Re: [gentoo-science] sci-libs/mpir for the main tree

[Christopher Schwan <cschwan@students.uni-mainz.de>]

Hi,

On Tuesday 09 November 2010 09:19:54 François Bissey wrote:
> > Hi,
> > 
> > my next migration victim will be mpir, the friendly clone of gmp.  The
> > current ebuild is the same in sage-on-gentoo and science.  It has this
> > assembler stuff in it that I don't understand.  Who did this? What is
> > the latest here, can we remove the fat TODO-banner (or DO it?).
> > 
> > Any other hints/objections?  (Yes, I know that there is a bump
> > waiting...)
> 
> Hi Thomas,
> 
> Christopher did it. mpir like gmp suffer from executable stacks.

I followed the instructions listed in number 6 of the following page: 
http://www.gentoo.org/proj/en/hardened/gnu-stack.xml . However, the fix is 
incomplete (some architectures still have executable stacks) and I had some 
problems with BASH:

for i in $(find . -type f -name '*.asm') ; do
	echo $i >/dev/null
	cat >> $i <<-EOF
		#if defined(__linux__) && defined(__ELF__)
		.section .note.GNU-stack,"",%progbits
		#endif
	EOF
done

If I remove the line with "echo" (which *should* be completely useless), the 
cat command does not patch files - WHY ?! Also, mpir seemed to have dropped 
yasm beginning with mpir-2.1 (?), so I think at least one loop in mpir's 
ebuild is superfluous.

> There are talk on sage-devel which is very close to mpir upstream
> to take a different approach: using an m4 macro and a linker flag
> to remove them -Wl,-z,noexecstack.

This seems to be a better idea.

> The motivation to fix this is fedora 14 which doesn't allow executable
> stacks by default.
> I think the warning could be removed for now but the ebuild will probably
> need a little TLC in the near future.
> 
> Francois

Christopher