Re: FreeBSD-SA-06:14.fpu

On Sun, 30 Apr 2006 16:59:49 +0800
David Xu <davidxu@xxxxxxxxxxx> wrote:

Igor Sysoev wrote:

The last security advisory FreeBSD-SA-06:14.fpu
ftp://ftp.freebsd.org/pub/FreeBSD/CERT/advisories/FreeBSD-SA-06:14.fpu.asc
that fixes very doubtful security bug in AMD CPUs, also
adds unnecessary penalty in FPU context switch for all other
SSE-enabled CPUs.


Igor Sysoev
http://sysoev.ru/en/

Probably it should only be applied to AMD CPU but not Intel and others,
it is easy to check cpu vendor and put a
if (bug_fxsave)
fpu_clean_state();

in file npx.c.

David Xu

Shouldn't we use an existing variable which is already in L1 instead of
the new dummy_variable? Or isn't this noticable in performance?

btw Linux does it this way:
http://www.kernel.org/git/?p=linux/kernel/git/stable/linux-2.6.16.y.git;a=commitdiff;h=7466f9e72dac13452d871a3fb72fc7bd9c93c864

regards
Marius

P.S. I have no idea what variable we could use.
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Relevant Pages

  • FreeBSD-SA-06:14.fpu
    ... that fixes very doubtful security bug in AMD CPUs, ... adds unnecessary penalty in FPU context switch for all other ... SSE-enabled CPUs. ...
    (freebsd-current)
  • Re: FreeBSD-SA-06:14.fpu
    ... that fixes very doubtful security bug in AMD CPUs, ... adds unnecessary penalty in FPU context switch for all other ...
    (freebsd-current)