On Tue, Jul 01, 2025 at 10:33:37PM -0700, Yonghong Song wrote:
> 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@xxxxxxxxxx>
> Signed-off-by: Yonghong Song <yonghong.song@xxxxxxxxx>
Acked-by: Jiri Olsa <jolsa@xxxxxxxxxx>
jirka
> ---
> 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
>
>
