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bpf: Avoid putting struct bpf_scc_callchain variables on the stack 

Add a 'struct bpf_scc_callchain callchain_buf' field in bpf_verifier_env.
This way, the previous bpf_scc_callchain local variables can be
replaced by taking address of env->callchain_buf. 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>
Acked-by: Jiri Olsa <jolsa@kernel.org>
Acked-by: Eduard Zingerman <eddyz87@gmail.com>
Signed-off-by: Yonghong Song <yonghong.song@linux.dev>
Link: https://lore.kernel.org/r/20250703141117.1485108-1-yonghong.song@linux.dev
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
pull/1309/head
Yonghong Song 2025-07-03 07:11:17 -07:00 committed by Alexei Starovoitov
parent 45e9cd38aa
commit 82bc4abf28
2 changed files with 19 additions and 18 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

1
include/linux/bpf_verifier.h
View File

@ -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_buf;
/* array of pointers to bpf_scc_info indexed by SCC id */
struct bpf_scc_info **scc_info;
u32 scc_cnt;

36
kernel/bpf/verifier.c
View File

@ -1914,19 +1914,19 @@ 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_buf;
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;
}
@ -1939,21 +1939,21 @@ 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_buf;
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;
@ -1968,22 +1968,22 @@ 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_buf;
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++;
@ -1999,12 +1999,12 @@ 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_buf;
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;