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.
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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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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
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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 sx_xlock(PIDHASHLOCK(p2->p_pid));
410 LIST_INSERT_HEAD(PIDHASH(p2->p_pid), p2, p_hash);
411 sx_xunlock(PIDHASHLOCK(p2->p_pid));
415 sx_xunlock(&allproc_lock);
416 sx_xunlock(&proctree_lock);
418 bcopy(&p1->p_startcopy, &p2->p_startcopy,
419 __rangeof(struct proc, p_startcopy, p_endcopy));
420 pargs_hold(p2->p_args);
424 bzero(&p2->p_startzero,
425 __rangeof(struct proc, p_startzero, p_endzero));
427 /* Tell the prison that we exist. */
428 prison_proc_hold(p2->p_ucred->cr_prison);
435 * Malloc things while we don't hold any locks.
437 if (fr->fr_flags & RFSIGSHARE)
440 newsigacts = sigacts_alloc();
445 if (fr->fr_flags & RFCFDG) {
446 fd = fdinit(p1->p_fd, false);
448 } else if (fr->fr_flags & RFFDG) {
449 fd = fdcopy(p1->p_fd);
452 fd = fdshare(p1->p_fd);
453 if (p1->p_fdtol == NULL)
454 p1->p_fdtol = filedesc_to_leader_alloc(NULL, NULL,
456 if ((fr->fr_flags & RFTHREAD) != 0) {
458 * Shared file descriptor table, and shared
462 FILEDESC_XLOCK(p1->p_fd);
463 fdtol->fdl_refcount++;
464 FILEDESC_XUNLOCK(p1->p_fd);
467 * Shared file descriptor table, and different
470 fdtol = filedesc_to_leader_alloc(p1->p_fdtol,
475 * Make a proc table entry for the new process.
476 * Start by zeroing the section of proc that is zero-initialized,
477 * then copy the section that is copied directly from the parent.
483 bzero(&td2->td_startzero,
484 __rangeof(struct thread, td_startzero, td_endzero));
486 bcopy(&td->td_startcopy, &td2->td_startcopy,
487 __rangeof(struct thread, td_startcopy, td_endcopy));
489 bcopy(&p2->p_comm, &td2->td_name, sizeof(td2->td_name));
490 td2->td_sigstk = td->td_sigstk;
491 td2->td_flags = TDF_INMEM;
492 td2->td_lend_user_pri = PRI_MAX;
496 td2->td_vnet_lpush = NULL;
500 * Allow the scheduler to initialize the child.
507 * Duplicate sub-structures as needed.
508 * Increase reference counts on shared objects.
510 p2->p_flag = P_INMEM;
511 p2->p_flag2 = p1->p_flag2 & (P2_NOTRACE | P2_NOTRACE_EXEC | P2_TRAPCAP);
512 p2->p_swtick = ticks;
513 if (p1->p_flag & P_PROFIL)
516 if (fr->fr_flags & RFSIGSHARE) {
517 p2->p_sigacts = sigacts_hold(p1->p_sigacts);
519 sigacts_copy(newsigacts, p1->p_sigacts);
520 p2->p_sigacts = newsigacts;
523 if (fr->fr_flags & RFTSIGZMB)
524 p2->p_sigparent = RFTSIGNUM(fr->fr_flags);
525 else if (fr->fr_flags & RFLINUXTHPN)
526 p2->p_sigparent = SIGUSR1;
528 p2->p_sigparent = SIGCHLD;
530 p2->p_textvp = p1->p_textvp;
534 if (p1->p_flag2 & P2_INHERIT_PROTECTED) {
535 p2->p_flag |= P_PROTECTED;
536 p2->p_flag2 |= P2_INHERIT_PROTECTED;
540 * p_limit is copy-on-write. Bump its refcount.
544 thread_cow_get_proc(td2, p2);
546 pstats_fork(p1->p_stats, p2->p_stats);
551 /* Bump references to the text vnode (for procfs). */
553 vrefact(p2->p_textvp);
556 * Set up linkage for kernel based threading.
558 if ((fr->fr_flags & RFTHREAD) != 0) {
559 mtx_lock(&ppeers_lock);
560 p2->p_peers = p1->p_peers;
562 p2->p_leader = p1->p_leader;
563 mtx_unlock(&ppeers_lock);
564 PROC_LOCK(p1->p_leader);
565 if ((p1->p_leader->p_flag & P_WEXIT) != 0) {
566 PROC_UNLOCK(p1->p_leader);
568 * The task leader is exiting, so process p1 is
569 * going to be killed shortly. Since p1 obviously
570 * isn't dead yet, we know that the leader is either
571 * sending SIGKILL's to all the processes in this
572 * task or is sleeping waiting for all the peers to
573 * exit. We let p1 complete the fork, but we need
574 * to go ahead and kill the new process p2 since
575 * the task leader may not get a chance to send
576 * SIGKILL to it. We leave it on the list so that
577 * the task leader will wait for this new process
581 kern_psignal(p2, SIGKILL);
584 PROC_UNLOCK(p1->p_leader);
590 sx_xlock(&proctree_lock);
591 PGRP_LOCK(p1->p_pgrp);
596 * Preserve some more flags in subprocess. P_PROFIL has already
599 p2->p_flag |= p1->p_flag & P_SUGID;
600 td2->td_pflags |= (td->td_pflags & TDP_ALTSTACK) | TDP_FORKING;
601 SESS_LOCK(p1->p_session);
602 if (p1->p_session->s_ttyvp != NULL && p1->p_flag & P_CONTROLT)
603 p2->p_flag |= P_CONTROLT;
604 SESS_UNLOCK(p1->p_session);
605 if (fr->fr_flags & RFPPWAIT)
606 p2->p_flag |= P_PPWAIT;
608 p2->p_pgrp = p1->p_pgrp;
609 LIST_INSERT_AFTER(p1, p2, p_pglist);
610 PGRP_UNLOCK(p1->p_pgrp);
611 LIST_INIT(&p2->p_children);
612 LIST_INIT(&p2->p_orphans);
614 callout_init_mtx(&p2->p_itcallout, &p2->p_mtx, 0);
617 * If PF_FORK is set, the child process inherits the
618 * procfs ioctl flags from its parent.
620 if (p1->p_pfsflags & PF_FORK) {
621 p2->p_stops = p1->p_stops;
622 p2->p_pfsflags = p1->p_pfsflags;
626 * This begins the section where we must prevent the parent
627 * from being swapped.
633 * Attach the new process to its parent.
635 * If RFNOWAIT is set, the newly created process becomes a child
636 * of init. This effectively disassociates the child from the
639 if ((fr->fr_flags & RFNOWAIT) != 0) {
643 p2->p_reaper = (p1->p_treeflag & P_TREE_REAPER) != 0 ?
648 p2->p_oppid = pptr->p_pid;
649 LIST_INSERT_HEAD(&pptr->p_children, p2, p_sibling);
650 LIST_INIT(&p2->p_reaplist);
651 LIST_INSERT_HEAD(&p2->p_reaper->p_reaplist, p2, p_reapsibling);
652 if (p2->p_reaper == p1)
653 p2->p_reapsubtree = p2->p_pid;
654 sx_xunlock(&proctree_lock);
656 /* Inform accounting that we have forked. */
657 p2->p_acflag = AFORK;
665 * Finish creating the child process. It will return via a different
666 * execution path later. (ie: directly into user mode)
668 vm_forkproc(td, p2, td2, vm2, fr->fr_flags);
670 if (fr->fr_flags == (RFFDG | RFPROC)) {
672 VM_CNT_ADD(v_forkpages, p2->p_vmspace->vm_dsize +
673 p2->p_vmspace->vm_ssize);
674 } else if (fr->fr_flags == (RFFDG | RFPROC | RFPPWAIT | RFMEM)) {
675 VM_CNT_INC(v_vforks);
676 VM_CNT_ADD(v_vforkpages, p2->p_vmspace->vm_dsize +
677 p2->p_vmspace->vm_ssize);
678 } else if (p1 == &proc0) {
679 VM_CNT_INC(v_kthreads);
680 VM_CNT_ADD(v_kthreadpages, p2->p_vmspace->vm_dsize +
681 p2->p_vmspace->vm_ssize);
683 VM_CNT_INC(v_rforks);
684 VM_CNT_ADD(v_rforkpages, p2->p_vmspace->vm_dsize +
685 p2->p_vmspace->vm_ssize);
689 * Associate the process descriptor with the process before anything
690 * can happen that might cause that process to need the descriptor.
691 * However, don't do this until after fork(2) can no longer fail.
693 if (fr->fr_flags & RFPROCDESC)
694 procdesc_new(p2, fr->fr_pd_flags);
697 * Both processes are set up, now check if any loadable modules want
698 * to adjust anything.
700 EVENTHANDLER_DIRECT_INVOKE(process_fork, p1, p2, fr->fr_flags);
703 * Set the child start time and mark the process as being complete.
707 microuptime(&p2->p_stats->p_start);
709 p2->p_state = PRS_NORMAL;
714 * Tell the DTrace fasttrap provider about the new process so that any
715 * tracepoints inherited from the parent can be removed. We have to do
716 * this only after p_state is PRS_NORMAL since the fasttrap module will
717 * use pfind() later on.
719 if ((fr->fr_flags & RFMEM) == 0 && dtrace_fasttrap_fork)
720 dtrace_fasttrap_fork(p1, p2);
722 if (fr->fr_flags & RFPPWAIT) {
723 td->td_pflags |= TDP_RFPPWAIT;
724 td->td_rfppwait_p = p2;
725 td->td_dbgflags |= TDB_VFORK;
730 * Now can be swapped.
736 * Tell any interested parties about the new process.
738 knote_fork(p1->p_klist, p2->p_pid);
739 SDT_PROBE3(proc, , , create, p2, p1, fr->fr_flags);
741 if (fr->fr_flags & RFPROCDESC) {
742 procdesc_finit(p2->p_procdesc, fp_procdesc);
743 fdrop(fp_procdesc, td);
747 * Speculative check for PTRACE_FORK. PTRACE_FORK is not
748 * synced with forks in progress so it is OK if we miss it
751 if ((p1->p_ptevents & PTRACE_FORK) != 0) {
752 sx_xlock(&proctree_lock);
756 * p1->p_ptevents & p1->p_pptr are protected by both
757 * process and proctree locks for modifications,
758 * so owning proctree_lock allows the race-free read.
760 if ((p1->p_ptevents & PTRACE_FORK) != 0) {
762 * Arrange for debugger to receive the fork event.
764 * We can report PL_FLAG_FORKED regardless of
765 * P_FOLLOWFORK settings, but it does not make a sense
768 td->td_dbgflags |= TDB_FORK;
769 td->td_dbg_forked = p2->p_pid;
770 td2->td_dbgflags |= TDB_STOPATFORK;
771 proc_set_traced(p2, true);
773 "do_fork: attaching to new child pid %d: oppid %d",
774 p2->p_pid, p2->p_oppid);
775 proc_reparent(p2, p1->p_pptr, false);
778 sx_xunlock(&proctree_lock);
781 racct_proc_fork_done(p2);
783 if ((fr->fr_flags & RFSTOPPED) == 0) {
784 if (fr->fr_pidp != NULL)
785 *fr->fr_pidp = p2->p_pid;
787 * If RFSTOPPED not requested, make child runnable and
792 sched_add(td2, SRQ_BORING);
800 fork1(struct thread *td, struct fork_req *fr)
802 struct proc *p1, *newproc;
805 struct file *fp_procdesc;
806 vm_ooffset_t mem_charged;
807 int error, nprocs_new, ok;
809 static struct timeval lastfail;
812 flags = fr->fr_flags;
813 pages = fr->fr_pages;
815 if ((flags & RFSTOPPED) != 0)
816 MPASS(fr->fr_procp != NULL && fr->fr_pidp == NULL);
818 MPASS(fr->fr_procp == NULL);
820 /* Check for the undefined or unimplemented flags. */
821 if ((flags & ~(RFFLAGS | RFTSIGFLAGS(RFTSIGMASK))) != 0)
824 /* Signal value requires RFTSIGZMB. */
825 if ((flags & RFTSIGFLAGS(RFTSIGMASK)) != 0 && (flags & RFTSIGZMB) == 0)
828 /* Can't copy and clear. */
829 if ((flags & (RFFDG|RFCFDG)) == (RFFDG|RFCFDG))
832 /* Check the validity of the signal number. */
833 if ((flags & RFTSIGZMB) != 0 && (u_int)RFTSIGNUM(flags) > _SIG_MAXSIG)
836 if ((flags & RFPROCDESC) != 0) {
837 /* Can't not create a process yet get a process descriptor. */
838 if ((flags & RFPROC) == 0)
841 /* Must provide a place to put a procdesc if creating one. */
842 if (fr->fr_pd_fd == NULL)
845 /* Check if we are using supported flags. */
846 if ((fr->fr_pd_flags & ~PD_ALLOWED_AT_FORK) != 0)
853 * Here we don't create a new process, but we divorce
854 * certain parts of a process from itself.
856 if ((flags & RFPROC) == 0) {
857 if (fr->fr_procp != NULL)
858 *fr->fr_procp = NULL;
859 else if (fr->fr_pidp != NULL)
861 return (fork_norfproc(td, flags));
869 * Increment the nprocs resource before allocations occur.
870 * Although process entries are dynamically created, we still
871 * keep a global limit on the maximum number we will
872 * create. There are hard-limits as to the number of processes
873 * that can run, established by the KVA and memory usage for
876 * Don't allow a nonprivileged user to use the last ten
877 * processes; don't let root exceed the limit.
879 nprocs_new = atomic_fetchadd_int(&nprocs, 1) + 1;
880 if ((nprocs_new >= maxproc - 10 && priv_check_cred(td->td_ucred,
881 PRIV_MAXPROC, 0) != 0) || nprocs_new >= maxproc) {
883 sx_xlock(&allproc_lock);
884 if (ppsratecheck(&lastfail, &curfail, 1)) {
885 printf("maxproc limit exceeded by uid %u (pid %d); "
886 "see tuning(7) and login.conf(5)\n",
887 td->td_ucred->cr_ruid, p1->p_pid);
889 sx_xunlock(&allproc_lock);
894 * If required, create a process descriptor in the parent first; we
895 * will abandon it if something goes wrong. We don't finit() until
898 if (flags & RFPROCDESC) {
899 error = procdesc_falloc(td, &fp_procdesc, fr->fr_pd_fd,
900 fr->fr_pd_flags, fr->fr_pd_fcaps);
907 pages = kstack_pages;
908 /* Allocate new proc. */
909 newproc = uma_zalloc(proc_zone, M_WAITOK);
910 td2 = FIRST_THREAD_IN_PROC(newproc);
912 td2 = thread_alloc(pages);
917 proc_linkup(newproc, td2);
919 if (td2->td_kstack == 0 || td2->td_kstack_pages != pages) {
920 if (td2->td_kstack != 0)
921 vm_thread_dispose(td2);
922 if (!thread_alloc_stack(td2, pages)) {
929 if ((flags & RFMEM) == 0) {
930 vm2 = vmspace_fork(p1->p_vmspace, &mem_charged);
935 if (!swap_reserve(mem_charged)) {
937 * The swap reservation failed. The accounting
938 * from the entries of the copied vm2 will be
939 * subtracted in vmspace_free(), so force the
942 swap_reserve_force(mem_charged);
950 * XXX: This is ugly; when we copy resource usage, we need to bump
951 * per-cred resource counters.
953 proc_set_cred_init(newproc, crhold(td->td_ucred));
956 * Initialize resource accounting for the child process.
958 error = racct_proc_fork(p1, newproc);
965 mac_proc_init(newproc);
967 newproc->p_klist = knlist_alloc(&newproc->p_mtx);
968 STAILQ_INIT(&newproc->p_ktr);
970 /* We have to lock the process tree while we look for a pid. */
971 sx_xlock(&proctree_lock);
972 sx_xlock(&allproc_lock);
975 * Increment the count of procs running with this uid. Don't allow
976 * a nonprivileged user to exceed their current limit.
978 * XXXRW: Can we avoid privilege here if it's not needed?
980 error = priv_check_cred(td->td_ucred, PRIV_PROC_LIMIT, 0);
982 ok = chgproccnt(td->td_ucred->cr_ruidinfo, 1, 0);
984 ok = chgproccnt(td->td_ucred->cr_ruidinfo, 1,
985 lim_cur(td, RLIMIT_NPROC));
988 do_fork(td, fr, newproc, td2, vm2, fp_procdesc);
993 sx_xunlock(&allproc_lock);
994 sx_xunlock(&proctree_lock);
996 mac_proc_destroy(newproc);
998 racct_proc_exit(newproc);
1000 crfree(newproc->p_ucred);
1001 newproc->p_ucred = NULL;
1005 uma_zfree(proc_zone, newproc);
1006 if ((flags & RFPROCDESC) != 0 && fp_procdesc != NULL) {
1007 fdclose(td, fp_procdesc, *fr->fr_pd_fd);
1008 fdrop(fp_procdesc, td);
1010 atomic_add_int(&nprocs, -1);
1011 pause("fork", hz / 2);
1016 * Handle the return of a child process from fork1(). This function
1017 * is called from the MD fork_trampoline() entry point.
1020 fork_exit(void (*callout)(void *, struct trapframe *), void *arg,
1021 struct trapframe *frame)
1029 KASSERT(p->p_state == PRS_NORMAL, ("executing process is still new"));
1031 CTR4(KTR_PROC, "fork_exit: new thread %p (td_sched %p, pid %d, %s)",
1032 td, td_get_sched(td), p->p_pid, td->td_name);
1034 sched_fork_exit(td);
1036 * Processes normally resume in mi_switch() after being
1037 * cpu_switch()'ed to, but when children start up they arrive here
1038 * instead, so we must do much the same things as mi_switch() would.
1040 if ((dtd = PCPU_GET(deadthread))) {
1041 PCPU_SET(deadthread, NULL);
1047 * cpu_fork_kthread_handler intercepts this function call to
1048 * have this call a non-return function to stay in kernel mode.
1049 * initproc has its own fork handler, but it does return.
1051 KASSERT(callout != NULL, ("NULL callout in fork_exit"));
1052 callout(arg, frame);
1055 * Check if a kernel thread misbehaved and returned from its main
1058 if (p->p_flag & P_KPROC) {
1059 printf("Kernel thread \"%s\" (pid %d) exited prematurely.\n",
1060 td->td_name, p->p_pid);
1063 mtx_assert(&Giant, MA_NOTOWNED);
1065 if (p->p_sysent->sv_schedtail != NULL)
1066 (p->p_sysent->sv_schedtail)(td);
1067 td->td_pflags &= ~TDP_FORKING;
1071 * Simplified back end of syscall(), used when returning from fork()
1072 * directly into user mode. This function is passed in to fork_exit()
1073 * as the first parameter and is called when returning to a new
1077 fork_return(struct thread *td, struct trapframe *frame)
1082 if (td->td_dbgflags & TDB_STOPATFORK) {
1084 if ((p->p_flag & P_TRACED) != 0) {
1086 * Inform the debugger if one is still present.
1088 td->td_dbgflags |= TDB_CHILD | TDB_SCX | TDB_FSTP;
1089 ptracestop(td, SIGSTOP, NULL);
1090 td->td_dbgflags &= ~(TDB_CHILD | TDB_SCX);
1093 * ... otherwise clear the request.
1095 td->td_dbgflags &= ~TDB_STOPATFORK;
1098 } else if (p->p_flag & P_TRACED || td->td_dbgflags & TDB_BORN) {
1100 * This is the start of a new thread in a traced
1101 * process. Report a system call exit event.
1104 td->td_dbgflags |= TDB_SCX;
1105 _STOPEVENT(p, S_SCX, td->td_sa.code);
1106 if ((p->p_ptevents & PTRACE_SCX) != 0 ||
1107 (td->td_dbgflags & TDB_BORN) != 0)
1108 ptracestop(td, SIGTRAP, NULL);
1109 td->td_dbgflags &= ~(TDB_SCX | TDB_BORN);
1116 if (KTRPOINT(td, KTR_SYSRET))
1117 ktrsysret(SYS_fork, 0, 0);