text: /*-
   * Copyright (c) 1982, 1986, 1989, 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.
   *
   *	@(#)sys_generic.c	8.5 (Berkeley) 1/21/94
   */
  
  #include <sys/cdefs.h>
  __FBSDID("$FreeBSD$");
  
  #include "opt_capsicum.h"
  #include "opt_compat.h"
  #include "opt_ktrace.h"
  
  #include <sys/param.h>
  #include <sys/systm.h>
  #include <sys/sysproto.h>
  #include <sys/capsicum.h>
  #include <sys/filedesc.h>
  #include <sys/filio.h>
  #include <sys/fcntl.h>
  #include <sys/file.h>
  #include <sys/lock.h>
  #include <sys/proc.h>
  #include <sys/signalvar.h>
  #include <sys/socketvar.h>
  #include <sys/uio.h>
  #include <sys/kernel.h>
  #include <sys/ktr.h>
  #include <sys/limits.h>
  #include <sys/malloc.h>
  #include <sys/poll.h>
  #include <sys/resourcevar.h>
  #include <sys/selinfo.h>
  #include <sys/sleepqueue.h>
  #include <sys/syscallsubr.h>
  #include <sys/sysctl.h>
  #include <sys/sysent.h>
  #include <sys/vnode.h>
  #include <sys/bio.h>
  #include <sys/buf.h>
  #include <sys/condvar.h>
  #ifdef KTRACE
  #include <sys/ktrace.h>
  #endif
  
  #include <security/audit/audit.h>
  
  /*
   * The following macro defines how many bytes will be allocated from
   * the stack instead of memory allocated when passing the IOCTL data
   * structures from userspace and to the kernel. Some IOCTLs having
   * small data structures are used very frequently and this small
   * buffer on the stack gives a significant speedup improvement for
   * those requests. The value of this define should be greater or equal
   * to 64 bytes and should also be power of two. The data structure is
   * currently hard-aligned to a 8-byte boundary on the stack. This
   * should currently be sufficient for all supported platforms.
   */
  #define	SYS_IOCTL_SMALL_SIZE	128	/* bytes */
  #define	SYS_IOCTL_SMALL_ALIGN	8	/* bytes */
  
  #ifdef __LP64__
  static int iosize_max_clamp = 0;
  SYSCTL_INT(_debug, OID_AUTO, iosize_max_clamp, CTLFLAG_RW,
      &iosize_max_clamp, 0, "Clamp max i/o size to INT_MAX");
  static int devfs_iosize_max_clamp = 1;
  SYSCTL_INT(_debug, OID_AUTO, devfs_iosize_max_clamp, CTLFLAG_RW,
      &devfs_iosize_max_clamp, 0, "Clamp max i/o size to INT_MAX for devices");
  #endif
  
  /*
   * Assert that the return value of read(2) and write(2) syscalls fits
   * into a register.  If not, an architecture will need to provide the
   * usermode wrappers to reconstruct the result.
   */
  CTASSERT(sizeof(register_t) >= sizeof(size_t));
  
  static MALLOC_DEFINE(M_IOCTLOPS, "ioctlops", "ioctl data buffer");
  static MALLOC_DEFINE(M_SELECT, "select", "select() buffer");
  MALLOC_DEFINE(M_IOV, "iov", "large iov's");
  
  static int	pollout(struct thread *, struct pollfd *, struct pollfd *,
  		    u_int);
  static int	pollscan(struct thread *, struct pollfd *, u_int);
  static int	pollrescan(struct thread *);
  static int	selscan(struct thread *, fd_mask **, fd_mask **, int);
  static int	selrescan(struct thread *, fd_mask **, fd_mask **);
  static void	selfdalloc(struct thread *, void *);
  static void	selfdfree(struct seltd *, struct selfd *);
  static int	dofileread(struct thread *, int, struct file *, struct uio *,
  		    off_t, int);
  static int	dofilewrite(struct thread *, int, struct file *, struct uio *,
  		    off_t, int);
  static void	doselwakeup(struct selinfo *, int);
  static void	seltdinit(struct thread *);
  static int	seltdwait(struct thread *, sbintime_t, sbintime_t);
  static void	seltdclear(struct thread *);
  
  /*
   * One seltd per-thread allocated on demand as needed.
   *
   *	t - protected by st_mtx
   * 	k - Only accessed by curthread or read-only
   */
  struct seltd {
  	STAILQ_HEAD(, selfd)	st_selq;	/* (k) List of selfds. */
  	struct selfd		*st_free1;	/* (k) free fd for read set. */
  	struct selfd		*st_free2;	/* (k) free fd for write set. */
  	struct mtx		st_mtx;		/* Protects struct seltd */
  	struct cv		st_wait;	/* (t) Wait channel. */
  	int			st_flags;	/* (t) SELTD_ flags. */
  };
  
  #define	SELTD_PENDING	0x0001			/* We have pending events. */
  #define	SELTD_RESCAN	0x0002			/* Doing a rescan. */
  
  /*
   * One selfd allocated per-thread per-file-descriptor.
   *	f - protected by sf_mtx
   */
  struct selfd {
  	STAILQ_ENTRY(selfd)	sf_link;	/* (k) fds owned by this td. */
  	TAILQ_ENTRY(selfd)	sf_threads;	/* (f) fds on this selinfo. */
  	struct selinfo		*sf_si;		/* (f) selinfo when linked. */
  	struct mtx		*sf_mtx;	/* Pointer to selinfo mtx. */
  	struct seltd		*sf_td;		/* (k) owning seltd. */
  	void			*sf_cookie;	/* (k) fd or pollfd. */
  	u_int			sf_refs;
  };
  
  static uma_zone_t selfd_zone;
  static struct mtx_pool *mtxpool_select;
  
  #ifdef __LP64__
  size_t
  devfs_iosize_max(void)
  {
  
  	return (devfs_iosize_max_clamp || SV_CURPROC_FLAG(SV_ILP32) ?
  	    INT_MAX : SSIZE_MAX);
  }
  
  size_t
  iosize_max(void)
  {
  
  	return (iosize_max_clamp || SV_CURPROC_FLAG(SV_ILP32) ?
  	    INT_MAX : SSIZE_MAX);
  }
  #endif
  
  #ifndef _SYS_SYSPROTO_H_
  struct read_args {
  	int	fd;
  	void	*buf;
  	size_t	nbyte;
  };
  #endif
  int
  sys_read(td, uap)
  	struct thread *td;
  	struct read_args *uap;
  {
  	struct uio auio;
  	struct iovec aiov;
  	int error;
  
  	if (uap->nbyte > IOSIZE_MAX)
  		return (EINVAL);
  	aiov.iov_base = uap->buf;
  	aiov.iov_len = uap->nbyte;
  	auio.uio_iov = &aiov;
  	auio.uio_iovcnt = 1;
  	auio.uio_resid = uap->nbyte;
  	auio.uio_segflg = UIO_USERSPACE;
  	error = kern_readv(td, uap->fd, &auio);
  	return(error);
  }
  
  /*
   * Positioned read system call
   */
  #ifndef _SYS_SYSPROTO_H_
  struct pread_args {
  	int	fd;
  	void	*buf;
  	size_t	nbyte;
  	int	pad;
  	off_t	offset;
  };
  #endif
  int
  sys_pread(td, uap)
  	struct thread *td;
  	struct pread_args *uap;
  {
  	struct uio auio;
  	struct iovec aiov;
  	int error;
  
  	if (uap->nbyte > IOSIZE_MAX)
  		return (EINVAL);
  	aiov.iov_base = uap->buf;
  	aiov.iov_len = uap->nbyte;
  	auio.uio_iov = &aiov;
  	auio.uio_iovcnt = 1;
  	auio.uio_resid = uap->nbyte;
  	auio.uio_segflg = UIO_USERSPACE;
  	error = kern_preadv(td, uap->fd, &auio, uap->offset);
  	return(error);
  }
  
  #if defined(COMPAT_FREEBSD6)
  int
  freebsd6_pread(td, uap)
  	struct thread *td;
  	struct freebsd6_pread_args *uap;
  {
  	struct pread_args oargs;
  
  	oargs.fd = uap->fd;
  	oargs.buf = uap->buf;
  	oargs.nbyte = uap->nbyte;
  	oargs.offset = uap->offset;
  	return (sys_pread(td, &oargs));
  }
  #endif
  
  /*
   * Scatter read system call.
   */
  #ifndef _SYS_SYSPROTO_H_
  struct readv_args {
  	int	fd;
  	struct	iovec *iovp;
  	u_int	iovcnt;
  };
  #endif
  int
  sys_readv(struct thread *td, struct readv_args *uap)
  {
  	struct uio *auio;
  	int error;
  
  	error = copyinuio(uap->iovp, uap->iovcnt, &auio);
  	if (error)
  		return (error);
  	error = kern_readv(td, uap->fd, auio);
  	free(auio, M_IOV);
  	return (error);
  }
  
  int
  kern_readv(struct thread *td, int fd, struct uio *auio)
  {
  	struct file *fp;
  	cap_rights_t rights;
  	int error;
  
  	error = fget_read(td, fd, cap_rights_init(&rights, CAP_READ), &fp);
  	if (error)
  		return (error);
  	error = dofileread(td, fd, fp, auio, (off_t)-1, 0);
  	fdrop(fp, td);
  	return (error);
  }
  
  /*
   * Scatter positioned read system call.
   */
  #ifndef _SYS_SYSPROTO_H_
  struct preadv_args {
  	int	fd;
  	struct	iovec *iovp;
  	u_int	iovcnt;
  	off_t	offset;
  };
  #endif
  int
  sys_preadv(struct thread *td, struct preadv_args *uap)
  {
  	struct uio *auio;
  	int error;
  
  	error = copyinuio(uap->iovp, uap->iovcnt, &auio);
  	if (error)
  		return (error);
  	error = kern_preadv(td, uap->fd, auio, uap->offset);
  	free(auio, M_IOV);
  	return (error);
  }
  
  int
  kern_preadv(td, fd, auio, offset)
  	struct thread *td;
  	int fd;
  	struct uio *auio;
  	off_t offset;
  {
  	struct file *fp;
  	cap_rights_t rights;
  	int error;
  
  	error = fget_read(td, fd, cap_rights_init(&rights, CAP_PREAD), &fp);
  	if (error)
  		return (error);
  	if (!(fp->f_ops->fo_flags & DFLAG_SEEKABLE))
  		error = ESPIPE;
  	else if (offset < 0 && fp->f_vnode->v_type != VCHR)
  		error = EINVAL;
  	else
  		error = dofileread(td, fd, fp, auio, offset, FOF_OFFSET);
  	fdrop(fp, td);
  	return (error);
  }
  
  /*
   * Common code for readv and preadv that reads data in
   * from a file using the passed in uio, offset, and flags.
   */
  static int
  dofileread(td, fd, fp, auio, offset, flags)
  	struct thread *td;
  	int fd;
  	struct file *fp;
  	struct uio *auio;
  	off_t offset;
  	int flags;
  {
  	ssize_t cnt;
  	int error;
  #ifdef KTRACE
  	struct uio *ktruio = NULL;
  #endif
  
  	/* Finish zero length reads right here */
  	if (auio->uio_resid == 0) {
  		td->td_retval[0] = 0;
  		return(0);
  	}
  	auio->uio_rw = UIO_READ;
  	auio->uio_offset = offset;
  	auio->uio_td = td;
  #ifdef KTRACE
  	if (KTRPOINT(td, KTR_GENIO)) 
  		ktruio = cloneuio(auio);
  #endif
  	cnt = auio->uio_resid;
  	if ((error = fo_read(fp, auio, td->td_ucred, flags, td))) {
  		if (auio->uio_resid != cnt && (error == ERESTART ||
  		    error == EINTR || error == EWOULDBLOCK))
  			error = 0;
  	}
  	cnt -= auio->uio_resid;
  #ifdef KTRACE
  	if (ktruio != NULL) {
  		ktruio->uio_resid = cnt;
  		ktrgenio(fd, UIO_READ, ktruio, error);
  	}
  #endif
  	td->td_retval[0] = cnt;
  	return (error);
  }
  
  #ifndef _SYS_SYSPROTO_H_
  struct write_args {
  	int	fd;
  	const void *buf;
  	size_t	nbyte;
  };
  #endif
  int
  sys_write(td, uap)
  	struct thread *td;
  	struct write_args *uap;
  {
  	struct uio auio;
  	struct iovec aiov;
  	int error;
  
  	if (uap->nbyte > IOSIZE_MAX)
  		return (EINVAL);
  	aiov.iov_base = (void *)(uintptr_t)uap->buf;
  	aiov.iov_len = uap->nbyte;
  	auio.uio_iov = &aiov;
  	auio.uio_iovcnt = 1;
  	auio.uio_resid = uap->nbyte;
  	auio.uio_segflg = UIO_USERSPACE;
  	error = kern_writev(td, uap->fd, &auio);
  	return(error);
  }
  
  /*
   * Positioned write system call.
   */
  #ifndef _SYS_SYSPROTO_H_
  struct pwrite_args {
  	int	fd;
  	const void *buf;
  	size_t	nbyte;
  	int	pad;
  	off_t	offset;
  };
  #endif
  int
  sys_pwrite(td, uap)
  	struct thread *td;
  	struct pwrite_args *uap;
  {
  	struct uio auio;
  	struct iovec aiov;
  	int error;
  
  	if (uap->nbyte > IOSIZE_MAX)
  		return (EINVAL);
  	aiov.iov_base = (void *)(uintptr_t)uap->buf;
  	aiov.iov_len = uap->nbyte;
  	auio.uio_iov = &aiov;
  	auio.uio_iovcnt = 1;
  	auio.uio_resid = uap->nbyte;
  	auio.uio_segflg = UIO_USERSPACE;
  	error = kern_pwritev(td, uap->fd, &auio, uap->offset);
  	return(error);
  }
  
  #if defined(COMPAT_FREEBSD6)
  int
  freebsd6_pwrite(td, uap)
  	struct thread *td;
  	struct freebsd6_pwrite_args *uap;
  {
  	struct pwrite_args oargs;
  
  	oargs.fd = uap->fd;
  	oargs.buf = uap->buf;
  	oargs.nbyte = uap->nbyte;
  	oargs.offset = uap->offset;
  	return (sys_pwrite(td, &oargs));
  }
  #endif
  
  /*
   * Gather write system call.
   */
  #ifndef _SYS_SYSPROTO_H_
  struct writev_args {
  	int	fd;
  	struct	iovec *iovp;
  	u_int	iovcnt;
  };
  #endif
  int
  sys_writev(struct thread *td, struct writev_args *uap)
  {
  	struct uio *auio;
  	int error;
  
  	error = copyinuio(uap->iovp, uap->iovcnt, &auio);
  	if (error)
  		return (error);
  	error = kern_writev(td, uap->fd, auio);
  	free(auio, M_IOV);
  	return (error);
  }
  
  int
  kern_writev(struct thread *td, int fd, struct uio *auio)
  {
  	struct file *fp;
  	cap_rights_t rights;
  	int error;
  
  	error = fget_write(td, fd, cap_rights_init(&rights, CAP_WRITE), &fp);
  	if (error)
  		return (error);
  	error = dofilewrite(td, fd, fp, auio, (off_t)-1, 0);
  	fdrop(fp, td);
  	return (error);
  }
  
  /*
   * Gather positioned write system call.
   */
  #ifndef _SYS_SYSPROTO_H_
  struct pwritev_args {
  	int	fd;
  	struct	iovec *iovp;
  	u_int	iovcnt;
  	off_t	offset;
  };
  #endif
  int
  sys_pwritev(struct thread *td, struct pwritev_args *uap)
  {
  	struct uio *auio;
  	int error;
  
  	error = copyinuio(uap->iovp, uap->iovcnt, &auio);
  	if (error)
  		return (error);
  	error = kern_pwritev(td, uap->fd, auio, uap->offset);
  	free(auio, M_IOV);
  	return (error);
  }
  
  int
  kern_pwritev(td, fd, auio, offset)
  	struct thread *td;
  	struct uio *auio;
  	int fd;
  	off_t offset;
  {
  	struct file *fp;
  	cap_rights_t rights;
  	int error;
  
  	error = fget_write(td, fd, cap_rights_init(&rights, CAP_PWRITE), &fp);
  	if (error)
  		return (error);
  	if (!(fp->f_ops->fo_flags & DFLAG_SEEKABLE))
  		error = ESPIPE;
  	else if (offset < 0 && fp->f_vnode->v_type != VCHR)
  		error = EINVAL;
  	else
  		error = dofilewrite(td, fd, fp, auio, offset, FOF_OFFSET);
  	fdrop(fp, td);
  	return (error);
  }
  
  /*
   * Common code for writev and pwritev that writes data to
   * a file using the passed in uio, offset, and flags.
   */
  static int
  dofilewrite(td, fd, fp, auio, offset, flags)
  	struct thread *td;
  	int fd;
  	struct file *fp;
  	struct uio *auio;
  	off_t offset;
  	int flags;
  {
  	ssize_t cnt;
  	int error;
  #ifdef KTRACE
  	struct uio *ktruio = NULL;
  #endif
  
  	auio->uio_rw = UIO_WRITE;
  	auio->uio_td = td;
  	auio->uio_offset = offset;
  #ifdef KTRACE
  	if (KTRPOINT(td, KTR_GENIO))
  		ktruio = cloneuio(auio);
  #endif
  	cnt = auio->uio_resid;
  	if (fp->f_type == DTYPE_VNODE &&
  	    (fp->f_vnread_flags & FDEVFS_VNODE) == 0)
  		bwillwrite();
  	if ((error = fo_write(fp, auio, td->td_ucred, flags, td))) {
  		if (auio->uio_resid != cnt && (error == ERESTART ||
  		    error == EINTR || error == EWOULDBLOCK))
  			error = 0;
  		/* Socket layer is responsible for issuing SIGPIPE. */
  		if (fp->f_type != DTYPE_SOCKET && error == EPIPE) {
  			PROC_LOCK(td->td_proc);
  			tdsignal(td, SIGPIPE);
  			PROC_UNLOCK(td->td_proc);
  		}
  	}
  	cnt -= auio->uio_resid;
  #ifdef KTRACE
  	if (ktruio != NULL) {
  		ktruio->uio_resid = cnt;
  		ktrgenio(fd, UIO_WRITE, ktruio, error);
  	}
  #endif
  	td->td_retval[0] = cnt;
  	return (error);
  }
  
  /*
   * Truncate a file given a file descriptor.
   *
   * Can't use fget_write() here, since must return EINVAL and not EBADF if the
   * descriptor isn't writable.
   */
  int
  kern_ftruncate(td, fd, length)
  	struct thread *td;
  	int fd;
  	off_t length;
  {
  	struct file *fp;
  	cap_rights_t rights;
  	int error;
  
  	AUDIT_ARG_FD(fd);
  	if (length < 0)
  		return (EINVAL);
  	error = fget(td, fd, cap_rights_init(&rights, CAP_FTRUNCATE), &fp);
  	if (error)
  		return (error);
  	AUDIT_ARG_FILE(td->td_proc, fp);
  	if (!(fp->f_flag & FWRITE)) {
  		fdrop(fp, td);
  		return (EINVAL);
  	}
  	error = fo_truncate(fp, length, td->td_ucred, td);
  	fdrop(fp, td);
  	return (error);
  }
  
  #ifndef _SYS_SYSPROTO_H_
  struct ftruncate_args {
  	int	fd;
  	int	pad;
  	off_t	length;
  };
  #endif
  int
  sys_ftruncate(td, uap)
  	struct thread *td;
  	struct ftruncate_args *uap;
  {
  
  	return (kern_ftruncate(td, uap->fd, uap->length));
  }
  
  #if defined(COMPAT_43)
  #ifndef _SYS_SYSPROTO_H_
  struct oftruncate_args {
  	int	fd;
  	long	length;
  };
  #endif
  int
  oftruncate(td, uap)
  	struct thread *td;
  	struct oftruncate_args *uap;
  {
  
  	return (kern_ftruncate(td, uap->fd, uap->length));
  }
  #endif /* COMPAT_43 */
  
  #ifndef _SYS_SYSPROTO_H_
  struct ioctl_args {
  	int	fd;
  	u_long	com;
  	caddr_t	data;
  };
  #endif
  /* ARGSUSED */
  int
  sys_ioctl(struct thread *td, struct ioctl_args *uap)
  {
  	u_char smalldata[SYS_IOCTL_SMALL_SIZE] __aligned(SYS_IOCTL_SMALL_ALIGN);
  	u_long com;
  	int arg, error;
  	u_int size;
  	caddr_t data;
  
  	if (uap->com > 0xffffffff) {
  		printf(
  		    "WARNING pid %d (%s): ioctl sign-extension ioctl %lx\n",
  		    td->td_proc->p_pid, td->td_name, uap->com);
  		uap->com &= 0xffffffff;
  	}
  	com = uap->com;
  
  	/*
  	 * Interpret high order word to find amount of data to be
  	 * copied to/from the user's address space.
  	 */
  	size = IOCPARM_LEN(com);
  	if ((size > IOCPARM_MAX) ||
  	    ((com & (IOC_VOID  | IOC_IN | IOC_OUT)) == 0) ||
  #if defined(COMPAT_FREEBSD5) || defined(COMPAT_FREEBSD4) || defined(COMPAT_43)
  	    ((com & IOC_OUT) && size == 0) ||
  #else
  	    ((com & (IOC_IN | IOC_OUT)) && size == 0) ||
  #endif
  	    ((com & IOC_VOID) && size > 0 && size != sizeof(int)))
  		return (ENOTTY);
  
  	if (size > 0) {
  		if (com & IOC_VOID) {
  			/* Integer argument. */
  			arg = (intptr_t)uap->data;
  			data = (void *)&arg;
  			size = 0;
  		} else {
  			if (size > SYS_IOCTL_SMALL_SIZE)
  				data = malloc((u_long)size, M_IOCTLOPS, M_WAITOK);
  			else
  				data = smalldata;
  		}
  	} else
  		data = (void *)&uap->data;
  	if (com & IOC_IN) {
  		error = copyin(uap->data, data, (u_int)size);
  		if (error != 0)
  			goto out;
  	} else if (com & IOC_OUT) {
  		/*
  		 * Zero the buffer so the user always
  		 * gets back something deterministic.
  		 */
  		bzero(data, size);
  	}
  
  	error = kern_ioctl(td, uap->fd, com, data);
  
  	if (error == 0 && (com & IOC_OUT))
  		error = copyout(data, uap->data, (u_int)size);
  
  out:
  	if (size > SYS_IOCTL_SMALL_SIZE)
  		free(data, M_IOCTLOPS);
  	return (error);
  }
  
  int
  kern_ioctl(struct thread *td, int fd, u_long com, caddr_t data)
  {
  	struct file *fp;
  	struct filedesc *fdp;
  #ifndef CAPABILITIES
  	cap_rights_t rights;
  #endif
  	int error, tmp, locked;
  
  	AUDIT_ARG_FD(fd);
  	AUDIT_ARG_CMD(com);
  
  	fdp = td->td_proc->p_fd;
  
  	switch (com) {
  	case FIONCLEX:
  	case FIOCLEX:
  		FILEDESC_XLOCK(fdp);
  		locked = LA_XLOCKED;
  		break;
  	default:
  #ifdef CAPABILITIES
  		FILEDESC_SLOCK(fdp);
  		locked = LA_SLOCKED;
  #else
  		locked = LA_UNLOCKED;
  #endif
  		break;
  	}
  
  #ifdef CAPABILITIES
  	if ((fp = fget_locked(fdp, fd)) == NULL) {
  		error = EBADF;
  		goto out;
  	}
  	if ((error = cap_ioctl_check(fdp, fd, com)) != 0) {
  		fp = NULL;	/* fhold() was not called yet */
  		goto out;
  	}
  	fhold(fp);
  	if (locked == LA_SLOCKED) {
  		FILEDESC_SUNLOCK(fdp);
  		locked = LA_UNLOCKED;
  	}
  #else
  	error = fget(td, fd, cap_rights_init(&rights, CAP_IOCTL), &fp);
  	if (error != 0) {
  		fp = NULL;
  		goto out;
  	}
  #endif
  	if ((fp->f_flag & (FREAD | FWRITE)) == 0) {
  		error = EBADF;
  		goto out;
  	}
  
  	switch (com) {
  	case FIONCLEX:
  		fdp->fd_ofiles[fd].fde_flags &= ~UF_EXCLOSE;
  		goto out;
  	case FIOCLEX:
  		fdp->fd_ofiles[fd].fde_flags |= UF_EXCLOSE;
  		goto out;
  	case FIONBIO:
  		if ((tmp = *(int *)data))
  			atomic_set_int(&fp->f_flag, FNONBLOCK);
  		else
  			atomic_clear_int(&fp->f_flag, FNONBLOCK);
  		data = (void *)&tmp;
  		break;
  	case FIOASYNC:
  		if ((tmp = *(int *)data))
  			atomic_set_int(&fp->f_flag, FASYNC);
  		else
  			atomic_clear_int(&fp->f_flag, FASYNC);
  		data = (void *)&tmp;
  		break;
  	}
  
  	error = fo_ioctl(fp, com, data, td->td_ucred, td);
  out:
  	switch (locked) {
  	case LA_XLOCKED:
  		FILEDESC_XUNLOCK(fdp);
  		break;
  #ifdef CAPABILITIES
  	case LA_SLOCKED:
  		FILEDESC_SUNLOCK(fdp);
  		break;
  #endif
  	default:
  		FILEDESC_UNLOCK_ASSERT(fdp);
  		break;
  	}
  	if (fp != NULL)
  		fdrop(fp, td);
  	return (error);
  }
  
  int
  poll_no_poll(int events)
  {
  	/*
  	 * Return true for read/write.  If the user asked for something
  	 * special, return POLLNVAL, so that clients have a way of
  	 * determining reliably whether or not the extended
  	 * functionality is present without hard-coding knowledge
  	 * of specific filesystem implementations.
  	 */
  	if (events & ~POLLSTANDARD)
  		return (POLLNVAL);
  
  	return (events & (POLLIN | POLLOUT | POLLRDNORM | POLLWRNORM));
  }
  
  int
  sys_pselect(struct thread *td, struct pselect_args *uap)
  {
  	struct timespec ts;
  	struct timeval tv, *tvp;
  	sigset_t set, *uset;
  	int error;
  
  	if (uap->ts != NULL) {
  		error = copyin(uap->ts, &ts, sizeof(ts));
  		if (error != 0)
  		    return (error);
  		TIMESPEC_TO_TIMEVAL(&tv, &ts);
  		tvp = &tv;
  	} else
  		tvp = NULL;
  	if (uap->sm != NULL) {
  		error = copyin(uap->sm, &set, sizeof(set));
  		if (error != 0)
  			return (error);
  		uset = &set;
  	} else
  		uset = NULL;
  	return (kern_pselect(td, uap->nd, uap->in, uap->ou, uap->ex, tvp,
  	    uset, NFDBITS));
  }
  
  int
  kern_pselect(struct thread *td, int nd, fd_set *in, fd_set *ou, fd_set *ex,
      struct timeval *tvp, sigset_t *uset, int abi_nfdbits)
  {
  	int error;
  #ifndef FSTACK
  	if (uset != NULL) {
  		error = kern_sigprocmask(td, SIG_SETMASK, uset,
  		    &td->td_oldsigmask, 0);
  		if (error != 0)
  			return (error);
  		td->td_pflags |= TDP_OLDMASK;
  		/*
  		 * Make sure that ast() is called on return to
  		 * usermode and TDP_OLDMASK is cleared, restoring old
  		 * sigmask.
  		 */
  		thread_lock(td);
  		td->td_flags |= TDF_ASTPENDING;
  		thread_unlock(td);
  	}
  #endif
  	error = kern_select(td, nd, in, ou, ex, tvp, abi_nfdbits);
  	return (error);
  }
  
  #ifndef _SYS_SYSPROTO_H_
  struct select_args {
  	int	nd;
  	fd_set	*in, *ou, *ex;
  	struct	timeval *tv;
  };
  #endif
  int
  sys_select(struct thread *td, struct select_args *uap)
  {
  	struct timeval tv, *tvp;
  	int error;
  
  	if (uap->tv != NULL) {
  		error = copyin(uap->tv, &tv, sizeof(tv));
  		if (error)
  			return (error);
  		tvp = &tv;
  	} else
  		tvp = NULL;
  
  	return (kern_select(td, uap->nd, uap->in, uap->ou, uap->ex, tvp,
  	    NFDBITS));
  }
  
  /*
   * In the unlikely case when user specified n greater then the last
   * open file descriptor, check that no bits are set after the last
   * valid fd.  We must return EBADF if any is set.
   *
   * There are applications that rely on the behaviour.
   *
   * nd is fd_lastfile + 1.
   */
  static int
  select_check_badfd(fd_set *fd_in, int nd, int ndu, int abi_nfdbits)
  {
  	char *addr, *oaddr;
  	int b, i, res;
  	uint8_t bits;
  
  	if (nd >= ndu || fd_in == NULL)
  		return (0);
  
  	oaddr = NULL;
  	bits = 0; /* silence gcc */
  	for (i = nd; i < ndu; i++) {
  		b = i / NBBY;
  #if BYTE_ORDER == LITTLE_ENDIAN
  		addr = (char *)fd_in + b;
  #else
  		addr = (char *)fd_in;
  		if (abi_nfdbits == NFDBITS) {
  			addr += rounddown(b, sizeof(fd_mask)) +
  			    sizeof(fd_mask) - 1 - b % sizeof(fd_mask);
  		} else {
  			addr += rounddown(b, sizeof(uint32_t)) +
  			    sizeof(uint32_t) - 1 - b % sizeof(uint32_t);
  		}
  #endif
  		if (addr != oaddr) {
  			res = fubyte(addr);
  			if (res == -1)
  				return (EFAULT);
  			oaddr = addr;
  			bits = res;
  		}
  		if ((bits & (1 << (i % NBBY))) != 0)
  			return (EBADF);
  	}
  	return (0);
  }
  
  int
  kern_select(struct thread *td, int nd, fd_set *fd_in, fd_set *fd_ou,
      fd_set *fd_ex, struct timeval *tvp, int abi_nfdbits)
  {
  	struct filedesc *fdp;
  	/*
  	 * The magic 2048 here is chosen to be just enough for FD_SETSIZE
  	 * infds with the new FD_SETSIZE of 1024, and more than enough for
  	 * FD_SETSIZE infds, outfds and exceptfds with the old FD_SETSIZE
  	 * of 256.
  	 */
  	fd_mask s_selbits[howmany(2048, NFDBITS)];
  	fd_mask *ibits[3], *obits[3], *selbits, *sbp;
  	struct timeval rtv;
  	sbintime_t asbt, precision, rsbt;
  	u_int nbufbytes, ncpbytes, ncpubytes, nfdbits;
  	int error, lf, ndu;
  
  	if (nd < 0)
  		return (EINVAL);
  	fdp = td->td_proc->p_fd;
  	ndu = nd;
  	lf = fdp->fd_lastfile;
  	if (nd > lf + 1)
  		nd = lf + 1;
  
  	error = select_check_badfd(fd_in, nd, ndu, abi_nfdbits);
  	if (error != 0)
  		return (error);
  	error = select_check_badfd(fd_ou, nd, ndu, abi_nfdbits);
  	if (error != 0)
  		return (error);
  	error = select_check_badfd(fd_ex, nd, ndu, abi_nfdbits);
  	if (error != 0)
  		return (error);
  
  	/*
  	 * Allocate just enough bits for the non-null fd_sets.  Use the
  	 * preallocated auto buffer if possible.
  	 */
  	nfdbits = roundup(nd, NFDBITS);
  	ncpbytes = nfdbits / NBBY;
  	ncpubytes = roundup(nd, abi_nfdbits) / NBBY;
  	nbufbytes = 0;
  	if (fd_in != NULL)
  		nbufbytes += 2 * ncpbytes;
  	if (fd_ou != NULL)
  		nbufbytes += 2 * ncpbytes;
  	if (fd_ex != NULL)
  		nbufbytes += 2 * ncpbytes;
  	if (nbufbytes <= sizeof s_selbits)
  		selbits = &s_selbits[0];
  	else
  		selbits = malloc(nbufbytes, M_SELECT, M_WAITOK);
  
  	/*
  	 * Assign pointers into the bit buffers and fetch the input bits.
  	 * Put the output buffers together so that they can be bzeroed
  	 * together.
  	 */
  	sbp = selbits;
  #define	getbits(name, x) \
  	do {								\
  		if (name == NULL) {					\
  			ibits[x] = NULL;				\
  			obits[x] = NULL;				\
  		} else {						\
  			ibits[x] = sbp + nbufbytes / 2 / sizeof *sbp;	\
  			obits[x] = sbp;					\
  			sbp += ncpbytes / sizeof *sbp;			\
  			error = copyin(name, ibits[x], ncpubytes);	\
  			if (error != 0)					\
  				goto done;				\
  			bzero((char *)ibits[x] + ncpubytes,		\
  			    ncpbytes - ncpubytes);			\
  		}							\
  	} while (0)
  	getbits(fd_in, 0);
  	getbits(fd_ou, 1);
  	getbits(fd_ex, 2);
  #undef	getbits
  
  #if BYTE_ORDER == BIG_ENDIAN && defined(__LP64__)
  	/*
  	 * XXX: swizzle_fdset assumes that if abi_nfdbits != NFDBITS,
  	 * we are running under 32-bit emulation. This should be more
  	 * generic.
  	 */
  #define swizzle_fdset(bits)						\
  	if (abi_nfdbits != NFDBITS && bits != NULL) {			\
  		int i;							\
  		for (i = 0; i < ncpbytes / sizeof *sbp; i++)		\
  			bits[i] = (bits[i] >> 32) | (bits[i] << 32);	\
  	}
  #else
  #define swizzle_fdset(bits)
  #endif
  
  	/* Make sure the bit order makes it through an ABI transition */
  	swizzle_fdset(ibits[0]);
  	swizzle_fdset(ibits[1]);
  	swizzle_fdset(ibits[2]);
  	
  	if (nbufbytes != 0)
  		bzero(selbits, nbufbytes / 2);
  
  	precision = 0;
  	if (tvp != NULL) {
  		rtv = *tvp;
  		if (rtv.tv_sec < 0 || rtv.tv_usec < 0 ||
  		    rtv.tv_usec >= 1000000) {
  			error = EINVAL;
  			goto done;
  		}
  		if (!timevalisset(&rtv))
  			asbt = 0;
  		else if (rtv.tv_sec <= INT32_MAX) {
  			rsbt = tvtosbt(rtv);
  			precision = rsbt;
  			precision >>= tc_precexp;
  			if (TIMESEL(&asbt, rsbt))
  				asbt += tc_tick_sbt;
  			if (asbt <= SBT_MAX - rsbt)
  				asbt += rsbt;
  			else
  				asbt = -1;
  		} else
  			asbt = -1;
  	} else
  		asbt = -1;
  	seltdinit(td);
  	/* Iterate until the timeout expires or descriptors become ready. */
  	for (;;) {
  		error = selscan(td, ibits, obits, nd);
  		if (error || td->td_retval[0] != 0)
  			break;
  		error = seltdwait(td, asbt, precision);
  		if (error)
  			break;
  		error = selrescan(td, ibits, obits);
  		if (error || td->td_retval[0] != 0)
  			break;
  	}
  	seltdclear(td);
  
  done:
  	/* select is not restarted after signals... */
  	if (error == ERESTART)
  		error = EINTR;
  	if (error == EWOULDBLOCK)
  		error = 0;
  
  	/* swizzle bit order back, if necessary */
  	swizzle_fdset(obits[0]);
  	swizzle_fdset(obits[1]);
  	swizzle_fdset(obits[2]);
  #undef swizzle_fdset
  
  #define	putbits(name, x) \
  	if (name && (error2 = copyout(obits[x], name, ncpubytes))) \
  		error = error2;
  	if (error == 0) {
  		int error2;
  
  		putbits(fd_in, 0);
  		putbits(fd_ou, 1);
  		putbits(fd_ex, 2);
  #undef putbits
  	}
  	if (selbits != &s_selbits[0])
  		free(selbits, M_SELECT);
  
  	return (error);
  }
  /* 
   * Convert a select bit set to poll flags.
   *
   * The backend always returns POLLHUP/POLLERR if appropriate and we
   * return this as a set bit in any set.
   */
  static int select_flags[3] = {
      POLLRDNORM | POLLHUP | POLLERR,
      POLLWRNORM | POLLHUP | POLLERR,
      POLLRDBAND | POLLERR
  };
  
  /*
   * Compute the fo_poll flags required for a fd given by the index and
   * bit position in the fd_mask array.
   */
  static __inline int
  selflags(fd_mask **ibits, int idx, fd_mask bit)
  {
  	int flags;
  	int msk;
  
  	flags = 0;
  	for (msk = 0; msk < 3; msk++) {
  		if (ibits[msk] == NULL)
  			continue;
  		if ((ibits[msk][idx] & bit) == 0)
  			continue;
  		flags |= select_flags[msk];
  	}
  	return (flags);
  }
  
  /*
   * Set the appropriate output bits given a mask of fired events and the
   * input bits originally requested.
   */
  static __inline int
  selsetbits(fd_mask **ibits, fd_mask **obits, int idx, fd_mask bit, int events)
  {
  	int msk;
  	int n;
  
  	n = 0;
  	for (msk = 0; msk < 3; msk++) {
  		if ((events & select_flags[msk]) == 0)
  			continue;
  		if (ibits[msk] == NULL)
  			continue;
  		if ((ibits[msk][idx] & bit) == 0)
  			continue;
  		/*
  		 * XXX Check for a duplicate set.  This can occur because a
  		 * socket calls selrecord() twice for each poll() call
  		 * resulting in two selfds per real fd.  selrescan() will
  		 * call selsetbits twice as a result.
  		 */
  		if ((obits[msk][idx] & bit) != 0)
  			continue;
  		obits[msk][idx] |= bit;
  		n++;
  	}
  
  	return (n);
  }
  
  static __inline int
  getselfd_cap(struct filedesc *fdp, int fd, struct file **fpp)
  {
  	cap_rights_t rights;
  
  	cap_rights_init(&rights, CAP_EVENT);
  
  	return (fget_unlocked(fdp, fd, &rights, fpp, NULL));
  }
  
  /*
   * Traverse the list of fds attached to this thread's seltd and check for
   * completion.
   */
  static int
  selrescan(struct thread *td, fd_mask **ibits, fd_mask **obits)
  {
  	struct filedesc *fdp;
  	struct selinfo *si;
  	struct seltd *stp;
  	struct selfd *sfp;
  	struct selfd *sfn;
  	struct file *fp;
  	fd_mask bit;
  	int fd, ev, n, idx;
  	int error;
  
  	fdp = td->td_proc->p_fd;
  	stp = td->td_sel;
  	n = 0;
  	STAILQ_FOREACH_SAFE(sfp, &stp->st_selq, sf_link, sfn) {
  		fd = (int)(uintptr_t)sfp->sf_cookie;
  		si = sfp->sf_si;
  		selfdfree(stp, sfp);
  		/* If the selinfo wasn't cleared the event didn't fire. */
  		if (si != NULL)
  			continue;
  		error = getselfd_cap(fdp, fd, &fp);
  		if (error)
  			return (error);
  		idx = fd / NFDBITS;
  		bit = (fd_mask)1 << (fd % NFDBITS);
  		ev = fo_poll(fp, selflags(ibits, idx, bit), td->td_ucred, td);
  		fdrop(fp, td);
  		if (ev != 0)
  			n += selsetbits(ibits, obits, idx, bit, ev);
  	}
  	stp->st_flags = 0;
  	td->td_retval[0] = n;
  	return (0);
  }
  
  /*
   * Perform the initial filedescriptor scan and register ourselves with
   * each selinfo.
   */
  static int
  selscan(td, ibits, obits, nfd)
  	struct thread *td;
  	fd_mask **ibits, **obits;
  	int nfd;
  {
  	struct filedesc *fdp;
  	struct file *fp;
  	fd_mask bit;
  	int ev, flags, end, fd;
  	int n, idx;
  	int error;
  
  	fdp = td->td_proc->p_fd;
  	n = 0;
  	for (idx = 0, fd = 0; fd < nfd; idx++) {
  		end = imin(fd + NFDBITS, nfd);
  		for (bit = 1; fd < end; bit <<= 1, fd++) {
  			/* Compute the list of events we're interested in. */
  			flags = selflags(ibits, idx, bit);
  			if (flags == 0)
  				continue;
  			error = getselfd_cap(fdp, fd, &fp);
  			if (error)
  				return (error);
  			selfdalloc(td, (void *)(uintptr_t)fd);
  			ev = fo_poll(fp, flags, td->td_ucred, td);
  			fdrop(fp, td);
  			if (ev != 0)
  				n += selsetbits(ibits, obits, idx, bit, ev);
  		}
  	}
  
  	td->td_retval[0] = n;
  	return (0);
  }
  
  int
  sys_poll(struct thread *td, struct poll_args *uap)
  {
  	struct timespec ts, *tsp;
  
  	if (uap->timeout != INFTIM) {
  		if (uap->timeout < 0)
  			return (EINVAL);
  		ts.tv_sec = uap->timeout / 1000;
  		ts.tv_nsec = (uap->timeout % 1000) * 1000000;
  		tsp = &ts;
  	} else
  		tsp = NULL;
  
  	return (kern_poll(td, uap->fds, uap->nfds, tsp, NULL));
  }
  
  int
  kern_poll(struct thread *td, struct pollfd *fds, u_int nfds,
      struct timespec *tsp, sigset_t *uset)
  {
  	struct pollfd *bits;
  	struct pollfd smallbits[32];
  	sbintime_t sbt, precision, tmp;
  	time_t over;
  	struct timespec ts;
  	int error;
  	size_t ni;
  
  	precision = 0;
  	if (tsp != NULL) {
  		if (tsp->tv_sec < 0)
  			return (EINVAL);
  		if (tsp->tv_nsec < 0 || tsp->tv_nsec >= 1000000000)
  			return (EINVAL);
  		if (tsp->tv_sec == 0 && tsp->tv_nsec == 0)
  			sbt = 0;
  		else {
  			ts = *tsp;
  			if (ts.tv_sec > INT32_MAX / 2) {
  				over = ts.tv_sec - INT32_MAX / 2;
  				ts.tv_sec -= over;
  			} else
  				over = 0;
  			tmp = tstosbt(ts);
  			precision = tmp;
  			precision >>= tc_precexp;
  			if (TIMESEL(&sbt, tmp))
  				sbt += tc_tick_sbt;
  			sbt += tmp;
  		}
  	} else
  		sbt = -1;
  
  	if (nfds > maxfilesperproc && nfds > FD_SETSIZE) 
  		return (EINVAL);
  	ni = nfds * sizeof(struct pollfd);
  	if (ni > sizeof(smallbits))
  		bits = malloc(ni, M_TEMP, M_WAITOK);
  	else
  		bits = smallbits;
  	error = copyin(fds, bits, ni);
  	if (error)
  		goto done;
  
  #ifndef FSTACK
  	if (uset != NULL) {
  		error = kern_sigprocmask(td, SIG_SETMASK, uset,
  		    &td->td_oldsigmask, 0);
  		if (error)
  			goto done;
  		td->td_pflags |= TDP_OLDMASK;
  		/*
  		 * Make sure that ast() is called on return to
  		 * usermode and TDP_OLDMASK is cleared, restoring old
  		 * sigmask.
  		 */
  		thread_lock(td);
  		td->td_flags |= TDF_ASTPENDING;
  		thread_unlock(td);
  	}
  #endif
  
  	seltdinit(td);
  	/* Iterate until the timeout expires or descriptors become ready. */
  	for (;;) {
  		error = pollscan(td, bits, nfds);
  		if (error || td->td_retval[0] != 0)
  			break;
  		error = seltdwait(td, sbt, precision);
  		if (error)
  			break;
  		error = pollrescan(td);
  		if (error || td->td_retval[0] != 0)
  			break;
  	}
  	seltdclear(td);
  
  done:
  	/* poll is not restarted after signals... */
  	if (error == ERESTART)
  		error = EINTR;
  	if (error == EWOULDBLOCK)
  		error = 0;
  	if (error == 0) {
  		error = pollout(td, bits, fds, nfds);
  		if (error)
  			goto out;
  	}
  out:
  	if (ni > sizeof(smallbits))
  		free(bits, M_TEMP);
  	return (error);
  }
  
  int
  sys_ppoll(struct thread *td, struct ppoll_args *uap)
  {
  	struct timespec ts, *tsp;
  	sigset_t set, *ssp;
  	int error;
  
  	if (uap->ts != NULL) {
  		error = copyin(uap->ts, &ts, sizeof(ts));
  		if (error)
  			return (error);
  		tsp = &ts;
  	} else
  		tsp = NULL;
  	if (uap->set != NULL) {
  		error = copyin(uap->set, &set, sizeof(set));
  		if (error)
  			return (error);
  		ssp = &set;
  	} else
  		ssp = NULL;
  	/*
  	 * fds is still a pointer to user space. kern_poll() will
  	 * take care of copyin that array to the kernel space.
  	 */
  
  	return (kern_poll(td, uap->fds, uap->nfds, tsp, ssp));
  }
  
  static int
  pollrescan(struct thread *td)
  {
  	struct seltd *stp;
  	struct selfd *sfp;
  	struct selfd *sfn;
  	struct selinfo *si;
  	struct filedesc *fdp;
  	struct file *fp;
  	struct pollfd *fd;
  #ifdef CAPABILITIES
  	cap_rights_t rights;
  #endif
  	int n;
  
  	n = 0;
  	fdp = td->td_proc->p_fd;
  	stp = td->td_sel;
  	FILEDESC_SLOCK(fdp);
  	STAILQ_FOREACH_SAFE(sfp, &stp->st_selq, sf_link, sfn) {
  		fd = (struct pollfd *)sfp->sf_cookie;
  		si = sfp->sf_si;
  		selfdfree(stp, sfp);
  		/* If the selinfo wasn't cleared the event didn't fire. */
  		if (si != NULL)
  			continue;
  		fp = fdp->fd_ofiles[fd->fd].fde_file;
  #ifdef CAPABILITIES
  		if (fp == NULL ||
  		    cap_check(cap_rights(fdp, fd->fd),
  		    cap_rights_init(&rights, CAP_EVENT)) != 0)
  #else
  		if (fp == NULL)
  #endif
  		{
  			fd->revents = POLLNVAL;
  			n++;
  			continue;
  		}
  
  		/*
  		 * Note: backend also returns POLLHUP and
  		 * POLLERR if appropriate.
  		 */
  		fd->revents = fo_poll(fp, fd->events, td->td_ucred, td);
  		if (fd->revents != 0)
  			n++;
  	}
  	FILEDESC_SUNLOCK(fdp);
  	stp->st_flags = 0;
  	td->td_retval[0] = n;
  	return (0);
  }
  
  
  static int
  pollout(td, fds, ufds, nfd)
  	struct thread *td;
  	struct pollfd *fds;
  	struct pollfd *ufds;
  	u_int nfd;
  {
  	int error = 0;
  	u_int i = 0;
  	u_int n = 0;
  
  	for (i = 0; i < nfd; i++) {
  		error = copyout(&fds->revents, &ufds->revents,
  		    sizeof(ufds->revents));
  		if (error)
  			return (error);
  		if (fds->revents != 0)
  			n++;
  		fds++;
  		ufds++;
  	}
  	td->td_retval[0] = n;
  	return (0);
  }
  
  static int
  pollscan(td, fds, nfd)
  	struct thread *td;
  	struct pollfd *fds;
  	u_int nfd;
  {
  	struct filedesc *fdp = td->td_proc->p_fd;
  	struct file *fp;
  #ifdef CAPABILITIES
  	cap_rights_t rights;
  #endif
  	int i, n = 0;
  
  	FILEDESC_SLOCK(fdp);
  	for (i = 0; i < nfd; i++, fds++) {
  		if (fds->fd > fdp->fd_lastfile) {
  			fds->revents = POLLNVAL;
  			n++;
  		} else if (fds->fd < 0) {
  			fds->revents = 0;
  		} else {
  			fp = fdp->fd_ofiles[fds->fd].fde_file;
  #ifdef CAPABILITIES
  			if (fp == NULL ||
  			    cap_check(cap_rights(fdp, fds->fd),
  			    cap_rights_init(&rights, CAP_EVENT)) != 0)
  #else
  			if (fp == NULL)
  #endif
  			{
  				fds->revents = POLLNVAL;
  				n++;
  			} else {
  				/*
  				 * Note: backend also returns POLLHUP and
  				 * POLLERR if appropriate.
  				 */
  				selfdalloc(td, fds);
  				fds->revents = fo_poll(fp, fds->events,
  				    td->td_ucred, td);
  				/*
  				 * POSIX requires POLLOUT to be never
  				 * set simultaneously with POLLHUP.
  				 */
  				if ((fds->revents & POLLHUP) != 0)
  					fds->revents &= ~POLLOUT;
  
  				if (fds->revents != 0)
  					n++;
  			}
  		}
  	}
  	FILEDESC_SUNLOCK(fdp);
  	td->td_retval[0] = n;
  	return (0);
  }
  
  /*
   * OpenBSD poll system call.
   *
   * XXX this isn't quite a true representation..  OpenBSD uses select ops.
   */
  #ifndef _SYS_SYSPROTO_H_
  struct openbsd_poll_args {
  	struct pollfd *fds;
  	u_int	nfds;
  	int	timeout;
  };
  #endif
  int
  sys_openbsd_poll(td, uap)
  	register struct thread *td;
  	register struct openbsd_poll_args *uap;
  {
  	return (sys_poll(td, (struct poll_args *)uap));
  }
  
  /*
   * XXX This was created specifically to support netncp and netsmb.  This
   * allows the caller to specify a socket to wait for events on.  It returns
   * 0 if any events matched and an error otherwise.  There is no way to
   * determine which events fired.
   */
  int
  selsocket(struct socket *so, int events, struct timeval *tvp, struct thread *td)
  {
  	struct timeval rtv;
  	sbintime_t asbt, precision, rsbt;
  	int error;
  
  	precision = 0;	/* stupid gcc! */
  	if (tvp != NULL) {
  		rtv = *tvp;
  		if (rtv.tv_sec < 0 || rtv.tv_usec < 0 || 
  		    rtv.tv_usec >= 1000000)
  			return (EINVAL);
  		if (!timevalisset(&rtv))
  			asbt = 0;
  		else if (rtv.tv_sec <= INT32_MAX) {
  			rsbt = tvtosbt(rtv);
  			precision = rsbt;
  			precision >>= tc_precexp;
  			if (TIMESEL(&asbt, rsbt))
  				asbt += tc_tick_sbt;
  			if (asbt <= SBT_MAX - rsbt)
  				asbt += rsbt;
  			else
  				asbt = -1;
  		} else
  			asbt = -1;
  	} else
  		asbt = -1;
  	seltdinit(td);
  	/*
  	 * Iterate until the timeout expires or the socket becomes ready.
  	 */
  	for (;;) {
  		selfdalloc(td, NULL);
  		error = sopoll(so, events, NULL, td);
  		/* error here is actually the ready events. */
  		if (error)
  			return (0);
  		error = seltdwait(td, asbt, precision);
  		if (error)
  			break;
  	}
  	seltdclear(td);
  	/* XXX Duplicates ncp/smb behavior. */
  	if (error == ERESTART)
  		error = 0;
  	return (error);
  }
  
  /*
   * Preallocate two selfds associated with 'cookie'.  Some fo_poll routines
   * have two select sets, one for read and another for write.
   */
  static void
  selfdalloc(struct thread *td, void *cookie)
  {
  	struct seltd *stp;
  
  	stp = td->td_sel;
  	if (stp->st_free1 == NULL)
  		stp->st_free1 = uma_zalloc(selfd_zone, M_WAITOK|M_ZERO);
  	stp->st_free1->sf_td = stp;
  	stp->st_free1->sf_cookie = cookie;
  	if (stp->st_free2 == NULL)
  		stp->st_free2 = uma_zalloc(selfd_zone, M_WAITOK|M_ZERO);
  	stp->st_free2->sf_td = stp;
  	stp->st_free2->sf_cookie = cookie;
  }
  
  static void
  selfdfree(struct seltd *stp, struct selfd *sfp)
  {
  	STAILQ_REMOVE(&stp->st_selq, sfp, selfd, sf_link);
  	if (sfp->sf_si != NULL) {
  		mtx_lock(sfp->sf_mtx);
  		if (sfp->sf_si != NULL) {
  			TAILQ_REMOVE(&sfp->sf_si->si_tdlist, sfp, sf_threads);
  			refcount_release(&sfp->sf_refs);
  		}
  		mtx_unlock(sfp->sf_mtx);
  	}
  	if (refcount_release(&sfp->sf_refs))
  		uma_zfree(selfd_zone, sfp);
  }
  
  /* Drain the waiters tied to all the selfd belonging the specified selinfo. */
  void
  seldrain(sip)
          struct selinfo *sip;
  {
  
  	/*
  	 * This feature is already provided by doselwakeup(), thus it is
  	 * enough to go for it.
  	 * Eventually, the context, should take care to avoid races
  	 * between thread calling select()/poll() and file descriptor
  	 * detaching, but, again, the races are just the same as
  	 * selwakeup().
  	 */
          doselwakeup(sip, -1);
  }
  
  /*
   * Record a select request.
   */
  void
  selrecord(selector, sip)
  	struct thread *selector;
  	struct selinfo *sip;
  {
  	struct selfd *sfp;
  	struct seltd *stp;
  	struct mtx *mtxp;
  
  	stp = selector->td_sel;
  	/*
  	 * Don't record when doing a rescan.
  	 */
  	if (stp->st_flags & SELTD_RESCAN)
  		return;
  	/*
  	 * Grab one of the preallocated descriptors.
  	 */
  	sfp = NULL;
  	if ((sfp = stp->st_free1) != NULL)
  		stp->st_free1 = NULL;
  	else if ((sfp = stp->st_free2) != NULL)
  		stp->st_free2 = NULL;
  	else
  		panic("selrecord: No free selfd on selq");
  	mtxp = sip->si_mtx;
  	if (mtxp == NULL)
  		mtxp = mtx_pool_find(mtxpool_select, sip);
  	/*
  	 * Initialize the sfp and queue it in the thread.
  	 */
  	sfp->sf_si = sip;
  	sfp->sf_mtx = mtxp;
  	refcount_init(&sfp->sf_refs, 2);
  	STAILQ_INSERT_TAIL(&stp->st_selq, sfp, sf_link);
  	/*
  	 * Now that we've locked the sip, check for initialization.
  	 */
  	mtx_lock(mtxp);
  	if (sip->si_mtx == NULL) {
  		sip->si_mtx = mtxp;
  		TAILQ_INIT(&sip->si_tdlist);
  	}
  	/*
  	 * Add this thread to the list of selfds listening on this selinfo.
  	 */
  	TAILQ_INSERT_TAIL(&sip->si_tdlist, sfp, sf_threads);
  	mtx_unlock(sip->si_mtx);
  }
  
  /* Wake up a selecting thread. */
  void
  selwakeup(sip)
  	struct selinfo *sip;
  {
  	doselwakeup(sip, -1);
  }
  
  /* Wake up a selecting thread, and set its priority. */
  void
  selwakeuppri(sip, pri)
  	struct selinfo *sip;
  	int pri;
  {
  	doselwakeup(sip, pri);
  }
  
  /*
   * Do a wakeup when a selectable event occurs.
   */
  static void
  doselwakeup(sip, pri)
  	struct selinfo *sip;
  	int pri;
  {
  	struct selfd *sfp;
  	struct selfd *sfn;
  	struct seltd *stp;
  
  	/* If it's not initialized there can't be any waiters. */
  	if (sip->si_mtx == NULL)
  		return;
  	/*
  	 * Locking the selinfo locks all selfds associated with it.
  	 */
  	mtx_lock(sip->si_mtx);
  	TAILQ_FOREACH_SAFE(sfp, &sip->si_tdlist, sf_threads, sfn) {
  		/*
  		 * Once we remove this sfp from the list and clear the
  		 * sf_si seltdclear will know to ignore this si.
  		 */
  		TAILQ_REMOVE(&sip->si_tdlist, sfp, sf_threads);
  		sfp->sf_si = NULL;
  		stp = sfp->sf_td;
  		mtx_lock(&stp->st_mtx);
  		stp->st_flags |= SELTD_PENDING;
  		cv_broadcastpri(&stp->st_wait, pri);
  		mtx_unlock(&stp->st_mtx);
  		if (refcount_release(&sfp->sf_refs))
  			uma_zfree(selfd_zone, sfp);
  	}
  	mtx_unlock(sip->si_mtx);
  }
  
  static void
  seltdinit(struct thread *td)
  {
  	struct seltd *stp;
  
  	if ((stp = td->td_sel) != NULL)
  		goto out;
  	td->td_sel = stp = malloc(sizeof(*stp), M_SELECT, M_WAITOK|M_ZERO);
  	mtx_init(&stp->st_mtx, "sellck", NULL, MTX_DEF);
  	cv_init(&stp->st_wait, "select");
  out:
  	stp->st_flags = 0;
  	STAILQ_INIT(&stp->st_selq);
  }
  
  static int
  seltdwait(struct thread *td, sbintime_t sbt, sbintime_t precision)
  {
  	struct seltd *stp;
  	int error;
  
  	stp = td->td_sel;
  	/*
  	 * An event of interest may occur while we do not hold the seltd
  	 * locked so check the pending flag before we sleep.
  	 */
  	mtx_lock(&stp->st_mtx);
  	/*
  	 * Any further calls to selrecord will be a rescan.
  	 */
  	stp->st_flags |= SELTD_RESCAN;
  	if (stp->st_flags & SELTD_PENDING) {
  		mtx_unlock(&stp->st_mtx);
  		return (0);
  	}
  	if (sbt == 0)
  		error = EWOULDBLOCK;
  	else if (sbt != -1)
  		error = cv_timedwait_sig_sbt(&stp->st_wait, &stp->st_mtx,
  		    sbt, precision, C_ABSOLUTE);
  	else
  		error = cv_wait_sig(&stp->st_wait, &stp->st_mtx);
  	mtx_unlock(&stp->st_mtx);
  
  	return (error);
  }
  
  void
  seltdfini(struct thread *td)
  {
  	struct seltd *stp;
  
  	stp = td->td_sel;
  	if (stp == NULL)
  		return;
  	if (stp->st_free1)
  		uma_zfree(selfd_zone, stp->st_free1);
  	if (stp->st_free2)
  		uma_zfree(selfd_zone, stp->st_free2);
  	td->td_sel = NULL;
  	free(stp, M_SELECT);
  }
  
  /*
   * Remove the references to the thread from all of the objects we were
   * polling.
   */
  static void
  seltdclear(struct thread *td)
  {
  	struct seltd *stp;
  	struct selfd *sfp;
  	struct selfd *sfn;
  
  	stp = td->td_sel;
  	STAILQ_FOREACH_SAFE(sfp, &stp->st_selq, sf_link, sfn)
  		selfdfree(stp, sfp);
  	stp->st_flags = 0;
  }
  
  static void selectinit(void *);
  SYSINIT(select, SI_SUB_SYSCALLS, SI_ORDER_ANY, selectinit, NULL);
  static void
  selectinit(void *dummy __unused)
  {
  
  	selfd_zone = uma_zcreate("selfd", sizeof(struct selfd), NULL, NULL,
  	    NULL, NULL, UMA_ALIGN_PTR, 0);
  	mtxpool_select = mtx_pool_create("select mtxpool", 128, MTX_DEF);
  }
  
  /*
   * Set up a syscall return value that follows the convention specified for
   * posix_* functions.
   */
  int
  kern_posix_error(struct thread *td, int error)
  {
  
  	if (error <= 0)
  		return (error);
  	td->td_errno = error;
  	td->td_pflags |= TDP_NERRNO;
  	td->td_retval[0] = error;
  	return (0);
  }
  