fast/syscall-free gettimeofday ?

Scott Long scottl at
Thu Jun 16 00:59:01 UTC 2011

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.


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