Messages in this thread | | | Date | Mon, 27 Apr 2015 12:09:34 +0200 | From | Borislav Petkov <> | Subject | Re: [PATCH] x86_64, asm: Work around AMD SYSRET SS descriptor attribute issue |
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On Mon, Apr 27, 2015 at 12:07:14PM +0200, Denys Vlasenko wrote: > /* Only three 0x66 prefixes for NOP for fast decode on all CPUs */ > ALTERNATIVE ".byte 0x66,0x66,0x66,0x90 \ > .byte 0x66,0x66,0x66,0x90 \ > .byte 0x66,0x66,0x66,0x90", > "shl $(64 - (__VIRTUAL_MASK_SHIFT+1)), %rcx \ > sar $(64 - (__VIRTUAL_MASK_SHIFT+1)), %rcx \ > cmpq %rcx, %r11 \ > jne opportunistic_sysret_failed" > X86_BUG_SYSRET_CANONICAL_RCX > > would be better than letting ALTERNATIVE to generate 13 one-byte NOPs.
We already do everything automagically, see: arch/x86/kernel/alternative.c: optimize_nops()
:-)
-- Regards/Gruss, Boris.
ECO tip #101: Trim your mails when you reply. --
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