KVM: x86 emulator: consolidate immediate decode into a function

Signed-off-by: Avi Kivity <avi@redhat.com>

diff --git a/arch/x86/kvm/emulate.c b/arch/x86/kvm/emulate.c
index ed192d220201738b3dc4e1a6ab0404aae5a138b5..95543a6beb5386aa3d3b8b7c487724a089881733 100644 (file)
--- a/arch/x86/kvm/emulate.c
+++ b/arch/x86/kvm/emulate.c
@@ -2541,6 +2541,55 @@ static struct opcode twobyte_table[256] = {
 #undef GD
 #undef I
 
+static unsigned imm_size(struct decode_cache *c)
+{
+       unsigned size;
+
+       size = (c->d & ByteOp) ? 1 : c->op_bytes;
+       if (size == 8)
+               size = 4;
+       return size;
+}
+
+static int decode_imm(struct x86_emulate_ctxt *ctxt, struct operand *op,
+                     unsigned size, bool sign_extension)
+{
+       struct decode_cache *c = &ctxt->decode;
+       struct x86_emulate_ops *ops = ctxt->ops;
+       int rc = X86EMUL_CONTINUE;
+
+       op->type = OP_IMM;
+       op->bytes = size;
+       op->addr.mem = c->eip;
+       /* NB. Immediates are sign-extended as necessary. */
+       switch (op->bytes) {
+       case 1:
+               op->val = insn_fetch(s8, 1, c->eip);
+               break;
+       case 2:
+               op->val = insn_fetch(s16, 2, c->eip);
+               break;
+       case 4:
+               op->val = insn_fetch(s32, 4, c->eip);
+               break;
+       }
+       if (!sign_extension) {
+               switch (op->bytes) {
+               case 1:
+                       op->val &= 0xff;
+                       break;
+               case 2:
+                       op->val &= 0xffff;
+                       break;
+               case 4:
+                       op->val &= 0xffffffff;
+                       break;
+               }
+       }
+done:
+       return rc;
+}
+
 int
 x86_decode_insn(struct x86_emulate_ctxt *ctxt)
 {
@@ -2730,52 +2779,19 @@ done_prefixes:
                c->src = memop;
                break;
        case SrcImmU16:
-               c->src.bytes = 2;
-               goto srcimm;
+               rc = decode_imm(ctxt, &c->src, 2, false);
+               break;
        case SrcImm:
+               rc = decode_imm(ctxt, &c->src, imm_size(c), true);
+               break;
        case SrcImmU:
-               c->src.bytes = (c->d & ByteOp) ? 1 : c->op_bytes;
-               if (c->src.bytes == 8)
-                       c->src.bytes = 4;
-       srcimm:
-               c->src.type = OP_IMM;
-               c->src.addr.mem = c->eip;
-               /* NB. Immediates are sign-extended as necessary. */
-               switch (c->src.bytes) {
-               case 1:
-                       c->src.val = insn_fetch(s8, 1, c->eip);
-                       break;
-               case 2:
-                       c->src.val = insn_fetch(s16, 2, c->eip);
-                       break;
-               case 4:
-                       c->src.val = insn_fetch(s32, 4, c->eip);
-                       break;
-               }
-               if ((c->d & SrcMask) == SrcImmU
-                   || (c->d & SrcMask) == SrcImmU16) {
-                       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;
-                       }
-               }
+               rc = decode_imm(ctxt, &c->src, imm_size(c), false);
                break;
        case SrcImmByte:
+               rc = decode_imm(ctxt, &c->src, 1, true);
+               break;
        case SrcImmUByte:
-               c->src.type = OP_IMM;
-               c->src.addr.mem = c->eip;
-               c->src.bytes = 1;
-               if ((c->d & SrcMask) == SrcImmByte)
-                       c->src.val = insn_fetch(s8, 1, c->eip);
-               else
-                       c->src.val = insn_fetch(u8, 1, c->eip);
+               rc = decode_imm(ctxt, &c->src, 1, false);
                break;
        case SrcAcc:
                c->src.type = OP_REG;
@@ -2807,6 +2823,9 @@ done_prefixes:
                break;
        }
 
+       if (rc != X86EMUL_CONTINUE)
+               goto done;
+
        /*
         * Decode and fetch the second source operand: register, memory
         * or immediate.
@@ -2819,10 +2838,7 @@ done_prefixes:
                c->src2.val = c->regs[VCPU_REGS_RCX] & 0x8;
                break;
        case Src2ImmByte:
-               c->src2.type = OP_IMM;
-               c->src2.addr.mem = c->eip;
-               c->src2.bytes = 1;
-               c->src2.val = insn_fetch(u8, 1, c->eip);
+               rc = decode_imm(ctxt, &c->src2, 1, true);
                break;
        case Src2One:
                c->src2.bytes = 1;
@@ -2830,6 +2846,9 @@ done_prefixes:
                break;
        }
 
+       if (rc != X86EMUL_CONTINUE)
+               goto done;
+
        /* Decode and fetch the destination operand: register or memory. */
        switch (c->d & DstMask) {
        case DstReg: