* 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.
* %sccs.include.redist.c%
* @(#)kern_fork.c 8.7 (Berkeley) %G%
#include <sys/filedesc.h>
#include <sys/resourcevar.h>
return (fork1(p
, 0, retval
));
return (fork1(p
, 1, retval
));
int nprocs
= 1; /* process 0 */
fork1(p1
, isvfork
, retval
)
register struct proc
*p1
;
register struct proc
*p2
;
static int nextpid
, pidchecked
= 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_cred
->p_ruid
;
if ((nprocs
>= maxproc
- 1 && uid
!= 0) || nprocs
>= maxproc
) {
* 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 (uid
!= 0 && count
> p1
->p_rlimit
[RLIMIT_NPROC
].rlim_cur
) {
(void)chgproccnt(uid
, -1);
MALLOC(newproc
, struct proc
*, sizeof(struct proc
), M_PROC
, M_WAITOK
);
* Find an unused process ID. We remember a range of unused IDs
* ready to use (from nextpid+1 through pidchecked-1).
* 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
) {
if (nextpid
>= pidchecked
) {
* Scan the active and zombie procs 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.
for (; p2
!= 0; p2
= p2
->p_list
.le_next
) {
while (p2
->p_pid
== nextpid
||
p2
->p_pgrp
->pg_id
== nextpid
) {
if (nextpid
>= pidchecked
)
if (p2
->p_pid
> nextpid
&& pidchecked
> p2
->p_pid
)
if (p2
->p_pgrp
->pg_id
> nextpid
&&
pidchecked
> p2
->p_pgrp
->pg_id
)
pidchecked
= p2
->p_pgrp
->pg_id
;
p2
->p_stat
= SIDL
; /* protect against others */
LIST_INSERT_HEAD(&allproc
, p2
, p_list
);
p2
->p_forw
= p2
->p_back
= NULL
; /* shouldn't be necessary */
LIST_INSERT_HEAD(PIDHASH(p2
->p_pid
), p2
, p_hash
);
* 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.
(unsigned) ((caddr_t
)&p2
->p_endzero
- (caddr_t
)&p2
->p_startzero
));
bcopy(&p1
->p_startcopy
, &p2
->p_startcopy
,
(unsigned) ((caddr_t
)&p2
->p_endcopy
- (caddr_t
)&p2
->p_startcopy
));
* Duplicate sub-structures as needed.
* Increase reference counts on shared objects.
* The p_stats and p_sigacts substructs are set in vm_fork.
if (p1
->p_flag
& P_PROFIL
)
MALLOC(p2
->p_cred
, struct pcred
*, sizeof(struct pcred
),
bcopy(p1
->p_cred
, p2
->p_cred
, sizeof(*p2
->p_cred
));
p2
->p_cred
->p_refcnt
= 1;
/* bump references to the text vnode (for procfs) */
p2
->p_textvp
= p1
->p_textvp
;
* 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
if (p1
->p_limit
->p_lflags
& PL_SHAREMOD
)
p2
->p_limit
= limcopy(p1
->p_limit
);
p2
->p_limit
= p1
->p_limit
;
if (p1
->p_session
->s_ttyvp
!= NULL
&& p1
->p_flag
& P_CONTROLT
)
p2
->p_flag
|= P_CONTROLT
;
LIST_INSERT_AFTER(p1
, p2
, p_pglist
);
LIST_INSERT_HEAD(&p1
->p_children
, p2
, p_sibling
);
LIST_INIT(&p2
->p_children
);
* 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
)
* This begins the section where we must prevent the parent
* Set return values for child before vm_fork,
* so they can be copied to child stack.
* We return parent pid, and mark as child in retval[1].
* NOTE: the kernel stack may be at a different location in the child
* process, and thus addresses of automatic variables (including retval)
* may be invalid after vm_fork returns in the child process.
if (vm_fork(p1
, p2
, isvfork
)) {
* Child process. Set start time and get to work.
p2
->p_stats
->p_start
= time
;
* Make child runnable and add to run queue.
* 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
)
tsleep(p1
, PWAIT
, "ppwait", 0);
* Return child pid to parent process,
* marking us as parent via retval[1].