ANSIfy the remaining K&R functions. Remove two bzero-after-malloc's in
[dragonfly.git] / sys / kern / kern_fork.c
CommitLineData
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1/*
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.
9 *
10 * Redistribution and use in source and binary forms, with or without
11 * modification, are permitted provided that the following conditions
12 * are met:
13 * 1. Redistributions of source code must retain the above copyright
14 * notice, this list of conditions and the following disclaimer.
15 * 2. Redistributions in binary form must reproduce the above copyright
16 * notice, this list of conditions and the following disclaimer in the
17 * documentation and/or other materials provided with the distribution.
18 * 3. All advertising materials mentioning features or use of this software
19 * must display the following acknowledgement:
20 * This product includes software developed by the University of
21 * California, Berkeley and its contributors.
22 * 4. Neither the name of the University nor the names of its contributors
23 * may be used to endorse or promote products derived from this software
24 * without specific prior written permission.
25 *
26 * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
27 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
28 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
29 * ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
30 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
31 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
32 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
33 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
34 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
35 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
36 * SUCH DAMAGE.
37 *
38 * @(#)kern_fork.c 8.6 (Berkeley) 4/8/94
5bc7cd8d 39 * $FreeBSD: src/sys/kern/kern_fork.c,v 1.72.2.14 2003/06/26 04:15:10 silby Exp $
1fa2b4b4 40 * $DragonFly: src/sys/kern/kern_fork.c,v 1.25 2004/06/04 20:35:36 dillon Exp $
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41 */
42
43#include "opt_ktrace.h"
44
45#include <sys/param.h>
46#include <sys/systm.h>
47#include <sys/sysproto.h>
48#include <sys/filedesc.h>
49#include <sys/kernel.h>
50#include <sys/sysctl.h>
51#include <sys/malloc.h>
52#include <sys/proc.h>
53#include <sys/resourcevar.h>
54#include <sys/vnode.h>
55#include <sys/acct.h>
56#include <sys/ktrace.h>
57#include <sys/unistd.h>
58#include <sys/jail.h>
e30f9e2c 59#include <sys/caps.h>
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60
61#include <vm/vm.h>
62#include <sys/lock.h>
63#include <vm/pmap.h>
64#include <vm/vm_map.h>
65#include <vm/vm_extern.h>
66#include <vm/vm_zone.h>
67
68#include <sys/vmmeter.h>
69#include <sys/user.h>
70
71static MALLOC_DEFINE(M_ATFORK, "atfork", "atfork callback");
72
73/*
74 * These are the stuctures used to create a callout list for things to do
75 * when forking a process
76 */
77struct forklist {
78 forklist_fn function;
79 TAILQ_ENTRY(forklist) next;
80};
81
82TAILQ_HEAD(forklist_head, forklist);
83static struct forklist_head fork_list = TAILQ_HEAD_INITIALIZER(fork_list);
84
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85int forksleep; /* Place for fork1() to sleep on. */
86
87/* ARGSUSED */
88int
41c20dac 89fork(struct fork_args *uap)
984263bc 90{
41c20dac 91 struct proc *p = curproc;
984263bc 92 struct proc *p2;
41c20dac 93 int error;
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94
95 error = fork1(p, RFFDG | RFPROC, &p2);
96 if (error == 0) {
7d0bac62 97 start_forked_proc(p, p2);
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98 uap->sysmsg_fds[0] = p2->p_pid;
99 uap->sysmsg_fds[1] = 0;
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100 }
101 return error;
102}
103
104/* ARGSUSED */
105int
41c20dac 106vfork(struct vfork_args *uap)
984263bc 107{
41c20dac 108 struct proc *p = curproc;
984263bc 109 struct proc *p2;
41c20dac 110 int error;
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111
112 error = fork1(p, RFFDG | RFPROC | RFPPWAIT | RFMEM, &p2);
113 if (error == 0) {
7d0bac62 114 start_forked_proc(p, p2);
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115 uap->sysmsg_fds[0] = p2->p_pid;
116 uap->sysmsg_fds[1] = 0;
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117 }
118 return error;
119}
120
121int
41c20dac 122rfork(struct rfork_args *uap)
984263bc 123{
41c20dac 124 struct proc *p = curproc;
984263bc 125 struct proc *p2;
41c20dac 126 int error;
984263bc 127
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128 /* Don't allow kernel only flags */
129 if ((uap->flags & RFKERNELONLY) != 0)
130 return (EINVAL);
131
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132 error = fork1(p, uap->flags, &p2);
133 if (error == 0) {
7d0bac62 134 start_forked_proc(p, p2);
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135 uap->sysmsg_fds[0] = p2 ? p2->p_pid : 0;
136 uap->sysmsg_fds[1] = 0;
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137 }
138 return error;
139}
140
141
142int nprocs = 1; /* process 0 */
143static int nextpid = 0;
144
145/*
146 * Random component to nextpid generation. We mix in a random factor to make
147 * it a little harder to predict. We sanity check the modulus value to avoid
148 * doing it in critical paths. Don't let it be too small or we pointlessly
149 * waste randomness entropy, and don't let it be impossibly large. Using a
150 * modulus that is too big causes a LOT more process table scans and slows
151 * down fork processing as the pidchecked caching is defeated.
152 */
153static int randompid = 0;
154
155static int
156sysctl_kern_randompid(SYSCTL_HANDLER_ARGS)
157{
158 int error, pid;
159
160 pid = randompid;
161 error = sysctl_handle_int(oidp, &pid, 0, req);
162 if (error || !req->newptr)
163 return (error);
164 if (pid < 0 || pid > PID_MAX - 100) /* out of range */
165 pid = PID_MAX - 100;
166 else if (pid < 2) /* NOP */
167 pid = 0;
168 else if (pid < 100) /* Make it reasonable */
169 pid = 100;
170 randompid = pid;
171 return (error);
172}
173
174SYSCTL_PROC(_kern, OID_AUTO, randompid, CTLTYPE_INT|CTLFLAG_RW,
175 0, 0, sysctl_kern_randompid, "I", "Random PID modulus");
176
177int
303c76d5 178fork1(struct proc *p1, int flags, struct proc **procp)
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179{
180 struct proc *p2, *pptr;
181 uid_t uid;
182 struct proc *newproc;
183 int ok;
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184 static int curfail = 0, pidchecked = 0;
185 static struct timeval lastfail;
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186 struct forklist *ep;
187 struct filedesc_to_leader *fdtol;
188
189 if ((flags & (RFFDG|RFCFDG)) == (RFFDG|RFCFDG))
190 return (EINVAL);
191
192 /*
193 * Here we don't create a new process, but we divorce
194 * certain parts of a process from itself.
195 */
196 if ((flags & RFPROC) == 0) {
197
198 vm_fork(p1, 0, flags);
199
200 /*
201 * Close all file descriptors.
202 */
203 if (flags & RFCFDG) {
204 struct filedesc *fdtmp;
205 fdtmp = fdinit(p1);
206 fdfree(p1);
207 p1->p_fd = fdtmp;
208 }
209
210 /*
211 * Unshare file descriptors (from parent.)
212 */
213 if (flags & RFFDG) {
214 if (p1->p_fd->fd_refcnt > 1) {
215 struct filedesc *newfd;
216 newfd = fdcopy(p1);
217 fdfree(p1);
218 p1->p_fd = newfd;
219 }
220 }
221 *procp = NULL;
222 return (0);
223 }
224
225 /*
226 * Although process entries are dynamically created, we still keep
227 * a global limit on the maximum number we will create. Don't allow
228 * a nonprivileged user to use the last ten processes; don't let root
229 * exceed the limit. The variable nprocs is the current number of
230 * processes, maxproc is the limit.
231 */
41c20dac 232 uid = p1->p_ucred->cr_ruid;
984263bc 233 if ((nprocs >= maxproc - 10 && uid != 0) || nprocs >= maxproc) {
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234 if (ppsratecheck(&lastfail, &curfail, 1))
235 printf("maxproc limit exceeded by uid %d, please "
236 "see tuning(7) and login.conf(5).\n", uid);
377d4740 237 tsleep(&forksleep, 0, "fork", hz / 2);
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238 return (EAGAIN);
239 }
240 /*
241 * Increment the nprocs resource before blocking can occur. There
242 * are hard-limits as to the number of processes that can run.
243 */
244 nprocs++;
245
246 /*
247 * Increment the count of procs running with this uid. Don't allow
248 * a nonprivileged user to exceed their current limit.
249 */
41c20dac 250 ok = chgproccnt(p1->p_ucred->cr_ruidinfo, 1,
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251 (uid != 0) ? p1->p_rlimit[RLIMIT_NPROC].rlim_cur : 0);
252 if (!ok) {
253 /*
254 * Back out the process count
255 */
256 nprocs--;
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257 if (ppsratecheck(&lastfail, &curfail, 1))
258 printf("maxproc limit exceeded by uid %d, please "
259 "see tuning(7) and login.conf(5).\n", uid);
377d4740 260 tsleep(&forksleep, 0, "fork", hz / 2);
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261 return (EAGAIN);
262 }
263
264 /* Allocate new proc. */
265 newproc = zalloc(proc_zone);
266
267 /*
268 * Setup linkage for kernel based threading
269 */
303c76d5 270 if ((flags & RFTHREAD) != 0) {
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271 newproc->p_peers = p1->p_peers;
272 p1->p_peers = newproc;
273 newproc->p_leader = p1->p_leader;
274 } else {
275 newproc->p_peers = 0;
276 newproc->p_leader = newproc;
277 }
278
279 newproc->p_wakeup = 0;
984263bc 280 newproc->p_vmspace = NULL;
1fa2b4b4 281 TAILQ_INIT(&newproc->p_sysmsgq);
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282
283 /*
284 * Find an unused process ID. We remember a range of unused IDs
285 * ready to use (from nextpid+1 through pidchecked-1).
286 */
287 nextpid++;
288 if (randompid)
289 nextpid += arc4random() % randompid;
290retry:
291 /*
292 * If the process ID prototype has wrapped around,
293 * restart somewhat above 0, as the low-numbered procs
294 * tend to include daemons that don't exit.
295 */
296 if (nextpid >= PID_MAX) {
297 nextpid = nextpid % PID_MAX;
298 if (nextpid < 100)
299 nextpid += 100;
300 pidchecked = 0;
301 }
302 if (nextpid >= pidchecked) {
303 int doingzomb = 0;
304
305 pidchecked = PID_MAX;
306 /*
307 * Scan the active and zombie procs to check whether this pid
308 * is in use. Remember the lowest pid that's greater
309 * than nextpid, so we can avoid checking for a while.
310 */
311 p2 = LIST_FIRST(&allproc);
312again:
313 for (; p2 != 0; p2 = LIST_NEXT(p2, p_list)) {
314 while (p2->p_pid == nextpid ||
315 p2->p_pgrp->pg_id == nextpid ||
316 p2->p_session->s_sid == nextpid) {
317 nextpid++;
318 if (nextpid >= pidchecked)
319 goto retry;
320 }
321 if (p2->p_pid > nextpid && pidchecked > p2->p_pid)
322 pidchecked = p2->p_pid;
323 if (p2->p_pgrp->pg_id > nextpid &&
324 pidchecked > p2->p_pgrp->pg_id)
325 pidchecked = p2->p_pgrp->pg_id;
326 if (p2->p_session->s_sid > nextpid &&
327 pidchecked > p2->p_session->s_sid)
328 pidchecked = p2->p_session->s_sid;
329 }
330 if (!doingzomb) {
331 doingzomb = 1;
332 p2 = LIST_FIRST(&zombproc);
333 goto again;
334 }
335 }
336
337 p2 = newproc;
338 p2->p_stat = SIDL; /* protect against others */
339 p2->p_pid = nextpid;
340 LIST_INSERT_HEAD(&allproc, p2, p_list);
341 LIST_INSERT_HEAD(PIDHASH(p2->p_pid), p2, p_hash);
342
343 /*
344 * Make a proc table entry for the new process.
345 * Start by zeroing the section of proc that is zero-initialized,
346 * then copy the section that is copied directly from the parent.
347 */
348 bzero(&p2->p_startzero,
349 (unsigned) ((caddr_t)&p2->p_endzero - (caddr_t)&p2->p_startzero));
350 bcopy(&p1->p_startcopy, &p2->p_startcopy,
351 (unsigned) ((caddr_t)&p2->p_endcopy - (caddr_t)&p2->p_startcopy));
352
353 p2->p_aioinfo = NULL;
354
355 /*
356 * Duplicate sub-structures as needed.
357 * Increase reference counts on shared objects.
358 * The p_stats and p_sigacts substructs are set in vm_fork.
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359 *
360 * P_CP_RELEASED indicates that the process is starting out in
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361 * the kernel (in the fork trampoline). The flag will be cleared
362 * when the new process calls userret() and acquires its current
363 * process designation for the return to userland.
984263bc 364 */
a2a5ad0d 365 p2->p_flag = P_INMEM | P_CP_RELEASED;
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366 if (p1->p_flag & P_PROFIL)
367 startprofclock(p2);
dadab5e9 368 p2->p_ucred = crhold(p1->p_ucred);
984263bc 369
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370 if (p2->p_ucred->cr_prison) {
371 p2->p_ucred->cr_prison->pr_ref++;
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372 p2->p_flag |= P_JAILED;
373 }
374
375 if (p2->p_args)
376 p2->p_args->ar_ref++;
377
378 if (flags & RFSIGSHARE) {
379 p2->p_procsig = p1->p_procsig;
380 p2->p_procsig->ps_refcnt++;
381 if (p1->p_sigacts == &p1->p_addr->u_sigacts) {
382 struct sigacts *newsigacts;
383 int s;
384
385 /* Create the shared sigacts structure */
386 MALLOC(newsigacts, struct sigacts *,
387 sizeof(struct sigacts), M_SUBPROC, M_WAITOK);
388 s = splhigh();
389 /*
390 * Set p_sigacts to the new shared structure.
391 * Note that this is updating p1->p_sigacts at the
392 * same time, since p_sigacts is just a pointer to
393 * the shared p_procsig->ps_sigacts.
394 */
395 p2->p_sigacts = newsigacts;
396 bcopy(&p1->p_addr->u_sigacts, p2->p_sigacts,
397 sizeof(*p2->p_sigacts));
398 *p2->p_sigacts = p1->p_addr->u_sigacts;
399 splx(s);
400 }
401 } else {
402 MALLOC(p2->p_procsig, struct procsig *, sizeof(struct procsig),
403 M_SUBPROC, M_WAITOK);
404 bcopy(p1->p_procsig, p2->p_procsig, sizeof(*p2->p_procsig));
405 p2->p_procsig->ps_refcnt = 1;
406 p2->p_sigacts = NULL; /* finished in vm_fork() */
407 }
408 if (flags & RFLINUXTHPN)
409 p2->p_sigparent = SIGUSR1;
410 else
411 p2->p_sigparent = SIGCHLD;
412
413 /* bump references to the text vnode (for procfs) */
414 p2->p_textvp = p1->p_textvp;
415 if (p2->p_textvp)
597aea93 416 vref(p2->p_textvp);
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417
418 if (flags & RFCFDG) {
419 p2->p_fd = fdinit(p1);
420 fdtol = NULL;
421 } else if (flags & RFFDG) {
422 p2->p_fd = fdcopy(p1);
423 fdtol = NULL;
424 } else {
425 p2->p_fd = fdshare(p1);
426 if (p1->p_fdtol == NULL)
427 p1->p_fdtol =
428 filedesc_to_leader_alloc(NULL,
429 p1->p_leader);
430 if ((flags & RFTHREAD) != 0) {
431 /*
432 * Shared file descriptor table and
433 * shared process leaders.
434 */
435 fdtol = p1->p_fdtol;
436 fdtol->fdl_refcount++;
437 } else {
438 /*
439 * Shared file descriptor table, and
440 * different process leaders
441 */
98a7f915 442 fdtol = filedesc_to_leader_alloc(p1->p_fdtol, p2);
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443 }
444 }
445 p2->p_fdtol = fdtol;
446
447 /*
448 * If p_limit is still copy-on-write, bump refcnt,
449 * otherwise get a copy that won't be modified.
450 * (If PL_SHAREMOD is clear, the structure is shared
451 * copy-on-write.)
452 */
303c76d5 453 if (p1->p_limit->p_lflags & PL_SHAREMOD) {
984263bc 454 p2->p_limit = limcopy(p1->p_limit);
303c76d5 455 } else {
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456 p2->p_limit = p1->p_limit;
457 p2->p_limit->p_refcnt++;
458 }
459
460 /*
461 * Preserve some more flags in subprocess. P_PROFIL has already
462 * been preserved.
463 */
464 p2->p_flag |= p1->p_flag & (P_SUGID | P_ALTSTACK);
465 if (p1->p_session->s_ttyvp != NULL && p1->p_flag & P_CONTROLT)
466 p2->p_flag |= P_CONTROLT;
467 if (flags & RFPPWAIT)
468 p2->p_flag |= P_PPWAIT;
469
470 LIST_INSERT_AFTER(p1, p2, p_pglist);
471
472 /*
473 * Attach the new process to its parent.
474 *
475 * If RFNOWAIT is set, the newly created process becomes a child
476 * of init. This effectively disassociates the child from the
477 * parent.
478 */
479 if (flags & RFNOWAIT)
480 pptr = initproc;
481 else
482 pptr = p1;
483 p2->p_pptr = pptr;
484 LIST_INSERT_HEAD(&pptr->p_children, p2, p_sibling);
485 LIST_INIT(&p2->p_children);
98a7f915 486 varsymset_init(&p2->p_varsymset, &p1->p_varsymset);
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487
488#ifdef KTRACE
489 /*
490 * Copy traceflag and tracefile if enabled. If not inherited,
491 * these were zeroed above but we still could have a trace race
492 * so make sure p2's p_tracep is NULL.
493 */
494 if ((p1->p_traceflag & KTRFAC_INHERIT) && p2->p_tracep == NULL) {
495 p2->p_traceflag = p1->p_traceflag;
496 if ((p2->p_tracep = p1->p_tracep) != NULL)
597aea93 497 vref(p2->p_tracep);
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498 }
499#endif
500
501 /*
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502 * Give the child process an estcpu skewed towards the batch side
503 * of the parent. This prevents batch programs from glitching
504 * interactive programs when they are first started. If the child
505 * is not a batch program it's priority will be corrected by the
506 * scheduler.
984263bc 507 */
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508 p2->p_estcpu_fork = p2->p_estcpu =
509 ESTCPULIM(p1->p_estcpu + ESTCPURAMP);
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510
511 /*
512 * This begins the section where we must prevent the parent
513 * from being swapped.
514 */
515 PHOLD(p1);
516
517 /*
518 * Finish creating the child process. It will return via a different
519 * execution path later. (ie: directly into user mode)
520 */
521 vm_fork(p1, p2, flags);
e30f9e2c 522 caps_fork(p1, p2, flags);
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523
524 if (flags == (RFFDG | RFPROC)) {
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525 mycpu->gd_cnt.v_forks++;
526 mycpu->gd_cnt.v_forkpages += p2->p_vmspace->vm_dsize + p2->p_vmspace->vm_ssize;
984263bc 527 } else if (flags == (RFFDG | RFPROC | RFPPWAIT | RFMEM)) {
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528 mycpu->gd_cnt.v_vforks++;
529 mycpu->gd_cnt.v_vforkpages += p2->p_vmspace->vm_dsize + p2->p_vmspace->vm_ssize;
984263bc 530 } else if (p1 == &proc0) {
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531 mycpu->gd_cnt.v_kthreads++;
532 mycpu->gd_cnt.v_kthreadpages += p2->p_vmspace->vm_dsize + p2->p_vmspace->vm_ssize;
984263bc 533 } else {
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534 mycpu->gd_cnt.v_rforks++;
535 mycpu->gd_cnt.v_rforkpages += p2->p_vmspace->vm_dsize + p2->p_vmspace->vm_ssize;
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536 }
537
538 /*
539 * Both processes are set up, now check if any loadable modules want
540 * to adjust anything.
541 * What if they have an error? XXX
542 */
543 TAILQ_FOREACH(ep, &fork_list, next) {
544 (*ep->function)(p1, p2, flags);
545 }
546
547 /*
548 * Make child runnable and add to run queue.
549 */
550 microtime(&(p2->p_stats->p_start));
551 p2->p_acflag = AFORK;
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552
553 /*
554 * tell any interested parties about the new process
555 */
556 KNOTE(&p1->p_klist, NOTE_FORK | p2->p_pid);
557
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558 /*
559 * Return child proc pointer to parent.
560 */
561 *procp = p2;
562 return (0);
563}
564
565/*
566 * The next two functionms are general routines to handle adding/deleting
567 * items on the fork callout list.
568 *
569 * at_fork():
570 * Take the arguments given and put them onto the fork callout list,
571 * However first make sure that it's not already there.
572 * Returns 0 on success or a standard error number.
573 */
984263bc 574int
303c76d5 575at_fork(forklist_fn function)
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576{
577 struct forklist *ep;
578
579#ifdef INVARIANTS
580 /* let the programmer know if he's been stupid */
303c76d5 581 if (rm_at_fork(function)) {
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582 printf("WARNING: fork callout entry (%p) already present\n",
583 function);
303c76d5 584 }
984263bc 585#endif
679246c3 586 ep = malloc(sizeof(*ep), M_ATFORK, M_WAITOK|M_ZERO);
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587 ep->function = function;
588 TAILQ_INSERT_TAIL(&fork_list, ep, next);
589 return (0);
590}
591
592/*
593 * Scan the exit callout list for the given item and remove it..
594 * Returns the number of items removed (0 or 1)
595 */
984263bc 596int
303c76d5 597rm_at_fork(forklist_fn function)
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598{
599 struct forklist *ep;
600
601 TAILQ_FOREACH(ep, &fork_list, next) {
602 if (ep->function == function) {
603 TAILQ_REMOVE(&fork_list, ep, next);
604 free(ep, M_ATFORK);
605 return(1);
606 }
607 }
608 return (0);
609}
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610
611/*
612 * Add a forked process to the run queue after any remaining setup, such
613 * as setting the fork handler, has been completed.
614 */
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615void
616start_forked_proc(struct proc *p1, struct proc *p2)
617{
618 /*
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619 * Move from SIDL to RUN queue, and activate the process's thread.
620 * Activation of the thread effectively makes the process "a"
621 * current process, so we do not setrunqueue().
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622 */
623 KASSERT(p2->p_stat == SIDL,
624 ("cannot start forked process, bad status: %p", p2));
4dcad57e 625 resetpriority(p2);
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626 (void) splhigh();
627 p2->p_stat = SRUN;
628 setrunqueue(p2);
629 (void) spl0();
630
631 /*
632 * Now can be swapped.
633 */
634 PRELE(p1);
635
636 /*
637 * Preserve synchronization semantics of vfork. If waiting for
638 * child to exec or exit, set P_PPWAIT on child, and sleep on our
639 * proc (in case of exit).
640 */
641 while (p2->p_flag & P_PPWAIT)
377d4740 642 tsleep(p1, 0, "ppwait", 0);
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643}
644