Net2/usr/src/sys/kern/kern_fork.c
/*
* Copyright (c) 1982, 1986, 1989, 1991 Regents of the University of California.
* All rights reserved.
*
* 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 7.29 (Berkeley) 5/15/91
*/
#include "param.h"
#include "systm.h"
#include "map.h"
#include "filedesc.h"
#include "kernel.h"
#include "malloc.h"
#include "proc.h"
#include "resourcevar.h"
#include "vnode.h"
#include "seg.h"
#include "file.h"
#include "acct.h"
#include "ktrace.h"
/* ARGSUSED */
fork(p, uap, retval)
struct proc *p;
void *uap;
int retval[];
{
return (fork1(p, 0, retval));
}
/* ARGSUSED */
vfork(p, uap, retval)
struct proc *p;
void *uap;
int retval[];
{
return (fork1(p, 1, retval));
}
int nprocs = 1; /* process 0 */
fork1(p1, isvfork, retval)
register struct proc *p1;
int isvfork, retval[];
{
register struct proc *p2;
register int count, uid;
static int nextpid, pidchecked = 0;
count = 0;
if ((uid = p1->p_ucred->cr_uid) != 0) {
for (p2 = allproc; p2; p2 = p2->p_nxt)
if (p2->p_ucred->cr_uid == uid)
count++;
for (p2 = zombproc; p2; p2 = p2->p_nxt)
if (p2->p_ucred->cr_uid == uid)
count++;
}
/*
* Although process entries are dynamically entries,
* we still keep a global limit on the maximum number
* we will create. Don't allow a nonprivileged user
* to exceed its current limit or to bring us within one
* of the global limit; don't let root exceed the limit.
* nprocs is the current number of processes,
* maxproc is the limit.
*/
if (nprocs >= maxproc || uid == 0 && nprocs >= maxproc + 1) {
tablefull("proc");
return (EAGAIN);
}
if (count > p1->p_rlimit[RLIMIT_NPROC].rlim_cur)
return (EAGAIN);
/*
* Find an unused process ID.
* We remember a range of unused IDs ready to use
* (from nextpid+1 through pidchecked-1).
*/
nextpid++;
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 (nextpid >= PID_MAX) {
nextpid = 100;
pidchecked = 0;
}
if (nextpid >= 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 nextpid, so we can avoid checking for a while.
*/
p2 = allproc;
again:
for (; p2 != NULL; p2 = p2->p_nxt) {
if (p2->p_pid == nextpid ||
p2->p_pgrp->pg_id == nextpid) {
nextpid++;
if (nextpid >= pidchecked)
goto retry;
}
if (p2->p_pid > nextpid && pidchecked > p2->p_pid)
pidchecked = p2->p_pid;
if (p2->p_pgrp->pg_id > nextpid &&
pidchecked > p2->p_pgrp->pg_id)
pidchecked = p2->p_pgrp->pg_id;
}
if (!doingzomb) {
doingzomb = 1;
p2 = zombproc;
goto again;
}
}
/*
* Allocate new proc.
* Link onto allproc (this should probably be delayed).
*/
MALLOC(p2, struct proc *, sizeof(struct proc), M_PROC, M_WAITOK);
nprocs++;
p2->p_nxt = allproc;
p2->p_nxt->p_prev = &p2->p_nxt; /* allproc is never NULL */
p2->p_prev = &allproc;
allproc = p2;
p2->p_link = NULL; /* shouldn't be necessary */
p2->p_rlink = NULL; /* shouldn't be necessary */
/*
* 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));
bcopy(&p1->p_startcopy, &p2->p_startcopy,
(unsigned) ((caddr_t)&p2->p_endcopy - (caddr_t)&p2->p_startcopy));
p2->p_spare[0] = 0; /* XXX - should be in zero range */
p2->p_spare[1] = 0; /* XXX - should be in zero range */
p2->p_spare[2] = 0; /* XXX - should be in zero range */
p2->p_spare[3] = 0; /* XXX - should be in zero range */
/*
* Duplicate sub-structures as needed.
* Increase reference counts on shared objects.
* The p_stats and p_sigacts substructs are set in vm_fork.
*/
MALLOC(p2->p_cred, struct pcred *, sizeof(struct pcred),
M_SUBPROC, M_WAITOK);
bcopy(p1->p_cred, p2->p_cred, sizeof(*p2->p_cred));
p2->p_cred->p_refcnt = 1;
crhold(p1->p_ucred);
p2->p_fd = fdcopy(p1);
/*
* 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.)
*/
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++;
}
p2->p_flag = SLOAD | (p1->p_flag & SHPUX);
if (p1->p_session->s_ttyvp != NULL && p1->p_flag & SCTTY)
p2->p_flag |= SCTTY;
if (isvfork)
p2->p_flag |= SPPWAIT;
p2->p_stat = SIDL;
p2->p_pid = nextpid;
{
struct proc **hash = &pidhash[PIDHASH(p2->p_pid)];
p2->p_hash = *hash;
*hash = p2;
}
p2->p_pgrpnxt = p1->p_pgrpnxt;
p1->p_pgrpnxt = p2;
p2->p_pptr = p1;
p2->p_osptr = p1->p_cptr;
if (p1->p_cptr)
p1->p_cptr->p_ysptr = p2;
p1->p_cptr = p2;
#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)
VREF(p2->p_tracep);
}
#endif
#if defined(tahoe)
p2->p_vmspace->p_ckey = p1->p_vmspace->p_ckey; /* XXX move this */
#endif
/*
* This begins the section where we must prevent the parent
* from being swapped.
*/
p1->p_flag |= SKEEP;
/*
* 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.
*/
retval[0] = p1->p_pid;
retval[1] = 1;
if (vm_fork(p1, p2, isvfork)) {
/*
* Child process. Set start time and get to work.
*/
(void) splclock();
p2->p_stats->p_start = time;
(void) spl0();
p2->p_acflag = AFORK;
return (0);
}
/*
* Make child runnable and add to run queue.
*/
(void) splhigh();
p2->p_stat = SRUN;
setrq(p2);
(void) spl0();
/*
* Now can be swapped.
*/
p1->p_flag &= ~SKEEP;
/*
* Preserve synchronization semantics of vfork.
* If waiting for child to exec or exit, set SPPWAIT
* on child, and sleep on our proc (in case of exit).
*/
if (isvfork)
while (p2->p_flag & SPPWAIT)
tsleep((caddr_t)p1, PWAIT, "ppwait", 0);
/*
* Return child pid to parent process,
* marking us as parent via retval[1].
*/
retval[0] = p2->p_pid;
retval[1] = 0;
return (0);
}