NetBSD/sys/kern/kern_fork.c

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/* $NetBSD: kern_fork.c,v 1.42 1998/05/02 18:33:20 christos Exp $ */
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/*
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* Copyright (c) 1982, 1986, 1989, 1991, 1993
* The Regents of the University of California. All rights reserved.
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* (c) UNIX System Laboratories, Inc.
* All or some portions of this file are derived from material licensed
* to the University of California by American Telephone and Telegraph
* Co. or Unix System Laboratories, Inc. and are reproduced herein with
* the permission of UNIX System Laboratories, Inc.
*
* Redistribution and use in source and binary forms, with or without
* modification, are permitted provided that the following conditions
* are met:
* 1. Redistributions of source code must retain the above copyright
* notice, this list of conditions and the following disclaimer.
* 2. Redistributions in binary form must reproduce the above copyright
* notice, this list of conditions and the following disclaimer in the
* documentation and/or other materials provided with the distribution.
* 3. All advertising materials mentioning features or use of this software
* must display the following acknowledgement:
* This product includes software developed by the University of
* California, Berkeley and its contributors.
* 4. Neither the name of the University nor the names of its contributors
* may be used to endorse or promote products derived from this software
* without specific prior written permission.
*
* THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
* ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
* IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
* ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
* FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
* DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
* OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
* HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
* LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
* OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
* SUCH DAMAGE.
*
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* @(#)kern_fork.c 8.8 (Berkeley) 2/14/95
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*/
#include "opt_uvm.h"
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#include <sys/param.h>
#include <sys/systm.h>
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#include <sys/map.h>
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#include <sys/filedesc.h>
#include <sys/kernel.h>
#include <sys/malloc.h>
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#include <sys/mount.h>
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#include <sys/proc.h>
#include <sys/resourcevar.h>
#include <sys/vnode.h>
#include <sys/file.h>
#include <sys/acct.h>
#include <sys/ktrace.h>
#include <sys/vmmeter.h>
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#include <sys/syscallargs.h>
#include <vm/vm.h>
#include <vm/vm_kern.h>
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#if defined(UVM)
#include <uvm/uvm_extern.h>
#endif
int nprocs = 1; /* process 0 */
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/*ARGSUSED*/
int
sys_fork(p, v, retval)
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struct proc *p;
void *v;
register_t *retval;
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{
return (fork1(p, 0, retval, NULL));
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}
/*
* vfork(2) system call compatible with 4.4BSD (i.e. BSD with Mach VM).
* Address space is not shared, but parent is blocked until child exit.
*/
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/*ARGSUSED*/
int
sys_vfork(p, v, retval)
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struct proc *p;
void *v;
register_t *retval;
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{
return (fork1(p, FORK_PPWAIT, retval, NULL));
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}
/*
* New vfork(2) system call for NetBSD, which implements original 3BSD vfork(2)
* semantics. Address space is shared, and parent is blocked until child exit.
*/
/*ARGSUSED*/
int
sys___vfork14(p, v, retval)
struct proc *p;
void *v;
register_t *retval;
{
return (fork1(p, FORK_PPWAIT|FORK_SHAREVM, retval, NULL));
}
int
fork1(p1, flags, retval, rnewprocp)
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register struct proc *p1;
int flags;
register_t *retval;
struct proc **rnewprocp;
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{
register struct proc *p2;
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register uid_t uid;
struct proc *newproc;
int count;
vm_offset_t uaddr;
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static int nextpid, pidchecked = 0;
/*
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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
* 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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uid = p1->p_cred->p_ruid;
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if ((nprocs >= maxproc - 1 && uid != 0) || nprocs >= maxproc) {
tablefull("proc");
return (EAGAIN);
}
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/*
* Increment the count of procs running with this uid. Don't allow
* a nonprivileged user to exceed their current limit.
*/
count = chgproccnt(uid, 1);
if (uid != 0 && count > p1->p_rlimit[RLIMIT_NPROC].rlim_cur) {
(void)chgproccnt(uid, -1);
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return (EAGAIN);
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}
/*
* Allocate virtual address space for the U-area now, while it
* is still easy to abort the fork operation if we're out of
* kernel virtual address space. The actual U-area pages will
* be allocated and wired in vm_fork().
*/
#if defined(UVM)
uaddr = uvm_km_valloc(kernel_map, USPACE);
#else
uaddr = kmem_alloc_pageable(kernel_map, USPACE);
#endif
if (uaddr == 0) {
(void)chgproccnt(uid, -1);
return (ENOMEM);
}
/*
* We are now committed to the fork. From here on, we may
* block on resources, but resource allocation may NOT fail.
*/
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/* Allocate new proc. */
MALLOC(newproc, struct proc *, sizeof(struct proc), M_PROC, M_WAITOK);
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/*
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* Find an unused process ID. We remember a range of unused IDs
* ready to use (from nextpid+1 through pidchecked-1).
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*/
nextpid++;
retry:
/*
* If the process ID prototype has wrapped around,
* restart somewhat above 0, as the low-numbered procs
* tend to include daemons that don't exit.
*/
if (nextpid >= PID_MAX) {
nextpid = 100;
pidchecked = 0;
}
if (nextpid >= pidchecked) {
int doingzomb = 0;
pidchecked = PID_MAX;
/*
* Scan the active and zombie procs to check whether this pid
* is in use. Remember the lowest pid that's greater
* than nextpid, so we can avoid checking for a while.
*/
p2 = allproc.lh_first;
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again:
for (; p2 != 0; p2 = p2->p_list.le_next) {
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while (p2->p_pid == nextpid ||
p2->p_pgrp->pg_id == nextpid ||
p2->p_session->s_sid == nextpid) {
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nextpid++;
if (nextpid >= pidchecked)
goto retry;
}
if (p2->p_pid > nextpid && pidchecked > p2->p_pid)
pidchecked = p2->p_pid;
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if (p2->p_pgrp->pg_id > nextpid &&
pidchecked > p2->p_pgrp->pg_id)
pidchecked = p2->p_pgrp->pg_id;
if (p2->p_session->s_sid > nextpid &&
pidchecked > p2->p_session->s_sid)
pidchecked = p2->p_session->s_sid;
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}
if (!doingzomb) {
doingzomb = 1;
p2 = zombproc.lh_first;
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goto again;
}
}
nprocs++;
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p2 = newproc;
p2->p_stat = SIDL; /* protect against others */
p2->p_pid = nextpid;
LIST_INSERT_HEAD(&allproc, p2, p_list);
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p2->p_forw = p2->p_back = NULL; /* shouldn't be necessary */
LIST_INSERT_HEAD(PIDHASH(p2->p_pid), p2, p_hash);
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/*
* Make a proc table entry for the new process.
* Start by zeroing the section of proc that is zero-initialized,
* then copy the section that is copied directly from the parent.
*/
bzero(&p2->p_startzero,
(unsigned) ((caddr_t)&p2->p_endzero - (caddr_t)&p2->p_startzero));
bcopy(&p1->p_startcopy, &p2->p_startcopy,
(unsigned) ((caddr_t)&p2->p_endcopy - (caddr_t)&p2->p_startcopy));
/*
* Duplicate sub-structures as needed.
* Increase reference counts on shared objects.
* The p_stats and p_sigacts substructs are set in vm_fork.
*/
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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)
startprofclock(p2);
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MALLOC(p2->p_cred, struct pcred *, sizeof(struct pcred),
M_SUBPROC, M_WAITOK);
bcopy(p1->p_cred, p2->p_cred, sizeof(*p2->p_cred));
p2->p_cred->p_refcnt = 1;
crhold(p1->p_ucred);
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/* bump references to the text vnode (for procfs) */
p2->p_textvp = p1->p_textvp;
if (p2->p_textvp)
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VREF(p2->p_textvp);
p2->p_fd = fdcopy(p1);
/*
* If p_limit is still copy-on-write, bump refcnt,
* otherwise get a copy that won't be modified.
* (If PL_SHAREMOD is clear, the structure is shared
* copy-on-write.)
*/
if (p1->p_limit->p_lflags & PL_SHAREMOD)
p2->p_limit = limcopy(p1->p_limit);
else {
p2->p_limit = p1->p_limit;
p2->p_limit->p_refcnt++;
}
if (p1->p_session->s_ttyvp != NULL && p1->p_flag & P_CONTROLT)
p2->p_flag |= P_CONTROLT;
if (flags & FORK_PPWAIT)
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p2->p_flag |= P_PPWAIT;
LIST_INSERT_AFTER(p1, p2, p_pglist);
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p2->p_pptr = p1;
LIST_INSERT_HEAD(&p1->p_children, p2, p_sibling);
LIST_INIT(&p2->p_children);
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#ifdef KTRACE
/*
* Copy traceflag and tracefile if enabled.
* If not inherited, these were zeroed above.
*/
if (p1->p_traceflag&KTRFAC_INHERIT) {
p2->p_traceflag = p1->p_traceflag;
if ((p2->p_tracep = p1->p_tracep) != NULL)
ktradref(p2);
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}
#endif
/*
* This begins the section where we must prevent the parent
* from being swapped.
*/
PHOLD(p1);
/*
* Finish creating the child process. It will return through a
* different path later.
*/
p2->p_addr = (struct user *)uaddr;
#if defined(UVM)
uvm_fork(p1, p2, (flags & FORK_SHAREVM) ? TRUE : FALSE);
#else
vm_fork(p1, p2, (flags & FORK_SHAREVM) ? TRUE : FALSE);
#endif
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/*
* Make child runnable, set start time, and add to run queue.
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*/
(void) splstatclock();
p2->p_stats->p_start = time;
p2->p_acflag = AFORK;
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p2->p_stat = SRUN;
setrunqueue(p2);
(void) spl0();
/*
* Now can be swapped.
*/
PRELE(p1);
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/*
* Update stats now that we know the fork was successful.
*/
#if defined(UVM)
uvmexp.forks++;
if (flags & FORK_PPWAIT)
uvmexp.forks_ppwait++;
if (flags & FORK_SHAREVM)
uvmexp.forks_sharevm++;
#else
cnt.v_forks++;
if (flags & FORK_PPWAIT)
cnt.v_forks_ppwait++;
if (flags & FORK_SHAREVM)
cnt.v_forks_sharevm++;
#endif
/*
* Pass a pointer to the new process to the caller.
*/
if (rnewprocp != NULL)
*rnewprocp = p2;
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/*
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* 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).
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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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/*
* Return child pid to parent process,
* marking us as parent via retval[1].
*/
if (retval != NULL) {
retval[0] = p2->p_pid;
retval[1] = 0;
}
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return (0);
}