Re: [PATCH bpf-next v2 3/3] selftests/bpf: Enable some of the blocked cpuv4 instruction tests for bpf-gcc

[sashiko-bot@kernel.org]

Thank you for your contribution! Sashiko AI review found 1 potential issue(s) to consider:
- [Medium] The newly added `#ifdef __BPF_FEATURE_ADDR_SPACE_CAST` guard unintentionally drops 5 arena tests from the default test_progs flavour for clang.
--

--- Patch [3]: [PATCH bpf-next v2 3/3] selftests/bpf: Enable some of the blocked cpuv4 instruction tests for bpf-gcc ---
commit ad6608dfd47ddd6a7068cdc6e0e6d467ec3558b8
Author: Vineet Gupta <vineet.gupta@linux.dev>

selftests/bpf: Enable some of the blocked cpuv4 instruction tests for bpf-gcc

This commit relaxes clang-only checks in BPF selftests by adding specific
feature checks like __BPF_FEATURE_LDSX to allow building under bpf-gcc.
It also wraps arena tests with __BPF_FEATURE_ADDR_SPACE_CAST to skip them
on bpf-gcc.

> diff --git a/tools/testing/selftests/bpf/progs/verifier_ldsx.c b/tools/testing/selftests/bpf/progs/verifier_ldsx.c
> index e58ea69e38549..75762e11b443f 100644
> --- a/tools/testing/selftests/bpf/progs/verifier_ldsx.c
> +++ b/tools/testing/selftests/bpf/progs/verifier_ldsx.c
[ ... ]
> @@ -263,6 +257,14 @@ __naked void ldsx_ctx_8(void)
>  	: __clobber_all);
>  }
>  
> +#ifdef __BPF_FEATURE_ADDR_SPACE_CAST
> +
> +struct {
> +	__uint(type, BPF_MAP_TYPE_ARENA);
> +	__uint(map_flags, BPF_F_MMAPABLE);
> +	__uint(max_entries, 1);
> +} arena SEC(".maps");
> +

[Severity: Medium]
Does this inner guard unintentionally drop the arena tests for clang under
the default test_progs flavour?

The commit message notes that clang only defines feature macros like this at
-mcpu=v4, but successfully assembles the inline asm at -mcpu=v3. Because of
this, you kept the clang version checks on the file's main guard to avoid
removing tests where they run today.

However, since this inner guard lacks a || __clang_major__ >= 18 fallback,
clang at -mcpu=v3 evaluates this as false, silently dropping the arena map
and the subsequent 5 arena tests from the default test flavour.

>  SEC("syscall")
>  __description("Arena LDSX Disasm")
>  __success
[ ... ]

-- 
Sashiko AI review · https://sashiko.dev/#/patchset/20260824210142.3933580-1-vineet.gupta@linux.dev?part=3