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Subject: Re: 32 bit userland on G5
From: David Woodhouse <dwmw2@infradead.org>
To: Paul Mackerras <paulus@samba.org>
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Date: Wed, 14 Jun 2006 01:04:14 +0100
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On Wed, 2006-06-14 at 09:46 +1000, Paul Mackerras wrote:
> > We already did it in Fedora. We don't default to READ_IMPLIES_EXEC 
> > for 32-bit processes on the 64-bit kernel.
> 
> By patching include/asm-powerpc/elf.h? 

By patching fs/binfmt_elf.c -- it's part of the exec-shield patch.
http://cvs.fedora.redhat.com/viewcvs/devel/kernel/linux-2.6-execshield.patch?rev=1.20&view=auto

shinybook /home/dwmw2 $ cat foo.c
int foo[2] = { 0x3860005a, 0x4e800020 };
int main(void)
{
        int (*foofn)(void) = (void *)foo;
        int f = foofn();
        printf("%x\n", f);
}
shinybook /home/dwmw2 $ ./foo
5a
shinybook /home/dwmw2 $ scp foo pmac: ; ssh pmac
foo                                             100% 9996     9.8KB/s
00:00
Last login: Wed Jun 14 00:58:26 2006 from shinybook-bcm.infradead.org
pmac /home/dwmw2 $ ./foo
Segmentation fault
pmac /home/dwmw2 $ setarch ppc -X ./foo
5a

-- 
dwmw2