freebsd-src/sys/kern/tty_tty.c
Kirk McKusick f2a2857bb3 Add snapshots to the fast filesystem. Most of the changes support
the gating of system calls that cause modifications to the underlying
filesystem. The gating can be enabled by any filesystem that needs
to consistently suspend operations by adding the vop_stdgetwritemount
to their set of vnops. Once gating is enabled, the function
vfs_write_suspend stops all new write operations to a filesystem,
allows any filesystem modifying system calls already in progress
to complete, then sync's the filesystem to disk and returns. The
function vfs_write_resume allows the suspended write operations to
begin again. Gating is not added by default for all filesystems as
for SMP systems it adds two extra locks to such critical kernel
paths as the write system call. Thus, gating should only be added
as needed.

Details on the use and current status of snapshots in FFS can be
found in /sys/ufs/ffs/README.snapshot so for brevity and timelyness
is not included here. Unless and until you create a snapshot file,
these changes should have no effect on your system (famous last words).
2000-07-11 22:07:57 +00:00

202 lines
5.4 KiB
C

/*-
* Copyright (c) 1982, 1986, 1991, 1993
* The Regents of the University of California. All rights reserved.
*
* Redistribution and use in source and binary forms, with or without
* modification, are permitted provided that the following conditions
* are met:
* 1. Redistributions of source code must retain the above copyright
* notice, this list of conditions and the following disclaimer.
* 2. Redistributions in binary form must reproduce the above copyright
* notice, this list of conditions and the following disclaimer in the
* documentation and/or other materials provided with the distribution.
* 3. All advertising materials mentioning features or use of this software
* must display the following acknowledgement:
* This product includes software developed by the University of
* California, Berkeley and its contributors.
* 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.
*
* @(#)tty_tty.c 8.2 (Berkeley) 9/23/93
* $FreeBSD$
*/
/*
* Indirect driver for controlling tty.
*/
#include <sys/param.h>
#include <sys/systm.h>
#include <sys/conf.h>
#include <sys/lock.h>
#include <sys/proc.h>
#include <sys/ttycom.h>
#include <sys/vnode.h>
#include <sys/kernel.h>
static d_open_t cttyopen;
static d_read_t cttyread;
static d_write_t cttywrite;
static d_ioctl_t cttyioctl;
static d_poll_t cttypoll;
#define CDEV_MAJOR 1
/* Don't make this static, since fdesc_vnops uses it. */
struct cdevsw ctty_cdevsw = {
/* open */ cttyopen,
/* close */ nullclose,
/* read */ cttyread,
/* write */ cttywrite,
/* ioctl */ cttyioctl,
/* poll */ cttypoll,
/* mmap */ nommap,
/* strategy */ nostrategy,
/* name */ "ctty",
/* maj */ CDEV_MAJOR,
/* dump */ nodump,
/* psize */ nopsize,
/* flags */ D_TTY,
/* bmaj */ -1
};
#define cttyvp(p) ((p)->p_flag & P_CONTROLT ? (p)->p_session->s_ttyvp : NULL)
/*ARGSUSED*/
static int
cttyopen(dev, flag, mode, p)
dev_t dev;
int flag, mode;
struct proc *p;
{
struct vnode *ttyvp = cttyvp(p);
int error;
if (ttyvp == NULL)
return (ENXIO);
vn_lock(ttyvp, LK_EXCLUSIVE | LK_RETRY, p);
#ifdef PARANOID
/*
* Since group is tty and mode is 620 on most terminal lines
* and since sessions protect terminals from processes outside
* your session, this check is probably no longer necessary.
* Since it inhibits setuid root programs that later switch
* to another user from accessing /dev/tty, we have decided
* to delete this test. (mckusick 5/93)
*/
error = VOP_ACCESS(ttyvp,
(flag&FREAD ? VREAD : 0) | (flag&FWRITE ? VWRITE : 0), p->p_ucred, p);
if (!error)
#endif /* PARANOID */
error = VOP_OPEN(ttyvp, flag, NOCRED, p);
VOP_UNLOCK(ttyvp, 0, p);
return (error);
}
/*ARGSUSED*/
static int
cttyread(dev, uio, flag)
dev_t dev;
struct uio *uio;
int flag;
{
struct proc *p = uio->uio_procp;
register struct vnode *ttyvp = cttyvp(p);
int error;
if (ttyvp == NULL)
return (EIO);
vn_lock(ttyvp, LK_EXCLUSIVE | LK_RETRY, p);
error = VOP_READ(ttyvp, uio, flag, NOCRED);
VOP_UNLOCK(ttyvp, 0, p);
return (error);
}
/*ARGSUSED*/
static int
cttywrite(dev, uio, flag)
dev_t dev;
struct uio *uio;
int flag;
{
struct proc *p = uio->uio_procp;
struct vnode *ttyvp = cttyvp(uio->uio_procp);
struct mount *mp;
int error;
if (ttyvp == NULL)
return (EIO);
mp = NULL;
if (ttyvp->v_type != VCHR &&
(error = vn_start_write(ttyvp, &mp, V_WAIT | PCATCH)) != 0)
return (error);
vn_lock(ttyvp, LK_EXCLUSIVE | LK_RETRY, p);
error = VOP_WRITE(ttyvp, uio, flag, NOCRED);
VOP_UNLOCK(ttyvp, 0, p);
vn_finished_write(mp);
return (error);
}
/*ARGSUSED*/
static int
cttyioctl(dev, cmd, addr, flag, p)
dev_t dev;
u_long cmd;
caddr_t addr;
int flag;
struct proc *p;
{
struct vnode *ttyvp = cttyvp(p);
if (ttyvp == NULL)
return (EIO);
if (cmd == TIOCSCTTY) /* don't allow controlling tty to be set */
return EINVAL; /* to controlling tty -- infinite recursion */
if (cmd == TIOCNOTTY) {
if (!SESS_LEADER(p)) {
p->p_flag &= ~P_CONTROLT;
return (0);
} else
return (EINVAL);
}
return (VOP_IOCTL(ttyvp, cmd, addr, flag, NOCRED, p));
}
/*ARGSUSED*/
static int
cttypoll(dev, events, p)
dev_t dev;
int events;
struct proc *p;
{
struct vnode *ttyvp = cttyvp(p);
if (ttyvp == NULL)
/* try operation to get EOF/failure */
return (seltrue(dev, events, p));
return (VOP_POLL(ttyvp, events, p->p_ucred, p));
}
static void ctty_drvinit __P((void *unused));
static void
ctty_drvinit(unused)
void *unused;
{
make_dev(&ctty_cdevsw, 0, 0, 0, 0666, "tty");
}
SYSINIT(cttydev,SI_SUB_DRIVERS,SI_ORDER_MIDDLE+CDEV_MAJOR,ctty_drvinit,NULL)