bc093719ca
The last half year I've been working on a replacement TTY layer for the FreeBSD kernel. The new TTY layer was designed to improve the following: - Improved driver model: The old TTY layer has a driver model that is not abstract enough to make it friendly to use. A good example is the output path, where the device drivers directly access the output buffers. This means that an in-kernel PPP implementation must always convert network buffers into TTY buffers. If a PPP implementation would be built on top of the new TTY layer (still needs a hooks layer, though), it would allow the PPP implementation to directly hand the data to the TTY driver. - Improved hotplugging: With the old TTY layer, it isn't entirely safe to destroy TTY's from the system. This implementation has a two-step destructing design, where the driver first abandons the TTY. After all threads have left the TTY, the TTY layer calls a routine in the driver, which can be used to free resources (unit numbers, etc). The pts(4) driver also implements this feature, which means posix_openpt() will now return PTY's that are created on the fly. - Improved performance: One of the major improvements is the per-TTY mutex, which is expected to improve scalability when compared to the old Giant locking. Another change is the unbuffered copying to userspace, which is both used on TTY device nodes and PTY masters. Upgrading should be quite straightforward. Unlike previous versions, existing kernel configuration files do not need to be changed, except when they reference device drivers that are listed in UPDATING. Obtained from: //depot/projects/mpsafetty/... Approved by: philip (ex-mentor) Discussed: on the lists, at BSDCan, at the DevSummit Sponsored by: Snow B.V., the Netherlands dcons(4) fixed by: kan
126 lines
3.7 KiB
C
126 lines
3.7 KiB
C
/*-
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* Copyright (c) 2008 Ed Schouten <ed@FreeBSD.org>
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* All rights reserved.
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*
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* Portions of this software were developed under sponsorship from Snow
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* B.V., the Netherlands.
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*
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* Redistribution and use in source and binary forms, with or without
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* modification, are permitted provided that the following conditions
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* are met:
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* 1. Redistributions of source code must retain the above copyright
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* notice, this list of conditions and the following disclaimer.
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* 2. Redistributions in binary form must reproduce the above copyright
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* notice, this list of conditions and the following disclaimer in the
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* documentation and/or other materials provided with the distribution.
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*
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* THIS SOFTWARE IS PROVIDED BY THE AUTHOR AND CONTRIBUTORS ``AS IS'' AND
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* ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
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* IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
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* ARE DISCLAIMED. IN NO EVENT SHALL THE AUTHOR OR CONTRIBUTORS BE LIABLE
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* FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
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* DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
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* OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
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* HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
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* LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
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* OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
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* SUCH DAMAGE.
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*/
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#include <sys/cdefs.h>
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__FBSDID("$FreeBSD$");
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#include <sys/param.h>
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#include <sys/conf.h>
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#include <sys/eventhandler.h>
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#include <sys/fcntl.h>
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#include <sys/kernel.h>
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#include <sys/proc.h>
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#include <sys/systm.h>
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#include <sys/tty.h>
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/*
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* This driver implements a BSD-style compatibility naming scheme for
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* the pts(4) driver. We just call into pts(4) to create the actual PTY.
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* To make sure we don't use the same PTY multiple times, we abuse
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* si_drv1 inside the cdev to mark whether the PTY is in use.
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*/
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static int pty_warningcnt = 10;
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static int
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ptydev_fdopen(struct cdev *dev, int fflags, struct thread *td, struct file *fp)
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{
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int u, error;
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char name[] = "ttyXX";
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if (!atomic_cmpset_ptr((uintptr_t *)&dev->si_drv1, 0, 1))
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return (EBUSY);
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/* Generate device name and create PTY. */
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u = dev2unit(dev);
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name[3] = u >> 8;
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name[4] = u;
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error = pts_alloc_external(fflags & (FREAD|FWRITE), td, fp, dev, name);
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if (error != 0) {
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destroy_dev_sched(dev);
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return (error);
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}
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/* Raise a warning when a legacy PTY has been allocated. */
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if (pty_warningcnt > 0) {
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pty_warningcnt--;
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printf("pid %d (%s) is using legacy pty devices%s\n",
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td->td_proc->p_pid, td->td_name,
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pty_warningcnt ? "" : " - not logging anymore");
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}
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return (0);
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}
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static struct cdevsw ptydev_cdevsw = {
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.d_version = D_VERSION,
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.d_fdopen = ptydev_fdopen,
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.d_name = "ptydev",
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};
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static void
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pty_clone(void *arg, struct ucred *cr, char *name, int namelen,
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struct cdev **dev)
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{
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int u;
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/* Cloning is already satisfied. */
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if (*dev != NULL)
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return;
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/* Only catch /dev/ptyXX. */
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if (namelen != 5 || bcmp(name, "pty", 3) != 0)
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return;
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/* Only catch /dev/pty[l-sL-S]X. */
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if (!(name[3] >= 'l' && name[3] <= 's') &&
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!(name[3] >= 'L' && name[3] <= 'S'))
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return;
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/* Only catch /dev/pty[l-sL-S][0-9a-v]. */
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if (!(name[4] >= '0' && name[4] <= '9') &&
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!(name[4] >= 'a' && name[4] <= 'v'))
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return;
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/* Create the controller device node. */
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u = (unsigned int)name[3] << 8 | name[4];
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*dev = make_dev_credf(MAKEDEV_REF, &ptydev_cdevsw, u,
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NULL, UID_ROOT, GID_WHEEL, 0666, name);
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}
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static void
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pty_init(void *unused)
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{
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EVENTHANDLER_REGISTER(dev_clone, pty_clone, 0, 1000);
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}
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SYSINIT(pty, SI_SUB_DRIVERS, SI_ORDER_MIDDLE, pty_init, NULL);
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