Line data Source code
1 : // SPDX-License-Identifier: GPL-2.0
2 : /*
3 : * Copyright (C) 2000 - 2007 Jeff Dike (jdike@{linux.intel,addtoit}.com)
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 <os.h>
15 : #include <um_malloc.h>
16 :
17 0 : void generic_close(int fd, void *unused)
18 : {
19 0 : close(fd);
20 0 : }
21 :
22 0 : int generic_read(int fd, char *c_out, void *unused)
23 : {
24 : int n;
25 :
26 0 : n = read(fd, c_out, sizeof(*c_out));
27 0 : if (n > 0)
28 : return n;
29 0 : else if (n == 0)
30 : return -EIO;
31 0 : else if (errno == EAGAIN)
32 : return 0;
33 0 : return -errno;
34 : }
35 :
36 : /* XXX Trivial wrapper around write */
37 :
38 746 : int generic_write(int fd, const char *buf, int n, void *unused)
39 : {
40 : int err;
41 :
42 746 : err = write(fd, buf, n);
43 746 : if (err > 0)
44 : return err;
45 0 : else if (errno == EAGAIN)
46 : return 0;
47 0 : else if (err == 0)
48 : return -EIO;
49 0 : return -errno;
50 : }
51 :
52 0 : int generic_window_size(int fd, void *unused, unsigned short *rows_out,
53 : unsigned short *cols_out)
54 : {
55 : struct winsize size;
56 : int ret;
57 :
58 0 : if (ioctl(fd, TIOCGWINSZ, &size) < 0)
59 0 : return -errno;
60 :
61 0 : ret = ((*rows_out != size.ws_row) || (*cols_out != size.ws_col));
62 :
63 0 : *rows_out = size.ws_row;
64 0 : *cols_out = size.ws_col;
65 :
66 0 : return ret;
67 : }
68 :
69 0 : void generic_free(void *data)
70 : {
71 0 : kfree(data);
72 0 : }
73 :
74 746 : int generic_console_write(int fd, const char *buf, int n)
75 : {
76 : sigset_t old, no_sigio;
77 : struct termios save, new;
78 : int err;
79 :
80 746 : if (isatty(fd)) {
81 0 : sigemptyset(&no_sigio);
82 0 : sigaddset(&no_sigio, SIGIO);
83 0 : if (sigprocmask(SIG_BLOCK, &no_sigio, &old))
84 : goto error;
85 :
86 0 : CATCH_EINTR(err = tcgetattr(fd, &save));
87 0 : if (err)
88 : goto error;
89 0 : new = save;
90 : /*
91 : * The terminal becomes a bit less raw, to handle \n also as
92 : * "Carriage Return", not only as "New Line". Otherwise, the new
93 : * line won't start at the first column.
94 : */
95 0 : new.c_oflag |= OPOST;
96 0 : CATCH_EINTR(err = tcsetattr(fd, TCSAFLUSH, &new));
97 0 : if (err)
98 : goto error;
99 : }
100 746 : err = generic_write(fd, buf, n, NULL);
101 : /*
102 : * Restore raw mode, in any case; we *must* ignore any error apart
103 : * EINTR, except for debug.
104 : */
105 746 : if (isatty(fd)) {
106 0 : CATCH_EINTR(tcsetattr(fd, TCSAFLUSH, &save));
107 0 : sigprocmask(SIG_SETMASK, &old, NULL);
108 : }
109 :
110 : return err;
111 : error:
112 0 : return -errno;
113 : }
114 :
115 : /*
116 : * UML SIGWINCH handling
117 : *
118 : * The point of this is to handle SIGWINCH on consoles which have host
119 : * ttys and relay them inside UML to whatever might be running on the
120 : * console and cares about the window size (since SIGWINCH notifies
121 : * about terminal size changes).
122 : *
123 : * So, we have a separate thread for each host tty attached to a UML
124 : * device (side-issue - I'm annoyed that one thread can't have
125 : * multiple controlling ttys for the purpose of handling SIGWINCH, but
126 : * I imagine there are other reasons that doesn't make any sense).
127 : *
128 : * SIGWINCH can't be received synchronously, so you have to set up to
129 : * receive it as a signal. That being the case, if you are going to
130 : * wait for it, it is convenient to sit in sigsuspend() and wait for
131 : * the signal to bounce you out of it (see below for how we make sure
132 : * to exit only on SIGWINCH).
133 : */
134 :
135 0 : static void winch_handler(int sig)
136 : {
137 0 : }
138 :
139 : struct winch_data {
140 : int pty_fd;
141 : int pipe_fd;
142 : };
143 :
144 0 : static int winch_thread(void *arg)
145 : {
146 0 : struct winch_data *data = arg;
147 : sigset_t sigs;
148 : int pty_fd, pipe_fd;
149 : int count;
150 0 : char c = 1;
151 :
152 0 : pty_fd = data->pty_fd;
153 0 : pipe_fd = data->pipe_fd;
154 0 : count = write(pipe_fd, &c, sizeof(c));
155 0 : if (count != sizeof(c))
156 0 : printk(UM_KERN_ERR "winch_thread : failed to write "
157 : "synchronization byte, err = %d\n", -count);
158 :
159 : /*
160 : * We are not using SIG_IGN on purpose, so don't fix it as I thought to
161 : * do! If using SIG_IGN, the sigsuspend() call below would not stop on
162 : * SIGWINCH.
163 : */
164 :
165 0 : signal(SIGWINCH, winch_handler);
166 0 : sigfillset(&sigs);
167 : /* Block all signals possible. */
168 0 : if (sigprocmask(SIG_SETMASK, &sigs, NULL) < 0) {
169 0 : printk(UM_KERN_ERR "winch_thread : sigprocmask failed, "
170 : "errno = %d\n", errno);
171 0 : exit(1);
172 : }
173 : /* In sigsuspend(), block anything else than SIGWINCH. */
174 0 : sigdelset(&sigs, SIGWINCH);
175 :
176 0 : if (setsid() < 0) {
177 0 : printk(UM_KERN_ERR "winch_thread : setsid failed, errno = %d\n",
178 : errno);
179 0 : exit(1);
180 : }
181 :
182 0 : if (ioctl(pty_fd, TIOCSCTTY, 0) < 0) {
183 0 : printk(UM_KERN_ERR "winch_thread : TIOCSCTTY failed on "
184 : "fd %d err = %d\n", pty_fd, errno);
185 0 : exit(1);
186 : }
187 :
188 0 : if (tcsetpgrp(pty_fd, os_getpid()) < 0) {
189 0 : printk(UM_KERN_ERR "winch_thread : tcsetpgrp failed on "
190 : "fd %d err = %d\n", pty_fd, errno);
191 0 : exit(1);
192 : }
193 :
194 : /*
195 : * These are synchronization calls between various UML threads on the
196 : * host - since they are not different kernel threads, we cannot use
197 : * kernel semaphores. We don't use SysV semaphores because they are
198 : * persistent.
199 : */
200 0 : count = read(pipe_fd, &c, sizeof(c));
201 0 : if (count != sizeof(c))
202 0 : printk(UM_KERN_ERR "winch_thread : failed to read "
203 : "synchronization byte, err = %d\n", errno);
204 :
205 : while(1) {
206 : /*
207 : * This will be interrupted by SIGWINCH only, since
208 : * other signals are blocked.
209 : */
210 0 : sigsuspend(&sigs);
211 :
212 0 : count = write(pipe_fd, &c, sizeof(c));
213 0 : if (count != sizeof(c))
214 0 : printk(UM_KERN_ERR "winch_thread : write failed, "
215 : "err = %d\n", errno);
216 : }
217 : }
218 :
219 0 : static int winch_tramp(int fd, struct tty_port *port, int *fd_out,
220 : unsigned long *stack_out)
221 : {
222 : struct winch_data data;
223 : int fds[2], n, err, pid;
224 : char c;
225 :
226 0 : err = os_pipe(fds, 1, 1);
227 0 : if (err < 0) {
228 0 : printk(UM_KERN_ERR "winch_tramp : os_pipe failed, err = %d\n",
229 : -err);
230 : goto out;
231 : }
232 :
233 0 : data = ((struct winch_data) { .pty_fd = fd,
234 0 : .pipe_fd = fds[1] } );
235 : /*
236 : * CLONE_FILES so this thread doesn't hold open files which are open
237 : * now, but later closed in a different thread. This is a
238 : * problem with /dev/net/tun, which if held open by this
239 : * thread, prevents the TUN/TAP device from being reused.
240 : */
241 0 : pid = run_helper_thread(winch_thread, &data, CLONE_FILES, stack_out);
242 0 : if (pid < 0) {
243 0 : err = pid;
244 0 : printk(UM_KERN_ERR "fork of winch_thread failed - errno = %d\n",
245 : -err);
246 : goto out_close;
247 : }
248 :
249 0 : *fd_out = fds[0];
250 0 : n = read(fds[0], &c, sizeof(c));
251 0 : if (n != sizeof(c)) {
252 0 : printk(UM_KERN_ERR "winch_tramp : failed to read "
253 : "synchronization byte\n");
254 0 : printk(UM_KERN_ERR "read failed, err = %d\n", errno);
255 0 : printk(UM_KERN_ERR "fd %d will not support SIGWINCH\n", fd);
256 0 : err = -EINVAL;
257 : goto out_close;
258 : }
259 :
260 0 : err = os_set_fd_block(*fd_out, 0);
261 0 : if (err) {
262 0 : printk(UM_KERN_ERR "winch_tramp: failed to set thread_fd "
263 : "non-blocking.\n");
264 : goto out_close;
265 : }
266 :
267 : return pid;
268 :
269 : out_close:
270 0 : close(fds[1]);
271 0 : close(fds[0]);
272 : out:
273 : return err;
274 : }
275 :
276 0 : void register_winch(int fd, struct tty_port *port)
277 : {
278 : unsigned long stack;
279 0 : int pid, thread, count, thread_fd = -1;
280 0 : char c = 1;
281 :
282 0 : if (!isatty(fd))
283 0 : return;
284 :
285 0 : pid = tcgetpgrp(fd);
286 0 : if (is_skas_winch(pid, fd, port)) {
287 0 : register_winch_irq(-1, fd, -1, port, 0);
288 0 : return;
289 : }
290 :
291 0 : if (pid == -1) {
292 0 : thread = winch_tramp(fd, port, &thread_fd, &stack);
293 0 : if (thread < 0)
294 : return;
295 :
296 0 : register_winch_irq(thread_fd, fd, thread, port, stack);
297 :
298 0 : count = write(thread_fd, &c, sizeof(c));
299 0 : if (count != sizeof(c))
300 0 : printk(UM_KERN_ERR "register_winch : failed to write "
301 : "synchronization byte, err = %d\n", errno);
302 : }
303 : }
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