asm.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

#include	"l.h"

long	OFFSET;
/*
long	BADOFFSET	=	-1;

		if(OFFSET <= BADOFFSET && OFFSET+4 > BADOFFSET)\
			abort();\
		OFFSET += 4;\

		if(OFFSET == BADOFFSET)\
			abort();\
		OFFSET++;\
*/

#define LPUT(l) { \
		if (little) { \
			LLEPUT(l); \
		} else { \
			LBEPUT(l); \
		} \
	}

#define	LLEPUT(c)\
	{\
		cbp[0] = (c);\
		cbp[1] = (c)>>8;\
		cbp[2] = (c)>>16;\
		cbp[3] = (c)>>24;\
		cbp += 4;\
		cbc -= 4;\
		if(cbc <= 0)\
			cflush();\
	}

#define	LBEPUT(c)\
	{\
		cbp[0] = (c)>>24;\
		cbp[1] = (c)>>16;\
		cbp[2] = (c)>>8;\
		cbp[3] = (c);\
		cbp += 4;\
		cbc -= 4;\
		if(cbc <= 0)\
			cflush();\
	}


#define	CPUT(c)\
	{\
		cbp[0] = (c);\
		cbp++;\
		cbc--;\
		if(cbc <= 0)\
			cflush();\
	}

void
objput(long l)	/* emit long in byte order appropriate to object machine */
{
	LPUT(l);
}

void
lput(long l)		/* emit long in big-endian byte order */
{
	LBEPUT(l);
}

long
entryvalue(void)
{
	char *a;
	Sym *s;

	a = INITENTRY;
	if(*a >= '0' && *a <= '9')
		return atolwhex(a);
	s = lookup(a, 0);
	if(s->type == 0)
		return INITTEXT;
	if(s->type != STEXT && s->type != SLEAF)
		diag("entry not text: %s", s->name);
	return s->value;
}

void
asmb(void)
{
	Prog *p;
	long t, etext;
	Optab *o;

	if(debug['v'])
		Bprint(&bso, "%5.2f asm\n", cputime());
	Bflush(&bso);
	OFFSET = HEADR;
	seek(cout, OFFSET, 0);
	pc = INITTEXT;
	for(p = firstp; p != P; p = p->link) {
		if(p->as == ATEXT) {
			curtext = p;
			autosize = p->to.offset + 4;
		}
		if(p->pc != pc) {
			diag("phase error %lux sb %lux",
				p->pc, pc);
			if(!debug['a'])
				prasm(curp);
			pc = p->pc;
		}
		curp = p;
		o = oplook(p);	/* could probably avoid this call */
		if(asmout(p, o, 0)) {
			p = p->link;
			pc += 4;
		}
		pc += o->size;
	}
	if(debug['a'])
		Bprint(&bso, "\n");
	Bflush(&bso);
	cflush();

	etext = INITTEXT + textsize;
	for(t = pc; t < etext; t += sizeof(buf)-100) {
		if(etext-t > sizeof(buf)-100)
			datblk(t, sizeof(buf)-100, 1);
		else
			datblk(t, etext-t, 1);
	}

	Bflush(&bso);
	cflush();

	curtext = P;
	switch(HEADTYPE) {
	case 0:
	case 4:
		OFFSET = rnd(HEADR+textsize, 4096);
		seek(cout, OFFSET, 0);
		break;
	case 1:
	case 2:
	case 3:
	case 5:
	case 6:
		OFFSET = HEADR+textsize;
		seek(cout, OFFSET, 0);
		break;
	}
	for(t = 0; t < datsize; t += sizeof(buf)-100) {
		if(datsize-t > sizeof(buf)-100)
			datblk(t, sizeof(buf)-100, 0);
		else
			datblk(t, datsize-t, 0);
	}

	symsize = 0;
	lcsize = 0;
	if(!debug['s']) {
		if(debug['v'])
			Bprint(&bso, "%5.2f sym\n", cputime());
		Bflush(&bso);
		switch(HEADTYPE) {
		case 0:
		case 4:
			OFFSET = rnd(HEADR+textsize, 4096)+datsize;
			seek(cout, OFFSET, 0);
			break;
		case 3:
		case 2:
		case 1:
		case 5:
		case 6:
			OFFSET = HEADR+textsize+datsize;
			seek(cout, OFFSET, 0);
			break;
		}
		if(!debug['s'])
			asmsym();
		if(debug['v'])
			Bprint(&bso, "%5.2f pc\n", cputime());
		Bflush(&bso);
		if(!debug['s'])
			asmlc();
		cflush();
	}

	if(debug['v'])
		Bprint(&bso, "%5.2f header\n", cputime());
	Bflush(&bso);
	OFFSET = 0;
	seek(cout, OFFSET, 0);
	switch(HEADTYPE) {
	case 0:
		lput(0x160L<<16);		/* magic and sections */
		lput(0L);			/* time and date */
		lput(rnd(HEADR+textsize, 4096)+datsize);
		lput(symsize);			/* nsyms */
		lput((0x38L<<16)|7L);		/* size of optional hdr and flags */
		lput((0413<<16)|0437L);		/* magic and version */
		lput(rnd(HEADR+textsize, 4096));	/* sizes */
		lput(datsize);
		lput(bsssize);
		lput(entryvalue());		/* va of entry */
		lput(INITTEXT-HEADR);		/* va of base of text */
		lput(INITDAT);			/* va of base of data */
		lput(INITDAT+datsize);		/* va of base of bss */
		lput(~0L);			/* gp reg mask */
		lput(0L);
		lput(0L);
		lput(0L);
		lput(0L);
		lput(~0L);			/* gp value ?? */
		break;
	case 1:
		lput(0x160L<<16);		/* magic and sections */
		lput(0L);			/* time and date */
		lput(HEADR+textsize+datsize);
		lput(symsize);			/* nsyms */
		lput((0x38L<<16)|7L);		/* size of optional hdr and flags */

		lput((0407<<16)|0437L);		/* magic and version */
		lput(textsize);			/* sizes */
		lput(datsize);
		lput(bsssize);
		lput(entryvalue());		/* va of entry */
		lput(INITTEXT);			/* va of base of text */
		lput(INITDAT);			/* va of base of data */
		lput(INITDAT+datsize);		/* va of base of bss */
		lput(~0L);			/* gp reg mask */
		lput(lcsize);
		lput(0L);
		lput(0L);
		lput(0L);
		lput(~0L);			/* gp value ?? */
		lput(0L);			/* complete mystery */
		break;
	case 2:
		if (little)
			t = 24;
		else
			t = 16;
		lput(((((4*t)+0)*t)+7));	/* magic */
		lput(textsize);			/* sizes */
		lput(datsize);
		lput(bsssize);
		lput(symsize);			/* nsyms */
		lput(entryvalue());		/* va of entry */
		lput(0L);
		lput(lcsize);
		break;
	case 3:
		lput((0x160L<<16)|3L);		/* magic and sections */
		lput(time(0));			/* time and date */
		lput(HEADR+textsize+datsize);
		lput(symsize);			/* nsyms */
		lput((0x38L<<16)|7L);		/* size of optional hdr and flags */

		lput((0407<<16)|0437L);		/* magic and version */
		lput(textsize);			/* sizes */
		lput(datsize);
		lput(bsssize);
		lput(entryvalue());		/* va of entry */
		lput(INITTEXT);			/* va of base of text */
		lput(INITDAT);			/* va of base of data */
		lput(INITDAT+datsize);		/* va of base of bss */
		lput(~0L);			/* gp reg mask */
		lput(lcsize);
		lput(0L);
		lput(0L);
		lput(0L);
		lput(~0L);			/* gp value ?? */

		strnput(".text", 8);		/* text segment */
		lput(INITTEXT);			/* address */
		lput(INITTEXT);
		lput(textsize);
		lput(HEADR);
		lput(0L);
		lput(HEADR+textsize+datsize+symsize);
		lput(lcsize);			/* line number size */
		lput(0x20L);			/* flags */

		strnput(".data", 8);		/* data segment */
		lput(INITDAT);			/* address */
		lput(INITDAT);
		lput(datsize);
		lput(HEADR+textsize);
		lput(0L);
		lput(0L);
		lput(0L);
		lput(0x40L);			/* flags */

		strnput(".bss", 8);		/* bss segment */
		lput(INITDAT+datsize);		/* address */
		lput(INITDAT+datsize);
		lput(bsssize);
		lput(0L);
		lput(0L);
		lput(0L);
		lput(0L);
		lput(0x80L);			/* flags */
		break;
	case 4:

		lput((0x160L<<16)|3L);		/* magic and sections */
		lput(time(0));			/* time and date */
		lput(rnd(HEADR+textsize, 4096)+datsize);
		lput(symsize);			/* nsyms */
		lput((0x38L<<16)|7L);		/* size of optional hdr and flags */

		lput((0413<<16)|01012L);	/* magic and version */
		lput(textsize);			/* sizes */
		lput(datsize);
		lput(bsssize);
		lput(entryvalue());		/* va of entry */
		lput(INITTEXT);			/* va of base of text */
		lput(INITDAT);			/* va of base of data */
		lput(INITDAT+datsize);		/* va of base of bss */
		lput(~0L);			/* gp reg mask */
		lput(lcsize);
		lput(0L);
		lput(0L);
		lput(0L);
		lput(~0L);			/* gp value ?? */

		strnput(".text", 8);		/* text segment */
		lput(INITTEXT);			/* address */
		lput(INITTEXT);
		lput(textsize);
		lput(HEADR);
		lput(0L);
		lput(HEADR+textsize+datsize+symsize);
		lput(lcsize);			/* line number size */
		lput(0x20L);			/* flags */

		strnput(".data", 8);		/* data segment */
		lput(INITDAT);			/* address */
		lput(INITDAT);
		lput(datsize);
		lput(rnd(HEADR+textsize, 4096));	/* sizes */
		lput(0L);
		lput(0L);
		lput(0L);
		lput(0x40L);			/* flags */

		strnput(".bss", 8);		/* bss segment */
		lput(INITDAT+datsize);		/* address */
		lput(INITDAT+datsize);
		lput(bsssize);
		lput(0L);
		lput(0L);
		lput(0L);
		lput(0L);
		lput(0x80L);			/* flags */
		break;
	case 5:
		strnput("\177ELF", 4);		/* e_ident */
		CPUT(1);			/* class = 32 bit */
		CPUT(2);			/* data = MSB */
		CPUT(1);			/* version = CURRENT */
		strnput("", 9);
		lput((2L<<16)|8L);		/* type = EXEC; machine = MIPS */
		lput(1L);			/* version = CURRENT */
		lput(entryvalue());		/* entry vaddr */
		lput(52L);			/* offset to first phdr */
		lput(0L);			/* offset to first shdr */
		lput(0L);			/* flags = MIPS */
		lput((52L<<16)|32L);		/* Ehdr & Phdr sizes*/
		lput((3L<<16)|0L);		/* # Phdrs & Shdr size */
		lput((0L<<16)|0L);		/* # Shdrs & shdr string size */

		/* TODO: only these few words are in native byte order? */
		objput(1L);			/* text - type = PT_LOAD */
		objput(0L);			/* file offset */
		objput(INITTEXT-HEADR);		/* vaddr */
		objput(INITTEXT-HEADR);		/* paddr */
		objput(HEADR+textsize);		/* file size */
		objput(HEADR+textsize);		/* memory size */
		objput(0x05L);			/* protections = RX */
		objput(0x10000L);		/* alignment code?? */

		lput(1L);			/* data - type = PT_LOAD */
		lput(HEADR+textsize);		/* file offset */
		lput(INITDAT);			/* vaddr */
		lput(INITDAT);			/* paddr */
		lput(datsize);			/* file size */
		lput(datsize+bsssize);		/* memory size */
		lput(0x06L);			/* protections = RW */
		lput(0x10000L);			/* alignment code?? */

		lput(0L);			/* data - type = PT_NULL */
		lput(HEADR+textsize+datsize);	/* file offset */
		lput(0L);
		lput(0L);
		lput(symsize);			/* symbol table size */
		lput(lcsize);			/* line number size */
		lput(0x04L);			/* protections = R */
		lput(0x04L);			/* alignment code?? */
		break;
	case 6:
		break;
	}
	cflush();
}

void
strnput(char *s, int n)
{
	for(; *s; s++){
		CPUT(*s);
		n--;
	}
	for(; n > 0; n--)
		CPUT(0);
}

void
cflush(void)
{
	int n;

	n = sizeof(buf.cbuf) - cbc;
	if(n)
		write(cout, buf.cbuf, n);
	cbp = buf.cbuf;
	cbc = sizeof(buf.cbuf);
}

void
nopstat(char *f, Count *c)
{
	if(c->outof)
	Bprint(&bso, "%s delay %ld/%ld (%.2f)\n", f,
		c->outof - c->count, c->outof,
		(double)(c->outof - c->count)/c->outof);
}

void
asmsym(void)
{
	Prog *p;
	Auto *a;
	Sym *s;
	int h;

	s = lookup("etext", 0);
	if(s->type == STEXT)
		putsymb(s->name, 'T', s->value, s->version);

	for(h=0; h<NHASH; h++)
		for(s=hash[h]; s!=S; s=s->link)
			switch(s->type) {
			case SCONST:
				putsymb(s->name, 'D', s->value, s->version);
				continue;

			case SSTRING:
				putsymb(s->name, 'T', s->value, s->version);
				continue;

			case SDATA:
				putsymb(s->name, 'D', s->value+INITDAT, s->version);
				continue;

			case SBSS:
				putsymb(s->name, 'B', s->value+INITDAT, s->version);
				continue;

			case SFILE:
				putsymb(s->name, 'f', s->value, s->version);
				continue;
			}

	for(p=textp; p!=P; p=p->cond) {
		s = p->from.sym;
		if(s->type != STEXT && s->type != SLEAF)
			continue;