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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 1.53 2006/06/05 18:02:14 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 TAILQ_INIT(&p2->p_lwp.lwp_sysmsgq);
264 LIST_INIT(&p2->p_lwps);
270 LIST_INSERT_HEAD(&p2->p_lwps, lp2, lwp_list);
276 * Setting the state to SIDL protects the partially initialized
277 * process once it starts getting hooked into the rest of the system.
280 proc_add_allproc(p2);
283 * Make a proc table entry for the new process.
284 * Start by zeroing the section of proc that is zero-initialized,
285 * then copy the section that is copied directly from the parent.
287 bzero(&p2->p_startzero,
288 (unsigned) ((caddr_t)&p2->p_endzero - (caddr_t)&p2->p_startzero));
289 bzero(&lp2->lwp_startzero,
290 (unsigned) ((caddr_t)&lp2->lwp_endzero -
291 (caddr_t)&lp2->lwp_startzero));
292 bcopy(&p1->p_startcopy, &p2->p_startcopy,
293 (unsigned) ((caddr_t)&p2->p_endcopy - (caddr_t)&p2->p_startcopy));
294 bcopy(&p1->p_lwp.lwp_startcopy, &lp2->lwp_startcopy,
295 (unsigned) ((caddr_t)&lp2->lwp_endcopy -
296 (caddr_t)&lp2->lwp_startcopy));
298 p2->p_aioinfo = NULL;
301 * Duplicate sub-structures as needed.
302 * Increase reference counts on shared objects.
303 * The p_stats and p_sigacts substructs are set in vm_fork.
304 * p_lock is in the copy area and must be cleared.
308 if (p1->p_flag & P_PROFIL)
310 p2->p_ucred = crhold(p1->p_ucred);
312 if (jailed(p2->p_ucred))
313 p2->p_flag |= P_JAILED;
316 p2->p_args->ar_ref++;
318 if (flags & RFSIGSHARE) {
319 p2->p_procsig = p1->p_procsig;
320 p2->p_procsig->ps_refcnt++;
321 if (p1->p_sigacts == &p1->p_addr->u_sigacts) {
322 struct sigacts *newsigacts;
324 /* Create the shared sigacts structure */
325 MALLOC(newsigacts, struct sigacts *,
326 sizeof(struct sigacts), M_SUBPROC, M_WAITOK);
329 * Set p_sigacts to the new shared structure.
330 * Note that this is updating p1->p_sigacts at the
331 * same time, since p_sigacts is just a pointer to
332 * the shared p_procsig->ps_sigacts.
334 p2->p_sigacts = newsigacts;
335 bcopy(&p1->p_addr->u_sigacts, p2->p_sigacts,
336 sizeof(*p2->p_sigacts));
337 *p2->p_sigacts = p1->p_addr->u_sigacts;
341 MALLOC(p2->p_procsig, struct procsig *, sizeof(struct procsig),
342 M_SUBPROC, M_WAITOK);
343 bcopy(p1->p_procsig, p2->p_procsig, sizeof(*p2->p_procsig));
344 p2->p_procsig->ps_refcnt = 1;
345 p2->p_sigacts = NULL; /* finished in vm_fork() */
347 if (flags & RFLINUXTHPN)
348 p2->p_sigparent = SIGUSR1;
350 p2->p_sigparent = SIGCHLD;
352 /* bump references to the text vnode (for procfs) */
353 p2->p_textvp = p1->p_textvp;
357 if (flags & RFCFDG) {
358 p2->p_fd = fdinit(p1);
360 } else if (flags & RFFDG) {
361 p2->p_fd = fdcopy(p1);
364 p2->p_fd = fdshare(p1);
365 if (p1->p_fdtol == NULL)
367 filedesc_to_leader_alloc(NULL,
369 if ((flags & RFTHREAD) != 0) {
371 * Shared file descriptor table and
372 * shared process leaders.
375 fdtol->fdl_refcount++;
378 * Shared file descriptor table, and
379 * different process leaders
381 fdtol = filedesc_to_leader_alloc(p1->p_fdtol, p2);
385 p2->p_limit = plimit_fork(p1->p_limit);
388 * Preserve some more flags in subprocess. P_PROFIL has already
391 p2->p_flag |= p1->p_flag & (P_SUGID | P_ALTSTACK);
392 if (p1->p_session->s_ttyvp != NULL && p1->p_flag & P_CONTROLT)
393 p2->p_flag |= P_CONTROLT;
394 if (flags & RFPPWAIT)
395 p2->p_flag |= P_PPWAIT;
398 * Once we are on a pglist we may receive signals. XXX we might
399 * race a ^C being sent to the process group by not receiving it
400 * at all prior to this line.
402 LIST_INSERT_AFTER(p1, p2, p_pglist);
405 * Attach the new process to its parent.
407 * If RFNOWAIT is set, the newly created process becomes a child
408 * of init. This effectively disassociates the child from the
411 if (flags & RFNOWAIT)
416 LIST_INSERT_HEAD(&pptr->p_children, p2, p_sibling);
417 LIST_INIT(&p2->p_children);
418 varsymset_init(&p2->p_varsymset, &p1->p_varsymset);
419 callout_init(&p2->p_ithandle);
423 * Copy traceflag and tracefile if enabled. If not inherited,
424 * these were zeroed above but we still could have a trace race
425 * so make sure p2's p_tracenode is NULL.
427 if ((p1->p_traceflag & KTRFAC_INHERIT) && p2->p_tracenode == NULL) {
428 p2->p_traceflag = p1->p_traceflag;
429 p2->p_tracenode = ktrinherit(p1->p_tracenode);
434 * Inherit the scheduler and initialize scheduler-related fields.
435 * Set cpbase to the last timeout that occured (not the upcoming
438 * A critical section is required since a timer IPI can update
439 * scheduler specific data.
442 p2->p_usched = p1->p_usched;
443 lp2->lwp_cpbase = mycpu->gd_schedclock.time -
444 mycpu->gd_schedclock.periodic;
445 p2->p_usched->heuristic_forking(&p1->p_lwp, lp2);
449 * This begins the section where we must prevent the parent
450 * from being swapped.
455 * Finish creating the child process. It will return via a different
456 * execution path later. (ie: directly into user mode)
458 vm_fork(p1, p2, flags);
459 caps_fork(p1, p2, flags);
461 if (flags == (RFFDG | RFPROC)) {
462 mycpu->gd_cnt.v_forks++;
463 mycpu->gd_cnt.v_forkpages += p2->p_vmspace->vm_dsize + p2->p_vmspace->vm_ssize;
464 } else if (flags == (RFFDG | RFPROC | RFPPWAIT | RFMEM)) {
465 mycpu->gd_cnt.v_vforks++;
466 mycpu->gd_cnt.v_vforkpages += p2->p_vmspace->vm_dsize + p2->p_vmspace->vm_ssize;
467 } else if (p1 == &proc0) {
468 mycpu->gd_cnt.v_kthreads++;
469 mycpu->gd_cnt.v_kthreadpages += p2->p_vmspace->vm_dsize + p2->p_vmspace->vm_ssize;
471 mycpu->gd_cnt.v_rforks++;
472 mycpu->gd_cnt.v_rforkpages += p2->p_vmspace->vm_dsize + p2->p_vmspace->vm_ssize;
476 * Both processes are set up, now check if any loadable modules want
477 * to adjust anything.
478 * What if they have an error? XXX
480 TAILQ_FOREACH(ep, &fork_list, next) {
481 (*ep->function)(p1, p2, flags);
485 * Set the start time. Note that the process is not runnable. The
486 * caller is responsible for making it runnable.
488 microtime(&p2->p_start);
489 p2->p_acflag = AFORK;
492 * tell any interested parties about the new process
494 KNOTE(&p1->p_klist, NOTE_FORK | p2->p_pid);
497 * Return child proc pointer to parent.
504 * The next two functionms are general routines to handle adding/deleting
505 * items on the fork callout list.
508 * Take the arguments given and put them onto the fork callout list,
509 * However first make sure that it's not already there.
510 * Returns 0 on success or a standard error number.
513 at_fork(forklist_fn function)
518 /* let the programmer know if he's been stupid */
519 if (rm_at_fork(function)) {
520 printf("WARNING: fork callout entry (%p) already present\n",
524 ep = malloc(sizeof(*ep), M_ATFORK, M_WAITOK|M_ZERO);
525 ep->function = function;
526 TAILQ_INSERT_TAIL(&fork_list, ep, next);
531 * Scan the exit callout list for the given item and remove it..
532 * Returns the number of items removed (0 or 1)
535 rm_at_fork(forklist_fn function)
539 TAILQ_FOREACH(ep, &fork_list, next) {
540 if (ep->function == function) {
541 TAILQ_REMOVE(&fork_list, ep, next);
550 * Add a forked process to the run queue after any remaining setup, such
551 * as setting the fork handler, has been completed.
554 start_forked_proc(struct lwp *lp1, struct proc *p2)
558 KKASSERT(p2 != NULL && p2->p_nthreads == 1);
560 lp2 = LIST_FIRST(&p2->p_lwps);
563 * Move from SIDL to RUN queue, and activate the process's thread.
564 * Activation of the thread effectively makes the process "a"
565 * current process, so we do not setrunqueue().
567 * YYY setrunqueue works here but we should clean up the trampoline
568 * code so we just schedule the LWKT thread and let the trampoline
569 * deal with the userland scheduler on return to userland.
571 KASSERT(p2->p_stat == SIDL,
572 ("cannot start forked process, bad status: %p", p2));
573 p2->p_usched->resetpriority(lp2);
576 p2->p_usched->setrunqueue(lp2);
580 * Now can be swapped.
582 PRELE(lp1->lwp_proc);
585 * Preserve synchronization semantics of vfork. If waiting for
586 * child to exec or exit, set P_PPWAIT on child, and sleep on our
587 * proc (in case of exit).
589 while (p2->p_flag & P_PPWAIT)
590 tsleep(lp1->lwp_proc, 0, "ppwait", 0);