diff options
Diffstat (limited to 'sys/kern/kern_fork.c')
-rw-r--r-- | sys/kern/kern_fork.c | 580 |
1 files changed, 580 insertions, 0 deletions
diff --git a/sys/kern/kern_fork.c b/sys/kern/kern_fork.c new file mode 100644 index 0000000..35aa113 --- /dev/null +++ b/sys/kern/kern_fork.c @@ -0,0 +1,580 @@ +/* + * 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 + * $FreeBSD$ + */ + +#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 <sys/jail.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> + +#include <sys/user.h> + +static MALLOC_DEFINE(M_ATFORK, "atfork", "atfork callback"); + +static int fast_vfork = 1; +SYSCTL_INT(_kern, OID_AUTO, fast_vfork, CTLFLAG_RW, &fast_vfork, 0, + "flag to indicate whether we have a fast vfork()"); + +/* + * These are the stuctures used to create a callout list for things to do + * when forking a process + */ +struct forklist { + forklist_fn function; + TAILQ_ENTRY(forklist) next; +}; + +TAILQ_HEAD(forklist_head, forklist); +static struct forklist_head fork_list = TAILQ_HEAD_INITIALIZER(fork_list); + +#ifndef _SYS_SYSPROTO_H_ +struct fork_args { + int dummy; +}; +#endif + +/* ARGSUSED */ +int +fork(p, uap) + struct proc *p; + struct fork_args *uap; +{ + int error; + struct proc *p2; + + error = fork1(p, RFFDG | RFPROC, &p2); + if (error == 0) { + p->p_retval[0] = p2->p_pid; + p->p_retval[1] = 0; + } + return error; +} + +/* ARGSUSED */ +int +vfork(p, uap) + struct proc *p; + struct vfork_args *uap; +{ + int error; + struct proc *p2; + + error = fork1(p, RFFDG | RFPROC | RFPPWAIT | RFMEM, &p2); + if (error == 0) { + p->p_retval[0] = p2->p_pid; + p->p_retval[1] = 0; + } + return error; +} + +int +rfork(p, uap) + struct proc *p; + struct rfork_args *uap; +{ + int error; + struct proc *p2; + + error = fork1(p, uap->flags, &p2); + if (error == 0) { + p->p_retval[0] = p2 ? p2->p_pid : 0; + p->p_retval[1] = 0; + } + return error; +} + + +int nprocs = 1; /* process 0 */ +static int nextpid = 0; + +/* + * Random component to nextpid generation. We mix in a random factor to make + * it a little harder to predict. We sanity check the modulus value to avoid + * doing it in critical paths. Don't let it be too small or we pointlessly + * waste randomness entropy, and don't let it be impossibly large. Using a + * modulus that is too big causes a LOT more process table scans and slows + * down fork processing as the pidchecked caching is defeated. + */ +static int randompid = 0; + +static int +sysctl_kern_randompid SYSCTL_HANDLER_ARGS +{ + int error, pid; + + pid = randompid; + error = sysctl_handle_int(oidp, &pid, 0, req); + if (error || !req->newptr) + return (error); + if (pid < 0 || pid > PID_MAX - 100) /* out of range */ + pid = PID_MAX - 100; + else if (pid < 2) /* NOP */ + pid = 0; + else if (pid < 100) /* Make it reasonable */ + pid = 100; + randompid = pid; + return (error); +} + +SYSCTL_PROC(_kern, OID_AUTO, randompid, CTLTYPE_INT|CTLFLAG_RW, + 0, 0, sysctl_kern_randompid, "I", "Random PID modulus"); + +int +fork1(p1, flags, procp) + struct proc *p1; + int flags; + struct proc **procp; +{ + struct proc *p2, *pptr; + uid_t uid; + struct proc *newproc; + int ok; + static int pidchecked = 0; + struct forklist *ep; + + if ((flags & (RFFDG|RFCFDG)) == (RFFDG|RFCFDG)) + return (EINVAL); + + /* + * Here we don't create a new process, but we divorce + * certain parts of a process from itself. + */ + if ((flags & RFPROC) == 0) { + + vm_fork(p1, 0, flags); + + /* + * 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; + } + } + *procp = NULL; + 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. + */ + ok = chgproccnt(uid, 1, p1->p_rlimit[RLIMIT_NPROC].rlim_cur); + if (uid != 0 && !ok) { + /* + * 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; + + newproc->p_vmspace = NULL; + + /* + * Find an unused process ID. We remember a range of unused IDs + * ready to use (from nextpid+1 through pidchecked-1). + */ + nextpid++; + if (randompid) + nextpid += arc4random() % randompid; +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 = nextpid % PID_MAX; + if (nextpid < 100) + 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 = LIST_FIRST(&allproc); +again: + for (; p2 != 0; p2 = LIST_NEXT(p2, p_list)) { + 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 = LIST_FIRST(&zombproc); + 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); + + if (p2->p_prison) { + p2->p_prison->pr_ref++; + p2->p_flag |= P_JAILED; + } + + if (p2->p_args) + p2->p_args->ar_ref++; + + 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; + + /* 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; + bcopy(&p1->p_addr->u_sigacts, p2->p_sigacts, + sizeof(*p2->p_sigacts)); + *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, p2->p_procsig, sizeof(*p2->p_procsig)); + p2->p_procsig->ps_refcnt = 1; + p2->p_sigacts = NULL; /* finished in vm_fork() */ + } + if (flags & RFLINUXTHPN) + p2->p_sigparent = SIGUSR1; + else + p2->p_sigparent = SIGCHLD; + + /* 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. + */ + PHOLD(p1); + + /* + * 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 loadable modules want + * to adjust anything. + * What if they have an error? XXX + */ + TAILQ_FOREACH(ep, &fork_list, next) { + (*ep->function)(p1, p2, flags); + } + + /* + * 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. + */ + PRELE(p1); + + /* + * tell any interested parties about the new process + */ + KNOTE(&p1->p_klist, NOTE_FORK | p2->p_pid); + + /* + * 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 proc pointer to parent. + */ + *procp = p2; + 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; +{ + struct forklist *ep; + +#ifdef INVARIANTS + /* let the programmer know if he's been stupid */ + if (rm_at_fork(function)) + printf("WARNING: fork callout entry (%p) already present\n", + function); +#endif + ep = malloc(sizeof(*ep), M_ATFORK, M_NOWAIT); + if (ep == NULL) + return (ENOMEM); + ep->function = function; + TAILQ_INSERT_TAIL(&fork_list, ep, next); + return (0); +} + +/* + * Scan the exit callout list for the given item and remove it.. + * Returns the number of items removed (0 or 1) + */ + +int +rm_at_fork(function) + forklist_fn function; +{ + struct forklist *ep; + + TAILQ_FOREACH(ep, &fork_list, next) { + if (ep->function == function) { + TAILQ_REMOVE(&fork_list, ep, next); + free(ep, M_ATFORK); + return(1); + } + } + return (0); +} |