Re: [PATCH bpf-next v2 1/8] selftests/bpf: Build callx tests with GCC that defines __BPF_FEATURE_CALLX

[Vineet Gupta <vineet.gupta@linux.dev>]

  10/28/26 2:22 PM, bot+bpf-ci@kernel.org wrote:
>> selftests/bpf: Build callx tests with GCC that defines __BPF_FEATURE_CALLX
> TL;DR:
> - data_in_arena.c use_ops() isn't converted to CAN_USE_CALLX, so GCC with
>    callx support may still call add1() directly; commit message claims all
>    tests converted
> - Commit message typo (nit)
>
>> selftests/bpf: Build callx tests with GCC that defines __BPF_FEATURE_CALLX
>>
>> Commit 7cd1f73b37ea ("selftests/bpf: Fix build of callx tests with GCC")
>> gated the callx progs on __clang__. GCC had indirect call support which was
>> recently refurbished along with a __BPF_FEATURE_CALLX macro [1], so gate
>> on that as well so once this GCC is released, the tests start passing.
>>
>> Put the arch and compiler conditions in a CAN_USE_CALLX macro in
>> bpf_misc.h, and use it all the test programs.
>>
>> While at it, mark the placeholder programs left for unsupported
>> toolchains and arches with __skip(), so they report SKIP rather than OK.
>>
>> [1] https://gcc.gnu.org/git/?p=gcc.git;a=commit;h=ffe3ead4a8ad704b557b0cfa4f823df647c65a0d
>>
>> Measured on bpf-next with a stock bpf-gcc that defines
>> __BPF_FEATURE_CALLX, test_progs before and after: 76 subtests run that
>> previously did not exist in the report, 75 OK and one @unpriv SKIP,
>> with no failures.  The two dummy placeholders retire and
>> callx_rodata_lskel goes SKIP -> OK.
>>
>> Signed-off-by: Vineet Gupta <vineet.gupta@linux.dev>
> The commit message says CAN_USE_CALLX is used in all the test programs, but
> use_ops() in progs/data_in_arena.c is not converted.  It still gates its
> indirect call on __clang__ and keeps the same comment this patch removes from
> the other files:
>
> progs/data_in_arena.c:use_ops() {
>      ...
> #ifdef __clang__
> 	return ops.fn(*ops.data) + ops.name[1];
> #else
> 	/* gcc doesn't support indirect calls */
> 	return add1(*ops.data) + ops.name[1];
> #endif
>      ...
> }
>
> With a GCC that defines __BPF_FEATURE_CALLX, doesn't this still take the
> #else branch and call add1() directly?  That means the GCC build never makes
> the callx through a function pointer in .data.rel.ro, and the "gcc doesn't
> support indirect calls" comment is now wrong for that compiler.
>
> A grep for "indirect call" under progs/ and prog_tests/ shows this is the
> only remaining gate.  None of the later patches in the series touch
> data_in_arena.c.
>
> Should use_ops() be converted to CAN_USE_CALLX as well?  That would need
> data_in_arena.c to include bpf_misc.h, and it would add the x86/arm64/riscv64
> arch gate that clang builds of this file don't have today.  Otherwise, could
> the commit message be adjusted so it doesn't say all the test programs were
> converted?

Yes it missed the grep. Will be fixed in v3.
Do note that this also adds the JIT gate which is the right thing to do 
- the prior __clang__ only check would generate callx even for arches 
not supporting callx.



> This isn't a bug, but there is a missing word in the commit message:
>> bpf_misc.h, and use it all the test programs.
> This should read "use it in all the test programs".

Right, will fix that as well.

Thx,
-Vineet

> ---
> 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/40768193895