netdev - Re: [PATCH bpf-next] bpf, mips: Fix build errors about __NR

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Date:   Wed, 24 Nov 2021 12:50:49 -0800
From:   Andrii Nakryiko <andrii.nakryiko@...il.com>
To:     Tiezhu Yang <yangtiezhu@...ngson.cn>
Cc:     Alexei Starovoitov <ast@...nel.org>,
        Daniel Borkmann <daniel@...earbox.net>,
        Andrii Nakryiko <andrii@...nel.org>,
        Networking <netdev@...r.kernel.org>, bpf <bpf@...r.kernel.org>,
        open list <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH bpf-next] bpf, mips: Fix build errors about __NR_bpf undeclared

On Wed, Nov 24, 2021 at 1:00 AM Tiezhu Yang <yangtiezhu@...ngson.cn> wrote:
>
> Add the __NR_bpf definitions to fix the following build errors for mips.
>
>  $ cd tools/bpf/bpftool
>  $ make
>  [...]
>  bpf.c:54:4: error: #error __NR_bpf not defined. libbpf does not support your arch.
>   #  error __NR_bpf not defined. libbpf does not support your arch.
>      ^~~~~
>  bpf.c: In function ‘sys_bpf’:
>  bpf.c:66:17: error: ‘__NR_bpf’ undeclared (first use in this function); did you mean ‘__NR_brk’?
>    return syscall(__NR_bpf, cmd, attr, size);
>                   ^~~~~~~~
>                   __NR_brk
>  [...]
>  In file included from gen_loader.c:15:0:
>  skel_internal.h: In function ‘skel_sys_bpf’:
>  skel_internal.h:53:17: error: ‘__NR_bpf’ undeclared (first use in this function); did you mean ‘__NR_brk’?
>    return syscall(__NR_bpf, cmd, attr, size);
>                   ^~~~~~~~
>                   __NR_brk
>
> We can see the following generated definitions:
>
>  $ grep -r "#define __NR_bpf" arch/mips
>  arch/mips/include/generated/uapi/asm/unistd_o32.h:#define __NR_bpf (__NR_Linux + 355)
>  arch/mips/include/generated/uapi/asm/unistd_n64.h:#define __NR_bpf (__NR_Linux + 315)
>  arch/mips/include/generated/uapi/asm/unistd_n32.h:#define __NR_bpf (__NR_Linux + 319)
>
> So use the GCC pre-defined macro _ABIO32, _ABIN32 and _ABI64 [1] to define
> the corresponding __NR_bpf.
>
> This patch is similar with commit bad1926dd2f6 ("bpf, s390: fix build for
> libbpf and selftest suite").
>
> [1] https://gcc.gnu.org/git/?p=gcc.git;a=blob;f=gcc/config/mips/mips.h#l549
>
> Signed-off-by: Tiezhu Yang <yangtiezhu@...ngson.cn>
> ---
>  tools/build/feature/test-bpf.c |  6 ++++++
>  tools/lib/bpf/bpf.c            |  6 ++++++
>  tools/lib/bpf/skel_internal.h  | 10 ++++++++++
>  3 files changed, 22 insertions(+)
>
> diff --git a/tools/build/feature/test-bpf.c b/tools/build/feature/test-bpf.c
> index 82070ea..ebc7a2a 100644
> --- a/tools/build/feature/test-bpf.c
> +++ b/tools/build/feature/test-bpf.c
> @@ -14,6 +14,12 @@
>  #  define __NR_bpf 349
>  # elif defined(__s390__)
>  #  define __NR_bpf 351
> +# elif defined(__mips__) && defined(_ABIO32)
> +#  define __NR_bpf (__NR_Linux + 355)
> +# elif defined(__mips__) && defined(_ABIN32)
> +#  define __NR_bpf (__NR_Linux + 319)
> +# elif defined(__mips__) && defined(_ABI64)
> +#  define __NR_bpf (__NR_Linux + 315)

Is it possible to use a final number without __NR_Linux? All the other
cases have final numbers, no relative numbers

>  # else
>  #  error __NR_bpf not defined. libbpf does not support your arch.
>  # endif
> diff --git a/tools/lib/bpf/bpf.c b/tools/lib/bpf/bpf.c
> index 94560ba..60422404 100644
> --- a/tools/lib/bpf/bpf.c
> +++ b/tools/lib/bpf/bpf.c
> @@ -50,6 +50,12 @@
>  #  define __NR_bpf 351
>  # elif defined(__arc__)
>  #  define __NR_bpf 280
> +# elif defined(__mips__) && defined(_ABIO32)
> +#  define __NR_bpf (__NR_Linux + 355)
> +# elif defined(__mips__) && defined(_ABIN32)
> +#  define __NR_bpf (__NR_Linux + 319)
> +# elif defined(__mips__) && defined(_ABI64)
> +#  define __NR_bpf (__NR_Linux + 315)
>  # else
>  #  error __NR_bpf not defined. libbpf does not support your arch.
>  # endif
> diff --git a/tools/lib/bpf/skel_internal.h b/tools/lib/bpf/skel_internal.h
> index 9cf6670..6ff4939 100644
> --- a/tools/lib/bpf/skel_internal.h
> +++ b/tools/lib/bpf/skel_internal.h
> @@ -7,6 +7,16 @@
>  #include <sys/syscall.h>
>  #include <sys/mman.h>
>
> +#ifndef __NR_bpf
> +# if defined(__mips__) && defined(_ABIO32)
> +#  define __NR_bpf (__NR_Linux + 355)
> +# elif defined(__mips__) && defined(_ABIN32)
> +#  define __NR_bpf (__NR_Linux + 319)
> +# elif defined(__mips__) && defined(_ABI64)
> +#  define __NR_bpf (__NR_Linux + 315)
> +# endif
> +#endif
> +
>  /* This file is a base header for auto-generated *.lskel.h files.
>   * Its contents will change and may become part of auto-generation in the future.
>   *
> --
> 2.1.0
>