per page execute

[linas at austin.ibm.com]

I'm reading some old email ...

On Wed, Dec 31, 2003 at 08:48:41AM +1030, Alan Modra wrote:
>
> 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.

Dumb question: can you pad out the .got to a 4K boundary?
Yes, that's a bogus fix is the kernel page size is different.

--linas

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