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
generic_close(int fd,void * unused)19 void generic_close(int fd, void *unused)
20 {
21 close(fd);
22 }
23
generic_read(int fd,char * c_out,void * unused)24 int 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
generic_write(int fd,const char * buf,int n,void * unused)40 int 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
generic_window_size(int fd,void * unused,unsigned short * rows_out,unsigned short * cols_out)54 int 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
generic_free(void * data)71 void generic_free(void *data)
72 {
73 kfree(data);
74 }
75
generic_console_write(int fd,const char * buf,int n)76 int 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;
113 error:
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
winch_handler(int sig)137 static void winch_handler(int sig)
138 {
139 }
140
141 struct winch_data {
142 int pty_fd;
143 int pipe_fd;
144 };
145
winch_thread(void * arg)146 static 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
winch_tramp(int fd,struct tty_struct * tty,int * fd_out,unsigned long * stack_out)221 static 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
register_winch(int fd,struct tty_struct * tty)276 void 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 }
299