Re: New vsyscall emulation breaks JITs

From: H. Peter Anvin
Date: Tue Aug 09 2011 - 20:57:47 EST

Linus Torvalds <torvalds@xxxxxxxxxxxxxxxxxxxx> wrote:

>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

Very promising idea indeed.
Sent from my mobile phone. Please excuse my brevity and lack of formatting.
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