* [PATCH] bpf: Add env_type_is_resolved() in front of env_stack_push() in btf_resolve()
@ 2021-09-02 6:37 jiasheng
2021-09-07 22:24 ` Martin KaFai Lau
0 siblings, 1 reply; 3+ messages in thread
From: jiasheng @ 2021-09-02 6:37 UTC (permalink / raw)
To: bpf; +Cc: jiasheng
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@iscas.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
^ permalink raw reply related [flat|nested] 3+ messages in thread
* Re: [PATCH] bpf: Add env_type_is_resolved() in front of env_stack_push() in btf_resolve()
2021-09-02 6:37 [PATCH] bpf: Add env_type_is_resolved() in front of env_stack_push() in btf_resolve() jiasheng
@ 2021-09-07 22:24 ` Martin KaFai Lau
2021-09-08 0:25 ` Andrii Nakryiko
0 siblings, 1 reply; 3+ messages in thread
From: Martin KaFai Lau @ 2021-09-07 22:24 UTC (permalink / raw)
To: jiasheng; +Cc: bpf
On Thu, Sep 02, 2021 at 06:37:13AM +0000, jiasheng wrote:
> 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.
It does not justify a change like this just because
one of its usage looks different and then concluded that
it _might_ be forgotten.
Does it have a bug or not? If there is, please
provide an explanation on how to reproduce it first.
>
> Signed-off-by: jiasheng <jiasheng@iscas.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
>
^ permalink raw reply [flat|nested] 3+ messages in thread
* Re: [PATCH] bpf: Add env_type_is_resolved() in front of env_stack_push() in btf_resolve()
2021-09-07 22:24 ` Martin KaFai Lau
@ 2021-09-08 0:25 ` Andrii Nakryiko
0 siblings, 0 replies; 3+ messages in thread
From: Andrii Nakryiko @ 2021-09-08 0:25 UTC (permalink / raw)
To: Martin KaFai Lau; +Cc: jiasheng, bpf
On Tue, Sep 7, 2021 at 3:37 PM Martin KaFai Lau <kafai@fb.com> wrote:
>
> On Thu, Sep 02, 2021 at 06:37:13AM +0000, jiasheng wrote:
> > 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.
> It does not justify a change like this just because
> one of its usage looks different and then concluded that
> it _might_ be forgotten.
>
> Does it have a bug or not? If there is, please
> provide an explanation on how to reproduce it first.
>
Both places that call btf_resolve() check that env_type_is_resolved()
first, so there is no issue here.
> >
> > Signed-off-by: jiasheng <jiasheng@iscas.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
> >
^ permalink raw reply [flat|nested] 3+ messages in thread
end of thread, other threads:[~2021-09-08 0:25 UTC | newest]
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2021-09-02 6:37 [PATCH] bpf: Add env_type_is_resolved() in front of env_stack_push() in btf_resolve() jiasheng
2021-09-07 22:24 ` Martin KaFai Lau
2021-09-08 0:25 ` Andrii Nakryiko
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