linux-kernel - Re: [PATCH 01/16] lib/raid6/test: fix build on distros whose /bin/sh is not bash

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Message-ID: <CAK7LNATXz=x7M-HOfWLf1fc_km5qBYa5u1i3Bj30C7aoJPGjSA@mail.gmail.com>
Date:   Thu, 26 Mar 2020 15:48:56 +0900
From:   Masahiro Yamada <masahiroy@...nel.org>
To:     Nick Desaulniers <ndesaulniers@...gle.com>
Cc:     LKML <linux-kernel@...r.kernel.org>,
        "David S . Miller" <davem@...emloft.net>,
        Linus Torvalds <torvalds@...ux-foundation.org>,
        Kees Cook <keescook@...omium.org>,
        clang-built-linux <clang-built-linux@...glegroups.com>,
        Herbert Xu <herbert@...dor.apana.org.au>,
        "open list:HARDWARE RANDOM NUMBER GENERATOR CORE" 
        <linux-crypto@...r.kernel.org>, Ingo Molnar <mingo@...hat.com>,
        Thomas Gleixner <tglx@...utronix.de>,
        Borislav Petkov <bp@...en8.de>,
        Peter Zijlstra <peterz@...radead.org>,
        "H . Peter Anvin" <hpa@...or.com>,
        "maintainer:X86 ARCHITECTURE (32-BIT AND 64-BIT)" <x86@...nel.org>,
        Linux Kbuild mailing list <linux-kbuild@...r.kernel.org>,
        Jim Kukunas <james.t.kukunas@...ux.intel.com>,
        NeilBrown <neilb@...e.de>,
        Yuanhan Liu <yuanhan.liu@...ux.intel.com>
Subject: Re: [PATCH 01/16] lib/raid6/test: fix build on distros whose /bin/sh
 is not bash

On Wed, Mar 25, 2020 at 1:36 AM Nick Desaulniers
<ndesaulniers@...gle.com> wrote:
>
> On Tue, Mar 24, 2020 at 1:49 AM Masahiro Yamada <masahiroy@...nel.org> wrote:
> >
> > You can test raid6 library code from user-space, like this:
> >
> >   $ cd lib/raid6/test
> >   $ make
> >
> > The command in $(shell ...) function is evaluated by /bin/sh by default.
> > (or, you can change the default shell by setting 'SHELL' in Makefile)
> >
> > Currently '>&/dev/null' is used to sink both stdout and stderr. Because
> > this code is bash-ism, it only works when /bin/sh is a symbolic link to
> > bash (this is the case on RHEL etc.)
> >
> > This does not work on Ubuntu where /bin/sh is a symbolic link to dash.
> >
> > I see lots of
> >
> >   /bin/sh: 1: Syntax error: Bad fd number
> >
> > and
> >
> >   warning "your version of binutils lacks ... support"
> >
> > Replace it with portable '>/dev/null 2>&1'.
> >
> > Fixes: 4f8c55c5ad49 ("lib/raid6: build proper files on corresponding arch")
> > Signed-off-by: Masahiro Yamada <masahiroy@...nel.org>
> > Acked-by: H. Peter Anvin (Intel) <hpa@...or.com>
> > ---
> >
> >  lib/raid6/test/Makefile | 6 +++---
> >  1 file changed, 3 insertions(+), 3 deletions(-)
> >
> > diff --git a/lib/raid6/test/Makefile b/lib/raid6/test/Makefile
> > index 3ab8720aa2f8..b9e6c3648be1 100644
> > --- a/lib/raid6/test/Makefile
> > +++ b/lib/raid6/test/Makefile
> > @@ -35,13 +35,13 @@ endif
> >  ifeq ($(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 &&    \
>
> These should all use $(CC) rather than hardcode gcc.


Right, I had noticed this.

We often fall between
"let's fix this too while we are here"
vs
"do not do multiple things in a single patch"


If we replace gcc -> $(CC),
we also need to touch line 51 for consistency:

       gcc -c -x c - >/dev/null && rm ./-.o && echo yes)

..., which is not our main interest now.

So, I leave it to a follow-up patch
if somebody has interest in it.


-- 
Best Regards
Masahiro Yamada