504 lines
12 KiB
C
504 lines
12 KiB
C
/*
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* Copyright (c) 1982, 1986, 1989, 1991, 1993
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* The Regents of the University of California. All rights reserved.
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* (c) UNIX System Laboratories, Inc.
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* All or some portions of this file are derived from material licensed
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* to the University of California by American Telephone and Telegraph
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* Co. or Unix System Laboratories, Inc. and are reproduced herein with
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* the permission of UNIX System Laboratories, Inc.
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*
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* Redistribution and use in source and binary forms, with or without
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* modification, are permitted provided that the following conditions
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* are met:
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* 1. Redistributions of source code must retain the above copyright
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* notice, this list of conditions and the following disclaimer.
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* 2. Redistributions in binary form must reproduce the above copyright
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* notice, this list of conditions and the following disclaimer in the
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* documentation and/or other materials provided with the distribution.
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* 3. All advertising materials mentioning features or use of this software
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* must display the following acknowledgement:
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* This product includes software developed by the University of
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* California, Berkeley and its contributors.
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* 4. Neither the name of the University nor the names of its contributors
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* may be used to endorse or promote products derived from this software
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* without specific prior written permission.
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*
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* THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
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* ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
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* IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
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* ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
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* FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
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* DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
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* OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
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* HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
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* LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
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* OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
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* SUCH DAMAGE.
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*
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* @(#)kern_fork.c 8.6 (Berkeley) 4/8/94
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* $Id: kern_fork.c,v 1.46 1997/08/22 15:10:00 peter Exp $
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*/
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#include "opt_ktrace.h"
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#include <sys/param.h>
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#include <sys/systm.h>
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#include <sys/sysproto.h>
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#include <sys/filedesc.h>
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#include <sys/kernel.h>
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#include <sys/sysctl.h>
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#include <sys/malloc.h>
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#include <sys/proc.h>
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#include <sys/resourcevar.h>
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#include <sys/vnode.h>
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#include <sys/acct.h>
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#include <sys/ktrace.h>
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#include <sys/unistd.h>
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#include <vm/vm.h>
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#include <vm/vm_param.h>
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#include <sys/lock.h>
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#include <vm/pmap.h>
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#include <vm/vm_map.h>
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#include <vm/vm_extern.h>
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#include <vm/vm_inherit.h>
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#ifdef SMP
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int fast_vfork = 0; /* Doesn't work on SMP yet */
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#else
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int fast_vfork = 1;
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#endif
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SYSCTL_INT(_kern, OID_AUTO, fast_vfork, CTLFLAG_RW, &fast_vfork, 0, "");
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static int fork1 __P((struct proc *p, int flags, int *retval));
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/*
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* These are the stuctures used to create a callout list for things to do
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* when forking a process
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*/
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typedef struct fork_list_element {
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struct fork_list_element *next;
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forklist_fn function;
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} *fle_p;
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static fle_p fork_list;
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#ifndef _SYS_SYSPROTO_H_
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struct fork_args {
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int dummy;
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};
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#endif
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/* ARGSUSED */
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int
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fork(p, uap, retval)
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struct proc *p;
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struct fork_args *uap;
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int retval[];
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{
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return (fork1(p, (RFFDG|RFPROC), retval));
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}
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/* ARGSUSED */
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int
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vfork(p, uap, retval)
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struct proc *p;
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struct vfork_args *uap;
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int retval[];
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{
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return (fork1(p, (RFFDG|RFPROC|RFPPWAIT|(fast_vfork ? RFMEM : 0)),
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retval));
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}
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/* ARGSUSED */
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int
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rfork(p, uap, retval)
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struct proc *p;
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struct rfork_args *uap;
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int retval[];
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{
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return (fork1(p, uap->flags, retval));
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}
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int nprocs = 1; /* process 0 */
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static int nextpid = 0;
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static int
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fork1(p1, flags, retval)
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register struct proc *p1;
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int flags;
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int retval[];
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{
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register struct proc *p2, *pptr;
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register uid_t uid;
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struct proc *newproc;
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int count;
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static int pidchecked = 0;
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fle_p ep ;
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ep = fork_list;
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if ((flags & (RFFDG|RFCFDG)) == (RFFDG|RFCFDG))
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return (EINVAL);
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#ifdef SMP
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/*
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* FATAL now, we cannot have the same PTD on both cpus, the PTD
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* needs to move out of PTmap and be per-process, even for shared
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* page table processes. Unfortunately, this means either removing
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* PTD[] as a fixed virtual address, or move it to the per-cpu map
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* area for SMP mode. Both cases require seperate management of
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* the per-process-even-if-PTmap-is-shared PTD.
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*/
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if (flags & RFMEM) {
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printf("shared address space fork attempted: pid: %d\n",
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p1->p_pid);
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return (EOPNOTSUPP);
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}
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#endif
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/*
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* Here we don't create a new process, but we divorce
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* certain parts of a process from itself.
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*/
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if ((flags & RFPROC) == 0) {
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/*
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* Divorce the memory, if it is shared, essentially
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* this changes shared memory amongst threads, into
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* COW locally.
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*/
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if ((flags & RFMEM) == 0) {
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if (p1->p_vmspace->vm_refcnt > 1) {
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vmspace_unshare(p1);
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}
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}
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/*
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* Close all file descriptors.
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*/
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if (flags & RFCFDG) {
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struct filedesc *fdtmp;
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fdtmp = fdinit(p1);
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fdfree(p1);
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p1->p_fd = fdtmp;
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}
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/*
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* Unshare file descriptors (from parent.)
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*/
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if (flags & RFFDG) {
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if (p1->p_fd->fd_refcnt > 1) {
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struct filedesc *newfd;
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newfd = fdcopy(p1);
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fdfree(p1);
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p1->p_fd = newfd;
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}
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}
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return (0);
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}
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/*
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* Although process entries are dynamically created, we still keep
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* a global limit on the maximum number we will create. Don't allow
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* a nonprivileged user to use the last process; don't let root
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* exceed the limit. The variable nprocs is the current number of
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* processes, maxproc is the limit.
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*/
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uid = p1->p_cred->p_ruid;
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if ((nprocs >= maxproc - 1 && uid != 0) || nprocs >= maxproc) {
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tablefull("proc");
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return (EAGAIN);
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}
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/*
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* Increment the nprocs resource before blocking can occur. There
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* are hard-limits as to the number of processes that can run.
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*/
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nprocs++;
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/*
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* Increment the count of procs running with this uid. Don't allow
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* a nonprivileged user to exceed their current limit.
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*/
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count = chgproccnt(uid, 1);
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if (uid != 0 && count > p1->p_rlimit[RLIMIT_NPROC].rlim_cur) {
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(void)chgproccnt(uid, -1);
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/*
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* Back out the process count
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*/
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nprocs--;
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return (EAGAIN);
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}
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/* Allocate new proc. */
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MALLOC(newproc, struct proc *, sizeof(struct proc), M_PROC, M_WAITOK);
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/*
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* Setup linkage for kernel based threading
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*/
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if((flags & RFTHREAD) != 0) {
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newproc->p_peers = p1->p_peers;
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p1->p_peers = newproc;
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newproc->p_leader = p1->p_leader;
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} else {
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newproc->p_peers = 0;
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newproc->p_leader = newproc;
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}
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newproc->p_wakeup = 0;
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/*
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* Find an unused process ID. We remember a range of unused IDs
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* ready to use (from nextpid+1 through pidchecked-1).
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*/
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nextpid++;
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retry:
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/*
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* If the process ID prototype has wrapped around,
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* restart somewhat above 0, as the low-numbered procs
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* tend to include daemons that don't exit.
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*/
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if (nextpid >= PID_MAX) {
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nextpid = 100;
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pidchecked = 0;
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}
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if (nextpid >= pidchecked) {
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int doingzomb = 0;
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pidchecked = PID_MAX;
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/*
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* Scan the active and zombie procs to check whether this pid
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* is in use. Remember the lowest pid that's greater
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* than nextpid, so we can avoid checking for a while.
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*/
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p2 = allproc.lh_first;
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again:
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for (; p2 != 0; p2 = p2->p_list.le_next) {
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while (p2->p_pid == nextpid ||
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p2->p_pgrp->pg_id == nextpid) {
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nextpid++;
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if (nextpid >= pidchecked)
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goto retry;
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}
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if (p2->p_pid > nextpid && pidchecked > p2->p_pid)
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pidchecked = p2->p_pid;
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if (p2->p_pgrp->pg_id > nextpid &&
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pidchecked > p2->p_pgrp->pg_id)
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pidchecked = p2->p_pgrp->pg_id;
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}
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if (!doingzomb) {
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doingzomb = 1;
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p2 = zombproc.lh_first;
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goto again;
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}
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}
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p2 = newproc;
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p2->p_stat = SIDL; /* protect against others */
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p2->p_pid = nextpid;
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LIST_INSERT_HEAD(&allproc, p2, p_list);
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LIST_INSERT_HEAD(PIDHASH(p2->p_pid), p2, p_hash);
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/*
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* Make a proc table entry for the new process.
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* Start by zeroing the section of proc that is zero-initialized,
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* then copy the section that is copied directly from the parent.
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*/
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bzero(&p2->p_startzero,
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(unsigned) ((caddr_t)&p2->p_endzero - (caddr_t)&p2->p_startzero));
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bcopy(&p1->p_startcopy, &p2->p_startcopy,
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(unsigned) ((caddr_t)&p2->p_endcopy - (caddr_t)&p2->p_startcopy));
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p2->p_aioinfo = NULL;
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/*
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* Duplicate sub-structures as needed.
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* Increase reference counts on shared objects.
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* The p_stats and p_sigacts substructs are set in vm_fork.
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*/
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p2->p_flag = P_INMEM;
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if (p1->p_flag & P_PROFIL)
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startprofclock(p2);
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MALLOC(p2->p_cred, struct pcred *, sizeof(struct pcred),
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M_SUBPROC, M_WAITOK);
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bcopy(p1->p_cred, p2->p_cred, sizeof(*p2->p_cred));
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p2->p_cred->p_refcnt = 1;
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crhold(p1->p_ucred);
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/* bump references to the text vnode (for procfs) */
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p2->p_textvp = p1->p_textvp;
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if (p2->p_textvp)
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VREF(p2->p_textvp);
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if (flags & RFCFDG)
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p2->p_fd = fdinit(p1);
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else if (flags & RFFDG)
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p2->p_fd = fdcopy(p1);
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else
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p2->p_fd = fdshare(p1);
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/*
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* If p_limit is still copy-on-write, bump refcnt,
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* otherwise get a copy that won't be modified.
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* (If PL_SHAREMOD is clear, the structure is shared
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* copy-on-write.)
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*/
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if (p1->p_limit->p_lflags & PL_SHAREMOD)
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p2->p_limit = limcopy(p1->p_limit);
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else {
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p2->p_limit = p1->p_limit;
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p2->p_limit->p_refcnt++;
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}
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/*
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* Preserve some flags in subprocess.
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*/
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p2->p_flag |= p1->p_flag & P_SUGID;
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if (p1->p_session->s_ttyvp != NULL && p1->p_flag & P_CONTROLT)
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p2->p_flag |= P_CONTROLT;
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if (flags & RFPPWAIT)
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p2->p_flag |= P_PPWAIT;
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LIST_INSERT_AFTER(p1, p2, p_pglist);
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/*
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* Attach the new process to its parent.
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*
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* If RFNOWAIT is set, the newly created process becomes a child
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* of init. This effectively disassociates the child from the
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* parent.
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*/
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if (flags & RFNOWAIT)
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pptr = initproc;
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else
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pptr = p1;
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p2->p_pptr = pptr;
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LIST_INSERT_HEAD(&pptr->p_children, p2, p_sibling);
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LIST_INIT(&p2->p_children);
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#ifdef KTRACE
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/*
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* Copy traceflag and tracefile if enabled.
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* If not inherited, these were zeroed above.
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*/
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if (p1->p_traceflag&KTRFAC_INHERIT) {
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p2->p_traceflag = p1->p_traceflag;
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if ((p2->p_tracep = p1->p_tracep) != NULL)
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VREF(p2->p_tracep);
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}
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#endif
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/*
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* set priority of child to be that of parent
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*/
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p2->p_estcpu = p1->p_estcpu;
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/*
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* This begins the section where we must prevent the parent
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* from being swapped.
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*/
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p1->p_flag |= P_NOSWAP;
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/*
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* Finish creating the child process. It will return via a different
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* execution path later. (ie: directly into user mode)
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*/
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vm_fork(p1, p2, flags);
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/*
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* Both processes are set up, now check if any LKMs want
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* to adjust anything.
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* What if they have an error? XXX
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*/
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while (ep) {
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(*ep->function)(p1, p2, flags);
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ep = ep->next;
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}
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/*
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* Make child runnable and add to run queue.
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*/
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microtime(&(p2->p_stats->p_start));
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p2->p_acflag = AFORK;
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(void) splhigh();
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p2->p_stat = SRUN;
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setrunqueue(p2);
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(void) spl0();
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/*
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* Now can be swapped.
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*/
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p1->p_flag &= ~P_NOSWAP;
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/*
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* Preserve synchronization semantics of vfork. If waiting for
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* child to exec or exit, set P_PPWAIT on child, and sleep on our
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* proc (in case of exit).
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*/
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while (p2->p_flag & P_PPWAIT)
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tsleep(p1, PWAIT, "ppwait", 0);
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/*
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* Return child pid to parent process,
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* marking us as parent via retval[1].
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*/
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retval[0] = p2->p_pid;
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retval[1] = 0;
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return (0);
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}
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/*
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* The next two functionms are general routines to handle adding/deleting
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* items on the fork callout list.
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*
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* at_fork():
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* Take the arguments given and put them onto the fork callout list,
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* However first make sure that it's not already there.
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* Returns 0 on success or a standard error number.
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*/
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int
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at_fork(function)
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forklist_fn function;
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{
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fle_p ep;
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/* let the programmer know if he's been stupid */
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if (rm_at_fork(function))
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printf("fork callout entry already present\n");
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ep = malloc(sizeof(*ep), M_TEMP, M_NOWAIT);
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if (ep == NULL)
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return (ENOMEM);
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ep->next = fork_list;
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ep->function = function;
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fork_list = ep;
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return (0);
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}
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/*
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* Scan the exit callout list for the given items and remove them.
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* Returns the number of items removed.
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* Theoretically this value can only be 0 or 1.
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*/
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int
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rm_at_fork(function)
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forklist_fn function;
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{
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fle_p *epp, ep;
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int count;
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count= 0;
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epp = &fork_list;
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ep = *epp;
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while (ep) {
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if (ep->function == function) {
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*epp = ep->next;
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free(ep, M_TEMP);
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count++;
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} else {
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epp = &ep->next;
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}
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ep = *epp;
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}
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return (count);
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}
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