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Date:   Tue, 14 Jan 2020 13:50:05 -0800
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Subject: Re: [PATCH v3] x86/vmlinux: Fix vmlinux.lds.S with pre-2.23 binutils
To:     Borislav Petkov <bp@alien8.de>, Kees Cook <keescook@chromium.org>
CC:     Arvind Sankar <nivedita@alum.mit.edu>,
        Thomas Gleixner <tglx@linutronix.de>,
        Ingo Molnar <mingo@redhat.com>, x86@kernel.org,
        linux-kernel@vger.kernel.org,
        Thomas Lendacky <Thomas.Lendacky@amd.com>,
        Mauro Rossi <issor.oruam@gmail.com>,
        Michael Matz <matz@suse.de>
From:   hpa@zytor.com
Message-ID: <27433E59-971A-4885-B74C-2D6844372FE6@zytor.com>
Sender: linux-kernel-owner@vger.kernel.org
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On January 14, 2020 8:51:35 AM PST, Borislav Petkov <bp@alien8=2Ede> wrote:
>On Mon, Jan 13, 2020 at 05:53:32PM -0800, Kees Cook wrote:
>> NAK: linkers can add things at the end of =2Etext that will go missing
>from
>> the kernel if _etext isn't _outside_ the =2Etext section, truly beyond
>the
>> end of the =2Etext section=2E This patch will break Control Flow
>Integrity
>> checking since the jump tables are at the end of =2Etext=2E
>
>Err, which linkers are those? Please elaborate=2E
>
>In any case, after reading the thread, I can't help but favor the idea
>of us bumping min binutils version to 2=2E23=2E
>
>Michael (on Cc) says that the 2=2E21 was kinda broken wrt to the symbols
>fun outside of sections, 2=2E22 tried to fix it, see
>
>fd952815307f ("x86-32, relocs: Whitelist more symbols for ld bug
>workaround")
>
>which Arvind pointed out and 2=2E23 fixed it for real=2E
>
>Now, 2=2E23 is still very ancient=2E I'm looking at our releases: openSUS=
E
>12=2E1 has the minimum supported gcc version 4=2E6 by the kernel and
>also the minimum binutils version 2=2E21 which we support according to
>Documentation/process/changes=2Erst
>
>Now, openSUSE 12=2E1 is ancient and we ourselves advise people to update
>to current distros so I don't think anyone would still run it=2E
>
>So, considering that upping the binutils version would save us from all
>this trouble I say we try it after 5=2E5 releases for a maximum time of a
>full 5=2E6 release cycle and see who complains=2E
>
>Considering how no one triggered this yet until Arvind, I think no one
>would complain=2E But I might be wrong=2E
>
>So what do people think? hpa?

I'm all for dumping support for an ancient, known buggy binutils=2E
--=20
Sent from my Android device with K-9 Mail=2E Please excuse my brevity=2E