From 6cd44b0be52cf00bfb26ea606187b046f166fcee Mon Sep 17 00:00:00 2001 From: Eugene Korenevsky Date: Tue, 19 May 2015 11:57:31 +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 test_x86_emulate: extend EFLAGS check of CMPXCHG test CMPXCHG: in the case of inequality of the rAX and the operand, need to check CF, PF, AF, SF and OF flags as well. This adjustment covers the fix of incorrect comparison during CMPXCHG emulation. Signed-off-by: Eugene Korenevsky master commit: 2232628ecbab42e7700287204daad71a3ce2208c master date: 2015-05-04 11:55:41 +0200 master commit: 20fd4b70a7647656812b8f276510e09b252db9f7 master date: 2015-05-04 12:03:19 +0200 --- tools/tests/x86_emulator/test_x86_emulator.c | 2 +- xen/arch/x86/x86_emulate/x86_emulate.c | 3 ++- 2 files changed, 3 insertions(+), 2 deletions(-) diff --git a/tools/tests/x86_emulator/test_x86_emulator.c b/tools/tests/x86_emulator/test_x86_emulator.c index 31666747e3..906fc6f398 100644 --- a/tools/tests/x86_emulator/test_x86_emulator.c +++ b/tools/tests/x86_emulator/test_x86_emulator.c @@ -286,7 +286,7 @@ int main(int argc, char **argv) rc = x86_emulate(&ctxt, &emulops); if ( (rc != X86EMUL_OKAY) || (*res != 0x923456AA) || - ((regs.eflags&0x240) != 0x200) || + ((regs.eflags&0xad5) != 0xa91) || (regs.eax != 0xAABBCCAA) || (regs.ecx != 0xFF) || (regs.eip != (unsigned long)&instr[4]) ) diff --git a/xen/arch/x86/x86_emulate/x86_emulate.c b/xen/arch/x86/x86_emulate/x86_emulate.c index 219e14376f..4c90101f9c 100644 --- a/xen/arch/x86/x86_emulate/x86_emulate.c +++ b/xen/arch/x86/x86_emulate/x86_emulate.c @@ -4257,7 +4257,8 @@ 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. */