Commit 1c73ef66 authored by Avi Kivity's avatar Avi Kivity
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KVM: x86 emulator: Hoist modrm and abs decoding into separate functions 



Signed-off-by: default avatarAvi Kivity <avi@qumranet.com>
parent 3b6fff19

drivers/kvm/x86_emulate.c

+177 −160
Original line number Diff line number Diff line
@@ -548,122 +548,20 @@ static void decode_register_operand(struct operand *op, 
	op->orig_val = op->val;

}



int

x86_decode_insn(struct x86_emulate_ctxt *ctxt, struct x86_emulate_ops *ops)

static int decode_modrm(struct x86_emulate_ctxt *ctxt,

			struct x86_emulate_ops *ops)

{

	struct decode_cache *c = &ctxt->decode;

	u8 sib;

	int rc = 0;

	int mode = ctxt->mode;

	int index_reg = 0, base_reg = 0, scale, rip_relative = 0;

	int rc = 0;



	/* Shadow copy of register state. Committed on successful emulation. */



	memset(c, 0, sizeof(struct decode_cache));

	c->eip = ctxt->vcpu->rip;

	memcpy(c->regs, ctxt->vcpu->regs, sizeof c->regs);



	switch (mode) {

	case X86EMUL_MODE_REAL:

	case X86EMUL_MODE_PROT16:

		c->op_bytes = c->ad_bytes = 2;

		break;

	case X86EMUL_MODE_PROT32:

		c->op_bytes = c->ad_bytes = 4;

		break;

#ifdef CONFIG_X86_64

	case X86EMUL_MODE_PROT64:

		c->op_bytes = 4;

		c->ad_bytes = 8;

		break;

#endif

	default:

		return -1;

	}



	/* Legacy prefixes. */

	for (;;) {

		switch (c->b = insn_fetch(u8, 1, c->eip)) {

		case 0x66:	/* operand-size override */

			c->op_bytes ^= 6;	/* switch between 2/4 bytes */

			break;

		case 0x67:	/* address-size override */

			if (mode == X86EMUL_MODE_PROT64)

				/* switch between 4/8 bytes */

				c->ad_bytes ^= 12;

			else

				/* switch between 2/4 bytes */

				c->ad_bytes ^= 6;

			break;

		case 0x2e:	/* CS override */

			c->override_base = &ctxt->cs_base;

			break;

		case 0x3e:	/* DS override */

			c->override_base = &ctxt->ds_base;

			break;

		case 0x26:	/* ES override */

			c->override_base = &ctxt->es_base;

			break;

		case 0x64:	/* FS override */

			c->override_base = &ctxt->fs_base;

			break;

		case 0x65:	/* GS override */

			c->override_base = &ctxt->gs_base;

			break;

		case 0x36:	/* SS override */

			c->override_base = &ctxt->ss_base;

			break;

		case 0x40 ... 0x4f: /* REX */

			if (mode != X86EMUL_MODE_PROT64)

				goto done_prefixes;

			c->rex_prefix = c->b;

			continue;

		case 0xf0:	/* LOCK */

			c->lock_prefix = 1;

			break;

		case 0xf2:	/* REPNE/REPNZ */

		case 0xf3:	/* REP/REPE/REPZ */

			c->rep_prefix = 1;

			break;

		default:

			goto done_prefixes;

		}



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



		c->rex_prefix = 0;

	}



done_prefixes:



	/* REX prefix. */

	if (c->rex_prefix) {

		if (c->rex_prefix & 8)

			c->op_bytes = 8;	/* REX.W */

		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). */

	c->d = opcode_table[c->b];

	if (c->d == 0) {

		/* Two-byte opcode? */

		if (c->b == 0x0f) {

			c->twobyte = 1;

			c->b = insn_fetch(u8, 1, c->eip);

			c->d = twobyte_table[c->b];

		}



		/* Unrecognised? */

		if (c->d == 0) {

			DPRINTF("Cannot emulate %02x\n", c->b);

			return -1;

		}

	}



	/* ModRM and SIB bytes. */

	if (c->d & ModRM) {

	c->modrm = insn_fetch(u8, 1, c->eip);

	c->modrm_mod |= (c->modrm & 0xc0) >> 6;

	c->modrm_reg |= (c->modrm & 0x38) >> 3;
@@ -674,7 +572,7 @@ x86_decode_insn(struct x86_emulate_ctxt *ctxt, struct x86_emulate_ops *ops) 
	if (c->modrm_mod == 3) {

		c->modrm_val = *(unsigned long *)

			decode_register(c->modrm_rm, c->regs, c->d & ByteOp);

			goto modrm_done;

		return rc;

	}



	if (c->ad_bytes == 2) {
@@ -687,8 +585,7 @@ x86_decode_insn(struct x86_emulate_ctxt *ctxt, struct x86_emulate_ops *ops) 
		switch (c->modrm_mod) {

		case 0:

			if (c->modrm_rm == 6)

					c->modrm_ea +=

						insn_fetch(u16, 2, c->eip);

				c->modrm_ea += insn_fetch(u16, 2, c->eip);

			break;

		case 1:

			c->modrm_ea += insn_fetch(s8, 1, c->eip);
@@ -742,8 +639,7 @@ x86_decode_insn(struct x86_emulate_ctxt *ctxt, struct x86_emulate_ops *ops) 
			switch (base_reg) {

			case 5:

				if (c->modrm_mod != 0)

						c->modrm_ea +=

							c->regs[base_reg];

					c->modrm_ea += c->regs[base_reg];

				else

					c->modrm_ea +=

						insn_fetch(s32, 4, c->eip);
@@ -755,15 +651,13 @@ x86_decode_insn(struct x86_emulate_ctxt *ctxt, struct x86_emulate_ops *ops) 
			case 4:

				break;

			default:

					c->modrm_ea +=

						c->regs[index_reg] << scale;



				c->modrm_ea += c->regs[index_reg] << scale;

			}

			break;

		case 5:

			if (c->modrm_mod != 0)

				c->modrm_ea += c->regs[c->modrm_rm];

				else if (mode == X86EMUL_MODE_PROT64)

			else if (ctxt->mode == X86EMUL_MODE_PROT64)

				rip_relative = 1;

			break;

		default:
@@ -773,8 +667,7 @@ x86_decode_insn(struct x86_emulate_ctxt *ctxt, struct x86_emulate_ops *ops) 
		switch (c->modrm_mod) {

		case 0:

			if (c->modrm_rm == 5)

					c->modrm_ea +=

						insn_fetch(s32, 4, c->eip);

				c->modrm_ea += insn_fetch(s32, 4, c->eip);

			break;

		case 1:

			c->modrm_ea += insn_fetch(s8, 1, c->eip);
@@ -800,9 +693,16 @@ x86_decode_insn(struct x86_emulate_ctxt *ctxt, struct x86_emulate_ops *ops) 
					c->modrm_ea += c->op_bytes;

		}

	}

modrm_done:

		;

	} else if (c->d & MemAbs) {

done:

	return rc;

}



static int decode_abs(struct x86_emulate_ctxt *ctxt,

		      struct x86_emulate_ops *ops)

{

	struct decode_cache *c = &ctxt->decode;

	int rc = 0;



	switch (c->ad_bytes) {

	case 2:

		c->modrm_ea = insn_fetch(u16, 2, c->eip);
@@ -814,9 +714,126 @@ x86_decode_insn(struct x86_emulate_ctxt *ctxt, struct x86_emulate_ops *ops) 
		c->modrm_ea = insn_fetch(u64, 8, c->eip);

		break;

	}

done:

	return rc;

}



int

x86_decode_insn(struct x86_emulate_ctxt *ctxt, struct x86_emulate_ops *ops)

{

	struct decode_cache *c = &ctxt->decode;

	int rc = 0;

	int mode = ctxt->mode;



	/* Shadow copy of register state. Committed on successful emulation. */



	memset(c, 0, sizeof(struct decode_cache));

	c->eip = ctxt->vcpu->rip;

	memcpy(c->regs, ctxt->vcpu->regs, sizeof c->regs);



	switch (mode) {

	case X86EMUL_MODE_REAL:

	case X86EMUL_MODE_PROT16:

		c->op_bytes = c->ad_bytes = 2;

		break;

	case X86EMUL_MODE_PROT32:

		c->op_bytes = c->ad_bytes = 4;

		break;

#ifdef CONFIG_X86_64

	case X86EMUL_MODE_PROT64:

		c->op_bytes = 4;

		c->ad_bytes = 8;

		break;

#endif

	default:

		return -1;

	}



	/* Legacy prefixes. */

	for (;;) {

		switch (c->b = insn_fetch(u8, 1, c->eip)) {

		case 0x66:	/* operand-size override */

			c->op_bytes ^= 6;	/* switch between 2/4 bytes */

			break;

		case 0x67:	/* address-size override */

			if (mode == X86EMUL_MODE_PROT64)

				/* switch between 4/8 bytes */

				c->ad_bytes ^= 12;

			else

				/* switch between 2/4 bytes */

				c->ad_bytes ^= 6;

			break;

		case 0x2e:	/* CS override */

			c->override_base = &ctxt->cs_base;

			break;

		case 0x3e:	/* DS override */

			c->override_base = &ctxt->ds_base;

			break;

		case 0x26:	/* ES override */

			c->override_base = &ctxt->es_base;

			break;

		case 0x64:	/* FS override */

			c->override_base = &ctxt->fs_base;

			break;

		case 0x65:	/* GS override */

			c->override_base = &ctxt->gs_base;

			break;

		case 0x36:	/* SS override */

			c->override_base = &ctxt->ss_base;

			break;

		case 0x40 ... 0x4f: /* REX */

			if (mode != X86EMUL_MODE_PROT64)

				goto done_prefixes;

			c->rex_prefix = c->b;

			continue;

		case 0xf0:	/* LOCK */

			c->lock_prefix = 1;

			break;

		case 0xf2:	/* REPNE/REPNZ */

		case 0xf3:	/* REP/REPE/REPZ */

			c->rep_prefix = 1;

			break;

		default:

			goto done_prefixes;

		}



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



		c->rex_prefix = 0;

	}



done_prefixes:



	/* REX prefix. */

	if (c->rex_prefix)

		if (c->rex_prefix & 8)

			c->op_bytes = 8;	/* REX.W */



	/* Opcode byte(s). */

	c->d = opcode_table[c->b];

	if (c->d == 0) {

		/* Two-byte opcode? */

		if (c->b == 0x0f) {

			c->twobyte = 1;

			c->b = insn_fetch(u8, 1, c->eip);

			c->d = twobyte_table[c->b];

		}



		/* Unrecognised? */

		if (c->d == 0) {

			DPRINTF("Cannot emulate %02x\n", c->b);

			return -1;

		}

	}



	/* ModRM and SIB bytes. */

	if (c->d & ModRM)

		rc = decode_modrm(ctxt, ops);

	else if (c->d & MemAbs)

		rc = decode_abs(ctxt, ops);

	if (rc)

		goto done;



	if (!c->override_base)

		c->override_base = &ctxt->ds_base;

	if (mode == X86EMUL_MODE_PROT64 &&