linux-kernel - Re: [PATCH] powerpc/vdso32: mark __kernel_datapage_offset as STV

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Message-ID: <CAKwvOd=JYqzJthPqTjRZkE+8dDKDqVig-nb7=iYDS_UEKn3+Qg@mail.gmail.com>
Date:   Wed, 3 Jun 2020 16:50:27 -0700
From:   Nick Desaulniers <ndesaulniers@...gle.com>
To:     Nathan Chancellor <natechancellor@...il.com>,
        Christophe Leroy <christophe.leroy@....fr>,
        Fangrui Song <maskray@...gle.com>,
        Michael Ellerman <mpe@...erman.id.au>
Cc:     Benjamin Herrenschmidt <benh@...nel.crashing.org>,
        Paul Mackerras <paulus@...ba.org>,
        linuxppc-dev <linuxppc-dev@...ts.ozlabs.org>,
        LKML <linux-kernel@...r.kernel.org>,
        clang-built-linux <clang-built-linux@...glegroups.com>
Subject: Re: [PATCH] powerpc/vdso32: mark __kernel_datapage_offset as STV_PROTECTED

On Thu, Feb 6, 2020 at 10:42 PM Nathan Chancellor
<natechancellor@...il.com> wrote:
>
> On Wed, Feb 05, 2020 at 07:25:59AM +0100, Christophe Leroy wrote:
> >
> >
> > Le 05/02/2020 à 01:50, Fangrui Song a écrit :
> > > A PC-relative relocation (R_PPC_REL16_LO in this case) referencing a
> > > preemptible symbol in a -shared link is not allowed.  GNU ld's powerpc
> > > port is permissive and allows it [1], but lld will report an error after
> > > https://git.kernel.org/pub/scm/linux/kernel/git/powerpc/linux.git/commit/?id=ec0895f08f99515194e9fcfe1338becf6f759d38
> >
> > Note that there is a series whose first two patches aim at dropping
> > __kernel_datapage_offset . See
> > https://patchwork.ozlabs.org/project/linuxppc-dev/list/?series=156045 and
> > especially patches https://patchwork.ozlabs.org/patch/1231467/ and
> > https://patchwork.ozlabs.org/patch/1231461/
> >
> > Those patches can be applied independentely of the rest.
> >
> > Christophe
>
> If that is the case, it would be nice if those could be fast tracked to
> 5.6 because as it stands now, all PowerPC builds that were working with
> ld.lld are now broken. Either that or take this patch and rebase that
> series on this one.

So do we still need Fangrui's patch or is it moot?  I'm doing a scrub
of our bug tracker and this issue is still open:
https://github.com/ClangBuiltLinux/linux/issues/851
but it looks like all of our ppc LE targets are linking with LLD just fine
https://travis-ci.com/github/ClangBuiltLinux/continuous-integration/builds/169379039
though it sounds like
https://github.com/ClangBuiltLinux/linux/issues/774
may be a blocker?
Though I don't see Cristophe's
https://patchwork.ozlabs.org/project/linuxppc-dev/patch/5f97f7c921ffc2113ada0f32924e409bccc8277a.1580399657.git.christophe.leroy@c-s.fr/
in mainline or -next.  Was the series not accepted?


>
> Cheers,
> Nathan
>
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--
Thanks,
~Nick Desaulniers