linux-kernel - Re: [PATCH v2 1/9] lib/raid6/test: fix build on distros whose /bin/sh is not bash

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Date:   Mon, 23 Mar 2020 17:22:11 -0700
From:   "H. Peter Anvin" <hpa@...or.com>
To:     Masahiro Yamada <masahiroy@...nel.org>, x86@...nel.org,
        Ingo Molnar <mingo@...nel.org>,
        Thomas Gleixner <tglx@...utronix.de>,
        Borislav Petkov <bp@...en8.de>, linux-crypto@...r.kernel.org
Cc:     linux-kernel@...r.kernel.org,
        "Jason A . Donenfeld" <Jason@...c4.com>,
        Jim Kukunas <james.t.kukunas@...ux.intel.com>,
        NeilBrown <neilb@...e.de>,
        Yuanhan Liu <yuanhan.liu@...ux.intel.com>
Subject: Re: [PATCH v2 1/9] lib/raid6/test: fix build on distros whose /bin/sh
 is not bash

On 2020-03-23 17:13, Masahiro Yamada wrote:
> You can test raid6 library code from user-space, like this:
> 
>   $ cd lib/raid6/test
>   $ make
> 
> The command in $(shell ...) function is evaluated by /bin/sh by default.
> (or, you can change the default shell by setting 'SHELL' in Makefile)
> 
> Currently '>&/dev/null' is used to sink both stdout and stderr. Because
> this code is bash-ism, it only works when /bin/sh is a symbolic link to
> bash (this is the case on RHEL etc.)
> 
> This does not work on Ubuntu where /bin/sh is a symbolic link to dash.
> 
> I see lots of
> 
>   /bin/sh: 1: Syntax error: Bad fd number
> 
> and
> 
>   warning "your version of binutils lacks ... support"
> 
> Replace it with portable '>/dev/null 2>&1'.
> 
> Fixes: 4f8c55c5ad49 ("lib/raid6: build proper files on corresponding arch")
> Signed-off-by: Masahiro Yamada <masahiroy@...nel.org>

Acked-by: H. Peter Anvin (Intel) <hpa@...or.com>

> ---
> 
> Changes in v2:
>   - New patch
> 
>  lib/raid6/test/Makefile | 6 +++---
>  1 file changed, 3 insertions(+), 3 deletions(-)
> 
> diff --git a/lib/raid6/test/Makefile b/lib/raid6/test/Makefile
> index 3ab8720aa2f8..b9e6c3648be1 100644
> --- a/lib/raid6/test/Makefile
> +++ b/lib/raid6/test/Makefile
> @@ -35,13 +35,13 @@ endif
>  ifeq ($(IS_X86),yes)
>          OBJS   += mmx.o sse1.o sse2.o avx2.o recov_ssse3.o recov_avx2.o avx512.o recov_avx512.o
>          CFLAGS += $(shell echo "pshufb %xmm0, %xmm0" |		\
> -                    gcc -c -x assembler - >&/dev/null &&	\
> +                    gcc -c -x assembler - >/dev/null 2>&1 &&	\
>                      rm ./-.o && echo -DCONFIG_AS_SSSE3=1)
>          CFLAGS += $(shell echo "vpbroadcastb %xmm0, %ymm1" |	\
> -                    gcc -c -x assembler - >&/dev/null &&	\
> +                    gcc -c -x assembler - >/dev/null 2>&1 &&	\
>                      rm ./-.o && echo -DCONFIG_AS_AVX2=1)
>  	CFLAGS += $(shell echo "vpmovm2b %k1, %zmm5" |          \
> -		    gcc -c -x assembler - >&/dev/null &&        \
> +		    gcc -c -x assembler - >/dev/null 2>&1 &&	\
>  		    rm ./-.o && echo -DCONFIG_AS_AVX512=1)
>  else ifeq ($(HAS_NEON),yes)
>          OBJS   += neon.o neon1.o neon2.o neon4.o neon8.o recov_neon.o recov_neon_inner.o
>