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/* $OpenBSD: kern_fork.c,v 1.191 2016/10/22 02:55:36 guenther Exp $ */
/* $NetBSD: kern_fork.c,v 1.29 1996/02/09 18:59:34 christos Exp $ */
/*
* 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/param.h>
#include <sys/systm.h>
#include <sys/filedesc.h>
#include <sys/kernel.h>
#include <sys/malloc.h>
#include <sys/mount.h>
#include <sys/proc.h>
#include <sys/exec.h>
#include <sys/resourcevar.h>
#include <sys/signalvar.h>
#include <sys/vnode.h>
#include <sys/vmmeter.h>
#include <sys/file.h>
#include <sys/acct.h>
#include <sys/ktrace.h>
#include <sys/sched.h>
#include <sys/sysctl.h>
#include <sys/pool.h>
#include <sys/mman.h>
#include <sys/ptrace.h>
#include <sys/atomic.h>
#include <sys/pledge.h>
#include <sys/unistd.h>
#include <sys/syscallargs.h>
#include <uvm/uvm.h>
#ifdef __HAVE_MD_TCB
# include <machine/tcb.h>
#endif
int nprocesses = 1; /* process 0 */
int nthreads = 1; /* proc 0 */
int randompid; /* when set to 1, pid's go random */
struct forkstat forkstat;
void fork_return(void *);
void tfork_child_return(void *);
int pidtaken(pid_t);
void process_new(struct proc *, struct process *, int);
void
fork_return(void *arg)
{
struct proc *p = (struct proc *)arg;
if (p->p_p->ps_flags & PS_TRACED)
psignal(p, SIGTRAP);
child_return(p);
}
int
sys_fork(struct proc *p, void *v, register_t *retval)
{
int flags;
flags = FORK_FORK;
if (p->p_p->ps_ptmask & PTRACE_FORK)
flags |= FORK_PTRACE;
return (fork1(p, flags, NULL, 0, fork_return, NULL, retval, NULL));
}
int
sys_vfork(struct proc *p, void *v, register_t *retval)
{
return (fork1(p, FORK_VFORK|FORK_PPWAIT, NULL, 0, NULL,
NULL, retval, NULL));
}
int
sys___tfork(struct proc *p, void *v, register_t *retval)
{
struct sys___tfork_args /* {
syscallarg(const struct __tfork) *param;
syscallarg(size_t) psize;
} */ *uap = v;
size_t psize = SCARG(uap, psize);
struct __tfork param = { 0 };
int flags;
int error;
if (psize == 0 || psize > sizeof(param))
return (EINVAL);
if ((error = copyin(SCARG(uap, param), ¶m, psize)))
return (error);
#ifdef KTRACE
if (KTRPOINT(p, KTR_STRUCT))
ktrstruct(p, "tfork", ¶m, sizeof(param));
#endif
flags = FORK_TFORK | FORK_THREAD | FORK_SIGHAND | FORK_SHAREVM
| FORK_SHAREFILES;
return (fork1(p, flags, param.tf_stack, param.tf_tid,
tfork_child_return, param.tf_tcb, retval, NULL));
}
void
tfork_child_return(void *arg)
{
struct proc *p = curproc;
TCB_SET(p, arg);
child_return(p);
}
/*
* Initialize common bits of a process structure, given the initial thread.
*/
void
process_initialize(struct process *pr, struct proc *p)
{
/* initialize the thread links */
pr->ps_mainproc = p;
TAILQ_INIT(&pr->ps_threads);
TAILQ_INSERT_TAIL(&pr->ps_threads, p, p_thr_link);
pr->ps_refcnt = 1;
p->p_p = pr;
/* give the process the same creds as the initial thread */
pr->ps_ucred = p->p_ucred;
crhold(pr->ps_ucred);
KASSERT(p->p_ucred->cr_ref >= 2); /* new thread and new process */
LIST_INIT(&pr->ps_children);
timeout_set(&pr->ps_realit_to, realitexpire, pr);
}
/*
* Allocate and initialize a new process.
*/
void
process_new(struct proc *p, struct process *parent, int flags)
{
struct process *pr;
pr = pool_get(&process_pool, PR_WAITOK);
/*
* Make a process structure 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(&pr->ps_startzero, 0,
(caddr_t)&pr->ps_endzero - (caddr_t)&pr->ps_startzero);
memcpy(&pr->ps_startcopy, &parent->ps_startcopy,
(caddr_t)&pr->ps_endcopy - (caddr_t)&pr->ps_startcopy);
process_initialize(pr, p);
/* post-copy fixups */
pr->ps_pptr = parent;
pr->ps_limit->p_refcnt++;
/* bump references to the text vnode (for sysctl) */
pr->ps_textvp = parent->ps_textvp;
if (pr->ps_textvp)
vref(pr->ps_textvp);
pr->ps_flags = parent->ps_flags &
(PS_SUGID | PS_SUGIDEXEC | PS_PLEDGE | PS_WXNEEDED);
if (parent->ps_session->s_ttyvp != NULL)
pr->ps_flags |= parent->ps_flags & PS_CONTROLT;
/*
* Duplicate sub-structures as needed.
* Increase reference counts on shared objects.
*/
if (flags & FORK_SHAREFILES)
pr->ps_fd = fdshare(parent);
else
pr->ps_fd = fdcopy(parent);
if (flags & FORK_SIGHAND)
pr->ps_sigacts = sigactsshare(parent);
else
pr->ps_sigacts = sigactsinit(parent);
if (flags & FORK_SHAREVM)
pr->ps_vmspace = uvmspace_share(parent);
else
pr->ps_vmspace = uvmspace_fork(parent);
if (pr->ps_pledgepaths)
pr->ps_pledgepaths->wl_ref++;
if (parent->ps_flags & PS_PROFIL)
startprofclock(pr);
if (flags & FORK_PTRACE)
pr->ps_flags |= parent->ps_flags & PS_TRACED;
if (flags & FORK_NOZOMBIE)
pr->ps_flags |= PS_NOZOMBIE;
if (flags & FORK_SYSTEM)
pr->ps_flags |= PS_SYSTEM;
/* mark as embryo to protect against others */
pr->ps_flags |= PS_EMBRYO;
/* Force visibility of all of the above changes */
membar_producer();
/* it's sufficiently inited to be globally visible */
LIST_INSERT_HEAD(&allprocess, pr, ps_list);
}
/* print the 'table full' message once per 10 seconds */
struct timeval fork_tfmrate = { 10, 0 };
int
fork1(struct proc *curp, int flags, void *stack, pid_t *tidptr,
void (*func)(void *), void *arg, register_t *retval,
struct proc **rnewprocp)
{
struct process *curpr = curp->p_p;
struct process *pr;
struct proc *p;
uid_t uid;
struct vmspace *vm;
int count;
vaddr_t uaddr;
int s;
struct ptrace_state *newptstat = NULL;
/* sanity check some flag combinations */
if (flags & FORK_THREAD) {
if ((flags & FORK_SHAREFILES) == 0 ||
(flags & FORK_SIGHAND) == 0 ||
(flags & FORK_SYSTEM) != 0)
return (EINVAL);
}
if (flags & FORK_SIGHAND && (flags & FORK_SHAREVM) == 0)
return (EINVAL);
/*
* Although process entries are dynamically created, we still keep
* a global limit on the maximum number we will create. We reserve
* the last 5 processes to root. The variable nprocesses is the
* current number of processes, maxprocess is the limit. Similar
* rules for threads (struct proc): we reserve the last 5 to root;
* the variable nthreads is the current number of procs, maxthread is
* the limit.
*/
uid = curp->p_ucred->cr_ruid;
if ((nthreads >= maxthread - 5 && uid != 0) || nthreads >= maxthread) {
static struct timeval lasttfm;
if (ratecheck(&lasttfm, &fork_tfmrate))
tablefull("proc");
return (EAGAIN);
}
nthreads++;
if ((flags & FORK_THREAD) == 0) {
if ((nprocesses >= maxprocess - 5 && uid != 0) ||
nprocesses >= maxprocess) {
static struct timeval lasttfm;
if (ratecheck(&lasttfm, &fork_tfmrate))
tablefull("process");
nthreads--;
return (EAGAIN);
}
nprocesses++;
/*
* Increment the count of processes running with
* this uid. Don't allow a nonprivileged user to
* exceed their current limit.
*/
count = chgproccnt(uid, 1);
if (uid != 0 && count > curp->p_rlimit[RLIMIT_NPROC].rlim_cur) {
(void)chgproccnt(uid, -1);
nprocesses--;
nthreads--;
return (EAGAIN);
}
}
uaddr = uvm_uarea_alloc();
if (uaddr == 0) {
if ((flags & FORK_THREAD) == 0) {
(void)chgproccnt(uid, -1);
nprocesses--;
}
nthreads--;
return (ENOMEM);
}
/*
* From now on, we're committed to the fork and cannot fail.
*/
/* Allocate new proc. */
p = pool_get(&proc_pool, PR_WAITOK);
p->p_stat = SIDL; /* protect against others */
p->p_flag = 0;
/*
* 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(&p->p_startzero, 0,
(caddr_t)&p->p_endzero - (caddr_t)&p->p_startzero);
memcpy(&p->p_startcopy, &curp->p_startcopy,
(caddr_t)&p->p_endcopy - (caddr_t)&p->p_startcopy);
crhold(p->p_ucred);
/*
* Initialize the timeouts.
*/
timeout_set(&p->p_sleep_to, endtsleep, p);
if (flags & FORK_THREAD) {
atomic_setbits_int(&p->p_flag, P_THREAD);
p->p_p = pr = curpr;
pr->ps_refcnt++;
} else {
process_new(p, curpr, flags);
pr = p->p_p;
}
p->p_fd = pr->ps_fd;
p->p_vmspace = pr->ps_vmspace;
if (pr->ps_flags & PS_SYSTEM)
atomic_setbits_int(&p->p_flag, P_SYSTEM);
if (flags & FORK_PPWAIT) {
atomic_setbits_int(&pr->ps_flags, PS_PPWAIT);
atomic_setbits_int(&curpr->ps_flags, PS_ISPWAIT);
}
#ifdef KTRACE
/*
* Copy traceflag and tracefile if enabled.
* If not inherited, these were zeroed above.
*/
if ((flags & FORK_THREAD) == 0 && curpr->ps_traceflag & KTRFAC_INHERIT)
ktrsettrace(pr, curpr->ps_traceflag, curpr->ps_tracevp,
curpr->ps_tracecred);
#endif
/*
* set priority of child to be that of parent
* XXX should move p_estcpu into the region of struct proc which gets
* copied.
*/
scheduler_fork_hook(curp, p);
if (flags & FORK_THREAD)
sigstkinit(&p->p_sigstk);
/*
* If emulation has thread fork hook, call it now.
*/
if (pr->ps_emul->e_proc_fork)
(*pr->ps_emul->e_proc_fork)(p, curp);
p->p_addr = (struct user *)uaddr;
/*
* Finish creating the child thread. cpu_fork() will copy
* and update the pcb and make the child ready to run. If
* this is a normal user fork, the child will exit directly
* to user mode via child_return() on its first time slice
* and will not return here. If this is a kernel thread,
* the specified entry point will be executed.
*/
cpu_fork(curp, p, stack, 0, func ? func : child_return, arg ? arg : p);
vm = pr->ps_vmspace;
if (flags & FORK_FORK) {
forkstat.cntfork++;
forkstat.sizfork += vm->vm_dsize + vm->vm_ssize;
} else if (flags & FORK_VFORK) {
forkstat.cntvfork++;
forkstat.sizvfork += vm->vm_dsize + vm->vm_ssize;
} else if (flags & FORK_TFORK) {
forkstat.cnttfork++;
} else {
forkstat.cntkthread++;
forkstat.sizkthread += vm->vm_dsize + vm->vm_ssize;
}
if (pr->ps_flags & PS_TRACED && flags & FORK_FORK)
newptstat = malloc(sizeof(*newptstat), M_SUBPROC, M_WAITOK);
p->p_pid = allocpid();
LIST_INSERT_HEAD(&allproc, p, p_list);
LIST_INSERT_HEAD(PIDHASH(p->p_pid), p, p_hash);
if ((flags & FORK_THREAD) == 0) {
LIST_INSERT_AFTER(curpr, pr, ps_pglist);
LIST_INSERT_HEAD(&curpr->ps_children, pr, ps_sibling);
if (pr->ps_flags & PS_TRACED) {
pr->ps_oppid = curpr->ps_pid;
if (pr->ps_pptr != curpr->ps_pptr)
proc_reparent(pr, curpr->ps_pptr);
/*
* Set ptrace status.
*/
if (flags & FORK_FORK) {
pr->ps_ptstat = newptstat;
newptstat = NULL;
curpr->ps_ptstat->pe_report_event = PTRACE_FORK;
pr->ps_ptstat->pe_report_event = PTRACE_FORK;
curpr->ps_ptstat->pe_other_pid = pr->ps_pid;
pr->ps_ptstat->pe_other_pid = curpr->ps_pid;
}
}
} else {
TAILQ_INSERT_TAIL(&pr->ps_threads, p, p_thr_link);
/*
* if somebody else wants to take us to single threaded mode,
* count ourselves in.
*/
if (pr->ps_single) {
curpr->ps_singlecount++;
atomic_setbits_int(&p->p_flag, P_SUSPSINGLE);
}
}
if (tidptr != NULL) {
pid_t pid = p->p_pid + THREAD_PID_OFFSET;
if (copyout(&pid, tidptr, sizeof(pid)))
psignal(curp, SIGSEGV);
}
/*
* For new processes, set accounting bits and mark as complete.
*/
if ((flags & FORK_THREAD) == 0) {
getnanotime(&pr->ps_start);
pr->ps_acflag = AFORK;
atomic_clearbits_int(&pr->ps_flags, PS_EMBRYO);
}
/*
* Make child runnable and add to run queue.
*/
if ((flags & FORK_IDLE) == 0) {
SCHED_LOCK(s);
p->p_stat = SRUN;
p->p_cpu = sched_choosecpu_fork(curp, flags);
setrunqueue(p);
SCHED_UNLOCK(s);
} else
p->p_cpu = arg;
if (newptstat)
free(newptstat, M_SUBPROC, sizeof(*newptstat));
/*
* Notify any interested parties about the new process.
*/
if ((flags & FORK_THREAD) == 0)
KNOTE(&curpr->ps_klist, NOTE_FORK | p->p_pid);
/*
* 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 = p;
/*
* Preserve synchronization semantics of vfork. If waiting for
* child to exec or exit, set PS_PPWAIT on child and PS_ISPWAIT
* on ourselves, and sleep on our process for the latter flag
* to go away.
* XXX Need to stop other rthreads in the parent
*/
if (flags & FORK_PPWAIT)
while (curpr->ps_flags & PS_ISPWAIT)
tsleep(curpr, PWAIT, "ppwait", 0);
/*
* If we're tracing the child, alert the parent too.
*/
if ((flags & FORK_PTRACE) && (curpr->ps_flags & PS_TRACED))
psignal(curp, SIGTRAP);
/*
* Return child pid to parent process,
* marking us as parent via retval[1].
*/
if (retval != NULL) {
retval[0] = p->p_pid +
(flags & FORK_THREAD ? THREAD_PID_OFFSET : 0);
retval[1] = 0;
}
return (0);
}
/*
* Checks for current use of a pid, either as a pid or pgid.
*/
pid_t oldpids[128];
int
ispidtaken(pid_t pid)
{
uint32_t i;
for (i = 0; i < nitems(oldpids); i++)
if (pid == oldpids[i])
return (1);
if (pfind(pid) != NULL)
return (1);
if (pgfind(pid) != NULL)
return (1);
if (zombiefind(pid) != NULL)
return (1);
return (0);
}
/* Find an unused pid */
pid_t
allocpid(void)
{
static pid_t lastpid;
pid_t pid;
if (!randompid) {
/* only used early on for system processes */
pid = ++lastpid;
} else {
/* Find an unused pid satisfying lastpid < pid <= PID_MAX */
do {
pid = arc4random_uniform(PID_MAX - lastpid) + 1 +
lastpid;
} while (ispidtaken(pid));
}
return pid;
}
void
freepid(pid_t pid)
{
static uint32_t idx;
oldpids[idx++ % nitems(oldpids)] = pid;
}
#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)
{
SCHED_ASSERT_LOCKED();
__mp_unlock(&sched_lock);
spl0();
SCHED_ASSERT_UNLOCKED();
KERNEL_ASSERT_UNLOCKED();
KERNEL_LOCK();
}
#endif
|