Re: [PATCH bpf-next v1 3/7] selftests/bpf: report SKIP for arena tests a compiler cannot build

[sashiko-bot@kernel.org]

Thank you for your contribution! Sashiko AI review found 1 potential issue(s) to consider:
- [Medium] selftests/bpf: missing __skip_without_arena fallback in jit_insns_arena.c
--

commit f37e4c1aa3e5f2decfc920dfa156617c4a66522b
Author: Vineet Gupta <vineet.gupta@linux.dev>

selftests/bpf: report SKIP for arena tests a compiler cannot build

This commit adds a __skip_without_arena macro and #else fallback programs
to BPF selftest files guarded by __BPF_FEATURE_ADDR_SPACE_CAST so that
test_progs reports those subtests as skipped when built with a compiler
that lacks arena address space support.

> diff --git a/tools/testing/selftests/bpf/progs/bpf_misc.h b/tools/testing/selftests/bpf/progs/bpf_misc.h
> index 1b264480e128f..ed1ed1b5bd097 100644
> --- a/tools/testing/selftests/bpf/progs/bpf_misc.h
> +++ b/tools/testing/selftests/bpf/progs/bpf_misc.h
> @@ -156,6 +160,16 @@
>  #define __success		__test_tag("test_expect_success")
>  #define __description(desc)	__test_tag("test_description=" desc)
>  #define __skip(reason)		__test_tag("test_skip=" reason)
> +
> +/*
> + * Without compiler arena support, report the test as SKIP rather than let it
> + * pass vacuously or fail to load.
> + */
> +#ifdef __BPF_FEATURE_ADDR_SPACE_CAST
> +#define __skip_without_arena
> +#else
> +#define __skip_without_arena	__skip("compiler does not support the arena address space")
> +#endif

[Severity: Medium]
Should tools/testing/selftests/bpf/progs/jit_insns_arena.c also receive an
#else fallback with a dummy arena_unsupported() program marked
__skip_without_arena?

In tools/testing/selftests/bpf/progs/jit_insns_arena.c, both BPF programs
in the file (arena_zero_off() and cast_to_user()) are inside a
__BPF_FEATURE_ADDR_SPACE_CAST guard without an #else branch:

tools/testing/selftests/bpf/progs/jit_insns_arena.c:
    #if defined(__BPF_FEATURE_ADDR_SPACE_CAST)
    SEC("syscall")
    __success __retval(0)
    int arena_zero_off(void *ctx)
    {
        ...
    }

    SEC("syscall")
    __success __retval(0)
    int cast_to_user(void *ctx)
    {
        ...
    }
    #endif

    char _license[] SEC("license") = "GPL";

When built with a compiler that does not define
__BPF_FEATURE_ADDR_SPACE_CAST, such as stock bpf-gcc, jit_insns_arena.c
compiles to an object with zero BPF programs. When test_jit_insns() in
tools/testing/selftests/bpf/prog_tests/jit_insns.c runs:

    test_jit_insns() -> RUN_TESTS(jit_insns_arena) -> test_loader__run_subtests()

it silently executes zero subtests for jit_insns_arena instead of reporting
a skipped subtest.

-- 
Sashiko AI review · https://sashiko.dev/#/patchset/20261028000411.4010967-1-vineet.gupta@linux.dev?part=3