Re: New vsyscall emulation breaks JITs

[H. Peter Anvin]

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.
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