From: Yonghong Song <yonghong.song@linux.dev>
To: bpf@vger.kernel.org
Cc: Alexei Starovoitov <ast@kernel.org>,
Andrii Nakryiko <andrii@kernel.org>,
Daniel Borkmann <daniel@iogearbox.net>,
kernel-team@fb.com, Martin KaFai Lau <martin.lau@kernel.org>,
Arnd Bergmann <arnd@kernel.org>
Subject: [PATCH bpf-next 2/2] bpf: Avoid putting struct bpf_scc_callchain variables on the stack
Date: Tue, 1 Jul 2025 22:33:37 -0700 [thread overview]
Message-ID: <20250702053337.1991752-1-yonghong.song@linux.dev> (raw)
In-Reply-To: <20250702053332.1991516-1-yonghong.song@linux.dev>
Add a 'struct bpf_scc_callchain callchain' field in bpf_verifier_env.
This way, the previous bpf_scc_callchain local variables can be
replaced by taking address of env->callchain. This can reduce stack
usage and fix the following error:
kernel/bpf/verifier.c:19921:12: error: stack frame size (1368) exceeds limit (1280) in 'do_check'
[-Werror,-Wframe-larger-than]
Reported-by: Arnd Bergmann <arnd@kernel.org>
Signed-off-by: Yonghong Song <yonghong.song@linux.dev>
---
include/linux/bpf_verifier.h | 1 +
kernel/bpf/verifier.c | 36 ++++++++++++++++++------------------
2 files changed, 19 insertions(+), 18 deletions(-)
diff --git a/include/linux/bpf_verifier.h b/include/linux/bpf_verifier.h
index 7e459e839f8b..e2c175d608bb 100644
--- a/include/linux/bpf_verifier.h
+++ b/include/linux/bpf_verifier.h
@@ -841,6 +841,7 @@ struct bpf_verifier_env {
char tmp_str_buf[TMP_STR_BUF_LEN];
struct bpf_insn insn_buf[INSN_BUF_SIZE];
struct bpf_insn epilogue_buf[INSN_BUF_SIZE];
+ struct bpf_scc_callchain callchain;
/* array of pointers to bpf_scc_info indexed by SCC id */
struct bpf_scc_info **scc_info;
u32 scc_cnt;
diff --git a/kernel/bpf/verifier.c b/kernel/bpf/verifier.c
index 29faef51065d..b334e6434eb4 100644
--- a/kernel/bpf/verifier.c
+++ b/kernel/bpf/verifier.c
@@ -1913,19 +1913,19 @@ static char *format_callchain(struct bpf_verifier_env *env, struct bpf_scc_callc
*/
static int maybe_enter_scc(struct bpf_verifier_env *env, struct bpf_verifier_state *st)
{
- struct bpf_scc_callchain callchain;
+ struct bpf_scc_callchain *callchain = &env->callchain;
struct bpf_scc_visit *visit;
- if (!compute_scc_callchain(env, st, &callchain))
+ if (!compute_scc_callchain(env, st, callchain))
return 0;
- visit = scc_visit_lookup(env, &callchain);
- visit = visit ?: scc_visit_alloc(env, &callchain);
+ visit = scc_visit_lookup(env, callchain);
+ visit = visit ?: scc_visit_alloc(env, callchain);
if (!visit)
return -ENOMEM;
if (!visit->entry_state) {
visit->entry_state = st;
if (env->log.level & BPF_LOG_LEVEL2)
- verbose(env, "SCC enter %s\n", format_callchain(env, &callchain));
+ verbose(env, "SCC enter %s\n", format_callchain(env, callchain));
}
return 0;
}
@@ -1938,21 +1938,21 @@ static int propagate_backedges(struct bpf_verifier_env *env, struct bpf_scc_visi
*/
static int maybe_exit_scc(struct bpf_verifier_env *env, struct bpf_verifier_state *st)
{
- struct bpf_scc_callchain callchain;
+ struct bpf_scc_callchain *callchain = &env->callchain;
struct bpf_scc_visit *visit;
- if (!compute_scc_callchain(env, st, &callchain))
+ if (!compute_scc_callchain(env, st, callchain))
return 0;
- visit = scc_visit_lookup(env, &callchain);
+ visit = scc_visit_lookup(env, callchain);
if (!visit) {
verifier_bug(env, "scc exit: no visit info for call chain %s",
- format_callchain(env, &callchain));
+ format_callchain(env, callchain));
return -EFAULT;
}
if (visit->entry_state != st)
return 0;
if (env->log.level & BPF_LOG_LEVEL2)
- verbose(env, "SCC exit %s\n", format_callchain(env, &callchain));
+ verbose(env, "SCC exit %s\n", format_callchain(env, callchain));
visit->entry_state = NULL;
env->num_backedges -= visit->num_backedges;
visit->num_backedges = 0;
@@ -1967,22 +1967,22 @@ static int add_scc_backedge(struct bpf_verifier_env *env,
struct bpf_verifier_state *st,
struct bpf_scc_backedge *backedge)
{
- struct bpf_scc_callchain callchain;
+ struct bpf_scc_callchain *callchain = &env->callchain;
struct bpf_scc_visit *visit;
- if (!compute_scc_callchain(env, st, &callchain)) {
+ if (!compute_scc_callchain(env, st, callchain)) {
verifier_bug(env, "add backedge: no SCC in verification path, insn_idx %d",
st->insn_idx);
return -EFAULT;
}
- visit = scc_visit_lookup(env, &callchain);
+ visit = scc_visit_lookup(env, callchain);
if (!visit) {
verifier_bug(env, "add backedge: no visit info for call chain %s",
- format_callchain(env, &callchain));
+ format_callchain(env, callchain));
return -EFAULT;
}
if (env->log.level & BPF_LOG_LEVEL2)
- verbose(env, "SCC backedge %s\n", format_callchain(env, &callchain));
+ verbose(env, "SCC backedge %s\n", format_callchain(env, callchain));
backedge->next = visit->backedges;
visit->backedges = backedge;
visit->num_backedges++;
@@ -1998,12 +1998,12 @@ static int add_scc_backedge(struct bpf_verifier_env *env,
static bool incomplete_read_marks(struct bpf_verifier_env *env,
struct bpf_verifier_state *st)
{
- struct bpf_scc_callchain callchain;
+ struct bpf_scc_callchain *callchain = &env->callchain;
struct bpf_scc_visit *visit;
- if (!compute_scc_callchain(env, st, &callchain))
+ if (!compute_scc_callchain(env, st, callchain))
return false;
- visit = scc_visit_lookup(env, &callchain);
+ visit = scc_visit_lookup(env, callchain);
if (!visit)
return false;
return !!visit->backedges;
--
2.47.1
next prev parent reply other threads:[~2025-07-02 5:33 UTC|newest]
Thread overview: 7+ messages / expand[flat|nested] mbox.gz Atom feed top
2025-07-02 5:33 [PATCH bpf-next 1/2] bpf: Reduce stack frame size by using env->insn_buf for bpf insns Yonghong Song
2025-07-02 5:33 ` Yonghong Song [this message]
2025-07-02 8:49 ` [PATCH bpf-next 2/2] bpf: Avoid putting struct bpf_scc_callchain variables on the stack Jiri Olsa
2025-07-02 8:54 ` [PATCH bpf-next 1/2] bpf: Reduce stack frame size by using env->insn_buf for bpf insns Jiri Olsa
2025-07-02 9:28 ` Arnd Bergmann
2025-07-02 15:09 ` Alexei Starovoitov
2025-07-02 15:29 ` Yonghong Song
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