/* * 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 #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 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; 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"); #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; 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); } /* * 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_ucred->cr_ruid; if ((nprocs >= maxproc - 10 && uid != 0) || nprocs >= maxproc) { 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++; /* * Increment the count of procs running with this uid. Don't allow * a nonprivileged user to exceed their current limit. */ ok = chgproccnt(p1->p_ucred->cr_ruidinfo, 1, (uid != 0) ? p1->p_rlimit[RLIMIT_NPROC].rlim_cur : 0); if (!ok) { /* * Back out the process count */ nprocs--; tsleep(&forksleep, PUSER, "fork", hz / 2); return (EAGAIN); } /* Allocate new proc. */ newproc = uma_zalloc(proc_zone, M_WAITOK); /* * 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 = NULL; newproc->p_leader = newproc; } newproc->p_vmspace = NULL; /* * 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. */ sx_xlock(&allproc_lock); 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); /* * 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)); 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 PROC_UNLOCK(p1); /* * 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); mtx_init(&p2->p_mtx, "process lock", MTX_DEF); PROC_LOCK(p2); /* 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); PROC_LOCK(p1); p2->p_ucred = crhold(p1->p_ucred); td2->td_ucred = crhold(p2->p_ucred); /* XXXKSE */ 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_uarea->u_sigacts) { struct sigacts *newsigacts; PROC_UNLOCK(p1); PROC_UNLOCK(p2); /* Create the shared sigacts structure */ MALLOC(newsigacts, struct sigacts *, sizeof(struct sigacts), M_SUBPROC, M_WAITOK); PROC_LOCK(p2); PROC_LOCK(p1); /* * 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; *p2->p_sigacts = p1->p_uarea->u_sigacts; } } else { PROC_UNLOCK(p1); PROC_UNLOCK(p2); MALLOC(p2->p_procsig, struct procsig *, sizeof(struct procsig), M_SUBPROC, M_WAITOK); PROC_LOCK(p2); PROC_LOCK(p1); 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; PROC_UNLOCK(p1); PROC_UNLOCK(p2); if (p2->p_textvp) VREF(p2->p_textvp); 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); PROC_LOCK(p2); p2->p_fd = fd; /* * 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.) */ PROC_LOCK(p1); 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. 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); PROC_UNLOCK(p1); PROC_UNLOCK(p2); /* * 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; sx_xlock(&proctree_lock); PROC_LOCK(p2); p2->p_pptr = pptr; PROC_UNLOCK(p2); LIST_INSERT_HEAD(&pptr->p_children, p2, p_sibling); sx_xunlock(&proctree_lock); PROC_LOCK(p2); 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 */ PROC_LOCK(p1); #ifdef KTRACE /* * Copy traceflag and tracefile if enabled. If not inherited, * these were zeroed above but we still could have a trace race * so make sure p2's p_tracep is NULL. */ if ((p1->p_traceflag & KTRFAC_INHERIT) && p2->p_tracep == NULL) { p2->p_traceflag = p1->p_traceflag; if ((p2->p_tracep = p1->p_tracep) != NULL) { PROC_UNLOCK(p1); PROC_UNLOCK(p2); VREF(p2->p_tracep); PROC_LOCK(p2); PROC_LOCK(p1); } } #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); 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 */ 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 //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); #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->td_proc, KTR_SYSRET)) { ktrsysret(td->td_proc->p_tracep, SYS_fork, 0, 0); } #endif mtx_assert(&Giant, MA_NOTOWNED); }