/* * 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 1.30 2004/10/12 19:20:46 dillon 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 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); int forksleep; /* Place for fork1() to sleep on. */ /* ARGSUSED */ int fork(struct fork_args *uap) { struct proc *p = curproc; struct proc *p2; int error; error = fork1(p, RFFDG | RFPROC, &p2); if (error == 0) { start_forked_proc(p, p2); uap->sysmsg_fds[0] = p2->p_pid; uap->sysmsg_fds[1] = 0; } return error; } /* ARGSUSED */ int vfork(struct vfork_args *uap) { struct proc *p = curproc; struct proc *p2; int error; error = fork1(p, RFFDG | RFPROC | RFPPWAIT | RFMEM, &p2); if (error == 0) { start_forked_proc(p, 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 } */ int rfork(struct rfork_args *uap) { struct proc *p = curproc; struct proc *p2; int error; if ((uap->flags & RFKERNELONLY) != 0) return (EINVAL); error = fork1(p, uap->flags, &p2); if (error == 0) { if (p2) start_forked_proc(p, p2); uap->sysmsg_fds[0] = p2 ? p2->p_pid : 0; uap->sysmsg_fds[1] = 0; } return error; } int nprocs = 1; /* process 0 */ static int nextpid = 0; /* * Random component to nextpid 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; pid = randompid; error = sysctl_handle_int(oidp, &pid, 0, req); if (error || !req->newptr) return (error); 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; return (error); } SYSCTL_PROC(_kern, OID_AUTO, randompid, CTLTYPE_INT|CTLFLAG_RW, 0, 0, sysctl_kern_randompid, "I", "Random PID modulus"); int fork1(struct proc *p1, int flags, struct proc **procp) { struct proc *p2, *pptr; uid_t uid; struct proc *newproc; int ok; static int curfail = 0, pidchecked = 0; static struct timeval lastfail; struct forklist *ep; struct filedesc_to_leader *fdtol; if ((flags & (RFFDG|RFCFDG)) == (RFFDG|RFCFDG)) return (EINVAL); /* * Here we don't create a new process, but we divorce * certain parts of a process from itself. */ if ((flags & RFPROC) == 0) { vm_fork(p1, 0, flags); /* * Close all file descriptors. */ if (flags & RFCFDG) { struct filedesc *fdtmp; fdtmp = fdinit(p1); fdfree(p1); p1->p_fd = fdtmp; } /* * Unshare file descriptors (from parent.) */ if (flags & RFFDG) { if (p1->p_fd->fd_refcnt > 1) { struct filedesc *newfd; newfd = fdcopy(p1); fdfree(p1); p1->p_fd = newfd; } } *procp = NULL; return (0); } /* * 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 = p1->p_ucred->cr_ruid; if ((nprocs >= maxproc - 10 && uid != 0) || nprocs >= maxproc) { if (ppsratecheck(&lastfail, &curfail, 1)) printf("maxproc limit exceeded by uid %d, please " "see tuning(7) and login.conf(5).\n", uid); tsleep(&forksleep, 0, "fork", hz / 2); return (EAGAIN); } /* * 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(p1->p_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)) printf("maxproc limit exceeded by uid %d, please " "see tuning(7) and login.conf(5).\n", uid); tsleep(&forksleep, 0, "fork", hz / 2); return (EAGAIN); } /* Allocate new proc. */ newproc = zalloc(proc_zone); /* * Setup linkage for kernel based threading */ if ((flags & RFTHREAD) != 0) { newproc->p_peers = p1->p_peers; p1->p_peers = newproc; newproc->p_leader = p1->p_leader; } else { newproc->p_peers = 0; newproc->p_leader = newproc; } newproc->p_wakeup = 0; newproc->p_vmspace = NULL; TAILQ_INIT(&newproc->p_sysmsgq); /* * Find an unused process ID. We remember a range of unused IDs * ready to use (from nextpid+1 through pidchecked-1). */ nextpid++; if (randompid) nextpid += 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 (nextpid >= PID_MAX) { nextpid = nextpid % PID_MAX; if (nextpid < 100) nextpid += 100; pidchecked = 0; } if (nextpid >= 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 nextpid, so we can avoid checking for a while. */ p2 = LIST_FIRST(&allproc); again: for (; p2 != 0; p2 = LIST_NEXT(p2, p_list)) { while (p2->p_pid == nextpid || p2->p_pgrp->pg_id == nextpid || p2->p_session->s_sid == nextpid) { nextpid++; if (nextpid >= pidchecked) goto retry; } if (p2->p_pid > nextpid && pidchecked > p2->p_pid) pidchecked = p2->p_pid; if (p2->p_pgrp->pg_id > nextpid && pidchecked > p2->p_pgrp->pg_id) pidchecked = p2->p_pgrp->pg_id; if (p2->p_session->s_sid > nextpid && pidchecked > p2->p_session->s_sid) pidchecked = p2->p_session->s_sid; } if (!doingzomb) { doingzomb = 1; p2 = LIST_FIRST(&zombproc); goto again; } } p2 = newproc; p2->p_stat = SIDL; /* protect against others */ p2->p_pid = nextpid; LIST_INSERT_HEAD(&allproc, p2, p_list); LIST_INSERT_HEAD(PIDHASH(p2->p_pid), p2, p_hash); /* * 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. */ bzero(&p2->p_startzero, (unsigned) ((caddr_t)&p2->p_endzero - (caddr_t)&p2->p_startzero)); bcopy(&p1->p_startcopy, &p2->p_startcopy, (unsigned) ((caddr_t)&p2->p_endcopy - (caddr_t)&p2->p_startcopy)); p2->p_aioinfo = NULL; /* * Duplicate sub-structures as needed. * Increase reference counts on shared objects. * The p_stats and p_sigacts substructs are set in vm_fork. */ p2->p_flag = P_INMEM; if (p1->p_flag & P_PROFIL) startprofclock(p2); p2->p_ucred = crhold(p1->p_ucred); if (p2->p_ucred->cr_prison) { p2->p_ucred->cr_prison->pr_ref++; p2->p_flag |= P_JAILED; } if (p2->p_args) p2->p_args->ar_ref++; if (flags & RFSIGSHARE) { p2->p_procsig = p1->p_procsig; p2->p_procsig->ps_refcnt++; if (p1->p_sigacts == &p1->p_addr->u_sigacts) { struct sigacts *newsigacts; int s; /* Create the shared sigacts structure */ MALLOC(newsigacts, struct sigacts *, sizeof(struct sigacts), M_SUBPROC, M_WAITOK); s = splhigh(); /* * Set p_sigacts to the new shared structure. * Note that this is updating p1->p_sigacts at the * same time, since p_sigacts is just a pointer to * the shared p_procsig->ps_sigacts. */ p2->p_sigacts = newsigacts; bcopy(&p1->p_addr->u_sigacts, p2->p_sigacts, sizeof(*p2->p_sigacts)); *p2->p_sigacts = p1->p_addr->u_sigacts; splx(s); } } else { MALLOC(p2->p_procsig, struct procsig *, sizeof(struct procsig), M_SUBPROC, M_WAITOK); bcopy(p1->p_procsig, p2->p_procsig, sizeof(*p2->p_procsig)); p2->p_procsig->ps_refcnt = 1; p2->p_sigacts = NULL; /* finished in vm_fork() */ } 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); if (flags & RFCFDG) { p2->p_fd = fdinit(p1); fdtol = NULL; } else if (flags & RFFDG) { p2->p_fd = fdcopy(p1); fdtol = NULL; } else { p2->p_fd = fdshare(p1); if (p1->p_fdtol == NULL) p1->p_fdtol = filedesc_to_leader_alloc(NULL, p1->p_leader); 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; /* * If p_limit is still copy-on-write, bump refcnt, * otherwise get a copy that won't be modified. * (If PL_SHAREMOD is clear, the structure is shared * copy-on-write.) */ if (p1->p_limit->p_lflags & PL_SHAREMOD) { p2->p_limit = limcopy(p1->p_limit); } else { p2->p_limit = p1->p_limit; p2->p_limit->p_refcnt++; } /* * Preserve some more flags in subprocess. P_PROFIL has already * been preserved. */ p2->p_flag |= p1->p_flag & (P_SUGID | P_ALTSTACK); 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; /* * 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. */ LIST_INSERT_AFTER(p1, p2, p_pglist); /* * 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); LIST_INIT(&p2->p_children); 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_tracep is NULL. */ if ((p1->p_traceflag & KTRFAC_INHERIT) && p2->p_tracep == NULL) { p2->p_traceflag = p1->p_traceflag; if ((p2->p_tracep = p1->p_tracep) != NULL) vref(p2->p_tracep); } #endif /* * Give the child process an estcpu skewed towards the batch side * of the parent. This prevents batch programs from glitching * interactive programs when they are first started. If the child * is not a batch program it's priority will be corrected by the * scheduler. * * The interactivity model always starts at 0 (par value). */ p2->p_estcpu_fork = p2->p_estcpu = ESTCPULIM(p1->p_estcpu + ESTCPURAMP); p2->p_interactive = 0; /* * This begins the section where we must prevent the parent * from being swapped. */ PHOLD(p1); /* * Finish creating the child process. It will return via a different * execution path later. (ie: directly into user mode) */ vm_fork(p1, p2, flags); caps_fork(p1, p2, flags); if (flags == (RFFDG | RFPROC)) { 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)) { 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); } /* * Make child runnable and add to run queue. */ microtime(&p2->p_thread->td_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; return (0); } /* * 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)) { printf("WARNING: fork callout entry (%p) already present\n", function); } #endif ep = malloc(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); free(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 proc *p1, struct 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 && p2->p_stat == SIDL, ("cannot start forked process, bad status: %p", p2)); resetpriority(p2); (void) splhigh(); p2->p_stat = SRUN; setrunqueue(p2); (void) spl0(); /* * Now can be swapped. */ PRELE(p1); /* * 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(p1, 0, "ppwait", 0); }