netdev - [PATCH] bpf: Add env_type_is_resolved() in front of env_stack_push() in btf

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Date:   Thu,  2 Sep 2021 06:37:00 +0000
From:   jiasheng <jiasheng@...as.ac.cn>
To:     netdev@...r.kernel.org
Cc:     jiasheng <jiasheng@...as.ac.cn>
Subject: [PATCH] bpf: Add env_type_is_resolved() in front of env_stack_push() in btf_resolve()

We have found that in the complied files env_stack_push()
appear more than 10 times, and under at least 90% circumstances
that env_type_is_resolved() and env_stack_push() appear in pairs.
For example, they appear together in the btf_modifier_resolve()
of the file complie from 'kernel/bpf/btf.c'.
But we have found that in the btf_resolve(), there is only
env_stack_push() instead of the pair.
Therefore, we consider that the env_type_is_resolved()
might be forgotten.

Signed-off-by: jiasheng <jiasheng@...as.ac.cn>
---
 kernel/bpf/btf.c | 3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

diff --git a/kernel/bpf/btf.c b/kernel/bpf/btf.c
index f982a9f0..454c249 100644
--- a/kernel/bpf/btf.c
+++ b/kernel/bpf/btf.c
@@ -4002,7 +4002,8 @@ static int btf_resolve(struct btf_verifier_env *env,
 	int err = 0;

 	env->resolve_mode = RESOLVE_TBD;
-	env_stack_push(env, t, type_id);
+	if (env_type_is_resolved(env, type_id))
+		env_stack_push(env, t, type_id);
 	while (!err && (v = env_stack_peak(env))) {
 		env->log_type_id = v->type_id;
 		err = btf_type_ops(v->t)->resolve(env, v);
-- 
2.7.4