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Diffstat (limited to 'sys/kern/kern_fork.c')
| -rw-r--r-- | sys/kern/kern_fork.c | 546 |
1 files changed, 546 insertions, 0 deletions
diff --git a/sys/kern/kern_fork.c b/sys/kern/kern_fork.c new file mode 100644 index 0000000..732712b --- /dev/null +++ b/sys/kern/kern_fork.c @@ -0,0 +1,546 @@ +/* + * 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. 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 8.6 (Berkeley) 4/8/94 + * $Id: kern_fork.c,v 1.53 1998/12/19 02:55:33 julian Exp $ + */ + +#include "opt_ktrace.h" + +#include <sys/param.h> +#include <sys/systm.h> +#include <sys/sysproto.h> +#include <sys/filedesc.h> +#include <sys/kernel.h> +#include <sys/sysctl.h> +#include <sys/malloc.h> +#include <sys/proc.h> +#include <sys/resourcevar.h> +#include <sys/vnode.h> +#include <sys/acct.h> +#include <sys/ktrace.h> +#include <sys/unistd.h> + +#include <vm/vm.h> +#include <sys/lock.h> +#include <vm/pmap.h> +#include <vm/vm_map.h> +#include <vm/vm_extern.h> +#include <vm/vm_zone.h> + +#ifdef COMPAT_LINUX_THREADS +#include <machine/frame.h> +#include <sys/user.h> +#endif /* COMPAT_LINUX_THREADS */ +#ifdef SMP +static int fast_vfork = 0; /* Doesn't work on SMP yet. */ +#else +static int fast_vfork = 1; +#endif +SYSCTL_INT(_kern, OID_AUTO, fast_vfork, CTLFLAG_RW, &fast_vfork, 0, ""); + +/* + * These are the stuctures used to create a callout list for things to do + * when forking a process + */ +typedef struct fork_list_element { + struct fork_list_element *next; + forklist_fn function; +} *fle_p; + +static fle_p fork_list; + +#ifndef _SYS_SYSPROTO_H_ +struct fork_args { + int dummy; +}; +#endif + +/* ARGSUSED */ +int +fork(p, uap) + struct proc *p; + struct fork_args *uap; +{ + + return (fork1(p, RFFDG | RFPROC)); +} + +/* ARGSUSED */ +int +vfork(p, uap) + struct proc *p; + struct vfork_args *uap; +{ + + return (fork1(p, RFFDG | RFPROC | RFPPWAIT | (fast_vfork ? RFMEM : 0))); +} + +/* ARGSUSED */ +int +rfork(p, uap) + struct proc *p; + struct rfork_args *uap; +{ + + return (fork1(p, uap->flags)); +} + + +int nprocs = 1; /* process 0 */ +static int nextpid = 0; + +int +fork1(p1, flags) + register struct proc *p1; + int flags; +{ + register struct proc *p2, *pptr; + register uid_t uid; + struct proc *newproc; + int count; + static int pidchecked = 0; + fle_p ep ; + + ep = fork_list; + + if ((flags & (RFFDG|RFCFDG)) == (RFFDG|RFCFDG)) + return (EINVAL); + +#ifdef SMP + /* + * FATAL now, we cannot have the same PTD on both cpus, the PTD + * needs to move out of PTmap and be per-process, even for shared + * page table processes. Unfortunately, this means either removing + * PTD[] as a fixed virtual address, or move it to the per-cpu map + * area for SMP mode. Both cases require seperate management of + * the per-process-even-if-PTmap-is-shared PTD. + */ + if (flags & RFMEM) { + printf("shared address space fork attempted: pid: %d\n", + p1->p_pid); + return (EOPNOTSUPP); + } +#endif + + /* + * Here we don't create a new process, but we divorce + * certain parts of a process from itself. + */ + if ((flags & RFPROC) == 0) { + + /* + * Divorce the memory, if it is shared, essentially + * this changes shared memory amongst threads, into + * COW locally. + */ + if ((flags & RFMEM) == 0) { + if (p1->p_vmspace->vm_refcnt > 1) { + vmspace_unshare(p1); + } + } + + /* + * Close all file descriptors. + */ + if (flags & RFCFDG) { + struct filedesc *fdtmp; + fdtmp = fdinit(p1); + fdfree(p1); + p1->p_fd = fdtmp; + } + + /* + * Unshare file descriptors (from parent.) + */ + if (flags & RFFDG) { + if (p1->p_fd->fd_refcnt > 1) { + struct filedesc *newfd; + newfd = fdcopy(p1); + fdfree(p1); + p1->p_fd = newfd; + } + } + return (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) { + tablefull("proc"); + return (EAGAIN); + } + /* + * Increment the nprocs resource before blocking can occur. There + * are hard-limits as to the number of processes that can run. + */ + nprocs++; + + /* + * 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); + /* + * Back out the process count + */ + nprocs--; + return (EAGAIN); + } + + /* Allocate new proc. */ + newproc = zalloc(proc_zone); + +/* + * Setup linkage for kernel based threading + */ + if((flags & RFTHREAD) != 0) { + newproc->p_peers = p1->p_peers; + p1->p_peers = newproc; + newproc->p_leader = p1->p_leader; + } else { + newproc->p_peers = 0; + newproc->p_leader = newproc; + } + + newproc->p_wakeup = 0; + + /* + * 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.lh_first; +again: + for (; p2 != 0; p2 = p2->p_list.le_next) { + while (p2->p_pid == nextpid || + p2->p_pgrp->pg_id == nextpid || + p2->p_session->s_sid == 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 (p2->p_session->s_sid > nextpid && + pidchecked > p2->p_session->s_sid) + pidchecked = p2->p_session->s_sid; + } + if (!doingzomb) { + doingzomb = 1; + p2 = zombproc.lh_first; + goto again; + } + } + + p2 = newproc; + p2->p_stat = SIDL; /* protect against others */ + p2->p_pid = nextpid; + LIST_INSERT_HEAD(&allproc, p2, p_list); + 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. + */ + 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_aioinfo = NULL; + + /* + * Duplicate sub-structures as needed. + * Increase reference counts on shared objects. + * The p_stats and p_sigacts substructs are set in vm_fork. + */ + p2->p_flag = P_INMEM; + if (p1->p_flag & P_PROFIL) + startprofclock(p2); + 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); + +#ifdef COMPAT_LINUX_THREADS + if (flags & RFSIGSHARE) { + p2->p_procsig = p1->p_procsig; + p2->p_procsig->ps_refcnt++; + if (p1->p_sigacts == &p1->p_addr->u_sigacts) { + struct sigacts *newsigacts; + int s; + + if (p2->p_procsig->ps_refcnt != 2) + printf ("PID:%d Creating shared sigacts with procsig->ps_refcnt %d\n", + p2->p_pid, p2->p_procsig->ps_refcnt); + /* Create the shared sigacts structure */ + MALLOC (newsigacts, struct sigacts *, sizeof (struct sigacts), + M_SUBPROC, M_WAITOK); + s = splhigh(); + /* Set p_sigacts to the new shared structure. Note that this + * is updating p1->p_sigacts at the same time, since p_sigacts + * is just a pointer to the shared p_procsig->ps_sigacts. + */ + p2->p_sigacts = newsigacts; + /* Copy in the values from the u area */ + *p2->p_sigacts = p1->p_addr->u_sigacts; + splx (s); + } + } else { + MALLOC (p2->p_procsig, struct procsig *, sizeof(struct procsig), + M_SUBPROC, M_WAITOK); + bcopy(&p1->p_procsig->ps_begincopy, &p2->p_procsig->ps_begincopy, + (unsigned)&p1->p_procsig->ps_endcopy - + (unsigned)&p1->p_procsig->ps_begincopy); + p2->p_procsig->ps_refcnt = 1; + /* Note that we fill in the values of sigacts in vm_fork */ + p2->p_sigacts = NULL; + } + if (flags & RFLINUXTHPN) { + p2->p_sigparent = SIGUSR1; + } +#endif /* COMPAT_LINUX_THREADS */ + /* bump references to the text vnode (for procfs) */ + p2->p_textvp = p1->p_textvp; + if (p2->p_textvp) + VREF(p2->p_textvp); + + if (flags & RFCFDG) + p2->p_fd = fdinit(p1); + else if (flags & RFFDG) + p2->p_fd = fdcopy(p1); + else + p2->p_fd = fdshare(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++; + } + + /* + * Preserve some more flags in subprocess. P_PROFIL has already + * been preserved. + */ + p2->p_flag |= p1->p_flag & P_SUGID; + if (p1->p_session->s_ttyvp != NULL && p1->p_flag & P_CONTROLT) + p2->p_flag |= P_CONTROLT; + if (flags & RFPPWAIT) + p2->p_flag |= P_PPWAIT; + + LIST_INSERT_AFTER(p1, p2, p_pglist); + + /* + * 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 (flags & RFNOWAIT) + pptr = initproc; + else + pptr = p1; + p2->p_pptr = pptr; + LIST_INSERT_HEAD(&pptr->p_children, p2, p_sibling); + LIST_INIT(&p2->p_children); + +#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 + + /* + * set priority of child to be that of parent + */ + p2->p_estcpu = p1->p_estcpu; + + /* + * This begins the section where we must prevent the parent + * from being swapped. + */ + p1->p_flag |= P_NOSWAP; + + /* + * Finish creating the child process. It will return via a different + * execution path later. (ie: directly into user mode) + */ + vm_fork(p1, p2, flags); + + /* + * Both processes are set up, now check if any LKMs want + * to adjust anything. + * What if they have an error? XXX + */ + while (ep) { + (*ep->function)(p1, p2, flags); + ep = ep->next; + } + + /* + * Make child runnable and add to run queue. + */ + microtime(&(p2->p_stats->p_start)); + p2->p_acflag = AFORK; + (void) splhigh(); + p2->p_stat = SRUN; + setrunqueue(p2); + (void) spl0(); + + /* + * Now can be swapped. + */ + p1->p_flag &= ~P_NOSWAP; + + /* + * 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 p1->p_retval[1]. + */ + p1->p_retval[0] = p2->p_pid; + p1->p_retval[1] = 0; + return (0); +} + +/* + * The next two functionms are general routines to handle adding/deleting + * items on the fork callout list. + * + * at_fork(): + * Take the arguments given and put them onto the fork callout list, + * However first make sure that it's not already there. + * Returns 0 on success or a standard error number. + */ +int +at_fork(function) + forklist_fn function; +{ + fle_p ep; + + /* let the programmer know if he's been stupid */ + if (rm_at_fork(function)) + printf("fork callout entry already present\n"); + ep = malloc(sizeof(*ep), M_TEMP, M_NOWAIT); + if (ep == NULL) + return (ENOMEM); + ep->next = fork_list; + ep->function = function; + fork_list = ep; + return (0); +} + +/* + * Scan the exit callout list for the given items and remove them. + * Returns the number of items removed. + * Theoretically this value can only be 0 or 1. + */ +int +rm_at_fork(function) + forklist_fn function; +{ + fle_p *epp, ep; + int count; + + count= 0; + epp = &fork_list; + ep = *epp; + while (ep) { + if (ep->function == function) { + *epp = ep->next; + free(ep, M_TEMP); + count++; + } else { + epp = &ep->next; + } + ep = *epp; + } + return (count); +} |
