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SubjectRe: Stack overflows.

> With all the interest in buffer overflows lately, I was wondering if intel
> MM allows you to make the stack frame non-executable? I think someone made
> a patch for Solaris Sparc that does exactally that. (non supported by Sun,
> of course)

The trampolines generated by GCC for code like


or for certain objective C constructs assume that the stack frame is
executable. Trampolines are being used in the GNU libc and it's dynamic
linker, so it's a really bad idea to make the stack non-executable.

If you really want to make the stack non-executable see the documentation
for mprotect(2).

Btw, performancewise trampolines really suck on architecture that have to
maintain their I/D-cache consistence in software like 68k or MIPS. Even
Intel from Pentium on get a performance hit so better don't use them.


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