/* * 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. * 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 __FBSDID("$FreeBSD$"); #include "opt_ktrace.h" #include "opt_mac.h" #include #include #include #include #include #include #include #include #include #include #include #include #include #include #include #include #include #include #include #include #include #include #include #include #include #include #include #include #include #include #include #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; { struct proc *p2; int error; /* 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; error = sysctl_wire_old_buffer(req, sizeof(int)); if (error != 0) return(error); 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; int flags; int pages; struct proc **procp; { struct proc *p1, *p2, *pptr; uid_t uid; struct proc *newproc; int ok, trypid; static int curfail, pidchecked = 0; static struct timeval lastfail; struct filedesc *fd; struct filedesc_to_leader *fdtol; struct thread *td2; struct ksegrp *kg2; struct sigacts *newsigacts; int error; /* Can't copy and clear. */ if ((flags & (RFFDG|RFCFDG)) == (RFFDG|RFCFDG)) return (EINVAL); p1 = td->td_proc; /* * 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); } *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_HADTHREADS) { /* * 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); 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 knlist_init(&newproc->p_klist, &newproc->p_mtx); /* We have to lock the process tree while we look for a pid. */ sx_slock(&proctree_lock); /* * 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 && suser_cred(td->td_ucred, SUSER_RUID) != 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) ? lim_cur(p1, RLIMIT_NPROC) : 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 != NULL && (p2->p_pgrp->pg_id == trypid || (p2->p_session != NULL && 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 != NULL) { if (p2->p_pgrp->pg_id > trypid && pidchecked > p2->p_pgrp->pg_id) pidchecked = p2->p_pgrp->pg_id; if (p2->p_session != NULL && 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; } } sx_sunlock(&proctree_lock); /* * 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); /* 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(&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 td2->td_sigstk = td->td_sigstk; /* * 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(td, td2); 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; p2->p_textvp = p1->p_textvp; p2->p_fd = fd; p2->p_fdtol = fdtol; /* * p_limit is copy-on-write. Bump its refcount. */ p2->p_limit = lim_hold(p1->p_limit); PROC_UNLOCK(p1); PROC_UNLOCK(p2); /* Bump references to the text vnode (for procfs) */ if (p2->p_textvp) vref(p2->p_textvp); /* * Set up 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; td2->td_pflags |= td->td_pflags & TDP_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; p2->p_pgrp = p1->p_pgrp; LIST_INSERT_AFTER(p1, p2, p_pglist); PGRP_UNLOCK(p1->p_pgrp); LIST_INIT(&p2->p_children); callout_init(&p2->p_itcallout, CALLOUT_MPSAFE); #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)) { atomic_add_int(&cnt.v_forks, 1); atomic_add_int(&cnt.v_forkpages, p2->p_vmspace->vm_dsize + p2->p_vmspace->vm_ssize); } else if (flags == (RFFDG | RFPROC | RFPPWAIT | RFMEM)) { atomic_add_int(&cnt.v_vforks, 1); atomic_add_int(&cnt.v_vforkpages, p2->p_vmspace->vm_dsize + p2->p_vmspace->vm_ssize); } else if (p1 == &proc0) { atomic_add_int(&cnt.v_kthreads, 1); atomic_add_int(&cnt.v_kthreadpages, p2->p_vmspace->vm_dsize + p2->p_vmspace->vm_ssize); } else { atomic_add_int(&cnt.v_rforks, 1); atomic_add_int(&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); /* * Set the child start time and mark the process as being complete. */ microuptime(&p2->p_stats->p_start); mtx_lock_spin(&sched_lock); p2->p_state = PRS_NORMAL; /* * If RFSTOPPED not requested, make child runnable and add to * run queue. */ if ((flags & RFSTOPPED) == 0) { TD_SET_CAN_RUN(td2); setrunqueue(td2, SRQ_BORING); } mtx_unlock_spin(&sched_lock); /* * Now can be swapped. */ PROC_LOCK(p1); _PRELE(p1); /* * Tell any interested parties about the new process. */ KNOTE_LOCKED(&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_HADTHREADS) { PROC_LOCK(p1); thread_single_end(); PROC_UNLOCK(p1); } /* * Return child proc pointer to parent. */ *procp = p2; return (0); fail: sx_sunlock(&proctree_lock); 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); #ifdef MAC mac_destroy_proc(newproc); #endif uma_zfree(proc_zone, newproc); if (p1->p_flag & P_HADTHREADS) { PROC_LOCK(p1); thread_single_end(); PROC_UNLOCK(p1); } tsleep(&forksleep, PUSER, "fork", hz / 2); 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 proc *p; struct thread *td; /* * Finish setting up thread glue so that it begins execution in a * non-nested critical section with sched_lock held but not recursed. */ td = curthread; p = td->td_proc; td->td_oncpu = PCPU_GET(cpuid); KASSERT(p->p_state == PRS_NORMAL, ("executing process is still new")); sched_lock.mtx_lock = (uintptr_t)td; mtx_assert(&sched_lock, MA_OWNED | MA_NOTRECURSED); cpu_critical_fork_exit(); CTR4(KTR_PROC, "fork_exit: new thread %p (kse %p, pid %d, %s)", td, td->td_sched, p->p_pid, p->p_comm); /* * Processes normally resume in mi_switch() after being * cpu_switch()'ed to, but when children start up they arrive here * instead, so we must do much the same things as mi_switch() would. */ if ((td = PCPU_GET(deadthread))) { PCPU_SET(deadthread, NULL); thread_stash(td); } td = curthread; 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); 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); }