;\n1749:\t\t\treturn \u0026bpf_skb_output_proto;\n1750:\t\tcase BPF_FUNC_xdp_output:\n1751:\t\t\treturn \u0026bpf_xdp_output_proto;\n1752:\t\tcase BPF_FUNC_skc_to_tcp6_sock:\n1753:\t\t\treturn \u0026bpf_skc_to_tcp6_sock_proto;\n1754:\t\tcase BPF_FUNC_skc_to_tcp_sock:\n1755:\t\t\treturn \u0026bpf_skc_to_tcp_sock_proto;\n1756:\t\tcase BPF_FUNC_skc_to_tcp_timewait_sock:\n1757:\t\t\treturn \u0026bpf_skc_to_tcp_timewait_sock_proto;\n1758:\t\tcase BPF_FUNC_skc_to_tcp_request_sock:\n1759:\t\t\treturn \u0026bpf_skc_to_tcp_request_sock_proto;\n1760:\t\tcase BPF_FUNC_skc_to_udp6_sock:\n1761:\t\t\treturn \u0026bpf_skc_to_udp6_sock_proto;\n1762:\t\tcase BPF_FUNC_skc_to_unix_sock:\n1763:\t\t\treturn \u0026bpf_skc_to_unix_sock_proto;\n1764:\t\tcase BPF_FUNC_skc_to_mptcp_sock:\n1765:\t\t\treturn \u0026bpf_skc_to_mptcp_sock_proto;\n1766:\t\tcase BPF_FUNC_sk_storage_get:\n1767:\t\t\treturn \u0026bpf_sk_storage_get_tracing_proto;\n1768:\t\tcase BPF_FUNC_sk_storage_delete:\n1769:\t\t\treturn \u0026bpf_sk_storage_delete_tracing_proto;\n"
}

gemini-3.8-flash

null

null

							input: 5984
							output: 21
							thoughts: 20
						

Okay, here's my take on those thoughts, tailored for an expert audience, and delivered as a first-person summary:

**Digging into `tracing_prog_func_proto`**

Alright, let's get down to it. My immediate impulse is to understand the purpose and usage of this function, `tracing_prog_func_proto`. Specifically, I want to drill down and uncover who, within this system, actually *calls* it. What modules, subsystems, or potentially even higher-level features are leveraging this tracing functionality? The name itself suggests a function related to program tracing, but the 'proto' at the end is intriguing – is this a prototype, a protocol definition, or something else entirely? I need to clarify that before I can really understand its role and impact.

{
  "Expression": "tracing_prog_func_proto"
}

{
  "Output": "include/linux/bpf.h=4046=extern const struct bpf_func_proto bpf_cgrp_storage_delete_proto;\ninclude/linux/bpf.h-4047-\ninclude/linux/bpf.h:4048:const struct bpf_func_proto *tracing_prog_func_proto(\ninclude/linux/bpf.h-4049-  enum bpf_func_id func_id, const struct bpf_prog *prog);\n--\nkernel/bpf/bpf_lsm.c=248=bpf_lsm_func_proto(enum bpf_func_id func_id, const struct bpf_prog *prog)\n--\nkernel/bpf/bpf_lsm.c-303-\tdefault:\nkernel/bpf/bpf_lsm.c:304:\t\treturn tracing_prog_func_proto(func_id, prog);\nkernel/bpf/bpf_lsm.c-305-\t}\n--\nkernel/bpf/syscall.c=6582=const struct bpf_func_proto * __weak\nkernel/bpf/syscall.c:6583:tracing_prog_func_proto(enum bpf_func_id func_id, const struct bpf_prog *prog)\nkernel/bpf/syscall.c-6584-{\n--\nkernel/bpf/syscall.c=6634=syscall_prog_func_proto(enum bpf_func_id func_id, const struct bpf_prog *prog)\n--\nkernel/bpf/syscall.c-6646-\tdefault:\nkernel/bpf/syscall.c:6647:\t\treturn tracing_prog_func_proto(func_id, prog);\nkernel/bpf/syscall.c-6648-\t}\n--\nkernel/trace/bpf_trace.c=1739=const struct bpf_func_proto *\nkernel/trace/bpf_trace.c:1740:tracing_prog_func_proto(enum bpf_func_id func_id, const struct bpf_prog *prog)\nkernel/trace/bpf_trace.c-1741-{\n--\nkernel/trace/bpf_trace.c=1850=const struct bpf_verifier_ops tracing_verifier_ops = {\nkernel/trace/bpf_trace.c:1851:\t.get_func_proto  = tracing_prog_func_proto,\nkernel/trace/bpf_trace.c-1852-\t.is_valid_access = tracing_prog_is_valid_access,\n"
}

gemini-3.8-flash

null

null

							input: 6841
							output: 23
							thoughts: 225
						

**Analyzing a Recent Patch**

Okay, so I need to understand this change. Ideally, I'd jump straight into `git log` to get the full story, but it looks like the CLI is unavailable. No worries, I have the commit header. "Author: syz-cluster, Date: Sep 24, 2026, syz-cluster: applied patch under review." Alright, that gives me a starting point. Now, let's dissect the problem and what this patch is addressing.

The commit mentions `tracing_prog_func_proto` and the use of `BPF_FUNC_skb_output`. Ah, it seems `BPF_FUNC_skb_output` was previously permitted in all tracing programs, or at least for those using `tracing_verifier_ops`. I need to figure out *why* that was the case. What’s the rationale? Time to dig deeper.

Let's look at `bpf_skb_output` itself. The helper function takes `(void *ctx, ...)`. Now, the `ctx` in this context is supposed to be an SKB, correct? So let's double check that, and therefore the definition of `bpf_skb_output_proto`. Knowing that should help me understand if this patch makes sense.

{
  "Expression": "bpf_skb_output_proto"
}

{
  "Output": "kernel/trace/bpf_trace.c=1655=static const struct bpf_func_proto bpf_perf_event_output_proto_raw_tp = {\n--\nkernel/trace/bpf_trace.c-1665-\nkernel/trace/bpf_trace.c:1666:extern const struct bpf_func_proto bpf_skb_output_proto;\nkernel/trace/bpf_trace.c-1667-extern const struct bpf_func_proto bpf_xdp_output_proto;\n--\nkernel/trace/bpf_trace.c=1740=tracing_prog_func_proto(enum bpf_func_id func_id, const struct bpf_prog *prog)\n--\nkernel/trace/bpf_trace.c-1748-\t\t\treturn NULL;\nkernel/trace/bpf_trace.c:1749:\t\treturn \u0026bpf_skb_output_proto;\nkernel/trace/bpf_trace.c-1750-\tcase BPF_FUNC_xdp_output:\n--\nnet/core/filter.c=4885=BTF_ID_LIST_SINGLE(bpf_skb_output_btf_ids, struct, sk_buff)\nnet/core/filter.c-4886-\nnet/core/filter.c:4887:const struct bpf_func_proto bpf_skb_output_proto = {\nnet/core/filter.c-4888-\t.func\t\t= bpf_skb_event_output,\n"
}

gemini-3.8-flash

null

null

							input: 7764
							output: 36
							thoughts: 20
						

Here's my attempt at summarizing the thought process, tailored for an expert audience:

**Diving into `net/core/filter.c` - Line 4887 and Beyond**

Okay, let's zero in on `net/core/filter.c`, specifically around line 4887. I'm going to start there and see what jumps out. I suspect we're looking at the core of the packet filtering implementation, probably dealing with the BPF engine or some crucial part of the XDP layer, given the context. My immediate hunch is that this location likely involves either:

*   **Instruction interpretation or dispatch:** Given its location in the filtering code, I'm expecting to see the core logic for either interpreting BPF instructions or managing the dispatch to different filter modules (e.g., tc filters, XDP programs, etc.).
*   **Packet matching and action execution:** It could be within the section where packet data is evaluated against the filter rules, and actions are determined based on the evaluation result. This is likely intertwined with the instruction interpretation, but I'm checking to clarify that.
*   **Resource allocation or management:** Potentially there is some type of critical resource allocation or management related to the filtering process, and it lives in the section to manage those critical elements.
I'll begin the examination and let the code itself guide me. I'll be looking for clues on how the kernel handles the low-level processing. Specifically, I'll be looking to clarify how the filter code handles different packet types, and ensure that the code is dealing with complex filter expressions safely and efficiently. I'll need to confirm that any critical sections are properly protected, and that there are no obvious performance bottlenecks. I'm also going to watch for any potential buffer overflows or other security vulnerabilities.

{
  "File": "net/core/filter.c",
  "FirstLine": 4880,
  "LineCount": 40
}

{
  "Contents": "4880:\t\t.arg3_type\t= ARG_ANYTHING,\n4881:\t\t.arg4_type\t= ARG_PTR_TO_MEM | MEM_RDONLY,\n4882:\t\t.arg5_type\t= ARG_MEM_SIZE_OR_ZERO,\n4883:\t};\n4884:\t\n4885:\tBTF_ID_LIST_SINGLE(bpf_skb_output_btf_ids, struct, sk_buff)\n4886:\t\n4887:\tconst struct bpf_func_proto bpf_skb_output_proto = {\n4888:\t\t.func\t\t= bpf_skb_event_output,\n4889:\t\t.gpl_only\t= true,\n4890:\t\t.ret_type\t= RET_INTEGER,\n4891:\t\t.arg1_type\t= ARG_PTR_TO_BTF_ID,\n4892:\t\t.arg1_btf_id\t= \u0026bpf_skb_output_btf_ids[0],\n4893:\t\t.arg2_type\t= ARG_CONST_MAP_PTR,\n4894:\t\t.arg3_type\t= ARG_ANYTHING,\n4895:\t\t.arg4_type\t= ARG_PTR_TO_MEM | MEM_RDONLY,\n4896:\t\t.arg5_type\t= ARG_MEM_SIZE_OR_ZERO,\n4897:\t};\n4898:\t\n4899:\tstatic unsigned short bpf_tunnel_key_af(u64 flags)\n4900:\t{\n4901:\t\treturn flags \u0026 BPF_F_TUNINFO_IPV6 ? AF_INET6 : AF_INET;\n4902:\t}\n4903:\t\n4904:\tBPF_CALL_4(bpf_skb_get_tunnel_key, struct sk_buff *, skb, struct bpf_tunnel_key *, to,\n4905:\t\t   u32, size, u64, flags)\n4906:\t{\n4907:\t\tconst struct ip_tunnel_info *info = skb_tunnel_info(skb);\n4908:\t\tu8 compat[sizeof(struct bpf_tunnel_key)];\n4909:\t\tvoid *to_orig = to;\n4910:\t\tint err;\n4911:\t\n4912:\t\tif (unlikely(!info || (flags \u0026 ~(BPF_F_TUNINFO_IPV6 |\n4913:\t\t\t\t\t\t BPF_F_TUNINFO_FLAGS)))) {\n4914:\t\t\terr = -EINVAL;\n4915:\t\t\tgoto err_clear;\n4916:\t\t}\n4917:\t\tif (ip_tunnel_info_af(info) != bpf_tunnel_key_af(flags)) {\n4918:\t\t\terr = -EPROTO;\n4919:\t\t\tgoto err_clear;\n"
}

gemini-3.8-flash

null

null

							input: 8953
							output: 23
							thoughts: 277
						

**Analyzing `bpf_skb_event_output` and SKBs in eBPF Tracing**

Okay, let's break this down. I'm looking at `bpf_skb_event_output`. The way it's set up, `arg1_type` is `ARG_PTR_TO_BTF_ID`, and specifically, `.arg1_btf_id` points to `bpf_skb_output_btf_ids[0]`, which, if I remember correctly, is the `struct sk_buff`. Makes sense.

Now, I'm considering tracing programs attached with probes like `fentry`, `fexit`, or `fsession`. The verifier allows access to function arguments within these probes. If the function's signature has a pointer like `struct sk_buff *skb` as an argument, in `fentry`, that `skb` is guaranteed to be valid.

Here's where it gets interesting and potentially problematic. In the `fexit` or `fsession` (return probe) cases, the target function might have *already* consumed or freed the `skb`! Think about it, functions like `kfree_skb(skb)`, or the numerous network functions that free the `skb`, `napi_consume_skb(skb)`, or `dev_queue_xmit(skb)`. Those functions are expected to do exactly that.

So, the target function returns, and then the `fexit` or `fsession` probe fires, but at that point, `skb` is a dangling pointer! This is a classic potential use-after-free scenario.

Wait a second… does `bpf_skb_output` dereference the `skb` at all? That's the critical question here. If it does, we have a serious issue. Gotta check `bpf_skb_event_output` now to make sure I'm not missing something fundamental.

{
  "Expression": "bpf_skb_event_output"
}

{
  "Output": "net/core/filter.c=4847=static unsigned long bpf_skb_copy(void *dst_buff, const void *skb,\n--\nnet/core/filter.c-4859-\nnet/core/filter.c:4860:BPF_CALL_5(bpf_skb_event_output, struct sk_buff *, skb, struct bpf_map *, map,\nnet/core/filter.c-4861-\t   u64, flags, void *, meta, u64, meta_size)\n--\nnet/core/filter.c-4873-\nnet/core/filter.c:4874:static const struct bpf_func_proto bpf_skb_event_output_proto = {\nnet/core/filter.c:4875:\t.func\t\t= bpf_skb_event_output,\nnet/core/filter.c-4876-\t.gpl_only\t= true,\n--\nnet/core/filter.c=4887=const struct bpf_func_proto bpf_skb_output_proto = {\nnet/core/filter.c:4888:\t.func\t\t= bpf_skb_event_output,\nnet/core/filter.c-4889-\t.gpl_only\t= true,\n--\nnet/core/filter.c=8561=sk_filter_func_proto(enum bpf_func_id func_id, const struct bpf_prog *prog)\n--\nnet/core/filter.c-8574-\tcase BPF_FUNC_perf_event_output:\nnet/core/filter.c:8575:\t\treturn \u0026bpf_skb_event_output_proto;\nnet/core/filter.c-8576-\tdefault:\n--\nnet/core/filter.c=8585=cg_skb_func_proto(enum bpf_func_id func_id, const struct bpf_prog *prog)\n--\nnet/core/filter.c-8600-\tcase BPF_FUNC_perf_event_output:\nnet/core/filter.c:8601:\t\treturn \u0026bpf_skb_event_output_proto;\nnet/core/filter.c-8602-#ifdef CONFIG_SOCK_CGROUP_DATA\n--\nnet/core/filter.c=8634=tc_cls_act_func_proto(enum bpf_func_id func_id, const struct bpf_prog *prog)\n--\nnet/core/filter.c-8695-\tcase BPF_FUNC_perf_event_output:\nnet/core/filter.c:8696:\t\treturn \u0026bpf_skb_event_output_proto;\nnet/core/filter.c-8697-\tcase BPF_FUNC_get_smp_processor_id:\n--\nnet/core/filter.c=8928=sk_skb_func_proto(enum bpf_func_id func_id, const struct bpf_prog *prog)\n--\nnet/core/filter.c-8951-\tcase BPF_FUNC_perf_event_output:\nnet/core/filter.c:8952:\t\treturn \u0026bpf_skb_event_output_proto;\nnet/core/filter.c-8953-#ifdef CONFIG_INET\n--\nnet/core/filter.c=8980=lwt_out_func_proto(enum bpf_func_id func_id, const struct bpf_prog *prog)\n--\nnet/core/filter.c-8995-\tcase BPF_FUNC_perf_event_output:\nnet/core/filter.c:8996:\t\treturn \u0026bpf_skb_event_output_proto;\nnet/core/filter.c-8997-\tcase BPF_FUNC_get_smp_processor_id:\n"
}

gemini-3.8-flash

null

null

							input: 10654
							output: 36
							thoughts: 15
						

Okay, here's my interpretation of what's going on, formatted as you requested:

**Deconstructing `bpf_skb_event_output`**

Alright, let's dive into this `bpf_skb_event_output` function, shall we? My initial thought is, based on the name, this is likely related to capturing or outputting network events associated with SKBs (Socket Buffers) within a BPF (Berkeley Packet Filter) context. Given my experience, I'm already mentally parsing the potential use cases: this could be anything from logging packet metadata for analysis, to triggering security alerts based on certain packet characteristics, or maybe even implementing network monitoring at a very granular level.

The "event output" part suggests that we're talking about taking some information derived from an SKB and pushing it somewhere. Is it logging to a ring buffer?  Is it sending the data to user space via perf events? Or perhaps pushing data into a tracing buffer for later inspection? Understanding the output mechanism is key to understanding the function's overall utility and performance implications.

My next step is to consider the context. Where does this function live within the BPF ecosystem? Is it part of the tracing infrastructure? Is it used in conjunction with a particular BPF helper or map type? The details of this function will really start to come into focus when I've got that context sorted out. I'll need to know whether its intended for use in tc, XDP, or netfilter programs or perhaps within eBPF programs.

I'm expecting to see parameters related to the SKB itself (probably a pointer), data I/O-related, and potentially an event identifier or code. I'm also ready to analyze the return value: a simple success/failure code, or something more nuanced that might indicate things like buffer exhaustion or memory allocation issues. Knowing what it returns provides clues on how a BPF program would integrate with this function.

{
  "File": "net/core/filter.c",
  "FirstLine": 4860,
  "LineCount": 25
}

{
  "Contents": "4860:\tBPF_CALL_5(bpf_skb_event_output, struct sk_buff *, skb, struct bpf_map *, map,\n4861:\t\t   u64, flags, void *, meta, u64, meta_size)\n4862:\t{\n4863:\t\tu64 skb_size = (flags \u0026 BPF_F_CTXLEN_MASK) \u003e\u003e 32;\n4864:\t\n4865:\t\tif (unlikely(flags \u0026 ~(BPF_F_CTXLEN_MASK | BPF_F_INDEX_MASK)))\n4866:\t\t\treturn -EINVAL;\n4867:\t\tif (unlikely(!skb || skb_size \u003e skb-\u003elen))\n4868:\t\t\treturn -EFAULT;\n4869:\t\n4870:\t\treturn bpf_event_output(map, flags, meta, meta_size, skb, skb_size,\n4871:\t\t\t\t\tbpf_skb_copy);\n4872:\t}\n4873:\t\n4874:\tstatic const struct bpf_func_proto bpf_skb_event_output_proto = {\n4875:\t\t.func\t\t= bpf_skb_event_output,\n4876:\t\t.gpl_only\t= true,\n4877:\t\t.ret_type\t= RET_INTEGER,\n4878:\t\t.arg1_type\t= ARG_PTR_TO_CTX,\n4879:\t\t.arg2_type\t= ARG_CONST_MAP_PTR,\n4880:\t\t.arg3_type\t= ARG_ANYTHING,\n4881:\t\t.arg4_type\t= ARG_PTR_TO_MEM | MEM_RDONLY,\n4882:\t\t.arg5_type\t= ARG_MEM_SIZE_OR_ZERO,\n4883:\t};\n4884:\t\n"
}

gemini-3.8-flash

null

null

							input: 11608
							output: 36
							thoughts: 68
						

Okay, here's my interpretation of this code snippet, filtered through the lens of my expert understanding:

**Suspicions Regarding Potential Data Corruption in BPF SKB Handling**

Hmm, this is interesting. The `bpf_skb_event_output` function immediately jumps out at me because it directly accesses `skb->len` with a potential for a race condition or a NULL pointer dereference. The check `if (unlikely(!skb || skb_size > skb->len))` is supposed to prevent issues, which is good, but it still feels a bit risky to me. It's a classic race condition scenario, isn't it? A quick check for `skb` being null is good practice, but if the `skb` is freed between the initial `!skb` check and the `skb->len` dereference, we're in trouble. We might need some memory barriers and atomics here. This is definitely something I'd want to audit carefully.

And then, looking at `bpf_skb_copy` which is probably the follow up function to that previous check, I start to formulate some more ideas about what might be going on, I think that the check of `skb_size > skb->len` is intended to prevent this, but the function's assumptions might make it vulnerable in certain circumstances. This needs a deeper dive. The potential for out-of-bounds reads and writes because of assumptions about `skb_len` gives me pause. I'm going to have to carefully consider the context in which `bpf_skb_copy` is called.

{
  "File": "net/core/filter.c",
  "FirstLine": 4845,
  "LineCount": 20
}

{
  "Contents": "4845:\t};\n4846:\t\n4847:\tstatic unsigned long bpf_skb_copy(void *dst_buff, const void *skb,\n4848:\t\t\t\t\t  unsigned long off, unsigned long len)\n4849:\t{\n4850:\t\tvoid *ptr = skb_header_pointer(skb, off, len, dst_buff);\n4851:\t\n4852:\t\tif (unlikely(!ptr))\n4853:\t\t\treturn len;\n4854:\t\tif (ptr != dst_buff)\n4855:\t\t\tmemcpy(dst_buff, ptr, len);\n4856:\t\n4857:\t\treturn 0;\n4858:\t}\n4859:\t\n4860:\tBPF_CALL_5(bpf_skb_event_output, struct sk_buff *, skb, struct bpf_map *, map,\n4861:\t\t   u64, flags, void *, meta, u64, meta_size)\n4862:\t{\n4863:\t\tu64 skb_size = (flags \u0026 BPF_F_CTXLEN_MASK) \u003e\u003e 32;\n4864:\t\n"
}

gemini-3.8-flash

null

null

							input: 12382
							output: 23
							thoughts: 152
						

**Use-After-Free Concerns with eBPF and `skb_output`**

Okay, so I'm looking at this code and immediately I see it's dereferencing `skb` using `skb_header_pointer`. The problem that jumps out at me, especially with BPF programs, is the potential for use-after-free. If this program is attached to an `fexit` or `fsession` hook, which execute *after* a function returns, those pointer arguments, namely `skb`, could have already been freed by the target function! That's a classic use-after-free scenario waiting to happen. Allowing `BPF_FUNC_skb_output` in `fexit` or `fsession` contexts is a huge red flag.

But wait a minute… what about `xdp_output`? Does `xdp_output` have the same issue? Is it also running after the target function? I need to clarify that. This is something I have to be absolutely sure about. And, hang on... why wasn't `xdp_output` explicitly checked in the code I was looking at? Or, is it even possible to call `xdp_output`? This needs deeper investigation. I'm going to check the implementation of `BPF_FUNC_xdp_output` right now and see exactly how it works. I need to be sure this isn't another ticking time bomb.

{
  "Expression": "BPF_FUNC_xdp_output"
}

{
  "Output": "kernel/bpf/verifier.c=9643=static int check_map_func_compatibility(struct bpf_verifier_env *env,\n--\nkernel/bpf/verifier.c-9659-\t\t    func_id != BPF_FUNC_perf_event_read_value \u0026\u0026\nkernel/bpf/verifier.c:9660:\t\t    func_id != BPF_FUNC_xdp_output)\nkernel/bpf/verifier.c-9661-\t\t\tgoto error;\n--\nkernel/bpf/verifier.c-9790-\tcase BPF_FUNC_skb_output:\nkernel/bpf/verifier.c:9791:\tcase BPF_FUNC_xdp_output:\nkernel/bpf/verifier.c-9792-\t\tif (map-\u003emap_type != BPF_MAP_TYPE_PERF_EVENT_ARRAY)\n--\nkernel/trace/bpf_trace.c=1740=tracing_prog_func_proto(enum bpf_func_id func_id, const struct bpf_prog *prog)\n--\nkernel/trace/bpf_trace.c-1749-\t\treturn \u0026bpf_skb_output_proto;\nkernel/trace/bpf_trace.c:1750:\tcase BPF_FUNC_xdp_output:\nkernel/trace/bpf_trace.c-1751-\t\treturn \u0026bpf_xdp_output_proto;\n"
}

gemini-3.8-flash

null

null

							input: 13231
							output: 23
							thoughts: 16
						

Okay, let's break this down. Here's how I'd approach summarizing the prompt, given my assumed expertise:

**My Immediate Evaluation of "bpf_xdp_output_proto"**

Alright, "bpf_xdp_output_proto"... right away, I'm thinking XDP, BPF, and potentially network packet handling. My mind jumps to the kernel-level, low-latency processing, and the power of programmable data paths. The specific "proto" suggests this is concerned with, or at least capable of manipulating, protocol information within the XDP framework. So, this isn't just a generic XDP function, it's something specifically tuned for outputting and handling protocol data. I need to understand what this function *does* with that protocol data. Does it simply read it? Does it modify it? Does it use the protocol information to direct the packet, filter it, or encapsulate it? I'm already envisioning scenarios: maybe we're setting the EtherType, altering VLAN tags, modifying IP headers – the possibilities within the XDP context are vast. I immediately wonder about efficiency: is this implementation optimized for performance? What are the potential overheads associated with the protocol manipulation, if any? I'm also curious about its integration with other XDP helpers and features. Does it interact with existing XDP maps or ring buffers? Are there any specific limitations I should be aware of, like potential constraints on packet size or allowable protocol modifications? The term "proto" also brings to mind that it is, perhaps, used for protocol inspection to perform some form of traffic control. The documentation, if it exists, is going to be my first place to start. I'll need to know the exact signature and usage to fully grasp its utility, but my initial impression is this could be a powerful tool for sophisticated packet processing within XDP.

{
  "Expression": "bpf_xdp_output_proto"
}

{
  "Output": "kernel/trace/bpf_trace.c=1666=extern const struct bpf_func_proto bpf_skb_output_proto;\nkernel/trace/bpf_trace.c:1667:extern const struct bpf_func_proto bpf_xdp_output_proto;\nkernel/trace/bpf_trace.c-1668-extern const struct bpf_func_proto bpf_xdp_get_buff_len_trace_proto;\n--\nkernel/trace/bpf_trace.c=1740=tracing_prog_func_proto(enum bpf_func_id func_id, const struct bpf_prog *prog)\n--\nkernel/trace/bpf_trace.c-1750-\tcase BPF_FUNC_xdp_output:\nkernel/trace/bpf_trace.c:1751:\t\treturn \u0026bpf_xdp_output_proto;\nkernel/trace/bpf_trace.c-1752-\tcase BPF_FUNC_skc_to_tcp6_sock:\n--\nnet/core/filter.c=5299=BTF_ID_LIST_SINGLE(bpf_xdp_output_btf_ids, struct, xdp_buff)\nnet/core/filter.c-5300-\nnet/core/filter.c:5301:const struct bpf_func_proto bpf_xdp_output_proto = {\nnet/core/filter.c-5302-\t.func\t\t= bpf_xdp_event_output,\n"
}

gemini-3.8-flash

null

null

							input: 14049
							output: 29
							thoughts: 901
						

**WorthFuzzing: A Deep Dive into BPF Tracing Code**

Okay, first things first, this patch introduces a new function, `tracing_prog_may_run_after_target`, and modifies the `bpf_skb_output` helper function within the BPF verifier. The key is in `kernel/trace/bpf_trace.c`. I need to determine if this code is *reachable* and *fuzzable*.

I quickly realize this is directly related to the BPF verifier, triggered when a BPF program of type `BPF_PROG_TYPE_TRACING` is loaded via the `bpf()` syscall. Specifically, the verifier will call `tracing_prog_func_proto` when checking tracing programs with types such as `BPF_TRACE_FEXIT`, `BPF_TRACE_FENTRY`, or `BPF_TRACE_FSESSION`. This means this code *is* core BPF verifier and tracing code!

Now, the important question: is this worth fuzzing? According to the "WorthFuzzing" criteria, modifications in core subsystems like BPF and tracing, which are directly user-accessible via the `bpf()` syscall, are prime candidates for fuzzing. The patch *definitely* touches reachable executable code.

Let me consider the negative criteria. Is this code non-kernel, structurally unreachable, or exclusive to some architecture? Absolutely not! This code lives within the kernel and is directly executed within a standard virtualized environment (QEMU/GCE) via the `sys_bpf` system call. The patch doesn't fall into any of the negative criteria, so that means `WorthFuzzing = true`.

I need to confirm this by checking the configuration options and see which configuration is needed to make the code reachable. I will check the `kernel/trace/Makefile` or `kernel/trace/bpf_trace.c` source file to determine which `CONFIG` options are required to enable `bpf_trace.c` and specifically `tracing_prog_func_proto`.

I have the path. Now, I need to evaluate and create the `EnableConfigs`, `FocusSymbols`, and `Reasoning`.

{
  "Expression": "bpf_trace\\.o",
  "PathPrefix": "kernel/trace"
}

{
  "Output": "kernel/trace/Makefile=54=KCOV_INSTRUMENT_trace_irqsoff.o := n\nkernel/trace/Makefile-55-\nkernel/trace/Makefile:56:CFLAGS_bpf_trace.o := -I$(src)\nkernel/trace/Makefile-57-\n--\nkernel/trace/Makefile=109=obj-$(CONFIG_USER_EVENTS) += trace_events_user.o\nkernel/trace/Makefile:110:obj-$(CONFIG_BPF_EVENTS) += bpf_trace.o\nkernel/trace/Makefile-111-obj-$(CONFIG_KPROBE_EVENTS) += trace_kprobe.o\n"
}

gemini-3.8-flash

null

null

							input: 15618
							output: 19
							thoughts: 41
						

Here's my thought process, as it stands:

**BPF Event Compilation Investigation**

Okay, so `CONFIG_BPF_EVENTS` is definitely linked to the compilation of `bpf_trace.o`. That's a key piece of information. Now, I need to understand the relationship and impact. My next step is clear: I need to dig into the kernel configuration files, specifically looking for the definition or dependency of `BPF_EVENTS`. My instincts tell me the logical place to start is within `kernel/trace/Kconfig`, but I'll also do a broader search to see if it's referenced elsewhere. This is likely the path to understanding how the BPF tracepoints are enabled and configured within this particular build. The details of that configuration are what's going to tell me what's enabled when it's compiled, and if this could be the source of my problem.

{
  "Expression": "config BPF_EVENTS"
}

{
  "Output": "kernel/trace/Kconfig=851=config EPROBE_EVENTS\n--\nkernel/trace/Kconfig-864-\nkernel/trace/Kconfig:865:config BPF_EVENTS\nkernel/trace/Kconfig-866-\tdepends on BPF_SYSCALL\n"
}

gemini-3.8-flash

null

null

							input: 15950
							output: 34
							thoughts: 18
						

Here's a summary of my thought process, as requested:

**Diving into the Tracepoint Configuration**

Alright, let's get down to brass tacks. I need to get a better handle on how this tracepoint system is configured within the kernel. Time to dig into the `kernel/trace/Kconfig` file. Specifically, I'll start around line 865. That's usually a good place to begin to get a sense of the relevant options and their dependencies. I'm looking for the core elements that define how these tracing features are enabled and disabled during the build process. I'll need to understand the relationships between different configuration symbols and how they influence the overall tracing capabilities. This should give me a solid foundation for evaluating how tracepoints are integrated and controlled within the kernel's configuration. I expect to get a feel for what features are enabled by default and what the key options are for customising the tracing setup.

{
  "File": "kernel/trace/Kconfig",
  "FirstLine": 860,
  "LineCount": 20
}

{
  "Contents": " 860:\t\t  events. It can be used to limit what fields are recorded in\n 861:\t\t  an event or even dereference a field of an event. It can\n 862:\t\t  convert the type of an event field. For example, turn an\n 863:\t\t  address into a string.\n 864:\t\n 865:\tconfig BPF_EVENTS\n 866:\t\tdepends on BPF_SYSCALL\n 867:\t\tdepends on (KPROBE_EVENTS || UPROBE_EVENTS) \u0026\u0026 PERF_EVENTS\n 868:\t\tbool\n 869:\t\tdefault y\n 870:\t\thelp\n 871:\t\t  This allows the user to attach BPF programs to kprobe, uprobe, and\n 872:\t\t  tracepoint events.\n 873:\t\n 874:\tconfig DYNAMIC_EVENTS\n 875:\t\tdef_bool n\n 876:\t\n 877:\tconfig PROBE_EVENTS\n 878:\t\tdef_bool n\n 879:\t\n"
}

gemini-3.8-flash

null

null

							input: 16480
							output: 24
							thoughts: 194
						

Okay, let me break this down.

**My Analysis of BPF Function Compilation and Tracing**

Alright, I'm digging into this `tracing_prog_func_proto` code and there's something interesting that I see. That `switch` statement, particularly the part involving `BPF_FUNC_skb_output`, is conditionally compiled. The `#ifdef CONFIG_NET` directive is pretty explicit. *That means that `BPF_FUNC_skb_output` is only going to be included in that table if the `CONFIG_NET` kernel configuration option is enabled.* Makes sense, it is networking-related, after all. Also, as an aside, I know `CONFIG_BPF_SYSCALL` is a hard requirement in general for BPF functionality, so I'm filing that away as a given here.

Now, what about the bigger picture? This is about tracing, fentry/fexit, and BPF programs. I need to make sure I know the build configuration dependencies for those. What kernel configuration options actually enable support for `BPF_TRACE_FENTRY`, `BPF_TRACE_FEXIT`, and, critically, `BPF_PROG_TYPE_TRACING`? I should probably check the Kconfig files for those symbols to be sure. It's important to understand the build requirements. I know where to look. I'll need to double check those specific configuration options to be sure I understand the full scope of what's going on here.

{
  "Expression": "BPF_PROG_TYPE_TRACING"
}

{
  "Output": "Documentation/bpf/bpf_prog_run.rst=26=following types:\n--\nDocumentation/bpf/bpf_prog_run.rst-40-- ``BPF_PROG_TYPE_SYSCALL``\nDocumentation/bpf/bpf_prog_run.rst:41:- ``BPF_PROG_TYPE_TRACING``\nDocumentation/bpf/bpf_prog_run.rst-42-- ``BPF_PROG_TYPE_NETFILTER``\n--\nDocumentation/bpf/drgn.rst=27=The main use-case `bpf_inspect.py`_ covers is to show BPF programs of types\nDocumentation/bpf/drgn.rst:28:``BPF_PROG_TYPE_EXT`` and ``BPF_PROG_TYPE_TRACING`` attached to other BPF\nDocumentation/bpf/drgn.rst-29-programs via ``freplace``/``fentry``/``fexit``/``fsession`` mechanisms, since\n--\nDocumentation/bpf/drgn.rst=49=Find BPF programs attached to BPF program ``test_pkt_access``::\n--\nDocumentation/bpf/drgn.rst-52-         650: BPF_PROG_TYPE_SCHED_CLS          test_pkt_access\nDocumentation/bpf/drgn.rst:53:         654: BPF_PROG_TYPE_TRACING            test_main                        linked:[650-\u003e25: BPF_TRAMP_FEXIT test_pkt_access-\u003etest_pkt_access()]\nDocumentation/bpf/drgn.rst:54:         655: BPF_PROG_TYPE_TRACING            test_subprog1                    linked:[650-\u003e29: BPF_TRAMP_FEXIT test_pkt_access-\u003etest_pkt_access_subprog1()]\nDocumentation/bpf/drgn.rst:55:         656: BPF_PROG_TYPE_TRACING            test_subprog2                    linked:[650-\u003e31: BPF_TRAMP_FEXIT test_pkt_access-\u003etest_pkt_access_subprog2()]\nDocumentation/bpf/drgn.rst:56:         657: BPF_PROG_TYPE_TRACING            test_subprog3                    linked:[650-\u003e21: BPF_TRAMP_FEXIT test_pkt_access-\u003etest_pkt_access_subprog3()]\nDocumentation/bpf/drgn.rst-57-         658: BPF_PROG_TYPE_EXT                new_get_skb_len                  linked:[650-\u003e16: BPF_TRAMP_REPLACE test_pkt_access-\u003eget_skb_len()]\n--\nDocumentation/bpf/kfuncs.rst=529=type. An example is shown below::\n--\nDocumentation/bpf/kfuncs.rst-542-        {\nDocumentation/bpf/kfuncs.rst:543:                return register_btf_kfunc_id_set(BPF_PROG_TYPE_TRACING, \u0026bpf_task_kfunc_set);\nDocumentation/bpf/kfuncs.rst-544-        }\n--\nDocumentation/bpf/libbpf/program_types.rst=18=described in more detail in the footnotes.\n--\nDocumentation/bpf/libbpf/program_types.rst-197-+-------------------------------------------+----------------------------------------+----------------------------------+-----------+\nDocumentation/bpf/libbpf/program_types.rst:198:| ``BPF_PROG_TYPE_TRACING``                 | ``BPF_MODIFY_RETURN``                  | ``fmod_ret+`` [#fentry]_         |           |\nDocumentation/bpf/libbpf/program_types.rst-199-+                                           +                                        +----------------------------------+-----------+\n--\ninclude/linux/bpf_types.h=47=BPF_PROG_TYPE(BPF_PROG_TYPE_RAW_TRACEPOINT_WRITABLE, raw_tracepoint_writable,\ninclude/linux/bpf_types.h-48-\t      struct bpf_raw_tracepoint_args, u64)\ninclude/linux/bpf_types.h:49:BPF_PROG_TYPE(BPF_PROG_TYPE_TRACING, tracing,\ninclude/linux/bpf_types.h-50-\t      void *, void *)\n--\ninclude/linux/bpf_verifier.h=1368=static inline bool bpf_prog_check_recur(const struct bpf_prog *prog)\n--\ninclude/linux/bpf_verifier.h-1370-\tswitch (resolve_prog_type(prog)) {\ninclude/linux/bpf_verifier.h:1371:\tcase BPF_PROG_TYPE_TRACING:\ninclude/linux/bpf_verifier.h-1372-\t\treturn prog-\u003eexpected_attach_type != BPF_TRACE_ITER;\n--\ninclude/uapi/linux/bpf.h=1062=enum bpf_prog_type {\n--\ninclude/uapi/linux/bpf.h-1088-\tBPF_PROG_TYPE_CGROUP_SOCKOPT,\ninclude/uapi/linux/bpf.h:1089:\tBPF_PROG_TYPE_TRACING,\ninclude/uapi/linux/bpf.h-1090-\tBPF_PROG_TYPE_STRUCT_OPS,\n--\nkernel/bpf/btf.c=6249=static int btf_validate_prog_ctx_type(struct bpf_verifier_log *log, const struct btf *btf,\n--\nkernel/bpf/btf.c-6311-\t\tbreak;\nkernel/bpf/btf.c:6312:\tcase BPF_PROG_TYPE_TRACING:\nkernel/bpf/btf.c-6313-\t\tswitch (attach_type) {\n--\nkernel/bpf/btf.c=6648=static bool prog_args_trusted(const struct bpf_prog *prog)\n--\nkernel/bpf/btf.c-6652-\tswitch (prog-\u003etype) {\nkernel/bpf/btf.c:6653:\tcase BPF_PROG_TYPE_TRACING:\nkernel/bpf/btf.c-6654-\t\treturn atype == BPF_TRACE_RAW_TP || atype == BPF_TRACE_ITER;\n--\nkernel/bpf/btf.c=9160=static int bpf_prog_type_to_kfunc_hook(enum bpf_prog_type prog_type)\n--\nkernel/bpf/btf.c-9170-\t\treturn BTF_KFUNC_HOOK_STRUCT_OPS;\nkernel/bpf/btf.c:9171:\tcase BPF_PROG_TYPE_TRACING:\nkernel/bpf/btf.c-9172-\tcase BPF_PROG_TYPE_TRACEPOINT:\n--\nkernel/bpf/core.c=2503=static bool __bpf_prog_map_compatible(struct bpf_map *map,\n--\nkernel/bpf/core.c-2552-\t\t\tswitch (prog_type) {\nkernel/bpf/core.c:2553:\t\t\tcase BPF_PROG_TYPE_TRACING:\nkernel/bpf/core.c-2554-\t\t\tcase BPF_PROG_TYPE_LSM:\n--\nkernel/bpf/cpumask.c=515=static int __init cpumask_kfunc_init(void)\n--\nkernel/bpf/cpumask.c-525-\tret = bpf_mem_alloc_init(\u0026bpf_cpumask_ma, sizeof(struct bpf_cpumask), false);\nkernel/bpf/cpumask.c:526:\tret = ret ?: register_btf_kfunc_id_set(BPF_PROG_TYPE_TRACING, \u0026cpumask_kfunc_set);\nkernel/bpf/cpumask.c-527-\tret = ret ?: register_btf_kfunc_id_set(BPF_PROG_TYPE_STRUCT_OPS, \u0026cpumask_kfunc_set);\n--\nkernel/bpf/fixups.c=1540=int bpf_do_misc_fixups(struct bpf_verifier_env *env)\n--\nkernel/bpf/fixups.c-2251-\t\t/* Implement bpf_get_func_arg inline. */\nkernel/bpf/fixups.c:2252:\t\tif (prog_type == BPF_PROG_TYPE_TRACING \u0026\u0026\nkernel/bpf/fixups.c-2253-\t\t    insn-\u003eimm == BPF_FUNC_get_func_arg) {\n--\nkernel/bpf/fixups.c-2285-\t\t/* Implement bpf_get_func_ret inline. */\nkernel/bpf/fixups.c:2286:\t\tif (prog_type == BPF_PROG_TYPE_TRACING \u0026\u0026\nkernel/bpf/fixups.c-2287-\t\t    insn-\u003eimm == BPF_FUNC_get_func_ret) {\n--\nkernel/bpf/fixups.c-2317-\t\t/* Implement get_func_arg_cnt inline. */\nkernel/bpf/fixups.c:2318:\t\tif (prog_type == BPF_PROG_TYPE_TRACING \u0026\u0026\nkernel/bpf/fixups.c-2319-\t\t    insn-\u003eimm == BPF_FUNC_get_func_arg_cnt) {\n--\nkernel/bpf/fixups.c-2343-\t\t/* Implement bpf_get_func_ip inline. */\nkernel/bpf/fixups.c:2344:\t\tif (prog_type == BPF_PROG_TYPE_TRACING \u0026\u0026\nkernel/bpf/fixups.c-2345-\t\t    insn-\u003eimm == BPF_FUNC_get_func_ip) {\n--\nkernel/bpf/helpers.c=5113=static int __init kfunc_init(void)\n--\nkernel/bpf/helpers.c-5128-\nkernel/bpf/helpers.c:5129:\tret = register_btf_kfunc_id_set(BPF_PROG_TYPE_TRACING, \u0026generic_kfunc_set);\nkernel/bpf/helpers.c-5130-\tret = ret ?: register_btf_kfunc_id_set(BPF_PROG_TYPE_SCHED_CLS, \u0026generic_kfunc_set);\n--\nkernel/bpf/syscall.c=2731=bpf_prog_load_check_attach(enum bpf_prog_type prog_type,\n--\nkernel/bpf/syscall.c-2744-\t\tswitch (prog_type) {\nkernel/bpf/syscall.c:2745:\t\tcase BPF_PROG_TYPE_TRACING:\nkernel/bpf/syscall.c-2746-\t\tcase BPF_PROG_TYPE_LSM:\n--\nkernel/bpf/syscall.c-2755-\tif (multi_func) {\nkernel/bpf/syscall.c:2756:\t\tif (prog_type != BPF_PROG_TYPE_TRACING)\nkernel/bpf/syscall.c-2757-\t\t\treturn -EINVAL;\n--\nkernel/bpf/syscall.c-2765-\nkernel/bpf/syscall.c:2766:\tif (dst_prog \u0026\u0026 prog_type != BPF_PROG_TYPE_TRACING \u0026\u0026\nkernel/bpf/syscall.c-2767-\t    prog_type != BPF_PROG_TYPE_EXT)\n--\nkernel/bpf/syscall.c=2877=static bool is_perfmon_prog_type(enum bpf_prog_type prog_type)\n--\nkernel/bpf/syscall.c-2884-\tcase BPF_PROG_TYPE_RAW_TRACEPOINT_WRITABLE:\nkernel/bpf/syscall.c:2885:\tcase BPF_PROG_TYPE_TRACING:\nkernel/bpf/syscall.c-2886-\tcase BPF_PROG_TYPE_LSM:\n--\nkernel/bpf/syscall.c=2920=static int bpf_prog_load(union bpf_attr *attr, bpfptr_t uattr, struct bpf_log_attr *attr_log)\n--\nkernel/bpf/syscall.c-3118-\t */\nkernel/bpf/syscall.c:3119:\tif (type == BPF_PROG_TYPE_TRACING \u0026\u0026 dst_prog \u0026\u0026\nkernel/bpf/syscall.c:3120:\t    dst_prog-\u003etype == BPF_PROG_TYPE_TRACING) {\nkernel/bpf/syscall.c-3121-\t\tprog-\u003eaux-\u003eattach_tracing_prog = true;\n--\nkernel/bpf/syscall.c=3637=static int bpf_tracing_prog_attach(struct bpf_prog *prog,\n--\nkernel/bpf/syscall.c-3650-\tswitch (prog-\u003etype) {\nkernel/bpf/syscall.c:3651:\tcase BPF_PROG_TYPE_TRACING:\nkernel/bpf/syscall.c-3652-\t\tif (prog-\u003eexpected_attach_type != BPF_TRACE_FENTRY \u0026\u0026\n--\nkernel/bpf/syscall.c-3685-\t\t * part would be changed to implement the same for\nkernel/bpf/syscall.c:3686:\t\t * BPF_PROG_TYPE_TRACING, do not forget to update the way how\nkernel/bpf/syscall.c-3687-\t\t * attach_tracing_prog flag is set.\n--\nkernel/bpf/syscall.c-3747-\t\t */\nkernel/bpf/syscall.c:3748:\t\tif (prog-\u003etype != BPF_PROG_TYPE_TRACING \u0026\u0026\nkernel/bpf/syscall.c-3749-\t\t    prog-\u003etype != BPF_PROG_TYPE_LSM) {\n--\nkernel/bpf/syscall.c=4300=static int bpf_raw_tp_link_attach(struct bpf_prog *prog,\n--\nkernel/bpf/syscall.c-4311-\tswitch (prog-\u003etype) {\nkernel/bpf/syscall.c:4312:\tcase BPF_PROG_TYPE_TRACING:\nkernel/bpf/syscall.c-4313-\tcase BPF_PROG_TYPE_EXT:\n--\nkernel/bpf/syscall.c-4319-\t\t\treturn -EINVAL;\nkernel/bpf/syscall.c:4320:\t\tif (prog-\u003etype == BPF_PROG_TYPE_TRACING \u0026\u0026\nkernel/bpf/syscall.c-4321-\t\t    prog-\u003eexpected_attach_type == BPF_TRACE_RAW_TP) {\n--\nkernel/bpf/syscall.c=4401=attach_type_to_prog_type(enum bpf_attach_type attach_type)\n--\nkernel/bpf/syscall.c-4457-\tcase BPF_MODIFY_RETURN:\nkernel/bpf/syscall.c:4458:\t\treturn BPF_PROG_TYPE_TRACING;\nkernel/bpf/syscall.c-4459-\tcase BPF_LSM_MAC:\n--\nkernel/bpf/syscall.c=5797=static int link_create(union bpf_attr *attr, bpfptr_t uattr)\n--\nkernel/bpf/syscall.c-5834-\tcase BPF_PROG_TYPE_LSM:\nkernel/bpf/syscall.c:5835:\tcase BPF_PROG_TYPE_TRACING:\nkernel/bpf/syscall.c-5836-\t\tif (attr-\u003elink_create.attach_type != prog-\u003eexpected_attach_type) {\n--\nkernel/bpf/trampoline.c=177=bool bpf_prog_has_trampoline(const struct bpf_prog *prog)\n--\nkernel/bpf/trampoline.c-182-\tswitch (ptype) {\nkernel/bpf/trampoline.c:183:\tcase BPF_PROG_TYPE_TRACING:\nkernel/bpf/trampoline.c-184-\t\tif (eatype == BPF_TRACE_FENTRY || eatype == BPF_TRACE_FEXIT ||\n--\nkernel/bpf/verifier.c=5326=static enum priv_stack_mode bpf_enable_priv_stack(struct bpf_prog *prog)\n--\nkernel/bpf/verifier.c-5340-\t\treturn PRIV_STACK_ADAPTIVE;\nkernel/bpf/verifier.c:5341:\tcase BPF_PROG_TYPE_TRACING:\nkernel/bpf/verifier.c-5342-\tcase BPF_PROG_TYPE_LSM:\n--\nkernel/bpf/verifier.c=9604=static bool may_update_sockmap(struct bpf_verifier_env *env, int func_id)\n--\nkernel/bpf/verifier.c-9616-\tswitch (type) {\nkernel/bpf/verifier.c:9617:\tcase BPF_PROG_TYPE_TRACING:\nkernel/bpf/verifier.c-9618-\t\tif (eatype == BPF_TRACE_ITER)\n--\nkernel/bpf/verifier.c=11369=static int check_get_func_ip(struct bpf_verifier_env *env)\n--\nkernel/bpf/verifier.c-11373-\nkernel/bpf/verifier.c:11374:\tif (type == BPF_PROG_TYPE_TRACING) {\nkernel/bpf/verifier.c-11375-\t\tif (!bpf_prog_has_trampoline(env-\u003eprog)) {\n--\nkernel/bpf/verifier.c=13670=static bool check_css_task_iter_allowlist(struct bpf_verifier_env *env)\n--\nkernel/bpf/verifier.c-13676-\t\treturn true;\nkernel/bpf/verifier.c:13677:\tcase BPF_PROG_TYPE_TRACING:\nkernel/bpf/verifier.c-13678-\t\tif (env-\u003eprog-\u003eexpected_attach_type == BPF_TRACE_ITER)\n--\nkernel/bpf/verifier.c=14091=static int check_kfunc_call(struct bpf_verifier_env *env, struct bpf_insn *insn,\n--\nkernel/bpf/verifier.c-14197-\t     /* is_tracing_prog_type() for now doesn't cover non-iterator tracing progs. */\nkernel/bpf/verifier.c:14198:\t     (prog_type == BPF_PROG_TYPE_TRACING \u0026\u0026 env-\u003eprog-\u003eexpected_attach_type != BPF_TRACE_ITER\nkernel/bpf/verifier.c-14199-\t      \u0026\u0026 !env-\u003eprog-\u003esleepable))) {\n--\nkernel/bpf/verifier.c=17771=static bool return_retval_range(struct bpf_verifier_env *env, struct bpf_retval_range *range)\n--\nkernel/bpf/verifier.c-17814-\t\tbreak;\nkernel/bpf/verifier.c:17815:\tcase BPF_PROG_TYPE_TRACING:\nkernel/bpf/verifier.c-17816-\t\tswitch (env-\u003eprog-\u003eexpected_attach_type) {\n--\nkernel/bpf/verifier.c=20344=static int btf_id_allow_sleepable(u32 btf_id, unsigned long addr, const struct bpf_prog *prog,\n--\nkernel/bpf/verifier.c-20353-\tswitch (prog-\u003etype) {\nkernel/bpf/verifier.c:20354:\tcase BPF_PROG_TYPE_TRACING:\nkernel/bpf/verifier.c-20355-\t\tt = btf_type_by_id(btf, btf_id);\n--\nkernel/bpf/verifier.c=20451=int bpf_check_attach_target(struct bpf_verifier_log *log,\n--\nkernel/bpf/verifier.c-20457-\tbool prog_extension = prog-\u003etype == BPF_PROG_TYPE_EXT;\nkernel/bpf/verifier.c:20458:\tbool prog_tracing = prog-\u003etype == BPF_PROG_TYPE_TRACING;\nkernel/bpf/verifier.c-20459-\tchar trace_symbol[KSYM_SYMBOL_LEN];\n--\nkernel/bpf/verifier.c-20578-\t\t}\nkernel/bpf/verifier.c:20579:\t\tif (tgt_prog-\u003etype == BPF_PROG_TYPE_TRACING \u0026\u0026\nkernel/bpf/verifier.c-20580-\t\t    prog_extension \u0026\u0026\n--\nkernel/bpf/verifier.c=20847=static bool can_be_sleepable(struct bpf_prog *prog)\nkernel/bpf/verifier.c-20848-{\nkernel/bpf/verifier.c:20849:\tif (prog-\u003etype == BPF_PROG_TYPE_TRACING) {\nkernel/bpf/verifier.c-20850-\t\tswitch (prog-\u003eexpected_attach_type) {\n--\nkernel/bpf/verifier.c=20874=static int check_attach_btf_id(struct bpf_verifier_env *env)\n--\nkernel/bpf/verifier.c-20899-\nkernel/bpf/verifier.c:20900:\tif (prog-\u003etype != BPF_PROG_TYPE_TRACING \u0026\u0026\nkernel/bpf/verifier.c-20901-\t    prog-\u003etype != BPF_PROG_TYPE_LSM \u0026\u0026\n--\nkernel/bpf/verifier.c-20938-\t\t\treturn ret;\nkernel/bpf/verifier.c:20939:\t} else if (prog-\u003etype == BPF_PROG_TYPE_TRACING \u0026\u0026\nkernel/bpf/verifier.c-20940-\t\t   btf_id_set_contains(\u0026btf_id_deny, btf_id)) {\n--\nkernel/bpf/verifier.c-20957-\t */\nkernel/bpf/verifier.c:20958:\tif (prog-\u003etype == BPF_PROG_TYPE_TRACING \u0026\u0026\nkernel/bpf/verifier.c-20959-\t    is_tracing_multi(prog-\u003eexpected_attach_type))\n--\nkernel/cgroup/rstat.c=766=static int __init bpf_rstat_kfunc_init(void)\nkernel/cgroup/rstat.c-767-{\nkernel/cgroup/rstat.c:768:\treturn register_btf_kfunc_id_set(BPF_PROG_TYPE_TRACING,\nkernel/cgroup/rstat.c-769-\t\t\t\t\t \u0026bpf_rstat_kfunc_set);\n--\nkernel/sched/ext/cid.c=1160=int scx_cid_kfunc_init(void)\n--\nkernel/sched/ext/cid.c-1163-\t\tregister_btf_kfunc_id_set(BPF_PROG_TYPE_STRUCT_OPS, \u0026scx_kfunc_set_cid) ?:\nkernel/sched/ext/cid.c:1164:\t\tregister_btf_kfunc_id_set(BPF_PROG_TYPE_TRACING, \u0026scx_kfunc_set_cid) ?:\nkernel/sched/ext/cid.c-1165-\t\tregister_btf_kfunc_id_set(BPF_PROG_TYPE_SYSCALL, \u0026scx_kfunc_set_cid);\n--\nkernel/sched/ext/ext.c=10898=static int __init scx_init(void)\n--\nkernel/sched/ext/ext.c-10998-\t\t\t\t\t     \u0026scx_kfunc_set_any)) ||\nkernel/sched/ext/ext.c:10999:\t    (ret = register_btf_kfunc_id_set(BPF_PROG_TYPE_TRACING,\nkernel/sched/ext/ext.c-11000-\t\t\t\t\t     \u0026scx_kfunc_set_any)) ||\n--\nkernel/sched/ext/idle.c=1525=static const struct btf_kfunc_id_set scx_kfunc_set_idle = {\n--\nkernel/sched/ext/idle.c-1534- * contexts where @p's pi_lock state is unknown. Keep them out of\nkernel/sched/ext/idle.c:1535: * BPF_PROG_TYPE_TRACING by registering them in their own set which is exposed\nkernel/sched/ext/idle.c-1536- * only to STRUCT_OPS and SYSCALL programs.\n--\nkernel/sched/ext/idle.c=1554=int scx_idle_init(void)\n--\nkernel/sched/ext/idle.c-1556-\treturn register_btf_kfunc_id_set(BPF_PROG_TYPE_STRUCT_OPS, \u0026scx_kfunc_set_idle) ?:\nkernel/sched/ext/idle.c:1557:\t       register_btf_kfunc_id_set(BPF_PROG_TYPE_TRACING, \u0026scx_kfunc_set_idle) ?:\nkernel/sched/ext/idle.c-1558-\t       register_btf_kfunc_id_set(BPF_PROG_TYPE_SYSCALL, \u0026scx_kfunc_set_idle) ?:\n--\nkernel/trace/bpf_trace.c=977=static bool bpf_d_path_allowed(const struct bpf_prog *prog)\nkernel/trace/bpf_trace.c-978-{\nkernel/trace/bpf_trace.c:979:\tif (prog-\u003etype == BPF_PROG_TYPE_TRACING \u0026\u0026\nkernel/trace/bpf_trace.c-980-\t    prog-\u003eexpected_attach_type == BPF_TRACE_ITER)\n--\nkernel/trace/bpf_trace.c=1335=static inline bool is_trace_fsession(const struct bpf_prog *prog)\nkernel/trace/bpf_trace.c-1336-{\nkernel/trace/bpf_trace.c:1337:\treturn prog-\u003etype == BPF_PROG_TYPE_TRACING \u0026\u0026\nkernel/trace/bpf_trace.c-1338-\t       (prog-\u003eexpected_attach_type == BPF_TRACE_FSESSION ||\n--\nkernel/trace/bpf_trace.c=1740=tracing_prog_func_proto(enum bpf_func_id func_id, const struct bpf_prog *prog)\n--\nkernel/trace/bpf_trace.c-1803-\tcase BPF_FUNC_get_attach_cookie:\nkernel/trace/bpf_trace.c:1804:\t\tif (prog-\u003etype == BPF_PROG_TYPE_TRACING \u0026\u0026\nkernel/trace/bpf_trace.c-1805-\t\t    prog-\u003eexpected_attach_type == BPF_TRACE_RAW_TP)\n--\nkernel/trace/bpf_trace.c=3475=static int __init bpf_trace_kfuncs_init(void)\n--\nkernel/trace/bpf_trace.c-3479-\terr = err ?: register_btf_kfunc_id_set(BPF_PROG_TYPE_KPROBE, \u0026bpf_session_kfunc_set);\nkernel/trace/bpf_trace.c:3480:\terr = err ?: register_btf_kfunc_id_set(BPF_PROG_TYPE_TRACING, \u0026bpf_session_kfunc_set);\nkernel/trace/bpf_trace.c-3481-\n--\nnet/bpf/test_run.c=1888=static int __init bpf_prog_test_run_init(void)\n--\nnet/bpf/test_run.c-1903-\tret = ret ?: register_btf_kfunc_id_set(BPF_PROG_TYPE_SCHED_CLS, \u0026bpf_prog_test_kfunc_set);\nnet/bpf/test_run.c:1904:\tret = ret ?: register_btf_kfunc_id_set(BPF_PROG_TYPE_TRACING, \u0026bpf_prog_test_kfunc_set);\nnet/bpf/test_run.c-1905-\tret = ret ?: register_btf_kfunc_id_set(BPF_PROG_TYPE_SYSCALL, \u0026bpf_prog_test_kfunc_set);\n--\nnet/core/filter.c=12887=static int __init bpf_kfunc_init(void)\n--\nnet/core/filter.c-12900-\tret = ret ?: register_btf_kfunc_id_set(BPF_PROG_TYPE_NETFILTER, \u0026bpf_kfunc_set_skb);\nnet/core/filter.c:12901:\tret = ret ?: register_btf_kfunc_id_set(BPF_PROG_TYPE_TRACING, \u0026bpf_kfunc_set_skb);\nnet/core/filter.c-12902-\tret = ret ?: register_btf_kfunc_id_set(BPF_PROG_TYPE_STRUCT_OPS, \u0026bpf_kfunc_set_skb);\n--\nnet/core/filter.c=12968=static int init_subsystem(void)\nnet/core/filter.c-12969-{\nnet/core/filter.c:12970:\treturn register_btf_kfunc_id_set(BPF_PROG_TYPE_TRACING, \u0026bpf_sk_iter_kfunc_set);\nnet/core/filter.c-12971-}\n--\nsamples/bpf/xdp_sample_user.h=52=static inline char *safe_strncpy(char *dst, const char *src, size_t size)\n--\nsamples/bpf/xdp_sample_user.h-63-\t({                                                                     \\\nsamples/bpf/xdp_sample_user.h:64:\t\tif (bpf_program__type(skel-\u003eprogs.name) != BPF_PROG_TYPE_TRACING)\\\nsamples/bpf/xdp_sample_user.h-65-\t\t\treturn -EINVAL;                                        \\\n--\ntools/bpf/bpftool/gen.c=579=static void codegen_attach_detach(struct bpf_object *obj, const char *obj_name)\n--\ntools/bpf/bpftool/gen.c-599-\t\t\tbreak;\ntools/bpf/bpftool/gen.c:600:\t\tcase BPF_PROG_TYPE_TRACING:\ntools/bpf/bpftool/gen.c-601-\t\tcase BPF_PROG_TYPE_LSM:\n--\ntools/include/uapi/linux/bpf.h=1062=enum bpf_prog_type {\n--\ntools/include/uapi/linux/bpf.h-1088-\tBPF_PROG_TYPE_CGROUP_SOCKOPT,\ntools/include/uapi/linux/bpf.h:1089:\tBPF_PROG_TYPE_TRACING,\ntools/include/uapi/linux/bpf.h-1090-\tBPF_PROG_TYPE_STRUCT_OPS,\n--\ntools/lib/bpf/libbpf.c=202=static const char * const prog_type_name[] = {\n--\ntools/lib/bpf/libbpf.c-228-\t[BPF_PROG_TYPE_CGROUP_SOCKOPT]\t\t= \"cgroup_sockopt\",\ntools/lib/bpf/libbpf.c:229:\t[BPF_PROG_TYPE_TRACING]\t\t\t= \"tracing\",\ntools/lib/bpf/libbpf.c-230-\t[BPF_PROG_TYPE_STRUCT_OPS]\t\t= \"struct_ops\",\n--\ntools/lib/bpf/libbpf.c=3555=static bool prog_needs_vmlinux_btf(struct bpf_program *prog)\n--\ntools/lib/bpf/libbpf.c-3560-\ntools/lib/bpf/libbpf.c:3561:\t/* BPF_PROG_TYPE_TRACING programs which do not attach to other programs\ntools/lib/bpf/libbpf.c-3562-\t * also need vmlinux BTF\ntools/lib/bpf/libbpf.c-3563-\t */\ntools/lib/bpf/libbpf.c:3564:\tif (prog-\u003etype == BPF_PROG_TYPE_TRACING \u0026\u0026 !prog-\u003eattach_prog_fd)\ntools/lib/bpf/libbpf.c-3565-\t\treturn true;\n--\ntools/lib/bpf/libbpf_probes.c=106=static int probe_prog_load(enum bpf_prog_type prog_type,\n--\ntools/lib/bpf/libbpf_probes.c-134-\t\tbreak;\ntools/lib/bpf/libbpf_probes.c:135:\tcase BPF_PROG_TYPE_TRACING:\ntools/lib/bpf/libbpf_probes.c-136-\tcase BPF_PROG_TYPE_LSM:\n--\ntools/lib/bpf/libbpf_probes.c-139-\t\topts.log_level = 1;\ntools/lib/bpf/libbpf_probes.c:140:\t\tif (prog_type == BPF_PROG_TYPE_TRACING)\ntools/lib/bpf/libbpf_probes.c-141-\t\t\topts.expected_attach_type = BPF_TRACE_FENTRY;\n--\ntools/lib/bpf/libbpf_probes.c=436=int libbpf_probe_bpf_helper(enum bpf_prog_type prog_type, enum bpf_func_id helper_id,\n--\ntools/lib/bpf/libbpf_probes.c-453-\tswitch (prog_type) {\ntools/lib/bpf/libbpf_probes.c:454:\tcase BPF_PROG_TYPE_TRACING:\ntools/lib/bpf/libbpf_probes.c-455-\tcase BPF_PROG_TYPE_EXT:\n--\ntools/testing/selftests/bpf/prog_tests/fexit_bpf2bpf.c=482=static int load_fentry(int attach_prog_fd, int attach_btf_id)\n--\ntools/testing/selftests/bpf/prog_tests/fexit_bpf2bpf.c-493-\ntools/testing/selftests/bpf/prog_tests/fexit_bpf2bpf.c:494:\treturn bpf_prog_load(BPF_PROG_TYPE_TRACING,\ntools/testing/selftests/bpf/prog_tests/fexit_bpf2bpf.c-495-\t\t\t     \"bind4_fentry\",\n--\ntools/testing/selftests/bpf/prog_tests/fexit_stress.c=6=void serial_test_fexit_stress(void)\n--\ntools/testing/selftests/bpf/prog_tests/fexit_stress.c-37-\tfor (i = 0; i \u003c bpf_max_tramp_links; i++) {\ntools/testing/selftests/bpf/prog_tests/fexit_stress.c:38:\t\tfexit_fd[i] = bpf_prog_load(BPF_PROG_TYPE_TRACING, NULL, \"GPL\",\ntools/testing/selftests/bpf/prog_tests/fexit_stress.c-39-\t\t\t\t\t    trace_program,\n--\ntools/testing/selftests/bpf/prog_tests/module_fentry_shadow.c=56=void test_module_fentry_shadow(void)\n--\ntools/testing/selftests/bpf/prog_tests/module_fentry_shadow.c-101-\t\tload_opts.attach_btf_obj_fd = btf_fd[i];\ntools/testing/selftests/bpf/prog_tests/module_fentry_shadow.c:102:\t\tprog_fd[i] = bpf_prog_load(BPF_PROG_TYPE_TRACING, NULL, \"GPL\",\ntools/testing/selftests/bpf/prog_tests/module_fentry_shadow.c-103-\t\t\t\t\t   trace_program,\n--\ntools/testing/selftests/bpf/test_kmods/bpf_testmod.c=2424=static int bpf_testmod_init(void)\n--\ntools/testing/selftests/bpf/test_kmods/bpf_testmod.c-2436-\tret = ret ?: register_btf_kfunc_id_set(BPF_PROG_TYPE_SCHED_CLS, \u0026bpf_testmod_kfunc_set);\ntools/testing/selftests/bpf/test_kmods/bpf_testmod.c:2437:\tret = ret ?: register_btf_kfunc_id_set(BPF_PROG_TYPE_TRACING, \u0026bpf_testmod_kfunc_set);\ntools/testing/selftests/bpf/test_kmods/bpf_testmod.c-2438-\tret = ret ?: register_btf_kfunc_id_set(BPF_PROG_TYPE_SYSCALL, \u0026bpf_testmod_kfunc_set);\n--\ntools/testing/selftests/bpf/test_verifier.c=1504=static void do_test_single(struct bpf_test *test, bool unpriv,\n--\ntools/testing/selftests/bpf/test_verifier.c-1571-\ntools/testing/selftests/bpf/test_verifier.c:1572:\tif ((prog_type == BPF_PROG_TYPE_TRACING ||\ntools/testing/selftests/bpf/test_verifier.c-1573-\t     prog_type == BPF_PROG_TYPE_LSM) \u0026\u0026 test-\u003ekfunc) {\n--\ntools/testing/selftests/bpf/test_verifier.c-1605-\ntools/testing/selftests/bpf/test_verifier.c:1606:\t/* BPF_PROG_TYPE_TRACING requires more setup and\ntools/testing/selftests/bpf/test_verifier.c-1607-\t * bpf_probe_prog_type won't give correct answer\ntools/testing/selftests/bpf/test_verifier.c-1608-\t */\ntools/testing/selftests/bpf/test_verifier.c:1609:\tif (fd_prog \u003c 0 \u0026\u0026 prog_type != BPF_PROG_TYPE_TRACING \u0026\u0026\ntools/testing/selftests/bpf/test_verifier.c-1610-\t    !libbpf_probe_bpf_prog_type(prog_type, NULL)) {\n--\ntools/testing/selftests/bpf/verifier/atomic_fetch_add.c-100-\t},\ntools/testing/selftests/bpf/verifier/atomic_fetch_add.c:101:\t.prog_type = BPF_PROG_TYPE_TRACING,\ntools/testing/selftests/bpf/verifier/atomic_fetch_add.c-102-\t.expected_attach_type = BPF_TRACE_FENTRY,\n--\ntools/testing/selftests/bpf/verifier/sleepable.c-6-\t},\ntools/testing/selftests/bpf/verifier/sleepable.c:7:\t.prog_type = BPF_PROG_TYPE_TRACING,\ntools/testing/selftests/bpf/verifier/sleepable.c-8-\t.expected_attach_type = BPF_TRACE_FENTRY,\n--\ntools/testing/selftests/bpf/verifier/sleepable.c-19-\t},\ntools/testing/selftests/bpf/verifier/sleepable.c:20:\t.prog_type = BPF_PROG_TYPE_TRACING,\ntools/testing/selftests/bpf/verifier/sleepable.c-21-\t.expected_attach_type = BPF_TRACE_FENTRY,\n--\ntools/testing/selftests/bpf/verifier/sleepable.c-32-\t},\ntools/testing/selftests/bpf/verifier/sleepable.c:33:\t.prog_type = BPF_PROG_TYPE_TRACING,\ntools/testing/selftests/bpf/verifier/sleepable.c-34-\t.expected_attach_type = BPF_MODIFY_RETURN,\n--\ntools/testing/selftests/bpf/verifier/sleepable.c-45-\t},\ntools/testing/selftests/bpf/verifier/sleepable.c:46:\t.prog_type = BPF_PROG_TYPE_TRACING,\ntools/testing/selftests/bpf/verifier/sleepable.c-47-\t.expected_attach_type = BPF_TRACE_ITER,\n--\ntools/testing/selftests/bpf/verifier/sleepable.c-83-\t},\ntools/testing/selftests/bpf/verifier/sleepable.c:84:\t.prog_type = BPF_PROG_TYPE_TRACING,\ntools/testing/selftests/bpf/verifier/sleepable.c-85-\t.expected_attach_type = BPF_TRACE_RAW_TP,\n--\ntools/testing/selftests/bpf/verifier/sleepable.c-96-\t},\ntools/testing/selftests/bpf/verifier/sleepable.c:97:\t.prog_type = BPF_PROG_TYPE_TRACING,\ntools/testing/selftests/bpf/verifier/sleepable.c-98-\t.expected_attach_type = BPF_TRACE_RAW_TP,\n"
}

gemini-3.8-flash

null

null

							input: 27644
							output: 32
							thoughts: 120
						

Okay, let's break this down.

**Investigating BPF Program Type Dependency**

Right, so I'm digging into something that uses `BPF_PROG_TYPE_TRACING`. First, the hunch is that it's relying on `BPF_EVENTS`. I need to confirm that relationship. Okay, let's start by finding where `BPF_PROG_TYPE_TRACING` is defined. I'll check `include/linux/bpf_types.h` to see how it's registered:

```c
BPF_PROG_TYPE(BPF_PROG_TYPE_TRACING, tracing,
	      void *, void *)
```

Got it. Now that I know the type and how it's set up, I'll need to look at `kernel/bpf/syscall.c` or wherever else that `bpf_types.h` is included to get the rest of the picture. That should tell me how it's used.

{
  "Expression": "BPF_PROG_TYPE\\(BPF_PROG_TYPE_TRACING"
}

{
  "Output": "include/linux/bpf_types.h=47=BPF_PROG_TYPE(BPF_PROG_TYPE_RAW_TRACEPOINT_WRITABLE, raw_tracepoint_writable,\ninclude/linux/bpf_types.h-48-\t      struct bpf_raw_tracepoint_args, u64)\ninclude/linux/bpf_types.h:49:BPF_PROG_TYPE(BPF_PROG_TYPE_TRACING, tracing,\ninclude/linux/bpf_types.h-50-\t      void *, void *)\n"
}

gemini-3.8-flash

null

null

							input: 28161
							output: 22
							thoughts: 264
						

**My Analysis of the `tracing_verifier_ops` and Dependencies**

Okay, so I'm diving into the `tracing_verifier_ops`, it looks like it's defined in `kernel/trace/bpf_trace.c`. Specifically:

```c
const struct bpf_verifier_ops tracing_verifier_ops = {
	.get_func_proto  = tracing_prog_func_proto,
	.is_valid_access = tracing_prog_is_valid_access,
};
```

Right, and *that* file, `kernel/trace/bpf_trace.c`, only gets compiled when `CONFIG_BPF_EVENTS` is enabled. Time to check the dependency tree... Ah, here it is:

```
config BPF_EVENTS
	depends on BPF_SYSCALL
	depends on (KPROBE_EVENTS || UPROBE_EVENTS) && PERF_EVENTS
```

Makes sense. Now, let's look at `tracing_prog_func_proto`, which is crucial here. I remember seeing something about `BPF_FUNC_skb_output` being conditionally compiled under `#ifdef CONFIG_NET`. Gotta keep that in mind.

Also, I'm pretty sure `BPF_TRACE_FEXIT`, `BPF_TRACE_FSESSION`, and even potentially the whole trampoline tracing mechanism itself is somehow connected to `CONFIG_BPF_JIT`. I should probably confirm that hunch. Time to dig into functions like `bpf_prog_has_trampoline` or the `BPF_TRAMPOLINE` symbol to see if that connection holds.

no matches

{
  "Expression": "config BPF_TRAMPOLINE"
}

{
  "error": "no matches"
}

gemini-3.8-flash

null

null

							input: 28815
							output: 30
							thoughts: 16
						

Okay, here's my summarized thought process, presented as if I'm thinking it:

**Finding the Kconfig Configuration for BPF Trampolines**

Alright, time to get to work. I need to figure out how `bpf_trampoline` is configured within the kernel. My first instinct, given I'm working with the kernel's build system, is to look directly in `Kconfig`. That's where all the build-time configuration options are defined. So, let's fire up a search. I'll need to use my editor's search functionality or, if I'm feeling particularly efficient, leverage `grep` or a similar tool directly on the `Kconfig` files themselves. The goal is to pinpoint the exact definition and dependencies associated with `bpf_trampoline`. Once I have that, I can determine under what conditions it's enabled, what other options it relies on, and potentially understand its overall role in the kernel's build. Knowing this context is crucial for understanding its functionality and potential interactions with other kernel subsystems, ultimately allowing me to analyze or modify the code with confidence.

{
  "Expression": "bpf_trampoline",
  "PathPrefix": "kernel/bpf/"
}

{
  "Output": "\nFull output is too long, showing 500 out of 628 lines.\nUse more precise expression if possible.\n\nkernel/bpf/bpf_struct_ops.c=124=static void *bpf_struct_ops_image_alloc(void)\n--\nkernel/bpf/bpf_struct_ops.c-131-\t\treturn ERR_PTR(err);\nkernel/bpf/bpf_struct_ops.c:132:\timage = arch_alloc_bpf_trampoline(PAGE_SIZE);\nkernel/bpf/bpf_struct_ops.c-133-\tif (!image) {\n--\nkernel/bpf/bpf_struct_ops.c=141=void bpf_struct_ops_image_free(void *image)\n--\nkernel/bpf/bpf_struct_ops.c-143-\tif (image) {\nkernel/bpf/bpf_struct_ops.c:144:\t\tarch_free_bpf_trampoline(image, PAGE_SIZE);\nkernel/bpf/bpf_struct_ops.c-145-\t\tbpf_jit_uncharge_modmem(PAGE_SIZE);\n--\nkernel/bpf/bpf_struct_ops.c=638=int bpf_struct_ops_prepare_trampoline(struct bpf_tramp_nodes *tnodes,\n--\nkernel/bpf/bpf_struct_ops.c-654-\nkernel/bpf/bpf_struct_ops.c:655:\tsize = arch_bpf_trampoline_size(model, flags, tnodes, stub_func);\nkernel/bpf/bpf_struct_ops.c-656-\tif (size \u003c= 0)\n--\nkernel/bpf/bpf_struct_ops.c-669-\nkernel/bpf/bpf_struct_ops.c:670:\tsize = arch_prepare_bpf_trampoline(NULL, image + image_off,\nkernel/bpf/bpf_struct_ops.c-671-\t\t\t\t\t   image + image_off + size,\n--\nkernel/bpf/bpf_struct_ops.c=727=static long bpf_struct_ops_map_update_elem(struct bpf_map *map, void *key,\n--\nkernel/bpf/bpf_struct_ops.c-908-\tfor (i = 0; i \u003c st_map-\u003eimage_pages_cnt; i++) {\nkernel/bpf/bpf_struct_ops.c:909:\t\terr = arch_protect_bpf_trampoline(st_map-\u003eimage_pages[i],\nkernel/bpf/bpf_struct_ops.c-910-\t\t\t\t\t\t  PAGE_SIZE);\n--\nkernel/bpf/cgroup.c=354=static void bpf_cgroup_link_auto_detach(struct bpf_cgroup_link *link)\n--\nkernel/bpf/cgroup.c-361-\tif (link-\u003elink.prog-\u003eexpected_attach_type == BPF_LSM_CGROUP)\nkernel/bpf/cgroup.c:362:\t\tbpf_trampoline_unlink_cgroup_shim(link-\u003elink.prog);\nkernel/bpf/cgroup.c-363-\tcgroup_put(link-\u003ecgroup);\n--\nkernel/bpf/cgroup.c=451=static void cgroup_bpf_release(struct work_struct *work)\n--\nkernel/bpf/cgroup.c-471-\t\t\t\tif (pl-\u003eprog-\u003eexpected_attach_type == BPF_LSM_CGROUP)\nkernel/bpf/cgroup.c:472:\t\t\t\t\tbpf_trampoline_unlink_cgroup_shim(pl-\u003eprog);\nkernel/bpf/cgroup.c-473-\t\t\t\tbpf_prog_put(pl-\u003eprog);\n--\nkernel/bpf/cgroup.c=958=static int __cgroup_bpf_attach(struct cgroup *cgrp,\n--\nkernel/bpf/cgroup.c-1046-\tif (type == BPF_LSM_CGROUP) {\nkernel/bpf/cgroup.c:1047:\t\terr = bpf_trampoline_link_cgroup_shim(new_prog, atype, type);\nkernel/bpf/cgroup.c-1048-\t\tif (err)\n--\nkernel/bpf/cgroup.c-1058-\t\tif (type == BPF_LSM_CGROUP)\nkernel/bpf/cgroup.c:1059:\t\t\tbpf_trampoline_unlink_cgroup_shim(old_prog);\nkernel/bpf/cgroup.c-1060-\t\tbpf_prog_put(old_prog);\n--\nkernel/bpf/cgroup.c-1068-\tif (type == BPF_LSM_CGROUP)\nkernel/bpf/cgroup.c:1069:\t\tbpf_trampoline_unlink_cgroup_shim(new_prog);\nkernel/bpf/cgroup.c-1070-\n--\nkernel/bpf/cgroup.c=1350=static int __cgroup_bpf_detach(struct cgroup *cgrp, struct bpf_prog *prog,\n--\nkernel/bpf/cgroup.c-1405-\t\tif (type == BPF_LSM_CGROUP)\nkernel/bpf/cgroup.c:1406:\t\t\tbpf_trampoline_unlink_cgroup_shim(old_prog);\nkernel/bpf/cgroup.c-1407-\t\tbpf_prog_put(old_prog);\n--\nkernel/bpf/cgroup.c=1602=static void bpf_cgroup_link_release(struct bpf_link *link)\n--\nkernel/bpf/cgroup.c-1624-\tif (link-\u003eattach_type == BPF_LSM_CGROUP)\nkernel/bpf/cgroup.c:1625:\t\tbpf_trampoline_unlink_cgroup_shim(cg_link-\u003elink.prog);\nkernel/bpf/cgroup.c-1626-\n--\nkernel/bpf/core.c=3062=static void bpf_prog_free_deferred(struct work_struct *work)\n--\nkernel/bpf/core.c-3085-\tif (aux-\u003edst_trampoline)\nkernel/bpf/core.c:3086:\t\tbpf_trampoline_put(aux-\u003edst_trampoline);\nkernel/bpf/core.c-3087-\tfor (i = 0; i \u003c aux-\u003ereal_func_cnt; i++) {\n--\nkernel/bpf/syscall.c=3571=static void bpf_tracing_link_release(struct bpf_link *link)\n--\nkernel/bpf/syscall.c-3576-\nkernel/bpf/syscall.c:3577:\terr = bpf_trampoline_unlink_prog(\u0026tr_link-\u003elink.node,\nkernel/bpf/syscall.c-3578-\t\t\t\t\ttr_link-\u003etrampoline,\nkernel/bpf/syscall.c-3579-\t\t\t\t\ttr_link-\u003etgt_prog);\nkernel/bpf/syscall.c:3580:\tWARN_ONCE(err, \"bpf_trampoline_unlink_prog failed: %d\\n\", err);\nkernel/bpf/syscall.c-3581-\nkernel/bpf/syscall.c:3582:\tbpf_trampoline_put(tr_link-\u003etrampoline);\nkernel/bpf/syscall.c-3583-\n--\nkernel/bpf/syscall.c=3596=static void bpf_tracing_link_show_fdinfo(const struct bpf_link *link,\n--\nkernel/bpf/syscall.c-3602-\nkernel/bpf/syscall.c:3603:\tbpf_trampoline_unpack_key(tr_link-\u003etrampoline-\u003ekey,\nkernel/bpf/syscall.c-3604-\t\t\t\t  \u0026target_obj_id, \u0026target_btf_id);\n--\nkernel/bpf/syscall.c=3616=static int bpf_tracing_link_fill_link_info(const struct bpf_link *link,\n--\nkernel/bpf/syscall.c-3622-\tinfo-\u003etracing.cookie = tr_link-\u003elink.node.cookie;\nkernel/bpf/syscall.c:3623:\tbpf_trampoline_unpack_key(tr_link-\u003etrampoline-\u003ekey,\nkernel/bpf/syscall.c-3624-\t\t\t\t  \u0026info-\u003etracing.target_obj_id,\n--\nkernel/bpf/syscall.c=3637=static int bpf_tracing_prog_attach(struct bpf_prog *prog,\n--\nkernel/bpf/syscall.c-3644-\tstruct bpf_prog *tgt_prog = NULL;\nkernel/bpf/syscall.c:3645:\tstruct bpf_trampoline *tr = NULL;\nkernel/bpf/syscall.c-3646-\tstruct bpf_tracing_link *link;\n--\nkernel/bpf/syscall.c-3700-\nkernel/bpf/syscall.c:3701:\t\tkey = bpf_trampoline_compute_key(tgt_prog, NULL, btf_id);\nkernel/bpf/syscall.c-3702-\t}\n--\nkernel/bpf/syscall.c-3743-\t\t * Allow re-attach for TRACING and LSM programs. If it's\nkernel/bpf/syscall.c:3744:\t\t * currently linked, bpf_trampoline_link_prog will fail.\nkernel/bpf/syscall.c-3745-\t\t * EXT programs need to specify tgt_prog_fd, so they\n--\nkernel/bpf/syscall.c-3758-\t\tbtf_id = prog-\u003eaux-\u003eattach_btf_id;\nkernel/bpf/syscall.c:3759:\t\tkey = bpf_trampoline_compute_key(NULL, prog-\u003eaux-\u003eattach_btf, btf_id);\nkernel/bpf/syscall.c-3760-\t}\n--\nkernel/bpf/syscall.c-3779-\nkernel/bpf/syscall.c:3780:\t\ttr = bpf_trampoline_get(key, \u0026tgt_info);\nkernel/bpf/syscall.c-3781-\t\tif (!tr) {\n--\nkernel/bpf/syscall.c-3817-\nkernel/bpf/syscall.c:3818:\terr = bpf_trampoline_link_prog(\u0026link-\u003elink.node, tr, tgt_prog);\nkernel/bpf/syscall.c-3819-\tif (err) {\n--\nkernel/bpf/syscall.c-3837-\t\t/* we allocated a new trampoline, so free the old one */\nkernel/bpf/syscall.c:3838:\t\tbpf_trampoline_put(prog-\u003eaux-\u003edst_trampoline);\nkernel/bpf/syscall.c-3839-\n--\nkernel/bpf/syscall.c-3846-\tif (tr \u0026\u0026 tr != prog-\u003eaux-\u003edst_trampoline)\nkernel/bpf/syscall.c:3847:\t\tbpf_trampoline_put(tr);\nkernel/bpf/syscall.c-3848-\tmutex_unlock(\u0026prog-\u003eaux-\u003edst_mutex);\n--\nkernel/bpf/trampoline.c=42=static struct {\n--\nkernel/bpf/trampoline.c-46-\nkernel/bpf/trampoline.c:47:static struct mutex *select_trampoline_lock(struct bpf_trampoline *tr)\nkernel/bpf/trampoline.c-48-{\n--\nkernel/bpf/trampoline.c-51-\nkernel/bpf/trampoline.c:52:static void trampoline_lock(struct bpf_trampoline *tr)\nkernel/bpf/trampoline.c-53-{\n--\nkernel/bpf/trampoline.c-56-\nkernel/bpf/trampoline.c:57:static void trampoline_unlock(struct bpf_trampoline *tr)\nkernel/bpf/trampoline.c-58-{\n--\nkernel/bpf/trampoline.c-61-\nkernel/bpf/trampoline.c:62:struct bpf_trampoline_ops {\nkernel/bpf/trampoline.c:63:\tint (*register_fentry)(struct bpf_trampoline *tr, struct bpf_tramp_image *im, void *data);\nkernel/bpf/trampoline.c:64:\tint (*unregister_fentry)(struct bpf_trampoline *tr, u32 orig_flags, void *data);\nkernel/bpf/trampoline.c:65:\tint (*modify_fentry)(struct bpf_trampoline *tr, u32 orig_flags, struct bpf_tramp_image *im,\nkernel/bpf/trampoline.c-66-\t\t\t     bool lock_direct_mutex, void *data);\n--\nkernel/bpf/trampoline.c-69-#ifdef CONFIG_DYNAMIC_FTRACE_WITH_DIRECT_CALLS\nkernel/bpf/trampoline.c:70:static int bpf_trampoline_update(struct bpf_trampoline *tr, bool lock_direct_mutex,\nkernel/bpf/trampoline.c:71:\t\t\t\t const struct bpf_trampoline_ops *ops, void *data);\nkernel/bpf/trampoline.c:72:static const struct bpf_trampoline_ops trampoline_ops;\nkernel/bpf/trampoline.c-73-\nkernel/bpf/trampoline.c-74-#ifdef CONFIG_HAVE_SINGLE_FTRACE_DIRECT_OPS\nkernel/bpf/trampoline.c:75:static struct bpf_trampoline *direct_ops_ip_lookup(struct ftrace_ops *ops, unsigned long ip)\nkernel/bpf/trampoline.c-76-{\nkernel/bpf/trampoline.c-77-\tstruct hlist_head *head_ip;\nkernel/bpf/trampoline.c:78:\tstruct bpf_trampoline *tr;\nkernel/bpf/trampoline.c-79-\n--\nkernel/bpf/trampoline.c-91-#else\nkernel/bpf/trampoline.c:92:static struct bpf_trampoline *direct_ops_ip_lookup(struct ftrace_ops *ops, unsigned long ip)\nkernel/bpf/trampoline.c-93-{\n--\nkernel/bpf/trampoline.c=98=static int bpf_tramp_ftrace_ops_func(struct ftrace_ops *ops, unsigned long ip,\n--\nkernel/bpf/trampoline.c-100-{\nkernel/bpf/trampoline.c:101:\tstruct bpf_trampoline *tr;\nkernel/bpf/trampoline.c-102-\tint ret = 0;\n--\nkernel/bpf/trampoline.c-156-\t\t    !(tr-\u003eflags \u0026 BPF_TRAMP_F_ORIG_STACK))\nkernel/bpf/trampoline.c:157:\t\t\tret = bpf_trampoline_update(tr, false /* lock_direct_mutex */,\nkernel/bpf/trampoline.c-158-\t\t\t\t\t\t    \u0026trampoline_ops, NULL);\n--\nkernel/bpf/trampoline.c-163-\t\tif (tr-\u003eflags \u0026 BPF_TRAMP_F_ORIG_STACK)\nkernel/bpf/trampoline.c:164:\t\t\tret = bpf_trampoline_update(tr, false /* lock_direct_mutex */,\nkernel/bpf/trampoline.c-165-\t\t\t\t\t\t    \u0026trampoline_ops, NULL);\n--\nkernel/bpf/trampoline.c=225=struct ftrace_ops direct_ops = {\n--\nkernel/bpf/trampoline.c-228-\nkernel/bpf/trampoline.c:229:static int direct_ops_alloc(struct bpf_trampoline *tr)\nkernel/bpf/trampoline.c-230-{\n--\nkernel/bpf/trampoline.c-234-\nkernel/bpf/trampoline.c:235:static void direct_ops_free(struct bpf_trampoline *tr) { }\nkernel/bpf/trampoline.c-236-\nkernel/bpf/trampoline.c:237:static struct ftrace_hash *hash_from_ip(struct bpf_trampoline *tr, void *ptr)\nkernel/bpf/trampoline.c-238-{\n--\nkernel/bpf/trampoline.c-247-\t\treturn NULL;\nkernel/bpf/trampoline.c:248:\tif (bpf_trampoline_use_jmp(tr-\u003eflags))\nkernel/bpf/trampoline.c-249-\t\taddr = ftrace_jmp_set(addr);\n--\nkernel/bpf/trampoline.c-256-\nkernel/bpf/trampoline.c:257:static int direct_ops_add(struct bpf_trampoline *tr, void *addr)\nkernel/bpf/trampoline.c-258-{\n--\nkernel/bpf/trampoline.c-268-\nkernel/bpf/trampoline.c:269:static int direct_ops_del(struct bpf_trampoline *tr, void *addr)\nkernel/bpf/trampoline.c-270-{\n--\nkernel/bpf/trampoline.c-280-\nkernel/bpf/trampoline.c:281:static int direct_ops_mod(struct bpf_trampoline *tr, void *addr, bool lock_direct_mutex)\nkernel/bpf/trampoline.c-282-{\n--\nkernel/bpf/trampoline.c-298- */\nkernel/bpf/trampoline.c:299:static int direct_ops_alloc(struct bpf_trampoline *tr)\nkernel/bpf/trampoline.c-300-{\n--\nkernel/bpf/trampoline.c-308-\nkernel/bpf/trampoline.c:309:static void direct_ops_free(struct bpf_trampoline *tr)\nkernel/bpf/trampoline.c-310-{\n--\nkernel/bpf/trampoline.c-316-\nkernel/bpf/trampoline.c:317:static int direct_ops_add(struct bpf_trampoline *tr, void *ptr)\nkernel/bpf/trampoline.c-318-{\n--\nkernel/bpf/trampoline.c-322-\nkernel/bpf/trampoline.c:323:\tif (bpf_trampoline_use_jmp(tr-\u003eflags))\nkernel/bpf/trampoline.c-324-\t\taddr = ftrace_jmp_set(addr);\n--\nkernel/bpf/trampoline.c-331-\nkernel/bpf/trampoline.c:332:static int direct_ops_del(struct bpf_trampoline *tr, void *addr)\nkernel/bpf/trampoline.c-333-{\n--\nkernel/bpf/trampoline.c-336-\nkernel/bpf/trampoline.c:337:static int direct_ops_mod(struct bpf_trampoline *tr, void *ptr, bool lock_direct_mutex)\nkernel/bpf/trampoline.c-338-{\n--\nkernel/bpf/trampoline.c-341-\nkernel/bpf/trampoline.c:342:\tif (bpf_trampoline_use_jmp(tr-\u003eflags))\nkernel/bpf/trampoline.c-343-\t\taddr = ftrace_jmp_set(addr);\n--\nkernel/bpf/trampoline.c-349-#else\nkernel/bpf/trampoline.c:350:static void direct_ops_free(struct bpf_trampoline *tr) { }\nkernel/bpf/trampoline.c-351-\nkernel/bpf/trampoline.c:352:static int direct_ops_alloc(struct bpf_trampoline *tr)\nkernel/bpf/trampoline.c-353-{\n--\nkernel/bpf/trampoline.c-356-\nkernel/bpf/trampoline.c:357:static int direct_ops_add(struct bpf_trampoline *tr, void *addr)\nkernel/bpf/trampoline.c-358-{\n--\nkernel/bpf/trampoline.c-361-\nkernel/bpf/trampoline.c:362:static int direct_ops_del(struct bpf_trampoline *tr, void *addr)\nkernel/bpf/trampoline.c-363-{\n--\nkernel/bpf/trampoline.c-366-\nkernel/bpf/trampoline.c:367:static int direct_ops_mod(struct bpf_trampoline *tr, void *ptr, bool lock_direct_mutex)\nkernel/bpf/trampoline.c-368-{\n--\nkernel/bpf/trampoline.c-372-\nkernel/bpf/trampoline.c:373:static struct bpf_trampoline *bpf_trampoline_lookup(u64 key, unsigned long ip)\nkernel/bpf/trampoline.c-374-{\nkernel/bpf/trampoline.c:375:\tstruct bpf_trampoline *tr;\nkernel/bpf/trampoline.c-376-\tstruct hlist_head *head;\n--\nkernel/bpf/trampoline.c-410-\nkernel/bpf/trampoline.c:411:static int bpf_trampoline_update_fentry(struct bpf_trampoline *tr, u32 orig_flags,\nkernel/bpf/trampoline.c-412-\t\t\t\t\tvoid *old_addr, void *new_addr)\n--\nkernel/bpf/trampoline.c-418-\t\tnew_t = BPF_MOD_NOP;\nkernel/bpf/trampoline.c:419:\telse if (bpf_trampoline_use_jmp(tr-\u003eflags))\nkernel/bpf/trampoline.c-420-\t\tnew_t = BPF_MOD_JUMP;\n--\nkernel/bpf/trampoline.c-423-\t\told_t = BPF_MOD_NOP;\nkernel/bpf/trampoline.c:424:\telse if (bpf_trampoline_use_jmp(orig_flags))\nkernel/bpf/trampoline.c-425-\t\told_t = BPF_MOD_JUMP;\n--\nkernel/bpf/trampoline.c=430=static void bpf_tramp_image_put(struct bpf_tramp_image *im);\nkernel/bpf/trampoline.c-431-\nkernel/bpf/trampoline.c:432:static int unregister_fentry(struct bpf_trampoline *tr, u32 orig_flags, void *data __maybe_unused)\nkernel/bpf/trampoline.c-433-{\n--\nkernel/bpf/trampoline.c-439-\telse\nkernel/bpf/trampoline.c:440:\t\tret = bpf_trampoline_update_fentry(tr, orig_flags, old_addr, NULL);\nkernel/bpf/trampoline.c-441-\n--\nkernel/bpf/trampoline.c-449-\nkernel/bpf/trampoline.c:450:static int modify_fentry(struct bpf_trampoline *tr, u32 orig_flags, struct bpf_tramp_image *im,\nkernel/bpf/trampoline.c-451-\t\t\t bool lock_direct_mutex, void *data __maybe_unused)\n--\nkernel/bpf/trampoline.c-459-\t} else {\nkernel/bpf/trampoline.c:460:\t\tret = bpf_trampoline_update_fentry(tr, orig_flags, old_addr,\nkernel/bpf/trampoline.c-461-\t\t\t\t\t\t   new_addr);\n--\nkernel/bpf/trampoline.c-472-/* first time registering */\nkernel/bpf/trampoline.c:473:static int register_fentry(struct bpf_trampoline *tr, struct bpf_tramp_image *im,\nkernel/bpf/trampoline.c-474-\t\t\t   void *data __maybe_unused)\n--\nkernel/bpf/trampoline.c-490-\t} else {\nkernel/bpf/trampoline.c:491:\t\tret = bpf_trampoline_update_fentry(tr, 0, NULL, new_addr);\nkernel/bpf/trampoline.c-492-\t}\n--\nkernel/bpf/trampoline.c-500-\nkernel/bpf/trampoline.c:501:static const struct bpf_trampoline_ops trampoline_ops = {\nkernel/bpf/trampoline.c-502-\t.register_fentry   = register_fentry,\n--\nkernel/bpf/trampoline.c=507=static struct bpf_tramp_nodes *\nkernel/bpf/trampoline.c:508:bpf_trampoline_get_progs(const struct bpf_trampoline *tr, int *total, bool *ip_arg)\nkernel/bpf/trampoline.c-509-{\n--\nkernel/bpf/trampoline.c=562=static void bpf_tramp_image_free(struct bpf_tramp_image *im)\n--\nkernel/bpf/trampoline.c-564-\tbpf_image_ksym_del(\u0026im-\u003eksym);\nkernel/bpf/trampoline.c:565:\tarch_free_bpf_trampoline(im-\u003eimage, im-\u003esize);\nkernel/bpf/trampoline.c-566-\tbpf_jit_uncharge_modmem(im-\u003esize);\n--\nkernel/bpf/trampoline.c=661=static struct bpf_tramp_image *bpf_tramp_image_alloc(u64 key, int size)\n--\nkernel/bpf/trampoline.c-677-\terr = -ENOMEM;\nkernel/bpf/trampoline.c:678:\tim-\u003eimage = image = arch_alloc_bpf_trampoline(size);\nkernel/bpf/trampoline.c-679-\tif (!image)\n--\nkernel/bpf/trampoline.c-687-\tINIT_LIST_HEAD_RCU(\u0026ksym-\u003elnode);\nkernel/bpf/trampoline.c:688:\tsnprintf(ksym-\u003ename, KSYM_NAME_LEN, \"bpf_trampoline_%llu\", key);\nkernel/bpf/trampoline.c-689-\tbpf_image_ksym_init(image, size, ksym);\n--\nkernel/bpf/trampoline.c-693-out_free_image:\nkernel/bpf/trampoline.c:694:\tarch_free_bpf_trampoline(im-\u003eimage, im-\u003esize);\nkernel/bpf/trampoline.c-695-out_uncharge:\n--\nkernel/bpf/trampoline.c-702-\nkernel/bpf/trampoline.c:703:void bpf_trampoline_set_flags(struct bpf_trampoline *tr, u32 flags)\nkernel/bpf/trampoline.c-704-{\n--\nkernel/bpf/trampoline.c-709-\nkernel/bpf/trampoline.c:710:static int bpf_trampoline_update(struct bpf_trampoline *tr, bool lock_direct_mutex,\nkernel/bpf/trampoline.c:711:\t\t\t\t const struct bpf_trampoline_ops *ops, void *data)\nkernel/bpf/trampoline.c-712-{\n--\nkernel/bpf/trampoline.c-718-\nkernel/bpf/trampoline.c:719:\ttnodes = bpf_trampoline_get_progs(tr, \u0026total, \u0026ip_arg);\nkernel/bpf/trampoline.c-720-\tif (IS_ERR(tnodes))\n--\nkernel/bpf/trampoline.c-761-\nkernel/bpf/trampoline.c:762:\tsize = arch_bpf_trampoline_size(\u0026tr-\u003efunc.model, tr-\u003eflags,\nkernel/bpf/trampoline.c-763-\t\t\t\t\ttnodes, tr-\u003efunc.addr);\n--\nkernel/bpf/trampoline.c-779-\nkernel/bpf/trampoline.c:780:\terr = arch_prepare_bpf_trampoline(im, im-\u003eimage, im-\u003eimage + size,\nkernel/bpf/trampoline.c-781-\t\t\t\t\t  \u0026tr-\u003efunc.model, tr-\u003eflags, tnodes,\n--\nkernel/bpf/trampoline.c-785-\nkernel/bpf/trampoline.c:786:\terr = arch_protect_bpf_trampoline(im-\u003eimage, im-\u003esize);\nkernel/bpf/trampoline.c-787-\tif (err)\n--\nkernel/bpf/trampoline.c=864=static struct bpf_tramp_node *fsession_exit(struct bpf_tramp_node *node)\n--\nkernel/bpf/trampoline.c-881-\nkernel/bpf/trampoline.c:882:static int bpf_trampoline_add_prog(struct bpf_trampoline *tr,\nkernel/bpf/trampoline.c-883-\t\t\t\t   struct bpf_tramp_node *node,\n--\nkernel/bpf/trampoline.c-922-\nkernel/bpf/trampoline.c:923:static void bpf_trampoline_remove_prog(struct bpf_trampoline *tr,\nkernel/bpf/trampoline.c-924-\t\t\t\t       struct bpf_tramp_node *node)\n--\nkernel/bpf/trampoline.c-941-\nkernel/bpf/trampoline.c:942:static int __bpf_trampoline_link_prog(struct bpf_tramp_node *node,\nkernel/bpf/trampoline.c:943:\t\t\t\t      struct bpf_trampoline *tr,\nkernel/bpf/trampoline.c-944-\t\t\t\t      struct bpf_prog *tgt_prog,\nkernel/bpf/trampoline.c:945:\t\t\t\t      const struct bpf_trampoline_ops *ops,\nkernel/bpf/trampoline.c-946-\t\t\t\t      void *data)\n--\nkernel/bpf/trampoline.c-980-\t}\nkernel/bpf/trampoline.c:981:\terr = bpf_trampoline_add_prog(tr, node, cnt);\nkernel/bpf/trampoline.c-982-\tif (err)\nkernel/bpf/trampoline.c-983-\t\treturn err;\nkernel/bpf/trampoline.c:984:\terr = bpf_trampoline_update(tr, true /* lock_direct_mutex */, ops, data);\nkernel/bpf/trampoline.c-985-\tif (err)\nkernel/bpf/trampoline.c:986:\t\tbpf_trampoline_remove_prog(tr, node);\nkernel/bpf/trampoline.c-987-\treturn err;\n--\nkernel/bpf/trampoline.c-989-\nkernel/bpf/trampoline.c:990:int bpf_trampoline_link_prog(struct bpf_tramp_node *node,\nkernel/bpf/trampoline.c:991:\t\t\t     struct bpf_trampoline *tr,\nkernel/bpf/trampoline.c-992-\t\t\t     struct bpf_prog *tgt_prog)\n--\nkernel/bpf/trampoline.c-996-\ttrampoline_lock(tr);\nkernel/bpf/trampoline.c:997:\terr = __bpf_trampoline_link_prog(node, tr, tgt_prog, \u0026trampoline_ops, NULL);\nkernel/bpf/trampoline.c-998-\ttrampoline_unlock(tr);\n--\nkernel/bpf/trampoline.c-1001-\nkernel/bpf/trampoline.c:1002:static int __bpf_trampoline_unlink_prog(struct bpf_tramp_node *node,\nkernel/bpf/trampoline.c:1003:\t\t\t\t\tstruct bpf_trampoline *tr,\nkernel/bpf/trampoline.c-1004-\t\t\t\t\tstruct bpf_prog *tgt_prog,\nkernel/bpf/trampoline.c:1005:\t\t\t\t\tconst struct bpf_trampoline_ops *ops,\nkernel/bpf/trampoline.c-1006-\t\t\t\t\tvoid *data)\n--\nkernel/bpf/trampoline.c-1021-\t}\nkernel/bpf/trampoline.c:1022:\tbpf_trampoline_remove_prog(tr, node);\nkernel/bpf/trampoline.c:1023:\treturn bpf_trampoline_update(tr, true /* lock_direct_mutex */, ops, data);\nkernel/bpf/trampoline.c-1024-}\nkernel/bpf/trampoline.c-1025-\nkernel/bpf/trampoline.c:1026:/* bpf_trampoline_unlink_prog() should never fail. */\nkernel/bpf/trampoline.c:1027:int bpf_trampoline_unlink_prog(struct bpf_tramp_node *node,\nkernel/bpf/trampoline.c:1028:\t\t\t       struct bpf_trampoline *tr,\nkernel/bpf/trampoline.c-1029-\t\t\t       struct bpf_prog *tgt_prog)\n--\nkernel/bpf/trampoline.c-1033-\ttrampoline_lock(tr);\nkernel/bpf/trampoline.c:1034:\terr = __bpf_trampoline_unlink_prog(node, tr, tgt_prog, \u0026trampoline_ops, NULL);\nkernel/bpf/trampoline.c-1035-\ttrampoline_unlock(tr);\n--\nkernel/bpf/trampoline.c=1040=static void bpf_shim_tramp_link_release(struct bpf_link *link)\n--\nkernel/bpf/trampoline.c-1045-\nkernel/bpf/trampoline.c:1046:\t/* paired with 'shim_link-\u003etrampoline = tr' in bpf_trampoline_link_cgroup_shim */\nkernel/bpf/trampoline.c-1047-\tif (!shim_link-\u003etrampoline)\n--\nkernel/bpf/trampoline.c-1049-\nkernel/bpf/trampoline.c:1050:\terr = bpf_trampoline_unlink_prog(\u0026shim_link-\u003elink.node, shim_link-\u003etrampoline, NULL);\nkernel/bpf/trampoline.c:1051:\tWARN_ONCE(err, \"bpf_trampoline_unlink_prog failed: %d\\n\", err);\nkernel/bpf/trampoline.c-1052-\nkernel/bpf/trampoline.c:1053:\tbpf_trampoline_put(shim_link-\u003etrampoline);\nkernel/bpf/trampoline.c-1054-}\n--\nkernel/bpf/trampoline.c=1069=static struct bpf_shim_tramp_link *cgroup_shim_alloc(const struct bpf_prog *prog,\n--\nkernel/bpf/trampoline.c-1104-\nkernel/bpf/trampoline.c:1105:static struct bpf_shim_tramp_link *cgroup_shim_find(struct bpf_trampoline *tr,\nkernel/bpf/trampoline.c-1106-\t\t\t\t\t\t    bpf_func_t bpf_func)\n--\nkernel/bpf/trampoline.c-1122-\nkernel/bpf/trampoline.c:1123:int bpf_trampoline_link_cgroup_shim(struct bpf_prog *prog,\nkernel/bpf/trampoline.c-1124-\t\t\t\t    int cgroup_atype,\n--\nkernel/bpf/trampoline.c-1128-\tstruct bpf_attach_target_info tgt_info = {};\nkernel/bpf/trampoline.c:1129:\tstruct bpf_trampoline *tr;\nkernel/bpf/trampoline.c-1130-\tbpf_func_t bpf_func;\n--\nkernel/bpf/trampoline.c-1139-\nkernel/bpf/trampoline.c:1140:\tkey = bpf_trampoline_compute_key(NULL, prog-\u003eaux-\u003eattach_btf,\nkernel/bpf/trampoline.c-1141-\t\t\t\t\t prog-\u003eaux-\u003eattach_btf_id);\n--\nkernel/bpf/trampoline.c-1143-\tbpf_lsm_find_cgroup_shim(prog, \u0026bpf_func);\nkernel/bpf/trampoline.c:1144:\ttr = bpf_trampoline_get(key, \u0026tgt_info);\nkernel/bpf/trampoline.c-1145-\tif (!tr)\n--\nkernel/bpf/trampoline.c-1153-\t\ttrampoline_unlock(tr);\nkernel/bpf/trampoline.c:1154:\t\tbpf_trampoline_put(tr); /* bpf_trampoline_get above */\nkernel/bpf/trampoline.c-1155-\t\treturn 0;\n--\nkernel/bpf/trampoline.c-1165-\nkernel/bpf/trampoline.c:1166:\terr = __bpf_trampoline_link_prog(\u0026shim_link-\u003elink.node, tr, NULL, \u0026trampoline_ops, NULL);\nkernel/bpf/trampoline.c-1167-\tif (err)\n--\nkernel/bpf/trampoline.c-1182-\t/* have to release tr while _not_ holding pool mutex for trampoline */\nkernel/bpf/trampoline.c:1183:\tbpf_trampoline_put(tr); /* bpf_trampoline_get above */\nkernel/bpf/trampoline.c-1184-\n--\nkernel/bpf/trampoline.c-1187-\nkernel/bpf/trampoline.c:1188:void bpf_trampoline_unlink_cgroup_shim(struct bpf_prog *prog)\nkernel/bpf/trampoline.c-1189-{\nkernel/bpf/trampoline.c-1190-\tstruct bpf_shim_tramp_link *shim_link = NULL;\nkernel/bpf/trampoline.c:1191:\tstruct bpf_trampoline *tr;\nkernel/bpf/trampoline.c-1192-\tbpf_func_t bpf_func;\n--\nkernel/bpf/trampoline.c-1194-\nkernel/bpf/trampoline.c:1195:\tkey = bpf_trampoline_compute_key(NULL, prog-\u003eaux-\u003eattach_btf,\nkernel/bpf/trampoline.c-1196-\t\t\t\t\t prog-\u003eaux-\u003eattach_btf_id);\n--\nkernel/bpf/trampoline.c-1198-\tbpf_lsm_find_cgroup_shim(prog, \u0026bpf_func);\nkernel/bpf/trampoline.c:1199:\ttr = bpf_trampoline_lookup(key, 0);\nkernel/bpf/trampoline.c-1200-\tif (WARN_ON_ONCE(!tr))\n--\nkernel/bpf/trampoline.c-1209-\nkernel/bpf/trampoline.c:1210:\tbpf_trampoline_put(tr); /* bpf_trampoline_lookup above */\nkernel/bpf/trampoline.c-1211-}\n--\nkernel/bpf/trampoline.c-1213-\nkernel/bpf/trampoline.c:1214:struct bpf_trampoline *bpf_trampoline_get(u64 key,\nkernel/bpf/trampoline.c-1215-\t\t\t\t\t  struct bpf_attach_target_info *tgt_info)\nkernel/bpf/trampoline.c-1216-{\nkernel/bpf/trampoline.c:1217:\tstruct bpf_trampoline *tr;\nkernel/bpf/trampoline.c-1218-\nkernel/bpf/trampoline.c:1219:\ttr = bpf_trampoline_lookup(key, tgt_info-\u003etgt_addr);\nkernel/bpf/trampoline.c-1220-\tif (!tr)\n--\nkernel/bpf/trampoline.c-1233-\nkernel/bpf/trampoline.c:1234:void bpf_trampoline_put(struct bpf_trampoline *tr)\nkernel/bpf/trampoline.c-1235-{\n--\nkernel/bpf/trampoline.c=1443=void notrace __bpf_tramp_exit(struct bpf_tramp_image *tr)\n--\nkernel/bpf/trampoline.c-1447-\nkernel/bpf/trampoline.c:1448:bpf_trampoline_enter_t bpf_trampoline_enter(const struct bpf_prog *prog)\nkernel/bpf/trampoline.c-1449-{\n--\nkernel/bpf/trampoline.c-1462-\nkernel/bpf/trampoline.c:1463:bpf_trampoline_exit_t bpf_trampoline_exit(const struct bpf_prog *prog)\nkernel/bpf/trampoline.c-1464-{\n--\nkernel/bpf/trampoline.c=1478=int __weak\nkernel/bpf/trampoline.c:1479:arch_prepare_bpf_trampoline(struct bpf_tramp_image *im, void *image, void *image_end,\nkernel/bpf/trampoline.c-1480-\t\t\t    const struct btf_func_model *m, u32 flags,\n--\nkernel/bpf/trampoline.c-1486-\n\n"
}

gemini-3.8-flash

null

null

							input: 39715
							output: 40
							thoughts: 154
						

**Analyzing BPF Functionality within the Kernel Tracepoints**

Okay, so I'm digging into how the BPF functionality interacts with tracepoints, specifically within `bpf_trace.c`. My initial observation is this snippet:

```c
#ifdef CONFIG_NET
	case BPF_FUNC_skb_output:
		if (tracing_prog_may_run_after_target(prog))
			return NULL;
		return &bpf_skb_output_proto;
```

This immediately directs my attention to `BPF_FUNC_skb_output` and the associated checks. Now, I need to understand when the `tracing_prog_func_proto` is compiled, and whether it's conditionally included based on any `#ifdef` directives. My gut feeling is that any conditional inclusion of the function itself could affect its usage and how the overall BPF program validation and execution occurs within tracing. So, I’m going to focus my attention on inspecting lines 1730-1860 within `kernel/trace/bpf_trace.c`. That's where I expect to find the pertinent details, especially given the context of the code I've already glanced at.

{
  "File": "kernel/trace/bpf_trace.c",
  "FirstLine": 1738,
  "LineCount": 100
}

{
  "Contents": "1738:\t\n1739:\tconst struct bpf_func_proto *\n1740:\ttracing_prog_func_proto(enum bpf_func_id func_id, const struct bpf_prog *prog)\n1741:\t{\n1742:\t\tconst struct bpf_func_proto *fn;\n1743:\t\n1744:\t\tswitch (func_id) {\n1745:\t#ifdef CONFIG_NET\n1746:\t\tcase BPF_FUNC_skb_output:\n1747:\t\t\tif (tracing_prog_may_run_after_target(prog))\n1748:\t\t\t\treturn NULL;\n1749:\t\t\treturn \u0026bpf_skb_output_proto;\n1750:\t\tcase BPF_FUNC_xdp_output:\n1751:\t\t\treturn \u0026bpf_xdp_output_proto;\n1752:\t\tcase BPF_FUNC_skc_to_tcp6_sock:\n1753:\t\t\treturn \u0026bpf_skc_to_tcp6_sock_proto;\n1754:\t\tcase BPF_FUNC_skc_to_tcp_sock:\n1755:\t\t\treturn \u0026bpf_skc_to_tcp_sock_proto;\n1756:\t\tcase BPF_FUNC_skc_to_tcp_timewait_sock:\n1757:\t\t\treturn \u0026bpf_skc_to_tcp_timewait_sock_proto;\n1758:\t\tcase BPF_FUNC_skc_to_tcp_request_sock:\n1759:\t\t\treturn \u0026bpf_skc_to_tcp_request_sock_proto;\n1760:\t\tcase BPF_FUNC_skc_to_udp6_sock:\n1761:\t\t\treturn \u0026bpf_skc_to_udp6_sock_proto;\n1762:\t\tcase BPF_FUNC_skc_to_unix_sock:\n1763:\t\t\treturn \u0026bpf_skc_to_unix_sock_proto;\n1764:\t\tcase BPF_FUNC_skc_to_mptcp_sock:\n1765:\t\t\treturn \u0026bpf_skc_to_mptcp_sock_proto;\n1766:\t\tcase BPF_FUNC_sk_storage_get:\n1767:\t\t\treturn \u0026bpf_sk_storage_get_tracing_proto;\n1768:\t\tcase BPF_FUNC_sk_storage_delete:\n1769:\t\t\treturn \u0026bpf_sk_storage_delete_tracing_proto;\n1770:\t\tcase BPF_FUNC_sock_from_file:\n1771:\t\t\treturn \u0026bpf_sock_from_file_proto;\n1772:\t\tcase BPF_FUNC_get_socket_cookie:\n1773:\t\t\treturn \u0026bpf_get_socket_ptr_cookie_proto;\n1774:\t\tcase BPF_FUNC_xdp_get_buff_len:\n1775:\t\t\treturn \u0026bpf_xdp_get_buff_len_trace_proto;\n1776:\t#endif\n1777:\t\tcase BPF_FUNC_seq_printf:\n1778:\t\t\treturn prog-\u003eexpected_attach_type == BPF_TRACE_ITER ?\n1779:\t\t\t       \u0026bpf_seq_printf_proto :\n1780:\t\t\t       NULL;\n1781:\t\tcase BPF_FUNC_seq_write:\n1782:\t\t\treturn prog-\u003eexpected_attach_type == BPF_TRACE_ITER ?\n1783:\t\t\t       \u0026bpf_seq_write_proto :\n1784:\t\t\t       NULL;\n1785:\t\tcase BPF_FUNC_seq_printf_btf:\n1786:\t\t\treturn prog-\u003eexpected_attach_type == BPF_TRACE_ITER ?\n1787:\t\t\t       \u0026bpf_seq_printf_btf_proto :\n1788:\t\t\t       NULL;\n1789:\t\tcase BPF_FUNC_d_path:\n1790:\t\t\treturn \u0026bpf_d_path_proto;\n1791:\t\tcase BPF_FUNC_get_func_arg:\n1792:\t\t\tif (bpf_prog_has_trampoline(prog) ||\n1793:\t\t\t    prog-\u003eexpected_attach_type == BPF_TRACE_RAW_TP)\n1794:\t\t\t\treturn \u0026bpf_get_func_arg_proto;\n1795:\t\t\treturn NULL;\n1796:\t\tcase BPF_FUNC_get_func_ret:\n1797:\t\t\treturn bpf_prog_has_trampoline(prog) ? \u0026bpf_get_func_ret_proto : NULL;\n1798:\t\tcase BPF_FUNC_get_func_arg_cnt:\n1799:\t\t\tif (bpf_prog_has_trampoline(prog) ||\n1800:\t\t\t    prog-\u003eexpected_attach_type == BPF_TRACE_RAW_TP)\n1801:\t\t\t\treturn \u0026bpf_get_func_arg_cnt_proto;\n1802:\t\t\treturn NULL;\n1803:\t\tcase BPF_FUNC_get_attach_cookie:\n1804:\t\t\tif (prog-\u003etype == BPF_PROG_TYPE_TRACING \u0026\u0026\n1805:\t\t\t    prog-\u003eexpected_attach_type == BPF_TRACE_RAW_TP)\n1806:\t\t\t\treturn \u0026bpf_get_attach_cookie_proto_tracing;\n1807:\t\t\treturn bpf_prog_has_trampoline(prog) ? \u0026bpf_get_attach_cookie_proto_tracing : NULL;\n1808:\t\tdefault:\n1809:\t\t\tfn = raw_tp_prog_func_proto(func_id, prog);\n1810:\t\t\tif (!fn \u0026\u0026 prog-\u003eexpected_attach_type == BPF_TRACE_ITER)\n1811:\t\t\t\tfn = bpf_iter_get_func_proto(func_id, prog);\n1812:\t\t\treturn fn;\n1813:\t\t}\n1814:\t}\n1815:\t\n1816:\tstatic bool raw_tp_prog_is_valid_access(int off, int size,\n1817:\t\t\t\t\t\tenum bpf_access_type type,\n1818:\t\t\t\t\t\tconst struct bpf_prog *prog,\n1819:\t\t\t\t\t\tstruct bpf_insn_access_aux *info)\n1820:\t{\n1821:\t\treturn bpf_tracing_ctx_access(off, size, type);\n1822:\t}\n1823:\t\n1824:\tstatic bool tracing_prog_is_valid_access(int off, int size,\n1825:\t\t\t\t\t\t enum bpf_access_type type,\n1826:\t\t\t\t\t\t const struct bpf_prog *prog,\n1827:\t\t\t\t\t\t struct bpf_insn_access_aux *info)\n1828:\t{\n1829:\t\treturn bpf_tracing_btf_ctx_access(off, size, type, prog, info);\n1830:\t}\n1831:\t\n1832:\tint __weak bpf_prog_test_run_tracing(struct bpf_prog *prog,\n1833:\t\t\t\t\t     const union bpf_attr *kattr,\n1834:\t\t\t\t\t     union bpf_attr __user *uattr)\n1835:\t{\n1836:\t\treturn -ENOTSUPP;\n1837:\t}\n"
}

gemini-3.8-flash

null

null

							input: 42051
							output: 29
							thoughts: 381
						

**Analyzing the `tracing_prog_func_proto` Function**

Okay, let's break this down. My initial thought was to locate `tracing_prog_func_proto`, which I know is defined in `kernel/trace/bpf_trace.c`. I was also considering the relationship with `tracing_prog_may_run_after_target`, a static inline function, also in that file. My instinct was that, because it's static inline, it would be inlined directly into `tracing_prog_func_proto`, which piqued my interest as to whether `tracing_prog_func_proto` could be a symbol of particular focus.

But wait a minute... Let's check the symbol table; ensure `tracing_prog_func_proto` isn't static. Yep, it isn't! Turns out it's an extern function declared in `include/linux/bpf.h` and defined in `kernel/trace/bpf_trace.c`. That means it's available outside its file, so it must be more widely used than I initially thought. I quickly shifted gears and began to evaluate its ubiquity.

Ah, no! It's not *that* ubiquitous. It's only invoked during BPF verification, specifically when verifying BPF programs of the `BPF_PROG_TYPE_TRACING` type, or as a fallback for `BPF_PROG_TYPE_LSM` and `BPF_PROG_TYPE_SYSCALL` if necessary, when helper functions are called.

The next question: what's the entry point in the verification process that calls `tracing_prog_func_proto`? That would be `check_helper_call` in `kernel/bpf/verifier.c`. So now, my next check will be on `kernel/bpf/verifier.c` and locating `get_func_proto`.

{
  "Expression": "get_func_proto",
  "PathPrefix": "kernel/bpf"
}

{
  "Output": "kernel/bpf/bpf_iter.c=369=const struct bpf_func_proto *\nkernel/bpf/bpf_iter.c:370:bpf_iter_get_func_proto(enum bpf_func_id func_id, const struct bpf_prog *prog)\nkernel/bpf/bpf_iter.c-371-{\n--\nkernel/bpf/bpf_iter.c-380-\t\t\treg_info = tinfo-\u003ereg_info;\nkernel/bpf/bpf_iter.c:381:\t\t\tif (reg_info-\u003eget_func_proto)\nkernel/bpf/bpf_iter.c:382:\t\t\t\tfn = reg_info-\u003eget_func_proto(func_id, prog);\nkernel/bpf/bpf_iter.c-383-\t\t\tbreak;\n--\nkernel/bpf/bpf_lsm.c=436=const struct bpf_verifier_ops lsm_verifier_ops = {\nkernel/bpf/bpf_lsm.c:437:\t.get_func_proto\t\t= bpf_lsm_func_proto,\nkernel/bpf/bpf_lsm.c-438-\t.is_valid_access\t= bpf_tracing_btf_ctx_access,\n--\nkernel/bpf/cgroup.c=2088=const struct bpf_verifier_ops cg_dev_verifier_ops = {\nkernel/bpf/cgroup.c:2089:\t.get_func_proto\t\t= cgroup_dev_func_proto,\nkernel/bpf/cgroup.c-2090-\t.is_valid_access\t= cgroup_dev_is_valid_access,\n--\nkernel/bpf/cgroup.c=2704=const struct bpf_verifier_ops cg_sysctl_verifier_ops = {\nkernel/bpf/cgroup.c:2705:\t.get_func_proto\t\t= sysctl_func_proto,\nkernel/bpf/cgroup.c-2706-\t.is_valid_access\t= sysctl_is_valid_access,\n--\nkernel/bpf/cgroup.c=2927=const struct bpf_verifier_ops cg_sockopt_verifier_ops = {\nkernel/bpf/cgroup.c:2928:\t.get_func_proto\t\t= cg_sockopt_func_proto,\nkernel/bpf/cgroup.c-2929-\t.is_valid_access\t= cg_sockopt_is_valid_access,\n--\nkernel/bpf/fixups.c=1540=int bpf_do_misc_fixups(struct bpf_verifier_env *env)\n--\nkernel/bpf/fixups.c-2431-patch_call_imm:\nkernel/bpf/fixups.c:2432:\t\tfn = env-\u003eops-\u003eget_func_proto(insn-\u003eimm, env-\u003eprog);\nkernel/bpf/fixups.c-2433-\t\t/* all functions that have prototype and verifier allowed\n--\nkernel/bpf/helpers.c-35-/* If kernel subsystem is allowing eBPF programs to call this function,\nkernel/bpf/helpers.c:36: * inside its own verifier_ops-\u003eget_func_proto() callback it should return\nkernel/bpf/helpers.c-37- * bpf_map_lookup_elem_proto, so that verifier can properly check the arguments\n--\nkernel/bpf/syscall.c=6651=const struct bpf_verifier_ops bpf_syscall_verifier_ops = {\nkernel/bpf/syscall.c:6652:\t.get_func_proto  = syscall_prog_func_proto,\nkernel/bpf/syscall.c-6653-\t.is_valid_access = syscall_prog_is_valid_access,\n--\nkernel/bpf/verifier.c=11454=int bpf_get_helper_proto(struct bpf_verifier_env *env, int func_id,\n--\nkernel/bpf/verifier.c-11459-\nkernel/bpf/verifier.c:11460:\tif (!env-\u003eops-\u003eget_func_proto)\nkernel/bpf/verifier.c-11461-\t\treturn -EINVAL;\nkernel/bpf/verifier.c-11462-\nkernel/bpf/verifier.c:11463:\t*ptr = env-\u003eops-\u003eget_func_proto(func_id, env-\u003eprog);\nkernel/bpf/verifier.c-11464-\treturn *ptr \u0026\u0026 (*ptr)-\u003efunc ? 0 : -EINVAL;\n"
}

gemini-3.8-flash

null

null

							input: 44037
							output: 30
							thoughts: 1279
						

**Analyzing BPF Tracing Functionality**

Okay, so I'm looking into the interactions within the BPF tracing code, specifically how helper function prototypes are retrieved and used. The initial call chain leads me to `bpf_get_helper_proto`, which then uses the `env->ops->get_func_proto` call. This, in turn, invokes `tracing_prog_func_proto`. My first thought is, where else is this `tracing_prog_func_proto` function used? It turns out it's central to several key areas: `syscall_prog_func_proto`, `bpf_lsm_func_proto` and `bpf_do_misc_fixups`.

The verifier's entry point, `bpf_check`, is too general to be relevant in this case. But `tracing_prog_func_proto` in `bpf_trace.c` - *that's* the specific function I'm interested in, the modified, non-static function.

Now, I was wondering about `tracing_prog_may_run_after_target`. Is this a symbol or inline? Turns out it's a `static inline` function. Since it's inline, the compiler will most likely inline it directly into `tracing_prog_func_proto`. So, `tracing_prog_func_proto` is definitely the right symbol to focus on. Section 4 confirms that the focus should be the non-static caller.

`bpf_get_helper_proto` is used universally, so not relevant. But `tracing_prog_func_proto`? That's specific to tracing BPF programs, which is exactly what I need.

Next, I need to look at other potentially related functions. For example, `bpf_skb_event_output`, the function that would be invoked if `BPF_FUNC_skb_output` had succeeded, is forbidden in `fexit` and `fsession`, but it's *still allowed* in `fentry`! So I need to keep that in mind.

I also need to see where `bpf_tracing_func_proto` is used, and it's called for raw_tp.

Now, what about configurations? Let's figure out what's required for `bpf_trace.c` to be used. I look into `BPF_EVENTS`. The config entry shows that it *depends* on `BPF_SYSCALL`, `PERF_EVENTS`, and `KPROBE_EVENTS` or `UPROBE_EVENTS`. It's a `bool` without a prompt, so it will default to 'y' only if dependencies are met. We need `BPF_SYSCALL`, `BPF_EVENTS`, and `NET`. What about `BPF_JIT`? Does `BPF_PROG_TYPE_TRACING` require it? I need to double-check that.

no matches

{
  "Expression": "BPF_PROG_TYPE_TRACING.*BPF_JIT"
}

{
  "error": "no matches"
}

gemini-3.8-flash

null

null

							input: 45994
							output: 24
							thoughts: 36
						

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

**Diving into the BPF Verifier for Tracing Programs**

Right, let's get into the nitty-gritty. I'm thinking, let's go straight to the heart of the matter: `kernel/bpf/verifier.c`. Specifically, I need to understand how the verifier handles `BPF_PROG_TYPE_TRACING` programs, and, more precisely, the interaction with JIT compilation or BTF data. I need to refresh my memory on the conditional checks that deal with these aspects of tracing programs in the verifier. What's the exact flow and decision path? I expect the code to contain specific checks. I need to confirm whether it is looking at JIT capabilities during the initial verification process or if the JIT check occurs during the execution phase. Furthermore, I need to confirm how BTF data influences the verification, if at all. Are there specific checks related to the existence or validity of BTF information? I need to focus on this because I know BTF can significantly impact how tracing programs interact with data structures and function calls. Understanding this verification process is crucial for assessing potential vulnerabilities or limitations in tracing program execution.

{
  "Expression": "bpf_prog_load_check_attach"
}

{
  "Output": "kernel/bpf/syscall.c=2730=static int\nkernel/bpf/syscall.c:2731:bpf_prog_load_check_attach(enum bpf_prog_type prog_type,\nkernel/bpf/syscall.c-2732-\t\t\t   enum bpf_attach_type expected_attach_type,\n--\nkernel/bpf/syscall.c=2920=static int bpf_prog_load(union bpf_attr *attr, bpfptr_t uattr, struct bpf_log_attr *attr_log)\n--\nkernel/bpf/syscall.c-3032-\nkernel/bpf/syscall.c:3033:\tif (bpf_prog_load_check_attach(type, attr-\u003eexpected_attach_type,\nkernel/bpf/syscall.c-3034-\t\t\t\t       attach_btf, attr-\u003eattach_btf_id,\n"
}

gemini-3.8-flash

null

null

							input: 46553
							output: 37
							thoughts: 27
						

Here's my summary, as though I'm reading and processing the thoughts:

**Analyzing `bpf_prog_load_check_attach`**

Alright, let's dive into the `bpf_prog_load_check_attach` function within `kernel/bpf/syscall.c`. I need to understand the logic flow here, particularly how it relates to program loading and attachment. I'm focusing on the checks and safeguards implemented to ensure stability and security. I'll be looking for potential vulnerabilities or areas where optimization might be possible, specifically in the context of advanced BPF program design and deployment. I’ll keep an eye out for how this function interacts with the verifier, and the role it plays in resource management.

{
  "File": "kernel/bpf/syscall.c",
  "FirstLine": 2731,
  "LineCount": 40
}

{
  "Contents": "2731:\tbpf_prog_load_check_attach(enum bpf_prog_type prog_type,\n2732:\t\t\t\t   enum bpf_attach_type expected_attach_type,\n2733:\t\t\t\t   struct btf *attach_btf, u32 btf_id,\n2734:\t\t\t\t   struct bpf_prog *dst_prog,\n2735:\t\t\t\t   bool multi_func)\n2736:\t{\n2737:\t\tif (btf_id) {\n2738:\t\t\tif (btf_id \u003e BTF_MAX_TYPE)\n2739:\t\t\t\treturn -EINVAL;\n2740:\t\n2741:\t\t\tif (!attach_btf \u0026\u0026 !dst_prog)\n2742:\t\t\t\treturn -EINVAL;\n2743:\t\n2744:\t\t\tswitch (prog_type) {\n2745:\t\t\tcase BPF_PROG_TYPE_TRACING:\n2746:\t\t\tcase BPF_PROG_TYPE_LSM:\n2747:\t\t\tcase BPF_PROG_TYPE_STRUCT_OPS:\n2748:\t\t\tcase BPF_PROG_TYPE_EXT:\n2749:\t\t\t\tbreak;\n2750:\t\t\tdefault:\n2751:\t\t\t\treturn -EINVAL;\n2752:\t\t\t}\n2753:\t\t}\n2754:\t\n2755:\t\tif (multi_func) {\n2756:\t\t\tif (prog_type != BPF_PROG_TYPE_TRACING)\n2757:\t\t\t\treturn -EINVAL;\n2758:\t\t\tif (!attach_btf || btf_id)\n2759:\t\t\t\treturn -EINVAL;\n2760:\t\t\treturn 0;\n2761:\t\t}\n2762:\t\n2763:\t\tif (attach_btf \u0026\u0026 (!btf_id || dst_prog))\n2764:\t\t\treturn -EINVAL;\n2765:\t\n2766:\t\tif (dst_prog \u0026\u0026 prog_type != BPF_PROG_TYPE_TRACING \u0026\u0026\n2767:\t\t    prog_type != BPF_PROG_TYPE_EXT)\n2768:\t\t\treturn -EINVAL;\n2769:\t\n2770:\t\tswitch (prog_type) {\n"
}

gemini-3.8-flash

null

null

							input: 47370
							output: 37
							thoughts: 18
						

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

**Diving into `bpf_prog_load_check_attach`**

Alright, so the next logical step is to dig into the `bpf_prog_load_check_attach` function. Given the context, I'm expecting this is the crucial point where the BPF program undergoes its validation and attachment checks. I'll need to understand the specifics of how the kernel is handling those steps. I anticipate the code will involve a thorough examination of the program's instructions against pre-defined rules, considering the target attachment point, and potentially other contextual factors like security policies. I'm keen to see if they're using any specific BPF helpers during this validation phase, as that could provide insights into performance optimization or debugging techniques. I'll be looking to see if the implementation accounts for all of the potential failure cases. Most importantly, I'm hoping to understand the exact error conditions being checked for, to better determine how to debug a failing program.

{
  "File": "kernel/bpf/syscall.c",
  "FirstLine": 2770,
  "LineCount": 40
}

{
  "Contents": "2770:\t\tswitch (prog_type) {\n2771:\t\tcase BPF_PROG_TYPE_CGROUP_SOCK:\n2772:\t\t\tswitch (expected_attach_type) {\n2773:\t\t\tcase BPF_CGROUP_INET_SOCK_CREATE:\n2774:\t\t\tcase BPF_CGROUP_INET_SOCK_RELEASE:\n2775:\t\t\tcase BPF_CGROUP_INET4_POST_BIND:\n2776:\t\t\tcase BPF_CGROUP_INET6_POST_BIND:\n2777:\t\t\t\treturn 0;\n2778:\t\t\tdefault:\n2779:\t\t\t\treturn -EINVAL;\n2780:\t\t\t}\n2781:\t\tcase BPF_PROG_TYPE_CGROUP_SOCK_ADDR:\n2782:\t\t\tswitch (expected_attach_type) {\n2783:\t\t\tcase BPF_CGROUP_INET4_BIND:\n2784:\t\t\tcase BPF_CGROUP_INET6_BIND:\n2785:\t\t\tcase BPF_CGROUP_INET4_CONNECT:\n2786:\t\t\tcase BPF_CGROUP_INET6_CONNECT:\n2787:\t\t\tcase BPF_CGROUP_UNIX_CONNECT:\n2788:\t\t\tcase BPF_CGROUP_INET4_GETPEERNAME:\n2789:\t\t\tcase BPF_CGROUP_INET6_GETPEERNAME:\n2790:\t\t\tcase BPF_CGROUP_UNIX_GETPEERNAME:\n2791:\t\t\tcase BPF_CGROUP_INET4_GETSOCKNAME:\n2792:\t\t\tcase BPF_CGROUP_INET6_GETSOCKNAME:\n2793:\t\t\tcase BPF_CGROUP_UNIX_GETSOCKNAME:\n2794:\t\t\tcase BPF_CGROUP_UDP4_SENDMSG:\n2795:\t\t\tcase BPF_CGROUP_UDP6_SENDMSG:\n2796:\t\t\tcase BPF_CGROUP_UNIX_SENDMSG:\n2797:\t\t\tcase BPF_CGROUP_UDP4_RECVMSG:\n2798:\t\t\tcase BPF_CGROUP_UDP6_RECVMSG:\n2799:\t\t\tcase BPF_CGROUP_UNIX_RECVMSG:\n2800:\t\t\t\treturn 0;\n2801:\t\t\tdefault:\n2802:\t\t\t\treturn -EINVAL;\n2803:\t\t\t}\n2804:\t\tcase BPF_PROG_TYPE_CGROUP_SKB:\n2805:\t\t\tswitch (expected_attach_type) {\n2806:\t\t\tcase BPF_CGROUP_INET_INGRESS:\n2807:\t\t\tcase BPF_CGROUP_INET_EGRESS:\n2808:\t\t\t\treturn 0;\n2809:\t\t\tdefault:\n"
}

gemini-3.8-flash

null

null

							input: 48387
							output: 40
							thoughts: 30
						

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

**Examining BPF Program Type Attachment Logic**

Okay, let's zero in on how we're handling `BPF_PROG_TYPE_TRACING` within `bpf_prog_load_check_attach`. My immediate concern is with ensuring the proper verification and attachment process for tracing programs, given the potential for significant security and performance implications. I want to delve into the specifics of this `case` statement to confirm that all sanity checks, resource limitations, and interaction models with other BPF program types are rigorously enforced. I'm looking for any potential vulnerabilities or logical flaws related to the attach point, especially considering the tracing context. It needs to align with the overall BPF security policy and expected behavior. I'm keen to confirm that we're properly considering the kernel version, the specific tracing event (if applicable), and any interaction with hardware or other system resources. I expect to be looking at the following in particular:

*   **Security:** How we're validating the code's safety, preventing infinite loops, and ensuring that tracing programs cannot crash or misbehave, whether due to faulty code or crafted malicious inputs.
*   **Performance:** The impact on system calls and CPU load when tracing, especially given the kernel context.
*   **Resource Allocation:** Memory usage, and ensuring tracing doesn't starve other critical system processes.
*   **Error handling and recovery:** Robust handling in case of conflicts or failures during the attachment process.
*   **Compatibility:** How it works in conjunction with other BPF program types.
*   **Restrictions:** Ensuring that the program can't escape its sandboxed context.

My main goal is to be confident this branch handles all edge cases and is robust against misuse or accidental misconfiguration. I'm expecting to see clean, well-documented code that makes the intention and limitations of the tracing functionality clear.

{
  "Expression": "case BPF_PROG_TYPE_TRACING:",
  "PathPrefix": "kernel/bpf/syscall.c"
}

{
  "Output": "kernel/bpf/syscall.c=2731=bpf_prog_load_check_attach(enum bpf_prog_type prog_type,\n--\nkernel/bpf/syscall.c-2744-\t\tswitch (prog_type) {\nkernel/bpf/syscall.c:2745:\t\tcase BPF_PROG_TYPE_TRACING:\nkernel/bpf/syscall.c-2746-\t\tcase BPF_PROG_TYPE_LSM:\n--\nkernel/bpf/syscall.c=2877=static bool is_perfmon_prog_type(enum bpf_prog_type prog_type)\n--\nkernel/bpf/syscall.c-2884-\tcase BPF_PROG_TYPE_RAW_TRACEPOINT_WRITABLE:\nkernel/bpf/syscall.c:2885:\tcase BPF_PROG_TYPE_TRACING:\nkernel/bpf/syscall.c-2886-\tcase BPF_PROG_TYPE_LSM:\n--\nkernel/bpf/syscall.c=3637=static int bpf_tracing_prog_attach(struct bpf_prog *prog,\n--\nkernel/bpf/syscall.c-3650-\tswitch (prog-\u003etype) {\nkernel/bpf/syscall.c:3651:\tcase BPF_PROG_TYPE_TRACING:\nkernel/bpf/syscall.c-3652-\t\tif (prog-\u003eexpected_attach_type != BPF_TRACE_FENTRY \u0026\u0026\n--\nkernel/bpf/syscall.c=4300=static int bpf_raw_tp_link_attach(struct bpf_prog *prog,\n--\nkernel/bpf/syscall.c-4311-\tswitch (prog-\u003etype) {\nkernel/bpf/syscall.c:4312:\tcase BPF_PROG_TYPE_TRACING:\nkernel/bpf/syscall.c-4313-\tcase BPF_PROG_TYPE_EXT:\n--\nkernel/bpf/syscall.c=5797=static int link_create(union bpf_attr *attr, bpfptr_t uattr)\n--\nkernel/bpf/syscall.c-5834-\tcase BPF_PROG_TYPE_LSM:\nkernel/bpf/syscall.c:5835:\tcase BPF_PROG_TYPE_TRACING:\nkernel/bpf/syscall.c-5836-\t\tif (attr-\u003elink_create.attach_type != prog-\u003eexpected_attach_type) {\n"
}

gemini-3.8-flash

null

null

							input: 49499
							output: 40
							thoughts: 72
						

Here's my take on the thought process, as requested:

**Navigating the BPF Codebase**

Okay, so I'm looking into how tracing BPF programs are loaded. It looks like the check `type == BPF_PROG_TYPE_TRACING` is happening inside `bpf_prog_load`. I need to figure out how this specific tracing program type is handled, so my next logical step is to trace where that condition, and by extension, the `BPF_PROG_TYPE_TRACING` value, is dealt with in the `kernel/bpf/syscall.c` file. I need to understand the control flow.

{
  "Expression": "type == BPF_PROG_TYPE_TRACING",
  "PathPrefix": "kernel/bpf/syscall.c"
}

{
  "Output": "kernel/bpf/syscall.c=2920=static int bpf_prog_load(union bpf_attr *attr, bpfptr_t uattr, struct bpf_log_attr *attr_log)\n--\nkernel/bpf/syscall.c-3118-\t */\nkernel/bpf/syscall.c:3119:\tif (type == BPF_PROG_TYPE_TRACING \u0026\u0026 dst_prog \u0026\u0026\nkernel/bpf/syscall.c:3120:\t    dst_prog-\u003etype == BPF_PROG_TYPE_TRACING) {\nkernel/bpf/syscall.c-3121-\t\tprog-\u003eaux-\u003eattach_tracing_prog = true;\n--\nkernel/bpf/syscall.c=4300=static int bpf_raw_tp_link_attach(struct bpf_prog *prog,\n--\nkernel/bpf/syscall.c-4319-\t\t\treturn -EINVAL;\nkernel/bpf/syscall.c:4320:\t\tif (prog-\u003etype == BPF_PROG_TYPE_TRACING \u0026\u0026\nkernel/bpf/syscall.c-4321-\t\t    prog-\u003eexpected_attach_type == BPF_TRACE_RAW_TP) {\n"
}

gemini-3.8-flash

null

null

							input: 50062
							output: 37
							thoughts: 277
						

**My Analysis of `bpf_prog_load` and Tracing**

Okay, let's break this down. I'm focusing on what happens when `bpf_prog_load` is called specifically with `BPF_PROG_TYPE_TRACING`. The initial question is: what are the dependencies? Does it need `CONFIG_BPF_SYSCALL`? Yes, of course. And `CONFIG_BPF_EVENTS`? Seems likely, since `bpf_trace.c` wouldn't even be compiled without it, which would cause immediate failure.

But hold on, let me double-check something. Let's dig into `kernel/bpf/syscall.c` and specifically line 6580. Ah, here we are! I see a `__weak` definition for `tracing_prog_func_proto` at line 6582-6584, which means it can be overriden! Now, to truly understand the implication, I need to read through lines 6580 to 6600. Knowing that `tracing_prog_func_proto` is `__weak` sheds a whole new light on how tracing programs are handled and loaded in this context. This is the key piece of the puzzle I was looking for. Now I have a good handle on where to find the source.

{
  "File": "kernel/bpf/syscall.c",
  "FirstLine": 6580,
  "LineCount": 25
}

{
  "Contents": "6580:\t};\n6581:\t\n6582:\tconst struct bpf_func_proto * __weak\n6583:\ttracing_prog_func_proto(enum bpf_func_id func_id, const struct bpf_prog *prog)\n6584:\t{\n6585:\t\treturn bpf_base_func_proto(func_id, prog);\n6586:\t}\n6587:\t\n6588:\tBPF_CALL_1(bpf_sys_close, u32, fd)\n6589:\t{\n6590:\t\t/* When bpf program calls this helper there should not be\n6591:\t\t * an fdget() without matching completed fdput().\n6592:\t\t * This helper is allowed in the following callchain only:\n6593:\t\t * sys_bpf-\u003eprog_test_run-\u003ebpf_prog-\u003ebpf_sys_close\n6594:\t\t */\n6595:\t\treturn close_fd(fd);\n6596:\t}\n6597:\t\n6598:\tstatic const struct bpf_func_proto bpf_sys_close_proto = {\n6599:\t\t.func\t\t= bpf_sys_close,\n6600:\t\t.gpl_only\t= false,\n6601:\t\t.might_sleep\t= true,\n6602:\t\t.ret_type\t= RET_INTEGER,\n6603:\t\t.arg1_type\t= ARG_ANYTHING,\n6604:\t};\n"
}

gemini-3.8-flash

null

null

							input: 51072
							output: 30
							thoughts: 439
						

**My Analysis of BPF Tracing Dependencies**

Okay, let me break this down. It's becoming clearer. If `CONFIG_BPF_EVENTS` is *not* enabled, then the kernel isn't building `kernel/trace/bpf_trace.o`. That's important. Consequently, `tracing_prog_func_proto` defaults to the weak version in `kernel/bpf/syscall.c`. This only gives me `bpf_base_func_proto`. So, the more comprehensive version in `kernel/trace/bpf_trace.c`, the one with the changes I'm interested in, *requires* `CONFIG_BPF_EVENTS=y`.

And `CONFIG_BPF_EVENTS` isn't a freebie, it needs `CONFIG_BPF_SYSCALL`, `CONFIG_PERF_EVENTS`, and at least one of either `CONFIG_KPROBE_EVENTS` or `CONFIG_UPROBE_EVENTS`. Got it. A whole chain.

Now, inside `tracing_prog_func_proto`, there's a specific block of code:

```c
#ifdef CONFIG_NET
	case BPF_FUNC_skb_output:
		if (tracing_prog_may_run_after_target(prog))
			return NULL;
		return &bpf_skb_output_proto;
```

And it's `#ifdef CONFIG_NET`. So, naturally, that code block needs `CONFIG_NET` to be compiled. Okay.

Now, what about `CONFIG_DEBUG_INFO_BTF`? To load a tracing program, especially one that attaches to a BTF ID, does it *require* it? I had a hunch...

Aha! The selftest is enlightening. Looking at the `SEC` declarations:

`SEC("fentry/skb_tx_error")`
`SEC("fexit/skb_tx_error")`

`fentry` and `fexit` are attaching to kernel functions *via* BTF! That clinches it. Kernel BTF *is* needed to resolve the target function's BTF ID. So, for those to work, I'm thinking I'll need `CONFIG_DEBUG_INFO_BTF=y`.

But wait! Can I load a `BPF_PROG_TYPE_TRACING` with `BPF_TRACE_FEXIT` without BTF? I should check `kernel/bpf/verifier.c`. Specifically, I need to look into `check_attach_btf_id`. That's where I'll find my answer.

{
  "Expression": "btf_vmlinux",
  "PathPrefix": "kernel/bpf"
}

{
  "Output": "kernel/bpf/bpf_struct_ops.c=83=enum {\n--\nkernel/bpf/bpf_struct_ops.c-87-\nkernel/bpf/bpf_struct_ops.c:88:extern struct btf *btf_vmlinux;\nkernel/bpf/bpf_struct_ops.c-89-\nkernel/bpf/bpf_struct_ops.c=90=static bool is_valid_value_type(struct btf *btf, s32 value_id,\n--\nkernel/bpf/bpf_struct_ops.c-105-\tmt = btf_type_by_id(btf, member-\u003etype);\nkernel/bpf/bpf_struct_ops.c:106:\tcommon_value_type = btf_type_by_id(btf_vmlinux,\nkernel/bpf/bpf_struct_ops.c-107-\t\t\t\t\t   st_ops_ids[IDX_ST_OPS_COMMON_VALUE_ID]);\n--\nkernel/bpf/bpf_struct_ops.c=727=static long bpf_struct_ops_map_update_elem(struct bpf_map *map, void *key,\n--\nkernel/bpf/bpf_struct_ops.c-785-\ttname = btf_name_by_offset(st_map-\u003ebtf, t-\u003ename_off);\nkernel/bpf/bpf_struct_ops.c:786:\tmodule_type = btf_type_by_id(btf_vmlinux, st_ops_ids[IDX_MODULE_ID]);\nkernel/bpf/bpf_struct_ops.c-787-\tfor_each_member(i, t, member) {\n--\nkernel/bpf/bpf_struct_ops.c=991=static void bpf_struct_ops_map_seq_show_elem(struct bpf_map *map, void *key,\n--\nkernel/bpf/bpf_struct_ops.c-1004-\t\tbtf_type_seq_show(st_map-\u003ebtf,\nkernel/bpf/bpf_struct_ops.c:1005:\t\t\t\t  map-\u003ebtf_vmlinux_value_type_id,\nkernel/bpf/bpf_struct_ops.c-1006-\t\t\t\t  value, m);\n--\nkernel/bpf/bpf_struct_ops.c=1056=static int bpf_struct_ops_map_alloc_check(union bpf_attr *attr)\n--\nkernel/bpf/bpf_struct_ops.c-1059-\t    (attr-\u003emap_flags \u0026 ~(BPF_F_LINK | BPF_F_VTYPE_BTF_OBJ_FD)) ||\nkernel/bpf/bpf_struct_ops.c:1060:\t    !attr-\u003ebtf_vmlinux_value_type_id)\nkernel/bpf/bpf_struct_ops.c-1061-\t\treturn -EINVAL;\n--\nkernel/bpf/bpf_struct_ops.c=1078=static struct bpf_map *bpf_struct_ops_map_alloc(union bpf_attr *attr)\n--\nkernel/bpf/bpf_struct_ops.c-1106-\t} else {\nkernel/bpf/bpf_struct_ops.c:1107:\t\tbtf = bpf_get_btf_vmlinux();\nkernel/bpf/bpf_struct_ops.c-1108-\t\tif (IS_ERR(btf))\n--\nkernel/bpf/bpf_struct_ops.c-1113-\nkernel/bpf/bpf_struct_ops.c:1114:\tst_ops_desc = bpf_struct_ops_find_value(btf, attr-\u003ebtf_vmlinux_value_type_id);\nkernel/bpf/bpf_struct_ops.c-1115-\tif (!st_ops_desc) {\n--\nkernel/bpf/bpf_struct_ops.c=1612=void bpf_map_struct_ops_info_fill(struct bpf_map_info *info, struct bpf_map *map)\n--\nkernel/bpf/bpf_struct_ops.c-1615-\nkernel/bpf/bpf_struct_ops.c:1616:\tinfo-\u003ebtf_vmlinux_id = btf_obj_id(st_map-\u003ebtf);\nkernel/bpf/bpf_struct_ops.c-1617-}\n--\nkernel/bpf/btf.c=680=s32 bpf_find_btf_id(const char *name, u32 kind, struct btf **btf_p)\n--\nkernel/bpf/btf.c-685-\nkernel/bpf/btf.c:686:\tbtf = bpf_get_btf_vmlinux();\nkernel/bpf/btf.c-687-\tif (IS_ERR(btf))\n--\nkernel/bpf/btf.c=6089=extern char __stop_BTF[];\nkernel/bpf/btf.c:6090:extern struct btf *btf_vmlinux;\nkernel/bpf/btf.c-6091-\n--\nkernel/bpf/btf.c=6122=static const struct btf_type *find_canonical_prog_ctx_type(enum bpf_prog_type prog_type)\n--\nkernel/bpf/btf.c-6134-\t */\nkernel/bpf/btf.c:6135:\treturn btf_type_by_id(btf_vmlinux, ctx_type-\u003etype);\nkernel/bpf/btf.c-6136-}\n--\nkernel/bpf/btf.c=6163=bool btf_is_prog_ctx_type(struct bpf_verifier_log *log, const struct btf *btf,\n--\nkernel/bpf/btf.c-6203-\tif (!ctx_type) {\nkernel/bpf/btf.c:6204:\t\tbpf_log(log, \"btf_vmlinux is malformed\\n\");\nkernel/bpf/btf.c-6205-\t\t/* should not happen */\n--\nkernel/bpf/btf.c-6208-again:\nkernel/bpf/btf.c:6209:\tctx_tname = btf_name_by_offset(btf_vmlinux, ctx_type-\u003ename_off);\nkernel/bpf/btf.c-6210-\tif (!ctx_tname) {\n--\nkernel/bpf/btf.c-6233-\t\twhile (btf_type_is_modifier(ctx_type))\nkernel/bpf/btf.c:6234:\t\t\tctx_type = btf_type_by_id(btf_vmlinux, ctx_type-\u003etype);\nkernel/bpf/btf.c-6235-\t\tgoto again;\n--\nkernel/bpf/btf.c=6249=static int btf_validate_prog_ctx_type(struct bpf_verifier_log *log, const struct btf *btf,\n--\nkernel/bpf/btf.c-6357-\t\t/* should not happen */\nkernel/bpf/btf.c:6358:\t\tbpf_log(log, \"btf_vmlinux is malformed\\n\");\nkernel/bpf/btf.c-6359-\t\treturn -EINVAL;\n--\nkernel/bpf/btf.c-6363-\twhile (btf_type_is_modifier(ctx_type))\nkernel/bpf/btf.c:6364:\t\tctx_type = btf_type_by_id(btf_vmlinux, ctx_type-\u003etype);\nkernel/bpf/btf.c-6365-\n--\nkernel/bpf/btf.c-6374-\nkernel/bpf/btf.c:6375:\tctx_tname = btf_name_by_offset(btf_vmlinux, ctx_type-\u003ename_off);\nkernel/bpf/btf.c-6376-\tif (!__btf_type_is_struct(t) || strcmp(ctx_tname, tname) != 0) {\n--\nkernel/bpf/btf.c=6395=int get_kern_ctx_btf_id(struct bpf_verifier_log *log, enum bpf_prog_type prog_type)\n--\nkernel/bpf/btf.c-6405-\tkctx_type_id = kctx_member-\u003etype;\nkernel/bpf/btf.c:6406:\tkctx_type = btf_type_by_id(btf_vmlinux, kctx_type_id);\nkernel/bpf/btf.c-6407-\tif (!btf_type_is_struct(kctx_type)) {\n--\nkernel/bpf/btf.c=6470=struct btf *btf_parse_vmlinux(void)\n--\nkernel/bpf/btf.c-6486-\nkernel/bpf/btf.c:6487:\t/* btf_parse_vmlinux() runs under btf_vmlinux_lock */\nkernel/bpf/btf.c-6488-\tbpf_ctx_convert.t = btf_type_by_id(btf, bpf_ctx_convert_btf_id[0]);\n--\nkernel/bpf/btf.c=6512=static struct btf *btf_parse_module(const char *module_name, const void *data,\n--\nkernel/bpf/btf.c-6520-\nkernel/bpf/btf.c:6521:\tvmlinux_btf = bpf_get_btf_vmlinux();\nkernel/bpf/btf.c-6522-\tif (IS_ERR(vmlinux_btf))\n--\nkernel/bpf/btf.c=6881=bool btf_ctx_access(int off, int size, enum bpf_access_type type,\n--\nkernel/bpf/btf.c-7039-\t\t\tinfo-\u003ereg_type = ctx_arg_info-\u003ereg_type;\nkernel/bpf/btf.c:7040:\t\t\tinfo-\u003ebtf = ctx_arg_info-\u003ebtf ? : btf_vmlinux;\nkernel/bpf/btf.c-7041-\t\t\tinfo-\u003ebtf_id = ctx_arg_info-\u003ebtf_id;\n--\nkernel/bpf/btf.c-7096-\t\tif (ret \u003e 0) {\nkernel/bpf/btf.c:7097:\t\t\tinfo-\u003ebtf = btf_vmlinux;\nkernel/bpf/btf.c-7098-\t\t\tinfo-\u003ebtf_id = ret;\n--\nkernel/bpf/btf.c=8059=int btf_prepare_func_args(struct bpf_verifier_env *env, int subprog)\n--\nkernel/bpf/btf.c-8222-\nkernel/bpf/btf.c:8223:\t\t\tvmlinux_btf = bpf_get_btf_vmlinux();\nkernel/bpf/btf.c-8224-\t\t\tref_t = btf_type_by_id(vmlinux_btf, kern_type_id);\n--\nkernel/bpf/btf.c=8763=struct btf *btf_get_module_btf(const struct module *module)\n--\nkernel/bpf/btf.c-8770-\tif (!module) {\nkernel/bpf/btf.c:8771:\t\tbtf = bpf_get_btf_vmlinux();\nkernel/bpf/btf.c-8772-\t\tif (!IS_ERR_OR_NULL(btf))\n--\nkernel/bpf/btf.c=8941=static int btf_check_kfunc_name(struct btf *btf, const char *func_name, u32 kind)\n--\nkernel/bpf/btf.c-8950-\nkernel/bpf/btf.c:8951:\tid = btf_find_by_name_kind(bpf_get_btf_vmlinux(), func_name, kind);\nkernel/bpf/btf.c-8952-\tif (id \u003e= 0) {\n--\nkernel/bpf/btf.c=9725=bpf_core_find_cands(struct bpf_core_ctx *ctx, u32 local_type_id)\n--\nkernel/bpf/btf.c-9735-\nkernel/bpf/btf.c:9736:\tmain_btf = bpf_get_btf_vmlinux();\nkernel/bpf/btf.c-9737-\tif (IS_ERR(main_btf))\n--\nkernel/bpf/inode.c=661=static int find_bpffs_btf_enums(struct bpffs_btf_enums *info)\n--\nkernel/bpf/inode.c-676-\nkernel/bpf/inode.c:677:\tbtf = bpf_get_btf_vmlinux();\nkernel/bpf/inode.c-678-\tif (IS_ERR(btf))\n--\nkernel/bpf/syscall.c=1385=static int map_create_alloc(union bpf_attr *attr, bpfptr_t uattr, struct bpf_verifier_log *log,\n--\nkernel/bpf/syscall.c-1407-\nkernel/bpf/syscall.c:1408:\tif (attr-\u003ebtf_vmlinux_value_type_id) {\nkernel/bpf/syscall.c-1409-\t\tif (attr-\u003emap_type != BPF_MAP_TYPE_STRUCT_OPS) {\nkernel/bpf/syscall.c:1410:\t\t\tbpf_log(log, \"btf_vmlinux_value_type_id can only be used with struct_ops maps.\\n\");\nkernel/bpf/syscall.c-1411-\t\t\treturn -EINVAL;\n--\nkernel/bpf/syscall.c-1413-\t\tif (attr-\u003ebtf_key_type_id || attr-\u003ebtf_value_type_id) {\nkernel/bpf/syscall.c:1414:\t\t\tbpf_log(log, \"btf_vmlinux_value_type_id is mutually exclusive with btf_key_type_id and btf_value_type_id.\\n\");\nkernel/bpf/syscall.c-1415-\t\t\treturn -EINVAL;\n--\nkernel/bpf/syscall.c-1567-\t     */\nkernel/bpf/syscall.c:1568:\t    attr-\u003ebtf_vmlinux_value_type_id) {\nkernel/bpf/syscall.c-1569-\t\tstruct btf *btf;\n--\nkernel/bpf/syscall.c-1592-\t\tmap-\u003ebtf_value_type_id = attr-\u003ebtf_value_type_id;\nkernel/bpf/syscall.c:1593:\t\tmap-\u003ebtf_vmlinux_value_type_id =\nkernel/bpf/syscall.c:1594:\t\t\tattr-\u003ebtf_vmlinux_value_type_id;\nkernel/bpf/syscall.c-1595-\t}\n--\nkernel/bpf/syscall.c=2920=static int bpf_prog_load(union bpf_attr *attr, bpfptr_t uattr, struct bpf_log_attr *attr_log)\n--\nkernel/bpf/syscall.c-3020-\t\t/* fall back to vmlinux BTF, if BTF type ID is specified */\nkernel/bpf/syscall.c:3021:\t\tattach_btf = bpf_get_btf_vmlinux();\nkernel/bpf/syscall.c-3022-\t\tif (IS_ERR(attach_btf)) {\n--\nkernel/bpf/syscall.c=5393=static int bpf_map_get_info_by_fd(struct file *file,\n--\nkernel/bpf/syscall.c-5426-\t}\nkernel/bpf/syscall.c:5427:\tinfo.btf_vmlinux_value_type_id = map-\u003ebtf_vmlinux_value_type_id;\nkernel/bpf/syscall.c-5428-\tif (map-\u003emap_type == BPF_MAP_TYPE_STRUCT_OPS)\n--\nkernel/bpf/sysfs_btf.c=18=static int btf_sysfs_vmlinux_mmap(struct file *filp, struct kobject *kobj,\n--\nkernel/bpf/sysfs_btf.c-45-\nkernel/bpf/sysfs_btf.c:46:static struct bin_attribute bin_attr_btf_vmlinux __ro_after_init = {\nkernel/bpf/sysfs_btf.c-47-\t.attr = { .name = \"vmlinux\", .mode = 0444, },\n--\nkernel/bpf/sysfs_btf.c=52=struct kobject *btf_kobj;\nkernel/bpf/sysfs_btf.c-53-\nkernel/bpf/sysfs_btf.c:54:static int __init btf_vmlinux_init(void)\nkernel/bpf/sysfs_btf.c-55-{\nkernel/bpf/sysfs_btf.c:56:\tbin_attr_btf_vmlinux.private = __start_BTF;\nkernel/bpf/sysfs_btf.c:57:\tbin_attr_btf_vmlinux.size = __stop_BTF - __start_BTF;\nkernel/bpf/sysfs_btf.c-58-\nkernel/bpf/sysfs_btf.c:59:\tif (bin_attr_btf_vmlinux.size == 0)\nkernel/bpf/sysfs_btf.c-60-\t\treturn 0;\n--\nkernel/bpf/sysfs_btf.c-65-\nkernel/bpf/sysfs_btf.c:66:\treturn sysfs_create_bin_file(btf_kobj, \u0026bin_attr_btf_vmlinux);\nkernel/bpf/sysfs_btf.c-67-}\nkernel/bpf/sysfs_btf.c-68-\nkernel/bpf/sysfs_btf.c:69:subsys_initcall(btf_vmlinux_init);\n--\nkernel/bpf/trampoline.c=20=const struct bpf_prog_ops bpf_extension_prog_ops = {\n--\nkernel/bpf/trampoline.c-22-\nkernel/bpf/trampoline.c:23:/* btf_vmlinux has ~22k attachable functions. 1k htab is enough. */\nkernel/bpf/trampoline.c-24-#define TRAMPOLINE_HASH_BITS 10\n--\nkernel/bpf/verifier.c=260=struct bpf_kfunc_meta {\n--\nkernel/bpf/verifier.c-267-\nkernel/bpf/verifier.c:268:struct btf *btf_vmlinux;\nkernel/bpf/verifier.c-269-\n--\nkernel/bpf/verifier.c=316=static DEFINE_MUTEX(bpf_verifier_lock);\nkernel/bpf/verifier.c:317:static DEFINE_MUTEX(btf_vmlinux_lock);\nkernel/bpf/verifier.c-318-static DEFINE_MUTEX(bpf_percpu_ma_lock);\n--\nkernel/bpf/verifier.c=2724=static struct btf *find_kfunc_desc_btf(struct bpf_verifier_env *env, s16 offset)\n--\nkernel/bpf/verifier.c-2736-\t}\nkernel/bpf/verifier.c:2737:\treturn btf_vmlinux ?: ERR_PTR(-ENOENT);\nkernel/bpf/verifier.c-2738-}\n--\nkernel/bpf/verifier.c=2740=static struct btf *find_kfunc_desc_btf_cached(struct bpf_verifier_env *env, s16 offset)\n--\nkernel/bpf/verifier.c-2746-\tif (!offset)\nkernel/bpf/verifier.c:2747:\t\treturn btf_vmlinux ?: ERR_PTR(-ENOENT);\nkernel/bpf/verifier.c-2748-\tif (offset \u003c 0)\n--\nkernel/bpf/verifier.c=2855=int bpf_add_kfunc_call(struct bpf_verifier_env *env, u32 func_id, u16 offset)\n--\nkernel/bpf/verifier.c-2870-\tif (!tab) {\nkernel/bpf/verifier.c:2871:\t\tif (!btf_vmlinux) {\nkernel/bpf/verifier.c-2872-\t\t\tverbose(env, \"calling kernel function is not supported without CONFIG_DEBUG_INFO_BTF\\n\");\n--\nkernel/bpf/verifier.c=6241=static int check_ptr_to_map_access(struct bpf_verifier_env *env,\n--\nkernel/bpf/verifier.c-6254-\nkernel/bpf/verifier.c:6255:\tif (!btf_vmlinux) {\nkernel/bpf/verifier.c-6256-\t\tverbose(env, \"map_ptr access not supported without CONFIG_DEBUG_INFO_BTF\\n\");\n--\nkernel/bpf/verifier.c-6265-\nkernel/bpf/verifier.c:6266:\tt = btf_type_by_id(btf_vmlinux, *map-\u003eops-\u003emap_btf_id);\nkernel/bpf/verifier.c:6267:\ttname = btf_name_by_offset(btf_vmlinux, t-\u003ename_off);\nkernel/bpf/verifier.c-6268-\n--\nkernel/bpf/verifier.c-6289-\tret = mark_btf_ld_reg(env, \u0026map_reg, 0, PTR_TO_BTF_ID,\nkernel/bpf/verifier.c:6290:\t\t\t      btf_vmlinux, *map-\u003eops-\u003emap_btf_id, 0);\nkernel/bpf/verifier.c-6291-\tif (ret \u003c 0)\n--\nkernel/bpf/verifier.c-6297-\tif (value_regno \u003e= 0) {\nkernel/bpf/verifier.c:6298:\t\tret = mark_btf_ld_reg(env, regs, value_regno, ret, btf_vmlinux, btf_id, flag);\nkernel/bpf/verifier.c-6299-\t\tif (ret \u003c 0)\n--\nkernel/bpf/verifier.c=8905=static int check_func_arg(struct bpf_verifier_env *env, u32 arg, u32 slot, u32 prev_slot,\n--\nkernel/bpf/verifier.c-9048-\t\tconst u32 *arg_btf_id = fn-\u003earg_btf_id[arg];\nkernel/bpf/verifier.c:9049:\t\tconst struct btf *arg_btf = meta-\u003ebtf ?: btf_vmlinux;\nkernel/bpf/verifier.c-9050-\n--\nkernel/bpf/verifier.c-9177-\t\t}\nkernel/bpf/verifier.c:9178:\t\tif (meta-\u003ebtf == btf_vmlinux) {\nkernel/bpf/verifier.c-9179-\t\t\tmeta-\u003earg_btf = reg-\u003ebtf;\n--\nkernel/bpf/verifier.c=10334=static int btf_check_func_arg_match(struct bpf_verifier_env *env, int subprog,\n--\nkernel/bpf/verifier.c-10452-\t\t\t\terr = process_arg_ptr_to_btf_id(env, reg, argno, arg-\u003earg_type,\nkernel/bpf/verifier.c:10453:\t\t\t\t\t\t\t\tbtf_vmlinux, arg-\u003ebtf_id,\nkernel/bpf/verifier.c-10454-\t\t\t\t\t\t\t\t\u0026meta, env-\u003einsn_idx);\n--\nkernel/bpf/verifier.c=10827=static int set_find_vma_callback_state(struct bpf_verifier_env *env,\n--\nkernel/bpf/verifier.c-10840-\t__mark_reg_known_zero(\u0026callee-\u003eregs[BPF_REG_2]);\nkernel/bpf/verifier.c:10841:\tcallee-\u003eregs[BPF_REG_2].btf =  btf_vmlinux;\nkernel/bpf/verifier.c-10842-\tcallee-\u003eregs[BPF_REG_2].btf_id = btf_tracing_ids[BTF_TRACING_TYPE_VMA];\n--\nkernel/bpf/verifier.c=11508=static int check_helper_call(struct bpf_verifier_env *env, struct bpf_insn *insn,\n--\nkernel/bpf/verifier.c-11891-\t\t\t}\nkernel/bpf/verifier.c:11892:\t\t\tret_btf = btf_vmlinux;\nkernel/bpf/verifier.c-11893-\t\t\tret_btf_id = *fn-\u003eret_btf_id;\n--\nkernel/bpf/verifier.c=12221=static bool __is_kfunc_ptr_arg_type(const struct btf *btf,\n--\nkernel/bpf/verifier.c-12234-\t\treturn false;\nkernel/bpf/verifier.c:12235:\treturn btf_types_are_same(btf, res_id, btf_vmlinux, kf_arg_btf_ids[type]);\nkernel/bpf/verifier.c-12236-}\n--\nkernel/bpf/verifier.c=12283=static bool is_rbtree_node_type(const struct btf_type *t)\nkernel/bpf/verifier.c-12284-{\nkernel/bpf/verifier.c:12285:\treturn t == btf_type_by_id(btf_vmlinux, kf_arg_btf_ids[KF_ARG_RB_NODE_ID]);\nkernel/bpf/verifier.c-12286-}\n--\nkernel/bpf/verifier.c=12288=static bool is_list_node_type(const struct btf_type *t)\nkernel/bpf/verifier.c-12289-{\nkernel/bpf/verifier.c:12290:\treturn t == btf_type_by_id(btf_vmlinux, kf_arg_btf_ids[KF_ARG_LIST_NODE_ID]);\nkernel/bpf/verifier.c-12291-}\n--\nkernel/bpf/verifier.c=12433=static int resolve_func_arg_type(struct bpf_verifier_env *env,\n--\nkernel/bpf/verifier.c-12456-\tref_id = *meta-\u003efn-\u003earg_btf_id[arg];\nkernel/bpf/verifier.c:12457:\tbtf = is_kfunc_arg_map(meta-\u003ebtf, \u0026args[arg]) ? btf_vmlinux : meta-\u003ebtf;\nkernel/bpf/verifier.c-12458-\tref_t = btf_type_skip_modifiers(btf, ref_id, \u0026ref_id);\n--\nkernel/bpf/verifier.c=13117=static int process_arg_ptr_to_btf_id(struct bpf_verifier_env *env, struct bpf_reg_state *reg,\n--\nkernel/bpf/verifier.c-13131-\t} else {\nkernel/bpf/verifier.c:13132:\t\treg_btf = btf_vmlinux;\nkernel/bpf/verifier.c-13133-\t\treg_btf_id = *reg2btf_ids[base_type(reg-\u003etype)];\n--\nkernel/bpf/verifier.c=13514=__process_kf_arg_ptr_to_graph_root(struct bpf_verifier_env *env,\n--\nkernel/bpf/verifier.c-13524-\nkernel/bpf/verifier.c:13525:\tif (meta-\u003ebtf != btf_vmlinux) {\nkernel/bpf/verifier.c-13526-\t\tverifier_bug(env, \"unexpected btf mismatch in kfunc call\");\n--\nkernel/bpf/verifier.c=13581=__process_kf_arg_ptr_to_graph_node(struct bpf_verifier_env *env,\n--\nkernel/bpf/verifier.c-13592-\nkernel/bpf/verifier.c:13593:\tif (meta-\u003ebtf != btf_vmlinux) {\nkernel/bpf/verifier.c-13594-\t\tverifier_bug(env, \"unexpected btf mismatch in kfunc call\");\n--\nkernel/bpf/verifier.c=13920=static int check_special_kfunc(struct bpf_verifier_env *env, struct bpf_call_arg_meta *meta,\n--\nkernel/bpf/verifier.c-13926-\nkernel/bpf/verifier.c:13927:\tif (meta-\u003ebtf != btf_vmlinux)\nkernel/bpf/verifier.c-13928-\t\treturn 0;\n--\nkernel/bpf/verifier.c=14091=static int check_kfunc_call(struct bpf_verifier_env *env, struct bpf_insn *insn,\n--\nkernel/bpf/verifier.c-14350-\tif (is_kfunc_acquire(\u0026meta) \u0026\u0026 !btf_type_is_struct_ptr(meta.btf, t)) {\nkernel/bpf/verifier.c:14351:\t\tif (meta.btf != btf_vmlinux ||\nkernel/bpf/verifier.c-14352-\t\t    (!is_bpf_obj_new_kfunc(meta.func_id) \u0026\u0026\n--\nkernel/bpf/verifier.c-14361-\t\tret_nregs = mark_kfunc_ret_regs(env, regs, t-\u003esize);\nkernel/bpf/verifier.c:14362:\t\tif (meta.btf == btf_vmlinux \u0026\u0026 (meta.func_id == special_kfunc_list[KF_bpf_res_spin_lock] ||\nkernel/bpf/verifier.c-14363-\t\t    meta.func_id == special_kfunc_list[KF_bpf_res_spin_lock_irqsave]))\n--\nkernel/bpf/verifier.c-14519-\t} else if (btf_type_is_void(t)) {\nkernel/bpf/verifier.c:14520:\t\tif (meta.btf == btf_vmlinux) {\nkernel/bpf/verifier.c-14521-\t\t\tif (is_bpf_obj_drop_kfunc(meta.func_id) ||\n--\nkernel/bpf/verifier.c=19120=static int check_pseudo_btf_id(struct bpf_verifier_env *env,\n--\nkernel/bpf/verifier.c-19135-\t} else {\nkernel/bpf/verifier.c:19136:\t\tif (!btf_vmlinux) {\nkernel/bpf/verifier.c-19137-\t\t\tverbose(env, \"kernel is missing BTF, make sure CONFIG_DEBUG_INFO_BTF=y is specified in Kconfig.\\n\");\n--\nkernel/bpf/verifier.c-19139-\t\t}\nkernel/bpf/verifier.c:19140:\t\tbtf_get(btf_vmlinux);\nkernel/bpf/verifier.c:19141:\t\tbtf = btf_vmlinux;\nkernel/bpf/verifier.c-19142-\t}\n--\nkernel/bpf/verifier.c=19525=static int check_insn_fields(struct bpf_verifier_env *env, struct bpf_insn *insn)\n--\nkernel/bpf/verifier.c-19582- *\nkernel/bpf/verifier.c:19583: * NOTE: btf_vmlinux is required for converting pseudo btf_id.\nkernel/bpf/verifier.c-19584- */\n--\nkernel/bpf/verifier.c=19835=static int do_check_common(struct bpf_verifier_env *env, int subprog)\n--\nkernel/bpf/verifier.c-19930-\t\t\t\tmark_reg_known_zero(env, regs, i);\nkernel/bpf/verifier.c:19931:\t\t\t\treg-\u003ebtf = bpf_get_btf_vmlinux(); /* can't fail at this point */\nkernel/bpf/verifier.c-19932-\t\t\t\treg-\u003ebtf_id = arg-\u003ebtf_id;\n--\nkernel/bpf/verifier.c=20974=int bpf_check_attach_btf_id_multi(struct btf *btf, struct bpf_prog *prog, u32 btf_id,\n--\nkernel/bpf/verifier.c-21030-\nkernel/bpf/verifier.c:21031:struct btf *bpf_get_btf_vmlinux(void)\nkernel/bpf/verifier.c-21032-{\nkernel/bpf/verifier.c-21033-\t/* Pairs with the smp_store_release() on the parse path below. */\nkernel/bpf/verifier.c:21034:\tstruct btf *btf = smp_load_acquire(\u0026btf_vmlinux);\nkernel/bpf/verifier.c-21035-\nkernel/bpf/verifier.c-21036-\tif (!btf \u0026\u0026 IS_ENABLED(CONFIG_DEBUG_INFO_BTF)) {\nkernel/bpf/verifier.c:21037:\t\tmutex_lock(\u0026btf_vmlinux_lock);\nkernel/bpf/verifier.c:21038:\t\tbtf = btf_vmlinux;\nkernel/bpf/verifier.c-21039-\t\tif (!btf) {\n--\nkernel/bpf/verifier.c-21046-\t\t\t */\nkernel/bpf/verifier.c:21047:\t\t\tsmp_store_release(\u0026btf_vmlinux, btf);\nkernel/bpf/verifier.c-21048-\t\t}\nkernel/bpf/verifier.c:21049:\t\tmutex_unlock(\u0026btf_vmlinux_lock);\nkernel/bpf/verifier.c-21050-\t}\n--\nkernel/bpf/verifier.c=21563=int bpf_check(struct bpf_prog **prog, union bpf_attr *attr, bpfptr_t uattr,\n--\nkernel/bpf/verifier.c-21624-\nkernel/bpf/verifier.c:21625:\tbpf_get_btf_vmlinux();\nkernel/bpf/verifier.c-21626-\n--\nkernel/bpf/verifier.c-21645-\nkernel/bpf/verifier.c:21646:\tif (IS_ERR(btf_vmlinux)) {\nkernel/bpf/verifier.c-21647-\t\t/* Either gcc or pahole or kernel are broken. */\nkernel/bpf/verifier.c-21648-\t\tverbose(env, \"in-kernel BTF is malformed\\n\");\nkernel/bpf/verifier.c:21649:\t\tret = PTR_ERR(btf_vmlinux);\nkernel/bpf/verifier.c-21650-\t\tgoto skip_full_check;\n"
}

gemini-3.8-flash

null

null

							input: 61368
							output: 179
							thoughts: 1793
						

**BPF Tracing Vulnerability Assessment and Fuzzing Strategy**

Okay, so I need to assess this patch related to BPF tracing and determine a fuzzing strategy. First, the core of the issue seems to stem from the interaction between `bpf_skb_output` (specifically, `bpf_skb_event_output`) and `fexit` BPF programs.  `CONFIG_DEBUG_INFO_BTF` is a must-have, since this all hinges on BPF tracing and BTF IDs.  I've confirmed that we need to enable `BPF_SYSCALL`, `BPF_EVENTS`, `DEBUG_INFO_BTF`, and `NET`.  `BPF_EVENTS` depends on `KPROBE_EVENTS` or `UPROBE_EVENTS` *and* `PERF_EVENTS`, which is standard.

The patch itself focuses on preventing use-after-free issues when `bpf_skb_output` is called from an `fexit` program because the kernel might have freed or consumed the `sk_buff` pointer. Essentially, if a tracing program runs *after* the target function has executed, it's unsafe to dereference the `sk_buff`.  `tracing_prog_func_proto` is the key function here; it's where the check `tracing_prog_may_run_after_target` is introduced. Since `tracing_prog_func_proto` is non-static, it will definitely be a symbol in vmlinux.  The relevant code is in `kernel/trace/bpf_trace.c` and selftests, `tools/testing/selftests/bpf/progs/verifier_helper_restricted.c`.

I've examined the code. The patch adds a check within `tracing_prog_func_proto` to determine if a tracing program might run after the target function has finished. If so, `bpf_skb_output` isn't allowed. `tracing_prog_may_run_after_target` is where this determination is made.  It seems the vulnerability arises when an `fexit` BPF program calls `bpf_skb_output`.  `fentry` programs are not affected.

The critical path for fuzzing is definitely the execution of `tracing_prog_func_proto`, particularly the check for those types of `expected_attach_type` and the conditional call to `bpf_skb_output`.  This is reachable because privileged users can load tracing programs via the `sys_bpf` syscall with `BPF_PROG_TYPE_TRACING` and `BPF_TRACE_FEXIT` (or `BPF_TRACE_FENTRY`).

Therefore, this patch is worth fuzzing. The key functions to target are `tracing_prog_func_proto`, and potentially `bpf_skb_event_output`, to ensure the logic and checks are correctly implemented, and that no similar issues occur with other attach types or helper functions, or if this restriction can be bypassed, or that we cause verifier regressions.

To be clear:
*   `WorthFuzzing`: **true**
*   `FocusSymbols`: `["tracing_prog_func_proto"]` (and optionally `bpf_skb_event_output`)
*   `EnableConfigs`: `["BPF_SYSCALL", "BPF_EVENTS", "DEBUG_INFO_BTF", "NET"]`
All configs are standard. I'm satisfied. Time to set-results.

{
  "EnableConfigs": [
    "BPF_SYSCALL",
    "BPF_EVENTS",
    "DEBUG_INFO_BTF",
    "NET"
  ],
  "FocusSymbols": [
    "tracing_prog_func_proto",
    "bpf_skb_event_output"
  ],
  "Reasoning": "The patch updates BPF tracing verifier helper validation by introducing tracing_prog_may_run_after_target() to disallow bpf_skb_output in tracing programs that run after the target function (such as BPF_TRACE_FEXIT and BPF_TRACE_FSESSION), where skb pointer arguments may have already been consumed/freed. This modifies reachable logic in the core BPF subsystem exercised via the bpf() syscall during program verification and execution.",
  "WorthFuzzing": true
}

{
  "EnableConfigs": [
    "BPF_SYSCALL",
    "BPF_EVENTS",
    "DEBUG_INFO_BTF",
    "NET"
  ],
  "FocusSymbols": [
    "tracing_prog_func_proto",
    "bpf_skb_event_output"
  ],
  "Reasoning": "The patch updates BPF tracing verifier helper validation by introducing tracing_prog_may_run_after_target() to disallow bpf_skb_output in tracing programs that run after the target function (such as BPF_TRACE_FEXIT and BPF_TRACE_FSESSION), where skb pointer arguments may have already been consumed/freed. This modifies reachable logic in the core BPF subsystem exercised via the bpf() syscall during program verification and execution.",
  "WorthFuzzing": true
}

{
  "WorthFuzzing": true
}

null

core

null

{
  "KMSANReasoning": "The patch modifies `tracing_prog_func_proto` to forbid `bpf_skb_output` in tracing programs that run after the target function finishes execution (`BPF_TRACE_FEXIT`, `BPF_TRACE_FEXIT_MULTI`, `BPF_TRACE_FSESSION`, `BPF_TRACE_FSESSION_MULTI`). This prevents potential use-after-free (UAF) accesses where a target function consumes or frees the `skb` argument before the exit/session tracing program executes.\n\nUse-after-free conditions on freed kernel objects are tracked and detected by KASAN. The patch adds a verifier check and does not allocate memory, initialize kernel structures, alter buffer bounds, or expose any uninitialized stack or heap data to userspace or control flow. Since there is no risk of uninitialized memory reads or information disclosure, a dedicated KMSAN fuzzing session is not warranted.",
  "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 a038671b729c160aefbc07025a4e09ed56b52568
Author: syz-cluster <triage@syzkaller.com>
Date:   Thu Sep 24 03:40:25 2026 +0000

    syz-cluster: applied patch under review

diff --git a/kernel/trace/bpf_trace.c b/kernel/trace/bpf_trace.c
index 29260951aa871..29c83e2938cd0 100644
--- a/kernel/trace/bpf_trace.c
+++ b/kernel/trace/bpf_trace.c
@@ -1339,6 +1339,20 @@ static inline bool is_trace_fsession(const struct bpf_prog *prog)
 		prog->expected_attach_type == BPF_TRACE_FSESSION_MULTI);
 }
 
+static inline bool tracing_prog_may_run_after_target(const struct bpf_prog *prog)
+{
+	/* The target may consume pointer arguments before these programs run. */
+	switch (prog->expected_attach_type) {
+	case BPF_TRACE_FEXIT:
+	case BPF_TRACE_FEXIT_MULTI:
+	case BPF_TRACE_FSESSION:
+	case BPF_TRACE_FSESSION_MULTI:
+		return true;
+	default:
+		return false;
+	}
+}
+
 static const struct bpf_func_proto *
 kprobe_prog_func_proto(enum bpf_func_id func_id, const struct bpf_prog *prog)
 {
@@ -1730,6 +1744,8 @@ tracing_prog_func_proto(enum bpf_func_id func_id, const struct bpf_prog *prog)
 	switch (func_id) {
 #ifdef CONFIG_NET
 	case BPF_FUNC_skb_output:
+		if (tracing_prog_may_run_after_target(prog))
+			return NULL;
 		return &bpf_skb_output_proto;
 	case BPF_FUNC_xdp_output:
 		return &bpf_xdp_output_proto;
diff --git a/tools/testing/selftests/bpf/progs/verifier_helper_restricted.c b/tools/testing/selftests/bpf/progs/verifier_helper_restricted.c
index 889c9b78b912e..058e71927cd5c 100644
--- a/tools/testing/selftests/bpf/progs/verifier_helper_restricted.c
+++ b/tools/testing/selftests/bpf/progs/verifier_helper_restricted.c
@@ -3,6 +3,7 @@
 
 #include <linux/bpf.h>
 #include <bpf/bpf_helpers.h>
+#include <bpf/bpf_tracing.h>
 #include "bpf_misc.h"
 
 struct val {
@@ -17,6 +18,13 @@ struct {
 	__type(value, struct val);
 } map_spin_lock SEC(".maps");
 
+struct {
+	__uint(type, BPF_MAP_TYPE_PERF_EVENT_ARRAY);
+	__uint(max_entries, 1);
+	__type(key, __u32);
+	__type(value, __u32);
+} perf_event_map SEC(".maps");
+
 SEC("kprobe")
 __description("bpf_ktime_get_coarse_ns is forbidden in BPF_PROG_TYPE_KPROBE")
 __failure __msg("program of this type cannot use helper bpf_ktime_get_coarse_ns")
@@ -165,4 +173,28 @@ l0_%=:	exit;						\
 	: __clobber_all);
 }
 
+SEC("fentry/skb_tx_error")
+__description("bpf_skb_output is allowed in BPF_TRACE_FENTRY")
+__success
+int BPF_PROG(skb_output_fentry, void *skb)
+{
+	__u64 meta = 0;
+
+	bpf_skb_output(skb, &perf_event_map, BPF_F_CURRENT_CPU,
+		       &meta, sizeof(meta));
+	return 0;
+}
+
+SEC("fexit/skb_tx_error")
+__description("bpf_skb_output is forbidden in BPF_TRACE_FEXIT")
+__failure __msg("program of this type cannot use helper bpf_skb_output")
+int BPF_PROG(skb_output_fexit, void *skb)
+{
+	__u64 meta = 0;
+
+	bpf_skb_output(skb, &perf_event_map, BPF_F_CURRENT_CPU,
+		       &meta, sizeof(meta));
+	return 0;
+}
+
 char _license[] SEC("license") = "GPL";

gemini-3.8-flash

null

null

							input: 3070
							output: 39
							thoughts: 819
						

**KMSAN Fuzzing Evaluation for BPF Patch**

Okay, so I'm looking at this patch and my initial thought is: does this change warrant a dedicated KMSAN fuzzing session? Let's break it down.

Essentially, this patch modifies the `tracing_prog_func_proto` function within `bpf_trace.c`. Specifically, it concerns the `BPF_FUNC_skb_output` BPF function. The key here is the introduction of a new check: `tracing_prog_may_run_after_target(prog)`. This function seems to determine if the BPF program in question might execute *after* the target function, which is interesting.

If `tracing_prog_may_run_after_target(prog)` returns true (meaning the program is an `FEXIT`, `FEXIT_MULTI`, `FSESSION`, or `FSESSION_MULTI` type), the patch now returns `NULL` for the `bpf_skb_output` function. The comment provides the rationale: "The target may consume pointer arguments before these programs run." I see, this is a UAF issue. When the target function runs, the skb argument might be consumed (e.g., `kfree_skb`), and if the `FEXIT` or `FSESSION` BPF program then tries to use this *already-freed* pointer via `bpf_skb_output`, we've got a classic Use-After-Free scenario. The patch elegantly mitigates this by making the verifier reject any BPF program using `bpf_skb_output` in the mentioned context.

To decide on KMSAN fuzzing, I'll need to confirm that `bpf_skb_output` is only called within the contexts where this UAF could occur, and that this change alone doesn't trigger a new issue. I'll need to do some more digging around `tracing_prog_func_proto` and `bpf_skb_output_proto` to get a clearer picture. Given the nature of the fix, KMSAN fuzzing might be warranted to ensure this UAF protection is effective and doesn't introduce any new memory safety problems.

{
  "Expression": "bpf_skb_output_proto",
  "PathPrefix": "kernel/trace/bpf_trace.c"
}

{
  "Output": "kernel/trace/bpf_trace.c=1655=static const struct bpf_func_proto bpf_perf_event_output_proto_raw_tp = {\n--\nkernel/trace/bpf_trace.c-1665-\nkernel/trace/bpf_trace.c:1666:extern const struct bpf_func_proto bpf_skb_output_proto;\nkernel/trace/bpf_trace.c-1667-extern const struct bpf_func_proto bpf_xdp_output_proto;\n--\nkernel/trace/bpf_trace.c=1740=tracing_prog_func_proto(enum bpf_func_id func_id, const struct bpf_prog *prog)\n--\nkernel/trace/bpf_trace.c-1748-\t\t\treturn NULL;\nkernel/trace/bpf_trace.c:1749:\t\treturn \u0026bpf_skb_output_proto;\nkernel/trace/bpf_trace.c-1750-\tcase BPF_FUNC_xdp_output:\n"
}

gemini-3.8-flash

null

null

							input: 4673
							output: 39
							thoughts: 26
						

Okay, let's dive into this. Here's my take on those thoughts, as if they're my own:

**Analyzing `tracing_prog_func_proto` in `kernel/trace/bpf_trace.c`**

Alright, time to get my hands dirty. I need to take a look at `tracing_prog_func_proto` specifically within the context of `kernel/trace/bpf_trace.c`. I'm immediately thinking about how it fits into the broader BPF tracing architecture. Is this a critical struct definition? What functions use this? I'm anticipating that this is most likely the function prototype used for BPF programs attached to tracepoints or kprobes, given the naming convention. I'm keen to understand how it interfaces with the BPF VM, how it handles arguments, return values, and, most importantly, how it's integrated with the trace infrastructure. Knowing this function's exact signature is key to understanding the control flow and data manipulation within BPF trace programs. I need to figure out the calling conventions and understand how it handles the interaction between the kernel space and BPF programs running in the user space. This seems like a core piece of the tracing puzzle.

{
  "File": "kernel/trace/bpf_trace.c",
  "FirstLine": 1730,
  "LineCount": 40
}

{
  "Contents": "1730:\t\tcase BPF_FUNC_get_stack:\n1731:\t\t\treturn \u0026bpf_get_stack_proto_raw_tp;\n1732:\t\tcase BPF_FUNC_get_attach_cookie:\n1733:\t\t\treturn \u0026bpf_get_attach_cookie_proto_tracing;\n1734:\t\tdefault:\n1735:\t\t\treturn bpf_tracing_func_proto(func_id, prog);\n1736:\t\t}\n1737:\t}\n1738:\t\n1739:\tconst struct bpf_func_proto *\n1740:\ttracing_prog_func_proto(enum bpf_func_id func_id, const struct bpf_prog *prog)\n1741:\t{\n1742:\t\tconst struct bpf_func_proto *fn;\n1743:\t\n1744:\t\tswitch (func_id) {\n1745:\t#ifdef CONFIG_NET\n1746:\t\tcase BPF_FUNC_skb_output:\n1747:\t\t\tif (tracing_prog_may_run_after_target(prog))\n1748:\t\t\t\treturn NULL;\n1749:\t\t\treturn \u0026bpf_skb_output_proto;\n1750:\t\tcase BPF_FUNC_xdp_output:\n1751:\t\t\treturn \u0026bpf_xdp_output_proto;\n1752:\t\tcase BPF_FUNC_skc_to_tcp6_sock:\n1753:\t\t\treturn \u0026bpf_skc_to_tcp6_sock_proto;\n1754:\t\tcase BPF_FUNC_skc_to_tcp_sock:\n1755:\t\t\treturn \u0026bpf_skc_to_tcp_sock_proto;\n1756:\t\tcase BPF_FUNC_skc_to_tcp_timewait_sock:\n1757:\t\t\treturn \u0026bpf_skc_to_tcp_timewait_sock_proto;\n1758:\t\tcase BPF_FUNC_skc_to_tcp_request_sock:\n1759:\t\t\treturn \u0026bpf_skc_to_tcp_request_sock_proto;\n1760:\t\tcase BPF_FUNC_skc_to_udp6_sock:\n1761:\t\t\treturn \u0026bpf_skc_to_udp6_sock_proto;\n1762:\t\tcase BPF_FUNC_skc_to_unix_sock:\n1763:\t\t\treturn \u0026bpf_skc_to_unix_sock_proto;\n1764:\t\tcase BPF_FUNC_skc_to_mptcp_sock:\n1765:\t\t\treturn \u0026bpf_skc_to_mptcp_sock_proto;\n1766:\t\tcase BPF_FUNC_sk_storage_get:\n1767:\t\t\treturn \u0026bpf_sk_storage_get_tracing_proto;\n1768:\t\tcase BPF_FUNC_sk_storage_delete:\n1769:\t\t\treturn \u0026bpf_sk_storage_delete_tracing_proto;\n"
}

gemini-3.8-flash

null

null

							input: 5777
							output: 217
							thoughts: 757
						

**Analyzing the KMSAN Needs for a BPF Patch**

Okay, let's break this down. My initial assessment is that this patch, which restricts the `bpf_skb_output` helper in `fexit/fsession` BPF programs, is *unlikely* to require KMSAN. The core problem this patch addresses is a classic use-after-free (UAF) scenario. Essentially, a tracing program attached to a function that could free or consume an `skb` might attempt to access that same `skb` pointer after it's been invalidated, if `bpf_skb_output` is used. That's *textbook* KASAN territory.

My concern is always whether the patch itself introduces new potential KMSAN risks. Let me run through the usual suspects:

1.  **User-space exposure:** No, this patch is *restricting* a helper, not introducing new structures or data paths to userspace.
2.  **Uninitialized conditionals:** The code checks `prog->expected_attach_type`, which is a verified `bpf_prog` struct. No uninitialized memory issues here.
3.  **Complex data structures:** Again, no complex structures are being allocated or initialized in a way that might lead to later uninitialized reads.
4.  **Bounds/Length issues:** Nothing here alters existing buffers in a way that risks uninitialized byte accesses.

The patch author correctly noted that this change primarily aims to prevent use-after-free, which is already well-handled by KASAN, and that stack/heap structures touched are fully initialized. Therefore, there's no reason to flag this as a KMSAN issue.

The "NeedsKMSAN=false" criteria perfectly aligns. The patch deals with preventing an existing memory safety problem, not creating a new one. The UAF problem it addresses is *already* directly covered by KASAN.

The key is in understanding the distinction: the patch is restricting a *helper* to avoid a known KASAN-detectable bug, not introducing potential KMSAN-specific vulnerabilities like info-leaks. KASAN handles the dangling pointer issue. KMSAN is not applicable in this scenario.

{
  "KMSANReasoning": "The patch modifies `tracing_prog_func_proto` to forbid `bpf_skb_output` in tracing programs that run after the target function finishes execution (`BPF_TRACE_FEXIT`, `BPF_TRACE_FEXIT_MULTI`, `BPF_TRACE_FSESSION`, `BPF_TRACE_FSESSION_MULTI`). This prevents potential use-after-free (UAF) accesses where a target function consumes or frees the `skb` argument before the exit/session tracing program executes.\n\nUse-after-free conditions on freed kernel objects are tracked and detected by KASAN. The patch adds a verifier check and does not allocate memory, initialize kernel structures, alter buffer bounds, or expose any uninitialized stack or heap data to userspace or control flow. Since there is no risk of uninitialized memory reads or information disclosure, a dedicated KMSAN fuzzing session is not warranted.",
  "NeedsKMSAN": false
}

{
  "KMSANReasoning": "The patch modifies `tracing_prog_func_proto` to forbid `bpf_skb_output` in tracing programs that run after the target function finishes execution (`BPF_TRACE_FEXIT`, `BPF_TRACE_FEXIT_MULTI`, `BPF_TRACE_FSESSION`, `BPF_TRACE_FSESSION_MULTI`). This prevents potential use-after-free (UAF) accesses where a target function consumes or frees the `skb` argument before the exit/session tracing program executes.\n\nUse-after-free conditions on freed kernel objects are tracked and detected by KASAN. The patch adds a verifier check and does not allocate memory, initialize kernel structures, alter buffer bounds, or expose any uninitialized stack or heap data to userspace or control flow. Since there is no risk of uninitialized memory reads or information disclosure, a dedicated KMSAN fuzzing session is not warranted.",
  "NeedsKMSAN": false
}