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From:   "Jason A. Donenfeld" <Jason@zx2c4.com>
Date:   Mon, 23 Mar 2020 15:11:55 -0600
Message-ID: <CAHmME9o3Vef022V6fb1b3JOFOmjKXBBroiYU83kOewKHJ3MyQA@mail.gmail.com>
Subject: Re: [PATCH] Documentation/changes: Raise minimum supported binutils
 version to 2.23
To:     Kees Cook <keescook@chromium.org>
Cc:     Borislav Petkov <bp@alien8.de>,
        Arvind Sankar <nivedita@alum.mit.edu>,
        "H. Peter Anvin" <hpa@zytor.com>,
        Thomas Gleixner <tglx@linutronix.de>,
        Ingo Molnar <mingo@redhat.com>, X86 ML <x86@kernel.org>,
        LKML <linux-kernel@vger.kernel.org>,
        Thomas Lendacky <Thomas.Lendacky@amd.com>,
        Mauro Rossi <issor.oruam@gmail.com>,
        Michael Matz <matz@suse.de>,
        Masahiro Yamada <masahiroy@kernel.org>
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Sender: linux-kernel-owner@vger.kernel.org
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On Mon, Mar 23, 2020 at 2:51 PM Kees Cook <keescook@chromium.org> wrote:
>
> On Mon, Mar 23, 2020 at 02:44:54PM -0600, Jason A. Donenfeld wrote:
> > On Mon, Mar 16, 2020 at 05:02:59PM +0100, Borislav Petkov wrote:
> > > Long overdue patch, see below.
> > >
> > > Plan is to queue it after 5.7-rc1.
> > >
> > > ---
> > > From: Borislav Petkov <bp@suse.de>
> > > Date: Mon, 16 Mar 2020 16:28:36 +0100
> > > Subject: [PATCH] Documentation/changes: Raise minimum supported binutilsa version to 2.23
> > >
> > > The currently minimum-supported binutils version 2.21 has the problem of
> > > promoting symbols which are defined outside of a section into absolute.
> > > According to Arvind:
> > >
> > >   binutils-2.21 and -2.22. An x86-64 defconfig will fail with
> > >           Invalid absolute R_X86_64_32S relocation: _etext
> > >   and after fixing that one, with
> > >           Invalid absolute R_X86_64_32S relocation: __end_of_kernel_reserve
> > >
> > > Those two versions of binutils have a bug when it comes to handling
> > > symbols defined outside of a section and binutils 2.23 has the proper
> > > fix, see: https://sourceware.org/legacy-ml/binutils/2012-06/msg00155.html
> > >
> > > Therefore, up to the fixed version directly, skipping the broken ones.
> > >
> > > Currently shipping distros already have the fixed binutils version so
> > > there should be no breakage resulting from this.
> > >
> > > For more details about the whole thing, see the thread in Link.
> >
> > That sounds very good to me. Then we'll be able to use ADX instructions
> > without ifdefs.
> >
> > Acked-by: Jason A. Donenfeld <Jason@zx2c4.com>
>
> Can you send these now and we can land in 5.7 with the doc change?

By the way, while we're in the process of updating dependencies, what
if we ratched the minimum binutils on x86 up to 2.25 (which is still
quite old)? In this case, we could get rid of *all* of the CONFIG_AS_*
ifdefs throughout.

Jason