summaryrefslogtreecommitdiffstats
path: root/sys/kern/kern_fork.c
blob: 60639c9fcb84ef794014f5f8ebcc5d3c83f29b39 (plain)
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
198
199
200
201
202
203
204
205
206
207
208
209
210
211
212
213
214
215
216
217
218
219
220
221
222
223
224
225
226
227
228
229
230
231
232
233
234
235
236
237
238
239
240
241
242
243
244
245
246
247
248
249
250
251
252
253
254
255
256
257
258
259
260
261
262
263
264
265
266
267
268
269
270
271
272
273
274
275
276
277
278
279
280
281
282
283
284
285
286
287
288
289
290
291
292
293
294
295
296
297
298
299
300
301
302
303
304
305
306
307
308
309
310
311
312
313
314
315
316
317
318
319
320
321
322
323
324
325
326
327
328
329
330
331
332
333
334
335
336
337
338
339
340
341
342
343
344
345
346
347
348
349
350
351
352
353
354
355
356
357
358
359
360
361
362
363
364
365
366
367
368
369
370
371
372
373
374
375
376
377
378
379
380
381
382
383
384
385
386
387
388
389
390
391
392
393
394
395
396
397
398
399
400
401
402
403
404
405
406
407
408
409
410
411
412
413
414
415
416
417
418
419
420
421
422
423
424
425
426
427
428
429
430
431
432
433
434
435
436
437
438
439
440
441
442
443
444
445
446
447
448
449
450
451
452
453
454
455
456
457
458
459
460
461
462
463
464
465
466
467
468
469
470
471
472
473
474
475
476
477
478
479
480
481
482
483
484
485
486
487
488
489
490
491
492
493
494
495
496
497
498
499
500
501
502
503
504
505
506
507
508
509
510
511
512
513
514
515
516
517
518
519
520
521
522
523
524
525
526
527
528
529
530
531
532
533
534
535
536
537
538
539
540
541
542
543
544
545
546
547
548
549
550
551
552
553
554
555
556
557
558
559
560
561
562
563
564
565
566
567
568
569
570
571
572
573
574
575
576
577
578
579
580
581
582
583
584
585
586
587
588
589
590
591
592
593
594
595
596
597
598
599
600
601
602
603
604
605
606
607
608
609
610
611
612
613
614
615
616
617
618
619
620
621
622
623
624
625
626
627
628
629
630
631
632
633
634
635
636
637
638
639
640
641
642
643
644
645
646
647
648
649
650
651
652
653
654
655
656
657
658
659
660
661
662
663
664
665
666
667
668
669
670
671
672
673
674
675
676
677
678
679
680
681
682
683
684
685
686
687
688
689
690
691
692
693
694
695
696
697
698
699
700
701
702
703
704
705
706
707
708
709
710
711
712
713
714
715
716
717
718
719
720
721
722
723
724
725
726
727
728
729
730
731
732
733
734
735
736
737
738
739
740
741
742
743
744
745
746
747
748
749
750
751
752
753
754
755
756
757
758
759
760
761
762
763
764
765
766
767
768
769
770
771
772
773
774
775
776
777
778
779
780
781
782
783
784
785
786
787
788
789
790
791
792
793
794
795
796
797
798
799
800
801
802
803
804
805
806
807
808
809
810
811
812
813
814
815
816
817
818
819
820
821
822
823
824
825
826
827
828
829
830
831
832
833
834
835
836
837
838
839
840
841
842
843
844
845
846
847
848
849
850
851
852
853
854
855
856
857
858
859
860
861
862
863
864
865
866
867
868
869
870
871
872
873
874
875
876
877
878
879
880
881
882
883
884
885
886
887
888
889
890
891
892
893
894
895
896
897
898
899
900
901
902
903
904
905
906
907
908
909
910
911
912
913
914
915
916
917
918
919
920
921
922
923
924
925
926
927
928
929
930
931
932
933
934
935
936
937
938
939
940
941
942
943
944
945
946
947
948
949
950
951
952
953
954
955
956
957
958
959
960
961
962
963
964
965
966
967
968
969
970
971
972
973
974
975
976
977
978
979
980
981
982
983
984
985
986
987
988
989
990
991
992
993
994
995
996
997
998
999
1000
1001
1002
1003
1004
1005
1006
1007
1008
1009
1010
1011
1012
1013
1014
1015
1016
1017
1018
1019
1020
1021
1022
1023
1024
1025
1026
1027
1028
1029
1030
1031
1032
1033
1034
1035
1036
1037
1038
1039
1040
1041
1042
1043
1044
1045
1046
1047
1048
1049
1050
1051
1052
1053
1054
1055
1056
1057
/*-
 * Copyright (c) 1982, 1986, 1989, 1991, 1993
 *	The Regents of the University of California.  All rights reserved.
 * (c) UNIX System Laboratories, Inc.
 * All or some portions of this file are derived from material licensed
 * to the University of California by American Telephone and Telegraph
 * Co. or Unix System Laboratories, Inc. and are reproduced herein with
 * the permission of UNIX System Laboratories, Inc.
 *
 * Redistribution and use in source and binary forms, with or without
 * modification, are permitted provided that the following conditions
 * are met:
 * 1. Redistributions of source code must retain the above copyright
 *    notice, this list of conditions and the following disclaimer.
 * 2. Redistributions in binary form must reproduce the above copyright
 *    notice, this list of conditions and the following disclaimer in the
 *    documentation and/or other materials provided with the distribution.
 * 4. Neither the name of the University nor the names of its contributors
 *    may be used to endorse or promote products derived from this software
 *    without specific prior written permission.
 *
 * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
 * ARE DISCLAIMED.  IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
 * SUCH DAMAGE.
 *
 *	@(#)kern_fork.c	8.6 (Berkeley) 4/8/94
 */

#include <sys/cdefs.h>
__FBSDID("$FreeBSD$");

#include "opt_kdtrace.h"
#include "opt_ktrace.h"
#include "opt_kstack_pages.h"
#include "opt_procdesc.h"

#include <sys/param.h>
#include <sys/systm.h>
#include <sys/sysproto.h>
#include <sys/eventhandler.h>
#include <sys/fcntl.h>
#include <sys/filedesc.h>
#include <sys/jail.h>
#include <sys/kernel.h>
#include <sys/kthread.h>
#include <sys/sysctl.h>
#include <sys/lock.h>
#include <sys/malloc.h>
#include <sys/mutex.h>
#include <sys/priv.h>
#include <sys/proc.h>
#include <sys/procdesc.h>
#include <sys/pioctl.h>
#include <sys/racct.h>
#include <sys/resourcevar.h>
#include <sys/sched.h>
#include <sys/syscall.h>
#include <sys/vmmeter.h>
#include <sys/vnode.h>
#include <sys/acct.h>
#include <sys/ktr.h>
#include <sys/ktrace.h>
#include <sys/unistd.h>	
#include <sys/sdt.h>
#include <sys/sx.h>
#include <sys/sysent.h>
#include <sys/signalvar.h>

#include <security/audit/audit.h>
#include <security/mac/mac_framework.h>

#include <vm/vm.h>
#include <vm/pmap.h>
#include <vm/vm_map.h>
#include <vm/vm_extern.h>
#include <vm/uma.h>

#ifdef KDTRACE_HOOKS
#include <sys/dtrace_bsd.h>
dtrace_fork_func_t	dtrace_fasttrap_fork;
#endif

SDT_PROVIDER_DECLARE(proc);
SDT_PROBE_DEFINE(proc, kernel, , create, create);
SDT_PROBE_ARGTYPE(proc, kernel, , create, 0, "struct proc *");
SDT_PROBE_ARGTYPE(proc, kernel, , create, 1, "struct proc *");
SDT_PROBE_ARGTYPE(proc, kernel, , create, 2, "int");

#ifndef _SYS_SYSPROTO_H_
struct fork_args {
	int     dummy;
};
#endif

/* ARGSUSED */
int
sys_fork(struct thread *td, struct fork_args *uap)
{
	int error;
	struct proc *p2;

	error = fork1(td, RFFDG | RFPROC, 0, &p2, NULL, 0);
	if (error == 0) {
		td->td_retval[0] = p2->p_pid;
		td->td_retval[1] = 0;
	}
	return (error);
}

/* ARGUSED */
int
sys_pdfork(td, uap)
	struct thread *td;
	struct pdfork_args *uap;
{
#ifdef PROCDESC
	int error, fd;
	struct proc *p2;

	/*
	 * It is necessary to return fd by reference because 0 is a valid file
	 * descriptor number, and the child needs to be able to distinguish
	 * itself from the parent using the return value.
	 */
	error = fork1(td, RFFDG | RFPROC | RFPROCDESC, 0, &p2,
	    &fd, uap->flags);
	if (error == 0) {
		td->td_retval[0] = p2->p_pid;
		td->td_retval[1] = 0;
		error = copyout(&fd, uap->fdp, sizeof(fd));
	}
	return (error);
#else
	return (ENOSYS);
#endif
}

/* ARGSUSED */
int
sys_vfork(struct thread *td, struct vfork_args *uap)
{
	int error, flags;
	struct proc *p2;

#ifdef XEN
	flags = RFFDG | RFPROC; /* validate that this is still an issue */
#else
	flags = RFFDG | RFPROC | RFPPWAIT | RFMEM;
#endif		
	error = fork1(td, flags, 0, &p2, NULL, 0);
	if (error == 0) {
		td->td_retval[0] = p2->p_pid;
		td->td_retval[1] = 0;
	}
	return (error);
}

int
sys_rfork(struct thread *td, struct rfork_args *uap)
{
	struct proc *p2;
	int error;

	/* Don't allow kernel-only flags. */
	if ((uap->flags & RFKERNELONLY) != 0)
		return (EINVAL);

	AUDIT_ARG_FFLAGS(uap->flags);
	error = fork1(td, uap->flags, 0, &p2, NULL, 0);
	if (error == 0) {
		td->td_retval[0] = p2 ? p2->p_pid : 0;
		td->td_retval[1] = 0;
	}
	return (error);
}

int	nprocs = 1;		/* process 0 */
int	lastpid = 0;
SYSCTL_INT(_kern, OID_AUTO, lastpid, CTLFLAG_RD, &lastpid, 0, 
    "Last used PID");

/*
 * Random component to lastpid generation.  We mix in a random factor to make
 * it a little harder to predict.  We sanity check the modulus value to avoid
 * doing it in critical paths.  Don't let it be too small or we pointlessly
 * waste randomness entropy, and don't let it be impossibly large.  Using a
 * modulus that is too big causes a LOT more process table scans and slows
 * down fork processing as the pidchecked caching is defeated.
 */
static int randompid = 0;

static int
sysctl_kern_randompid(SYSCTL_HANDLER_ARGS)
{
	int error, pid;

	error = sysctl_wire_old_buffer(req, sizeof(int));
	if (error != 0)
		return(error);
	sx_xlock(&allproc_lock);
	pid = randompid;
	error = sysctl_handle_int(oidp, &pid, 0, req);
	if (error == 0 && req->newptr != NULL) {
		if (pid < 0 || pid > PID_MAX - 100)	/* out of range */
			pid = PID_MAX - 100;
		else if (pid < 2)			/* NOP */
			pid = 0;
		else if (pid < 100)			/* Make it reasonable */
			pid = 100;
		randompid = pid;
	}
	sx_xunlock(&allproc_lock);
	return (error);
}

SYSCTL_PROC(_kern, OID_AUTO, randompid, CTLTYPE_INT|CTLFLAG_RW,
    0, 0, sysctl_kern_randompid, "I", "Random PID modulus");

static int
fork_findpid(int flags)
{
	struct proc *p;
	int trypid;
	static int pidchecked = 0;

	/*
	 * Requires allproc_lock in order to iterate over the list
	 * of processes, and proctree_lock to access p_pgrp.
	 */
	sx_assert(&allproc_lock, SX_LOCKED);
	sx_assert(&proctree_lock, SX_LOCKED);

	/*
	 * Find an unused process ID.  We remember a range of unused IDs
	 * ready to use (from lastpid+1 through pidchecked-1).
	 *
	 * If RFHIGHPID is set (used during system boot), do not allocate
	 * low-numbered pids.
	 */
	trypid = lastpid + 1;
	if (flags & RFHIGHPID) {
		if (trypid < 10)
			trypid = 10;
	} else {
		if (randompid)
			trypid += arc4random() % randompid;
	}
retry:
	/*
	 * If the process ID prototype has wrapped around,
	 * restart somewhat above 0, as the low-numbered procs
	 * tend to include daemons that don't exit.
	 */
	if (trypid >= PID_MAX) {
		trypid = trypid % PID_MAX;
		if (trypid < 100)
			trypid += 100;
		pidchecked = 0;
	}
	if (trypid >= pidchecked) {
		int doingzomb = 0;

		pidchecked = PID_MAX;
		/*
		 * Scan the active and zombie procs to check whether this pid
		 * is in use.  Remember the lowest pid that's greater
		 * than trypid, so we can avoid checking for a while.
		 */
		p = LIST_FIRST(&allproc);
again:
		for (; p != NULL; p = LIST_NEXT(p, p_list)) {
			while (p->p_pid == trypid ||
			    (p->p_pgrp != NULL &&
			    (p->p_pgrp->pg_id == trypid ||
			    (p->p_session != NULL &&
			    p->p_session->s_sid == trypid)))) {
				trypid++;
				if (trypid >= pidchecked)
					goto retry;
			}
			if (p->p_pid > trypid && pidchecked > p->p_pid)
				pidchecked = p->p_pid;
			if (p->p_pgrp != NULL) {
				if (p->p_pgrp->pg_id > trypid &&
				    pidchecked > p->p_pgrp->pg_id)
					pidchecked = p->p_pgrp->pg_id;
				if (p->p_session != NULL &&
				    p->p_session->s_sid > trypid &&
				    pidchecked > p->p_session->s_sid)
					pidchecked = p->p_session->s_sid;
			}
		}
		if (!doingzomb) {
			doingzomb = 1;
			p = LIST_FIRST(&zombproc);
			goto again;
		}
	}

	/*
	 * RFHIGHPID does not mess with the lastpid counter during boot.
	 */
	if (flags & RFHIGHPID)
		pidchecked = 0;
	else
		lastpid = trypid;

	return (trypid);
}

static int
fork_norfproc(struct thread *td, int flags)
{
	int error;
	struct proc *p1;

	KASSERT((flags & RFPROC) == 0,
	    ("fork_norfproc called with RFPROC set"));
	p1 = td->td_proc;

	if (((p1->p_flag & (P_HADTHREADS|P_SYSTEM)) == P_HADTHREADS) &&
	    (flags & (RFCFDG | RFFDG))) {
		PROC_LOCK(p1);
		if (thread_single(SINGLE_BOUNDARY)) {
			PROC_UNLOCK(p1);
			return (ERESTART);
		}
		PROC_UNLOCK(p1);
	}

	error = vm_forkproc(td, NULL, NULL, NULL, flags);
	if (error)
		goto fail;

	/*
	 * Close all file descriptors.
	 */
	if (flags & RFCFDG) {
		struct filedesc *fdtmp;
		fdtmp = fdinit(td->td_proc->p_fd);
		fdfree(td);
		p1->p_fd = fdtmp;
	}

	/*
	 * Unshare file descriptors (from parent).
	 */
	if (flags & RFFDG) 
		fdunshare(p1, td);

fail:
	if (((p1->p_flag & (P_HADTHREADS|P_SYSTEM)) == P_HADTHREADS) &&
	    (flags & (RFCFDG | RFFDG))) {
		PROC_LOCK(p1);
		thread_single_end();
		PROC_UNLOCK(p1);
	}
	return (error);
}

static void
do_fork(struct thread *td, int flags, struct proc *p2, struct thread *td2,
    struct vmspace *vm2, int pdflags)
{
	struct proc *p1, *pptr;
	int p2_held, trypid;
	struct filedesc *fd;
	struct filedesc_to_leader *fdtol;
	struct sigacts *newsigacts;

	sx_assert(&proctree_lock, SX_SLOCKED);
	sx_assert(&allproc_lock, SX_XLOCKED);

	p2_held = 0;
	p1 = td->td_proc;

	/*
	 * Increment the nprocs resource before blocking can occur.  There
	 * are hard-limits as to the number of processes that can run.
	 */
	nprocs++;

	trypid = fork_findpid(flags);

	sx_sunlock(&proctree_lock);

	p2->p_state = PRS_NEW;		/* protect against others */
	p2->p_pid = trypid;
	AUDIT_ARG_PID(p2->p_pid);
	LIST_INSERT_HEAD(&allproc, p2, p_list);
	LIST_INSERT_HEAD(PIDHASH(p2->p_pid), p2, p_hash);
	tidhash_add(td2);
	PROC_LOCK(p2);
	PROC_LOCK(p1);

	sx_xunlock(&allproc_lock);

	bcopy(&p1->p_startcopy, &p2->p_startcopy,
	    __rangeof(struct proc, p_startcopy, p_endcopy));
	pargs_hold(p2->p_args);
	PROC_UNLOCK(p1);

	bzero(&p2->p_startzero,
	    __rangeof(struct proc, p_startzero, p_endzero));

	p2->p_ucred = crhold(td->td_ucred);

	/* Tell the prison that we exist. */
	prison_proc_hold(p2->p_ucred->cr_prison);

	PROC_UNLOCK(p2);

	/*
	 * Malloc things while we don't hold any locks.
	 */
	if (flags & RFSIGSHARE)
		newsigacts = NULL;
	else
		newsigacts = sigacts_alloc();

	/*
	 * Copy filedesc.
	 */
	if (flags & RFCFDG) {
		fd = fdinit(p1->p_fd);
		fdtol = NULL;
	} else if (flags & RFFDG) {
		fd = fdcopy(p1->p_fd);
		fdtol = NULL;
	} else {
		fd = fdshare(p1->p_fd);
		if (p1->p_fdtol == NULL)
			p1->p_fdtol = filedesc_to_leader_alloc(NULL, NULL,
			    p1->p_leader);
		if ((flags & RFTHREAD) != 0) {
			/*
			 * Shared file descriptor table, and shared
			 * process leaders.
			 */
			fdtol = p1->p_fdtol;
			FILEDESC_XLOCK(p1->p_fd);
			fdtol->fdl_refcount++;
			FILEDESC_XUNLOCK(p1->p_fd);
		} else {
			/* 
			 * Shared file descriptor table, and different
			 * process leaders.
			 */
			fdtol = filedesc_to_leader_alloc(p1->p_fdtol,
			    p1->p_fd, p2);
		}
	}
	/*
	 * Make a proc table entry for the new process.
	 * Start by zeroing the section of proc that is zero-initialized,
	 * then copy the section that is copied directly from the parent.
	 */

	PROC_LOCK(p2);
	PROC_LOCK(p1);

	bzero(&td2->td_startzero,
	    __rangeof(struct thread, td_startzero, td_endzero));

	bcopy(&td->td_startcopy, &td2->td_startcopy,
	    __rangeof(struct thread, td_startcopy, td_endcopy));

	bcopy(&p2->p_comm, &td2->td_name, sizeof(td2->td_name));
	td2->td_sigstk = td->td_sigstk;
	td2->td_sigmask = td->td_sigmask;
	td2->td_flags = TDF_INMEM;
	td2->td_lend_user_pri = PRI_MAX;

#ifdef VIMAGE
	td2->td_vnet = NULL;
	td2->td_vnet_lpush = NULL;
#endif

	/*
	 * Allow the scheduler to initialize the child.
	 */
	thread_lock(td);
	sched_fork(td, td2);
	thread_unlock(td);

	/*
	 * Duplicate sub-structures as needed.
	 * Increase reference counts on shared objects.
	 */
	p2->p_flag = P_INMEM;
	p2->p_swtick = ticks;
	if (p1->p_flag & P_PROFIL)
		startprofclock(p2);
	td2->td_ucred = crhold(p2->p_ucred);

	if (flags & RFSIGSHARE) {
		p2->p_sigacts = sigacts_hold(p1->p_sigacts);
	} else {
		sigacts_copy(newsigacts, p1->p_sigacts);
		p2->p_sigacts = newsigacts;
	}

	if (flags & RFTSIGZMB)
	        p2->p_sigparent = RFTSIGNUM(flags);
	else if (flags & RFLINUXTHPN)
	        p2->p_sigparent = SIGUSR1;
	else
	        p2->p_sigparent = SIGCHLD;

	p2->p_textvp = p1->p_textvp;
	p2->p_fd = fd;
	p2->p_fdtol = fdtol;

	/*
	 * p_limit is copy-on-write.  Bump its refcount.
	 */
	lim_fork(p1, p2);

	pstats_fork(p1->p_stats, p2->p_stats);

	PROC_UNLOCK(p1);
	PROC_UNLOCK(p2);

	/* Bump references to the text vnode (for procfs). */
	if (p2->p_textvp)
		vref(p2->p_textvp);

	/*
	 * Set up linkage for kernel based threading.
	 */
	if ((flags & RFTHREAD) != 0) {
		mtx_lock(&ppeers_lock);
		p2->p_peers = p1->p_peers;
		p1->p_peers = p2;
		p2->p_leader = p1->p_leader;
		mtx_unlock(&ppeers_lock);
		PROC_LOCK(p1->p_leader);
		if ((p1->p_leader->p_flag & P_WEXIT) != 0) {
			PROC_UNLOCK(p1->p_leader);
			/*
			 * The task leader is exiting, so process p1 is
			 * going to be killed shortly.  Since p1 obviously
			 * isn't dead yet, we know that the leader is either
			 * sending SIGKILL's to all the processes in this
			 * task or is sleeping waiting for all the peers to
			 * exit.  We let p1 complete the fork, but we need
			 * to go ahead and kill the new process p2 since
			 * the task leader may not get a chance to send
			 * SIGKILL to it.  We leave it on the list so that
			 * the task leader will wait for this new process
			 * to commit suicide.
			 */
			PROC_LOCK(p2);
			kern_psignal(p2, SIGKILL);
			PROC_UNLOCK(p2);
		} else
			PROC_UNLOCK(p1->p_leader);
	} else {
		p2->p_peers = NULL;
		p2->p_leader = p2;
	}

	sx_xlock(&proctree_lock);
	PGRP_LOCK(p1->p_pgrp);
	PROC_LOCK(p2);
	PROC_LOCK(p1);

	/*
	 * Preserve some more flags in subprocess.  P_PROFIL has already
	 * been preserved.
	 */
	p2->p_flag |= p1->p_flag & P_SUGID;
	td2->td_pflags |= td->td_pflags & TDP_ALTSTACK;
	SESS_LOCK(p1->p_session);
	if (p1->p_session->s_ttyvp != NULL && p1->p_flag & P_CONTROLT)
		p2->p_flag |= P_CONTROLT;
	SESS_UNLOCK(p1->p_session);
	if (flags & RFPPWAIT)
		p2->p_flag |= P_PPWAIT;

	p2->p_pgrp = p1->p_pgrp;
	LIST_INSERT_AFTER(p1, p2, p_pglist);
	PGRP_UNLOCK(p1->p_pgrp);
	LIST_INIT(&p2->p_children);

	callout_init(&p2->p_itcallout, CALLOUT_MPSAFE);

	/*
	 * If PF_FORK is set, the child process inherits the
	 * procfs ioctl flags from its parent.
	 */
	if (p1->p_pfsflags & PF_FORK) {
		p2->p_stops = p1->p_stops;
		p2->p_pfsflags = p1->p_pfsflags;
	}

	/*
	 * This begins the section where we must prevent the parent
	 * from being swapped.
	 */
	_PHOLD(p1);
	PROC_UNLOCK(p1);

	/*
	 * Attach the new process to its parent.
	 *
	 * If RFNOWAIT is set, the newly created process becomes a child
	 * of init.  This effectively disassociates the child from the
	 * parent.
	 */
	if (flags & RFNOWAIT)
		pptr = initproc;
	else
		pptr = p1;
	p2->p_pptr = pptr;
	LIST_INSERT_HEAD(&pptr->p_children, p2, p_sibling);
	sx_xunlock(&proctree_lock);

	/* Inform accounting that we have forked. */
	p2->p_acflag = AFORK;
	PROC_UNLOCK(p2);

#ifdef KTRACE
	ktrprocfork(p1, p2);
#endif

	/*
	 * Finish creating the child process.  It will return via a different
	 * execution path later.  (ie: directly into user mode)
	 */
	vm_forkproc(td, p2, td2, vm2, flags);

	if (flags == (RFFDG | RFPROC)) {
		PCPU_INC(cnt.v_forks);
		PCPU_ADD(cnt.v_forkpages, p2->p_vmspace->vm_dsize +
		    p2->p_vmspace->vm_ssize);
	} else if (flags == (RFFDG | RFPROC | RFPPWAIT | RFMEM)) {
		PCPU_INC(cnt.v_vforks);
		PCPU_ADD(cnt.v_vforkpages, p2->p_vmspace->vm_dsize +
		    p2->p_vmspace->vm_ssize);
	} else if (p1 == &proc0) {
		PCPU_INC(cnt.v_kthreads);
		PCPU_ADD(cnt.v_kthreadpages, p2->p_vmspace->vm_dsize +
		    p2->p_vmspace->vm_ssize);
	} else {
		PCPU_INC(cnt.v_rforks);
		PCPU_ADD(cnt.v_rforkpages, p2->p_vmspace->vm_dsize +
		    p2->p_vmspace->vm_ssize);
	}

#ifdef PROCDESC
	/*
	 * Associate the process descriptor with the process before anything
	 * can happen that might cause that process to need the descriptor.
	 * However, don't do this until after fork(2) can no longer fail.
	 */
	if (flags & RFPROCDESC)
		procdesc_new(p2, pdflags);
#endif

	/*
	 * Both processes are set up, now check if any loadable modules want
	 * to adjust anything.
	 */
	EVENTHANDLER_INVOKE(process_fork, p1, p2, flags);

	/*
	 * Set the child start time and mark the process as being complete.
	 */
	PROC_LOCK(p2);
	PROC_LOCK(p1);
	microuptime(&p2->p_stats->p_start);
	PROC_SLOCK(p2);
	p2->p_state = PRS_NORMAL;
	PROC_SUNLOCK(p2);

#ifdef KDTRACE_HOOKS
	/*
	 * Tell the DTrace fasttrap provider about the new process
	 * if it has registered an interest. We have to do this only after
	 * p_state is PRS_NORMAL since the fasttrap module will use pfind()
	 * later on.
	 */
	if (dtrace_fasttrap_fork)
		dtrace_fasttrap_fork(p1, p2);
#endif
	if ((p1->p_flag & (P_TRACED | P_FOLLOWFORK)) == (P_TRACED |
	    P_FOLLOWFORK)) {
		/*
		 * Arrange for debugger to receive the fork event.
		 *
		 * We can report PL_FLAG_FORKED regardless of
		 * P_FOLLOWFORK settings, but it does not make a sense
		 * for runaway child.
		 */
		td->td_dbgflags |= TDB_FORK;
		td->td_dbg_forked = p2->p_pid;
		td2->td_dbgflags |= TDB_STOPATFORK;
		_PHOLD(p2);
		p2_held = 1;
	}
	PROC_UNLOCK(p2);
	if ((flags & RFSTOPPED) == 0) {
		/*
		 * If RFSTOPPED not requested, make child runnable and
		 * add to run queue.
		 */
		thread_lock(td2);
		TD_SET_CAN_RUN(td2);
		sched_add(td2, SRQ_BORING);
		thread_unlock(td2);
	}

	/*
	 * Now can be swapped.
	 */
	_PRELE(p1);
	PROC_UNLOCK(p1);

	/*
	 * Tell any interested parties about the new process.
	 */
	knote_fork(&p1->p_klist, p2->p_pid);
	SDT_PROBE(proc, kernel, , create, p2, p1, flags, 0, 0);

	/*
	 * Wait until debugger is attached to child.
	 */
	PROC_LOCK(p2);
	while ((td2->td_dbgflags & TDB_STOPATFORK) != 0)
		cv_wait(&p2->p_dbgwait, &p2->p_mtx);
	if (p2_held)
		_PRELE(p2);

	/*
	 * Preserve synchronization semantics of vfork.  If waiting for
	 * child to exec or exit, set P_PPWAIT on child, and sleep on our
	 * proc (in case of exit).
	 */
	while (p2->p_flag & P_PPWAIT)
		cv_wait(&p2->p_pwait, &p2->p_mtx);
	PROC_UNLOCK(p2);
}

int
fork1(struct thread *td, int flags, int pages, struct proc **procp,
    int *procdescp, int pdflags)
{
	struct proc *p1;
	struct proc *newproc;
	int ok;
	struct thread *td2;
	struct vmspace *vm2;
	vm_ooffset_t mem_charged;
	int error;
	static int curfail;
	static struct timeval lastfail;
#ifdef PROCDESC
	struct file *fp_procdesc = NULL;
#endif

	/* Check for the undefined or unimplemented flags. */
	if ((flags & ~(RFFLAGS | RFTSIGFLAGS(RFTSIGMASK))) != 0)
		return (EINVAL);

	/* Signal value requires RFTSIGZMB. */
	if ((flags & RFTSIGFLAGS(RFTSIGMASK)) != 0 && (flags & RFTSIGZMB) == 0)
		return (EINVAL);

	/* Can't copy and clear. */
	if ((flags & (RFFDG|RFCFDG)) == (RFFDG|RFCFDG))
		return (EINVAL);

	/* Check the validity of the signal number. */
	if ((flags & RFTSIGZMB) != 0 && (u_int)RFTSIGNUM(flags) > _SIG_MAXSIG)
		return (EINVAL);

#ifdef PROCDESC
	if ((flags & RFPROCDESC) != 0) {
		/* Can't not create a process yet get a process descriptor. */
		if ((flags & RFPROC) == 0)
			return (EINVAL);

		/* Must provide a place to put a procdesc if creating one. */
		if (procdescp == NULL)
			return (EINVAL);
	}
#endif

	p1 = td->td_proc;

	/*
	 * Here we don't create a new process, but we divorce
	 * certain parts of a process from itself.
	 */
	if ((flags & RFPROC) == 0) {
		*procp = NULL;
		return (fork_norfproc(td, flags));
	}

#ifdef PROCDESC
	/*
	 * If required, create a process descriptor in the parent first; we
	 * will abandon it if something goes wrong. We don't finit() until
	 * later.
	 */
	if (flags & RFPROCDESC) {
		error = falloc(td, &fp_procdesc, procdescp, 0);
		if (error != 0)
			return (error);
	}
#endif

	mem_charged = 0;
	vm2 = NULL;
	if (pages == 0)
		pages = KSTACK_PAGES;
	/* Allocate new proc. */
	newproc = uma_zalloc(proc_zone, M_WAITOK);
	td2 = FIRST_THREAD_IN_PROC(newproc);
	if (td2 == NULL) {
		td2 = thread_alloc(pages);
		if (td2 == NULL) {
			error = ENOMEM;
			goto fail1;
		}
		proc_linkup(newproc, td2);
	} else {
		if (td2->td_kstack == 0 || td2->td_kstack_pages != pages) {
			if (td2->td_kstack != 0)
				vm_thread_dispose(td2);
			if (!thread_alloc_stack(td2, pages)) {
				error = ENOMEM;
				goto fail1;
			}
		}
	}

	if ((flags & RFMEM) == 0) {
		vm2 = vmspace_fork(p1->p_vmspace, &mem_charged);
		if (vm2 == NULL) {
			error = ENOMEM;
			goto fail1;
		}
		if (!swap_reserve(mem_charged)) {
			/*
			 * The swap reservation failed. The accounting
			 * from the entries of the copied vm2 will be
			 * substracted in vmspace_free(), so force the
			 * reservation there.
			 */
			swap_reserve_force(mem_charged);
			error = ENOMEM;
			goto fail1;
		}
	} else
		vm2 = NULL;

	/*
	 * XXX: This is ugly; when we copy resource usage, we need to bump
	 *      per-cred resource counters.
	 */
	newproc->p_ucred = p1->p_ucred;

	/*
	 * Initialize resource accounting for the child process.
	 */
	error = racct_proc_fork(p1, newproc);
	if (error != 0) {
		error = EAGAIN;
		goto fail1;
	}

#ifdef MAC
	mac_proc_init(newproc);
#endif
	knlist_init_mtx(&newproc->p_klist, &newproc->p_mtx);
	STAILQ_INIT(&newproc->p_ktr);

	/* We have to lock the process tree while we look for a pid. */
	sx_slock(&proctree_lock);

	/*
	 * Although process entries are dynamically created, we still keep
	 * a global limit on the maximum number we will create.  Don't allow
	 * a nonprivileged user to use the last ten processes; don't let root
	 * exceed the limit. The variable nprocs is the current number of
	 * processes, maxproc is the limit.
	 */
	sx_xlock(&allproc_lock);
	if ((nprocs >= maxproc - 10 && priv_check_cred(td->td_ucred,
	    PRIV_MAXPROC, 0) != 0) || nprocs >= maxproc) {
		error = EAGAIN;
		goto fail;
	}

	/*
	 * Increment the count of procs running with this uid. Don't allow
	 * a nonprivileged user to exceed their current limit.
	 *
	 * XXXRW: Can we avoid privilege here if it's not needed?
	 */
	error = priv_check_cred(td->td_ucred, PRIV_PROC_LIMIT, 0);
	if (error == 0)
		ok = chgproccnt(td->td_ucred->cr_ruidinfo, 1, 0);
	else {
		PROC_LOCK(p1);
		ok = chgproccnt(td->td_ucred->cr_ruidinfo, 1,
		    lim_cur(p1, RLIMIT_NPROC));
		PROC_UNLOCK(p1);
	}
	if (ok) {
		do_fork(td, flags, newproc, td2, vm2, pdflags);

		/*
		 * Return child proc pointer to parent.
		 */
		*procp = newproc;
#ifdef PROCDESC
		if (flags & RFPROCDESC)
			procdesc_finit(newproc->p_procdesc, fp_procdesc);
#endif
		racct_proc_fork_done(newproc);
		return (0);
	}

	error = EAGAIN;
fail:
	sx_sunlock(&proctree_lock);
	if (ppsratecheck(&lastfail, &curfail, 1))
		printf("maxproc limit exceeded by uid %i, please see tuning(7) and login.conf(5).\n",
		    td->td_ucred->cr_ruid);
	sx_xunlock(&allproc_lock);
#ifdef MAC
	mac_proc_destroy(newproc);
#endif
fail1:
	racct_proc_exit(newproc);
	if (vm2 != NULL)
		vmspace_free(vm2);
	uma_zfree(proc_zone, newproc);
#ifdef PROCDESC
	if (((flags & RFPROCDESC) != 0) && (fp_procdesc != NULL))
		fdrop(fp_procdesc, td);
#endif
	pause("fork", hz / 2);
	return (error);
}

/*
 * Handle the return of a child process from fork1().  This function
 * is called from the MD fork_trampoline() entry point.
 */
void
fork_exit(void (*callout)(void *, struct trapframe *), void *arg,
    struct trapframe *frame)
{
	struct proc *p;
	struct thread *td;
	struct thread *dtd;

	td = curthread;
	p = td->td_proc;
	KASSERT(p->p_state == PRS_NORMAL, ("executing process is still new"));

	CTR4(KTR_PROC, "fork_exit: new thread %p (td_sched %p, pid %d, %s)",
		td, td->td_sched, p->p_pid, td->td_name);

	sched_fork_exit(td);
	/*
	* Processes normally resume in mi_switch() after being
	* cpu_switch()'ed to, but when children start up they arrive here
	* instead, so we must do much the same things as mi_switch() would.
	*/
	if ((dtd = PCPU_GET(deadthread))) {
		PCPU_SET(deadthread, NULL);
		thread_stash(dtd);
	}
	thread_unlock(td);

	/*
	 * cpu_set_fork_handler intercepts this function call to
	 * have this call a non-return function to stay in kernel mode.
	 * initproc has its own fork handler, but it does return.
	 */
	KASSERT(callout != NULL, ("NULL callout in fork_exit"));
	callout(arg, frame);

	/*
	 * Check if a kernel thread misbehaved and returned from its main
	 * function.
	 */
	if (p->p_flag & P_KTHREAD) {
		printf("Kernel thread \"%s\" (pid %d) exited prematurely.\n",
		    td->td_name, p->p_pid);
		kproc_exit(0);
	}
	mtx_assert(&Giant, MA_NOTOWNED);

	if (p->p_sysent->sv_schedtail != NULL)
		(p->p_sysent->sv_schedtail)(td);
}

/*
 * Simplified back end of syscall(), used when returning from fork()
 * directly into user mode.  Giant is not held on entry, and must not
 * be held on return.  This function is passed in to fork_exit() as the
 * first parameter and is called when returning to a new userland process.
 */
void
fork_return(struct thread *td, struct trapframe *frame)
{
	struct proc *p, *dbg;

	if (td->td_dbgflags & TDB_STOPATFORK) {
		p = td->td_proc;
		sx_xlock(&proctree_lock);
		PROC_LOCK(p);
		if ((p->p_pptr->p_flag & (P_TRACED | P_FOLLOWFORK)) ==
		    (P_TRACED | P_FOLLOWFORK)) {
			/*
			 * If debugger still wants auto-attach for the
			 * parent's children, do it now.
			 */
			dbg = p->p_pptr->p_pptr;
			p->p_flag |= P_TRACED;
			p->p_oppid = p->p_pptr->p_pid;
			proc_reparent(p, dbg);
			sx_xunlock(&proctree_lock);
			ptracestop(td, SIGSTOP);
		} else {
			/*
			 * ... otherwise clear the request.
			 */
			sx_xunlock(&proctree_lock);
			td->td_dbgflags &= ~TDB_STOPATFORK;
			cv_broadcast(&p->p_dbgwait);
		}
		PROC_UNLOCK(p);
	}

	userret(td, frame);

#ifdef KTRACE
	if (KTRPOINT(td, KTR_SYSRET))
		ktrsysret(SYS_fork, 0, 0);
#endif
	mtx_assert(&Giant, MA_NOTOWNED);
}
OpenPOWER on IntegriCloud