From 2232628ecbab42e7700287204daad71a3ce2208c Mon Sep 17 00:00:00 2001 From: Eugene Korenevsky Date: Mon, 4 May 2015 11:55:41 +0200 Subject: [PATCH] x86_emulate: fix EFLAGS setting of CMPXCHG emulation CMPXCHG sets CF, PF, AF, SF, and OF flags according to the results of the comparison the rAX with the operand of the instruction. rAX must be the first argument of the comparison (a minuend), the operand must be the second one (a subtrahend). Due to improper order of comparison arguments, CF, PF, AF, SF and OF flags were set incorrectly in the case of inequality. Need to swap them. Signed-off-by: Eugene Korenevsky --- xen/arch/x86/x86_emulate/x86_emulate.c | 3 ++- 1 file changed, 2 insertions(+), 1 deletion(-) diff --git a/xen/arch/x86/x86_emulate/x86_emulate.c b/xen/arch/x86/x86_emulate/x86_emulate.c index ae32c82d2f..6c6c58a8ea 100644 --- a/xen/arch/x86/x86_emulate/x86_emulate.c +++ b/xen/arch/x86/x86_emulate/x86_emulate.c @@ -4343,7 +4343,8 @@ x86_emulate( /* Save real source value, then compare EAX against destination. */ src.orig_val = src.val; src.val = _regs.eax; - emulate_2op_SrcV("cmp", src, dst, _regs.eflags); + /* cmp: %%eax - dst ==> dst and src swapped for macro invocation */ + emulate_2op_SrcV("cmp", dst, src, _regs.eflags); if ( _regs.eflags & EFLG_ZF ) { /* Success: write back to memory. */ -- 2.30.2