cc3116a938
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
96 lines
2.9 KiB
C
96 lines
2.9 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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#ifndef lint
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__FBSDID("$FreeBSD$");
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#endif /* not lint */
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#include "namespace.h"
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#include <sys/param.h>
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#include <sys/ioctl.h>
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#include <errno.h>
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#include <paths.h>
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#include "un-namespace.h"
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/*
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* __isptmaster(): return whether the file descriptor refers to a
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* pseudo-terminal master device.
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*/
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static int
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__isptmaster(int fildes)
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{
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if (_ioctl(fildes, TIOCPTMASTER) == 0)
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return (0);
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if (errno != EBADF)
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errno = EINVAL;
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return (-1);
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}
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/*
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* In our implementation, grantpt() and unlockpt() don't actually have
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* any use, because PTY's are created on the fly and already have proper
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* permissions upon creation.
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*
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* Just make sure `fildes' actually points to a real PTY master device.
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*/
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__strong_reference(__isptmaster, grantpt);
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__strong_reference(__isptmaster, unlockpt);
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/*
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* ptsname(): return the pathname of the slave pseudo-terminal device
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* associated with the specified master.
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*/
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char *
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ptsname(int fildes)
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{
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static char pt_slave[sizeof _PATH_DEV + SPECNAMELEN] = _PATH_DEV;
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struct fiodgname_arg fgn;
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char *ret = NULL;
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int sverrno = errno;
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/* Make sure fildes points to a master device. */
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if (__isptmaster(fildes) != 0)
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goto done;
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/* Obtain the device name through FIODGNAME. */
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fgn.len = sizeof pt_slave - (sizeof _PATH_DEV - 1);
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fgn.buf = pt_slave + (sizeof _PATH_DEV - 1);
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if (_ioctl(fildes, FIODGNAME, &fgn) == 0)
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ret = pt_slave;
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done: /* Make sure ptsname() does not overwrite errno. */
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errno = sverrno;
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return (ret);
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}
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