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8e6fa660f2
freebsd-dev/sys/kern/kern_fork.c
John Baldwin 8e6fa660f2 Fix some locking nits with the p_state field of struct proc: 
- Hold the proc lock while changing the state from PRS_NEW to PRS_NORMAL
  in fork to honor the locking requirements.  While here, expand the scope
  of the PROC_LOCK() on the new process (p2) to avoid some LORs.  Previously
  the code was locking the new child process (p2) after it had locked the
  parent process (p1).  However, when locking two processes, the safe order
  is to lock the child first, then the parent.
- Fix various places that were checking p_state against PRS_NEW without
  having the process locked to use PROC_LOCK().  Every place was already
  locking the process, just after the PRS_NEW check.
- Remove or reduce the use of PROC_SLOCK() for places that were checking
  p_state against PRS_NEW.  The PROC_LOCK() alone is sufficient for reading
  the current state.
- Reorder fill_kinfo_proc() slightly so it only acquires PROC_SLOCK() once.

MFC after:	1 week
2011-03-24 18:40:11 +00:00

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/*-
* 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.
* 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
*/
#include <sys/cdefs.h>
__FBSDID("$FreeBSD$");
#include "opt_kdtrace.h"
#include "opt_ktrace.h"
#include "opt_kstack_pages.h"
#include <sys/param.h>
#include <sys/systm.h>
#include <sys/sysproto.h>
#include <sys/eventhandler.h>
#include <sys/filedesc.h>
#include <sys/jail.h>
#include <sys/kernel.h>
#include <sys/kthread.h>
#include <sys/sysctl.h>
#include <sys/lock.h>
#include <sys/malloc.h>
#include <sys/mutex.h>
#include <sys/priv.h>
#include <sys/proc.h>
#include <sys/pioctl.h>
#include <sys/resourcevar.h>
#include <sys/sched.h>
#include <sys/syscall.h>
#include <sys/vmmeter.h>
#include <sys/vnode.h>
#include <sys/acct.h>
#include <sys/ktr.h>
#include <sys/ktrace.h>
#include <sys/unistd.h>
#include <sys/sdt.h>
#include <sys/sx.h>
#include <sys/sysent.h>
#include <sys/signalvar.h>
#include <security/audit/audit.h>
#include <security/mac/mac_framework.h>
#include <vm/vm.h>
#include <vm/pmap.h>
#include <vm/vm_map.h>
#include <vm/vm_extern.h>
#include <vm/uma.h>
#ifdef KDTRACE_HOOKS
#include <sys/dtrace_bsd.h>
dtrace_fork_func_t dtrace_fasttrap_fork;
#endif
SDT_PROVIDER_DECLARE(proc);
SDT_PROBE_DEFINE(proc, kernel, , create, create);
SDT_PROBE_ARGTYPE(proc, kernel, , create, 0, "struct proc *");
SDT_PROBE_ARGTYPE(proc, kernel, , create, 1, "struct proc *");
SDT_PROBE_ARGTYPE(proc, kernel, , create, 2, "int");
#ifndef _SYS_SYSPROTO_H_
struct fork_args {
int dummy;
};
#endif
/* ARGSUSED */
int
fork(struct thread *td, struct fork_args *uap)
{
int error;
struct proc *p2;
error = fork1(td, RFFDG | RFPROC, 0, &p2);
if (error == 0) {
td->td_retval[0] = p2->p_pid;
td->td_retval[1] = 0;
}
return (error);
}
/* ARGSUSED */
int
vfork(struct thread *td, struct vfork_args *uap)
{
int error, flags;
struct proc *p2;
#ifdef XEN
flags = RFFDG | RFPROC; /* validate that this is still an issue */
#else
flags = RFFDG | RFPROC | RFPPWAIT | RFMEM;
#endif
error = fork1(td, flags, 0, &p2);
if (error == 0) {
td->td_retval[0] = p2->p_pid;
td->td_retval[1] = 0;
}
return (error);
}
int
rfork(struct thread *td, struct rfork_args *uap)
{
struct proc *p2;
int error;
/* Don't allow kernel-only flags. */
if ((uap->flags & RFKERNELONLY) != 0)
return (EINVAL);
AUDIT_ARG_FFLAGS(uap->flags);
error = fork1(td, uap->flags, 0, &p2);
if (error == 0) {
td->td_retval[0] = p2 ? p2->p_pid : 0;
td->td_retval[1] = 0;
}
return (error);
}
int nprocs = 1; /* process 0 */
int lastpid = 0;
SYSCTL_INT(_kern, OID_AUTO, lastpid, CTLFLAG_RD, &lastpid, 0,
"Last used PID");
/*
* Random component to lastpid 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;
error = sysctl_wire_old_buffer(req, sizeof(int));
if (error != 0)
return(error);
sx_xlock(&allproc_lock);
pid = randompid;
error = sysctl_handle_int(oidp, &pid, 0, req);
if (error == 0 && req->newptr != NULL) {
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;
}
sx_xunlock(&allproc_lock);
return (error);
}
SYSCTL_PROC(_kern, OID_AUTO, randompid, CTLTYPE_INT|CTLFLAG_RW,
0, 0, sysctl_kern_randompid, "I", "Random PID modulus");
static int
fork_findpid(int flags)
{
struct proc *p;
int trypid;
static int pidchecked = 0;
/*
* Requires allproc_lock in order to iterate over the list
* of processes, and proctree_lock to access p_pgrp.
*/
sx_assert(&allproc_lock, SX_LOCKED);
sx_assert(&proctree_lock, SX_LOCKED);
/*
* Find an unused process ID. We remember a range of unused IDs
* ready to use (from lastpid+1 through pidchecked-1).
*
* If RFHIGHPID is set (used during system boot), do not allocate
* low-numbered pids.
*/
trypid = lastpid + 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.
*/
p = LIST_FIRST(&allproc);
again:
for (; p != NULL; p = LIST_NEXT(p, p_list)) {
while (p->p_pid == trypid ||
(p->p_pgrp != NULL &&
(p->p_pgrp->pg_id == trypid ||
(p->p_session != NULL &&
p->p_session->s_sid == trypid)))) {
trypid++;
if (trypid >= pidchecked)
goto retry;
}
if (p->p_pid > trypid && pidchecked > p->p_pid)
pidchecked = p->p_pid;
if (p->p_pgrp != NULL) {
if (p->p_pgrp->pg_id > trypid &&
pidchecked > p->p_pgrp->pg_id)
pidchecked = p->p_pgrp->pg_id;
if (p->p_session != NULL &&
p->p_session->s_sid > trypid &&
pidchecked > p->p_session->s_sid)
pidchecked = p->p_session->s_sid;
}
}
if (!doingzomb) {
doingzomb = 1;
p = LIST_FIRST(&zombproc);
goto again;
}
}
/*
* RFHIGHPID does not mess with the lastpid counter during boot.
*/
if (flags & RFHIGHPID)
pidchecked = 0;
else
lastpid = trypid;
return (trypid);
}
static int
fork_norfproc(struct thread *td, int flags)
{
int error;
struct proc *p1;
KASSERT((flags & RFPROC) == 0,
("fork_norfproc called with RFPROC set"));
p1 = td->td_proc;
if (((p1->p_flag & (P_HADTHREADS|P_SYSTEM)) == P_HADTHREADS) &&
(flags & (RFCFDG | RFFDG))) {
PROC_LOCK(p1);
if (thread_single(SINGLE_BOUNDARY)) {
PROC_UNLOCK(p1);
return (ERESTART);
}
PROC_UNLOCK(p1);
}
error = vm_forkproc(td, NULL, NULL, NULL, flags);
if (error)
goto fail;
/*
* Close all file descriptors.
*/
if (flags & RFCFDG) {
struct filedesc *fdtmp;
fdtmp = fdinit(td->td_proc->p_fd);
fdfree(td);
p1->p_fd = fdtmp;
}
/*
* Unshare file descriptors (from parent).
*/
if (flags & RFFDG)
fdunshare(p1, td);
fail:
if (((p1->p_flag & (P_HADTHREADS|P_SYSTEM)) == P_HADTHREADS) &&
(flags & (RFCFDG | RFFDG))) {
PROC_LOCK(p1);
thread_single_end();
PROC_UNLOCK(p1);
}
return (error);
}
static void
do_fork(struct thread *td, int flags, struct proc *p2, struct thread *td2,
struct vmspace *vm2)
{
struct proc *p1, *pptr;
int p2_held, trypid;
struct filedesc *fd;
struct filedesc_to_leader *fdtol;
struct sigacts *newsigacts;
sx_assert(&proctree_lock, SX_SLOCKED);
sx_assert(&allproc_lock, SX_XLOCKED);
p2_held = 0;
p1 = td->td_proc;
/*
* Increment the nprocs resource before blocking can occur. There
* are hard-limits as to the number of processes that can run.
*/
nprocs++;
trypid = fork_findpid(flags);
sx_sunlock(&proctree_lock);
p2->p_state = PRS_NEW; /* protect against others */
p2->p_pid = trypid;
AUDIT_ARG_PID(p2->p_pid);
LIST_INSERT_HEAD(&allproc, p2, p_list);
LIST_INSERT_HEAD(PIDHASH(p2->p_pid), p2, p_hash);
tidhash_add(td2);
PROC_LOCK(p2);
PROC_LOCK(p1);
sx_xunlock(&allproc_lock);
bcopy(&p1->p_startcopy, &p2->p_startcopy,
__rangeof(struct proc, p_startcopy, p_endcopy));
pargs_hold(p2->p_args);
PROC_UNLOCK(p1);
bzero(&p2->p_startzero,
__rangeof(struct proc, p_startzero, p_endzero));
p2->p_ucred = crhold(td->td_ucred);
/* Tell the prison that we exist. */
prison_proc_hold(p2->p_ucred->cr_prison);
PROC_UNLOCK(p2);
/*
* Malloc things while we don't hold any locks.
*/
if (flags & RFSIGSHARE)
newsigacts = NULL;
else
newsigacts = sigacts_alloc();
/*
* Copy filedesc.
*/
if (flags & RFCFDG) {
fd = fdinit(p1->p_fd);
fdtol = NULL;
} else if (flags & RFFDG) {
fd = fdcopy(p1->p_fd);
fdtol = NULL;
} else {
fd = fdshare(p1->p_fd);
if (p1->p_fdtol == NULL)
p1->p_fdtol = filedesc_to_leader_alloc(NULL, NULL,
p1->p_leader);
if ((flags & RFTHREAD) != 0) {
/*
* Shared file descriptor table, and shared
* process leaders.
*/
fdtol = p1->p_fdtol;
FILEDESC_XLOCK(p1->p_fd);
fdtol->fdl_refcount++;
FILEDESC_XUNLOCK(p1->p_fd);
} else {
/*
* Shared file descriptor table, and different
* process leaders.
*/
fdtol = filedesc_to_leader_alloc(p1->p_fdtol,
p1->p_fd, p2);
}
}
/*
* 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.
*/
PROC_LOCK(p2);
PROC_LOCK(p1);
bzero(&td2->td_startzero,
__rangeof(struct thread, td_startzero, td_endzero));
bcopy(&td->td_startcopy, &td2->td_startcopy,
__rangeof(struct thread, td_startcopy, td_endcopy));
bcopy(&p2->p_comm, &td2->td_name, sizeof(td2->td_name));
td2->td_sigstk = td->td_sigstk;
td2->td_sigmask = td->td_sigmask;
td2->td_flags = TDF_INMEM;
td2->td_lend_user_pri = PRI_MAX;
#ifdef VIMAGE
td2->td_vnet = NULL;
td2->td_vnet_lpush = NULL;
#endif
/*
* Allow the scheduler to initialize the child.
*/
thread_lock(td);
sched_fork(td, td2);
thread_unlock(td);
/*
* Duplicate sub-structures as needed.
* Increase reference counts on shared objects.
*/
p2->p_flag = P_INMEM;
p2->p_swtick = ticks;
if (p1->p_flag & P_PROFIL)
startprofclock(p2);
td2->td_ucred = crhold(p2->p_ucred);
if (flags & RFSIGSHARE) {
p2->p_sigacts = sigacts_hold(p1->p_sigacts);
} else {
sigacts_copy(newsigacts, p1->p_sigacts);
p2->p_sigacts = newsigacts;
}
if (flags & RFLINUXTHPN)
p2->p_sigparent = SIGUSR1;
else
p2->p_sigparent = SIGCHLD;
p2->p_textvp = p1->p_textvp;
p2->p_fd = fd;
p2->p_fdtol = fdtol;
/*
* p_limit is copy-on-write. Bump its refcount.
*/
lim_fork(p1, p2);
pstats_fork(p1->p_stats, p2->p_stats);
PROC_UNLOCK(p1);
PROC_UNLOCK(p2);
/* Bump references to the text vnode (for procfs). */
if (p2->p_textvp)
vref(p2->p_textvp);
/*
* Set up linkage for kernel based threading.
*/
if ((flags & RFTHREAD) != 0) {
mtx_lock(&ppeers_lock);
p2->p_peers = p1->p_peers;
p1->p_peers = p2;
p2->p_leader = p1->p_leader;
mtx_unlock(&ppeers_lock);
PROC_LOCK(p1->p_leader);
if ((p1->p_leader->p_flag & P_WEXIT) != 0) {
PROC_UNLOCK(p1->p_leader);
/*
* The task leader is exiting, so process p1 is
* going to be killed shortly. Since p1 obviously
* isn't dead yet, we know that the leader is either
* sending SIGKILL's to all the processes in this
* task or is sleeping waiting for all the peers to
* exit. We let p1 complete the fork, but we need
* to go ahead and kill the new process p2 since
* the task leader may not get a chance to send
* SIGKILL to it. We leave it on the list so that
* the task leader will wait for this new process
* to commit suicide.
*/
PROC_LOCK(p2);
psignal(p2, SIGKILL);
PROC_UNLOCK(p2);
} else
PROC_UNLOCK(p1->p_leader);
} else {
p2->p_peers = NULL;
p2->p_leader = p2;
}
sx_xlock(&proctree_lock);
PGRP_LOCK(p1->p_pgrp);
PROC_LOCK(p2);
PROC_LOCK(p1);
/*
* Preserve some more flags in subprocess. P_PROFIL has already
* been preserved.
*/
p2->p_flag |= p1->p_flag & P_SUGID;
td2->td_pflags |= td->td_pflags & TDP_ALTSTACK;
SESS_LOCK(p1->p_session);
if (p1->p_session->s_ttyvp != NULL && p1->p_flag & P_CONTROLT)
p2->p_flag |= P_CONTROLT;
SESS_UNLOCK(p1->p_session);
if (flags & RFPPWAIT)
p2->p_flag |= P_PPWAIT;
p2->p_pgrp = p1->p_pgrp;
LIST_INSERT_AFTER(p1, p2, p_pglist);
PGRP_UNLOCK(p1->p_pgrp);
LIST_INIT(&p2->p_children);
callout_init(&p2->p_itcallout, CALLOUT_MPSAFE);
/*
* If PF_FORK is set, the child process inherits the
* procfs ioctl flags from its parent.
*/
if (p1->p_pfsflags & PF_FORK) {
p2->p_stops = p1->p_stops;
p2->p_pfsflags = p1->p_pfsflags;
}
/*
* This begins the section where we must prevent the parent
* from being swapped.
*/
_PHOLD(p1);
PROC_UNLOCK(p1);
/*
* 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;
p2->p_pptr = pptr;
LIST_INSERT_HEAD(&pptr->p_children, p2, p_sibling);
sx_xunlock(&proctree_lock);
/* Inform accounting that we have forked. */
p2->p_acflag = AFORK;
PROC_UNLOCK(p2);
#ifdef KTRACE
ktrprocfork(p1, p2);
#endif
/*
* Finish creating the child process. It will return via a different
* execution path later. (ie: directly into user mode)
*/
vm_forkproc(td, p2, td2, vm2, flags);
if (flags == (RFFDG | RFPROC)) {
PCPU_INC(cnt.v_forks);
PCPU_ADD(cnt.v_forkpages, p2->p_vmspace->vm_dsize +
p2->p_vmspace->vm_ssize);
} else if (flags == (RFFDG | RFPROC | RFPPWAIT | RFMEM)) {
PCPU_INC(cnt.v_vforks);
PCPU_ADD(cnt.v_vforkpages, p2->p_vmspace->vm_dsize +
p2->p_vmspace->vm_ssize);
} else if (p1 == &proc0) {
PCPU_INC(cnt.v_kthreads);
PCPU_ADD(cnt.v_kthreadpages, p2->p_vmspace->vm_dsize +
p2->p_vmspace->vm_ssize);
} else {
PCPU_INC(cnt.v_rforks);
PCPU_ADD(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.
*/
EVENTHANDLER_INVOKE(process_fork, p1, p2, flags);
/*
* Set the child start time and mark the process as being complete.
*/
PROC_LOCK(p2);
PROC_LOCK(p1);
microuptime(&p2->p_stats->p_start);
PROC_SLOCK(p2);
p2->p_state = PRS_NORMAL;
PROC_SUNLOCK(p2);
#ifdef KDTRACE_HOOKS
/*
* Tell the DTrace fasttrap provider about the new process
* if it has registered an interest. We have to do this only after
* p_state is PRS_NORMAL since the fasttrap module will use pfind()
* later on.
*/
if (dtrace_fasttrap_fork)
dtrace_fasttrap_fork(p1, p2);
#endif
if ((p1->p_flag & (P_TRACED | P_FOLLOWFORK)) == (P_TRACED |
P_FOLLOWFORK)) {
/*
* Arrange for debugger to receive the fork event.
*
* We can report PL_FLAG_FORKED regardless of
* P_FOLLOWFORK settings, but it does not make a sense
* for runaway child.
*/
td->td_dbgflags |= TDB_FORK;
td->td_dbg_forked = p2->p_pid;
td2->td_dbgflags |= TDB_STOPATFORK;
_PHOLD(p2);
p2_held = 1;
}
PROC_UNLOCK(p2);
if ((flags & RFSTOPPED) == 0) {
/*
* If RFSTOPPED not requested, make child runnable and
* add to run queue.
*/
thread_lock(td2);
TD_SET_CAN_RUN(td2);
sched_add(td2, SRQ_BORING);
thread_unlock(td2);
}
/*
* Now can be swapped.
*/
_PRELE(p1);
PROC_UNLOCK(p1);
/*
* Tell any interested parties about the new process.
*/
knote_fork(&p1->p_klist, p2->p_pid);
SDT_PROBE(proc, kernel, , create, p2, p1, flags, 0, 0);
/*
* Wait until debugger is attached to child.
*/
PROC_LOCK(p2);
while ((td2->td_dbgflags & TDB_STOPATFORK) != 0)
cv_wait(&p2->p_dbgwait, &p2->p_mtx);
if (p2_held)
_PRELE(p2);
/*
* 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)
cv_wait(&p2->p_pwait, &p2->p_mtx);
PROC_UNLOCK(p2);
}
int
fork1(struct thread *td, int flags, int pages, struct proc **procp)
{
struct proc *p1;
struct proc *newproc;
int ok;
struct thread *td2;
struct vmspace *vm2;
vm_ooffset_t mem_charged;
int error;
static int curfail;
static struct timeval lastfail;
/* Can't copy and clear. */
if ((flags & (RFFDG|RFCFDG)) == (RFFDG|RFCFDG))
return (EINVAL);
p1 = td->td_proc;
/*
* Here we don't create a new process, but we divorce
* certain parts of a process from itself.
*/
if ((flags & RFPROC) == 0) {
*procp = NULL;
return (fork_norfproc(td, flags));
}
mem_charged = 0;
vm2 = NULL;
if (pages == 0)
pages = KSTACK_PAGES;
/* Allocate new proc. */
newproc = uma_zalloc(proc_zone, M_WAITOK);
td2 = FIRST_THREAD_IN_PROC(newproc);
if (td2 == NULL) {
td2 = thread_alloc(pages);
if (td2 == NULL) {
error = ENOMEM;
goto fail1;
}
proc_linkup(newproc, td2);
} else {
if (td2->td_kstack == 0 || td2->td_kstack_pages != pages) {
if (td2->td_kstack != 0)
vm_thread_dispose(td2);
if (!thread_alloc_stack(td2, pages)) {
error = ENOMEM;
goto fail1;
}
}
}
if ((flags & RFMEM) == 0) {
vm2 = vmspace_fork(p1->p_vmspace, &mem_charged);
if (vm2 == NULL) {
error = ENOMEM;
goto fail1;
}
if (!swap_reserve(mem_charged)) {
/*
* The swap reservation failed. The accounting
* from the entries of the copied vm2 will be
* substracted in vmspace_free(), so force the
* reservation there.
*/
swap_reserve_force(mem_charged);
error = ENOMEM;
goto fail1;
}
} else
vm2 = NULL;
#ifdef MAC
mac_proc_init(newproc);
#endif
knlist_init_mtx(&newproc->p_klist, &newproc->p_mtx);
STAILQ_INIT(&newproc->p_ktr);
/* We have to lock the process tree while we look for a pid. */
sx_slock(&proctree_lock);
/*
* 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 ten processes; don't let root
* exceed the limit. The variable nprocs is the current number of
* processes, maxproc is the limit.
*/
sx_xlock(&allproc_lock);
if ((nprocs >= maxproc - 10 && priv_check_cred(td->td_ucred,
PRIV_MAXPROC, 0) != 0) || nprocs >= maxproc) {
error = EAGAIN;
goto fail;
}
/*
* Increment the count of procs running with this uid. Don't allow
* a nonprivileged user to exceed their current limit.
*
* XXXRW: Can we avoid privilege here if it's not needed?
*/
error = priv_check_cred(td->td_ucred, PRIV_PROC_LIMIT, 0);
if (error == 0)
ok = chgproccnt(td->td_ucred->cr_ruidinfo, 1, 0);
else {
PROC_LOCK(p1);
ok = chgproccnt(td->td_ucred->cr_ruidinfo, 1,
lim_cur(p1, RLIMIT_NPROC));
PROC_UNLOCK(p1);
}
if (ok) {
do_fork(td, flags, newproc, td2, vm2);
/*
* Return child proc pointer to parent.
*/
*procp = newproc;
return (0);
}
error = EAGAIN;
fail:
sx_sunlock(&proctree_lock);
if (ppsratecheck(&lastfail, &curfail, 1))
printf("maxproc limit exceeded by uid %i, please see tuning(7) and login.conf(5).\n",
td->td_ucred->cr_ruid);
sx_xunlock(&allproc_lock);
#ifdef MAC
mac_proc_destroy(newproc);
#endif
fail1:
if (vm2 != NULL)
vmspace_free(vm2);
uma_zfree(proc_zone, newproc);
pause("fork", hz / 2);
return (error);
}
/*
* Handle the return of a child process from fork1(). This function
* is called from the MD fork_trampoline() entry point.
*/
void
fork_exit(void (*callout)(void *, struct trapframe *), void *arg,
struct trapframe *frame)
{
struct proc *p;
struct thread *td;
struct thread *dtd;
td = curthread;
p = td->td_proc;
KASSERT(p->p_state == PRS_NORMAL, ("executing process is still new"));
CTR4(KTR_PROC, "fork_exit: new thread %p (td_sched %p, pid %d, %s)",
td, td->td_sched, p->p_pid, td->td_name);
sched_fork_exit(td);
/*
* Processes normally resume in mi_switch() after being
* cpu_switch()'ed to, but when children start up they arrive here
* instead, so we must do much the same things as mi_switch() would.
*/
if ((dtd = PCPU_GET(deadthread))) {
PCPU_SET(deadthread, NULL);
thread_stash(dtd);
}
thread_unlock(td);
/*
* 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.
*/
if (p->p_flag & P_KTHREAD) {
printf("Kernel thread \"%s\" (pid %d) exited prematurely.\n",
td->td_name, p->p_pid);
kproc_exit(0);
}
mtx_assert(&Giant, MA_NOTOWNED);
if (p->p_sysent->sv_schedtail != NULL)
(p->p_sysent->sv_schedtail)(td);
}
/*
* 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(struct thread *td, struct trapframe *frame)
{
struct proc *p, *dbg;
if (td->td_dbgflags & TDB_STOPATFORK) {
p = td->td_proc;
sx_xlock(&proctree_lock);
PROC_LOCK(p);
if ((p->p_pptr->p_flag & (P_TRACED | P_FOLLOWFORK)) ==
(P_TRACED | P_FOLLOWFORK)) {
/*
* If debugger still wants auto-attach for the
* parent's children, do it now.
*/
dbg = p->p_pptr->p_pptr;
p->p_flag |= P_TRACED;
p->p_oppid = p->p_pptr->p_pid;
proc_reparent(p, dbg);
sx_xunlock(&proctree_lock);
ptracestop(td, SIGSTOP);
} else {
/*
* ... otherwise clear the request.
*/
sx_xunlock(&proctree_lock);
td->td_dbgflags &= ~TDB_STOPATFORK;
cv_broadcast(&p->p_dbgwait);
}
PROC_UNLOCK(p);
}
userret(td, frame);
#ifdef KTRACE
if (KTRPOINT(td, KTR_SYSRET))
ktrsysret(SYS_fork, 0, 0);
#endif
mtx_assert(&Giant, MA_NOTOWNED);
}
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