[unix-history] / sys / kern / kern_fork.c

/*
 * Copyright (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.
 */
/*
 * 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.
 *
 *	from: @(#)kern_fork.c	7.29 (Berkeley) 5/15/91
 *	$Id: kern_fork.c,v 1.7 1994/03/14 21:54:15 davidg Exp $
 */

#include "param.h"
#include "systm.h"
#include "filedesc.h"
#include "kernel.h"
#include "malloc.h"
#include "proc.h"
#include "resourcevar.h"
#include "vnode.h"
#include "file.h"
#include "acct.h"
#include "ktrace.h"
#include "vm/vm.h"

static int fork1(struct proc *, int, int *);

/* ARGSUSED */
int
fork(p, uap, retval)
	struct proc *p;
	void *uap;
	int retval[];
{

	return (fork1(p, 0, retval));
}

/* ARGSUSED */
int
vfork(p, uap, retval)
	struct proc *p;
	void *uap;
	int retval[];
{

	return (fork1(p, 1, retval));
}

int	nprocs = 1;		/* process 0 */

static int
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++;

	/* Initialize all fields to zero */
	bzero((struct proc *)p2, sizeof(struct proc));

	p2->p_nxt = allproc;
	p2->p_nxt->p_prev = &p2->p_nxt;		/* allproc is never NULL */
	p2->p_prev = &allproc;
	allproc = p2;

	/*
	 * Make a proc table entry for the new process.
	 * Copy the section that is copied directly from the parent.
	 */
	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.
	 */
	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

	/*
	 * set priority of child to be that of parent
	 */
	p2->p_cpu = p1->p_cpu;

	/*
	 * 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;
/*
		vm_map_init_pmap(&p2->p_vmspace->vm_map);
*/
		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);
}
Commit	Line	Data
169d8a33 RG	1	/*
	2	* Copyright (c) UNIX System Laboratories, Inc. All or some portions
	3	* of this file are derived from material licensed to the
	4	* University of California by American Telephone and Telegraph Co.
	5	* or UNIX System Laboratories, Inc. and are reproduced herein with
	6	* the permission of UNIX System Laboratories, Inc.
	7	*/
15637ed4 RG	8	/*
	9	* Copyright (c) 1982, 1986, 1989, 1991 Regents of the University of California.
	10	* All rights reserved.
	11	*
	12	* Redistribution and use in source and binary forms, with or without
	13	* modification, are permitted provided that the following conditions
	14	* are met:
	15	* 1. Redistributions of source code must retain the above copyright
	16	* notice, this list of conditions and the following disclaimer.
	17	* 2. Redistributions in binary form must reproduce the above copyright
	18	* notice, this list of conditions and the following disclaimer in the
	19	* documentation and/or other materials provided with the distribution.
	20	* 3. All advertising materials mentioning features or use of this software
	21	* must display the following acknowledgement:
	22	* This product includes software developed by the University of
	23	* California, Berkeley and its contributors.
	24	* 4. Neither the name of the University nor the names of its contributors
	25	* may be used to endorse or promote products derived from this software
	26	* without specific prior written permission.
	27	*
	28	* THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
	29	* ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
	30	* IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
	31	* ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
	32	* FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
	33	* DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
	34	* OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
	35	* HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
	36	* LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
	37	* OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
	38	* SUCH DAMAGE.
	39	*
600f7f07	40	* from: @(#)kern_fork.c 7.29 (Berkeley) 5/15/91
169d8a33	41	* $Id: kern_fork.c,v 1.7 1994/03/14 21:54:15 davidg Exp $
15637ed4 RG	42	*/
	43
	44	#include "param.h"
	45	#include "systm.h"
	46	#include "filedesc.h"
	47	#include "kernel.h"
	48	#include "malloc.h"
	49	#include "proc.h"
	50	#include "resourcevar.h"
	51	#include "vnode.h"
	52	#include "file.h"
	53	#include "acct.h"
	54	#include "ktrace.h"
	55	#include "vm/vm.h"
	56
fde1aeb2 GW	57	static int fork1(struct proc , int, int );
fde1aeb2 GW	58
15637ed4	59	/* ARGSUSED */
4c45483e	60	int
15637ed4 RG	61	fork(p, uap, retval)
	62	struct proc *p;
	63	void *uap;
	64	int retval[];
	65	{
	66
	67	return (fork1(p, 0, retval));
	68	}
	69
	70	/* ARGSUSED */
4c45483e	71	int
15637ed4 RG	72	vfork(p, uap, retval)
	73	struct proc *p;
	74	void *uap;
	75	int retval[];
	76	{
	77
	78	return (fork1(p, 1, retval));
	79	}
	80
	81	int nprocs = 1; /* process 0 */
	82
fde1aeb2	83	static int
15637ed4 RG	84	fork1(p1, isvfork, retval)
	85	register struct proc *p1;
	86	int isvfork, retval[];
	87	{
	88	register struct proc *p2;
	89	register int count, uid;
	90	static int nextpid, pidchecked = 0;
	91
	92	count = 0;
	93	if ((uid = p1->p_ucred->cr_uid) != 0) {
	94	for (p2 = allproc; p2; p2 = p2->p_nxt)
	95	if (p2->p_ucred->cr_uid == uid)
	96	count++;
	97	for (p2 = zombproc; p2; p2 = p2->p_nxt)
	98	if (p2->p_ucred->cr_uid == uid)
	99	count++;
	100	}
	101	/*
	102	* Although process entries are dynamically entries,
	103	* we still keep a global limit on the maximum number
	104	* we will create. Don't allow a nonprivileged user
	105	* to exceed its current limit or to bring us within one
	106	* of the global limit; don't let root exceed the limit.
	107	* nprocs is the current number of processes,
	108	* maxproc is the limit.
	109	*/
	110	if (nprocs >= maxproc \|\| uid == 0 && nprocs >= maxproc + 1) {
	111	tablefull("proc");
	112	return (EAGAIN);
	113	}
	114	if (count > p1->p_rlimit[RLIMIT_NPROC].rlim_cur)
	115	return (EAGAIN);
	116
	117	/*
	118	* Find an unused process ID.
	119	* We remember a range of unused IDs ready to use
	120	* (from nextpid+1 through pidchecked-1).
	121	*/
	122	nextpid++;
	123	retry:
	124	/*
	125	* If the process ID prototype has wrapped around,
	126	* restart somewhat above 0, as the low-numbered procs
	127	* tend to include daemons that don't exit.
	128	*/
	129	if (nextpid >= PID_MAX) {
	130	nextpid = 100;
	131	pidchecked = 0;
	132	}
	133	if (nextpid >= pidchecked) {
	134	int doingzomb = 0;
	135
	136	pidchecked = PID_MAX;
	137	/*
	138	* Scan the active and zombie procs to check whether this pid
	139	* is in use. Remember the lowest pid that's greater
	140	* than nextpid, so we can avoid checking for a while.
	141	*/
	142	p2 = allproc;
	143	again:
	144	for (; p2 != NULL; p2 = p2->p_nxt) {
	145	if (p2->p_pid == nextpid \|\|
	146	p2->p_pgrp->pg_id == nextpid) {
	147	nextpid++;
148	if (nextpid >= pidchecked)
149	goto retry;
150	}
151	if (p2->p_pid > nextpid && pidchecked > p2->p_pid)
152	pidchecked = p2->p_pid;
153	if (p2->p_pgrp->pg_id > nextpid &&
154	pidchecked > p2->p_pgrp->pg_id)
155	pidchecked = p2->p_pgrp->pg_id;
156	}
157	if (!doingzomb) {
158	doingzomb = 1;
159	p2 = zombproc;
160	goto again;
161	}
162	}
163
164
165	/*
166	* Allocate new proc.
167	* Link onto allproc (this should probably be delayed).
168	*/
169	MALLOC(p2, struct proc *, sizeof(struct proc), M_PROC, M_WAITOK);
170	nprocs++;
a9d36f61 DG	171
	172	/* Initialize all fields to zero */
	173	bzero((struct proc *)p2, sizeof(struct proc));
	174
15637ed4 RG	175	p2->p_nxt = allproc;
	176	p2->p_nxt->p_prev = &p2->p_nxt; /* allproc is never NULL */
	177	p2->p_prev = &allproc;
	178	allproc = p2;
15637ed4 RG	179
	180	/*
	181	* Make a proc table entry for the new process.
a9d36f61	182	* Copy the section that is copied directly from the parent.
15637ed4	183	*/
15637ed4 RG	184	bcopy(&p1->p_startcopy, &p2->p_startcopy,
15637ed4 RG	185	(unsigned) ((caddr_t)&p2->p_endcopy - (caddr_t)&p2->p_startcopy));
15637ed4 RG	186
	187	/*
	188	* Duplicate sub-structures as needed.
	189	* Increase reference counts on shared objects.
	190	* The p_stats and p_sigacts substructs are set in vm_fork.
	191	*/
	192	MALLOC(p2->p_cred, struct pcred *, sizeof(struct pcred),
	193	M_SUBPROC, M_WAITOK);
	194	bcopy(p1->p_cred, p2->p_cred, sizeof(*p2->p_cred));
	195	p2->p_cred->p_refcnt = 1;
	196	crhold(p1->p_ucred);
	197
	198	p2->p_fd = fdcopy(p1);
	199	/*
	200	* If p_limit is still copy-on-write, bump refcnt,
	201	* otherwise get a copy that won't be modified.
	202	* (If PL_SHAREMOD is clear, the structure is shared
	203	* copy-on-write.)
	204	*/
	205	if (p1->p_limit->p_lflags & PL_SHAREMOD)
	206	p2->p_limit = limcopy(p1->p_limit);
	207	else {
	208	p2->p_limit = p1->p_limit;
	209	p2->p_limit->p_refcnt++;
	210	}
	211
	212	p2->p_flag = SLOAD \| (p1->p_flag & SHPUX);
	213	if (p1->p_session->s_ttyvp != NULL && p1->p_flag & SCTTY)
	214	p2->p_flag \|= SCTTY;
	215	if (isvfork)
	216	p2->p_flag \|= SPPWAIT;
	217	p2->p_stat = SIDL;
	218	p2->p_pid = nextpid;
	219	{
	220	struct proc **hash = &pidhash[PIDHASH(p2->p_pid)];
	221
	222	p2->p_hash = *hash;
	223	*hash = p2;
	224	}
	225	p2->p_pgrpnxt = p1->p_pgrpnxt;
	226	p1->p_pgrpnxt = p2;
	227	p2->p_pptr = p1;
	228	p2->p_osptr = p1->p_cptr;
	229	if (p1->p_cptr)
	230	p1->p_cptr->p_ysptr = p2;
	231	p1->p_cptr = p2;
	232	#ifdef KTRACE
	233	/*
	234	* Copy traceflag and tracefile if enabled.
	235	* If not inherited, these were zeroed above.
	236	*/
	237	if (p1->p_traceflag&KTRFAC_INHERIT) {
	238	p2->p_traceflag = p1->p_traceflag;
	239	if ((p2->p_tracep = p1->p_tracep) != NULL)
	240	VREF(p2->p_tracep);
	241	}
	242	#endif
	243
	244	#if defined(tahoe)
	245	p2->p_vmspace->p_ckey = p1->p_vmspace->p_ckey; /* XXX move this */
	246	#endif
	247
41aefbec DG	248	/*
	249	* set priority of child to be that of parent
	250	*/
	251	p2->p_cpu = p1->p_cpu;
	252
15637ed4 RG	253	/*
	254	* This begins the section where we must prevent the parent
	255	* from being swapped.
	256	*/
	257	p1->p_flag \|= SKEEP;
	258	/*
	259	* Set return values for child before vm_fork,
	260	* so they can be copied to child stack.
	261	* We return parent pid, and mark as child in retval[1].
	262	* NOTE: the kernel stack may be at a different location in the child
	263	* process, and thus addresses of automatic variables (including retval)
	264	* may be invalid after vm_fork returns in the child process.
	265	*/
	266	retval[0] = p1->p_pid;
	267	retval[1] = 1;
	268	if (vm_fork(p1, p2, isvfork)) {
	269	/*
	270	* Child process. Set start time and get to work.
	271	*/
	272	(void) splclock();
	273	p2->p_stats->p_start = time;
	274	(void) spl0();
	275	p2->p_acflag = AFORK;
41aefbec DG	276	/*
	277	vm_map_init_pmap(&p2->p_vmspace->vm_map);
	278	*/
15637ed4 RG	279	return (0);
	280	}
	281
	282	/*
	283	* Make child runnable and add to run queue.
	284	*/
	285	(void) splhigh();
	286	p2->p_stat = SRUN;
	287	setrq(p2);
	288	(void) spl0();
	289
	290	/*
	291	* Now can be swapped.
	292	*/
	293	p1->p_flag &= ~SKEEP;
	294
	295	/*
	296	* Preserve synchronization semantics of vfork.
	297	* If waiting for child to exec or exit, set SPPWAIT
	298	* on child, and sleep on our proc (in case of exit).
	299	*/
	300	if (isvfork)
	301	while (p2->p_flag & SPPWAIT)
	302	tsleep((caddr_t)p1, PWAIT, "ppwait", 0);
	303
	304	/*
	305	* Return child pid to parent process,
	306	* marking us as parent via retval[1].
	307	*/
	308	retval[0] = p2->p_pid;
	309	retval[1] = 0;
	310	return (0);
	311	}