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("$FreeBSD$");
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
sys_fork(struct thread * td,struct fork_args * uap)102 sys_fork(struct thread *td, struct fork_args *uap)
103 {
104 int error;
105 struct proc *p2;
106
107 error = fork1(td, RFFDG | RFPROC, 0, &p2, NULL, 0, NULL);
108 if (error == 0) {
109 td->td_retval[0] = p2->p_pid;
110 td->td_retval[1] = 0;
111 }
112 return (error);
113 }
114
115 /* ARGUSED */
116 int
sys_pdfork(td,uap)117 sys_pdfork(td, uap)
118 struct thread *td;
119 struct pdfork_args *uap;
120 {
121 int error, fd;
122 struct proc *p2;
123
124 /*
125 * It is necessary to return fd by reference because 0 is a valid file
126 * descriptor number, and the child needs to be able to distinguish
127 * itself from the parent using the return value.
128 */
129 error = fork1(td, RFFDG | RFPROC | RFPROCDESC, 0, &p2,
130 &fd, uap->flags, NULL);
131 if (error == 0) {
132 td->td_retval[0] = p2->p_pid;
133 td->td_retval[1] = 0;
134 error = copyout(&fd, uap->fdp, sizeof(fd));
135 }
136 return (error);
137 }
138
139 /* ARGSUSED */
140 int
sys_vfork(struct thread * td,struct vfork_args * uap)141 sys_vfork(struct thread *td, struct vfork_args *uap)
142 {
143 int error, flags;
144 struct proc *p2;
145
146 flags = RFFDG | RFPROC | RFPPWAIT | RFMEM;
147 error = fork1(td, flags, 0, &p2, NULL, 0, NULL);
148 if (error == 0) {
149 td->td_retval[0] = p2->p_pid;
150 td->td_retval[1] = 0;
151 }
152 return (error);
153 }
154
155 int
sys_rfork(struct thread * td,struct rfork_args * uap)156 sys_rfork(struct thread *td, struct rfork_args *uap)
157 {
158 struct proc *p2;
159 int error;
160
161 /* Don't allow kernel-only flags. */
162 if ((uap->flags & RFKERNELONLY) != 0)
163 return (EINVAL);
164
165 AUDIT_ARG_FFLAGS(uap->flags);
166 error = fork1(td, uap->flags, 0, &p2, NULL, 0, NULL);
167 if (error == 0) {
168 td->td_retval[0] = p2 ? p2->p_pid : 0;
169 td->td_retval[1] = 0;
170 }
171 return (error);
172 }
173
174 int nprocs = 1; /* process 0 */
175 int lastpid = 0;
176 SYSCTL_INT(_kern, OID_AUTO, lastpid, CTLFLAG_RD, &lastpid, 0,
177 "Last used PID");
178
179 /*
180 * Random component to lastpid generation. We mix in a random factor to make
181 * it a little harder to predict. We sanity check the modulus value to avoid
182 * doing it in critical paths. Don't let it be too small or we pointlessly
183 * waste randomness entropy, and don't let it be impossibly large. Using a
184 * modulus that is too big causes a LOT more process table scans and slows
185 * down fork processing as the pidchecked caching is defeated.
186 */
187 static int randompid = 0;
188
189 static int
sysctl_kern_randompid(SYSCTL_HANDLER_ARGS)190 sysctl_kern_randompid(SYSCTL_HANDLER_ARGS)
191 {
192 int error, pid;
193
194 error = sysctl_wire_old_buffer(req, sizeof(int));
195 if (error != 0)
196 return(error);
197 sx_xlock(&allproc_lock);
198 pid = randompid;
199 error = sysctl_handle_int(oidp, &pid, 0, req);
200 if (error == 0 && req->newptr != NULL) {
201 if (pid < 0 || pid > pid_max - 100) /* out of range */
202 pid = pid_max - 100;
203 else if (pid < 2) /* NOP */
204 pid = 0;
205 else if (pid < 100) /* Make it reasonable */
206 pid = 100;
207 randompid = pid;
208 }
209 sx_xunlock(&allproc_lock);
210 return (error);
211 }
212
213 SYSCTL_PROC(_kern, OID_AUTO, randompid, CTLTYPE_INT|CTLFLAG_RW,
214 0, 0, sysctl_kern_randompid, "I", "Random PID modulus");
215
216 static int
fork_findpid(int flags)217 fork_findpid(int flags)
218 {
219 struct proc *p;
220 int trypid;
221 static int pidchecked = 0;
222
223 /*
224 * Requires allproc_lock in order to iterate over the list
225 * of processes, and proctree_lock to access p_pgrp.
226 */
227 sx_assert(&allproc_lock, SX_LOCKED);
228 sx_assert(&proctree_lock, SX_LOCKED);
229
230 /*
231 * Find an unused process ID. We remember a range of unused IDs
232 * ready to use (from lastpid+1 through pidchecked-1).
233 *
234 * If RFHIGHPID is set (used during system boot), do not allocate
235 * low-numbered pids.
236 */
237 trypid = lastpid + 1;
238 if (flags & RFHIGHPID) {
239 if (trypid < 10)
240 trypid = 10;
241 } else {
242 if (randompid)
243 trypid += arc4random() % randompid;
244 }
245 retry:
246 /*
247 * If the process ID prototype has wrapped around,
248 * restart somewhat above 0, as the low-numbered procs
249 * tend to include daemons that don't exit.
250 */
251 if (trypid >= pid_max) {
252 trypid = trypid % pid_max;
253 if (trypid < 100)
254 trypid += 100;
255 pidchecked = 0;
256 }
257 if (trypid >= pidchecked) {
258 int doingzomb = 0;
259
260 pidchecked = PID_MAX;
261 /*
262 * Scan the active and zombie procs to check whether this pid
263 * is in use. Remember the lowest pid that's greater
264 * than trypid, so we can avoid checking for a while.
265 *
266 * Avoid reuse of the process group id, session id or
267 * the reaper subtree id. Note that for process group
268 * and sessions, the amount of reserved pids is
269 * limited by process limit. For the subtree ids, the
270 * id is kept reserved only while there is a
271 * non-reaped process in the subtree, so amount of
272 * reserved pids is limited by process limit times
273 * two.
274 */
275 p = LIST_FIRST(&allproc);
276 again:
277 for (; p != NULL; p = LIST_NEXT(p, p_list)) {
278 while (p->p_pid == trypid ||
279 p->p_reapsubtree == trypid ||
280 (p->p_pgrp != NULL &&
281 (p->p_pgrp->pg_id == trypid ||
282 (p->p_session != NULL &&
283 p->p_session->s_sid == trypid)))) {
284 trypid++;
285 if (trypid >= pidchecked)
286 goto retry;
287 }
288 if (p->p_pid > trypid && pidchecked > p->p_pid)
289 pidchecked = p->p_pid;
290 if (p->p_pgrp != NULL) {
291 if (p->p_pgrp->pg_id > trypid &&
292 pidchecked > p->p_pgrp->pg_id)
293 pidchecked = p->p_pgrp->pg_id;
294 if (p->p_session != NULL &&
295 p->p_session->s_sid > trypid &&
296 pidchecked > p->p_session->s_sid)
297 pidchecked = p->p_session->s_sid;
298 }
299 }
300 if (!doingzomb) {
301 doingzomb = 1;
302 p = LIST_FIRST(&zombproc);
303 goto again;
304 }
305 }
306
307 /*
308 * RFHIGHPID does not mess with the lastpid counter during boot.
309 */
310 if (flags & RFHIGHPID)
311 pidchecked = 0;
312 else
313 lastpid = trypid;
314
315 return (trypid);
316 }
317
318 static int
fork_norfproc(struct thread * td,int flags)319 fork_norfproc(struct thread *td, int flags)
320 {
321 int error;
322 struct proc *p1;
323
324 KASSERT((flags & RFPROC) == 0,
325 ("fork_norfproc called with RFPROC set"));
326 p1 = td->td_proc;
327
328 if (((p1->p_flag & (P_HADTHREADS|P_SYSTEM)) == P_HADTHREADS) &&
329 (flags & (RFCFDG | RFFDG))) {
330 PROC_LOCK(p1);
331 if (thread_single(p1, SINGLE_BOUNDARY)) {
332 PROC_UNLOCK(p1);
333 return (ERESTART);
334 }
335 PROC_UNLOCK(p1);
336 }
337
338 error = vm_forkproc(td, NULL, NULL, NULL, flags);
339 if (error)
340 goto fail;
341
342 /*
343 * Close all file descriptors.
344 */
345 if (flags & RFCFDG) {
346 struct filedesc *fdtmp;
347 fdtmp = fdinit(td->td_proc->p_fd, false);
348 fdescfree(td);
349 p1->p_fd = fdtmp;
350 }
351
352 /*
353 * Unshare file descriptors (from parent).
354 */
355 if (flags & RFFDG)
356 fdunshare(td);
357
358 fail:
359 if (((p1->p_flag & (P_HADTHREADS|P_SYSTEM)) == P_HADTHREADS) &&
360 (flags & (RFCFDG | RFFDG))) {
361 PROC_LOCK(p1);
362 thread_single_end(p1, SINGLE_BOUNDARY);
363 PROC_UNLOCK(p1);
364 }
365 return (error);
366 }
367
368 static void
do_fork(struct thread * td,int flags,struct proc * p2,struct thread * td2,struct vmspace * vm2,int pdflags)369 do_fork(struct thread *td, int flags, struct proc *p2, struct thread *td2,
370 struct vmspace *vm2, int pdflags)
371 {
372 struct proc *p1, *pptr;
373 int p2_held, trypid;
374 struct filedesc *fd;
375 struct filedesc_to_leader *fdtol;
376 struct sigacts *newsigacts;
377
378 sx_assert(&proctree_lock, SX_SLOCKED);
379 sx_assert(&allproc_lock, SX_XLOCKED);
380
381 p2_held = 0;
382 p1 = td->td_proc;
383
384 trypid = fork_findpid(flags);
385
386 sx_sunlock(&proctree_lock);
387
388 p2->p_state = PRS_NEW; /* protect against others */
389 p2->p_pid = trypid;
390 AUDIT_ARG_PID(p2->p_pid);
391 LIST_INSERT_HEAD(&allproc, p2, p_list);
392 allproc_gen++;
393 LIST_INSERT_HEAD(PIDHASH(p2->p_pid), p2, p_hash);
394 tidhash_add(td2);
395 PROC_LOCK(p2);
396 PROC_LOCK(p1);
397
398 sx_xunlock(&allproc_lock);
399
400 bcopy(&p1->p_startcopy, &p2->p_startcopy,
401 __rangeof(struct proc, p_startcopy, p_endcopy));
402 pargs_hold(p2->p_args);
403
404 PROC_UNLOCK(p1);
405
406 bzero(&p2->p_startzero,
407 __rangeof(struct proc, p_startzero, p_endzero));
408
409 /* Tell the prison that we exist. */
410 prison_proc_hold(p2->p_ucred->cr_prison);
411
412 PROC_UNLOCK(p2);
413
414 /*
415 * Malloc things while we don't hold any locks.
416 */
417 if (flags & RFSIGSHARE)
418 newsigacts = NULL;
419 else
420 newsigacts = sigacts_alloc();
421
422 /*
423 * Copy filedesc.
424 */
425 if (flags & RFCFDG) {
426 fd = fdinit(p1->p_fd, false);
427 fdtol = NULL;
428 } else if (flags & RFFDG) {
429 fd = fdcopy(p1->p_fd);
430 fdtol = NULL;
431 } else {
432 fd = fdshare(p1->p_fd);
433 if (p1->p_fdtol == NULL)
434 p1->p_fdtol = filedesc_to_leader_alloc(NULL, NULL,
435 p1->p_leader);
436 if ((flags & RFTHREAD) != 0) {
437 /*
438 * Shared file descriptor table, and shared
439 * process leaders.
440 */
441 fdtol = p1->p_fdtol;
442 FILEDESC_XLOCK(p1->p_fd);
443 fdtol->fdl_refcount++;
444 FILEDESC_XUNLOCK(p1->p_fd);
445 } else {
446 /*
447 * Shared file descriptor table, and different
448 * process leaders.
449 */
450 fdtol = filedesc_to_leader_alloc(p1->p_fdtol,
451 p1->p_fd, p2);
452 }
453 }
454 /*
455 * Make a proc table entry for the new process.
456 * Start by zeroing the section of proc that is zero-initialized,
457 * then copy the section that is copied directly from the parent.
458 */
459
460 PROC_LOCK(p2);
461 PROC_LOCK(p1);
462
463 bzero(&td2->td_startzero,
464 __rangeof(struct thread, td_startzero, td_endzero));
465
466 bcopy(&td->td_startcopy, &td2->td_startcopy,
467 __rangeof(struct thread, td_startcopy, td_endcopy));
468
469 bcopy(&p2->p_comm, &td2->td_name, sizeof(td2->td_name));
470 td2->td_sigstk = td->td_sigstk;
471 td2->td_flags = TDF_INMEM;
472 td2->td_lend_user_pri = PRI_MAX;
473
474 #ifdef VIMAGE
475 td2->td_vnet = NULL;
476 td2->td_vnet_lpush = NULL;
477 #endif
478
479 /*
480 * Allow the scheduler to initialize the child.
481 */
482 thread_lock(td);
483 sched_fork(td, td2);
484 thread_unlock(td);
485
486 /*
487 * Duplicate sub-structures as needed.
488 * Increase reference counts on shared objects.
489 */
490 p2->p_flag = P_INMEM;
491 p2->p_flag2 = p1->p_flag2 & (P2_NOTRACE | P2_NOTRACE_EXEC);
492 p2->p_swtick = ticks;
493 if (p1->p_flag & P_PROFIL)
494 startprofclock(p2);
495
496 /*
497 * Whilst the proc lock is held, copy the VM domain data out
498 * using the VM domain method.
499 */
500 vm_domain_policy_init(&p2->p_vm_dom_policy);
501 vm_domain_policy_localcopy(&p2->p_vm_dom_policy,
502 &p1->p_vm_dom_policy);
503
504 if (flags & RFSIGSHARE) {
505 p2->p_sigacts = sigacts_hold(p1->p_sigacts);
506 } else {
507 sigacts_copy(newsigacts, p1->p_sigacts);
508 p2->p_sigacts = newsigacts;
509 }
510
511 if (flags & RFTSIGZMB)
512 p2->p_sigparent = RFTSIGNUM(flags);
513 else if (flags & RFLINUXTHPN)
514 p2->p_sigparent = SIGUSR1;
515 else
516 p2->p_sigparent = SIGCHLD;
517
518 p2->p_textvp = p1->p_textvp;
519 p2->p_fd = fd;
520 p2->p_fdtol = fdtol;
521
522 if (p1->p_flag2 & P2_INHERIT_PROTECTED) {
523 p2->p_flag |= P_PROTECTED;
524 p2->p_flag2 |= P2_INHERIT_PROTECTED;
525 }
526
527 /*
528 * p_limit is copy-on-write. Bump its refcount.
529 */
530 lim_fork(p1, p2);
531
532 thread_cow_get_proc(td2, p2);
533
534 pstats_fork(p1->p_stats, p2->p_stats);
535
536 PROC_UNLOCK(p1);
537 PROC_UNLOCK(p2);
538
539 /* Bump references to the text vnode (for procfs). */
540 if (p2->p_textvp)
541 vref(p2->p_textvp);
542
543 /*
544 * Set up linkage for kernel based threading.
545 */
546 if ((flags & RFTHREAD) != 0) {
547 mtx_lock(&ppeers_lock);
548 p2->p_peers = p1->p_peers;
549 p1->p_peers = p2;
550 p2->p_leader = p1->p_leader;
551 mtx_unlock(&ppeers_lock);
552 PROC_LOCK(p1->p_leader);
553 if ((p1->p_leader->p_flag & P_WEXIT) != 0) {
554 PROC_UNLOCK(p1->p_leader);
555 /*
556 * The task leader is exiting, so process p1 is
557 * going to be killed shortly. Since p1 obviously
558 * isn't dead yet, we know that the leader is either
559 * sending SIGKILL's to all the processes in this
560 * task or is sleeping waiting for all the peers to
561 * exit. We let p1 complete the fork, but we need
562 * to go ahead and kill the new process p2 since
563 * the task leader may not get a chance to send
564 * SIGKILL to it. We leave it on the list so that
565 * the task leader will wait for this new process
566 * to commit suicide.
567 */
568 PROC_LOCK(p2);
569 kern_psignal(p2, SIGKILL);
570 PROC_UNLOCK(p2);
571 } else
572 PROC_UNLOCK(p1->p_leader);
573 } else {
574 p2->p_peers = NULL;
575 p2->p_leader = p2;
576 }
577
578 sx_xlock(&proctree_lock);
579 PGRP_LOCK(p1->p_pgrp);
580 PROC_LOCK(p2);
581 PROC_LOCK(p1);
582
583 /*
584 * Preserve some more flags in subprocess. P_PROFIL has already
585 * been preserved.
586 */
587 p2->p_flag |= p1->p_flag & P_SUGID;
588 td2->td_pflags |= (td->td_pflags & TDP_ALTSTACK) | TDP_FORKING;
589 SESS_LOCK(p1->p_session);
590 if (p1->p_session->s_ttyvp != NULL && p1->p_flag & P_CONTROLT)
591 p2->p_flag |= P_CONTROLT;
592 SESS_UNLOCK(p1->p_session);
593 if (flags & RFPPWAIT)
594 p2->p_flag |= P_PPWAIT;
595
596 p2->p_pgrp = p1->p_pgrp;
597 LIST_INSERT_AFTER(p1, p2, p_pglist);
598 PGRP_UNLOCK(p1->p_pgrp);
599 LIST_INIT(&p2->p_children);
600 LIST_INIT(&p2->p_orphans);
601
602 callout_init_mtx(&p2->p_itcallout, &p2->p_mtx, 0);
603
604 /*
605 * If PF_FORK is set, the child process inherits the
606 * procfs ioctl flags from its parent.
607 */
608 if (p1->p_pfsflags & PF_FORK) {
609 p2->p_stops = p1->p_stops;
610 p2->p_pfsflags = p1->p_pfsflags;
611 }
612
613 /*
614 * This begins the section where we must prevent the parent
615 * from being swapped.
616 */
617 _PHOLD(p1);
618 PROC_UNLOCK(p1);
619
620 /*
621 * Attach the new process to its parent.
622 *
623 * If RFNOWAIT is set, the newly created process becomes a child
624 * of init. This effectively disassociates the child from the
625 * parent.
626 */
627 if ((flags & RFNOWAIT) != 0) {
628 pptr = p1->p_reaper;
629 p2->p_reaper = pptr;
630 } else {
631 p2->p_reaper = (p1->p_treeflag & P_TREE_REAPER) != 0 ?
632 p1 : p1->p_reaper;
633 pptr = p1;
634 }
635 p2->p_pptr = pptr;
636 LIST_INSERT_HEAD(&pptr->p_children, p2, p_sibling);
637 LIST_INIT(&p2->p_reaplist);
638 LIST_INSERT_HEAD(&p2->p_reaper->p_reaplist, p2, p_reapsibling);
639 if (p2->p_reaper == p1)
640 p2->p_reapsubtree = p2->p_pid;
641 sx_xunlock(&proctree_lock);
642
643 /* Inform accounting that we have forked. */
644 p2->p_acflag = AFORK;
645 PROC_UNLOCK(p2);
646
647 #ifdef KTRACE
648 ktrprocfork(p1, p2);
649 #endif
650
651 /*
652 * Finish creating the child process. It will return via a different
653 * execution path later. (ie: directly into user mode)
654 */
655 vm_forkproc(td, p2, td2, vm2, flags);
656
657 if (flags == (RFFDG | RFPROC)) {
658 PCPU_INC(cnt.v_forks);
659 PCPU_ADD(cnt.v_forkpages, p2->p_vmspace->vm_dsize +
660 p2->p_vmspace->vm_ssize);
661 } else if (flags == (RFFDG | RFPROC | RFPPWAIT | RFMEM)) {
662 PCPU_INC(cnt.v_vforks);
663 PCPU_ADD(cnt.v_vforkpages, p2->p_vmspace->vm_dsize +
664 p2->p_vmspace->vm_ssize);
665 } else if (p1 == &proc0) {
666 PCPU_INC(cnt.v_kthreads);
667 PCPU_ADD(cnt.v_kthreadpages, p2->p_vmspace->vm_dsize +
668 p2->p_vmspace->vm_ssize);
669 } else {
670 PCPU_INC(cnt.v_rforks);
671 PCPU_ADD(cnt.v_rforkpages, p2->p_vmspace->vm_dsize +
672 p2->p_vmspace->vm_ssize);
673 }
674
675 /*
676 * Associate the process descriptor with the process before anything
677 * can happen that might cause that process to need the descriptor.
678 * However, don't do this until after fork(2) can no longer fail.
679 */
680 if (flags & RFPROCDESC)
681 procdesc_new(p2, pdflags);
682
683 /*
684 * Both processes are set up, now check if any loadable modules want
685 * to adjust anything.
686 */
687 EVENTHANDLER_INVOKE(process_fork, p1, p2, flags);
688
689 /*
690 * Set the child start time and mark the process as being complete.
691 */
692 PROC_LOCK(p2);
693 PROC_LOCK(p1);
694 microuptime(&p2->p_stats->p_start);
695 PROC_SLOCK(p2);
696 p2->p_state = PRS_NORMAL;
697 PROC_SUNLOCK(p2);
698
699 #ifdef KDTRACE_HOOKS
700 /*
701 * Tell the DTrace fasttrap provider about the new process so that any
702 * tracepoints inherited from the parent can be removed. We have to do
703 * this only after p_state is PRS_NORMAL since the fasttrap module will
704 * use pfind() later on.
705 */
706 if ((flags & RFMEM) == 0 && dtrace_fasttrap_fork)
707 dtrace_fasttrap_fork(p1, p2);
708 #endif
709 if ((p1->p_flag & (P_TRACED | P_FOLLOWFORK)) == (P_TRACED |
710 P_FOLLOWFORK)) {
711 /*
712 * Arrange for debugger to receive the fork event.
713 *
714 * We can report PL_FLAG_FORKED regardless of
715 * P_FOLLOWFORK settings, but it does not make a sense
716 * for runaway child.
717 */
718 td->td_dbgflags |= TDB_FORK;
719 td->td_dbg_forked = p2->p_pid;
720 td2->td_dbgflags |= TDB_STOPATFORK;
721 _PHOLD(p2);
722 p2_held = 1;
723 }
724 if (flags & RFPPWAIT) {
725 td->td_pflags |= TDP_RFPPWAIT;
726 td->td_rfppwait_p = p2;
727 }
728 PROC_UNLOCK(p2);
729 if ((flags & RFSTOPPED) == 0) {
730 /*
731 * If RFSTOPPED not requested, make child runnable and
732 * add to run queue.
733 */
734 thread_lock(td2);
735 TD_SET_CAN_RUN(td2);
736 sched_add(td2, SRQ_BORING);
737 thread_unlock(td2);
738 }
739
740 /*
741 * Now can be swapped.
742 */
743 _PRELE(p1);
744 PROC_UNLOCK(p1);
745
746 /*
747 * Tell any interested parties about the new process.
748 */
749 knote_fork(&p1->p_klist, p2->p_pid);
750 SDT_PROBE3(proc, , , create, p2, p1, flags);
751
752 /*
753 * Wait until debugger is attached to child.
754 */
755 PROC_LOCK(p2);
756 while ((td2->td_dbgflags & TDB_STOPATFORK) != 0)
757 cv_wait(&p2->p_dbgwait, &p2->p_mtx);
758 if (p2_held)
759 _PRELE(p2);
760 PROC_UNLOCK(p2);
761 }
762
763 int
fork1(struct thread * td,int flags,int pages,struct proc ** procp,int * procdescp,int pdflags,struct filecaps * fcaps)764 fork1(struct thread *td, int flags, int pages, struct proc **procp,
765 int *procdescp, int pdflags, struct filecaps *fcaps)
766 {
767 struct proc *p1, *newproc;
768 struct thread *td2;
769 struct vmspace *vm2;
770 struct file *fp_procdesc;
771 vm_ooffset_t mem_charged;
772 int error, nprocs_new, ok;
773 static int curfail;
774 static struct timeval lastfail;
775
776 /* Check for the undefined or unimplemented flags. */
777 if ((flags & ~(RFFLAGS | RFTSIGFLAGS(RFTSIGMASK))) != 0)
778 return (EINVAL);
779
780 /* Signal value requires RFTSIGZMB. */
781 if ((flags & RFTSIGFLAGS(RFTSIGMASK)) != 0 && (flags & RFTSIGZMB) == 0)
782 return (EINVAL);
783
784 /* Can't copy and clear. */
785 if ((flags & (RFFDG|RFCFDG)) == (RFFDG|RFCFDG))
786 return (EINVAL);
787
788 /* Check the validity of the signal number. */
789 if ((flags & RFTSIGZMB) != 0 && (u_int)RFTSIGNUM(flags) > _SIG_MAXSIG)
790 return (EINVAL);
791
792 if ((flags & RFPROCDESC) != 0) {
793 /* Can't not create a process yet get a process descriptor. */
794 if ((flags & RFPROC) == 0)
795 return (EINVAL);
796
797 /* Must provide a place to put a procdesc if creating one. */
798 if (procdescp == NULL)
799 return (EINVAL);
800 }
801
802 p1 = td->td_proc;
803
804 /*
805 * Here we don't create a new process, but we divorce
806 * certain parts of a process from itself.
807 */
808 if ((flags & RFPROC) == 0) {
809 *procp = NULL;
810 return (fork_norfproc(td, flags));
811 }
812
813 fp_procdesc = NULL;
814 newproc = NULL;
815 vm2 = NULL;
816
817 /*
818 * Increment the nprocs resource before allocations occur.
819 * Although process entries are dynamically created, we still
820 * keep a global limit on the maximum number we will
821 * create. There are hard-limits as to the number of processes
822 * that can run, established by the KVA and memory usage for
823 * the process data.
824 *
825 * Don't allow a nonprivileged user to use the last ten
826 * processes; don't let root exceed the limit.
827 */
828 nprocs_new = atomic_fetchadd_int(&nprocs, 1) + 1;
829 if ((nprocs_new >= maxproc - 10 && priv_check_cred(td->td_ucred,
830 PRIV_MAXPROC, 0) != 0) || nprocs_new >= maxproc) {
831 error = EAGAIN;
832 sx_xlock(&allproc_lock);
833 if (ppsratecheck(&lastfail, &curfail, 1)) {
834 printf("maxproc limit exceeded by uid %u (pid %d); "
835 "see tuning(7) and login.conf(5)\n",
836 td->td_ucred->cr_ruid, p1->p_pid);
837 }
838 sx_xunlock(&allproc_lock);
839 goto fail2;
840 }
841
842 /*
843 * If required, create a process descriptor in the parent first; we
844 * will abandon it if something goes wrong. We don't finit() until
845 * later.
846 */
847 if (flags & RFPROCDESC) {
848 error = falloc_caps(td, &fp_procdesc, procdescp, 0, fcaps);
849 if (error != 0)
850 goto fail2;
851 }
852
853 mem_charged = 0;
854 if (pages == 0)
855 pages = kstack_pages;
856 /* Allocate new proc. */
857 newproc = uma_zalloc(proc_zone, M_WAITOK);
858 td2 = FIRST_THREAD_IN_PROC(newproc);
859 if (td2 == NULL) {
860 td2 = thread_alloc(pages);
861 if (td2 == NULL) {
862 error = ENOMEM;
863 goto fail2;
864 }
865 proc_linkup(newproc, td2);
866 } else {
867 if (td2->td_kstack == 0 || td2->td_kstack_pages != pages) {
868 if (td2->td_kstack != 0)
869 vm_thread_dispose(td2);
870 if (!thread_alloc_stack(td2, pages)) {
871 error = ENOMEM;
872 goto fail2;
873 }
874 }
875 }
876
877 if ((flags & RFMEM) == 0) {
878 vm2 = vmspace_fork(p1->p_vmspace, &mem_charged);
879 if (vm2 == NULL) {
880 error = ENOMEM;
881 goto fail2;
882 }
883 if (!swap_reserve(mem_charged)) {
884 /*
885 * The swap reservation failed. The accounting
886 * from the entries of the copied vm2 will be
887 * substracted in vmspace_free(), so force the
888 * reservation there.
889 */
890 swap_reserve_force(mem_charged);
891 error = ENOMEM;
892 goto fail2;
893 }
894 } else
895 vm2 = NULL;
896
897 /*
898 * XXX: This is ugly; when we copy resource usage, we need to bump
899 * per-cred resource counters.
900 */
901 proc_set_cred_init(newproc, crhold(td->td_ucred));
902
903 /*
904 * Initialize resource accounting for the child process.
905 */
906 error = racct_proc_fork(p1, newproc);
907 if (error != 0) {
908 error = EAGAIN;
909 goto fail1;
910 }
911
912 #ifdef MAC
913 mac_proc_init(newproc);
914 #endif
915 knlist_init_mtx(&newproc->p_klist, &newproc->p_mtx);
916 STAILQ_INIT(&newproc->p_ktr);
917
918 /* We have to lock the process tree while we look for a pid. */
919 sx_slock(&proctree_lock);
920 sx_xlock(&allproc_lock);
921
922 /*
923 * Increment the count of procs running with this uid. Don't allow
924 * a nonprivileged user to exceed their current limit.
925 *
926 * XXXRW: Can we avoid privilege here if it's not needed?
927 */
928 error = priv_check_cred(td->td_ucred, PRIV_PROC_LIMIT, 0);
929 if (error == 0)
930 ok = chgproccnt(td->td_ucred->cr_ruidinfo, 1, 0);
931 else {
932 ok = chgproccnt(td->td_ucred->cr_ruidinfo, 1,
933 lim_cur(td, RLIMIT_NPROC));
934 }
935 if (ok) {
936 do_fork(td, flags, newproc, td2, vm2, pdflags);
937
938 /*
939 * Return child proc pointer to parent.
940 */
941 *procp = newproc;
942 if (flags & RFPROCDESC) {
943 procdesc_finit(newproc->p_procdesc, fp_procdesc);
944 fdrop(fp_procdesc, td);
945 }
946 racct_proc_fork_done(newproc);
947 return (0);
948 }
949
950 error = EAGAIN;
951 sx_sunlock(&proctree_lock);
952 sx_xunlock(&allproc_lock);
953 #ifdef MAC
954 mac_proc_destroy(newproc);
955 #endif
956 racct_proc_exit(newproc);
957 fail1:
958 crfree(newproc->p_ucred);
959 newproc->p_ucred = NULL;
960 fail2:
961 if (vm2 != NULL)
962 vmspace_free(vm2);
963 uma_zfree(proc_zone, newproc);
964 if ((flags & RFPROCDESC) != 0 && fp_procdesc != NULL) {
965 fdclose(td, fp_procdesc, *procdescp);
966 fdrop(fp_procdesc, td);
967 }
968 atomic_add_int(&nprocs, -1);
969 pause("fork", hz / 2);
970 return (error);
971 }
972
973 /*
974 * Handle the return of a child process from fork1(). This function
975 * is called from the MD fork_trampoline() entry point.
976 */
977 void
fork_exit(void (* callout)(void *,struct trapframe *),void * arg,struct trapframe * frame)978 fork_exit(void (*callout)(void *, struct trapframe *), void *arg,
979 struct trapframe *frame)
980 {
981 struct proc *p;
982 struct thread *td;
983 struct thread *dtd;
984
985 td = curthread;
986 p = td->td_proc;
987 KASSERT(p->p_state == PRS_NORMAL, ("executing process is still new"));
988
989 CTR4(KTR_PROC, "fork_exit: new thread %p (td_sched %p, pid %d, %s)",
990 td, td->td_sched, p->p_pid, td->td_name);
991
992 sched_fork_exit(td);
993 /*
994 * Processes normally resume in mi_switch() after being
995 * cpu_switch()'ed to, but when children start up they arrive here
996 * instead, so we must do much the same things as mi_switch() would.
997 */
998 if ((dtd = PCPU_GET(deadthread))) {
999 PCPU_SET(deadthread, NULL);
1000 thread_stash(dtd);
1001 }
1002 thread_unlock(td);
1003
1004 /*
1005 * cpu_set_fork_handler intercepts this function call to
1006 * have this call a non-return function to stay in kernel mode.
1007 * initproc has its own fork handler, but it does return.
1008 */
1009 KASSERT(callout != NULL, ("NULL callout in fork_exit"));
1010 callout(arg, frame);
1011
1012 /*
1013 * Check if a kernel thread misbehaved and returned from its main
1014 * function.
1015 */
1016 if (p->p_flag & P_KTHREAD) {
1017 printf("Kernel thread \"%s\" (pid %d) exited prematurely.\n",
1018 td->td_name, p->p_pid);
1019 kproc_exit(0);
1020 }
1021 mtx_assert(&Giant, MA_NOTOWNED);
1022
1023 if (p->p_sysent->sv_schedtail != NULL)
1024 (p->p_sysent->sv_schedtail)(td);
1025 td->td_pflags &= ~TDP_FORKING;
1026 }
1027
1028 /*
1029 * Simplified back end of syscall(), used when returning from fork()
1030 * directly into user mode. Giant is not held on entry, and must not
1031 * be held on return. This function is passed in to fork_exit() as the
1032 * first parameter and is called when returning to a new userland process.
1033 */
1034 void
fork_return(struct thread * td,struct trapframe * frame)1035 fork_return(struct thread *td, struct trapframe *frame)
1036 {
1037 struct proc *p, *dbg;
1038
1039 p = td->td_proc;
1040 if (td->td_dbgflags & TDB_STOPATFORK) {
1041 sx_xlock(&proctree_lock);
1042 PROC_LOCK(p);
1043 if ((p->p_pptr->p_flag & (P_TRACED | P_FOLLOWFORK)) ==
1044 (P_TRACED | P_FOLLOWFORK)) {
1045 /*
1046 * If debugger still wants auto-attach for the
1047 * parent's children, do it now.
1048 */
1049 dbg = p->p_pptr->p_pptr;
1050 p->p_flag |= P_TRACED;
1051 p->p_oppid = p->p_pptr->p_pid;
1052 CTR2(KTR_PTRACE,
1053 "fork_return: attaching to new child pid %d: oppid %d",
1054 p->p_pid, p->p_oppid);
1055 proc_reparent(p, dbg);
1056 sx_xunlock(&proctree_lock);
1057 td->td_dbgflags |= TDB_CHILD | TDB_SCX;
1058 ptracestop(td, SIGSTOP);
1059 td->td_dbgflags &= ~(TDB_CHILD | TDB_SCX);
1060 } else {
1061 /*
1062 * ... otherwise clear the request.
1063 */
1064 sx_xunlock(&proctree_lock);
1065 td->td_dbgflags &= ~TDB_STOPATFORK;
1066 cv_broadcast(&p->p_dbgwait);
1067 }
1068 PROC_UNLOCK(p);
1069 } else if (p->p_flag & P_TRACED || td->td_dbgflags & TDB_BORN) {
1070 /*
1071 * This is the start of a new thread in a traced
1072 * process. Report a system call exit event.
1073 */
1074 PROC_LOCK(p);
1075 td->td_dbgflags |= TDB_SCX;
1076 _STOPEVENT(p, S_SCX, td->td_dbg_sc_code);
1077 if ((p->p_stops & S_PT_SCX) != 0 ||
1078 (td->td_dbgflags & TDB_BORN) != 0)
1079 ptracestop(td, SIGTRAP);
1080 td->td_dbgflags &= ~(TDB_SCX | TDB_BORN);
1081 PROC_UNLOCK(p);
1082 }
1083
1084 userret(td, frame);
1085
1086 #ifdef KTRACE
1087 if (KTRPOINT(td, KTR_SYSRET))
1088 ktrsysret(SYS_fork, 0, 0);
1089 #endif
1090 }
1091