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List:       linuxppc64-dev
Subject:    per page execute
From:       amodra () bigpond ! net ! au (Alan Modra)
Date:       2003-12-30 22:30:41
Message-ID: 20031230221841.GB22998 () bubble ! sa ! bigpond ! net ! au
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On Sat, Dec 27, 2003 at 11:15:25PM +1100, Anton Blanchard wrote:
>   [25] .plt NOBITS 10010c08 000c00 0000c0 00 WAX 0   0  4
>   [26] .bss NOBITS 10010cc8 000c00 000004 00  WA 0   0  1
>
> Look how the non executable bss butts right onto the executable plt.
> Even with the patch below, we are failing some security tests that try
> and exec stuff out of the bss. Thats because the stuff ends up in the same
> page as the plt. Alan, could this be considered a toolchain bug?

Possibly.  What about .got (exec) and adjacent .sdata (non-exec)?  The
ABI says that shared libs access .sdata via the got pointer, so
there's no hope of separating them.

--
Alan Modra
IBM OzLabs - Linux Technology Centre

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