netdev - Re: [PATCH bpf-next v2] selftests/bpf: suppress readelf stderr when probing for BTF support

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Date:   Thu, 24 Jan 2019 10:14:38 -0800
From:   Song Liu <liu.song.a23@...il.com>
To:     Stanislav Fomichev <sdf@...gle.com>
Cc:     Networking <netdev@...r.kernel.org>,
        "David S . Miller" <davem@...emloft.net>,
        Alexei Starovoitov <ast@...nel.org>,
        Daniel Borkmann <daniel@...earbox.net>
Subject: Re: [PATCH bpf-next v2] selftests/bpf: suppress readelf stderr when
 probing for BTF support

On Thu, Jan 24, 2019 at 8:57 AM Stanislav Fomichev <sdf@...gle.com> wrote:
>
> Before:
> $ make -s -C tools/testing/selftests/bpf
> readelf: Error: Missing knowledge of 32-bit reloc types used in DWARF
> sections of machine number 247
> readelf: Warning: unable to apply unsupported reloc type 10 to section
> .debug_info
> readelf: Warning: unable to apply unsupported reloc type 1 to section
> .debug_info
> readelf: Warning: unable to apply unsupported reloc type 10 to section
> .debug_info
>
> After:
> $ make -s -C tools/testing/selftests/bpf
>
> v2:
> * use llvm-readelf instead of redirecting binutils' readelf stderr to
>   /dev/null
>
> Signed-off-by: Stanislav Fomichev <sdf@...gle.com>

This looks good.

Acked-by: Song Liu <songliubraving@...com>

Thanks!

> ---
>  tools/testing/selftests/bpf/Makefile | 3 ++-
>  1 file changed, 2 insertions(+), 1 deletion(-)
>
> diff --git a/tools/testing/selftests/bpf/Makefile b/tools/testing/selftests/bpf/Makefile
> index 70229de510f5..1cca5f2567c2 100644
> --- a/tools/testing/selftests/bpf/Makefile
> +++ b/tools/testing/selftests/bpf/Makefile
> @@ -95,6 +95,7 @@ $(BPFOBJ): force
>  CLANG ?= clang
>  LLC   ?= llc
>  LLVM_OBJCOPY ?= llvm-objcopy
> +LLVM_READELF ?= llvm-readelf
>  BTF_PAHOLE ?= pahole
>
>  PROBE := $(shell $(LLC) -march=bpf -mcpu=probe -filetype=null /dev/null 2>&1)
> @@ -131,7 +132,7 @@ BTF_PAHOLE_PROBE := $(shell $(BTF_PAHOLE) --help 2>&1 | grep BTF)
>  BTF_OBJCOPY_PROBE := $(shell $(LLVM_OBJCOPY) --help 2>&1 | grep -i 'usage.*llvm')
>  BTF_LLVM_PROBE := $(shell echo "int main() { return 0; }" | \
>                           $(CLANG) -target bpf -O2 -g -c -x c - -o ./llvm_btf_verify.o; \
> -                         readelf -S ./llvm_btf_verify.o | grep BTF; \
> +                         $(LLVM_READELF) -S ./llvm_btf_verify.o | grep BTF; \
>                           /bin/rm -f ./llvm_btf_verify.o)
>
>  ifneq ($(BTF_LLVM_PROBE),)
> --
> 2.20.1.321.g9e740568ce-goog
>