/*
* 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 8.6 (Berkeley) 4/8/94
* $FreeBSD$
*/
#include "opt_ktrace.h"
#include <sys/param.h>
#include <sys/systm.h>
#include <sys/sysproto.h>
#include <sys/filedesc.h>
#include <sys/kernel.h>
#include <sys/sysctl.h>
#include <sys/lock.h>
#include <sys/malloc.h>
#include <sys/mutex.h>
#include <sys/proc.h>
#include <sys/resourcevar.h>
#include <sys/syscall.h>
#include <sys/vnode.h>
#include <sys/acct.h>
#include <sys/ktr.h>
#include <sys/ktrace.h>
#include <sys/kthread.h>
#include <sys/unistd.h>
#include <sys/jail.h>
#include <sys/sx.h>
#include <vm/vm.h>
#include <vm/pmap.h>
#include <vm/vm_map.h>
#include <vm/vm_extern.h>
#include <vm/vm_zone.h>
#include <sys/vmmeter.h>
#include <sys/user.h>
static MALLOC_DEFINE(M_ATFORK, "atfork", "atfork callback");
static int fast_vfork = 1;
SYSCTL_INT(_kern, OID_AUTO, fast_vfork, CTLFLAG_RW, &fast_vfork, 0,
"flag to indicate whether we have a fast vfork()");
/*
* These are the stuctures used to create a callout list for things to do
* when forking a process
*/
struct forklist {
forklist_fn function;
TAILQ_ENTRY(forklist) next;
};
static struct sx fork_list_lock;
TAILQ_HEAD(forklist_head, forklist);
static struct forklist_head fork_list = TAILQ_HEAD_INITIALIZER(fork_list);
#ifndef _SYS_SYSPROTO_H_
struct fork_args {
int dummy;
};
#endif
static void
init_fork_list(void *data __unused)
{
sx_init(&fork_list_lock, "fork list");
}
SYSINIT(fork_list, SI_SUB_INTRINSIC, SI_ORDER_ANY, init_fork_list, NULL);
/* ARGSUSED */
int
fork(p, uap)
struct proc *p;
struct fork_args *uap;
{
int error;
struct proc *p2;
error = fork1(p, RFFDG | RFPROC, &p2);
if (error == 0) {
p->p_retval[0] = p2->p_pid;
p->p_retval[1] = 0;
}
return error;
}
/* ARGSUSED */
int
vfork(p, uap)
struct proc *p;
struct vfork_args *uap;
{
int error;
struct proc *p2;
error = fork1(p, RFFDG | RFPROC | RFPPWAIT | RFMEM, &p2);
if (error == 0) {
p->p_retval[0] = p2->p_pid;
p->p_retval[1] = 0;
}
return error;
}
int
rfork(p, uap)
struct proc *p;
struct rfork_args *uap;
{
int error;
struct proc *p2;
/* mask kernel only flags out of the user flags */
error = fork1(p, uap->flags & ~RFKERNELONLY, &p2);
if (error == 0) {
p->p_retval[0] = p2 ? p2->p_pid : 0;
p->p_retval[1] = 0;
}
return error;
}
int nprocs = 1; /* process 0 */
static int nextpid = 0;
SYSCTL_INT(_kern, OID_AUTO, lastpid, CTLFLAG_RD, &nextpid, 0,
"Last used PID");
/*
* Random component to nextpid generation. We mix in a random factor to make
* it a little harder to predict. We sanity check the modulus value to avoid
* doing it in critical paths. Don't let it be too small or we pointlessly
* waste randomness entropy, and don't let it be impossibly large. Using a
* modulus that is too big causes a LOT more process table scans and slows
* down fork processing as the pidchecked caching is defeated.
*/
static int randompid = 0;
static int
sysctl_kern_randompid(SYSCTL_HANDLER_ARGS)
{
int error, pid;
pid = randompid;
error = sysctl_handle_int(oidp, &pid, 0, req);
if (error || !req->newptr)
return (error);
if (pid < 0 || pid > PID_MAX - 100) /* out of range */
pid = PID_MAX - 100;
else if (pid < 2) /* NOP */
pid = 0;
else if (pid < 100) /* Make it reasonable */
pid = 100;
randompid = pid;
return (error);
}
SYSCTL_PROC(_kern, OID_AUTO, randompid, CTLTYPE_INT|CTLFLAG_RW,
0, 0, sysctl_kern_randompid, "I", "Random PID modulus");
int
fork1(p1, flags, procp)
struct proc *p1; /* parent proc */
int flags;
struct proc **procp; /* child proc */
{
struct proc *p2, *pptr;
uid_t uid;
struct proc *newproc;
int trypid;
int ok;
static int pidchecked = 0;
struct forklist *ep;
struct filedesc *fd;
/* Can't copy and clear */
if ((flags & (RFFDG|RFCFDG)) == (RFFDG|RFCFDG))
return (EINVAL);
/*
* Here we don't create a new process, but we divorce
* certain parts of a process from itself.
*/
if ((flags & RFPROC) == 0) {
vm_fork(p1, 0, flags);
mtx_assert(&vm_mtx, MA_NOTOWNED);
/*
* Close all file descriptors.
*/
if (flags & RFCFDG) {
struct filedesc *fdtmp;
fdtmp = fdinit(p1);
PROC_LOCK(p1);
fdfree(p1);
p1->p_fd = fdtmp;
PROC_UNLOCK(p1);
}
/*
* Unshare file descriptors (from parent.)
*/
if (flags & RFFDG) {
if (p1->p_fd->fd_refcnt > 1) {
struct filedesc *newfd;
newfd = fdcopy(p1);
PROC_LOCK(p1);
fdfree(p1);
p1->p_fd = newfd;
PROC_UNLOCK(p1);
}
}
*procp = NULL;
return (0);
}
/*
* 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_ucred->cr_ruid;
if ((nprocs >= maxproc - 1 && uid != 0) || nprocs >= maxproc) {
tablefull("proc");
return (EAGAIN);
}
/*
* Increment the nprocs resource before blocking can occur. There
* are hard-limits as to the number of processes that can run.
*/
nprocs++;
/*
* Increment the count of procs running with this uid. Don't allow
* a nonprivileged user to exceed their current limit.
*/
ok = chgproccnt(p1->p_ucred->cr_ruidinfo, 1,
(uid != 0) ? p1->p_rlimit[RLIMIT_NPROC].rlim_cur : 0);
if (!ok) {
/*
* Back out the process count
*/
nprocs--;
return (EAGAIN);
}
/* Allocate new proc. */
newproc = zalloc(proc_zone);
/*
* Setup linkage for kernel based threading
*/
if((flags & RFTHREAD) != 0) {
newproc->p_peers = p1->p_peers;
p1->p_peers = newproc;
newproc->p_leader = p1->p_leader;
} else {
newproc->p_peers = NULL;
newproc->p_leader = newproc;
}
newproc->p_vmspace = NULL;
/*
* Find an unused process ID. We remember a range of unused IDs
* ready to use (from nextpid+1 through pidchecked-1).
*
* If RFHIGHPID is set (used during system boot), do not allocate
* low-numbered pids.
*/
sx_xlock(&allproc_lock);
trypid = nextpid + 1;
if (flags & RFHIGHPID) {
if (trypid < 10) {
trypid = 10;
}
} else {
if (randompid)
trypid += arc4random() % randompid;
}
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 (trypid >= PID_MAX) {
trypid = trypid % PID_MAX;
if (trypid < 100)
trypid += 100;
pidchecked = 0;
}
if (trypid >= 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 trypid, so we can avoid checking for a while.
*/
p2 = LIST_FIRST(&allproc);
again:
for (; p2 != NULL; p2 = LIST_NEXT(p2, p_list)) {
while (p2->p_pid == trypid ||
p2->p_pgrp->pg_id == trypid ||
p2->p_session->s_sid == trypid) {
trypid++;
if (trypid >= pidchecked)
goto retry;
}
if (p2->p_pid > trypid && pidchecked > p2->p_pid)
pidchecked = p2->p_pid;
if (p2->p_pgrp->pg_id > trypid &&
pidchecked > p2->p_pgrp->pg_id)
pidchecked = p2->p_pgrp->pg_id;
if (p2->p_session->s_sid > trypid &&
pidchecked > p2->p_session->s_sid)
pidchecked = p2->p_session->s_sid;
}
if (!doingzomb) {
doingzomb = 1;
p2 = LIST_FIRST(&zombproc);
goto again;
}
}
/*
* RFHIGHPID does not mess with the nextpid counter during boot.
*/
if (flags & RFHIGHPID)
pidchecked = 0;
else
nextpid = trypid;
p2 = newproc;
p2->p_stat = SIDL; /* protect against others */
p2->p_pid = trypid;
LIST_INSERT_HEAD(&allproc, p2, p_list);
LIST_INSERT_HEAD(PIDHASH(p2->p_pid), p2, p_hash);
sx_xunlock(&allproc_lock);
/*
* 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));
PROC_LOCK(p1);
bcopy(&p1->p_startcopy, &p2->p_startcopy,
(unsigned) ((caddr_t)&p2->p_endcopy - (caddr_t)&p2->p_startcopy));
PROC_UNLOCK(p1);
mtx_init(&p2->p_mtx, "process lock", MTX_DEF);
PROC_LOCK(p2);
/*
* Duplicate sub-structures as needed.
* Increase reference counts on shared objects.
* The p_stats and p_sigacts substructs are set in vm_fork.
*/
p2->p_flag = 0;
mtx_lock_spin(&sched_lock);
p2->p_sflag = PS_INMEM;
if (p1->p_sflag & PS_PROFIL)
startprofclock(p2);
mtx_unlock_spin(&sched_lock);
/*
* We start off holding one spinlock after fork: sched_lock.
*/
p2->p_spinlocks = 1;
PROC_LOCK(p1);
crhold(p1->p_ucred);
p2->p_ucred = p1->p_ucred;
if (p2->p_args)
p2->p_args->ar_ref++;
if (flags & RFSIGSHARE) {
p2->p_procsig = p1->p_procsig;
p2->p_procsig->ps_refcnt++;
if (p1->p_sigacts == &p1->p_addr->u_sigacts) {
struct sigacts *newsigacts;
PROC_UNLOCK(p1);
PROC_UNLOCK(p2);
/* Create the shared sigacts structure */
MALLOC(newsigacts, struct sigacts *,
sizeof(struct sigacts), M_SUBPROC, M_WAITOK);
PROC_LOCK(p2);
PROC_LOCK(p1);
/*
* Set p_sigacts to the new shared structure.
* Note that this is updating p1->p_sigacts at the
* same time, since p_sigacts is just a pointer to
* the shared p_procsig->ps_sigacts.
*/
p2->p_sigacts = newsigacts;
bcopy(&p1->p_addr->u_sigacts, p2->p_sigacts,
sizeof(*p2->p_sigacts));
*p2->p_sigacts = p1->p_addr->u_sigacts;
}
} else {
PROC_UNLOCK(p1);
PROC_UNLOCK(p2);
MALLOC(p2->p_procsig, struct procsig *, sizeof(struct procsig),
M_SUBPROC, M_WAITOK);
PROC_LOCK(p2);
PROC_LOCK(p1);
bcopy(p1->p_procsig, p2->p_procsig, sizeof(*p2->p_procsig));
p2->p_procsig->ps_refcnt = 1;
p2->p_sigacts = NULL; /* finished in vm_fork() */
}
if (flags & RFLINUXTHPN)
p2->p_sigparent = SIGUSR1;
else
p2->p_sigparent = SIGCHLD;
/* bump references to the text vnode (for procfs) */
p2->p_textvp = p1->p_textvp;
PROC_UNLOCK(p1);
PROC_UNLOCK(p2);
if (p2->p_textvp)
VREF(p2->p_textvp);
if (flags & RFCFDG)
fd = fdinit(p1);
else if (flags & RFFDG)
fd = fdcopy(p1);
else
fd = fdshare(p1);
PROC_LOCK(p2);
p2->p_fd = fd;
/*
* 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.)
*/
PROC_LOCK(p1);
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++;
}
/*
* Preserve some more flags in subprocess. PS_PROFIL has already
* been preserved.
*/
p2->p_flag |= p1->p_flag & (P_SUGID | P_ALTSTACK);
if (p1->p_session->s_ttyvp != NULL && p1->p_flag & P_CONTROLT)
p2->p_flag |= P_CONTROLT;
if (flags & RFPPWAIT)
p2->p_flag |= P_PPWAIT;
LIST_INSERT_AFTER(p1, p2, p_pglist);
PROC_UNLOCK(p1);
PROC_UNLOCK(p2);
/*
* Attach the new process to its parent.
*
* If RFNOWAIT is set, the newly created process becomes a child
* of init. This effectively disassociates the child from the
* parent.
*/
if (flags & RFNOWAIT)
pptr = initproc;
else
pptr = p1;
sx_xlock(&proctree_lock);
PROC_LOCK(p2);
p2->p_pptr = pptr;
PROC_UNLOCK(p2);
LIST_INSERT_HEAD(&pptr->p_children, p2, p_sibling);
sx_xunlock(&proctree_lock);
PROC_LOCK(p2);
LIST_INIT(&p2->p_children);
LIST_INIT(&p2->p_contested);
callout_init(&p2->p_itcallout, 0);
callout_init(&p2->p_slpcallout, 1);
PROC_LOCK(p1);
#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) {
PROC_UNLOCK(p1);
PROC_UNLOCK(p2);
VREF(p2->p_tracep);
PROC_LOCK(p2);
PROC_LOCK(p1);
}
}
#endif
/*
* set priority of child to be that of parent
*/
mtx_lock_spin(&sched_lock);
p2->p_estcpu = p1->p_estcpu;
mtx_unlock_spin(&sched_lock);
/*
* This begins the section where we must prevent the parent
* from being swapped.
*/
_PHOLD(p1);
PROC_UNLOCK(p1);
PROC_UNLOCK(p2);
/*
* Finish creating the child process. It will return via a different
* execution path later. (ie: directly into user mode)
*/
vm_fork(p1, p2, flags);
mtx_assert(&vm_mtx, MA_NOTOWNED);
if (flags == (RFFDG | RFPROC)) {
cnt.v_forks++;
cnt.v_forkpages += p2->p_vmspace->vm_dsize + p2->p_vmspace->vm_ssize;
} else if (flags == (RFFDG | RFPROC | RFPPWAIT | RFMEM)) {
cnt.v_vforks++;
cnt.v_vforkpages += p2->p_vmspace->vm_dsize + p2->p_vmspace->vm_ssize;
} else if (p1 == &proc0) {
cnt.v_kthreads++;
cnt.v_kthreadpages += p2->p_vmspace->vm_dsize + p2->p_vmspace->vm_ssize;
} else {
cnt.v_rforks++;
cnt.v_rforkpages += p2->p_vmspace->vm_dsize + p2->p_vmspace->vm_ssize;
}
/*
* Both processes are set up, now check if any loadable modules want
* to adjust anything.
* What if they have an error? XXX
*/
sx_slock(&fork_list_lock);
TAILQ_FOREACH(ep, &fork_list, next) {
(*ep->function)(p1, p2, flags);
}
sx_sunlock(&fork_list_lock);
/*
* 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) {
mtx_lock_spin(&sched_lock);
p2->p_stat = SRUN;
setrunqueue(p2);
mtx_unlock_spin(&sched_lock);
}
/*
* Now can be swapped.
*/
PROC_LOCK(p1);
_PRELE(p1);
/*
* tell any interested parties about the new process
*/
KNOTE(&p1->p_klist, NOTE_FORK | p2->p_pid);
PROC_UNLOCK(p1);
/*
* 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).
*/
PROC_LOCK(p2);
while (p2->p_flag & P_PPWAIT)
msleep(p1, &p2->p_mtx, PWAIT, "ppwait", 0);
PROC_UNLOCK(p2);
/*
* 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;
sx_xlock(&fork_list_lock);
TAILQ_INSERT_TAIL(&fork_list, ep, next);
sx_xunlock(&fork_list_lock);
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;
sx_xlock(&fork_list_lock);
TAILQ_FOREACH(ep, &fork_list, next) {
if (ep->function == function) {
TAILQ_REMOVE(&fork_list, ep, next);
sx_xunlock(&fork_list_lock);
free(ep, M_ATFORK);
return(1);
}
}
sx_xunlock(&fork_list_lock);
return (0);
}
/*
* Handle the return of a child process from fork1(). This function
* is called from the MD fork_trampoline() entry point.
*/
void
fork_exit(callout, arg, frame)
void (*callout)(void *, struct trapframe *);
void *arg;
struct trapframe *frame;
{
struct proc *p;
p = curproc;
/*
* Setup the sched_lock state so that we can release it.
*/
sched_lock.mtx_lock = (uintptr_t)p;
sched_lock.mtx_recurse = 0;
/*
* XXX: We really shouldn't have to do this.
*/
mtx_intr_enable(&sched_lock);
mtx_unlock_spin(&sched_lock);
#ifdef SMP
if (PCPU_GET(switchtime.tv_sec) == 0)
microuptime(PCPU_PTR(switchtime));
PCPU_SET(switchticks, ticks);
#endif
/*
* cpu_set_fork_handler intercepts this function call to
* have this call a non-return function to stay in kernel mode.
* initproc has its own fork handler, but it does return.
*/
KASSERT(callout != NULL, ("NULL callout in fork_exit"));
callout(arg, frame);
/*
* Check if a kernel thread misbehaved and returned from its main
* function.
*/
PROC_LOCK(p);
if (p->p_flag & P_KTHREAD) {
PROC_UNLOCK(p);
mtx_lock(&Giant);
printf("Kernel thread \"%s\" (pid %d) exited prematurely.\n",
p->p_comm, p->p_pid);
kthread_exit(0);
}
PROC_UNLOCK(p);
mtx_assert(&Giant, MA_NOTOWNED);
}
/*
* Simplified back end of syscall(), used when returning from fork()
* directly into user mode. Giant is not held on entry, and must not
* be held on return. This function is passed in to fork_exit() as the
* first parameter and is called when returning to a new userland process.
*/
void
fork_return(p, frame)
struct proc *p;
struct trapframe *frame;
{
userret(p, frame, 0);
#ifdef KTRACE
if (KTRPOINT(p, KTR_SYSRET)) {
if (!mtx_owned(&Giant))
mtx_lock(&Giant);
ktrsysret(p->p_tracep, SYS_fork, 0, 0);
}
#endif
if (mtx_owned(&Giant))
mtx_unlock(&Giant);
mtx_assert(&Giant, MA_NOTOWNED);
}
