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

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Message-ID: <49918E86.4020304@kernel.org>
Date:	Tue, 10 Feb 2009 23:26:14 +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:
>>> 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.
>> Can't reproduce with gcc-4.1 or 4.2.  Any chance you're using distcc
>> w/ a build machine w/ glibc < 2.4?  __stack_chk_guard is the symbol
>> gcc fetches stack canary from if TLS is not supported, so somehow gcc
>> thought that TLS wasn't available while building head64.
> 
> yeah - i also used distcc. Maybe the nostackp makefile magic gets confused
> about that?

It seems that even with the same gcc versions, gcc built against libc
w/o TLS support generates __stack_chk_guard, so if you mix the two
flavors, the has-stack-protector check can be compiled on machines w/
TLS while some other files end up being built on machines w/o TLS
support thus circumventing the support check.  Can you please see
whether non-distcc build fails too?

Thanks.

-- 
tejun
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