plan9fox/sys/src/9/teg2/syscall.c

/* we use l1 and l2 cache ops to help stability. */

#include "u.h"
#include "../port/lib.h"
#include "mem.h"
#include "dat.h"
#include "fns.h"
#include "../port/error.h"
#include "../port/systab.h"

#include <tos.h>
#include "ureg.h"

#include "arm.h"

enum {
	Psrsysbits = PsrMask | PsrDfiq | PsrDirq | PsrDasabt | PsrMbz,
};

typedef struct {
	uintptr	ip;
	Ureg*	arg0;
	char*	arg1;
	char	msg[ERRMAX];
	Ureg*	old;
	Ureg	ureg;
} NFrame;

/*
 *   Return user to state before notify()
 */
static void
noted(Ureg* cur, uintptr arg0)
{
	NFrame *nf;
	Ureg *nur;

	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;
	fpunoted();

	nf = up->ureg;

	/* sanity clause */
	if(!okaddr((uintptr)nf, sizeof(NFrame), 0)){
		qunlock(&up->debug);
		pprint("bad ureg in noted %#p\n", nf);
		pexit("Suicide", 0);
	}

	/* don't let user change system flags */
	nur = &nf->ureg;
	nur->psr &= Psrsysbits;
	nur->psr |= cur->psr & ~Psrsysbits;

	memmove(cur, nur, sizeof(Ureg));

	switch((int)arg0){
	case NCONT:
	case NRSTR:
		if(!okaddr(nur->pc, BY2WD, 0) || !okaddr(nur->sp, BY2WD, 0)){
			qunlock(&up->debug);
			pprint("suicide: trap in noted\n");
			pexit("Suicide", 0);
		}
		up->ureg = nf->old;
		qunlock(&up->debug);
		break;
	case NSAVE:
		if(!okaddr(nur->pc, BY2WD, 0) || !okaddr(nur->sp, BY2WD, 0)){
			qunlock(&up->debug);
			pprint("suicide: trap in noted\n");
			pexit("Suicide", 0);
		}
		qunlock(&up->debug);

		splhi();
		nf->arg1 = nf->msg;
		nf->arg0 = &nf->ureg;
		nf->ip = 0;
		cur->sp = (uintptr)nf;
		cur->r0 = (uintptr)nf->arg0;
		break;
	default:
		up->lastnote.flag = NDebug;
		/*FALLTHROUGH*/
	case NDFLT:
		qunlock(&up->debug);
		if(up->lastnote.flag == NDebug)
			pprint("suicide: %s\n", up->lastnote.msg);
		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;
	Note *n;
	u32int s;
	uintptr sp;
	NFrame *nf;

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

	fpunotify(ureg);

	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-23)	/* " pc=0x0123456789abcdef\0" */
			l = ERRMAX-23;
		snprint(n->msg + l, sizeof n->msg - l, " pc=%#lux", ureg->pc);
	}

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

	if(up->notified){
		qunlock(&up->debug);
		splhi();
		return 0;
	}
		
	if(up->notify == nil){
		qunlock(&up->debug);
		pexit(n->msg, n->flag != NDebug);
	}
	if(!okaddr((uintptr)up->notify, 1, 0)){
		qunlock(&up->debug);
		pprint("suicide: notify function address %#p\n", up->notify);
		pexit("Suicide", 0);
	}

	sp = ureg->sp - sizeof(NFrame);
	if(!okaddr(sp, sizeof(NFrame), 1)){
		qunlock(&up->debug);
		pprint("suicide: notify stack address %#p\n", sp);
		pexit("Suicide", 0);
	}

	nf = (void*)sp;
	memmove(&nf->ureg, ureg, sizeof(Ureg));
	nf->old = up->ureg;
	up->ureg = nf;
	memmove(nf->msg, up->note[0].msg, ERRMAX);
	nf->arg1 = nf->msg;
	nf->arg0 = &nf->ureg;
	nf->ip = 0;

	ureg->sp = sp;
	ureg->pc = (uintptr)up->notify;
	ureg->r0 = (uintptr)nf->arg0;

	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);

	l1cache->wb();				/* is this needed? */
	return 1;
}

void
syscall(Ureg* ureg)
{
	char *e;
	u32int s;
	ulong sp;
	long ret;
	int i, scallnr;
	vlong startns, stopns;

	if(!userureg(ureg))
		panic("syscall: from kernel: pc %#lux r14 %#lux psr %#lux",
			ureg->pc, ureg->r14, ureg->psr);

	cycles(&up->kentry);

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

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

	if(up->procctl == Proc_tracesyscall){
		/*
		 * Redundant validaddr.  Do we care?
		 * Tracing syscalls is not exactly a fast path...
		 * Beware, validaddr currently does a pexit rather
		 * than an error if there's a problem; that might
		 * change in the future.
		 */
		if(sp < (USTKTOP-BY2PG) || sp > (USTKTOP-sizeof(Sargs)-BY2WD))
			validaddr(sp, sizeof(Sargs)+BY2WD, 0);

		syscallfmt(scallnr, ureg->pc, (va_list)(sp+BY2WD));
		up->procctl = Proc_stopme;
		procctl();
		if (up->syscalltrace) 
			free(up->syscalltrace);
		up->syscalltrace = nil;
	}

	up->nerrlab = 0;
	ret = -1;
	startns = todget(nil);

	l1cache->wb();			/* system is more stable with this */
	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];

	/*	iprint("%s: syscall %s\n", up->text, sysctab[scallnr]?sysctab[scallnr]:"huh?"); */

		ret = systab[scallnr]((va_list)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=%#p pc=%#p\n",
				up->errlab[i].sp, up->errlab[i].pc);
		panic("error stack");
	}

	/*
	 *  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(up->procctl == Proc_tracesyscall){
		stopns = todget(nil);
		sysretfmt(scallnr, (va_list)(sp+BY2WD), ret, startns, stopns);
		s = splhi();
		up->procctl = Proc_stopme;
		procctl();
		splx(s);
		if(up->syscalltrace)
			free(up->syscalltrace);
		up->syscalltrace = nil;
	}

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

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

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

	l1cache->wb();			/* system is more stable with this */

	/* if we delayed sched because we held a lock, sched now */
	if(up->delaysched){
		sched();
		splhi();
	}
	kexit(ureg);
}

uintptr
execregs(uintptr 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 %#ux sp %#ux nargs %ld\n", up->pid, ureg->pc, ureg->r13, nargs);
	allcache->wbse(ureg, sizeof *ureg);		/* is this needed? */

	/*
	 * return the address of kernel/user shared data
	 * (e.g. clock stuff)
	 */
	return USTKTOP-sizeof(Tos);
}

void
sysprocsetup(Proc* p)
{
	fpusysprocsetup(p);
}

/* 
 *  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;

	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;
}