FreeBSD/Linux Kernel Cross Reference
sys/kern/kern_fork.c
1 /*-
2 * Copyright (c) 1982, 1986, 1989, 1991, 1993
3 * The Regents of the University of California. All rights reserved.
4 * (c) UNIX System Laboratories, Inc.
5 * All or some portions of this file are derived from material licensed
6 * to the University of California by American Telephone and Telegraph
7 * Co. or Unix System Laboratories, Inc. and are reproduced herein with
8 * the permission of UNIX System Laboratories, Inc.
9 *
10 * Redistribution and use in source and binary forms, with or without
11 * modification, are permitted provided that the following conditions
12 * are met:
13 * 1. Redistributions of source code must retain the above copyright
14 * notice, this list of conditions and the following disclaimer.
15 * 2. Redistributions in binary form must reproduce the above copyright
16 * notice, this list of conditions and the following disclaimer in the
17 * documentation and/or other materials provided with the distribution.
18 * 4. Neither the name of the University nor the names of its contributors
19 * may be used to endorse or promote products derived from this software
20 * without specific prior written permission.
21 *
22 * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
23 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
24 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
25 * ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
26 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
27 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
28 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
29 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
30 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
31 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
32 * SUCH DAMAGE.
33 *
34 * @(#)kern_fork.c 8.6 (Berkeley) 4/8/94
35 */
36
37 #include <sys/cdefs.h>
38 __FBSDID("$FreeBSD: src/sys/kern/kern_fork.c,v 1.295 2008/07/23 08:45:25 kib Exp $");
39
40 #include "opt_kdtrace.h"
41 #include "opt_ktrace.h"
42 #include "opt_mac.h"
43
44 #include <sys/param.h>
45 #include <sys/systm.h>
46 #include <sys/sysproto.h>
47 #include <sys/eventhandler.h>
48 #include <sys/filedesc.h>
49 #include <sys/kernel.h>
50 #include <sys/kthread.h>
51 #include <sys/sysctl.h>
52 #include <sys/lock.h>
53 #include <sys/malloc.h>
54 #include <sys/mutex.h>
55 #include <sys/priv.h>
56 #include <sys/proc.h>
57 #include <sys/pioctl.h>
58 #include <sys/resourcevar.h>
59 #include <sys/sched.h>
60 #include <sys/syscall.h>
61 #include <sys/vmmeter.h>
62 #include <sys/vnode.h>
63 #include <sys/acct.h>
64 #include <sys/ktr.h>
65 #include <sys/ktrace.h>
66 #include <sys/unistd.h>
67 #include <sys/sdt.h>
68 #include <sys/sx.h>
69 #include <sys/signalvar.h>
70
71 #include <security/audit/audit.h>
72 #include <security/mac/mac_framework.h>
73
74 #include <vm/vm.h>
75 #include <vm/pmap.h>
76 #include <vm/vm_map.h>
77 #include <vm/vm_extern.h>
78 #include <vm/uma.h>
79
80 #ifdef KDTRACE_HOOKS
81 #include <sys/dtrace_bsd.h>
82 dtrace_fork_func_t dtrace_fasttrap_fork;
83 #endif
84
85 SDT_PROVIDER_DECLARE(proc);
86 SDT_PROBE_DEFINE(proc, kernel, , create);
87 SDT_PROBE_ARGTYPE(proc, kernel, , create, 0, "struct proc *");
88 SDT_PROBE_ARGTYPE(proc, kernel, , create, 1, "struct proc *");
89 SDT_PROBE_ARGTYPE(proc, kernel, , create, 2, "int");
90
91 #ifndef _SYS_SYSPROTO_H_
92 struct fork_args {
93 int dummy;
94 };
95 #endif
96
97 /* ARGSUSED */
98 int
99 fork(td, uap)
100 struct thread *td;
101 struct fork_args *uap;
102 {
103 int error;
104 struct proc *p2;
105
106 error = fork1(td, RFFDG | RFPROC, 0, &p2);
107 if (error == 0) {
108 td->td_retval[0] = p2->p_pid;
109 td->td_retval[1] = 0;
110 }
111 return (error);
112 }
113
114 /* ARGSUSED */
115 int
116 vfork(td, uap)
117 struct thread *td;
118 struct vfork_args *uap;
119 {
120 int error;
121 struct proc *p2;
122
123 error = fork1(td, RFFDG | RFPROC | RFPPWAIT | RFMEM, 0, &p2);
124 if (error == 0) {
125 td->td_retval[0] = p2->p_pid;
126 td->td_retval[1] = 0;
127 }
128 return (error);
129 }
130
131 int
132 rfork(td, uap)
133 struct thread *td;
134 struct rfork_args *uap;
135 {
136 struct proc *p2;
137 int error;
138
139 /* Don't allow kernel-only flags. */
140 if ((uap->flags & RFKERNELONLY) != 0)
141 return (EINVAL);
142
143 AUDIT_ARG(fflags, uap->flags);
144 error = fork1(td, uap->flags, 0, &p2);
145 if (error == 0) {
146 td->td_retval[0] = p2 ? p2->p_pid : 0;
147 td->td_retval[1] = 0;
148 }
149 return (error);
150 }
151
152 int nprocs = 1; /* process 0 */
153 int lastpid = 0;
154 SYSCTL_INT(_kern, OID_AUTO, lastpid, CTLFLAG_RD, &lastpid, 0,
155 "Last used PID");
156
157 /*
158 * Random component to lastpid generation. We mix in a random factor to make
159 * it a little harder to predict. We sanity check the modulus value to avoid
160 * doing it in critical paths. Don't let it be too small or we pointlessly
161 * waste randomness entropy, and don't let it be impossibly large. Using a
162 * modulus that is too big causes a LOT more process table scans and slows
163 * down fork processing as the pidchecked caching is defeated.
164 */
165 static int randompid = 0;
166
167 static int
168 sysctl_kern_randompid(SYSCTL_HANDLER_ARGS)
169 {
170 int error, pid;
171
172 error = sysctl_wire_old_buffer(req, sizeof(int));
173 if (error != 0)
174 return(error);
175 sx_xlock(&allproc_lock);
176 pid = randompid;
177 error = sysctl_handle_int(oidp, &pid, 0, req);
178 if (error == 0 && req->newptr != NULL) {
179 if (pid < 0 || pid > PID_MAX - 100) /* out of range */
180 pid = PID_MAX - 100;
181 else if (pid < 2) /* NOP */
182 pid = 0;
183 else if (pid < 100) /* Make it reasonable */
184 pid = 100;
185 randompid = pid;
186 }
187 sx_xunlock(&allproc_lock);
188 return (error);
189 }
190
191 SYSCTL_PROC(_kern, OID_AUTO, randompid, CTLTYPE_INT|CTLFLAG_RW,
192 0, 0, sysctl_kern_randompid, "I", "Random PID modulus");
193
194 int
195 fork1(td, flags, pages, procp)
196 struct thread *td;
197 int flags;
198 int pages;
199 struct proc **procp;
200 {
201 struct proc *p1, *p2, *pptr;
202 struct proc *newproc;
203 int ok, trypid;
204 static int curfail, pidchecked = 0;
205 static struct timeval lastfail;
206 struct filedesc *fd;
207 struct filedesc_to_leader *fdtol;
208 struct thread *td2;
209 struct sigacts *newsigacts;
210 struct vmspace *vm2;
211 int error;
212
213 /* Can't copy and clear. */
214 if ((flags & (RFFDG|RFCFDG)) == (RFFDG|RFCFDG))
215 return (EINVAL);
216
217 p1 = td->td_proc;
218
219 /*
220 * Here we don't create a new process, but we divorce
221 * certain parts of a process from itself.
222 */
223 if ((flags & RFPROC) == 0) {
224 if (((p1->p_flag & (P_HADTHREADS|P_SYSTEM)) == P_HADTHREADS) &&
225 (flags & (RFCFDG | RFFDG))) {
226 PROC_LOCK(p1);
227 if (thread_single(SINGLE_BOUNDARY)) {
228 PROC_UNLOCK(p1);
229 return (ERESTART);
230 }
231 PROC_UNLOCK(p1);
232 }
233
234 error = vm_forkproc(td, NULL, NULL, NULL, flags);
235 if (error)
236 goto norfproc_fail;
237
238 /*
239 * Close all file descriptors.
240 */
241 if (flags & RFCFDG) {
242 struct filedesc *fdtmp;
243 fdtmp = fdinit(td->td_proc->p_fd);
244 fdfree(td);
245 p1->p_fd = fdtmp;
246 }
247
248 /*
249 * Unshare file descriptors (from parent).
250 */
251 if (flags & RFFDG)
252 fdunshare(p1, td);
253
254 norfproc_fail:
255 if (((p1->p_flag & (P_HADTHREADS|P_SYSTEM)) == P_HADTHREADS) &&
256 (flags & (RFCFDG | RFFDG))) {
257 PROC_LOCK(p1);
258 thread_single_end();
259 PROC_UNLOCK(p1);
260 }
261 *procp = NULL;
262 return (error);
263 }
264
265 /*
266 * XXX
267 * We did have single-threading code here
268 * however it proved un-needed and caused problems
269 */
270
271 vm2 = NULL;
272 /* Allocate new proc. */
273 newproc = uma_zalloc(proc_zone, M_WAITOK);
274 if (TAILQ_EMPTY(&newproc->p_threads)) {
275 td2 = thread_alloc();
276 if (td2 == NULL) {
277 error = ENOMEM;
278 goto fail1;
279 }
280 proc_linkup(newproc, td2);
281 } else
282 td2 = FIRST_THREAD_IN_PROC(newproc);
283
284 /* Allocate and switch to an alternate kstack if specified. */
285 if (pages != 0) {
286 if (!vm_thread_new_altkstack(td2, pages)) {
287 error = ENOMEM;
288 goto fail1;
289 }
290 }
291 if ((flags & RFMEM) == 0) {
292 vm2 = vmspace_fork(p1->p_vmspace);
293 if (vm2 == NULL) {
294 error = ENOMEM;
295 goto fail1;
296 }
297 }
298 #ifdef MAC
299 mac_proc_init(newproc);
300 #endif
301 knlist_init(&newproc->p_klist, &newproc->p_mtx, NULL, NULL, NULL);
302 STAILQ_INIT(&newproc->p_ktr);
303
304 /* We have to lock the process tree while we look for a pid. */
305 sx_slock(&proctree_lock);
306
307 /*
308 * Although process entries are dynamically created, we still keep
309 * a global limit on the maximum number we will create. Don't allow
310 * a nonprivileged user to use the last ten processes; don't let root
311 * exceed the limit. The variable nprocs is the current number of
312 * processes, maxproc is the limit.
313 */
314 sx_xlock(&allproc_lock);
315 if ((nprocs >= maxproc - 10 && priv_check_cred(td->td_ucred,
316 PRIV_MAXPROC, 0) != 0) || nprocs >= maxproc) {
317 error = EAGAIN;
318 goto fail;
319 }
320
321 /*
322 * Increment the count of procs running with this uid. Don't allow
323 * a nonprivileged user to exceed their current limit.
324 *
325 * XXXRW: Can we avoid privilege here if it's not needed?
326 */
327 error = priv_check_cred(td->td_ucred, PRIV_PROC_LIMIT, 0);
328 if (error == 0)
329 ok = chgproccnt(td->td_ucred->cr_ruidinfo, 1, 0);
330 else {
331 PROC_LOCK(p1);
332 ok = chgproccnt(td->td_ucred->cr_ruidinfo, 1,
333 lim_cur(p1, RLIMIT_NPROC));
334 PROC_UNLOCK(p1);
335 }
336 if (!ok) {
337 error = EAGAIN;
338 goto fail;
339 }
340
341 /*
342 * Increment the nprocs resource before blocking can occur. There
343 * are hard-limits as to the number of processes that can run.
344 */
345 nprocs++;
346
347 /*
348 * Find an unused process ID. We remember a range of unused IDs
349 * ready to use (from lastpid+1 through pidchecked-1).
350 *
351 * If RFHIGHPID is set (used during system boot), do not allocate
352 * low-numbered pids.
353 */
354 trypid = lastpid + 1;
355 if (flags & RFHIGHPID) {
356 if (trypid < 10)
357 trypid = 10;
358 } else {
359 if (randompid)
360 trypid += arc4random() % randompid;
361 }
362 retry:
363 /*
364 * If the process ID prototype has wrapped around,
365 * restart somewhat above 0, as the low-numbered procs
366 * tend to include daemons that don't exit.
367 */
368 if (trypid >= PID_MAX) {
369 trypid = trypid % PID_MAX;
370 if (trypid < 100)
371 trypid += 100;
372 pidchecked = 0;
373 }
374 if (trypid >= pidchecked) {
375 int doingzomb = 0;
376
377 pidchecked = PID_MAX;
378 /*
379 * Scan the active and zombie procs to check whether this pid
380 * is in use. Remember the lowest pid that's greater
381 * than trypid, so we can avoid checking for a while.
382 */
383 p2 = LIST_FIRST(&allproc);
384 again:
385 for (; p2 != NULL; p2 = LIST_NEXT(p2, p_list)) {
386 while (p2->p_pid == trypid ||
387 (p2->p_pgrp != NULL &&
388 (p2->p_pgrp->pg_id == trypid ||
389 (p2->p_session != NULL &&
390 p2->p_session->s_sid == trypid)))) {
391 trypid++;
392 if (trypid >= pidchecked)
393 goto retry;
394 }
395 if (p2->p_pid > trypid && pidchecked > p2->p_pid)
396 pidchecked = p2->p_pid;
397 if (p2->p_pgrp != NULL) {
398 if (p2->p_pgrp->pg_id > trypid &&
399 pidchecked > p2->p_pgrp->pg_id)
400 pidchecked = p2->p_pgrp->pg_id;
401 if (p2->p_session != NULL &&
402 p2->p_session->s_sid > trypid &&
403 pidchecked > p2->p_session->s_sid)
404 pidchecked = p2->p_session->s_sid;
405 }
406 }
407 if (!doingzomb) {
408 doingzomb = 1;
409 p2 = LIST_FIRST(&zombproc);
410 goto again;
411 }
412 }
413 sx_sunlock(&proctree_lock);
414
415 /*
416 * RFHIGHPID does not mess with the lastpid counter during boot.
417 */
418 if (flags & RFHIGHPID)
419 pidchecked = 0;
420 else
421 lastpid = trypid;
422
423 p2 = newproc;
424 p2->p_state = PRS_NEW; /* protect against others */
425 p2->p_pid = trypid;
426 /*
427 * Allow the scheduler to initialize the child.
428 */
429 thread_lock(td);
430 sched_fork(td, td2);
431 thread_unlock(td);
432 AUDIT_ARG(pid, p2->p_pid);
433 LIST_INSERT_HEAD(&allproc, p2, p_list);
434 LIST_INSERT_HEAD(PIDHASH(p2->p_pid), p2, p_hash);
435
436 PROC_LOCK(p2);
437 PROC_LOCK(p1);
438
439 sx_xunlock(&allproc_lock);
440
441 bcopy(&p1->p_startcopy, &p2->p_startcopy,
442 __rangeof(struct proc, p_startcopy, p_endcopy));
443 pargs_hold(p2->p_args);
444 PROC_UNLOCK(p1);
445
446 bzero(&p2->p_startzero,
447 __rangeof(struct proc, p_startzero, p_endzero));
448
449 p2->p_ucred = crhold(td->td_ucred);
450 PROC_UNLOCK(p2);
451
452 /*
453 * Malloc things while we don't hold any locks.
454 */
455 if (flags & RFSIGSHARE)
456 newsigacts = NULL;
457 else
458 newsigacts = sigacts_alloc();
459
460 /*
461 * Copy filedesc.
462 */
463 if (flags & RFCFDG) {
464 fd = fdinit(p1->p_fd);
465 fdtol = NULL;
466 } else if (flags & RFFDG) {
467 fd = fdcopy(p1->p_fd);
468 fdtol = NULL;
469 } else {
470 fd = fdshare(p1->p_fd);
471 if (p1->p_fdtol == NULL)
472 p1->p_fdtol =
473 filedesc_to_leader_alloc(NULL,
474 NULL,
475 p1->p_leader);
476 if ((flags & RFTHREAD) != 0) {
477 /*
478 * Shared file descriptor table and
479 * shared process leaders.
480 */
481 fdtol = p1->p_fdtol;
482 FILEDESC_XLOCK(p1->p_fd);
483 fdtol->fdl_refcount++;
484 FILEDESC_XUNLOCK(p1->p_fd);
485 } else {
486 /*
487 * Shared file descriptor table, and
488 * different process leaders
489 */
490 fdtol = filedesc_to_leader_alloc(p1->p_fdtol,
491 p1->p_fd,
492 p2);
493 }
494 }
495 /*
496 * Make a proc table entry for the new process.
497 * Start by zeroing the section of proc that is zero-initialized,
498 * then copy the section that is copied directly from the parent.
499 */
500
501 PROC_LOCK(p2);
502 PROC_LOCK(p1);
503
504 bzero(&td2->td_startzero,
505 __rangeof(struct thread, td_startzero, td_endzero));
506
507 bcopy(&td->td_startcopy, &td2->td_startcopy,
508 __rangeof(struct thread, td_startcopy, td_endcopy));
509
510 bcopy(&p2->p_comm, &td2->td_name, sizeof(td2->td_name));
511 td2->td_sigstk = td->td_sigstk;
512 td2->td_sigmask = td->td_sigmask;
513 td2->td_flags = TDF_INMEM;
514
515 /*
516 * Duplicate sub-structures as needed.
517 * Increase reference counts on shared objects.
518 */
519 p2->p_flag = P_INMEM;
520 p2->p_swtick = ticks;
521 if (p1->p_flag & P_PROFIL)
522 startprofclock(p2);
523 td2->td_ucred = crhold(p2->p_ucred);
524
525 if (flags & RFSIGSHARE) {
526 p2->p_sigacts = sigacts_hold(p1->p_sigacts);
527 } else {
528 sigacts_copy(newsigacts, p1->p_sigacts);
529 p2->p_sigacts = newsigacts;
530 }
531 if (flags & RFLINUXTHPN)
532 p2->p_sigparent = SIGUSR1;
533 else
534 p2->p_sigparent = SIGCHLD;
535
536 p2->p_textvp = p1->p_textvp;
537 p2->p_fd = fd;
538 p2->p_fdtol = fdtol;
539
540 /*
541 * p_limit is copy-on-write. Bump its refcount.
542 */
543 lim_fork(p1, p2);
544
545 pstats_fork(p1->p_stats, p2->p_stats);
546
547 PROC_UNLOCK(p1);
548 PROC_UNLOCK(p2);
549
550 /* Bump references to the text vnode (for procfs) */
551 if (p2->p_textvp)
552 vref(p2->p_textvp);
553
554 /*
555 * Set up linkage for kernel based threading.
556 */
557 if ((flags & RFTHREAD) != 0) {
558 mtx_lock(&ppeers_lock);
559 p2->p_peers = p1->p_peers;
560 p1->p_peers = p2;
561 p2->p_leader = p1->p_leader;
562 mtx_unlock(&ppeers_lock);
563 PROC_LOCK(p1->p_leader);
564 if ((p1->p_leader->p_flag & P_WEXIT) != 0) {
565 PROC_UNLOCK(p1->p_leader);
566 /*
567 * The task leader is exiting, so process p1 is
568 * going to be killed shortly. Since p1 obviously
569 * isn't dead yet, we know that the leader is either
570 * sending SIGKILL's to all the processes in this
571 * task or is sleeping waiting for all the peers to
572 * exit. We let p1 complete the fork, but we need
573 * to go ahead and kill the new process p2 since
574 * the task leader may not get a chance to send
575 * SIGKILL to it. We leave it on the list so that
576 * the task leader will wait for this new process
577 * to commit suicide.
578 */
579 PROC_LOCK(p2);
580 psignal(p2, SIGKILL);
581 PROC_UNLOCK(p2);
582 } else
583 PROC_UNLOCK(p1->p_leader);
584 } else {
585 p2->p_peers = NULL;
586 p2->p_leader = p2;
587 }
588
589 sx_xlock(&proctree_lock);
590 PGRP_LOCK(p1->p_pgrp);
591 PROC_LOCK(p2);
592 PROC_LOCK(p1);
593
594 /*
595 * Preserve some more flags in subprocess. P_PROFIL has already
596 * been preserved.
597 */
598 p2->p_flag |= p1->p_flag & P_SUGID;
599 td2->td_pflags |= td->td_pflags & TDP_ALTSTACK;
600 SESS_LOCK(p1->p_session);
601 if (p1->p_session->s_ttyvp != NULL && p1->p_flag & P_CONTROLT)
602 p2->p_flag |= P_CONTROLT;
603 SESS_UNLOCK(p1->p_session);
604 if (flags & RFPPWAIT)
605 p2->p_flag |= P_PPWAIT;
606
607 p2->p_pgrp = p1->p_pgrp;
608 LIST_INSERT_AFTER(p1, p2, p_pglist);
609 PGRP_UNLOCK(p1->p_pgrp);
610 LIST_INIT(&p2->p_children);
611
612 callout_init(&p2->p_itcallout, CALLOUT_MPSAFE);
613
614 #ifdef KTRACE
615 /*
616 * Copy traceflag and tracefile if enabled.
617 */
618 mtx_lock(&ktrace_mtx);
619 KASSERT(p2->p_tracevp == NULL, ("new process has a ktrace vnode"));
620 if (p1->p_traceflag & KTRFAC_INHERIT) {
621 p2->p_traceflag = p1->p_traceflag;
622 if ((p2->p_tracevp = p1->p_tracevp) != NULL) {
623 VREF(p2->p_tracevp);
624 KASSERT(p1->p_tracecred != NULL,
625 ("ktrace vnode with no cred"));
626 p2->p_tracecred = crhold(p1->p_tracecred);
627 }
628 }
629 mtx_unlock(&ktrace_mtx);
630 #endif
631
632 /*
633 * If PF_FORK is set, the child process inherits the
634 * procfs ioctl flags from its parent.
635 */
636 if (p1->p_pfsflags & PF_FORK) {
637 p2->p_stops = p1->p_stops;
638 p2->p_pfsflags = p1->p_pfsflags;
639 }
640
641 #ifdef KDTRACE_HOOKS
642 /*
643 * Tell the DTrace fasttrap provider about the new process
644 * if it has registered an interest.
645 */
646 if (dtrace_fasttrap_fork)
647 dtrace_fasttrap_fork(p1, p2);
648 #endif
649
650 /*
651 * This begins the section where we must prevent the parent
652 * from being swapped.
653 */
654 _PHOLD(p1);
655 PROC_UNLOCK(p1);
656
657 /*
658 * Attach the new process to its parent.
659 *
660 * If RFNOWAIT is set, the newly created process becomes a child
661 * of init. This effectively disassociates the child from the
662 * parent.
663 */
664 if (flags & RFNOWAIT)
665 pptr = initproc;
666 else
667 pptr = p1;
668 p2->p_pptr = pptr;
669 LIST_INSERT_HEAD(&pptr->p_children, p2, p_sibling);
670 sx_xunlock(&proctree_lock);
671
672 /* Inform accounting that we have forked. */
673 p2->p_acflag = AFORK;
674 PROC_UNLOCK(p2);
675
676 /*
677 * Finish creating the child process. It will return via a different
678 * execution path later. (ie: directly into user mode)
679 */
680 vm_forkproc(td, p2, td2, vm2, flags);
681
682 if (flags == (RFFDG | RFPROC)) {
683 PCPU_INC(cnt.v_forks);
684 PCPU_ADD(cnt.v_forkpages, p2->p_vmspace->vm_dsize +
685 p2->p_vmspace->vm_ssize);
686 } else if (flags == (RFFDG | RFPROC | RFPPWAIT | RFMEM)) {
687 PCPU_INC(cnt.v_vforks);
688 PCPU_ADD(cnt.v_vforkpages, p2->p_vmspace->vm_dsize +
689 p2->p_vmspace->vm_ssize);
690 } else if (p1 == &proc0) {
691 PCPU_INC(cnt.v_kthreads);
692 PCPU_ADD(cnt.v_kthreadpages, p2->p_vmspace->vm_dsize +
693 p2->p_vmspace->vm_ssize);
694 } else {
695 PCPU_INC(cnt.v_rforks);
696 PCPU_ADD(cnt.v_rforkpages, p2->p_vmspace->vm_dsize +
697 p2->p_vmspace->vm_ssize);
698 }
699
700 /*
701 * Both processes are set up, now check if any loadable modules want
702 * to adjust anything.
703 * What if they have an error? XXX
704 */
705 EVENTHANDLER_INVOKE(process_fork, p1, p2, flags);
706
707 /*
708 * Set the child start time and mark the process as being complete.
709 */
710 microuptime(&p2->p_stats->p_start);
711 PROC_SLOCK(p2);
712 p2->p_state = PRS_NORMAL;
713 PROC_SUNLOCK(p2);
714
715 /*
716 * If RFSTOPPED not requested, make child runnable and add to
717 * run queue.
718 */
719 if ((flags & RFSTOPPED) == 0) {
720 thread_lock(td2);
721 TD_SET_CAN_RUN(td2);
722 sched_add(td2, SRQ_BORING);
723 thread_unlock(td2);
724 }
725
726 /*
727 * Now can be swapped.
728 */
729 PROC_LOCK(p1);
730 _PRELE(p1);
731 PROC_UNLOCK(p1);
732
733 /*
734 * Tell any interested parties about the new process.
735 */
736 knote_fork(&p1->p_klist, p2->p_pid);
737 SDT_PROBE(proc, kernel, , create, p2, p1, flags, 0, 0);
738
739 /*
740 * Preserve synchronization semantics of vfork. If waiting for
741 * child to exec or exit, set P_PPWAIT on child, and sleep on our
742 * proc (in case of exit).
743 */
744 PROC_LOCK(p2);
745 while (p2->p_flag & P_PPWAIT)
746 msleep(p1, &p2->p_mtx, PWAIT, "ppwait", 0);
747 PROC_UNLOCK(p2);
748
749 /*
750 * Return child proc pointer to parent.
751 */
752 *procp = p2;
753 return (0);
754 fail:
755 sx_sunlock(&proctree_lock);
756 if (ppsratecheck(&lastfail, &curfail, 1))
757 printf("maxproc limit exceeded by uid %i, please see tuning(7) and login.conf(5).\n",
758 td->td_ucred->cr_ruid);
759 sx_xunlock(&allproc_lock);
760 #ifdef MAC
761 mac_proc_destroy(newproc);
762 #endif
763 fail1:
764 if (vm2 != NULL)
765 vmspace_free(vm2);
766 uma_zfree(proc_zone, newproc);
767 pause("fork", hz / 2);
768 return (error);
769 }
770
771 /*
772 * Handle the return of a child process from fork1(). This function
773 * is called from the MD fork_trampoline() entry point.
774 */
775 void
776 fork_exit(callout, arg, frame)
777 void (*callout)(void *, struct trapframe *);
778 void *arg;
779 struct trapframe *frame;
780 {
781 struct proc *p;
782 struct thread *td;
783 struct thread *dtd;
784
785 td = curthread;
786 p = td->td_proc;
787 KASSERT(p->p_state == PRS_NORMAL, ("executing process is still new"));
788
789 CTR4(KTR_PROC, "fork_exit: new thread %p (td_sched %p, pid %d, %s)",
790 td, td->td_sched, p->p_pid, td->td_name);
791
792 sched_fork_exit(td);
793 /*
794 * Processes normally resume in mi_switch() after being
795 * cpu_switch()'ed to, but when children start up they arrive here
796 * instead, so we must do much the same things as mi_switch() would.
797 */
798 if ((dtd = PCPU_GET(deadthread))) {
799 PCPU_SET(deadthread, NULL);
800 thread_stash(dtd);
801 }
802 thread_unlock(td);
803
804 /*
805 * cpu_set_fork_handler intercepts this function call to
806 * have this call a non-return function to stay in kernel mode.
807 * initproc has its own fork handler, but it does return.
808 */
809 KASSERT(callout != NULL, ("NULL callout in fork_exit"));
810 callout(arg, frame);
811
812 /*
813 * Check if a kernel thread misbehaved and returned from its main
814 * function.
815 */
816 if (p->p_flag & P_KTHREAD) {
817 printf("Kernel thread \"%s\" (pid %d) exited prematurely.\n",
818 td->td_name, p->p_pid);
819 kproc_exit(0);
820 }
821 mtx_assert(&Giant, MA_NOTOWNED);
822
823 EVENTHANDLER_INVOKE(schedtail, p);
824 }
825
826 /*
827 * Simplified back end of syscall(), used when returning from fork()
828 * directly into user mode. Giant is not held on entry, and must not
829 * be held on return. This function is passed in to fork_exit() as the
830 * first parameter and is called when returning to a new userland process.
831 */
832 void
833 fork_return(td, frame)
834 struct thread *td;
835 struct trapframe *frame;
836 {
837
838 userret(td, frame);
839 #ifdef KTRACE
840 if (KTRPOINT(td, KTR_SYSRET))
841 ktrsysret(SYS_fork, 0, 0);
842 #endif
843 mtx_assert(&Giant, MA_NOTOWNED);
844 }
845
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