Commit 35c843c4 authored by Wei Yongjun's avatar Wei Yongjun Committed by Avi Kivity
Browse files

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: default avatarWei Yongjun <yjwei@cn.fujitsu.com>
Reviewed-by: default avatarPaolo Bonzini <pbonzini@redhat.com>
Signed-off-by: default avatarAvi Kivity <avi@redhat.com>
parent 8744aa9a

arch/x86/kvm/emulate.c

+18 −6
Original line number Diff line number Diff line
@@ -723,6 +723,22 @@ done: 
	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 @@ done_prefixes: 
			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:

CRA Git | Maintained and supported by SUSTech CRA and CCSE