fast/syscall-free gettimeofday ?

[Scott Long]

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

On Jun 14, 2011, at 10:08 AM, K. Macy wrote:

> http://svnweb.freebsd.org/base/head/sys/sys/imgact.h
> 
> 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 ?
>> 
>> cheers
>> luigi
>> _______________________________________________
>> freebsd-current at freebsd.org mailing list
>> http://lists.freebsd.org/mailman/listinfo/freebsd-current
>> To unsubscribe, send any mail to "freebsd-current-unsubscribe at freebsd.org"
>> 
> _______________________________________________
> freebsd-current at freebsd.org mailing list
> http://lists.freebsd.org/mailman/listinfo/freebsd-current
> To unsubscribe, send any mail to "freebsd-current-unsubscribe at freebsd.org"