diff options
Diffstat (limited to 'sys/kern/kern_fork.c')
| -rw-r--r-- | sys/kern/kern_fork.c | 315 |
1 files changed, 315 insertions, 0 deletions
diff --git a/sys/kern/kern_fork.c b/sys/kern/kern_fork.c new file mode 100644 index 0000000..8bec2fa --- /dev/null +++ b/sys/kern/kern_fork.c @@ -0,0 +1,315 @@ +/* + * 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 + */ + +#include <sys/param.h> +#include <sys/systm.h> +#include <sys/map.h> +#include <sys/filedesc.h> +#include <sys/kernel.h> +#include <sys/malloc.h> +#include <sys/proc.h> +#include <sys/resourcevar.h> +#include <sys/vnode.h> +#include <sys/file.h> +#include <sys/acct.h> +#include <sys/ktrace.h> + +struct fork_args { + int dummy; +}; +/* ARGSUSED */ +fork(p, uap, retval) + struct proc *p; + struct fork_args *uap; + int retval[]; +{ + + return (fork1(p, 0, retval)); +} + +/* ARGSUSED */ +vfork(p, uap, retval) + struct proc *p; + struct fork_args *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 uid_t uid; + struct proc *newproc; + struct proc **hash; + int count; + 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) { + tablefull("proc"); + return (EAGAIN); + } + /* + * 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); + return (EAGAIN); + } + + /* Allocate new proc. */ + 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). + */ + 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 = (struct proc *)allproc; +again: + for (; p2 != NULL; p2 = p2->p_next) { + while (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; + } + } + + + /* + * Link onto allproc (this should probably be delayed). + * Heavy use of volatile here to prevent the compiler from + * rearranging code. Yes, it *is* terribly ugly, but at least + * it works. + */ + nprocs++; + p2 = newproc; +#define Vp2 ((volatile struct proc *)p2) + Vp2->p_stat = SIDL; /* protect against others */ + Vp2->p_pid = nextpid; + /* + * This is really: + * p2->p_next = allproc; + * allproc->p_prev = &p2->p_next; + * p2->p_prev = &allproc; + * allproc = p2; + * The assignment via allproc is legal since it is never NULL. + */ + *(volatile struct proc **)&Vp2->p_next = allproc; + *(volatile struct proc ***)&allproc->p_prev = + (volatile struct proc **)&Vp2->p_next; + *(volatile struct proc ***)&Vp2->p_prev = &allproc; + allproc = Vp2; +#undef Vp2 + p2->p_forw = p2->p_back = NULL; /* shouldn't be necessary */ + + /* Insert on the hash chain. */ + hash = &pidhash[PIDHASH(p2->p_pid)]; + p2->p_hash = *hash; + *hash = p2; + + /* + * 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)); + + /* + * 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); + + /* bump references to the text vnode (for procfs) */ + p2->p_textvp = p1->p_textvp; + if (p2->p_textvp) + VREF(p2->p_textvp); + + 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++; + } + + if (p1->p_session->s_ttyvp != NULL && p1->p_flag & P_CONTROLT) + p2->p_flag |= P_CONTROLT; + if (isvfork) + p2->p_flag |= P_PPWAIT; + 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 + + /* + * This begins the section where we must prevent the parent + * from being swapped. + */ + p1->p_flag |= P_NOSWAP; + /* + * 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; + 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). + */ + if (isvfork) + while (p2->p_flag & P_PPWAIT) + tsleep(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); +} |
