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/11.2/sys/kern/kern_fork.c 333162 2018-05-02 07:57:36Z kib $");
39
40 #include "opt_ktrace.h"
41 #include "opt_kstack_pages.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/fcntl.h>
48 #include <sys/filedesc.h>
49 #include <sys/jail.h>
50 #include <sys/kernel.h>
51 #include <sys/kthread.h>
52 #include <sys/sysctl.h>
53 #include <sys/lock.h>
54 #include <sys/malloc.h>
55 #include <sys/mutex.h>
56 #include <sys/priv.h>
57 #include <sys/proc.h>
58 #include <sys/procdesc.h>
59 #include <sys/pioctl.h>
60 #include <sys/ptrace.h>
61 #include <sys/racct.h>
62 #include <sys/resourcevar.h>
63 #include <sys/sched.h>
64 #include <sys/syscall.h>
65 #include <sys/vmmeter.h>
66 #include <sys/vnode.h>
67 #include <sys/acct.h>
68 #include <sys/ktr.h>
69 #include <sys/ktrace.h>
70 #include <sys/unistd.h>
71 #include <sys/sdt.h>
72 #include <sys/sx.h>
73 #include <sys/sysent.h>
74 #include <sys/signalvar.h>
75
76 #include <security/audit/audit.h>
77 #include <security/mac/mac_framework.h>
78
79 #include <vm/vm.h>
80 #include <vm/pmap.h>
81 #include <vm/vm_map.h>
82 #include <vm/vm_extern.h>
83 #include <vm/uma.h>
84 #include <vm/vm_domain.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, , , create, "struct proc *", "struct proc *", "int");
93
94 #ifndef _SYS_SYSPROTO_H_
95 struct fork_args {
96 int dummy;
97 };
98 #endif
99
100 EVENTHANDLER_LIST_DECLARE(process_fork);
101
102 /* ARGSUSED */
103 int
104 sys_fork(struct thread *td, struct fork_args *uap)
105 {
106 struct fork_req fr;
107 int error, pid;
108
109 bzero(&fr, sizeof(fr));
110 fr.fr_flags = RFFDG | RFPROC;
111 fr.fr_pidp = &pid;
112 error = fork1(td, &fr);
113 if (error == 0) {
114 td->td_retval[0] = pid;
115 td->td_retval[1] = 0;
116 }
117 return (error);
118 }
119
120 /* ARGUSED */
121 int
122 sys_pdfork(struct thread *td, struct pdfork_args *uap)
123 {
124 struct fork_req fr;
125 int error, fd, pid;
126
127 bzero(&fr, sizeof(fr));
128 fr.fr_flags = RFFDG | RFPROC | RFPROCDESC;
129 fr.fr_pidp = &pid;
130 fr.fr_pd_fd = &fd;
131 fr.fr_pd_flags = uap->flags;
132 /*
133 * It is necessary to return fd by reference because 0 is a valid file
134 * descriptor number, and the child needs to be able to distinguish
135 * itself from the parent using the return value.
136 */
137 error = fork1(td, &fr);
138 if (error == 0) {
139 td->td_retval[0] = pid;
140 td->td_retval[1] = 0;
141 error = copyout(&fd, uap->fdp, sizeof(fd));
142 }
143 return (error);
144 }
145
146 /* ARGSUSED */
147 int
148 sys_vfork(struct thread *td, struct vfork_args *uap)
149 {
150 struct fork_req fr;
151 int error, pid;
152
153 bzero(&fr, sizeof(fr));
154 fr.fr_flags = RFFDG | RFPROC | RFPPWAIT | RFMEM;
155 fr.fr_pidp = &pid;
156 error = fork1(td, &fr);
157 if (error == 0) {
158 td->td_retval[0] = pid;
159 td->td_retval[1] = 0;
160 }
161 return (error);
162 }
163
164 int
165 sys_rfork(struct thread *td, struct rfork_args *uap)
166 {
167 struct fork_req fr;
168 int error, pid;
169
170 /* Don't allow kernel-only flags. */
171 if ((uap->flags & RFKERNELONLY) != 0)
172 return (EINVAL);
173
174 AUDIT_ARG_FFLAGS(uap->flags);
175 bzero(&fr, sizeof(fr));
176 fr.fr_flags = uap->flags;
177 fr.fr_pidp = &pid;
178 error = fork1(td, &fr);
179 if (error == 0) {
180 td->td_retval[0] = pid;
181 td->td_retval[1] = 0;
182 }
183 return (error);
184 }
185
186 int nprocs = 1; /* process 0 */
187 int lastpid = 0;
188 SYSCTL_INT(_kern, OID_AUTO, lastpid, CTLFLAG_RD, &lastpid, 0,
189 "Last used PID");
190
191 /*
192 * Random component to lastpid generation. We mix in a random factor to make
193 * it a little harder to predict. We sanity check the modulus value to avoid
194 * doing it in critical paths. Don't let it be too small or we pointlessly
195 * waste randomness entropy, and don't let it be impossibly large. Using a
196 * modulus that is too big causes a LOT more process table scans and slows
197 * down fork processing as the pidchecked caching is defeated.
198 */
199 static int randompid = 0;
200
201 static int
202 sysctl_kern_randompid(SYSCTL_HANDLER_ARGS)
203 {
204 int error, pid;
205
206 error = sysctl_wire_old_buffer(req, sizeof(int));
207 if (error != 0)
208 return(error);
209 sx_xlock(&allproc_lock);
210 pid = randompid;
211 error = sysctl_handle_int(oidp, &pid, 0, req);
212 if (error == 0 && req->newptr != NULL) {
213 if (pid == 0)
214 randompid = 0;
215 else if (pid == 1)
216 /* generate a random PID modulus between 100 and 1123 */
217 randompid = 100 + arc4random() % 1024;
218 else if (pid < 0 || pid > pid_max - 100)
219 /* out of range */
220 randompid = pid_max - 100;
221 else if (pid < 100)
222 /* Make it reasonable */
223 randompid = 100;
224 else
225 randompid = pid;
226 }
227 sx_xunlock(&allproc_lock);
228 return (error);
229 }
230
231 SYSCTL_PROC(_kern, OID_AUTO, randompid, CTLTYPE_INT|CTLFLAG_RW,
232 0, 0, sysctl_kern_randompid, "I", "Random PID modulus. Special values: 0: disable, 1: choose random value");
233
234 static int
235 fork_findpid(int flags)
236 {
237 struct proc *p;
238 int trypid;
239 static int pidchecked = 0;
240
241 /*
242 * Requires allproc_lock in order to iterate over the list
243 * of processes, and proctree_lock to access p_pgrp.
244 */
245 sx_assert(&allproc_lock, SX_LOCKED);
246 sx_assert(&proctree_lock, SX_LOCKED);
247
248 /*
249 * Find an unused process ID. We remember a range of unused IDs
250 * ready to use (from lastpid+1 through pidchecked-1).
251 *
252 * If RFHIGHPID is set (used during system boot), do not allocate
253 * low-numbered pids.
254 */
255 trypid = lastpid + 1;
256 if (flags & RFHIGHPID) {
257 if (trypid < 10)
258 trypid = 10;
259 } else {
260 if (randompid)
261 trypid += arc4random() % randompid;
262 }
263 retry:
264 /*
265 * If the process ID prototype has wrapped around,
266 * restart somewhat above 0, as the low-numbered procs
267 * tend to include daemons that don't exit.
268 */
269 if (trypid >= pid_max) {
270 trypid = trypid % pid_max;
271 if (trypid < 100)
272 trypid += 100;
273 pidchecked = 0;
274 }
275 if (trypid >= pidchecked) {
276 int doingzomb = 0;
277
278 pidchecked = PID_MAX;
279 /*
280 * Scan the active and zombie procs to check whether this pid
281 * is in use. Remember the lowest pid that's greater
282 * than trypid, so we can avoid checking for a while.
283 *
284 * Avoid reuse of the process group id, session id or
285 * the reaper subtree id. Note that for process group
286 * and sessions, the amount of reserved pids is
287 * limited by process limit. For the subtree ids, the
288 * id is kept reserved only while there is a
289 * non-reaped process in the subtree, so amount of
290 * reserved pids is limited by process limit times
291 * two.
292 */
293 p = LIST_FIRST(&allproc);
294 again:
295 for (; p != NULL; p = LIST_NEXT(p, p_list)) {
296 while (p->p_pid == trypid ||
297 p->p_reapsubtree == trypid ||
298 (p->p_pgrp != NULL &&
299 (p->p_pgrp->pg_id == trypid ||
300 (p->p_session != NULL &&
301 p->p_session->s_sid == trypid)))) {
302 trypid++;
303 if (trypid >= pidchecked)
304 goto retry;
305 }
306 if (p->p_pid > trypid && pidchecked > p->p_pid)
307 pidchecked = p->p_pid;
308 if (p->p_pgrp != NULL) {
309 if (p->p_pgrp->pg_id > trypid &&
310 pidchecked > p->p_pgrp->pg_id)
311 pidchecked = p->p_pgrp->pg_id;
312 if (p->p_session != NULL &&
313 p->p_session->s_sid > trypid &&
314 pidchecked > p->p_session->s_sid)
315 pidchecked = p->p_session->s_sid;
316 }
317 }
318 if (!doingzomb) {
319 doingzomb = 1;
320 p = LIST_FIRST(&zombproc);
321 goto again;
322 }
323 }
324
325 /*
326 * RFHIGHPID does not mess with the lastpid counter during boot.
327 */
328 if (flags & RFHIGHPID)
329 pidchecked = 0;
330 else
331 lastpid = trypid;
332
333 return (trypid);
334 }
335
336 static int
337 fork_norfproc(struct thread *td, int flags)
338 {
339 int error;
340 struct proc *p1;
341
342 KASSERT((flags & RFPROC) == 0,
343 ("fork_norfproc called with RFPROC set"));
344 p1 = td->td_proc;
345
346 if (((p1->p_flag & (P_HADTHREADS|P_SYSTEM)) == P_HADTHREADS) &&
347 (flags & (RFCFDG | RFFDG))) {
348 PROC_LOCK(p1);
349 if (thread_single(p1, SINGLE_BOUNDARY)) {
350 PROC_UNLOCK(p1);
351 return (ERESTART);
352 }
353 PROC_UNLOCK(p1);
354 }
355
356 error = vm_forkproc(td, NULL, NULL, NULL, flags);
357 if (error)
358 goto fail;
359
360 /*
361 * Close all file descriptors.
362 */
363 if (flags & RFCFDG) {
364 struct filedesc *fdtmp;
365 fdtmp = fdinit(td->td_proc->p_fd, false);
366 fdescfree(td);
367 p1->p_fd = fdtmp;
368 }
369
370 /*
371 * Unshare file descriptors (from parent).
372 */
373 if (flags & RFFDG)
374 fdunshare(td);
375
376 fail:
377 if (((p1->p_flag & (P_HADTHREADS|P_SYSTEM)) == P_HADTHREADS) &&
378 (flags & (RFCFDG | RFFDG))) {
379 PROC_LOCK(p1);
380 thread_single_end(p1, SINGLE_BOUNDARY);
381 PROC_UNLOCK(p1);
382 }
383 return (error);
384 }
385
386 static void
387 do_fork(struct thread *td, struct fork_req *fr, struct proc *p2, struct thread *td2,
388 struct vmspace *vm2, struct file *fp_procdesc)
389 {
390 struct proc *p1, *pptr;
391 int trypid;
392 struct filedesc *fd;
393 struct filedesc_to_leader *fdtol;
394 struct sigacts *newsigacts;
395
396 sx_assert(&proctree_lock, SX_SLOCKED);
397 sx_assert(&allproc_lock, SX_XLOCKED);
398
399 p1 = td->td_proc;
400
401 trypid = fork_findpid(fr->fr_flags);
402
403 sx_sunlock(&proctree_lock);
404
405 p2->p_state = PRS_NEW; /* protect against others */
406 p2->p_pid = trypid;
407 AUDIT_ARG_PID(p2->p_pid);
408 LIST_INSERT_HEAD(&allproc, p2, p_list);
409 allproc_gen++;
410 LIST_INSERT_HEAD(PIDHASH(p2->p_pid), p2, p_hash);
411 tidhash_add(td2);
412 PROC_LOCK(p2);
413 PROC_LOCK(p1);
414
415 sx_xunlock(&allproc_lock);
416
417 bcopy(&p1->p_startcopy, &p2->p_startcopy,
418 __rangeof(struct proc, p_startcopy, p_endcopy));
419 p2->p_elf_machine = p1->p_elf_machine;
420 p2->p_elf_flags = p1->p_elf_flags;
421 pargs_hold(p2->p_args);
422
423 PROC_UNLOCK(p1);
424
425 bzero(&p2->p_startzero,
426 __rangeof(struct proc, p_startzero, p_endzero));
427 p2->p_ptevents = 0;
428 p2->p_pdeathsig = 0;
429
430 /* Tell the prison that we exist. */
431 prison_proc_hold(p2->p_ucred->cr_prison);
432
433 PROC_UNLOCK(p2);
434
435 /*
436 * Malloc things while we don't hold any locks.
437 */
438 if (fr->fr_flags & RFSIGSHARE)
439 newsigacts = NULL;
440 else
441 newsigacts = sigacts_alloc();
442
443 /*
444 * Copy filedesc.
445 */
446 if (fr->fr_flags & RFCFDG) {
447 fd = fdinit(p1->p_fd, false);
448 fdtol = NULL;
449 } else if (fr->fr_flags & RFFDG) {
450 fd = fdcopy(p1->p_fd);
451 fdtol = NULL;
452 } else {
453 fd = fdshare(p1->p_fd);
454 if (p1->p_fdtol == NULL)
455 p1->p_fdtol = filedesc_to_leader_alloc(NULL, NULL,
456 p1->p_leader);
457 if ((fr->fr_flags & RFTHREAD) != 0) {
458 /*
459 * Shared file descriptor table, and shared
460 * process leaders.
461 */
462 fdtol = p1->p_fdtol;
463 FILEDESC_XLOCK(p1->p_fd);
464 fdtol->fdl_refcount++;
465 FILEDESC_XUNLOCK(p1->p_fd);
466 } else {
467 /*
468 * Shared file descriptor table, and different
469 * process leaders.
470 */
471 fdtol = filedesc_to_leader_alloc(p1->p_fdtol,
472 p1->p_fd, p2);
473 }
474 }
475 /*
476 * Make a proc table entry for the new process.
477 * Start by zeroing the section of proc that is zero-initialized,
478 * then copy the section that is copied directly from the parent.
479 */
480
481 PROC_LOCK(p2);
482 PROC_LOCK(p1);
483
484 bzero(&td2->td_startzero,
485 __rangeof(struct thread, td_startzero, td_endzero));
486 td2->td_sleeptimo = 0;
487 td2->td_vslock_sz = 0;
488 bzero(&td2->td_si, sizeof(td2->td_si));
489
490 bcopy(&td->td_startcopy, &td2->td_startcopy,
491 __rangeof(struct thread, td_startcopy, td_endcopy));
492 td2->td_sa = td->td_sa;
493
494 bcopy(&p2->p_comm, &td2->td_name, sizeof(td2->td_name));
495 td2->td_sigstk = td->td_sigstk;
496 td2->td_flags = TDF_INMEM;
497 td2->td_lend_user_pri = PRI_MAX;
498
499 #ifdef VIMAGE
500 td2->td_vnet = NULL;
501 td2->td_vnet_lpush = NULL;
502 #endif
503
504 /*
505 * Allow the scheduler to initialize the child.
506 */
507 thread_lock(td);
508 sched_fork(td, td2);
509 thread_unlock(td);
510
511 /*
512 * Duplicate sub-structures as needed.
513 * Increase reference counts on shared objects.
514 */
515 p2->p_flag = P_INMEM;
516 p2->p_flag2 = p1->p_flag2 & (P2_NOTRACE | P2_NOTRACE_EXEC | P2_TRAPCAP);
517 p2->p_swtick = ticks;
518 if (p1->p_flag & P_PROFIL)
519 startprofclock(p2);
520
521 /*
522 * Whilst the proc lock is held, copy the VM domain data out
523 * using the VM domain method.
524 */
525 vm_domain_policy_init(&p2->p_vm_dom_policy);
526 vm_domain_policy_localcopy(&p2->p_vm_dom_policy,
527 &p1->p_vm_dom_policy);
528
529 if (fr->fr_flags & RFSIGSHARE) {
530 p2->p_sigacts = sigacts_hold(p1->p_sigacts);
531 } else {
532 sigacts_copy(newsigacts, p1->p_sigacts);
533 p2->p_sigacts = newsigacts;
534 }
535
536 if (fr->fr_flags & RFTSIGZMB)
537 p2->p_sigparent = RFTSIGNUM(fr->fr_flags);
538 else if (fr->fr_flags & RFLINUXTHPN)
539 p2->p_sigparent = SIGUSR1;
540 else
541 p2->p_sigparent = SIGCHLD;
542
543 p2->p_textvp = p1->p_textvp;
544 p2->p_fd = fd;
545 p2->p_fdtol = fdtol;
546
547 if (p1->p_flag2 & P2_INHERIT_PROTECTED) {
548 p2->p_flag |= P_PROTECTED;
549 p2->p_flag2 |= P2_INHERIT_PROTECTED;
550 }
551
552 /*
553 * p_limit is copy-on-write. Bump its refcount.
554 */
555 lim_fork(p1, p2);
556
557 thread_cow_get_proc(td2, p2);
558
559 pstats_fork(p1->p_stats, p2->p_stats);
560
561 PROC_UNLOCK(p1);
562 PROC_UNLOCK(p2);
563
564 /* Bump references to the text vnode (for procfs). */
565 if (p2->p_textvp)
566 vrefact(p2->p_textvp);
567
568 /*
569 * Set up linkage for kernel based threading.
570 */
571 if ((fr->fr_flags & RFTHREAD) != 0) {
572 mtx_lock(&ppeers_lock);
573 p2->p_peers = p1->p_peers;
574 p1->p_peers = p2;
575 p2->p_leader = p1->p_leader;
576 mtx_unlock(&ppeers_lock);
577 PROC_LOCK(p1->p_leader);
578 if ((p1->p_leader->p_flag & P_WEXIT) != 0) {
579 PROC_UNLOCK(p1->p_leader);
580 /*
581 * The task leader is exiting, so process p1 is
582 * going to be killed shortly. Since p1 obviously
583 * isn't dead yet, we know that the leader is either
584 * sending SIGKILL's to all the processes in this
585 * task or is sleeping waiting for all the peers to
586 * exit. We let p1 complete the fork, but we need
587 * to go ahead and kill the new process p2 since
588 * the task leader may not get a chance to send
589 * SIGKILL to it. We leave it on the list so that
590 * the task leader will wait for this new process
591 * to commit suicide.
592 */
593 PROC_LOCK(p2);
594 kern_psignal(p2, SIGKILL);
595 PROC_UNLOCK(p2);
596 } else
597 PROC_UNLOCK(p1->p_leader);
598 } else {
599 p2->p_peers = NULL;
600 p2->p_leader = p2;
601 }
602
603 sx_xlock(&proctree_lock);
604 PGRP_LOCK(p1->p_pgrp);
605 PROC_LOCK(p2);
606 PROC_LOCK(p1);
607
608 /*
609 * Preserve some more flags in subprocess. P_PROFIL has already
610 * been preserved.
611 */
612 p2->p_flag |= p1->p_flag & P_SUGID;
613 td2->td_pflags |= (td->td_pflags & TDP_ALTSTACK) | TDP_FORKING;
614 SESS_LOCK(p1->p_session);
615 if (p1->p_session->s_ttyvp != NULL && p1->p_flag & P_CONTROLT)
616 p2->p_flag |= P_CONTROLT;
617 SESS_UNLOCK(p1->p_session);
618 if (fr->fr_flags & RFPPWAIT)
619 p2->p_flag |= P_PPWAIT;
620
621 p2->p_pgrp = p1->p_pgrp;
622 LIST_INSERT_AFTER(p1, p2, p_pglist);
623 PGRP_UNLOCK(p1->p_pgrp);
624 LIST_INIT(&p2->p_children);
625 LIST_INIT(&p2->p_orphans);
626
627 callout_init_mtx(&p2->p_itcallout, &p2->p_mtx, 0);
628
629 /*
630 * If PF_FORK is set, the child process inherits the
631 * procfs ioctl flags from its parent.
632 */
633 if (p1->p_pfsflags & PF_FORK) {
634 p2->p_stops = p1->p_stops;
635 p2->p_pfsflags = p1->p_pfsflags;
636 }
637
638 /*
639 * This begins the section where we must prevent the parent
640 * from being swapped.
641 */
642 _PHOLD(p1);
643 PROC_UNLOCK(p1);
644
645 /*
646 * Attach the new process to its parent.
647 *
648 * If RFNOWAIT is set, the newly created process becomes a child
649 * of init. This effectively disassociates the child from the
650 * parent.
651 */
652 if ((fr->fr_flags & RFNOWAIT) != 0) {
653 pptr = p1->p_reaper;
654 p2->p_reaper = pptr;
655 } else {
656 p2->p_reaper = (p1->p_treeflag & P_TREE_REAPER) != 0 ?
657 p1 : p1->p_reaper;
658 pptr = p1;
659 }
660 p2->p_pptr = pptr;
661 LIST_INSERT_HEAD(&pptr->p_children, p2, p_sibling);
662 LIST_INIT(&p2->p_reaplist);
663 LIST_INSERT_HEAD(&p2->p_reaper->p_reaplist, p2, p_reapsibling);
664 if (p2->p_reaper == p1)
665 p2->p_reapsubtree = p2->p_pid;
666 sx_xunlock(&proctree_lock);
667
668 /* Inform accounting that we have forked. */
669 p2->p_acflag = AFORK;
670 PROC_UNLOCK(p2);
671
672 #ifdef KTRACE
673 ktrprocfork(p1, p2);
674 #endif
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, fr->fr_flags);
681
682 if (fr->fr_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 (fr->fr_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 * Associate the process descriptor with the process before anything
702 * can happen that might cause that process to need the descriptor.
703 * However, don't do this until after fork(2) can no longer fail.
704 */
705 if (fr->fr_flags & RFPROCDESC)
706 procdesc_new(p2, fr->fr_pd_flags);
707
708 /*
709 * Both processes are set up, now check if any loadable modules want
710 * to adjust anything.
711 */
712 EVENTHANDLER_DIRECT_INVOKE(process_fork, p1, p2, fr->fr_flags);
713
714 /*
715 * Set the child start time and mark the process as being complete.
716 */
717 PROC_LOCK(p2);
718 PROC_LOCK(p1);
719 microuptime(&p2->p_stats->p_start);
720 PROC_SLOCK(p2);
721 p2->p_state = PRS_NORMAL;
722 PROC_SUNLOCK(p2);
723
724 #ifdef KDTRACE_HOOKS
725 /*
726 * Tell the DTrace fasttrap provider about the new process so that any
727 * tracepoints inherited from the parent can be removed. We have to do
728 * this only after p_state is PRS_NORMAL since the fasttrap module will
729 * use pfind() later on.
730 */
731 if ((fr->fr_flags & RFMEM) == 0 && dtrace_fasttrap_fork)
732 dtrace_fasttrap_fork(p1, p2);
733 #endif
734 /*
735 * Hold the process so that it cannot exit after we make it runnable,
736 * but before we wait for the debugger.
737 */
738 _PHOLD(p2);
739 if (p1->p_ptevents & PTRACE_FORK) {
740 /*
741 * Arrange for debugger to receive the fork event.
742 *
743 * We can report PL_FLAG_FORKED regardless of
744 * P_FOLLOWFORK settings, but it does not make a sense
745 * for runaway child.
746 */
747 td->td_dbgflags |= TDB_FORK;
748 td->td_dbg_forked = p2->p_pid;
749 td2->td_dbgflags |= TDB_STOPATFORK;
750 }
751 if (fr->fr_flags & RFPPWAIT) {
752 td->td_pflags |= TDP_RFPPWAIT;
753 td->td_rfppwait_p = p2;
754 td->td_dbgflags |= TDB_VFORK;
755 }
756 PROC_UNLOCK(p2);
757
758 /*
759 * Now can be swapped.
760 */
761 _PRELE(p1);
762 PROC_UNLOCK(p1);
763
764 /*
765 * Tell any interested parties about the new process.
766 */
767 knote_fork(p1->p_klist, p2->p_pid);
768 SDT_PROBE3(proc, , , create, p2, p1, fr->fr_flags);
769
770 if (fr->fr_flags & RFPROCDESC) {
771 procdesc_finit(p2->p_procdesc, fp_procdesc);
772 fdrop(fp_procdesc, td);
773 }
774
775 if ((fr->fr_flags & RFSTOPPED) == 0) {
776 /*
777 * If RFSTOPPED not requested, make child runnable and
778 * add to run queue.
779 */
780 thread_lock(td2);
781 TD_SET_CAN_RUN(td2);
782 sched_add(td2, SRQ_BORING);
783 thread_unlock(td2);
784 if (fr->fr_pidp != NULL)
785 *fr->fr_pidp = p2->p_pid;
786 } else {
787 *fr->fr_procp = p2;
788 }
789
790 PROC_LOCK(p2);
791 /*
792 * Wait until debugger is attached to child.
793 */
794 while (td2->td_proc == p2 && (td2->td_dbgflags & TDB_STOPATFORK) != 0)
795 cv_wait(&p2->p_dbgwait, &p2->p_mtx);
796 _PRELE(p2);
797 racct_proc_fork_done(p2);
798 PROC_UNLOCK(p2);
799 }
800
801 int
802 fork1(struct thread *td, struct fork_req *fr)
803 {
804 struct proc *p1, *newproc;
805 struct thread *td2;
806 struct vmspace *vm2;
807 struct file *fp_procdesc;
808 vm_ooffset_t mem_charged;
809 int error, nprocs_new, ok;
810 static int curfail;
811 static struct timeval lastfail;
812 int flags, pages;
813
814 flags = fr->fr_flags;
815 pages = fr->fr_pages;
816
817 if ((flags & RFSTOPPED) != 0)
818 MPASS(fr->fr_procp != NULL && fr->fr_pidp == NULL);
819 else
820 MPASS(fr->fr_procp == NULL);
821
822 /* Check for the undefined or unimplemented flags. */
823 if ((flags & ~(RFFLAGS | RFTSIGFLAGS(RFTSIGMASK))) != 0)
824 return (EINVAL);
825
826 /* Signal value requires RFTSIGZMB. */
827 if ((flags & RFTSIGFLAGS(RFTSIGMASK)) != 0 && (flags & RFTSIGZMB) == 0)
828 return (EINVAL);
829
830 /* Can't copy and clear. */
831 if ((flags & (RFFDG|RFCFDG)) == (RFFDG|RFCFDG))
832 return (EINVAL);
833
834 /* Check the validity of the signal number. */
835 if ((flags & RFTSIGZMB) != 0 && (u_int)RFTSIGNUM(flags) > _SIG_MAXSIG)
836 return (EINVAL);
837
838 if ((flags & RFPROCDESC) != 0) {
839 /* Can't not create a process yet get a process descriptor. */
840 if ((flags & RFPROC) == 0)
841 return (EINVAL);
842
843 /* Must provide a place to put a procdesc if creating one. */
844 if (fr->fr_pd_fd == NULL)
845 return (EINVAL);
846
847 /* Check if we are using supported flags. */
848 if ((fr->fr_pd_flags & ~PD_ALLOWED_AT_FORK) != 0)
849 return (EINVAL);
850 }
851
852 p1 = td->td_proc;
853
854 /*
855 * Here we don't create a new process, but we divorce
856 * certain parts of a process from itself.
857 */
858 if ((flags & RFPROC) == 0) {
859 if (fr->fr_procp != NULL)
860 *fr->fr_procp = NULL;
861 else if (fr->fr_pidp != NULL)
862 *fr->fr_pidp = 0;
863 return (fork_norfproc(td, flags));
864 }
865
866 fp_procdesc = NULL;
867 newproc = NULL;
868 vm2 = NULL;
869
870 /*
871 * Increment the nprocs resource before allocations occur.
872 * Although process entries are dynamically created, we still
873 * keep a global limit on the maximum number we will
874 * create. There are hard-limits as to the number of processes
875 * that can run, established by the KVA and memory usage for
876 * the process data.
877 *
878 * Don't allow a nonprivileged user to use the last ten
879 * processes; don't let root exceed the limit.
880 */
881 nprocs_new = atomic_fetchadd_int(&nprocs, 1) + 1;
882 if ((nprocs_new >= maxproc - 10 && priv_check_cred(td->td_ucred,
883 PRIV_MAXPROC, 0) != 0) || nprocs_new >= maxproc) {
884 error = EAGAIN;
885 sx_xlock(&allproc_lock);
886 if (ppsratecheck(&lastfail, &curfail, 1)) {
887 printf("maxproc limit exceeded by uid %u (pid %d); "
888 "see tuning(7) and login.conf(5)\n",
889 td->td_ucred->cr_ruid, p1->p_pid);
890 }
891 sx_xunlock(&allproc_lock);
892 goto fail2;
893 }
894
895 /*
896 * If required, create a process descriptor in the parent first; we
897 * will abandon it if something goes wrong. We don't finit() until
898 * later.
899 */
900 if (flags & RFPROCDESC) {
901 error = procdesc_falloc(td, &fp_procdesc, fr->fr_pd_fd,
902 fr->fr_pd_flags, fr->fr_pd_fcaps);
903 if (error != 0)
904 goto fail2;
905 }
906
907 mem_charged = 0;
908 if (pages == 0)
909 pages = kstack_pages;
910 /* Allocate new proc. */
911 newproc = uma_zalloc(proc_zone, M_WAITOK);
912 td2 = FIRST_THREAD_IN_PROC(newproc);
913 if (td2 == NULL) {
914 td2 = thread_alloc(pages);
915 if (td2 == NULL) {
916 error = ENOMEM;
917 goto fail2;
918 }
919 proc_linkup(newproc, td2);
920 } else {
921 if (td2->td_kstack == 0 || td2->td_kstack_pages != pages) {
922 if (td2->td_kstack != 0)
923 vm_thread_dispose(td2);
924 if (!thread_alloc_stack(td2, pages)) {
925 error = ENOMEM;
926 goto fail2;
927 }
928 }
929 }
930
931 if ((flags & RFMEM) == 0) {
932 vm2 = vmspace_fork(p1->p_vmspace, &mem_charged);
933 if (vm2 == NULL) {
934 error = ENOMEM;
935 goto fail2;
936 }
937 if (!swap_reserve(mem_charged)) {
938 /*
939 * The swap reservation failed. The accounting
940 * from the entries of the copied vm2 will be
941 * subtracted in vmspace_free(), so force the
942 * reservation there.
943 */
944 swap_reserve_force(mem_charged);
945 error = ENOMEM;
946 goto fail2;
947 }
948 } else
949 vm2 = NULL;
950
951 /*
952 * XXX: This is ugly; when we copy resource usage, we need to bump
953 * per-cred resource counters.
954 */
955 proc_set_cred_init(newproc, crhold(td->td_ucred));
956
957 /*
958 * Initialize resource accounting for the child process.
959 */
960 error = racct_proc_fork(p1, newproc);
961 if (error != 0) {
962 error = EAGAIN;
963 goto fail1;
964 }
965
966 #ifdef MAC
967 mac_proc_init(newproc);
968 #endif
969 newproc->p_klist = knlist_alloc(&newproc->p_mtx);
970 STAILQ_INIT(&newproc->p_ktr);
971
972 /* We have to lock the process tree while we look for a pid. */
973 sx_slock(&proctree_lock);
974 sx_xlock(&allproc_lock);
975
976 /*
977 * Increment the count of procs running with this uid. Don't allow
978 * a nonprivileged user to exceed their current limit.
979 *
980 * XXXRW: Can we avoid privilege here if it's not needed?
981 */
982 error = priv_check_cred(td->td_ucred, PRIV_PROC_LIMIT, 0);
983 if (error == 0)
984 ok = chgproccnt(td->td_ucred->cr_ruidinfo, 1, 0);
985 else {
986 ok = chgproccnt(td->td_ucred->cr_ruidinfo, 1,
987 lim_cur(td, RLIMIT_NPROC));
988 }
989 if (ok) {
990 do_fork(td, fr, newproc, td2, vm2, fp_procdesc);
991 return (0);
992 }
993
994 error = EAGAIN;
995 sx_sunlock(&proctree_lock);
996 sx_xunlock(&allproc_lock);
997 #ifdef MAC
998 mac_proc_destroy(newproc);
999 #endif
1000 racct_proc_exit(newproc);
1001 fail1:
1002 crfree(newproc->p_ucred);
1003 newproc->p_ucred = NULL;
1004 fail2:
1005 if (vm2 != NULL)
1006 vmspace_free(vm2);
1007 uma_zfree(proc_zone, newproc);
1008 if ((flags & RFPROCDESC) != 0 && fp_procdesc != NULL) {
1009 fdclose(td, fp_procdesc, *fr->fr_pd_fd);
1010 fdrop(fp_procdesc, td);
1011 }
1012 atomic_add_int(&nprocs, -1);
1013 pause("fork", hz / 2);
1014 return (error);
1015 }
1016
1017 /*
1018 * Handle the return of a child process from fork1(). This function
1019 * is called from the MD fork_trampoline() entry point.
1020 */
1021 void
1022 fork_exit(void (*callout)(void *, struct trapframe *), void *arg,
1023 struct trapframe *frame)
1024 {
1025 struct proc *p;
1026 struct thread *td;
1027 struct thread *dtd;
1028
1029 td = curthread;
1030 p = td->td_proc;
1031 KASSERT(p->p_state == PRS_NORMAL, ("executing process is still new"));
1032
1033 CTR4(KTR_PROC, "fork_exit: new thread %p (td_sched %p, pid %d, %s)",
1034 td, td_get_sched(td), p->p_pid, td->td_name);
1035
1036 sched_fork_exit(td);
1037 /*
1038 * Processes normally resume in mi_switch() after being
1039 * cpu_switch()'ed to, but when children start up they arrive here
1040 * instead, so we must do much the same things as mi_switch() would.
1041 */
1042 if ((dtd = PCPU_GET(deadthread))) {
1043 PCPU_SET(deadthread, NULL);
1044 thread_stash(dtd);
1045 }
1046 thread_unlock(td);
1047
1048 /*
1049 * cpu_fork_kthread_handler intercepts this function call to
1050 * have this call a non-return function to stay in kernel mode.
1051 * initproc has its own fork handler, but it does return.
1052 */
1053 KASSERT(callout != NULL, ("NULL callout in fork_exit"));
1054 callout(arg, frame);
1055
1056 /*
1057 * Check if a kernel thread misbehaved and returned from its main
1058 * function.
1059 */
1060 if (p->p_flag & P_KPROC) {
1061 printf("Kernel thread \"%s\" (pid %d) exited prematurely.\n",
1062 td->td_name, p->p_pid);
1063 kthread_exit();
1064 }
1065 mtx_assert(&Giant, MA_NOTOWNED);
1066
1067 if (p->p_sysent->sv_schedtail != NULL)
1068 (p->p_sysent->sv_schedtail)(td);
1069 td->td_pflags &= ~TDP_FORKING;
1070 }
1071
1072 /*
1073 * Simplified back end of syscall(), used when returning from fork()
1074 * directly into user mode. This function is passed in to fork_exit()
1075 * as the first parameter and is called when returning to a new
1076 * userland process.
1077 */
1078 void
1079 fork_return(struct thread *td, struct trapframe *frame)
1080 {
1081 struct proc *p, *dbg;
1082
1083 p = td->td_proc;
1084 if (td->td_dbgflags & TDB_STOPATFORK) {
1085 sx_xlock(&proctree_lock);
1086 PROC_LOCK(p);
1087 if (p->p_pptr->p_ptevents & PTRACE_FORK) {
1088 /*
1089 * If debugger still wants auto-attach for the
1090 * parent's children, do it now.
1091 */
1092 dbg = p->p_pptr->p_pptr;
1093 proc_set_traced(p, true);
1094 CTR2(KTR_PTRACE,
1095 "fork_return: attaching to new child pid %d: oppid %d",
1096 p->p_pid, p->p_oppid);
1097 proc_reparent(p, dbg);
1098 sx_xunlock(&proctree_lock);
1099 td->td_dbgflags |= TDB_CHILD | TDB_SCX | TDB_FSTP;
1100 ptracestop(td, SIGSTOP, NULL);
1101 td->td_dbgflags &= ~(TDB_CHILD | TDB_SCX);
1102 } else {
1103 /*
1104 * ... otherwise clear the request.
1105 */
1106 sx_xunlock(&proctree_lock);
1107 td->td_dbgflags &= ~TDB_STOPATFORK;
1108 cv_broadcast(&p->p_dbgwait);
1109 }
1110 PROC_UNLOCK(p);
1111 } else if (p->p_flag & P_TRACED || td->td_dbgflags & TDB_BORN) {
1112 /*
1113 * This is the start of a new thread in a traced
1114 * process. Report a system call exit event.
1115 */
1116 PROC_LOCK(p);
1117 td->td_dbgflags |= TDB_SCX;
1118 _STOPEVENT(p, S_SCX, td->td_sa.code);
1119 if ((p->p_ptevents & PTRACE_SCX) != 0 ||
1120 (td->td_dbgflags & TDB_BORN) != 0)
1121 ptracestop(td, SIGTRAP, NULL);
1122 td->td_dbgflags &= ~(TDB_SCX | TDB_BORN);
1123 PROC_UNLOCK(p);
1124 }
1125
1126 userret(td, frame);
1127
1128 #ifdef KTRACE
1129 if (KTRPOINT(td, KTR_SYSRET))
1130 ktrsysret(SYS_fork, 0, 0);
1131 #endif
1132 }
Cache object: 24fe1f75241f0d5af8b90a59b58a2399
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