diff mbox series

[bpf,09/12] selftests/bpf: test widening for iterating callbacks

Message ID 20231116021803.9982-10-eddyz87@gmail.com (mailing list archive)
State Superseded
Delegated to: BPF
Headers show
Series verify callbacks as if they are called unknown number of times | expand

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Commit Message

Eduard Zingerman Nov. 16, 2023, 2:18 a.m. UTC 
A test case to verify that imprecise scalars widening is applied to
callback bodies on repetative iteration.

Signed-off-by: Eduard Zingerman <eddyz87@gmail.com>
---
 .../bpf/progs/verifier_iterating_callbacks.c  | 20 +++++++++++++++++++
 1 file changed, 20 insertions(+)

Comments

Andrii Nakryiko Nov. 17, 2023, 4:47 p.m. UTC | #1 
On Wed, Nov 15, 2023 at 9:18 PM Eduard Zingerman <eddyz87@gmail.com> wrote:
>
> A test case to verify that imprecise scalars widening is applied to
> callback bodies on repetative iteration.

typo: repetitive? repeating? successive? subsequent?

>
> Signed-off-by: Eduard Zingerman <eddyz87@gmail.com>
> ---
>  .../bpf/progs/verifier_iterating_callbacks.c  | 20 +++++++++++++++++++
>  1 file changed, 20 insertions(+)
>
> diff --git a/tools/testing/selftests/bpf/progs/verifier_iterating_callbacks.c b/tools/testing/selftests/bpf/progs/verifier_iterating_callbacks.c
> index fa9429f77a81..598c1e984b26 100644
> --- a/tools/testing/selftests/bpf/progs/verifier_iterating_callbacks.c
> +++ b/tools/testing/selftests/bpf/progs/verifier_iterating_callbacks.c
> @@ -25,6 +25,7 @@ struct buf_context {
>
>  struct num_context {
>         __u64 i;
> +       __u64 j;
>  };
>
>  __u8 choice_arr[2] = { 0, 1 };
> @@ -69,6 +70,25 @@ int unsafe_on_zero_iter(void *unused)
>         return choice_arr[loop_ctx.i];
>  }
>
> +static int widening_cb(__u32 idx, struct num_context *ctx)
> +{
> +       ++ctx->i;
> +       return 0;
> +}
> +
> +SEC("?raw_tp")
> +__success
> +int widening(void *unused)
> +{
> +       struct num_context loop_ctx = { .i = 0, .j = 1 };
> +
> +       bpf_loop(100, widening_cb, &loop_ctx, 0);
> +       /* loop_ctx.j is not changed during callback iteration,
> +        * verifier should not apply widening to it.
> +        */
> +       return choice_arr[loop_ctx.j];

would the test be a bit more interesting if you use loop_ctx.i here?
`return choice_arr[loop_ctx.i & 1];` ?



> +}
> +
>  static int loop_detection_cb(__u32 idx, struct num_context *ctx)
>  {
>         for (;;) {}
> --
> 2.42.0
>
Eduard Zingerman Nov. 17, 2023, 6:53 p.m. UTC | #2 
On Fri, 2023-11-17 at 11:47 -0500, Andrii Nakryiko wrote:
> On Wed, Nov 15, 2023 at 9:18 PM Eduard Zingerman <eddyz87@gmail.com> wrote:
> > 
> > A test case to verify that imprecise scalars widening is applied to
> > callback bodies on repetative iteration.
> 
> typo: repetitive? repeating? successive? subsequent?

I'll configure spell-checking, I promise.

[...]
> > +static int widening_cb(__u32 idx, struct num_context *ctx)
> > +{
> > +       ++ctx->i;
> > +       return 0;
> > +}
> > +
> > +SEC("?raw_tp")
> > +__success
> > +int widening(void *unused)
> > +{
> > +       struct num_context loop_ctx = { .i = 0, .j = 1 };
> > +
> > +       bpf_loop(100, widening_cb, &loop_ctx, 0);
> > +       /* loop_ctx.j is not changed during callback iteration,
> > +        * verifier should not apply widening to it.
> > +        */
> > +       return choice_arr[loop_ctx.j];
> 
> would the test be a bit more interesting if you use loop_ctx.i here?
> `return choice_arr[loop_ctx.i & 1];` ? 

It would force precision for 'loop_ctx.i', precise values are not widened.

> 
> > +}
> > +
Andrii Nakryiko Nov. 17, 2023, 8:28 p.m. UTC | #3 
On Fri, Nov 17, 2023 at 1:53 PM Eduard Zingerman <eddyz87@gmail.com> wrote:
>
> On Fri, 2023-11-17 at 11:47 -0500, Andrii Nakryiko wrote:
> > On Wed, Nov 15, 2023 at 9:18 PM Eduard Zingerman <eddyz87@gmail.com> wrote:
> > >
> > > A test case to verify that imprecise scalars widening is applied to
> > > callback bodies on repetative iteration.
> >
> > typo: repetitive? repeating? successive? subsequent?
>
> I'll configure spell-checking, I promise.

no worries, I only notice it because gmail highlights it. I was rather
wondering if "repetitive iteration" is the right way to explain this.

>
> [...]
> > > +static int widening_cb(__u32 idx, struct num_context *ctx)
> > > +{
> > > +       ++ctx->i;
> > > +       return 0;
> > > +}
> > > +
> > > +SEC("?raw_tp")
> > > +__success
> > > +int widening(void *unused)
> > > +{
> > > +       struct num_context loop_ctx = { .i = 0, .j = 1 };
> > > +
> > > +       bpf_loop(100, widening_cb, &loop_ctx, 0);
> > > +       /* loop_ctx.j is not changed during callback iteration,
> > > +        * verifier should not apply widening to it.
> > > +        */
> > > +       return choice_arr[loop_ctx.j];
> >
> > would the test be a bit more interesting if you use loop_ctx.i here?
> > `return choice_arr[loop_ctx.i & 1];` ?
>
> It would force precision for 'loop_ctx.i', precise values are not widened.

ah, right, ok

>
> >
> > > +}
> > > +
>
>
diff mbox series

Patch

diff --git a/tools/testing/selftests/bpf/progs/verifier_iterating_callbacks.c b/tools/testing/selftests/bpf/progs/verifier_iterating_callbacks.c
index fa9429f77a81..598c1e984b26 100644
--- a/tools/testing/selftests/bpf/progs/verifier_iterating_callbacks.c
+++ b/tools/testing/selftests/bpf/progs/verifier_iterating_callbacks.c
@@ -25,6 +25,7 @@  struct buf_context {
 
 struct num_context {
 	__u64 i;
+	__u64 j;
 };
 
 __u8 choice_arr[2] = { 0, 1 };
@@ -69,6 +70,25 @@  int unsafe_on_zero_iter(void *unused)
 	return choice_arr[loop_ctx.i];
 }
 
+static int widening_cb(__u32 idx, struct num_context *ctx)
+{
+	++ctx->i;
+	return 0;
+}
+
+SEC("?raw_tp")
+__success
+int widening(void *unused)
+{
+	struct num_context loop_ctx = { .i = 0, .j = 1 };
+
+	bpf_loop(100, widening_cb, &loop_ctx, 0);
+	/* loop_ctx.j is not changed during callback iteration,
+	 * verifier should not apply widening to it.
+	 */
+	return choice_arr[loop_ctx.j];
+}
+
 static int loop_detection_cb(__u32 idx, struct num_context *ctx)
 {
 	for (;;) {}