text: /*-
   * 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: releng/9.3/sys/kern/sys_procdesc.c 244172 2012-12-13 06:17:05Z kib $");
  
  #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;
  	procdesc_free(pd);
  }
  
  /*
   * procdesc_close() - last close on a process descriptor.  If the process is
   * still running, terminate with SIGKILL (unless PD_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;
  	PROC_LOCK(p);
  	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_SLOCK(p);
  		proc_reap(curthread, p, NULL, 0);
  	} 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.
  		 */
  		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 & PD_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 */
  