KVM: x86 emulator: fix negative bit offset BitOp instruction emulation
If bit offset operands is a negative number, BitOp instruction
will return wrong value. This patch fix it.
Signed-off-by: Wei Yongjun <yjwei@cn.fujitsu.com>
Reviewed-by: Paolo Bonzini <pbonzini@redhat.com>
Signed-off-by: Avi Kivity <avi@redhat.com>
diff --git a/arch/x86/kvm/emulate.c b/arch/x86/kvm/emulate.c
index 175b416..5fc441c 100644
--- a/arch/x86/kvm/emulate.c
+++ b/arch/x86/kvm/emulate.c
@@ -723,6 +723,22 @@
return rc;
}
+static void fetch_bit_operand(struct decode_cache *c)
+{
+ long sv, mask;
+
+ if (c->dst.type == OP_MEM) {
+ mask = ~(c->dst.bytes * 8 - 1);
+
+ if (c->src.bytes == 2)
+ sv = (s16)c->src.val & (s16)mask;
+ else if (c->src.bytes == 4)
+ sv = (s32)c->src.val & (s32)mask;
+
+ c->dst.addr.mem += (sv >> 3);
+ }
+}
+
static int read_emulated(struct x86_emulate_ctxt *ctxt,
struct x86_emulate_ops *ops,
unsigned long addr, void *dest, unsigned size)
@@ -2638,12 +2654,8 @@
c->dst.bytes = 8;
else
c->dst.bytes = (c->d & ByteOp) ? 1 : c->op_bytes;
- if (c->dst.type == OP_MEM && (c->d & BitOp)) {
- unsigned long mask = ~(c->dst.bytes * 8 - 1);
-
- c->dst.addr.mem = c->dst.addr.mem +
- (c->src.val & mask) / 8;
- }
+ if (c->d & BitOp)
+ fetch_bit_operand(c);
c->dst.orig_val = c->dst.val;
break;
case DstAcc: