Re: [PATCH (sh-2.6) 1/2] sh: add stack smashing protection support

[Mike Frysinger <vapier@gentoo.org>]

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On Thursday, December 09, 2010 11:45:30 Carmelo AMOROSO wrote:
> On 12/9/2010 5:07 PM, Mike Frysinger wrote:
> > On Thursday, December 09, 2010 10:56:26 Carmelo AMOROSO wrote:
> >> I agree with you that the Kconfig and Makefile changes are not arch
> >> specific, so these changes can be moved to a common code (even if I
> >> don't know if other archs do support SSP).
> >> In the current kernel, only x86 and ARM added this support, so I'm
> >> wondering if, moving SSP to the common Makefile, it needs to depend on
> >> x86, ARM, SH being configured ?
> > 
> > i'm not sure it does.  ssp is designed to be arch independent, so really
> > you only need a new enough gcc version.  which means i dont think it
> > needs to depend on any arch code and you can simply add to the Makefile
> > a compiler check.
> 
> agreed, but if arch wants to implement the per-task canary feature, some
> change into arch specific code is required.

yes, but that doesnt mean the common symbol definition needs to be duplicated

> >> Regarding the __stack_chk_guard symbol defined in process[_32].c, I
> >> don't know if all archs need to define this global variable to implement
> >> SSP. For sure x86 does not need it. It depends on how the gcc implements
> >> this feature. This was mainly the reason for which we defined it
> >> specifically in an arch specific code.
> > 
> > the common gcc code too outputs __stack_chk_guard references.  none of
> > that is in arch-specific places.
> 
> a simple test on x86 just prints reference to __stack_chk_fail only (not
> reference to the global variable guard)
> 
> gcc is 4.3.0-8 (Fedora C9)

gcc will reference both __stack_chk_fail and __stack_chk_guard depending on 
the code.  i think you only need to test that gcc accepts -fstack-protector 
and then assume the rest ... i dont think you need to come up with random 
pieces of code and cajole the symbol references out of gcc.

along those lines, i see your patch adding __stack_chk_guard, but where is 
__stack_chk_fail ?
-mike

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