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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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().
322 if ((p1->p_flag & (P_HADTHREADS | P_SYSTEM)) == P_HADTHREADS &&
323 ((flags & (RFCFDG | RFFDG)) != 0 || (flags & RFMEM) == 0)) {
325 while (p1->p_singlethr > 0) {
326 error = msleep(&p1->p_singlethr, &p1->p_mtx,
327 PWAIT | PCATCH, "rfork1t", 0);
334 if (thread_single(p1, SINGLE_BOUNDARY)) {
341 error = vm_forkproc(td, NULL, NULL, NULL, flags);
346 * Close all file descriptors.
348 if (flags & RFCFDG) {
349 struct filedesc *fdtmp;
350 struct pwddesc *pdtmp;
351 pdtmp = pdinit(td->td_proc->p_pd, false);
352 fdtmp = fdinit(td->td_proc->p_fd, false, NULL);
360 * Unshare file descriptors (from parent).
368 if ((p1->p_flag & (P_HADTHREADS | P_SYSTEM)) == P_HADTHREADS &&
369 ((flags & (RFCFDG | RFFDG)) != 0 || (flags & RFMEM) == 0)) {
371 thread_single_end(p1, SINGLE_BOUNDARY);
378 do_fork(struct thread *td, struct fork_req *fr, struct proc *p2, struct thread *td2,
379 struct vmspace *vm2, struct file *fp_procdesc)
381 struct proc *p1, *pptr;
383 struct filedesc_to_leader *fdtol;
385 struct sigacts *newsigacts;
390 bcopy(&p1->p_startcopy, &p2->p_startcopy,
391 __rangeof(struct proc, p_startcopy, p_endcopy));
392 pargs_hold(p2->p_args);
395 bzero(&p2->p_startzero,
396 __rangeof(struct proc, p_startzero, p_endzero));
399 /* Tell the prison that we exist. */
400 prison_proc_hold(p2->p_ucred->cr_prison);
402 p2->p_state = PRS_NEW; /* protect against others */
403 p2->p_pid = fork_findpid(fr->fr_flags);
404 AUDIT_ARG_PID(p2->p_pid);
405 TSFORK(p2->p_pid, p1->p_pid);
407 sx_xlock(&allproc_lock);
408 LIST_INSERT_HEAD(&allproc, p2, p_list);
410 sx_xunlock(&allproc_lock);
412 sx_xlock(PIDHASHLOCK(p2->p_pid));
413 LIST_INSERT_HEAD(PIDHASH(p2->p_pid), p2, p_hash);
414 sx_xunlock(PIDHASHLOCK(p2->p_pid));
419 * Malloc things while we don't hold any locks.
421 if (fr->fr_flags & RFSIGSHARE)
424 newsigacts = sigacts_alloc();
429 if (fr->fr_flags & RFCFDG) {
430 pd = pdinit(p1->p_pd, false);
431 fd = fdinit(p1->p_fd, false, NULL);
433 } else if (fr->fr_flags & RFFDG) {
434 if (fr->fr_flags2 & FR2_SHARE_PATHS)
435 pd = pdshare(p1->p_pd);
437 pd = pdcopy(p1->p_pd);
438 fd = fdcopy(p1->p_fd);
441 if (fr->fr_flags2 & FR2_SHARE_PATHS)
442 pd = pdcopy(p1->p_pd);
444 pd = pdshare(p1->p_pd);
445 fd = fdshare(p1->p_fd);
446 if (p1->p_fdtol == NULL)
447 p1->p_fdtol = filedesc_to_leader_alloc(NULL, NULL,
449 if ((fr->fr_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;
504 p2->p_flag2 = p1->p_flag2 & (P2_ASLR_DISABLE | P2_ASLR_ENABLE |
505 P2_ASLR_IGNSTART | P2_NOTRACE | P2_NOTRACE_EXEC |
506 P2_PROTMAX_ENABLE | P2_PROTMAX_DISABLE | P2_TRAPCAP |
507 P2_STKGAP_DISABLE | P2_STKGAP_DISABLE_EXEC | P2_NO_NEW_PRIVS |
508 P2_WXORX_DISABLE | P2_WXORX_ENABLE_EXEC);
509 p2->p_swtick = ticks;
510 if (p1->p_flag & P_PROFIL)
513 if (fr->fr_flags & RFSIGSHARE) {
514 p2->p_sigacts = sigacts_hold(p1->p_sigacts);
516 sigacts_copy(newsigacts, p1->p_sigacts);
517 p2->p_sigacts = newsigacts;
518 if ((fr->fr_flags2 & (FR2_DROPSIG_CAUGHT | FR2_KPROC)) != 0) {
519 mtx_lock(&p2->p_sigacts->ps_mtx);
520 if ((fr->fr_flags2 & FR2_DROPSIG_CAUGHT) != 0)
522 if ((fr->fr_flags2 & FR2_KPROC) != 0)
523 p2->p_sigacts->ps_flag |= PS_NOCLDWAIT;
524 mtx_unlock(&p2->p_sigacts->ps_mtx);
528 if (fr->fr_flags & RFTSIGZMB)
529 p2->p_sigparent = RFTSIGNUM(fr->fr_flags);
530 else if (fr->fr_flags & RFLINUXTHPN)
531 p2->p_sigparent = SIGUSR1;
533 p2->p_sigparent = SIGCHLD;
535 if ((fr->fr_flags2 & FR2_KPROC) != 0) {
536 p2->p_flag |= P_SYSTEM | P_KPROC;
537 td2->td_pflags |= TDP_KTHREAD;
540 p2->p_textvp = p1->p_textvp;
541 p2->p_textdvp = p1->p_textdvp;
545 p2->p_elf_brandinfo = p1->p_elf_brandinfo;
547 if (p1->p_flag2 & P2_INHERIT_PROTECTED) {
548 p2->p_flag |= P_PROTECTED;
549 p2->p_flag2 |= P2_INHERIT_PROTECTED;
553 * p_limit is copy-on-write. Bump its refcount.
557 thread_cow_get_proc(td2, p2);
559 pstats_fork(p1->p_stats, p2->p_stats);
565 * Bump references to the text vnode and directory, and copy
568 if (p2->p_textvp != NULL)
569 vrefact(p2->p_textvp);
570 if (p2->p_textdvp != NULL)
571 vrefact(p2->p_textdvp);
572 p2->p_binname = p1->p_binname == NULL ? NULL :
573 strdup(p1->p_binname, M_PARGS);
576 * Set up linkage for kernel based threading.
578 if ((fr->fr_flags & RFTHREAD) != 0) {
579 mtx_lock(&ppeers_lock);
580 p2->p_peers = p1->p_peers;
582 p2->p_leader = p1->p_leader;
583 mtx_unlock(&ppeers_lock);
584 PROC_LOCK(p1->p_leader);
585 if ((p1->p_leader->p_flag & P_WEXIT) != 0) {
586 PROC_UNLOCK(p1->p_leader);
588 * The task leader is exiting, so process p1 is
589 * going to be killed shortly. Since p1 obviously
590 * isn't dead yet, we know that the leader is either
591 * sending SIGKILL's to all the processes in this
592 * task or is sleeping waiting for all the peers to
593 * exit. We let p1 complete the fork, but we need
594 * to go ahead and kill the new process p2 since
595 * the task leader may not get a chance to send
596 * SIGKILL to it. We leave it on the list so that
597 * the task leader will wait for this new process
601 kern_psignal(p2, SIGKILL);
604 PROC_UNLOCK(p1->p_leader);
610 sx_xlock(&proctree_lock);
611 PGRP_LOCK(p1->p_pgrp);
616 * Preserve some more flags in subprocess. P_PROFIL has already
619 p2->p_flag |= p1->p_flag & P_SUGID;
620 td2->td_pflags |= (td->td_pflags & (TDP_ALTSTACK |
621 TDP_SIGFASTBLOCK)) | TDP_FORKING;
622 SESS_LOCK(p1->p_session);
623 if (p1->p_session->s_ttyvp != NULL && p1->p_flag & P_CONTROLT)
624 p2->p_flag |= P_CONTROLT;
625 SESS_UNLOCK(p1->p_session);
626 if (fr->fr_flags & RFPPWAIT)
627 p2->p_flag |= P_PPWAIT;
629 p2->p_pgrp = p1->p_pgrp;
630 LIST_INSERT_AFTER(p1, p2, p_pglist);
631 PGRP_UNLOCK(p1->p_pgrp);
632 LIST_INIT(&p2->p_children);
633 LIST_INIT(&p2->p_orphans);
635 callout_init_mtx(&p2->p_itcallout, &p2->p_mtx, 0);
636 TAILQ_INIT(&p2->p_kqtim_stop);
639 * This begins the section where we must prevent the parent
640 * from being swapped.
646 * Attach the new process to its parent.
648 * If RFNOWAIT is set, the newly created process becomes a child
649 * of init. This effectively disassociates the child from the
652 if ((fr->fr_flags & RFNOWAIT) != 0) {
656 p2->p_reaper = (p1->p_treeflag & P_TREE_REAPER) != 0 ?
661 p2->p_oppid = pptr->p_pid;
662 LIST_INSERT_HEAD(&pptr->p_children, p2, p_sibling);
663 LIST_INIT(&p2->p_reaplist);
664 LIST_INSERT_HEAD(&p2->p_reaper->p_reaplist, p2, p_reapsibling);
665 if (p2->p_reaper == p1 && p1 != initproc) {
666 p2->p_reapsubtree = p2->p_pid;
667 proc_id_set_cond(PROC_ID_REAP, p2->p_pid);
669 sx_xunlock(&proctree_lock);
671 /* Inform accounting that we have forked. */
672 p2->p_acflag = AFORK;
680 * Finish creating the child process. It will return via a different
681 * execution path later. (ie: directly into user mode)
683 vm_forkproc(td, p2, td2, vm2, fr->fr_flags);
685 if (fr->fr_flags == (RFFDG | RFPROC)) {
687 VM_CNT_ADD(v_forkpages, p2->p_vmspace->vm_dsize +
688 p2->p_vmspace->vm_ssize);
689 } else if (fr->fr_flags == (RFFDG | RFPROC | RFPPWAIT | RFMEM)) {
690 VM_CNT_INC(v_vforks);
691 VM_CNT_ADD(v_vforkpages, p2->p_vmspace->vm_dsize +
692 p2->p_vmspace->vm_ssize);
693 } else if (p1 == &proc0) {
694 VM_CNT_INC(v_kthreads);
695 VM_CNT_ADD(v_kthreadpages, p2->p_vmspace->vm_dsize +
696 p2->p_vmspace->vm_ssize);
698 VM_CNT_INC(v_rforks);
699 VM_CNT_ADD(v_rforkpages, p2->p_vmspace->vm_dsize +
700 p2->p_vmspace->vm_ssize);
704 * Associate the process descriptor with the process before anything
705 * can happen that might cause that process to need the descriptor.
706 * However, don't do this until after fork(2) can no longer fail.
708 if (fr->fr_flags & RFPROCDESC)
709 procdesc_new(p2, fr->fr_pd_flags);
712 * Both processes are set up, now check if any loadable modules want
713 * to adjust anything.
715 EVENTHANDLER_DIRECT_INVOKE(process_fork, p1, p2, fr->fr_flags);
718 * Set the child start time and mark the process as being complete.
722 microuptime(&p2->p_stats->p_start);
724 p2->p_state = PRS_NORMAL;
729 * Tell the DTrace fasttrap provider about the new process so that any
730 * tracepoints inherited from the parent can be removed. We have to do
731 * this only after p_state is PRS_NORMAL since the fasttrap module will
732 * use pfind() later on.
734 if ((fr->fr_flags & RFMEM) == 0 && dtrace_fasttrap_fork)
735 dtrace_fasttrap_fork(p1, p2);
737 if (fr->fr_flags & RFPPWAIT) {
738 td->td_pflags |= TDP_RFPPWAIT;
739 td->td_rfppwait_p = p2;
740 td->td_dbgflags |= TDB_VFORK;
745 * Tell any interested parties about the new process.
747 knote_fork(p1->p_klist, p2->p_pid);
750 * Now can be swapped.
754 SDT_PROBE3(proc, , , create, p2, p1, fr->fr_flags);
756 if (fr->fr_flags & RFPROCDESC) {
757 procdesc_finit(p2->p_procdesc, fp_procdesc);
758 fdrop(fp_procdesc, td);
762 * Speculative check for PTRACE_FORK. PTRACE_FORK is not
763 * synced with forks in progress so it is OK if we miss it
766 if ((p1->p_ptevents & PTRACE_FORK) != 0) {
767 sx_xlock(&proctree_lock);
771 * p1->p_ptevents & p1->p_pptr are protected by both
772 * process and proctree locks for modifications,
773 * so owning proctree_lock allows the race-free read.
775 if ((p1->p_ptevents & PTRACE_FORK) != 0) {
777 * Arrange for debugger to receive the fork event.
779 * We can report PL_FLAG_FORKED regardless of
780 * P_FOLLOWFORK settings, but it does not make a sense
783 td->td_dbgflags |= TDB_FORK;
784 td->td_dbg_forked = p2->p_pid;
785 td2->td_dbgflags |= TDB_STOPATFORK;
786 proc_set_traced(p2, true);
788 "do_fork: attaching to new child pid %d: oppid %d",
789 p2->p_pid, p2->p_oppid);
790 proc_reparent(p2, p1->p_pptr, false);
793 sx_xunlock(&proctree_lock);
796 racct_proc_fork_done(p2);
798 if ((fr->fr_flags & RFSTOPPED) == 0) {
799 if (fr->fr_pidp != NULL)
800 *fr->fr_pidp = p2->p_pid;
802 * If RFSTOPPED not requested, make child runnable and
807 sched_add(td2, SRQ_BORING);
814 fork_rfppwait(struct thread *td)
818 MPASS(td->td_pflags & TDP_RFPPWAIT);
822 * Preserve synchronization semantics of vfork. If
823 * waiting for child to exec or exit, fork set
824 * P_PPWAIT on child, and there we sleep on our proc
827 * Do it after the ptracestop() above is finished, to
828 * not block our debugger until child execs or exits
829 * to finish vfork wait.
831 td->td_pflags &= ~TDP_RFPPWAIT;
832 p2 = td->td_rfppwait_p;
835 while (p2->p_flag & P_PPWAIT) {
837 if (thread_suspend_check_needed()) {
839 thread_suspend_check(0);
845 cv_timedwait(&p2->p_pwait, &p2->p_mtx, hz);
849 if (td->td_dbgflags & TDB_VFORK) {
851 if (p->p_ptevents & PTRACE_VFORK)
852 ptracestop(td, SIGTRAP, NULL);
853 td->td_dbgflags &= ~TDB_VFORK;
859 fork1(struct thread *td, struct fork_req *fr)
861 struct proc *p1, *newproc;
865 struct file *fp_procdesc;
866 vm_ooffset_t mem_charged;
867 int error, nprocs_new;
869 static struct timeval lastfail;
872 flags = fr->fr_flags;
873 pages = fr->fr_pages;
875 if ((flags & RFSTOPPED) != 0)
876 MPASS(fr->fr_procp != NULL && fr->fr_pidp == NULL);
878 MPASS(fr->fr_procp == NULL);
880 /* Check for the undefined or unimplemented flags. */
881 if ((flags & ~(RFFLAGS | RFTSIGFLAGS(RFTSIGMASK))) != 0)
884 /* Signal value requires RFTSIGZMB. */
885 if ((flags & RFTSIGFLAGS(RFTSIGMASK)) != 0 && (flags & RFTSIGZMB) == 0)
888 /* Can't copy and clear. */
889 if ((flags & (RFFDG|RFCFDG)) == (RFFDG|RFCFDG))
892 /* Check the validity of the signal number. */
893 if ((flags & RFTSIGZMB) != 0 && (u_int)RFTSIGNUM(flags) > _SIG_MAXSIG)
896 if ((flags & RFPROCDESC) != 0) {
897 /* Can't not create a process yet get a process descriptor. */
898 if ((flags & RFPROC) == 0)
901 /* Must provide a place to put a procdesc if creating one. */
902 if (fr->fr_pd_fd == NULL)
905 /* Check if we are using supported flags. */
906 if ((fr->fr_pd_flags & ~PD_ALLOWED_AT_FORK) != 0)
913 * Here we don't create a new process, but we divorce
914 * certain parts of a process from itself.
916 if ((flags & RFPROC) == 0) {
917 if (fr->fr_procp != NULL)
918 *fr->fr_procp = NULL;
919 else if (fr->fr_pidp != NULL)
921 return (fork_norfproc(td, flags));
929 * Increment the nprocs resource before allocations occur.
930 * Although process entries are dynamically created, we still
931 * keep a global limit on the maximum number we will
932 * create. There are hard-limits as to the number of processes
933 * that can run, established by the KVA and memory usage for
936 * Don't allow a nonprivileged user to use the last ten
937 * processes; don't let root exceed the limit.
939 nprocs_new = atomic_fetchadd_int(&nprocs, 1) + 1;
940 if (nprocs_new >= maxproc - 10) {
941 if (priv_check_cred(td->td_ucred, PRIV_MAXPROC) != 0 ||
942 nprocs_new >= maxproc) {
944 sx_xlock(&allproc_lock);
945 if (ppsratecheck(&lastfail, &curfail, 1)) {
946 printf("maxproc limit exceeded by uid %u "
947 "(pid %d); see tuning(7) and "
949 td->td_ucred->cr_ruid, p1->p_pid);
951 sx_xunlock(&allproc_lock);
957 * If required, create a process descriptor in the parent first; we
958 * will abandon it if something goes wrong. We don't finit() until
961 if (flags & RFPROCDESC) {
962 error = procdesc_falloc(td, &fp_procdesc, fr->fr_pd_fd,
963 fr->fr_pd_flags, fr->fr_pd_fcaps);
966 AUDIT_ARG_FD(*fr->fr_pd_fd);
971 pages = kstack_pages;
972 /* Allocate new proc. */
973 newproc = uma_zalloc(proc_zone, M_WAITOK);
974 td2 = FIRST_THREAD_IN_PROC(newproc);
976 td2 = thread_alloc(pages);
981 proc_linkup(newproc, td2);
983 if (td2->td_kstack == 0 || td2->td_kstack_pages != pages) {
984 if (td2->td_kstack != 0)
985 vm_thread_dispose(td2);
986 if (!thread_alloc_stack(td2, pages)) {
993 if ((flags & RFMEM) == 0) {
994 vm2 = vmspace_fork(p1->p_vmspace, &mem_charged);
999 if (!swap_reserve(mem_charged)) {
1001 * The swap reservation failed. The accounting
1002 * from the entries of the copied vm2 will be
1003 * subtracted in vmspace_free(), so force the
1004 * reservation there.
1006 swap_reserve_force(mem_charged);
1014 * XXX: This is ugly; when we copy resource usage, we need to bump
1015 * per-cred resource counters.
1017 proc_set_cred_init(newproc, td->td_ucred);
1020 * Initialize resource accounting for the child process.
1022 error = racct_proc_fork(p1, newproc);
1029 mac_proc_init(newproc);
1031 newproc->p_klist = knlist_alloc(&newproc->p_mtx);
1032 STAILQ_INIT(&newproc->p_ktr);
1035 * Increment the count of procs running with this uid. Don't allow
1036 * a nonprivileged user to exceed their current limit.
1038 cred = td->td_ucred;
1039 if (!chgproccnt(cred->cr_ruidinfo, 1, lim_cur(td, RLIMIT_NPROC))) {
1040 if (priv_check_cred(cred, PRIV_PROC_LIMIT) != 0)
1042 chgproccnt(cred->cr_ruidinfo, 1, 0);
1045 do_fork(td, fr, newproc, td2, vm2, fp_procdesc);
1050 mac_proc_destroy(newproc);
1052 racct_proc_exit(newproc);
1054 proc_unset_cred(newproc);
1058 uma_zfree(proc_zone, newproc);
1059 if ((flags & RFPROCDESC) != 0 && fp_procdesc != NULL) {
1060 fdclose(td, fp_procdesc, *fr->fr_pd_fd);
1061 fdrop(fp_procdesc, td);
1063 atomic_add_int(&nprocs, -1);
1064 pause("fork", hz / 2);
1069 * Handle the return of a child process from fork1(). This function
1070 * is called from the MD fork_trampoline() entry point.
1073 fork_exit(void (*callout)(void *, struct trapframe *), void *arg,
1074 struct trapframe *frame)
1082 KASSERT(p->p_state == PRS_NORMAL, ("executing process is still new"));
1084 CTR4(KTR_PROC, "fork_exit: new thread %p (td_sched %p, pid %d, %s)",
1085 td, td_get_sched(td), p->p_pid, td->td_name);
1087 sched_fork_exit(td);
1089 * Processes normally resume in mi_switch() after being
1090 * cpu_switch()'ed to, but when children start up they arrive here
1091 * instead, so we must do much the same things as mi_switch() would.
1093 if ((dtd = PCPU_GET(deadthread))) {
1094 PCPU_SET(deadthread, NULL);
1100 * cpu_fork_kthread_handler intercepts this function call to
1101 * have this call a non-return function to stay in kernel mode.
1102 * initproc has its own fork handler, but it does return.
1104 KASSERT(callout != NULL, ("NULL callout in fork_exit"));
1105 callout(arg, frame);
1108 * Check if a kernel thread misbehaved and returned from its main
1111 if (p->p_flag & P_KPROC) {
1112 printf("Kernel thread \"%s\" (pid %d) exited prematurely.\n",
1113 td->td_name, p->p_pid);
1116 mtx_assert(&Giant, MA_NOTOWNED);
1118 if (p->p_sysent->sv_schedtail != NULL)
1119 (p->p_sysent->sv_schedtail)(td);
1120 td->td_pflags &= ~TDP_FORKING;
1124 * Simplified back end of syscall(), used when returning from fork()
1125 * directly into user mode. This function is passed in to fork_exit()
1126 * as the first parameter and is called when returning to a new
1130 fork_return(struct thread *td, struct trapframe *frame)
1135 if (td->td_dbgflags & TDB_STOPATFORK) {
1137 if ((p->p_flag & P_TRACED) != 0) {
1139 * Inform the debugger if one is still present.
1141 td->td_dbgflags |= TDB_CHILD | TDB_SCX | TDB_FSTP;
1142 ptracestop(td, SIGSTOP, NULL);
1143 td->td_dbgflags &= ~(TDB_CHILD | TDB_SCX);
1146 * ... otherwise clear the request.
1148 td->td_dbgflags &= ~TDB_STOPATFORK;
1151 } else if (p->p_flag & P_TRACED || td->td_dbgflags & TDB_BORN) {
1153 * This is the start of a new thread in a traced
1154 * process. Report a system call exit event.
1157 td->td_dbgflags |= TDB_SCX;
1158 if ((p->p_ptevents & PTRACE_SCX) != 0 ||
1159 (td->td_dbgflags & TDB_BORN) != 0)
1160 ptracestop(td, SIGTRAP, NULL);
1161 td->td_dbgflags &= ~(TDB_SCX | TDB_BORN);
1166 * If the prison was killed mid-fork, die along with it.
1168 if (!prison_isalive(td->td_ucred->cr_prison))
1169 exit1(td, 0, SIGKILL);
1174 if (KTRPOINT(td, KTR_SYSRET))
1175 ktrsysret(SYS_fork, 0, 0);