fast/syscall-free gettimeofday ?
scottl at samsco.org
Wed Jun 15 20:49:48 UTC 2011
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.
On Jun 14, 2011, at 10:08 AM, K. Macy wrote:
> kib added rudimentary support for this in January
> On Tue, Jun 14, 2011 at 6:11 PM, Luigi Rizzo <rizzo at iet.unipi.it> wrote:
>> there were discussions at some point on an imprecise but
>> fast implementations of gettimeofday() that would not require
>> a system call (perhaps mmapping some memory region which
>> is opportunistically updated).
>> Does anyone remember what happened about that ?
>> Otherwise, is there any place in the kernel where i can fetch
>> a struct timeval which is not off by more than, say 1 tick ?
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