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
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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_kdtrace.h"
41 #include "opt_ktrace.h"
42 #include "opt_kstack_pages.h"
44 #include <sys/param.h>
45 #include <sys/systm.h>
46 #include <sys/sysproto.h>
47 #include <sys/eventhandler.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/pioctl.h>
59 #include <sys/resourcevar.h>
60 #include <sys/sched.h>
61 #include <sys/syscall.h>
62 #include <sys/vmmeter.h>
63 #include <sys/vnode.h>
66 #include <sys/ktrace.h>
67 #include <sys/unistd.h>
70 #include <sys/signalvar.h>
72 #include <security/audit/audit.h>
73 #include <security/mac/mac_framework.h>
77 #include <vm/vm_map.h>
78 #include <vm/vm_extern.h>
82 #include <sys/dtrace_bsd.h>
83 dtrace_fork_func_t dtrace_fasttrap_fork;
86 SDT_PROVIDER_DECLARE(proc);
87 SDT_PROBE_DEFINE(proc, kernel, , create);
88 SDT_PROBE_ARGTYPE(proc, kernel, , create, 0, "struct proc *");
89 SDT_PROBE_ARGTYPE(proc, kernel, , create, 1, "struct proc *");
90 SDT_PROBE_ARGTYPE(proc, kernel, , create, 2, "int");
92 #ifndef _SYS_SYSPROTO_H_
102 struct fork_args *uap;
107 error = fork1(td, RFFDG | RFPROC, 0, &p2);
109 td->td_retval[0] = p2->p_pid;
110 td->td_retval[1] = 0;
119 struct vfork_args *uap;
125 flags = RFFDG | RFPROC; /* validate that this is still an issue */
127 flags = RFFDG | RFPROC | RFPPWAIT | RFMEM;
129 error = fork1(td, flags, 0, &p2);
131 td->td_retval[0] = p2->p_pid;
132 td->td_retval[1] = 0;
140 struct rfork_args *uap;
145 /* Don't allow kernel-only flags. */
146 if ((uap->flags & RFKERNELONLY) != 0)
149 AUDIT_ARG_FFLAGS(uap->flags);
150 error = fork1(td, uap->flags, 0, &p2);
152 td->td_retval[0] = p2 ? p2->p_pid : 0;
153 td->td_retval[1] = 0;
158 int nprocs = 1; /* process 0 */
160 SYSCTL_INT(_kern, OID_AUTO, lastpid, CTLFLAG_RD, &lastpid, 0,
164 * Random component to lastpid generation. We mix in a random factor to make
165 * it a little harder to predict. We sanity check the modulus value to avoid
166 * doing it in critical paths. Don't let it be too small or we pointlessly
167 * waste randomness entropy, and don't let it be impossibly large. Using a
168 * modulus that is too big causes a LOT more process table scans and slows
169 * down fork processing as the pidchecked caching is defeated.
171 static int randompid = 0;
174 sysctl_kern_randompid(SYSCTL_HANDLER_ARGS)
178 error = sysctl_wire_old_buffer(req, sizeof(int));
181 sx_xlock(&allproc_lock);
183 error = sysctl_handle_int(oidp, &pid, 0, req);
184 if (error == 0 && req->newptr != NULL) {
185 if (pid < 0 || pid > PID_MAX - 100) /* out of range */
187 else if (pid < 2) /* NOP */
189 else if (pid < 100) /* Make it reasonable */
193 sx_xunlock(&allproc_lock);
197 SYSCTL_PROC(_kern, OID_AUTO, randompid, CTLTYPE_INT|CTLFLAG_RW,
198 0, 0, sysctl_kern_randompid, "I", "Random PID modulus");
201 fork1(td, flags, pages, procp)
207 struct proc *p1, *p2, *pptr;
208 struct proc *newproc;
210 static int curfail, pidchecked = 0;
211 static struct timeval lastfail;
213 struct filedesc_to_leader *fdtol;
215 struct sigacts *newsigacts;
217 vm_ooffset_t mem_charged;
220 /* Can't copy and clear. */
221 if ((flags & (RFFDG|RFCFDG)) == (RFFDG|RFCFDG))
227 * Here we don't create a new process, but we divorce
228 * certain parts of a process from itself.
230 if ((flags & RFPROC) == 0) {
231 if (((p1->p_flag & (P_HADTHREADS|P_SYSTEM)) == P_HADTHREADS) &&
232 (flags & (RFCFDG | RFFDG))) {
234 if (thread_single(SINGLE_BOUNDARY)) {
241 error = vm_forkproc(td, NULL, NULL, NULL, flags);
246 * Close all file descriptors.
248 if (flags & RFCFDG) {
249 struct filedesc *fdtmp;
250 fdtmp = fdinit(td->td_proc->p_fd);
256 * Unshare file descriptors (from parent).
262 if (((p1->p_flag & (P_HADTHREADS|P_SYSTEM)) == P_HADTHREADS) &&
263 (flags & (RFCFDG | RFFDG))) {
274 * We did have single-threading code here
275 * however it proved un-needed and caused problems
281 pages = KSTACK_PAGES;
282 /* Allocate new proc. */
283 newproc = uma_zalloc(proc_zone, M_WAITOK);
284 td2 = FIRST_THREAD_IN_PROC(newproc);
286 td2 = thread_alloc(pages);
291 proc_linkup(newproc, td2);
293 if (td2->td_kstack == 0 || td2->td_kstack_pages != pages) {
294 if (td2->td_kstack != 0)
295 vm_thread_dispose(td2);
296 if (!thread_alloc_stack(td2, pages)) {
303 if ((flags & RFMEM) == 0) {
304 vm2 = vmspace_fork(p1->p_vmspace, &mem_charged);
309 if (!swap_reserve(mem_charged)) {
311 * The swap reservation failed. The accounting
312 * from the entries of the copied vm2 will be
313 * substracted in vmspace_free(), so force the
316 swap_reserve_force(mem_charged);
323 mac_proc_init(newproc);
325 knlist_init_mtx(&newproc->p_klist, &newproc->p_mtx);
326 STAILQ_INIT(&newproc->p_ktr);
328 /* We have to lock the process tree while we look for a pid. */
329 sx_slock(&proctree_lock);
332 * Although process entries are dynamically created, we still keep
333 * a global limit on the maximum number we will create. Don't allow
334 * a nonprivileged user to use the last ten processes; don't let root
335 * exceed the limit. The variable nprocs is the current number of
336 * processes, maxproc is the limit.
338 sx_xlock(&allproc_lock);
339 if ((nprocs >= maxproc - 10 && priv_check_cred(td->td_ucred,
340 PRIV_MAXPROC, 0) != 0) || nprocs >= maxproc) {
346 * Increment the count of procs running with this uid. Don't allow
347 * a nonprivileged user to exceed their current limit.
349 * XXXRW: Can we avoid privilege here if it's not needed?
351 error = priv_check_cred(td->td_ucred, PRIV_PROC_LIMIT, 0);
353 ok = chgproccnt(td->td_ucred->cr_ruidinfo, 1, 0);
356 ok = chgproccnt(td->td_ucred->cr_ruidinfo, 1,
357 lim_cur(p1, RLIMIT_NPROC));
366 * Increment the nprocs resource before blocking can occur. There
367 * are hard-limits as to the number of processes that can run.
372 * Find an unused process ID. We remember a range of unused IDs
373 * ready to use (from lastpid+1 through pidchecked-1).
375 * If RFHIGHPID is set (used during system boot), do not allocate
378 trypid = lastpid + 1;
379 if (flags & RFHIGHPID) {
384 trypid += arc4random() % randompid;
388 * If the process ID prototype has wrapped around,
389 * restart somewhat above 0, as the low-numbered procs
390 * tend to include daemons that don't exit.
392 if (trypid >= PID_MAX) {
393 trypid = trypid % PID_MAX;
398 if (trypid >= pidchecked) {
401 pidchecked = PID_MAX;
403 * Scan the active and zombie procs to check whether this pid
404 * is in use. Remember the lowest pid that's greater
405 * than trypid, so we can avoid checking for a while.
407 p2 = LIST_FIRST(&allproc);
409 for (; p2 != NULL; p2 = LIST_NEXT(p2, p_list)) {
410 while (p2->p_pid == trypid ||
411 (p2->p_pgrp != NULL &&
412 (p2->p_pgrp->pg_id == trypid ||
413 (p2->p_session != NULL &&
414 p2->p_session->s_sid == trypid)))) {
416 if (trypid >= pidchecked)
419 if (p2->p_pid > trypid && pidchecked > p2->p_pid)
420 pidchecked = p2->p_pid;
421 if (p2->p_pgrp != NULL) {
422 if (p2->p_pgrp->pg_id > trypid &&
423 pidchecked > p2->p_pgrp->pg_id)
424 pidchecked = p2->p_pgrp->pg_id;
425 if (p2->p_session != NULL &&
426 p2->p_session->s_sid > trypid &&
427 pidchecked > p2->p_session->s_sid)
428 pidchecked = p2->p_session->s_sid;
433 p2 = LIST_FIRST(&zombproc);
437 sx_sunlock(&proctree_lock);
440 * RFHIGHPID does not mess with the lastpid counter during boot.
442 if (flags & RFHIGHPID)
448 p2->p_state = PRS_NEW; /* protect against others */
451 * Allow the scheduler to initialize the child.
456 AUDIT_ARG_PID(p2->p_pid);
457 LIST_INSERT_HEAD(&allproc, p2, p_list);
458 LIST_INSERT_HEAD(PIDHASH(p2->p_pid), p2, p_hash);
463 sx_xunlock(&allproc_lock);
465 bcopy(&p1->p_startcopy, &p2->p_startcopy,
466 __rangeof(struct proc, p_startcopy, p_endcopy));
467 pargs_hold(p2->p_args);
470 bzero(&p2->p_startzero,
471 __rangeof(struct proc, p_startzero, p_endzero));
473 p2->p_ucred = crhold(td->td_ucred);
475 /* Tell the prison that we exist. */
476 prison_proc_hold(p2->p_ucred->cr_prison);
481 * Malloc things while we don't hold any locks.
483 if (flags & RFSIGSHARE)
486 newsigacts = sigacts_alloc();
491 if (flags & RFCFDG) {
492 fd = fdinit(p1->p_fd);
494 } else if (flags & RFFDG) {
495 fd = fdcopy(p1->p_fd);
498 fd = fdshare(p1->p_fd);
499 if (p1->p_fdtol == NULL)
501 filedesc_to_leader_alloc(NULL,
504 if ((flags & RFTHREAD) != 0) {
506 * Shared file descriptor table and
507 * shared process leaders.
510 FILEDESC_XLOCK(p1->p_fd);
511 fdtol->fdl_refcount++;
512 FILEDESC_XUNLOCK(p1->p_fd);
515 * Shared file descriptor table, and
516 * different process leaders
518 fdtol = filedesc_to_leader_alloc(p1->p_fdtol,
524 * Make a proc table entry for the new process.
525 * Start by zeroing the section of proc that is zero-initialized,
526 * then copy the section that is copied directly from the parent.
532 bzero(&td2->td_startzero,
533 __rangeof(struct thread, td_startzero, td_endzero));
534 bzero(&td2->td_rux, sizeof(td2->td_rux));
536 bcopy(&td->td_startcopy, &td2->td_startcopy,
537 __rangeof(struct thread, td_startcopy, td_endcopy));
539 bcopy(&p2->p_comm, &td2->td_name, sizeof(td2->td_name));
540 td2->td_sigstk = td->td_sigstk;
541 td2->td_sigmask = td->td_sigmask;
542 td2->td_flags = TDF_INMEM;
546 td2->td_vnet_lpush = NULL;
550 * Duplicate sub-structures as needed.
551 * Increase reference counts on shared objects.
553 p2->p_flag = P_INMEM;
554 p2->p_swtick = ticks;
555 if (p1->p_flag & P_PROFIL)
557 td2->td_ucred = crhold(p2->p_ucred);
559 if (flags & RFSIGSHARE) {
560 p2->p_sigacts = sigacts_hold(p1->p_sigacts);
562 sigacts_copy(newsigacts, p1->p_sigacts);
563 p2->p_sigacts = newsigacts;
565 if (flags & RFLINUXTHPN)
566 p2->p_sigparent = SIGUSR1;
568 p2->p_sigparent = SIGCHLD;
570 p2->p_textvp = p1->p_textvp;
575 * p_limit is copy-on-write. Bump its refcount.
579 pstats_fork(p1->p_stats, p2->p_stats);
584 /* Bump references to the text vnode (for procfs) */
589 * Set up linkage for kernel based threading.
591 if ((flags & RFTHREAD) != 0) {
592 mtx_lock(&ppeers_lock);
593 p2->p_peers = p1->p_peers;
595 p2->p_leader = p1->p_leader;
596 mtx_unlock(&ppeers_lock);
597 PROC_LOCK(p1->p_leader);
598 if ((p1->p_leader->p_flag & P_WEXIT) != 0) {
599 PROC_UNLOCK(p1->p_leader);
601 * The task leader is exiting, so process p1 is
602 * going to be killed shortly. Since p1 obviously
603 * isn't dead yet, we know that the leader is either
604 * sending SIGKILL's to all the processes in this
605 * task or is sleeping waiting for all the peers to
606 * exit. We let p1 complete the fork, but we need
607 * to go ahead and kill the new process p2 since
608 * the task leader may not get a chance to send
609 * SIGKILL to it. We leave it on the list so that
610 * the task leader will wait for this new process
614 psignal(p2, SIGKILL);
617 PROC_UNLOCK(p1->p_leader);
623 sx_xlock(&proctree_lock);
624 PGRP_LOCK(p1->p_pgrp);
629 * Preserve some more flags in subprocess. P_PROFIL has already
632 p2->p_flag |= p1->p_flag & P_SUGID;
633 td2->td_pflags |= td->td_pflags & TDP_ALTSTACK;
634 SESS_LOCK(p1->p_session);
635 if (p1->p_session->s_ttyvp != NULL && p1->p_flag & P_CONTROLT)
636 p2->p_flag |= P_CONTROLT;
637 SESS_UNLOCK(p1->p_session);
638 if (flags & RFPPWAIT)
639 p2->p_flag |= P_PPWAIT;
641 p2->p_pgrp = p1->p_pgrp;
642 LIST_INSERT_AFTER(p1, p2, p_pglist);
643 PGRP_UNLOCK(p1->p_pgrp);
644 LIST_INIT(&p2->p_children);
646 callout_init(&p2->p_itcallout, CALLOUT_MPSAFE);
650 * Copy traceflag and tracefile if enabled.
652 mtx_lock(&ktrace_mtx);
653 KASSERT(p2->p_tracevp == NULL, ("new process has a ktrace vnode"));
654 if (p1->p_traceflag & KTRFAC_INHERIT) {
655 p2->p_traceflag = p1->p_traceflag;
656 if ((p2->p_tracevp = p1->p_tracevp) != NULL) {
658 KASSERT(p1->p_tracecred != NULL,
659 ("ktrace vnode with no cred"));
660 p2->p_tracecred = crhold(p1->p_tracecred);
663 mtx_unlock(&ktrace_mtx);
667 * If PF_FORK is set, the child process inherits the
668 * procfs ioctl flags from its parent.
670 if (p1->p_pfsflags & PF_FORK) {
671 p2->p_stops = p1->p_stops;
672 p2->p_pfsflags = p1->p_pfsflags;
677 * Tell the DTrace fasttrap provider about the new process
678 * if it has registered an interest.
680 if (dtrace_fasttrap_fork)
681 dtrace_fasttrap_fork(p1, p2);
685 * This begins the section where we must prevent the parent
686 * from being swapped.
692 * Attach the new process to its parent.
694 * If RFNOWAIT is set, the newly created process becomes a child
695 * of init. This effectively disassociates the child from the
698 if (flags & RFNOWAIT)
703 LIST_INSERT_HEAD(&pptr->p_children, p2, p_sibling);
704 sx_xunlock(&proctree_lock);
706 /* Inform accounting that we have forked. */
707 p2->p_acflag = AFORK;
711 * Finish creating the child process. It will return via a different
712 * execution path later. (ie: directly into user mode)
714 vm_forkproc(td, p2, td2, vm2, flags);
716 if (flags == (RFFDG | RFPROC)) {
717 PCPU_INC(cnt.v_forks);
718 PCPU_ADD(cnt.v_forkpages, p2->p_vmspace->vm_dsize +
719 p2->p_vmspace->vm_ssize);
720 } else if (flags == (RFFDG | RFPROC | RFPPWAIT | RFMEM)) {
721 PCPU_INC(cnt.v_vforks);
722 PCPU_ADD(cnt.v_vforkpages, p2->p_vmspace->vm_dsize +
723 p2->p_vmspace->vm_ssize);
724 } else if (p1 == &proc0) {
725 PCPU_INC(cnt.v_kthreads);
726 PCPU_ADD(cnt.v_kthreadpages, p2->p_vmspace->vm_dsize +
727 p2->p_vmspace->vm_ssize);
729 PCPU_INC(cnt.v_rforks);
730 PCPU_ADD(cnt.v_rforkpages, p2->p_vmspace->vm_dsize +
731 p2->p_vmspace->vm_ssize);
735 * Both processes are set up, now check if any loadable modules want
736 * to adjust anything.
737 * What if they have an error? XXX
739 EVENTHANDLER_INVOKE(process_fork, p1, p2, flags);
742 * Set the child start time and mark the process as being complete.
744 microuptime(&p2->p_stats->p_start);
746 p2->p_state = PRS_NORMAL;
750 * If RFSTOPPED not requested, make child runnable and add to
753 if ((flags & RFSTOPPED) == 0) {
756 sched_add(td2, SRQ_BORING);
761 * Now can be swapped.
768 * Tell any interested parties about the new process.
770 knote_fork(&p1->p_klist, p2->p_pid);
771 SDT_PROBE(proc, kernel, , create, p2, p1, flags, 0, 0);
774 * Preserve synchronization semantics of vfork. If waiting for
775 * child to exec or exit, set P_PPWAIT on child, and sleep on our
776 * proc (in case of exit).
779 while (p2->p_flag & P_PPWAIT)
780 cv_wait(&p2->p_pwait, &p2->p_mtx);
784 * Return child proc pointer to parent.
789 sx_sunlock(&proctree_lock);
790 if (ppsratecheck(&lastfail, &curfail, 1))
791 printf("maxproc limit exceeded by uid %i, please see tuning(7) and login.conf(5).\n",
792 td->td_ucred->cr_ruid);
793 sx_xunlock(&allproc_lock);
795 mac_proc_destroy(newproc);
800 uma_zfree(proc_zone, newproc);
801 pause("fork", hz / 2);
806 * Handle the return of a child process from fork1(). This function
807 * is called from the MD fork_trampoline() entry point.
810 fork_exit(callout, arg, frame)
811 void (*callout)(void *, struct trapframe *);
813 struct trapframe *frame;
821 KASSERT(p->p_state == PRS_NORMAL, ("executing process is still new"));
823 CTR4(KTR_PROC, "fork_exit: new thread %p (td_sched %p, pid %d, %s)",
824 td, td->td_sched, p->p_pid, td->td_name);
828 * Processes normally resume in mi_switch() after being
829 * cpu_switch()'ed to, but when children start up they arrive here
830 * instead, so we must do much the same things as mi_switch() would.
832 if ((dtd = PCPU_GET(deadthread))) {
833 PCPU_SET(deadthread, NULL);
839 * cpu_set_fork_handler intercepts this function call to
840 * have this call a non-return function to stay in kernel mode.
841 * initproc has its own fork handler, but it does return.
843 KASSERT(callout != NULL, ("NULL callout in fork_exit"));
847 * Check if a kernel thread misbehaved and returned from its main
850 if (p->p_flag & P_KTHREAD) {
851 printf("Kernel thread \"%s\" (pid %d) exited prematurely.\n",
852 td->td_name, p->p_pid);
855 mtx_assert(&Giant, MA_NOTOWNED);
857 EVENTHANDLER_INVOKE(schedtail, p);
861 * Simplified back end of syscall(), used when returning from fork()
862 * directly into user mode. Giant is not held on entry, and must not
863 * be held on return. This function is passed in to fork_exit() as the
864 * first parameter and is called when returning to a new userland process.
867 fork_return(td, frame)
869 struct trapframe *frame;
874 if (KTRPOINT(td, KTR_SYSRET))
875 ktrsysret(SYS_fork, 0, 0);
877 mtx_assert(&Giant, MA_NOTOWNED);