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
17void generic_close(int fd, void *unused)
18{
19	close(fd);
20}
21
22int 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
38int 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
52int 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
69void generic_free(void *data)
70{
71	kfree(data);
72}
73
74int 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;
111error:
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
135static void winch_handler(int sig)
136{
137}
138
139struct winch_data {
140	int pty_fd;
141	int pipe_fd;
142};
143
144static __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
218wait_kill:
219	c = 2;
220	count = write(pipe_fd, &c, sizeof(c));
221	while (1)
222		pause();
223}
224
225static 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
282void 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(-1, fd, -1, port, 0);
294		return;
295	}
296
297	if (pid == -1) {
298		thread = winch_tramp(fd, port, &thread_fd, &stack);
299		if (thread < 0)
300			return;
301
302		register_winch_irq(thread_fd, fd, 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