/sys/kern/sys_procdesc.c
C | 532 lines | 318 code | 68 blank | 146 comment | 39 complexity | 44fffda414a7f9cc6f65b3d0fd2b0d25 MD5 | raw file
Possible License(s): MPL-2.0-no-copyleft-exception, BSD-3-Clause, LGPL-2.0, LGPL-2.1, BSD-2-Clause, 0BSD, JSON, AGPL-1.0, GPL-2.0
- /*-
- * Copyright (c) 2009 Robert N. M. Watson
- * All rights reserved.
- *
- * This software was developed at the University of Cambridge Computer
- * Laboratory with support from a grant from Google, 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.
- *
- * THIS SOFTWARE IS PROVIDED BY THE AUTHOR 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 AUTHOR 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.
- */
- /*-
- * FreeBSD process descriptor facility.
- *
- * Some processes are represented by a file descriptor, which will be used in
- * preference to signaling and pids for the purposes of process management,
- * and is, in effect, a form of capability. When a process descriptor is
- * used with a process, it ceases to be visible to certain traditional UNIX
- * process facilities, such as waitpid(2).
- *
- * Some semantics:
- *
- * - At most one process descriptor will exist for any process, although
- * references to that descriptor may be held from many processes (or even
- * be in flight between processes over a local domain socket).
- * - Last close on the process descriptor will terminate the process using
- * SIGKILL and reparent it to init so that there's a process to reap it
- * when it's done exiting.
- * - If the process exits before the descriptor is closed, it will not
- * generate SIGCHLD on termination, or be picked up by waitpid().
- * - The pdkill(2) system call may be used to deliver a signal to the process
- * using its process descriptor.
- * - The pdwait4(2) system call may be used to block (or not) on a process
- * descriptor to collect termination information.
- *
- * Open questions:
- *
- * - How to handle ptrace(2)?
- * - Will we want to add a pidtoprocdesc(2) system call to allow process
- * descriptors to be created for processes without pfork(2)?
- */
- #include <sys/cdefs.h>
- __FBSDID("$FreeBSD$");
- #include "opt_procdesc.h"
- #include <sys/param.h>
- #include <sys/capability.h>
- #include <sys/fcntl.h>
- #include <sys/file.h>
- #include <sys/filedesc.h>
- #include <sys/kernel.h>
- #include <sys/lock.h>
- #include <sys/mutex.h>
- #include <sys/poll.h>
- #include <sys/proc.h>
- #include <sys/procdesc.h>
- #include <sys/resourcevar.h>
- #include <sys/stat.h>
- #include <sys/sysproto.h>
- #include <sys/sysctl.h>
- #include <sys/systm.h>
- #include <sys/ucred.h>
- #include <security/audit/audit.h>
- #include <vm/uma.h>
- #ifdef PROCDESC
- FEATURE(process_descriptors, "Process Descriptors");
- static uma_zone_t procdesc_zone;
- static fo_rdwr_t procdesc_read;
- static fo_rdwr_t procdesc_write;
- static fo_truncate_t procdesc_truncate;
- static fo_ioctl_t procdesc_ioctl;
- static fo_poll_t procdesc_poll;
- static fo_kqfilter_t procdesc_kqfilter;
- static fo_stat_t procdesc_stat;
- static fo_close_t procdesc_close;
- static fo_chmod_t procdesc_chmod;
- static fo_chown_t procdesc_chown;
- static struct fileops procdesc_ops = {
- .fo_read = procdesc_read,
- .fo_write = procdesc_write,
- .fo_truncate = procdesc_truncate,
- .fo_ioctl = procdesc_ioctl,
- .fo_poll = procdesc_poll,
- .fo_kqfilter = procdesc_kqfilter,
- .fo_stat = procdesc_stat,
- .fo_close = procdesc_close,
- .fo_chmod = procdesc_chmod,
- .fo_chown = procdesc_chown,
- .fo_flags = DFLAG_PASSABLE,
- };
- /*
- * Initialize with VFS so that process descriptors are available along with
- * other file descriptor types. As long as it runs before init(8) starts,
- * there shouldn't be a problem.
- */
- static void
- procdesc_init(void *dummy __unused)
- {
- procdesc_zone = uma_zcreate("procdesc", sizeof(struct procdesc),
- NULL, NULL, NULL, NULL, UMA_ALIGN_PTR, 0);
- if (procdesc_zone == NULL)
- panic("procdesc_init: procdesc_zone not initialized");
- }
- SYSINIT(vfs, SI_SUB_VFS, SI_ORDER_ANY, procdesc_init, NULL);
- /*
- * Return a locked process given a process descriptor, or ESRCH if it has
- * died.
- */
- int
- procdesc_find(struct thread *td, int fd, cap_rights_t rights,
- struct proc **p)
- {
- struct procdesc *pd;
- struct file *fp;
- int error;
- error = fget(td, fd, rights, &fp);
- if (error)
- return (error);
- if (fp->f_type != DTYPE_PROCDESC) {
- error = EBADF;
- goto out;
- }
- pd = fp->f_data;
- sx_slock(&proctree_lock);
- if (pd->pd_proc != NULL) {
- *p = pd->pd_proc;
- PROC_LOCK(*p);
- } else
- error = ESRCH;
- sx_sunlock(&proctree_lock);
- out:
- fdrop(fp, td);
- return (error);
- }
- /*
- * Function to be used by procstat(1) sysctls when returning procdesc
- * information.
- */
- pid_t
- procdesc_pid(struct file *fp_procdesc)
- {
- struct procdesc *pd;
- KASSERT(fp_procdesc->f_type == DTYPE_PROCDESC,
- ("procdesc_pid: !procdesc"));
- pd = fp_procdesc->f_data;
- return (pd->pd_pid);
- }
- /*
- * Retrieve the PID associated with a process descriptor.
- */
- int
- kern_pdgetpid(struct thread *td, int fd, cap_rights_t rights, pid_t *pidp)
- {
- struct file *fp;
- int error;
- error = fget(td, fd, rights, &fp);
- if (error)
- return (error);
- if (fp->f_type != DTYPE_PROCDESC) {
- error = EBADF;
- goto out;
- }
- *pidp = procdesc_pid(fp);
- out:
- fdrop(fp, td);
- return (error);
- }
- /*
- * System call to return the pid of a process given its process descriptor.
- */
- int
- sys_pdgetpid(struct thread *td, struct pdgetpid_args *uap)
- {
- pid_t pid;
- int error;
- AUDIT_ARG_FD(uap->fd);
- error = kern_pdgetpid(td, uap->fd, CAP_PDGETPID, &pid);
- if (error == 0)
- error = copyout(&pid, uap->pidp, sizeof(pid));
- return (error);
- }
- /*
- * When a new process is forked by pdfork(), a file descriptor is allocated
- * by the fork code first, then the process is forked, and then we get a
- * chance to set up the process descriptor. Failure is not permitted at this
- * point, so procdesc_new() must succeed.
- */
- void
- procdesc_new(struct proc *p, int flags)
- {
- struct procdesc *pd;
- pd = uma_zalloc(procdesc_zone, M_WAITOK | M_ZERO);
- pd->pd_proc = p;
- pd->pd_pid = p->p_pid;
- p->p_procdesc = pd;
- pd->pd_flags = 0;
- if (flags & PD_DAEMON)
- pd->pd_flags |= PDF_DAEMON;
- PROCDESC_LOCK_INIT(pd);
- /*
- * Process descriptors start out with two references: one from their
- * struct file, and the other from their struct proc.
- */
- refcount_init(&pd->pd_refcount, 2);
- }
- /*
- * Initialize a file with a process descriptor.
- */
- void
- procdesc_finit(struct procdesc *pdp, struct file *fp)
- {
- finit(fp, FREAD | FWRITE, DTYPE_PROCDESC, pdp, &procdesc_ops);
- }
- static void
- procdesc_free(struct procdesc *pd)
- {
- /*
- * When the last reference is released, we assert that the descriptor
- * has been closed, but not that the process has exited, as we will
- * detach the descriptor before the process dies if the descript is
- * closed, as we can't wait synchronously.
- */
- if (refcount_release(&pd->pd_refcount)) {
- KASSERT(pd->pd_proc == NULL,
- ("procdesc_free: pd_proc != NULL"));
- KASSERT((pd->pd_flags & PDF_CLOSED),
- ("procdesc_free: !PDF_CLOSED"));
- PROCDESC_LOCK_DESTROY(pd);
- uma_zfree(procdesc_zone, pd);
- }
- }
- /*
- * procdesc_exit() - notify a process descriptor that its process is exiting.
- * We use the proctree_lock to ensure that process exit either happens
- * strictly before or strictly after a concurrent call to procdesc_close().
- */
- int
- procdesc_exit(struct proc *p)
- {
- struct procdesc *pd;
- sx_assert(&proctree_lock, SA_XLOCKED);
- PROC_LOCK_ASSERT(p, MA_OWNED);
- KASSERT(p->p_procdesc != NULL, ("procdesc_exit: p_procdesc NULL"));
- pd = p->p_procdesc;
- PROCDESC_LOCK(pd);
- KASSERT((pd->pd_flags & PDF_CLOSED) == 0 || p->p_pptr == initproc,
- ("procdesc_exit: closed && parent not init"));
- pd->pd_flags |= PDF_EXITED;
- /*
- * If the process descriptor has been closed, then we have nothing
- * to do; return 1 so that init will get SIGCHLD and do the reaping.
- * Clean up the procdesc now rather than letting it happen during
- * that reap.
- */
- if (pd->pd_flags & PDF_CLOSED) {
- PROCDESC_UNLOCK(pd);
- pd->pd_proc = NULL;
- p->p_procdesc = NULL;
- procdesc_free(pd);
- return (1);
- }
- if (pd->pd_flags & PDF_SELECTED) {
- pd->pd_flags &= ~PDF_SELECTED;
- selwakeup(&pd->pd_selinfo);
- }
- PROCDESC_UNLOCK(pd);
- return (0);
- }
- /*
- * When a process descriptor is reaped, perhaps as a result of close() or
- * pdwait4(), release the process's reference on the process descriptor.
- */
- void
- procdesc_reap(struct proc *p)
- {
- struct procdesc *pd;
- sx_assert(&proctree_lock, SA_XLOCKED);
- KASSERT(p->p_procdesc != NULL, ("procdesc_reap: p_procdesc == NULL"));
- pd = p->p_procdesc;
- pd->pd_proc = NULL;
- p->p_procdesc = NULL;
- procdesc_free(pd);
- }
- /*
- * procdesc_close() - last close on a process descriptor. If the process is
- * still running, terminate with SIGKILL (unless PDF_DAEMON is set) and let
- * init(8) clean up the mess; if not, we have to clean up the zombie ourselves.
- */
- static int
- procdesc_close(struct file *fp, struct thread *td)
- {
- struct procdesc *pd;
- struct proc *p;
- KASSERT(fp->f_type == DTYPE_PROCDESC, ("procdesc_close: !procdesc"));
- pd = fp->f_data;
- fp->f_ops = &badfileops;
- fp->f_data = NULL;
- sx_xlock(&proctree_lock);
- PROCDESC_LOCK(pd);
- pd->pd_flags |= PDF_CLOSED;
- PROCDESC_UNLOCK(pd);
- p = pd->pd_proc;
- if (p == NULL) {
- /*
- * This is the case where process' exit status was already
- * collected and procdesc_reap() was already called.
- */
- sx_xunlock(&proctree_lock);
- } else if (p->p_state == PRS_ZOMBIE) {
- /*
- * If the process is already dead and just awaiting reaping,
- * do that now. This will release the process's reference to
- * the process descriptor when it calls back into
- * procdesc_reap().
- */
- PROC_LOCK(p);
- PROC_SLOCK(p);
- proc_reap(curthread, p, NULL, 0, NULL);
- } else {
- /*
- * If the process is not yet dead, we need to kill it, but we
- * can't wait around synchronously for it to go away, as that
- * path leads to madness (and deadlocks). First, detach the
- * process from its descriptor so that its exit status will
- * be reported normally.
- */
- PROC_LOCK(p);
- pd->pd_proc = NULL;
- p->p_procdesc = NULL;
- procdesc_free(pd);
- /*
- * Next, reparent it to init(8) so that there's someone to
- * pick up the pieces; finally, terminate with prejudice.
- */
- p->p_sigparent = SIGCHLD;
- proc_reparent(p, initproc);
- if ((pd->pd_flags & PDF_DAEMON) == 0)
- kern_psignal(p, SIGKILL);
- PROC_UNLOCK(p);
- sx_xunlock(&proctree_lock);
- }
- /*
- * Release the file descriptor's reference on the process descriptor.
- */
- procdesc_free(pd);
- return (0);
- }
- static int
- procdesc_read(struct file *fp, struct uio *uio, struct ucred *active_cred,
- int flags, struct thread *td)
- {
- return (EOPNOTSUPP);
- }
- static int
- procdesc_write(struct file *fp, struct uio *uio, struct ucred *active_cred,
- int flags, struct thread *td)
- {
- return (EOPNOTSUPP);
- }
- static int
- procdesc_truncate(struct file *fp, off_t length, struct ucred *active_cred,
- struct thread *td)
- {
- return (EOPNOTSUPP);
- }
- static int
- procdesc_ioctl(struct file *fp, u_long com, void *data,
- struct ucred *active_cred, struct thread *td)
- {
- return (EOPNOTSUPP);
- }
- static int
- procdesc_poll(struct file *fp, int events, struct ucred *active_cred,
- struct thread *td)
- {
- struct procdesc *pd;
- int revents;
- revents = 0;
- pd = fp->f_data;
- PROCDESC_LOCK(pd);
- if (pd->pd_flags & PDF_EXITED)
- revents |= POLLHUP;
- if (revents == 0) {
- selrecord(td, &pd->pd_selinfo);
- pd->pd_flags |= PDF_SELECTED;
- }
- PROCDESC_UNLOCK(pd);
- return (revents);
- }
- static int
- procdesc_kqfilter(struct file *fp, struct knote *kn)
- {
- return (EOPNOTSUPP);
- }
- static int
- procdesc_stat(struct file *fp, struct stat *sb, struct ucred *active_cred,
- struct thread *td)
- {
- struct procdesc *pd;
- struct timeval pstart;
- /*
- * XXXRW: Perhaps we should cache some more information from the
- * process so that we can return it reliably here even after it has
- * died. For example, caching its credential data.
- */
- bzero(sb, sizeof(*sb));
- pd = fp->f_data;
- sx_slock(&proctree_lock);
- if (pd->pd_proc != NULL) {
- PROC_LOCK(pd->pd_proc);
- /* Set birth and [acm] times to process start time. */
- pstart = pd->pd_proc->p_stats->p_start;
- timevaladd(&pstart, &boottime);
- TIMEVAL_TO_TIMESPEC(&pstart, &sb->st_birthtim);
- sb->st_atim = sb->st_birthtim;
- sb->st_ctim = sb->st_birthtim;
- sb->st_mtim = sb->st_birthtim;
- if (pd->pd_proc->p_state != PRS_ZOMBIE)
- sb->st_mode = S_IFREG | S_IRWXU;
- else
- sb->st_mode = S_IFREG;
- sb->st_uid = pd->pd_proc->p_ucred->cr_ruid;
- sb->st_gid = pd->pd_proc->p_ucred->cr_rgid;
- PROC_UNLOCK(pd->pd_proc);
- } else
- sb->st_mode = S_IFREG;
- sx_sunlock(&proctree_lock);
- return (0);
- }
- static int
- procdesc_chmod(struct file *fp, mode_t mode, struct ucred *active_cred,
- struct thread *td)
- {
- return (EOPNOTSUPP);
- }
- static int
- procdesc_chown(struct file *fp, uid_t uid, gid_t gid, struct ucred *active_cred,
- struct thread *td)
- {
- return (EOPNOTSUPP);
- }
- #else /* !PROCDESC */
- int
- sys_pdgetpid(struct thread *td, struct pdgetpid_args *uap)
- {
- return (ENOSYS);
- }
- #endif /* PROCDESC */