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Re: GCC extension for protecting applications from format string attacks
- To: Richard Henderson <rth at redhat dot com>
- Subject: Re: GCC extension for protecting applications from format string attacks
- From: Richard Earnshaw <rearnsha at arm dot com>
- Date: Sat, 07 Apr 2001 13:14:31 +0100
- cc: Zack Weinberg <zackw at stanford dot edu>, Makoto Iwamura <iwamura at pb dot highway dot ne dot jp>, vuln-dev at securityfocus dot com, gcc-patches at gcc dot gnu dot org, etoh at jp dot ibm dot com, Richard dot Earnshaw at arm dot com
- Organization: ARM Ltd.
- Reply-To: Richard dot Earnshaw at arm dot com
> On Thu, Apr 05, 2001 at 11:51:03AM -0700, Zack Weinberg wrote:
> > To the best of my knowledge, all ABIs supported by GCC have
> > at least one call-clobbered register which is not used to pass
> > arguments.
>
> ARM has only 4 call clobbered registers and uses all of them
> in parameter passing. This presents nasty problems for the
> static chain register, for instance.
>
Actually, it has 5: r0-r3 + ip (aka r12 depending on your naming
preferences). But r12 is used in some ABI variants as part of the
prologue entry code, or as a scratch when calling into shared libraries,
so even that cannot be used for passing additional information.
R.