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38 * @(#)kern_fork.c 8.6 (Berkeley) 4/8/94
39 * $FreeBSD: src/sys/kern/kern_fork.c,v 1.72.2.14 2003/06/26 04:15:10 silby Exp $
40 * $DragonFly: src/sys/kern/kern_fork.c,v 1.55 2006/09/05 00:55:45 dillon Exp $
43 #include "opt_ktrace.h"
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>
53 #include <sys/resourcevar.h>
54 #include <sys/vnode.h>
56 #include <sys/ktrace.h>
57 #include <sys/unistd.h>
64 #include <vm/vm_map.h>
65 #include <vm/vm_extern.h>
66 #include <vm/vm_zone.h>
68 #include <sys/vmmeter.h>
70 #include <sys/thread2.h>
72 static MALLOC_DEFINE(M_ATFORK, "atfork", "atfork callback");
75 * These are the stuctures used to create a callout list for things to do
76 * when forking a process
80 TAILQ_ENTRY(forklist) next;
83 TAILQ_HEAD(forklist_head, forklist);
84 static struct forklist_head fork_list = TAILQ_HEAD_INITIALIZER(fork_list);
86 int forksleep; /* Place for fork1() to sleep on. */
90 sys_fork(struct fork_args *uap)
92 struct lwp *lp = curthread->td_lwp;
96 error = fork1(lp, RFFDG | RFPROC, &p2);
98 start_forked_proc(lp, p2);
99 uap->sysmsg_fds[0] = p2->p_pid;
100 uap->sysmsg_fds[1] = 0;
107 sys_vfork(struct vfork_args *uap)
109 struct lwp *lp = curthread->td_lwp;
113 error = fork1(lp, RFFDG | RFPROC | RFPPWAIT | RFMEM, &p2);
115 start_forked_proc(lp, p2);
116 uap->sysmsg_fds[0] = p2->p_pid;
117 uap->sysmsg_fds[1] = 0;
123 * Handle rforks. An rfork may (1) operate on the current process without
124 * creating a new, (2) create a new process that shared the current process's
125 * vmspace, signals, and/or descriptors, or (3) create a new process that does
126 * not share these things (normal fork).
128 * Note that we only call start_forked_proc() if a new process is actually
131 * rfork { int flags }
134 sys_rfork(struct rfork_args *uap)
136 struct lwp *lp = curthread->td_lwp;
140 if ((uap->flags & RFKERNELONLY) != 0)
143 error = fork1(lp, uap->flags, &p2);
146 start_forked_proc(lp, p2);
147 uap->sysmsg_fds[0] = p2 ? p2->p_pid : 0;
148 uap->sysmsg_fds[1] = 0;
154 int nprocs = 1; /* process 0 */
157 fork1(struct lwp *lp1, int flags, struct proc **procp)
159 struct proc *p1 = lp1->lwp_proc;
160 struct proc *p2, *pptr;
164 static int curfail = 0;
165 static struct timeval lastfail;
167 struct filedesc_to_leader *fdtol;
169 if ((flags & (RFFDG|RFCFDG)) == (RFFDG|RFCFDG))
173 * Here we don't create a new process, but we divorce
174 * certain parts of a process from itself.
176 if ((flags & RFPROC) == 0) {
178 vm_fork(p1, 0, flags);
181 * Close all file descriptors.
183 if (flags & RFCFDG) {
184 struct filedesc *fdtmp;
191 * Unshare file descriptors (from parent.)
194 if (p1->p_fd->fd_refcnt > 1) {
195 struct filedesc *newfd;
206 * Although process entries are dynamically created, we still keep
207 * a global limit on the maximum number we will create. Don't allow
208 * a nonprivileged user to use the last ten processes; don't let root
209 * exceed the limit. The variable nprocs is the current number of
210 * processes, maxproc is the limit.
212 uid = p1->p_ucred->cr_ruid;
213 if ((nprocs >= maxproc - 10 && uid != 0) || nprocs >= maxproc) {
214 if (ppsratecheck(&lastfail, &curfail, 1))
215 printf("maxproc limit exceeded by uid %d, please "
216 "see tuning(7) and login.conf(5).\n", uid);
217 tsleep(&forksleep, 0, "fork", hz / 2);
221 * Increment the nprocs resource before blocking can occur. There
222 * are hard-limits as to the number of processes that can run.
227 * Increment the count of procs running with this uid. Don't allow
228 * a nonprivileged user to exceed their current limit.
230 ok = chgproccnt(p1->p_ucred->cr_ruidinfo, 1,
231 (uid != 0) ? p1->p_rlimit[RLIMIT_NPROC].rlim_cur : 0);
234 * Back out the process count
237 if (ppsratecheck(&lastfail, &curfail, 1))
238 printf("maxproc limit exceeded by uid %d, please "
239 "see tuning(7) and login.conf(5).\n", uid);
240 tsleep(&forksleep, 0, "fork", hz / 2);
244 /* Allocate new proc. */
245 p2 = zalloc(proc_zone);
248 * Setup linkage for kernel based threading XXX lwp
250 if (flags & RFTHREAD) {
251 p2->p_peers = p1->p_peers;
253 p2->p_leader = p1->p_leader;
260 p2->p_vmspace = NULL;
261 p2->p_numposixlocks = 0;
262 p2->p_emuldata = NULL;
263 LIST_INIT(&p2->p_lwps);
269 LIST_INSERT_HEAD(&p2->p_lwps, lp2, lwp_list);
275 * Setting the state to SIDL protects the partially initialized
276 * process once it starts getting hooked into the rest of the system.
279 proc_add_allproc(p2);
282 * Make a proc table entry for the new process.
283 * Start by zeroing the section of proc that is zero-initialized,
284 * then copy the section that is copied directly from the parent.
286 bzero(&p2->p_startzero,
287 (unsigned) ((caddr_t)&p2->p_endzero - (caddr_t)&p2->p_startzero));
288 bzero(&lp2->lwp_startzero,
289 (unsigned) ((caddr_t)&lp2->lwp_endzero -
290 (caddr_t)&lp2->lwp_startzero));
291 bcopy(&p1->p_startcopy, &p2->p_startcopy,
292 (unsigned) ((caddr_t)&p2->p_endcopy - (caddr_t)&p2->p_startcopy));
293 bcopy(&p1->p_lwp.lwp_startcopy, &lp2->lwp_startcopy,
294 (unsigned) ((caddr_t)&lp2->lwp_endcopy -
295 (caddr_t)&lp2->lwp_startcopy));
297 p2->p_aioinfo = NULL;
300 * Duplicate sub-structures as needed.
301 * Increase reference counts on shared objects.
302 * The p_stats and p_sigacts substructs are set in vm_fork.
303 * p_lock is in the copy area and must be cleared.
307 if (p1->p_flag & P_PROFIL)
309 p2->p_ucred = crhold(p1->p_ucred);
311 if (jailed(p2->p_ucred))
312 p2->p_flag |= P_JAILED;
315 p2->p_args->ar_ref++;
317 if (flags & RFSIGSHARE) {
318 p2->p_procsig = p1->p_procsig;
319 p2->p_procsig->ps_refcnt++;
320 if (p1->p_sigacts == &p1->p_addr->u_sigacts) {
321 struct sigacts *newsigacts;
323 /* Create the shared sigacts structure */
324 MALLOC(newsigacts, struct sigacts *,
325 sizeof(struct sigacts), M_SUBPROC, M_WAITOK);
328 * Set p_sigacts to the new shared structure.
329 * Note that this is updating p1->p_sigacts at the
330 * same time, since p_sigacts is just a pointer to
331 * the shared p_procsig->ps_sigacts.
333 p2->p_sigacts = newsigacts;
334 bcopy(&p1->p_addr->u_sigacts, p2->p_sigacts,
335 sizeof(*p2->p_sigacts));
336 *p2->p_sigacts = p1->p_addr->u_sigacts;
340 MALLOC(p2->p_procsig, struct procsig *, sizeof(struct procsig),
341 M_SUBPROC, M_WAITOK);
342 bcopy(p1->p_procsig, p2->p_procsig, sizeof(*p2->p_procsig));
343 p2->p_procsig->ps_refcnt = 1;
344 p2->p_sigacts = NULL; /* finished in vm_fork() */
346 if (flags & RFLINUXTHPN)
347 p2->p_sigparent = SIGUSR1;
349 p2->p_sigparent = SIGCHLD;
351 /* bump references to the text vnode (for procfs) */
352 p2->p_textvp = p1->p_textvp;
356 if (flags & RFCFDG) {
357 p2->p_fd = fdinit(p1);
359 } else if (flags & RFFDG) {
360 p2->p_fd = fdcopy(p1);
363 p2->p_fd = fdshare(p1);
364 if (p1->p_fdtol == NULL)
366 filedesc_to_leader_alloc(NULL,
368 if ((flags & RFTHREAD) != 0) {
370 * Shared file descriptor table and
371 * shared process leaders.
374 fdtol->fdl_refcount++;
377 * Shared file descriptor table, and
378 * different process leaders
380 fdtol = filedesc_to_leader_alloc(p1->p_fdtol, p2);
384 p2->p_limit = plimit_fork(p1->p_limit);
387 * Preserve some more flags in subprocess. P_PROFIL has already
390 p2->p_flag |= p1->p_flag & (P_SUGID | P_ALTSTACK);
391 if (p1->p_session->s_ttyvp != NULL && p1->p_flag & P_CONTROLT)
392 p2->p_flag |= P_CONTROLT;
393 if (flags & RFPPWAIT)
394 p2->p_flag |= P_PPWAIT;
397 * Once we are on a pglist we may receive signals. XXX we might
398 * race a ^C being sent to the process group by not receiving it
399 * at all prior to this line.
401 LIST_INSERT_AFTER(p1, p2, p_pglist);
404 * Attach the new process to its parent.
406 * If RFNOWAIT is set, the newly created process becomes a child
407 * of init. This effectively disassociates the child from the
410 if (flags & RFNOWAIT)
415 LIST_INSERT_HEAD(&pptr->p_children, p2, p_sibling);
416 LIST_INIT(&p2->p_children);
417 varsymset_init(&p2->p_varsymset, &p1->p_varsymset);
418 callout_init(&p2->p_ithandle);
422 * Copy traceflag and tracefile if enabled. If not inherited,
423 * these were zeroed above but we still could have a trace race
424 * so make sure p2's p_tracenode is NULL.
426 if ((p1->p_traceflag & KTRFAC_INHERIT) && p2->p_tracenode == NULL) {
427 p2->p_traceflag = p1->p_traceflag;
428 p2->p_tracenode = ktrinherit(p1->p_tracenode);
433 * Inherit the scheduler and initialize scheduler-related fields.
434 * Set cpbase to the last timeout that occured (not the upcoming
437 * A critical section is required since a timer IPI can update
438 * scheduler specific data.
441 p2->p_usched = p1->p_usched;
442 lp2->lwp_cpbase = mycpu->gd_schedclock.time -
443 mycpu->gd_schedclock.periodic;
444 p2->p_usched->heuristic_forking(&p1->p_lwp, lp2);
448 * This begins the section where we must prevent the parent
449 * from being swapped.
454 * Finish creating the child process. It will return via a different
455 * execution path later. (ie: directly into user mode)
457 vm_fork(p1, p2, flags);
458 caps_fork(p1, p2, flags);
460 if (flags == (RFFDG | RFPROC)) {
461 mycpu->gd_cnt.v_forks++;
462 mycpu->gd_cnt.v_forkpages += p2->p_vmspace->vm_dsize + p2->p_vmspace->vm_ssize;
463 } else if (flags == (RFFDG | RFPROC | RFPPWAIT | RFMEM)) {
464 mycpu->gd_cnt.v_vforks++;
465 mycpu->gd_cnt.v_vforkpages += p2->p_vmspace->vm_dsize + p2->p_vmspace->vm_ssize;
466 } else if (p1 == &proc0) {
467 mycpu->gd_cnt.v_kthreads++;
468 mycpu->gd_cnt.v_kthreadpages += p2->p_vmspace->vm_dsize + p2->p_vmspace->vm_ssize;
470 mycpu->gd_cnt.v_rforks++;
471 mycpu->gd_cnt.v_rforkpages += p2->p_vmspace->vm_dsize + p2->p_vmspace->vm_ssize;
475 * Both processes are set up, now check if any loadable modules want
476 * to adjust anything.
477 * What if they have an error? XXX
479 TAILQ_FOREACH(ep, &fork_list, next) {
480 (*ep->function)(p1, p2, flags);
484 * Set the start time. Note that the process is not runnable. The
485 * caller is responsible for making it runnable.
487 microtime(&p2->p_start);
488 p2->p_acflag = AFORK;
491 * tell any interested parties about the new process
493 KNOTE(&p1->p_klist, NOTE_FORK | p2->p_pid);
496 * Return child proc pointer to parent.
503 * The next two functionms are general routines to handle adding/deleting
504 * items on the fork callout list.
507 * Take the arguments given and put them onto the fork callout list,
508 * However first make sure that it's not already there.
509 * Returns 0 on success or a standard error number.
512 at_fork(forklist_fn function)
517 /* let the programmer know if he's been stupid */
518 if (rm_at_fork(function)) {
519 printf("WARNING: fork callout entry (%p) already present\n",
523 ep = kmalloc(sizeof(*ep), M_ATFORK, M_WAITOK|M_ZERO);
524 ep->function = function;
525 TAILQ_INSERT_TAIL(&fork_list, ep, next);
530 * Scan the exit callout list for the given item and remove it..
531 * Returns the number of items removed (0 or 1)
534 rm_at_fork(forklist_fn function)
538 TAILQ_FOREACH(ep, &fork_list, next) {
539 if (ep->function == function) {
540 TAILQ_REMOVE(&fork_list, ep, next);
549 * Add a forked process to the run queue after any remaining setup, such
550 * as setting the fork handler, has been completed.
553 start_forked_proc(struct lwp *lp1, struct proc *p2)
557 KKASSERT(p2 != NULL && p2->p_nthreads == 1);
559 lp2 = LIST_FIRST(&p2->p_lwps);
562 * Move from SIDL to RUN queue, and activate the process's thread.
563 * Activation of the thread effectively makes the process "a"
564 * current process, so we do not setrunqueue().
566 * YYY setrunqueue works here but we should clean up the trampoline
567 * code so we just schedule the LWKT thread and let the trampoline
568 * deal with the userland scheduler on return to userland.
570 KASSERT(p2->p_stat == SIDL,
571 ("cannot start forked process, bad status: %p", p2));
572 p2->p_usched->resetpriority(lp2);
575 p2->p_usched->setrunqueue(lp2);
579 * Now can be swapped.
581 PRELE(lp1->lwp_proc);
584 * Preserve synchronization semantics of vfork. If waiting for
585 * child to exec or exit, set P_PPWAIT on child, and sleep on our
586 * proc (in case of exit).
588 while (p2->p_flag & P_PPWAIT)
589 tsleep(lp1->lwp_proc, 0, "ppwait", 0);