* [PATCH bpf-next] selftests/bpf: Fix map_kptr test.
@ 2023-02-14 23:50 Alexei Starovoitov
2023-02-15 3:02 ` Stanislav Fomichev
` (2 more replies)
0 siblings, 3 replies; 6+ messages in thread
From: Alexei Starovoitov @ 2023-02-14 23:50 UTC (permalink / raw)
To: davem; +Cc: daniel, andrii, martin.lau, memxor, netdev, bpf, kernel-team
From: Alexei Starovoitov <ast@kernel.org>
The compiler is optimizing out majority of unref_ptr read/writes, so the test
wasn't testing much. For example, one could delete '__kptr' tag from
'struct prog_test_ref_kfunc __kptr *unref_ptr;' and the test would still "pass".
Convert it to volatile stores. Confirmed by comparing bpf asm before/after.
Fixes: 2cbc469a6fc3 ("selftests/bpf: Add C tests for kptr")
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
---
tools/testing/selftests/bpf/progs/map_kptr.c | 12 +++++++-----
1 file changed, 7 insertions(+), 5 deletions(-)
diff --git a/tools/testing/selftests/bpf/progs/map_kptr.c b/tools/testing/selftests/bpf/progs/map_kptr.c
index eb8217803493..228ec45365a8 100644
--- a/tools/testing/selftests/bpf/progs/map_kptr.c
+++ b/tools/testing/selftests/bpf/progs/map_kptr.c
@@ -62,21 +62,23 @@ extern struct prog_test_ref_kfunc *
bpf_kfunc_call_test_kptr_get(struct prog_test_ref_kfunc **p, int a, int b) __ksym;
extern void bpf_kfunc_call_test_release(struct prog_test_ref_kfunc *p) __ksym;
+#define WRITE_ONCE(x, val) ((*(volatile typeof(x) *) &(x)) = (val))
+
static void test_kptr_unref(struct map_value *v)
{
struct prog_test_ref_kfunc *p;
p = v->unref_ptr;
/* store untrusted_ptr_or_null_ */
- v->unref_ptr = p;
+ WRITE_ONCE(v->unref_ptr, p);
if (!p)
return;
if (p->a + p->b > 100)
return;
/* store untrusted_ptr_ */
- v->unref_ptr = p;
+ WRITE_ONCE(v->unref_ptr, p);
/* store NULL */
- v->unref_ptr = NULL;
+ WRITE_ONCE(v->unref_ptr, NULL);
}
static void test_kptr_ref(struct map_value *v)
@@ -85,7 +87,7 @@ static void test_kptr_ref(struct map_value *v)
p = v->ref_ptr;
/* store ptr_or_null_ */
- v->unref_ptr = p;
+ WRITE_ONCE(v->unref_ptr, p);
if (!p)
return;
if (p->a + p->b > 100)
@@ -99,7 +101,7 @@ static void test_kptr_ref(struct map_value *v)
return;
}
/* store ptr_ */
- v->unref_ptr = p;
+ WRITE_ONCE(v->unref_ptr, p);
bpf_kfunc_call_test_release(p);
p = bpf_kfunc_call_test_acquire(&(unsigned long){0});
--
2.30.2
^ permalink raw reply related [flat|nested] 6+ messages in thread* Re: [PATCH bpf-next] selftests/bpf: Fix map_kptr test.
2023-02-14 23:50 [PATCH bpf-next] selftests/bpf: Fix map_kptr test Alexei Starovoitov
@ 2023-02-15 3:02 ` Stanislav Fomichev
2023-02-15 3:20 ` Alexei Starovoitov
2023-02-15 10:26 ` Kumar Kartikeya Dwivedi
2023-02-15 17:30 ` patchwork-bot+netdevbpf
2 siblings, 1 reply; 6+ messages in thread
From: Stanislav Fomichev @ 2023-02-15 3:02 UTC (permalink / raw)
To: Alexei Starovoitov
Cc: davem, daniel, andrii, martin.lau, memxor, netdev, bpf,
kernel-team
On 02/14, Alexei Starovoitov wrote:
> From: Alexei Starovoitov <ast@kernel.org>
> The compiler is optimizing out majority of unref_ptr read/writes, so the
> test
> wasn't testing much. For example, one could delete '__kptr' tag from
> 'struct prog_test_ref_kfunc __kptr *unref_ptr;' and the test would
> still "pass".
> Convert it to volatile stores. Confirmed by comparing bpf asm
> before/after.
> Fixes: 2cbc469a6fc3 ("selftests/bpf: Add C tests for kptr")
> Signed-off-by: Alexei Starovoitov <ast@kernel.org>
Acked-by: Stanislav Fomichev <sdf@google.com>
> ---
> tools/testing/selftests/bpf/progs/map_kptr.c | 12 +++++++-----
> 1 file changed, 7 insertions(+), 5 deletions(-)
> diff --git a/tools/testing/selftests/bpf/progs/map_kptr.c
> b/tools/testing/selftests/bpf/progs/map_kptr.c
> index eb8217803493..228ec45365a8 100644
> --- a/tools/testing/selftests/bpf/progs/map_kptr.c
> +++ b/tools/testing/selftests/bpf/progs/map_kptr.c
> @@ -62,21 +62,23 @@ extern struct prog_test_ref_kfunc *
> bpf_kfunc_call_test_kptr_get(struct prog_test_ref_kfunc **p, int a, int
> b) __ksym;
> extern void bpf_kfunc_call_test_release(struct prog_test_ref_kfunc *p)
> __ksym;
[..]
> +#define WRITE_ONCE(x, val) ((*(volatile typeof(x) *) &(x)) = (val))
(thinking out loud)
Maybe time for us to put these into some common headers in the
selftests.
progs/test_ksyms_btf_null_check.c READ_ONCE as well..
> +
> static void test_kptr_unref(struct map_value *v)
> {
> struct prog_test_ref_kfunc *p;
> p = v->unref_ptr;
> /* store untrusted_ptr_or_null_ */
> - v->unref_ptr = p;
> + WRITE_ONCE(v->unref_ptr, p);
> if (!p)
> return;
> if (p->a + p->b > 100)
> return;
> /* store untrusted_ptr_ */
> - v->unref_ptr = p;
> + WRITE_ONCE(v->unref_ptr, p);
> /* store NULL */
> - v->unref_ptr = NULL;
> + WRITE_ONCE(v->unref_ptr, NULL);
> }
> static void test_kptr_ref(struct map_value *v)
> @@ -85,7 +87,7 @@ static void test_kptr_ref(struct map_value *v)
> p = v->ref_ptr;
> /* store ptr_or_null_ */
> - v->unref_ptr = p;
> + WRITE_ONCE(v->unref_ptr, p);
> if (!p)
> return;
> if (p->a + p->b > 100)
> @@ -99,7 +101,7 @@ static void test_kptr_ref(struct map_value *v)
> return;
> }
> /* store ptr_ */
> - v->unref_ptr = p;
> + WRITE_ONCE(v->unref_ptr, p);
> bpf_kfunc_call_test_release(p);
> p = bpf_kfunc_call_test_acquire(&(unsigned long){0});
> --
> 2.30.2
^ permalink raw reply [flat|nested] 6+ messages in thread* Re: [PATCH bpf-next] selftests/bpf: Fix map_kptr test.
2023-02-15 3:02 ` Stanislav Fomichev
@ 2023-02-15 3:20 ` Alexei Starovoitov
2023-02-15 17:36 ` Stanislav Fomichev
0 siblings, 1 reply; 6+ messages in thread
From: Alexei Starovoitov @ 2023-02-15 3:20 UTC (permalink / raw)
To: Stanislav Fomichev
Cc: David S. Miller, Daniel Borkmann, Andrii Nakryiko,
Martin KaFai Lau, Kumar Kartikeya Dwivedi, Network Development,
bpf, Kernel Team
On Tue, Feb 14, 2023 at 7:02 PM Stanislav Fomichev <sdf@google.com> wrote:
>
> On 02/14, Alexei Starovoitov wrote:
> > From: Alexei Starovoitov <ast@kernel.org>
>
> > The compiler is optimizing out majority of unref_ptr read/writes, so the
> > test
> > wasn't testing much. For example, one could delete '__kptr' tag from
> > 'struct prog_test_ref_kfunc __kptr *unref_ptr;' and the test would
> > still "pass".
>
> > Convert it to volatile stores. Confirmed by comparing bpf asm
> > before/after.
>
> > Fixes: 2cbc469a6fc3 ("selftests/bpf: Add C tests for kptr")
> > Signed-off-by: Alexei Starovoitov <ast@kernel.org>
>
> Acked-by: Stanislav Fomichev <sdf@google.com>
>
> > ---
> > tools/testing/selftests/bpf/progs/map_kptr.c | 12 +++++++-----
> > 1 file changed, 7 insertions(+), 5 deletions(-)
>
> > diff --git a/tools/testing/selftests/bpf/progs/map_kptr.c
> > b/tools/testing/selftests/bpf/progs/map_kptr.c
> > index eb8217803493..228ec45365a8 100644
> > --- a/tools/testing/selftests/bpf/progs/map_kptr.c
> > +++ b/tools/testing/selftests/bpf/progs/map_kptr.c
> > @@ -62,21 +62,23 @@ extern struct prog_test_ref_kfunc *
> > bpf_kfunc_call_test_kptr_get(struct prog_test_ref_kfunc **p, int a, int
> > b) __ksym;
> > extern void bpf_kfunc_call_test_release(struct prog_test_ref_kfunc *p)
> > __ksym;
>
>
> [..]
>
> > +#define WRITE_ONCE(x, val) ((*(volatile typeof(x) *) &(x)) = (val))
>
> (thinking out loud)
>
> Maybe time for us to put these into some common headers in the
> selftests.
> progs/test_ksyms_btf_null_check.c READ_ONCE as well..
Not quite. There is no READ_ONCE there. Only comment about it :)
But yeah a follow up is necessary, but it's not that simple.
I think it's ok to use WRITE_ONCE here, but
saying it's a generic thing for all bpf programs to use
is not something we can do without defining a BPF memory model.
So it's a whole can of worms that I'd rather not open right now.
^ permalink raw reply [flat|nested] 6+ messages in thread* Re: [PATCH bpf-next] selftests/bpf: Fix map_kptr test.
2023-02-15 3:20 ` Alexei Starovoitov
@ 2023-02-15 17:36 ` Stanislav Fomichev
0 siblings, 0 replies; 6+ messages in thread
From: Stanislav Fomichev @ 2023-02-15 17:36 UTC (permalink / raw)
To: Alexei Starovoitov
Cc: David S. Miller, Daniel Borkmann, Andrii Nakryiko,
Martin KaFai Lau, Kumar Kartikeya Dwivedi, Network Development,
bpf, Kernel Team
On Tue, Feb 14, 2023 at 7:20 PM Alexei Starovoitov
<alexei.starovoitov@gmail.com> wrote:
>
> On Tue, Feb 14, 2023 at 7:02 PM Stanislav Fomichev <sdf@google.com> wrote:
> >
> > On 02/14, Alexei Starovoitov wrote:
> > > From: Alexei Starovoitov <ast@kernel.org>
> >
> > > The compiler is optimizing out majority of unref_ptr read/writes, so the
> > > test
> > > wasn't testing much. For example, one could delete '__kptr' tag from
> > > 'struct prog_test_ref_kfunc __kptr *unref_ptr;' and the test would
> > > still "pass".
> >
> > > Convert it to volatile stores. Confirmed by comparing bpf asm
> > > before/after.
> >
> > > Fixes: 2cbc469a6fc3 ("selftests/bpf: Add C tests for kptr")
> > > Signed-off-by: Alexei Starovoitov <ast@kernel.org>
> >
> > Acked-by: Stanislav Fomichev <sdf@google.com>
> >
> > > ---
> > > tools/testing/selftests/bpf/progs/map_kptr.c | 12 +++++++-----
> > > 1 file changed, 7 insertions(+), 5 deletions(-)
> >
> > > diff --git a/tools/testing/selftests/bpf/progs/map_kptr.c
> > > b/tools/testing/selftests/bpf/progs/map_kptr.c
> > > index eb8217803493..228ec45365a8 100644
> > > --- a/tools/testing/selftests/bpf/progs/map_kptr.c
> > > +++ b/tools/testing/selftests/bpf/progs/map_kptr.c
> > > @@ -62,21 +62,23 @@ extern struct prog_test_ref_kfunc *
> > > bpf_kfunc_call_test_kptr_get(struct prog_test_ref_kfunc **p, int a, int
> > > b) __ksym;
> > > extern void bpf_kfunc_call_test_release(struct prog_test_ref_kfunc *p)
> > > __ksym;
> >
> >
> > [..]
> >
> > > +#define WRITE_ONCE(x, val) ((*(volatile typeof(x) *) &(x)) = (val))
> >
> > (thinking out loud)
> >
> > Maybe time for us to put these into some common headers in the
> > selftests.
> > progs/test_ksyms_btf_null_check.c READ_ONCE as well..
>
> Not quite. There is no READ_ONCE there. Only comment about it :)
/* READ_ONCE */
*(volatile int *)active;
^^^ looks like a real read_once to me? not just a comment?
> But yeah a follow up is necessary, but it's not that simple.
> I think it's ok to use WRITE_ONCE here, but
> saying it's a generic thing for all bpf programs to use
> is not something we can do without defining a BPF memory model.
> So it's a whole can of worms that I'd rather not open right now.
SG!
^ permalink raw reply [flat|nested] 6+ messages in thread
* Re: [PATCH bpf-next] selftests/bpf: Fix map_kptr test.
2023-02-14 23:50 [PATCH bpf-next] selftests/bpf: Fix map_kptr test Alexei Starovoitov
2023-02-15 3:02 ` Stanislav Fomichev
@ 2023-02-15 10:26 ` Kumar Kartikeya Dwivedi
2023-02-15 17:30 ` patchwork-bot+netdevbpf
2 siblings, 0 replies; 6+ messages in thread
From: Kumar Kartikeya Dwivedi @ 2023-02-15 10:26 UTC (permalink / raw)
To: Alexei Starovoitov
Cc: davem, daniel, andrii, martin.lau, netdev, bpf, kernel-team
On Wed, Feb 15, 2023 at 12:50:51AM CET, Alexei Starovoitov wrote:
> From: Alexei Starovoitov <ast@kernel.org>
>
> The compiler is optimizing out majority of unref_ptr read/writes, so the test
> wasn't testing much. For example, one could delete '__kptr' tag from
> 'struct prog_test_ref_kfunc __kptr *unref_ptr;' and the test would still "pass".
>
> Convert it to volatile stores. Confirmed by comparing bpf asm before/after.
>
> Fixes: 2cbc469a6fc3 ("selftests/bpf: Add C tests for kptr")
> Signed-off-by: Alexei Starovoitov <ast@kernel.org>
> ---
Acked-by: Kumar Kartikeya Dwivedi <memxor@gmail.com>
There's also the same test in the test_verifier suite, so there's still coverage
for this case.
> tools/testing/selftests/bpf/progs/map_kptr.c | 12 +++++++-----
> 1 file changed, 7 insertions(+), 5 deletions(-)
>
> diff --git a/tools/testing/selftests/bpf/progs/map_kptr.c b/tools/testing/selftests/bpf/progs/map_kptr.c
> index eb8217803493..228ec45365a8 100644
> --- a/tools/testing/selftests/bpf/progs/map_kptr.c
> +++ b/tools/testing/selftests/bpf/progs/map_kptr.c
> @@ -62,21 +62,23 @@ extern struct prog_test_ref_kfunc *
> bpf_kfunc_call_test_kptr_get(struct prog_test_ref_kfunc **p, int a, int b) __ksym;
> extern void bpf_kfunc_call_test_release(struct prog_test_ref_kfunc *p) __ksym;
>
> +#define WRITE_ONCE(x, val) ((*(volatile typeof(x) *) &(x)) = (val))
> +
> static void test_kptr_unref(struct map_value *v)
> {
> struct prog_test_ref_kfunc *p;
>
> p = v->unref_ptr;
> /* store untrusted_ptr_or_null_ */
> - v->unref_ptr = p;
> + WRITE_ONCE(v->unref_ptr, p);
> if (!p)
> return;
> if (p->a + p->b > 100)
> return;
> /* store untrusted_ptr_ */
> - v->unref_ptr = p;
> + WRITE_ONCE(v->unref_ptr, p);
> /* store NULL */
> - v->unref_ptr = NULL;
> + WRITE_ONCE(v->unref_ptr, NULL);
> }
>
> static void test_kptr_ref(struct map_value *v)
> @@ -85,7 +87,7 @@ static void test_kptr_ref(struct map_value *v)
>
> p = v->ref_ptr;
> /* store ptr_or_null_ */
> - v->unref_ptr = p;
> + WRITE_ONCE(v->unref_ptr, p);
> if (!p)
> return;
> if (p->a + p->b > 100)
> @@ -99,7 +101,7 @@ static void test_kptr_ref(struct map_value *v)
> return;
> }
> /* store ptr_ */
> - v->unref_ptr = p;
> + WRITE_ONCE(v->unref_ptr, p);
> bpf_kfunc_call_test_release(p);
>
> p = bpf_kfunc_call_test_acquire(&(unsigned long){0});
> --
> 2.30.2
>
^ permalink raw reply [flat|nested] 6+ messages in thread* Re: [PATCH bpf-next] selftests/bpf: Fix map_kptr test.
2023-02-14 23:50 [PATCH bpf-next] selftests/bpf: Fix map_kptr test Alexei Starovoitov
2023-02-15 3:02 ` Stanislav Fomichev
2023-02-15 10:26 ` Kumar Kartikeya Dwivedi
@ 2023-02-15 17:30 ` patchwork-bot+netdevbpf
2 siblings, 0 replies; 6+ messages in thread
From: patchwork-bot+netdevbpf @ 2023-02-15 17:30 UTC (permalink / raw)
To: Alexei Starovoitov
Cc: davem, daniel, andrii, martin.lau, memxor, netdev, bpf,
kernel-team
Hello:
This patch was applied to bpf/bpf-next.git (master)
by Martin KaFai Lau <martin.lau@kernel.org>:
On Tue, 14 Feb 2023 15:50:51 -0800 you wrote:
> From: Alexei Starovoitov <ast@kernel.org>
>
> The compiler is optimizing out majority of unref_ptr read/writes, so the test
> wasn't testing much. For example, one could delete '__kptr' tag from
> 'struct prog_test_ref_kfunc __kptr *unref_ptr;' and the test would still "pass".
>
> Convert it to volatile stores. Confirmed by comparing bpf asm before/after.
>
> [...]
Here is the summary with links:
- [bpf-next] selftests/bpf: Fix map_kptr test.
https://git.kernel.org/bpf/bpf-next/c/62d101d5f422
You are awesome, thank you!
--
Deet-doot-dot, I am a bot.
https://korg.docs.kernel.org/patchwork/pwbot.html
^ permalink raw reply [flat|nested] 6+ messages in thread
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2023-02-14 23:50 [PATCH bpf-next] selftests/bpf: Fix map_kptr test Alexei Starovoitov
2023-02-15 3:02 ` Stanislav Fomichev
2023-02-15 3:20 ` Alexei Starovoitov
2023-02-15 17:36 ` Stanislav Fomichev
2023-02-15 10:26 ` Kumar Kartikeya Dwivedi
2023-02-15 17:30 ` patchwork-bot+netdevbpf
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