linux-kernel - Re: [PATCH v3 1/2] x86/mm: Identify the end of the kernel area to be reserved

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Date:   Wed, 24 Jul 2019 17:34:16 +0200
From:   Greg KH <gregkh@...uxfoundation.org>
To:     Thomas Gleixner <tglx@...utronix.de>
Cc:     "H.J. Lu" <hjl.tools@...il.com>,
        Mike Lothian <mike@...eburn.co.uk>,
        Tom Lendacky <thomas.lendacky@....com>, bhe@...hat.com,
        Borislav Petkov <bp@...en8.de>,
        Dave Hansen <dave.hansen@...ux.intel.com>, lijiang@...hat.com,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
        Andy Lutomirski <luto@...nel.org>,
        Ingo Molnar <mingo@...hat.com>,
        Peter Zijlstra <peterz@...radead.org>,
        the arch/x86 maintainers <x86@...nel.org>
Subject: Re: [PATCH v3 1/2] x86/mm: Identify the end of the kernel area to be
 reserved

On Tue, Jul 23, 2019 at 03:44:54PM +0200, Greg KH wrote:
> On Tue, Jul 23, 2019 at 03:31:32PM +0200, Thomas Gleixner wrote:
> > On Tue, 23 Jul 2019, Greg KH wrote:
> > > On Mon, Jul 15, 2019 at 01:16:48PM -0700, H.J. Lu wrote:
> > > > >
> > > > 
> > > > Since building a workable kernel for different kernel configurations isn't a
> > > > requirement for gold, I don't recommend gold for kernel.
> > > 
> > > Um, it worked before this commit, and now it doesn't.  "Some" companies
> > > are using gold for linking the kernel today...
> > 
> > gold is known to fail the kernel build. x32 vdso linking is not working
> > since years and just because it 'works' for some configurations and breaks
> > for no valid reasons even with those configurations is just not good
> > enough.
> > 
> > As there is obviously no priority for fixing gold to work proper with the
> > kernel, I'm not at all interested in these 'regression' reports and in odd
> > 'fixes' which just end up reverting or modifying perfectly valid changes
> > without understanding the root cause, i.e. the most horrible engineering
> > principle: duct-taping.
> > 
> > TBH, I'm tired of it. We fail the build for clang if it does not support
> > asm gotos and the clang people are actively working on fixing it and we're
> > helping them as much as we can. The companies who used clang nevertheless
> > have been on their own for years and if someone wants to use gold then
> > nobody is preventing them from doing so. They can keep their duct-tape in
> > their own trees.
> > 
> > See this thread for further discussion:
> > 
> >  https://lkml.kernel.org/r/alpine.DEB.2.21.1907161434260.1767@nanos.tec.linutronix.de
> 
> Sorry, I saw that after writing that.  You are right, if the others
> don't object, that's fine with me.  I'll go poke the various build
> systems that are failing right now on 5.3-rc1 and try to get them fixed
> for this reason.

Ok, I dug around and the gold linker is not being used here, only clang
to build the source and GNU ld to link, and I am still seeing this
error.

Hm, clang 8 does not cause this error, but clang 9 does.  Let me go poke
the people who are providing this version of clang to see if there's
something they can figure out.

greg k-h