KVM: x86 emulator: consolidate immediate decode into a function

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

1 files changed, 64 insertions, 45 deletions

diff --git a/arch/x86/kvm/emulate.c b/arch/x86/kvm/emulate.c
index ed192d220201..95543a6beb53 100644
--- 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: