linux-kernel - Re: [PATCHSET x86/master] add stack protector support for x86

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Message-ID: <499186FB.4070506@kernel.org>
Date:	Tue, 10 Feb 2009 22:54:03 +0900
From:	Tejun Heo <tj@...nel.org>
To:	Ingo Molnar <mingo@...e.hu>
CC:	hpa@...or.com, jeremy@...p.org, tglx@...utronix.de,
	linux-kernel@...r.kernel.org, x86@...nel.org, rusty@...tcorp.com.au
Subject: Re: [PATCHSET x86/master] add stack protector support for x86_32

Ingo Molnar wrote:
> * Ingo Molnar <mingo@...e.hu> wrote:
> 
>> [...] I might not get around testing it today and pushing it out into tip:master, 
>> but i pushed out the core/percpu bits, should you queue up further changes.
> 
> ok, activated it for -tip testing, and there's a 64-bit build failure caused by 
> it:
> 
> arch/x86/kernel/head64.o: In function `x86_64_start_reservations':
> head64.c:(.init.text+0x26): undefined reference to `__stack_chk_guard'
> head64.c:(.init.text+0xc2): undefined reference to `__stack_chk_guard'
> arch/x86/kernel/head64.o: In function `x86_64_start_kernel':
> head64.c:(.init.text+0x104): undefined reference to `__stack_chk_guard'
> head64.c:(.init.text+0x1cd): undefined reference to `__stack_chk_guard'
> arch/x86/kernel/head.o: In function `reserve_ebda_region':
> head.c:(.init.text+0xb): undefined reference to `__stack_chk_guard'
> arch/x86/kernel/head.o:head.c:(.init.text+0x87): more undefined references to 
> `__stack_chk_guard' follow

Call to __stack_chk_guard is probably generated automatically.
Strangely, my gcc only generates calls to __stack_chk_fail.

 > gcc --version
 gcc (SUSE Linux) 4.3.2 [gcc-4_3-branch revision 141291]
 Copyright (C) 2008 Free Software Foundation, Inc.
 This is free software; see the source for copying conditions.  There is NO
 warranty; not even for MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.
 > nm build/vmlinux|grep __stack_chk_
 00000000f0fdf6cb A __crc___stack_chk_fail
 ffffffff80d53e50 r __kcrctab___stack_chk_fail
 ffffffff80d5ff81 r __kstrtab___stack_chk_fail
 ffffffff80d3d140 r __ksymtab___stack_chk_fail
 ffffffff80248619 T __stack_chk_fail

I'll try other compilers but which version are you using?  The
difference is that before the patchset, -fno-stack-protector was
always added whether stackprotector was enabled or not so this problem
wasn't visible (at the cost of bogus stackprotector of course).  We'll
probably need to add __stack_chk_guard or disable if gcc generates
such symbol.  I'll play with different gccs.

Thanks.

-- 
tejun
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