2 * Copyright (c) 1982, 1986, 1989, 1991, 1993
3 * The Regents of the University of California. All rights reserved.
4 * (c) UNIX System Laboratories, Inc.
5 * All or some portions of this file are derived from material licensed
6 * to the University of California by American Telephone and Telegraph
7 * Co. or Unix System Laboratories, Inc. and are reproduced herein with
8 * the permission of UNIX System Laboratories, Inc.
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11 * modification, are permitted provided that the following conditions
13 * 1. Redistributions of source code must retain the above copyright
14 * notice, this list of conditions and the following disclaimer.
15 * 2. Redistributions in binary form must reproduce the above copyright
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19 * may be used to endorse or promote products derived from this software
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34 * @(#)kern_fork.c 8.6 (Berkeley) 4/8/94
37 #include <sys/cdefs.h>
38 __FBSDID("$FreeBSD$");
40 #include "opt_ktrace.h"
41 #include "opt_kstack_pages.h"
43 #include <sys/param.h>
44 #include <sys/systm.h>
45 #include <sys/sysproto.h>
46 #include <sys/eventhandler.h>
47 #include <sys/fcntl.h>
48 #include <sys/filedesc.h>
50 #include <sys/kernel.h>
51 #include <sys/kthread.h>
52 #include <sys/sysctl.h>
54 #include <sys/malloc.h>
55 #include <sys/mutex.h>
58 #include <sys/procdesc.h>
59 #include <sys/pioctl.h>
60 #include <sys/ptrace.h>
61 #include <sys/racct.h>
62 #include <sys/resourcevar.h>
63 #include <sys/sched.h>
64 #include <sys/syscall.h>
65 #include <sys/vmmeter.h>
66 #include <sys/vnode.h>
69 #include <sys/ktrace.h>
70 #include <sys/unistd.h>
73 #include <sys/sysent.h>
74 #include <sys/signalvar.h>
76 #include <security/audit/audit.h>
77 #include <security/mac/mac_framework.h>
81 #include <vm/vm_map.h>
82 #include <vm/vm_extern.h>
84 #include <vm/vm_domain.h>
87 #include <sys/dtrace_bsd.h>
88 dtrace_fork_func_t dtrace_fasttrap_fork;
91 SDT_PROVIDER_DECLARE(proc);
92 SDT_PROBE_DEFINE3(proc, , , create, "struct proc *", "struct proc *", "int");
94 #ifndef _SYS_SYSPROTO_H_
102 sys_fork(struct thread *td, struct fork_args *uap)
107 error = fork1(td, RFFDG | RFPROC, 0, &p2, NULL, 0, NULL);
109 td->td_retval[0] = p2->p_pid;
110 td->td_retval[1] = 0;
119 struct pdfork_args *uap;
125 * It is necessary to return fd by reference because 0 is a valid file
126 * descriptor number, and the child needs to be able to distinguish
127 * itself from the parent using the return value.
129 error = fork1(td, RFFDG | RFPROC | RFPROCDESC, 0, &p2,
130 &fd, uap->flags, NULL);
132 td->td_retval[0] = p2->p_pid;
133 td->td_retval[1] = 0;
134 error = copyout(&fd, uap->fdp, sizeof(fd));
141 sys_vfork(struct thread *td, struct vfork_args *uap)
146 flags = RFFDG | RFPROC | RFPPWAIT | RFMEM;
147 error = fork1(td, flags, 0, &p2, NULL, 0, NULL);
149 td->td_retval[0] = p2->p_pid;
150 td->td_retval[1] = 0;
156 sys_rfork(struct thread *td, struct rfork_args *uap)
161 /* Don't allow kernel-only flags. */
162 if ((uap->flags & RFKERNELONLY) != 0)
165 AUDIT_ARG_FFLAGS(uap->flags);
166 error = fork1(td, uap->flags, 0, &p2, NULL, 0, NULL);
168 td->td_retval[0] = p2 ? p2->p_pid : 0;
169 td->td_retval[1] = 0;
174 int nprocs = 1; /* process 0 */
176 SYSCTL_INT(_kern, OID_AUTO, lastpid, CTLFLAG_RD, &lastpid, 0,
180 * Random component to lastpid generation. We mix in a random factor to make
181 * it a little harder to predict. We sanity check the modulus value to avoid
182 * doing it in critical paths. Don't let it be too small or we pointlessly
183 * waste randomness entropy, and don't let it be impossibly large. Using a
184 * modulus that is too big causes a LOT more process table scans and slows
185 * down fork processing as the pidchecked caching is defeated.
187 static int randompid = 0;
190 sysctl_kern_randompid(SYSCTL_HANDLER_ARGS)
194 error = sysctl_wire_old_buffer(req, sizeof(int));
197 sx_xlock(&allproc_lock);
199 error = sysctl_handle_int(oidp, &pid, 0, req);
200 if (error == 0 && req->newptr != NULL) {
201 if (pid < 0 || pid > pid_max - 100) /* out of range */
203 else if (pid < 2) /* NOP */
205 else if (pid < 100) /* Make it reasonable */
209 sx_xunlock(&allproc_lock);
213 SYSCTL_PROC(_kern, OID_AUTO, randompid, CTLTYPE_INT|CTLFLAG_RW,
214 0, 0, sysctl_kern_randompid, "I", "Random PID modulus");
217 fork_findpid(int flags)
221 static int pidchecked = 0;
224 * Requires allproc_lock in order to iterate over the list
225 * of processes, and proctree_lock to access p_pgrp.
227 sx_assert(&allproc_lock, SX_LOCKED);
228 sx_assert(&proctree_lock, SX_LOCKED);
231 * Find an unused process ID. We remember a range of unused IDs
232 * ready to use (from lastpid+1 through pidchecked-1).
234 * If RFHIGHPID is set (used during system boot), do not allocate
237 trypid = lastpid + 1;
238 if (flags & RFHIGHPID) {
243 trypid += arc4random() % randompid;
247 * If the process ID prototype has wrapped around,
248 * restart somewhat above 0, as the low-numbered procs
249 * tend to include daemons that don't exit.
251 if (trypid >= pid_max) {
252 trypid = trypid % pid_max;
257 if (trypid >= pidchecked) {
260 pidchecked = PID_MAX;
262 * Scan the active and zombie procs to check whether this pid
263 * is in use. Remember the lowest pid that's greater
264 * than trypid, so we can avoid checking for a while.
266 * Avoid reuse of the process group id, session id or
267 * the reaper subtree id. Note that for process group
268 * and sessions, the amount of reserved pids is
269 * limited by process limit. For the subtree ids, the
270 * id is kept reserved only while there is a
271 * non-reaped process in the subtree, so amount of
272 * reserved pids is limited by process limit times
275 p = LIST_FIRST(&allproc);
277 for (; p != NULL; p = LIST_NEXT(p, p_list)) {
278 while (p->p_pid == trypid ||
279 p->p_reapsubtree == trypid ||
280 (p->p_pgrp != NULL &&
281 (p->p_pgrp->pg_id == trypid ||
282 (p->p_session != NULL &&
283 p->p_session->s_sid == trypid)))) {
285 if (trypid >= pidchecked)
288 if (p->p_pid > trypid && pidchecked > p->p_pid)
289 pidchecked = p->p_pid;
290 if (p->p_pgrp != NULL) {
291 if (p->p_pgrp->pg_id > trypid &&
292 pidchecked > p->p_pgrp->pg_id)
293 pidchecked = p->p_pgrp->pg_id;
294 if (p->p_session != NULL &&
295 p->p_session->s_sid > trypid &&
296 pidchecked > p->p_session->s_sid)
297 pidchecked = p->p_session->s_sid;
302 p = LIST_FIRST(&zombproc);
308 * RFHIGHPID does not mess with the lastpid counter during boot.
310 if (flags & RFHIGHPID)
319 fork_norfproc(struct thread *td, int flags)
324 KASSERT((flags & RFPROC) == 0,
325 ("fork_norfproc called with RFPROC set"));
328 if (((p1->p_flag & (P_HADTHREADS|P_SYSTEM)) == P_HADTHREADS) &&
329 (flags & (RFCFDG | RFFDG))) {
331 if (thread_single(p1, SINGLE_BOUNDARY)) {
338 error = vm_forkproc(td, NULL, NULL, NULL, flags);
343 * Close all file descriptors.
345 if (flags & RFCFDG) {
346 struct filedesc *fdtmp;
347 fdtmp = fdinit(td->td_proc->p_fd, false);
353 * Unshare file descriptors (from parent).
359 if (((p1->p_flag & (P_HADTHREADS|P_SYSTEM)) == P_HADTHREADS) &&
360 (flags & (RFCFDG | RFFDG))) {
362 thread_single_end(p1, SINGLE_BOUNDARY);
369 do_fork(struct thread *td, int flags, struct proc *p2, struct thread *td2,
370 struct vmspace *vm2, int pdflags)
372 struct proc *p1, *pptr;
375 struct filedesc_to_leader *fdtol;
376 struct sigacts *newsigacts;
378 sx_assert(&proctree_lock, SX_SLOCKED);
379 sx_assert(&allproc_lock, SX_XLOCKED);
384 trypid = fork_findpid(flags);
386 sx_sunlock(&proctree_lock);
388 p2->p_state = PRS_NEW; /* protect against others */
390 AUDIT_ARG_PID(p2->p_pid);
391 LIST_INSERT_HEAD(&allproc, p2, p_list);
393 LIST_INSERT_HEAD(PIDHASH(p2->p_pid), p2, p_hash);
398 sx_xunlock(&allproc_lock);
400 bcopy(&p1->p_startcopy, &p2->p_startcopy,
401 __rangeof(struct proc, p_startcopy, p_endcopy));
402 pargs_hold(p2->p_args);
406 bzero(&p2->p_startzero,
407 __rangeof(struct proc, p_startzero, p_endzero));
409 /* Tell the prison that we exist. */
410 prison_proc_hold(p2->p_ucred->cr_prison);
415 * Malloc things while we don't hold any locks.
417 if (flags & RFSIGSHARE)
420 newsigacts = sigacts_alloc();
425 if (flags & RFCFDG) {
426 fd = fdinit(p1->p_fd, false);
428 } else if (flags & RFFDG) {
429 fd = fdcopy(p1->p_fd);
432 fd = fdshare(p1->p_fd);
433 if (p1->p_fdtol == NULL)
434 p1->p_fdtol = filedesc_to_leader_alloc(NULL, NULL,
436 if ((flags & RFTHREAD) != 0) {
438 * Shared file descriptor table, and shared
442 FILEDESC_XLOCK(p1->p_fd);
443 fdtol->fdl_refcount++;
444 FILEDESC_XUNLOCK(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_NOTRACE | P2_NOTRACE_EXEC);
492 p2->p_swtick = ticks;
493 if (p1->p_flag & P_PROFIL)
497 * Whilst the proc lock is held, copy the VM domain data out
498 * using the VM domain method.
500 vm_domain_policy_init(&p2->p_vm_dom_policy);
501 vm_domain_policy_localcopy(&p2->p_vm_dom_policy,
502 &p1->p_vm_dom_policy);
504 if (flags & RFSIGSHARE) {
505 p2->p_sigacts = sigacts_hold(p1->p_sigacts);
507 sigacts_copy(newsigacts, p1->p_sigacts);
508 p2->p_sigacts = newsigacts;
511 if (flags & RFTSIGZMB)
512 p2->p_sigparent = RFTSIGNUM(flags);
513 else if (flags & RFLINUXTHPN)
514 p2->p_sigparent = SIGUSR1;
516 p2->p_sigparent = SIGCHLD;
518 p2->p_textvp = p1->p_textvp;
522 if (p1->p_flag2 & P2_INHERIT_PROTECTED) {
523 p2->p_flag |= P_PROTECTED;
524 p2->p_flag2 |= P2_INHERIT_PROTECTED;
528 * p_limit is copy-on-write. Bump its refcount.
532 thread_cow_get_proc(td2, p2);
534 pstats_fork(p1->p_stats, p2->p_stats);
539 /* Bump references to the text vnode (for procfs). */
544 * Set up linkage for kernel based threading.
546 if ((flags & RFTHREAD) != 0) {
547 mtx_lock(&ppeers_lock);
548 p2->p_peers = p1->p_peers;
550 p2->p_leader = p1->p_leader;
551 mtx_unlock(&ppeers_lock);
552 PROC_LOCK(p1->p_leader);
553 if ((p1->p_leader->p_flag & P_WEXIT) != 0) {
554 PROC_UNLOCK(p1->p_leader);
556 * The task leader is exiting, so process p1 is
557 * going to be killed shortly. Since p1 obviously
558 * isn't dead yet, we know that the leader is either
559 * sending SIGKILL's to all the processes in this
560 * task or is sleeping waiting for all the peers to
561 * exit. We let p1 complete the fork, but we need
562 * to go ahead and kill the new process p2 since
563 * the task leader may not get a chance to send
564 * SIGKILL to it. We leave it on the list so that
565 * the task leader will wait for this new process
569 kern_psignal(p2, SIGKILL);
572 PROC_UNLOCK(p1->p_leader);
578 sx_xlock(&proctree_lock);
579 PGRP_LOCK(p1->p_pgrp);
584 * Preserve some more flags in subprocess. P_PROFIL has already
587 p2->p_flag |= p1->p_flag & P_SUGID;
588 td2->td_pflags |= (td->td_pflags & TDP_ALTSTACK) | TDP_FORKING;
589 SESS_LOCK(p1->p_session);
590 if (p1->p_session->s_ttyvp != NULL && p1->p_flag & P_CONTROLT)
591 p2->p_flag |= P_CONTROLT;
592 SESS_UNLOCK(p1->p_session);
593 if (flags & RFPPWAIT)
594 p2->p_flag |= P_PPWAIT;
596 p2->p_pgrp = p1->p_pgrp;
597 LIST_INSERT_AFTER(p1, p2, p_pglist);
598 PGRP_UNLOCK(p1->p_pgrp);
599 LIST_INIT(&p2->p_children);
600 LIST_INIT(&p2->p_orphans);
602 callout_init_mtx(&p2->p_itcallout, &p2->p_mtx, 0);
605 * If PF_FORK is set, the child process inherits the
606 * procfs ioctl flags from its parent.
608 if (p1->p_pfsflags & PF_FORK) {
609 p2->p_stops = p1->p_stops;
610 p2->p_pfsflags = p1->p_pfsflags;
614 * This begins the section where we must prevent the parent
615 * from being swapped.
621 * Attach the new process to its parent.
623 * If RFNOWAIT is set, the newly created process becomes a child
624 * of init. This effectively disassociates the child from the
627 if ((flags & RFNOWAIT) != 0) {
631 p2->p_reaper = (p1->p_treeflag & P_TREE_REAPER) != 0 ?
636 LIST_INSERT_HEAD(&pptr->p_children, p2, p_sibling);
637 LIST_INIT(&p2->p_reaplist);
638 LIST_INSERT_HEAD(&p2->p_reaper->p_reaplist, p2, p_reapsibling);
639 if (p2->p_reaper == p1)
640 p2->p_reapsubtree = p2->p_pid;
641 sx_xunlock(&proctree_lock);
643 /* Inform accounting that we have forked. */
644 p2->p_acflag = AFORK;
652 * Finish creating the child process. It will return via a different
653 * execution path later. (ie: directly into user mode)
655 vm_forkproc(td, p2, td2, vm2, flags);
657 if (flags == (RFFDG | RFPROC)) {
658 PCPU_INC(cnt.v_forks);
659 PCPU_ADD(cnt.v_forkpages, p2->p_vmspace->vm_dsize +
660 p2->p_vmspace->vm_ssize);
661 } else if (flags == (RFFDG | RFPROC | RFPPWAIT | RFMEM)) {
662 PCPU_INC(cnt.v_vforks);
663 PCPU_ADD(cnt.v_vforkpages, p2->p_vmspace->vm_dsize +
664 p2->p_vmspace->vm_ssize);
665 } else if (p1 == &proc0) {
666 PCPU_INC(cnt.v_kthreads);
667 PCPU_ADD(cnt.v_kthreadpages, p2->p_vmspace->vm_dsize +
668 p2->p_vmspace->vm_ssize);
670 PCPU_INC(cnt.v_rforks);
671 PCPU_ADD(cnt.v_rforkpages, p2->p_vmspace->vm_dsize +
672 p2->p_vmspace->vm_ssize);
676 * Associate the process descriptor with the process before anything
677 * can happen that might cause that process to need the descriptor.
678 * However, don't do this until after fork(2) can no longer fail.
680 if (flags & RFPROCDESC)
681 procdesc_new(p2, pdflags);
684 * Both processes are set up, now check if any loadable modules want
685 * to adjust anything.
687 EVENTHANDLER_INVOKE(process_fork, p1, p2, flags);
690 * Set the child start time and mark the process as being complete.
694 microuptime(&p2->p_stats->p_start);
696 p2->p_state = PRS_NORMAL;
701 * Tell the DTrace fasttrap provider about the new process so that any
702 * tracepoints inherited from the parent can be removed. We have to do
703 * this only after p_state is PRS_NORMAL since the fasttrap module will
704 * use pfind() later on.
706 if ((flags & RFMEM) == 0 && dtrace_fasttrap_fork)
707 dtrace_fasttrap_fork(p1, p2);
709 if ((p1->p_flag & (P_TRACED | P_FOLLOWFORK)) == (P_TRACED |
712 * Arrange for debugger to receive the fork event.
714 * We can report PL_FLAG_FORKED regardless of
715 * P_FOLLOWFORK settings, but it does not make a sense
718 td->td_dbgflags |= TDB_FORK;
719 td->td_dbg_forked = p2->p_pid;
720 td2->td_dbgflags |= TDB_STOPATFORK;
724 if (flags & RFPPWAIT) {
725 td->td_pflags |= TDP_RFPPWAIT;
726 td->td_rfppwait_p = p2;
729 if ((flags & RFSTOPPED) == 0) {
731 * If RFSTOPPED not requested, make child runnable and
736 sched_add(td2, SRQ_BORING);
741 * Now can be swapped.
747 * Tell any interested parties about the new process.
749 knote_fork(&p1->p_klist, p2->p_pid);
750 SDT_PROBE3(proc, , , create, p2, p1, flags);
753 * Wait until debugger is attached to child.
756 while ((td2->td_dbgflags & TDB_STOPATFORK) != 0)
757 cv_wait(&p2->p_dbgwait, &p2->p_mtx);
764 fork1(struct thread *td, int flags, int pages, struct proc **procp,
765 int *procdescp, int pdflags, struct filecaps *fcaps)
767 struct proc *p1, *newproc;
770 struct file *fp_procdesc;
771 vm_ooffset_t mem_charged;
772 int error, nprocs_new, ok;
774 static struct timeval lastfail;
776 /* Check for the undefined or unimplemented flags. */
777 if ((flags & ~(RFFLAGS | RFTSIGFLAGS(RFTSIGMASK))) != 0)
780 /* Signal value requires RFTSIGZMB. */
781 if ((flags & RFTSIGFLAGS(RFTSIGMASK)) != 0 && (flags & RFTSIGZMB) == 0)
784 /* Can't copy and clear. */
785 if ((flags & (RFFDG|RFCFDG)) == (RFFDG|RFCFDG))
788 /* Check the validity of the signal number. */
789 if ((flags & RFTSIGZMB) != 0 && (u_int)RFTSIGNUM(flags) > _SIG_MAXSIG)
792 if ((flags & RFPROCDESC) != 0) {
793 /* Can't not create a process yet get a process descriptor. */
794 if ((flags & RFPROC) == 0)
797 /* Must provide a place to put a procdesc if creating one. */
798 if (procdescp == NULL)
805 * Here we don't create a new process, but we divorce
806 * certain parts of a process from itself.
808 if ((flags & RFPROC) == 0) {
810 return (fork_norfproc(td, flags));
818 * Increment the nprocs resource before allocations occur.
819 * Although process entries are dynamically created, we still
820 * keep a global limit on the maximum number we will
821 * create. There are hard-limits as to the number of processes
822 * that can run, established by the KVA and memory usage for
825 * Don't allow a nonprivileged user to use the last ten
826 * processes; don't let root exceed the limit.
828 nprocs_new = atomic_fetchadd_int(&nprocs, 1) + 1;
829 if ((nprocs_new >= maxproc - 10 && priv_check_cred(td->td_ucred,
830 PRIV_MAXPROC, 0) != 0) || nprocs_new >= maxproc) {
832 sx_xlock(&allproc_lock);
833 if (ppsratecheck(&lastfail, &curfail, 1)) {
834 printf("maxproc limit exceeded by uid %u (pid %d); "
835 "see tuning(7) and login.conf(5)\n",
836 td->td_ucred->cr_ruid, p1->p_pid);
838 sx_xunlock(&allproc_lock);
843 * If required, create a process descriptor in the parent first; we
844 * will abandon it if something goes wrong. We don't finit() until
847 if (flags & RFPROCDESC) {
848 error = falloc_caps(td, &fp_procdesc, procdescp, 0, fcaps);
855 pages = kstack_pages;
856 /* Allocate new proc. */
857 newproc = uma_zalloc(proc_zone, M_WAITOK);
858 td2 = FIRST_THREAD_IN_PROC(newproc);
860 td2 = thread_alloc(pages);
865 proc_linkup(newproc, td2);
867 if (td2->td_kstack == 0 || td2->td_kstack_pages != pages) {
868 if (td2->td_kstack != 0)
869 vm_thread_dispose(td2);
870 if (!thread_alloc_stack(td2, pages)) {
877 if ((flags & RFMEM) == 0) {
878 vm2 = vmspace_fork(p1->p_vmspace, &mem_charged);
883 if (!swap_reserve(mem_charged)) {
885 * The swap reservation failed. The accounting
886 * from the entries of the copied vm2 will be
887 * substracted in vmspace_free(), so force the
890 swap_reserve_force(mem_charged);
898 * XXX: This is ugly; when we copy resource usage, we need to bump
899 * per-cred resource counters.
901 proc_set_cred_init(newproc, crhold(td->td_ucred));
904 * Initialize resource accounting for the child process.
906 error = racct_proc_fork(p1, newproc);
913 mac_proc_init(newproc);
915 knlist_init_mtx(&newproc->p_klist, &newproc->p_mtx);
916 STAILQ_INIT(&newproc->p_ktr);
918 /* We have to lock the process tree while we look for a pid. */
919 sx_slock(&proctree_lock);
920 sx_xlock(&allproc_lock);
923 * Increment the count of procs running with this uid. Don't allow
924 * a nonprivileged user to exceed their current limit.
926 * XXXRW: Can we avoid privilege here if it's not needed?
928 error = priv_check_cred(td->td_ucred, PRIV_PROC_LIMIT, 0);
930 ok = chgproccnt(td->td_ucred->cr_ruidinfo, 1, 0);
932 ok = chgproccnt(td->td_ucred->cr_ruidinfo, 1,
933 lim_cur(td, RLIMIT_NPROC));
936 do_fork(td, flags, newproc, td2, vm2, pdflags);
939 * Return child proc pointer to parent.
942 if (flags & RFPROCDESC) {
943 procdesc_finit(newproc->p_procdesc, fp_procdesc);
944 fdrop(fp_procdesc, td);
946 racct_proc_fork_done(newproc);
951 sx_sunlock(&proctree_lock);
952 sx_xunlock(&allproc_lock);
954 mac_proc_destroy(newproc);
956 racct_proc_exit(newproc);
958 crfree(newproc->p_ucred);
959 newproc->p_ucred = NULL;
963 uma_zfree(proc_zone, newproc);
964 if ((flags & RFPROCDESC) != 0 && fp_procdesc != NULL) {
965 fdclose(td, fp_procdesc, *procdescp);
966 fdrop(fp_procdesc, td);
968 atomic_add_int(&nprocs, -1);
969 pause("fork", hz / 2);
974 * Handle the return of a child process from fork1(). This function
975 * is called from the MD fork_trampoline() entry point.
978 fork_exit(void (*callout)(void *, struct trapframe *), void *arg,
979 struct trapframe *frame)
987 KASSERT(p->p_state == PRS_NORMAL, ("executing process is still new"));
989 CTR4(KTR_PROC, "fork_exit: new thread %p (td_sched %p, pid %d, %s)",
990 td, td->td_sched, p->p_pid, td->td_name);
994 * Processes normally resume in mi_switch() after being
995 * cpu_switch()'ed to, but when children start up they arrive here
996 * instead, so we must do much the same things as mi_switch() would.
998 if ((dtd = PCPU_GET(deadthread))) {
999 PCPU_SET(deadthread, NULL);
1005 * cpu_set_fork_handler intercepts this function call to
1006 * have this call a non-return function to stay in kernel mode.
1007 * initproc has its own fork handler, but it does return.
1009 KASSERT(callout != NULL, ("NULL callout in fork_exit"));
1010 callout(arg, frame);
1013 * Check if a kernel thread misbehaved and returned from its main
1016 if (p->p_flag & P_KTHREAD) {
1017 printf("Kernel thread \"%s\" (pid %d) exited prematurely.\n",
1018 td->td_name, p->p_pid);
1021 mtx_assert(&Giant, MA_NOTOWNED);
1023 if (p->p_sysent->sv_schedtail != NULL)
1024 (p->p_sysent->sv_schedtail)(td);
1025 td->td_pflags &= ~TDP_FORKING;
1029 * Simplified back end of syscall(), used when returning from fork()
1030 * directly into user mode. Giant is not held on entry, and must not
1031 * be held on return. This function is passed in to fork_exit() as the
1032 * first parameter and is called when returning to a new userland process.
1035 fork_return(struct thread *td, struct trapframe *frame)
1037 struct proc *p, *dbg;
1040 if (td->td_dbgflags & TDB_STOPATFORK) {
1041 sx_xlock(&proctree_lock);
1043 if ((p->p_pptr->p_flag & (P_TRACED | P_FOLLOWFORK)) ==
1044 (P_TRACED | P_FOLLOWFORK)) {
1046 * If debugger still wants auto-attach for the
1047 * parent's children, do it now.
1049 dbg = p->p_pptr->p_pptr;
1050 p->p_flag |= P_TRACED;
1051 p->p_oppid = p->p_pptr->p_pid;
1053 "fork_return: attaching to new child pid %d: oppid %d",
1054 p->p_pid, p->p_oppid);
1055 proc_reparent(p, dbg);
1056 sx_xunlock(&proctree_lock);
1057 td->td_dbgflags |= TDB_CHILD | TDB_SCX;
1058 ptracestop(td, SIGSTOP);
1059 td->td_dbgflags &= ~(TDB_CHILD | TDB_SCX);
1062 * ... otherwise clear the request.
1064 sx_xunlock(&proctree_lock);
1065 td->td_dbgflags &= ~TDB_STOPATFORK;
1066 cv_broadcast(&p->p_dbgwait);
1069 } else if (p->p_flag & P_TRACED || td->td_dbgflags & TDB_BORN) {
1071 * This is the start of a new thread in a traced
1072 * process. Report a system call exit event.
1075 td->td_dbgflags |= TDB_SCX;
1076 _STOPEVENT(p, S_SCX, td->td_dbg_sc_code);
1077 if ((p->p_stops & S_PT_SCX) != 0 ||
1078 (td->td_dbgflags & TDB_BORN) != 0)
1079 ptracestop(td, SIGTRAP);
1080 td->td_dbgflags &= ~(TDB_SCX | TDB_BORN);
1087 if (KTRPOINT(td, KTR_SYSRET))
1088 ktrsysret(SYS_fork, 0, 0);