FreeBSD/Linux Kernel Cross Reference
sys/kern/kern_fork.c
1 /*-
2 * SPDX-License-Identifier: BSD-3-Clause
3 *
4 * Copyright (c) 1982, 1986, 1989, 1991, 1993
5 * The Regents of the University of California. All rights reserved.
6 * (c) UNIX System Laboratories, Inc.
7 * All or some portions of this file are derived from material licensed
8 * to the University of California by American Telephone and Telegraph
9 * Co. or Unix System Laboratories, Inc. and are reproduced herein with
10 * the permission of UNIX System Laboratories, Inc.
11 *
12 * Redistribution and use in source and binary forms, with or without
13 * modification, are permitted provided that the following conditions
14 * are met:
15 * 1. Redistributions of source code must retain the above copyright
16 * notice, this list of conditions and the following disclaimer.
17 * 2. Redistributions in binary form must reproduce the above copyright
18 * notice, this list of conditions and the following disclaimer in the
19 * documentation and/or other materials provided with the distribution.
20 * 3. Neither the name of the University nor the names of its contributors
21 * may be used to endorse or promote products derived from this software
22 * without specific prior written permission.
23 *
24 * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
25 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
26 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
27 * ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
28 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
29 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
30 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
31 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
32 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
33 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
34 * SUCH DAMAGE.
35 *
36 * @(#)kern_fork.c 8.6 (Berkeley) 4/8/94
37 */
38
39 #include <sys/cdefs.h>
40 __FBSDID("$FreeBSD$");
41
42 #include "opt_ktrace.h"
43 #include "opt_kstack_pages.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/ptrace.h>
63 #include <sys/racct.h>
64 #include <sys/resourcevar.h>
65 #include <sys/sched.h>
66 #include <sys/syscall.h>
67 #include <sys/vmmeter.h>
68 #include <sys/vnode.h>
69 #include <sys/acct.h>
70 #include <sys/ktr.h>
71 #include <sys/ktrace.h>
72 #include <sys/unistd.h>
73 #include <sys/sdt.h>
74 #include <sys/sx.h>
75 #include <sys/sysent.h>
76 #include <sys/signalvar.h>
77
78 #include <security/audit/audit.h>
79 #include <security/mac/mac_framework.h>
80
81 #include <vm/vm.h>
82 #include <vm/pmap.h>
83 #include <vm/vm_map.h>
84 #include <vm/vm_extern.h>
85 #include <vm/uma.h>
86
87 #ifdef KDTRACE_HOOKS
88 #include <sys/dtrace_bsd.h>
89 dtrace_fork_func_t dtrace_fasttrap_fork;
90 #endif
91
92 SDT_PROVIDER_DECLARE(proc);
93 SDT_PROBE_DEFINE3(proc, , , create, "struct proc *", "struct proc *", "int");
94
95 #ifndef _SYS_SYSPROTO_H_
96 struct fork_args {
97 int dummy;
98 };
99 #endif
100
101 EVENTHANDLER_LIST_DECLARE(process_fork);
102
103 /* ARGSUSED */
104 int
105 sys_fork(struct thread *td, struct fork_args *uap)
106 {
107 struct fork_req fr;
108 int error, pid;
109
110 bzero(&fr, sizeof(fr));
111 fr.fr_flags = RFFDG | RFPROC;
112 fr.fr_pidp = &pid;
113 error = fork1(td, &fr);
114 if (error == 0) {
115 td->td_retval[0] = pid;
116 td->td_retval[1] = 0;
117 }
118 return (error);
119 }
120
121 /* ARGUSED */
122 int
123 sys_pdfork(struct thread *td, struct pdfork_args *uap)
124 {
125 struct fork_req fr;
126 int error, fd, pid;
127
128 bzero(&fr, sizeof(fr));
129 fr.fr_flags = RFFDG | RFPROC | RFPROCDESC;
130 fr.fr_pidp = &pid;
131 fr.fr_pd_fd = &fd;
132 fr.fr_pd_flags = uap->flags;
133 /*
134 * It is necessary to return fd by reference because 0 is a valid file
135 * descriptor number, and the child needs to be able to distinguish
136 * itself from the parent using the return value.
137 */
138 error = fork1(td, &fr);
139 if (error == 0) {
140 td->td_retval[0] = pid;
141 td->td_retval[1] = 0;
142 error = copyout(&fd, uap->fdp, sizeof(fd));
143 }
144 return (error);
145 }
146
147 /* ARGSUSED */
148 int
149 sys_vfork(struct thread *td, struct vfork_args *uap)
150 {
151 struct fork_req fr;
152 int error, pid;
153
154 bzero(&fr, sizeof(fr));
155 fr.fr_flags = RFFDG | RFPROC | RFPPWAIT | RFMEM;
156 fr.fr_pidp = &pid;
157 error = fork1(td, &fr);
158 if (error == 0) {
159 td->td_retval[0] = pid;
160 td->td_retval[1] = 0;
161 }
162 return (error);
163 }
164
165 int
166 sys_rfork(struct thread *td, struct rfork_args *uap)
167 {
168 struct fork_req fr;
169 int error, pid;
170
171 /* Don't allow kernel-only flags. */
172 if ((uap->flags & RFKERNELONLY) != 0)
173 return (EINVAL);
174 /* RFSPAWN must not appear with others */
175 if ((uap->flags & RFSPAWN) != 0 && uap->flags != RFSPAWN)
176 return (EINVAL);
177
178 AUDIT_ARG_FFLAGS(uap->flags);
179 bzero(&fr, sizeof(fr));
180 if ((uap->flags & RFSPAWN) != 0) {
181 fr.fr_flags = RFFDG | RFPROC | RFPPWAIT | RFMEM;
182 fr.fr_flags2 = FR2_DROPSIG_CAUGHT;
183 } else {
184 fr.fr_flags = uap->flags;
185 }
186 fr.fr_pidp = &pid;
187 error = fork1(td, &fr);
188 if (error == 0) {
189 td->td_retval[0] = pid;
190 td->td_retval[1] = 0;
191 }
192 return (error);
193 }
194
195 int nprocs = 1; /* process 0 */
196 int lastpid = 0;
197 SYSCTL_INT(_kern, OID_AUTO, lastpid, CTLFLAG_RD, &lastpid, 0,
198 "Last used PID");
199
200 /*
201 * Random component to lastpid generation. We mix in a random factor to make
202 * it a little harder to predict. We sanity check the modulus value to avoid
203 * doing it in critical paths. Don't let it be too small or we pointlessly
204 * waste randomness entropy, and don't let it be impossibly large. Using a
205 * modulus that is too big causes a LOT more process table scans and slows
206 * down fork processing as the pidchecked caching is defeated.
207 */
208 static int randompid = 0;
209
210 static int
211 sysctl_kern_randompid(SYSCTL_HANDLER_ARGS)
212 {
213 int error, pid;
214
215 error = sysctl_wire_old_buffer(req, sizeof(int));
216 if (error != 0)
217 return(error);
218 sx_xlock(&allproc_lock);
219 pid = randompid;
220 error = sysctl_handle_int(oidp, &pid, 0, req);
221 if (error == 0 && req->newptr != NULL) {
222 if (pid == 0)
223 randompid = 0;
224 else if (pid == 1)
225 /* generate a random PID modulus between 100 and 1123 */
226 randompid = 100 + arc4random() % 1024;
227 else if (pid < 0 || pid > pid_max - 100)
228 /* out of range */
229 randompid = pid_max - 100;
230 else if (pid < 100)
231 /* Make it reasonable */
232 randompid = 100;
233 else
234 randompid = pid;
235 }
236 sx_xunlock(&allproc_lock);
237 return (error);
238 }
239
240 SYSCTL_PROC(_kern, OID_AUTO, randompid, CTLTYPE_INT|CTLFLAG_RW,
241 0, 0, sysctl_kern_randompid, "I", "Random PID modulus. Special values: 0: disable, 1: choose random value");
242
243 static int
244 fork_findpid(int flags)
245 {
246 struct proc *p;
247 int trypid;
248 static int pidchecked = 0;
249
250 /*
251 * Requires allproc_lock in order to iterate over the list
252 * of processes, and proctree_lock to access p_pgrp.
253 */
254 sx_assert(&allproc_lock, SX_LOCKED);
255 sx_assert(&proctree_lock, SX_LOCKED);
256
257 /*
258 * Find an unused process ID. We remember a range of unused IDs
259 * ready to use (from lastpid+1 through pidchecked-1).
260 *
261 * If RFHIGHPID is set (used during system boot), do not allocate
262 * low-numbered pids.
263 */
264 trypid = lastpid + 1;
265 if (flags & RFHIGHPID) {
266 if (trypid < 10)
267 trypid = 10;
268 } else {
269 if (randompid)
270 trypid += arc4random() % randompid;
271 }
272 retry:
273 /*
274 * If the process ID prototype has wrapped around,
275 * restart somewhat above 0, as the low-numbered procs
276 * tend to include daemons that don't exit.
277 */
278 if (trypid >= pid_max) {
279 trypid = trypid % pid_max;
280 if (trypid < 100)
281 trypid += 100;
282 pidchecked = 0;
283 }
284 if (trypid >= pidchecked) {
285 int doingzomb = 0;
286
287 pidchecked = PID_MAX;
288 /*
289 * Scan the active and zombie procs to check whether this pid
290 * is in use. Remember the lowest pid that's greater
291 * than trypid, so we can avoid checking for a while.
292 *
293 * Avoid reuse of the process group id, session id or
294 * the reaper subtree id. Note that for process group
295 * and sessions, the amount of reserved pids is
296 * limited by process limit. For the subtree ids, the
297 * id is kept reserved only while there is a
298 * non-reaped process in the subtree, so amount of
299 * reserved pids is limited by process limit times
300 * two.
301 */
302 p = LIST_FIRST(&allproc);
303 again:
304 for (; p != NULL; p = LIST_NEXT(p, p_list)) {
305 while (p->p_pid == trypid ||
306 p->p_reapsubtree == trypid ||
307 (p->p_pgrp != NULL &&
308 (p->p_pgrp->pg_id == trypid ||
309 (p->p_session != NULL &&
310 p->p_session->s_sid == trypid)))) {
311 trypid++;
312 if (trypid >= pidchecked)
313 goto retry;
314 }
315 if (p->p_pid > trypid && pidchecked > p->p_pid)
316 pidchecked = p->p_pid;
317 if (p->p_pgrp != NULL) {
318 if (p->p_pgrp->pg_id > trypid &&
319 pidchecked > p->p_pgrp->pg_id)
320 pidchecked = p->p_pgrp->pg_id;
321 if (p->p_session != NULL &&
322 p->p_session->s_sid > trypid &&
323 pidchecked > p->p_session->s_sid)
324 pidchecked = p->p_session->s_sid;
325 }
326 }
327 if (!doingzomb) {
328 doingzomb = 1;
329 p = LIST_FIRST(&zombproc);
330 goto again;
331 }
332 }
333
334 /*
335 * RFHIGHPID does not mess with the lastpid counter during boot.
336 */
337 if (flags & RFHIGHPID)
338 pidchecked = 0;
339 else
340 lastpid = trypid;
341
342 return (trypid);
343 }
344
345 static int
346 fork_norfproc(struct thread *td, int flags)
347 {
348 int error;
349 struct proc *p1;
350
351 KASSERT((flags & RFPROC) == 0,
352 ("fork_norfproc called with RFPROC set"));
353 p1 = td->td_proc;
354
355 if (((p1->p_flag & (P_HADTHREADS|P_SYSTEM)) == P_HADTHREADS) &&
356 (flags & (RFCFDG | RFFDG))) {
357 PROC_LOCK(p1);
358 if (thread_single(p1, SINGLE_BOUNDARY)) {
359 PROC_UNLOCK(p1);
360 return (ERESTART);
361 }
362 PROC_UNLOCK(p1);
363 }
364
365 error = vm_forkproc(td, NULL, NULL, NULL, flags);
366 if (error)
367 goto fail;
368
369 /*
370 * Close all file descriptors.
371 */
372 if (flags & RFCFDG) {
373 struct filedesc *fdtmp;
374 fdtmp = fdinit(td->td_proc->p_fd, false);
375 fdescfree(td);
376 p1->p_fd = fdtmp;
377 }
378
379 /*
380 * Unshare file descriptors (from parent).
381 */
382 if (flags & RFFDG)
383 fdunshare(td);
384
385 fail:
386 if (((p1->p_flag & (P_HADTHREADS|P_SYSTEM)) == P_HADTHREADS) &&
387 (flags & (RFCFDG | RFFDG))) {
388 PROC_LOCK(p1);
389 thread_single_end(p1, SINGLE_BOUNDARY);
390 PROC_UNLOCK(p1);
391 }
392 return (error);
393 }
394
395 static void
396 do_fork(struct thread *td, struct fork_req *fr, struct proc *p2, struct thread *td2,
397 struct vmspace *vm2, struct file *fp_procdesc)
398 {
399 struct proc *p1, *pptr;
400 int trypid;
401 struct filedesc *fd;
402 struct filedesc_to_leader *fdtol;
403 struct sigacts *newsigacts;
404
405 sx_assert(&proctree_lock, SX_LOCKED);
406 sx_assert(&allproc_lock, SX_XLOCKED);
407
408 p1 = td->td_proc;
409
410 trypid = fork_findpid(fr->fr_flags);
411
412 p2->p_state = PRS_NEW; /* protect against others */
413 p2->p_pid = trypid;
414 AUDIT_ARG_PID(p2->p_pid);
415 LIST_INSERT_HEAD(&allproc, p2, p_list);
416 allproc_gen++;
417 LIST_INSERT_HEAD(PIDHASH(p2->p_pid), p2, p_hash);
418 PROC_LOCK(p2);
419 PROC_LOCK(p1);
420
421 sx_xunlock(&allproc_lock);
422 sx_xunlock(&proctree_lock);
423
424 bcopy(&p1->p_startcopy, &p2->p_startcopy,
425 __rangeof(struct proc, p_startcopy, p_endcopy));
426 p2->p_fctl0 = p1->p_fctl0;
427 pargs_hold(p2->p_args);
428
429 PROC_UNLOCK(p1);
430
431 bzero(&p2->p_startzero,
432 __rangeof(struct proc, p_startzero, p_endzero));
433
434 /* Tell the prison that we exist. */
435 prison_proc_hold(p2->p_ucred->cr_prison);
436
437 PROC_UNLOCK(p2);
438
439 tidhash_add(td2);
440
441 /*
442 * Malloc things while we don't hold any locks.
443 */
444 if (fr->fr_flags & RFSIGSHARE)
445 newsigacts = NULL;
446 else
447 newsigacts = sigacts_alloc();
448
449 /*
450 * Copy filedesc.
451 */
452 if (fr->fr_flags & RFCFDG) {
453 fd = fdinit(p1->p_fd, false);
454 fdtol = NULL;
455 } else if (fr->fr_flags & RFFDG) {
456 fd = fdcopy(p1->p_fd);
457 fdtol = NULL;
458 } else {
459 fd = fdshare(p1->p_fd);
460 if (p1->p_fdtol == NULL)
461 p1->p_fdtol = filedesc_to_leader_alloc(NULL, NULL,
462 p1->p_leader);
463 if ((fr->fr_flags & RFTHREAD) != 0) {
464 /*
465 * Shared file descriptor table, and shared
466 * process leaders.
467 */
468 fdtol = p1->p_fdtol;
469 FILEDESC_XLOCK(p1->p_fd);
470 fdtol->fdl_refcount++;
471 FILEDESC_XUNLOCK(p1->p_fd);
472 } else {
473 /*
474 * Shared file descriptor table, and different
475 * process leaders.
476 */
477 fdtol = filedesc_to_leader_alloc(p1->p_fdtol,
478 p1->p_fd, p2);
479 }
480 }
481 /*
482 * Make a proc table entry for the new process.
483 * Start by zeroing the section of proc that is zero-initialized,
484 * then copy the section that is copied directly from the parent.
485 */
486
487 PROC_LOCK(p2);
488 PROC_LOCK(p1);
489
490 bzero(&td2->td_startzero,
491 __rangeof(struct thread, td_startzero, td_endzero));
492 td2->td_pflags2 = 0;
493 td2->td_errno = 0;
494
495 bcopy(&td->td_startcopy, &td2->td_startcopy,
496 __rangeof(struct thread, td_startcopy, td_endcopy));
497
498 bcopy(&p2->p_comm, &td2->td_name, sizeof(td2->td_name));
499 td2->td_sigstk = td->td_sigstk;
500 td2->td_flags = TDF_INMEM;
501 td2->td_lend_user_pri = PRI_MAX;
502
503 #ifdef VIMAGE
504 td2->td_vnet = NULL;
505 td2->td_vnet_lpush = NULL;
506 #endif
507
508 /*
509 * Allow the scheduler to initialize the child.
510 */
511 thread_lock(td);
512 sched_fork(td, td2);
513 thread_unlock(td);
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_flag2 = p1->p_flag2 & (P2_ASLR_DISABLE | P2_ASLR_ENABLE |
521 P2_ASLR_IGNSTART | P2_NOTRACE | P2_NOTRACE_EXEC |
522 P2_TRAPCAP |
523 P2_STKGAP_DISABLE | P2_STKGAP_DISABLE_EXEC);
524 p2->p_swtick = ticks;
525 if (p1->p_flag & P_PROFIL)
526 startprofclock(p2);
527
528 if (fr->fr_flags & RFSIGSHARE) {
529 p2->p_sigacts = sigacts_hold(p1->p_sigacts);
530 } else {
531 sigacts_copy(newsigacts, p1->p_sigacts);
532 p2->p_sigacts = newsigacts;
533 if ((fr->fr_flags2 & FR2_DROPSIG_CAUGHT) != 0) {
534 mtx_lock(&p2->p_sigacts->ps_mtx);
535 sig_drop_caught(p2);
536 mtx_unlock(&p2->p_sigacts->ps_mtx);
537 }
538 }
539
540 if (fr->fr_flags & RFTSIGZMB)
541 p2->p_sigparent = RFTSIGNUM(fr->fr_flags);
542 else if (fr->fr_flags & RFLINUXTHPN)
543 p2->p_sigparent = SIGUSR1;
544 else
545 p2->p_sigparent = SIGCHLD;
546
547 p2->p_textvp = p1->p_textvp;
548 p2->p_fd = fd;
549 p2->p_fdtol = fdtol;
550
551 if (p1->p_flag2 & P2_INHERIT_PROTECTED) {
552 p2->p_flag |= P_PROTECTED;
553 p2->p_flag2 |= P2_INHERIT_PROTECTED;
554 }
555
556 /*
557 * p_limit is copy-on-write. Bump its refcount.
558 */
559 lim_fork(p1, p2);
560
561 thread_cow_get_proc(td2, p2);
562
563 pstats_fork(p1->p_stats, p2->p_stats);
564
565 PROC_UNLOCK(p1);
566 PROC_UNLOCK(p2);
567
568 /* Bump references to the text vnode (for procfs). */
569 if (p2->p_textvp)
570 vrefact(p2->p_textvp);
571
572 /*
573 * Set up linkage for kernel based threading.
574 */
575 if ((fr->fr_flags & RFTHREAD) != 0) {
576 mtx_lock(&ppeers_lock);
577 p2->p_peers = p1->p_peers;
578 p1->p_peers = p2;
579 p2->p_leader = p1->p_leader;
580 mtx_unlock(&ppeers_lock);
581 PROC_LOCK(p1->p_leader);
582 if ((p1->p_leader->p_flag & P_WEXIT) != 0) {
583 PROC_UNLOCK(p1->p_leader);
584 /*
585 * The task leader is exiting, so process p1 is
586 * going to be killed shortly. Since p1 obviously
587 * isn't dead yet, we know that the leader is either
588 * sending SIGKILL's to all the processes in this
589 * task or is sleeping waiting for all the peers to
590 * exit. We let p1 complete the fork, but we need
591 * to go ahead and kill the new process p2 since
592 * the task leader may not get a chance to send
593 * SIGKILL to it. We leave it on the list so that
594 * the task leader will wait for this new process
595 * to commit suicide.
596 */
597 PROC_LOCK(p2);
598 kern_psignal(p2, SIGKILL);
599 PROC_UNLOCK(p2);
600 } else
601 PROC_UNLOCK(p1->p_leader);
602 } else {
603 p2->p_peers = NULL;
604 p2->p_leader = p2;
605 }
606
607 sx_xlock(&proctree_lock);
608 PGRP_LOCK(p1->p_pgrp);
609 PROC_LOCK(p2);
610 PROC_LOCK(p1);
611
612 /*
613 * Preserve some more flags in subprocess. P_PROFIL has already
614 * been preserved.
615 */
616 p2->p_flag |= p1->p_flag & P_SUGID;
617 td2->td_pflags |= (td->td_pflags & TDP_ALTSTACK) | TDP_FORKING;
618 SESS_LOCK(p1->p_session);
619 if (p1->p_session->s_ttyvp != NULL && p1->p_flag & P_CONTROLT)
620 p2->p_flag |= P_CONTROLT;
621 SESS_UNLOCK(p1->p_session);
622 if (fr->fr_flags & RFPPWAIT)
623 p2->p_flag |= P_PPWAIT;
624
625 p2->p_pgrp = p1->p_pgrp;
626 LIST_INSERT_AFTER(p1, p2, p_pglist);
627 PGRP_UNLOCK(p1->p_pgrp);
628 LIST_INIT(&p2->p_children);
629 LIST_INIT(&p2->p_orphans);
630
631 callout_init_mtx(&p2->p_itcallout, &p2->p_mtx, 0);
632
633 /*
634 * If PF_FORK is set, the child process inherits the
635 * procfs ioctl flags from its parent.
636 */
637 if (p1->p_pfsflags & PF_FORK) {
638 p2->p_stops = p1->p_stops;
639 p2->p_pfsflags = p1->p_pfsflags;
640 }
641
642 /*
643 * This begins the section where we must prevent the parent
644 * from being swapped.
645 */
646 _PHOLD(p1);
647 PROC_UNLOCK(p1);
648
649 /*
650 * Attach the new process to its parent.
651 *
652 * If RFNOWAIT is set, the newly created process becomes a child
653 * of init. This effectively disassociates the child from the
654 * parent.
655 */
656 if ((fr->fr_flags & RFNOWAIT) != 0) {
657 pptr = p1->p_reaper;
658 p2->p_reaper = pptr;
659 } else {
660 p2->p_reaper = (p1->p_treeflag & P_TREE_REAPER) != 0 ?
661 p1 : p1->p_reaper;
662 pptr = p1;
663 }
664 p2->p_pptr = pptr;
665 p2->p_oppid = pptr->p_pid;
666 LIST_INSERT_HEAD(&pptr->p_children, p2, p_sibling);
667 LIST_INIT(&p2->p_reaplist);
668 LIST_INSERT_HEAD(&p2->p_reaper->p_reaplist, p2, p_reapsibling);
669 if (p2->p_reaper == p1)
670 p2->p_reapsubtree = p2->p_pid;
671 sx_xunlock(&proctree_lock);
672
673 /* Inform accounting that we have forked. */
674 p2->p_acflag = AFORK;
675 PROC_UNLOCK(p2);
676
677 #ifdef KTRACE
678 ktrprocfork(p1, p2);
679 #endif
680
681 /*
682 * Finish creating the child process. It will return via a different
683 * execution path later. (ie: directly into user mode)
684 */
685 vm_forkproc(td, p2, td2, vm2, fr->fr_flags);
686
687 if (fr->fr_flags == (RFFDG | RFPROC)) {
688 VM_CNT_INC(v_forks);
689 VM_CNT_ADD(v_forkpages, p2->p_vmspace->vm_dsize +
690 p2->p_vmspace->vm_ssize);
691 } else if (fr->fr_flags == (RFFDG | RFPROC | RFPPWAIT | RFMEM)) {
692 VM_CNT_INC(v_vforks);
693 VM_CNT_ADD(v_vforkpages, p2->p_vmspace->vm_dsize +
694 p2->p_vmspace->vm_ssize);
695 } else if (p1 == &proc0) {
696 VM_CNT_INC(v_kthreads);
697 VM_CNT_ADD(v_kthreadpages, p2->p_vmspace->vm_dsize +
698 p2->p_vmspace->vm_ssize);
699 } else {
700 VM_CNT_INC(v_rforks);
701 VM_CNT_ADD(v_rforkpages, p2->p_vmspace->vm_dsize +
702 p2->p_vmspace->vm_ssize);
703 }
704
705 /*
706 * Associate the process descriptor with the process before anything
707 * can happen that might cause that process to need the descriptor.
708 * However, don't do this until after fork(2) can no longer fail.
709 */
710 if (fr->fr_flags & RFPROCDESC)
711 procdesc_new(p2, fr->fr_pd_flags);
712
713 /*
714 * Both processes are set up, now check if any loadable modules want
715 * to adjust anything.
716 */
717 EVENTHANDLER_DIRECT_INVOKE(process_fork, p1, p2, fr->fr_flags);
718
719 /*
720 * Set the child start time and mark the process as being complete.
721 */
722 PROC_LOCK(p2);
723 PROC_LOCK(p1);
724 microuptime(&p2->p_stats->p_start);
725 PROC_SLOCK(p2);
726 p2->p_state = PRS_NORMAL;
727 PROC_SUNLOCK(p2);
728
729 #ifdef KDTRACE_HOOKS
730 /*
731 * Tell the DTrace fasttrap provider about the new process so that any
732 * tracepoints inherited from the parent can be removed. We have to do
733 * this only after p_state is PRS_NORMAL since the fasttrap module will
734 * use pfind() later on.
735 */
736 if ((fr->fr_flags & RFMEM) == 0 && dtrace_fasttrap_fork)
737 dtrace_fasttrap_fork(p1, p2);
738 #endif
739 /*
740 * Hold the process so that it cannot exit after we make it runnable,
741 * but before we wait for the debugger.
742 */
743 _PHOLD(p2);
744 if (fr->fr_flags & RFPPWAIT) {
745 td->td_pflags |= TDP_RFPPWAIT;
746 td->td_rfppwait_p = p2;
747 td->td_dbgflags |= TDB_VFORK;
748 }
749 PROC_UNLOCK(p2);
750
751 /*
752 * Now can be swapped.
753 */
754 _PRELE(p1);
755 PROC_UNLOCK(p1);
756
757 /*
758 * Tell any interested parties about the new process.
759 */
760 knote_fork(p1->p_klist, p2->p_pid);
761 SDT_PROBE3(proc, , , create, p2, p1, fr->fr_flags);
762
763 if (fr->fr_flags & RFPROCDESC) {
764 procdesc_finit(p2->p_procdesc, fp_procdesc);
765 fdrop(fp_procdesc, td);
766 }
767
768 /*
769 * Speculative check for PTRACE_FORK. PTRACE_FORK is not
770 * synced with forks in progress so it is OK if we miss it
771 * if being set atm.
772 */
773 if ((p1->p_ptevents & PTRACE_FORK) != 0) {
774 sx_xlock(&proctree_lock);
775 PROC_LOCK(p2);
776
777 /*
778 * p1->p_ptevents & p1->p_pptr are protected by both
779 * process and proctree locks for modifications,
780 * so owning proctree_lock allows the race-free read.
781 */
782 if ((p1->p_ptevents & PTRACE_FORK) != 0) {
783 /*
784 * Arrange for debugger to receive the fork event.
785 *
786 * We can report PL_FLAG_FORKED regardless of
787 * P_FOLLOWFORK settings, but it does not make a sense
788 * for runaway child.
789 */
790 td->td_dbgflags |= TDB_FORK;
791 td->td_dbg_forked = p2->p_pid;
792 td2->td_dbgflags |= TDB_STOPATFORK;
793 proc_set_traced(p2, true);
794 CTR2(KTR_PTRACE,
795 "do_fork: attaching to new child pid %d: oppid %d",
796 p2->p_pid, p2->p_oppid);
797 proc_reparent(p2, p1->p_pptr, false);
798 }
799 PROC_UNLOCK(p2);
800 sx_xunlock(&proctree_lock);
801 }
802
803 if ((fr->fr_flags & RFSTOPPED) == 0) {
804 /*
805 * If RFSTOPPED not requested, make child runnable and
806 * add to run queue.
807 */
808 thread_lock(td2);
809 TD_SET_CAN_RUN(td2);
810 sched_add(td2, SRQ_BORING);
811 thread_unlock(td2);
812 if (fr->fr_pidp != NULL)
813 *fr->fr_pidp = p2->p_pid;
814 } else {
815 *fr->fr_procp = p2;
816 }
817
818 PROC_LOCK(p2);
819 _PRELE(p2);
820 racct_proc_fork_done(p2);
821 PROC_UNLOCK(p2);
822 }
823
824 int
825 fork1(struct thread *td, struct fork_req *fr)
826 {
827 struct proc *p1, *newproc;
828 struct thread *td2;
829 struct vmspace *vm2;
830 struct file *fp_procdesc;
831 vm_ooffset_t mem_charged;
832 int error, nprocs_new, ok;
833 static int curfail;
834 static struct timeval lastfail;
835 int flags, pages;
836
837 flags = fr->fr_flags;
838 pages = fr->fr_pages;
839
840 if ((flags & RFSTOPPED) != 0)
841 MPASS(fr->fr_procp != NULL && fr->fr_pidp == NULL);
842 else
843 MPASS(fr->fr_procp == NULL);
844
845 /* Check for the undefined or unimplemented flags. */
846 if ((flags & ~(RFFLAGS | RFTSIGFLAGS(RFTSIGMASK))) != 0)
847 return (EINVAL);
848
849 /* Signal value requires RFTSIGZMB. */
850 if ((flags & RFTSIGFLAGS(RFTSIGMASK)) != 0 && (flags & RFTSIGZMB) == 0)
851 return (EINVAL);
852
853 /* Can't copy and clear. */
854 if ((flags & (RFFDG|RFCFDG)) == (RFFDG|RFCFDG))
855 return (EINVAL);
856
857 /* Check the validity of the signal number. */
858 if ((flags & RFTSIGZMB) != 0 && (u_int)RFTSIGNUM(flags) > _SIG_MAXSIG)
859 return (EINVAL);
860
861 if ((flags & RFPROCDESC) != 0) {
862 /* Can't not create a process yet get a process descriptor. */
863 if ((flags & RFPROC) == 0)
864 return (EINVAL);
865
866 /* Must provide a place to put a procdesc if creating one. */
867 if (fr->fr_pd_fd == NULL)
868 return (EINVAL);
869
870 /* Check if we are using supported flags. */
871 if ((fr->fr_pd_flags & ~PD_ALLOWED_AT_FORK) != 0)
872 return (EINVAL);
873 }
874
875 p1 = td->td_proc;
876
877 /*
878 * Here we don't create a new process, but we divorce
879 * certain parts of a process from itself.
880 */
881 if ((flags & RFPROC) == 0) {
882 if (fr->fr_procp != NULL)
883 *fr->fr_procp = NULL;
884 else if (fr->fr_pidp != NULL)
885 *fr->fr_pidp = 0;
886 return (fork_norfproc(td, flags));
887 }
888
889 fp_procdesc = NULL;
890 newproc = NULL;
891 vm2 = NULL;
892
893 /*
894 * Increment the nprocs resource before allocations occur.
895 * Although process entries are dynamically created, we still
896 * keep a global limit on the maximum number we will
897 * create. There are hard-limits as to the number of processes
898 * that can run, established by the KVA and memory usage for
899 * the process data.
900 *
901 * Don't allow a nonprivileged user to use the last ten
902 * processes; don't let root exceed the limit.
903 */
904 nprocs_new = atomic_fetchadd_int(&nprocs, 1) + 1;
905 if (nprocs_new >= maxproc - 10) {
906 if (priv_check_cred(td->td_ucred, PRIV_MAXPROC, 0) != 0 ||
907 nprocs_new >= maxproc) {
908 error = EAGAIN;
909 sx_xlock(&allproc_lock);
910 if (ppsratecheck(&lastfail, &curfail, 1)) {
911 printf("maxproc limit exceeded by uid %u "
912 "(pid %d); see tuning(7) and "
913 "login.conf(5)\n",
914 td->td_ucred->cr_ruid, p1->p_pid);
915 }
916 sx_xunlock(&allproc_lock);
917 goto fail2;
918 }
919 }
920
921 /*
922 * If required, create a process descriptor in the parent first; we
923 * will abandon it if something goes wrong. We don't finit() until
924 * later.
925 */
926 if (flags & RFPROCDESC) {
927 error = procdesc_falloc(td, &fp_procdesc, fr->fr_pd_fd,
928 fr->fr_pd_flags, fr->fr_pd_fcaps);
929 if (error != 0)
930 goto fail2;
931 }
932
933 mem_charged = 0;
934 if (pages == 0)
935 pages = kstack_pages;
936 /* Allocate new proc. */
937 newproc = uma_zalloc(proc_zone, M_WAITOK);
938 td2 = FIRST_THREAD_IN_PROC(newproc);
939 if (td2 == NULL) {
940 td2 = thread_alloc(pages);
941 if (td2 == NULL) {
942 error = ENOMEM;
943 goto fail2;
944 }
945 proc_linkup(newproc, td2);
946 } else {
947 if (td2->td_kstack == 0 || td2->td_kstack_pages != pages) {
948 if (td2->td_kstack != 0)
949 vm_thread_dispose(td2);
950 if (!thread_alloc_stack(td2, pages)) {
951 error = ENOMEM;
952 goto fail2;
953 }
954 }
955 }
956
957 if ((flags & RFMEM) == 0) {
958 vm2 = vmspace_fork(p1->p_vmspace, &mem_charged);
959 if (vm2 == NULL) {
960 error = ENOMEM;
961 goto fail2;
962 }
963 if (!swap_reserve(mem_charged)) {
964 /*
965 * The swap reservation failed. The accounting
966 * from the entries of the copied vm2 will be
967 * subtracted in vmspace_free(), so force the
968 * reservation there.
969 */
970 swap_reserve_force(mem_charged);
971 error = ENOMEM;
972 goto fail2;
973 }
974 } else
975 vm2 = NULL;
976
977 /*
978 * XXX: This is ugly; when we copy resource usage, we need to bump
979 * per-cred resource counters.
980 */
981 proc_set_cred_init(newproc, crhold(td->td_ucred));
982
983 /*
984 * Initialize resource accounting for the child process.
985 */
986 error = racct_proc_fork(p1, newproc);
987 if (error != 0) {
988 error = EAGAIN;
989 goto fail1;
990 }
991
992 #ifdef MAC
993 mac_proc_init(newproc);
994 #endif
995 newproc->p_klist = knlist_alloc(&newproc->p_mtx);
996 STAILQ_INIT(&newproc->p_ktr);
997
998 /* We have to lock the process tree while we look for a pid. */
999 sx_xlock(&proctree_lock);
1000 sx_xlock(&allproc_lock);
1001
1002 /*
1003 * Increment the count of procs running with this uid. Don't allow
1004 * a nonprivileged user to exceed their current limit.
1005 *
1006 * XXXRW: Can we avoid privilege here if it's not needed?
1007 */
1008 error = priv_check_cred(td->td_ucred, PRIV_PROC_LIMIT, 0);
1009 if (error == 0)
1010 ok = chgproccnt(td->td_ucred->cr_ruidinfo, 1, 0);
1011 else {
1012 ok = chgproccnt(td->td_ucred->cr_ruidinfo, 1,
1013 lim_cur(td, RLIMIT_NPROC));
1014 }
1015 if (ok) {
1016 do_fork(td, fr, newproc, td2, vm2, fp_procdesc);
1017 return (0);
1018 }
1019
1020 error = EAGAIN;
1021 sx_xunlock(&allproc_lock);
1022 sx_xunlock(&proctree_lock);
1023 #ifdef MAC
1024 mac_proc_destroy(newproc);
1025 #endif
1026 racct_proc_exit(newproc);
1027 fail1:
1028 crfree(newproc->p_ucred);
1029 newproc->p_ucred = NULL;
1030 fail2:
1031 if (vm2 != NULL)
1032 vmspace_free(vm2);
1033 uma_zfree(proc_zone, newproc);
1034 if ((flags & RFPROCDESC) != 0 && fp_procdesc != NULL) {
1035 fdclose(td, fp_procdesc, *fr->fr_pd_fd);
1036 fdrop(fp_procdesc, td);
1037 }
1038 atomic_add_int(&nprocs, -1);
1039 pause("fork", hz / 2);
1040 return (error);
1041 }
1042
1043 /*
1044 * Handle the return of a child process from fork1(). This function
1045 * is called from the MD fork_trampoline() entry point.
1046 */
1047 void
1048 fork_exit(void (*callout)(void *, struct trapframe *), void *arg,
1049 struct trapframe *frame)
1050 {
1051 struct proc *p;
1052 struct thread *td;
1053 struct thread *dtd;
1054
1055 td = curthread;
1056 p = td->td_proc;
1057 KASSERT(p->p_state == PRS_NORMAL, ("executing process is still new"));
1058
1059 CTR4(KTR_PROC, "fork_exit: new thread %p (td_sched %p, pid %d, %s)",
1060 td, td_get_sched(td), p->p_pid, td->td_name);
1061
1062 sched_fork_exit(td);
1063 /*
1064 * Processes normally resume in mi_switch() after being
1065 * cpu_switch()'ed to, but when children start up they arrive here
1066 * instead, so we must do much the same things as mi_switch() would.
1067 */
1068 if ((dtd = PCPU_GET(deadthread))) {
1069 PCPU_SET(deadthread, NULL);
1070 thread_stash(dtd);
1071 }
1072 thread_unlock(td);
1073
1074 /*
1075 * cpu_fork_kthread_handler intercepts this function call to
1076 * have this call a non-return function to stay in kernel mode.
1077 * initproc has its own fork handler, but it does return.
1078 */
1079 KASSERT(callout != NULL, ("NULL callout in fork_exit"));
1080 callout(arg, frame);
1081
1082 /*
1083 * Check if a kernel thread misbehaved and returned from its main
1084 * function.
1085 */
1086 if (p->p_flag & P_KPROC) {
1087 printf("Kernel thread \"%s\" (pid %d) exited prematurely.\n",
1088 td->td_name, p->p_pid);
1089 kthread_exit();
1090 }
1091 mtx_assert(&Giant, MA_NOTOWNED);
1092
1093 if (p->p_sysent->sv_schedtail != NULL)
1094 (p->p_sysent->sv_schedtail)(td);
1095 td->td_pflags &= ~TDP_FORKING;
1096 }
1097
1098 /*
1099 * Simplified back end of syscall(), used when returning from fork()
1100 * directly into user mode. This function is passed in to fork_exit()
1101 * as the first parameter and is called when returning to a new
1102 * userland process.
1103 */
1104 void
1105 fork_return(struct thread *td, struct trapframe *frame)
1106 {
1107 struct proc *p;
1108
1109 p = td->td_proc;
1110 if (td->td_dbgflags & TDB_STOPATFORK) {
1111 PROC_LOCK(p);
1112 if ((p->p_flag & P_TRACED) != 0) {
1113 /*
1114 * Inform the debugger if one is still present.
1115 */
1116 td->td_dbgflags |= TDB_CHILD | TDB_SCX | TDB_FSTP;
1117 ptracestop(td, SIGSTOP, NULL);
1118 td->td_dbgflags &= ~(TDB_CHILD | TDB_SCX);
1119 } else {
1120 /*
1121 * ... otherwise clear the request.
1122 */
1123 td->td_dbgflags &= ~TDB_STOPATFORK;
1124 }
1125 PROC_UNLOCK(p);
1126 } else if (p->p_flag & P_TRACED || td->td_dbgflags & TDB_BORN) {
1127 /*
1128 * This is the start of a new thread in a traced
1129 * process. Report a system call exit event.
1130 */
1131 PROC_LOCK(p);
1132 td->td_dbgflags |= TDB_SCX;
1133 _STOPEVENT(p, S_SCX, td->td_sa.code);
1134 if ((p->p_ptevents & PTRACE_SCX) != 0 ||
1135 (td->td_dbgflags & TDB_BORN) != 0)
1136 ptracestop(td, SIGTRAP, NULL);
1137 td->td_dbgflags &= ~(TDB_SCX | TDB_BORN);
1138 PROC_UNLOCK(p);
1139 }
1140
1141 /*
1142 * If the prison was killed mid-fork, die along with it.
1143 */
1144 if (td->td_ucred->cr_prison->pr_flags & PR_REMOVE)
1145 exit1(td, 0, SIGKILL);
1146
1147 userret(td, frame);
1148
1149 #ifdef KTRACE
1150 if (KTRPOINT(td, KTR_SYSRET))
1151 ktrsysret(SYS_fork, 0, 0);
1152 #endif
1153 }
Cache object: addbd6f910b1c219d8d99fd0919905a8
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