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?
Ever? Note that SEP is enabled in SuSE 9.3, for instance.
Jeff
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