KVM: x86 emulator: Implement zero-extended immediate decoding

Absolute jumps use zero extended immediate operands.

Cc: stable@kernel.org
Signed-off-by: Avi Kivity <avi@redhat.com>

1 files changed, 15 insertions, 0 deletions

diff --git a/arch/x86/kvm/x86_emulate.c b/arch/x86/kvm/x86_emulate.c
index 616de4628d60..a30d5fc17eef 100644
--- a/arch/x86/kvm/x86_emulate.c
+++ b/arch/x86/kvm/x86_emulate.c
@@ -60,6 +60,7 @@
 #define SrcImmByte  (6<<4)      /* 8-bit sign-extended immediate operand. */
 #define SrcOne      (7<<4)      /* Implied '1' */
 #define SrcImmUByte (8<<4)      /* 8-bit unsigned immediate operand. */
+#define SrcImmU     (9<<4)      /* Immediate operand, unsigned */
 #define SrcMask     (0xf<<4)
 /* Generic ModRM decode. */
 #define ModRM       (1<<8)
@@ -1027,6 +1028,7 @@ done_prefixes:
                 c->src.type = OP_MEM;
                 break;
         case SrcImm:
+        case SrcImmU:
                 c->src.type = OP_IMM;
                 c->src.ptr = (unsigned long *)c->eip;
                 c->src.bytes = (c->d & ByteOp) ? 1 : c->op_bytes;
@@ -1044,6 +1046,19 @@ done_prefixes:
                         c->src.val = insn_fetch(s32, 4, c->eip);
                         break;
                 }
+                if ((c->d & SrcMask) == SrcImmU) {
+                        switch (c->src.bytes) {
+                        case 1:
+                                c->src.val &= 0xff;
+                                break;
+                        case 2:
+                                c->src.val &= 0xffff;
+                                break;
+                        case 4:
+                                c->src.val &= 0xffffffff;
+                                break;
+                        }
+                }
                 break;
         case SrcImmByte:
         case SrcImmUByte: