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Commit e09d082c authored by Avi Kivity's avatar Avi Kivity
Browse files

KVM: x86 emulator: add support for group decoding 



Certain x86 instructions use bits 3:5 of the byte following the opcode as an
opcode extension, with the decode sometimes depending on bits 6:7 as well.
Add support for this in the main decoding table rather than an ad-hock
adaptation per opcode.

Signed-off-by: default avatarAvi Kivity <avi@qumranet.com>
parent 1ae0a13d

arch/x86/kvm/x86_emulate.c

+27 −6
Original line number Diff line number Diff line
@@ -65,6 +65,9 @@ 
#define MemAbs      (1<<9)      /* Memory operand is absolute displacement */

#define String      (1<<10)     /* String instruction (rep capable) */

#define Stack       (1<<11)     /* Stack instruction (push/pop) */

#define Group       (1<<14)     /* Bits 3:5 of modrm byte extend opcode */

#define GroupDual   (1<<15)     /* Alternate decoding of mod == 3 */

#define GroupMask   0xff        /* Group number stored in bits 0:7 */



static u16 opcode_table[256] = {

	/* 0x00 - 0x07 */
@@ -229,6 +232,12 @@ static u16 twobyte_table[256] = { 
	0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0

};



static u16 group_table[] = {

};



static u16 group2_table[] = {

};



/* EFLAGS bit definitions. */

#define EFLG_OF (1<<11)

#define EFLG_DF (1<<10)
@@ -763,7 +772,7 @@ 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;

	int def_op_bytes, def_ad_bytes;

	int def_op_bytes, def_ad_bytes, group;



	/* Shadow copy of register state. Committed on successful emulation. */
@@ -864,13 +873,25 @@ x86_decode_insn(struct x86_emulate_ctxt *ctxt, struct x86_emulate_ops *ops) 
			c->b = insn_fetch(u8, 1, c->eip);

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

		}

	}



	if (c->d & Group) {

		group = c->d & GroupMask;

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

		--c->eip;



		group = (group << 3) + ((c->modrm >> 3) & 7);

		if ((c->d & GroupDual) && (c->modrm >> 6) == 3)

			c->d = group2_table[group];

		else

			c->d = group_table[group];

	}



	/* Unrecognised? */

	if (c->d == 0) {

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

		return -1;

	}

	}



	if (mode == X86EMUL_MODE_PROT64 && (c->d & Stack))

		c->op_bytes = 8;