linux-kernel - Re: [PATCH 7/7] Kbuild: lto: pass -m32/-m64 to to LDFINAL

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Date:   Fri, 2 Feb 2018 16:17:08 -0500 (EST)
From:   Nicolas Pitre <nicolas.pitre@...aro.org>
To:     Arnd Bergmann <arnd@...db.de>
cc:     Andi Kleen <ak@...ux.intel.com>,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
        Linux Kbuild mailing list <linux-kbuild@...r.kernel.org>
Subject: Re: [PATCH 7/7] Kbuild: lto: pass -m32/-m64 to to LDFINAL

On Fri, 2 Feb 2018, Arnd Bergmann wrote:

> On Fri, Feb 2, 2018 at 9:38 PM, Nicolas Pitre <nicolas.pitre@...aro.org> wrote:
> > On Fri, 2 Feb 2018, Arnd Bergmann wrote:
> >
> >> Do you have a git tree with other changes for LTO on ARM? I'd
> >> like to try that as well.
> >
> > I currently have only 2 other patches.
> >
> > You need commit 75fea300d73a that just hit mainline (you may cherry-pick
> > it easily if necessary).
> 
> Ok, I apparently have that already by basing on today's linux-next.

OK. linux-next has had it for quite a while.

> > Then the following:
> >
> > ----- >8
> > Subject: [PATCH] HACK: enable LTO on ARM
> >
> > Without the ${KBUILD_VMLINUX_LIBS} move the build fails with missing
> > memcpy all over the place. Didn't figure it out yet.
> 
> Added that now as well, thanks! I'll see what comes out of it.

I forgot: you'll need to hack your toolchain a bit too.

Here's the script I created to remember about the issue:

----- >8
#!/bin/bash

# work around https://gcc.gnu.org/bugzilla/show_bug.cgi?id=78353

GCC_ROOT=/opt/gcc-linaro-6.3.1-2017.05-x86_64_arm-linux-gnueabihf

set -e
set -x

cd $GCC_ROOT//arm-linux-gnueabihf/bin
[ -e fat-as ] && exit 1
mv as fat-as
cat > as << EOF
#!/bin/bash
exec -a "\$0" "\$(dirname "\$0")/fat-as" -mimplicit-it=always "\$@"
EOF
chmod +x as
8< -----

> Have you tried arm64 already? I suppose I could do the same change 
> there and see what happens.

No, didn't try arm64.


Nicolas