diff options
Diffstat (limited to 'sys/kern/kern_fork.c')
| -rw-r--r-- | sys/kern/kern_fork.c | 866 |
1 files changed, 866 insertions, 0 deletions
diff --git a/sys/kern/kern_fork.c b/sys/kern/kern_fork.c new file mode 100644 index 0000000..016653b --- /dev/null +++ b/sys/kern/kern_fork.c @@ -0,0 +1,866 @@ +/* + * 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/lock.h> +#include <sys/malloc.h> +#include <sys/mutex.h> +#include <sys/proc.h> +#include <sys/resourcevar.h> +#include <sys/syscall.h> +#include <sys/vnode.h> +#include <sys/acct.h> +#include <sys/ktr.h> +#include <sys/ktrace.h> +#include <sys/kthread.h> +#include <sys/unistd.h> +#include <sys/jail.h> +#include <sys/sx.h> + +#include <vm/vm.h> +#include <vm/pmap.h> +#include <vm/vm_map.h> +#include <vm/vm_extern.h> +#include <vm/uma.h> + +#include <sys/vmmeter.h> +#include <sys/user.h> +#include <machine/critical.h> + +static MALLOC_DEFINE(M_ATFORK, "atfork", "atfork callback"); + +/* + * 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; +}; + +static struct sx fork_list_lock; + +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 + +int forksleep; /* Place for fork1() to sleep on. */ + +static void +init_fork_list(void *data __unused) +{ + + sx_init(&fork_list_lock, "fork list"); +} +SYSINIT(fork_list, SI_SUB_INTRINSIC, SI_ORDER_ANY, init_fork_list, NULL); + +/* + * MPSAFE + */ +/* ARGSUSED */ +int +fork(td, uap) + struct thread *td; + struct fork_args *uap; +{ + int error; + struct proc *p2; + + mtx_lock(&Giant); + error = fork1(td, RFFDG | RFPROC, &p2); + if (error == 0) { + td->td_retval[0] = p2->p_pid; + td->td_retval[1] = 0; + } + mtx_unlock(&Giant); + return error; +} + +/* + * MPSAFE + */ +/* ARGSUSED */ +int +vfork(td, uap) + struct thread *td; + struct vfork_args *uap; +{ + int error; + struct proc *p2; + + mtx_lock(&Giant); + error = fork1(td, RFFDG | RFPROC | RFPPWAIT | RFMEM, &p2); + if (error == 0) { + td->td_retval[0] = p2->p_pid; + td->td_retval[1] = 0; + } + mtx_unlock(&Giant); + return error; +} + +/* + * MPSAFE + */ +int +rfork(td, uap) + struct thread *td; + struct rfork_args *uap; +{ + int error; + struct proc *p2; + + /* Don't allow kernel only flags. */ + if ((uap->flags & RFKERNELONLY) != 0) + return (EINVAL); + mtx_lock(&Giant); + error = fork1(td, uap->flags, &p2); + if (error == 0) { + td->td_retval[0] = p2 ? p2->p_pid : 0; + td->td_retval[1] = 0; + } + mtx_unlock(&Giant); + return error; +} + + +int nprocs = 1; /* process 0 */ +int lastpid = 0; +SYSCTL_INT(_kern, OID_AUTO, lastpid, CTLFLAG_RD, &lastpid, 0, + "Last used PID"); + +/* + * Random component to lastpid 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; + + sx_xlock(&allproc_lock); + pid = randompid; + error = sysctl_handle_int(oidp, &pid, 0, req); + if (error == 0 && req->newptr != NULL) { + 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; + } + sx_xunlock(&allproc_lock); + return (error); +} + +SYSCTL_PROC(_kern, OID_AUTO, randompid, CTLTYPE_INT|CTLFLAG_RW, + 0, 0, sysctl_kern_randompid, "I", "Random PID modulus"); + +#if 0 +void +kse_init(struct kse *kse1, struct kse *kse2) +{ +} + +void +thread_init(struct thread *thread1, struct thread *thread2) +{ +} + +void +ksegrp_init(struct ksegrp *ksegrp1, struct ksegrp *ksegrp2) +{ +} +#endif + +int +fork1(td, flags, procp) + struct thread *td; /* parent proc */ + int flags; + struct proc **procp; /* child proc */ +{ + struct proc *p2, *pptr; + uid_t uid; + struct proc *newproc; + int trypid; + int ok; + static int pidchecked = 0; + struct forklist *ep; + struct filedesc *fd; + struct proc *p1 = td->td_proc; + struct thread *td2; + struct kse *ke2; + struct ksegrp *kg2; + struct sigacts *newsigacts; + struct procsig *newprocsig; + + GIANT_REQUIRED; + + /* Can't copy and clear */ + 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_forkproc(td, NULL, NULL, flags); + + /* + * Close all file descriptors. + */ + if (flags & RFCFDG) { + struct filedesc *fdtmp; + fdtmp = fdinit(td); /* XXXKSE */ + PROC_LOCK(p1); + fdfree(td); /* XXXKSE */ + p1->p_fd = fdtmp; + PROC_UNLOCK(p1); + } + + /* + * Unshare file descriptors (from parent.) + */ + if (flags & RFFDG) { + FILEDESC_LOCK(p1->p_fd); + if (p1->p_fd->fd_refcnt > 1) { + struct filedesc *newfd; + + newfd = fdcopy(td); + FILEDESC_UNLOCK(p1->p_fd); + PROC_LOCK(p1); + fdfree(td); + p1->p_fd = newfd; + PROC_UNLOCK(p1); + } else + FILEDESC_UNLOCK(p1->p_fd); + } + *procp = NULL; + return (0); + } + + /* Allocate new proc. */ + newproc = uma_zalloc(proc_zone, M_WAITOK); + + /* + * 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. + */ + sx_xlock(&allproc_lock); + uid = td->td_ucred->cr_ruid; + if ((nprocs >= maxproc - 10 && uid != 0) || nprocs >= maxproc) { + sx_xunlock(&allproc_lock); + uma_zfree(proc_zone, newproc); + tsleep(&forksleep, PUSER, "fork", hz / 2); + return (EAGAIN); + } + /* + * Increment the count of procs running with this uid. Don't allow + * a nonprivileged user to exceed their current limit. + */ + PROC_LOCK(p1); + ok = chgproccnt(td->td_ucred->cr_ruidinfo, 1, + (uid != 0) ? p1->p_rlimit[RLIMIT_NPROC].rlim_cur : 0); + PROC_UNLOCK(p1); + if (!ok) { + sx_xunlock(&allproc_lock); + uma_zfree(proc_zone, newproc); + tsleep(&forksleep, PUSER, "fork", hz / 2); + return (EAGAIN); + } + + /* + * Increment the nprocs resource before blocking can occur. There + * are hard-limits as to the number of processes that can run. + */ + nprocs++; + + /* + * Find an unused process ID. We remember a range of unused IDs + * ready to use (from lastpid+1 through pidchecked-1). + * + * If RFHIGHPID is set (used during system boot), do not allocate + * low-numbered pids. + */ + trypid = lastpid + 1; + if (flags & RFHIGHPID) { + if (trypid < 10) { + trypid = 10; + } + } else { + if (randompid) + trypid += 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 (trypid >= PID_MAX) { + trypid = trypid % PID_MAX; + if (trypid < 100) + trypid += 100; + pidchecked = 0; + } + if (trypid >= 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 trypid, so we can avoid checking for a while. + */ + p2 = LIST_FIRST(&allproc); +again: + for (; p2 != NULL; p2 = LIST_NEXT(p2, p_list)) { + PROC_LOCK(p2); + while (p2->p_pid == trypid || + p2->p_pgrp->pg_id == trypid || + p2->p_session->s_sid == trypid) { + trypid++; + if (trypid >= pidchecked) { + PROC_UNLOCK(p2); + goto retry; + } + } + if (p2->p_pid > trypid && pidchecked > p2->p_pid) + pidchecked = p2->p_pid; + if (p2->p_pgrp->pg_id > trypid && + pidchecked > p2->p_pgrp->pg_id) + pidchecked = p2->p_pgrp->pg_id; + if (p2->p_session->s_sid > trypid && + pidchecked > p2->p_session->s_sid) + pidchecked = p2->p_session->s_sid; + PROC_UNLOCK(p2); + } + if (!doingzomb) { + doingzomb = 1; + p2 = LIST_FIRST(&zombproc); + goto again; + } + } + + /* + * RFHIGHPID does not mess with the lastpid counter during boot. + */ + if (flags & RFHIGHPID) + pidchecked = 0; + else + lastpid = trypid; + + p2 = newproc; + p2->p_stat = SIDL; /* protect against others */ + p2->p_pid = trypid; + LIST_INSERT_HEAD(&allproc, p2, p_list); + LIST_INSERT_HEAD(PIDHASH(p2->p_pid), p2, p_hash); + sx_xunlock(&allproc_lock); + + /* + * Malloc things while we don't hold any locks. + */ + if (flags & RFSIGSHARE) { + MALLOC(newsigacts, struct sigacts *, + sizeof(struct sigacts), M_SUBPROC, M_WAITOK); + newprocsig = NULL; + } else { + newsigacts = NULL; + MALLOC(newprocsig, struct procsig *, sizeof(struct procsig), + M_SUBPROC, M_WAITOK); + } + + /* + * Copy filedesc. + * XXX: This is busted. fd*() need to not take proc + * arguments or something. + */ + if (flags & RFCFDG) + fd = fdinit(td); + else if (flags & RFFDG) { + FILEDESC_LOCK(p1->p_fd); + fd = fdcopy(td); + FILEDESC_UNLOCK(p1->p_fd); + } else + fd = fdshare(p1); + + /* + * 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. + */ + td2 = thread_get(p2); + ke2 = &p2->p_kse; + kg2 = &p2->p_ksegrp; + +#define RANGEOF(type, start, end) (offsetof(type, end) - offsetof(type, start)) + + bzero(&p2->p_startzero, + (unsigned) RANGEOF(struct proc, p_startzero, p_endzero)); + bzero(&ke2->ke_startzero, + (unsigned) RANGEOF(struct kse, ke_startzero, ke_endzero)); + bzero(&td2->td_startzero, + (unsigned) RANGEOF(struct thread, td_startzero, td_endzero)); + bzero(&kg2->kg_startzero, + (unsigned) RANGEOF(struct ksegrp, kg_startzero, kg_endzero)); + + mtx_init(&p2->p_mtx, "process lock", NULL, MTX_DEF | MTX_DUPOK); + PROC_LOCK(p2); + PROC_LOCK(p1); + + bcopy(&p1->p_startcopy, &p2->p_startcopy, + (unsigned) RANGEOF(struct proc, p_startcopy, p_endcopy)); + bcopy(&td->td_kse->ke_startcopy, &ke2->ke_startcopy, + (unsigned) RANGEOF(struct kse, ke_startcopy, ke_endcopy)); + bcopy(&td->td_startcopy, &td2->td_startcopy, + (unsigned) RANGEOF(struct thread, td_startcopy, td_endcopy)); + bcopy(&td->td_ksegrp->kg_startcopy, &kg2->kg_startcopy, + (unsigned) RANGEOF(struct ksegrp, kg_startcopy, kg_endcopy)); +#undef RANGEOF + + /* + * XXXKSE Theoretically only the running thread would get copied + * Others in the kernel would be 'aborted' in the child. + * i.e return E*something* + */ + proc_linkup(p2, kg2, ke2, td2); + + /* note.. XXXKSE no pcb or u-area yet */ + + /* + * Duplicate sub-structures as needed. + * Increase reference counts on shared objects. + * The p_stats and p_sigacts substructs are set in vm_forkproc. + */ + p2->p_flag = 0; + mtx_lock_spin(&sched_lock); + p2->p_sflag = PS_INMEM; + if (p1->p_sflag & PS_PROFIL) + startprofclock(p2); + mtx_unlock_spin(&sched_lock); + p2->p_ucred = crhold(td->td_ucred); + td2->td_ucred = crhold(p2->p_ucred); /* XXXKSE */ + + /* + * Setup linkage for kernel based threading + */ + if((flags & RFTHREAD) != 0) { + /* + * XXX: This assumes a leader is a parent or grandparent of + * all processes in a task. + */ + if (p1->p_leader != p1) + PROC_LOCK(p1->p_leader); + p2->p_peers = p1->p_peers; + p1->p_peers = p2; + p2->p_leader = p1->p_leader; + if (p1->p_leader != p1) + PROC_UNLOCK(p1->p_leader); + } else { + p2->p_peers = NULL; + p2->p_leader = p2; + } + + pargs_hold(p2->p_args); + + if (flags & RFSIGSHARE) { + p2->p_procsig = p1->p_procsig; + p2->p_procsig->ps_refcnt++; + if (p1->p_sigacts == &p1->p_uarea->u_sigacts) { + /* + * 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; + newsigacts = NULL; + *p2->p_sigacts = p1->p_uarea->u_sigacts; + } + } else { + p2->p_procsig = newprocsig; + newprocsig = NULL; + bcopy(p1->p_procsig, p2->p_procsig, sizeof(*p2->p_procsig)); + p2->p_procsig->ps_refcnt = 1; + p2->p_sigacts = NULL; /* finished in vm_forkproc() */ + } + 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); + p2->p_fd = fd; + PROC_UNLOCK(p1); + PROC_UNLOCK(p2); + + /* + * 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++; + } + + sx_xlock(&proctree_lock); + PGRP_LOCK(p1->p_pgrp); + PROC_LOCK(p2); + PROC_LOCK(p1); + + /* + * Preserve some more flags in subprocess. PS_PROFIL has already + * been preserved. + */ + p2->p_flag |= p1->p_flag & (P_SUGID | P_ALTSTACK); + SESS_LOCK(p1->p_session); + if (p1->p_session->s_ttyvp != NULL && p1->p_flag & P_CONTROLT) + p2->p_flag |= P_CONTROLT; + SESS_UNLOCK(p1->p_session); + if (flags & RFPPWAIT) + p2->p_flag |= P_PPWAIT; + + LIST_INSERT_AFTER(p1, p2, p_pglist); + PGRP_UNLOCK(p1->p_pgrp); + LIST_INIT(&p2->p_children); + LIST_INIT(&td2->td_contested); /* XXXKSE only 1 thread? */ + + callout_init(&p2->p_itcallout, 0); + callout_init(&td2->td_slpcallout, 1); /* XXXKSE */ + +#ifdef KTRACE + /* + * Copy traceflag and tracefile if enabled. + */ + mtx_lock(&ktrace_mtx); + KASSERT(p2->p_tracep == NULL, ("new process has a ktrace vnode")); + if (p1->p_traceflag & KTRFAC_INHERIT) { + p2->p_traceflag = p1->p_traceflag; + if ((p2->p_tracep = p1->p_tracep) != NULL) + VREF(p2->p_tracep); + } + mtx_unlock(&ktrace_mtx); +#endif + + /* + * set priority of child to be that of parent + * XXXKSE hey! copying the estcpu seems dodgy.. should split it.. + */ + mtx_lock_spin(&sched_lock); + p2->p_ksegrp.kg_estcpu = p1->p_ksegrp.kg_estcpu; + mtx_unlock_spin(&sched_lock); + + /* + * This begins the section where we must prevent the parent + * from being swapped. + */ + _PHOLD(p1); + PROC_UNLOCK(p1); + + /* + * 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); + PROC_UNLOCK(p2); + sx_xunlock(&proctree_lock); + + /* + * XXXKSE: In KSE, there would be a race here if one thread was + * dieing due to a signal (or calling exit1() for that matter) while + * another thread was calling fork1(). Not sure how KSE wants to work + * around that. The problem is that up until the point above, if p1 + * gets killed, it won't find p2 in its list in order for it to be + * reparented. Alternatively, we could add a new p_flag that gets set + * before we reparent all the children that we check above and just + * use init as our parent if that if that flag is set. (Either that + * or abort the fork if the flag is set since our parent died trying + * to fork us (which is evil)). + */ + + KASSERT(newprocsig == NULL, ("unused newprocsig")); + if (newsigacts != NULL) + FREE(newsigacts, M_SUBPROC); + /* + * Finish creating the child process. It will return via a different + * execution path later. (ie: directly into user mode) + */ + vm_forkproc(td, p2, td2, flags); + + if (flags == (RFFDG | RFPROC)) { + cnt.v_forks++; + cnt.v_forkpages += p2->p_vmspace->vm_dsize + + p2->p_vmspace->vm_ssize; + } else if (flags == (RFFDG | RFPROC | RFPPWAIT | RFMEM)) { + cnt.v_vforks++; + cnt.v_vforkpages += p2->p_vmspace->vm_dsize + + p2->p_vmspace->vm_ssize; + } else if (p1 == &proc0) { + cnt.v_kthreads++; + cnt.v_kthreadpages += p2->p_vmspace->vm_dsize + + p2->p_vmspace->vm_ssize; + } else { + cnt.v_rforks++; + cnt.v_rforkpages += p2->p_vmspace->vm_dsize + + p2->p_vmspace->vm_ssize; + } + + /* + * Both processes are set up, now check if any loadable modules want + * to adjust anything. + * What if they have an error? XXX + */ + sx_slock(&fork_list_lock); + TAILQ_FOREACH(ep, &fork_list, next) { + (*ep->function)(p1, p2, flags); + } + sx_sunlock(&fork_list_lock); + + /* + * If RFSTOPPED not requested, make child runnable and add to + * run queue. + */ + microtime(&(p2->p_stats->p_start)); + p2->p_acflag = AFORK; + if ((flags & RFSTOPPED) == 0) { + mtx_lock_spin(&sched_lock); + p2->p_stat = SRUN; + setrunqueue(td2); + mtx_unlock_spin(&sched_lock); + } + + /* + * Now can be swapped. + */ + PROC_LOCK(p1); + _PRELE(p1); + + /* + * tell any interested parties about the new process + */ + KNOTE(&p1->p_klist, NOTE_FORK | p2->p_pid); + PROC_UNLOCK(p1); + + /* + * 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). + */ + PROC_LOCK(p2); + while (p2->p_flag & P_PPWAIT) + msleep(p1, &p2->p_mtx, PWAIT, "ppwait", 0); + PROC_UNLOCK(p2); + + /* + * 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; + sx_xlock(&fork_list_lock); + TAILQ_INSERT_TAIL(&fork_list, ep, next); + sx_xunlock(&fork_list_lock); + 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; + + sx_xlock(&fork_list_lock); + TAILQ_FOREACH(ep, &fork_list, next) { + if (ep->function == function) { + TAILQ_REMOVE(&fork_list, ep, next); + sx_xunlock(&fork_list_lock); + free(ep, M_ATFORK); + return(1); + } + } + sx_xunlock(&fork_list_lock); + return (0); +} + +/* + * Handle the return of a child process from fork1(). This function + * is called from the MD fork_trampoline() entry point. + */ +void +fork_exit(callout, arg, frame) + void (*callout)(void *, struct trapframe *); + void *arg; + struct trapframe *frame; +{ + struct thread *td = curthread; + struct proc *p = td->td_proc; + + td->td_kse->ke_oncpu = PCPU_GET(cpuid); + /* + * Finish setting up thread glue. We need to initialize + * the thread into a td_critnest=1 state. Some platforms + * may have already partially or fully initialized td_critnest + * and/or td_md.md_savecrit (when applciable). + * + * see <arch>/<arch>/critical.c + */ + sched_lock.mtx_lock = (uintptr_t)td; + sched_lock.mtx_recurse = 0; + cpu_critical_fork_exit(); + CTR3(KTR_PROC, "fork_exit: new proc %p (pid %d, %s)", p, p->p_pid, + p->p_comm); + if (PCPU_GET(switchtime.sec) == 0) + binuptime(PCPU_PTR(switchtime)); + PCPU_SET(switchticks, ticks); + mtx_unlock_spin(&sched_lock); + + /* + * cpu_set_fork_handler intercepts this function call to + * have this call a non-return function to stay in kernel mode. + * initproc has its own fork handler, but it does return. + */ + KASSERT(callout != NULL, ("NULL callout in fork_exit")); + callout(arg, frame); + + /* + * Check if a kernel thread misbehaved and returned from its main + * function. + */ + PROC_LOCK(p); + if (p->p_flag & P_KTHREAD) { + PROC_UNLOCK(p); + mtx_lock(&Giant); + printf("Kernel thread \"%s\" (pid %d) exited prematurely.\n", + p->p_comm, p->p_pid); + kthread_exit(0); + } + PROC_UNLOCK(p); + mtx_assert(&Giant, MA_NOTOWNED); +} + +/* + * Simplified back end of syscall(), used when returning from fork() + * directly into user mode. Giant is not held on entry, and must not + * be held on return. This function is passed in to fork_exit() as the + * first parameter and is called when returning to a new userland process. + */ +void +fork_return(td, frame) + struct thread *td; + struct trapframe *frame; +{ + + userret(td, frame, 0); +#ifdef KTRACE + if (KTRPOINT(td, KTR_SYSRET)) + ktrsysret(SYS_fork, 0, 0); +#endif + mtx_assert(&Giant, MA_NOTOWNED); +} |
