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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17 * documentation and/or other materials provided with the distribution.
18 * 4. Neither the name of the University nor the names of its contributors
19 * may be used to endorse or promote products derived from this software
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22 * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
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25 * ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
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31 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
34 * @(#)kern_fork.c 8.6 (Berkeley) 4/8/94
37 #include <sys/cdefs.h>
38 __FBSDID("$FreeBSD$");
40 #include "opt_kdtrace.h"
41 #include "opt_ktrace.h"
42 #include "opt_kstack_pages.h"
43 #include "opt_procdesc.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/racct.h>
63 #include <sys/resourcevar.h>
64 #include <sys/sched.h>
65 #include <sys/syscall.h>
66 #include <sys/vmmeter.h>
67 #include <sys/vnode.h>
70 #include <sys/ktrace.h>
71 #include <sys/unistd.h>
74 #include <sys/sysent.h>
75 #include <sys/signalvar.h>
77 #include <security/audit/audit.h>
78 #include <security/mac/mac_framework.h>
82 #include <vm/vm_map.h>
83 #include <vm/vm_extern.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, kernel, , create, "struct proc *",
93 "struct proc *", "int");
95 #ifndef _SYS_SYSPROTO_H_
103 sys_fork(struct thread *td, struct fork_args *uap)
108 error = fork1(td, RFFDG | RFPROC, 0, &p2, NULL, 0);
110 td->td_retval[0] = p2->p_pid;
111 td->td_retval[1] = 0;
120 struct pdfork_args *uap;
127 * It is necessary to return fd by reference because 0 is a valid file
128 * descriptor number, and the child needs to be able to distinguish
129 * itself from the parent using the return value.
131 error = fork1(td, RFFDG | RFPROC | RFPROCDESC, 0, &p2,
134 td->td_retval[0] = p2->p_pid;
135 td->td_retval[1] = 0;
136 error = copyout(&fd, uap->fdp, sizeof(fd));
146 sys_vfork(struct thread *td, struct vfork_args *uap)
151 flags = RFFDG | RFPROC | RFPPWAIT | RFMEM;
152 error = fork1(td, flags, 0, &p2, NULL, 0);
154 td->td_retval[0] = p2->p_pid;
155 td->td_retval[1] = 0;
161 sys_rfork(struct thread *td, struct rfork_args *uap)
166 /* Don't allow kernel-only flags. */
167 if ((uap->flags & RFKERNELONLY) != 0)
170 AUDIT_ARG_FFLAGS(uap->flags);
171 error = fork1(td, uap->flags, 0, &p2, NULL, 0);
173 td->td_retval[0] = p2 ? p2->p_pid : 0;
174 td->td_retval[1] = 0;
179 int nprocs = 1; /* process 0 */
181 SYSCTL_INT(_kern, OID_AUTO, lastpid, CTLFLAG_RD, &lastpid, 0,
185 * Random component to lastpid generation. We mix in a random factor to make
186 * it a little harder to predict. We sanity check the modulus value to avoid
187 * doing it in critical paths. Don't let it be too small or we pointlessly
188 * waste randomness entropy, and don't let it be impossibly large. Using a
189 * modulus that is too big causes a LOT more process table scans and slows
190 * down fork processing as the pidchecked caching is defeated.
192 static int randompid = 0;
195 sysctl_kern_randompid(SYSCTL_HANDLER_ARGS)
199 error = sysctl_wire_old_buffer(req, sizeof(int));
202 sx_xlock(&allproc_lock);
204 error = sysctl_handle_int(oidp, &pid, 0, req);
205 if (error == 0 && req->newptr != NULL) {
206 if (pid < 0 || pid > pid_max - 100) /* out of range */
208 else if (pid < 2) /* NOP */
210 else if (pid < 100) /* Make it reasonable */
214 sx_xunlock(&allproc_lock);
218 SYSCTL_PROC(_kern, OID_AUTO, randompid, CTLTYPE_INT|CTLFLAG_RW,
219 0, 0, sysctl_kern_randompid, "I", "Random PID modulus");
222 fork_findpid(int flags)
226 static int pidchecked = 0;
229 * Requires allproc_lock in order to iterate over the list
230 * of processes, and proctree_lock to access p_pgrp.
232 sx_assert(&allproc_lock, SX_LOCKED);
233 sx_assert(&proctree_lock, SX_LOCKED);
236 * Find an unused process ID. We remember a range of unused IDs
237 * ready to use (from lastpid+1 through pidchecked-1).
239 * If RFHIGHPID is set (used during system boot), do not allocate
242 trypid = lastpid + 1;
243 if (flags & RFHIGHPID) {
248 trypid += arc4random() % randompid;
252 * If the process ID prototype has wrapped around,
253 * restart somewhat above 0, as the low-numbered procs
254 * tend to include daemons that don't exit.
256 if (trypid >= pid_max) {
257 trypid = trypid % pid_max;
262 if (trypid >= pidchecked) {
265 pidchecked = PID_MAX;
267 * Scan the active and zombie procs to check whether this pid
268 * is in use. Remember the lowest pid that's greater
269 * than trypid, so we can avoid checking for a while.
271 * Avoid reuse of the process group id, session id or
272 * the reaper subtree id. Note that for process group
273 * and sessions, the amount of reserved pids is
274 * limited by process limit. For the subtree ids, the
275 * id is kept reserved only while there is a
276 * non-reaped process in the subtree, so amount of
277 * reserved pids is limited by process limit times
280 p = LIST_FIRST(&allproc);
282 for (; p != NULL; p = LIST_NEXT(p, p_list)) {
283 while (p->p_pid == trypid ||
284 p->p_reapsubtree == trypid ||
285 (p->p_pgrp != NULL &&
286 (p->p_pgrp->pg_id == trypid ||
287 (p->p_session != NULL &&
288 p->p_session->s_sid == trypid)))) {
290 if (trypid >= pidchecked)
293 if (p->p_pid > trypid && pidchecked > p->p_pid)
294 pidchecked = p->p_pid;
295 if (p->p_pgrp != NULL) {
296 if (p->p_pgrp->pg_id > trypid &&
297 pidchecked > p->p_pgrp->pg_id)
298 pidchecked = p->p_pgrp->pg_id;
299 if (p->p_session != NULL &&
300 p->p_session->s_sid > trypid &&
301 pidchecked > p->p_session->s_sid)
302 pidchecked = p->p_session->s_sid;
307 p = LIST_FIRST(&zombproc);
313 * RFHIGHPID does not mess with the lastpid counter during boot.
315 if (flags & RFHIGHPID)
324 fork_norfproc(struct thread *td, int flags)
329 KASSERT((flags & RFPROC) == 0,
330 ("fork_norfproc called with RFPROC set"));
333 if (((p1->p_flag & (P_HADTHREADS|P_SYSTEM)) == P_HADTHREADS) &&
334 (flags & (RFCFDG | RFFDG))) {
336 if (thread_single(p1, SINGLE_BOUNDARY)) {
343 error = vm_forkproc(td, NULL, NULL, NULL, flags);
348 * Close all file descriptors.
350 if (flags & RFCFDG) {
351 struct filedesc *fdtmp;
352 fdtmp = fdinit(td->td_proc->p_fd);
358 * Unshare file descriptors (from parent).
364 if (((p1->p_flag & (P_HADTHREADS|P_SYSTEM)) == P_HADTHREADS) &&
365 (flags & (RFCFDG | RFFDG))) {
367 thread_single_end(p1, SINGLE_BOUNDARY);
374 do_fork(struct thread *td, int flags, struct proc *p2, struct thread *td2,
375 struct vmspace *vm2, int pdflags)
377 struct proc *p1, *pptr;
380 struct filedesc_to_leader *fdtol;
381 struct sigacts *newsigacts;
383 sx_assert(&proctree_lock, SX_SLOCKED);
384 sx_assert(&allproc_lock, SX_XLOCKED);
390 * Increment the nprocs resource before blocking can occur. There
391 * are hard-limits as to the number of processes that can run.
395 trypid = fork_findpid(flags);
397 sx_sunlock(&proctree_lock);
399 p2->p_state = PRS_NEW; /* protect against others */
401 AUDIT_ARG_PID(p2->p_pid);
402 LIST_INSERT_HEAD(&allproc, p2, p_list);
404 LIST_INSERT_HEAD(PIDHASH(p2->p_pid), p2, p_hash);
409 sx_xunlock(&allproc_lock);
411 bcopy(&p1->p_startcopy, &p2->p_startcopy,
412 __rangeof(struct proc, p_startcopy, p_endcopy));
413 pargs_hold(p2->p_args);
416 bzero(&p2->p_startzero,
417 __rangeof(struct proc, p_startzero, p_endzero));
420 p2->p_ucred = crhold(td->td_ucred);
422 /* Tell the prison that we exist. */
423 prison_proc_hold(p2->p_ucred->cr_prison);
428 * Malloc things while we don't hold any locks.
430 if (flags & RFSIGSHARE)
433 newsigacts = sigacts_alloc();
438 if (flags & RFCFDG) {
439 fd = fdinit(p1->p_fd);
441 } else if (flags & RFFDG) {
442 fd = fdcopy(p1->p_fd);
445 fd = fdshare(p1->p_fd);
446 if (p1->p_fdtol == NULL)
447 p1->p_fdtol = filedesc_to_leader_alloc(NULL, NULL,
449 if ((flags & RFTHREAD) != 0) {
451 * Shared file descriptor table, and shared
455 FILEDESC_XLOCK(p1->p_fd);
456 fdtol->fdl_refcount++;
457 FILEDESC_XUNLOCK(p1->p_fd);
460 * Shared file descriptor table, and different
463 fdtol = filedesc_to_leader_alloc(p1->p_fdtol,
468 * Make a proc table entry for the new process.
469 * Start by zeroing the section of proc that is zero-initialized,
470 * then copy the section that is copied directly from the parent.
476 bzero(&td2->td_startzero,
477 __rangeof(struct thread, td_startzero, td_endzero));
479 bcopy(&td->td_startcopy, &td2->td_startcopy,
480 __rangeof(struct thread, td_startcopy, td_endcopy));
482 bcopy(&p2->p_comm, &td2->td_name, sizeof(td2->td_name));
483 td2->td_sigstk = td->td_sigstk;
484 td2->td_flags = TDF_INMEM;
485 td2->td_lend_user_pri = PRI_MAX;
489 td2->td_vnet_lpush = NULL;
493 * Allow the scheduler to initialize the child.
500 * Duplicate sub-structures as needed.
501 * Increase reference counts on shared objects.
503 p2->p_flag = P_INMEM;
505 p2->p_swtick = ticks;
506 if (p1->p_flag & P_PROFIL)
508 td2->td_ucred = crhold(p2->p_ucred);
510 if (flags & RFSIGSHARE) {
511 p2->p_sigacts = sigacts_hold(p1->p_sigacts);
513 sigacts_copy(newsigacts, p1->p_sigacts);
514 p2->p_sigacts = newsigacts;
517 if (flags & RFTSIGZMB)
518 p2->p_sigparent = RFTSIGNUM(flags);
519 else if (flags & RFLINUXTHPN)
520 p2->p_sigparent = SIGUSR1;
522 p2->p_sigparent = SIGCHLD;
524 p2->p_textvp = p1->p_textvp;
528 if (p1->p_flag2 & P2_INHERIT_PROTECTED) {
529 p2->p_flag |= P_PROTECTED;
530 p2->p_flag2 |= P2_INHERIT_PROTECTED;
534 * p_limit is copy-on-write. Bump its refcount.
538 pstats_fork(p1->p_stats, p2->p_stats);
543 /* Bump references to the text vnode (for procfs). */
548 * Set up linkage for kernel based threading.
550 if ((flags & RFTHREAD) != 0) {
551 mtx_lock(&ppeers_lock);
552 p2->p_peers = p1->p_peers;
554 p2->p_leader = p1->p_leader;
555 mtx_unlock(&ppeers_lock);
556 PROC_LOCK(p1->p_leader);
557 if ((p1->p_leader->p_flag & P_WEXIT) != 0) {
558 PROC_UNLOCK(p1->p_leader);
560 * The task leader is exiting, so process p1 is
561 * going to be killed shortly. Since p1 obviously
562 * isn't dead yet, we know that the leader is either
563 * sending SIGKILL's to all the processes in this
564 * task or is sleeping waiting for all the peers to
565 * exit. We let p1 complete the fork, but we need
566 * to go ahead and kill the new process p2 since
567 * the task leader may not get a chance to send
568 * SIGKILL to it. We leave it on the list so that
569 * the task leader will wait for this new process
573 kern_psignal(p2, SIGKILL);
576 PROC_UNLOCK(p1->p_leader);
582 sx_xlock(&proctree_lock);
583 PGRP_LOCK(p1->p_pgrp);
588 * Preserve some more flags in subprocess. P_PROFIL has already
591 p2->p_flag |= p1->p_flag & P_SUGID;
592 td2->td_pflags |= td->td_pflags & TDP_ALTSTACK;
593 SESS_LOCK(p1->p_session);
594 if (p1->p_session->s_ttyvp != NULL && p1->p_flag & P_CONTROLT)
595 p2->p_flag |= P_CONTROLT;
596 SESS_UNLOCK(p1->p_session);
597 if (flags & RFPPWAIT)
598 p2->p_flag |= P_PPWAIT;
600 p2->p_pgrp = p1->p_pgrp;
601 LIST_INSERT_AFTER(p1, p2, p_pglist);
602 PGRP_UNLOCK(p1->p_pgrp);
603 LIST_INIT(&p2->p_children);
604 LIST_INIT(&p2->p_orphans);
606 callout_init_mtx(&p2->p_itcallout, &p2->p_mtx, 0);
609 * If PF_FORK is set, the child process inherits the
610 * procfs ioctl flags from its parent.
612 if (p1->p_pfsflags & PF_FORK) {
613 p2->p_stops = p1->p_stops;
614 p2->p_pfsflags = p1->p_pfsflags;
618 * This begins the section where we must prevent the parent
619 * from being swapped.
625 * Attach the new process to its parent.
627 * If RFNOWAIT is set, the newly created process becomes a child
628 * of init. This effectively disassociates the child from the
631 if ((flags & RFNOWAIT) != 0) {
635 p2->p_reaper = (p1->p_treeflag & P_TREE_REAPER) != 0 ?
640 LIST_INSERT_HEAD(&pptr->p_children, p2, p_sibling);
641 LIST_INIT(&p2->p_reaplist);
642 LIST_INSERT_HEAD(&p2->p_reaper->p_reaplist, p2, p_reapsibling);
643 if (p2->p_reaper == p1)
644 p2->p_reapsubtree = p2->p_pid;
646 p2->p_reapsubtree = p1->p_reapsubtree;
647 sx_xunlock(&proctree_lock);
649 /* Inform accounting that we have forked. */
650 p2->p_acflag = AFORK;
658 * Finish creating the child process. It will return via a different
659 * execution path later. (ie: directly into user mode)
661 vm_forkproc(td, p2, td2, vm2, flags);
663 if (flags == (RFFDG | RFPROC)) {
664 PCPU_INC(cnt.v_forks);
665 PCPU_ADD(cnt.v_forkpages, p2->p_vmspace->vm_dsize +
666 p2->p_vmspace->vm_ssize);
667 } else if (flags == (RFFDG | RFPROC | RFPPWAIT | RFMEM)) {
668 PCPU_INC(cnt.v_vforks);
669 PCPU_ADD(cnt.v_vforkpages, p2->p_vmspace->vm_dsize +
670 p2->p_vmspace->vm_ssize);
671 } else if (p1 == &proc0) {
672 PCPU_INC(cnt.v_kthreads);
673 PCPU_ADD(cnt.v_kthreadpages, p2->p_vmspace->vm_dsize +
674 p2->p_vmspace->vm_ssize);
676 PCPU_INC(cnt.v_rforks);
677 PCPU_ADD(cnt.v_rforkpages, p2->p_vmspace->vm_dsize +
678 p2->p_vmspace->vm_ssize);
683 * Associate the process descriptor with the process before anything
684 * can happen that might cause that process to need the descriptor.
685 * However, don't do this until after fork(2) can no longer fail.
687 if (flags & RFPROCDESC)
688 procdesc_new(p2, pdflags);
692 * Both processes are set up, now check if any loadable modules want
693 * to adjust anything.
695 EVENTHANDLER_INVOKE(process_fork, p1, p2, flags);
698 * Set the child start time and mark the process as being complete.
702 microuptime(&p2->p_stats->p_start);
704 p2->p_state = PRS_NORMAL;
709 * Tell the DTrace fasttrap provider about the new process so that any
710 * tracepoints inherited from the parent can be removed. We have to do
711 * this only after p_state is PRS_NORMAL since the fasttrap module will
712 * use pfind() later on.
714 if ((flags & RFMEM) == 0 && dtrace_fasttrap_fork)
715 dtrace_fasttrap_fork(p1, p2);
717 if ((p1->p_flag & (P_TRACED | P_FOLLOWFORK)) == (P_TRACED |
720 * Arrange for debugger to receive the fork event.
722 * We can report PL_FLAG_FORKED regardless of
723 * P_FOLLOWFORK settings, but it does not make a sense
726 td->td_dbgflags |= TDB_FORK;
727 td->td_dbg_forked = p2->p_pid;
728 td2->td_dbgflags |= TDB_STOPATFORK;
732 if (flags & RFPPWAIT) {
733 td->td_pflags |= TDP_RFPPWAIT;
734 td->td_rfppwait_p = p2;
737 if ((flags & RFSTOPPED) == 0) {
739 * If RFSTOPPED not requested, make child runnable and
744 sched_add(td2, SRQ_BORING);
749 * Now can be swapped.
755 * Tell any interested parties about the new process.
757 knote_fork(&p1->p_klist, p2->p_pid);
758 SDT_PROBE(proc, kernel, , create, p2, p1, flags, 0, 0);
761 * Wait until debugger is attached to child.
764 while ((td2->td_dbgflags & TDB_STOPATFORK) != 0)
765 cv_wait(&p2->p_dbgwait, &p2->p_mtx);
772 fork1(struct thread *td, int flags, int pages, struct proc **procp,
773 int *procdescp, int pdflags)
776 struct proc *newproc;
780 vm_ooffset_t mem_charged;
783 static struct timeval lastfail;
785 struct file *fp_procdesc = NULL;
788 /* Check for the undefined or unimplemented flags. */
789 if ((flags & ~(RFFLAGS | RFTSIGFLAGS(RFTSIGMASK))) != 0)
792 /* Signal value requires RFTSIGZMB. */
793 if ((flags & RFTSIGFLAGS(RFTSIGMASK)) != 0 && (flags & RFTSIGZMB) == 0)
796 /* Can't copy and clear. */
797 if ((flags & (RFFDG|RFCFDG)) == (RFFDG|RFCFDG))
800 /* Check the validity of the signal number. */
801 if ((flags & RFTSIGZMB) != 0 && (u_int)RFTSIGNUM(flags) > _SIG_MAXSIG)
805 if ((flags & RFPROCDESC) != 0) {
806 /* Can't not create a process yet get a process descriptor. */
807 if ((flags & RFPROC) == 0)
810 /* Must provide a place to put a procdesc if creating one. */
811 if (procdescp == NULL)
819 * Here we don't create a new process, but we divorce
820 * certain parts of a process from itself.
822 if ((flags & RFPROC) == 0) {
824 return (fork_norfproc(td, flags));
829 * If required, create a process descriptor in the parent first; we
830 * will abandon it if something goes wrong. We don't finit() until
833 if (flags & RFPROCDESC) {
834 error = falloc(td, &fp_procdesc, procdescp, 0);
843 pages = KSTACK_PAGES;
844 /* Allocate new proc. */
845 newproc = uma_zalloc(proc_zone, M_WAITOK);
846 td2 = FIRST_THREAD_IN_PROC(newproc);
848 td2 = thread_alloc(pages);
853 proc_linkup(newproc, td2);
855 if (td2->td_kstack == 0 || td2->td_kstack_pages != pages) {
856 if (td2->td_kstack != 0)
857 vm_thread_dispose(td2);
858 if (!thread_alloc_stack(td2, pages)) {
865 if ((flags & RFMEM) == 0) {
866 vm2 = vmspace_fork(p1->p_vmspace, &mem_charged);
871 if (!swap_reserve(mem_charged)) {
873 * The swap reservation failed. The accounting
874 * from the entries of the copied vm2 will be
875 * substracted in vmspace_free(), so force the
878 swap_reserve_force(mem_charged);
886 * XXX: This is ugly; when we copy resource usage, we need to bump
887 * per-cred resource counters.
889 newproc->p_ucred = p1->p_ucred;
892 * Initialize resource accounting for the child process.
894 error = racct_proc_fork(p1, newproc);
901 mac_proc_init(newproc);
903 knlist_init_mtx(&newproc->p_klist, &newproc->p_mtx);
904 STAILQ_INIT(&newproc->p_ktr);
906 /* We have to lock the process tree while we look for a pid. */
907 sx_slock(&proctree_lock);
910 * Although process entries are dynamically created, we still keep
911 * a global limit on the maximum number we will create. Don't allow
912 * a nonprivileged user to use the last ten processes; don't let root
913 * exceed the limit. The variable nprocs is the current number of
914 * processes, maxproc is the limit.
916 sx_xlock(&allproc_lock);
917 if ((nprocs >= maxproc - 10 && priv_check_cred(td->td_ucred,
918 PRIV_MAXPROC, 0) != 0) || nprocs >= maxproc) {
924 * Increment the count of procs running with this uid. Don't allow
925 * a nonprivileged user to exceed their current limit.
927 * XXXRW: Can we avoid privilege here if it's not needed?
929 error = priv_check_cred(td->td_ucred, PRIV_PROC_LIMIT, 0);
931 ok = chgproccnt(td->td_ucred->cr_ruidinfo, 1, 0);
934 ok = chgproccnt(td->td_ucred->cr_ruidinfo, 1,
935 lim_cur(p1, RLIMIT_NPROC));
939 do_fork(td, flags, newproc, td2, vm2, pdflags);
942 * Return child proc pointer to parent.
946 if (flags & RFPROCDESC) {
947 procdesc_finit(newproc->p_procdesc, fp_procdesc);
948 fdrop(fp_procdesc, td);
951 racct_proc_fork_done(newproc);
957 sx_sunlock(&proctree_lock);
958 if (ppsratecheck(&lastfail, &curfail, 1))
959 printf("maxproc limit exceeded by uid %u (pid %d); see tuning(7) and login.conf(5)\n",
960 td->td_ucred->cr_ruid, p1->p_pid);
961 sx_xunlock(&allproc_lock);
963 mac_proc_destroy(newproc);
965 racct_proc_exit(newproc);
969 uma_zfree(proc_zone, newproc);
971 if ((flags & RFPROCDESC) != 0 && fp_procdesc != NULL) {
972 fdclose(td->td_proc->p_fd, fp_procdesc, *procdescp, td);
973 fdrop(fp_procdesc, td);
976 pause("fork", hz / 2);
981 * Handle the return of a child process from fork1(). This function
982 * is called from the MD fork_trampoline() entry point.
985 fork_exit(void (*callout)(void *, struct trapframe *), void *arg,
986 struct trapframe *frame)
994 KASSERT(p->p_state == PRS_NORMAL, ("executing process is still new"));
996 CTR4(KTR_PROC, "fork_exit: new thread %p (td_sched %p, pid %d, %s)",
997 td, td->td_sched, p->p_pid, td->td_name);
1001 * Processes normally resume in mi_switch() after being
1002 * cpu_switch()'ed to, but when children start up they arrive here
1003 * instead, so we must do much the same things as mi_switch() would.
1005 if ((dtd = PCPU_GET(deadthread))) {
1006 PCPU_SET(deadthread, NULL);
1012 * cpu_set_fork_handler intercepts this function call to
1013 * have this call a non-return function to stay in kernel mode.
1014 * initproc has its own fork handler, but it does return.
1016 KASSERT(callout != NULL, ("NULL callout in fork_exit"));
1017 callout(arg, frame);
1020 * Check if a kernel thread misbehaved and returned from its main
1023 if (p->p_flag & P_KTHREAD) {
1024 printf("Kernel thread \"%s\" (pid %d) exited prematurely.\n",
1025 td->td_name, p->p_pid);
1028 mtx_assert(&Giant, MA_NOTOWNED);
1030 if (p->p_sysent->sv_schedtail != NULL)
1031 (p->p_sysent->sv_schedtail)(td);
1035 * Simplified back end of syscall(), used when returning from fork()
1036 * directly into user mode. Giant is not held on entry, and must not
1037 * be held on return. This function is passed in to fork_exit() as the
1038 * first parameter and is called when returning to a new userland process.
1041 fork_return(struct thread *td, struct trapframe *frame)
1043 struct proc *p, *dbg;
1045 if (td->td_dbgflags & TDB_STOPATFORK) {
1047 sx_xlock(&proctree_lock);
1049 if ((p->p_pptr->p_flag & (P_TRACED | P_FOLLOWFORK)) ==
1050 (P_TRACED | P_FOLLOWFORK)) {
1052 * If debugger still wants auto-attach for the
1053 * parent's children, do it now.
1055 dbg = p->p_pptr->p_pptr;
1056 p->p_flag |= P_TRACED;
1057 p->p_oppid = p->p_pptr->p_pid;
1058 proc_reparent(p, dbg);
1059 sx_xunlock(&proctree_lock);
1060 td->td_dbgflags |= TDB_CHILD;
1061 ptracestop(td, SIGSTOP);
1062 td->td_dbgflags &= ~TDB_CHILD;
1065 * ... otherwise clear the request.
1067 sx_xunlock(&proctree_lock);
1068 td->td_dbgflags &= ~TDB_STOPATFORK;
1069 cv_broadcast(&p->p_dbgwait);
1077 if (KTRPOINT(td, KTR_SYSRET))
1078 ktrsysret(SYS_fork, 0, 0);