/* * 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 * $Id: kern_fork.c,v 1.46 1997/08/22 15:10:00 peter Exp $ */ #include "opt_ktrace.h" #include <sys/param.h> #include <sys/systm.h> #include <sys/sysproto.h> #include <sys/filedesc.h> #include <sys/kernel.h> #include <sys/sysctl.h> #include <sys/malloc.h> #include <sys/proc.h> #include <sys/resourcevar.h> #include <sys/vnode.h> #include <sys/acct.h> #include <sys/ktrace.h> #include <sys/unistd.h> #include <vm/vm.h> #include <vm/vm_param.h> #include <sys/lock.h> #include <vm/pmap.h> #include <vm/vm_map.h> #include <vm/vm_extern.h> #include <vm/vm_inherit.h> #ifdef SMP int fast_vfork = 0; /* Doesn't work on SMP yet */ #else int fast_vfork = 1; #endif SYSCTL_INT(_kern, OID_AUTO, fast_vfork, CTLFLAG_RW, &fast_vfork, 0, ""); static int fork1 __P((struct proc *p, int flags, int *retval)); /* * These are the stuctures used to create a callout list for things to do * when forking a process */ typedef struct fork_list_element { struct fork_list_element *next; forklist_fn function; } *fle_p; static fle_p fork_list; #ifndef _SYS_SYSPROTO_H_ struct fork_args { int dummy; }; #endif /* ARGSUSED */ int fork(p, uap, retval) struct proc *p; struct fork_args *uap; int retval[]; { return (fork1(p, (RFFDG|RFPROC), retval)); } /* ARGSUSED */ int vfork(p, uap, retval) struct proc *p; struct vfork_args *uap; int retval[]; { return (fork1(p, (RFFDG|RFPROC|RFPPWAIT|(fast_vfork ? RFMEM : 0)), retval)); } /* ARGSUSED */ int rfork(p, uap, retval) struct proc *p; struct rfork_args *uap; int retval[]; { return (fork1(p, uap->flags, retval)); } int nprocs = 1; /* process 0 */ static int nextpid = 0; static int fork1(p1, flags, retval) register struct proc *p1; int flags; int retval[]; { register struct proc *p2, *pptr; register uid_t uid; struct proc *newproc; int count; static int pidchecked = 0; fle_p ep ; ep = fork_list; if ((flags & (RFFDG|RFCFDG)) == (RFFDG|RFCFDG)) return (EINVAL); #ifdef SMP /* * FATAL now, we cannot have the same PTD on both cpus, the PTD * needs to move out of PTmap and be per-process, even for shared * page table processes. Unfortunately, this means either removing * PTD[] as a fixed virtual address, or move it to the per-cpu map * area for SMP mode. Both cases require seperate management of * the per-process-even-if-PTmap-is-shared PTD. */ if (flags & RFMEM) { printf("shared address space fork attempted: pid: %d\n", p1->p_pid); return (EOPNOTSUPP); } #endif /* * Here we don't create a new process, but we divorce * certain parts of a process from itself. */ if ((flags & RFPROC) == 0) { /* * Divorce the memory, if it is shared, essentially * this changes shared memory amongst threads, into * COW locally. */ if ((flags & RFMEM) == 0) { if (p1->p_vmspace->vm_refcnt > 1) { vmspace_unshare(p1); } } /* * 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; } } 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 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 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. */ count = chgproccnt(uid, 1); if (uid != 0 && count > p1->p_rlimit[RLIMIT_NPROC].rlim_cur) { (void)chgproccnt(uid, -1); /* * Back out the process count */ nprocs--; return (EAGAIN); } /* Allocate new proc. */ MALLOC(newproc, struct proc *, sizeof(struct proc), M_PROC, M_WAITOK); /* * 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; /* * 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; } } 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); 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); if (flags & RFCFDG) p2->p_fd = fdinit(p1); else if (flags & RFFDG) p2->p_fd = fdcopy(p1); else p2->p_fd = fdshare(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++; } /* * Preserve some flags in subprocess. */ 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; 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); #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 /* * set priority of child to be that of parent */ p2->p_estcpu = p1->p_estcpu; /* * This begins the section where we must prevent the parent * from being swapped. */ p1->p_flag |= P_NOSWAP; /* * Finish creating the child process. It will return via a different * execution path later. (ie: directly into user mode) */ vm_fork(p1, p2, flags); /* * Both processes are set up, now check if any LKMs want * to adjust anything. * What if they have an error? XXX */ while (ep) { (*ep->function)(p1, p2, flags); ep = ep->next; } /* * Make child runnable and add to run queue. */ microtime(&(p2->p_stats->p_start)); p2->p_acflag = AFORK; (void) splhigh(); p2->p_stat = SRUN; setrunqueue(p2); (void) spl0(); /* * Now can be swapped. */ p1->p_flag &= ~P_NOSWAP; /* * 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, 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); } /* * 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(function) forklist_fn function; { fle_p ep; /* let the programmer know if he's been stupid */ if (rm_at_fork(function)) printf("fork callout entry already present\n"); ep = malloc(sizeof(*ep), M_TEMP, M_NOWAIT); if (ep == NULL) return (ENOMEM); ep->next = fork_list; ep->function = function; fork_list = ep; return (0); } /* * Scan the exit callout list for the given items and remove them. * Returns the number of items removed. * Theoretically this value can only be 0 or 1. */ int rm_at_fork(function) forklist_fn function; { fle_p *epp, ep; int count; count= 0; epp = &fork_list; ep = *epp; while (ep) { if (ep->function == function) { *epp = ep->next; free(ep, M_TEMP); count++; } else { epp = &ep->next; } ep = *epp; } return (count); }