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.

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