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SubjectRe: [Announcement] "Exec Shield", new Linux security feature

On Fri, 2 May 2003, Carl-Daniel Hailfinger wrote:

> Ingo Molnar wrote:
> >
> > Furthermore, the kernel also remaps all PROT_EXEC mappings to the
> > so-called ASCII-armor area, which on x86 is the addresses 0-16MB. These
> [snipped]
> > In the above layout, the highest executable address is 0x01003fff, ie.
> > every executable address is in the ASCII-armor.
> If my math is correct,
> 0x01000000 is 16 MB boundary
> 0x01003fff is outside the ASCII-armor.

the ASCII-armor, more precisely, is between addresses 0x00000000 and
0x0100ffff. Ie. 16 MB + 64K. [in the remaining 64K the \0 character is in
the second byte of the address.] So the 0x01003fff address is still inside
the ASCII-armor.

> Another question: Last time I checked, there were some problems with
> binary only drivers (to name one, NVidia graphics) and a non-executable
> stack. Has this been resolved?

i'm not using any binary-only drivers, so i have no idea. But as long as
they use PROT_EXEC areas for code, they should be safe.


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