diff options
Diffstat (limited to 'sys/kern/kern_fork.c')
| -rw-r--r-- | sys/kern/kern_fork.c | 833 |
1 files changed, 833 insertions, 0 deletions
diff --git a/sys/kern/kern_fork.c b/sys/kern/kern_fork.c new file mode 100644 index 0000000..226a42c --- /dev/null +++ b/sys/kern/kern_fork.c @@ -0,0 +1,833 @@ +/* + * 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/cdefs.h> +__FBSDID("$FreeBSD$"); + +#include "opt_ktrace.h" +#include "opt_mac.h" + +#include <sys/param.h> +#include <sys/systm.h> +#include <sys/sysproto.h> +#include <sys/eventhandler.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/pioctl.h> +#include <sys/resourcevar.h> +#include <sys/sched.h> +#include <sys/syscall.h> +#include <sys/vnode.h> +#include <sys/acct.h> +#include <sys/mac.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> + +#ifndef _SYS_SYSPROTO_H_ +struct fork_args { + int dummy; +}; +#endif + +static int forksleep; /* Place for fork1() to sleep on. */ + +/* + * MPSAFE + */ +/* ARGSUSED */ +int +fork(td, uap) + struct thread *td; + struct fork_args *uap; +{ + int error; + struct proc *p2; + + error = fork1(td, RFFDG | RFPROC, 0, &p2); + if (error == 0) { + td->td_retval[0] = p2->p_pid; + td->td_retval[1] = 0; + } + return error; +} + +/* + * MPSAFE + */ +/* ARGSUSED */ +int +vfork(td, uap) + struct thread *td; + struct vfork_args *uap; +{ + int error; + struct proc *p2; + + error = fork1(td, RFFDG | RFPROC | RFPPWAIT | RFMEM, 0, &p2); + if (error == 0) { + td->td_retval[0] = p2->p_pid; + td->td_retval[1] = 0; + } + 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); + error = fork1(td, uap->flags, 0, &p2); + if (error == 0) { + td->td_retval[0] = p2 ? p2->p_pid : 0; + td->td_retval[1] = 0; + } + 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; + + sysctl_wire_old_buffer(req, sizeof(int)); + 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"); + +int +fork1(td, flags, pages, procp) + struct thread *td; /* parent proc */ + int flags; + int pages; + struct proc **procp; /* child proc */ +{ + struct proc *p2, *pptr; + uid_t uid; + struct proc *newproc; + int trypid; + int ok; + static int curfail, pidchecked = 0; + static struct timeval lastfail; + struct filedesc *fd; + struct filedesc_to_leader *fdtol; + struct proc *p1 = td->td_proc; + struct thread *td2; + struct kse *ke2; + struct ksegrp *kg2; + struct sigacts *newsigacts; + int error; + + /* Can't copy and clear */ + if ((flags & (RFFDG|RFCFDG)) == (RFFDG|RFCFDG)) + return (EINVAL); + + mtx_lock(&Giant); + /* + * 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->td_proc->p_fd); + fdfree(td); + p1->p_fd = fdtmp; + } + + /* + * 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->td_proc->p_fd); + FILEDESC_UNLOCK(p1->p_fd); + fdfree(td); + p1->p_fd = newfd; + } else + FILEDESC_UNLOCK(p1->p_fd); + } + mtx_unlock(&Giant); + *procp = NULL; + return (0); + } + + /* + * Note 1:1 allows for forking with one thread coming out on the + * other side with the expectation that the process is about to + * exec. + */ + if (p1->p_flag & P_SA) { + /* + * Idle the other threads for a second. + * Since the user space is copied, it must remain stable. + * In addition, all threads (from the user perspective) + * need to either be suspended or in the kernel, + * where they will try restart in the parent and will + * be aborted in the child. + */ + PROC_LOCK(p1); + if (thread_single(SINGLE_NO_EXIT)) { + /* Abort.. someone else is single threading before us */ + PROC_UNLOCK(p1); + mtx_unlock(&Giant); + return (ERESTART); + } + PROC_UNLOCK(p1); + /* + * All other activity in this process + * is now suspended at the user boundary, + * (or other safe places if we think of any). + */ + } + + /* Allocate new proc. */ + newproc = uma_zalloc(proc_zone, M_WAITOK); +#ifdef MAC + mac_init_proc(newproc); +#endif + + /* + * 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 ten processes; 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) { + error = EAGAIN; + goto fail; + } + + /* + * 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) { + error = EAGAIN; + goto fail; + } + + /* + * 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_state = PRS_NEW; /* 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) + newsigacts = NULL; + else + newsigacts = sigacts_alloc(); + + /* + * Copy filedesc. + */ + if (flags & RFCFDG) { + fd = fdinit(td->td_proc->p_fd); + fdtol = NULL; + } else if (flags & RFFDG) { + FILEDESC_LOCK(p1->p_fd); + fd = fdcopy(td->td_proc->p_fd); + FILEDESC_UNLOCK(p1->p_fd); + fdtol = NULL; + } else { + fd = fdshare(p1->p_fd); + if (p1->p_fdtol == NULL) + p1->p_fdtol = + filedesc_to_leader_alloc(NULL, + NULL, + p1->p_leader); + if ((flags & RFTHREAD) != 0) { + /* + * Shared file descriptor table and + * shared process leaders. + */ + fdtol = p1->p_fdtol; + FILEDESC_LOCK(p1->p_fd); + fdtol->fdl_refcount++; + FILEDESC_UNLOCK(p1->p_fd); + } else { + /* + * Shared file descriptor table, and + * different process leaders + */ + fdtol = filedesc_to_leader_alloc(p1->p_fdtol, + p1->p_fd, + 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. + */ + td2 = FIRST_THREAD_IN_PROC(p2); + kg2 = FIRST_KSEGRP_IN_PROC(p2); + ke2 = FIRST_KSE_IN_KSEGRP(kg2); + + /* Allocate and switch to an alternate kstack if specified */ + if (pages != 0) + vm_thread_new_altkstack(td2, pages); + + PROC_LOCK(p2); + PROC_LOCK(p1); + +#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)); + + bcopy(&p1->p_startcopy, &p2->p_startcopy, + (unsigned) RANGEOF(struct proc, p_startcopy, p_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 + + /* Set up the thread as an active thread (as if runnable). */ + ke2->ke_state = KES_THREAD; + ke2->ke_thread = td2; + td2->td_kse = ke2; + + /* + * Duplicate sub-structures as needed. + * Increase reference counts on shared objects. + * The p_stats substruct is set in vm_forkproc. + */ + p2->p_flag = 0; + if (p1->p_flag & P_PROFIL) + startprofclock(p2); + mtx_lock_spin(&sched_lock); + p2->p_sflag = PS_INMEM; + /* + * Allow the scheduler to adjust the priority of the child and + * parent while we hold the sched_lock. + */ + sched_fork(p1, p2); + + mtx_unlock_spin(&sched_lock); + p2->p_ucred = crhold(td->td_ucred); + td2->td_ucred = crhold(p2->p_ucred); /* XXXKSE */ + + pargs_hold(p2->p_args); + + if (flags & RFSIGSHARE) { + p2->p_sigacts = sigacts_hold(p1->p_sigacts); + } else { + sigacts_copy(newsigacts, p1->p_sigacts); + p2->p_sigacts = newsigacts; + } + 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; + p2->p_fdtol = fdtol; + PROC_UNLOCK(p1); + PROC_UNLOCK(p2); + + /* + * p_limit is copy-on-write, bump refcnt, + */ + p2->p_limit = p1->p_limit; + p2->p_limit->p_refcnt++; + + /* + * Setup linkage for kernel based threading + */ + if((flags & RFTHREAD) != 0) { + mtx_lock(&ppeers_lock); + p2->p_peers = p1->p_peers; + p1->p_peers = p2; + p2->p_leader = p1->p_leader; + mtx_unlock(&ppeers_lock); + PROC_LOCK(p1->p_leader); + if ((p1->p_leader->p_flag & P_WEXIT) != 0) { + PROC_UNLOCK(p1->p_leader); + /* + * The task leader is exiting, so process p1 is + * going to be killed shortly. Since p1 obviously + * isn't dead yet, we know that the leader is either + * sending SIGKILL's to all the processes in this + * task or is sleeping waiting for all the peers to + * exit. We let p1 complete the fork, but we need + * to go ahead and kill the new process p2 since + * the task leader may not get a chance to send + * SIGKILL to it. We leave it on the list so that + * the task leader will wait for this new process + * to commit suicide. + */ + PROC_LOCK(p2); + psignal(p2, SIGKILL); + PROC_UNLOCK(p2); + } else + PROC_UNLOCK(p1->p_leader); + } else { + p2->p_peers = NULL; + p2->p_leader = p2; + } + + sx_xlock(&proctree_lock); + PGRP_LOCK(p1->p_pgrp); + PROC_LOCK(p2); + PROC_LOCK(p1); + + /* + * Preserve some more flags in subprocess. P_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); + + callout_init(&p2->p_itcallout, 1); + +#ifdef KTRACE + /* + * Copy traceflag and tracefile if enabled. + */ + mtx_lock(&ktrace_mtx); + KASSERT(p2->p_tracevp == NULL, ("new process has a ktrace vnode")); + if (p1->p_traceflag & KTRFAC_INHERIT) { + p2->p_traceflag = p1->p_traceflag; + if ((p2->p_tracevp = p1->p_tracevp) != NULL) { + VREF(p2->p_tracevp); + KASSERT(p1->p_tracecred != NULL, + ("ktrace vnode with no cred")); + p2->p_tracecred = crhold(p1->p_tracecred); + } + } + mtx_unlock(&ktrace_mtx); +#endif + + /* + * If PF_FORK is set, the child process inherits the + * procfs ioctl flags from its parent. + */ + if (p1->p_pfsflags & PF_FORK) { + p2->p_stops = p1->p_stops; + p2->p_pfsflags = p1->p_pfsflags; + } + + /* + * 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); + sx_xunlock(&proctree_lock); + + /* Inform accounting that we have forked. */ + p2->p_acflag = AFORK; + PROC_UNLOCK(p2); + + /* + * 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 + */ + EVENTHANDLER_INVOKE(process_fork, p1, p2, flags); + + /* + * If RFSTOPPED not requested, make child runnable and add to + * run queue. + */ + microuptime(&p2->p_stats->p_start); + if ((flags & RFSTOPPED) == 0) { + mtx_lock_spin(&sched_lock); + p2->p_state = PRS_NORMAL; + TD_SET_CAN_RUN(td2); + 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); + + /* + * If other threads are waiting, let them continue now + */ + if (p1->p_flag & P_SA) { + PROC_LOCK(p1); + thread_single_end(); + PROC_UNLOCK(p1); + } + + /* + * Return child proc pointer to parent. + */ + mtx_unlock(&Giant); + *procp = p2; + return (0); +fail: + if (ppsratecheck(&lastfail, &curfail, 1)) + printf("maxproc limit exceeded by uid %i, please see tuning(7) and login.conf(5).\n", + uid); + sx_xunlock(&allproc_lock); + uma_zfree(proc_zone, newproc); + if (p1->p_flag & P_SA) { + PROC_LOCK(p1); + thread_single_end(); + PROC_UNLOCK(p1); + } + tsleep(&forksleep, PUSER, "fork", hz / 2); + mtx_unlock(&Giant); + return (error); +} + +/* + * 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; + struct proc *p; + + if ((td = PCPU_GET(deadthread))) { + PCPU_SET(deadthread, NULL); + thread_stash(td); + } + td = curthread; + p = td->td_proc; + td->td_oncpu = PCPU_GET(cpuid); + p->p_state = PRS_NORMAL; + /* + * 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 thread %p (pid %d, %s)", td, 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); +#ifdef DIAGNOSTIC + cred_free_thread(td); +#endif + 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); +} |
