612 lines
15 KiB
C
612 lines
15 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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* $FreeBSD$
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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/mutex.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/ktr.h>
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#include <sys/ktrace.h>
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#include <sys/unistd.h>
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#include <sys/jail.h>
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#include <vm/vm.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_zone.h>
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#include <sys/user.h>
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static MALLOC_DEFINE(M_ATFORK, "atfork", "atfork callback");
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static int fast_vfork = 1;
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SYSCTL_INT(_kern, OID_AUTO, fast_vfork, CTLFLAG_RW, &fast_vfork, 0,
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"flag to indicate whether we have a fast vfork()");
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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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struct forklist {
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forklist_fn function;
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TAILQ_ENTRY(forklist) next;
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};
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TAILQ_HEAD(forklist_head, forklist);
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static struct forklist_head fork_list = TAILQ_HEAD_INITIALIZER(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)
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struct proc *p;
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struct fork_args *uap;
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{
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int error;
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struct proc *p2;
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error = fork1(p, RFFDG | RFPROC, &p2);
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if (error == 0) {
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p->p_retval[0] = p2->p_pid;
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p->p_retval[1] = 0;
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}
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return error;
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}
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/* ARGSUSED */
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int
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vfork(p, uap)
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struct proc *p;
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struct vfork_args *uap;
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{
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int error;
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struct proc *p2;
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error = fork1(p, RFFDG | RFPROC | RFPPWAIT | RFMEM, &p2);
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if (error == 0) {
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p->p_retval[0] = p2->p_pid;
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p->p_retval[1] = 0;
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}
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return error;
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}
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int
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rfork(p, uap)
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struct proc *p;
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struct rfork_args *uap;
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{
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int error;
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struct proc *p2;
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/* mask kernel only flags out of the user flags */
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error = fork1(p, uap->flags & ~RFKERNELONLY, &p2);
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if (error == 0) {
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p->p_retval[0] = p2 ? p2->p_pid : 0;
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p->p_retval[1] = 0;
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}
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return error;
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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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/*
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* Random component to nextpid generation. We mix in a random factor to make
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* it a little harder to predict. We sanity check the modulus value to avoid
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* doing it in critical paths. Don't let it be too small or we pointlessly
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* waste randomness entropy, and don't let it be impossibly large. Using a
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* modulus that is too big causes a LOT more process table scans and slows
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* down fork processing as the pidchecked caching is defeated.
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*/
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static int randompid = 0;
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static int
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sysctl_kern_randompid(SYSCTL_HANDLER_ARGS)
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{
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int error, pid;
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pid = randompid;
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error = sysctl_handle_int(oidp, &pid, 0, req);
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if (error || !req->newptr)
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return (error);
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if (pid < 0 || pid > PID_MAX - 100) /* out of range */
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pid = PID_MAX - 100;
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else if (pid < 2) /* NOP */
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pid = 0;
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else if (pid < 100) /* Make it reasonable */
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pid = 100;
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randompid = pid;
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return (error);
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}
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SYSCTL_PROC(_kern, OID_AUTO, randompid, CTLTYPE_INT|CTLFLAG_RW,
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0, 0, sysctl_kern_randompid, "I", "Random PID modulus");
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int
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fork1(p1, flags, procp)
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struct proc *p1; /* parent proc */
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int flags;
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struct proc **procp; /* child proc */
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{
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struct proc *p2, *pptr;
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uid_t uid;
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struct proc *newproc;
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int trypid;
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int ok;
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static int pidchecked = 0;
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struct forklist *ep;
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/* Can't copy and clear */
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if ((flags & (RFFDG|RFCFDG)) == (RFFDG|RFCFDG))
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return (EINVAL);
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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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vm_fork(p1, 0, flags);
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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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*procp = NULL;
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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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ok = chgproccnt(p1->p_cred->p_uidinfo, 1,
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(uid != 0) ? p1->p_rlimit[RLIMIT_NPROC].rlim_cur : 0);
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if (!ok) {
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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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newproc = zalloc(proc_zone);
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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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newproc->p_vmspace = NULL;
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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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* If RFHIGHPID is set (used during system boot), do not allocate
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* low-numbered pids.
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*/
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trypid = nextpid + 1;
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if (flags & RFHIGHPID) {
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if (trypid < 10) {
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trypid = 10;
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}
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} else {
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if (randompid)
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trypid += arc4random() % randompid;
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}
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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 (trypid >= PID_MAX) {
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trypid = trypid % PID_MAX;
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if (trypid < 100)
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trypid += 100;
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pidchecked = 0;
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}
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if (trypid >= 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 trypid, so we can avoid checking for a while.
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*/
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p2 = LIST_FIRST(&allproc);
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again:
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for (; p2 != 0; p2 = LIST_NEXT(p2, p_list)) {
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while (p2->p_pid == trypid ||
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p2->p_pgrp->pg_id == trypid ||
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p2->p_session->s_sid == trypid) {
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trypid++;
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if (trypid >= pidchecked)
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goto retry;
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}
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if (p2->p_pid > trypid && pidchecked > p2->p_pid)
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pidchecked = p2->p_pid;
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if (p2->p_pgrp->pg_id > trypid &&
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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 > trypid &&
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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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if (!doingzomb) {
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doingzomb = 1;
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p2 = LIST_FIRST(&zombproc);
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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 = trypid;
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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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* RFHIGHPID does not mess with the nextpid counter during boot.
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*/
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if (flags & RFHIGHPID)
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pidchecked = 0;
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else
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nextpid = trypid;
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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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uihold(p1->p_cred->p_uidinfo);
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if (p2->p_prison) {
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p2->p_prison->pr_ref++;
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p2->p_flag |= P_JAILED;
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}
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if (p2->p_args)
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p2->p_args->ar_ref++;
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if (flags & RFSIGSHARE) {
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p2->p_procsig = p1->p_procsig;
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p2->p_procsig->ps_refcnt++;
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if (p1->p_sigacts == &p1->p_addr->u_sigacts) {
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struct sigacts *newsigacts;
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int s;
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/* Create the shared sigacts structure */
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MALLOC(newsigacts, struct sigacts *,
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sizeof(struct sigacts), M_SUBPROC, M_WAITOK);
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s = splhigh();
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/*
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* Set p_sigacts to the new shared structure.
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* Note that this is updating p1->p_sigacts at the
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* same time, since p_sigacts is just a pointer to
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* the shared p_procsig->ps_sigacts.
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*/
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p2->p_sigacts = newsigacts;
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bcopy(&p1->p_addr->u_sigacts, p2->p_sigacts,
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sizeof(*p2->p_sigacts));
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*p2->p_sigacts = p1->p_addr->u_sigacts;
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splx(s);
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}
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} else {
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MALLOC(p2->p_procsig, struct procsig *, sizeof(struct procsig),
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M_SUBPROC, M_WAITOK);
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bcopy(p1->p_procsig, p2->p_procsig, sizeof(*p2->p_procsig));
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p2->p_procsig->ps_refcnt = 1;
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p2->p_sigacts = NULL; /* finished in vm_fork() */
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}
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if (flags & RFLINUXTHPN)
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p2->p_sigparent = SIGUSR1;
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else
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p2->p_sigparent = SIGCHLD;
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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 more flags in subprocess. P_PROFIL has already
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* been preserved.
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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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LIST_INIT(&p2->p_heldmtx);
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LIST_INIT(&p2->p_contested);
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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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PHOLD(p1);
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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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*/
|
|
vm_fork(p1, p2, flags);
|
|
|
|
/*
|
|
* 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);
|
|
}
|
|
|
|
/*
|
|
* If RFSTOPPED not requested, make child runnable and add to
|
|
* run queue.
|
|
*/
|
|
microtime(&(p2->p_stats->p_start));
|
|
p2->p_acflag = AFORK;
|
|
if ((flags & RFSTOPPED) == 0) {
|
|
splhigh();
|
|
mtx_enter(&sched_lock, MTX_SPIN);
|
|
p2->p_stat = SRUN;
|
|
setrunqueue(p2);
|
|
mtx_exit(&sched_lock, MTX_SPIN);
|
|
spl0();
|
|
}
|
|
|
|
/*
|
|
* Now can be swapped.
|
|
*/
|
|
PRELE(p1);
|
|
|
|
/*
|
|
* tell any interested parties about the new process
|
|
*/
|
|
KNOTE(&p1->p_klist, NOTE_FORK | p2->p_pid);
|
|
|
|
/*
|
|
* 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 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(function)
|
|
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_NOWAIT);
|
|
if (ep == NULL)
|
|
return (ENOMEM);
|
|
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(function)
|
|
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);
|
|
}
|