diff options
Diffstat (limited to 'sys/kern/kern_fork.c')
-rw-r--r-- | sys/kern/kern_fork.c | 1052 |
1 files changed, 1052 insertions, 0 deletions
diff --git a/sys/kern/kern_fork.c b/sys/kern/kern_fork.c new file mode 100644 index 0000000..9cd1da9 --- /dev/null +++ b/sys/kern/kern_fork.c @@ -0,0 +1,1052 @@ +/*- + * 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 <sys/cdefs.h> +__FBSDID("$FreeBSD$"); + +#include "opt_kdtrace.h" +#include "opt_ktrace.h" +#include "opt_kstack_pages.h" +#include "opt_procdesc.h" + +#include <sys/param.h> +#include <sys/systm.h> +#include <sys/sysproto.h> +#include <sys/eventhandler.h> +#include <sys/fcntl.h> +#include <sys/filedesc.h> +#include <sys/jail.h> +#include <sys/kernel.h> +#include <sys/kthread.h> +#include <sys/sysctl.h> +#include <sys/lock.h> +#include <sys/malloc.h> +#include <sys/mutex.h> +#include <sys/priv.h> +#include <sys/proc.h> +#include <sys/procdesc.h> +#include <sys/pioctl.h> +#include <sys/racct.h> +#include <sys/resourcevar.h> +#include <sys/sched.h> +#include <sys/syscall.h> +#include <sys/vmmeter.h> +#include <sys/vnode.h> +#include <sys/acct.h> +#include <sys/ktr.h> +#include <sys/ktrace.h> +#include <sys/unistd.h> +#include <sys/sdt.h> +#include <sys/sx.h> +#include <sys/sysent.h> +#include <sys/signalvar.h> + +#include <security/audit/audit.h> +#include <security/mac/mac_framework.h> + +#include <vm/vm.h> +#include <vm/pmap.h> +#include <vm/vm_map.h> +#include <vm/vm_extern.h> +#include <vm/uma.h> + +#ifdef KDTRACE_HOOKS +#include <sys/dtrace_bsd.h> +dtrace_fork_func_t dtrace_fasttrap_fork; +#endif + +SDT_PROVIDER_DECLARE(proc); +SDT_PROBE_DEFINE3(proc, kernel, , create, create, "struct proc *", + "struct proc *", "int"); + +#ifndef _SYS_SYSPROTO_H_ +struct fork_args { + int dummy; +}; +#endif + +/* ARGSUSED */ +int +sys_fork(struct thread *td, struct fork_args *uap) +{ + int error; + struct proc *p2; + + error = fork1(td, RFFDG | RFPROC, 0, &p2, NULL, 0); + if (error == 0) { + td->td_retval[0] = p2->p_pid; + td->td_retval[1] = 0; + } + return (error); +} + +/* ARGUSED */ +int +sys_pdfork(td, uap) + struct thread *td; + struct pdfork_args *uap; +{ +#ifdef PROCDESC + int error, fd; + struct proc *p2; + + /* + * It is necessary to return fd by reference because 0 is a valid file + * descriptor number, and the child needs to be able to distinguish + * itself from the parent using the return value. + */ + error = fork1(td, RFFDG | RFPROC | RFPROCDESC, 0, &p2, + &fd, uap->flags); + if (error == 0) { + td->td_retval[0] = p2->p_pid; + td->td_retval[1] = 0; + error = copyout(&fd, uap->fdp, sizeof(fd)); + } + return (error); +#else + return (ENOSYS); +#endif +} + +/* ARGSUSED */ +int +sys_vfork(struct thread *td, struct vfork_args *uap) +{ + int error, flags; + struct proc *p2; + + flags = RFFDG | RFPROC | RFPPWAIT | RFMEM; + error = fork1(td, flags, 0, &p2, NULL, 0); + if (error == 0) { + td->td_retval[0] = p2->p_pid; + td->td_retval[1] = 0; + } + return (error); +} + +int +sys_rfork(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); + + AUDIT_ARG_FFLAGS(uap->flags); + error = fork1(td, uap->flags, 0, &p2, NULL, 0); + 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"); + +static int +fork_findpid(int flags) +{ + struct proc *p; + int trypid; + static int pidchecked = 0; + + /* + * Requires allproc_lock in order to iterate over the list + * of processes, and proctree_lock to access p_pgrp. + */ + sx_assert(&allproc_lock, SX_LOCKED); + sx_assert(&proctree_lock, SX_LOCKED); + + /* + * 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. + */ + p = LIST_FIRST(&allproc); +again: + for (; p != NULL; p = LIST_NEXT(p, p_list)) { + while (p->p_pid == trypid || + (p->p_pgrp != NULL && + (p->p_pgrp->pg_id == trypid || + (p->p_session != NULL && + p->p_session->s_sid == trypid)))) { + trypid++; + if (trypid >= pidchecked) + goto retry; + } + if (p->p_pid > trypid && pidchecked > p->p_pid) + pidchecked = p->p_pid; + if (p->p_pgrp != NULL) { + if (p->p_pgrp->pg_id > trypid && + pidchecked > p->p_pgrp->pg_id) + pidchecked = p->p_pgrp->pg_id; + if (p->p_session != NULL && + p->p_session->s_sid > trypid && + pidchecked > p->p_session->s_sid) + pidchecked = p->p_session->s_sid; + } + } + if (!doingzomb) { + doingzomb = 1; + p = LIST_FIRST(&zombproc); + goto again; + } + } + + /* + * RFHIGHPID does not mess with the lastpid counter during boot. + */ + if (flags & RFHIGHPID) + pidchecked = 0; + else + lastpid = trypid; + + return (trypid); +} + +static int +fork_norfproc(struct thread *td, int flags) +{ + int error; + struct proc *p1; + + KASSERT((flags & RFPROC) == 0, + ("fork_norfproc called with RFPROC set")); + p1 = td->td_proc; + + if (((p1->p_flag & (P_HADTHREADS|P_SYSTEM)) == P_HADTHREADS) && + (flags & (RFCFDG | RFFDG))) { + PROC_LOCK(p1); + if (thread_single(SINGLE_BOUNDARY)) { + PROC_UNLOCK(p1); + return (ERESTART); + } + PROC_UNLOCK(p1); + } + + error = vm_forkproc(td, NULL, NULL, NULL, flags); + if (error) + goto fail; + + /* + * Close all file descriptors. + */ + if (flags & RFCFDG) { + struct filedesc *fdtmp; + fdtmp = fdinit(td->td_proc->p_fd); + fdescfree(td); + p1->p_fd = fdtmp; + } + + /* + * Unshare file descriptors (from parent). + */ + if (flags & RFFDG) + fdunshare(p1, td); + +fail: + if (((p1->p_flag & (P_HADTHREADS|P_SYSTEM)) == P_HADTHREADS) && + (flags & (RFCFDG | RFFDG))) { + PROC_LOCK(p1); + thread_single_end(); + PROC_UNLOCK(p1); + } + return (error); +} + +static void +do_fork(struct thread *td, int flags, struct proc *p2, struct thread *td2, + struct vmspace *vm2, int pdflags) +{ + struct proc *p1, *pptr; + int p2_held, trypid; + struct filedesc *fd; + struct filedesc_to_leader *fdtol; + struct sigacts *newsigacts; + + sx_assert(&proctree_lock, SX_SLOCKED); + sx_assert(&allproc_lock, SX_XLOCKED); + + p2_held = 0; + p1 = td->td_proc; + + /* + * Increment the nprocs resource before blocking can occur. There + * are hard-limits as to the number of processes that can run. + */ + nprocs++; + + trypid = fork_findpid(flags); + + sx_sunlock(&proctree_lock); + + p2->p_state = PRS_NEW; /* protect against others */ + p2->p_pid = trypid; + AUDIT_ARG_PID(p2->p_pid); + LIST_INSERT_HEAD(&allproc, p2, p_list); + LIST_INSERT_HEAD(PIDHASH(p2->p_pid), p2, p_hash); + tidhash_add(td2); + PROC_LOCK(p2); + PROC_LOCK(p1); + + sx_xunlock(&allproc_lock); + + bcopy(&p1->p_startcopy, &p2->p_startcopy, + __rangeof(struct proc, p_startcopy, p_endcopy)); + pargs_hold(p2->p_args); + PROC_UNLOCK(p1); + + bzero(&p2->p_startzero, + __rangeof(struct proc, p_startzero, p_endzero)); + + p2->p_ucred = crhold(td->td_ucred); + + /* Tell the prison that we exist. */ + prison_proc_hold(p2->p_ucred->cr_prison); + + PROC_UNLOCK(p2); + + /* + * 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(p1->p_fd); + fdtol = NULL; + } else if (flags & RFFDG) { + fd = fdcopy(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_XLOCK(p1->p_fd); + fdtol->fdl_refcount++; + FILEDESC_XUNLOCK(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. + */ + + PROC_LOCK(p2); + PROC_LOCK(p1); + + bzero(&td2->td_startzero, + __rangeof(struct thread, td_startzero, td_endzero)); + + bcopy(&td->td_startcopy, &td2->td_startcopy, + __rangeof(struct thread, td_startcopy, td_endcopy)); + + bcopy(&p2->p_comm, &td2->td_name, sizeof(td2->td_name)); + td2->td_sigstk = td->td_sigstk; + td2->td_flags = TDF_INMEM; + td2->td_lend_user_pri = PRI_MAX; + +#ifdef VIMAGE + td2->td_vnet = NULL; + td2->td_vnet_lpush = NULL; +#endif + + /* + * Allow the scheduler to initialize the child. + */ + thread_lock(td); + sched_fork(td, td2); + thread_unlock(td); + + /* + * Duplicate sub-structures as needed. + * Increase reference counts on shared objects. + */ + p2->p_flag = P_INMEM; + p2->p_swtick = ticks; + if (p1->p_flag & P_PROFIL) + startprofclock(p2); + td2->td_ucred = crhold(p2->p_ucred); + + if (flags & RFSIGSHARE) { + p2->p_sigacts = sigacts_hold(p1->p_sigacts); + } else { + sigacts_copy(newsigacts, p1->p_sigacts); + p2->p_sigacts = newsigacts; + } + + if (flags & RFTSIGZMB) + p2->p_sigparent = RFTSIGNUM(flags); + else 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. + */ + lim_fork(p1, p2); + + pstats_fork(p1->p_stats, p2->p_stats); + + 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); + kern_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); + LIST_INIT(&p2->p_orphans); + + callout_init_mtx(&p2->p_itcallout, &p2->p_mtx, 0); + + /* + * 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); + +#ifdef KTRACE + ktrprocfork(p1, p2); +#endif + + /* + * Finish creating the child process. It will return via a different + * execution path later. (ie: directly into user mode) + */ + vm_forkproc(td, p2, td2, vm2, flags); + + if (flags == (RFFDG | RFPROC)) { + PCPU_INC(cnt.v_forks); + PCPU_ADD(cnt.v_forkpages, p2->p_vmspace->vm_dsize + + p2->p_vmspace->vm_ssize); + } else if (flags == (RFFDG | RFPROC | RFPPWAIT | RFMEM)) { + PCPU_INC(cnt.v_vforks); + PCPU_ADD(cnt.v_vforkpages, p2->p_vmspace->vm_dsize + + p2->p_vmspace->vm_ssize); + } else if (p1 == &proc0) { + PCPU_INC(cnt.v_kthreads); + PCPU_ADD(cnt.v_kthreadpages, p2->p_vmspace->vm_dsize + + p2->p_vmspace->vm_ssize); + } else { + PCPU_INC(cnt.v_rforks); + PCPU_ADD(cnt.v_rforkpages, p2->p_vmspace->vm_dsize + + p2->p_vmspace->vm_ssize); + } + +#ifdef PROCDESC + /* + * Associate the process descriptor with the process before anything + * can happen that might cause that process to need the descriptor. + * However, don't do this until after fork(2) can no longer fail. + */ + if (flags & RFPROCDESC) + procdesc_new(p2, pdflags); +#endif + + /* + * Both processes are set up, now check if any loadable modules want + * to adjust anything. + */ + EVENTHANDLER_INVOKE(process_fork, p1, p2, flags); + + /* + * Set the child start time and mark the process as being complete. + */ + PROC_LOCK(p2); + PROC_LOCK(p1); + microuptime(&p2->p_stats->p_start); + PROC_SLOCK(p2); + p2->p_state = PRS_NORMAL; + PROC_SUNLOCK(p2); + +#ifdef KDTRACE_HOOKS + /* + * Tell the DTrace fasttrap provider about the new process + * if it has registered an interest. We have to do this only after + * p_state is PRS_NORMAL since the fasttrap module will use pfind() + * later on. + */ + if (dtrace_fasttrap_fork) + dtrace_fasttrap_fork(p1, p2); +#endif + if ((p1->p_flag & (P_TRACED | P_FOLLOWFORK)) == (P_TRACED | + P_FOLLOWFORK)) { + /* + * Arrange for debugger to receive the fork event. + * + * We can report PL_FLAG_FORKED regardless of + * P_FOLLOWFORK settings, but it does not make a sense + * for runaway child. + */ + td->td_dbgflags |= TDB_FORK; + td->td_dbg_forked = p2->p_pid; + td2->td_dbgflags |= TDB_STOPATFORK; + _PHOLD(p2); + p2_held = 1; + } + if (flags & RFPPWAIT) { + td->td_pflags |= TDP_RFPPWAIT; + td->td_rfppwait_p = p2; + } + PROC_UNLOCK(p2); + if ((flags & RFSTOPPED) == 0) { + /* + * If RFSTOPPED not requested, make child runnable and + * add to run queue. + */ + thread_lock(td2); + TD_SET_CAN_RUN(td2); + sched_add(td2, SRQ_BORING); + thread_unlock(td2); + } + + /* + * Now can be swapped. + */ + _PRELE(p1); + PROC_UNLOCK(p1); + + /* + * Tell any interested parties about the new process. + */ + knote_fork(&p1->p_klist, p2->p_pid); + SDT_PROBE(proc, kernel, , create, p2, p1, flags, 0, 0); + + /* + * Wait until debugger is attached to child. + */ + PROC_LOCK(p2); + while ((td2->td_dbgflags & TDB_STOPATFORK) != 0) + cv_wait(&p2->p_dbgwait, &p2->p_mtx); + if (p2_held) + _PRELE(p2); + PROC_UNLOCK(p2); +} + +int +fork1(struct thread *td, int flags, int pages, struct proc **procp, + int *procdescp, int pdflags) +{ + struct proc *p1; + struct proc *newproc; + int ok; + struct thread *td2; + struct vmspace *vm2; + vm_ooffset_t mem_charged; + int error; + static int curfail; + static struct timeval lastfail; +#ifdef PROCDESC + struct file *fp_procdesc = NULL; +#endif + + /* Check for the undefined or unimplemented flags. */ + if ((flags & ~(RFFLAGS | RFTSIGFLAGS(RFTSIGMASK))) != 0) + return (EINVAL); + + /* Signal value requires RFTSIGZMB. */ + if ((flags & RFTSIGFLAGS(RFTSIGMASK)) != 0 && (flags & RFTSIGZMB) == 0) + return (EINVAL); + + /* Can't copy and clear. */ + if ((flags & (RFFDG|RFCFDG)) == (RFFDG|RFCFDG)) + return (EINVAL); + + /* Check the validity of the signal number. */ + if ((flags & RFTSIGZMB) != 0 && (u_int)RFTSIGNUM(flags) > _SIG_MAXSIG) + return (EINVAL); + +#ifdef PROCDESC + if ((flags & RFPROCDESC) != 0) { + /* Can't not create a process yet get a process descriptor. */ + if ((flags & RFPROC) == 0) + return (EINVAL); + + /* Must provide a place to put a procdesc if creating one. */ + if (procdescp == NULL) + return (EINVAL); + } +#endif + + 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) { + *procp = NULL; + return (fork_norfproc(td, flags)); + } + +#ifdef PROCDESC + /* + * If required, create a process descriptor in the parent first; we + * will abandon it if something goes wrong. We don't finit() until + * later. + */ + if (flags & RFPROCDESC) { + error = falloc(td, &fp_procdesc, procdescp, 0); + if (error != 0) + return (error); + } +#endif + + mem_charged = 0; + vm2 = NULL; + if (pages == 0) + pages = KSTACK_PAGES; + /* Allocate new proc. */ + newproc = uma_zalloc(proc_zone, M_WAITOK); + td2 = FIRST_THREAD_IN_PROC(newproc); + if (td2 == NULL) { + td2 = thread_alloc(pages); + if (td2 == NULL) { + error = ENOMEM; + goto fail1; + } + proc_linkup(newproc, td2); + } else { + if (td2->td_kstack == 0 || td2->td_kstack_pages != pages) { + if (td2->td_kstack != 0) + vm_thread_dispose(td2); + if (!thread_alloc_stack(td2, pages)) { + error = ENOMEM; + goto fail1; + } + } + } + + if ((flags & RFMEM) == 0) { + vm2 = vmspace_fork(p1->p_vmspace, &mem_charged); + if (vm2 == NULL) { + error = ENOMEM; + goto fail1; + } + if (!swap_reserve(mem_charged)) { + /* + * The swap reservation failed. The accounting + * from the entries of the copied vm2 will be + * substracted in vmspace_free(), so force the + * reservation there. + */ + swap_reserve_force(mem_charged); + error = ENOMEM; + goto fail1; + } + } else + vm2 = NULL; + + /* + * XXX: This is ugly; when we copy resource usage, we need to bump + * per-cred resource counters. + */ + newproc->p_ucred = p1->p_ucred; + + /* + * Initialize resource accounting for the child process. + */ + error = racct_proc_fork(p1, newproc); + if (error != 0) { + error = EAGAIN; + goto fail1; + } + +#ifdef MAC + mac_proc_init(newproc); +#endif + knlist_init_mtx(&newproc->p_klist, &newproc->p_mtx); + STAILQ_INIT(&newproc->p_ktr); + + /* 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); + if ((nprocs >= maxproc - 10 && priv_check_cred(td->td_ucred, + PRIV_MAXPROC, 0) != 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. + * + * XXXRW: Can we avoid privilege here if it's not needed? + */ + error = priv_check_cred(td->td_ucred, PRIV_PROC_LIMIT, 0); + if (error == 0) + ok = chgproccnt(td->td_ucred->cr_ruidinfo, 1, 0); + else { + PROC_LOCK(p1); + ok = chgproccnt(td->td_ucred->cr_ruidinfo, 1, + lim_cur(p1, RLIMIT_NPROC)); + PROC_UNLOCK(p1); + } + if (ok) { + do_fork(td, flags, newproc, td2, vm2, pdflags); + + /* + * Return child proc pointer to parent. + */ + *procp = newproc; +#ifdef PROCDESC + if (flags & RFPROCDESC) { + procdesc_finit(newproc->p_procdesc, fp_procdesc); + fdrop(fp_procdesc, td); + } +#endif + racct_proc_fork_done(newproc); + return (0); + } + + error = EAGAIN; +fail: + sx_sunlock(&proctree_lock); + if (ppsratecheck(&lastfail, &curfail, 1)) + printf("maxproc limit exceeded by uid %u (pid %d); see tuning(7) and login.conf(5)\n", + td->td_ucred->cr_ruid, p1->p_pid); + sx_xunlock(&allproc_lock); +#ifdef MAC + mac_proc_destroy(newproc); +#endif + racct_proc_exit(newproc); +fail1: + if (vm2 != NULL) + vmspace_free(vm2); + uma_zfree(proc_zone, newproc); +#ifdef PROCDESC + if ((flags & RFPROCDESC) != 0 && fp_procdesc != NULL) { + fdclose(td->td_proc->p_fd, fp_procdesc, *procdescp, td); + fdrop(fp_procdesc, td); + } +#endif + pause("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(void (*callout)(void *, struct trapframe *), void *arg, + struct trapframe *frame) +{ + struct proc *p; + struct thread *td; + struct thread *dtd; + + td = curthread; + p = td->td_proc; + KASSERT(p->p_state == PRS_NORMAL, ("executing process is still new")); + + CTR4(KTR_PROC, "fork_exit: new thread %p (td_sched %p, pid %d, %s)", + td, td->td_sched, p->p_pid, td->td_name); + + sched_fork_exit(td); + /* + * 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 ((dtd = PCPU_GET(deadthread))) { + PCPU_SET(deadthread, NULL); + thread_stash(dtd); + } + thread_unlock(td); + + /* + * 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. + */ + if (p->p_flag & P_KTHREAD) { + printf("Kernel thread \"%s\" (pid %d) exited prematurely.\n", + td->td_name, p->p_pid); + kproc_exit(0); + } + mtx_assert(&Giant, MA_NOTOWNED); + + if (p->p_sysent->sv_schedtail != NULL) + (p->p_sysent->sv_schedtail)(td); +} + +/* + * 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(struct thread *td, struct trapframe *frame) +{ + struct proc *p, *dbg; + + if (td->td_dbgflags & TDB_STOPATFORK) { + p = td->td_proc; + sx_xlock(&proctree_lock); + PROC_LOCK(p); + if ((p->p_pptr->p_flag & (P_TRACED | P_FOLLOWFORK)) == + (P_TRACED | P_FOLLOWFORK)) { + /* + * If debugger still wants auto-attach for the + * parent's children, do it now. + */ + dbg = p->p_pptr->p_pptr; + p->p_flag |= P_TRACED; + p->p_oppid = p->p_pptr->p_pid; + proc_reparent(p, dbg); + sx_xunlock(&proctree_lock); + td->td_dbgflags |= TDB_CHILD; + ptracestop(td, SIGSTOP); + td->td_dbgflags &= ~TDB_CHILD; + } else { + /* + * ... otherwise clear the request. + */ + sx_xunlock(&proctree_lock); + td->td_dbgflags &= ~TDB_STOPATFORK; + cv_broadcast(&p->p_dbgwait); + } + PROC_UNLOCK(p); + } + + userret(td, frame); + +#ifdef KTRACE + if (KTRPOINT(td, KTR_SYSRET)) + ktrsysret(SYS_fork, 0, 0); +#endif +} |