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/arch/um/drivers/chan_user.c

https://bitbucket.org/thekraven/iscream_thunderc-2.6.35
C | 298 lines | 200 code | 42 blank | 56 comment | 45 complexity | 3902d356196fd8bd3dcc4a88df6e9280 MD5 | raw file
Possible License(s): GPL-2.0, LGPL-2.0, AGPL-1.0
  1/*
  2 * Copyright (C) 2000 - 2007 Jeff Dike (jdike@{linux.intel,addtoit}.com)
  3 * Licensed under the GPL
  4 */
  5
  6#include <stdlib.h>
  7#include <unistd.h>
  8#include <errno.h>
  9#include <sched.h>
 10#include <signal.h>
 11#include <termios.h>
 12#include <sys/ioctl.h>
 13#include "chan_user.h"
 14#include "kern_constants.h"
 15#include "os.h"
 16#include "um_malloc.h"
 17#include "user.h"
 18
 19void generic_close(int fd, void *unused)
 20{
 21	close(fd);
 22}
 23
 24int generic_read(int fd, char *c_out, void *unused)
 25{
 26	int n;
 27
 28	n = read(fd, c_out, sizeof(*c_out));
 29	if (n > 0)
 30		return n;
 31	else if (errno == EAGAIN)
 32		return 0;
 33	else if (n == 0)
 34		return -EIO;
 35	return -errno;
 36}
 37
 38/* XXX Trivial wrapper around write */
 39
 40int generic_write(int fd, const char *buf, int n, void *unused)
 41{
 42	int err;
 43
 44	err = write(fd, buf, n);
 45	if (err > 0)
 46		return err;
 47	else if (errno == EAGAIN)
 48		return 0;
 49	else if (err == 0)
 50		return -EIO;
 51	return -errno;
 52}
 53
 54int generic_window_size(int fd, void *unused, unsigned short *rows_out,
 55			unsigned short *cols_out)
 56{
 57	struct winsize size;
 58	int ret;
 59
 60	if (ioctl(fd, TIOCGWINSZ, &size) < 0)
 61		return -errno;
 62
 63	ret = ((*rows_out != size.ws_row) || (*cols_out != size.ws_col));
 64
 65	*rows_out = size.ws_row;
 66	*cols_out = size.ws_col;
 67
 68	return ret;
 69}
 70
 71void generic_free(void *data)
 72{
 73	kfree(data);
 74}
 75
 76int generic_console_write(int fd, const char *buf, int n)
 77{
 78	sigset_t old, no_sigio;
 79	struct termios save, new;
 80	int err;
 81
 82	if (isatty(fd)) {
 83		sigemptyset(&no_sigio);
 84		sigaddset(&no_sigio, SIGIO);
 85		if (sigprocmask(SIG_BLOCK, &no_sigio, &old))
 86			goto error;
 87
 88		CATCH_EINTR(err = tcgetattr(fd, &save));
 89		if (err)
 90			goto error;
 91		new = save;
 92		/*
 93		 * The terminal becomes a bit less raw, to handle \n also as
 94		 * "Carriage Return", not only as "New Line". Otherwise, the new
 95		 * line won't start at the first column.
 96		 */
 97		new.c_oflag |= OPOST;
 98		CATCH_EINTR(err = tcsetattr(fd, TCSAFLUSH, &new));
 99		if (err)
100			goto error;
101	}
102	err = generic_write(fd, buf, n, NULL);
103	/*
104	 * Restore raw mode, in any case; we *must* ignore any error apart
105	 * EINTR, except for debug.
106	 */
107	if (isatty(fd)) {
108		CATCH_EINTR(tcsetattr(fd, TCSAFLUSH, &save));
109		sigprocmask(SIG_SETMASK, &old, NULL);
110	}
111
112	return err;
113error:
114	return -errno;
115}
116
117/*
118 * UML SIGWINCH handling
119 *
120 * The point of this is to handle SIGWINCH on consoles which have host
121 * ttys and relay them inside UML to whatever might be running on the
122 * console and cares about the window size (since SIGWINCH notifies
123 * about terminal size changes).
124 *
125 * So, we have a separate thread for each host tty attached to a UML
126 * device (side-issue - I'm annoyed that one thread can't have
127 * multiple controlling ttys for the purpose of handling SIGWINCH, but
128 * I imagine there are other reasons that doesn't make any sense).
129 *
130 * SIGWINCH can't be received synchronously, so you have to set up to
131 * receive it as a signal.  That being the case, if you are going to
132 * wait for it, it is convenient to sit in sigsuspend() and wait for
133 * the signal to bounce you out of it (see below for how we make sure
134 * to exit only on SIGWINCH).
135 */
136
137static void winch_handler(int sig)
138{
139}
140
141struct winch_data {
142	int pty_fd;
143	int pipe_fd;
144};
145
146static int winch_thread(void *arg)
147{
148	struct winch_data *data = arg;
149	sigset_t sigs;
150	int pty_fd, pipe_fd;
151	int count;
152	char c = 1;
153
154	pty_fd = data->pty_fd;
155	pipe_fd = data->pipe_fd;
156	count = write(pipe_fd, &c, sizeof(c));
157	if (count != sizeof(c))
158		printk(UM_KERN_ERR "winch_thread : failed to write "
159		       "synchronization byte, err = %d\n", -count);
160
161	/*
162	 * We are not using SIG_IGN on purpose, so don't fix it as I thought to
163	 * do! If using SIG_IGN, the sigsuspend() call below would not stop on
164	 * SIGWINCH.
165	 */
166
167	signal(SIGWINCH, winch_handler);
168	sigfillset(&sigs);
169	/* Block all signals possible. */
170	if (sigprocmask(SIG_SETMASK, &sigs, NULL) < 0) {
171		printk(UM_KERN_ERR "winch_thread : sigprocmask failed, "
172		       "errno = %d\n", errno);
173		exit(1);
174	}
175	/* In sigsuspend(), block anything else than SIGWINCH. */
176	sigdelset(&sigs, SIGWINCH);
177
178	if (setsid() < 0) {
179		printk(UM_KERN_ERR "winch_thread : setsid failed, errno = %d\n",
180		       errno);
181		exit(1);
182	}
183
184	if (ioctl(pty_fd, TIOCSCTTY, 0) < 0) {
185		printk(UM_KERN_ERR "winch_thread : TIOCSCTTY failed on "
186		       "fd %d err = %d\n", pty_fd, errno);
187		exit(1);
188	}
189
190	if (tcsetpgrp(pty_fd, os_getpid()) < 0) {
191		printk(UM_KERN_ERR "winch_thread : tcsetpgrp failed on "
192		       "fd %d err = %d\n", pty_fd, errno);
193		exit(1);
194	}
195
196	/*
197	 * These are synchronization calls between various UML threads on the
198	 * host - since they are not different kernel threads, we cannot use
199	 * kernel semaphores. We don't use SysV semaphores because they are
200	 * persistent.
201	 */
202	count = read(pipe_fd, &c, sizeof(c));
203	if (count != sizeof(c))
204		printk(UM_KERN_ERR "winch_thread : failed to read "
205		       "synchronization byte, err = %d\n", errno);
206
207	while(1) {
208		/*
209		 * This will be interrupted by SIGWINCH only, since
210		 * other signals are blocked.
211		 */
212		sigsuspend(&sigs);
213
214		count = write(pipe_fd, &c, sizeof(c));
215		if (count != sizeof(c))
216			printk(UM_KERN_ERR "winch_thread : write failed, "
217			       "err = %d\n", errno);
218	}
219}
220
221static int winch_tramp(int fd, struct tty_struct *tty, int *fd_out,
222		       unsigned long *stack_out)
223{
224	struct winch_data data;
225	int fds[2], n, err;
226	char c;
227
228	err = os_pipe(fds, 1, 1);
229	if (err < 0) {
230		printk(UM_KERN_ERR "winch_tramp : os_pipe failed, err = %d\n",
231		       -err);
232		goto out;
233	}
234
235	data = ((struct winch_data) { .pty_fd 		= fd,
236				      .pipe_fd 		= fds[1] } );
237	/*
238	 * CLONE_FILES so this thread doesn't hold open files which are open
239	 * now, but later closed in a different thread.  This is a
240	 * problem with /dev/net/tun, which if held open by this
241	 * thread, prevents the TUN/TAP device from being reused.
242	 */
243	err = run_helper_thread(winch_thread, &data, CLONE_FILES, stack_out);
244	if (err < 0) {
245		printk(UM_KERN_ERR "fork of winch_thread failed - errno = %d\n",
246		       -err);
247		goto out_close;
248	}
249
250	*fd_out = fds[0];
251	n = read(fds[0], &c, sizeof(c));
252	if (n != sizeof(c)) {
253		printk(UM_KERN_ERR "winch_tramp : failed to read "
254		       "synchronization byte\n");
255		printk(UM_KERN_ERR "read failed, err = %d\n", errno);
256		printk(UM_KERN_ERR "fd %d will not support SIGWINCH\n", fd);
257		err = -EINVAL;
258		goto out_close;
259	}
260
261	if (os_set_fd_block(*fd_out, 0)) {
262		printk(UM_KERN_ERR "winch_tramp: failed to set thread_fd "
263		       "non-blocking.\n");
264		goto out_close;
265	}
266
267	return err;
268
269 out_close:
270	close(fds[1]);
271	close(fds[0]);
272 out:
273	return err;
274}
275
276void register_winch(int fd, struct tty_struct *tty)
277{
278	unsigned long stack;
279	int pid, thread, count, thread_fd = -1;
280	char c = 1;
281
282	if (!isatty(fd))
283		return;
284
285	pid = tcgetpgrp(fd);
286	if (!is_skas_winch(pid, fd, tty) && (pid == -1)) {
287		thread = winch_tramp(fd, tty, &thread_fd, &stack);
288		if (thread < 0)
289			return;
290
291		register_winch_irq(thread_fd, fd, thread, tty, stack);
292
293		count = write(thread_fd, &c, sizeof(c));
294		if (count != sizeof(c))
295			printk(UM_KERN_ERR "register_winch : failed to write "
296			       "synchronization byte, err = %d\n", errno);
297	}
298}