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: releng/6.4/sys/kern/kern_fork.c 197715 2009-10-02 18:09:56Z simon $");
39
40 #include "opt_ktrace.h"
41 #include "opt_mac.h"
42
43 #include <sys/param.h>
44 #include <sys/systm.h>
45 #include <sys/sysproto.h>
46 #include <sys/eventhandler.h>
47 #include <sys/filedesc.h>
48 #include <sys/kernel.h>
49 #include <sys/kthread.h>
50 #include <sys/sysctl.h>
51 #include <sys/lock.h>
52 #include <sys/malloc.h>
53 #include <sys/mutex.h>
54 #include <sys/proc.h>
55 #include <sys/pioctl.h>
56 #include <sys/resourcevar.h>
57 #include <sys/sched.h>
58 #include <sys/syscall.h>
59 #include <sys/vmmeter.h>
60 #include <sys/vnode.h>
61 #include <sys/acct.h>
62 #include <sys/mac.h>
63 #include <sys/ktr.h>
64 #include <sys/ktrace.h>
65 #include <sys/unistd.h>
66 #include <sys/sx.h>
67 #include <sys/signalvar.h>
68
69 #include <security/audit/audit.h>
70
71 #include <vm/vm.h>
72 #include <vm/pmap.h>
73 #include <vm/vm_map.h>
74 #include <vm/vm_extern.h>
75 #include <vm/uma.h>
76
77
78 #ifndef _SYS_SYSPROTO_H_
79 struct fork_args {
80 int dummy;
81 };
82 #endif
83
84 static int forksleep; /* Place for fork1() to sleep on. */
85
86 /*
87 * MPSAFE
88 */
89 /* ARGSUSED */
90 int
91 fork(td, uap)
92 struct thread *td;
93 struct fork_args *uap;
94 {
95 int error;
96 struct proc *p2;
97
98 error = fork1(td, RFFDG | RFPROC, 0, &p2);
99 if (error == 0) {
100 td->td_retval[0] = p2->p_pid;
101 td->td_retval[1] = 0;
102 }
103 return (error);
104 }
105
106 /*
107 * MPSAFE
108 */
109 /* ARGSUSED */
110 int
111 vfork(td, uap)
112 struct thread *td;
113 struct vfork_args *uap;
114 {
115 int error;
116 struct proc *p2;
117
118 error = fork1(td, RFFDG | RFPROC | RFPPWAIT | RFMEM, 0, &p2);
119 if (error == 0) {
120 td->td_retval[0] = p2->p_pid;
121 td->td_retval[1] = 0;
122 }
123 return (error);
124 }
125
126 /*
127 * MPSAFE
128 */
129 int
130 rfork(td, uap)
131 struct thread *td;
132 struct rfork_args *uap;
133 {
134 struct proc *p2;
135 int error;
136
137 /* Don't allow kernel-only flags. */
138 if ((uap->flags & RFKERNELONLY) != 0)
139 return (EINVAL);
140
141 AUDIT_ARG(fflags, uap->flags);
142 error = fork1(td, uap->flags, 0, &p2);
143 if (error == 0) {
144 td->td_retval[0] = p2 ? p2->p_pid : 0;
145 td->td_retval[1] = 0;
146 }
147 return (error);
148 }
149
150 int nprocs = 1; /* process 0 */
151 int lastpid = 0;
152 SYSCTL_INT(_kern, OID_AUTO, lastpid, CTLFLAG_RD, &lastpid, 0,
153 "Last used PID");
154
155 /*
156 * Random component to lastpid generation. We mix in a random factor to make
157 * it a little harder to predict. We sanity check the modulus value to avoid
158 * doing it in critical paths. Don't let it be too small or we pointlessly
159 * waste randomness entropy, and don't let it be impossibly large. Using a
160 * modulus that is too big causes a LOT more process table scans and slows
161 * down fork processing as the pidchecked caching is defeated.
162 */
163 static int randompid = 0;
164
165 static int
166 sysctl_kern_randompid(SYSCTL_HANDLER_ARGS)
167 {
168 int error, pid;
169
170 error = sysctl_wire_old_buffer(req, sizeof(int));
171 if (error != 0)
172 return(error);
173 sx_xlock(&allproc_lock);
174 pid = randompid;
175 error = sysctl_handle_int(oidp, &pid, 0, req);
176 if (error == 0 && req->newptr != NULL) {
177 if (pid < 0 || pid > PID_MAX - 100) /* out of range */
178 pid = PID_MAX - 100;
179 else if (pid < 2) /* NOP */
180 pid = 0;
181 else if (pid < 100) /* Make it reasonable */
182 pid = 100;
183 randompid = pid;
184 }
185 sx_xunlock(&allproc_lock);
186 return (error);
187 }
188
189 SYSCTL_PROC(_kern, OID_AUTO, randompid, CTLTYPE_INT|CTLFLAG_RW,
190 0, 0, sysctl_kern_randompid, "I", "Random PID modulus");
191
192 int
193 fork1(td, flags, pages, procp)
194 struct thread *td;
195 int flags;
196 int pages;
197 struct proc **procp;
198 {
199 struct proc *p1, *p2, *pptr;
200 struct proc *newproc;
201 int ok, trypid;
202 static int curfail, pidchecked = 0;
203 static struct timeval lastfail;
204 struct filedesc *fd;
205 struct filedesc_to_leader *fdtol;
206 struct thread *td2;
207 struct ksegrp *kg2;
208 struct sigacts *newsigacts;
209 int error;
210
211 /* Can't copy and clear. */
212 if ((flags & (RFFDG|RFCFDG)) == (RFFDG|RFCFDG))
213 return (EINVAL);
214
215 p1 = td->td_proc;
216
217 /*
218 * Here we don't create a new process, but we divorce
219 * certain parts of a process from itself.
220 */
221 if ((flags & RFPROC) == 0) {
222 if ((p1->p_flag & P_HADTHREADS) &&
223 (flags & (RFCFDG | RFFDG))) {
224 PROC_LOCK(p1);
225 if (thread_single(SINGLE_BOUNDARY)) {
226 PROC_UNLOCK(p1);
227 return (ERESTART);
228 }
229 PROC_UNLOCK(p1);
230 }
231
232 vm_forkproc(td, NULL, NULL, flags);
233 /*
234 * Close all file descriptors.
235 */
236 if (flags & RFCFDG) {
237 struct filedesc *fdtmp;
238 fdtmp = fdinit(td->td_proc->p_fd);
239 fdfree(td);
240 p1->p_fd = fdtmp;
241 }
242
243 /*
244 * Unshare file descriptors (from parent).
245 */
246 if (flags & RFFDG)
247 fdunshare(p1, td);
248
249 if ((p1->p_flag & P_HADTHREADS) &&
250 (flags & (RFCFDG | RFFDG))) {
251 PROC_LOCK(p1);
252 thread_single_end();
253 PROC_UNLOCK(p1);
254 }
255 *procp = NULL;
256 return (0);
257 }
258
259 /* Allocate new proc. */
260 newproc = uma_zalloc(proc_zone, M_WAITOK);
261 #ifdef MAC
262 mac_init_proc(newproc);
263 #endif
264 #ifdef AUDIT
265 audit_proc_alloc(newproc);
266 #endif
267 knlist_init(&newproc->p_klist, &newproc->p_mtx, NULL, NULL, NULL);
268 STAILQ_INIT(&newproc->p_ktr);
269
270 /* We have to lock the process tree while we look for a pid. */
271 sx_slock(&proctree_lock);
272
273 /*
274 * Although process entries are dynamically created, we still keep
275 * a global limit on the maximum number we will create. Don't allow
276 * a nonprivileged user to use the last ten processes; don't let root
277 * exceed the limit. The variable nprocs is the current number of
278 * processes, maxproc is the limit.
279 */
280 sx_xlock(&allproc_lock);
281 if ((nprocs >= maxproc - 10 &&
282 suser_cred(td->td_ucred, SUSER_RUID) != 0) ||
283 nprocs >= maxproc) {
284 error = EAGAIN;
285 goto fail;
286 }
287
288 /*
289 * Increment the count of procs running with this uid. Don't allow
290 * a nonprivileged user to exceed their current limit.
291 */
292 error = suser_cred(td->td_ucred, SUSER_RUID | SUSER_ALLOWJAIL);
293 if (error == 0)
294 ok = chgproccnt(td->td_ucred->cr_ruidinfo, 1, 0);
295 else {
296 PROC_LOCK(p1);
297 ok = chgproccnt(td->td_ucred->cr_ruidinfo, 1,
298 lim_cur(p1, RLIMIT_NPROC));
299 PROC_UNLOCK(p1);
300 }
301 if (!ok) {
302 error = EAGAIN;
303 goto fail;
304 }
305
306 /*
307 * Increment the nprocs resource before blocking can occur. There
308 * are hard-limits as to the number of processes that can run.
309 */
310 nprocs++;
311
312 /*
313 * Find an unused process ID. We remember a range of unused IDs
314 * ready to use (from lastpid+1 through pidchecked-1).
315 *
316 * If RFHIGHPID is set (used during system boot), do not allocate
317 * low-numbered pids.
318 */
319 trypid = lastpid + 1;
320 if (flags & RFHIGHPID) {
321 if (trypid < 10)
322 trypid = 10;
323 } else {
324 if (randompid)
325 trypid += arc4random() % randompid;
326 }
327 retry:
328 /*
329 * If the process ID prototype has wrapped around,
330 * restart somewhat above 0, as the low-numbered procs
331 * tend to include daemons that don't exit.
332 */
333 if (trypid >= PID_MAX) {
334 trypid = trypid % PID_MAX;
335 if (trypid < 100)
336 trypid += 100;
337 pidchecked = 0;
338 }
339 if (trypid >= pidchecked) {
340 int doingzomb = 0;
341
342 pidchecked = PID_MAX;
343 /*
344 * Scan the active and zombie procs to check whether this pid
345 * is in use. Remember the lowest pid that's greater
346 * than trypid, so we can avoid checking for a while.
347 */
348 p2 = LIST_FIRST(&allproc);
349 again:
350 for (; p2 != NULL; p2 = LIST_NEXT(p2, p_list)) {
351 PROC_LOCK(p2);
352 while (p2->p_pid == trypid ||
353 (p2->p_pgrp != NULL &&
354 (p2->p_pgrp->pg_id == trypid ||
355 (p2->p_session != NULL &&
356 p2->p_session->s_sid == trypid)))) {
357 trypid++;
358 if (trypid >= pidchecked) {
359 PROC_UNLOCK(p2);
360 goto retry;
361 }
362 }
363 if (p2->p_pid > trypid && pidchecked > p2->p_pid)
364 pidchecked = p2->p_pid;
365 if (p2->p_pgrp != NULL) {
366 if (p2->p_pgrp->pg_id > trypid &&
367 pidchecked > p2->p_pgrp->pg_id)
368 pidchecked = p2->p_pgrp->pg_id;
369 if (p2->p_session != NULL &&
370 p2->p_session->s_sid > trypid &&
371 pidchecked > p2->p_session->s_sid)
372 pidchecked = p2->p_session->s_sid;
373 }
374 PROC_UNLOCK(p2);
375 }
376 if (!doingzomb) {
377 doingzomb = 1;
378 p2 = LIST_FIRST(&zombproc);
379 goto again;
380 }
381 }
382 sx_sunlock(&proctree_lock);
383
384 /*
385 * RFHIGHPID does not mess with the lastpid counter during boot.
386 */
387 if (flags & RFHIGHPID)
388 pidchecked = 0;
389 else
390 lastpid = trypid;
391
392 p2 = newproc;
393 p2->p_state = PRS_NEW; /* protect against others */
394 p2->p_pid = trypid;
395 AUDIT_ARG(pid, p2->p_pid);
396 LIST_INSERT_HEAD(&allproc, p2, p_list);
397 LIST_INSERT_HEAD(PIDHASH(p2->p_pid), p2, p_hash);
398
399 PROC_LOCK(p2);
400 PROC_LOCK(p1);
401
402 sx_xunlock(&allproc_lock);
403
404 bcopy(&p1->p_startcopy, &p2->p_startcopy,
405 __rangeof(struct proc, p_startcopy, p_endcopy));
406 PROC_UNLOCK(p1);
407
408 bzero(&p2->p_startzero,
409 __rangeof(struct proc, p_startzero, p_endzero));
410
411 p2->p_ucred = crhold(td->td_ucred);
412 PROC_UNLOCK(p2);
413
414 /*
415 * Malloc things while we don't hold any locks.
416 */
417 if (flags & RFSIGSHARE)
418 newsigacts = NULL;
419 else
420 newsigacts = sigacts_alloc();
421
422 /*
423 * Copy filedesc.
424 */
425 if (flags & RFCFDG) {
426 fd = fdinit(p1->p_fd);
427 fdtol = NULL;
428 } else if (flags & RFFDG) {
429 fd = fdcopy(p1->p_fd);
430 fdtol = NULL;
431 } else {
432 fd = fdshare(p1->p_fd);
433 if (p1->p_fdtol == NULL)
434 p1->p_fdtol =
435 filedesc_to_leader_alloc(NULL,
436 NULL,
437 p1->p_leader);
438 if ((flags & RFTHREAD) != 0) {
439 /*
440 * Shared file descriptor table and
441 * shared process leaders.
442 */
443 fdtol = p1->p_fdtol;
444 FILEDESC_LOCK_FAST(p1->p_fd);
445 fdtol->fdl_refcount++;
446 FILEDESC_UNLOCK_FAST(p1->p_fd);
447 } else {
448 /*
449 * Shared file descriptor table, and
450 * different process leaders
451 */
452 fdtol = filedesc_to_leader_alloc(p1->p_fdtol,
453 p1->p_fd,
454 p2);
455 }
456 }
457 /*
458 * Make a proc table entry for the new process.
459 * Start by zeroing the section of proc that is zero-initialized,
460 * then copy the section that is copied directly from the parent.
461 */
462 td2 = FIRST_THREAD_IN_PROC(p2);
463 kg2 = FIRST_KSEGRP_IN_PROC(p2);
464
465 /* Allocate and switch to an alternate kstack if specified. */
466 if (pages != 0)
467 vm_thread_new_altkstack(td2, pages);
468
469 PROC_LOCK(p2);
470 PROC_LOCK(p1);
471
472 bzero(&td2->td_startzero,
473 __rangeof(struct thread, td_startzero, td_endzero));
474 bzero(&kg2->kg_startzero,
475 __rangeof(struct ksegrp, kg_startzero, kg_endzero));
476
477 bcopy(&td->td_startcopy, &td2->td_startcopy,
478 __rangeof(struct thread, td_startcopy, td_endcopy));
479 bcopy(&td->td_ksegrp->kg_startcopy, &kg2->kg_startcopy,
480 __rangeof(struct ksegrp, kg_startcopy, kg_endcopy));
481
482 td2->td_sigstk = td->td_sigstk;
483 td2->td_sigmask = td->td_sigmask;
484
485 /*
486 * Duplicate sub-structures as needed.
487 * Increase reference counts on shared objects.
488 */
489 p2->p_flag = 0;
490 if (p1->p_flag & P_PROFIL)
491 startprofclock(p2);
492 mtx_lock_spin(&sched_lock);
493 p2->p_sflag = PS_INMEM;
494 /*
495 * Allow the scheduler to adjust the priority of the child and
496 * parent while we hold the sched_lock.
497 */
498 sched_fork(td, td2);
499
500 mtx_unlock_spin(&sched_lock);
501 td2->td_ucred = crhold(p2->p_ucred); /* XXXKSE */
502 #ifdef AUDIT
503 audit_proc_fork(p1, p2);
504 #endif
505 pargs_hold(p2->p_args);
506
507 if (flags & RFSIGSHARE) {
508 p2->p_sigacts = sigacts_hold(p1->p_sigacts);
509 } else {
510 sigacts_copy(newsigacts, p1->p_sigacts);
511 p2->p_sigacts = newsigacts;
512 }
513 if (flags & RFLINUXTHPN)
514 p2->p_sigparent = SIGUSR1;
515 else
516 p2->p_sigparent = SIGCHLD;
517
518 p2->p_textvp = p1->p_textvp;
519 p2->p_fd = fd;
520 p2->p_fdtol = fdtol;
521
522 /*
523 * p_limit is copy-on-write. Bump its refcount.
524 */
525 p2->p_limit = lim_hold(p1->p_limit);
526
527 pstats_fork(p1->p_stats, p2->p_stats);
528
529 PROC_UNLOCK(p1);
530 PROC_UNLOCK(p2);
531
532 /* Bump references to the text vnode (for procfs) */
533 if (p2->p_textvp)
534 vref(p2->p_textvp);
535
536 /*
537 * Set up linkage for kernel based threading.
538 */
539 if ((flags & RFTHREAD) != 0) {
540 mtx_lock(&ppeers_lock);
541 p2->p_peers = p1->p_peers;
542 p1->p_peers = p2;
543 p2->p_leader = p1->p_leader;
544 mtx_unlock(&ppeers_lock);
545 PROC_LOCK(p1->p_leader);
546 if ((p1->p_leader->p_flag & P_WEXIT) != 0) {
547 PROC_UNLOCK(p1->p_leader);
548 /*
549 * The task leader is exiting, so process p1 is
550 * going to be killed shortly. Since p1 obviously
551 * isn't dead yet, we know that the leader is either
552 * sending SIGKILL's to all the processes in this
553 * task or is sleeping waiting for all the peers to
554 * exit. We let p1 complete the fork, but we need
555 * to go ahead and kill the new process p2 since
556 * the task leader may not get a chance to send
557 * SIGKILL to it. We leave it on the list so that
558 * the task leader will wait for this new process
559 * to commit suicide.
560 */
561 PROC_LOCK(p2);
562 psignal(p2, SIGKILL);
563 PROC_UNLOCK(p2);
564 } else
565 PROC_UNLOCK(p1->p_leader);
566 } else {
567 p2->p_peers = NULL;
568 p2->p_leader = p2;
569 }
570
571 sx_xlock(&proctree_lock);
572 PGRP_LOCK(p1->p_pgrp);
573 PROC_LOCK(p2);
574 PROC_LOCK(p1);
575
576 /*
577 * Preserve some more flags in subprocess. P_PROFIL has already
578 * been preserved.
579 */
580 p2->p_flag |= p1->p_flag & P_SUGID;
581 td2->td_pflags |= td->td_pflags & TDP_ALTSTACK;
582 SESS_LOCK(p1->p_session);
583 if (p1->p_session->s_ttyvp != NULL && p1->p_flag & P_CONTROLT)
584 p2->p_flag |= P_CONTROLT;
585 SESS_UNLOCK(p1->p_session);
586 if (flags & RFPPWAIT)
587 p2->p_flag |= P_PPWAIT;
588
589 p2->p_pgrp = p1->p_pgrp;
590 LIST_INSERT_AFTER(p1, p2, p_pglist);
591 PGRP_UNLOCK(p1->p_pgrp);
592 LIST_INIT(&p2->p_children);
593
594 callout_init(&p2->p_itcallout, CALLOUT_MPSAFE);
595
596 #ifdef KTRACE
597 /*
598 * Copy traceflag and tracefile if enabled.
599 */
600 mtx_lock(&ktrace_mtx);
601 KASSERT(p2->p_tracevp == NULL, ("new process has a ktrace vnode"));
602 if (p1->p_traceflag & KTRFAC_INHERIT) {
603 p2->p_traceflag = p1->p_traceflag;
604 if ((p2->p_tracevp = p1->p_tracevp) != NULL) {
605 VREF(p2->p_tracevp);
606 KASSERT(p1->p_tracecred != NULL,
607 ("ktrace vnode with no cred"));
608 p2->p_tracecred = crhold(p1->p_tracecred);
609 }
610 }
611 mtx_unlock(&ktrace_mtx);
612 #endif
613
614 /*
615 * If PF_FORK is set, the child process inherits the
616 * procfs ioctl flags from its parent.
617 */
618 if (p1->p_pfsflags & PF_FORK) {
619 p2->p_stops = p1->p_stops;
620 p2->p_pfsflags = p1->p_pfsflags;
621 }
622
623 /*
624 * This begins the section where we must prevent the parent
625 * from being swapped.
626 */
627 _PHOLD(p1);
628 PROC_UNLOCK(p1);
629
630 /*
631 * Attach the new process to its parent.
632 *
633 * If RFNOWAIT is set, the newly created process becomes a child
634 * of init. This effectively disassociates the child from the
635 * parent.
636 */
637 if (flags & RFNOWAIT)
638 pptr = initproc;
639 else
640 pptr = p1;
641 p2->p_pptr = pptr;
642 LIST_INSERT_HEAD(&pptr->p_children, p2, p_sibling);
643 sx_xunlock(&proctree_lock);
644
645 /* Inform accounting that we have forked. */
646 p2->p_acflag = AFORK;
647 PROC_UNLOCK(p2);
648
649 /*
650 * Finish creating the child process. It will return via a different
651 * execution path later. (ie: directly into user mode)
652 */
653 vm_forkproc(td, p2, td2, flags);
654
655 if (flags == (RFFDG | RFPROC)) {
656 atomic_add_int(&cnt.v_forks, 1);
657 atomic_add_int(&cnt.v_forkpages, p2->p_vmspace->vm_dsize +
658 p2->p_vmspace->vm_ssize);
659 } else if (flags == (RFFDG | RFPROC | RFPPWAIT | RFMEM)) {
660 atomic_add_int(&cnt.v_vforks, 1);
661 atomic_add_int(&cnt.v_vforkpages, p2->p_vmspace->vm_dsize +
662 p2->p_vmspace->vm_ssize);
663 } else if (p1 == &proc0) {
664 atomic_add_int(&cnt.v_kthreads, 1);
665 atomic_add_int(&cnt.v_kthreadpages, p2->p_vmspace->vm_dsize +
666 p2->p_vmspace->vm_ssize);
667 } else {
668 atomic_add_int(&cnt.v_rforks, 1);
669 atomic_add_int(&cnt.v_rforkpages, p2->p_vmspace->vm_dsize +
670 p2->p_vmspace->vm_ssize);
671 }
672
673 /*
674 * Both processes are set up, now check if any loadable modules want
675 * to adjust anything.
676 * What if they have an error? XXX
677 */
678 EVENTHANDLER_INVOKE(process_fork, p1, p2, flags);
679
680 /*
681 * Set the child start time and mark the process as being complete.
682 */
683 microuptime(&p2->p_stats->p_start);
684 mtx_lock_spin(&sched_lock);
685 p2->p_state = PRS_NORMAL;
686
687 /*
688 * If RFSTOPPED not requested, make child runnable and add to
689 * run queue.
690 */
691 if ((flags & RFSTOPPED) == 0) {
692 TD_SET_CAN_RUN(td2);
693 setrunqueue(td2, SRQ_BORING);
694 }
695 mtx_unlock_spin(&sched_lock);
696
697 /*
698 * Now can be swapped.
699 */
700 PROC_LOCK(p1);
701 _PRELE(p1);
702 PROC_UNLOCK(p1);
703
704 /*
705 * Tell any interested parties about the new process.
706 */
707 knote_fork(&p1->p_klist, p2->p_pid);
708 /*
709 * Preserve synchronization semantics of vfork. If waiting for
710 * child to exec or exit, set P_PPWAIT on child, and sleep on our
711 * proc (in case of exit).
712 */
713 PROC_LOCK(p2);
714 while (p2->p_flag & P_PPWAIT)
715 msleep(p1, &p2->p_mtx, PWAIT, "ppwait", 0);
716 PROC_UNLOCK(p2);
717
718 /*
719 * Return child proc pointer to parent.
720 */
721 *procp = p2;
722 return (0);
723 fail:
724 sx_sunlock(&proctree_lock);
725 if (ppsratecheck(&lastfail, &curfail, 1))
726 printf("maxproc limit exceeded by uid %i, please see tuning(7) and login.conf(5).\n",
727 td->td_ucred->cr_ruid);
728 sx_xunlock(&allproc_lock);
729 #ifdef MAC
730 mac_destroy_proc(newproc);
731 #endif
732 #ifdef AUDIT
733 audit_proc_free(newproc);
734 #endif
735 uma_zfree(proc_zone, newproc);
736 tsleep(&forksleep, PUSER, "fork", hz / 2);
737 return (error);
738 }
739
740 /*
741 * Handle the return of a child process from fork1(). This function
742 * is called from the MD fork_trampoline() entry point.
743 */
744 void
745 fork_exit(callout, arg, frame)
746 void (*callout)(void *, struct trapframe *);
747 void *arg;
748 struct trapframe *frame;
749 {
750 struct proc *p;
751 struct thread *td;
752
753 /*
754 * Finish setting up thread glue so that it begins execution in a
755 * non-nested critical section with sched_lock held but not recursed.
756 */
757 td = curthread;
758 p = td->td_proc;
759 td->td_oncpu = PCPU_GET(cpuid);
760 KASSERT(p->p_state == PRS_NORMAL, ("executing process is still new"));
761
762 sched_lock.mtx_lock = (uintptr_t)td;
763 mtx_assert(&sched_lock, MA_OWNED | MA_NOTRECURSED);
764 CTR4(KTR_PROC, "fork_exit: new thread %p (kse %p, pid %d, %s)",
765 td, td->td_sched, p->p_pid, p->p_comm);
766
767 /*
768 * Processes normally resume in mi_switch() after being
769 * cpu_switch()'ed to, but when children start up they arrive here
770 * instead, so we must do much the same things as mi_switch() would.
771 */
772
773 if ((td = PCPU_GET(deadthread))) {
774 PCPU_SET(deadthread, NULL);
775 thread_stash(td);
776 }
777 td = curthread;
778 mtx_unlock_spin(&sched_lock);
779
780 /*
781 * cpu_set_fork_handler intercepts this function call to
782 * have this call a non-return function to stay in kernel mode.
783 * initproc has its own fork handler, but it does return.
784 */
785 KASSERT(callout != NULL, ("NULL callout in fork_exit"));
786 callout(arg, frame);
787
788 /*
789 * Check if a kernel thread misbehaved and returned from its main
790 * function.
791 */
792 PROC_LOCK(p);
793 if (p->p_flag & P_KTHREAD) {
794 PROC_UNLOCK(p);
795 printf("Kernel thread \"%s\" (pid %d) exited prematurely.\n",
796 p->p_comm, p->p_pid);
797 kthread_exit(0);
798 }
799 PROC_UNLOCK(p);
800 mtx_assert(&Giant, MA_NOTOWNED);
801 }
802
803 /*
804 * Simplified back end of syscall(), used when returning from fork()
805 * directly into user mode. Giant is not held on entry, and must not
806 * be held on return. This function is passed in to fork_exit() as the
807 * first parameter and is called when returning to a new userland process.
808 */
809 void
810 fork_return(td, frame)
811 struct thread *td;
812 struct trapframe *frame;
813 {
814
815 userret(td, frame, 0);
816 #ifdef KTRACE
817 if (KTRPOINT(td, KTR_SYSRET))
818 ktrsysret(SYS_fork, 0, 0);
819 #endif
820 mtx_assert(&Giant, MA_NOTOWNED);
821 }
Cache object: cbdd4e6f093b39c0f9514998ca0b36ce
|