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NetBSD/sys/kern/kern_fork.c

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/* $NetBSD: kern_fork.c,v 1.87 2001/11/12 15:25:09 lukem Exp $ */
/*-
* Copyright (c) 1999, 2001 The NetBSD Foundation, Inc.
* All rights reserved.
*
* This code is derived from software contributed to The NetBSD Foundation
* by Jason R. Thorpe of the Numerical Aerospace Simulation Facility,
* NASA Ames Research Center.
*
* 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 NetBSD
* Foundation, Inc. and its contributors.
* 4. Neither the name of The NetBSD Foundation 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 NETBSD FOUNDATION, INC. 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 FOUNDATION 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.
*/
/*
* Copyright (c) 1982, 1986, 1989, 1991, 1993
* The Regents of the University of California. All rights reserved.
* (c) UNIX System Laboratories, Inc.
* All or some portions of this file are derived from material licensed
* to the University of California by American Telephone and Telegraph
* Co. or Unix System Laboratories, Inc. and are reproduced herein with
* the permission of UNIX System Laboratories, Inc.
*
* Redistribution and use in source and binary forms, with or without
* modification, are permitted provided that the following conditions
* are met:
* 1. Redistributions of source code must retain the above copyright
* notice, this list of conditions and the following disclaimer.
* 2. Redistributions in binary form must reproduce the above copyright
* notice, this list of conditions and the following disclaimer in the
* documentation and/or other materials provided with the distribution.
* 3. All advertising materials mentioning features or use of this software
* must display the following acknowledgement:
* This product includes software developed by the University of
* California, Berkeley and its contributors.
* 4. Neither the name of the University nor the names of its contributors
* may be used to endorse or promote products derived from this software
* without specific prior written permission.
*
* THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
* ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
* IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
* ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
* FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
* DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
* OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
* HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
* LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
* OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
* SUCH DAMAGE.
*
* @(#)kern_fork.c 8.8 (Berkeley) 2/14/95
*/
#include <sys/cdefs.h>
__KERNEL_RCSID(0, "$NetBSD: kern_fork.c,v 1.87 2001/11/12 15:25:09 lukem Exp $");
#include "opt_ktrace.h"
#include "opt_multiprocessor.h"
#include <sys/param.h>
#include <sys/systm.h>
#include <sys/map.h>
#include <sys/filedesc.h>
#include <sys/kernel.h>
#include <sys/malloc.h>
#include <sys/pool.h>
#include <sys/mount.h>
#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>
#include <sys/sched.h>
#include <sys/signalvar.h>
#include <sys/syscallargs.h>
#include <uvm/uvm_extern.h>
int nprocs = 1; /* process 0 */
/*ARGSUSED*/
int
sys_fork(struct proc *p, void *v, register_t *retval)
{
return (fork1(p, 0, SIGCHLD, NULL, 0, NULL, NULL, retval, NULL));
}
/*
* 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.
*/
/*ARGSUSED*/
int
sys_vfork(struct proc *p, void *v, register_t *retval)
{
return (fork1(p, FORK_PPWAIT, SIGCHLD, NULL, 0, NULL, NULL,
retval, NULL));
}
/*
* 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(struct proc *p, void *v, register_t *retval)
{
return (fork1(p, FORK_PPWAIT|FORK_SHAREVM, SIGCHLD, NULL, 0,
NULL, NULL, retval, NULL));
}
/*
* Linux-compatible __clone(2) system call.
*/
int
sys___clone(struct proc *p, void *v, register_t *retval)
{
struct sys___clone_args /* {
syscallarg(int) flags;
syscallarg(void *) stack;
} */ *uap = v;
int flags, sig;
/*
* We don't support the CLONE_PID or CLONE_PTRACE flags.
*/
if (SCARG(uap, flags) & (CLONE_PID|CLONE_PTRACE))
return (EINVAL);
flags = 0;
if (SCARG(uap, flags) & CLONE_VM)
flags |= FORK_SHAREVM;
if (SCARG(uap, flags) & CLONE_FS)
flags |= FORK_SHARECWD;
if (SCARG(uap, flags) & CLONE_FILES)
flags |= FORK_SHAREFILES;
if (SCARG(uap, flags) & CLONE_SIGHAND)
flags |= FORK_SHARESIGS;
if (SCARG(uap, flags) & CLONE_VFORK)
flags |= FORK_PPWAIT;
sig = SCARG(uap, flags) & CLONE_CSIGNAL;
if (sig < 0 || sig >= _NSIG)
return (EINVAL);
/*
* Note that the Linux API does not provide a portable way of
* specifying the stack area; the caller must know if the stack
* grows up or down. So, we pass a stack size of 0, so that the
* code that makes this adjustment is a noop.
*/
return (fork1(p, flags, sig, SCARG(uap, stack), 0,
NULL, NULL, retval, NULL));
}
int
fork1(struct proc *p1, int flags, int exitsig, void *stack, size_t stacksize,
void (*func)(void *), void *arg, register_t *retval,
struct proc **rnewprocp)
{
struct proc *p2, *tp;
uid_t uid;
int count, s;
vaddr_t uaddr;
static int nextpid, pidchecked;
/*
* Although process entries are dynamically created, we still keep
* a global limit on the maximum number we will create. Don't allow
* a nonprivileged user to use the last process; don't let root
* exceed the limit. The variable nprocs is the current number of
* processes, maxproc is the limit.
*/
uid = p1->p_cred->p_ruid;
if (__predict_false((nprocs >= maxproc - 1 && uid != 0) ||
nprocs >= maxproc)) {
tablefull("proc", "increase kern.maxproc or NPROC");
return (EAGAIN);
}
nprocs++;
/*
* Increment the count of procs running with this uid. Don't allow
* a nonprivileged user to exceed their current limit.
*/
count = chgproccnt(uid, 1);
if (__predict_false(uid != 0 && count >
p1->p_rlimit[RLIMIT_NPROC].rlim_cur)) {
(void)chgproccnt(uid, -1);
nprocs--;
return (EAGAIN);
}
/*
* 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().
*/
#ifndef USPACE_ALIGN
#define USPACE_ALIGN 0
#endif
uaddr = uvm_km_valloc_align(kernel_map, USPACE, USPACE_ALIGN);
if (__predict_false(uaddr == 0)) {
(void)chgproccnt(uid, -1);
nprocs--;
return (ENOMEM);
}
/*
* We are now committed to the fork. From here on, we may
* block on resources, but resource allocation may NOT fail.
*/
/* Allocate new proc. */
p2 = pool_get(&proc_pool, PR_WAITOK);
/*
* 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.
*/
memset(&p2->p_startzero, 0,
(unsigned) ((caddr_t)&p2->p_endzero - (caddr_t)&p2->p_startzero));
memcpy(&p2->p_startcopy, &p1->p_startcopy,
(unsigned) ((caddr_t)&p2->p_endcopy - (caddr_t)&p2->p_startcopy));
#if !defined(MULTIPROCESSOR)
/*
* In the single-processor case, all processes will always run
* on the same CPU. So, initialize the child's CPU to the parent's
* now. In the multiprocessor case, the child's CPU will be
* initialized in the low-level context switch code when the
* process runs.
*/
p2->p_cpu = p1->p_cpu;
#else
/*
* zero child's cpu pointer so we don't get trash.
*/
p2->p_cpu = NULL;
#endif /* ! MULTIPROCESSOR */
/*
* Duplicate sub-structures as needed.
* Increase reference counts on shared objects.
* The p_stats and p_sigacts substructs are set in uvm_fork().
*/
p2->p_flag = P_INMEM | (p1->p_flag & P_SUGID);
p2->p_emul = p1->p_emul;
if (p1->p_flag & P_PROFIL)
startprofclock(p2);
p2->p_cred = pool_get(&pcred_pool, PR_WAITOK);
memcpy(p2->p_cred, p1->p_cred, sizeof(*p2->p_cred));
p2->p_cred->p_refcnt = 1;
crhold(p1->p_ucred);
/* bump references to the text vnode (for procfs) */
p2->p_textvp = p1->p_textvp;
if (p2->p_textvp)
VREF(p2->p_textvp);
if (flags & FORK_SHAREFILES)
fdshare(p1, p2);
else
p2->p_fd = fdcopy(p1);
if (flags & FORK_SHARECWD)
cwdshare(p1, p2);
else
p2->p_cwdi = cwdinit(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)
p2->p_flag |= P_PPWAIT;
LIST_INSERT_AFTER(p1, p2, p_pglist);
p2->p_pptr = p1;
LIST_INSERT_HEAD(&p1->p_children, p2, p_sibling);
LIST_INIT(&p2->p_children);
callout_init(&p2->p_realit_ch);
callout_init(&p2->p_tsleep_ch);
#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);
}
#endif
#ifdef __HAVE_SYSCALL_INTERN
(*p2->p_emul->e_syscall_intern)(p2);
#endif
scheduler_fork_hook(p1, p2);
/*
* Create signal actions for the child process.
*/
sigactsinit(p2, p1, flags & FORK_SHARESIGS);
/*
* If emulation has process fork hook, call it now.
*/
if (p2->p_emul->e_proc_fork)
(*p2->p_emul->e_proc_fork)(p2, p1);
/*
* 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;
uvm_fork(p1, p2, (flags & FORK_SHAREVM) ? TRUE : FALSE,
stack, stacksize,
(func != NULL) ? func : child_return,
(arg != NULL) ? arg : p2);
/*
* BEGIN PID ALLOCATION.
*/
s = proclist_lock_write();
/*
* Find an unused process ID. We remember a range of unused IDs
* ready to use (from nextpid+1 through pidchecked-1).
*/
nextpid++;
retry:
/*
* If the process ID prototype has wrapped around,
* restart somewhat above 0, as the low-numbered procs
* tend to include daemons that don't exit.
*/
if (nextpid >= PID_MAX) {
nextpid = 500;
pidchecked = 0;
}
if (nextpid >= pidchecked) {
const struct proclist_desc *pd;
pidchecked = PID_MAX;
/*
* Scan the process lists 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.
*/
pd = proclists;
again:
LIST_FOREACH(tp, pd->pd_list, p_list) {
while (tp->p_pid == nextpid ||
tp->p_pgrp->pg_id == nextpid ||
tp->p_session->s_sid == nextpid) {
nextpid++;
if (nextpid >= pidchecked)
goto retry;
}
if (tp->p_pid > nextpid && pidchecked > tp->p_pid)
pidchecked = tp->p_pid;
if (tp->p_pgrp->pg_id > nextpid &&
pidchecked > tp->p_pgrp->pg_id)
pidchecked = tp->p_pgrp->pg_id;
if (tp->p_session->s_sid > nextpid &&
pidchecked > tp->p_session->s_sid)
pidchecked = tp->p_session->s_sid;
}
/*
* If there's another list, scan it. If we have checked
* them all, we've found one!
*/
pd++;
if (pd->pd_list != NULL)
goto again;
}
/* Record the pid we've allocated. */
p2->p_pid = nextpid;
/* Record the signal to be delivered to the parent on exit. */
p2->p_exitsig = exitsig;
/*
* Put the proc on allproc before unlocking PID allocation
* so that waiters won't grab it as soon as we unlock.
*/
p2->p_stat = SIDL; /* protect against others */
p2->p_forw = p2->p_back = NULL; /* shouldn't be necessary */
LIST_INSERT_HEAD(&allproc, p2, p_list);
LIST_INSERT_HEAD(PIDHASH(p2->p_pid), p2, p_hash);
/*
* END PID ALLOCATION.
*/
proclist_unlock_write(s);
/*
* Make child runnable, set start time, and add to run queue.
*/
SCHED_LOCK(s);
p2->p_stats->p_start = time;
p2->p_acflag = AFORK;
p2->p_stat = SRUN;
setrunqueue(p2);
SCHED_UNLOCK(s);
/*
* Now can be swapped.
*/
PRELE(p1);
/*
* Update stats now that we know the fork was successful.
*/
uvmexp.forks++;
if (flags & FORK_PPWAIT)
uvmexp.forks_ppwait++;
if (flags & FORK_SHAREVM)
uvmexp.forks_sharevm++;
/*
* Pass a pointer to the new process to the caller.
*/
if (rnewprocp != NULL)
*rnewprocp = p2;
#ifdef KTRACE
if (KTRPOINT(p2, KTR_EMUL))
ktremul(p2);
#endif
/*
* 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).
*/
if (flags & FORK_PPWAIT)
while (p2->p_flag & P_PPWAIT)
tsleep(p1, PWAIT, "ppwait", 0);
/*
* Return child pid to parent process,
* marking us as parent via retval[1].
*/
if (retval != NULL) {
retval[0] = p2->p_pid;
retval[1] = 0;
}
return (0);
}
#if defined(MULTIPROCESSOR)
/*
* XXX This is a slight hack to get newly-formed processes to
* XXX acquire the kernel lock as soon as they run.
*/
void
proc_trampoline_mp(void)
{
struct proc *p;
p = curproc;
SCHED_ASSERT_UNLOCKED();
KERNEL_PROC_LOCK(p);
}
#endif
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