Re: fast/syscall-free gettimeofday ?

On Jun 15, 2011, at 6:44 PM, Julian Elischer wrote:
>> If this was to be extended with cached global syscall information like gettimeofday, would we want that to be in a separate page that is marked non-executable?  Is there any way to trick the kernel into leaking arbitrary (and thus executable) code?  Also, would it matter for jails?  Per-process info like getpid would obviously have to be a separate per-process page.
>> 
>> Scott
>> 
> In the talk about this sort of topic  I have seen mention at various times
> of a page per system, a page per jail, a page per process and a page per thread.
> 
> I'm not saying we want this all just that I've seen it mentionned..
> 
> The per-thread one is the most intersting to do challenge wise.

I guess that per-thread would be done via a pointer off of the TLS data, or would it be yet another bumping of the stack?  It would be interesting to see how expensive it is to go that direction.

Scott