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/10.0/sys/kern/kern_fork.c 255708 2013-09-19 18:53:42Z jhb $");
39
40 #include "opt_kdtrace.h"
41 #include "opt_ktrace.h"
42 #include "opt_kstack_pages.h"
43 #include "opt_procdesc.h"
44
45 #include <sys/param.h>
46 #include <sys/systm.h>
47 #include <sys/sysproto.h>
48 #include <sys/eventhandler.h>
49 #include <sys/fcntl.h>
50 #include <sys/filedesc.h>
51 #include <sys/jail.h>
52 #include <sys/kernel.h>
53 #include <sys/kthread.h>
54 #include <sys/sysctl.h>
55 #include <sys/lock.h>
56 #include <sys/malloc.h>
57 #include <sys/mutex.h>
58 #include <sys/priv.h>
59 #include <sys/proc.h>
60 #include <sys/procdesc.h>
61 #include <sys/pioctl.h>
62 #include <sys/racct.h>
63 #include <sys/resourcevar.h>
64 #include <sys/sched.h>
65 #include <sys/syscall.h>
66 #include <sys/vmmeter.h>
67 #include <sys/vnode.h>
68 #include <sys/acct.h>
69 #include <sys/ktr.h>
70 #include <sys/ktrace.h>
71 #include <sys/unistd.h>
72 #include <sys/sdt.h>
73 #include <sys/sx.h>
74 #include <sys/sysent.h>
75 #include <sys/signalvar.h>
76
77 #include <security/audit/audit.h>
78 #include <security/mac/mac_framework.h>
79
80 #include <vm/vm.h>
81 #include <vm/pmap.h>
82 #include <vm/vm_map.h>
83 #include <vm/vm_extern.h>
84 #include <vm/uma.h>
85
86 #ifdef KDTRACE_HOOKS
87 #include <sys/dtrace_bsd.h>
88 dtrace_fork_func_t dtrace_fasttrap_fork;
89 #endif
90
91 SDT_PROVIDER_DECLARE(proc);
92 SDT_PROBE_DEFINE3(proc, kernel, , create, create, "struct proc *",
93 "struct proc *", "int");
94
95 #ifndef _SYS_SYSPROTO_H_
96 struct fork_args {
97 int dummy;
98 };
99 #endif
100
101 /* ARGSUSED */
102 int
103 sys_fork(struct thread *td, struct fork_args *uap)
104 {
105 int error;
106 struct proc *p2;
107
108 error = fork1(td, RFFDG | RFPROC, 0, &p2, NULL, 0);
109 if (error == 0) {
110 td->td_retval[0] = p2->p_pid;
111 td->td_retval[1] = 0;
112 }
113 return (error);
114 }
115
116 /* ARGUSED */
117 int
118 sys_pdfork(td, uap)
119 struct thread *td;
120 struct pdfork_args *uap;
121 {
122 #ifdef PROCDESC
123 int error, fd;
124 struct proc *p2;
125
126 /*
127 * It is necessary to return fd by reference because 0 is a valid file
128 * descriptor number, and the child needs to be able to distinguish
129 * itself from the parent using the return value.
130 */
131 error = fork1(td, RFFDG | RFPROC | RFPROCDESC, 0, &p2,
132 &fd, uap->flags);
133 if (error == 0) {
134 td->td_retval[0] = p2->p_pid;
135 td->td_retval[1] = 0;
136 error = copyout(&fd, uap->fdp, sizeof(fd));
137 }
138 return (error);
139 #else
140 return (ENOSYS);
141 #endif
142 }
143
144 /* ARGSUSED */
145 int
146 sys_vfork(struct thread *td, struct vfork_args *uap)
147 {
148 int error, flags;
149 struct proc *p2;
150
151 flags = RFFDG | RFPROC | RFPPWAIT | RFMEM;
152 error = fork1(td, flags, 0, &p2, NULL, 0);
153 if (error == 0) {
154 td->td_retval[0] = p2->p_pid;
155 td->td_retval[1] = 0;
156 }
157 return (error);
158 }
159
160 int
161 sys_rfork(struct thread *td, struct rfork_args *uap)
162 {
163 struct proc *p2;
164 int error;
165
166 /* Don't allow kernel-only flags. */
167 if ((uap->flags & RFKERNELONLY) != 0)
168 return (EINVAL);
169
170 AUDIT_ARG_FFLAGS(uap->flags);
171 error = fork1(td, uap->flags, 0, &p2, NULL, 0);
172 if (error == 0) {
173 td->td_retval[0] = p2 ? p2->p_pid : 0;
174 td->td_retval[1] = 0;
175 }
176 return (error);
177 }
178
179 int nprocs = 1; /* process 0 */
180 int lastpid = 0;
181 SYSCTL_INT(_kern, OID_AUTO, lastpid, CTLFLAG_RD, &lastpid, 0,
182 "Last used PID");
183
184 /*
185 * Random component to lastpid generation. We mix in a random factor to make
186 * it a little harder to predict. We sanity check the modulus value to avoid
187 * doing it in critical paths. Don't let it be too small or we pointlessly
188 * waste randomness entropy, and don't let it be impossibly large. Using a
189 * modulus that is too big causes a LOT more process table scans and slows
190 * down fork processing as the pidchecked caching is defeated.
191 */
192 static int randompid = 0;
193
194 static int
195 sysctl_kern_randompid(SYSCTL_HANDLER_ARGS)
196 {
197 int error, pid;
198
199 error = sysctl_wire_old_buffer(req, sizeof(int));
200 if (error != 0)
201 return(error);
202 sx_xlock(&allproc_lock);
203 pid = randompid;
204 error = sysctl_handle_int(oidp, &pid, 0, req);
205 if (error == 0 && req->newptr != NULL) {
206 if (pid < 0 || pid > pid_max - 100) /* out of range */
207 pid = pid_max - 100;
208 else if (pid < 2) /* NOP */
209 pid = 0;
210 else if (pid < 100) /* Make it reasonable */
211 pid = 100;
212 randompid = pid;
213 }
214 sx_xunlock(&allproc_lock);
215 return (error);
216 }
217
218 SYSCTL_PROC(_kern, OID_AUTO, randompid, CTLTYPE_INT|CTLFLAG_RW,
219 0, 0, sysctl_kern_randompid, "I", "Random PID modulus");
220
221 static int
222 fork_findpid(int flags)
223 {
224 struct proc *p;
225 int trypid;
226 static int pidchecked = 0;
227
228 /*
229 * Requires allproc_lock in order to iterate over the list
230 * of processes, and proctree_lock to access p_pgrp.
231 */
232 sx_assert(&allproc_lock, SX_LOCKED);
233 sx_assert(&proctree_lock, SX_LOCKED);
234
235 /*
236 * Find an unused process ID. We remember a range of unused IDs
237 * ready to use (from lastpid+1 through pidchecked-1).
238 *
239 * If RFHIGHPID is set (used during system boot), do not allocate
240 * low-numbered pids.
241 */
242 trypid = lastpid + 1;
243 if (flags & RFHIGHPID) {
244 if (trypid < 10)
245 trypid = 10;
246 } else {
247 if (randompid)
248 trypid += arc4random() % randompid;
249 }
250 retry:
251 /*
252 * If the process ID prototype has wrapped around,
253 * restart somewhat above 0, as the low-numbered procs
254 * tend to include daemons that don't exit.
255 */
256 if (trypid >= pid_max) {
257 trypid = trypid % pid_max;
258 if (trypid < 100)
259 trypid += 100;
260 pidchecked = 0;
261 }
262 if (trypid >= pidchecked) {
263 int doingzomb = 0;
264
265 pidchecked = PID_MAX;
266 /*
267 * Scan the active and zombie procs to check whether this pid
268 * is in use. Remember the lowest pid that's greater
269 * than trypid, so we can avoid checking for a while.
270 */
271 p = LIST_FIRST(&allproc);
272 again:
273 for (; p != NULL; p = LIST_NEXT(p, p_list)) {
274 while (p->p_pid == trypid ||
275 (p->p_pgrp != NULL &&
276 (p->p_pgrp->pg_id == trypid ||
277 (p->p_session != NULL &&
278 p->p_session->s_sid == trypid)))) {
279 trypid++;
280 if (trypid >= pidchecked)
281 goto retry;
282 }
283 if (p->p_pid > trypid && pidchecked > p->p_pid)
284 pidchecked = p->p_pid;
285 if (p->p_pgrp != NULL) {
286 if (p->p_pgrp->pg_id > trypid &&
287 pidchecked > p->p_pgrp->pg_id)
288 pidchecked = p->p_pgrp->pg_id;
289 if (p->p_session != NULL &&
290 p->p_session->s_sid > trypid &&
291 pidchecked > p->p_session->s_sid)
292 pidchecked = p->p_session->s_sid;
293 }
294 }
295 if (!doingzomb) {
296 doingzomb = 1;
297 p = LIST_FIRST(&zombproc);
298 goto again;
299 }
300 }
301
302 /*
303 * RFHIGHPID does not mess with the lastpid counter during boot.
304 */
305 if (flags & RFHIGHPID)
306 pidchecked = 0;
307 else
308 lastpid = trypid;
309
310 return (trypid);
311 }
312
313 static int
314 fork_norfproc(struct thread *td, int flags)
315 {
316 int error;
317 struct proc *p1;
318
319 KASSERT((flags & RFPROC) == 0,
320 ("fork_norfproc called with RFPROC set"));
321 p1 = td->td_proc;
322
323 if (((p1->p_flag & (P_HADTHREADS|P_SYSTEM)) == P_HADTHREADS) &&
324 (flags & (RFCFDG | RFFDG))) {
325 PROC_LOCK(p1);
326 if (thread_single(SINGLE_BOUNDARY)) {
327 PROC_UNLOCK(p1);
328 return (ERESTART);
329 }
330 PROC_UNLOCK(p1);
331 }
332
333 error = vm_forkproc(td, NULL, NULL, NULL, flags);
334 if (error)
335 goto fail;
336
337 /*
338 * Close all file descriptors.
339 */
340 if (flags & RFCFDG) {
341 struct filedesc *fdtmp;
342 fdtmp = fdinit(td->td_proc->p_fd);
343 fdescfree(td);
344 p1->p_fd = fdtmp;
345 }
346
347 /*
348 * Unshare file descriptors (from parent).
349 */
350 if (flags & RFFDG)
351 fdunshare(p1, td);
352
353 fail:
354 if (((p1->p_flag & (P_HADTHREADS|P_SYSTEM)) == P_HADTHREADS) &&
355 (flags & (RFCFDG | RFFDG))) {
356 PROC_LOCK(p1);
357 thread_single_end();
358 PROC_UNLOCK(p1);
359 }
360 return (error);
361 }
362
363 static void
364 do_fork(struct thread *td, int flags, struct proc *p2, struct thread *td2,
365 struct vmspace *vm2, int pdflags)
366 {
367 struct proc *p1, *pptr;
368 int p2_held, trypid;
369 struct filedesc *fd;
370 struct filedesc_to_leader *fdtol;
371 struct sigacts *newsigacts;
372
373 sx_assert(&proctree_lock, SX_SLOCKED);
374 sx_assert(&allproc_lock, SX_XLOCKED);
375
376 p2_held = 0;
377 p1 = td->td_proc;
378
379 /*
380 * Increment the nprocs resource before blocking can occur. There
381 * are hard-limits as to the number of processes that can run.
382 */
383 nprocs++;
384
385 trypid = fork_findpid(flags);
386
387 sx_sunlock(&proctree_lock);
388
389 p2->p_state = PRS_NEW; /* protect against others */
390 p2->p_pid = trypid;
391 AUDIT_ARG_PID(p2->p_pid);
392 LIST_INSERT_HEAD(&allproc, p2, p_list);
393 LIST_INSERT_HEAD(PIDHASH(p2->p_pid), p2, p_hash);
394 tidhash_add(td2);
395 PROC_LOCK(p2);
396 PROC_LOCK(p1);
397
398 sx_xunlock(&allproc_lock);
399
400 bcopy(&p1->p_startcopy, &p2->p_startcopy,
401 __rangeof(struct proc, p_startcopy, p_endcopy));
402 pargs_hold(p2->p_args);
403 PROC_UNLOCK(p1);
404
405 bzero(&p2->p_startzero,
406 __rangeof(struct proc, p_startzero, p_endzero));
407
408 p2->p_ucred = crhold(td->td_ucred);
409
410 /* Tell the prison that we exist. */
411 prison_proc_hold(p2->p_ucred->cr_prison);
412
413 PROC_UNLOCK(p2);
414
415 /*
416 * Malloc things while we don't hold any locks.
417 */
418 if (flags & RFSIGSHARE)
419 newsigacts = NULL;
420 else
421 newsigacts = sigacts_alloc();
422
423 /*
424 * Copy filedesc.
425 */
426 if (flags & RFCFDG) {
427 fd = fdinit(p1->p_fd);
428 fdtol = NULL;
429 } else if (flags & RFFDG) {
430 fd = fdcopy(p1->p_fd);
431 fdtol = NULL;
432 } else {
433 fd = fdshare(p1->p_fd);
434 if (p1->p_fdtol == NULL)
435 p1->p_fdtol = filedesc_to_leader_alloc(NULL, NULL,
436 p1->p_leader);
437 if ((flags & RFTHREAD) != 0) {
438 /*
439 * Shared file descriptor table, and shared
440 * process leaders.
441 */
442 fdtol = p1->p_fdtol;
443 FILEDESC_XLOCK(p1->p_fd);
444 fdtol->fdl_refcount++;
445 FILEDESC_XUNLOCK(p1->p_fd);
446 } else {
447 /*
448 * Shared file descriptor table, and different
449 * process leaders.
450 */
451 fdtol = filedesc_to_leader_alloc(p1->p_fdtol,
452 p1->p_fd, p2);
453 }
454 }
455 /*
456 * Make a proc table entry for the new process.
457 * Start by zeroing the section of proc that is zero-initialized,
458 * then copy the section that is copied directly from the parent.
459 */
460
461 PROC_LOCK(p2);
462 PROC_LOCK(p1);
463
464 bzero(&td2->td_startzero,
465 __rangeof(struct thread, td_startzero, td_endzero));
466
467 bcopy(&td->td_startcopy, &td2->td_startcopy,
468 __rangeof(struct thread, td_startcopy, td_endcopy));
469
470 bcopy(&p2->p_comm, &td2->td_name, sizeof(td2->td_name));
471 td2->td_sigstk = td->td_sigstk;
472 td2->td_flags = TDF_INMEM;
473 td2->td_lend_user_pri = PRI_MAX;
474
475 #ifdef VIMAGE
476 td2->td_vnet = NULL;
477 td2->td_vnet_lpush = NULL;
478 #endif
479
480 /*
481 * Allow the scheduler to initialize the child.
482 */
483 thread_lock(td);
484 sched_fork(td, td2);
485 thread_unlock(td);
486
487 /*
488 * Duplicate sub-structures as needed.
489 * Increase reference counts on shared objects.
490 */
491 p2->p_flag = P_INMEM;
492 p2->p_flag2 = 0;
493 p2->p_swtick = ticks;
494 if (p1->p_flag & P_PROFIL)
495 startprofclock(p2);
496 td2->td_ucred = crhold(p2->p_ucred);
497
498 if (flags & RFSIGSHARE) {
499 p2->p_sigacts = sigacts_hold(p1->p_sigacts);
500 } else {
501 sigacts_copy(newsigacts, p1->p_sigacts);
502 p2->p_sigacts = newsigacts;
503 }
504
505 if (flags & RFTSIGZMB)
506 p2->p_sigparent = RFTSIGNUM(flags);
507 else if (flags & RFLINUXTHPN)
508 p2->p_sigparent = SIGUSR1;
509 else
510 p2->p_sigparent = SIGCHLD;
511
512 p2->p_textvp = p1->p_textvp;
513 p2->p_fd = fd;
514 p2->p_fdtol = fdtol;
515
516 if (p1->p_flag2 & P2_INHERIT_PROTECTED) {
517 p2->p_flag |= P_PROTECTED;
518 p2->p_flag2 |= P2_INHERIT_PROTECTED;
519 }
520
521 /*
522 * p_limit is copy-on-write. Bump its refcount.
523 */
524 lim_fork(p1, p2);
525
526 pstats_fork(p1->p_stats, p2->p_stats);
527
528 PROC_UNLOCK(p1);
529 PROC_UNLOCK(p2);
530
531 /* Bump references to the text vnode (for procfs). */
532 if (p2->p_textvp)
533 vref(p2->p_textvp);
534
535 /*
536 * Set up linkage for kernel based threading.
537 */
538 if ((flags & RFTHREAD) != 0) {
539 mtx_lock(&ppeers_lock);
540 p2->p_peers = p1->p_peers;
541 p1->p_peers = p2;
542 p2->p_leader = p1->p_leader;
543 mtx_unlock(&ppeers_lock);
544 PROC_LOCK(p1->p_leader);
545 if ((p1->p_leader->p_flag & P_WEXIT) != 0) {
546 PROC_UNLOCK(p1->p_leader);
547 /*
548 * The task leader is exiting, so process p1 is
549 * going to be killed shortly. Since p1 obviously
550 * isn't dead yet, we know that the leader is either
551 * sending SIGKILL's to all the processes in this
552 * task or is sleeping waiting for all the peers to
553 * exit. We let p1 complete the fork, but we need
554 * to go ahead and kill the new process p2 since
555 * the task leader may not get a chance to send
556 * SIGKILL to it. We leave it on the list so that
557 * the task leader will wait for this new process
558 * to commit suicide.
559 */
560 PROC_LOCK(p2);
561 kern_psignal(p2, SIGKILL);
562 PROC_UNLOCK(p2);
563 } else
564 PROC_UNLOCK(p1->p_leader);
565 } else {
566 p2->p_peers = NULL;
567 p2->p_leader = p2;
568 }
569
570 sx_xlock(&proctree_lock);
571 PGRP_LOCK(p1->p_pgrp);
572 PROC_LOCK(p2);
573 PROC_LOCK(p1);
574
575 /*
576 * Preserve some more flags in subprocess. P_PROFIL has already
577 * been preserved.
578 */
579 p2->p_flag |= p1->p_flag & P_SUGID;
580 td2->td_pflags |= td->td_pflags & TDP_ALTSTACK;
581 SESS_LOCK(p1->p_session);
582 if (p1->p_session->s_ttyvp != NULL && p1->p_flag & P_CONTROLT)
583 p2->p_flag |= P_CONTROLT;
584 SESS_UNLOCK(p1->p_session);
585 if (flags & RFPPWAIT)
586 p2->p_flag |= P_PPWAIT;
587
588 p2->p_pgrp = p1->p_pgrp;
589 LIST_INSERT_AFTER(p1, p2, p_pglist);
590 PGRP_UNLOCK(p1->p_pgrp);
591 LIST_INIT(&p2->p_children);
592 LIST_INIT(&p2->p_orphans);
593
594 callout_init_mtx(&p2->p_itcallout, &p2->p_mtx, 0);
595
596 /*
597 * If PF_FORK is set, the child process inherits the
598 * procfs ioctl flags from its parent.
599 */
600 if (p1->p_pfsflags & PF_FORK) {
601 p2->p_stops = p1->p_stops;
602 p2->p_pfsflags = p1->p_pfsflags;
603 }
604
605 /*
606 * This begins the section where we must prevent the parent
607 * from being swapped.
608 */
609 _PHOLD(p1);
610 PROC_UNLOCK(p1);
611
612 /*
613 * Attach the new process to its parent.
614 *
615 * If RFNOWAIT is set, the newly created process becomes a child
616 * of init. This effectively disassociates the child from the
617 * parent.
618 */
619 if (flags & RFNOWAIT)
620 pptr = initproc;
621 else
622 pptr = p1;
623 p2->p_pptr = pptr;
624 LIST_INSERT_HEAD(&pptr->p_children, p2, p_sibling);
625 sx_xunlock(&proctree_lock);
626
627 /* Inform accounting that we have forked. */
628 p2->p_acflag = AFORK;
629 PROC_UNLOCK(p2);
630
631 #ifdef KTRACE
632 ktrprocfork(p1, p2);
633 #endif
634
635 /*
636 * Finish creating the child process. It will return via a different
637 * execution path later. (ie: directly into user mode)
638 */
639 vm_forkproc(td, p2, td2, vm2, flags);
640
641 if (flags == (RFFDG | RFPROC)) {
642 PCPU_INC(cnt.v_forks);
643 PCPU_ADD(cnt.v_forkpages, p2->p_vmspace->vm_dsize +
644 p2->p_vmspace->vm_ssize);
645 } else if (flags == (RFFDG | RFPROC | RFPPWAIT | RFMEM)) {
646 PCPU_INC(cnt.v_vforks);
647 PCPU_ADD(cnt.v_vforkpages, p2->p_vmspace->vm_dsize +
648 p2->p_vmspace->vm_ssize);
649 } else if (p1 == &proc0) {
650 PCPU_INC(cnt.v_kthreads);
651 PCPU_ADD(cnt.v_kthreadpages, p2->p_vmspace->vm_dsize +
652 p2->p_vmspace->vm_ssize);
653 } else {
654 PCPU_INC(cnt.v_rforks);
655 PCPU_ADD(cnt.v_rforkpages, p2->p_vmspace->vm_dsize +
656 p2->p_vmspace->vm_ssize);
657 }
658
659 #ifdef PROCDESC
660 /*
661 * Associate the process descriptor with the process before anything
662 * can happen that might cause that process to need the descriptor.
663 * However, don't do this until after fork(2) can no longer fail.
664 */
665 if (flags & RFPROCDESC)
666 procdesc_new(p2, pdflags);
667 #endif
668
669 /*
670 * Both processes are set up, now check if any loadable modules want
671 * to adjust anything.
672 */
673 EVENTHANDLER_INVOKE(process_fork, p1, p2, flags);
674
675 /*
676 * Set the child start time and mark the process as being complete.
677 */
678 PROC_LOCK(p2);
679 PROC_LOCK(p1);
680 microuptime(&p2->p_stats->p_start);
681 PROC_SLOCK(p2);
682 p2->p_state = PRS_NORMAL;
683 PROC_SUNLOCK(p2);
684
685 #ifdef KDTRACE_HOOKS
686 /*
687 * Tell the DTrace fasttrap provider about the new process
688 * if it has registered an interest. We have to do this only after
689 * p_state is PRS_NORMAL since the fasttrap module will use pfind()
690 * later on.
691 */
692 if (dtrace_fasttrap_fork)
693 dtrace_fasttrap_fork(p1, p2);
694 #endif
695 if ((p1->p_flag & (P_TRACED | P_FOLLOWFORK)) == (P_TRACED |
696 P_FOLLOWFORK)) {
697 /*
698 * Arrange for debugger to receive the fork event.
699 *
700 * We can report PL_FLAG_FORKED regardless of
701 * P_FOLLOWFORK settings, but it does not make a sense
702 * for runaway child.
703 */
704 td->td_dbgflags |= TDB_FORK;
705 td->td_dbg_forked = p2->p_pid;
706 td2->td_dbgflags |= TDB_STOPATFORK;
707 _PHOLD(p2);
708 p2_held = 1;
709 }
710 if (flags & RFPPWAIT) {
711 td->td_pflags |= TDP_RFPPWAIT;
712 td->td_rfppwait_p = p2;
713 }
714 PROC_UNLOCK(p2);
715 if ((flags & RFSTOPPED) == 0) {
716 /*
717 * If RFSTOPPED not requested, make child runnable and
718 * add to run queue.
719 */
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 _PRELE(p1);
730 PROC_UNLOCK(p1);
731
732 /*
733 * Tell any interested parties about the new process.
734 */
735 knote_fork(&p1->p_klist, p2->p_pid);
736 SDT_PROBE(proc, kernel, , create, p2, p1, flags, 0, 0);
737
738 /*
739 * Wait until debugger is attached to child.
740 */
741 PROC_LOCK(p2);
742 while ((td2->td_dbgflags & TDB_STOPATFORK) != 0)
743 cv_wait(&p2->p_dbgwait, &p2->p_mtx);
744 if (p2_held)
745 _PRELE(p2);
746 PROC_UNLOCK(p2);
747 }
748
749 int
750 fork1(struct thread *td, int flags, int pages, struct proc **procp,
751 int *procdescp, int pdflags)
752 {
753 struct proc *p1;
754 struct proc *newproc;
755 int ok;
756 struct thread *td2;
757 struct vmspace *vm2;
758 vm_ooffset_t mem_charged;
759 int error;
760 static int curfail;
761 static struct timeval lastfail;
762 #ifdef PROCDESC
763 struct file *fp_procdesc = NULL;
764 #endif
765
766 /* Check for the undefined or unimplemented flags. */
767 if ((flags & ~(RFFLAGS | RFTSIGFLAGS(RFTSIGMASK))) != 0)
768 return (EINVAL);
769
770 /* Signal value requires RFTSIGZMB. */
771 if ((flags & RFTSIGFLAGS(RFTSIGMASK)) != 0 && (flags & RFTSIGZMB) == 0)
772 return (EINVAL);
773
774 /* Can't copy and clear. */
775 if ((flags & (RFFDG|RFCFDG)) == (RFFDG|RFCFDG))
776 return (EINVAL);
777
778 /* Check the validity of the signal number. */
779 if ((flags & RFTSIGZMB) != 0 && (u_int)RFTSIGNUM(flags) > _SIG_MAXSIG)
780 return (EINVAL);
781
782 #ifdef PROCDESC
783 if ((flags & RFPROCDESC) != 0) {
784 /* Can't not create a process yet get a process descriptor. */
785 if ((flags & RFPROC) == 0)
786 return (EINVAL);
787
788 /* Must provide a place to put a procdesc if creating one. */
789 if (procdescp == NULL)
790 return (EINVAL);
791 }
792 #endif
793
794 p1 = td->td_proc;
795
796 /*
797 * Here we don't create a new process, but we divorce
798 * certain parts of a process from itself.
799 */
800 if ((flags & RFPROC) == 0) {
801 *procp = NULL;
802 return (fork_norfproc(td, flags));
803 }
804
805 #ifdef PROCDESC
806 /*
807 * If required, create a process descriptor in the parent first; we
808 * will abandon it if something goes wrong. We don't finit() until
809 * later.
810 */
811 if (flags & RFPROCDESC) {
812 error = falloc(td, &fp_procdesc, procdescp, 0);
813 if (error != 0)
814 return (error);
815 }
816 #endif
817
818 mem_charged = 0;
819 vm2 = NULL;
820 if (pages == 0)
821 pages = KSTACK_PAGES;
822 /* Allocate new proc. */
823 newproc = uma_zalloc(proc_zone, M_WAITOK);
824 td2 = FIRST_THREAD_IN_PROC(newproc);
825 if (td2 == NULL) {
826 td2 = thread_alloc(pages);
827 if (td2 == NULL) {
828 error = ENOMEM;
829 goto fail1;
830 }
831 proc_linkup(newproc, td2);
832 } else {
833 if (td2->td_kstack == 0 || td2->td_kstack_pages != pages) {
834 if (td2->td_kstack != 0)
835 vm_thread_dispose(td2);
836 if (!thread_alloc_stack(td2, pages)) {
837 error = ENOMEM;
838 goto fail1;
839 }
840 }
841 }
842
843 if ((flags & RFMEM) == 0) {
844 vm2 = vmspace_fork(p1->p_vmspace, &mem_charged);
845 if (vm2 == NULL) {
846 error = ENOMEM;
847 goto fail1;
848 }
849 if (!swap_reserve(mem_charged)) {
850 /*
851 * The swap reservation failed. The accounting
852 * from the entries of the copied vm2 will be
853 * substracted in vmspace_free(), so force the
854 * reservation there.
855 */
856 swap_reserve_force(mem_charged);
857 error = ENOMEM;
858 goto fail1;
859 }
860 } else
861 vm2 = NULL;
862
863 /*
864 * XXX: This is ugly; when we copy resource usage, we need to bump
865 * per-cred resource counters.
866 */
867 newproc->p_ucred = p1->p_ucred;
868
869 /*
870 * Initialize resource accounting for the child process.
871 */
872 error = racct_proc_fork(p1, newproc);
873 if (error != 0) {
874 error = EAGAIN;
875 goto fail1;
876 }
877
878 #ifdef MAC
879 mac_proc_init(newproc);
880 #endif
881 knlist_init_mtx(&newproc->p_klist, &newproc->p_mtx);
882 STAILQ_INIT(&newproc->p_ktr);
883
884 /* We have to lock the process tree while we look for a pid. */
885 sx_slock(&proctree_lock);
886
887 /*
888 * Although process entries are dynamically created, we still keep
889 * a global limit on the maximum number we will create. Don't allow
890 * a nonprivileged user to use the last ten processes; don't let root
891 * exceed the limit. The variable nprocs is the current number of
892 * processes, maxproc is the limit.
893 */
894 sx_xlock(&allproc_lock);
895 if ((nprocs >= maxproc - 10 && priv_check_cred(td->td_ucred,
896 PRIV_MAXPROC, 0) != 0) || nprocs >= maxproc) {
897 error = EAGAIN;
898 goto fail;
899 }
900
901 /*
902 * Increment the count of procs running with this uid. Don't allow
903 * a nonprivileged user to exceed their current limit.
904 *
905 * XXXRW: Can we avoid privilege here if it's not needed?
906 */
907 error = priv_check_cred(td->td_ucred, PRIV_PROC_LIMIT, 0);
908 if (error == 0)
909 ok = chgproccnt(td->td_ucred->cr_ruidinfo, 1, 0);
910 else {
911 PROC_LOCK(p1);
912 ok = chgproccnt(td->td_ucred->cr_ruidinfo, 1,
913 lim_cur(p1, RLIMIT_NPROC));
914 PROC_UNLOCK(p1);
915 }
916 if (ok) {
917 do_fork(td, flags, newproc, td2, vm2, pdflags);
918
919 /*
920 * Return child proc pointer to parent.
921 */
922 *procp = newproc;
923 #ifdef PROCDESC
924 if (flags & RFPROCDESC) {
925 procdesc_finit(newproc->p_procdesc, fp_procdesc);
926 fdrop(fp_procdesc, td);
927 }
928 #endif
929 racct_proc_fork_done(newproc);
930 return (0);
931 }
932
933 error = EAGAIN;
934 fail:
935 sx_sunlock(&proctree_lock);
936 if (ppsratecheck(&lastfail, &curfail, 1))
937 printf("maxproc limit exceeded by uid %u (pid %d); see tuning(7) and login.conf(5)\n",
938 td->td_ucred->cr_ruid, p1->p_pid);
939 sx_xunlock(&allproc_lock);
940 #ifdef MAC
941 mac_proc_destroy(newproc);
942 #endif
943 racct_proc_exit(newproc);
944 fail1:
945 if (vm2 != NULL)
946 vmspace_free(vm2);
947 uma_zfree(proc_zone, newproc);
948 #ifdef PROCDESC
949 if ((flags & RFPROCDESC) != 0 && fp_procdesc != NULL) {
950 fdclose(td->td_proc->p_fd, fp_procdesc, *procdescp, td);
951 fdrop(fp_procdesc, td);
952 }
953 #endif
954 pause("fork", hz / 2);
955 return (error);
956 }
957
958 /*
959 * Handle the return of a child process from fork1(). This function
960 * is called from the MD fork_trampoline() entry point.
961 */
962 void
963 fork_exit(void (*callout)(void *, struct trapframe *), void *arg,
964 struct trapframe *frame)
965 {
966 struct proc *p;
967 struct thread *td;
968 struct thread *dtd;
969
970 td = curthread;
971 p = td->td_proc;
972 KASSERT(p->p_state == PRS_NORMAL, ("executing process is still new"));
973
974 CTR4(KTR_PROC, "fork_exit: new thread %p (td_sched %p, pid %d, %s)",
975 td, td->td_sched, p->p_pid, td->td_name);
976
977 sched_fork_exit(td);
978 /*
979 * Processes normally resume in mi_switch() after being
980 * cpu_switch()'ed to, but when children start up they arrive here
981 * instead, so we must do much the same things as mi_switch() would.
982 */
983 if ((dtd = PCPU_GET(deadthread))) {
984 PCPU_SET(deadthread, NULL);
985 thread_stash(dtd);
986 }
987 thread_unlock(td);
988
989 /*
990 * cpu_set_fork_handler intercepts this function call to
991 * have this call a non-return function to stay in kernel mode.
992 * initproc has its own fork handler, but it does return.
993 */
994 KASSERT(callout != NULL, ("NULL callout in fork_exit"));
995 callout(arg, frame);
996
997 /*
998 * Check if a kernel thread misbehaved and returned from its main
999 * function.
1000 */
1001 if (p->p_flag & P_KTHREAD) {
1002 printf("Kernel thread \"%s\" (pid %d) exited prematurely.\n",
1003 td->td_name, p->p_pid);
1004 kproc_exit(0);
1005 }
1006 mtx_assert(&Giant, MA_NOTOWNED);
1007
1008 if (p->p_sysent->sv_schedtail != NULL)
1009 (p->p_sysent->sv_schedtail)(td);
1010 }
1011
1012 /*
1013 * Simplified back end of syscall(), used when returning from fork()
1014 * directly into user mode. Giant is not held on entry, and must not
1015 * be held on return. This function is passed in to fork_exit() as the
1016 * first parameter and is called when returning to a new userland process.
1017 */
1018 void
1019 fork_return(struct thread *td, struct trapframe *frame)
1020 {
1021 struct proc *p, *dbg;
1022
1023 if (td->td_dbgflags & TDB_STOPATFORK) {
1024 p = td->td_proc;
1025 sx_xlock(&proctree_lock);
1026 PROC_LOCK(p);
1027 if ((p->p_pptr->p_flag & (P_TRACED | P_FOLLOWFORK)) ==
1028 (P_TRACED | P_FOLLOWFORK)) {
1029 /*
1030 * If debugger still wants auto-attach for the
1031 * parent's children, do it now.
1032 */
1033 dbg = p->p_pptr->p_pptr;
1034 p->p_flag |= P_TRACED;
1035 p->p_oppid = p->p_pptr->p_pid;
1036 proc_reparent(p, dbg);
1037 sx_xunlock(&proctree_lock);
1038 td->td_dbgflags |= TDB_CHILD;
1039 ptracestop(td, SIGSTOP);
1040 td->td_dbgflags &= ~TDB_CHILD;
1041 } else {
1042 /*
1043 * ... otherwise clear the request.
1044 */
1045 sx_xunlock(&proctree_lock);
1046 td->td_dbgflags &= ~TDB_STOPATFORK;
1047 cv_broadcast(&p->p_dbgwait);
1048 }
1049 PROC_UNLOCK(p);
1050 }
1051
1052 userret(td, frame);
1053
1054 #ifdef KTRACE
1055 if (KTRPOINT(td, KTR_SYSRET))
1056 ktrsysret(SYS_fork, 0, 0);
1057 #endif
1058 }
Cache object: 2ac7f69f177d934321a2f5958294bde3
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