xref: /freebsd/sys/kern/init_main.c (revision 0de89efe5c443f213c7ea28773ef2dc6cf3af2ed)
1 /*
2  * Copyright (c) 1995 Terrence R. Lambert
3  * All rights reserved.
4  *
5  * Copyright (c) 1982, 1986, 1989, 1991, 1992, 1993
6  *	The Regents of the University of California.  All rights reserved.
7  * (c) UNIX System Laboratories, Inc.
8  * All or some portions of this file are derived from material licensed
9  * to the University of California by American Telephone and Telegraph
10  * Co. or Unix System Laboratories, Inc. and are reproduced herein with
11  * the permission of UNIX System Laboratories, Inc.
12  *
13  * Redistribution and use in source and binary forms, with or without
14  * modification, are permitted provided that the following conditions
15  * are met:
16  * 1. Redistributions of source code must retain the above copyright
17  *    notice, this list of conditions and the following disclaimer.
18  * 2. Redistributions in binary form must reproduce the above copyright
19  *    notice, this list of conditions and the following disclaimer in the
20  *    documentation and/or other materials provided with the distribution.
21  * 3. All advertising materials mentioning features or use of this software
22  *    must display the following acknowledgement:
23  *	This product includes software developed by the University of
24  *	California, Berkeley and its contributors.
25  * 4. Neither the name of the University nor the names of its contributors
26  *    may be used to endorse or promote products derived from this software
27  *    without specific prior written permission.
28  *
29  * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
30  * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
31  * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
32  * ARE DISCLAIMED.  IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
33  * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
34  * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
35  * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
36  * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
37  * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
38  * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
39  * SUCH DAMAGE.
40  *
41  *	@(#)init_main.c	8.9 (Berkeley) 1/21/94
42  * $Id: init_main.c,v 1.71 1997/09/02 20:05:35 bde Exp $
43  */
44 
45 #include "opt_devfs.h"
46 
47 #include <sys/param.h>
48 #include <sys/file.h>
49 #include <sys/filedesc.h>
50 #include <sys/kernel.h>
51 #include <sys/mount.h>
52 #include <sys/sysctl.h>
53 #include <sys/proc.h>
54 #include <sys/resourcevar.h>
55 #include <sys/signalvar.h>
56 #include <sys/systm.h>
57 #include <sys/vnode.h>
58 #include <sys/sysent.h>
59 #include <sys/reboot.h>
60 #include <sys/sysproto.h>
61 #include <sys/vmmeter.h>
62 
63 #include <machine/cpu.h>
64 
65 #include <vm/vm.h>
66 #include <vm/vm_param.h>
67 #include <vm/vm_prot.h>
68 #include <sys/lock.h>
69 #include <vm/pmap.h>
70 #include <vm/vm_map.h>
71 #include <sys/user.h>
72 #include <sys/copyright.h>
73 
74 extern struct linker_set	sysinit_set;	/* XXX */
75 
76 extern void __main __P((void));
77 extern void main __P((void *framep));
78 extern void secondary_main __P((void));
79 
80 /* Components of the first process -- never freed. */
81 static struct session session0;
82 static struct pgrp pgrp0;
83 struct	proc proc0;
84 static struct pcred cred0;
85 static struct filedesc0 filedesc0;
86 static struct plimit limit0;
87 static struct vmspace vmspace0;
88 #ifndef SMP	/* per-cpu on smp */
89 struct	proc *curproc = &proc0;
90 #endif
91 struct	proc *initproc;
92 
93 int cmask = CMASK;
94 extern	struct user *proc0paddr;
95 
96 struct	vnode *rootvp;
97 int	boothowto;
98 
99 struct	timeval boottime;
100 SYSCTL_STRUCT(_kern, KERN_BOOTTIME, boottime,
101 	CTLFLAG_RW, &boottime, timeval, "");
102 
103 static int shutdowntimeout = 120;
104 SYSCTL_INT(_kern, OID_AUTO, shutdown_timeout,
105 	CTLFLAG_RW, &shutdowntimeout, 0, "");
106 
107 #ifndef SMP	/* per-cpu on smp */
108 struct	timeval runtime;
109 #endif
110 
111 /*
112  * Promiscuous argument pass for start_init()
113  *
114  * This is a kludge because we use a return from main() rather than a call
115  * to a new routine in locore.s to kick the kernel alive from locore.s.
116  */
117 static void	*init_framep;
118 
119 
120 #if __GNUC__ >= 2
121 void __main() {}
122 #endif
123 
124 
125 /*
126  * This ensures that there is at least one entry so that the sysinit_set
127  * symbol is not undefined.  A sybsystem ID of SI_SUB_DUMMY is never
128  * executed.
129  */
130 SYSINIT(placeholder, SI_SUB_DUMMY,SI_ORDER_ANY, NULL, NULL)
131 
132 
133 /*
134  * System startup; initialize the world, create process 0, mount root
135  * filesystem, and fork to create init and pagedaemon.  Most of the
136  * hard work is done in the lower-level initialization routines including
137  * startup(), which does memory initialization and autoconfiguration.
138  *
139  * This allows simple addition of new kernel subsystems that require
140  * boot time initialization.  It also allows substitution of subsystem
141  * (for instance, a scheduler, kernel profiler, or VM system) by object
142  * module.  Finally, it allows for optional "kernel threads", like an LFS
143  * cleaner.
144  */
145 void
146 main(framep)
147 	void *framep;
148 {
149 
150 	register struct sysinit **sipp;		/* system initialization*/
151 	register struct sysinit **xipp;		/* interior loop of sort*/
152 	register struct sysinit *save;		/* bubble*/
153 	int			rval[2];	/* SI_TYPE_KTHREAD support*/
154 
155 	/*
156 	 * Copy the locore.s frame pointer for proc0, this is forked into
157 	 * all other processes.
158 	 */
159 	init_framep = framep;
160 
161 #ifdef SMP
162 	/*
163 	 * XXX curproc is per-cpu in SMP, and exists in freshly mapped pages,
164 	 * so its value must be initialized now before it is used by various
165 	 * initialization routines.  proc0_init() isn't soon enough:
166 	 * among other things, configure() is called first, and may call
167 	 * setdumpdev(), which panics without a valid curproc.
168 	 */
169 	curproc = &proc0;
170 #endif /* SMP */
171 
172 	/*
173 	 * Perform a bubble sort of the system initialization objects by
174 	 * their subsystem (primary key) and order (secondary key).
175 	 *
176 	 * Since some things care about execution order, this is the
177 	 * operation which ensures continued function.
178 	 */
179 	for( sipp = (struct sysinit **)sysinit_set.ls_items; *sipp; sipp++) {
180 		for( xipp = sipp + 1; *xipp; xipp++) {
181 			if( (*sipp)->subsystem < (*xipp)->subsystem ||
182 			    ( (*sipp)->subsystem == (*xipp)->subsystem &&
183 			      (*sipp)->order < (*xipp)->order))
184 				continue;	/* skip*/
185 			save = *sipp;
186 			*sipp = *xipp;
187 			*xipp = save;
188 		}
189 	}
190 
191 	/*
192 	 * Traverse the (now) ordered list of system initialization tasks.
193 	 * Perform each task, and continue on to the next task.
194 	 *
195 	 * The last item on the list is expected to be the scheduler,
196 	 * which will not return.
197 	 */
198 	for( sipp = (struct sysinit **)sysinit_set.ls_items; *sipp; sipp++) {
199 		if( (*sipp)->subsystem == SI_SUB_DUMMY)
200 			continue;	/* skip dummy task(s)*/
201 
202 		switch( (*sipp)->type) {
203 		case SI_TYPE_DEFAULT:
204 			/* no special processing*/
205 			(*((*sipp)->func))( (*sipp)->udata);
206 			break;
207 
208 		case SI_TYPE_KTHREAD:
209 			/* kernel thread*/
210 			if (fork(&proc0, NULL, rval))
211 				panic("fork kernel process");
212 			cpu_set_fork_handler(pfind(rval[0]), (*sipp)->func, (*sipp)->udata);
213 			break;
214 
215 		default:
216 			panic( "init_main: unrecognized init type");
217 		}
218 	}
219 
220 	panic("Shouldn't get here!");
221 	/* NOTREACHED*/
222 }
223 
224 
225 /*
226  * Start a kernel process.  This is called after a fork() call in
227  * main() in the file kern/init_main.c.
228  *
229  * This function is used to start "internal" daemons.
230  */
231 /* ARGSUSED*/
232 void
233 kproc_start(udata)
234 	void *udata;
235 {
236 	struct kproc_desc	*kp = udata;
237 	struct proc		*p = curproc;
238 
239 #ifdef DIAGNOSTIC
240 	printf("Start pid=%d <%s>\n",p->p_pid, kp->arg0);
241 #endif
242 
243 
244 	/* save a global descriptor, if desired*/
245 	if( kp->global_procpp != NULL)
246 		*kp->global_procpp	= p;
247 
248 	/* this is a non-swapped system process*/
249 	p->p_flag |= P_INMEM | P_SYSTEM;
250 
251 	/* set up arg0 for 'ps', et al*/
252 	strcpy( p->p_comm, kp->arg0);
253 
254 	/* call the processes' main()...*/
255 	(*kp->func)();
256 
257 	/* NOTREACHED */
258 	panic("kproc_start: %s", kp->arg0);
259 }
260 
261 
262 /*
263  ***************************************************************************
264  ****
265  **** The following SYSINIT's belong elsewhere, but have not yet
266  **** been moved.
267  ****
268  ***************************************************************************
269  */
270 #ifdef OMIT
271 /*
272  * Handled by vfs_mountroot (bad idea) at this time... should be
273  * done the same as 4.4Lite2.
274  */
275 SYSINIT(swapinit, SI_SUB_SWAP, SI_ORDER_FIRST, swapinit, NULL)
276 #endif	/* OMIT*/
277 
278 static void print_caddr_t __P((void *data));
279 static void
280 print_caddr_t(data)
281 	void *data;
282 {
283 	printf("%s", (char *)data);
284 }
285 SYSINIT(announce, SI_SUB_COPYRIGHT, SI_ORDER_FIRST, print_caddr_t, copyright)
286 
287 
288 /*
289  ***************************************************************************
290  ****
291  **** The two following SYSINT's are proc0 specific glue code.  I am not
292  **** convinced that they can not be safely combined, but their order of
293  **** operation has been maintained as the same as the original init_main.c
294  **** for right now.
295  ****
296  **** These probably belong in init_proc.c or kern_proc.c, since they
297  **** deal with proc0 (the fork template process).
298  ****
299  ***************************************************************************
300  */
301 /* ARGSUSED*/
302 static void proc0_init __P((void *dummy));
303 static void
304 proc0_init(dummy)
305 	void *dummy;
306 {
307 	register struct proc		*p;
308 	register struct filedesc0	*fdp;
309 	register unsigned i;
310 
311 	/*
312 	 * Initialize the current process pointer (curproc) before
313 	 * any possible traps/probes to simplify trap processing.
314 	 */
315 	p = &proc0;
316 	curproc = p;			/* XXX redundant*/
317 
318 	/*
319 	 * Initialize process and pgrp structures.
320 	 */
321 	procinit();
322 
323 	/*
324 	 * Initialize sleep queue hash table
325 	 */
326 	sleepinit();
327 
328 	/*
329 	 * additional VM structures
330 	 */
331 	vm_init2();
332 
333 	/*
334 	 * Create process 0 (the swapper).
335 	 */
336 	LIST_INSERT_HEAD(&allproc, p, p_list);
337 	p->p_pgrp = &pgrp0;
338 	LIST_INSERT_HEAD(PGRPHASH(0), &pgrp0, pg_hash);
339 	LIST_INIT(&pgrp0.pg_members);
340 	LIST_INSERT_HEAD(&pgrp0.pg_members, p, p_pglist);
341 
342 	pgrp0.pg_session = &session0;
343 	session0.s_count = 1;
344 	session0.s_leader = p;
345 
346 	p->p_sysent = &aout_sysvec;
347 
348 	p->p_flag = P_INMEM | P_SYSTEM;
349 	p->p_stat = SRUN;
350 	p->p_nice = NZERO;
351 	p->p_rtprio.type = RTP_PRIO_NORMAL;
352 	p->p_rtprio.prio = 0;
353 
354 /*
355  * Link for kernel based threads
356  */
357 	p->p_peers = 0;
358 	p->p_leader = p;
359 
360 	bcopy("swapper", p->p_comm, sizeof ("swapper"));
361 
362 	/* Create credentials. */
363 	cred0.p_refcnt = 1;
364 	p->p_cred = &cred0;
365 	p->p_ucred = crget();
366 	p->p_ucred->cr_ngroups = 1;	/* group 0 */
367 
368 	/* Create the file descriptor table. */
369 	fdp = &filedesc0;
370 	p->p_fd = &fdp->fd_fd;
371 	fdp->fd_fd.fd_refcnt = 1;
372 	fdp->fd_fd.fd_cmask = cmask;
373 	fdp->fd_fd.fd_ofiles = fdp->fd_dfiles;
374 	fdp->fd_fd.fd_ofileflags = fdp->fd_dfileflags;
375 	fdp->fd_fd.fd_nfiles = NDFILE;
376 
377 	/* Create the limits structures. */
378 	p->p_limit = &limit0;
379 	for (i = 0; i < sizeof(p->p_rlimit)/sizeof(p->p_rlimit[0]); i++)
380 		limit0.pl_rlimit[i].rlim_cur =
381 		    limit0.pl_rlimit[i].rlim_max = RLIM_INFINITY;
382 	limit0.pl_rlimit[RLIMIT_NOFILE].rlim_cur =
383 	    limit0.pl_rlimit[RLIMIT_NOFILE].rlim_max = maxfiles;
384 	limit0.pl_rlimit[RLIMIT_NPROC].rlim_cur =
385 	    limit0.pl_rlimit[RLIMIT_NPROC].rlim_max = maxproc;
386 	i = ptoa(cnt.v_free_count);
387 	limit0.pl_rlimit[RLIMIT_RSS].rlim_max = i;
388 	limit0.pl_rlimit[RLIMIT_MEMLOCK].rlim_max = i;
389 	limit0.pl_rlimit[RLIMIT_MEMLOCK].rlim_cur = i / 3;
390 	limit0.p_refcnt = 1;
391 
392 	/* Allocate a prototype map so we have something to fork. */
393 	p->p_vmspace = &vmspace0;
394 	vmspace0.vm_refcnt = 1;
395 	pmap_pinit(&vmspace0.vm_pmap);
396 	vm_map_init(&vmspace0.vm_map, round_page(VM_MIN_ADDRESS),
397 	    trunc_page(VM_MAXUSER_ADDRESS), TRUE);
398 	vmspace0.vm_map.pmap = &vmspace0.vm_pmap;
399 	p->p_addr = proc0paddr;				/* XXX */
400 
401 #define INCOMPAT_LITES2
402 #ifdef INCOMPAT_LITES2
403 	/*
404 	 * proc0 needs to have a coherent frame base in it's stack.
405 	 */
406 	cpu_set_init_frame(p, init_framep);			/* XXX! */
407 #endif	/* INCOMPAT_LITES2*/
408 
409 	/*
410 	 * We continue to place resource usage info and signal
411 	 * actions in the user struct so they're pageable.
412 	 */
413 	p->p_stats = &p->p_addr->u_stats;
414 	p->p_sigacts = &p->p_addr->u_sigacts;
415 
416 	/*
417 	 * Charge root for one process.
418 	 */
419 	(void)chgproccnt(0, 1);
420 }
421 SYSINIT(p0init, SI_SUB_INTRINSIC, SI_ORDER_FIRST, proc0_init, NULL)
422 
423 /* ARGSUSED*/
424 static void proc0_post __P((void *dummy));
425 static void
426 proc0_post(dummy)
427 	void *dummy;
428 {
429 	struct timeval tv;
430 
431 	/*
432 	 * Now can look at time, having had a chance to verify the time
433 	 * from the file system.  Reset p->p_rtime as it may have been
434 	 * munched in mi_switch() after the time got set.
435 	 */
436 	gettime(&boottime);
437 	proc0.p_stats->p_start = runtime = mono_time = boottime;
438 	proc0.p_rtime.tv_sec = proc0.p_rtime.tv_usec = 0;
439 
440 	/*
441 	 * Give the ``random'' number generator a thump.
442 	 */
443 	microtime(&tv);
444 	srandom(tv.tv_sec ^ tv.tv_usec);
445 
446 	/* Initialize signal state for process 0. */
447 	siginit(&proc0);
448 }
449 SYSINIT(p0post, SI_SUB_INTRINSIC_POST, SI_ORDER_FIRST, proc0_post, NULL)
450 
451 
452 
453 
454 /*
455  ***************************************************************************
456  ****
457  **** The following SYSINIT's and glue code should be moved to the
458  **** respective files on a per subsystem basis.
459  ****
460  ***************************************************************************
461  */
462 /* ARGSUSED */
463 static void sched_setup __P((void *dummy));
464 static void
465 sched_setup(dummy)
466 	void *dummy;
467 {
468 	/* Kick off timeout driven events by calling first time. */
469 	roundrobin(NULL);
470 	schedcpu(NULL);
471 }
472 SYSINIT(sched_setup, SI_SUB_KICK_SCHEDULER, SI_ORDER_FIRST, sched_setup, NULL)
473 
474 /* ARGSUSED */
475 static void root_conf __P((void *dummy));
476 static void
477 root_conf(dummy)
478 	void *dummy;
479 {
480 	cpu_rootconf();
481 }
482 SYSINIT(root_conf, SI_SUB_ROOT_CONF, SI_ORDER_FIRST, root_conf, NULL)
483 
484 /* ARGSUSED */
485 static void dump_conf __P((void *dummy));
486 static void
487 dump_conf(dummy)
488 	void *dummy;
489 {
490 	cpu_dumpconf();
491 }
492 SYSINIT(dump_conf, SI_SUB_DUMP_CONF, SI_ORDER_FIRST, dump_conf, NULL)
493 
494 /* ARGSUSED*/
495 static void xxx_vfs_mountroot __P((void *fsnamep));
496 #ifdef BOOTP
497 extern void bootpc_init __P((void));
498 #endif
499 static void
500 xxx_vfs_mountroot(fsnamep)
501 	void *fsnamep;
502 {
503   /* XXX Add a separate SYSINIT entry */
504 #ifdef BOOTP
505 	bootpc_init();
506 #endif
507 	/* Mount the root file system. */
508 	if (vfs_mountrootfs(*((char **) fsnamep)))
509 		panic("cannot mount root");
510 }
511 SYSINIT(mountroot, SI_SUB_MOUNT_ROOT, SI_ORDER_FIRST, xxx_vfs_mountroot,
512 	&mountrootfsname)
513 
514 /* ARGSUSED*/
515 static void xxx_vfs_root_fdtab __P((void *dummy));
516 static void
517 xxx_vfs_root_fdtab(dummy)
518 	void *dummy;
519 {
520 	register struct filedesc0	*fdp = &filedesc0;
521 
522 	/* Get the vnode for '/'.  Set fdp->fd_fd.fd_cdir to reference it. */
523 	if (VFS_ROOT(mountlist.cqh_first, &rootvnode))
524 		panic("cannot find root vnode");
525 	fdp->fd_fd.fd_cdir = rootvnode;
526 	VREF(fdp->fd_fd.fd_cdir);
527 	VOP_UNLOCK(rootvnode, 0, &proc0);
528 	fdp->fd_fd.fd_rdir = NULL;
529 }
530 SYSINIT(retrofit, SI_SUB_ROOT_FDTAB, SI_ORDER_FIRST, xxx_vfs_root_fdtab, NULL)
531 
532 
533 /*
534  ***************************************************************************
535  ****
536  **** The following code probably belongs in another file, like
537  **** kern/init_init.c.  It is here for two reasons only:
538  ****
539  ****	1)	This code returns to startup the system; this is
540  ****		abnormal for a kernel thread.
541  ****	2)	This code promiscuously uses init_frame
542  ****
543  ***************************************************************************
544  */
545 
546 static void kthread_init __P((void *dummy));
547 SYSINIT_KT(init,SI_SUB_KTHREAD_INIT, SI_ORDER_FIRST, kthread_init, NULL)
548 
549 
550 extern void prepare_usermode __P((void));
551 static void start_init __P((struct proc *p));
552 
553 /* ARGSUSED*/
554 static void
555 kthread_init(dummy)
556 	void *dummy;
557 {
558 	/* Create process 1 (init(8)). */
559 	start_init(curproc);
560 
561 	prepare_usermode();
562 
563 	/*
564 	 * This returns to the fork trampoline, then to user mode.
565 	 */
566 	return;
567 }
568 
569 
570 /*
571  * List of paths to try when searching for "init".
572  */
573 static char *initpaths[] = {
574 	"/sbin/init",
575 	"/sbin/oinit",
576 	"/sbin/init.bak",
577 	"/stand/sysinstall",
578 	NULL,
579 };
580 
581 /*
582  * Start the initial user process; try exec'ing each pathname in "initpaths".
583  * The program is invoked with one argument containing the boot flags.
584  */
585 static void
586 start_init(p)
587 	struct proc *p;
588 {
589 	vm_offset_t addr;
590 	struct execve_args args;
591 	int options, i, retval[2], error;
592 	char **pathp, *path, *ucp, **uap, *arg0, *arg1;
593 
594 	initproc = p;
595 
596 	/*
597 	 * Need just enough stack to hold the faked-up "execve()" arguments.
598 	 */
599 	addr = trunc_page(VM_MAXUSER_ADDRESS - PAGE_SIZE);
600 	if (vm_map_find(&p->p_vmspace->vm_map, NULL, 0, &addr, PAGE_SIZE, FALSE, VM_PROT_ALL, VM_PROT_ALL, 0) != 0)
601 		panic("init: couldn't allocate argument space");
602 	p->p_vmspace->vm_maxsaddr = (caddr_t)addr;
603 	p->p_vmspace->vm_ssize = 1;
604 
605 	for (pathp = &initpaths[0]; (path = *pathp) != NULL; pathp++) {
606 		/*
607 		 * Move out the boot flag argument.
608 		 */
609 		options = 0;
610 		ucp = (char *)USRSTACK;
611 		(void)subyte(--ucp, 0);		/* trailing zero */
612 		if (boothowto & RB_SINGLE) {
613 			(void)subyte(--ucp, 's');
614 			options = 1;
615 		}
616 #ifdef notyet
617                 if (boothowto & RB_FASTBOOT) {
618 			(void)subyte(--ucp, 'f');
619 			options = 1;
620 		}
621 #endif
622 
623 #ifdef BOOTCDROM
624 		(void)subyte(--ucp, 'C');
625 		options = 1;
626 #endif
627 
628 #if defined(DEVFS) && defined(DEVFS_ROOT)
629 		(void)subyte(--ucp, 'd');
630 		options = 1;
631 #endif
632 		if (options == 0)
633 			(void)subyte(--ucp, '-');
634 		(void)subyte(--ucp, '-');		/* leading hyphen */
635 		arg1 = ucp;
636 
637 		/*
638 		 * Move out the file name (also arg 0).
639 		 */
640 		for (i = strlen(path) + 1; i >= 0; i--)
641 			(void)subyte(--ucp, path[i]);
642 		arg0 = ucp;
643 
644 		/*
645 		 * Move out the arg pointers.
646 		 */
647 		uap = (char **)((int)ucp & ~(NBPW-1));
648 		(void)suword((caddr_t)--uap, 0);	/* terminator */
649 		(void)suword((caddr_t)--uap, (int)arg1);
650 		(void)suword((caddr_t)--uap, (int)arg0);
651 
652 		/*
653 		 * Point at the arguments.
654 		 */
655 		args.fname = arg0;
656 		args.argv = uap;
657 		args.envv = NULL;
658 
659 		/*
660 		 * Now try to exec the program.  If can't for any reason
661 		 * other than it doesn't exist, complain.
662 		 *
663 		 * Otherwise return to main() which returns to btext
664 		 * which completes the system startup.
665 		 */
666 		if ((error = execve(p, &args, &retval[0])) == 0)
667 			return;
668 		if (error != ENOENT)
669 			printf("exec %s: error %d\n", path, error);
670 	}
671 	printf("init: not found\n");
672 	panic("no init");
673 }
674