[PATCH 28/55] KVM: x86 emulator: centralize decoding of one-byte register access insns

From: Avi Kivity
Date: Wed Dec 26 2007 - 06:16:22 EST

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Instructions like 'inc reg' that have the register operand encoded
in the opcode are currently specially decoded. Extend
decode_register_operand() to handle that case, indicated by having
DstReg or SrcReg without ModRM.

Signed-off-by: Avi Kivity <avi@xxxxxxxxxxxx>
---
drivers/kvm/x86_emulate.c | 103 ++++++++++++++++++++-------------------------
drivers/kvm/x86_emulate.h | 1 +
2 files changed, 47 insertions(+), 57 deletions(-)

diff --git a/drivers/kvm/x86_emulate.c b/drivers/kvm/x86_emulate.c
index 58ceb66..884e4a2 100644
--- a/drivers/kvm/x86_emulate.c
+++ b/drivers/kvm/x86_emulate.c
@@ -99,17 +99,13 @@ static u16 opcode_table[256] = {
ByteOp | DstReg | SrcMem | ModRM, DstReg | SrcMem | ModRM,
0, 0, 0, 0,
/* 0x40 - 0x47 */
- ImplicitOps, ImplicitOps, ImplicitOps, ImplicitOps,
- ImplicitOps, ImplicitOps, ImplicitOps, ImplicitOps,
+ DstReg, DstReg, DstReg, DstReg, DstReg, DstReg, DstReg, DstReg,
/* 0x48 - 0x4F */
- ImplicitOps, ImplicitOps, ImplicitOps, ImplicitOps,
- ImplicitOps, ImplicitOps, ImplicitOps, ImplicitOps,
+ DstReg, DstReg, DstReg, DstReg, DstReg, DstReg, DstReg, DstReg,
/* 0x50 - 0x57 */
- ImplicitOps, ImplicitOps, ImplicitOps, ImplicitOps,
- ImplicitOps, ImplicitOps, ImplicitOps, ImplicitOps,
+ SrcReg, SrcReg, SrcReg, SrcReg, SrcReg, SrcReg, SrcReg, SrcReg,
/* 0x58 - 0x5F */
- ImplicitOps, ImplicitOps, ImplicitOps, ImplicitOps,
- ImplicitOps, ImplicitOps, ImplicitOps, ImplicitOps,
+ DstReg, DstReg, DstReg, DstReg, DstReg, DstReg, DstReg, DstReg,
/* 0x60 - 0x67 */
0, 0, 0, DstReg | SrcMem32 | ModRM | Mov /* movsxd (x86/64) */ ,
0, 0, 0, 0,
@@ -525,13 +521,17 @@ static void decode_register_operand(struct operand *op,
int highbyte_regs,
int inhibit_bytereg)
{
+ unsigned reg = c->modrm_reg;
+
+ if (!(c->d & ModRM))
+ reg = (c->b & 7) | ((c->rex_prefix & 1) << 3);
op->type = OP_REG;
if ((c->d & ByteOp) && !inhibit_bytereg) {
- op->ptr = decode_register(c->modrm_reg, c->regs, highbyte_regs);
+ op->ptr = decode_register(reg, c->regs, highbyte_regs);
op->val = *(u8 *)op->ptr;
op->bytes = 1;
} else {
- op->ptr = decode_register(c->modrm_reg, c->regs, 0);
+ op->ptr = decode_register(reg, c->regs, 0);
op->bytes = c->op_bytes;
switch (op->bytes) {
case 2:
@@ -552,7 +552,7 @@ int
x86_decode_insn(struct x86_emulate_ctxt *ctxt, struct x86_emulate_ops *ops)
{
struct decode_cache *c = &ctxt->decode;
- u8 sib, rex_prefix = 0;
+ u8 sib;
int rc = 0;
int mode = ctxt->mode;
int index_reg = 0, base_reg = 0, scale, rip_relative = 0;
@@ -616,7 +616,7 @@ x86_decode_insn(struct x86_emulate_ctxt *ctxt, struct x86_emulate_ops *ops)
case 0x40 ... 0x4f: /* REX */
if (mode != X86EMUL_MODE_PROT64)
goto done_prefixes;
- rex_prefix = c->b;
+ c->rex_prefix = c->b;
continue;
case 0xf0: /* LOCK */
c->lock_prefix = 1;
@@ -631,18 +631,18 @@ x86_decode_insn(struct x86_emulate_ctxt *ctxt, struct x86_emulate_ops *ops)

/* Any legacy prefix after a REX prefix nullifies its effect. */

- rex_prefix = 0;
+ c->rex_prefix = 0;
}

done_prefixes:

/* REX prefix. */
- if (rex_prefix) {
- if (rex_prefix & 8)
+ if (c->rex_prefix) {
+ if (c->rex_prefix & 8)
c->op_bytes = 8; /* REX.W */
- c->modrm_reg = (rex_prefix & 4) << 1; /* REX.R */
- index_reg = (rex_prefix & 2) << 2; /* REX.X */
- c->modrm_rm = base_reg = (rex_prefix & 1) << 3; /* REG.B */
+ c->modrm_reg = (c->rex_prefix & 4) << 1; /* REX.R */
+ index_reg = (c->rex_prefix & 2) << 2; /* REX.X */
+ c->modrm_rm = base_reg = (c->rex_prefix & 1) << 3; /* REG.B */
}

/* Opcode byte(s). */
@@ -837,7 +837,7 @@ modrm_done:
case SrcNone:
break;
case SrcReg:
- decode_register_operand(&c->src, c, rex_prefix == 0, 0);
+ decode_register_operand(&c->src, c, c->rex_prefix == 0, 0);
break;
case SrcMem16:
c->src.bytes = 2;
@@ -895,7 +895,7 @@ modrm_done:
/* Special instructions do their own operand decoding. */
return 0;
case DstReg:
- decode_register_operand(&c->dst, c, rex_prefix == 0,
+ decode_register_operand(&c->dst, c, c->rex_prefix == 0,
c->twobyte && (c->b == 0xb6 || c->b == 0xb7));
break;
case DstMem:
@@ -1258,6 +1258,32 @@ x86_emulate_insn(struct x86_emulate_ctxt *ctxt, struct x86_emulate_ops *ops)
cmp: /* cmp */
emulate_2op_SrcV("cmp", c->src, c->dst, ctxt->eflags);
break;
+ case 0x40 ... 0x47: /* inc r16/r32 */
+ emulate_1op("inc", c->dst, ctxt->eflags);
+ break;
+ case 0x48 ... 0x4f: /* dec r16/r32 */
+ emulate_1op("dec", c->dst, ctxt->eflags);
+ break;
+ case 0x50 ... 0x57: /* push reg */
+ c->dst.type = OP_MEM;
+ c->dst.bytes = c->op_bytes;
+ c->dst.val = c->src.val;
+ register_address_increment(c->regs[VCPU_REGS_RSP],
+ -c->op_bytes);
+ c->dst.ptr = (void *) register_address(
+ ctxt->ss_base, c->regs[VCPU_REGS_RSP]);
+ break;
+ case 0x58 ... 0x5f: /* pop reg */
+ pop_instruction:
+ if ((rc = ops->read_std(register_address(ctxt->ss_base,
+ c->regs[VCPU_REGS_RSP]), c->dst.ptr,
+ c->op_bytes, ctxt->vcpu)) != 0)
+ goto done;
+
+ register_address_increment(c->regs[VCPU_REGS_RSP],
+ c->op_bytes);
+ c->dst.type = OP_NONE; /* Disable writeback. */
+ break;
case 0x63: /* movsxd */
if (ctxt->mode != X86EMUL_MODE_PROT64)
goto cannot_emulate;
@@ -1373,43 +1399,6 @@ special_insn:
if (c->twobyte)
goto twobyte_special_insn;
switch (c->b) {
- case 0x40 ... 0x47: /* inc r16/r32 */
- c->dst.bytes = c->op_bytes;
- c->dst.ptr = (unsigned long *)&c->regs[c->b & 0x7];
- c->dst.val = *c->dst.ptr;
- emulate_1op("inc", c->dst, ctxt->eflags);
- break;
- case 0x48 ... 0x4f: /* dec r16/r32 */
- c->dst.bytes = c->op_bytes;
- c->dst.ptr = (unsigned long *)&c->regs[c->b & 0x7];
- c->dst.val = *c->dst.ptr;
- emulate_1op("dec", c->dst, ctxt->eflags);
- break;
- case 0x50 ... 0x57: /* push reg */
- if (c->op_bytes == 2)
- c->src.val = (u16) c->regs[c->b & 0x7];
- else
- c->src.val = (u32) c->regs[c->b & 0x7];
- c->dst.type = OP_MEM;
- c->dst.bytes = c->op_bytes;
- c->dst.val = c->src.val;
- register_address_increment(c->regs[VCPU_REGS_RSP],
- -c->op_bytes);
- c->dst.ptr = (void *) register_address(
- ctxt->ss_base, c->regs[VCPU_REGS_RSP]);
- break;
- case 0x58 ... 0x5f: /* pop reg */
- c->dst.ptr = (unsigned long *)&c->regs[c->b & 0x7];
- pop_instruction:
- if ((rc = ops->read_std(register_address(ctxt->ss_base,
- c->regs[VCPU_REGS_RSP]), c->dst.ptr,
- c->op_bytes, ctxt->vcpu)) != 0)
- goto done;
-
- register_address_increment(c->regs[VCPU_REGS_RSP],
- c->op_bytes);
- c->dst.type = OP_NONE; /* Disable writeback. */
- break;
case 0x6a: /* push imm8 */
c->src.val = 0L;
c->src.val = insn_fetch(s8, 1, c->eip);
diff --git a/drivers/kvm/x86_emulate.h b/drivers/kvm/x86_emulate.h
index f03b128..e34868b 100644
--- a/drivers/kvm/x86_emulate.h
+++ b/drivers/kvm/x86_emulate.h
@@ -126,6 +126,7 @@ struct decode_cache {
u8 rep_prefix;
u8 op_bytes;
u8 ad_bytes;
+ u8 rex_prefix;
struct operand src;
struct operand dst;
unsigned long *override_base;
--
1.5.3.7

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Next message: Avi Kivity: "[PATCH 26/55] KVM: Portability: Move pio emulation functions to x86.c"
Previous message: Avi Kivity: "[PATCH 06/55] KVM: Per-architecture hypercall definitions"
In reply to: Avi Kivity: "Re: [PATCH 06/55] KVM: Per-architecture hypercall definitions"
Next in thread: Avi Kivity: "[PATCH 26/55] KVM: Portability: Move pio emulation functions to x86.c"
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