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/11.0/sys/kern/kern_fork.c 303789 2016-08-06 08:20:58Z 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 /* ARGSUSED */
101 int
102 sys_fork(struct thread *td, struct fork_args *uap)
103 {
104 struct fork_req fr;
105 int error, pid;
106
107 bzero(&fr, sizeof(fr));
108 fr.fr_flags = RFFDG | RFPROC;
109 fr.fr_pidp = &pid;
110 error = fork1(td, &fr);
111 if (error == 0) {
112 td->td_retval[0] = pid;
113 td->td_retval[1] = 0;
114 }
115 return (error);
116 }
117
118 /* ARGUSED */
119 int
120 sys_pdfork(struct thread *td, struct pdfork_args *uap)
121 {
122 struct fork_req fr;
123 int error, fd, pid;
124
125 bzero(&fr, sizeof(fr));
126 fr.fr_flags = RFFDG | RFPROC | RFPROCDESC;
127 fr.fr_pidp = &pid;
128 fr.fr_pd_fd = &fd;
129 fr.fr_pd_flags = uap->flags;
130 /*
131 * It is necessary to return fd by reference because 0 is a valid file
132 * descriptor number, and the child needs to be able to distinguish
133 * itself from the parent using the return value.
134 */
135 error = fork1(td, &fr);
136 if (error == 0) {
137 td->td_retval[0] = pid;
138 td->td_retval[1] = 0;
139 error = copyout(&fd, uap->fdp, sizeof(fd));
140 }
141 return (error);
142 }
143
144 /* ARGSUSED */
145 int
146 sys_vfork(struct thread *td, struct vfork_args *uap)
147 {
148 struct fork_req fr;
149 int error, pid;
150
151 bzero(&fr, sizeof(fr));
152 fr.fr_flags = RFFDG | RFPROC | RFPPWAIT | RFMEM;
153 fr.fr_pidp = &pid;
154 error = fork1(td, &fr);
155 if (error == 0) {
156 td->td_retval[0] = pid;
157 td->td_retval[1] = 0;
158 }
159 return (error);
160 }
161
162 int
163 sys_rfork(struct thread *td, struct rfork_args *uap)
164 {
165 struct fork_req fr;
166 int error, pid;
167
168 /* Don't allow kernel-only flags. */
169 if ((uap->flags & RFKERNELONLY) != 0)
170 return (EINVAL);
171
172 AUDIT_ARG_FFLAGS(uap->flags);
173 bzero(&fr, sizeof(fr));
174 fr.fr_flags = uap->flags;
175 fr.fr_pidp = &pid;
176 error = fork1(td, &fr);
177 if (error == 0) {
178 td->td_retval[0] = pid;
179 td->td_retval[1] = 0;
180 }
181 return (error);
182 }
183
184 int nprocs = 1; /* process 0 */
185 int lastpid = 0;
186 SYSCTL_INT(_kern, OID_AUTO, lastpid, CTLFLAG_RD, &lastpid, 0,
187 "Last used PID");
188
189 /*
190 * Random component to lastpid generation. We mix in a random factor to make
191 * it a little harder to predict. We sanity check the modulus value to avoid
192 * doing it in critical paths. Don't let it be too small or we pointlessly
193 * waste randomness entropy, and don't let it be impossibly large. Using a
194 * modulus that is too big causes a LOT more process table scans and slows
195 * down fork processing as the pidchecked caching is defeated.
196 */
197 static int randompid = 0;
198
199 static int
200 sysctl_kern_randompid(SYSCTL_HANDLER_ARGS)
201 {
202 int error, pid;
203
204 error = sysctl_wire_old_buffer(req, sizeof(int));
205 if (error != 0)
206 return(error);
207 sx_xlock(&allproc_lock);
208 pid = randompid;
209 error = sysctl_handle_int(oidp, &pid, 0, req);
210 if (error == 0 && req->newptr != NULL) {
211 if (pid < 0 || pid > pid_max - 100) /* out of range */
212 pid = pid_max - 100;
213 else if (pid < 2) /* NOP */
214 pid = 0;
215 else if (pid < 100) /* Make it reasonable */
216 pid = 100;
217 randompid = pid;
218 }
219 sx_xunlock(&allproc_lock);
220 return (error);
221 }
222
223 SYSCTL_PROC(_kern, OID_AUTO, randompid, CTLTYPE_INT|CTLFLAG_RW,
224 0, 0, sysctl_kern_randompid, "I", "Random PID modulus");
225
226 static int
227 fork_findpid(int flags)
228 {
229 struct proc *p;
230 int trypid;
231 static int pidchecked = 0;
232
233 /*
234 * Requires allproc_lock in order to iterate over the list
235 * of processes, and proctree_lock to access p_pgrp.
236 */
237 sx_assert(&allproc_lock, SX_LOCKED);
238 sx_assert(&proctree_lock, SX_LOCKED);
239
240 /*
241 * Find an unused process ID. We remember a range of unused IDs
242 * ready to use (from lastpid+1 through pidchecked-1).
243 *
244 * If RFHIGHPID is set (used during system boot), do not allocate
245 * low-numbered pids.
246 */
247 trypid = lastpid + 1;
248 if (flags & RFHIGHPID) {
249 if (trypid < 10)
250 trypid = 10;
251 } else {
252 if (randompid)
253 trypid += arc4random() % randompid;
254 }
255 retry:
256 /*
257 * If the process ID prototype has wrapped around,
258 * restart somewhat above 0, as the low-numbered procs
259 * tend to include daemons that don't exit.
260 */
261 if (trypid >= pid_max) {
262 trypid = trypid % pid_max;
263 if (trypid < 100)
264 trypid += 100;
265 pidchecked = 0;
266 }
267 if (trypid >= pidchecked) {
268 int doingzomb = 0;
269
270 pidchecked = PID_MAX;
271 /*
272 * Scan the active and zombie procs to check whether this pid
273 * is in use. Remember the lowest pid that's greater
274 * than trypid, so we can avoid checking for a while.
275 *
276 * Avoid reuse of the process group id, session id or
277 * the reaper subtree id. Note that for process group
278 * and sessions, the amount of reserved pids is
279 * limited by process limit. For the subtree ids, the
280 * id is kept reserved only while there is a
281 * non-reaped process in the subtree, so amount of
282 * reserved pids is limited by process limit times
283 * two.
284 */
285 p = LIST_FIRST(&allproc);
286 again:
287 for (; p != NULL; p = LIST_NEXT(p, p_list)) {
288 while (p->p_pid == trypid ||
289 p->p_reapsubtree == trypid ||
290 (p->p_pgrp != NULL &&
291 (p->p_pgrp->pg_id == trypid ||
292 (p->p_session != NULL &&
293 p->p_session->s_sid == trypid)))) {
294 trypid++;
295 if (trypid >= pidchecked)
296 goto retry;
297 }
298 if (p->p_pid > trypid && pidchecked > p->p_pid)
299 pidchecked = p->p_pid;
300 if (p->p_pgrp != NULL) {
301 if (p->p_pgrp->pg_id > trypid &&
302 pidchecked > p->p_pgrp->pg_id)
303 pidchecked = p->p_pgrp->pg_id;
304 if (p->p_session != NULL &&
305 p->p_session->s_sid > trypid &&
306 pidchecked > p->p_session->s_sid)
307 pidchecked = p->p_session->s_sid;
308 }
309 }
310 if (!doingzomb) {
311 doingzomb = 1;
312 p = LIST_FIRST(&zombproc);
313 goto again;
314 }
315 }
316
317 /*
318 * RFHIGHPID does not mess with the lastpid counter during boot.
319 */
320 if (flags & RFHIGHPID)
321 pidchecked = 0;
322 else
323 lastpid = trypid;
324
325 return (trypid);
326 }
327
328 static int
329 fork_norfproc(struct thread *td, int flags)
330 {
331 int error;
332 struct proc *p1;
333
334 KASSERT((flags & RFPROC) == 0,
335 ("fork_norfproc called with RFPROC set"));
336 p1 = td->td_proc;
337
338 if (((p1->p_flag & (P_HADTHREADS|P_SYSTEM)) == P_HADTHREADS) &&
339 (flags & (RFCFDG | RFFDG))) {
340 PROC_LOCK(p1);
341 if (thread_single(p1, SINGLE_BOUNDARY)) {
342 PROC_UNLOCK(p1);
343 return (ERESTART);
344 }
345 PROC_UNLOCK(p1);
346 }
347
348 error = vm_forkproc(td, NULL, NULL, NULL, flags);
349 if (error)
350 goto fail;
351
352 /*
353 * Close all file descriptors.
354 */
355 if (flags & RFCFDG) {
356 struct filedesc *fdtmp;
357 fdtmp = fdinit(td->td_proc->p_fd, false);
358 fdescfree(td);
359 p1->p_fd = fdtmp;
360 }
361
362 /*
363 * Unshare file descriptors (from parent).
364 */
365 if (flags & RFFDG)
366 fdunshare(td);
367
368 fail:
369 if (((p1->p_flag & (P_HADTHREADS|P_SYSTEM)) == P_HADTHREADS) &&
370 (flags & (RFCFDG | RFFDG))) {
371 PROC_LOCK(p1);
372 thread_single_end(p1, SINGLE_BOUNDARY);
373 PROC_UNLOCK(p1);
374 }
375 return (error);
376 }
377
378 static void
379 do_fork(struct thread *td, struct fork_req *fr, struct proc *p2, struct thread *td2,
380 struct vmspace *vm2, struct file *fp_procdesc)
381 {
382 struct proc *p1, *pptr;
383 int trypid;
384 struct filedesc *fd;
385 struct filedesc_to_leader *fdtol;
386 struct sigacts *newsigacts;
387
388 sx_assert(&proctree_lock, SX_SLOCKED);
389 sx_assert(&allproc_lock, SX_XLOCKED);
390
391 p1 = td->td_proc;
392
393 trypid = fork_findpid(fr->fr_flags);
394
395 sx_sunlock(&proctree_lock);
396
397 p2->p_state = PRS_NEW; /* protect against others */
398 p2->p_pid = trypid;
399 AUDIT_ARG_PID(p2->p_pid);
400 LIST_INSERT_HEAD(&allproc, p2, p_list);
401 allproc_gen++;
402 LIST_INSERT_HEAD(PIDHASH(p2->p_pid), p2, p_hash);
403 tidhash_add(td2);
404 PROC_LOCK(p2);
405 PROC_LOCK(p1);
406
407 sx_xunlock(&allproc_lock);
408
409 bcopy(&p1->p_startcopy, &p2->p_startcopy,
410 __rangeof(struct proc, p_startcopy, p_endcopy));
411 pargs_hold(p2->p_args);
412
413 PROC_UNLOCK(p1);
414
415 bzero(&p2->p_startzero,
416 __rangeof(struct proc, p_startzero, p_endzero));
417
418 /* Tell the prison that we exist. */
419 prison_proc_hold(p2->p_ucred->cr_prison);
420
421 PROC_UNLOCK(p2);
422
423 /*
424 * Malloc things while we don't hold any locks.
425 */
426 if (fr->fr_flags & RFSIGSHARE)
427 newsigacts = NULL;
428 else
429 newsigacts = sigacts_alloc();
430
431 /*
432 * Copy filedesc.
433 */
434 if (fr->fr_flags & RFCFDG) {
435 fd = fdinit(p1->p_fd, false);
436 fdtol = NULL;
437 } else if (fr->fr_flags & RFFDG) {
438 fd = fdcopy(p1->p_fd);
439 fdtol = NULL;
440 } else {
441 fd = fdshare(p1->p_fd);
442 if (p1->p_fdtol == NULL)
443 p1->p_fdtol = filedesc_to_leader_alloc(NULL, NULL,
444 p1->p_leader);
445 if ((fr->fr_flags & RFTHREAD) != 0) {
446 /*
447 * Shared file descriptor table, and shared
448 * process leaders.
449 */
450 fdtol = p1->p_fdtol;
451 FILEDESC_XLOCK(p1->p_fd);
452 fdtol->fdl_refcount++;
453 FILEDESC_XUNLOCK(p1->p_fd);
454 } else {
455 /*
456 * Shared file descriptor table, and different
457 * process leaders.
458 */
459 fdtol = filedesc_to_leader_alloc(p1->p_fdtol,
460 p1->p_fd, p2);
461 }
462 }
463 /*
464 * Make a proc table entry for the new process.
465 * Start by zeroing the section of proc that is zero-initialized,
466 * then copy the section that is copied directly from the parent.
467 */
468
469 PROC_LOCK(p2);
470 PROC_LOCK(p1);
471
472 bzero(&td2->td_startzero,
473 __rangeof(struct thread, td_startzero, td_endzero));
474
475 bcopy(&td->td_startcopy, &td2->td_startcopy,
476 __rangeof(struct thread, td_startcopy, td_endcopy));
477
478 bcopy(&p2->p_comm, &td2->td_name, sizeof(td2->td_name));
479 td2->td_sigstk = td->td_sigstk;
480 td2->td_flags = TDF_INMEM;
481 td2->td_lend_user_pri = PRI_MAX;
482
483 #ifdef VIMAGE
484 td2->td_vnet = NULL;
485 td2->td_vnet_lpush = NULL;
486 #endif
487
488 /*
489 * Allow the scheduler to initialize the child.
490 */
491 thread_lock(td);
492 sched_fork(td, td2);
493 thread_unlock(td);
494
495 /*
496 * Duplicate sub-structures as needed.
497 * Increase reference counts on shared objects.
498 */
499 p2->p_flag = P_INMEM;
500 p2->p_flag2 = p1->p_flag2 & (P2_NOTRACE | P2_NOTRACE_EXEC);
501 p2->p_swtick = ticks;
502 if (p1->p_flag & P_PROFIL)
503 startprofclock(p2);
504
505 /*
506 * Whilst the proc lock is held, copy the VM domain data out
507 * using the VM domain method.
508 */
509 vm_domain_policy_init(&p2->p_vm_dom_policy);
510 vm_domain_policy_localcopy(&p2->p_vm_dom_policy,
511 &p1->p_vm_dom_policy);
512
513 if (fr->fr_flags & RFSIGSHARE) {
514 p2->p_sigacts = sigacts_hold(p1->p_sigacts);
515 } else {
516 sigacts_copy(newsigacts, p1->p_sigacts);
517 p2->p_sigacts = newsigacts;
518 }
519
520 if (fr->fr_flags & RFTSIGZMB)
521 p2->p_sigparent = RFTSIGNUM(fr->fr_flags);
522 else if (fr->fr_flags & RFLINUXTHPN)
523 p2->p_sigparent = SIGUSR1;
524 else
525 p2->p_sigparent = SIGCHLD;
526
527 p2->p_textvp = p1->p_textvp;
528 p2->p_fd = fd;
529 p2->p_fdtol = fdtol;
530
531 if (p1->p_flag2 & P2_INHERIT_PROTECTED) {
532 p2->p_flag |= P_PROTECTED;
533 p2->p_flag2 |= P2_INHERIT_PROTECTED;
534 }
535
536 /*
537 * p_limit is copy-on-write. Bump its refcount.
538 */
539 lim_fork(p1, p2);
540
541 thread_cow_get_proc(td2, p2);
542
543 pstats_fork(p1->p_stats, p2->p_stats);
544
545 PROC_UNLOCK(p1);
546 PROC_UNLOCK(p2);
547
548 /* Bump references to the text vnode (for procfs). */
549 if (p2->p_textvp)
550 vref(p2->p_textvp);
551
552 /*
553 * Set up linkage for kernel based threading.
554 */
555 if ((fr->fr_flags & RFTHREAD) != 0) {
556 mtx_lock(&ppeers_lock);
557 p2->p_peers = p1->p_peers;
558 p1->p_peers = p2;
559 p2->p_leader = p1->p_leader;
560 mtx_unlock(&ppeers_lock);
561 PROC_LOCK(p1->p_leader);
562 if ((p1->p_leader->p_flag & P_WEXIT) != 0) {
563 PROC_UNLOCK(p1->p_leader);
564 /*
565 * The task leader is exiting, so process p1 is
566 * going to be killed shortly. Since p1 obviously
567 * isn't dead yet, we know that the leader is either
568 * sending SIGKILL's to all the processes in this
569 * task or is sleeping waiting for all the peers to
570 * exit. We let p1 complete the fork, but we need
571 * to go ahead and kill the new process p2 since
572 * the task leader may not get a chance to send
573 * SIGKILL to it. We leave it on the list so that
574 * the task leader will wait for this new process
575 * to commit suicide.
576 */
577 PROC_LOCK(p2);
578 kern_psignal(p2, SIGKILL);
579 PROC_UNLOCK(p2);
580 } else
581 PROC_UNLOCK(p1->p_leader);
582 } else {
583 p2->p_peers = NULL;
584 p2->p_leader = p2;
585 }
586
587 sx_xlock(&proctree_lock);
588 PGRP_LOCK(p1->p_pgrp);
589 PROC_LOCK(p2);
590 PROC_LOCK(p1);
591
592 /*
593 * Preserve some more flags in subprocess. P_PROFIL has already
594 * been preserved.
595 */
596 p2->p_flag |= p1->p_flag & P_SUGID;
597 td2->td_pflags |= (td->td_pflags & TDP_ALTSTACK) | TDP_FORKING;
598 SESS_LOCK(p1->p_session);
599 if (p1->p_session->s_ttyvp != NULL && p1->p_flag & P_CONTROLT)
600 p2->p_flag |= P_CONTROLT;
601 SESS_UNLOCK(p1->p_session);
602 if (fr->fr_flags & RFPPWAIT)
603 p2->p_flag |= P_PPWAIT;
604
605 p2->p_pgrp = p1->p_pgrp;
606 LIST_INSERT_AFTER(p1, p2, p_pglist);
607 PGRP_UNLOCK(p1->p_pgrp);
608 LIST_INIT(&p2->p_children);
609 LIST_INIT(&p2->p_orphans);
610
611 callout_init_mtx(&p2->p_itcallout, &p2->p_mtx, 0);
612
613 /*
614 * If PF_FORK is set, the child process inherits the
615 * procfs ioctl flags from its parent.
616 */
617 if (p1->p_pfsflags & PF_FORK) {
618 p2->p_stops = p1->p_stops;
619 p2->p_pfsflags = p1->p_pfsflags;
620 }
621
622 /*
623 * This begins the section where we must prevent the parent
624 * from being swapped.
625 */
626 _PHOLD(p1);
627 PROC_UNLOCK(p1);
628
629 /*
630 * Attach the new process to its parent.
631 *
632 * If RFNOWAIT is set, the newly created process becomes a child
633 * of init. This effectively disassociates the child from the
634 * parent.
635 */
636 if ((fr->fr_flags & RFNOWAIT) != 0) {
637 pptr = p1->p_reaper;
638 p2->p_reaper = pptr;
639 } else {
640 p2->p_reaper = (p1->p_treeflag & P_TREE_REAPER) != 0 ?
641 p1 : p1->p_reaper;
642 pptr = p1;
643 }
644 p2->p_pptr = pptr;
645 LIST_INSERT_HEAD(&pptr->p_children, p2, p_sibling);
646 LIST_INIT(&p2->p_reaplist);
647 LIST_INSERT_HEAD(&p2->p_reaper->p_reaplist, p2, p_reapsibling);
648 if (p2->p_reaper == p1)
649 p2->p_reapsubtree = p2->p_pid;
650 sx_xunlock(&proctree_lock);
651
652 /* Inform accounting that we have forked. */
653 p2->p_acflag = AFORK;
654 PROC_UNLOCK(p2);
655
656 #ifdef KTRACE
657 ktrprocfork(p1, p2);
658 #endif
659
660 /*
661 * Finish creating the child process. It will return via a different
662 * execution path later. (ie: directly into user mode)
663 */
664 vm_forkproc(td, p2, td2, vm2, fr->fr_flags);
665
666 if (fr->fr_flags == (RFFDG | RFPROC)) {
667 PCPU_INC(cnt.v_forks);
668 PCPU_ADD(cnt.v_forkpages, p2->p_vmspace->vm_dsize +
669 p2->p_vmspace->vm_ssize);
670 } else if (fr->fr_flags == (RFFDG | RFPROC | RFPPWAIT | RFMEM)) {
671 PCPU_INC(cnt.v_vforks);
672 PCPU_ADD(cnt.v_vforkpages, p2->p_vmspace->vm_dsize +
673 p2->p_vmspace->vm_ssize);
674 } else if (p1 == &proc0) {
675 PCPU_INC(cnt.v_kthreads);
676 PCPU_ADD(cnt.v_kthreadpages, p2->p_vmspace->vm_dsize +
677 p2->p_vmspace->vm_ssize);
678 } else {
679 PCPU_INC(cnt.v_rforks);
680 PCPU_ADD(cnt.v_rforkpages, p2->p_vmspace->vm_dsize +
681 p2->p_vmspace->vm_ssize);
682 }
683
684 /*
685 * Associate the process descriptor with the process before anything
686 * can happen that might cause that process to need the descriptor.
687 * However, don't do this until after fork(2) can no longer fail.
688 */
689 if (fr->fr_flags & RFPROCDESC)
690 procdesc_new(p2, fr->fr_pd_flags);
691
692 /*
693 * Both processes are set up, now check if any loadable modules want
694 * to adjust anything.
695 */
696 EVENTHANDLER_INVOKE(process_fork, p1, p2, fr->fr_flags);
697
698 /*
699 * Set the child start time and mark the process as being complete.
700 */
701 PROC_LOCK(p2);
702 PROC_LOCK(p1);
703 microuptime(&p2->p_stats->p_start);
704 PROC_SLOCK(p2);
705 p2->p_state = PRS_NORMAL;
706 PROC_SUNLOCK(p2);
707
708 #ifdef KDTRACE_HOOKS
709 /*
710 * Tell the DTrace fasttrap provider about the new process so that any
711 * tracepoints inherited from the parent can be removed. We have to do
712 * this only after p_state is PRS_NORMAL since the fasttrap module will
713 * use pfind() later on.
714 */
715 if ((fr->fr_flags & RFMEM) == 0 && dtrace_fasttrap_fork)
716 dtrace_fasttrap_fork(p1, p2);
717 #endif
718 /*
719 * Hold the process so that it cannot exit after we make it runnable,
720 * but before we wait for the debugger.
721 */
722 _PHOLD(p2);
723 if ((p1->p_flag & (P_TRACED | P_FOLLOWFORK)) == (P_TRACED |
724 P_FOLLOWFORK)) {
725 /*
726 * Arrange for debugger to receive the fork event.
727 *
728 * We can report PL_FLAG_FORKED regardless of
729 * P_FOLLOWFORK settings, but it does not make a sense
730 * for runaway child.
731 */
732 td->td_dbgflags |= TDB_FORK;
733 td->td_dbg_forked = p2->p_pid;
734 td2->td_dbgflags |= TDB_STOPATFORK;
735 }
736 if (fr->fr_flags & RFPPWAIT) {
737 td->td_pflags |= TDP_RFPPWAIT;
738 td->td_rfppwait_p = p2;
739 }
740 PROC_UNLOCK(p2);
741
742 /*
743 * Now can be swapped.
744 */
745 _PRELE(p1);
746 PROC_UNLOCK(p1);
747
748 /*
749 * Tell any interested parties about the new process.
750 */
751 knote_fork(p1->p_klist, p2->p_pid);
752 SDT_PROBE3(proc, , , create, p2, p1, fr->fr_flags);
753
754 if (fr->fr_flags & RFPROCDESC) {
755 procdesc_finit(p2->p_procdesc, fp_procdesc);
756 fdrop(fp_procdesc, td);
757 }
758
759 if ((fr->fr_flags & RFSTOPPED) == 0) {
760 /*
761 * If RFSTOPPED not requested, make child runnable and
762 * add to run queue.
763 */
764 thread_lock(td2);
765 TD_SET_CAN_RUN(td2);
766 sched_add(td2, SRQ_BORING);
767 thread_unlock(td2);
768 if (fr->fr_pidp != NULL)
769 *fr->fr_pidp = p2->p_pid;
770 } else {
771 *fr->fr_procp = p2;
772 }
773
774 PROC_LOCK(p2);
775 /*
776 * Wait until debugger is attached to child.
777 */
778 while (td2->td_proc == p2 && (td2->td_dbgflags & TDB_STOPATFORK) != 0)
779 cv_wait(&p2->p_dbgwait, &p2->p_mtx);
780 _PRELE(p2);
781 racct_proc_fork_done(p2);
782 PROC_UNLOCK(p2);
783 }
784
785 int
786 fork1(struct thread *td, struct fork_req *fr)
787 {
788 struct proc *p1, *newproc;
789 struct thread *td2;
790 struct vmspace *vm2;
791 struct file *fp_procdesc;
792 vm_ooffset_t mem_charged;
793 int error, nprocs_new, ok;
794 static int curfail;
795 static struct timeval lastfail;
796 int flags, pages;
797
798 flags = fr->fr_flags;
799 pages = fr->fr_pages;
800
801 if ((flags & RFSTOPPED) != 0)
802 MPASS(fr->fr_procp != NULL && fr->fr_pidp == NULL);
803 else
804 MPASS(fr->fr_procp == NULL);
805
806 /* Check for the undefined or unimplemented flags. */
807 if ((flags & ~(RFFLAGS | RFTSIGFLAGS(RFTSIGMASK))) != 0)
808 return (EINVAL);
809
810 /* Signal value requires RFTSIGZMB. */
811 if ((flags & RFTSIGFLAGS(RFTSIGMASK)) != 0 && (flags & RFTSIGZMB) == 0)
812 return (EINVAL);
813
814 /* Can't copy and clear. */
815 if ((flags & (RFFDG|RFCFDG)) == (RFFDG|RFCFDG))
816 return (EINVAL);
817
818 /* Check the validity of the signal number. */
819 if ((flags & RFTSIGZMB) != 0 && (u_int)RFTSIGNUM(flags) > _SIG_MAXSIG)
820 return (EINVAL);
821
822 if ((flags & RFPROCDESC) != 0) {
823 /* Can't not create a process yet get a process descriptor. */
824 if ((flags & RFPROC) == 0)
825 return (EINVAL);
826
827 /* Must provide a place to put a procdesc if creating one. */
828 if (fr->fr_pd_fd == NULL)
829 return (EINVAL);
830
831 /* Check if we are using supported flags. */
832 if ((fr->fr_pd_flags & ~PD_ALLOWED_AT_FORK) != 0)
833 return (EINVAL);
834 }
835
836 p1 = td->td_proc;
837
838 /*
839 * Here we don't create a new process, but we divorce
840 * certain parts of a process from itself.
841 */
842 if ((flags & RFPROC) == 0) {
843 if (fr->fr_procp != NULL)
844 *fr->fr_procp = NULL;
845 else if (fr->fr_pidp != NULL)
846 *fr->fr_pidp = 0;
847 return (fork_norfproc(td, flags));
848 }
849
850 fp_procdesc = NULL;
851 newproc = NULL;
852 vm2 = NULL;
853
854 /*
855 * Increment the nprocs resource before allocations occur.
856 * Although process entries are dynamically created, we still
857 * keep a global limit on the maximum number we will
858 * create. There are hard-limits as to the number of processes
859 * that can run, established by the KVA and memory usage for
860 * the process data.
861 *
862 * Don't allow a nonprivileged user to use the last ten
863 * processes; don't let root exceed the limit.
864 */
865 nprocs_new = atomic_fetchadd_int(&nprocs, 1) + 1;
866 if ((nprocs_new >= maxproc - 10 && priv_check_cred(td->td_ucred,
867 PRIV_MAXPROC, 0) != 0) || nprocs_new >= maxproc) {
868 error = EAGAIN;
869 sx_xlock(&allproc_lock);
870 if (ppsratecheck(&lastfail, &curfail, 1)) {
871 printf("maxproc limit exceeded by uid %u (pid %d); "
872 "see tuning(7) and login.conf(5)\n",
873 td->td_ucred->cr_ruid, p1->p_pid);
874 }
875 sx_xunlock(&allproc_lock);
876 goto fail2;
877 }
878
879 /*
880 * If required, create a process descriptor in the parent first; we
881 * will abandon it if something goes wrong. We don't finit() until
882 * later.
883 */
884 if (flags & RFPROCDESC) {
885 error = procdesc_falloc(td, &fp_procdesc, fr->fr_pd_fd,
886 fr->fr_pd_flags, fr->fr_pd_fcaps);
887 if (error != 0)
888 goto fail2;
889 }
890
891 mem_charged = 0;
892 if (pages == 0)
893 pages = kstack_pages;
894 /* Allocate new proc. */
895 newproc = uma_zalloc(proc_zone, M_WAITOK);
896 td2 = FIRST_THREAD_IN_PROC(newproc);
897 if (td2 == NULL) {
898 td2 = thread_alloc(pages);
899 if (td2 == NULL) {
900 error = ENOMEM;
901 goto fail2;
902 }
903 proc_linkup(newproc, td2);
904 } else {
905 if (td2->td_kstack == 0 || td2->td_kstack_pages != pages) {
906 if (td2->td_kstack != 0)
907 vm_thread_dispose(td2);
908 if (!thread_alloc_stack(td2, pages)) {
909 error = ENOMEM;
910 goto fail2;
911 }
912 }
913 }
914
915 if ((flags & RFMEM) == 0) {
916 vm2 = vmspace_fork(p1->p_vmspace, &mem_charged);
917 if (vm2 == NULL) {
918 error = ENOMEM;
919 goto fail2;
920 }
921 if (!swap_reserve(mem_charged)) {
922 /*
923 * The swap reservation failed. The accounting
924 * from the entries of the copied vm2 will be
925 * subtracted in vmspace_free(), so force the
926 * reservation there.
927 */
928 swap_reserve_force(mem_charged);
929 error = ENOMEM;
930 goto fail2;
931 }
932 } else
933 vm2 = NULL;
934
935 /*
936 * XXX: This is ugly; when we copy resource usage, we need to bump
937 * per-cred resource counters.
938 */
939 proc_set_cred_init(newproc, crhold(td->td_ucred));
940
941 /*
942 * Initialize resource accounting for the child process.
943 */
944 error = racct_proc_fork(p1, newproc);
945 if (error != 0) {
946 error = EAGAIN;
947 goto fail1;
948 }
949
950 #ifdef MAC
951 mac_proc_init(newproc);
952 #endif
953 newproc->p_klist = knlist_alloc(&newproc->p_mtx);
954 STAILQ_INIT(&newproc->p_ktr);
955
956 /* We have to lock the process tree while we look for a pid. */
957 sx_slock(&proctree_lock);
958 sx_xlock(&allproc_lock);
959
960 /*
961 * Increment the count of procs running with this uid. Don't allow
962 * a nonprivileged user to exceed their current limit.
963 *
964 * XXXRW: Can we avoid privilege here if it's not needed?
965 */
966 error = priv_check_cred(td->td_ucred, PRIV_PROC_LIMIT, 0);
967 if (error == 0)
968 ok = chgproccnt(td->td_ucred->cr_ruidinfo, 1, 0);
969 else {
970 ok = chgproccnt(td->td_ucred->cr_ruidinfo, 1,
971 lim_cur(td, RLIMIT_NPROC));
972 }
973 if (ok) {
974 do_fork(td, fr, newproc, td2, vm2, fp_procdesc);
975 return (0);
976 }
977
978 error = EAGAIN;
979 sx_sunlock(&proctree_lock);
980 sx_xunlock(&allproc_lock);
981 #ifdef MAC
982 mac_proc_destroy(newproc);
983 #endif
984 racct_proc_exit(newproc);
985 fail1:
986 crfree(newproc->p_ucred);
987 newproc->p_ucred = NULL;
988 fail2:
989 if (vm2 != NULL)
990 vmspace_free(vm2);
991 uma_zfree(proc_zone, newproc);
992 if ((flags & RFPROCDESC) != 0 && fp_procdesc != NULL) {
993 fdclose(td, fp_procdesc, *fr->fr_pd_fd);
994 fdrop(fp_procdesc, td);
995 }
996 atomic_add_int(&nprocs, -1);
997 pause("fork", hz / 2);
998 return (error);
999 }
1000
1001 /*
1002 * Handle the return of a child process from fork1(). This function
1003 * is called from the MD fork_trampoline() entry point.
1004 */
1005 void
1006 fork_exit(void (*callout)(void *, struct trapframe *), void *arg,
1007 struct trapframe *frame)
1008 {
1009 struct proc *p;
1010 struct thread *td;
1011 struct thread *dtd;
1012
1013 td = curthread;
1014 p = td->td_proc;
1015 KASSERT(p->p_state == PRS_NORMAL, ("executing process is still new"));
1016
1017 CTR4(KTR_PROC, "fork_exit: new thread %p (td_sched %p, pid %d, %s)",
1018 td, td_get_sched(td), p->p_pid, td->td_name);
1019
1020 sched_fork_exit(td);
1021 /*
1022 * Processes normally resume in mi_switch() after being
1023 * cpu_switch()'ed to, but when children start up they arrive here
1024 * instead, so we must do much the same things as mi_switch() would.
1025 */
1026 if ((dtd = PCPU_GET(deadthread))) {
1027 PCPU_SET(deadthread, NULL);
1028 thread_stash(dtd);
1029 }
1030 thread_unlock(td);
1031
1032 /*
1033 * cpu_fork_kthread_handler intercepts this function call to
1034 * have this call a non-return function to stay in kernel mode.
1035 * initproc has its own fork handler, but it does return.
1036 */
1037 KASSERT(callout != NULL, ("NULL callout in fork_exit"));
1038 callout(arg, frame);
1039
1040 /*
1041 * Check if a kernel thread misbehaved and returned from its main
1042 * function.
1043 */
1044 if (p->p_flag & P_KPROC) {
1045 printf("Kernel thread \"%s\" (pid %d) exited prematurely.\n",
1046 td->td_name, p->p_pid);
1047 kthread_exit();
1048 }
1049 mtx_assert(&Giant, MA_NOTOWNED);
1050
1051 if (p->p_sysent->sv_schedtail != NULL)
1052 (p->p_sysent->sv_schedtail)(td);
1053 td->td_pflags &= ~TDP_FORKING;
1054 }
1055
1056 /*
1057 * Simplified back end of syscall(), used when returning from fork()
1058 * directly into user mode. This function is passed in to fork_exit()
1059 * as the first parameter and is called when returning to a new
1060 * userland process.
1061 */
1062 void
1063 fork_return(struct thread *td, struct trapframe *frame)
1064 {
1065 struct proc *p, *dbg;
1066
1067 p = td->td_proc;
1068 if (td->td_dbgflags & TDB_STOPATFORK) {
1069 sx_xlock(&proctree_lock);
1070 PROC_LOCK(p);
1071 if ((p->p_pptr->p_flag & (P_TRACED | P_FOLLOWFORK)) ==
1072 (P_TRACED | P_FOLLOWFORK)) {
1073 /*
1074 * If debugger still wants auto-attach for the
1075 * parent's children, do it now.
1076 */
1077 dbg = p->p_pptr->p_pptr;
1078 p->p_flag |= P_TRACED;
1079 p->p_oppid = p->p_pptr->p_pid;
1080 CTR2(KTR_PTRACE,
1081 "fork_return: attaching to new child pid %d: oppid %d",
1082 p->p_pid, p->p_oppid);
1083 proc_reparent(p, dbg);
1084 sx_xunlock(&proctree_lock);
1085 td->td_dbgflags |= TDB_CHILD | TDB_SCX;
1086 ptracestop(td, SIGSTOP);
1087 td->td_dbgflags &= ~(TDB_CHILD | TDB_SCX);
1088 } else {
1089 /*
1090 * ... otherwise clear the request.
1091 */
1092 sx_xunlock(&proctree_lock);
1093 td->td_dbgflags &= ~TDB_STOPATFORK;
1094 cv_broadcast(&p->p_dbgwait);
1095 }
1096 PROC_UNLOCK(p);
1097 } else if (p->p_flag & P_TRACED || td->td_dbgflags & TDB_BORN) {
1098 /*
1099 * This is the start of a new thread in a traced
1100 * process. Report a system call exit event.
1101 */
1102 PROC_LOCK(p);
1103 td->td_dbgflags |= TDB_SCX;
1104 _STOPEVENT(p, S_SCX, td->td_dbg_sc_code);
1105 if ((p->p_stops & S_PT_SCX) != 0 ||
1106 (td->td_dbgflags & TDB_BORN) != 0)
1107 ptracestop(td, SIGTRAP);
1108 td->td_dbgflags &= ~(TDB_SCX | TDB_BORN);
1109 PROC_UNLOCK(p);
1110 }
1111
1112 userret(td, frame);
1113
1114 #ifdef KTRACE
1115 if (KTRPOINT(td, KTR_SYSRET))
1116 ktrsysret(SYS_fork, 0, 0);
1117 #endif
1118 }
Cache object: d099e23109f930a7dd1ca614fe294e8b
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