2db.c

这是一个同样来自贝尔实验室的和UNIX有着渊源的操作系统, 其简洁的设计和实现易于我们学习和理解

	{
	case 0x10:
		break;
	case 0x20:
		if (i16(ip, &ap->disp) < 0)
			return -1;
		break;
	case 0x30:
		if (i32(ip, &ap->disp) < 0)
			return -1;
		break;
	default:
		ip->errmsg = "bad EA displacement";
		return -1;
	}
	switch (ext&0x03)	/* outer displacement */
	{
	case 0x02:		/* 16 bit displacement */
		return i16(ip, &ap->outer);
	case 0x03:		/* 32 bit displacement */
		return i32(ip, &ap->outer);
	default:
		break;
	}
	return 1;
}

static int
ea(Inst *ip, int ea, Operand *ap, int mode)
{
	int type, size;

	type = 0;
	ap->ext = 0;
	switch((ea>>3)&0x07)
	{
	case 0x00:
		ap->eatype = Dreg;
		type = Dn;
		break;
	case 0x01:
		ap->eatype = Areg;
		type = An;
		break;
	case 0x02:
		ap->eatype = AInd;
		type = Ind;
		break;
	case 0x03:
		ap->eatype = APinc;
		type = Pinc;
		break;
	case 0x04:
		ap->eatype = APdec;
		type = Pdec;
		break;
	case 0x05:
		ap->eatype = ADisp;
		type = Bdisp;
		if (i16(ip, &ap->disp) < 0)
			return -1;
		break;
	case 0x06:
		ap->eatype = BXD;
		type = Bdisp;
		if (getdisp(ip, ap) < 0)
			return -1;
		break;
	case 0x07:
		switch(ea&0x07)
		{
		case 0x00:
			type = Abs;
			ap->eatype = ABS;
			if (i16(ip, &ap->immediate) < 0)
				return -1;
			break;
		case 0x01:
			type = Abs;
			ap->eatype = ABS;
			if (i32(ip, &ap->immediate) < 0)
				return -1;
			break;
		case 0x02:
			type = PCrel;
			ap->eatype = PDisp;
			if (i16(ip, &ap->disp) < 0)
				return -1;
			break;
		case 0x03:
			type = PCrel;
			ap->eatype = PXD;
			if (getdisp(ip, ap) < 0)
				return -1;
			break;
		case 0x04:
			type = Imm;
			if (getimm(ip, ap, mode) < 0)
				return -1;
			break;
		default:
			ip->errmsg = "bad EA mode";
			return -1;
		}
	}
		/* Allowable floating point EAs are restricted for packed,
		 * extended, and double precision operands
		 */
	if (mode == EAFLT) {
		size = (ip->raw[1]>>10)&0x07;
		if (size == 2 || size == 3 || size == 5)
			mode = EAM;
		else
			mode = EADI;
	}
	if (!(validea[mode]&type)) {
		ip->errmsg = "invalid EA";
		return -1;
	}
	return 1;
}

static int
decode(Inst *ip, Optable *op)
{
	int i, t, mode;
	Operand *ap;
	short opcode;

	opcode = ip->raw[0];
	for (i = 0; i < nelem(op->opdata) && op->opdata[i]; i++) {
		ap = &ip->and[i];
		mode = op->opdata[i];
		switch(mode)
		{
		case EAPI:		/* normal EA modes */
		case EACA:
		case EACAD:
		case EACAPI:
		case EACAPD:
		case EAMA:
		case EADA:
		case EAA:
		case EAC:
		case EACPI:
		case EACD:
		case EAD:
		case EAM:
		case EAM_B:
		case EADI:
		case EADI_L:
		case EADI_W:
		case EAALL:
		case EAALL_L:
		case EAALL_W:
		case EAALL_B:
		case EAFLT:
			if (ea(ip, opcode&0x3f, ap, mode) < 0)
				return -1;
			break;
		case EADDA:	/* stupid bit flop required */
			t = ((opcode>>9)&0x07)|((opcode>>3)&0x38);
			if (ea(ip, t, ap, EADA)< 0)
					return -1;
			break;
		case BREAC:	/* EAC JMP or CALL operand */
			if (ea(ip, opcode&0x3f, ap, EAC) < 0)
				return -1;
			break;
		case OP8:	/* weird movq instruction */
			ap->eatype = IMM;
			ap->immediate = opcode&0xff;
			if (opcode&0x80)
				ap->immediate |= ~0xff;
			break;
		case I8:	/* must be two-word opcode */
			ap->eatype = IMM;
			ap->immediate = ip->raw[1]&0xff;
			if (ap->immediate&0x80)
				ap->immediate |= ~0xff;
			break;
		case I16:	/* 16 bit immediate */
		case BR16:
			ap->eatype = IMM;
			if (i16(ip, &ap->immediate) < 0)
				return -1;
			break;
		case C16:	/* CAS2 16 bit immediate */
			ap->eatype = IMM;
			if (i16(ip, &ap->immediate) < 0)
				return -1;
			if (ap->immediate & 0x0e38) {
				ip->errmsg = "bad CAS2W operand";
				return 0;
			}
			break;
		case I32:	/* 32 bit immediate */
		case BR32:
			ap->eatype = IMM;
			if (i32(ip, &ap->immediate) < 0)
				return -1;
			break;
		case IV:	/* immediate data depends on size field */
			if (getimm(ip, ap, IV) < 0)
				return -1;
			break;
		case BR8:	/* branch displacement format */
			ap->eatype = IMM;
			ap->immediate = opcode&0xff;
			if (ap->immediate == 0) {
				if (i16(ip, &ap->immediate) < 0)
					return -1;
			} else if (ap->immediate == 0xff) {
				if (i32(ip, &ap->immediate) < 0)
					return -1;
			} else if (ap->immediate & 0x80)
				ap->immediate |= ~0xff;
			break;
		case STACK:	/* Dummy operand type for Return instructions */
		default:
			break;
		}
	}
	return 1;
}

static Optable *
instruction(Inst *ip)
{
	ushort opcode, op2;
	Optable *op;
	int class;

	ip->n = 0;
	if (getword(ip, ip->addr) < 0)
		return 0;
	opcode = ip->raw[0];
	if (get2(mymap, ip->addr+2, &op2) < 0)
		op2 = 0;
	class = (opcode>>12)&0x0f;
	for (op = optables[class]; op && op->format; op++) {
		if (op->opcode != (opcode&op->mask0))
			continue;
		if (op->op2 != (op2&op->mask1))
			continue;
		if (op->mask1)
			ip->raw[ip->n++] = op2;
		return op;
	}
	ip->errmsg = "Invalid opcode";
	return 0;
}

#pragma	varargck	argpos	bprint		2

static void
bprint(Inst *i, char *fmt, ...)
{
	va_list arg;

	va_start(arg, fmt);
	i->curr = vseprint(i->curr, i->end, fmt, arg);
	va_end(arg);
}

static	char	*regname[] =
{
	"R0", "R1", "R2", "R3", "R4", "R5", "R6", "R7", "A0",
	"A1", "A2", "A3", "A4", "A5", "A6", "A7", "PC", "SB"
};

static void
plocal(Inst *ip, Operand *ap)
{
	int ret;
	long offset;
	uvlong moved;
	Symbol s;

	offset = ap->disp;
	if (!findsym(ip->addr, CTEXT, &s))
		goto none;

	moved = pc2sp(ip->addr);
	if (moved == -1)
		goto none;

	if (offset > moved) {		/* above frame - must be argument */
		offset -= moved;
		ret = getauto(&s, offset-mach->szaddr, CPARAM, &s);
	} else				/* below frame - must be automatic */
		ret = getauto(&s, moved-offset, CPARAM, &s);
	if (ret)
		bprint(ip, "%s+%lux", s.name, offset);
	else
none:		bprint(ip, "%lux", ap->disp);
}

/*
 *	this guy does all the work of printing the base and index component
 *	of an EA.
 */
static int
pidx(Inst *ip, int ext, int reg, char *bfmt, char *ifmt, char *nobase)
{
	char *s;
	int printed;
	char buf[512];

	printed = 1;
	if (ext&0x80) {				/* Base suppressed */
		if (reg == 16)
			bprint(ip, bfmt, "(ZPC)");
		else if (nobase)
			bprint(ip, nobase);
		else
			printed = 0;
	} else					/* format base reg */
		bprint(ip, bfmt, regname[reg]);
	if (ext & 0x40)				/* index suppressed */
		return printed;
	switch ((ext>>9)&0x03)
	{
	case 0x01:
		s = "*2";
		break;
	case 0x02:
		s = "*4";
		break;
	case 0x03:
		s = "*8";
		break;
	default:
		if (ext&0x80)
			s = "*1";
		else
			s = "";
		break;
	}
	sprint(buf, "%s.%c%s", regname[(ext>>12)&0x0f], (ext&0x800) ? 'L' : 'W', s);
	if (!printed)
		bprint(ip, ifmt, buf);
	else
		bprint(ip, "(%s)", buf);
	return 1;
}

static void
prindex(Inst *ip, int reg, Operand *ap)
{
	short ext;
	int left;
	int disp;

	left = ip->end-ip->curr;
	if (left <= 0)
		return;
	ext = ap->ext;
	disp = ap->disp;
		/* look for static base register references */
	if ((ext&0xa0) == 0x20 && reg == 14 && mach->sb && disp) {
		reg = 17;		/* "A6" -> "SB" */
		disp += mach->sb;
	}
	if ((ext&0x100) == 0) {		/* brief form */
		if (reg == 15)
			plocal(ip, ap);
		else if (disp)
			ip->curr += symoff(ip->curr, left, disp, CANY);
		pidx(ip, ext&0xff00, reg, "(%s)", "(%s)", 0);
		return;
	}
	switch(ext&0x3f)	/* bd size, && i/is */
	{
	case 0x10:
		if (!pidx(ip, ext, reg, "(%s)", "(%s)", 0))
			bprint(ip, "#0");
		break;
	case 0x11:
		if (pidx(ip, ext, reg, "((%s)", "((%s)", 0))
			bprint(ip, ")");
		else
			bprint(ip, "#0");
		break;
	case 0x12:
	case 0x13:
		ip->curr += symoff(ip->curr, left, ap->outer, CANY);
		if (pidx(ip, ext, reg, "((%s)", "((%s)", 0))
			bprint(ip, ")");
		break;
	case 0x15:
		if (!pidx(ip, ext, reg, "((%s))", "(%s)", 0))
			bprint(ip, "#0");
		break;
	case 0x16:
	case 0x17:
		ip->curr += symoff(ip->curr, left, ap->outer, CANY);
		pidx(ip, ext, reg, "((%s))", "(%s)", 0);
		break;
	case 0x20:
	case 0x30:
		if (reg == 15)
			plocal(ip, ap);
		else
			ip->curr += symoff(ip->curr, left, disp, CANY);
		pidx(ip, ext, reg, "(%s)", "(%s)", 0);
		break;
	case 0x21:
	case 0x31:
		*ip->curr++ = '(';
		if (reg == 15)
			plocal(ip, ap);
		else
			ip->curr += symoff(ip->curr, left-1, disp, CANY);
		pidx(ip, ext, reg, "(%s)", "(%s)", 0);
		bprint(ip, ")");
		break;
	case 0x22:
	case 0x23:
	case 0x32:
	case 0x33:
		ip->curr += symoff(ip->curr, left, ap->outer, CANY);
		bprint(ip, "(");
		if (reg == 15)
			plocal(ip, ap);
		else
			ip->curr += symoff(ip->curr, ip->end-ip->curr, disp, CANY);
		pidx(ip, ext, reg, "(%s)", "(%s)", 0);
		bprint(ip, ")");
		break;
	case 0x25:
	case 0x35:
		*ip->curr++ = '(';
		if (reg == 15)
			plocal(ip, ap);
		else
			ip->curr += symoff(ip->curr, left-1, disp, CANY);
		if (!pidx(ip, ext, reg, "(%s))", "(%s)", "())"))
			bprint(ip, ")");
		break;
	case 0x26:
	case 0x27:
	case 0x36:
	case 0x37:
		ip->curr += symoff(ip->curr, left, ap->outer, CANY);
		bprint(ip, "(");
		if (reg == 15)
			plocal(ip, ap);
		else
			ip->curr += symoff(ip->curr, ip->end-ip->curr, disp, CANY);
		pidx(ip, ext, reg, "(%s))", "(%s)", "())");
		break;
	default:
		bprint(ip, "??%x??", ext);
		ip->errmsg = "bad EA";
		break;
	}
}

static	void
pea(int reg, Inst *ip, Operand *ap)
{
	int i, left;

	left = ip->end-ip->curr;
	if (left < 0)
		return;
	switch(ap->eatype)
	{
	case Dreg:
		bprint(ip, "R%d", reg);
		break;
	case Areg:
		bprint(ip, "A%d", reg);
		break;
	case AInd:
		bprint(ip, "(A%d)", reg);
		break;
	case APinc:
		bprint(ip, "(A%d)+", reg);
		break;
	case APdec:
		bprint(ip, "-(A%d)", reg);
		break;
	case PDisp:
		ip->curr += symoff(ip->curr, left, ip->addr+2+ap->disp, CANY);
		break;
	case PXD:
		prindex(ip, 16, ap);
		break;
	case ADisp:	/* references off the static base */
		if (reg == 6 && mach->sb && ap->disp) {
			ip->curr += symoff(ip->curr, left, ap->disp+mach->sb, CANY);
			bprint(ip, "(SB)");
			break;
		}
			/* reference autos and parameters off the stack */
		if (reg == 7)
			plocal(ip, ap);
		else
			ip->curr += symoff(ip->curr, left, ap->disp, CANY);
		bprint(ip, "(A%d)", reg);
		break;
	case BXD:
		prindex(ip, reg+8, ap);
		break;
	case ABS:
		ip->curr += symoff(ip->curr, left, ap->immediate, CANY);
		bprint(ip, "($0)");
		break;
	case IMM:
		*ip->curr++ = '$';
		ip->curr += symoff(ip->curr, left-1, ap->immediate, CANY);
		break;
	case IREAL:
		*ip->curr++ = '$';
		ip->curr += beieeesftos(ip->curr, left-1, (void*) ap->floater);
		break;
	case IDBL:
		*ip->curr++ = '$';
		ip->curr += beieeedftos(ip->curr, left-1, (void*) ap->floater);
		break;