SEP bit disabled in FC

[Dave Jones]

On Fri, Jun 10, 2005 at 09:32:55AM +0200, Arjan van de Ven wrote:
 > On Thu, 2005-06-09 at 21:25 -0400, Dave Jones wrote:
 > > On Thu, Jun 09, 2005 at 06:22:05PM -0700, Jeffrey Buell wrote:
 > >  > In arch/i386/kernel/cpu/common.c:
 > >  > 
 > >  >         /* hack: disable SEP for non-NX cpus; SEP breaks Execshield. */
 > >  >         #ifdef CONFIG_HIGHMEM64G
 > >  >         if (!test_bit(X86_FEATURE_NX, c->x86_capability))
 > >  >         #endif
 > >  >                 clear_bit(X86_FEATURE_SEP, c->x86_capability);
 > >  > 
 > >  > So, in order to enable Execshield, the SEP cpu bit (sysenter/sysexit) has to
 > >  > be turned off.  But this costs a lot of performance: as much as 2.5X in
 > >  > syscall-heavy benchmarks (e.g., process tests in lmbench).
 > >  > 
 > >  > How permanent is this hack?  Will Execshield be fixed (or removed) by FC5?
 > > 
 > > It was going to be reeanbled for FC4, but due to a last minute glitch,
 > > (which we think we fixed), we disabled for it for the release with
 > > the intention of reenabling it in the first kernel update that goes
 > > out for FC4.
 > 
 > You're confusing VDSO page with SEP.

Indeed.

		Dave