Re: fast/syscall-free gettimeofday ?

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@xxxxxxxxxxxx> 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@xxxxxxxxxxx mailing list
http://lists.freebsd.org/mailman/listinfo/freebsd-current
To unsubscribe, send any mail to "freebsd-current-unsubscribe@xxxxxxxxxxx"

_______________________________________________
freebsd-current@xxxxxxxxxxx mailing list
http://lists.freebsd.org/mailman/listinfo/freebsd-current
To unsubscribe, send any mail to "freebsd-current-unsubscribe@xxxxxxxxxxx"

_______________________________________________
freebsd-current@xxxxxxxxxxx mailing list
http://lists.freebsd.org/mailman/listinfo/freebsd-current
To unsubscribe, send any mail to "freebsd-current-unsubscribe@xxxxxxxxxxx"

Relevant Pages

  • Re: fast/syscall-free gettimeofday ?
    ... fast implementations of gettimeofday() that would not require ... a system call (perhaps mmapping some memory region which ...
    (freebsd-current)
  • fast/syscall-free gettimeofday ?
    ... fast implementations of gettimeofday() that would not require ... a system call (perhaps mmapping some memory region which ...
    (freebsd-current)