2 * SPDX-License-Identifier: BSD-3-Clause
4 * Copyright (c) 1982, 1986, 1989, 1991, 1993
5 * The Regents of the University of California. All rights reserved.
6 * (c) UNIX System Laboratories, Inc.
7 * All or some portions of this file are derived from material licensed
8 * to the University of California by American Telephone and Telegraph
9 * Co. or Unix System Laboratories, Inc. and are reproduced herein with
10 * the permission of UNIX System Laboratories, Inc.
12 * Redistribution and use in source and binary forms, with or without
13 * modification, are permitted provided that the following conditions
15 * 1. Redistributions of source code must retain the above copyright
16 * notice, this list of conditions and the following disclaimer.
17 * 2. Redistributions in binary form must reproduce the above copyright
18 * notice, this list of conditions and the following disclaimer in the
19 * documentation and/or other materials provided with the distribution.
20 * 3. Neither the name of the University nor the names of its contributors
21 * may be used to endorse or promote products derived from this software
22 * without specific prior written permission.
24 * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
25 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
26 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
27 * ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
28 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
29 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
30 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
31 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
32 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
33 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
36 * @(#)kern_fork.c 8.6 (Berkeley) 4/8/94
39 #include <sys/cdefs.h>
40 __FBSDID("$FreeBSD$");
42 #include "opt_ktrace.h"
43 #include "opt_kstack_pages.h"
45 #include <sys/param.h>
46 #include <sys/systm.h>
47 #include <sys/sysproto.h>
48 #include <sys/eventhandler.h>
49 #include <sys/fcntl.h>
50 #include <sys/filedesc.h>
52 #include <sys/kernel.h>
53 #include <sys/kthread.h>
54 #include <sys/sysctl.h>
56 #include <sys/malloc.h>
57 #include <sys/mutex.h>
60 #include <sys/procdesc.h>
61 #include <sys/pioctl.h>
62 #include <sys/ptrace.h>
63 #include <sys/racct.h>
64 #include <sys/resourcevar.h>
65 #include <sys/sched.h>
66 #include <sys/syscall.h>
67 #include <sys/vmmeter.h>
68 #include <sys/vnode.h>
71 #include <sys/ktrace.h>
72 #include <sys/unistd.h>
75 #include <sys/sysent.h>
76 #include <sys/signalvar.h>
78 #include <security/audit/audit.h>
79 #include <security/mac/mac_framework.h>
83 #include <vm/vm_map.h>
84 #include <vm/vm_extern.h>
88 #include <sys/dtrace_bsd.h>
89 dtrace_fork_func_t dtrace_fasttrap_fork;
92 SDT_PROVIDER_DECLARE(proc);
93 SDT_PROBE_DEFINE3(proc, , , create, "struct proc *", "struct proc *", "int");
95 #ifndef _SYS_SYSPROTO_H_
101 EVENTHANDLER_LIST_DECLARE(process_fork);
105 sys_fork(struct thread *td, struct fork_args *uap)
110 bzero(&fr, sizeof(fr));
111 fr.fr_flags = RFFDG | RFPROC;
113 error = fork1(td, &fr);
115 td->td_retval[0] = pid;
116 td->td_retval[1] = 0;
123 sys_pdfork(struct thread *td, struct pdfork_args *uap)
128 bzero(&fr, sizeof(fr));
129 fr.fr_flags = RFFDG | RFPROC | RFPROCDESC;
132 fr.fr_pd_flags = uap->flags;
134 * It is necessary to return fd by reference because 0 is a valid file
135 * descriptor number, and the child needs to be able to distinguish
136 * itself from the parent using the return value.
138 error = fork1(td, &fr);
140 td->td_retval[0] = pid;
141 td->td_retval[1] = 0;
142 error = copyout(&fd, uap->fdp, sizeof(fd));
149 sys_vfork(struct thread *td, struct vfork_args *uap)
154 bzero(&fr, sizeof(fr));
155 fr.fr_flags = RFFDG | RFPROC | RFPPWAIT | RFMEM;
157 error = fork1(td, &fr);
159 td->td_retval[0] = pid;
160 td->td_retval[1] = 0;
166 sys_rfork(struct thread *td, struct rfork_args *uap)
171 /* Don't allow kernel-only flags. */
172 if ((uap->flags & RFKERNELONLY) != 0)
175 AUDIT_ARG_FFLAGS(uap->flags);
176 bzero(&fr, sizeof(fr));
177 fr.fr_flags = uap->flags;
179 error = fork1(td, &fr);
181 td->td_retval[0] = pid;
182 td->td_retval[1] = 0;
187 int nprocs = 1; /* process 0 */
189 SYSCTL_INT(_kern, OID_AUTO, lastpid, CTLFLAG_RD, &lastpid, 0,
193 * Random component to lastpid generation. We mix in a random factor to make
194 * it a little harder to predict. We sanity check the modulus value to avoid
195 * doing it in critical paths. Don't let it be too small or we pointlessly
196 * waste randomness entropy, and don't let it be impossibly large. Using a
197 * modulus that is too big causes a LOT more process table scans and slows
198 * down fork processing as the pidchecked caching is defeated.
200 static int randompid = 0;
203 sysctl_kern_randompid(SYSCTL_HANDLER_ARGS)
207 error = sysctl_wire_old_buffer(req, sizeof(int));
210 sx_xlock(&allproc_lock);
212 error = sysctl_handle_int(oidp, &pid, 0, req);
213 if (error == 0 && req->newptr != NULL) {
217 /* generate a random PID modulus between 100 and 1123 */
218 randompid = 100 + arc4random() % 1024;
219 else if (pid < 0 || pid > pid_max - 100)
221 randompid = pid_max - 100;
223 /* Make it reasonable */
228 sx_xunlock(&allproc_lock);
232 SYSCTL_PROC(_kern, OID_AUTO, randompid, CTLTYPE_INT|CTLFLAG_RW,
233 0, 0, sysctl_kern_randompid, "I", "Random PID modulus. Special values: 0: disable, 1: choose random value");
236 fork_findpid(int flags)
240 static int pidchecked = 0;
243 * Requires allproc_lock in order to iterate over the list
244 * of processes, and proctree_lock to access p_pgrp.
246 sx_assert(&allproc_lock, SX_LOCKED);
247 sx_assert(&proctree_lock, SX_LOCKED);
250 * Find an unused process ID. We remember a range of unused IDs
251 * ready to use (from lastpid+1 through pidchecked-1).
253 * If RFHIGHPID is set (used during system boot), do not allocate
256 trypid = lastpid + 1;
257 if (flags & RFHIGHPID) {
262 trypid += arc4random() % randompid;
266 * If the process ID prototype has wrapped around,
267 * restart somewhat above 0, as the low-numbered procs
268 * tend to include daemons that don't exit.
270 if (trypid >= pid_max) {
271 trypid = trypid % pid_max;
276 if (trypid >= pidchecked) {
279 pidchecked = PID_MAX;
281 * Scan the active and zombie procs to check whether this pid
282 * is in use. Remember the lowest pid that's greater
283 * than trypid, so we can avoid checking for a while.
285 * Avoid reuse of the process group id, session id or
286 * the reaper subtree id. Note that for process group
287 * and sessions, the amount of reserved pids is
288 * limited by process limit. For the subtree ids, the
289 * id is kept reserved only while there is a
290 * non-reaped process in the subtree, so amount of
291 * reserved pids is limited by process limit times
294 p = LIST_FIRST(&allproc);
296 for (; p != NULL; p = LIST_NEXT(p, p_list)) {
297 while (p->p_pid == trypid ||
298 p->p_reapsubtree == trypid ||
299 (p->p_pgrp != NULL &&
300 (p->p_pgrp->pg_id == trypid ||
301 (p->p_session != NULL &&
302 p->p_session->s_sid == trypid)))) {
304 if (trypid >= pidchecked)
307 if (p->p_pid > trypid && pidchecked > p->p_pid)
308 pidchecked = p->p_pid;
309 if (p->p_pgrp != NULL) {
310 if (p->p_pgrp->pg_id > trypid &&
311 pidchecked > p->p_pgrp->pg_id)
312 pidchecked = p->p_pgrp->pg_id;
313 if (p->p_session != NULL &&
314 p->p_session->s_sid > trypid &&
315 pidchecked > p->p_session->s_sid)
316 pidchecked = p->p_session->s_sid;
321 p = LIST_FIRST(&zombproc);
327 * RFHIGHPID does not mess with the lastpid counter during boot.
329 if (flags & RFHIGHPID)
338 fork_norfproc(struct thread *td, int flags)
343 KASSERT((flags & RFPROC) == 0,
344 ("fork_norfproc called with RFPROC set"));
347 if (((p1->p_flag & (P_HADTHREADS|P_SYSTEM)) == P_HADTHREADS) &&
348 (flags & (RFCFDG | RFFDG))) {
350 if (thread_single(p1, SINGLE_BOUNDARY)) {
357 error = vm_forkproc(td, NULL, NULL, NULL, flags);
362 * Close all file descriptors.
364 if (flags & RFCFDG) {
365 struct filedesc *fdtmp;
366 fdtmp = fdinit(td->td_proc->p_fd, false);
372 * Unshare file descriptors (from parent).
378 if (((p1->p_flag & (P_HADTHREADS|P_SYSTEM)) == P_HADTHREADS) &&
379 (flags & (RFCFDG | RFFDG))) {
381 thread_single_end(p1, SINGLE_BOUNDARY);
388 do_fork(struct thread *td, struct fork_req *fr, struct proc *p2, struct thread *td2,
389 struct vmspace *vm2, struct file *fp_procdesc)
391 struct proc *p1, *pptr;
394 struct filedesc_to_leader *fdtol;
395 struct sigacts *newsigacts;
397 sx_assert(&proctree_lock, SX_LOCKED);
398 sx_assert(&allproc_lock, SX_XLOCKED);
402 trypid = fork_findpid(fr->fr_flags);
404 p2->p_state = PRS_NEW; /* protect against others */
406 AUDIT_ARG_PID(p2->p_pid);
407 LIST_INSERT_HEAD(&allproc, p2, p_list);
409 LIST_INSERT_HEAD(PIDHASH(p2->p_pid), p2, p_hash);
413 sx_xunlock(&allproc_lock);
414 sx_xunlock(&proctree_lock);
416 bcopy(&p1->p_startcopy, &p2->p_startcopy,
417 __rangeof(struct proc, p_startcopy, p_endcopy));
418 p2->p_fctl0 = p1->p_fctl0;
419 pargs_hold(p2->p_args);
423 bzero(&p2->p_startzero,
424 __rangeof(struct proc, p_startzero, p_endzero));
426 /* Tell the prison that we exist. */
427 prison_proc_hold(p2->p_ucred->cr_prison);
434 * Malloc things while we don't hold any locks.
436 if (fr->fr_flags & RFSIGSHARE)
439 newsigacts = sigacts_alloc();
444 if (fr->fr_flags & RFCFDG) {
445 fd = fdinit(p1->p_fd, false);
447 } else if (fr->fr_flags & RFFDG) {
448 fd = fdcopy(p1->p_fd);
451 fd = fdshare(p1->p_fd);
452 if (p1->p_fdtol == NULL)
453 p1->p_fdtol = filedesc_to_leader_alloc(NULL, NULL,
455 if ((fr->fr_flags & RFTHREAD) != 0) {
457 * Shared file descriptor table, and shared
461 FILEDESC_XLOCK(p1->p_fd);
462 fdtol->fdl_refcount++;
463 FILEDESC_XUNLOCK(p1->p_fd);
466 * Shared file descriptor table, and different
469 fdtol = filedesc_to_leader_alloc(p1->p_fdtol,
474 * Make a proc table entry for the new process.
475 * Start by zeroing the section of proc that is zero-initialized,
476 * then copy the section that is copied directly from the parent.
482 bzero(&td2->td_startzero,
483 __rangeof(struct thread, td_startzero, td_endzero));
485 bcopy(&td->td_startcopy, &td2->td_startcopy,
486 __rangeof(struct thread, td_startcopy, td_endcopy));
488 bcopy(&p2->p_comm, &td2->td_name, sizeof(td2->td_name));
489 td2->td_sigstk = td->td_sigstk;
490 td2->td_flags = TDF_INMEM;
491 td2->td_lend_user_pri = PRI_MAX;
495 td2->td_vnet_lpush = NULL;
499 * Allow the scheduler to initialize the child.
506 * Duplicate sub-structures as needed.
507 * Increase reference counts on shared objects.
509 p2->p_flag = P_INMEM;
510 p2->p_flag2 = p1->p_flag2 & (P2_NOTRACE | P2_NOTRACE_EXEC | P2_TRAPCAP);
511 p2->p_swtick = ticks;
512 if (p1->p_flag & P_PROFIL)
515 if (fr->fr_flags & RFSIGSHARE) {
516 p2->p_sigacts = sigacts_hold(p1->p_sigacts);
518 sigacts_copy(newsigacts, p1->p_sigacts);
519 p2->p_sigacts = newsigacts;
522 if (fr->fr_flags & RFTSIGZMB)
523 p2->p_sigparent = RFTSIGNUM(fr->fr_flags);
524 else if (fr->fr_flags & RFLINUXTHPN)
525 p2->p_sigparent = SIGUSR1;
527 p2->p_sigparent = SIGCHLD;
529 p2->p_textvp = p1->p_textvp;
533 if (p1->p_flag2 & P2_INHERIT_PROTECTED) {
534 p2->p_flag |= P_PROTECTED;
535 p2->p_flag2 |= P2_INHERIT_PROTECTED;
539 * p_limit is copy-on-write. Bump its refcount.
543 thread_cow_get_proc(td2, p2);
545 pstats_fork(p1->p_stats, p2->p_stats);
550 /* Bump references to the text vnode (for procfs). */
552 vrefact(p2->p_textvp);
555 * Set up linkage for kernel based threading.
557 if ((fr->fr_flags & RFTHREAD) != 0) {
558 mtx_lock(&ppeers_lock);
559 p2->p_peers = p1->p_peers;
561 p2->p_leader = p1->p_leader;
562 mtx_unlock(&ppeers_lock);
563 PROC_LOCK(p1->p_leader);
564 if ((p1->p_leader->p_flag & P_WEXIT) != 0) {
565 PROC_UNLOCK(p1->p_leader);
567 * The task leader is exiting, so process p1 is
568 * going to be killed shortly. Since p1 obviously
569 * isn't dead yet, we know that the leader is either
570 * sending SIGKILL's to all the processes in this
571 * task or is sleeping waiting for all the peers to
572 * exit. We let p1 complete the fork, but we need
573 * to go ahead and kill the new process p2 since
574 * the task leader may not get a chance to send
575 * SIGKILL to it. We leave it on the list so that
576 * the task leader will wait for this new process
580 kern_psignal(p2, SIGKILL);
583 PROC_UNLOCK(p1->p_leader);
589 sx_xlock(&proctree_lock);
590 PGRP_LOCK(p1->p_pgrp);
595 * Preserve some more flags in subprocess. P_PROFIL has already
598 p2->p_flag |= p1->p_flag & P_SUGID;
599 td2->td_pflags |= (td->td_pflags & TDP_ALTSTACK) | TDP_FORKING;
600 SESS_LOCK(p1->p_session);
601 if (p1->p_session->s_ttyvp != NULL && p1->p_flag & P_CONTROLT)
602 p2->p_flag |= P_CONTROLT;
603 SESS_UNLOCK(p1->p_session);
604 if (fr->fr_flags & RFPPWAIT)
605 p2->p_flag |= P_PPWAIT;
607 p2->p_pgrp = p1->p_pgrp;
608 LIST_INSERT_AFTER(p1, p2, p_pglist);
609 PGRP_UNLOCK(p1->p_pgrp);
610 LIST_INIT(&p2->p_children);
611 LIST_INIT(&p2->p_orphans);
613 callout_init_mtx(&p2->p_itcallout, &p2->p_mtx, 0);
616 * If PF_FORK is set, the child process inherits the
617 * procfs ioctl flags from its parent.
619 if (p1->p_pfsflags & PF_FORK) {
620 p2->p_stops = p1->p_stops;
621 p2->p_pfsflags = p1->p_pfsflags;
625 * This begins the section where we must prevent the parent
626 * from being swapped.
632 * Attach the new process to its parent.
634 * If RFNOWAIT is set, the newly created process becomes a child
635 * of init. This effectively disassociates the child from the
638 if ((fr->fr_flags & RFNOWAIT) != 0) {
642 p2->p_reaper = (p1->p_treeflag & P_TREE_REAPER) != 0 ?
647 LIST_INSERT_HEAD(&pptr->p_children, p2, p_sibling);
648 LIST_INIT(&p2->p_reaplist);
649 LIST_INSERT_HEAD(&p2->p_reaper->p_reaplist, p2, p_reapsibling);
650 if (p2->p_reaper == p1)
651 p2->p_reapsubtree = p2->p_pid;
652 sx_xunlock(&proctree_lock);
654 /* Inform accounting that we have forked. */
655 p2->p_acflag = AFORK;
663 * Finish creating the child process. It will return via a different
664 * execution path later. (ie: directly into user mode)
666 vm_forkproc(td, p2, td2, vm2, fr->fr_flags);
668 if (fr->fr_flags == (RFFDG | RFPROC)) {
670 VM_CNT_ADD(v_forkpages, p2->p_vmspace->vm_dsize +
671 p2->p_vmspace->vm_ssize);
672 } else if (fr->fr_flags == (RFFDG | RFPROC | RFPPWAIT | RFMEM)) {
673 VM_CNT_INC(v_vforks);
674 VM_CNT_ADD(v_vforkpages, p2->p_vmspace->vm_dsize +
675 p2->p_vmspace->vm_ssize);
676 } else if (p1 == &proc0) {
677 VM_CNT_INC(v_kthreads);
678 VM_CNT_ADD(v_kthreadpages, p2->p_vmspace->vm_dsize +
679 p2->p_vmspace->vm_ssize);
681 VM_CNT_INC(v_rforks);
682 VM_CNT_ADD(v_rforkpages, p2->p_vmspace->vm_dsize +
683 p2->p_vmspace->vm_ssize);
687 * Associate the process descriptor with the process before anything
688 * can happen that might cause that process to need the descriptor.
689 * However, don't do this until after fork(2) can no longer fail.
691 if (fr->fr_flags & RFPROCDESC)
692 procdesc_new(p2, fr->fr_pd_flags);
695 * Both processes are set up, now check if any loadable modules want
696 * to adjust anything.
698 EVENTHANDLER_DIRECT_INVOKE(process_fork, p1, p2, fr->fr_flags);
701 * Set the child start time and mark the process as being complete.
705 microuptime(&p2->p_stats->p_start);
707 p2->p_state = PRS_NORMAL;
712 * Tell the DTrace fasttrap provider about the new process so that any
713 * tracepoints inherited from the parent can be removed. We have to do
714 * this only after p_state is PRS_NORMAL since the fasttrap module will
715 * use pfind() later on.
717 if ((fr->fr_flags & RFMEM) == 0 && dtrace_fasttrap_fork)
718 dtrace_fasttrap_fork(p1, p2);
721 * Hold the process so that it cannot exit after we make it runnable,
722 * but before we wait for the debugger.
725 if (fr->fr_flags & RFPPWAIT) {
726 td->td_pflags |= TDP_RFPPWAIT;
727 td->td_rfppwait_p = p2;
728 td->td_dbgflags |= TDB_VFORK;
733 * Now can be swapped.
739 * Tell any interested parties about the new process.
741 knote_fork(p1->p_klist, p2->p_pid);
742 SDT_PROBE3(proc, , , create, p2, p1, fr->fr_flags);
744 if (fr->fr_flags & RFPROCDESC) {
745 procdesc_finit(p2->p_procdesc, fp_procdesc);
746 fdrop(fp_procdesc, td);
750 * Speculative check for PTRACE_FORK. PTRACE_FORK is not
751 * synced with forks in progress so it is OK if we miss it
754 if ((p1->p_ptevents & PTRACE_FORK) != 0) {
755 sx_xlock(&proctree_lock);
759 * p1->p_ptevents & p1->p_pptr are protected by both
760 * process and proctree locks for modifications,
761 * so owning proctree_lock allows the race-free read.
763 if ((p1->p_ptevents & PTRACE_FORK) != 0) {
765 * Arrange for debugger to receive the fork event.
767 * We can report PL_FLAG_FORKED regardless of
768 * P_FOLLOWFORK settings, but it does not make a sense
771 td->td_dbgflags |= TDB_FORK;
772 td->td_dbg_forked = p2->p_pid;
773 td2->td_dbgflags |= TDB_STOPATFORK;
774 proc_set_traced(p2, true);
776 "do_fork: attaching to new child pid %d: oppid %d",
777 p2->p_pid, p2->p_oppid);
778 proc_reparent(p2, p1->p_pptr);
781 sx_xunlock(&proctree_lock);
784 if ((fr->fr_flags & RFSTOPPED) == 0) {
786 * If RFSTOPPED not requested, make child runnable and
791 sched_add(td2, SRQ_BORING);
793 if (fr->fr_pidp != NULL)
794 *fr->fr_pidp = p2->p_pid;
801 racct_proc_fork_done(p2);
806 fork1(struct thread *td, struct fork_req *fr)
808 struct proc *p1, *newproc;
811 struct file *fp_procdesc;
812 vm_ooffset_t mem_charged;
813 int error, nprocs_new, ok;
815 static struct timeval lastfail;
818 flags = fr->fr_flags;
819 pages = fr->fr_pages;
821 if ((flags & RFSTOPPED) != 0)
822 MPASS(fr->fr_procp != NULL && fr->fr_pidp == NULL);
824 MPASS(fr->fr_procp == NULL);
826 /* Check for the undefined or unimplemented flags. */
827 if ((flags & ~(RFFLAGS | RFTSIGFLAGS(RFTSIGMASK))) != 0)
830 /* Signal value requires RFTSIGZMB. */
831 if ((flags & RFTSIGFLAGS(RFTSIGMASK)) != 0 && (flags & RFTSIGZMB) == 0)
834 /* Can't copy and clear. */
835 if ((flags & (RFFDG|RFCFDG)) == (RFFDG|RFCFDG))
838 /* Check the validity of the signal number. */
839 if ((flags & RFTSIGZMB) != 0 && (u_int)RFTSIGNUM(flags) > _SIG_MAXSIG)
842 if ((flags & RFPROCDESC) != 0) {
843 /* Can't not create a process yet get a process descriptor. */
844 if ((flags & RFPROC) == 0)
847 /* Must provide a place to put a procdesc if creating one. */
848 if (fr->fr_pd_fd == NULL)
851 /* Check if we are using supported flags. */
852 if ((fr->fr_pd_flags & ~PD_ALLOWED_AT_FORK) != 0)
859 * Here we don't create a new process, but we divorce
860 * certain parts of a process from itself.
862 if ((flags & RFPROC) == 0) {
863 if (fr->fr_procp != NULL)
864 *fr->fr_procp = NULL;
865 else if (fr->fr_pidp != NULL)
867 return (fork_norfproc(td, flags));
875 * Increment the nprocs resource before allocations occur.
876 * Although process entries are dynamically created, we still
877 * keep a global limit on the maximum number we will
878 * create. There are hard-limits as to the number of processes
879 * that can run, established by the KVA and memory usage for
882 * Don't allow a nonprivileged user to use the last ten
883 * processes; don't let root exceed the limit.
885 nprocs_new = atomic_fetchadd_int(&nprocs, 1) + 1;
886 if ((nprocs_new >= maxproc - 10 && priv_check_cred(td->td_ucred,
887 PRIV_MAXPROC, 0) != 0) || nprocs_new >= maxproc) {
889 sx_xlock(&allproc_lock);
890 if (ppsratecheck(&lastfail, &curfail, 1)) {
891 printf("maxproc limit exceeded by uid %u (pid %d); "
892 "see tuning(7) and login.conf(5)\n",
893 td->td_ucred->cr_ruid, p1->p_pid);
895 sx_xunlock(&allproc_lock);
900 * If required, create a process descriptor in the parent first; we
901 * will abandon it if something goes wrong. We don't finit() until
904 if (flags & RFPROCDESC) {
905 error = procdesc_falloc(td, &fp_procdesc, fr->fr_pd_fd,
906 fr->fr_pd_flags, fr->fr_pd_fcaps);
913 pages = kstack_pages;
914 /* Allocate new proc. */
915 newproc = uma_zalloc(proc_zone, M_WAITOK);
916 td2 = FIRST_THREAD_IN_PROC(newproc);
918 td2 = thread_alloc(pages);
923 proc_linkup(newproc, td2);
925 if (td2->td_kstack == 0 || td2->td_kstack_pages != pages) {
926 if (td2->td_kstack != 0)
927 vm_thread_dispose(td2);
928 if (!thread_alloc_stack(td2, pages)) {
935 if ((flags & RFMEM) == 0) {
936 vm2 = vmspace_fork(p1->p_vmspace, &mem_charged);
941 if (!swap_reserve(mem_charged)) {
943 * The swap reservation failed. The accounting
944 * from the entries of the copied vm2 will be
945 * subtracted in vmspace_free(), so force the
948 swap_reserve_force(mem_charged);
956 * XXX: This is ugly; when we copy resource usage, we need to bump
957 * per-cred resource counters.
959 proc_set_cred_init(newproc, crhold(td->td_ucred));
962 * Initialize resource accounting for the child process.
964 error = racct_proc_fork(p1, newproc);
971 mac_proc_init(newproc);
973 newproc->p_klist = knlist_alloc(&newproc->p_mtx);
974 STAILQ_INIT(&newproc->p_ktr);
976 /* We have to lock the process tree while we look for a pid. */
977 sx_xlock(&proctree_lock);
978 sx_xlock(&allproc_lock);
981 * Increment the count of procs running with this uid. Don't allow
982 * a nonprivileged user to exceed their current limit.
984 * XXXRW: Can we avoid privilege here if it's not needed?
986 error = priv_check_cred(td->td_ucred, PRIV_PROC_LIMIT, 0);
988 ok = chgproccnt(td->td_ucred->cr_ruidinfo, 1, 0);
990 ok = chgproccnt(td->td_ucred->cr_ruidinfo, 1,
991 lim_cur(td, RLIMIT_NPROC));
994 do_fork(td, fr, newproc, td2, vm2, fp_procdesc);
999 sx_xunlock(&allproc_lock);
1000 sx_xunlock(&proctree_lock);
1002 mac_proc_destroy(newproc);
1004 racct_proc_exit(newproc);
1006 crfree(newproc->p_ucred);
1007 newproc->p_ucred = NULL;
1011 uma_zfree(proc_zone, newproc);
1012 if ((flags & RFPROCDESC) != 0 && fp_procdesc != NULL) {
1013 fdclose(td, fp_procdesc, *fr->fr_pd_fd);
1014 fdrop(fp_procdesc, td);
1016 atomic_add_int(&nprocs, -1);
1017 pause("fork", hz / 2);
1022 * Handle the return of a child process from fork1(). This function
1023 * is called from the MD fork_trampoline() entry point.
1026 fork_exit(void (*callout)(void *, struct trapframe *), void *arg,
1027 struct trapframe *frame)
1035 KASSERT(p->p_state == PRS_NORMAL, ("executing process is still new"));
1037 CTR4(KTR_PROC, "fork_exit: new thread %p (td_sched %p, pid %d, %s)",
1038 td, td_get_sched(td), p->p_pid, td->td_name);
1040 sched_fork_exit(td);
1042 * Processes normally resume in mi_switch() after being
1043 * cpu_switch()'ed to, but when children start up they arrive here
1044 * instead, so we must do much the same things as mi_switch() would.
1046 if ((dtd = PCPU_GET(deadthread))) {
1047 PCPU_SET(deadthread, NULL);
1053 * cpu_fork_kthread_handler intercepts this function call to
1054 * have this call a non-return function to stay in kernel mode.
1055 * initproc has its own fork handler, but it does return.
1057 KASSERT(callout != NULL, ("NULL callout in fork_exit"));
1058 callout(arg, frame);
1061 * Check if a kernel thread misbehaved and returned from its main
1064 if (p->p_flag & P_KPROC) {
1065 printf("Kernel thread \"%s\" (pid %d) exited prematurely.\n",
1066 td->td_name, p->p_pid);
1069 mtx_assert(&Giant, MA_NOTOWNED);
1071 if (p->p_sysent->sv_schedtail != NULL)
1072 (p->p_sysent->sv_schedtail)(td);
1073 td->td_pflags &= ~TDP_FORKING;
1077 * Simplified back end of syscall(), used when returning from fork()
1078 * directly into user mode. This function is passed in to fork_exit()
1079 * as the first parameter and is called when returning to a new
1083 fork_return(struct thread *td, struct trapframe *frame)
1088 if (td->td_dbgflags & TDB_STOPATFORK) {
1090 if ((p->p_flag & P_TRACED) != 0) {
1092 * Inform the debugger if one is still present.
1094 td->td_dbgflags |= TDB_CHILD | TDB_SCX | TDB_FSTP;
1095 ptracestop(td, SIGSTOP, NULL);
1096 td->td_dbgflags &= ~(TDB_CHILD | TDB_SCX);
1099 * ... otherwise clear the request.
1101 td->td_dbgflags &= ~TDB_STOPATFORK;
1104 } else if (p->p_flag & P_TRACED || td->td_dbgflags & TDB_BORN) {
1106 * This is the start of a new thread in a traced
1107 * process. Report a system call exit event.
1110 td->td_dbgflags |= TDB_SCX;
1111 _STOPEVENT(p, S_SCX, td->td_sa.code);
1112 if ((p->p_ptevents & PTRACE_SCX) != 0 ||
1113 (td->td_dbgflags & TDB_BORN) != 0)
1114 ptracestop(td, SIGTRAP, NULL);
1115 td->td_dbgflags &= ~(TDB_SCX | TDB_BORN);
1122 if (KTRPOINT(td, KTR_SYSRET))
1123 ktrsysret(SYS_fork, 0, 0);