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
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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.
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20 * 3. Neither the name of the University nor the names of its contributors
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24 * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
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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/bitstring.h>
48 #include <sys/sysproto.h>
49 #include <sys/eventhandler.h>
50 #include <sys/fcntl.h>
51 #include <sys/filedesc.h>
53 #include <sys/kernel.h>
54 #include <sys/kthread.h>
55 #include <sys/sysctl.h>
57 #include <sys/malloc.h>
58 #include <sys/mutex.h>
61 #include <sys/procdesc.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_
103 sys_fork(struct thread *td, struct fork_args *uap)
108 bzero(&fr, sizeof(fr));
109 fr.fr_flags = RFFDG | RFPROC;
111 error = fork1(td, &fr);
113 td->td_retval[0] = pid;
114 td->td_retval[1] = 0;
121 sys_pdfork(struct thread *td, struct pdfork_args *uap)
126 bzero(&fr, sizeof(fr));
127 fr.fr_flags = RFFDG | RFPROC | RFPROCDESC;
130 fr.fr_pd_flags = uap->flags;
131 AUDIT_ARG_FFLAGS(uap->flags);
133 * It is necessary to return fd by reference because 0 is a valid file
134 * descriptor number, and the child needs to be able to distinguish
135 * itself from the parent using the return value.
137 error = fork1(td, &fr);
139 td->td_retval[0] = pid;
140 td->td_retval[1] = 0;
141 error = copyout(&fd, uap->fdp, sizeof(fd));
148 sys_vfork(struct thread *td, struct vfork_args *uap)
153 bzero(&fr, sizeof(fr));
154 fr.fr_flags = RFFDG | RFPROC | RFPPWAIT | RFMEM;
156 error = fork1(td, &fr);
158 td->td_retval[0] = pid;
159 td->td_retval[1] = 0;
165 sys_rfork(struct thread *td, struct rfork_args *uap)
170 /* Don't allow kernel-only flags. */
171 if ((uap->flags & RFKERNELONLY) != 0)
173 /* RFSPAWN must not appear with others */
174 if ((uap->flags & RFSPAWN) != 0 && uap->flags != RFSPAWN)
177 AUDIT_ARG_FFLAGS(uap->flags);
178 bzero(&fr, sizeof(fr));
179 if ((uap->flags & RFSPAWN) != 0) {
180 fr.fr_flags = RFFDG | RFPROC | RFPPWAIT | RFMEM;
181 fr.fr_flags2 = FR2_DROPSIG_CAUGHT;
183 fr.fr_flags = uap->flags;
186 error = fork1(td, &fr);
188 td->td_retval[0] = pid;
189 td->td_retval[1] = 0;
194 int __exclusive_cache_line nprocs = 1; /* process 0 */
196 SYSCTL_INT(_kern, OID_AUTO, lastpid, CTLFLAG_RD, &lastpid, 0,
200 * Random component to lastpid generation. We mix in a random factor to make
201 * it a little harder to predict. We sanity check the modulus value to avoid
202 * doing it in critical paths. Don't let it be too small or we pointlessly
203 * waste randomness entropy, and don't let it be impossibly large. Using a
204 * modulus that is too big causes a LOT more process table scans and slows
205 * down fork processing as the pidchecked caching is defeated.
207 static int randompid = 0;
210 sysctl_kern_randompid(SYSCTL_HANDLER_ARGS)
214 error = sysctl_wire_old_buffer(req, sizeof(int));
217 sx_xlock(&allproc_lock);
219 error = sysctl_handle_int(oidp, &pid, 0, req);
220 if (error == 0 && req->newptr != NULL) {
224 /* generate a random PID modulus between 100 and 1123 */
225 randompid = 100 + arc4random() % 1024;
226 else if (pid < 0 || pid > pid_max - 100)
228 randompid = pid_max - 100;
230 /* Make it reasonable */
235 sx_xunlock(&allproc_lock);
239 SYSCTL_PROC(_kern, OID_AUTO, randompid,
240 CTLTYPE_INT | CTLFLAG_RW | CTLFLAG_MPSAFE, 0, 0,
241 sysctl_kern_randompid, "I",
242 "Random PID modulus. Special values: 0: disable, 1: choose random value");
244 extern bitstr_t proc_id_pidmap;
245 extern bitstr_t proc_id_grpidmap;
246 extern bitstr_t proc_id_sessidmap;
247 extern bitstr_t proc_id_reapmap;
250 * Find an unused process ID
252 * If RFHIGHPID is set (used during system boot), do not allocate
256 fork_findpid(int flags)
262 * Avoid calling arc4random with procid_lock held.
265 if (__predict_false(randompid))
266 random = arc4random() % randompid;
268 mtx_lock(&procid_lock);
270 trypid = lastpid + 1;
271 if (flags & RFHIGHPID) {
278 if (trypid >= pid_max)
281 bit_ffc_at(&proc_id_pidmap, trypid, pid_max, &result);
283 KASSERT(trypid != 2, ("unexpectedly ran out of IDs"));
287 if (bit_test(&proc_id_grpidmap, result) ||
288 bit_test(&proc_id_sessidmap, result) ||
289 bit_test(&proc_id_reapmap, result)) {
295 * RFHIGHPID does not mess with the lastpid counter during boot.
297 if ((flags & RFHIGHPID) == 0)
300 bit_set(&proc_id_pidmap, result);
301 mtx_unlock(&procid_lock);
307 fork_norfproc(struct thread *td, int flags)
312 KASSERT((flags & RFPROC) == 0,
313 ("fork_norfproc called with RFPROC set"));
317 * Quiesce other threads if necessary. If RFMEM is not specified we
318 * must ensure that other threads do not concurrently create a second
319 * process sharing the vmspace, see vmspace_unshare().
321 if ((p1->p_flag & (P_HADTHREADS | P_SYSTEM)) == P_HADTHREADS &&
322 ((flags & (RFCFDG | RFFDG)) != 0 || (flags & RFMEM) == 0)) {
324 if (thread_single(p1, SINGLE_BOUNDARY)) {
331 error = vm_forkproc(td, NULL, NULL, NULL, flags);
336 * Close all file descriptors.
338 if ((flags & RFCFDG) != 0) {
339 struct filedesc *fdtmp;
340 struct pwddesc *pdtmp;
342 pdtmp = pdinit(td->td_proc->p_pd, false);
343 fdtmp = fdinit(td->td_proc->p_fd, false, NULL);
351 * Unshare file descriptors (from parent).
353 if ((flags & RFFDG) != 0) {
359 if ((p1->p_flag & (P_HADTHREADS | P_SYSTEM)) == P_HADTHREADS &&
360 ((flags & (RFCFDG | RFFDG)) != 0 || (flags & RFMEM) == 0)) {
362 thread_single_end(p1, SINGLE_BOUNDARY);
369 do_fork(struct thread *td, struct fork_req *fr, struct proc *p2, struct thread *td2,
370 struct vmspace *vm2, struct file *fp_procdesc)
372 struct proc *p1, *pptr;
374 struct filedesc_to_leader *fdtol;
376 struct sigacts *newsigacts;
381 bcopy(&p1->p_startcopy, &p2->p_startcopy,
382 __rangeof(struct proc, p_startcopy, p_endcopy));
383 pargs_hold(p2->p_args);
386 bzero(&p2->p_startzero,
387 __rangeof(struct proc, p_startzero, p_endzero));
389 /* Tell the prison that we exist. */
390 prison_proc_hold(p2->p_ucred->cr_prison);
392 p2->p_state = PRS_NEW; /* protect against others */
393 p2->p_pid = fork_findpid(fr->fr_flags);
394 AUDIT_ARG_PID(p2->p_pid);
395 TSFORK(p2->p_pid, p1->p_pid);
397 sx_xlock(&allproc_lock);
398 LIST_INSERT_HEAD(&allproc, p2, p_list);
400 sx_xunlock(&allproc_lock);
402 sx_xlock(PIDHASHLOCK(p2->p_pid));
403 LIST_INSERT_HEAD(PIDHASH(p2->p_pid), p2, p_hash);
404 sx_xunlock(PIDHASHLOCK(p2->p_pid));
409 * Malloc things while we don't hold any locks.
411 if (fr->fr_flags & RFSIGSHARE)
414 newsigacts = sigacts_alloc();
419 if (fr->fr_flags & RFCFDG) {
420 pd = pdinit(p1->p_pd, false);
421 fd = fdinit(p1->p_fd, false, NULL);
423 } else if (fr->fr_flags & RFFDG) {
424 if (fr->fr_flags2 & FR2_SHARE_PATHS)
425 pd = pdshare(p1->p_pd);
427 pd = pdcopy(p1->p_pd);
428 fd = fdcopy(p1->p_fd);
431 if (fr->fr_flags2 & FR2_SHARE_PATHS)
432 pd = pdcopy(p1->p_pd);
434 pd = pdshare(p1->p_pd);
435 fd = fdshare(p1->p_fd);
436 if (p1->p_fdtol == NULL)
437 p1->p_fdtol = filedesc_to_leader_alloc(NULL, NULL,
439 if ((fr->fr_flags & RFTHREAD) != 0) {
441 * Shared file descriptor table, and shared
444 fdtol = filedesc_to_leader_share(p1->p_fdtol, p1->p_fd);
447 * Shared file descriptor table, and different
450 fdtol = filedesc_to_leader_alloc(p1->p_fdtol,
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.
463 bzero(&td2->td_startzero,
464 __rangeof(struct thread, td_startzero, td_endzero));
466 bcopy(&td->td_startcopy, &td2->td_startcopy,
467 __rangeof(struct thread, td_startcopy, td_endcopy));
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;
476 td2->td_vnet_lpush = NULL;
480 * Allow the scheduler to initialize the child.
487 * Duplicate sub-structures as needed.
488 * Increase reference counts on shared objects.
490 p2->p_flag = P_INMEM;
491 p2->p_flag2 = p1->p_flag2 & (P2_ASLR_DISABLE | P2_ASLR_ENABLE |
492 P2_ASLR_IGNSTART | P2_NOTRACE | P2_NOTRACE_EXEC |
493 P2_PROTMAX_ENABLE | P2_PROTMAX_DISABLE | P2_TRAPCAP |
494 P2_STKGAP_DISABLE | P2_STKGAP_DISABLE_EXEC | P2_NO_NEW_PRIVS |
495 P2_WXORX_DISABLE | P2_WXORX_ENABLE_EXEC);
496 p2->p_swtick = ticks;
497 if (p1->p_flag & P_PROFIL)
500 if (fr->fr_flags & RFSIGSHARE) {
501 p2->p_sigacts = sigacts_hold(p1->p_sigacts);
503 sigacts_copy(newsigacts, p1->p_sigacts);
504 p2->p_sigacts = newsigacts;
505 if ((fr->fr_flags2 & (FR2_DROPSIG_CAUGHT | FR2_KPROC)) != 0) {
506 mtx_lock(&p2->p_sigacts->ps_mtx);
507 if ((fr->fr_flags2 & FR2_DROPSIG_CAUGHT) != 0)
509 if ((fr->fr_flags2 & FR2_KPROC) != 0)
510 p2->p_sigacts->ps_flag |= PS_NOCLDWAIT;
511 mtx_unlock(&p2->p_sigacts->ps_mtx);
515 if (fr->fr_flags & RFTSIGZMB)
516 p2->p_sigparent = RFTSIGNUM(fr->fr_flags);
517 else if (fr->fr_flags & RFLINUXTHPN)
518 p2->p_sigparent = SIGUSR1;
520 p2->p_sigparent = SIGCHLD;
522 if ((fr->fr_flags2 & FR2_KPROC) != 0) {
523 p2->p_flag |= P_SYSTEM | P_KPROC;
524 td2->td_pflags |= TDP_KTHREAD;
527 p2->p_textvp = p1->p_textvp;
528 p2->p_textdvp = p1->p_textdvp;
532 p2->p_elf_brandinfo = p1->p_elf_brandinfo;
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);
552 * Bump references to the text vnode and directory, and copy
555 if (p2->p_textvp != NULL)
556 vrefact(p2->p_textvp);
557 if (p2->p_textdvp != NULL)
558 vrefact(p2->p_textdvp);
559 p2->p_binname = p1->p_binname == NULL ? NULL :
560 strdup(p1->p_binname, M_PARGS);
563 * Set up linkage for kernel based threading.
565 if ((fr->fr_flags & RFTHREAD) != 0) {
566 mtx_lock(&ppeers_lock);
567 p2->p_peers = p1->p_peers;
569 p2->p_leader = p1->p_leader;
570 mtx_unlock(&ppeers_lock);
571 PROC_LOCK(p1->p_leader);
572 if ((p1->p_leader->p_flag & P_WEXIT) != 0) {
573 PROC_UNLOCK(p1->p_leader);
575 * The task leader is exiting, so process p1 is
576 * going to be killed shortly. Since p1 obviously
577 * isn't dead yet, we know that the leader is either
578 * sending SIGKILL's to all the processes in this
579 * task or is sleeping waiting for all the peers to
580 * exit. We let p1 complete the fork, but we need
581 * to go ahead and kill the new process p2 since
582 * the task leader may not get a chance to send
583 * SIGKILL to it. We leave it on the list so that
584 * the task leader will wait for this new process
588 kern_psignal(p2, SIGKILL);
591 PROC_UNLOCK(p1->p_leader);
597 sx_xlock(&proctree_lock);
598 PGRP_LOCK(p1->p_pgrp);
603 * Preserve some more flags in subprocess. P_PROFIL has already
606 p2->p_flag |= p1->p_flag & P_SUGID;
607 td2->td_pflags |= (td->td_pflags & (TDP_ALTSTACK |
608 TDP_SIGFASTBLOCK)) | TDP_FORKING;
609 SESS_LOCK(p1->p_session);
610 if (p1->p_session->s_ttyvp != NULL && p1->p_flag & P_CONTROLT)
611 p2->p_flag |= P_CONTROLT;
612 SESS_UNLOCK(p1->p_session);
613 if (fr->fr_flags & RFPPWAIT)
614 p2->p_flag |= P_PPWAIT;
616 p2->p_pgrp = p1->p_pgrp;
617 LIST_INSERT_AFTER(p1, p2, p_pglist);
618 PGRP_UNLOCK(p1->p_pgrp);
619 LIST_INIT(&p2->p_children);
620 LIST_INIT(&p2->p_orphans);
622 callout_init_mtx(&p2->p_itcallout, &p2->p_mtx, 0);
623 TAILQ_INIT(&p2->p_kqtim_stop);
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 && p1 != initproc) {
653 p2->p_reapsubtree = p2->p_pid;
654 proc_id_set_cond(PROC_ID_REAP, 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);
724 if (fr->fr_flags & RFPPWAIT) {
725 td->td_pflags |= TDP_RFPPWAIT;
726 td->td_rfppwait_p = p2;
727 td->td_dbgflags |= TDB_VFORK;
732 * Tell any interested parties about the new process.
734 knote_fork(p1->p_klist, p2->p_pid);
737 * Now can be swapped.
741 SDT_PROBE3(proc, , , create, p2, p1, fr->fr_flags);
743 if (fr->fr_flags & RFPROCDESC) {
744 procdesc_finit(p2->p_procdesc, fp_procdesc);
745 fdrop(fp_procdesc, td);
749 * Speculative check for PTRACE_FORK. PTRACE_FORK is not
750 * synced with forks in progress so it is OK if we miss it
753 if ((p1->p_ptevents & PTRACE_FORK) != 0) {
754 sx_xlock(&proctree_lock);
758 * p1->p_ptevents & p1->p_pptr are protected by both
759 * process and proctree locks for modifications,
760 * so owning proctree_lock allows the race-free read.
762 if ((p1->p_ptevents & PTRACE_FORK) != 0) {
764 * Arrange for debugger to receive the fork event.
766 * We can report PL_FLAG_FORKED regardless of
767 * P_FOLLOWFORK settings, but it does not make a sense
770 td->td_dbgflags |= TDB_FORK;
771 td->td_dbg_forked = p2->p_pid;
772 td2->td_dbgflags |= TDB_STOPATFORK;
773 proc_set_traced(p2, true);
775 "do_fork: attaching to new child pid %d: oppid %d",
776 p2->p_pid, p2->p_oppid);
777 proc_reparent(p2, p1->p_pptr, false);
780 sx_xunlock(&proctree_lock);
783 racct_proc_fork_done(p2);
785 if ((fr->fr_flags & RFSTOPPED) == 0) {
786 if (fr->fr_pidp != NULL)
787 *fr->fr_pidp = p2->p_pid;
789 * If RFSTOPPED not requested, make child runnable and
794 sched_add(td2, SRQ_BORING);
801 fork_rfppwait(struct thread *td)
805 MPASS(td->td_pflags & TDP_RFPPWAIT);
809 * Preserve synchronization semantics of vfork. If
810 * waiting for child to exec or exit, fork set
811 * P_PPWAIT on child, and there we sleep on our proc
814 * Do it after the ptracestop() above is finished, to
815 * not block our debugger until child execs or exits
816 * to finish vfork wait.
818 td->td_pflags &= ~TDP_RFPPWAIT;
819 p2 = td->td_rfppwait_p;
822 while (p2->p_flag & P_PPWAIT) {
824 if (thread_suspend_check_needed()) {
826 thread_suspend_check(0);
832 cv_timedwait(&p2->p_pwait, &p2->p_mtx, hz);
836 if (td->td_dbgflags & TDB_VFORK) {
838 if (p->p_ptevents & PTRACE_VFORK)
839 ptracestop(td, SIGTRAP, NULL);
840 td->td_dbgflags &= ~TDB_VFORK;
846 fork1(struct thread *td, struct fork_req *fr)
848 struct proc *p1, *newproc;
852 struct file *fp_procdesc;
853 vm_ooffset_t mem_charged;
854 int error, nprocs_new;
856 static struct timeval lastfail;
859 flags = fr->fr_flags;
860 pages = fr->fr_pages;
862 if ((flags & RFSTOPPED) != 0)
863 MPASS(fr->fr_procp != NULL && fr->fr_pidp == NULL);
865 MPASS(fr->fr_procp == NULL);
867 /* Check for the undefined or unimplemented flags. */
868 if ((flags & ~(RFFLAGS | RFTSIGFLAGS(RFTSIGMASK))) != 0)
871 /* Signal value requires RFTSIGZMB. */
872 if ((flags & RFTSIGFLAGS(RFTSIGMASK)) != 0 && (flags & RFTSIGZMB) == 0)
875 /* Can't copy and clear. */
876 if ((flags & (RFFDG|RFCFDG)) == (RFFDG|RFCFDG))
879 /* Check the validity of the signal number. */
880 if ((flags & RFTSIGZMB) != 0 && (u_int)RFTSIGNUM(flags) > _SIG_MAXSIG)
883 if ((flags & RFPROCDESC) != 0) {
884 /* Can't not create a process yet get a process descriptor. */
885 if ((flags & RFPROC) == 0)
888 /* Must provide a place to put a procdesc if creating one. */
889 if (fr->fr_pd_fd == NULL)
892 /* Check if we are using supported flags. */
893 if ((fr->fr_pd_flags & ~PD_ALLOWED_AT_FORK) != 0)
900 * Here we don't create a new process, but we divorce
901 * certain parts of a process from itself.
903 if ((flags & RFPROC) == 0) {
904 if (fr->fr_procp != NULL)
905 *fr->fr_procp = NULL;
906 else if (fr->fr_pidp != NULL)
908 return (fork_norfproc(td, flags));
916 * Increment the nprocs resource before allocations occur.
917 * Although process entries are dynamically created, we still
918 * keep a global limit on the maximum number we will
919 * create. There are hard-limits as to the number of processes
920 * that can run, established by the KVA and memory usage for
923 * Don't allow a nonprivileged user to use the last ten
924 * processes; don't let root exceed the limit.
926 nprocs_new = atomic_fetchadd_int(&nprocs, 1) + 1;
927 if (nprocs_new >= maxproc - 10) {
928 if (priv_check_cred(td->td_ucred, PRIV_MAXPROC) != 0 ||
929 nprocs_new >= maxproc) {
931 sx_xlock(&allproc_lock);
932 if (ppsratecheck(&lastfail, &curfail, 1)) {
933 printf("maxproc limit exceeded by uid %u "
934 "(pid %d); see tuning(7) and "
936 td->td_ucred->cr_ruid, p1->p_pid);
938 sx_xunlock(&allproc_lock);
944 * If required, create a process descriptor in the parent first; we
945 * will abandon it if something goes wrong. We don't finit() until
948 if (flags & RFPROCDESC) {
949 error = procdesc_falloc(td, &fp_procdesc, fr->fr_pd_fd,
950 fr->fr_pd_flags, fr->fr_pd_fcaps);
953 AUDIT_ARG_FD(*fr->fr_pd_fd);
958 pages = kstack_pages;
959 /* Allocate new proc. */
960 newproc = uma_zalloc(proc_zone, M_WAITOK);
961 td2 = FIRST_THREAD_IN_PROC(newproc);
963 td2 = thread_alloc(pages);
968 proc_linkup(newproc, td2);
970 if (td2->td_kstack == 0 || td2->td_kstack_pages != pages) {
971 if (td2->td_kstack != 0)
972 vm_thread_dispose(td2);
973 if (!thread_alloc_stack(td2, pages)) {
980 if ((flags & RFMEM) == 0) {
981 vm2 = vmspace_fork(p1->p_vmspace, &mem_charged);
986 if (!swap_reserve(mem_charged)) {
988 * The swap reservation failed. The accounting
989 * from the entries of the copied vm2 will be
990 * subtracted in vmspace_free(), so force the
993 swap_reserve_force(mem_charged);
1001 * XXX: This is ugly; when we copy resource usage, we need to bump
1002 * per-cred resource counters.
1004 proc_set_cred_init(newproc, td->td_ucred);
1007 * Initialize resource accounting for the child process.
1009 error = racct_proc_fork(p1, newproc);
1016 mac_proc_init(newproc);
1018 newproc->p_klist = knlist_alloc(&newproc->p_mtx);
1019 STAILQ_INIT(&newproc->p_ktr);
1022 * Increment the count of procs running with this uid. Don't allow
1023 * a nonprivileged user to exceed their current limit.
1025 cred = td->td_ucred;
1026 if (!chgproccnt(cred->cr_ruidinfo, 1, lim_cur(td, RLIMIT_NPROC))) {
1027 if (priv_check_cred(cred, PRIV_PROC_LIMIT) != 0)
1029 chgproccnt(cred->cr_ruidinfo, 1, 0);
1032 do_fork(td, fr, newproc, td2, vm2, fp_procdesc);
1037 mac_proc_destroy(newproc);
1039 racct_proc_exit(newproc);
1041 proc_unset_cred(newproc);
1045 uma_zfree(proc_zone, newproc);
1046 if ((flags & RFPROCDESC) != 0 && fp_procdesc != NULL) {
1047 fdclose(td, fp_procdesc, *fr->fr_pd_fd);
1048 fdrop(fp_procdesc, td);
1050 atomic_add_int(&nprocs, -1);
1051 pause("fork", hz / 2);
1056 * Handle the return of a child process from fork1(). This function
1057 * is called from the MD fork_trampoline() entry point.
1060 fork_exit(void (*callout)(void *, struct trapframe *), void *arg,
1061 struct trapframe *frame)
1069 KASSERT(p->p_state == PRS_NORMAL, ("executing process is still new"));
1071 CTR4(KTR_PROC, "fork_exit: new thread %p (td_sched %p, pid %d, %s)",
1072 td, td_get_sched(td), p->p_pid, td->td_name);
1074 sched_fork_exit(td);
1077 * Processes normally resume in mi_switch() after being
1078 * cpu_switch()'ed to, but when children start up they arrive here
1079 * instead, so we must do much the same things as mi_switch() would.
1081 if ((dtd = PCPU_GET(deadthread))) {
1082 PCPU_SET(deadthread, NULL);
1088 * cpu_fork_kthread_handler intercepts this function call to
1089 * have this call a non-return function to stay in kernel mode.
1090 * initproc has its own fork handler, but it does return.
1092 KASSERT(callout != NULL, ("NULL callout in fork_exit"));
1093 callout(arg, frame);
1096 * Check if a kernel thread misbehaved and returned from its main
1099 if (p->p_flag & P_KPROC) {
1100 printf("Kernel thread \"%s\" (pid %d) exited prematurely.\n",
1101 td->td_name, p->p_pid);
1104 mtx_assert(&Giant, MA_NOTOWNED);
1106 if (p->p_sysent->sv_schedtail != NULL)
1107 (p->p_sysent->sv_schedtail)(td);
1108 td->td_pflags &= ~TDP_FORKING;
1112 * Simplified back end of syscall(), used when returning from fork()
1113 * directly into user mode. This function is passed in to fork_exit()
1114 * as the first parameter and is called when returning to a new
1118 fork_return(struct thread *td, struct trapframe *frame)
1123 if (td->td_dbgflags & TDB_STOPATFORK) {
1125 if ((p->p_flag & P_TRACED) != 0) {
1127 * Inform the debugger if one is still present.
1129 td->td_dbgflags |= TDB_CHILD | TDB_SCX | TDB_FSTP;
1130 ptracestop(td, SIGSTOP, NULL);
1131 td->td_dbgflags &= ~(TDB_CHILD | TDB_SCX);
1134 * ... otherwise clear the request.
1136 td->td_dbgflags &= ~TDB_STOPATFORK;
1139 } else if (p->p_flag & P_TRACED || td->td_dbgflags & TDB_BORN) {
1141 * This is the start of a new thread in a traced
1142 * process. Report a system call exit event.
1145 td->td_dbgflags |= TDB_SCX;
1146 if ((p->p_ptevents & PTRACE_SCX) != 0 ||
1147 (td->td_dbgflags & TDB_BORN) != 0)
1148 ptracestop(td, SIGTRAP, NULL);
1149 td->td_dbgflags &= ~(TDB_SCX | TDB_BORN);
1154 * If the prison was killed mid-fork, die along with it.
1156 if (!prison_isalive(td->td_ucred->cr_prison))
1157 exit1(td, 0, SIGKILL);
1162 if (KTRPOINT(td, KTR_SYSRET))
1163 ktrsysret(SYS_fork, 0, 0);