forked from Minki/linux
4214a16b02
SYSEXIT is scary on 64-bit kernels -- SYSEXIT must be invoked with usergs and IRQs on. That means that we rely on STI to correctly mask interrupts for one instruction. This is okay by itself, but the semantics with respect to NMIs are unclear. Avoid the whole issue by using SYSRETL instead. For background, Intel CPUs don't allow SYSCALL from compat mode, but they do allow SYSRETL back to compat mode. Go figure. To avoid doing too much at once, this doesn't revamp the calling convention. We still return with EBP, EDX, and ECX on the user stack. Oddly this seems to be 30 cycles or so faster. Avoiding POPFQ and STI will account for under half of that, I think, so my best guess is that Intel just optimizes SYSRET much better than SYSEXIT. Signed-off-by: Andy Lutomirski <luto@kernel.org> Cc: Andy Lutomirski <luto@amacapital.net> Cc: Borislav Petkov <bp@alien8.de> Cc: Brian Gerst <brgerst@gmail.com> Cc: Denys Vlasenko <dvlasenk@redhat.com> Cc: Denys Vlasenko <vda.linux@googlemail.com> Cc: H. Peter Anvin <hpa@zytor.com> Cc: Linus Torvalds <torvalds@linux-foundation.org> Cc: Thomas Gleixner <tglx@linutronix.de> Link: http://lkml.kernel.org/r/57a0bf1b5230b2716a64ebe48e9bc1110f7ab433.1428019097.git.luto@kernel.org Signed-off-by: Ingo Molnar <mingo@kernel.org> |
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| .. | ||
| audit.c | ||
| ia32_aout.c | ||
| ia32_signal.c | ||
| ia32entry.S | ||
| Makefile | ||
| sys_ia32.c | ||