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.
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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, 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, NULL);
110 td->td_retval[0] = p2->p_pid;
111 td->td_retval[1] = 0;
120 struct pdfork_args *uap;
126 * It is necessary to return fd by reference because 0 is a valid file
127 * descriptor number, and the child needs to be able to distinguish
128 * itself from the parent using the return value.
130 error = fork1(td, RFFDG | RFPROC | RFPROCDESC, 0, &p2,
131 &fd, uap->flags, NULL);
133 td->td_retval[0] = p2->p_pid;
134 td->td_retval[1] = 0;
135 error = copyout(&fd, uap->fdp, sizeof(fd));
142 sys_vfork(struct thread *td, struct vfork_args *uap)
147 flags = RFFDG | RFPROC | RFPPWAIT | RFMEM;
148 error = fork1(td, flags, 0, &p2, NULL, 0, NULL);
150 td->td_retval[0] = p2->p_pid;
151 td->td_retval[1] = 0;
157 sys_rfork(struct thread *td, struct rfork_args *uap)
162 /* Don't allow kernel-only flags. */
163 if ((uap->flags & RFKERNELONLY) != 0)
166 AUDIT_ARG_FFLAGS(uap->flags);
167 error = fork1(td, uap->flags, 0, &p2, NULL, 0, NULL);
169 td->td_retval[0] = p2 ? p2->p_pid : 0;
170 td->td_retval[1] = 0;
175 int nprocs = 1; /* process 0 */
177 SYSCTL_INT(_kern, OID_AUTO, lastpid, CTLFLAG_RD, &lastpid, 0,
181 * Random component to lastpid generation. We mix in a random factor to make
182 * it a little harder to predict. We sanity check the modulus value to avoid
183 * doing it in critical paths. Don't let it be too small or we pointlessly
184 * waste randomness entropy, and don't let it be impossibly large. Using a
185 * modulus that is too big causes a LOT more process table scans and slows
186 * down fork processing as the pidchecked caching is defeated.
188 static int randompid = 0;
191 sysctl_kern_randompid(SYSCTL_HANDLER_ARGS)
195 error = sysctl_wire_old_buffer(req, sizeof(int));
198 sx_xlock(&allproc_lock);
200 error = sysctl_handle_int(oidp, &pid, 0, req);
201 if (error == 0 && req->newptr != NULL) {
202 if (pid < 0 || pid > pid_max - 100) /* out of range */
204 else if (pid < 2) /* NOP */
206 else if (pid < 100) /* Make it reasonable */
210 sx_xunlock(&allproc_lock);
214 SYSCTL_PROC(_kern, OID_AUTO, randompid, CTLTYPE_INT|CTLFLAG_RW,
215 0, 0, sysctl_kern_randompid, "I", "Random PID modulus");
218 fork_findpid(int flags)
222 static int pidchecked = 0;
225 * Requires allproc_lock in order to iterate over the list
226 * of processes, and proctree_lock to access p_pgrp.
228 sx_assert(&allproc_lock, SX_LOCKED);
229 sx_assert(&proctree_lock, SX_LOCKED);
232 * Find an unused process ID. We remember a range of unused IDs
233 * ready to use (from lastpid+1 through pidchecked-1).
235 * If RFHIGHPID is set (used during system boot), do not allocate
238 trypid = lastpid + 1;
239 if (flags & RFHIGHPID) {
244 trypid += arc4random() % randompid;
248 * If the process ID prototype has wrapped around,
249 * restart somewhat above 0, as the low-numbered procs
250 * tend to include daemons that don't exit.
252 if (trypid >= pid_max) {
253 trypid = trypid % pid_max;
258 if (trypid >= pidchecked) {
261 pidchecked = PID_MAX;
263 * Scan the active and zombie procs to check whether this pid
264 * is in use. Remember the lowest pid that's greater
265 * than trypid, so we can avoid checking for a while.
267 * Avoid reuse of the process group id, session id or
268 * the reaper subtree id. Note that for process group
269 * and sessions, the amount of reserved pids is
270 * limited by process limit. For the subtree ids, the
271 * id is kept reserved only while there is a
272 * non-reaped process in the subtree, so amount of
273 * reserved pids is limited by process limit times
276 p = LIST_FIRST(&allproc);
278 for (; p != NULL; p = LIST_NEXT(p, p_list)) {
279 while (p->p_pid == trypid ||
280 p->p_reapsubtree == trypid ||
281 (p->p_pgrp != NULL &&
282 (p->p_pgrp->pg_id == trypid ||
283 (p->p_session != NULL &&
284 p->p_session->s_sid == trypid)))) {
286 if (trypid >= pidchecked)
289 if (p->p_pid > trypid && pidchecked > p->p_pid)
290 pidchecked = p->p_pid;
291 if (p->p_pgrp != NULL) {
292 if (p->p_pgrp->pg_id > trypid &&
293 pidchecked > p->p_pgrp->pg_id)
294 pidchecked = p->p_pgrp->pg_id;
295 if (p->p_session != NULL &&
296 p->p_session->s_sid > trypid &&
297 pidchecked > p->p_session->s_sid)
298 pidchecked = p->p_session->s_sid;
303 p = LIST_FIRST(&zombproc);
309 * RFHIGHPID does not mess with the lastpid counter during boot.
311 if (flags & RFHIGHPID)
320 fork_norfproc(struct thread *td, int flags)
325 KASSERT((flags & RFPROC) == 0,
326 ("fork_norfproc called with RFPROC set"));
329 if (((p1->p_flag & (P_HADTHREADS|P_SYSTEM)) == P_HADTHREADS) &&
330 (flags & (RFCFDG | RFFDG))) {
332 if (thread_single(p1, SINGLE_BOUNDARY)) {
339 error = vm_forkproc(td, NULL, NULL, NULL, flags);
344 * Close all file descriptors.
346 if (flags & RFCFDG) {
347 struct filedesc *fdtmp;
348 fdtmp = fdinit(td->td_proc->p_fd, false);
354 * Unshare file descriptors (from parent).
360 if (((p1->p_flag & (P_HADTHREADS|P_SYSTEM)) == P_HADTHREADS) &&
361 (flags & (RFCFDG | RFFDG))) {
363 thread_single_end(p1, SINGLE_BOUNDARY);
370 do_fork(struct thread *td, int flags, struct proc *p2, struct thread *td2,
371 struct vmspace *vm2, int pdflags)
373 struct proc *p1, *pptr;
376 struct filedesc_to_leader *fdtol;
377 struct sigacts *newsigacts;
379 sx_assert(&proctree_lock, SX_SLOCKED);
380 sx_assert(&allproc_lock, SX_XLOCKED);
386 * Increment the nprocs resource before blocking can occur. There
387 * are hard-limits as to the number of processes that can run.
391 trypid = fork_findpid(flags);
393 sx_sunlock(&proctree_lock);
395 p2->p_state = PRS_NEW; /* protect against others */
397 AUDIT_ARG_PID(p2->p_pid);
398 LIST_INSERT_HEAD(&allproc, p2, p_list);
400 LIST_INSERT_HEAD(PIDHASH(p2->p_pid), p2, p_hash);
405 sx_xunlock(&allproc_lock);
407 bcopy(&p1->p_startcopy, &p2->p_startcopy,
408 __rangeof(struct proc, p_startcopy, p_endcopy));
409 pargs_hold(p2->p_args);
413 bzero(&p2->p_startzero,
414 __rangeof(struct proc, p_startzero, p_endzero));
416 /* Tell the prison that we exist. */
417 prison_proc_hold(p2->p_ucred->cr_prison);
422 * Malloc things while we don't hold any locks.
424 if (flags & RFSIGSHARE)
427 newsigacts = sigacts_alloc();
432 if (flags & RFCFDG) {
433 fd = fdinit(p1->p_fd, false);
435 } else if (flags & RFFDG) {
436 fd = fdcopy(p1->p_fd);
439 fd = fdshare(p1->p_fd);
440 if (p1->p_fdtol == NULL)
441 p1->p_fdtol = filedesc_to_leader_alloc(NULL, NULL,
443 if ((flags & RFTHREAD) != 0) {
445 * Shared file descriptor table, and shared
449 FILEDESC_XLOCK(p1->p_fd);
450 fdtol->fdl_refcount++;
451 FILEDESC_XUNLOCK(p1->p_fd);
454 * Shared file descriptor table, and different
457 fdtol = filedesc_to_leader_alloc(p1->p_fdtol,
462 * Make a proc table entry for the new process.
463 * Start by zeroing the section of proc that is zero-initialized,
464 * then copy the section that is copied directly from the parent.
470 bzero(&td2->td_startzero,
471 __rangeof(struct thread, td_startzero, td_endzero));
473 bcopy(&td->td_startcopy, &td2->td_startcopy,
474 __rangeof(struct thread, td_startcopy, td_endcopy));
476 bcopy(&p2->p_comm, &td2->td_name, sizeof(td2->td_name));
477 td2->td_sigstk = td->td_sigstk;
478 td2->td_flags = TDF_INMEM;
479 td2->td_lend_user_pri = PRI_MAX;
483 td2->td_vnet_lpush = NULL;
487 * Allow the scheduler to initialize the child.
494 * Duplicate sub-structures as needed.
495 * Increase reference counts on shared objects.
497 p2->p_flag = P_INMEM;
498 p2->p_flag2 = p1->p_flag2 & (P2_NOTRACE | P2_NOTRACE_EXEC);
499 p2->p_swtick = ticks;
500 if (p1->p_flag & P_PROFIL)
504 * Whilst the proc lock is held, copy the VM domain data out
505 * using the VM domain method.
507 vm_domain_policy_init(&p2->p_vm_dom_policy);
508 vm_domain_policy_localcopy(&p2->p_vm_dom_policy,
509 &p1->p_vm_dom_policy);
511 if (flags & RFSIGSHARE) {
512 p2->p_sigacts = sigacts_hold(p1->p_sigacts);
514 sigacts_copy(newsigacts, p1->p_sigacts);
515 p2->p_sigacts = newsigacts;
518 if (flags & RFTSIGZMB)
519 p2->p_sigparent = RFTSIGNUM(flags);
520 else if (flags & RFLINUXTHPN)
521 p2->p_sigparent = SIGUSR1;
523 p2->p_sigparent = SIGCHLD;
525 p2->p_textvp = p1->p_textvp;
529 if (p1->p_flag2 & P2_INHERIT_PROTECTED) {
530 p2->p_flag |= P_PROTECTED;
531 p2->p_flag2 |= P2_INHERIT_PROTECTED;
535 * p_limit is copy-on-write. Bump its refcount.
539 thread_cow_get_proc(td2, p2);
541 pstats_fork(p1->p_stats, p2->p_stats);
546 /* Bump references to the text vnode (for procfs). */
551 * Set up linkage for kernel based threading.
553 if ((flags & RFTHREAD) != 0) {
554 mtx_lock(&ppeers_lock);
555 p2->p_peers = p1->p_peers;
557 p2->p_leader = p1->p_leader;
558 mtx_unlock(&ppeers_lock);
559 PROC_LOCK(p1->p_leader);
560 if ((p1->p_leader->p_flag & P_WEXIT) != 0) {
561 PROC_UNLOCK(p1->p_leader);
563 * The task leader is exiting, so process p1 is
564 * going to be killed shortly. Since p1 obviously
565 * isn't dead yet, we know that the leader is either
566 * sending SIGKILL's to all the processes in this
567 * task or is sleeping waiting for all the peers to
568 * exit. We let p1 complete the fork, but we need
569 * to go ahead and kill the new process p2 since
570 * the task leader may not get a chance to send
571 * SIGKILL to it. We leave it on the list so that
572 * the task leader will wait for this new process
576 kern_psignal(p2, SIGKILL);
579 PROC_UNLOCK(p1->p_leader);
585 sx_xlock(&proctree_lock);
586 PGRP_LOCK(p1->p_pgrp);
591 * Preserve some more flags in subprocess. P_PROFIL has already
594 p2->p_flag |= p1->p_flag & P_SUGID;
595 td2->td_pflags |= td->td_pflags & TDP_ALTSTACK;
596 SESS_LOCK(p1->p_session);
597 if (p1->p_session->s_ttyvp != NULL && p1->p_flag & P_CONTROLT)
598 p2->p_flag |= P_CONTROLT;
599 SESS_UNLOCK(p1->p_session);
600 if (flags & RFPPWAIT)
601 p2->p_flag |= P_PPWAIT;
603 p2->p_pgrp = p1->p_pgrp;
604 LIST_INSERT_AFTER(p1, p2, p_pglist);
605 PGRP_UNLOCK(p1->p_pgrp);
606 LIST_INIT(&p2->p_children);
607 LIST_INIT(&p2->p_orphans);
609 callout_init_mtx(&p2->p_itcallout, &p2->p_mtx, 0);
612 * If PF_FORK is set, the child process inherits the
613 * procfs ioctl flags from its parent.
615 if (p1->p_pfsflags & PF_FORK) {
616 p2->p_stops = p1->p_stops;
617 p2->p_pfsflags = p1->p_pfsflags;
621 * This begins the section where we must prevent the parent
622 * from being swapped.
628 * Attach the new process to its parent.
630 * If RFNOWAIT is set, the newly created process becomes a child
631 * of init. This effectively disassociates the child from the
634 if ((flags & RFNOWAIT) != 0) {
638 p2->p_reaper = (p1->p_treeflag & P_TREE_REAPER) != 0 ?
643 LIST_INSERT_HEAD(&pptr->p_children, p2, p_sibling);
644 LIST_INIT(&p2->p_reaplist);
645 LIST_INSERT_HEAD(&p2->p_reaper->p_reaplist, p2, p_reapsibling);
646 if (p2->p_reaper == p1)
647 p2->p_reapsubtree = p2->p_pid;
648 sx_xunlock(&proctree_lock);
650 /* Inform accounting that we have forked. */
651 p2->p_acflag = AFORK;
659 * Finish creating the child process. It will return via a different
660 * execution path later. (ie: directly into user mode)
662 vm_forkproc(td, p2, td2, vm2, flags);
664 if (flags == (RFFDG | RFPROC)) {
665 PCPU_INC(cnt.v_forks);
666 PCPU_ADD(cnt.v_forkpages, p2->p_vmspace->vm_dsize +
667 p2->p_vmspace->vm_ssize);
668 } else if (flags == (RFFDG | RFPROC | RFPPWAIT | RFMEM)) {
669 PCPU_INC(cnt.v_vforks);
670 PCPU_ADD(cnt.v_vforkpages, p2->p_vmspace->vm_dsize +
671 p2->p_vmspace->vm_ssize);
672 } else if (p1 == &proc0) {
673 PCPU_INC(cnt.v_kthreads);
674 PCPU_ADD(cnt.v_kthreadpages, p2->p_vmspace->vm_dsize +
675 p2->p_vmspace->vm_ssize);
677 PCPU_INC(cnt.v_rforks);
678 PCPU_ADD(cnt.v_rforkpages, p2->p_vmspace->vm_dsize +
679 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);
691 * Both processes are set up, now check if any loadable modules want
692 * to adjust anything.
694 EVENTHANDLER_INVOKE(process_fork, p1, p2, flags);
697 * Set the child start time and mark the process as being complete.
701 microuptime(&p2->p_stats->p_start);
703 p2->p_state = PRS_NORMAL;
708 * Tell the DTrace fasttrap provider about the new process so that any
709 * tracepoints inherited from the parent can be removed. We have to do
710 * this only after p_state is PRS_NORMAL since the fasttrap module will
711 * use pfind() later on.
713 if ((flags & RFMEM) == 0 && dtrace_fasttrap_fork)
714 dtrace_fasttrap_fork(p1, p2);
716 if ((p1->p_flag & (P_TRACED | P_FOLLOWFORK)) == (P_TRACED |
719 * Arrange for debugger to receive the fork event.
721 * We can report PL_FLAG_FORKED regardless of
722 * P_FOLLOWFORK settings, but it does not make a sense
725 td->td_dbgflags |= TDB_FORK;
726 td->td_dbg_forked = p2->p_pid;
727 td2->td_dbgflags |= TDB_STOPATFORK;
731 if (flags & RFPPWAIT) {
732 td->td_pflags |= TDP_RFPPWAIT;
733 td->td_rfppwait_p = p2;
736 if ((flags & RFSTOPPED) == 0) {
738 * If RFSTOPPED not requested, make child runnable and
743 sched_add(td2, SRQ_BORING);
748 * Now can be swapped.
754 * Tell any interested parties about the new process.
756 knote_fork(&p1->p_klist, p2->p_pid);
757 SDT_PROBE3(proc, kernel, , create, p2, p1, flags);
760 * Wait until debugger is attached to child.
763 while ((td2->td_dbgflags & TDB_STOPATFORK) != 0)
764 cv_wait(&p2->p_dbgwait, &p2->p_mtx);
771 fork1(struct thread *td, int flags, int pages, struct proc **procp,
772 int *procdescp, int pdflags, struct filecaps *fcaps)
775 struct proc *newproc;
779 vm_ooffset_t mem_charged;
782 static struct timeval lastfail;
783 struct file *fp_procdesc = NULL;
785 /* Check for the undefined or unimplemented flags. */
786 if ((flags & ~(RFFLAGS | RFTSIGFLAGS(RFTSIGMASK))) != 0)
789 /* Signal value requires RFTSIGZMB. */
790 if ((flags & RFTSIGFLAGS(RFTSIGMASK)) != 0 && (flags & RFTSIGZMB) == 0)
793 /* Can't copy and clear. */
794 if ((flags & (RFFDG|RFCFDG)) == (RFFDG|RFCFDG))
797 /* Check the validity of the signal number. */
798 if ((flags & RFTSIGZMB) != 0 && (u_int)RFTSIGNUM(flags) > _SIG_MAXSIG)
801 if ((flags & RFPROCDESC) != 0) {
802 /* Can't not create a process yet get a process descriptor. */
803 if ((flags & RFPROC) == 0)
806 /* Must provide a place to put a procdesc if creating one. */
807 if (procdescp == NULL)
814 * Here we don't create a new process, but we divorce
815 * certain parts of a process from itself.
817 if ((flags & RFPROC) == 0) {
819 return (fork_norfproc(td, flags));
823 * If required, create a process descriptor in the parent first; we
824 * will abandon it if something goes wrong. We don't finit() until
827 if (flags & RFPROCDESC) {
828 error = falloc_caps(td, &fp_procdesc, procdescp, 0, fcaps);
836 pages = kstack_pages;
837 /* Allocate new proc. */
838 newproc = uma_zalloc(proc_zone, M_WAITOK);
839 td2 = FIRST_THREAD_IN_PROC(newproc);
841 td2 = thread_alloc(pages);
846 proc_linkup(newproc, td2);
848 if (td2->td_kstack == 0 || td2->td_kstack_pages != pages) {
849 if (td2->td_kstack != 0)
850 vm_thread_dispose(td2);
851 if (!thread_alloc_stack(td2, pages)) {
858 if ((flags & RFMEM) == 0) {
859 vm2 = vmspace_fork(p1->p_vmspace, &mem_charged);
864 if (!swap_reserve(mem_charged)) {
866 * The swap reservation failed. The accounting
867 * from the entries of the copied vm2 will be
868 * substracted in vmspace_free(), so force the
871 swap_reserve_force(mem_charged);
879 * XXX: This is ugly; when we copy resource usage, we need to bump
880 * per-cred resource counters.
882 proc_set_cred_init(newproc, crhold(td->td_ucred));
885 * Initialize resource accounting for the child process.
887 error = racct_proc_fork(p1, newproc);
894 mac_proc_init(newproc);
896 knlist_init_mtx(&newproc->p_klist, &newproc->p_mtx);
897 STAILQ_INIT(&newproc->p_ktr);
899 /* We have to lock the process tree while we look for a pid. */
900 sx_slock(&proctree_lock);
903 * Although process entries are dynamically created, we still keep
904 * a global limit on the maximum number we will create. Don't allow
905 * a nonprivileged user to use the last ten processes; don't let root
906 * exceed the limit. The variable nprocs is the current number of
907 * processes, maxproc is the limit.
909 sx_xlock(&allproc_lock);
910 if ((nprocs >= maxproc - 10 && priv_check_cred(td->td_ucred,
911 PRIV_MAXPROC, 0) != 0) || nprocs >= maxproc) {
917 * Increment the count of procs running with this uid. Don't allow
918 * a nonprivileged user to exceed their current limit.
920 * XXXRW: Can we avoid privilege here if it's not needed?
922 error = priv_check_cred(td->td_ucred, PRIV_PROC_LIMIT, 0);
924 ok = chgproccnt(td->td_ucred->cr_ruidinfo, 1, 0);
926 ok = chgproccnt(td->td_ucred->cr_ruidinfo, 1,
927 lim_cur(td, RLIMIT_NPROC));
930 do_fork(td, flags, newproc, td2, vm2, pdflags);
933 * Return child proc pointer to parent.
936 if (flags & RFPROCDESC) {
937 procdesc_finit(newproc->p_procdesc, fp_procdesc);
938 fdrop(fp_procdesc, td);
940 racct_proc_fork_done(newproc);
946 sx_sunlock(&proctree_lock);
947 if (ppsratecheck(&lastfail, &curfail, 1))
948 printf("maxproc limit exceeded by uid %u (pid %d); see tuning(7) and login.conf(5)\n",
949 td->td_ucred->cr_ruid, p1->p_pid);
950 sx_xunlock(&allproc_lock);
952 mac_proc_destroy(newproc);
954 racct_proc_exit(newproc);
956 crfree(newproc->p_ucred);
957 newproc->p_ucred = NULL;
961 uma_zfree(proc_zone, newproc);
962 if ((flags & RFPROCDESC) != 0 && fp_procdesc != NULL) {
963 fdclose(td, fp_procdesc, *procdescp);
964 fdrop(fp_procdesc, td);
966 pause("fork", hz / 2);
971 * Handle the return of a child process from fork1(). This function
972 * is called from the MD fork_trampoline() entry point.
975 fork_exit(void (*callout)(void *, struct trapframe *), void *arg,
976 struct trapframe *frame)
984 KASSERT(p->p_state == PRS_NORMAL, ("executing process is still new"));
986 CTR4(KTR_PROC, "fork_exit: new thread %p (td_sched %p, pid %d, %s)",
987 td, td->td_sched, p->p_pid, td->td_name);
991 * Processes normally resume in mi_switch() after being
992 * cpu_switch()'ed to, but when children start up they arrive here
993 * instead, so we must do much the same things as mi_switch() would.
995 if ((dtd = PCPU_GET(deadthread))) {
996 PCPU_SET(deadthread, NULL);
1002 * cpu_set_fork_handler intercepts this function call to
1003 * have this call a non-return function to stay in kernel mode.
1004 * initproc has its own fork handler, but it does return.
1006 KASSERT(callout != NULL, ("NULL callout in fork_exit"));
1007 callout(arg, frame);
1010 * Check if a kernel thread misbehaved and returned from its main
1013 if (p->p_flag & P_KTHREAD) {
1014 printf("Kernel thread \"%s\" (pid %d) exited prematurely.\n",
1015 td->td_name, p->p_pid);
1018 mtx_assert(&Giant, MA_NOTOWNED);
1020 if (p->p_sysent->sv_schedtail != NULL)
1021 (p->p_sysent->sv_schedtail)(td);
1025 * Simplified back end of syscall(), used when returning from fork()
1026 * directly into user mode. Giant is not held on entry, and must not
1027 * be held on return. This function is passed in to fork_exit() as the
1028 * first parameter and is called when returning to a new userland process.
1031 fork_return(struct thread *td, struct trapframe *frame)
1033 struct proc *p, *dbg;
1036 if (td->td_dbgflags & TDB_STOPATFORK) {
1037 sx_xlock(&proctree_lock);
1039 if ((p->p_pptr->p_flag & (P_TRACED | P_FOLLOWFORK)) ==
1040 (P_TRACED | P_FOLLOWFORK)) {
1042 * If debugger still wants auto-attach for the
1043 * parent's children, do it now.
1045 dbg = p->p_pptr->p_pptr;
1046 p->p_flag |= P_TRACED;
1047 p->p_oppid = p->p_pptr->p_pid;
1049 "fork_return: attaching to new child pid %d: oppid %d",
1050 p->p_pid, p->p_oppid);
1051 proc_reparent(p, dbg);
1052 sx_xunlock(&proctree_lock);
1053 td->td_dbgflags |= TDB_CHILD | TDB_SCX;
1054 ptracestop(td, SIGSTOP);
1055 td->td_dbgflags &= ~(TDB_CHILD | TDB_SCX);
1058 * ... otherwise clear the request.
1060 sx_xunlock(&proctree_lock);
1061 td->td_dbgflags &= ~TDB_STOPATFORK;
1062 cv_broadcast(&p->p_dbgwait);
1065 } else if (p->p_flag & P_TRACED) {
1067 * This is the start of a new thread in a traced
1068 * process. Report a system call exit event.
1071 td->td_dbgflags |= TDB_SCX;
1072 _STOPEVENT(p, S_SCX, td->td_dbg_sc_code);
1073 if ((p->p_stops & S_PT_SCX) != 0)
1074 ptracestop(td, SIGTRAP);
1075 td->td_dbgflags &= ~TDB_SCX;
1082 if (KTRPOINT(td, KTR_SYSRET))
1083 ktrsysret(SYS_fork, 0, 0);