trap.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

	int clockintr, i;
	Vctl *v;

	va = intrregs->icip;

	if(va & (1<<IRQtimer0))
		clockintr = 1;
	else
		clockintr = 0;
	for(i = 0; i < 32; i++){
		if(((1<<i) & va) == 0)
			continue;
		for(v = vctl[i]; v != nil; v = v->next){
			v->f(ur, v->a);
			va &= ~(1<<i);
		}
	}
	if(va)
		print("unknown interrupt: %lux\n", va);

	return clockintr;
}

/*
 *  here on gpio interrupts
 */
static void
gpiointr(Ureg *ur, void*)
{
	ulong va;
	int i;
	Vctl *v;

	va = gpioregs->edgestatus;
	gpioregs->edgestatus = va;

	for(i = 0; i < 27; i++){
		if(((1<<i) & va) == 0)
			continue;
		for(v = gpiovctl[i]; v != nil; v = v->next){
			v->f(ur, v->a);
			va &= ~(1<<i);
		}
	}
	if(va)
		print("unknown gpio interrupt: %lux\n", va);
}

/*
 *  system calls
 */
#include "../port/systab.h"

/*
 *  Syscall is called directly from assembler without going through trap().
 */
void
syscall(Ureg* ureg)
{
	char *e;
	ulong	sp;
	long	ret;
	int	i, scallnr;

	if((ureg->psr & PsrMask) != PsrMusr) {
		panic("syscall: pc 0x%lux r14 0x%lux cs 0x%lux\n", ureg->pc, ureg->r14, ureg->psr);
	}

	m->syscall++;
	up->insyscall = 1;
	up->pc = ureg->pc;
	up->dbgreg = ureg;

	scallnr = ureg->r0;
	up->scallnr = scallnr;
	spllo();

	sp = ureg->sp;
	up->nerrlab = 0;
	ret = -1;
	if(!waserror()){
		if(scallnr >= nsyscall){
			pprint("bad sys call number %d pc %lux\n",
				scallnr, ureg->pc);
			postnote(up, 1, "sys: bad sys call", NDebug);
			error(Ebadarg);
		}

		if(sp<(USTKTOP-BY2PG) || sp>(USTKTOP-sizeof(Sargs)-BY2WD))
			validaddr(sp, sizeof(Sargs)+BY2WD, 0);

		up->s = *((Sargs*)(sp+BY2WD));
		up->psstate = sysctab[scallnr];

		ret = systab[scallnr](up->s.args);
		poperror();
	}else{
		/* failure: save the error buffer for errstr */
		e = up->syserrstr;
		up->syserrstr = up->errstr;
		up->errstr = e;
	}
	if(up->nerrlab){
		print("bad errstack [%d]: %d extra\n", scallnr, up->nerrlab);
		for(i = 0; i < NERR; i++)
			print("sp=%lux pc=%lux\n",
				up->errlab[i].sp, up->errlab[i].pc);
		panic("error stack");
	}

	up->insyscall = 0;
	up->psstate = 0;

	/*
	 *  Put return value in frame.  On the x86 the syscall is
	 *  just another trap and the return value from syscall is
	 *  ignored.  On other machines the return value is put into
	 *  the results register by caller of syscall.
	 */
	ureg->r0 = ret;

	if(scallnr == NOTED)
		noted(ureg, *(ulong*)(sp+BY2WD));

	if(up->delaysched)
		sched();

	splhi();
	if(scallnr != RFORK && (up->procctl || up->nnote))
		notify(ureg);
}

/*
 *   Return user to state before notify()
 */
void
noted(Ureg* ureg, ulong arg0)
{
	Ureg *nureg;
	ulong oureg, sp;

	qlock(&up->debug);
	if(arg0!=NRSTR && !up->notified) {
		qunlock(&up->debug);
		pprint("call to noted() when not notified\n");
		pexit("Suicide", 0);
	}
	up->notified = 0;

	nureg = up->ureg;	/* pointer to user returned Ureg struct */

	/* sanity clause */
	oureg = (ulong)nureg;
	if(!okaddr((ulong)oureg-BY2WD, BY2WD+sizeof(Ureg), 0)){
		pprint("bad ureg in noted or call to noted when not notified\n");
		qunlock(&up->debug);
		pexit("Suicide", 0);
	}

	/* don't let user change system flags */
	nureg->psr = (ureg->psr & ~(PsrMask|PsrDfiq|PsrDirq)) |
			(nureg->psr & (PsrMask|PsrDfiq|PsrDirq));

	memmove(ureg, nureg, sizeof(Ureg));

	switch(arg0){
	case NCONT:
	case NRSTR:
		if(!okaddr(nureg->pc, 1, 0) || !okaddr(nureg->sp, BY2WD, 0)){
			qunlock(&up->debug);
			pprint("suicide: trap in noted\n");
			pexit("Suicide", 0);
		}
		up->ureg = (Ureg*)(*(ulong*)(oureg-BY2WD));
		qunlock(&up->debug);
		break;

	case NSAVE:
		if(!okaddr(nureg->pc, BY2WD, 0)
		|| !okaddr(nureg->sp, BY2WD, 0)){
			qunlock(&up->debug);
			pprint("suicide: trap in noted\n");
			pexit("Suicide", 0);
		}
		qunlock(&up->debug);
		sp = oureg-4*BY2WD-ERRMAX;
		splhi();
		ureg->sp = sp;
		((ulong*)sp)[1] = oureg;	/* arg 1 0(FP) is ureg* */
		((ulong*)sp)[0] = 0;		/* arg 0 is pc */
		break;

	default:
		pprint("unknown noted arg 0x%lux\n", arg0);
		up->lastnote.flag = NDebug;
		/* fall through */
		
	case NDFLT:
		if(up->lastnote.flag == NDebug){ 
			qunlock(&up->debug);
			pprint("suicide: %s\n", up->lastnote.msg);
		} else
			qunlock(&up->debug);
		pexit(up->lastnote.msg, up->lastnote.flag!=NDebug);
	}
}

/*
 *  Call user, if necessary, with note.
 *  Pass user the Ureg struct and the note on his stack.
 */
int
notify(Ureg* ureg)
{
	int l;
	ulong s, sp;
	Note *n;

	if(up->procctl)
		procctl(up);
	if(up->nnote == 0)
		return 0;

	s = spllo();
	qlock(&up->debug);
	up->notepending = 0;
	n = &up->note[0];
	if(strncmp(n->msg, "sys:", 4) == 0){
		l = strlen(n->msg);
		if(l > ERRMAX-15)	/* " pc=0x12345678\0" */
			l = ERRMAX-15;
		sprint(n->msg+l, " pc=0x%.8lux", ureg->pc);
	}

	if(n->flag!=NUser && (up->notified || up->notify==0)){
		if(n->flag == NDebug)
			pprint("suicide: %s\n", n->msg);
		qunlock(&up->debug);
		pexit(n->msg, n->flag!=NDebug);
	}

	if(up->notified) {
		qunlock(&up->debug);
		splhi();
		return 0;
	}
		
	if(!up->notify){
		qunlock(&up->debug);
		pexit(n->msg, n->flag!=NDebug);
	}
	sp = ureg->sp;
	sp -= sizeof(Ureg);

	if(!okaddr((ulong)up->notify, 1, 0)
	|| !okaddr(sp-ERRMAX-4*BY2WD, sizeof(Ureg)+ERRMAX+4*BY2WD, 1)){
		pprint("suicide: bad address in notify\n");
		qunlock(&up->debug);
		pexit("Suicide", 0);
	}

	up->ureg = (void*)sp;
	memmove((Ureg*)sp, ureg, sizeof(Ureg));
	*(Ureg**)(sp-BY2WD) = up->ureg;	/* word under Ureg is old up->ureg */
	up->ureg = (void*)sp;
	sp -= BY2WD+ERRMAX;
	memmove((char*)sp, up->note[0].msg, ERRMAX);
	sp -= 3*BY2WD;
	*(ulong*)(sp+2*BY2WD) = sp+3*BY2WD;	/* arg 2 is string */
	*(ulong*)(sp+1*BY2WD) = (ulong)up->ureg;	/* arg 1 is ureg* */
	*(ulong*)(sp+0*BY2WD) = 0;		/* arg 0 is pc */
	ureg->sp = sp;
	ureg->pc = (ulong)up->notify;
	up->notified = 1;
	up->nnote--;
	memmove(&up->lastnote, &up->note[0], sizeof(Note));
	memmove(&up->note[0], &up->note[1], up->nnote*sizeof(Note));

	qunlock(&up->debug);
	splx(s);
	return 1;
}

/* Give enough context in the ureg to produce a kernel stack for
 * a sleeping process
 */
void
setkernur(Ureg *ureg, Proc *p)
{
	ureg->pc = p->sched.pc;
	ureg->sp = p->sched.sp+4;
	ureg->r14 = (ulong)sched;
}

/*
 *  return the userpc the last exception happened at
 */
ulong
userpc(void)
{
	Ureg *ureg;

	ureg = (Ureg*)up->dbgreg;
	return ureg->pc;
}

/* This routine must save the values of registers the user is not permitted
 * to write from devproc and then restore the saved values before returning.
 */
void
setregisters(Ureg* ureg, char* pureg, char* uva, int n)
{
	USED(ureg, pureg, uva, n);
}

/*
 *  this is the body for all kproc's
 */
static void
linkproc(void)
{
	spllo();
	up->kpfun(up->kparg);
	pexit("kproc exiting", 0);
}

/*
 *  setup stack and initial PC for a new kernel proc.  This is architecture
 *  dependent because of the starting stack location
 */
void
kprocchild(Proc *p, void (*func)(void*), void *arg)
{
	p->sched.pc = (ulong)linkproc;
	p->sched.sp = (ulong)p->kstack+KSTACK;

	p->kpfun = func;
	p->kparg = arg;
}


/* 
 *  Craft a return frame which will cause the child to pop out of
 *  the scheduler in user mode with the return register zero.  Set
 *  pc to point to a l.s return function.
 */
void
forkchild(Proc *p, Ureg *ureg)
{
	Ureg *cureg;

//print("%lud setting up for forking child %lud\n", up->pid, p->pid);
	p->sched.sp = (ulong)p->kstack+KSTACK-sizeof(Ureg);
	p->sched.pc = (ulong)forkret;

	cureg = (Ureg*)(p->sched.sp);
	memmove(cureg, ureg, sizeof(Ureg));

	/* syscall returns 0 for child */
	cureg->r0 = 0;

	/* Things from bottom of syscall which were never executed */
	p->psstate = 0;
	p->insyscall = 0;
}

/*
 *  setup stack, initial PC, and any arch dependent regs for an execing user proc.
 */
long
execregs(ulong entry, ulong ssize, ulong nargs)
{
	ulong *sp;
	Ureg *ureg;

	sp = (ulong*)(USTKTOP - ssize);
	*--sp = nargs;

	ureg = up->dbgreg;
	memset(ureg, 0, 15*sizeof(ulong));
	ureg->r13 = (ulong)sp;
	ureg->pc = entry;
//print("%lud: EXECREGS pc 0x%lux sp 0x%lux\n", up->pid, ureg->pc, ureg->r13);
	return USTKTOP-sizeof(Tos);		/* address of kernel/user shared data */
}

/*
 * Fill in enough of Ureg to get a stack trace, and call a function.
 * Used by debugging interface rdb.
 */
void
callwithureg(void (*fn)(Ureg*))
{
	Ureg ureg;
	ureg.pc = getcallerpc(&fn);
	ureg.sp = (ulong)&fn;
	fn(&ureg);
}

static void
_dumpstack(Ureg *ureg)
{
	ulong l, v, i;
	ulong *p;
	extern ulong etext;

	if(up == 0){
		iprint("no current proc\n");
		return;
	}

	iprint("ktrace /kernel/path %.8lux %.8lux %.8lux\n", ureg->pc, ureg->sp, ureg->r14);
	i = 0;
	for(l=(ulong)&l; l<(ulong)(up->kstack+KSTACK); l+=4){
		v = *(ulong*)l;
		if(KTZERO < v && v < (ulong)&etext && (v&3)==0){
			v -= 4;
			p = (ulong*)v;
			if((*p & 0x0f000000) == 0x0b000000){
				iprint("%.8lux=%.8lux ", l, v);
				i++;
			}
		}
		if(i == 4){
			i = 0;
			iprint("\n");
		}
	}
	if(i)
		iprint("\n");
}

void
dumpstack(void)
{
	callwithureg(_dumpstack);
}

/*
 *  pc output by ps
 */
ulong
dbgpc(Proc *p)
{
	Ureg *ureg;

	ureg = p->dbgreg;
	if(ureg == 0)
		return 0;

	return ureg->pc;
}

/*
 * called in sysfile.c
 */
void
evenaddr(ulong addr)
{
	if(addr & 3){
		postnote(up, 1, "sys: odd address", NDebug);
		error(Ebadarg);
	}
}