376 lines
10 KiB
C
376 lines
10 KiB
C
/* $NetBSD: kern_fork.c,v 1.54 1999/03/24 05:51:23 mrg Exp $ */
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/*
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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 8.8 (Berkeley) 2/14/95
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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/map.h>
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#include <sys/filedesc.h>
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#include <sys/kernel.h>
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#include <sys/malloc.h>
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#include <sys/pool.h>
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#include <sys/mount.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/file.h>
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#include <sys/acct.h>
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#include <sys/ktrace.h>
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#include <sys/vmmeter.h>
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#include <sys/sched.h>
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#include <sys/syscallargs.h>
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#include <vm/vm.h>
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#include <vm/vm_kern.h>
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#include <uvm/uvm_extern.h>
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int nprocs = 1; /* process 0 */
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/*ARGSUSED*/
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int
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sys_fork(p, v, retval)
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struct proc *p;
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void *v;
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register_t *retval;
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{
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return (fork1(p, 0, retval, NULL));
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}
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/*
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* vfork(2) system call compatible with 4.4BSD (i.e. BSD with Mach VM).
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* Address space is not shared, but parent is blocked until child exit.
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*/
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/*ARGSUSED*/
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int
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sys_vfork(p, v, retval)
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struct proc *p;
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void *v;
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register_t *retval;
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{
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return (fork1(p, FORK_PPWAIT, retval, NULL));
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}
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/*
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* New vfork(2) system call for NetBSD, which implements original 3BSD vfork(2)
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* semantics. Address space is shared, and parent is blocked until child exit.
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*/
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/*ARGSUSED*/
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int
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sys___vfork14(p, v, retval)
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struct proc *p;
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void *v;
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register_t *retval;
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{
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return (fork1(p, FORK_PPWAIT|FORK_SHAREVM, retval, NULL));
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}
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int
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fork1(p1, flags, retval, rnewprocp)
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register struct proc *p1;
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int flags;
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register_t *retval;
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struct proc **rnewprocp;
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{
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register struct proc *p2;
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register uid_t uid;
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struct proc *newproc;
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int count, s;
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vaddr_t uaddr;
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static int nextpid, pidchecked = 0;
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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 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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return (EAGAIN);
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}
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/*
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* Allocate virtual address space for the U-area now, while it
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* is still easy to abort the fork operation if we're out of
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* kernel virtual address space. The actual U-area pages will
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* be allocated and wired in vm_fork().
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*/
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uaddr = uvm_km_valloc(kernel_map, USPACE);
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if (uaddr == 0) {
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(void)chgproccnt(uid, -1);
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return (ENOMEM);
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}
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/*
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* We are now committed to the fork. From here on, we may
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* block on resources, but resource allocation may NOT fail.
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*/
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/* Allocate new proc. */
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newproc = pool_get(&proc_pool, PR_WAITOK);
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/*
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* BEGIN PID ALLOCATION. (Lock PID allocation variables eventually).
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*/
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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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const struct proclist_desc *pd;
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pidchecked = PID_MAX;
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/*
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* Scan the process lists 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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pd = proclists;
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again:
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for (p2 = LIST_FIRST(pd->pd_list); p2 != 0;
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p2 = LIST_NEXT(p2, p_list)) {
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while (p2->p_pid == nextpid ||
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p2->p_pgrp->pg_id == nextpid ||
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p2->p_session->s_sid == 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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if (p2->p_session->s_sid > nextpid &&
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pidchecked > p2->p_session->s_sid)
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pidchecked = p2->p_session->s_sid;
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}
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/*
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* If there's another list, scan it. If we have checked
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* them all, we've found one!
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*/
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pd++;
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if (pd->pd_list != NULL)
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goto again;
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}
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nprocs++;
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p2 = newproc;
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/* Record the pid we've allocated. */
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p2->p_pid = nextpid;
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/*
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* Put the proc on allproc before unlocking PID allocation
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* so that waiters won't grab it as soon as we unlock.
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*/
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LIST_INSERT_HEAD(&allproc, p2, p_list);
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/*
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* END PID ALLOCATION. (Unlock PID allocation variables).
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*/
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p2->p_stat = SIDL; /* protect against others */
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p2->p_forw = p2->p_back = NULL; /* shouldn't be necessary */
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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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memset(&p2->p_startzero, 0,
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(unsigned) ((caddr_t)&p2->p_endzero - (caddr_t)&p2->p_startzero));
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memcpy(&p2->p_startcopy, &p1->p_startcopy,
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(unsigned) ((caddr_t)&p2->p_endcopy - (caddr_t)&p2->p_startcopy));
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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 | (p1->p_flag & P_SUGID);
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p2->p_emul = p1->p_emul;
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if (p1->p_flag & P_PROFIL)
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startprofclock(p2);
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p2->p_cred = pool_get(&pcred_pool, PR_WAITOK);
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memcpy(p2->p_cred, p1->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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p2->p_fd = fdcopy(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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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 & FORK_PPWAIT)
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p2->p_flag |= P_PPWAIT;
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LIST_INSERT_AFTER(p1, p2, p_pglist);
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p2->p_pptr = p1;
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LIST_INSERT_HEAD(&p1->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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ktradref(p2);
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}
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#endif
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scheduler_fork_hook(p1, p2);
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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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PHOLD(p1);
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/*
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* Finish creating the child process. It will return through a
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* different path later.
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*/
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p2->p_addr = (struct user *)uaddr;
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uvm_fork(p1, p2, (flags & FORK_SHAREVM) ? TRUE : FALSE);
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/*
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* Make child runnable, set start time, and add to run queue.
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*/
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s = splstatclock();
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p2->p_stats->p_start = time;
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p2->p_acflag = AFORK;
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p2->p_stat = SRUN;
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setrunqueue(p2);
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splx(s);
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/*
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* Now can be swapped.
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*/
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PRELE(p1);
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/*
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* Update stats now that we know the fork was successful.
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*/
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uvmexp.forks++;
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if (flags & FORK_PPWAIT)
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uvmexp.forks_ppwait++;
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if (flags & FORK_SHAREVM)
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uvmexp.forks_sharevm++;
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/*
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* Pass a pointer to the new process to the caller.
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*/
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if (rnewprocp != NULL)
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*rnewprocp = p2;
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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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if (flags & FORK_PPWAIT)
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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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if (retval != NULL) {
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retval[0] = p2->p_pid;
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retval[1] = 0;
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}
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return (0);
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}
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