Re: [PATCH bpf-next v1 1/2] selftests/bpf: Check alignment flag if expected result is REJECT

[Paul Chaignon <paul.chaignon@gmail.com>]

On Tue, Mar 10, 2026 at 02:45:06PM +0800, Tiezhu Yang wrote:
> CONFIG_HAVE_EFFICIENT_UNALIGNED_ACCESS is set unconditionally for the
> most archs such as x86_64, aarch64, ppc64el and s390x, but this config
> may be not set by users for riscv64 and loongarch64.
> 
> If CONFIG_HAVE_EFFICIENT_UNALIGNED_ACCESS is not set, the BPF verifier
> detects if a program has unaligned access and then rejects them. So it
> should also check the flag F_NEEDS_EFFICIENT_UNALIGNED_ACCESS if the
> expected result is REJECT and set alignment_prevented_execution as 1,
> then the message "(NOTE: not executed due to unknown alignment)" can
> be printed for some testcases of test_verifier to reflect the reality.

I don't think we should print this message for those rejected tests. It
doesn't reflect the reality: these tests were not executed because they
were rejected, not because of unknown alignment. And we know they were
rejected not because of an unknown alignment since we've set
BPF_F_ANY_ALIGNMENT.

> 
> Signed-off-by: Tiezhu Yang <yangtiezhu@loongson.cn>
> ---
>  tools/testing/selftests/bpf/test_verifier.c | 5 +++++
>  1 file changed, 5 insertions(+)
> 
> diff --git a/tools/testing/selftests/bpf/test_verifier.c b/tools/testing/selftests/bpf/test_verifier.c
> index a8ae03c57bba..a1ae2f044e96 100644
> --- a/tools/testing/selftests/bpf/test_verifier.c
> +++ b/tools/testing/selftests/bpf/test_verifier.c
> @@ -1640,6 +1640,11 @@ static void do_test_single(struct bpf_test *test, bool unpriv,
>  			printf("FAIL\nUnexpected success to load!\n");
>  			goto fail_log;
>  		}
> +#ifndef CONFIG_HAVE_EFFICIENT_UNALIGNED_ACCESS
> +		if (fd_prog < 0 &&
> +		    (test->flags & F_NEEDS_EFFICIENT_UNALIGNED_ACCESS))
> +			alignment_prevented_execution = 1;
> +#endif
>  		if (!expected_err || !cmp_str_seq(bpf_vlog, expected_err)) {
>  			printf("FAIL\nUnexpected error message!\n\tEXP: %s\n\tRES: %s\n",
>  			      expected_err, bpf_vlog);
> -- 
> 2.42.0
> 
>