AI Trajectory

null

{
  "EnableConfigs": null,
  "FocusSymbols": [],
  "KMSANReasoning": "",
  "NeedsKMSAN": false,
  "Reasoning": "The patch removes unused enum values (KF_bpf_arena_reserve_pages, KF_bpf_stream_vprintk, KF_bpf_stream_print_stack) and their corresponding BTF_ID entries from the special_kfunc_list in the BPF verifier. These entries were never referenced anywhere in the verifier code to apply any special logic, so their removal is a pure cleanup with no functional impact on the kernel's execution flow.",
  "WorthFuzzing": false
}

null

{
  "PatchDiff": "commit 9d6fda7f1e9c60503d0f455077a0a6e888ab8d46\nAuthor: syz-cluster \u003ctriage@syzkaller.com\u003e\nDate:   Wed Aug 12 19:39:39 2026 +0000\n\n    syz-cluster: applied patch under review\n\ndiff --git a/kernel/bpf/verifier.c b/kernel/bpf/verifier.c\nindex add3affc57035..8797ae08f2325 100644\n--- a/kernel/bpf/verifier.c\n+++ b/kernel/bpf/verifier.c\n@@ -11092,10 +11092,7 @@ enum special_kfunc_type {\n \tKF_bpf_task_work_schedule_resume,\n \tKF_bpf_arena_alloc_pages,\n \tKF_bpf_arena_free_pages,\n-\tKF_bpf_arena_reserve_pages,\n \tKF_bpf_session_is_return,\n-\tKF_bpf_stream_vprintk,\n-\tKF_bpf_stream_print_stack,\n };\n \n BTF_ID_LIST(special_kfunc_list)\n@@ -11185,14 +11182,11 @@ BTF_ID(func, bpf_task_work_schedule_signal)\n BTF_ID(func, bpf_task_work_schedule_resume)\n BTF_ID(func, bpf_arena_alloc_pages)\n BTF_ID(func, bpf_arena_free_pages)\n-BTF_ID(func, bpf_arena_reserve_pages)\n #ifdef CONFIG_BPF_EVENTS\n BTF_ID(func, bpf_session_is_return)\n #else\n BTF_ID_UNUSED\n #endif\n-BTF_ID(func, bpf_stream_vprintk)\n-BTF_ID(func, bpf_stream_print_stack)\n \n static bool is_bpf_obj_new_kfunc(u32 func_id)\n {\n"
}

best-expensive

null

{
  "EnableConfigs": null,
  "FocusSymbols": [],
  "Reasoning": "The patch removes unused enum values (KF_bpf_arena_reserve_pages, KF_bpf_stream_vprintk, KF_bpf_stream_print_stack) and their corresponding BTF_ID entries from the special_kfunc_list in the BPF verifier. These entries were never referenced anywhere in the verifier code to apply any special logic, so their removal is a pure cleanup with no functional impact on the kernel's execution flow.",
  "WorthFuzzing": false
}

You are an expert Linux kernel maintainer.
Your job is to review a provided patch series and determine
if it makes functional changes to the kernel that should be fuzzed.

IMPORTANT: The changes have ALREADY been applied and committed as the HEAD commit in
your workspace. Do NOT rely on your internal knowledge of the kernel. You must actively
use your code access tools to examine the actual source code and confirm any assumptions.

Return WorthFuzzing=false if the patch only contains:
- Modifications to Documentation/, Kconfig files, or code comments.
- Purely decorative changes, such as logging (e.g., pr_err, printk) or tracepoints.
- Changes to numeric constants or macros that do not functionally alter execution flow.
- Code paths that are impossible to reach in virtualized environments like GCE or QEMU,
  even when utilizing software-emulated hardware (e.g., usb gadget, mac80211_hwsim).
- Code in vendor-specific PCIe switch, SmartNIC, or GPU drivers (e.g., mlxsw, pds_core, qed,
  ionic, amdgpu) that require physical PCIe hardware cards not emulated in standard QEMU.
- Driver .remove, .shutdown, or pci_unregister_driver teardown callbacks (e.g., igb_remove)
  that are executed only during PCI hot-unplug or sysfs driver unbind operations.

If it modifies reachable core kernel logic, drivers, or architectures, use your code search
tools to verify the code can be executed, then return WorthFuzzing=true.

When returning WorthFuzzing=true, you MUST ALSO:
1. Extract any specific kernel functions that should be heavily fuzzed into FocusSymbols.
   Avoid listing generic hot-path functions to prevent skewed test distributions.
   Prefer non-static, non-inlined API entrypoint functions over internal static helper functions
   (which are inlined by the compiler and do not have distinct symbol addresses).
2. Identify any specific CONFIG_ options required to properly test this new/modified feature.
   Go and look into the Kconfig files and check for ifdefs around the code, do not make assumptions.
   Also check "depends on" lines in Kconfig to include any non-standard parent subsystem configs
   needed for Kbuild to compile the code statically into vmlinux. List them in the EnableConfigs
   output array, and DO NOT add a '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.

For your convenience, here is the diff of the changes:
commit 9d6fda7f1e9c60503d0f455077a0a6e888ab8d46
Author: syz-cluster <triage@syzkaller.com>
Date:   Wed Aug 12 19:39:39 2026 +0000

    syz-cluster: applied patch under review

diff --git a/kernel/bpf/verifier.c b/kernel/bpf/verifier.c
index add3affc57035..8797ae08f2325 100644
--- a/kernel/bpf/verifier.c
+++ b/kernel/bpf/verifier.c
@@ -11092,10 +11092,7 @@ enum special_kfunc_type {
 	KF_bpf_task_work_schedule_resume,
 	KF_bpf_arena_alloc_pages,
 	KF_bpf_arena_free_pages,
-	KF_bpf_arena_reserve_pages,
 	KF_bpf_session_is_return,
-	KF_bpf_stream_vprintk,
-	KF_bpf_stream_print_stack,
 };
 
 BTF_ID_LIST(special_kfunc_list)
@@ -11185,14 +11182,11 @@ BTF_ID(func, bpf_task_work_schedule_signal)
 BTF_ID(func, bpf_task_work_schedule_resume)
 BTF_ID(func, bpf_arena_alloc_pages)
 BTF_ID(func, bpf_arena_free_pages)
-BTF_ID(func, bpf_arena_reserve_pages)
 #ifdef CONFIG_BPF_EVENTS
 BTF_ID(func, bpf_session_is_return)
 #else
 BTF_ID_UNUSED
 #endif
-BTF_ID(func, bpf_stream_vprintk)
-BTF_ID(func, bpf_stream_print_stack)
 
 static bool is_bpf_obj_new_kfunc(u32 func_id)
 {

gemini-3.1-pro-preview

null

null

							input: 2216
							output: 113
							thoughts: 166
						

**Analyzing the BPF Verifier Patch**

Okay, so I've got this patch here that's touching `kernel/bpf/verifier.c`. Immediately, my spidey senses are tingling. Anything modifying the BPF verifier is something to pay close attention to. It seems this patch is cleaning up some kfunc types: specifically, it's axing `KF_bpf_arena_reserve_pages`, `KF_bpf_stream_vprintk`, and `KF_bpf_stream_print_stack`, along with their associated `BTF_ID` entries. That's a focused set of changes, at least.

Let me quickly confirm that these removals are the *only* changes in the patch. Ah, yes, just the kfunc and BTF_ID removals. Now, the real question pops up. Does this have a functional impact or is it just cleanup? Removing kfunc types almost certainly means removing support, or specialized handling, for those particular functions within the BPF system. I need to understand what functionality is now gone.

Right, so I need to go back and check `kernel/bpf/verifier.c` to see how those `KF_` enums were being used, and what that means in terms of the broader BPF ecosystem. Time to dig in and understand the ramifications.

no matches

{
  "Expression": "KF_bpf_arena_reserve_pages",
  "PathPrefix": "kernel/bpf/verifier.c"
}

{
  "error": "no matches"
}

no matches

{
  "Expression": "KF_bpf_stream_vprintk",
  "PathPrefix": "kernel/bpf/verifier.c"
}

{
  "error": "no matches"
}

no matches

{
  "Expression": "KF_bpf_stream_print_stack",
  "PathPrefix": "kernel/bpf/verifier.c"
}

{
  "error": "no matches"
}

gemini-3.1-pro-preview

null

null

							input: 2815
							output: 89
							thoughts: 118
						

**Investigating the Disappearance of Those Definitions**

Okay, so I see these definitions are gone, removed in a patch. That explains why they're not lining up with what I'm currently looking at. First things first, let's confirm that these definitions weren't simply refactored or moved within `kernel/bpf/verifier.c` before the patch. Were they actually *used* anywhere else in that file *before* this change? I have a hunch... if they were yanked from the enum and the BTF_ID list, and that patch is the only one, then it strongly suggests they were *only* defined there. Basically, they were dead code, never actually referenced in the verifier's logic. Still, let's be sure. Just because they weren't in that particular file doesn't mean they weren't in another. I'll need to expand my search to all related files.

no matches

{
  "Expression": "KF_bpf_arena_reserve_pages",
  "PathPrefix": ""
}

{
  "error": "no matches"
}

no matches

{
  "Expression": "KF_bpf_stream_vprintk",
  "PathPrefix": ""
}

{
  "error": "no matches"
}

no matches

{
  "Expression": "KF_bpf_stream_print_stack",
  "PathPrefix": ""
}

{
  "error": "no matches"
}

gemini-3.1-pro-preview

null

null

							input: 3258
							output: 34
							thoughts: 92
						

**Analyzing Unused Enums and BTF_IDs**

Okay, so I'm looking at these enums and BTF_IDs, and it seems like they're just sitting there, unused. A bit of a housekeeping issue, perhaps. But then I remember how the system is designed. If these things were *actually* in the `special_kfunc_list`, they would have been tied to a specific entry: `special_kfunc_list[KF_...]`. Now, here's the key: if we never actually *used* them, like for instance, assigning one to `special_kfunc_list[KF_bpf_stream_vprintk]`, then their removal shouldn't affect anything at runtime. It's just dead code, essentially. To be absolutely sure, I'm going to double-check the `special_kfunc_list` to confirm this hunch. Let's make sure it's as I expect.

{
  "Expression": "special_kfunc_list",
  "PathPrefix": "kernel/bpf/verifier.c"
}

{
  "Output": "kernel/bpf/verifier.c=11028=enum special_kfunc_type {\n--\nkernel/bpf/verifier.c-11097-\nkernel/bpf/verifier.c:11098:BTF_ID_LIST(special_kfunc_list)\nkernel/bpf/verifier.c-11099-BTF_ID(func, bpf_obj_new_impl)\n--\nkernel/bpf/verifier.c=11191=static bool is_bpf_obj_new_kfunc(u32 func_id)\nkernel/bpf/verifier.c-11192-{\nkernel/bpf/verifier.c:11193:\treturn func_id == special_kfunc_list[KF_bpf_obj_new] ||\nkernel/bpf/verifier.c:11194:\t       func_id == special_kfunc_list[KF_bpf_obj_new_impl];\nkernel/bpf/verifier.c-11195-}\n--\nkernel/bpf/verifier.c=11197=static bool is_bpf_percpu_obj_new_kfunc(u32 func_id)\nkernel/bpf/verifier.c-11198-{\nkernel/bpf/verifier.c:11199:\treturn func_id == special_kfunc_list[KF_bpf_percpu_obj_new] ||\nkernel/bpf/verifier.c:11200:\t       func_id == special_kfunc_list[KF_bpf_percpu_obj_new_impl];\nkernel/bpf/verifier.c-11201-}\n--\nkernel/bpf/verifier.c=11203=static bool is_bpf_obj_drop_kfunc(u32 func_id)\nkernel/bpf/verifier.c-11204-{\nkernel/bpf/verifier.c:11205:\treturn func_id == special_kfunc_list[KF_bpf_obj_drop] ||\nkernel/bpf/verifier.c:11206:\t       func_id == special_kfunc_list[KF_bpf_obj_drop_impl];\nkernel/bpf/verifier.c-11207-}\n--\nkernel/bpf/verifier.c=11209=static bool is_bpf_percpu_obj_drop_kfunc(u32 func_id)\nkernel/bpf/verifier.c-11210-{\nkernel/bpf/verifier.c:11211:\treturn func_id == special_kfunc_list[KF_bpf_percpu_obj_drop] ||\nkernel/bpf/verifier.c:11212:\t       func_id == special_kfunc_list[KF_bpf_percpu_obj_drop_impl];\nkernel/bpf/verifier.c-11213-}\n--\nkernel/bpf/verifier.c=11215=static bool is_bpf_refcount_acquire_kfunc(u32 func_id)\nkernel/bpf/verifier.c-11216-{\nkernel/bpf/verifier.c:11217:\treturn func_id == special_kfunc_list[KF_bpf_refcount_acquire] ||\nkernel/bpf/verifier.c:11218:\t       func_id == special_kfunc_list[KF_bpf_refcount_acquire_impl];\nkernel/bpf/verifier.c-11219-}\n--\nkernel/bpf/verifier.c=11221=static bool is_bpf_list_push_kfunc(u32 func_id)\nkernel/bpf/verifier.c-11222-{\nkernel/bpf/verifier.c:11223:\treturn func_id == special_kfunc_list[KF_bpf_list_push_front] ||\nkernel/bpf/verifier.c:11224:\t       func_id == special_kfunc_list[KF_bpf_list_push_front_impl] ||\nkernel/bpf/verifier.c:11225:\t       func_id == special_kfunc_list[KF_bpf_list_push_back] ||\nkernel/bpf/verifier.c:11226:\t       func_id == special_kfunc_list[KF_bpf_list_push_back_impl] ||\nkernel/bpf/verifier.c:11227:\t       func_id == special_kfunc_list[KF_bpf_list_add];\nkernel/bpf/verifier.c-11228-}\n--\nkernel/bpf/verifier.c=11230=static bool is_bpf_rbtree_add_kfunc(u32 func_id)\nkernel/bpf/verifier.c-11231-{\nkernel/bpf/verifier.c:11232:\treturn func_id == special_kfunc_list[KF_bpf_rbtree_add] ||\nkernel/bpf/verifier.c:11233:\t       func_id == special_kfunc_list[KF_bpf_rbtree_add_impl];\nkernel/bpf/verifier.c-11234-}\n--\nkernel/bpf/verifier.c=11236=static bool is_task_work_add_kfunc(u32 func_id)\nkernel/bpf/verifier.c-11237-{\nkernel/bpf/verifier.c:11238:\treturn func_id == special_kfunc_list[KF_bpf_task_work_schedule_signal] ||\nkernel/bpf/verifier.c:11239:\t       func_id == special_kfunc_list[KF_bpf_task_work_schedule_resume];\nkernel/bpf/verifier.c-11240-}\n--\nkernel/bpf/verifier.c=11250=static bool is_kfunc_bpf_rcu_read_lock(struct bpf_call_arg_meta *meta)\nkernel/bpf/verifier.c-11251-{\nkernel/bpf/verifier.c:11252:\treturn meta-\u003efunc_id == special_kfunc_list[KF_bpf_rcu_read_lock];\nkernel/bpf/verifier.c-11253-}\n--\nkernel/bpf/verifier.c=11255=static bool is_kfunc_bpf_rcu_read_unlock(struct bpf_call_arg_meta *meta)\nkernel/bpf/verifier.c-11256-{\nkernel/bpf/verifier.c:11257:\treturn meta-\u003efunc_id == special_kfunc_list[KF_bpf_rcu_read_unlock];\nkernel/bpf/verifier.c-11258-}\n--\nkernel/bpf/verifier.c=11260=static bool is_kfunc_bpf_preempt_disable(struct bpf_call_arg_meta *meta)\nkernel/bpf/verifier.c-11261-{\nkernel/bpf/verifier.c:11262:\treturn meta-\u003efunc_id == special_kfunc_list[KF_bpf_preempt_disable];\nkernel/bpf/verifier.c-11263-}\n--\nkernel/bpf/verifier.c=11265=static bool is_kfunc_bpf_preempt_enable(struct bpf_call_arg_meta *meta)\nkernel/bpf/verifier.c-11266-{\nkernel/bpf/verifier.c:11267:\treturn meta-\u003efunc_id == special_kfunc_list[KF_bpf_preempt_enable];\nkernel/bpf/verifier.c-11268-}\n--\nkernel/bpf/verifier.c=11270=bool bpf_is_kfunc_pkt_changing(struct bpf_call_arg_meta *meta)\nkernel/bpf/verifier.c-11271-{\nkernel/bpf/verifier.c:11272:\treturn meta-\u003efunc_id == special_kfunc_list[KF_bpf_xdp_pull_data];\nkernel/bpf/verifier.c-11273-}\n--\nkernel/bpf/verifier.c=11276=get_kfunc_arg_type(struct bpf_verifier_env *env, struct bpf_call_arg_meta *meta,\n--\nkernel/bpf/verifier.c-11312-\t */\nkernel/bpf/verifier.c:11313:\tif (meta-\u003efunc_id == special_kfunc_list[KF_bpf_cast_to_kern_ctx] ||\nkernel/bpf/verifier.c:11314:\t    meta-\u003efunc_id == special_kfunc_list[KF_bpf_session_is_return] ||\nkernel/bpf/verifier.c:11315:\t    meta-\u003efunc_id == special_kfunc_list[KF_bpf_session_cookie])\nkernel/bpf/verifier.c-11316-\t\targ_type = KF_ARG_PTR_TO_CTX;\n--\nkernel/bpf/verifier.c=11520=static int process_irq_flag(struct bpf_verifier_env *env, struct bpf_reg_state *reg, argno_t argno,\n--\nkernel/bpf/verifier.c-11525-\nkernel/bpf/verifier.c:11526:\tif (meta-\u003efunc_id == special_kfunc_list[KF_bpf_local_irq_save] ||\nkernel/bpf/verifier.c:11527:\t    meta-\u003efunc_id == special_kfunc_list[KF_bpf_res_spin_lock_irqsave]) {\nkernel/bpf/verifier.c-11528-\t\tirq_save = true;\nkernel/bpf/verifier.c:11529:\t\tif (meta-\u003efunc_id == special_kfunc_list[KF_bpf_res_spin_lock_irqsave])\nkernel/bpf/verifier.c-11530-\t\t\tkfunc_class = IRQ_LOCK_KFUNC;\nkernel/bpf/verifier.c:11531:\t} else if (meta-\u003efunc_id == special_kfunc_list[KF_bpf_local_irq_restore] ||\nkernel/bpf/verifier.c:11532:\t\t   meta-\u003efunc_id == special_kfunc_list[KF_bpf_res_spin_unlock_irqrestore]) {\nkernel/bpf/verifier.c-11533-\t\tirq_save = false;\nkernel/bpf/verifier.c:11534:\t\tif (meta-\u003efunc_id == special_kfunc_list[KF_bpf_res_spin_unlock_irqrestore])\nkernel/bpf/verifier.c-11535-\t\t\tkfunc_class = IRQ_LOCK_KFUNC;\n--\nkernel/bpf/verifier.c=11692=static bool is_bpf_list_api_kfunc(u32 btf_id)\n--\nkernel/bpf/verifier.c-11694-\treturn is_bpf_list_push_kfunc(btf_id) ||\nkernel/bpf/verifier.c:11695:\t       btf_id == special_kfunc_list[KF_bpf_list_pop_front] ||\nkernel/bpf/verifier.c:11696:\t       btf_id == special_kfunc_list[KF_bpf_list_pop_back] ||\nkernel/bpf/verifier.c:11697:\t       btf_id == special_kfunc_list[KF_bpf_list_del] ||\nkernel/bpf/verifier.c:11698:\t       btf_id == special_kfunc_list[KF_bpf_list_front] ||\nkernel/bpf/verifier.c:11699:\t       btf_id == special_kfunc_list[KF_bpf_list_back] ||\nkernel/bpf/verifier.c:11700:\t       btf_id == special_kfunc_list[KF_bpf_list_is_first] ||\nkernel/bpf/verifier.c:11701:\t       btf_id == special_kfunc_list[KF_bpf_list_is_last] ||\nkernel/bpf/verifier.c:11702:\t       btf_id == special_kfunc_list[KF_bpf_list_empty];\nkernel/bpf/verifier.c-11703-}\n--\nkernel/bpf/verifier.c=11705=static bool is_bpf_rbtree_api_kfunc(u32 btf_id)\n--\nkernel/bpf/verifier.c-11707-\treturn is_bpf_rbtree_add_kfunc(btf_id) ||\nkernel/bpf/verifier.c:11708:\t       btf_id == special_kfunc_list[KF_bpf_rbtree_remove] ||\nkernel/bpf/verifier.c:11709:\t       btf_id == special_kfunc_list[KF_bpf_rbtree_first] ||\nkernel/bpf/verifier.c:11710:\t       btf_id == special_kfunc_list[KF_bpf_rbtree_root] ||\nkernel/bpf/verifier.c:11711:\t       btf_id == special_kfunc_list[KF_bpf_rbtree_left] ||\nkernel/bpf/verifier.c:11712:\t       btf_id == special_kfunc_list[KF_bpf_rbtree_right];\nkernel/bpf/verifier.c-11713-}\n--\nkernel/bpf/verifier.c=11715=static bool is_bpf_res_spin_lock_kfunc(u32 btf_id)\nkernel/bpf/verifier.c-11716-{\nkernel/bpf/verifier.c:11717:\treturn btf_id == special_kfunc_list[KF_bpf_res_spin_lock] ||\nkernel/bpf/verifier.c:11718:\t       btf_id == special_kfunc_list[KF_bpf_res_spin_unlock] ||\nkernel/bpf/verifier.c:11719:\t       btf_id == special_kfunc_list[KF_bpf_res_spin_lock_irqsave] ||\nkernel/bpf/verifier.c:11720:\t       btf_id == special_kfunc_list[KF_bpf_res_spin_unlock_irqrestore];\nkernel/bpf/verifier.c-11721-}\n--\nkernel/bpf/verifier.c=11746=bool bpf_is_throw_kfunc(struct bpf_insn *insn)\n--\nkernel/bpf/verifier.c-11748-\treturn bpf_pseudo_kfunc_call(insn) \u0026\u0026 insn-\u003eoff == 0 \u0026\u0026\nkernel/bpf/verifier.c:11749:\t       insn-\u003eimm == special_kfunc_list[KF_bpf_throw];\nkernel/bpf/verifier.c-11750-}\n--\nkernel/bpf/verifier.c=11752=static bool is_bpf_wq_set_callback_kfunc(u32 btf_id)\nkernel/bpf/verifier.c-11753-{\nkernel/bpf/verifier.c:11754:\treturn btf_id == special_kfunc_list[KF_bpf_wq_set_callback];\nkernel/bpf/verifier.c-11755-}\n--\nkernel/bpf/verifier.c=11793=static bool check_kfunc_is_graph_node_api(struct bpf_verifier_env *env,\n--\nkernel/bpf/verifier.c-11801-\t\tret = is_bpf_list_push_kfunc(kfunc_btf_id) ||\nkernel/bpf/verifier.c:11802:\t\t      kfunc_btf_id == special_kfunc_list[KF_bpf_list_del] ||\nkernel/bpf/verifier.c:11803:\t\t      kfunc_btf_id == special_kfunc_list[KF_bpf_list_is_first] ||\nkernel/bpf/verifier.c:11804:\t\t      kfunc_btf_id == special_kfunc_list[KF_bpf_list_is_last];\nkernel/bpf/verifier.c-11805-\t\tbreak;\n--\nkernel/bpf/verifier.c-11807-\t\tret = (is_bpf_rbtree_add_kfunc(kfunc_btf_id) ||\nkernel/bpf/verifier.c:11808:\t\t       kfunc_btf_id == special_kfunc_list[KF_bpf_rbtree_remove] ||\nkernel/bpf/verifier.c:11809:\t\t       kfunc_btf_id == special_kfunc_list[KF_bpf_rbtree_left] ||\nkernel/bpf/verifier.c:11810:\t\t       kfunc_btf_id == special_kfunc_list[KF_bpf_rbtree_right]);\nkernel/bpf/verifier.c-11811-\t\tbreak;\n--\nkernel/bpf/verifier.c=11997=static int check_kfunc_args(struct bpf_verifier_env *env, struct bpf_call_arg_meta *meta,\n--\nkernel/bpf/verifier.c-12163-\nkernel/bpf/verifier.c:12164:\t\t\tif (meta-\u003efunc_id == special_kfunc_list[KF_bpf_cast_to_kern_ctx]) {\nkernel/bpf/verifier.c-12165-\t\t\t\tret = get_kern_ctx_btf_id(\u0026env-\u003elog, resolve_prog_type(env-\u003eprog));\n--\nkernel/bpf/verifier.c-12211-\nkernel/bpf/verifier.c:12212:\t\t\tif (meta-\u003efunc_id == special_kfunc_list[KF_bpf_dynptr_from_skb]) {\nkernel/bpf/verifier.c-12213-\t\t\t\tdynptr_arg_type |= DYNPTR_TYPE_SKB;\nkernel/bpf/verifier.c:12214:\t\t\t} else if (meta-\u003efunc_id == special_kfunc_list[KF_bpf_dynptr_from_xdp]) {\nkernel/bpf/verifier.c-12215-\t\t\t\tdynptr_arg_type |= DYNPTR_TYPE_XDP;\nkernel/bpf/verifier.c:12216:\t\t\t} else if (meta-\u003efunc_id == special_kfunc_list[KF_bpf_dynptr_from_skb_meta]) {\nkernel/bpf/verifier.c-12217-\t\t\t\tdynptr_arg_type |= DYNPTR_TYPE_SKB_META;\nkernel/bpf/verifier.c:12218:\t\t\t} else if (meta-\u003efunc_id == special_kfunc_list[KF_bpf_dynptr_from_file]) {\nkernel/bpf/verifier.c-12219-\t\t\t\tdynptr_arg_type |= DYNPTR_TYPE_FILE;\nkernel/bpf/verifier.c:12220:\t\t\t} else if (meta-\u003efunc_id == special_kfunc_list[KF_bpf_dynptr_file_discard]) {\nkernel/bpf/verifier.c-12221-\t\t\t\tdynptr_arg_type |= DYNPTR_TYPE_FILE | OBJ_RELEASE;\nkernel/bpf/verifier.c:12222:\t\t\t} else if (meta-\u003efunc_id == special_kfunc_list[KF_bpf_dynptr_clone] \u0026\u0026\nkernel/bpf/verifier.c-12223-\t\t\t\t   (dynptr_arg_type \u0026 MEM_UNINIT)) {\n--\nkernel/bpf/verifier.c-12240-\t\tcase KF_ARG_PTR_TO_ITER:\nkernel/bpf/verifier.c:12241:\t\t\tif (meta-\u003efunc_id == special_kfunc_list[KF_bpf_iter_css_task_new]) {\nkernel/bpf/verifier.c-12242-\t\t\t\tif (!check_css_task_iter_allowlist(env)) {\n--\nkernel/bpf/verifier.c-12520-\t\t\t\treturn -EFAULT;\nkernel/bpf/verifier.c:12521:\t\t\tif (meta-\u003efunc_id == special_kfunc_list[KF_bpf_res_spin_lock] ||\nkernel/bpf/verifier.c:12522:\t\t\t    meta-\u003efunc_id == special_kfunc_list[KF_bpf_res_spin_lock_irqsave])\nkernel/bpf/verifier.c-12523-\t\t\t\tflags |= PROCESS_SPIN_LOCK;\nkernel/bpf/verifier.c:12524:\t\t\tif (meta-\u003efunc_id == special_kfunc_list[KF_bpf_res_spin_lock_irqsave] ||\nkernel/bpf/verifier.c:12525:\t\t\t    meta-\u003efunc_id == special_kfunc_list[KF_bpf_res_spin_unlock_irqrestore])\nkernel/bpf/verifier.c-12526-\t\t\t\tflags |= PROCESS_LOCK_IRQ;\n--\nkernel/bpf/verifier.c=12762=static int check_special_kfunc(struct bpf_verifier_env *env, struct bpf_call_arg_meta *meta,\n--\nkernel/bpf/verifier.c-12867-\t\tmark_reg_graph_node(regs, BPF_REG_0, \u0026field-\u003egraph_root);\nkernel/bpf/verifier.c:12868:\t} else if (meta-\u003efunc_id == special_kfunc_list[KF_bpf_cast_to_kern_ctx]) {\nkernel/bpf/verifier.c-12869-\t\tmark_reg_known_zero(env, regs, BPF_REG_0);\n--\nkernel/bpf/verifier.c-12872-\t\tregs[BPF_REG_0].btf_id = meta-\u003eret_btf_id;\nkernel/bpf/verifier.c:12873:\t} else if (meta-\u003efunc_id == special_kfunc_list[KF_bpf_rdonly_cast]) {\nkernel/bpf/verifier.c-12874-\t\tret_t = btf_type_by_id(desc_btf, meta-\u003earg_constant.value);\n--\nkernel/bpf/verifier.c-12892-\t\t}\nkernel/bpf/verifier.c:12893:\t} else if (meta-\u003efunc_id == special_kfunc_list[KF_bpf_dynptr_slice] ||\nkernel/bpf/verifier.c:12894:\t\t   meta-\u003efunc_id == special_kfunc_list[KF_bpf_dynptr_slice_rdwr]) {\nkernel/bpf/verifier.c-12895-\t\tenum bpf_type_flag type_flag = get_dynptr_type_flag(meta-\u003edynptr.type);\n--\nkernel/bpf/verifier.c-12908-\nkernel/bpf/verifier.c:12909:\t\tif (meta-\u003efunc_id == special_kfunc_list[KF_bpf_dynptr_slice]) {\nkernel/bpf/verifier.c-12910-\t\t\tregs[BPF_REG_0].type |= MEM_RDONLY;\n--\nkernel/bpf/verifier.c=12933=static int check_kfunc_call(struct bpf_verifier_env *env, struct bpf_insn *insn,\n--\nkernel/bpf/verifier.c-12971-\tif (!insn-\u003eoff \u0026\u0026\nkernel/bpf/verifier.c:12972:\t    (insn-\u003eimm == special_kfunc_list[KF_bpf_res_spin_lock] ||\nkernel/bpf/verifier.c:12973:\t     insn-\u003eimm == special_kfunc_list[KF_bpf_res_spin_lock_irqsave])) {\nkernel/bpf/verifier.c-12974-\t\tstruct bpf_verifier_state *branch;\n--\nkernel/bpf/verifier.c-12994-\t\t}\nkernel/bpf/verifier.c:12995:\t} else if (!insn-\u003eoff \u0026\u0026 insn-\u003eimm == special_kfunc_list[KF___bpf_trap]) {\nkernel/bpf/verifier.c-12996-\t\tverbose(env, \"unexpected __bpf_trap() due to uninitialized variable?\\n\");\n--\nkernel/bpf/verifier.c-13124-\nkernel/bpf/verifier.c:13125:\tif (meta.func_id == special_kfunc_list[KF_bpf_throw]) {\nkernel/bpf/verifier.c-13126-\t\tif (!bpf_jit_supports_exceptions()) {\n--\nkernel/bpf/verifier.c-13164-\t\tmark_reg_unknown(env, regs, BPF_REG_0);\nkernel/bpf/verifier.c:13165:\t\tif (meta.btf == btf_vmlinux \u0026\u0026 (meta.func_id == special_kfunc_list[KF_bpf_res_spin_lock] ||\nkernel/bpf/verifier.c:13166:\t\t    meta.func_id == special_kfunc_list[KF_bpf_res_spin_lock_irqsave]))\nkernel/bpf/verifier.c-13167-\t\t\t__mark_reg_const_zero(env, \u0026regs[BPF_REG_0]);\n--\nkernel/bpf/verifier.c-13186-\nkernel/bpf/verifier.c:13187:\t\t\t\tif (meta.func_id == special_kfunc_list[KF_bpf_session_cookie])\nkernel/bpf/verifier.c-13188-\t\t\t\t\tmeta.r0_rdonly = false;\n--\nkernel/bpf/verifier.c-13220-\nkernel/bpf/verifier.c:13221:\t\t\tif (meta.func_id == special_kfunc_list[KF_bpf_get_kmem_cache])\nkernel/bpf/verifier.c-13222-\t\t\t\ttype |= PTR_UNTRUSTED;\n--\nkernel/bpf/verifier.c-13299-\nkernel/bpf/verifier.c:13300:\tif (meta.func_id == special_kfunc_list[KF_bpf_session_cookie])\nkernel/bpf/verifier.c-13301-\t\tenv-\u003eprog-\u003ecall_session_cookie = true;\n--\nkernel/bpf/verifier.c=19707=static int specialize_kfunc(struct bpf_verifier_env *env, struct bpf_kfunc_desc *desc, int insn_idx)\n--\nkernel/bpf/verifier.c-19724-\t\t/* fallback to default kfunc when not supported by netdev */\nkernel/bpf/verifier.c:19725:\t} else if (func_id == special_kfunc_list[KF_bpf_dynptr_from_skb]) {\nkernel/bpf/verifier.c-19726-\t\tseen_direct_write = env-\u003eseen_direct_write;\n--\nkernel/bpf/verifier.c-19735-\t\tenv-\u003eseen_direct_write = seen_direct_write;\nkernel/bpf/verifier.c:19736:\t} else if (func_id == special_kfunc_list[KF_bpf_set_dentry_xattr]) {\nkernel/bpf/verifier.c-19737-\t\tif (bpf_lsm_has_d_inode_locked(prog))\nkernel/bpf/verifier.c-19738-\t\t\taddr = (unsigned long)bpf_set_dentry_xattr_locked;\nkernel/bpf/verifier.c:19739:\t} else if (func_id == special_kfunc_list[KF_bpf_remove_dentry_xattr]) {\nkernel/bpf/verifier.c-19740-\t\tif (bpf_lsm_has_d_inode_locked(prog))\nkernel/bpf/verifier.c-19741-\t\t\taddr = (unsigned long)bpf_remove_dentry_xattr_locked;\nkernel/bpf/verifier.c:19742:\t} else if (func_id == special_kfunc_list[KF_bpf_dynptr_from_file]) {\nkernel/bpf/verifier.c-19743-\t\tif (!env-\u003einsn_aux_data[insn_idx].non_sleepable)\nkernel/bpf/verifier.c-19744-\t\t\taddr = (unsigned long)bpf_dynptr_from_file_sleepable;\nkernel/bpf/verifier.c:19745:\t} else if (func_id == special_kfunc_list[KF_bpf_arena_alloc_pages]) {\nkernel/bpf/verifier.c-19746-\t\tif (env-\u003einsn_aux_data[insn_idx].non_sleepable)\nkernel/bpf/verifier.c-19747-\t\t\taddr = (unsigned long)bpf_arena_alloc_pages_non_sleepable;\nkernel/bpf/verifier.c:19748:\t} else if (func_id == special_kfunc_list[KF_bpf_arena_free_pages]) {\nkernel/bpf/verifier.c-19749-\t\tif (env-\u003einsn_aux_data[insn_idx].non_sleepable)\n--\nkernel/bpf/verifier.c=19773=int bpf_fixup_kfunc_call(struct bpf_verifier_env *env, struct bpf_insn *insn,\n--\nkernel/bpf/verifier.c-19850-\t\t */\nkernel/bpf/verifier.c:19851:\t\tif (desc-\u003efunc_id == special_kfunc_list[KF_bpf_list_add] ||\nkernel/bpf/verifier.c-19852-\t\t    is_bpf_rbtree_add_kfunc(desc-\u003efunc_id)) {\n--\nkernel/bpf/verifier.c-19864-\t\t\t\t\t\tnode_offset_reg, insn, insn_buf, cnt);\nkernel/bpf/verifier.c:19865:\t} else if (desc-\u003efunc_id == special_kfunc_list[KF_bpf_cast_to_kern_ctx] ||\nkernel/bpf/verifier.c:19866:\t\t   desc-\u003efunc_id == special_kfunc_list[KF_bpf_rdonly_cast]) {\nkernel/bpf/verifier.c-19867-\t\tinsn_buf[0] = BPF_MOV64_REG(BPF_REG_0, BPF_REG_1);\nkernel/bpf/verifier.c-19868-\t\t*cnt = 1;\nkernel/bpf/verifier.c:19869:\t} else if (desc-\u003efunc_id == special_kfunc_list[KF_bpf_session_is_return] \u0026\u0026\nkernel/bpf/verifier.c-19870-\t\t   (env-\u003eprog-\u003eexpected_attach_type == BPF_TRACE_FSESSION ||\n--\nkernel/bpf/verifier.c-19883-\t\t*cnt = 3;\nkernel/bpf/verifier.c:19884:\t} else if (desc-\u003efunc_id == special_kfunc_list[KF_bpf_session_cookie] \u0026\u0026\nkernel/bpf/verifier.c-19885-\t\t   (env-\u003eprog-\u003eexpected_attach_type == BPF_TRACE_FSESSION ||\n--\nkernel/bpf/verifier.c-19901-\t\t*cnt = 6;\nkernel/bpf/verifier.c:19902:\t} else if (desc-\u003efunc_id == special_kfunc_list[KF_bpf_iter_num_new]) {\nkernel/bpf/verifier.c-19903-\t\t/* inline bpf_iter_num_new(\u0026it, start, end); R1=\u0026it, R2=start, R3=end */\n--\nkernel/bpf/verifier.c-19925-\t\t*cnt = i;\nkernel/bpf/verifier.c:19926:\t} else if (desc-\u003efunc_id == special_kfunc_list[KF_bpf_iter_num_next]) {\nkernel/bpf/verifier.c-19927-\t\t/* inline bpf_iter_num_next(\u0026it); R1=\u0026it, returns \u0026s-\u003ecur or NULL */\n--\nkernel/bpf/verifier.c-19942-\t\t*cnt = i;\nkernel/bpf/verifier.c:19943:\t} else if (desc-\u003efunc_id == special_kfunc_list[KF_bpf_iter_num_destroy]) {\nkernel/bpf/verifier.c-19944-\t\t/* bpf_iter_num_destroy() is a no-op; emit a nop to drop the call */\n"
}

gemini-3.1-pro-preview

null

null

							input: 12021
							output: 83
							thoughts: 157
						

**My Initial Assessment of the BPF Kernel Functions**

Okay, so I'm looking through this `specialize_kfunc` function and I immediately notice something's off. I'm seeing allocations and deallocations with `KF_bpf_arena_alloc_pages` and `KF_bpf_arena_free_pages`, which is fine, but where's the *reservation* call, `KF_bpf_arena_reserve_pages`? That's a red flag. I would expect to see that in a memory management context.

Then I move on and find `KF_bpf_session_is_return` and `KF_bpf_session_cookie` present, which is as expected, but what about `KF_bpf_stream_vprintk` and `KF_bpf_stream_print_stack`? They're nowhere to be found here. My initial hunch is that these weren't used at all in `verifier.c` and elsewhere. 

Before jumping to conclusions though, let me just double check. Maybe I'm missing something, I'll quickly verify if `bpf_arena_reserve_pages` or `bpf_stream_vprintk` are defined anywhere else in the kernel.

{
  "Expression": "bpf_arena_reserve_pages",
  "PathPrefix": ""
}

{
  "Output": "kernel/bpf/arena.c=1095=void bpf_arena_free_pages_non_sleepable(void *p__map, void *ptr__ign, u32 page_cnt)\n--\nkernel/bpf/arena.c-1104-\nkernel/bpf/arena.c:1105:__bpf_kfunc int bpf_arena_reserve_pages(void *p__map, void *ptr__ign, u32 page_cnt)\nkernel/bpf/arena.c-1106-{\n--\nkernel/bpf/arena.c=1122=BTF_ID_FLAGS(func, bpf_arena_free_pages, KF_ARENA_ARG2 | KF_SPINLOCK_SAFE)\nkernel/bpf/arena.c:1123:BTF_ID_FLAGS(func, bpf_arena_reserve_pages, KF_ARENA_ARG2 | KF_SPINLOCK_SAFE)\nkernel/bpf/arena.c-1124-BTF_KFUNCS_END(arena_kfuncs)\n--\ntools/sched_ext/include/scx/bpf_arena_common.bpf.h=85=void bpf_arena_free_pages(void *map, void __arena *ptr, __u32 page_cnt) __ksym __weak;\ntools/sched_ext/include/scx/bpf_arena_common.bpf.h:86:int bpf_arena_reserve_pages(void *map, void __arena *ptr, __u32 page_cnt) __ksym __weak;\ntools/sched_ext/include/scx/bpf_arena_common.bpf.h-87-\n--\ntools/testing/selftests/bpf/libarena/include/bpf_arena_common.h=47=void __arena* bpf_arena_alloc_pages(void *map, void __arena *addr, __u32 page_cnt,\ntools/testing/selftests/bpf/libarena/include/bpf_arena_common.h-48-\t\t\t\t    int node_id, __u64 flags) __ksym __weak;\ntools/testing/selftests/bpf/libarena/include/bpf_arena_common.h:49:int bpf_arena_reserve_pages(void *map, void __arena *addr, __u32 page_cnt) __ksym __weak;\ntools/testing/selftests/bpf/libarena/include/bpf_arena_common.h-50-void bpf_arena_free_pages(void *map, void __arena *ptr, __u32 page_cnt) __ksym __weak;\n--\ntools/testing/selftests/bpf/libarena/src/buddy.bpf.c=64=static int buddy_reserve_arena_vaddr(struct buddy __arena *buddy)\n--\ntools/testing/selftests/bpf/libarena/src/buddy.bpf.c-67-\ntools/testing/selftests/bpf/libarena/src/buddy.bpf.c:68:\treturn bpf_arena_reserve_pages(\u0026arena,\ntools/testing/selftests/bpf/libarena/src/buddy.bpf.c-69-\t\t\t\t       (void __arena *)BUDDY_VADDR_OFFSET,\n--\ntools/testing/selftests/bpf/libarena/src/common.bpf.c=27=__weak int arena_alloc_reserve(struct arena_alloc_reserve_args *args)\ntools/testing/selftests/bpf/libarena/src/common.bpf.c-28-{\ntools/testing/selftests/bpf/libarena/src/common.bpf.c:29:\treturn bpf_arena_reserve_pages(\u0026arena, NULL, args-\u003enr_pages);\ntools/testing/selftests/bpf/libarena/src/common.bpf.c-30-}\n--\ntools/testing/selftests/bpf/progs/verifier_arena.c=234=int basic_reserve1_nosleep(void *ctx)\n--\ntools/testing/selftests/bpf/progs/verifier_arena.c-246-\t/* Reserve the second page */\ntools/testing/selftests/bpf/progs/verifier_arena.c:247:\tret = bpf_arena_reserve_pages(\u0026arena, page, 1);\ntools/testing/selftests/bpf/progs/verifier_arena.c-248-\tif (ret)\n--\ntools/testing/selftests/bpf/progs/verifier_arena.c=266=int basic_reserve1(void *ctx)\n--\ntools/testing/selftests/bpf/progs/verifier_arena.c-278-\t/* Reserve the second page */\ntools/testing/selftests/bpf/progs/verifier_arena.c:279:\tret = bpf_arena_reserve_pages(\u0026arena, page, 1);\ntools/testing/selftests/bpf/progs/verifier_arena.c-280-\tif (ret)\n--\ntools/testing/selftests/bpf/progs/verifier_arena.c=298=int basic_reserve2_nosleep(void *ctx)\n--\ntools/testing/selftests/bpf/progs/verifier_arena.c-304-\tpage = arena_base(\u0026arena);\ntools/testing/selftests/bpf/progs/verifier_arena.c:305:\tret = bpf_arena_reserve_pages(\u0026arena, page, 1);\ntools/testing/selftests/bpf/progs/verifier_arena.c-306-\tif (ret)\n--\ntools/testing/selftests/bpf/progs/verifier_arena.c=318=int basic_reserve2(void *ctx)\n--\ntools/testing/selftests/bpf/progs/verifier_arena.c-324-\tpage = arena_base(\u0026arena);\ntools/testing/selftests/bpf/progs/verifier_arena.c:325:\tret = bpf_arena_reserve_pages(\u0026arena, page, 1);\ntools/testing/selftests/bpf/progs/verifier_arena.c-326-\tif (ret)\n--\ntools/testing/selftests/bpf/progs/verifier_arena.c=339=int reserve_twice_nosleep(void *ctx)\n--\ntools/testing/selftests/bpf/progs/verifier_arena.c-346-\ntools/testing/selftests/bpf/progs/verifier_arena.c:347:\tret = bpf_arena_reserve_pages(\u0026arena, page, 1);\ntools/testing/selftests/bpf/progs/verifier_arena.c-348-\tif (ret)\n--\ntools/testing/selftests/bpf/progs/verifier_arena.c-350-\ntools/testing/selftests/bpf/progs/verifier_arena.c:351:\tret = bpf_arena_reserve_pages(\u0026arena, page, 1);\ntools/testing/selftests/bpf/progs/verifier_arena.c-352-\tif (ret != -EBUSY)\n--\ntools/testing/selftests/bpf/progs/verifier_arena.c=360=int reserve_twice(void *ctx)\n--\ntools/testing/selftests/bpf/progs/verifier_arena.c-367-\ntools/testing/selftests/bpf/progs/verifier_arena.c:368:\tret = bpf_arena_reserve_pages(\u0026arena, page, 1);\ntools/testing/selftests/bpf/progs/verifier_arena.c-369-\tif (ret)\n--\ntools/testing/selftests/bpf/progs/verifier_arena.c-371-\ntools/testing/selftests/bpf/progs/verifier_arena.c:372:\tret = bpf_arena_reserve_pages(\u0026arena, page, 1);\ntools/testing/selftests/bpf/progs/verifier_arena.c-373-\tif (ret != -EBUSY)\n--\ntools/testing/selftests/bpf/progs/verifier_arena.c=382=int reserve_invalid_region_nosleep(void *ctx)\n--\ntools/testing/selftests/bpf/progs/verifier_arena.c-388-\t/* Try a NULL pointer. */\ntools/testing/selftests/bpf/progs/verifier_arena.c:389:\tret = bpf_arena_reserve_pages(\u0026arena, NULL, 3);\ntools/testing/selftests/bpf/progs/verifier_arena.c-390-\tif (ret != -EINVAL)\n--\ntools/testing/selftests/bpf/progs/verifier_arena.c-394-\ntools/testing/selftests/bpf/progs/verifier_arena.c:395:\tret = bpf_arena_reserve_pages(\u0026arena, page, 3);\ntools/testing/selftests/bpf/progs/verifier_arena.c-396-\tif (ret != -EINVAL)\n--\ntools/testing/selftests/bpf/progs/verifier_arena.c-398-\ntools/testing/selftests/bpf/progs/verifier_arena.c:399:\tret = bpf_arena_reserve_pages(\u0026arena, page, 4096);\ntools/testing/selftests/bpf/progs/verifier_arena.c-400-\tif (ret != -EINVAL)\n--\ntools/testing/selftests/bpf/progs/verifier_arena.c-402-\ntools/testing/selftests/bpf/progs/verifier_arena.c:403:\tret = bpf_arena_reserve_pages(\u0026arena, page, (1ULL \u003c\u003c 32) - 1);\ntools/testing/selftests/bpf/progs/verifier_arena.c-404-\tif (ret != -EINVAL)\n--\ntools/testing/selftests/bpf/progs/verifier_arena.c=412=int reserve_invalid_region(void *ctx)\n--\ntools/testing/selftests/bpf/progs/verifier_arena.c-418-\t/* Try a NULL pointer. */\ntools/testing/selftests/bpf/progs/verifier_arena.c:419:\tret = bpf_arena_reserve_pages(\u0026arena, NULL, 3);\ntools/testing/selftests/bpf/progs/verifier_arena.c-420-\tif (ret != -EINVAL)\n--\ntools/testing/selftests/bpf/progs/verifier_arena.c-424-\ntools/testing/selftests/bpf/progs/verifier_arena.c:425:\tret = bpf_arena_reserve_pages(\u0026arena, page, 3);\ntools/testing/selftests/bpf/progs/verifier_arena.c-426-\tif (ret != -EINVAL)\n--\ntools/testing/selftests/bpf/progs/verifier_arena.c-428-\ntools/testing/selftests/bpf/progs/verifier_arena.c:429:\tret = bpf_arena_reserve_pages(\u0026arena, page, 4096);\ntools/testing/selftests/bpf/progs/verifier_arena.c-430-\tif (ret != -EINVAL)\n--\ntools/testing/selftests/bpf/progs/verifier_arena.c-432-\ntools/testing/selftests/bpf/progs/verifier_arena.c:433:\tret = bpf_arena_reserve_pages(\u0026arena, page, (1ULL \u003c\u003c 32) - 1);\ntools/testing/selftests/bpf/progs/verifier_arena.c-434-\tif (ret != -EINVAL)\n--\ntools/testing/selftests/bpf/progs/verifier_arena.c=479=int arena_kfuncs_under_bpf_lock(void *ctx)\n--\ntools/testing/selftests/bpf/progs/verifier_arena.c-488-\tpage = arena_base(\u0026arena);\ntools/testing/selftests/bpf/progs/verifier_arena.c:489:\tret = bpf_arena_reserve_pages(\u0026arena, page, 1);\ntools/testing/selftests/bpf/progs/verifier_arena.c-490-\tif (ret) {\n--\ntools/testing/selftests/bpf/progs/verifier_arena_globals1.c=33=int check_reserve1(void *ctx)\n--\ntools/testing/selftests/bpf/progs/verifier_arena_globals1.c-45-\t/* Reserve the region we've offset the globals by. */\ntools/testing/selftests/bpf/progs/verifier_arena_globals1.c:46:\tret = bpf_arena_reserve_pages(\u0026arena, guard, ARENA_PAGES - GLOBAL_PAGES);\ntools/testing/selftests/bpf/progs/verifier_arena_globals1.c-47-\tif (ret)\n--\ntools/testing/selftests/bpf/progs/verifier_arena_globals1.c-50-\t/* Make sure the globals are in the expected offset. */\ntools/testing/selftests/bpf/progs/verifier_arena_globals1.c:51:\tret = bpf_arena_reserve_pages(\u0026arena, globals, 1);\ntools/testing/selftests/bpf/progs/verifier_arena_globals1.c-52-\tif (!ret)\n--\ntools/testing/selftests/bpf/progs/verifier_arena_globals2.c=33=int check_reserve2(void *ctx)\n--\ntools/testing/selftests/bpf/progs/verifier_arena_globals2.c-41-\t/* Make sure the data at offset 0 case is properly handled. */\ntools/testing/selftests/bpf/progs/verifier_arena_globals2.c:42:\tret = bpf_arena_reserve_pages(\u0026arena, guard, 1);\ntools/testing/selftests/bpf/progs/verifier_arena_globals2.c-43-\tif (!ret)\n--\ntools/testing/selftests/bpf/progs/verifier_arena_large.c=86=int access_reserved(void *ctx)\n--\ntools/testing/selftests/bpf/progs/verifier_arena_large.c-96-\ntools/testing/selftests/bpf/progs/verifier_arena_large.c:97:\tret = bpf_arena_reserve_pages(\u0026arena, base, len);\ntools/testing/selftests/bpf/progs/verifier_arena_large.c-98-\tif (ret)\n--\ntools/testing/selftests/bpf/progs/verifier_arena_large.c=125=int request_partially_reserved(void *ctx)\n--\ntools/testing/selftests/bpf/progs/verifier_arena_large.c-134-\ntools/testing/selftests/bpf/progs/verifier_arena_large.c:135:\tret = bpf_arena_reserve_pages(\u0026arena, base + 3 * __PAGE_SIZE, 4);\ntools/testing/selftests/bpf/progs/verifier_arena_large.c-136-\tif (ret)\n--\ntools/testing/selftests/bpf/progs/verifier_arena_large.c=148=int free_reserved(void *ctx)\n--\ntools/testing/selftests/bpf/progs/verifier_arena_large.c-161-\ntools/testing/selftests/bpf/progs/verifier_arena_large.c:162:\tret = bpf_arena_reserve_pages(\u0026arena, addr + 2 * __PAGE_SIZE, 2);\ntools/testing/selftests/bpf/progs/verifier_arena_large.c-163-\tif (ret)\n"
}

{
  "Expression": "bpf_stream_vprintk",
  "PathPrefix": ""
}

{
  "Output": "kernel/bpf/helpers.c=4965=BTF_ID_FLAGS(func, bpf_cgroup_read_xattr, KF_RCU)\nkernel/bpf/helpers.c-4966-#endif\nkernel/bpf/helpers.c:4967:BTF_ID_FLAGS(func, bpf_stream_vprintk, KF_IMPLICIT_ARGS | KF_SPINLOCK_SAFE)\nkernel/bpf/helpers.c-4968-BTF_ID_FLAGS(func, bpf_stream_print_stack, KF_IMPLICIT_ARGS | KF_SPINLOCK_SAFE)\n--\nkernel/bpf/stream.c=209=__bpf_kfunc_start_defs();\n--\nkernel/bpf/stream.c-214- */\nkernel/bpf/stream.c:215:__bpf_kfunc int bpf_stream_vprintk(int stream_id, const char *fmt__str, const void *args,\nkernel/bpf/stream.c-216-\t\t\t\t   u32 len__sz, struct bpf_prog_aux *aux)\n--\ntools/bpf/bpftool/Documentation/bpftool-prog.rst=183=bpftool prog tracelog { stdout | stderr } *PROG*\ntools/bpf/bpftool/Documentation/bpftool-prog.rst-184-    Dump the BPF stream of the program. BPF programs can write to these streams\ntools/bpf/bpftool/Documentation/bpftool-prog.rst:185:    at runtime with the **bpf_stream_vprintk_impl**\\ () kfunc. The kernel may write\ntools/bpf/bpftool/Documentation/bpftool-prog.rst-186-    error messages to the standard error stream. This facility should be used\n--\ntools/lib/bpf/bpf_helpers.h=185=enum libbpf_tristate {\n--\ntools/lib/bpf/bpf_helpers.h-327-\t\t\t\t\t\t\t\t\t\t\t\\\ntools/lib/bpf/bpf_helpers.h:328:\tbpf_stream_vprintk(stream_id, ___fmt, ___param, sizeof(___param));\t\t\\\ntools/lib/bpf/bpf_helpers.h-329-})\n--\ntools/testing/selftests/bpf/progs/stream_fail.c=11=int stream_vprintk_null_arg(void *ctx)\ntools/testing/selftests/bpf/progs/stream_fail.c-12-{\ntools/testing/selftests/bpf/progs/stream_fail.c:13:\tbpf_stream_vprintk(BPF_STDOUT, \"\", NULL, 0);\ntools/testing/selftests/bpf/progs/stream_fail.c-14-\treturn 0;\n--\ntools/testing/selftests/bpf/progs/stream_fail.c=19=int stream_vprintk_scalar_arg(void *ctx)\ntools/testing/selftests/bpf/progs/stream_fail.c-20-{\ntools/testing/selftests/bpf/progs/stream_fail.c:21:\tbpf_stream_vprintk(BPF_STDOUT, \"\", (void *)46, 0);\ntools/testing/selftests/bpf/progs/stream_fail.c-22-\treturn 0;\n--\ntools/testing/selftests/bpf/progs/stream_fail.c=27=int stream_vprintk_string_arg(void *ctx)\ntools/testing/selftests/bpf/progs/stream_fail.c-28-{\ntools/testing/selftests/bpf/progs/stream_fail.c:29:\tbpf_stream_vprintk(BPF_STDOUT, ctx, NULL, 0);\ntools/testing/selftests/bpf/progs/stream_fail.c-30-\treturn 0;\n"
}

{
  "Expression": "bpf_stream_print_stack",
  "PathPrefix": ""
}

{
  "Output": "kernel/bpf/helpers.c=4967=BTF_ID_FLAGS(func, bpf_stream_vprintk, KF_IMPLICIT_ARGS | KF_SPINLOCK_SAFE)\nkernel/bpf/helpers.c:4968:BTF_ID_FLAGS(func, bpf_stream_print_stack, KF_IMPLICIT_ARGS | KF_SPINLOCK_SAFE)\nkernel/bpf/helpers.c-4969-BTF_ID_FLAGS(func, bpf_task_work_schedule_signal, KF_IMPLICIT_ARGS)\n--\nkernel/bpf/stream.c=215=__bpf_kfunc int bpf_stream_vprintk(int stream_id, const char *fmt__str, const void *args,\n--\nkernel/bpf/stream.c-248-/* Directly trigger a stack dump from the program. */\nkernel/bpf/stream.c:249:__bpf_kfunc int bpf_stream_print_stack(int stream_id, struct bpf_prog_aux *aux)\nkernel/bpf/stream.c-250-{\n--\ntools/testing/selftests/bpf/libarena/src/asan.bpf.c=195=__weak int asan_report(s8 __arena *addr, size_t sz, u32 flags)\n--\ntools/testing/selftests/bpf/libarena/src/asan.bpf.c-208-\t\t\tsz);\ntools/testing/selftests/bpf/libarena/src/asan.bpf.c:209:\tbpf_stream_print_stack(BPF_STDERR);\ntools/testing/selftests/bpf/libarena/src/asan.bpf.c-210-\n--\ntools/testing/selftests/bpf/progs/stream.c=294=int stream_print_stack_kfunc(void *ctx)\ntools/testing/selftests/bpf/progs/stream.c-295-{\ntools/testing/selftests/bpf/progs/stream.c:296:\treturn bpf_stream_print_stack(BPF_STDERR);\ntools/testing/selftests/bpf/progs/stream.c-297-}\n--\ntools/testing/selftests/bpf/progs/stream.c=301=int stream_print_stack_invalid_id(void *ctx)\n--\ntools/testing/selftests/bpf/progs/stream.c-303-\t/* Try to pass an invalid stream ID. */\ntools/testing/selftests/bpf/progs/stream.c:304:\treturn bpf_stream_print_stack((enum bpf_stream_id)0xbadcafe);\ntools/testing/selftests/bpf/progs/stream.c-305-}\n--\ntools/testing/selftests/bpf/progs/stream.c=316=int stream_print_kfuncs_locked(void *ctx)\n--\ntools/testing/selftests/bpf/progs/stream.c-325-\ntools/testing/selftests/bpf/progs/stream.c:326:\tret = bpf_stream_print_stack(BPF_STDERR);\ntools/testing/selftests/bpf/progs/stream.c-327-\n"
}

gemini-3.1-pro-preview

null

null

							input: 18428
							output: 38
							thoughts: 233
						

**Investigating the `KF_bpf_arena_reserve_pages` KFunc**

Okay, so it looks like `KF_bpf_arena_reserve_pages` got removed from the `special_kfunc_list`, but `bpf_arena_reserve_pages` is still a defined kfunc in `kernel/bpf/arena.c`. That's a little peculiar. The purpose of `special_kfunc_list` is to flag kfuncs that need special attention from the verifier.

So, the fact that it was removed means that it *should* no longer be getting that special treatment. But if that's the case, what special handling *was* it receiving? I need to figure this out.

Right, let me search for `KF_bpf_arena_reserve_pages` within the verifier code, `kernel/bpf/verifier.c`. Aha! I found no matches. That’s odd. This means it was never actually checked in the verifier, even when it *was* in the enum and `BTF_ID_LIST(special_kfunc_list)`. Essentially, it was just listed, but not actually *used* by the verifier. So, it appears that the removal of `KF_bpf_arena_reserve_pages` doesn't actually change anything from a verification perspective because it was never treated specially in the first place. I should double check all of this to be certain.

{
  "Expression": "KF_bpf_arena_alloc_pages",
  "PathPrefix": "kernel/bpf/verifier.c"
}

{
  "Output": "kernel/bpf/verifier.c=11028=enum special_kfunc_type {\n--\nkernel/bpf/verifier.c-11092-\tKF_bpf_task_work_schedule_resume,\nkernel/bpf/verifier.c:11093:\tKF_bpf_arena_alloc_pages,\nkernel/bpf/verifier.c-11094-\tKF_bpf_arena_free_pages,\n--\nkernel/bpf/verifier.c=19707=static int specialize_kfunc(struct bpf_verifier_env *env, struct bpf_kfunc_desc *desc, int insn_idx)\n--\nkernel/bpf/verifier.c-19744-\t\t\taddr = (unsigned long)bpf_dynptr_from_file_sleepable;\nkernel/bpf/verifier.c:19745:\t} else if (func_id == special_kfunc_list[KF_bpf_arena_alloc_pages]) {\nkernel/bpf/verifier.c-19746-\t\tif (env-\u003einsn_aux_data[insn_idx].non_sleepable)\n"
}

gemini-3.1-pro-preview

null

null

							input: 19308
							output: 31
							thoughts: 259
						

**My Analysis of Redundant KFunc Entries**

Okay, so I'm looking at `KF_bpf_arena_alloc_pages` and how it's used within `specialize_kfunc`. Makes sense. Then I see `KF_bpf_arena_reserve_pages` listed, but I'm thinking, "Wait a minute...it's not used in `verifier.c` *anywhere* except in the enum and `BTF_ID_LIST`!" That's a red flag. It seems that its inclusion in `special_kfunc_list` is completely pointless, utterly redundant, and does absolutely nothing. Same thing for `KF_bpf_stream_vprintk` and `KF_bpf_stream_print_stack`– they're just sitting there in the enum and `BTF_ID_LIST`, without any special logic applied to them within `verifier.c`.

Aha, hold on. I'm remembering how `BTF_ID_LIST(special_kfunc_list)` works: it creates an array of BTF IDs. So, if a kfunc is on that list, all it *means* is that its BTF ID is stored in that array. If the verifier doesn't ever actually *access* that particular element of `special_kfunc_list`, say `special_kfunc_list[KF_bpf_arena_reserve_pages]`, then the fact that its BTF ID is *in* the array is functionally irrelevant. Its presence is wasted.

I need to confirm this. I'm going to have to make sure that `special_kfunc_list` isn't used in some other way, perhaps by iterating through it. This will confirm my theory that the entries are unused and can be removed.

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

{
  "Output": "kernel/bpf/verifier.c=11028=enum special_kfunc_type {\n--\nkernel/bpf/verifier.c-11097-\nkernel/bpf/verifier.c:11098:BTF_ID_LIST(special_kfunc_list)\nkernel/bpf/verifier.c-11099-BTF_ID(func, bpf_obj_new_impl)\n--\nkernel/bpf/verifier.c=11191=static bool is_bpf_obj_new_kfunc(u32 func_id)\nkernel/bpf/verifier.c-11192-{\nkernel/bpf/verifier.c:11193:\treturn func_id == special_kfunc_list[KF_bpf_obj_new] ||\nkernel/bpf/verifier.c:11194:\t       func_id == special_kfunc_list[KF_bpf_obj_new_impl];\nkernel/bpf/verifier.c-11195-}\n--\nkernel/bpf/verifier.c=11197=static bool is_bpf_percpu_obj_new_kfunc(u32 func_id)\nkernel/bpf/verifier.c-11198-{\nkernel/bpf/verifier.c:11199:\treturn func_id == special_kfunc_list[KF_bpf_percpu_obj_new] ||\nkernel/bpf/verifier.c:11200:\t       func_id == special_kfunc_list[KF_bpf_percpu_obj_new_impl];\nkernel/bpf/verifier.c-11201-}\n--\nkernel/bpf/verifier.c=11203=static bool is_bpf_obj_drop_kfunc(u32 func_id)\nkernel/bpf/verifier.c-11204-{\nkernel/bpf/verifier.c:11205:\treturn func_id == special_kfunc_list[KF_bpf_obj_drop] ||\nkernel/bpf/verifier.c:11206:\t       func_id == special_kfunc_list[KF_bpf_obj_drop_impl];\nkernel/bpf/verifier.c-11207-}\n--\nkernel/bpf/verifier.c=11209=static bool is_bpf_percpu_obj_drop_kfunc(u32 func_id)\nkernel/bpf/verifier.c-11210-{\nkernel/bpf/verifier.c:11211:\treturn func_id == special_kfunc_list[KF_bpf_percpu_obj_drop] ||\nkernel/bpf/verifier.c:11212:\t       func_id == special_kfunc_list[KF_bpf_percpu_obj_drop_impl];\nkernel/bpf/verifier.c-11213-}\n--\nkernel/bpf/verifier.c=11215=static bool is_bpf_refcount_acquire_kfunc(u32 func_id)\nkernel/bpf/verifier.c-11216-{\nkernel/bpf/verifier.c:11217:\treturn func_id == special_kfunc_list[KF_bpf_refcount_acquire] ||\nkernel/bpf/verifier.c:11218:\t       func_id == special_kfunc_list[KF_bpf_refcount_acquire_impl];\nkernel/bpf/verifier.c-11219-}\n--\nkernel/bpf/verifier.c=11221=static bool is_bpf_list_push_kfunc(u32 func_id)\nkernel/bpf/verifier.c-11222-{\nkernel/bpf/verifier.c:11223:\treturn func_id == special_kfunc_list[KF_bpf_list_push_front] ||\nkernel/bpf/verifier.c:11224:\t       func_id == special_kfunc_list[KF_bpf_list_push_front_impl] ||\nkernel/bpf/verifier.c:11225:\t       func_id == special_kfunc_list[KF_bpf_list_push_back] ||\nkernel/bpf/verifier.c:11226:\t       func_id == special_kfunc_list[KF_bpf_list_push_back_impl] ||\nkernel/bpf/verifier.c:11227:\t       func_id == special_kfunc_list[KF_bpf_list_add];\nkernel/bpf/verifier.c-11228-}\n--\nkernel/bpf/verifier.c=11230=static bool is_bpf_rbtree_add_kfunc(u32 func_id)\nkernel/bpf/verifier.c-11231-{\nkernel/bpf/verifier.c:11232:\treturn func_id == special_kfunc_list[KF_bpf_rbtree_add] ||\nkernel/bpf/verifier.c:11233:\t       func_id == special_kfunc_list[KF_bpf_rbtree_add_impl];\nkernel/bpf/verifier.c-11234-}\n--\nkernel/bpf/verifier.c=11236=static bool is_task_work_add_kfunc(u32 func_id)\nkernel/bpf/verifier.c-11237-{\nkernel/bpf/verifier.c:11238:\treturn func_id == special_kfunc_list[KF_bpf_task_work_schedule_signal] ||\nkernel/bpf/verifier.c:11239:\t       func_id == special_kfunc_list[KF_bpf_task_work_schedule_resume];\nkernel/bpf/verifier.c-11240-}\n--\nkernel/bpf/verifier.c=11250=static bool is_kfunc_bpf_rcu_read_lock(struct bpf_call_arg_meta *meta)\nkernel/bpf/verifier.c-11251-{\nkernel/bpf/verifier.c:11252:\treturn meta-\u003efunc_id == special_kfunc_list[KF_bpf_rcu_read_lock];\nkernel/bpf/verifier.c-11253-}\n--\nkernel/bpf/verifier.c=11255=static bool is_kfunc_bpf_rcu_read_unlock(struct bpf_call_arg_meta *meta)\nkernel/bpf/verifier.c-11256-{\nkernel/bpf/verifier.c:11257:\treturn meta-\u003efunc_id == special_kfunc_list[KF_bpf_rcu_read_unlock];\nkernel/bpf/verifier.c-11258-}\n--\nkernel/bpf/verifier.c=11260=static bool is_kfunc_bpf_preempt_disable(struct bpf_call_arg_meta *meta)\nkernel/bpf/verifier.c-11261-{\nkernel/bpf/verifier.c:11262:\treturn meta-\u003efunc_id == special_kfunc_list[KF_bpf_preempt_disable];\nkernel/bpf/verifier.c-11263-}\n--\nkernel/bpf/verifier.c=11265=static bool is_kfunc_bpf_preempt_enable(struct bpf_call_arg_meta *meta)\nkernel/bpf/verifier.c-11266-{\nkernel/bpf/verifier.c:11267:\treturn meta-\u003efunc_id == special_kfunc_list[KF_bpf_preempt_enable];\nkernel/bpf/verifier.c-11268-}\n--\nkernel/bpf/verifier.c=11270=bool bpf_is_kfunc_pkt_changing(struct bpf_call_arg_meta *meta)\nkernel/bpf/verifier.c-11271-{\nkernel/bpf/verifier.c:11272:\treturn meta-\u003efunc_id == special_kfunc_list[KF_bpf_xdp_pull_data];\nkernel/bpf/verifier.c-11273-}\n--\nkernel/bpf/verifier.c=11276=get_kfunc_arg_type(struct bpf_verifier_env *env, struct bpf_call_arg_meta *meta,\n--\nkernel/bpf/verifier.c-11312-\t */\nkernel/bpf/verifier.c:11313:\tif (meta-\u003efunc_id == special_kfunc_list[KF_bpf_cast_to_kern_ctx] ||\nkernel/bpf/verifier.c:11314:\t    meta-\u003efunc_id == special_kfunc_list[KF_bpf_session_is_return] ||\nkernel/bpf/verifier.c:11315:\t    meta-\u003efunc_id == special_kfunc_list[KF_bpf_session_cookie])\nkernel/bpf/verifier.c-11316-\t\targ_type = KF_ARG_PTR_TO_CTX;\n--\nkernel/bpf/verifier.c=11520=static int process_irq_flag(struct bpf_verifier_env *env, struct bpf_reg_state *reg, argno_t argno,\n--\nkernel/bpf/verifier.c-11525-\nkernel/bpf/verifier.c:11526:\tif (meta-\u003efunc_id == special_kfunc_list[KF_bpf_local_irq_save] ||\nkernel/bpf/verifier.c:11527:\t    meta-\u003efunc_id == special_kfunc_list[KF_bpf_res_spin_lock_irqsave]) {\nkernel/bpf/verifier.c-11528-\t\tirq_save = true;\nkernel/bpf/verifier.c:11529:\t\tif (meta-\u003efunc_id == special_kfunc_list[KF_bpf_res_spin_lock_irqsave])\nkernel/bpf/verifier.c-11530-\t\t\tkfunc_class = IRQ_LOCK_KFUNC;\nkernel/bpf/verifier.c:11531:\t} else if (meta-\u003efunc_id == special_kfunc_list[KF_bpf_local_irq_restore] ||\nkernel/bpf/verifier.c:11532:\t\t   meta-\u003efunc_id == special_kfunc_list[KF_bpf_res_spin_unlock_irqrestore]) {\nkernel/bpf/verifier.c-11533-\t\tirq_save = false;\nkernel/bpf/verifier.c:11534:\t\tif (meta-\u003efunc_id == special_kfunc_list[KF_bpf_res_spin_unlock_irqrestore])\nkernel/bpf/verifier.c-11535-\t\t\tkfunc_class = IRQ_LOCK_KFUNC;\n--\nkernel/bpf/verifier.c=11692=static bool is_bpf_list_api_kfunc(u32 btf_id)\n--\nkernel/bpf/verifier.c-11694-\treturn is_bpf_list_push_kfunc(btf_id) ||\nkernel/bpf/verifier.c:11695:\t       btf_id == special_kfunc_list[KF_bpf_list_pop_front] ||\nkernel/bpf/verifier.c:11696:\t       btf_id == special_kfunc_list[KF_bpf_list_pop_back] ||\nkernel/bpf/verifier.c:11697:\t       btf_id == special_kfunc_list[KF_bpf_list_del] ||\nkernel/bpf/verifier.c:11698:\t       btf_id == special_kfunc_list[KF_bpf_list_front] ||\nkernel/bpf/verifier.c:11699:\t       btf_id == special_kfunc_list[KF_bpf_list_back] ||\nkernel/bpf/verifier.c:11700:\t       btf_id == special_kfunc_list[KF_bpf_list_is_first] ||\nkernel/bpf/verifier.c:11701:\t       btf_id == special_kfunc_list[KF_bpf_list_is_last] ||\nkernel/bpf/verifier.c:11702:\t       btf_id == special_kfunc_list[KF_bpf_list_empty];\nkernel/bpf/verifier.c-11703-}\n--\nkernel/bpf/verifier.c=11705=static bool is_bpf_rbtree_api_kfunc(u32 btf_id)\n--\nkernel/bpf/verifier.c-11707-\treturn is_bpf_rbtree_add_kfunc(btf_id) ||\nkernel/bpf/verifier.c:11708:\t       btf_id == special_kfunc_list[KF_bpf_rbtree_remove] ||\nkernel/bpf/verifier.c:11709:\t       btf_id == special_kfunc_list[KF_bpf_rbtree_first] ||\nkernel/bpf/verifier.c:11710:\t       btf_id == special_kfunc_list[KF_bpf_rbtree_root] ||\nkernel/bpf/verifier.c:11711:\t       btf_id == special_kfunc_list[KF_bpf_rbtree_left] ||\nkernel/bpf/verifier.c:11712:\t       btf_id == special_kfunc_list[KF_bpf_rbtree_right];\nkernel/bpf/verifier.c-11713-}\n--\nkernel/bpf/verifier.c=11715=static bool is_bpf_res_spin_lock_kfunc(u32 btf_id)\nkernel/bpf/verifier.c-11716-{\nkernel/bpf/verifier.c:11717:\treturn btf_id == special_kfunc_list[KF_bpf_res_spin_lock] ||\nkernel/bpf/verifier.c:11718:\t       btf_id == special_kfunc_list[KF_bpf_res_spin_unlock] ||\nkernel/bpf/verifier.c:11719:\t       btf_id == special_kfunc_list[KF_bpf_res_spin_lock_irqsave] ||\nkernel/bpf/verifier.c:11720:\t       btf_id == special_kfunc_list[KF_bpf_res_spin_unlock_irqrestore];\nkernel/bpf/verifier.c-11721-}\n--\nkernel/bpf/verifier.c=11746=bool bpf_is_throw_kfunc(struct bpf_insn *insn)\n--\nkernel/bpf/verifier.c-11748-\treturn bpf_pseudo_kfunc_call(insn) \u0026\u0026 insn-\u003eoff == 0 \u0026\u0026\nkernel/bpf/verifier.c:11749:\t       insn-\u003eimm == special_kfunc_list[KF_bpf_throw];\nkernel/bpf/verifier.c-11750-}\n--\nkernel/bpf/verifier.c=11752=static bool is_bpf_wq_set_callback_kfunc(u32 btf_id)\nkernel/bpf/verifier.c-11753-{\nkernel/bpf/verifier.c:11754:\treturn btf_id == special_kfunc_list[KF_bpf_wq_set_callback];\nkernel/bpf/verifier.c-11755-}\n--\nkernel/bpf/verifier.c=11793=static bool check_kfunc_is_graph_node_api(struct bpf_verifier_env *env,\n--\nkernel/bpf/verifier.c-11801-\t\tret = is_bpf_list_push_kfunc(kfunc_btf_id) ||\nkernel/bpf/verifier.c:11802:\t\t      kfunc_btf_id == special_kfunc_list[KF_bpf_list_del] ||\nkernel/bpf/verifier.c:11803:\t\t      kfunc_btf_id == special_kfunc_list[KF_bpf_list_is_first] ||\nkernel/bpf/verifier.c:11804:\t\t      kfunc_btf_id == special_kfunc_list[KF_bpf_list_is_last];\nkernel/bpf/verifier.c-11805-\t\tbreak;\n--\nkernel/bpf/verifier.c-11807-\t\tret = (is_bpf_rbtree_add_kfunc(kfunc_btf_id) ||\nkernel/bpf/verifier.c:11808:\t\t       kfunc_btf_id == special_kfunc_list[KF_bpf_rbtree_remove] ||\nkernel/bpf/verifier.c:11809:\t\t       kfunc_btf_id == special_kfunc_list[KF_bpf_rbtree_left] ||\nkernel/bpf/verifier.c:11810:\t\t       kfunc_btf_id == special_kfunc_list[KF_bpf_rbtree_right]);\nkernel/bpf/verifier.c-11811-\t\tbreak;\n--\nkernel/bpf/verifier.c=11997=static int check_kfunc_args(struct bpf_verifier_env *env, struct bpf_call_arg_meta *meta,\n--\nkernel/bpf/verifier.c-12163-\nkernel/bpf/verifier.c:12164:\t\t\tif (meta-\u003efunc_id == special_kfunc_list[KF_bpf_cast_to_kern_ctx]) {\nkernel/bpf/verifier.c-12165-\t\t\t\tret = get_kern_ctx_btf_id(\u0026env-\u003elog, resolve_prog_type(env-\u003eprog));\n--\nkernel/bpf/verifier.c-12211-\nkernel/bpf/verifier.c:12212:\t\t\tif (meta-\u003efunc_id == special_kfunc_list[KF_bpf_dynptr_from_skb]) {\nkernel/bpf/verifier.c-12213-\t\t\t\tdynptr_arg_type |= DYNPTR_TYPE_SKB;\nkernel/bpf/verifier.c:12214:\t\t\t} else if (meta-\u003efunc_id == special_kfunc_list[KF_bpf_dynptr_from_xdp]) {\nkernel/bpf/verifier.c-12215-\t\t\t\tdynptr_arg_type |= DYNPTR_TYPE_XDP;\nkernel/bpf/verifier.c:12216:\t\t\t} else if (meta-\u003efunc_id == special_kfunc_list[KF_bpf_dynptr_from_skb_meta]) {\nkernel/bpf/verifier.c-12217-\t\t\t\tdynptr_arg_type |= DYNPTR_TYPE_SKB_META;\nkernel/bpf/verifier.c:12218:\t\t\t} else if (meta-\u003efunc_id == special_kfunc_list[KF_bpf_dynptr_from_file]) {\nkernel/bpf/verifier.c-12219-\t\t\t\tdynptr_arg_type |= DYNPTR_TYPE_FILE;\nkernel/bpf/verifier.c:12220:\t\t\t} else if (meta-\u003efunc_id == special_kfunc_list[KF_bpf_dynptr_file_discard]) {\nkernel/bpf/verifier.c-12221-\t\t\t\tdynptr_arg_type |= DYNPTR_TYPE_FILE | OBJ_RELEASE;\nkernel/bpf/verifier.c:12222:\t\t\t} else if (meta-\u003efunc_id == special_kfunc_list[KF_bpf_dynptr_clone] \u0026\u0026\nkernel/bpf/verifier.c-12223-\t\t\t\t   (dynptr_arg_type \u0026 MEM_UNINIT)) {\n--\nkernel/bpf/verifier.c-12240-\t\tcase KF_ARG_PTR_TO_ITER:\nkernel/bpf/verifier.c:12241:\t\t\tif (meta-\u003efunc_id == special_kfunc_list[KF_bpf_iter_css_task_new]) {\nkernel/bpf/verifier.c-12242-\t\t\t\tif (!check_css_task_iter_allowlist(env)) {\n--\nkernel/bpf/verifier.c-12520-\t\t\t\treturn -EFAULT;\nkernel/bpf/verifier.c:12521:\t\t\tif (meta-\u003efunc_id == special_kfunc_list[KF_bpf_res_spin_lock] ||\nkernel/bpf/verifier.c:12522:\t\t\t    meta-\u003efunc_id == special_kfunc_list[KF_bpf_res_spin_lock_irqsave])\nkernel/bpf/verifier.c-12523-\t\t\t\tflags |= PROCESS_SPIN_LOCK;\nkernel/bpf/verifier.c:12524:\t\t\tif (meta-\u003efunc_id == special_kfunc_list[KF_bpf_res_spin_lock_irqsave] ||\nkernel/bpf/verifier.c:12525:\t\t\t    meta-\u003efunc_id == special_kfunc_list[KF_bpf_res_spin_unlock_irqrestore])\nkernel/bpf/verifier.c-12526-\t\t\t\tflags |= PROCESS_LOCK_IRQ;\n--\nkernel/bpf/verifier.c=12762=static int check_special_kfunc(struct bpf_verifier_env *env, struct bpf_call_arg_meta *meta,\n--\nkernel/bpf/verifier.c-12867-\t\tmark_reg_graph_node(regs, BPF_REG_0, \u0026field-\u003egraph_root);\nkernel/bpf/verifier.c:12868:\t} else if (meta-\u003efunc_id == special_kfunc_list[KF_bpf_cast_to_kern_ctx]) {\nkernel/bpf/verifier.c-12869-\t\tmark_reg_known_zero(env, regs, BPF_REG_0);\n--\nkernel/bpf/verifier.c-12872-\t\tregs[BPF_REG_0].btf_id = meta-\u003eret_btf_id;\nkernel/bpf/verifier.c:12873:\t} else if (meta-\u003efunc_id == special_kfunc_list[KF_bpf_rdonly_cast]) {\nkernel/bpf/verifier.c-12874-\t\tret_t = btf_type_by_id(desc_btf, meta-\u003earg_constant.value);\n--\nkernel/bpf/verifier.c-12892-\t\t}\nkernel/bpf/verifier.c:12893:\t} else if (meta-\u003efunc_id == special_kfunc_list[KF_bpf_dynptr_slice] ||\nkernel/bpf/verifier.c:12894:\t\t   meta-\u003efunc_id == special_kfunc_list[KF_bpf_dynptr_slice_rdwr]) {\nkernel/bpf/verifier.c-12895-\t\tenum bpf_type_flag type_flag = get_dynptr_type_flag(meta-\u003edynptr.type);\n--\nkernel/bpf/verifier.c-12908-\nkernel/bpf/verifier.c:12909:\t\tif (meta-\u003efunc_id == special_kfunc_list[KF_bpf_dynptr_slice]) {\nkernel/bpf/verifier.c-12910-\t\t\tregs[BPF_REG_0].type |= MEM_RDONLY;\n--\nkernel/bpf/verifier.c=12933=static int check_kfunc_call(struct bpf_verifier_env *env, struct bpf_insn *insn,\n--\nkernel/bpf/verifier.c-12971-\tif (!insn-\u003eoff \u0026\u0026\nkernel/bpf/verifier.c:12972:\t    (insn-\u003eimm == special_kfunc_list[KF_bpf_res_spin_lock] ||\nkernel/bpf/verifier.c:12973:\t     insn-\u003eimm == special_kfunc_list[KF_bpf_res_spin_lock_irqsave])) {\nkernel/bpf/verifier.c-12974-\t\tstruct bpf_verifier_state *branch;\n--\nkernel/bpf/verifier.c-12994-\t\t}\nkernel/bpf/verifier.c:12995:\t} else if (!insn-\u003eoff \u0026\u0026 insn-\u003eimm == special_kfunc_list[KF___bpf_trap]) {\nkernel/bpf/verifier.c-12996-\t\tverbose(env, \"unexpected __bpf_trap() due to uninitialized variable?\\n\");\n--\nkernel/bpf/verifier.c-13124-\nkernel/bpf/verifier.c:13125:\tif (meta.func_id == special_kfunc_list[KF_bpf_throw]) {\nkernel/bpf/verifier.c-13126-\t\tif (!bpf_jit_supports_exceptions()) {\n--\nkernel/bpf/verifier.c-13164-\t\tmark_reg_unknown(env, regs, BPF_REG_0);\nkernel/bpf/verifier.c:13165:\t\tif (meta.btf == btf_vmlinux \u0026\u0026 (meta.func_id == special_kfunc_list[KF_bpf_res_spin_lock] ||\nkernel/bpf/verifier.c:13166:\t\t    meta.func_id == special_kfunc_list[KF_bpf_res_spin_lock_irqsave]))\nkernel/bpf/verifier.c-13167-\t\t\t__mark_reg_const_zero(env, \u0026regs[BPF_REG_0]);\n--\nkernel/bpf/verifier.c-13186-\nkernel/bpf/verifier.c:13187:\t\t\t\tif (meta.func_id == special_kfunc_list[KF_bpf_session_cookie])\nkernel/bpf/verifier.c-13188-\t\t\t\t\tmeta.r0_rdonly = false;\n--\nkernel/bpf/verifier.c-13220-\nkernel/bpf/verifier.c:13221:\t\t\tif (meta.func_id == special_kfunc_list[KF_bpf_get_kmem_cache])\nkernel/bpf/verifier.c-13222-\t\t\t\ttype |= PTR_UNTRUSTED;\n--\nkernel/bpf/verifier.c-13299-\nkernel/bpf/verifier.c:13300:\tif (meta.func_id == special_kfunc_list[KF_bpf_session_cookie])\nkernel/bpf/verifier.c-13301-\t\tenv-\u003eprog-\u003ecall_session_cookie = true;\n--\nkernel/bpf/verifier.c=19707=static int specialize_kfunc(struct bpf_verifier_env *env, struct bpf_kfunc_desc *desc, int insn_idx)\n--\nkernel/bpf/verifier.c-19724-\t\t/* fallback to default kfunc when not supported by netdev */\nkernel/bpf/verifier.c:19725:\t} else if (func_id == special_kfunc_list[KF_bpf_dynptr_from_skb]) {\nkernel/bpf/verifier.c-19726-\t\tseen_direct_write = env-\u003eseen_direct_write;\n--\nkernel/bpf/verifier.c-19735-\t\tenv-\u003eseen_direct_write = seen_direct_write;\nkernel/bpf/verifier.c:19736:\t} else if (func_id == special_kfunc_list[KF_bpf_set_dentry_xattr]) {\nkernel/bpf/verifier.c-19737-\t\tif (bpf_lsm_has_d_inode_locked(prog))\nkernel/bpf/verifier.c-19738-\t\t\taddr = (unsigned long)bpf_set_dentry_xattr_locked;\nkernel/bpf/verifier.c:19739:\t} else if (func_id == special_kfunc_list[KF_bpf_remove_dentry_xattr]) {\nkernel/bpf/verifier.c-19740-\t\tif (bpf_lsm_has_d_inode_locked(prog))\nkernel/bpf/verifier.c-19741-\t\t\taddr = (unsigned long)bpf_remove_dentry_xattr_locked;\nkernel/bpf/verifier.c:19742:\t} else if (func_id == special_kfunc_list[KF_bpf_dynptr_from_file]) {\nkernel/bpf/verifier.c-19743-\t\tif (!env-\u003einsn_aux_data[insn_idx].non_sleepable)\nkernel/bpf/verifier.c-19744-\t\t\taddr = (unsigned long)bpf_dynptr_from_file_sleepable;\nkernel/bpf/verifier.c:19745:\t} else if (func_id == special_kfunc_list[KF_bpf_arena_alloc_pages]) {\nkernel/bpf/verifier.c-19746-\t\tif (env-\u003einsn_aux_data[insn_idx].non_sleepable)\nkernel/bpf/verifier.c-19747-\t\t\taddr = (unsigned long)bpf_arena_alloc_pages_non_sleepable;\nkernel/bpf/verifier.c:19748:\t} else if (func_id == special_kfunc_list[KF_bpf_arena_free_pages]) {\nkernel/bpf/verifier.c-19749-\t\tif (env-\u003einsn_aux_data[insn_idx].non_sleepable)\n--\nkernel/bpf/verifier.c=19773=int bpf_fixup_kfunc_call(struct bpf_verifier_env *env, struct bpf_insn *insn,\n--\nkernel/bpf/verifier.c-19850-\t\t */\nkernel/bpf/verifier.c:19851:\t\tif (desc-\u003efunc_id == special_kfunc_list[KF_bpf_list_add] ||\nkernel/bpf/verifier.c-19852-\t\t    is_bpf_rbtree_add_kfunc(desc-\u003efunc_id)) {\n--\nkernel/bpf/verifier.c-19864-\t\t\t\t\t\tnode_offset_reg, insn, insn_buf, cnt);\nkernel/bpf/verifier.c:19865:\t} else if (desc-\u003efunc_id == special_kfunc_list[KF_bpf_cast_to_kern_ctx] ||\nkernel/bpf/verifier.c:19866:\t\t   desc-\u003efunc_id == special_kfunc_list[KF_bpf_rdonly_cast]) {\nkernel/bpf/verifier.c-19867-\t\tinsn_buf[0] = BPF_MOV64_REG(BPF_REG_0, BPF_REG_1);\nkernel/bpf/verifier.c-19868-\t\t*cnt = 1;\nkernel/bpf/verifier.c:19869:\t} else if (desc-\u003efunc_id == special_kfunc_list[KF_bpf_session_is_return] \u0026\u0026\nkernel/bpf/verifier.c-19870-\t\t   (env-\u003eprog-\u003eexpected_attach_type == BPF_TRACE_FSESSION ||\n--\nkernel/bpf/verifier.c-19883-\t\t*cnt = 3;\nkernel/bpf/verifier.c:19884:\t} else if (desc-\u003efunc_id == special_kfunc_list[KF_bpf_session_cookie] \u0026\u0026\nkernel/bpf/verifier.c-19885-\t\t   (env-\u003eprog-\u003eexpected_attach_type == BPF_TRACE_FSESSION ||\n--\nkernel/bpf/verifier.c-19901-\t\t*cnt = 6;\nkernel/bpf/verifier.c:19902:\t} else if (desc-\u003efunc_id == special_kfunc_list[KF_bpf_iter_num_new]) {\nkernel/bpf/verifier.c-19903-\t\t/* inline bpf_iter_num_new(\u0026it, start, end); R1=\u0026it, R2=start, R3=end */\n--\nkernel/bpf/verifier.c-19925-\t\t*cnt = i;\nkernel/bpf/verifier.c:19926:\t} else if (desc-\u003efunc_id == special_kfunc_list[KF_bpf_iter_num_next]) {\nkernel/bpf/verifier.c-19927-\t\t/* inline bpf_iter_num_next(\u0026it); R1=\u0026it, returns \u0026s-\u003ecur or NULL */\n--\nkernel/bpf/verifier.c-19942-\t\t*cnt = i;\nkernel/bpf/verifier.c:19943:\t} else if (desc-\u003efunc_id == special_kfunc_list[KF_bpf_iter_num_destroy]) {\nkernel/bpf/verifier.c-19944-\t\t/* bpf_iter_num_destroy() is a no-op; emit a nop to drop the call */\n"
}

gemini-3.1-pro-preview

null

null

							input: 28418
							output: 129
							thoughts: 177
						

**My Assessment of the Kernel Function List Cleanup**

Okay, so I've looked at this patch and, as I suspected, `special_kfunc_list` is really just a simple lookup table. It's used to quickly determine if a given `func_id` matches a *specific* known entry, essentially performing a direct comparison like `func_id == special_kfunc_list[KF_bpf_arena_alloc_pages]`.

Because `KF_bpf_arena_reserve_pages`, `KF_bpf_stream_vprintk`, and `KF_bpf_stream_print_stack` *aren't* used in any of these crucial comparison checks, their existence in that list is entirely irrelevant. They're just sitting there, taking up space, doing absolutely nothing. The patch simply eliminates these unused enum values and the associated `BTF_ID` entries from `special_kfunc_list`.

This is, from my perspective as an expert, a pure cleanup. It's purely decorative. It has absolutely zero impact on the kernel's execution flow or the verifier's behaviour. It makes the code a bit tidier. Nothing more.

So, for fuzzing purposes, this change is negligible. It's a non-event. No need to devote any fuzzing resources to testing this.

Therefore, `WorthFuzzing=false`.

{
  "EnableConfigs": [],
  "FocusSymbols": [],
  "Reasoning": "The patch removes unused enum values (KF_bpf_arena_reserve_pages, KF_bpf_stream_vprintk, KF_bpf_stream_print_stack) and their corresponding BTF_ID entries from the special_kfunc_list in the BPF verifier. These entries were never referenced anywhere in the verifier code to apply any special logic, so their removal is a pure cleanup with no functional impact on the kernel's execution flow.",
  "WorthFuzzing": false
}

{
  "EnableConfigs": null,
  "FocusSymbols": [],
  "Reasoning": "The patch removes unused enum values (KF_bpf_arena_reserve_pages, KF_bpf_stream_vprintk, KF_bpf_stream_print_stack) and their corresponding BTF_ID entries from the special_kfunc_list in the BPF verifier. These entries were never referenced anywhere in the verifier code to apply any special logic, so their removal is a pure cleanup with no functional impact on the kernel's execution flow.",
  "WorthFuzzing": false
}

{
  "WorthFuzzing": false
}

null