KVM: emulator: emulate AAM

This is used by SGABIOS, KVM breaks with emulate_invalid_guest_state=1.

AAM needs the source operand to be unsigned; do the same in AAD as well
for consistency, even though it does not affect the result.

Reported-by: Jun'ichi Nomura <j-nomura@ce.jp.nec.com>
Cc: stable@vger.kernel.org # 3.9
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
Signed-off-by: Gleb Natapov <gleb@redhat.com>

1 files changed, 24 insertions, 1 deletions

diff --git a/arch/x86/kvm/emulate.c b/arch/x86/kvm/emulate.c
index 8e517bba6a7c..55322a7c113d 100644
--- a/arch/x86/kvm/emulate.c
+++ b/arch/x86/kvm/emulate.c
@@ -2996,6 +2996,28 @@ static int em_das(struct x86_emulate_ctxt *ctxt)
         return X86EMUL_CONTINUE;
 }
 
+static int em_aam(struct x86_emulate_ctxt *ctxt)
+{
+        u8 al, ah;
+
+        if (ctxt->src.val == 0)
+                return emulate_de(ctxt);
+
+        al = ctxt->dst.val & 0xff;
+        ah = al / ctxt->src.val;
+        al %= ctxt->src.val;
+
+        ctxt->dst.val = (ctxt->dst.val & 0xffff0000) | al | (ah << 8);
+
+        /* Set PF, ZF, SF */
+        ctxt->src.type = OP_IMM;
+        ctxt->src.val = 0;
+        ctxt->src.bytes = 1;
+        fastop(ctxt, em_or);
+
+        return X86EMUL_CONTINUE;
+}
+
 static int em_aad(struct x86_emulate_ctxt *ctxt)
 {
         u8 al = ctxt->dst.val & 0xff;
@@ -3936,7 +3958,8 @@ static const struct opcode opcode_table[256] = {
         /* 0xD0 - 0xD7 */
         G(Src2One | ByteOp, group2), G(Src2One, group2),
         G(Src2CL | ByteOp, group2), G(Src2CL, group2),
-        N, I(DstAcc | SrcImmByte | No64, em_aad), N, N,
+        I(DstAcc | SrcImmUByte | No64, em_aam),
+        I(DstAcc | SrcImmUByte | No64, em_aad), N, N,
         /* 0xD8 - 0xDF */
         N, E(0, &escape_d9), N, E(0, &escape_db), N, E(0, &escape_dd), N, N,
         /* 0xE0 - 0xE7 */