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 | void generic_close(int fd, void *unused) |
18 | { |
19 | close(fd); |
20 | } |
21 | |
22 | int generic_read(int fd, __u8 *c_out, void *unused) |
23 | { |
24 | int n; |
25 | |
26 | n = read(fd, c_out, sizeof(*c_out)); |
27 | if (n > 0) |
28 | return n; |
29 | else if (n == 0) |
30 | return -EIO; |
31 | else if (errno == EAGAIN) |
32 | return 0; |
33 | return -errno; |
34 | } |
35 | |
36 | /* XXX Trivial wrapper around write */ |
37 | |
38 | int generic_write(int fd, const __u8 *buf, size_t n, void *unused) |
39 | { |
40 | int err; |
41 | |
42 | err = write(fd, buf, n); |
43 | if (err > 0) |
44 | return err; |
45 | else if (errno == EAGAIN) |
46 | return 0; |
47 | else if (err == 0) |
48 | return -EIO; |
49 | return -errno; |
50 | } |
51 | |
52 | 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 | if (ioctl(fd, TIOCGWINSZ, &size) < 0) |
59 | return -errno; |
60 | |
61 | ret = ((*rows_out != size.ws_row) || (*cols_out != size.ws_col)); |
62 | |
63 | *rows_out = size.ws_row; |
64 | *cols_out = size.ws_col; |
65 | |
66 | return ret; |
67 | } |
68 | |
69 | void generic_free(void *data) |
70 | { |
71 | kfree(data); |
72 | } |
73 | |
74 | 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 | if (isatty(fd)) { |
81 | sigemptyset(&no_sigio); |
82 | sigaddset(&no_sigio, SIGIO); |
83 | if (sigprocmask(SIG_BLOCK, &no_sigio, &old)) |
84 | goto error; |
85 | |
86 | CATCH_EINTR(err = tcgetattr(fd, &save)); |
87 | if (err) |
88 | goto error; |
89 | 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 | new.c_oflag |= OPOST; |
96 | CATCH_EINTR(err = tcsetattr(fd, TCSAFLUSH, &new)); |
97 | if (err) |
98 | goto error; |
99 | } |
100 | 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 | if (isatty(fd)) { |
106 | CATCH_EINTR(tcsetattr(fd, TCSAFLUSH, &save)); |
107 | sigprocmask(SIG_SETMASK, &old, NULL); |
108 | } |
109 | |
110 | return err; |
111 | error: |
112 | 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 | static void winch_handler(int sig) |
136 | { |
137 | } |
138 | |
139 | struct winch_data { |
140 | int pty_fd; |
141 | int pipe_fd; |
142 | }; |
143 | |
144 | static __noreturn int winch_thread(void *arg) |
145 | { |
146 | struct winch_data *data = arg; |
147 | sigset_t sigs; |
148 | int pty_fd, pipe_fd; |
149 | int count; |
150 | char c = 1; |
151 | |
152 | pty_fd = data->pty_fd; |
153 | pipe_fd = data->pipe_fd; |
154 | count = write(pipe_fd, &c, sizeof(c)); |
155 | if (count != sizeof(c)) |
156 | os_info("winch_thread : failed to write synchronization byte, err = %d\n" , |
157 | -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 | signal(SIGWINCH, winch_handler); |
166 | sigfillset(&sigs); |
167 | /* Block all signals possible. */ |
168 | if (sigprocmask(SIG_SETMASK, &sigs, NULL) < 0) { |
169 | os_info("winch_thread : sigprocmask failed, errno = %d\n" , |
170 | errno); |
171 | goto wait_kill; |
172 | } |
173 | /* In sigsuspend(), block anything else than SIGWINCH. */ |
174 | sigdelset(&sigs, SIGWINCH); |
175 | |
176 | if (setsid() < 0) { |
177 | os_info("winch_thread : setsid failed, errno = %d\n" , |
178 | errno); |
179 | goto wait_kill; |
180 | } |
181 | |
182 | if (ioctl(pty_fd, TIOCSCTTY, 0) < 0) { |
183 | os_info("winch_thread : TIOCSCTTY failed on " |
184 | "fd %d err = %d\n" , pty_fd, errno); |
185 | goto wait_kill; |
186 | } |
187 | |
188 | if (tcsetpgrp(pty_fd, os_getpid()) < 0) { |
189 | os_info("winch_thread : tcsetpgrp failed on fd %d err = %d\n" , |
190 | pty_fd, errno); |
191 | goto wait_kill; |
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 | count = read(pipe_fd, &c, sizeof(c)); |
201 | if (count != sizeof(c)) |
202 | os_info("winch_thread : failed to read synchronization byte, err = %d\n" , |
203 | errno); |
204 | |
205 | while(1) { |
206 | /* |
207 | * This will be interrupted by SIGWINCH only, since |
208 | * other signals are blocked. |
209 | */ |
210 | sigsuspend(&sigs); |
211 | |
212 | count = write(pipe_fd, &c, sizeof(c)); |
213 | if (count != sizeof(c)) |
214 | os_info("winch_thread : write failed, err = %d\n" , |
215 | errno); |
216 | } |
217 | |
218 | wait_kill: |
219 | c = 2; |
220 | count = write(pipe_fd, &c, sizeof(c)); |
221 | while (1) |
222 | pause(); |
223 | } |
224 | |
225 | static int winch_tramp(int fd, struct tty_port *port, int *fd_out, |
226 | unsigned long *stack_out) |
227 | { |
228 | struct winch_data data; |
229 | int fds[2], n, err, pid; |
230 | char c; |
231 | |
232 | err = os_pipe(fds, 1, 1); |
233 | if (err < 0) { |
234 | printk(UM_KERN_ERR "winch_tramp : os_pipe failed, err = %d\n" , |
235 | -err); |
236 | goto out; |
237 | } |
238 | |
239 | data = ((struct winch_data) { .pty_fd = fd, |
240 | .pipe_fd = fds[1] } ); |
241 | /* |
242 | * CLONE_FILES so this thread doesn't hold open files which are open |
243 | * now, but later closed in a different thread. This is a |
244 | * problem with /dev/net/tun, which if held open by this |
245 | * thread, prevents the TUN/TAP device from being reused. |
246 | */ |
247 | pid = run_helper_thread(winch_thread, &data, CLONE_FILES, stack_out); |
248 | if (pid < 0) { |
249 | err = pid; |
250 | printk(UM_KERN_ERR "fork of winch_thread failed - errno = %d\n" , |
251 | -err); |
252 | goto out_close; |
253 | } |
254 | |
255 | *fd_out = fds[0]; |
256 | n = read(fds[0], &c, sizeof(c)); |
257 | if (n != sizeof(c)) { |
258 | printk(UM_KERN_ERR "winch_tramp : failed to read " |
259 | "synchronization byte\n" ); |
260 | printk(UM_KERN_ERR "read failed, err = %d\n" , errno); |
261 | printk(UM_KERN_ERR "fd %d will not support SIGWINCH\n" , fd); |
262 | err = -EINVAL; |
263 | goto out_close; |
264 | } |
265 | |
266 | err = os_set_fd_block(*fd_out, 0); |
267 | if (err) { |
268 | printk(UM_KERN_ERR "winch_tramp: failed to set thread_fd " |
269 | "non-blocking.\n" ); |
270 | goto out_close; |
271 | } |
272 | |
273 | return pid; |
274 | |
275 | out_close: |
276 | close(fds[1]); |
277 | close(fds[0]); |
278 | out: |
279 | return err; |
280 | } |
281 | |
282 | void register_winch(int fd, struct tty_port *port) |
283 | { |
284 | unsigned long stack; |
285 | int pid, thread, count, thread_fd = -1; |
286 | char c = 1; |
287 | |
288 | if (!isatty(fd)) |
289 | return; |
290 | |
291 | pid = tcgetpgrp(fd); |
292 | if (is_skas_winch(pid, fd, port)) { |
293 | register_winch_irq(fd: -1, tty_fd: fd, pid: -1, port, stack: 0); |
294 | return; |
295 | } |
296 | |
297 | if (pid == -1) { |
298 | thread = winch_tramp(fd, port, fd_out: &thread_fd, stack_out: &stack); |
299 | if (thread < 0) |
300 | return; |
301 | |
302 | register_winch_irq(fd: thread_fd, tty_fd: fd, pid: thread, port, stack); |
303 | |
304 | count = write(thread_fd, &c, sizeof(c)); |
305 | if (count != sizeof(c)) |
306 | printk(UM_KERN_ERR "register_winch : failed to write " |
307 | "synchronization byte, err = %d\n" , errno); |
308 | } |
309 | } |
310 | |