linux-kernel - Re: [PATCH] arm: vdso: pass --be8 to linker if necessary

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Message-ID: <20190531083724.uc32co24qxfodlty@shell.armlinux.org.uk>
Date:   Fri, 31 May 2019 09:37:24 +0100
From:   Russell King - ARM Linux admin <linux@...linux.org.uk>
To:     Masahiro Yamada <yamada.masahiro@...ionext.com>
Cc:     "Jason A. Donenfeld" <Jason@...c4.com>,
        linux-arm-kernel <linux-arm-kernel@...ts.infradead.org>,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
        Arnd Bergmann <arnd@...db.de>,
        Ard Biesheuvel <ard.biesheuvel@...aro.org>
Subject: Re: [PATCH] arm: vdso: pass --be8 to linker if necessary

On Fri, May 31, 2019 at 11:01:23AM +0900, Masahiro Yamada wrote:
> Hi Jason,
> 
> Thanks for catching this.
> 
> On Thu, May 30, 2019 at 3:26 AM Jason A. Donenfeld <Jason@...c4.com> wrote:
> >
> > The commit fe00e50b2db8 ("ARM: 8858/1: vdso: use $(LD) instead of $(CC)
> > to link VDSO") removed the passing of CFLAGS, since ld doesn't take
> > those directly. However, prior, big-endian ARM was relying on gcc to
> > translate its -mbe8 option into ld's --be8 option. Lacking this, ld
> 
> 
> 'git grep -- -mbe8' has no hit.

It isn't -mbe8, it is --be8

$ arm-linux-gcc --target-help
...
  --be8                       Output BE8 format image

> 
> Is it a toolchain internal flag?
> 
> 
> 
> > generated be32 code, making the VDSO generate SIGILL when called by
> > userspace.
> >
> > This commit passes --be8 if CONFIG_CPU_ENDIAN_BE8 is enabled.
> >
> > Signed-off-by: Jason A. Donenfeld <Jason@...c4.com>
> > Cc: Masahiro Yamada <yamada.masahiro@...ionext.com>
> > Cc: Russell King <rmk+kernel@...linux.org.uk>
> > Cc: Arnd Bergmann <arnd@...db.de>
> > Cc: Ard Biesheuvel <ard.biesheuvel@...aro.org>
> > ---
> >  arch/arm/vdso/Makefile | 5 +++--
> >  1 file changed, 3 insertions(+), 2 deletions(-)
> >
> > diff --git a/arch/arm/vdso/Makefile b/arch/arm/vdso/Makefile
> > index fadf554d9391..1f5ec9741e6d 100644
> > --- a/arch/arm/vdso/Makefile
> > +++ b/arch/arm/vdso/Makefile
> > @@ -10,9 +10,10 @@ obj-vdso := $(addprefix $(obj)/, $(obj-vdso))
> >  ccflags-y := -fPIC -fno-common -fno-builtin -fno-stack-protector
> >  ccflags-y += -DDISABLE_BRANCH_PROFILING
> >
> > -ldflags-y = -Bsymbolic --no-undefined -soname=linux-vdso.so.1 \
> > +ldflags-$(CONFIG_CPU_ENDIAN_BE8) := --be8
> > +ldflags-y := -Bsymbolic --no-undefined -soname=linux-vdso.so.1 \
> >             -z max-page-size=4096 -z common-page-size=4096 \
> > -           -nostdlib -shared \
> > +           -nostdlib -shared $(ldflags-y) \
> >             $(call ld-option, --hash-style=sysv) \
> >             $(call ld-option, --build-id) \
> >             -T
> > --
> > 2.21.0
> >
> 
> 
> --
> Best Regards
> Masahiro Yamada
> 

-- 
RMK's Patch system: https://www.armlinux.org.uk/developer/patches/
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