linux-kernel - Re: [PATCH] arm64: errata: Check for --fix-cortex-a53-843419 and --fix-cortex-a53

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Message-ID: <20161102212747.GL22791@arm.com>
Date:   Wed, 2 Nov 2016 21:27:48 +0000
From:   Will Deacon <will.deacon@....com>
To:     Markus Mayer <markus.mayer@...adcom.com>
Cc:     Markus Mayer <code@...yer.net>,
        Catalin Marinas <catalin.marinas@....com>,
        ARM Kernel Mailing List 
        <linux-arm-kernel@...ts.infradead.org>,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH] arm64: errata: Check for --fix-cortex-a53-843419 and
 --fix-cortex-a53

On Wed, Nov 02, 2016 at 02:07:17PM -0700, Markus Mayer wrote:
> On 2 November 2016 at 14:03, Will Deacon <will.deacon@....com> wrote:
> > On Mon, Oct 31, 2016 at 12:44:14PM -0700, Markus Mayer wrote:
> >> From: Markus Mayer <mmayer@...adcom.com>
> >>
> >> The new errata check leads to a warning with some older versions of the
> >> linker that do know how to work around the errata, but still use the
> >> original name of the command line option: --fix-cortex-a53. The commit
> >> in question that changed the name of the option can be found at [1].
> >> It looks like only "gold" is affected by this rename. Traditional "ld"
> >> isn't. (There, the argument was always called --fix-cortex-a53-843419.)
> >>
> >> To allow older versions of gold to properly handle the erratum if they
> >> can, check whether ld supports the old name of this option in addition
> >> to checking the new one.
> >>
> >> [1] https://sourceware.org/git/gitweb.cgi?p=binutils-gdb.git;a=commitdiff;h=7a2a1c793578a8468604e661dda025ecb8d0bd20;hp=cfbf0e3c5b637d66b2b1aeadecae9c187b825b2f
> >>
> >> Signed-off-by: Markus Mayer <mmayer@...adcom.com>
> >
> > If newer versions of gold accept the correct option name, why do we care?
> 
> Because Documentation/Changes states that the minimum requirement for
> binutils is 2.12. Right now, that is not really true. And not
> everybody can always use the newest toolchain, for various reasons.

Well the kernel still builds, right? Can binutils 2.12 even work around
843419? For people who can't use a recent toolchain, then they don't get
erratum workaround and we warn them about it.

> The question I am asking is: What do we have to lose by supporting both options?

We end up passing "--fix-cortex-a53" to the linker, without knowing what it
might do in the future.

Will