Re: [PATCH bpf 2/2] selftests/bpf: cover the exception callback using its own BPF stack

[bot+bpf-ci]

> diff --git a/tools/testing/selftests/bpf/progs/exceptions.c b/tools/testing/selftests/bpf/progs/exceptions.c
> index c8d716fbd4191..cac4e082139a7 100644
> --- a/tools/testing/selftests/bpf/progs/exceptions.c
> +++ b/tools/testing/selftests/bpf/progs/exceptions.c
> @@ -212,6 +212,35 @@ int exception_throw_subprog(struct __sk_buff *ctx)
>  	return 0;
>  }
>
> +__u64 exception_cb_stack_src = 0x1234;
> +
> +/* The address handed to the helper has to be this callback's own stack
> + * slot, not one from a frame that is already gone.
> + */
> +__noinline int exception_cb_stack(u64 cookie)
> +{
> +	volatile __u64 val = 0xdead;
> +
> +	bpf_probe_read_kernel((void *)&val, sizeof(val), &exception_cb_stack_src);
> +	return val;
> +}
> +
> +/* Throws from a subprogram that has a stack of its own. */
> +__noinline static int throwing_subprog_stack(struct __sk_buff *ctx)
> +{
> +	volatile __u64 pad[4] = {};

This isn't a bug, but would 'u64' fit the surrounding declarations in this
file a little better than '__u64' for the three new locals/globals?
Looking at the rest of progs/exceptions.c, every other scalar declaration
uses the short kernel spelling: 'static __noinline int static_func(u64 i)',
'__noinline int exception_cb_mod(u64 cookie)', 'volatile u64 cookie = c;',
and 'u64 time = bpf_ktime_get_ns();'. The new code at lines 215, 222, and
231 is the only place in the file that switches to the '__u64' spelling,
and it sits directly next to 'exception_cb_stack(u64 cookie)' which uses
the other form in the same signature.

> +
> +	bpf_throw(pad[0]);
> +	return 0;
> +}
> +
> +SEC("tc")
> +__exception_cb(exception_cb_stack)
> +int exception_throw_subprog_stack_cb(struct __sk_buff *ctx)
> +{
> +	return throwing_subprog_stack(ctx);
> +}
> +


---
AI reviewed your patch. Please fix the bug or email reply why it's not a bug.
See: https://github.com/kernel-patches/vmtest/blob/master/ci/claude/README.md

CI run summary: https://github.com/kernel-patches/bpf/actions/runs/33848479344