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
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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
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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
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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_ASLR_DISABLE | P2_ASLR_ENABLE |
511 P2_ASLR_IGNSTART | P2_NOTRACE | P2_NOTRACE_EXEC |
513 P2_STKGAP_DISABLE | P2_STKGAP_DISABLE_EXEC);
514 p2->p_swtick = ticks;
515 if (p1->p_flag & P_PROFIL)
518 if (fr->fr_flags & RFSIGSHARE) {
519 p2->p_sigacts = sigacts_hold(p1->p_sigacts);
521 sigacts_copy(newsigacts, p1->p_sigacts);
522 p2->p_sigacts = newsigacts;
525 if (fr->fr_flags & RFTSIGZMB)
526 p2->p_sigparent = RFTSIGNUM(fr->fr_flags);
527 else if (fr->fr_flags & RFLINUXTHPN)
528 p2->p_sigparent = SIGUSR1;
530 p2->p_sigparent = SIGCHLD;
532 p2->p_textvp = p1->p_textvp;
536 if (p1->p_flag2 & P2_INHERIT_PROTECTED) {
537 p2->p_flag |= P_PROTECTED;
538 p2->p_flag2 |= P2_INHERIT_PROTECTED;
542 * p_limit is copy-on-write. Bump its refcount.
546 thread_cow_get_proc(td2, p2);
548 pstats_fork(p1->p_stats, p2->p_stats);
553 /* Bump references to the text vnode (for procfs). */
555 vrefact(p2->p_textvp);
558 * Set up linkage for kernel based threading.
560 if ((fr->fr_flags & RFTHREAD) != 0) {
561 mtx_lock(&ppeers_lock);
562 p2->p_peers = p1->p_peers;
564 p2->p_leader = p1->p_leader;
565 mtx_unlock(&ppeers_lock);
566 PROC_LOCK(p1->p_leader);
567 if ((p1->p_leader->p_flag & P_WEXIT) != 0) {
568 PROC_UNLOCK(p1->p_leader);
570 * The task leader is exiting, so process p1 is
571 * going to be killed shortly. Since p1 obviously
572 * isn't dead yet, we know that the leader is either
573 * sending SIGKILL's to all the processes in this
574 * task or is sleeping waiting for all the peers to
575 * exit. We let p1 complete the fork, but we need
576 * to go ahead and kill the new process p2 since
577 * the task leader may not get a chance to send
578 * SIGKILL to it. We leave it on the list so that
579 * the task leader will wait for this new process
583 kern_psignal(p2, SIGKILL);
586 PROC_UNLOCK(p1->p_leader);
592 sx_xlock(&proctree_lock);
593 PGRP_LOCK(p1->p_pgrp);
598 * Preserve some more flags in subprocess. P_PROFIL has already
601 p2->p_flag |= p1->p_flag & P_SUGID;
602 td2->td_pflags |= (td->td_pflags & TDP_ALTSTACK) | TDP_FORKING;
603 SESS_LOCK(p1->p_session);
604 if (p1->p_session->s_ttyvp != NULL && p1->p_flag & P_CONTROLT)
605 p2->p_flag |= P_CONTROLT;
606 SESS_UNLOCK(p1->p_session);
607 if (fr->fr_flags & RFPPWAIT)
608 p2->p_flag |= P_PPWAIT;
610 p2->p_pgrp = p1->p_pgrp;
611 LIST_INSERT_AFTER(p1, p2, p_pglist);
612 PGRP_UNLOCK(p1->p_pgrp);
613 LIST_INIT(&p2->p_children);
614 LIST_INIT(&p2->p_orphans);
616 callout_init_mtx(&p2->p_itcallout, &p2->p_mtx, 0);
619 * If PF_FORK is set, the child process inherits the
620 * procfs ioctl flags from its parent.
622 if (p1->p_pfsflags & PF_FORK) {
623 p2->p_stops = p1->p_stops;
624 p2->p_pfsflags = p1->p_pfsflags;
628 * This begins the section where we must prevent the parent
629 * from being swapped.
635 * Attach the new process to its parent.
637 * If RFNOWAIT is set, the newly created process becomes a child
638 * of init. This effectively disassociates the child from the
641 if ((fr->fr_flags & RFNOWAIT) != 0) {
645 p2->p_reaper = (p1->p_treeflag & P_TREE_REAPER) != 0 ?
650 p2->p_oppid = pptr->p_pid;
651 LIST_INSERT_HEAD(&pptr->p_children, p2, p_sibling);
652 LIST_INIT(&p2->p_reaplist);
653 LIST_INSERT_HEAD(&p2->p_reaper->p_reaplist, p2, p_reapsibling);
654 if (p2->p_reaper == p1)
655 p2->p_reapsubtree = p2->p_pid;
656 sx_xunlock(&proctree_lock);
658 /* Inform accounting that we have forked. */
659 p2->p_acflag = AFORK;
667 * Finish creating the child process. It will return via a different
668 * execution path later. (ie: directly into user mode)
670 vm_forkproc(td, p2, td2, vm2, fr->fr_flags);
672 if (fr->fr_flags == (RFFDG | RFPROC)) {
674 VM_CNT_ADD(v_forkpages, p2->p_vmspace->vm_dsize +
675 p2->p_vmspace->vm_ssize);
676 } else if (fr->fr_flags == (RFFDG | RFPROC | RFPPWAIT | RFMEM)) {
677 VM_CNT_INC(v_vforks);
678 VM_CNT_ADD(v_vforkpages, p2->p_vmspace->vm_dsize +
679 p2->p_vmspace->vm_ssize);
680 } else if (p1 == &proc0) {
681 VM_CNT_INC(v_kthreads);
682 VM_CNT_ADD(v_kthreadpages, p2->p_vmspace->vm_dsize +
683 p2->p_vmspace->vm_ssize);
685 VM_CNT_INC(v_rforks);
686 VM_CNT_ADD(v_rforkpages, p2->p_vmspace->vm_dsize +
687 p2->p_vmspace->vm_ssize);
691 * Associate the process descriptor with the process before anything
692 * can happen that might cause that process to need the descriptor.
693 * However, don't do this until after fork(2) can no longer fail.
695 if (fr->fr_flags & RFPROCDESC)
696 procdesc_new(p2, fr->fr_pd_flags);
699 * Both processes are set up, now check if any loadable modules want
700 * to adjust anything.
702 EVENTHANDLER_DIRECT_INVOKE(process_fork, p1, p2, fr->fr_flags);
705 * Set the child start time and mark the process as being complete.
709 microuptime(&p2->p_stats->p_start);
711 p2->p_state = PRS_NORMAL;
716 * Tell the DTrace fasttrap provider about the new process so that any
717 * tracepoints inherited from the parent can be removed. We have to do
718 * this only after p_state is PRS_NORMAL since the fasttrap module will
719 * use pfind() later on.
721 if ((fr->fr_flags & RFMEM) == 0 && dtrace_fasttrap_fork)
722 dtrace_fasttrap_fork(p1, p2);
725 * Hold the process so that it cannot exit after we make it runnable,
726 * but before we wait for the debugger.
729 if (fr->fr_flags & RFPPWAIT) {
730 td->td_pflags |= TDP_RFPPWAIT;
731 td->td_rfppwait_p = p2;
732 td->td_dbgflags |= TDB_VFORK;
737 * Now can be swapped.
743 * Tell any interested parties about the new process.
745 knote_fork(p1->p_klist, p2->p_pid);
746 SDT_PROBE3(proc, , , create, p2, p1, fr->fr_flags);
748 if (fr->fr_flags & RFPROCDESC) {
749 procdesc_finit(p2->p_procdesc, fp_procdesc);
750 fdrop(fp_procdesc, td);
754 * Speculative check for PTRACE_FORK. PTRACE_FORK is not
755 * synced with forks in progress so it is OK if we miss it
758 if ((p1->p_ptevents & PTRACE_FORK) != 0) {
759 sx_xlock(&proctree_lock);
763 * p1->p_ptevents & p1->p_pptr are protected by both
764 * process and proctree locks for modifications,
765 * so owning proctree_lock allows the race-free read.
767 if ((p1->p_ptevents & PTRACE_FORK) != 0) {
769 * Arrange for debugger to receive the fork event.
771 * We can report PL_FLAG_FORKED regardless of
772 * P_FOLLOWFORK settings, but it does not make a sense
775 td->td_dbgflags |= TDB_FORK;
776 td->td_dbg_forked = p2->p_pid;
777 td2->td_dbgflags |= TDB_STOPATFORK;
778 proc_set_traced(p2, true);
780 "do_fork: attaching to new child pid %d: oppid %d",
781 p2->p_pid, p2->p_oppid);
782 proc_reparent(p2, p1->p_pptr, false);
785 sx_xunlock(&proctree_lock);
788 if ((fr->fr_flags & RFSTOPPED) == 0) {
790 * If RFSTOPPED not requested, make child runnable and
795 sched_add(td2, SRQ_BORING);
797 if (fr->fr_pidp != NULL)
798 *fr->fr_pidp = p2->p_pid;
805 racct_proc_fork_done(p2);
810 fork1(struct thread *td, struct fork_req *fr)
812 struct proc *p1, *newproc;
815 struct file *fp_procdesc;
816 vm_ooffset_t mem_charged;
817 int error, nprocs_new, ok;
819 static struct timeval lastfail;
822 flags = fr->fr_flags;
823 pages = fr->fr_pages;
825 if ((flags & RFSTOPPED) != 0)
826 MPASS(fr->fr_procp != NULL && fr->fr_pidp == NULL);
828 MPASS(fr->fr_procp == NULL);
830 /* Check for the undefined or unimplemented flags. */
831 if ((flags & ~(RFFLAGS | RFTSIGFLAGS(RFTSIGMASK))) != 0)
834 /* Signal value requires RFTSIGZMB. */
835 if ((flags & RFTSIGFLAGS(RFTSIGMASK)) != 0 && (flags & RFTSIGZMB) == 0)
838 /* Can't copy and clear. */
839 if ((flags & (RFFDG|RFCFDG)) == (RFFDG|RFCFDG))
842 /* Check the validity of the signal number. */
843 if ((flags & RFTSIGZMB) != 0 && (u_int)RFTSIGNUM(flags) > _SIG_MAXSIG)
846 if ((flags & RFPROCDESC) != 0) {
847 /* Can't not create a process yet get a process descriptor. */
848 if ((flags & RFPROC) == 0)
851 /* Must provide a place to put a procdesc if creating one. */
852 if (fr->fr_pd_fd == NULL)
855 /* Check if we are using supported flags. */
856 if ((fr->fr_pd_flags & ~PD_ALLOWED_AT_FORK) != 0)
863 * Here we don't create a new process, but we divorce
864 * certain parts of a process from itself.
866 if ((flags & RFPROC) == 0) {
867 if (fr->fr_procp != NULL)
868 *fr->fr_procp = NULL;
869 else if (fr->fr_pidp != NULL)
871 return (fork_norfproc(td, flags));
879 * Increment the nprocs resource before allocations occur.
880 * Although process entries are dynamically created, we still
881 * keep a global limit on the maximum number we will
882 * create. There are hard-limits as to the number of processes
883 * that can run, established by the KVA and memory usage for
886 * Don't allow a nonprivileged user to use the last ten
887 * processes; don't let root exceed the limit.
889 nprocs_new = atomic_fetchadd_int(&nprocs, 1) + 1;
890 if (nprocs_new >= maxproc - 10) {
891 if (priv_check_cred(td->td_ucred, PRIV_MAXPROC, 0) != 0 ||
892 nprocs_new >= maxproc) {
894 sx_xlock(&allproc_lock);
895 if (ppsratecheck(&lastfail, &curfail, 1)) {
896 printf("maxproc limit exceeded by uid %u "
897 "(pid %d); see tuning(7) and "
899 td->td_ucred->cr_ruid, p1->p_pid);
901 sx_xunlock(&allproc_lock);
907 * If required, create a process descriptor in the parent first; we
908 * will abandon it if something goes wrong. We don't finit() until
911 if (flags & RFPROCDESC) {
912 error = procdesc_falloc(td, &fp_procdesc, fr->fr_pd_fd,
913 fr->fr_pd_flags, fr->fr_pd_fcaps);
920 pages = kstack_pages;
921 /* Allocate new proc. */
922 newproc = uma_zalloc(proc_zone, M_WAITOK);
923 td2 = FIRST_THREAD_IN_PROC(newproc);
925 td2 = thread_alloc(pages);
930 proc_linkup(newproc, td2);
932 if (td2->td_kstack == 0 || td2->td_kstack_pages != pages) {
933 if (td2->td_kstack != 0)
934 vm_thread_dispose(td2);
935 if (!thread_alloc_stack(td2, pages)) {
942 if ((flags & RFMEM) == 0) {
943 vm2 = vmspace_fork(p1->p_vmspace, &mem_charged);
948 if (!swap_reserve(mem_charged)) {
950 * The swap reservation failed. The accounting
951 * from the entries of the copied vm2 will be
952 * subtracted in vmspace_free(), so force the
955 swap_reserve_force(mem_charged);
963 * XXX: This is ugly; when we copy resource usage, we need to bump
964 * per-cred resource counters.
966 proc_set_cred_init(newproc, crhold(td->td_ucred));
969 * Initialize resource accounting for the child process.
971 error = racct_proc_fork(p1, newproc);
978 mac_proc_init(newproc);
980 newproc->p_klist = knlist_alloc(&newproc->p_mtx);
981 STAILQ_INIT(&newproc->p_ktr);
983 /* We have to lock the process tree while we look for a pid. */
984 sx_xlock(&proctree_lock);
985 sx_xlock(&allproc_lock);
988 * Increment the count of procs running with this uid. Don't allow
989 * a nonprivileged user to exceed their current limit.
991 * XXXRW: Can we avoid privilege here if it's not needed?
993 error = priv_check_cred(td->td_ucred, PRIV_PROC_LIMIT, 0);
995 ok = chgproccnt(td->td_ucred->cr_ruidinfo, 1, 0);
997 ok = chgproccnt(td->td_ucred->cr_ruidinfo, 1,
998 lim_cur(td, RLIMIT_NPROC));
1001 do_fork(td, fr, newproc, td2, vm2, fp_procdesc);
1006 sx_xunlock(&allproc_lock);
1007 sx_xunlock(&proctree_lock);
1009 mac_proc_destroy(newproc);
1011 racct_proc_exit(newproc);
1013 crfree(newproc->p_ucred);
1014 newproc->p_ucred = NULL;
1018 uma_zfree(proc_zone, newproc);
1019 if ((flags & RFPROCDESC) != 0 && fp_procdesc != NULL) {
1020 fdclose(td, fp_procdesc, *fr->fr_pd_fd);
1021 fdrop(fp_procdesc, td);
1023 atomic_add_int(&nprocs, -1);
1024 pause("fork", hz / 2);
1029 * Handle the return of a child process from fork1(). This function
1030 * is called from the MD fork_trampoline() entry point.
1033 fork_exit(void (*callout)(void *, struct trapframe *), void *arg,
1034 struct trapframe *frame)
1042 KASSERT(p->p_state == PRS_NORMAL, ("executing process is still new"));
1044 CTR4(KTR_PROC, "fork_exit: new thread %p (td_sched %p, pid %d, %s)",
1045 td, td_get_sched(td), p->p_pid, td->td_name);
1047 sched_fork_exit(td);
1049 * Processes normally resume in mi_switch() after being
1050 * cpu_switch()'ed to, but when children start up they arrive here
1051 * instead, so we must do much the same things as mi_switch() would.
1053 if ((dtd = PCPU_GET(deadthread))) {
1054 PCPU_SET(deadthread, NULL);
1060 * cpu_fork_kthread_handler intercepts this function call to
1061 * have this call a non-return function to stay in kernel mode.
1062 * initproc has its own fork handler, but it does return.
1064 KASSERT(callout != NULL, ("NULL callout in fork_exit"));
1065 callout(arg, frame);
1068 * Check if a kernel thread misbehaved and returned from its main
1071 if (p->p_flag & P_KPROC) {
1072 printf("Kernel thread \"%s\" (pid %d) exited prematurely.\n",
1073 td->td_name, p->p_pid);
1076 mtx_assert(&Giant, MA_NOTOWNED);
1078 if (p->p_sysent->sv_schedtail != NULL)
1079 (p->p_sysent->sv_schedtail)(td);
1080 td->td_pflags &= ~TDP_FORKING;
1084 * Simplified back end of syscall(), used when returning from fork()
1085 * directly into user mode. This function is passed in to fork_exit()
1086 * as the first parameter and is called when returning to a new
1090 fork_return(struct thread *td, struct trapframe *frame)
1095 if (td->td_dbgflags & TDB_STOPATFORK) {
1097 if ((p->p_flag & P_TRACED) != 0) {
1099 * Inform the debugger if one is still present.
1101 td->td_dbgflags |= TDB_CHILD | TDB_SCX | TDB_FSTP;
1102 ptracestop(td, SIGSTOP, NULL);
1103 td->td_dbgflags &= ~(TDB_CHILD | TDB_SCX);
1106 * ... otherwise clear the request.
1108 td->td_dbgflags &= ~TDB_STOPATFORK;
1111 } else if (p->p_flag & P_TRACED || td->td_dbgflags & TDB_BORN) {
1113 * This is the start of a new thread in a traced
1114 * process. Report a system call exit event.
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);
1129 if (KTRPOINT(td, KTR_SYSRET))
1130 ktrsysret(SYS_fork, 0, 0);