linux-kernel - Re: [PATCH bpf-next 3/3] selftests/bpf: Check __ARCH_WANT_SET_GET_RLIMIT before syscall(__NR

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Date:   Wed, 22 Feb 2023 10:06:58 -0800
From:   Alexei Starovoitov <alexei.starovoitov@...il.com>
To:     Tiezhu Yang <yangtiezhu@...ngson.cn>
Cc:     Alexei Starovoitov <ast@...nel.org>,
        Daniel Borkmann <daniel@...earbox.net>,
        Andrii Nakryiko <andrii@...nel.org>, bpf <bpf@...r.kernel.org>,
        LKML <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH bpf-next 3/3] selftests/bpf: Check __ARCH_WANT_SET_GET_RLIMIT
 before syscall(__NR_getrlimit)

On Wed, Feb 22, 2023 at 3:55 AM Tiezhu Yang <yangtiezhu@...ngson.cn> wrote:
>
> __NR_getrlimit is defined only if __ARCH_WANT_SET_GET_RLIMIT is defined:
>
>   #ifdef __ARCH_WANT_SET_GET_RLIMIT
>   /* getrlimit and setrlimit are superseded with prlimit64 */
>   #define __NR_getrlimit 163
>   ...
>   #endif
>
> Some archs do not define __ARCH_WANT_SET_GET_RLIMIT, it should check
> __ARCH_WANT_SET_GET_RLIMIT before syscall(__NR_getrlimit) to fix the
> following build error:
>
>     TEST-OBJ [test_progs] user_ringbuf.test.o
>   tools/testing/selftests/bpf/prog_tests/user_ringbuf.c: In function 'kick_kernel_cb':
>   tools/testing/selftests/bpf/prog_tests/user_ringbuf.c:593:17: error: '__NR_getrlimit' undeclared (first use in this function)
>     593 |         syscall(__NR_getrlimit);
>         |                 ^~~~~~~~~~~~~~
>   tools/testing/selftests/bpf/prog_tests/user_ringbuf.c:593:17: note: each undeclared identifier is reported only once for each function it appears in
>   make: *** [Makefile:573: tools/testing/selftests/bpf/user_ringbuf.test.o] Error 1
>   make: Leaving directory 'tools/testing/selftests/bpf'
>
> Signed-off-by: Tiezhu Yang <yangtiezhu@...ngson.cn>
> ---
>  tools/testing/selftests/bpf/prog_tests/user_ringbuf.c | 2 ++
>  1 file changed, 2 insertions(+)
>
> diff --git a/tools/testing/selftests/bpf/prog_tests/user_ringbuf.c b/tools/testing/selftests/bpf/prog_tests/user_ringbuf.c
> index 3a13e10..0550307 100644
> --- a/tools/testing/selftests/bpf/prog_tests/user_ringbuf.c
> +++ b/tools/testing/selftests/bpf/prog_tests/user_ringbuf.c
> @@ -590,7 +590,9 @@ static void *kick_kernel_cb(void *arg)
>         /* Kick the kernel, causing it to drain the ring buffer and then wake
>          * up the test thread waiting on epoll.
>          */
> +#ifdef __ARCH_WANT_SET_GET_RLIMIT
>         syscall(__NR_getrlimit);
> +#endif

This is clearly breaks user_ringbuf test on x86:
https://github.com/kernel-patches/bpf/actions/runs/4242660318/jobs/7374845859

Please do not send patches that make selftest compile on your favorite arch.
Make sure the patches work correctly on other archs too.