Date: Wed, 15 Jun 2011 14:33:27 -0600 From: Scott Long <scottl@samsco.org> To: "K. Macy" <kmacy@freebsd.org> Cc: Luigi Rizzo <rizzo@iet.unipi.it>, current@freebsd.org Subject: Re: fast/syscall-free gettimeofday ? Message-ID: <4A46AC77-BEE5-4401-8896-4E4F1A5304B0@samsco.org> In-Reply-To: <BANLkTinOq73nGQT88NByuOgH3ByuA=ZLJA@mail.gmail.com> References: <20110614161105.GA17306@onelab2.iet.unipi.it> <BANLkTinOq73nGQT88NByuOgH3ByuA=ZLJA@mail.gmail.com>
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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@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@freebsd.org mailing list >> http://lists.freebsd.org/mailman/listinfo/freebsd-current >> To unsubscribe, send any mail to "freebsd-current-unsubscribe@freebsd.org" >> > _______________________________________________ > freebsd-current@freebsd.org mailing list > http://lists.freebsd.org/mailman/listinfo/freebsd-current > To unsubscribe, send any mail to "freebsd-current-unsubscribe@freebsd.org"
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