obj.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

		goto eof;
	r = bsize - bloc;
	if(r < 100 && r < c) {		/* enough for largest prog */
		bsize = readsome(f, buf.xbuf, bloc, bsize, c);
		if(bsize == 0)
			goto eof;
		bloc = buf.xbuf;
		goto loop;
	}
	o = bloc[0] | (bloc[1] << 8);
	if(o <= AXXX || o >= ALAST) {
		if(o < 0)
			goto eof;
		diag("%s: opcode out of range %d", pn, o);
		print("	probably not a .8 file\n");
		errorexit();
	}

	if(o == ANAME || o == ASIGNAME) {
		sig = 0;
		if(o == ASIGNAME) {
			sig = bloc[2] | (bloc[3]<<8) | (bloc[4]<<16) | (bloc[5]<<24);
			bloc += 4;
			c -= 4;
		}
		stop = memchr(&bloc[4], 0, bsize-&bloc[4]);
		if(stop == 0){
			bsize = readsome(f, buf.xbuf, bloc, bsize, c);
			if(bsize == 0)
				goto eof;
			bloc = buf.xbuf;
			stop = memchr(&bloc[4], 0, bsize-&bloc[4]);
			if(stop == 0){
				fprint(2, "%s: name too long\n", pn);
				errorexit();
			}
		}
		v = bloc[2];	/* type */
		o = bloc[3];	/* sym */
		bloc += 4;
		c -= 4;

		r = 0;
		if(v == D_STATIC)
			r = version;
		s = lookup((char*)bloc, r);
		c -= &stop[1] - bloc;
		bloc = stop + 1;

		if(debug['S'] && r == 0)
			sig = 1729;
		if(sig != 0){
			if(s->sig != 0 && s->sig != sig)
				diag("incompatible type signatures %lux(%s) and %lux(%s) for %s", s->sig, filen[s->file], sig, pn, s->name);
			s->sig = sig;
			s->file = files-1;
		}

		if(debug['W'])
			print("	ANAME	%s\n", s->name);
		h[o] = s;
		if((v == D_EXTERN || v == D_STATIC) && s->type == 0)
			s->type = SXREF;
		if(v == D_FILE) {
			if(s->type != SFILE) {
				histgen++;
				s->type = SFILE;
				s->value = histgen;
			}
			if(histfrogp < MAXHIST) {
				histfrog[histfrogp] = s;
				histfrogp++;
			} else
				collapsefrog(s);
		}
		goto loop;
	}

	while(nhunk < sizeof(Prog))
		gethunk();
	p = (Prog*)hunk;
	nhunk -= sizeof(Prog);
	hunk += sizeof(Prog);

	p->as = o;
	p->line = bloc[2] | (bloc[3] << 8) | (bloc[4] << 16) | (bloc[5] << 24);
	p->back = 2;
	r = zaddr(bloc+6, &p->from, h) + 6;
	r += zaddr(bloc+r, &p->to, h);
	bloc += r;
	c -= r;

	if(debug['W'])
		print("%P\n", p);

	switch(p->as) {
	case AHISTORY:
		if(p->to.offset == -1) {
			addlib(pn);
			histfrogp = 0;
			goto loop;
		}
		addhist(p->line, D_FILE);		/* 'z' */
		if(p->to.offset)
			addhist(p->to.offset, D_FILE1);	/* 'Z' */
		histfrogp = 0;
		goto loop;

	case AEND:
		histtoauto();
		if(curtext != P)
			curtext->to.autom = curauto;
		curauto = 0;
		curtext = P;
		if(c)
			goto newloop;
		return;

	case AGLOBL:
		s = p->from.sym;
		if(s->type == 0 || s->type == SXREF) {
			s->type = SBSS;
			s->value = 0;
		}
		if(s->type != SBSS) {
			diag("%s: redefinition: %s in %s",
				pn, s->name, TNAME);
			s->type = SBSS;
			s->value = 0;
		}
		if(p->to.offset > s->value)
			s->value = p->to.offset;
		goto loop;

	case ADYNT:
		if(p->to.sym == S) {
			diag("DYNT without a sym\n%P", p);
			break;
		}
		di = p->to.sym;
		p->from.scale = 4;
		if(di->type == SXREF) {
			if(debug['z'])
				Bprint(&bso, "%P set to %d\n", p, dtype);
			di->type = SCONST;
			di->value = dtype;
			dtype += 4;
		}
		if(p->from.sym == S)
			break;

		p->from.offset = di->value;
		p->from.sym->type = SDATA;
		if(curtext == P) {
			diag("DYNT not in text: %P", p);
			break;
		}
		p->to.sym = curtext->from.sym;
		p->to.type = D_ADDR;
		p->to.index = D_EXTERN;
		goto data;

	case AINIT:
		if(p->from.sym == S) {
			diag("INIT without a sym\n%P", p);
			break;
		}
		if(di == S) {
			diag("INIT without previous DYNT\n%P", p);
			break;
		}
		p->from.offset = di->value;
		p->from.sym->type = SDATA;
		goto data;

	case ADATA:
	data:
		if(edatap == P)
			datap = p;
		else
			edatap->link = p;
		edatap = p;
		p->link = P;
		goto loop;

	case AGOK:
		diag("%s: GOK opcode in %s", pn, TNAME);
		pc++;
		goto loop;

	case ATEXT:
		if(curtext != P) {
			histtoauto();
			curtext->to.autom = curauto;
			curauto = 0;
		}
		skip = 0;
		curtext = p;
		s = p->from.sym;
		if(s == S) {
			diag("%s: no TEXT symbol: %P", pn, p);
			errorexit();
		}
		if(s->type != 0 && s->type != SXREF) {
			if(p->from.scale & DUPOK) {
				skip = 1;
				goto casdef;
			}
			diag("%s: redefinition: %s\n%P", pn, s->name, p);
		}
		s->type = STEXT;
		s->value = pc;
		lastp->link = p;
		lastp = p;
		p->pc = pc;
		pc++;
		if(textp == P) {
			textp = p;
			etextp = p;
			goto loop;
		}
		etextp->pcond = p;
		etextp = p;
		goto loop;

	case AFMOVF:
	case AFADDF:
	case AFSUBF:
	case AFSUBRF:
	case AFMULF:
	case AFDIVF:
	case AFDIVRF:
	case AFCOMF:
	case AFCOMFP:
		if(skip)
			goto casdef;
		if(p->from.type == D_FCONST) {
			/* size sb 9 max */
			sprint(literal, "$%lux", ieeedtof(&p->from.ieee));
			s = lookup(literal, 0);
			if(s->type == 0) {
				s->type = SBSS;
				s->value = 4;
				t = prg();
				t->as = ADATA;
				t->line = p->line;
				t->from.type = D_EXTERN;
				t->from.sym = s;
				t->from.scale = 4;
				t->to = p->from;
				if(edatap == P)
					datap = t;
				else
					edatap->link = t;
				edatap = t;
				t->link = P;
			}
			p->from.type = D_EXTERN;
			p->from.sym = s;
			p->from.offset = 0;
		}
		goto casdef;

	case AFMOVD:
	case AFADDD:
	case AFSUBD:
	case AFSUBRD:
	case AFMULD:
	case AFDIVD:
	case AFDIVRD:
	case AFCOMD:
	case AFCOMDP:
		if(skip)
			goto casdef;
		if(p->from.type == D_FCONST) {
			/* size sb 18 max */
			sprint(literal, "$%lux.%lux",
				p->from.ieee.l, p->from.ieee.h);
			s = lookup(literal, 0);
			if(s->type == 0) {
				s->type = SBSS;
				s->value = 8;
				t = prg();
				t->as = ADATA;
				t->line = p->line;
				t->from.type = D_EXTERN;
				t->from.sym = s;
				t->from.scale = 8;
				t->to = p->from;
				if(edatap == P)
					datap = t;
				else
					edatap->link = t;
				edatap = t;
				t->link = P;
			}
			p->from.type = D_EXTERN;
			p->from.sym = s;
			p->from.offset = 0;
		}
		goto casdef;

	casdef:
	default:
		if(skip)
			nopout(p);

		if(p->to.type == D_BRANCH)
			p->to.offset += ipc;
		lastp->link = p;
		lastp = p;
		p->pc = pc;
		pc++;
		goto loop;
	}
	goto loop;

eof:
	diag("truncated object file: %s", pn);
}

Sym*
lookup(char *symb, int v)
{
	Sym *s;
	char *p;
	long h;
	int l, c;

	h = v;
	for(p=symb; c = *p; p++)
		h = h+h+h + c;
	l = (p - symb) + 1;
	if(h < 0)
		h = ~h;
	h %= NHASH;
	for(s = hash[h]; s != S; s = s->link)
		if(s->version == v)
		if(memcmp(s->name, symb, l) == 0)
			return s;

	while(nhunk < sizeof(Sym))
		gethunk();
	s = (Sym*)hunk;
	nhunk -= sizeof(Sym);
	hunk += sizeof(Sym);

	s->name = malloc(l + 1);
	memmove(s->name, symb, l);

	s->link = hash[h];
	s->type = 0;
	s->version = v;
	s->value = 0;
	s->sig = 0;
	hash[h] = s;
	nsymbol++;
	return s;
}

Prog*
prg(void)
{
	Prog *p;

	while(nhunk < sizeof(Prog))
		gethunk();
	p = (Prog*)hunk;
	nhunk -= sizeof(Prog);
	hunk += sizeof(Prog);

	*p = zprg;
	return p;
}

Prog*
copyp(Prog *q)
{
	Prog *p;

	p = prg();
	*p = *q;
	return p;
}

Prog*
appendp(Prog *q)
{
	Prog *p;

	p = prg();
	p->link = q->link;
	q->link = p;
	p->line = q->line;
	return p;
}

void
gethunk(void)
{
	char *h;
	long nh;

	nh = NHUNK;
	if(thunk >= 5L*NHUNK) {
		nh = 5L*NHUNK;
		if(thunk >= 25L*NHUNK)
			nh = 25L*NHUNK;
	}
	h = mysbrk(nh);
	if(h == (char*)-1) {
		diag("out of memory");
		errorexit();
	}
	hunk = h;
	nhunk = nh;
	thunk += nh;
}

void
doprof1(void)
{
	Sym *s;
	long n;
	Prog *p, *q;

	if(debug['v'])
		Bprint(&bso, "%5.2f profile 1\n", cputime());
	Bflush(&bso);
	s = lookup("__mcount", 0);
	n = 1;
	for(p = firstp->link; p != P; p = p->link) {
		if(p->as == ATEXT) {
			q = prg();
			q->line = p->line;
			q->link = datap;
			datap = q;
			q->as = ADATA;
			q->from.type = D_EXTERN;
			q->from.offset = n*4;
			q->from.sym = s;
			q->from.scale = 4;
			q->to = p->from;
			q->to.type = D_CONST;

			q = prg();
			q->line = p->line;
			q->pc = p->pc;
			q->link = p->link;
			p->link = q;
			p = q;
			p->as = AADDL;
			p->from.type = D_CONST;
			p->from.offset = 1;
			p->to.type = D_EXTERN;
			p->to.sym = s;
			p->to.offset = n*4 + 4;

			n += 2;
			continue;
		}
	}
	q = prg();
	q->line = 0;
	q->link = datap;
	datap = q;

	q->as = ADATA;
	q->from.type = D_EXTERN;
	q->from.sym = s;
	q->from.scale = 4;
	q->to.type = D_CONST;
	q->to.offset = n;

	s->type = SBSS;
	s->value = n*4;
}

void
doprof2(void)
{
	Sym *s2, *s4;
	Prog *p, *q, *ps2, *ps4;

	if(debug['v'])
		Bprint(&bso, "%5.2f profile 2\n", cputime());
	Bflush(&bso);

	s2 = lookup("_profin", 0);
	s4 = lookup("_profout", 0);
	if(s2->type != STEXT || s4->type != STEXT) {
		diag("_profin/_profout not defined");
		return;
	}

	ps2 = P;
	ps4 = P;
	for(p = firstp; p != P; p = p->link) {
		if(p->as == ATEXT) {
			if(p->from.sym == s2) {
				p->from.scale = 1;
				ps2 = p;
			}
			if(p->from.sym == s4) {
				p->from.scale = 1;
				ps4 = p;
			}
		}
	}
	for(p = firstp; p != P; p = p->link) {
		if(p->as == ATEXT) {
			curtext = p;

			if(p->from.scale & NOPROF) {	/* dont profile */
				for(;;) {
					q = p->link;
					if(q == P)
						break;
					if(q->as == ATEXT)
						break;
					p = q;
				}
				continue;
			}

			/*
			 * JMPL	profin
			 */
			q = prg();
			q->line = p->line;
			q->pc = p->pc;
			q->link = p->link;
			p->link = q;
			p = q;
			p->as = ACALL;
			p->to.type = D_BRANCH;
			p->pcond = ps2;
			p->to.sym = s2;

			continue;
		}
		if(p->as == ARET) {
			/*
			 * RET
			 */
			q = prg();
			q->as = ARET;
			q->from = p->from;
			q->to = p->to;
			q->link = p->link;
			p->link = q;

			/*
			 * JAL	profout
			 */
			p->as = ACALL;
			p->from = zprg.from;
			p->to = zprg.to;
			p->to.type = D_BRANCH;
			p->pcond = ps4;
			p->to.sym = s4;

			p = q;

			continue;
		}
	}
}

void
nuxiinit(void)
{
	int i, c;

	for(i=0; i<4; i++) {
		c = find1(0x04030201L, i+1);
		if(i < 2)
			inuxi2[i] = c;
		if(i < 1)
			inuxi1[i] = c;
		inuxi4[i] = c;
		fnuxi4[i] = c;
		fnuxi8[i] = c;
		fnuxi8[i+4] = c+4;
	}
	if(debug['v']) {
		Bprint(&bso, "inuxi = ");
		for(i=0; i<1; i++)
			Bprint(&bso, "%d", inuxi1[i]);
		Bprint(&bso, " ");
		for(i=0; i<2; i++)
			Bprint(&bso, "%d", inuxi2[i]);
		Bprint(&bso, " ");
		for(i=0; i<4; i++)
			Bprint(&bso, "%d", inuxi4[i]);
		Bprint(&bso, "\nfnuxi = ");
		for(i=0; i<4; i++)
			Bprint(&bso, "%d", fnuxi4[i]);
		Bprint(&bso, " ");
		for(i=0; i<8; i++)
			Bprint(&bso, "%d", fnuxi8[i]);
		Bprint(&bso, "\n");
	}
	Bflush(&bso);
}

int
find1(long l, int c)
{
	char *p;
	int i;

	p = (char*)&l;
	for(i=0; i<4; i++)
		if(*p++ == c)
			return i;
	return 0;
}

int
find2(long l, int c)
{
	short *p;
	int i;

	p = (short*)&l;
	for(i=0; i<4; i+=2) {
		if(((*p >> 8) & 0xff) == c)
			return i;
		if((*p++ & 0xff) == c)
			return i+1;
	}
	return 0;
}

long
ieeedtof(Ieee *e)
{
	int exp;
	long v;

	if(e->h == 0)
		return 0;
	exp = (e->h>>20) & ((1L<<11)-1L);
	exp -= (1L<<10) - 2L;
	v = (e->h & 0xfffffL) << 3;
	v |= (e->l >> 29) & 0x7L;
	if((e->l >> 28) & 1) {
		v++;
		if(v & 0x800000L) {
			v = (v & 0x7fffffL) >> 1;
			exp++;
		}
	}
	if(exp <= -126 || exp >= 130)
		diag("double fp to single fp overflow");
	v |= ((exp + 126) & 0xffL) << 23;
	v |= e->h & 0x80000000L;
	return v;
}

double
ieeedtod(Ieee *ieeep)
{
	Ieee e;
	double fr;
	int exp;

	if(ieeep->h & (1L<<31)) {
		e.h = ieeep->h & ~(1L<<31);
		e.l = ieeep->l;
		return -ieeedtod(&e);
	}
	if(ieeep->l == 0 && ieeep->h == 0)
		return 0;
	fr = ieeep->l & ((1L<<16)-1L);
	fr /= 1L<<16;
	fr += (ieeep->l>>16) & ((1L<<16)-1L);
	fr /= 1L<<16;
	fr += (ieeep->h & (1L<<20)-1L) | (1L<<20);
	fr /= 1L<<21;
	exp = (ieeep->h>>20) & ((1L<<11)-1L);
	exp -= (1L<<10) - 2L;
	return ldexp(fr, exp);
}

void
undefsym(Sym *s)
{
	int n;

	n = imports;
	if(s->value != 0)
		diag("value != 0 on SXREF");
	if(n >= 1<<Rindex)
		diag("import index %d out of range", n);
	s->value = n<<Roffset;
	s->type = SUNDEF;
	imports++;
}

void
zerosig(char *sp)
{
	Sym *s;

	s = lookup(sp, 0);
	s->sig = 0;
}

void
readundefs(char *f, int t)
{
	int i, n;
	Sym *s;
	Biobuf *b;
	char *l, buf[256], *fields[64];

	if(f == nil)
		return;
	b = Bopen(f, OREAD);
	if(b == nil){
		diag("could not open %s: %r", f);
		errorexit();
	}
	while((l = Brdline(b, '\n')) != nil){
		n = Blinelen(b);
		if(n >= sizeof(buf)){
			diag("%s: line too long", f);
			errorexit();
		}
		memmove(buf, l, n);
		buf[n-1] = '\0';
		n = getfields(buf, fields, nelem(fields), 1, " \t\r\n");
		if(n == nelem(fields)){
			diag("%s: bad format", f);
			errorexit();
		}
		for(i = 0; i < n; i++){
			s = lookup(fields[i], 0);
			s->type = SXREF;
			s->subtype = t;
			if(t == SIMPORT)
				nimports++;
			else
				nexports++;
		}
	}
	Bterm(b);
}