Commit 82bc4abf authored by Yonghong Song's avatar Yonghong Song Committed by Alexei Starovoitov
Browse files

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: default avatarArnd Bergmann <arnd@kernel.org>
Acked-by: default avatarJiri Olsa <jolsa@kernel.org>
Acked-by: default avatarEduard Zingerman <eddyz87@gmail.com>
Signed-off-by: default avatarYonghong Song <yonghong.song@linux.dev>
Link: https://lore.kernel.org/r/20250703141117.1485108-1-yonghong.song@linux.dev


Signed-off-by: default avatarAlexei Starovoitov <ast@kernel.org>
parent 45e9cd38

include/linux/bpf_verifier.h

+1 −0
Original line number Diff line number Diff line
@@ -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;

kernel/bpf/verifier.c

+18 −18
Original line number Diff line number Diff line
@@ -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;