/* $NetBSD: kern_fork.c,v 1.27 1995/12/10 08:26:02 mycroft Exp $ */ /* * 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 */ #include #include #include #include #include #include #include #include #include #include #include #include int nprocs = 1; /* process 0 */ int sys_fork(p, v, retval) struct proc *p; void *v; register_t *retval; { return (fork1(p, 0, retval)); } int sys_vfork(p, v, retval) struct proc *p; void *v; register_t *retval; { return (fork1(p, 1, retval)); } int fork1(p1, isvfork, retval) register struct proc *p1; int isvfork; register_t *retval; { register struct proc *p2; register uid_t uid; struct proc *newproc; struct proc **hash; int count; static int nextpid, pidchecked = 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 process; don't let root * exceed the limit. The variable nprocs is the current number of * processes, maxproc is the limit. */ uid = p1->p_cred->p_ruid; if ((nprocs >= maxproc - 1 && uid != 0) || nprocs >= maxproc) { tablefull("proc"); return (EAGAIN); } /* * Increment the count of procs running with this uid. Don't allow * a nonprivileged user to exceed their current limit. */ count = chgproccnt(uid, 1); if (uid != 0 && count > p1->p_rlimit[RLIMIT_NPROC].rlim_cur) { (void)chgproccnt(uid, -1); return (EAGAIN); } /* Allocate new proc. */ MALLOC(newproc, struct proc *, sizeof(struct proc), M_PROC, M_WAITOK); /* * Find an unused process ID. We remember a range of unused IDs * ready to use (from nextpid+1 through pidchecked-1). */ nextpid++; 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 = 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 = allproc.lh_first; again: for (; p2 != 0; p2 = p2->p_list.le_next) { while (p2->p_pid == nextpid || p2->p_pgrp->pg_id == 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 (!doingzomb) { doingzomb = 1; p2 = zombproc.lh_first; goto again; } } nprocs++; p2 = newproc; p2->p_stat = SIDL; /* protect against others */ p2->p_pid = nextpid; LIST_INSERT_HEAD(&allproc, p2, p_list); p2->p_forw = p2->p_back = NULL; /* shouldn't be necessary */ 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)); /* * 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; p2->p_emul = p1->p_emul; if (p1->p_flag & P_PROFIL) startprofclock(p2); MALLOC(p2->p_cred, struct pcred *, sizeof(struct pcred), M_SUBPROC, M_WAITOK); bcopy(p1->p_cred, p2->p_cred, sizeof(*p2->p_cred)); p2->p_cred->p_refcnt = 1; crhold(p1->p_ucred); /* bump references to the text vnode (for procfs) */ p2->p_textvp = p1->p_textvp; if (p2->p_textvp) VREF(p2->p_textvp); p2->p_fd = fdcopy(p1); /* * 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++; } if (p1->p_session->s_ttyvp != NULL && p1->p_flag & P_CONTROLT) p2->p_flag |= P_CONTROLT; if (isvfork) p2->p_flag |= P_PPWAIT; LIST_INSERT_AFTER(p1, p2, p_pglist); p2->p_pptr = p1; LIST_INSERT_HEAD(&p1->p_children, p2, p_sibling); LIST_INIT(&p2->p_children); #ifdef KTRACE /* * Copy traceflag and tracefile if enabled. * If not inherited, these were zeroed above. */ if (p1->p_traceflag&KTRFAC_INHERIT) { p2->p_traceflag = p1->p_traceflag; if ((p2->p_tracep = p1->p_tracep) != NULL) VREF(p2->p_tracep); } #endif /* * This begins the section where we must prevent the parent * from being swapped. */ p1->p_holdcnt++; #ifdef __FORK_BRAINDAMAGE /* * Set return values for child before vm_fork, * so they can be copied to child stack. * We return 0, rather than the traditional behaviour of modifying the * return value in the system call stub. * NOTE: the kernel stack may be at a different location in the child * process, and thus addresses of automatic variables (including retval) * may be invalid after vm_fork returns in the child process. */ retval[0] = 0; retval[1] = 1; if (vm_fork(p1, p2)) return (0); #else /* * Finish creating the child process. It will return through a * different path later. */ vm_fork(p1, p2); #endif /* * Make child runnable, set start time, and add to run queue. */ (void) splstatclock(); p2->p_stats->p_start = time; p2->p_acflag = AFORK; p2->p_stat = SRUN; setrunqueue(p2); (void) spl0(); /* * Now can be swapped. */ p1->p_holdcnt--; /* * 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). */ if (isvfork) while (p2->p_flag & P_PPWAIT) tsleep(p1, PWAIT, "ppwait", 0); /* * Return child pid to parent process, * marking us as parent via retval[1]. */ retval[0] = p2->p_pid; retval[1] = 0; return (0); }