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From:   Arvind Sankar <nivedita@alum.mit.edu>
Date:   Tue, 24 Mar 2020 18:01:47 -0400
To:     Arvind Sankar <nivedita@alum.mit.edu>
Cc:     Borislav Petkov <bp@alien8.de>,
        Linus Torvalds <torvalds@linux-foundation.org>,
        "Jason A. Donenfeld" <Jason@zx2c4.com>,
        Masahiro Yamada <masahiroy@kernel.org>,
        Kees Cook <keescook@chromium.org>,
        "H. Peter Anvin" <hpa@zytor.com>,
        Thomas Gleixner <tglx@linutronix.de>,
        Ingo Molnar <mingo@redhat.com>, X86 ML <x86@kernel.org>,
        Linux Kernel Mailing List <linux-kernel@vger.kernel.org>,
        Thomas Lendacky <Thomas.Lendacky@amd.com>,
        Mauro Rossi <issor.oruam@gmail.com>,
        Michael Matz <matz@suse.de>
Subject: Re: [PATCH] Documentation/changes: Raise minimum supported binutils
 version to 2.23
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On Tue, Mar 24, 2020 at 05:42:05PM -0400, Arvind Sankar wrote:
> On Tue, Mar 24, 2020 at 05:48:12PM +0100, Borislav Petkov wrote:
> > On Tue, Mar 24, 2020 at 09:37:13AM -0700, Linus Torvalds wrote:
> > > I think it's ok. It's not going to cause any _subtle_ failures, it's
> > > going to cause very clear "oh, now it doesn't build" errors.
> > > 
> > > No?
> > > 
> > > And binutils 2.23 is what, 7+ years old by now and apparently had
> > > known failure cases too.
> > > 
> > > But if there are silent and subtle failures, that might be a reason to
> > > be careful. Are there?
> > 
> > Well, not that I know of and that's why I'm being overly cautious. Maybe
> > too cautious but a lot of hectic testing of last minute fixes in the
> > past have taught me to take my time.
> > 
> > And since it doesn't really matter when the patch goes in - there's
> > always the next merge window - I would prefer to take our time and have
> > it simmer in -next for max period.
> > 
> > So yeah, 2.23 has been tested for a long time now and it is very likely
> > that nothing would happen and if you think it's ok, then sure. Then if
> > you happen to see urgent pull requests with build or some other fixes,
> > at least you'll be prepared. :-)
> > 
> 
> This is just a documentation patch right? Nothing actually changes with
> the build. The only possible thing that we would potentially have to
> deal with is
> 
> (1) people noticing the doc change and complaining that they
> still need to use binutils-2.21 for some reason -- but they can't
> currently build an x86 kernel without patches anyway, so...

The __end_of_kernel_reserve symbol that breaks with the 2.21-2.22
binutils was added in v5.3, so we've already gone 3 kernel versions
without complaints.

> 
> (2) people noticing the doc change and suggesting moving to 2.26 or some
> later version instead of 2.23.