/* * 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. * 3. All advertising materials mentioning features or use of this software * must display the following acknowledgement: * This product includes software developed by the University of * California, Berkeley and its contributors. * 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 * $FreeBSD: src/sys/kern/kern_fork.c,v 1.72.2.14 2003/06/26 04:15:10 silby Exp $ * $DragonFly: src/sys/kern/kern_fork.c,v 1.77 2008/05/18 20:02:02 nth Exp $ */ #include "opt_ktrace.h" #include #include #include #include #include #include #include #include #include #include #include #include #include #include #include #include #include #include #include #include #include #include #include #include #include #include static MALLOC_DEFINE(M_ATFORK, "atfork", "atfork callback"); /* * These are the stuctures used to create a callout list for things to do * when forking a process */ struct forklist { forklist_fn function; TAILQ_ENTRY(forklist) next; }; TAILQ_HEAD(forklist_head, forklist); static struct forklist_head fork_list = TAILQ_HEAD_INITIALIZER(fork_list); static struct lwp *lwp_fork(struct lwp *, struct proc *, int flags); int forksleep; /* Place for fork1() to sleep on. */ /* * Red-Black tree support for LWPs */ static int rb_lwp_compare(struct lwp *lp1, struct lwp *lp2) { if (lp1->lwp_tid < lp2->lwp_tid) return(-1); if (lp1->lwp_tid > lp2->lwp_tid) return(1); return(0); } RB_GENERATE2(lwp_rb_tree, lwp, u.lwp_rbnode, rb_lwp_compare, lwpid_t, lwp_tid); /* * Fork system call * * MPALMOSTSAFE */ int sys_fork(struct fork_args *uap) { struct lwp *lp = curthread->td_lwp; struct proc *p2; int error; error = fork1(lp, RFFDG | RFPROC | RFPGLOCK, &p2); if (error == 0) { start_forked_proc(lp, p2); uap->sysmsg_fds[0] = p2->p_pid; uap->sysmsg_fds[1] = 0; } return error; } /* * MPALMOSTSAFE */ int sys_vfork(struct vfork_args *uap) { struct lwp *lp = curthread->td_lwp; struct proc *p2; int error; error = fork1(lp, RFFDG | RFPROC | RFPPWAIT | RFMEM | RFPGLOCK, &p2); if (error == 0) { start_forked_proc(lp, p2); uap->sysmsg_fds[0] = p2->p_pid; uap->sysmsg_fds[1] = 0; } return error; } /* * Handle rforks. An rfork may (1) operate on the current process without * creating a new, (2) create a new process that shared the current process's * vmspace, signals, and/or descriptors, or (3) create a new process that does * not share these things (normal fork). * * Note that we only call start_forked_proc() if a new process is actually * created. * * rfork { int flags } * * MPALMOSTSAFE */ int sys_rfork(struct rfork_args *uap) { struct lwp *lp = curthread->td_lwp; struct proc *p2; int error; if ((uap->flags & RFKERNELONLY) != 0) return (EINVAL); error = fork1(lp, uap->flags | RFPGLOCK, &p2); if (error == 0) { if (p2) start_forked_proc(lp, p2); uap->sysmsg_fds[0] = p2 ? p2->p_pid : 0; uap->sysmsg_fds[1] = 0; } return error; } /* * MPALMOSTSAFE */ int sys_lwp_create(struct lwp_create_args *uap) { struct proc *p = curproc; struct lwp *lp; struct lwp_params params; int error; error = copyin(uap->params, ¶ms, sizeof(params)); if (error) goto fail2; lwkt_gettoken(&p->p_token); plimit_lwp_fork(p); /* force exclusive access */ lp = lwp_fork(curthread->td_lwp, p, RFPROC); error = cpu_prepare_lwp(lp, ¶ms); if (params.tid1 != NULL && (error = copyout(&lp->lwp_tid, params.tid1, sizeof(lp->lwp_tid)))) goto fail; if (params.tid2 != NULL && (error = copyout(&lp->lwp_tid, params.tid2, sizeof(lp->lwp_tid)))) goto fail; /* * Now schedule the new lwp. */ p->p_usched->resetpriority(lp); crit_enter(); lp->lwp_stat = LSRUN; p->p_usched->setrunqueue(lp); crit_exit(); lwkt_reltoken(&p->p_token); return (0); fail: lwp_rb_tree_RB_REMOVE(&p->p_lwp_tree, lp); --p->p_nthreads; /* lwp_dispose expects an exited lwp, and a held proc */ lp->lwp_flag |= LWP_WEXIT; lp->lwp_thread->td_flags |= TDF_EXITING; PHOLD(p); lwp_dispose(lp); lwkt_reltoken(&p->p_token); fail2: return (error); } int nprocs = 1; /* process 0 */ int fork1(struct lwp *lp1, int flags, struct proc **procp) { struct proc *p1 = lp1->lwp_proc; struct proc *p2, *pptr; struct pgrp *p1grp; struct pgrp *plkgrp; uid_t uid; int ok, error; static int curfail = 0; static struct timeval lastfail; struct forklist *ep; struct filedesc_to_leader *fdtol; if ((flags & (RFFDG|RFCFDG)) == (RFFDG|RFCFDG)) return (EINVAL); lwkt_gettoken(&p1->p_token); plkgrp = NULL; /* * Here we don't create a new process, but we divorce * certain parts of a process from itself. */ if ((flags & RFPROC) == 0) { /* * This kind of stunt does not work anymore if * there are native threads (lwps) running */ if (p1->p_nthreads != 1) { error = EINVAL; goto done; } vm_fork(p1, 0, flags); /* * Close all file descriptors. */ if (flags & RFCFDG) { struct filedesc *fdtmp; fdtmp = fdinit(p1); fdfree(p1, fdtmp); } /* * Unshare file descriptors (from parent.) */ if (flags & RFFDG) { if (p1->p_fd->fd_refcnt > 1) { struct filedesc *newfd; error = fdcopy(p1, &newfd); if (error != 0) { error = ENOMEM; goto done; } fdfree(p1, newfd); } } *procp = NULL; error = 0; goto done; } /* * Interlock against process group signal delivery. If signals * are pending after the interlock is obtained we have to restart * the system call to process the signals. If we don't the child * can miss a pgsignal (such as ^C) sent during the fork. * * We can't use CURSIG() here because it will process any STOPs * and cause the process group lock to be held indefinitely. If * a STOP occurs, the fork will be restarted after the CONT. */ p1grp = p1->p_pgrp; if ((flags & RFPGLOCK) && (plkgrp = p1->p_pgrp) != NULL) { pgref(plkgrp); lockmgr(&plkgrp->pg_lock, LK_SHARED); if (CURSIG_NOBLOCK(lp1)) { error = ERESTART; goto done; } } /* * 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. */ uid = lp1->lwp_thread->td_ucred->cr_ruid; if ((nprocs >= maxproc - 10 && uid != 0) || nprocs >= maxproc) { if (ppsratecheck(&lastfail, &curfail, 1)) kprintf("maxproc limit exceeded by uid %d, please " "see tuning(7) and login.conf(5).\n", uid); tsleep(&forksleep, 0, "fork", hz / 2); error = EAGAIN; goto done; } /* * Increment the nprocs resource before blocking can occur. There * are hard-limits as to the number of processes that can run. */ nprocs++; /* * Increment the count of procs running with this uid. Don't allow * a nonprivileged user to exceed their current limit. */ ok = chgproccnt(lp1->lwp_thread->td_ucred->cr_ruidinfo, 1, (uid != 0) ? p1->p_rlimit[RLIMIT_NPROC].rlim_cur : 0); if (!ok) { /* * Back out the process count */ nprocs--; if (ppsratecheck(&lastfail, &curfail, 1)) kprintf("maxproc limit exceeded by uid %d, please " "see tuning(7) and login.conf(5).\n", uid); tsleep(&forksleep, 0, "fork", hz / 2); error = EAGAIN; goto done; } /* Allocate new proc. */ p2 = kmalloc(sizeof(struct proc), M_PROC, M_WAITOK|M_ZERO); /* * Setup linkage for kernel based threading XXX lwp */ if (flags & RFTHREAD) { p2->p_peers = p1->p_peers; p1->p_peers = p2; p2->p_leader = p1->p_leader; } else { p2->p_leader = p2; } RB_INIT(&p2->p_lwp_tree); spin_init(&p2->p_spin); lwkt_token_init(&p2->p_token, "iproc"); p2->p_lasttid = -1; /* first tid will be 0 */ /* * Setting the state to SIDL protects the partially initialized * process once it starts getting hooked into the rest of the system. */ p2->p_stat = SIDL; proc_add_allproc(p2); /* * Make a proc table entry for the new process. * The whole structure was zeroed above, so copy the section that is * copied directly from the parent. */ bcopy(&p1->p_startcopy, &p2->p_startcopy, (unsigned) ((caddr_t)&p2->p_endcopy - (caddr_t)&p2->p_startcopy)); /* * Duplicate sub-structures as needed. Increase reference counts * on shared objects. * * NOTE: because we are now on the allproc list it is possible for * other consumers to gain temporary references to p2 * (p2->p_lock can change). */ if (p1->p_flag & P_PROFIL) startprofclock(p2); p2->p_ucred = crhold(lp1->lwp_thread->td_ucred); if (jailed(p2->p_ucred)) p2->p_flag |= P_JAILED; if (p2->p_args) refcount_acquire(&p2->p_args->ar_ref); p2->p_usched = p1->p_usched; /* XXX: verify copy of the secondary iosched stuff */ dsched_new_proc(p2); if (flags & RFSIGSHARE) { p2->p_sigacts = p1->p_sigacts; refcount_acquire(&p2->p_sigacts->ps_refcnt); } else { p2->p_sigacts = kmalloc(sizeof(*p2->p_sigacts), M_SUBPROC, M_WAITOK); bcopy(p1->p_sigacts, p2->p_sigacts, sizeof(*p2->p_sigacts)); refcount_init(&p2->p_sigacts->ps_refcnt, 1); } if (flags & RFLINUXTHPN) p2->p_sigparent = SIGUSR1; else p2->p_sigparent = SIGCHLD; /* bump references to the text vnode (for procfs) */ p2->p_textvp = p1->p_textvp; if (p2->p_textvp) vref(p2->p_textvp); /* copy namecache handle to the text file */ if (p1->p_textnch.mount) cache_copy(&p1->p_textnch, &p2->p_textnch); /* * Handle file descriptors */ if (flags & RFCFDG) { p2->p_fd = fdinit(p1); fdtol = NULL; } else if (flags & RFFDG) { error = fdcopy(p1, &p2->p_fd); if (error != 0) { error = ENOMEM; goto done; } fdtol = NULL; } else { p2->p_fd = fdshare(p1); if (p1->p_fdtol == NULL) { lwkt_gettoken(&p1->p_token); p1->p_fdtol = filedesc_to_leader_alloc(NULL, p1->p_leader); lwkt_reltoken(&p1->p_token); } if ((flags & RFTHREAD) != 0) { /* * Shared file descriptor table and * shared process leaders. */ fdtol = p1->p_fdtol; fdtol->fdl_refcount++; } else { /* * Shared file descriptor table, and * different process leaders */ fdtol = filedesc_to_leader_alloc(p1->p_fdtol, p2); } } p2->p_fdtol = fdtol; p2->p_limit = plimit_fork(p1); /* * Preserve some more flags in subprocess. P_PROFIL has already * been preserved. */ p2->p_flag |= p1->p_flag & P_SUGID; if (p1->p_session->s_ttyvp != NULL && p1->p_flag & P_CONTROLT) p2->p_flag |= P_CONTROLT; if (flags & RFPPWAIT) p2->p_flag |= P_PPWAIT; /* * Inherit the virtual kernel structure (allows a virtual kernel * to fork to simulate multiple cpus). */ if (p1->p_vkernel) vkernel_inherit(p1, p2); /* * Once we are on a pglist we may receive signals. XXX we might * race a ^C being sent to the process group by not receiving it * at all prior to this line. */ pgref(p1grp); lwkt_gettoken(&p1grp->pg_token); LIST_INSERT_AFTER(p1, p2, p_pglist); lwkt_reltoken(&p1grp->pg_token); /* * 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_INIT(&p2->p_children); lwkt_gettoken(&pptr->p_token); LIST_INSERT_HEAD(&pptr->p_children, p2, p_sibling); lwkt_reltoken(&pptr->p_token); varsymset_init(&p2->p_varsymset, &p1->p_varsymset); callout_init(&p2->p_ithandle); #ifdef KTRACE /* * Copy traceflag and tracefile if enabled. If not inherited, * these were zeroed above but we still could have a trace race * so make sure p2's p_tracenode is NULL. */ if ((p1->p_traceflag & KTRFAC_INHERIT) && p2->p_tracenode == NULL) { p2->p_traceflag = p1->p_traceflag; p2->p_tracenode = ktrinherit(p1->p_tracenode); } #endif /* * This begins the section where we must prevent the parent * from being swapped. * * Gets PRELE'd in the caller in start_forked_proc(). */ PHOLD(p1); vm_fork(p1, p2, flags); /* * Create the first lwp associated with the new proc. * It will return via a different execution path later, directly * into userland, after it was put on the runq by * start_forked_proc(). */ lwp_fork(lp1, p2, flags); if (flags == (RFFDG | RFPROC | RFPGLOCK)) { mycpu->gd_cnt.v_forks++; mycpu->gd_cnt.v_forkpages += p2->p_vmspace->vm_dsize + p2->p_vmspace->vm_ssize; } else if (flags == (RFFDG | RFPROC | RFPPWAIT | RFMEM | RFPGLOCK)) { mycpu->gd_cnt.v_vforks++; mycpu->gd_cnt.v_vforkpages += p2->p_vmspace->vm_dsize + p2->p_vmspace->vm_ssize; } else if (p1 == &proc0) { mycpu->gd_cnt.v_kthreads++; mycpu->gd_cnt.v_kthreadpages += p2->p_vmspace->vm_dsize + p2->p_vmspace->vm_ssize; } else { mycpu->gd_cnt.v_rforks++; mycpu->gd_cnt.v_rforkpages += p2->p_vmspace->vm_dsize + p2->p_vmspace->vm_ssize; } /* * Both processes are set up, now check if any loadable modules want * to adjust anything. * What if they have an error? XXX */ TAILQ_FOREACH(ep, &fork_list, next) { (*ep->function)(p1, p2, flags); } /* * Set the start time. Note that the process is not runnable. The * caller is responsible for making it runnable. */ microtime(&p2->p_start); p2->p_acflag = AFORK; /* * tell any interested parties about the new process */ KNOTE(&p1->p_klist, NOTE_FORK | p2->p_pid); /* * Return child proc pointer to parent. */ *procp = p2; error = 0; done: lwkt_reltoken(&p1->p_token); if (plkgrp) { lockmgr(&plkgrp->pg_lock, LK_RELEASE); pgrel(plkgrp); } return (error); } static struct lwp * lwp_fork(struct lwp *origlp, struct proc *destproc, int flags) { struct lwp *lp; struct thread *td; lp = kmalloc(sizeof(struct lwp), M_LWP, M_WAITOK|M_ZERO); lp->lwp_proc = destproc; lp->lwp_vmspace = destproc->p_vmspace; lp->lwp_stat = LSRUN; bcopy(&origlp->lwp_startcopy, &lp->lwp_startcopy, (unsigned) ((caddr_t)&lp->lwp_endcopy - (caddr_t)&lp->lwp_startcopy)); lp->lwp_flag |= origlp->lwp_flag & LWP_ALTSTACK; /* * Set cpbase to the last timeout that occured (not the upcoming * timeout). * * A critical section is required since a timer IPI can update * scheduler specific data. */ crit_enter(); lp->lwp_cpbase = mycpu->gd_schedclock.time - mycpu->gd_schedclock.periodic; destproc->p_usched->heuristic_forking(origlp, lp); crit_exit(); lp->lwp_cpumask &= usched_mastermask; td = lwkt_alloc_thread(NULL, LWKT_THREAD_STACK, -1, 0); lp->lwp_thread = td; td->td_proc = destproc; td->td_lwp = lp; td->td_switch = cpu_heavy_switch; lwkt_setpri(td, TDPRI_KERN_USER); lwkt_set_comm(td, "%s", destproc->p_comm); /* * cpu_fork will copy and update the pcb, set up the kernel stack, * and make the child ready to run. */ cpu_fork(origlp, lp, flags); caps_fork(origlp->lwp_thread, lp->lwp_thread); kqueue_init(&lp->lwp_kqueue, destproc->p_fd); /* * Assign a TID to the lp. Loop until the insert succeeds (returns * NULL). */ lp->lwp_tid = destproc->p_lasttid; do { if (++lp->lwp_tid < 0) lp->lwp_tid = 1; } while (lwp_rb_tree_RB_INSERT(&destproc->p_lwp_tree, lp) != NULL); destproc->p_lasttid = lp->lwp_tid; destproc->p_nthreads++; return (lp); } /* * The next two functionms are general routines to handle adding/deleting * items on the fork callout list. * * at_fork(): * Take the arguments given and put them onto the fork callout list, * However first make sure that it's not already there. * Returns 0 on success or a standard error number. */ int at_fork(forklist_fn function) { struct forklist *ep; #ifdef INVARIANTS /* let the programmer know if he's been stupid */ if (rm_at_fork(function)) { kprintf("WARNING: fork callout entry (%p) already present\n", function); } #endif ep = kmalloc(sizeof(*ep), M_ATFORK, M_WAITOK|M_ZERO); ep->function = function; TAILQ_INSERT_TAIL(&fork_list, ep, next); return (0); } /* * Scan the exit callout list for the given item and remove it.. * Returns the number of items removed (0 or 1) */ int rm_at_fork(forklist_fn function) { struct forklist *ep; TAILQ_FOREACH(ep, &fork_list, next) { if (ep->function == function) { TAILQ_REMOVE(&fork_list, ep, next); kfree(ep, M_ATFORK); return(1); } } return (0); } /* * Add a forked process to the run queue after any remaining setup, such * as setting the fork handler, has been completed. */ void start_forked_proc(struct lwp *lp1, struct proc *p2) { struct lwp *lp2 = ONLY_LWP_IN_PROC(p2); /* * Move from SIDL to RUN queue, and activate the process's thread. * Activation of the thread effectively makes the process "a" * current process, so we do not setrunqueue(). * * YYY setrunqueue works here but we should clean up the trampoline * code so we just schedule the LWKT thread and let the trampoline * deal with the userland scheduler on return to userland. */ KASSERT(p2->p_stat == SIDL, ("cannot start forked process, bad status: %p", p2)); p2->p_usched->resetpriority(lp2); crit_enter(); p2->p_stat = SACTIVE; lp2->lwp_stat = LSRUN; p2->p_usched->setrunqueue(lp2); crit_exit(); /* * Now can be swapped. */ PRELE(lp1->lwp_proc); /* * 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) tsleep(lp1->lwp_proc, 0, "ppwait", 0); }