If bit offset operands is a negative number, BitOp instruction will return wrong value. This patch fix it.
Signed-off-by: Wei Yongjun <[email protected]> --- 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: -- 1.7.0.4 -- To unsubscribe from this list: send the line "unsubscribe kvm" in the body of a message to [email protected] More majordomo info at http://vger.kernel.org/majordomo-info.html
