On 08/06/2010 09:17 AM, Wei Yongjun wrote:
> If bit offset operands is a negative number, BitOp instruction
> will return wrong value. This patch fix it.
>
> Signed-off-by: Wei Yongjun<yjwei@xxxxxxxxxxxxxx>
> ---
> arch/x86/kvm/emulate.c | 32 ++++++++++++++++++++++++++------
> 1 files changed, 26 insertions(+), 6 deletions(-)
>
> diff --git a/arch/x86/kvm/emulate.c b/arch/x86/kvm/emulate.c
> index 0e360c6..470c7eb 100644
> --- a/arch/x86/kvm/emulate.c
> +++ b/arch/x86/kvm/emulate.c
> @@ -724,6 +724,30 @@ done:
> return rc;
> }
>
> +static void fetch_bit_operand(struct decode_cache *c)
> +{
> + unsigned long mask, byte_offset;
> +
> + if (c->dst.type == OP_MEM) {
> + if (c->src.bytes == 2)
> + c->src.val = (s16)c->src.val;
> + else if (c->src.bytes == 4)
> + c->src.val = (s32)c->src.val;
> +
> + mask = ~(c->dst.bytes * 8 - 1);
> +
> + if ((long)c->src.val< 0) {
> + /* negative bit offset */
> + byte_offset = c->dst.bytes +
> + ((-c->src.val - 1)& mask) / 8;
> + c->dst.addr.mem -= byte_offset;
> + } else {
> + /* positive bit offset */
> + c->dst.addr.mem += (c->src.val& mask) / 8;
> + }
> + }
> +}
> +
> static int read_emulated(struct x86_emulate_ctxt *ctxt,
> struct x86_emulate_ops *ops,
> unsigned long addr, void *dest, unsigned size)
> @@ -2646,12 +2670,8 @@ 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:
The whole series looks good now. Thanks!
Reviewed-by: Paolo Bonzini <pbonzini@xxxxxxxxxx>
Paolo
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