Re: New vsyscall emulation breaks JITs

From: Linus Torvalds
Date: Tue Aug 09 2011 - 18:36:39 EST


On Tue, Aug 9, 2011 at 2:04 PM, Andrew Lutomirski <luto@xxxxxxx> wrote:
>
> Here's a different proposal, then:
>
> What if the kernel had the sequence:
>
> mov $__NR_whatever,%eax
> syscall
> ret
>
> in the vsyscall page but marked the vsyscall page NX.

This sounds like a sound idea. And then the difference between "fast
and native" and "slow and trapping" ends up literally being just the
NX bit.

Linus
--
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@xxxxxxxxxxxxxxx
More majordomo info at http://vger.kernel.org/majordomo-info.html
Please read the FAQ at http://www.tux.org/lkml/