5db.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

				if((v & (1U<<31)) == 0)
					return 0;
				return 0xFFFFFFFF;
			}
			return ASR(v, s);
		case 6:					/* RORIMM */
			if(s == 0) {
				ulong c = (rget(map, "PSR") >> 29) & 1;

				return (c << 31) | LSR(v, 1);
			}
			return ROR(v, s);
		case 7:					/* RORREG */
			sprint(buf, "R%ld", (s>>1)&0xF);
			s = rget(map, buf);
			if(s == 0 || (s & 0xF) == 0)
				return v;
			return ROR(v, s & 0xF);
		}
	}
}

static int
nbits(ulong v)
{
	int n = 0;
	int i;

	for(i=0; i < 32 ; i++) {
		if(v & 1) ++n;
		v >>= 1;
	}

	return n;
}

static ulong
armmaddr(Map *map, Rgetter rget, Instr *i)
{
	ulong v;
	ulong nb;
	char buf[8];
	ulong rn;

	rn = (i->w >> 16) & 0xf;
	sprint(buf,"R%ld", rn);

	v = rget(map, buf);
	nb = nbits(i->w & ((1 << 15) - 1));

	switch((i->w >> 23) & 3) {
	default:
	case 0: return (v - (nb*4)) + 4;
	case 1: return v;
	case 2: return v - (nb*4);
	case 3: return v + 4;
	}
}

static uvlong
armaddr(Map *map, Rgetter rget, Instr *i)
{
	char buf[8];
	ulong rn;

	sprint(buf, "R%ld", (i->w >> 16) & 0xf);
	rn = rget(map, buf);

	if((i->w & (1<<24)) == 0) {			/* POSTIDX */
		sprint(buf, "R%ld", rn);
		return rget(map, buf);
	}

	if((i->w & (1<<25)) == 0) {			/* OFFSET */
		sprint(buf, "R%ld", rn);
		if(i->w & (1U<<23))
			return rget(map, buf) + (i->w & BITS(0,11));
		return rget(map, buf) - (i->w & BITS(0,11));
	} else {					/* REGOFF */
		ulong index = 0;
		uchar c;
		uchar rm;

		sprint(buf, "R%ld", i->w & 0xf);
		rm = rget(map, buf);

		switch((i->w & BITS(5,6)) >> 5) {
		case 0: index = rm << ((i->w & BITS(7,11)) >> 7);	break;
		case 1: index = LSR(rm, ((i->w & BITS(7,11)) >> 7));	break;
		case 2: index = ASR(rm, ((i->w & BITS(7,11)) >> 7));	break;
		case 3:
			if((i->w & BITS(7,11)) == 0) {
				c = (rget(map, "PSR") >> 29) & 1;
				index = c << 31 | LSR(rm, 1);
			} else {
				index = ROR(rm, ((i->w & BITS(7,11)) >> 7));
			}
			break;
		}
		if(i->w & (1<<23))
			return rn + index;
		return rn - index;
	}
}

static uvlong
armfadd(Map *map, Rgetter rget, Instr *i, uvlong pc)
{
	char buf[8];
	int r;

	r = (i->w >> 12) & 0xf;
	if(r != 15 || !armcondpass(map, rget, (i->w >> 28) & 0xf))
		return pc+4;

	r = (i->w >> 16) & 0xf;
	sprint(buf, "R%d", r);

	return rget(map, buf) + armshiftval(map, rget, i);
}

static uvlong
armfmovm(Map *map, Rgetter rget, Instr *i, uvlong pc)
{
	ulong v;
	ulong addr;

	v = i->w & 1<<15;
	if(!v || !armcondpass(map, rget, (i->w>>28)&0xf))
		return pc+4;

	addr = armmaddr(map, rget, i) + nbits(i->w & BITS(0,15));
	if(get4(map, addr, &v) < 0) {
		werrstr("can't read addr: %r");
		return -1;
	}
	return v;
}

static uvlong
armfbranch(Map *map, Rgetter rget, Instr *i, uvlong pc)
{
	if(!armcondpass(map, rget, (i->w >> 28) & 0xf))
		return pc+4;

	return pc + (((signed long)i->w << 8) >> 6) + 8;
}

static uvlong
armfmov(Map *map, Rgetter rget, Instr *i, uvlong pc)
{
	ulong rd, v;

	rd = (i->w >> 12) & 0xf;
	if(rd != 15 || !armcondpass(map, rget, (i->w>>28)&0xf))
		return pc+4;

	 /* LDR */
	/* BUG: Needs LDH/B, too */
	if(((i->w>>26)&0x3) == 1) {
		if(get4(map, armaddr(map, rget, i), &v) < 0) {
			werrstr("can't read instruction: %r");
			return pc+4;
		}
		return v;
	}

	 /* MOV */
	v = armshiftval(map, rget, i);

	return v;
}

static Opcode opcodes[] =
{
	"AND%C%S",	armdps, 0,	"R%s,R%n,R%d",
	"EOR%C%S",	armdps, 0,	"R%s,R%n,R%d",
	"SUB%C%S",	armdps, 0,	"R%s,R%n,R%d",
	"RSB%C%S",	armdps, 0,	"R%s,R%n,R%d",
	"ADD%C%S",	armdps, armfadd,	"R%s,R%n,R%d",
	"ADC%C%S",	armdps, 0,	"R%s,R%n,R%d",
	"SBC%C%S",	armdps, 0,	"R%s,R%n,R%d",
	"RSC%C%S",	armdps, 0,	"R%s,R%n,R%d",
	"TST%C%S",	armdps, 0,	"R%s,R%n",
	"TEQ%C%S",	armdps, 0,	"R%s,R%n",
	"CMP%C%S",	armdps, 0,	"R%s,R%n",
	"CMN%C%S",	armdps, 0,	"R%s,R%n",
	"ORR%C%S",	armdps, 0,	"R%s,R%n,R%d",
	"MOVW%C%S",	armdps, armfmov,	"R%s,R%d",
	"BIC%C%S",	armdps, 0,	"R%s,R%n,R%d",
	"MVN%C%S",	armdps, 0,	"R%s,R%d",

/* 16 */
	"AND%C%S",	armdps, 0,	"(R%s%h%m),R%n,R%d",
	"EOR%C%S",	armdps, 0,	"(R%s%h%m),R%n,R%d",
	"SUB%C%S",	armdps, 0,	"(R%s%h%m),R%n,R%d",
	"RSB%C%S",	armdps, 0,	"(R%s%h%m),R%n,R%d",
	"ADD%C%S",	armdps, armfadd,	"(R%s%h%m),R%n,R%d",
	"ADC%C%S",	armdps, 0,	"(R%s%h%m),R%n,R%d",
	"SBC%C%S",	armdps, 0,	"(R%s%h%m),R%n,R%d",
	"RSC%C%S",	armdps, 0,	"(R%s%h%m),R%n,R%d",
	"TST%C%S",	armdps, 0,	"(R%s%h%m),R%n",
	"TEQ%C%S",	armdps, 0,	"(R%s%h%m),R%n",
	"CMP%C%S",	armdps, 0,	"(R%s%h%m),R%n",
	"CMN%C%S",	armdps, 0,	"(R%s%h%m),R%n",
	"ORR%C%S",	armdps, 0,	"(R%s%h%m),R%n,R%d",
	"MOVW%C%S",	armdps, armfmov,	"(R%s%h%m),R%d",
	"BIC%C%S",	armdps, 0,	"(R%s%h%m),R%n,R%d",
	"MVN%C%S",	armdps, 0,	"(R%s%h%m),R%d",

/* 32 */
	"AND%C%S",	armdps, 0,	"(R%s%hR%M),R%n,R%d",
	"EOR%C%S",	armdps, 0,	"(R%s%hR%M),R%n,R%d",
	"SUB%C%S",	armdps, 0,	"(R%s%hR%M),R%n,R%d",
	"RSB%C%S",	armdps, 0,	"(R%s%hR%M),R%n,R%d",
	"ADD%C%S",	armdps, armfadd,	"(R%s%hR%M),R%n,R%d",
	"ADC%C%S",	armdps, 0,	"(R%s%hR%M),R%n,R%d",
	"SBC%C%S",	armdps, 0,	"(R%s%hR%M),R%n,R%d",
	"RSC%C%S",	armdps, 0,	"(R%s%hR%M),R%n,R%d",
	"TST%C%S",	armdps, 0,	"(R%s%hR%M),R%n",
	"TEQ%C%S",	armdps, 0,	"(R%s%hR%M),R%n",
	"CMP%C%S",	armdps, 0,	"(R%s%hR%M),R%n",
	"CMN%C%S",	armdps, 0,	"(R%s%hR%M),R%n",
	"ORR%C%S",	armdps, 0,	"(R%s%hR%M),R%n,R%d",
	"MOVW%C%S",	armdps, armfmov,	"(R%s%hR%M),R%d",
	"BIC%C%S",	armdps, 0,	"(R%s%hR%M),R%n,R%d",
	"MVN%C%S",	armdps, 0,	"(R%s%hR%M),R%d",

/* 48 */
	"AND%C%S",	armdpi, 0,	"$#%i,R%n,R%d",
	"EOR%C%S",	armdpi, 0,	"$#%i,R%n,R%d",
	"SUB%C%S",	armdpi, 0,	"$#%i,R%n,R%d",
	"RSB%C%S",	armdpi, 0,	"$#%i,R%n,R%d",
	"ADD%C%S",	armdpi, armfadd,	"$#%i,R%n,R%d",
	"ADC%C%S",	armdpi, 0,	"$#%i,R%n,R%d",
	"SBC%C%S",	armdpi, 0,	"$#%i,R%n,R%d",
	"RSC%C%S",	armdpi, 0,	"$#%i,R%n,R%d",
	"TST%C%S",	armdpi, 0,	"$#%i,R%n",
	"TEQ%C%S",	armdpi, 0,	"$#%i,R%n",
	"CMP%C%S",	armdpi, 0,	"$#%i,R%n",
	"CMN%C%S",	armdpi, 0,	"$#%i,R%n",
	"ORR%C%S",	armdpi, 0,	"$#%i,R%n,R%d",
	"MOVW%C%S",	armdpi, armfmov,	"$#%i,R%d",
	"BIC%C%S",	armdpi, 0,	"$#%i,R%n,R%d",
	"MVN%C%S",	armdpi, 0,	"$#%i,R%d",

/* 48+16 */
	"MUL%C%S",	armdpi, 0,	"R%M,R%s,R%n",
	"MULA%C%S",	armdpi, 0,	"R%M,R%s,R%n,R%d",
	"SWPW",		armdpi, 0,	"R%s,(R%n),R%d",
	"SWPB",		armdpi, 0,	"R%s,(R%n),R%d",

/* 48+16+4 */
	"MOV%u%C%p",	armhwby, 0,	"R%d,(R%n%UR%M)",
	"MOV%u%C%p",	armhwby, 0,	"R%d,%I",
	"MOV%u%C%p",	armhwby, armfmov,	"(R%n%UR%M),R%d",
	"MOV%u%C%p",	armhwby, armfmov,	"%I,R%d",

/* 48+24 */
	"MOVW%C%p",	armsdti, 0,	"R%d,%I",
	"MOVB%C%p",	armsdti, 0,	"R%d,%I",
	"MOVW%C%p",	armsdti, armfmov,	"%I,R%d",
	"MOVBU%C%p",	armsdti, armfmov,	"%I,R%d",

	"MOVW%C%p",	armsdts, 0,	"R%d,(R%s%h%m)(R%n)",
	"MOVB%C%p",	armsdts, 0,	"R%d,(R%s%h%m)(R%n)",
	"MOVW%C%p",	armsdts, armfmov,	"(R%s%h%m)(R%n),R%d",
	"MOVBU%C%p",	armsdts, armfmov,	"(R%s%h%m)(R%n),R%d",

	"MOVM%C%P%a",	armbdt, armfmovm,		"[%r],(R%n)",
	"MOVM%C%P%a",	armbdt, armfmovm,		"(R%n),[%r]",

	"B%C",		armb, armfbranch,		"%b",
	"BL%C",		armb, armfbranch,		"%b",

	"CDP%C",	armco, 0,		"",
	"CDP%C",	armco, 0,		"",
	"MCR%C",	armco, 0,		"",
	"MRC%C",	armco, 0,		"",

/* 48+24+4+4+2+2+4 */
	"MULLU%C%S",	armdpi, 0,	"R%M,R%s,(R%n,R%d)",
	"MULALU%C%S",	armdpi, 0,	"R%M,R%s,(R%n,R%d)",
	"MULL%C%S",	armdpi, 0,	"R%M,R%s,(R%n,R%d)",
	"MULAL%C%S",	armdpi, 0,	"R%M,R%s,(R%n,R%d)",

/* 48+24+4+4+2+2+4+4 */
	"UNK",		armunk, 0,	"",
};

static void
gaddr(Instr *i)
{
	*i->curr++ = '$';
	i->curr += gsymoff(i->curr, i->end-i->curr, i->imm, CANY);
}

static	char *mode[] = { 0, "IA", "DB", "IB" };
static	char *pw[] = { "P", "PW", 0, "W" };
static	char *sw[] = { 0, "W", "S", "SW" };

static void
format(char *mnemonic, Instr *i, char *f)
{
	int j, k, m, n;
	int g;
	char *fmt;

	if(mnemonic)
		format(0, i, mnemonic);
	if(f == 0)
		return;
	if(mnemonic)
		if(i->curr < i->end)
			*i->curr++ = '\t';
	for ( ; *f && i->curr < i->end; f++) {
		if(*f != '%') {
			*i->curr++ = *f;
			continue;
		}
		switch (*++f) {

		case 'C':	/* .CONDITION */
			if(cond[i->cond])
				bprint(i, ".%s", cond[i->cond]);
			break;

		case 'S':	/* .STORE */
			if(i->store)
				bprint(i, ".S");
			break;

		case 'P':	/* P & U bits for block move */
			n = (i->w >>23) & 0x3;
			if (mode[n])
				bprint(i, ".%s", mode[n]);
			break;

		case 'p':	/* P & W bits for single data xfer*/
			if (pw[i->store])
				bprint(i, ".%s", pw[i->store]);
			break;

		case 'a':	/* S & W bits for single data xfer*/
			if (sw[i->store])
				bprint(i, ".%s", sw[i->store]);
			break;

		case 's':
			bprint(i, "%d", i->rs & 0xf);
			break;
				
		case 'M':
			bprint(i, "%lud", (i->w>>8) & 0xf);
			break;
				
		case 'm':
			bprint(i, "%lud", (i->w>>7) & 0x1f);
			break;

		case 'h':
			bprint(i, shtype[(i->w>>5) & 0x3]);
			break;

		case 'u':		/* Signed/unsigned Byte/Halfword */
			bprint(i, hb[(i->w>>5) & 0x3]);
			break;

		case 'I':
			if (i->rn == 13) {
				if (plocal(i))
					break;
			}
			g = 0;
			fmt = "#%lx(R%d)";
			if (i->rn == 15) {
				/* convert load of offset(PC) to a load immediate */
				if (get4(i->map, i->addr+i->imm+8, (ulong*)&i->imm) > 0)
				{
					g = 1;
					fmt = "";
				}
			}
			if (mach->sb)
			{
				if (i->rd == 11) {
					ulong nxti;

					if (get4(i->map, i->addr+4, &nxti) > 0) {
						if ((nxti & 0x0e0f0fff) == 0x060c000b) {
							i->imm += mach->sb;
							g = 1;
							fmt = "-SB";
						}
					}
				}
				if (i->rn == 12)
				{
					i->imm += mach->sb;
					g = 1;
					fmt = "-SB(SB)";
				}
			}
			if (g)
			{
				gaddr(i);
				bprint(i, fmt, i->rn);
			}
			else
				bprint(i, fmt, i->imm, i->rn);
			break;
		case 'U':		/* Add/subtract from base */
			bprint(i, addsub[(i->w >> 23) & 1]);
			break;

		case 'n':
			bprint(i, "%d", i->rn);
			break;

		case 'd':
			bprint(i, "%d", i->rd);
			break;

		case 'i':
			bprint(i, "%lux", i->imm);
			break;

		case 'b':
			i->curr += symoff(i->curr, i->end-i->curr,
				i->imm, CTEXT);
			break;

		case 'g':
			i->curr += gsymoff(i->curr, i->end-i->curr,
				i->imm, CANY);
			break;

		case 'r':
			n = i->imm&0xffff;
			j = 0;
			k = 0;
			while(n) {
				m = j;
				while(n&0x1) {
					j++;
					n >>= 1;
				}
				if(j != m) {
					if(k)
						bprint(i, ",");
					if(j == m+1)
						bprint(i, "R%d", m);
					else
						bprint(i, "R%d-R%d", m, j-1);
					k = 1;
				}
				j++;
				n >>= 1;
			}
			break;

		case '\0':
			*i->curr++ = '%';
			return;

		default:
			bprint(i, "%%%c", *f);
			break;
		}
	}
	*i->curr = 0;
}

static int
printins(Map *map, uvlong pc, char *buf, int n)
{
	Instr i;

	i.curr = buf;
	i.end = buf+n-1;
	if(decode(map, pc, &i) < 0)
		return -1;

	(*opcodes[i.op].fmt)(&opcodes[i.op], &i);
	return 4;
}

static int
arminst(Map *map, uvlong pc, char modifier, char *buf, int n)
{
	USED(modifier);
	return printins(map, pc, buf, n);
}

static int
armdas(Map *map, uvlong pc, char *buf, int n)
{
	Instr i;

	i.curr = buf;
	i.end = buf+n;
	if(decode(map, pc, &i) < 0)
		return -1;
	if(i.end-i.curr > 8)
		i.curr = _hexify(buf, i.w, 7);
	*i.curr = 0;
	return 4;
}

static int
arminstlen(Map *map, uvlong pc)
{
	Instr i;

	if(decode(map, pc, &i) < 0)
		return -1;
	return 4;
}

static int
armfoll(Map *map, uvlong pc, Rgetter rget, uvlong *foll)
{
	uvlong d;
	Instr i;

	if(decode(map, pc, &i) < 0)
		return -1;

	if(opcodes[i.op].foll) {
		d = (*opcodes[i.op].foll)(map, rget, &i, pc);
		if(d == -1)
			return -1;
	} else
		d = pc+4;

	foll[0] = d;
	return 1;
}