/* $NetBSD: kern_fork.c,v 1.126 2006/07/17 15:29:06 ad Exp $ */ /*- * Copyright (c) 1999, 2001, 2004 The NetBSD Foundation, Inc. * All rights reserved. * * This code is derived from software contributed to The NetBSD Foundation * by Jason R. Thorpe of the Numerical Aerospace Simulation Facility, * NASA Ames Research Center. * This code is derived from software contributed to The NetBSD Foundation * by Charles M. Hannum. * * 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 NetBSD * Foundation, Inc. and its contributors. * 4. Neither the name of The NetBSD Foundation 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 NETBSD FOUNDATION, INC. 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 FOUNDATION 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. */ /* * 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. 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 8.8 (Berkeley) 2/14/95 */ #include __KERNEL_RCSID(0, "$NetBSD: kern_fork.c,v 1.126 2006/07/17 15:29:06 ad Exp $"); #include "opt_ktrace.h" #include "opt_systrace.h" #include "opt_multiprocessor.h" #include #include #include #include #include #include #include #include #include #include #include #include #include #include #include #include #include #include #include #include #include #include int nprocs = 1; /* process 0 */ /* * Number of ticks to sleep if fork() would fail due to process hitting * limits. Exported in miliseconds to userland via sysctl. */ int forkfsleep = 0; /*ARGSUSED*/ int sys_fork(struct lwp *l, void *v, register_t *retval) { return (fork1(l, 0, SIGCHLD, NULL, 0, NULL, NULL, retval, NULL)); } /* * vfork(2) system call compatible with 4.4BSD (i.e. BSD with Mach VM). * Address space is not shared, but parent is blocked until child exit. */ /*ARGSUSED*/ int sys_vfork(struct lwp *l, void *v, register_t *retval) { return (fork1(l, FORK_PPWAIT, SIGCHLD, NULL, 0, NULL, NULL, retval, NULL)); } /* * New vfork(2) system call for NetBSD, which implements original 3BSD vfork(2) * semantics. Address space is shared, and parent is blocked until child exit. */ /*ARGSUSED*/ int sys___vfork14(struct lwp *l, void *v, register_t *retval) { return (fork1(l, FORK_PPWAIT|FORK_SHAREVM, SIGCHLD, NULL, 0, NULL, NULL, retval, NULL)); } /* * Linux-compatible __clone(2) system call. */ int sys___clone(struct lwp *l, void *v, register_t *retval) { struct sys___clone_args /* { syscallarg(int) flags; syscallarg(void *) stack; } */ *uap = v; int flags, sig; /* * We don't support the CLONE_PID or CLONE_PTRACE flags. */ if (SCARG(uap, flags) & (CLONE_PID|CLONE_PTRACE)) return (EINVAL); /* * Linux enforces CLONE_VM with CLONE_SIGHAND, do same. */ if (SCARG(uap, flags) & CLONE_SIGHAND && (SCARG(uap, flags) & CLONE_VM) == 0) return (EINVAL); flags = 0; if (SCARG(uap, flags) & CLONE_VM) flags |= FORK_SHAREVM; if (SCARG(uap, flags) & CLONE_FS) flags |= FORK_SHARECWD; if (SCARG(uap, flags) & CLONE_FILES) flags |= FORK_SHAREFILES; if (SCARG(uap, flags) & CLONE_SIGHAND) flags |= FORK_SHARESIGS; if (SCARG(uap, flags) & CLONE_VFORK) flags |= FORK_PPWAIT; sig = SCARG(uap, flags) & CLONE_CSIGNAL; if (sig < 0 || sig >= _NSIG) return (EINVAL); /* * Note that the Linux API does not provide a portable way of * specifying the stack area; the caller must know if the stack * grows up or down. So, we pass a stack size of 0, so that the * code that makes this adjustment is a noop. */ return (fork1(l, flags, sig, SCARG(uap, stack), 0, NULL, NULL, retval, NULL)); } /* print the 'table full' message once per 10 seconds */ struct timeval fork_tfmrate = { 10, 0 }; int fork1(struct lwp *l1, int flags, int exitsig, void *stack, size_t stacksize, void (*func)(void *), void *arg, register_t *retval, struct proc **rnewprocp) { struct proc *p1, *p2, *parent; uid_t uid; struct lwp *l2; int count, s; vaddr_t uaddr; boolean_t inmem; /* * 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 few processes; don't let root * exceed the limit. The variable nprocs is the current number of * processes, maxproc is the limit. */ p1 = l1->l_proc; uid = kauth_cred_getuid(p1->p_cred); if (__predict_false((nprocs >= maxproc - 5 && uid != 0) || nprocs >= maxproc)) { static struct timeval lasttfm; if (ratecheck(&lasttfm, &fork_tfmrate)) tablefull("proc", "increase kern.maxproc or NPROC"); if (forkfsleep) (void)tsleep(&nprocs, PUSER, "forkmx", forkfsleep); return (EAGAIN); } nprocs++; /* * 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 (__predict_false(uid != 0 && count > p1->p_rlimit[RLIMIT_NPROC].rlim_cur)) { (void)chgproccnt(uid, -1); nprocs--; if (forkfsleep) (void)tsleep(&nprocs, PUSER, "forkulim", forkfsleep); return (EAGAIN); } /* * Allocate virtual address space for the U-area now, while it * is still easy to abort the fork operation if we're out of * kernel virtual address space. The actual U-area pages will * be allocated and wired in uvm_fork() if needed. */ inmem = uvm_uarea_alloc(&uaddr); if (__predict_false(uaddr == 0)) { (void)chgproccnt(uid, -1); nprocs--; return (ENOMEM); } /* * We are now committed to the fork. From here on, we may * block on resources, but resource allocation may NOT fail. */ /* Allocate new proc. */ p2 = proc_alloc(); /* * 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. */ memset(&p2->p_startzero, 0, (unsigned) ((caddr_t)&p2->p_endzero - (caddr_t)&p2->p_startzero)); memcpy(&p2->p_startcopy, &p1->p_startcopy, (unsigned) ((caddr_t)&p2->p_endcopy - (caddr_t)&p2->p_startcopy)); simple_lock_init(&p2->p_sigctx.ps_silock); CIRCLEQ_INIT(&p2->p_sigctx.ps_siginfo); simple_lock_init(&p2->p_lock); LIST_INIT(&p2->p_lwps); /* * Duplicate sub-structures as needed. * Increase reference counts on shared objects. * The p_stats and p_sigacts substructs are set in uvm_fork(). * Inherit flags we want to keep. The flags related to SIGCHLD * handling are important in order to keep a consistent behaviour * for the child after the fork. */ p2->p_flag = p1->p_flag & (P_SUGID | P_STOPFORK | P_STOPEXEC | P_NOCLDSTOP | P_NOCLDWAIT | P_CLDSIGIGN); p2->p_emul = p1->p_emul; p2->p_execsw = p1->p_execsw; if (p1->p_flag & P_PROFIL) startprofclock(p2); kauth_cred_hold(p1->p_cred); p2->p_cred = p1->p_cred; LIST_INIT(&p2->p_raslist); #if defined(__HAVE_RAS) ras_fork(p1, p2); #endif /* bump references to the text vnode (for procfs) */ p2->p_textvp = p1->p_textvp; if (p2->p_textvp) VREF(p2->p_textvp); if (flags & FORK_SHAREFILES) fdshare(p1, p2); else if (flags & FORK_CLEANFILES) p2->p_fd = fdinit(p1); else p2->p_fd = fdcopy(p1); if (flags & FORK_SHARECWD) cwdshare(p1, p2); else p2->p_cwdi = cwdinit(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 { simple_lock(&p1->p_limit->p_slock); p1->p_limit->p_refcnt++; simple_unlock(&p1->p_limit->p_slock); p2->p_limit = p1->p_limit; } if (p1->p_session->s_ttyvp != NULL && p1->p_flag & P_CONTROLT) p2->p_flag |= P_CONTROLT; if (flags & FORK_PPWAIT) p2->p_flag |= P_PPWAIT; parent = (flags & FORK_NOWAIT) ? initproc : p1; p2->p_pptr = parent; LIST_INIT(&p2->p_children); s = proclist_lock_write(); LIST_INSERT_AFTER(p1, p2, p_pglist); LIST_INSERT_HEAD(&parent->p_children, p2, p_sibling); proclist_unlock_write(s); #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) ktradref(p2); } #endif scheduler_fork_hook(p1, p2); /* * Create signal actions for the child process. */ sigactsinit(p2, p1, flags & FORK_SHARESIGS); /* * p_stats. * Copy parts of p_stats, and zero out the rest. */ p2->p_stats = pstatscopy(p1->p_stats); /* * If emulation has process fork hook, call it now. */ if (p2->p_emul->e_proc_fork) (*p2->p_emul->e_proc_fork)(p2, p1, flags); /* * ...and finally, any other random fork hooks that subsystems * might have registered. */ doforkhooks(p2, p1); /* * This begins the section where we must prevent the parent * from being swapped. */ PHOLD(l1); uvm_proc_fork(p1, p2, (flags & FORK_SHAREVM) ? TRUE : FALSE); /* * Finish creating the child process. * It will return through a different path later. */ newlwp(l1, p2, uaddr, inmem, 0, stack, stacksize, (func != NULL) ? func : child_return, arg, &l2); /* Now safe for scheduler to see child process */ s = proclist_lock_write(); p2->p_exitsig = exitsig; /* signal for parent on exit */ LIST_INSERT_HEAD(&allproc, p2, p_list); proclist_unlock_write(s); #ifdef SYSTRACE /* Tell systrace what's happening. */ if (ISSET(p1->p_flag, P_SYSTRACE)) systrace_sys_fork(p1, p2); #endif #ifdef __HAVE_SYSCALL_INTERN (*p2->p_emul->e_syscall_intern)(p2); #endif /* * Make child runnable, set start time, and add to run queue * except if the parent requested the child to start in SSTOP state. */ SCHED_LOCK(s); getmicrotime(&p2->p_stats->p_start); p2->p_acflag = AFORK; if (p1->p_flag & P_STOPFORK) { p2->p_nrlwps = 0; p1->p_nstopchild++; p2->p_stat = SSTOP; l2->l_stat = LSSTOP; } else { p2->p_nrlwps = 1; p2->p_stat = SACTIVE; l2->l_stat = LSRUN; setrunqueue(l2); } SCHED_UNLOCK(s); /* * Now can be swapped. */ PRELE(l1); /* * Notify any interested parties about the new process. */ KNOTE(&p1->p_klist, NOTE_FORK | p2->p_pid); /* * Update stats now that we know the fork was successful. */ uvmexp.forks++; if (flags & FORK_PPWAIT) uvmexp.forks_ppwait++; if (flags & FORK_SHAREVM) uvmexp.forks_sharevm++; /* * Pass a pointer to the new process to the caller. */ if (rnewprocp != NULL) *rnewprocp = p2; #ifdef KTRACE if (KTRPOINT(p2, KTR_EMUL)) p2->p_traceflag |= KTRFAC_TRC_EMUL; #endif /* * 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 (flags & FORK_PPWAIT) while (p2->p_flag & P_PPWAIT) tsleep(p1, PWAIT, "ppwait", 0); /* * Return child pid to parent process, * marking us as parent via retval[1]. */ if (retval != NULL) { retval[0] = p2->p_pid; retval[1] = 0; } return (0); } #if defined(MULTIPROCESSOR) /* * XXX This is a slight hack to get newly-formed processes to * XXX acquire the kernel lock as soon as they run. */ void proc_trampoline_mp(void) { struct lwp *l; l = curlwp; SCHED_ASSERT_UNLOCKED(); KERNEL_PROC_LOCK(l); } #endif