From: Kumar Kartikeya Dwivedi <memxor@gmail.com>
To: bpf@vger.kernel.org
Cc: Andrii Nakryiko <andrii@kernel.org>,
Alexei Starovoitov <ast@kernel.org>,
Daniel Borkmann <daniel@iogearbox.net>,
Eduard Zingerman <eddyz87@gmail.com>,
Emil Tsalapatis <emil@etsalapatis.com>,
kkd@meta.com, kernel-team@meta.com
Subject: [PATCH bpf-next v2 1/3] bpf: Show more useful info in stack depth stats
Date: Mon, 3 Aug 2026 00:52:05 +0200 [thread overview]
Message-ID: <20260802225209.2511758-2-memxor@gmail.com> (raw)
In-Reply-To: <20260802225209.2511758-1-memxor@gmail.com>
Currently, stack depth statistics are too crude, listing captured depths in
subprogram-number order. Since libbpf determines those numbers, it is hard to
associate each depth with its subprogram name.
Print the maximum stack depth and each subprogram on separate lines:
stack depth max <depth>
stack depth subprog <number> <name> <depth>
When no subprogram name is available, print <unknown>.
Suggested-by: Andrii Nakryiko <andrii@kernel.org>
Signed-off-by: Kumar Kartikeya Dwivedi <memxor@gmail.com>
---
kernel/bpf/verifier.c | 13 +++++++----
.../bpf/progs/verifier_basic_stack.c | 4 ++--
.../bpf/progs/verifier_bpf_fastcall.c | 23 ++++++++++++-------
.../bpf/progs/verifier_private_stack.c | 15 +++++++++---
.../selftests/bpf/progs/verifier_var_off.c | 4 ++--
5 files changed, 40 insertions(+), 19 deletions(-)
diff --git a/kernel/bpf/verifier.c b/kernel/bpf/verifier.c
index b274004fccfd..3b61897ed0d2 100644
--- a/kernel/bpf/verifier.c
+++ b/kernel/bpf/verifier.c
@@ -18777,10 +18777,15 @@ static void print_verification_stats(struct bpf_verifier_env *env)
if (env->log.level & BPF_LOG_STATS) {
verbose(env, "verification time %lld usec\n",
div_u64(env->verification_time, 1000));
- verbose(env, "stack depth %d", env->subprog_info[0].stack_depth);
- for (i = 1; i < subprog_cnt; i++)
- verbose(env, "+%d", env->subprog_info[i].stack_depth);
- verbose(env, " max %d\n", env->max_stack_depth);
+ verbose(env, "stack depth max %d\n", env->max_stack_depth);
+ for (i = 0; i < subprog_cnt; i++) {
+ const char *name = env->subprog_info[i].name;
+
+ if (!name || !name[0])
+ name = "<unknown>";
+ verbose(env, "stack depth subprog %d %s %d\n", i, name,
+ env->subprog_info[i].stack_depth);
+ }
verbose(env, "insns processed %d", env->subprog_info[0].insn_processed);
for (i = 1; i < subprog_cnt; i++)
if (bpf_subprog_is_global(env, i))
diff --git a/tools/testing/selftests/bpf/progs/verifier_basic_stack.c b/tools/testing/selftests/bpf/progs/verifier_basic_stack.c
index fb62e09f2114..61ec8790fd21 100644
--- a/tools/testing/selftests/bpf/progs/verifier_basic_stack.c
+++ b/tools/testing/selftests/bpf/progs/verifier_basic_stack.c
@@ -27,7 +27,7 @@ __naked void stack_out_of_bounds(void)
SEC("socket")
__description("uninitialized stack1")
-__success __log_level(4) __msg("stack depth 8")
+__success __log_level(4) __msg("stack depth subprog 0 uninitialized_stack1 8")
__failure_unpriv __msg_unpriv("invalid read from stack")
__naked void uninitialized_stack1(void)
{
@@ -45,7 +45,7 @@ __naked void uninitialized_stack1(void)
SEC("socket")
__description("uninitialized stack2")
-__success __log_level(4) __msg("stack depth 8")
+__success __log_level(4) __msg("stack depth subprog 0 uninitialized_stack2 8")
__failure_unpriv __msg_unpriv("invalid read from stack")
__naked void uninitialized_stack2(void)
{
diff --git a/tools/testing/selftests/bpf/progs/verifier_bpf_fastcall.c b/tools/testing/selftests/bpf/progs/verifier_bpf_fastcall.c
index 83707faea049..cb36866bfed3 100644
--- a/tools/testing/selftests/bpf/progs/verifier_bpf_fastcall.c
+++ b/tools/testing/selftests/bpf/progs/verifier_bpf_fastcall.c
@@ -10,7 +10,7 @@
SEC("raw_tp")
__arch_x86_64
-__log_level(4) __msg("stack depth 8")
+__log_level(4) __msg("stack depth subprog 0 simple 8")
__xlated("4: r5 = 5")
__xlated("5: r0 = ")
__xlated("6: r0 = &(void __percpu *)(r0)")
@@ -96,7 +96,7 @@ __naked void canary_zero_spills(void)
SEC("raw_tp")
__arch_x86_64
-__log_level(4) __msg("stack depth 16")
+__log_level(4) __msg("stack depth subprog 0 wrong_reg_in_pattern1 16")
__xlated("1: *(u64 *)(r10 -16) = r1")
__xlated("...")
__xlated("3: r0 = &(void __percpu *)(r0)")
@@ -598,7 +598,7 @@ __naked static void subprogs_use_independent_offsets_aux(void)
SEC("raw_tp")
__arch_x86_64
-__log_level(4) __msg("stack depth 8")
+__log_level(4) __msg("stack depth subprog 0 helper_call_does_not_prevent_bpf_fastcall 8")
__xlated("2: r0 = &(void __percpu *)(r0)")
__success
__naked void helper_call_does_not_prevent_bpf_fastcall(void)
@@ -620,7 +620,7 @@ __naked void helper_call_does_not_prevent_bpf_fastcall(void)
SEC("raw_tp")
__arch_x86_64
-__log_level(4) __msg("stack depth 24")
+__log_level(4) __msg("stack depth subprog 0 may_goto_interaction_x86_64 24")
/* may_goto counter at -24 */
__xlated("0: *(u64 *)(r10 -24) =")
/* may_goto timestamp at -16 */
@@ -661,7 +661,7 @@ __naked void may_goto_interaction_x86_64(void)
SEC("raw_tp")
__arch_arm64
__arch_riscv64
-__log_level(4) __msg("stack depth 24")
+__log_level(4) __msg("stack depth subprog 0 may_goto_interaction 24")
/* may_goto counter at -24 */
__xlated("0: *(u64 *)(r10 -24) =")
/* may_goto timestamp at -16 */
@@ -708,7 +708,9 @@ __naked static void dummy_loop_callback(void)
SEC("raw_tp")
__arch_x86_64
-__log_level(4) __msg("stack depth 32+0")
+__log_level(4)
+__msg("stack depth subprog 0 bpf_loop_interaction1 32")
+__msg("stack depth subprog 1 dummy_loop_callback 0")
__xlated("2: r1 = 1")
__xlated("3: r0 =")
__xlated("4: r0 = &(void __percpu *)(r0)")
@@ -756,7 +758,9 @@ __naked int bpf_loop_interaction1(void)
SEC("raw_tp")
__arch_x86_64
-__log_level(4) __msg("stack depth 40+0")
+__log_level(4)
+__msg("stack depth subprog 0 bpf_loop_interaction2 40")
+__msg("stack depth subprog 1 dummy_loop_callback 0")
/* call bpf_get_smp_processor_id */
__xlated("2: r1 = 42")
__xlated("3: r0 =")
@@ -800,7 +804,10 @@ __naked int bpf_loop_interaction2(void)
SEC("raw_tp")
__arch_x86_64
-__log_level(4) __msg("stack depth 512+0 max 512")
+__log_level(4)
+__msg("stack depth max 512")
+__msg("stack depth subprog 0 cumulative_stack_depth 512")
+__msg("stack depth subprog 1 cumulative_stack_depth_subprog 0")
/* just to print xlated version when debugging */
__xlated("r0 = &(void __percpu *)(r0)")
__success
diff --git a/tools/testing/selftests/bpf/progs/verifier_private_stack.c b/tools/testing/selftests/bpf/progs/verifier_private_stack.c
index bb8206e10880..c818898836c1 100644
--- a/tools/testing/selftests/bpf/progs/verifier_private_stack.c
+++ b/tools/testing/selftests/bpf/progs/verifier_private_stack.c
@@ -86,7 +86,9 @@ __naked static void cumulative_stack_depth_subprog(void)
SEC("kprobe")
__description("Private stack, subtree > MAX_BPF_STACK")
__success
-__log_level(4) __msg("stack depth 512+32 max 512")
+__log_level(4) __msg("stack depth max 512")
+__msg("stack depth subprog 0 private_stack_nested_1 512")
+__msg("stack depth subprog 1 cumulative_stack_depth_subprog 32")
__arch_x86_64
/* private stack fp for the main prog */
__jited(" movabsq $0x{{.*}}, %r9")
@@ -331,7 +333,11 @@ SEC("fentry/bpf_fentry_test9")
__description("Private stack, async callback, potential nesting")
__success __retval(0)
__load_if_JITed()
-__log_level(4) __msg("stack depth 8+0+256+0 max 272")
+__log_level(4) __msg("stack depth max 272")
+__msg("stack depth subprog 0 private_stack_async_callback_2 8")
+__msg("stack depth subprog 1 timer_cb1 0")
+__msg("stack depth subprog 2 subprog1 256")
+__msg("stack depth subprog 3 subprog2 0")
__arch_x86_64
__jited(" subq $0x100, %rsp")
__arch_arm64
@@ -355,7 +361,10 @@ int private_stack_async_callback_2(void)
SEC("fentry/bpf_fentry_test9")
__description("private stack, max stack depth is private stack")
__success
-__log_level(4) __msg("stack depth 8+256+0 max 256")
+__log_level(4) __msg("stack depth max 256")
+__msg("stack depth subprog 0 private_stack_max_depth 8")
+__msg("stack depth subprog 1 subprog1 256")
+__msg("stack depth subprog 2 subprog2 0")
int private_stack_max_depth(void)
{
int x = 0;
diff --git a/tools/testing/selftests/bpf/progs/verifier_var_off.c b/tools/testing/selftests/bpf/progs/verifier_var_off.c
index 24cd0a763673..df436bbc9ecf 100644
--- a/tools/testing/selftests/bpf/progs/verifier_var_off.c
+++ b/tools/testing/selftests/bpf/progs/verifier_var_off.c
@@ -198,7 +198,7 @@ __success
/* Check that the maximum stack depth is correctly maintained according to the
* maximum possible variable offset.
*/
-__log_level(4) __msg("stack depth 16")
+__log_level(4) __msg("stack depth subprog 0 stack_write_priv_vs_unpriv 16")
__failure_unpriv
/* Variable stack access is rejected for unprivileged.
*/
@@ -238,7 +238,7 @@ __success
/* Check that the maximum stack depth is correctly maintained according to the
* maximum possible variable offset.
*/
-__log_level(4) __msg("stack depth 16")
+__log_level(4) __msg("stack depth subprog 0 stack_write_followed_by_read 16")
__failure_unpriv
__msg_unpriv("R2 variable stack access prohibited for !root")
__retval(0)
--
2.53.0
next prev parent reply other threads:[~2026-08-02 22:52 UTC|newest]
Thread overview: 8+ messages / expand[flat|nested] mbox.gz Atom feed top
2026-08-02 22:52 [PATCH bpf-next v2 0/3] Improve stack depth verification stats output Kumar Kartikeya Dwivedi
2026-08-02 22:52 ` Kumar Kartikeya Dwivedi [this message]
2026-08-02 23:04 ` [PATCH bpf-next v2 1/3] bpf: Show more useful info in stack depth stats sashiko-bot
2026-08-02 23:09 ` Kumar Kartikeya Dwivedi
2026-08-03 0:21 ` bot+bpf-ci
2026-08-03 0:40 ` Kumar Kartikeya Dwivedi
2026-08-02 22:52 ` [PATCH bpf-next v2 2/3] selftests/bpf: Adjust veristat stack depth parsing Kumar Kartikeya Dwivedi
2026-08-02 22:52 ` [PATCH bpf-next v2 3/3] selftests/bpf: Test stack depth stats without BTF subprog names Kumar Kartikeya Dwivedi
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