linux-kernel - Re: [tip:x86/kaslr] x86, relocs: Add more per-cpu gold special cases

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Message-ID: <20131015160329.GA16003@gmail.com>
Date:	Tue, 15 Oct 2013 18:03:30 +0200
From:	Ingo Molnar <mingo@...nel.org>
To:	Kees Cook <keescook@...omium.org>
Cc:	"H. Peter Anvin" <hpa@...or.com>,
	LKML <linux-kernel@...r.kernel.org>,
	Michael Davidson <md@...gle.com>,
	Thomas Gleixner <tglx@...utronix.de>,
	"H. Peter Anvin" <hpa@...ux.intel.com>,
	"linux-tip-commits@...r.kernel.org" 
	<linux-tip-commits@...r.kernel.org>
Subject: Re: [tip:x86/kaslr] x86, relocs: Add more per-cpu gold special cases


* Kees Cook <keescook@...omium.org> wrote:

> On Mon, Oct 14, 2013 at 11:04 PM, Ingo Molnar <mingo@...nel.org> wrote:
> >
> > * Kees Cook <keescook@...omium.org> wrote:
> >
> >> On Mon, Oct 14, 2013 at 9:28 AM, H. Peter Anvin <hpa@...or.com> wrote:
> >> > On 10/14/2013 07:19 AM, H. Peter Anvin wrote:
> >> >> My guess is that the 95 addresses are randomized and the 82 address is an address which failed to relocate.
> >> >
> >> >> ffffffff82a04a58 is:
> >> >> ffffffff82a03000 t init_per_cpu__gdt_page
> >> >
> >> >
> >> > Specifically, it looks like the percpu stuff isn't getting set up correctly.
> >>
> >> It wouldn't surprise me if there are even more percpu things to fix.
> >> It's the main area we've continued to trip over while working on this
> >> with various linkers. Which linker and version are you seeing this
> >> with?
> >
> > The failure I saw triggered with fairly modern userspace:
> >
> >  GNU ld version 2.23.52.0.1-9.fc19 20130226
> >
> >  gcc version 4.8.1 20130603 (Red Hat 4.8.1-1) (GCC)
> 
> Can you try with the gold linker?  When not using Gold, I can produce a 
> similar crash with GNU ld ver 2.23.2 but not 2.22.

I'm not set up for Gold - but maybe others can try your experiment.

If you can see/reproduce the 2.23 crash then maybe that fix will work for 
my testcase as well.

Thanks,

	Ingo
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