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freebsd-dev/sys/kern/kern_fork.c
Mateusz Guzik 5afb134c32 vfs: add vrefact, to be used when the vnode has to be already active 
This allows blind increment of relevant counters which under contention
is cheaper than inc-not-zero loops at least on amd64.

Use it in some of the places which are guaranteed to see already active
vnodes.

Reviewed by:	kib (previous version)
2016-12-12 15:37:11 +00:00

1117 lines
28 KiB
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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.
* 3. 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_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/fcntl.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/procdesc.h>
#include <sys/pioctl.h>
#include <sys/ptrace.h>
#include <sys/racct.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>
#include <vm/vm_domain.h>
#ifdef KDTRACE_HOOKS
#include <sys/dtrace_bsd.h>
dtrace_fork_func_t dtrace_fasttrap_fork;
#endif
SDT_PROVIDER_DECLARE(proc);
SDT_PROBE_DEFINE3(proc, , , create, "struct proc *", "struct proc *", "int");
#ifndef _SYS_SYSPROTO_H_
struct fork_args {
int dummy;
};
#endif
/* ARGSUSED */
int
sys_fork(struct thread *td, struct fork_args *uap)
{
struct fork_req fr;
int error, pid;
bzero(&fr, sizeof(fr));
fr.fr_flags = RFFDG | RFPROC;
fr.fr_pidp = &pid;
error = fork1(td, &fr);
if (error == 0) {
td->td_retval[0] = pid;
td->td_retval[1] = 0;
}
return (error);
}
/* ARGUSED */
int
sys_pdfork(struct thread *td, struct pdfork_args *uap)
{
struct fork_req fr;
int error, fd, pid;
bzero(&fr, sizeof(fr));
fr.fr_flags = RFFDG | RFPROC | RFPROCDESC;
fr.fr_pidp = &pid;
fr.fr_pd_fd = &fd;
fr.fr_pd_flags = uap->flags;
/*
* It is necessary to return fd by reference because 0 is a valid file
* descriptor number, and the child needs to be able to distinguish
* itself from the parent using the return value.
*/
error = fork1(td, &fr);
if (error == 0) {
td->td_retval[0] = pid;
td->td_retval[1] = 0;
error = copyout(&fd, uap->fdp, sizeof(fd));
}
return (error);
}
/* ARGSUSED */
int
sys_vfork(struct thread *td, struct vfork_args *uap)
{
struct fork_req fr;
int error, pid;
bzero(&fr, sizeof(fr));
fr.fr_flags = RFFDG | RFPROC | RFPPWAIT | RFMEM;
fr.fr_pidp = &pid;
error = fork1(td, &fr);
if (error == 0) {
td->td_retval[0] = pid;
td->td_retval[1] = 0;
}
return (error);
}
int
sys_rfork(struct thread *td, struct rfork_args *uap)
{
struct fork_req fr;
int error, pid;
/* Don't allow kernel-only flags. */
if ((uap->flags & RFKERNELONLY) != 0)
return (EINVAL);
AUDIT_ARG_FFLAGS(uap->flags);
bzero(&fr, sizeof(fr));
fr.fr_flags = uap->flags;
fr.fr_pidp = &pid;
error = fork1(td, &fr);
if (error == 0) {
td->td_retval[0] = pid;
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.
*
* Avoid reuse of the process group id, session id or
* the reaper subtree id. Note that for process group
* and sessions, the amount of reserved pids is
* limited by process limit. For the subtree ids, the
* id is kept reserved only while there is a
* non-reaped process in the subtree, so amount of
* reserved pids is limited by process limit times
* two.
*/
p = LIST_FIRST(&allproc);
again:
for (; p != NULL; p = LIST_NEXT(p, p_list)) {
while (p->p_pid == trypid ||
p->p_reapsubtree == 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(p1, 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, false);
fdescfree(td);
p1->p_fd = fdtmp;
}
/*
* Unshare file descriptors (from parent).
*/
if (flags & RFFDG)
fdunshare(td);
fail:
if (((p1->p_flag & (P_HADTHREADS|P_SYSTEM)) == P_HADTHREADS) &&
(flags & (RFCFDG | RFFDG))) {
PROC_LOCK(p1);
thread_single_end(p1, SINGLE_BOUNDARY);
PROC_UNLOCK(p1);
}
return (error);
}
static void
do_fork(struct thread *td, struct fork_req *fr, struct proc *p2, struct thread *td2,
struct vmspace *vm2, struct file *fp_procdesc)
{
struct proc *p1, *pptr;
int trypid;
struct filedesc *fd;
struct filedesc_to_leader *fdtol;
struct sigacts *newsigacts;
sx_assert(&proctree_lock, SX_SLOCKED);
sx_assert(&allproc_lock, SX_XLOCKED);
p1 = td->td_proc;
trypid = fork_findpid(fr->fr_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);
allproc_gen++;
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));
/* 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 (fr->fr_flags & RFSIGSHARE)
newsigacts = NULL;
else
newsigacts = sigacts_alloc();
/*
* Copy filedesc.
*/
if (fr->fr_flags & RFCFDG) {
fd = fdinit(p1->p_fd, false);
fdtol = NULL;
} else if (fr->fr_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 ((fr->fr_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_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_flag2 = p1->p_flag2 & (P2_NOTRACE | P2_NOTRACE_EXEC | P2_TRAPCAP);
p2->p_swtick = ticks;
if (p1->p_flag & P_PROFIL)
startprofclock(p2);
/*
* Whilst the proc lock is held, copy the VM domain data out
* using the VM domain method.
*/
vm_domain_policy_init(&p2->p_vm_dom_policy);
vm_domain_policy_localcopy(&p2->p_vm_dom_policy,
&p1->p_vm_dom_policy);
if (fr->fr_flags & RFSIGSHARE) {
p2->p_sigacts = sigacts_hold(p1->p_sigacts);
} else {
sigacts_copy(newsigacts, p1->p_sigacts);
p2->p_sigacts = newsigacts;
}
if (fr->fr_flags & RFTSIGZMB)
p2->p_sigparent = RFTSIGNUM(fr->fr_flags);
else if (fr->fr_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;
if (p1->p_flag2 & P2_INHERIT_PROTECTED) {
p2->p_flag |= P_PROTECTED;
p2->p_flag2 |= P2_INHERIT_PROTECTED;
}
/*
* p_limit is copy-on-write. Bump its refcount.
*/
lim_fork(p1, p2);
thread_cow_get_proc(td2, 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)
vrefact(p2->p_textvp);
/*
* Set up linkage for kernel based threading.
*/
if ((fr->fr_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);
kern_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) | TDP_FORKING;
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 (fr->fr_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);
LIST_INIT(&p2->p_orphans);
callout_init_mtx(&p2->p_itcallout, &p2->p_mtx, 0);
/*
* 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 ((fr->fr_flags & RFNOWAIT) != 0) {
pptr = p1->p_reaper;
p2->p_reaper = pptr;
} else {
p2->p_reaper = (p1->p_treeflag & P_TREE_REAPER) != 0 ?
p1 : p1->p_reaper;
pptr = p1;
}
p2->p_pptr = pptr;
LIST_INSERT_HEAD(&pptr->p_children, p2, p_sibling);
LIST_INIT(&p2->p_reaplist);
LIST_INSERT_HEAD(&p2->p_reaper->p_reaplist, p2, p_reapsibling);
if (p2->p_reaper == p1)
p2->p_reapsubtree = p2->p_pid;
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, fr->fr_flags);
if (fr->fr_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 (fr->fr_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);
}
/*
* Associate the process descriptor with the process before anything
* can happen that might cause that process to need the descriptor.
* However, don't do this until after fork(2) can no longer fail.
*/
if (fr->fr_flags & RFPROCDESC)
procdesc_new(p2, fr->fr_pd_flags);
/*
* Both processes are set up, now check if any loadable modules want
* to adjust anything.
*/
EVENTHANDLER_INVOKE(process_fork, p1, p2, fr->fr_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 so that any
* tracepoints inherited from the parent can be removed. We have to do
* this only after p_state is PRS_NORMAL since the fasttrap module will
* use pfind() later on.
*/
if ((fr->fr_flags & RFMEM) == 0 && dtrace_fasttrap_fork)
dtrace_fasttrap_fork(p1, p2);
#endif
/*
* Hold the process so that it cannot exit after we make it runnable,
* but before we wait for the debugger.
*/
_PHOLD(p2);
if (p1->p_ptevents & PTRACE_FORK) {
/*
* 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;
}
if (fr->fr_flags & RFPPWAIT) {
td->td_pflags |= TDP_RFPPWAIT;
td->td_rfppwait_p = p2;
td->td_dbgflags |= TDB_VFORK;
}
PROC_UNLOCK(p2);
/*
* 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_PROBE3(proc, , , create, p2, p1, fr->fr_flags);
if (fr->fr_flags & RFPROCDESC) {
procdesc_finit(p2->p_procdesc, fp_procdesc);
fdrop(fp_procdesc, td);
}
if ((fr->fr_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);
if (fr->fr_pidp != NULL)
*fr->fr_pidp = p2->p_pid;
} else {
*fr->fr_procp = p2;
}
PROC_LOCK(p2);
/*
* Wait until debugger is attached to child.
*/
while (td2->td_proc == p2 && (td2->td_dbgflags & TDB_STOPATFORK) != 0)
cv_wait(&p2->p_dbgwait, &p2->p_mtx);
_PRELE(p2);
racct_proc_fork_done(p2);
PROC_UNLOCK(p2);
}
int
fork1(struct thread *td, struct fork_req *fr)
{
struct proc *p1, *newproc;
struct thread *td2;
struct vmspace *vm2;
struct file *fp_procdesc;
vm_ooffset_t mem_charged;
int error, nprocs_new, ok;
static int curfail;
static struct timeval lastfail;
int flags, pages;
flags = fr->fr_flags;
pages = fr->fr_pages;
if ((flags & RFSTOPPED) != 0)
MPASS(fr->fr_procp != NULL && fr->fr_pidp == NULL);
else
MPASS(fr->fr_procp == NULL);
/* Check for the undefined or unimplemented flags. */
if ((flags & ~(RFFLAGS | RFTSIGFLAGS(RFTSIGMASK))) != 0)
return (EINVAL);
/* Signal value requires RFTSIGZMB. */
if ((flags & RFTSIGFLAGS(RFTSIGMASK)) != 0 && (flags & RFTSIGZMB) == 0)
return (EINVAL);
/* Can't copy and clear. */
if ((flags & (RFFDG|RFCFDG)) == (RFFDG|RFCFDG))
return (EINVAL);
/* Check the validity of the signal number. */
if ((flags & RFTSIGZMB) != 0 && (u_int)RFTSIGNUM(flags) > _SIG_MAXSIG)
return (EINVAL);
if ((flags & RFPROCDESC) != 0) {
/* Can't not create a process yet get a process descriptor. */
if ((flags & RFPROC) == 0)
return (EINVAL);
/* Must provide a place to put a procdesc if creating one. */
if (fr->fr_pd_fd == NULL)
return (EINVAL);
/* Check if we are using supported flags. */
if ((fr->fr_pd_flags & ~PD_ALLOWED_AT_FORK) != 0)
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) {
if (fr->fr_procp != NULL)
*fr->fr_procp = NULL;
else if (fr->fr_pidp != NULL)
*fr->fr_pidp = 0;
return (fork_norfproc(td, flags));
}
fp_procdesc = NULL;
newproc = NULL;
vm2 = NULL;
/*
* Increment the nprocs resource before allocations occur.
* Although process entries are dynamically created, we still
* keep a global limit on the maximum number we will
* create. There are hard-limits as to the number of processes
* that can run, established by the KVA and memory usage for
* the process data.
*
* Don't allow a nonprivileged user to use the last ten
* processes; don't let root exceed the limit.
*/
nprocs_new = atomic_fetchadd_int(&nprocs, 1) + 1;
if ((nprocs_new >= maxproc - 10 && priv_check_cred(td->td_ucred,
PRIV_MAXPROC, 0) != 0) || nprocs_new >= maxproc) {
error = EAGAIN;
sx_xlock(&allproc_lock);
if (ppsratecheck(&lastfail, &curfail, 1)) {
printf("maxproc limit exceeded by uid %u (pid %d); "
"see tuning(7) and login.conf(5)\n",
td->td_ucred->cr_ruid, p1->p_pid);
}
sx_xunlock(&allproc_lock);
goto fail2;
}
/*
* If required, create a process descriptor in the parent first; we
* will abandon it if something goes wrong. We don't finit() until
* later.
*/
if (flags & RFPROCDESC) {
error = procdesc_falloc(td, &fp_procdesc, fr->fr_pd_fd,
fr->fr_pd_flags, fr->fr_pd_fcaps);
if (error != 0)
goto fail2;
}
mem_charged = 0;
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 fail2;
}
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 fail2;
}
}
}
if ((flags & RFMEM) == 0) {
vm2 = vmspace_fork(p1->p_vmspace, &mem_charged);
if (vm2 == NULL) {
error = ENOMEM;
goto fail2;
}
if (!swap_reserve(mem_charged)) {
/*
* The swap reservation failed. The accounting
* from the entries of the copied vm2 will be
* subtracted in vmspace_free(), so force the
* reservation there.
*/
swap_reserve_force(mem_charged);
error = ENOMEM;
goto fail2;
}
} else
vm2 = NULL;
/*
* XXX: This is ugly; when we copy resource usage, we need to bump
* per-cred resource counters.
*/
proc_set_cred_init(newproc, crhold(td->td_ucred));
/*
* Initialize resource accounting for the child process.
*/
error = racct_proc_fork(p1, newproc);
if (error != 0) {
error = EAGAIN;
goto fail1;
}
#ifdef MAC
mac_proc_init(newproc);
#endif
newproc->p_klist = knlist_alloc(&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);
sx_xlock(&allproc_lock);
/*
* 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 {
ok = chgproccnt(td->td_ucred->cr_ruidinfo, 1,
lim_cur(td, RLIMIT_NPROC));
}
if (ok) {
do_fork(td, fr, newproc, td2, vm2, fp_procdesc);
return (0);
}
error = EAGAIN;
sx_sunlock(&proctree_lock);
sx_xunlock(&allproc_lock);
#ifdef MAC
mac_proc_destroy(newproc);
#endif
racct_proc_exit(newproc);
fail1:
crfree(newproc->p_ucred);
newproc->p_ucred = NULL;
fail2:
if (vm2 != NULL)
vmspace_free(vm2);
uma_zfree(proc_zone, newproc);
if ((flags & RFPROCDESC) != 0 && fp_procdesc != NULL) {
fdclose(td, fp_procdesc, *fr->fr_pd_fd);
fdrop(fp_procdesc, td);
}
atomic_add_int(&nprocs, -1);
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_get_sched(td), 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_fork_kthread_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_KPROC) {
printf("Kernel thread \"%s\" (pid %d) exited prematurely.\n",
td->td_name, p->p_pid);
kthread_exit();
}
mtx_assert(&Giant, MA_NOTOWNED);
if (p->p_sysent->sv_schedtail != NULL)
(p->p_sysent->sv_schedtail)(td);
td->td_pflags &= ~TDP_FORKING;
}
/*
* Simplified back end of syscall(), used when returning from fork()
* directly into user mode. 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;
p = td->td_proc;
if (td->td_dbgflags & TDB_STOPATFORK) {
sx_xlock(&proctree_lock);
PROC_LOCK(p);
if (p->p_pptr->p_ptevents & PTRACE_FORK) {
/*
* If debugger still wants auto-attach for the
* parent's children, do it now.
*/
dbg = p->p_pptr->p_pptr;
proc_set_traced(p, true);
CTR2(KTR_PTRACE,
"fork_return: attaching to new child pid %d: oppid %d",
p->p_pid, p->p_oppid);
proc_reparent(p, dbg);
sx_xunlock(&proctree_lock);
td->td_dbgflags |= TDB_CHILD | TDB_SCX | TDB_FSTP;
ptracestop(td, SIGSTOP);
td->td_dbgflags &= ~(TDB_CHILD | TDB_SCX);
} else {
/*
* ... otherwise clear the request.
*/
sx_xunlock(&proctree_lock);
td->td_dbgflags &= ~TDB_STOPATFORK;
cv_broadcast(&p->p_dbgwait);
}
PROC_UNLOCK(p);
} else if (p->p_flag & P_TRACED || td->td_dbgflags & TDB_BORN) {
/*
* This is the start of a new thread in a traced
* process. Report a system call exit event.
*/
PROC_LOCK(p);
td->td_dbgflags |= TDB_SCX;
_STOPEVENT(p, S_SCX, td->td_dbg_sc_code);
if ((p->p_ptevents & PTRACE_SCX) != 0 ||
(td->td_dbgflags & TDB_BORN) != 0)
ptracestop(td, SIGTRAP);
td->td_dbgflags &= ~(TDB_SCX | TDB_BORN);
PROC_UNLOCK(p);
}
userret(td, frame);
#ifdef KTRACE
if (KTRPOINT(td, KTR_SYSRET))
ktrsysret(SYS_fork, 0, 0);
#endif
}
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