1 // SPDX-License-Identifier: GPL-2.0
2 /*
3  * Copyright (C) 2002 - 2008 Jeff Dike (jdike@{addtoit,linux.intel}.com)
4  */
5 
6 #include <linux/minmax.h>
7 #include <unistd.h>
8 #include <errno.h>
9 #include <fcntl.h>
10 #include <poll.h>
11 #include <pty.h>
12 #include <sched.h>
13 #include <signal.h>
14 #include <string.h>
15 #include <kern_util.h>
16 #include <init.h>
17 #include <os.h>
18 #include <sigio.h>
19 #include <um_malloc.h>
20 
21 /*
22  * Protected by sigio_lock(), also used by sigio_cleanup, which is an
23  * exitcall.
24  */
25 static int write_sigio_pid = -1;
26 static unsigned long write_sigio_stack;
27 
28 /*
29  * These arrays are initialized before the sigio thread is started, and
30  * the descriptors closed after it is killed.  So, it can't see them change.
31  * On the UML side, they are changed under the sigio_lock.
32  */
33 #define SIGIO_FDS_INIT {-1, -1}
34 
35 static int write_sigio_fds[2] = SIGIO_FDS_INIT;
36 static int sigio_private[2] = SIGIO_FDS_INIT;
37 
38 struct pollfds {
39 	struct pollfd *poll;
40 	int size;
41 	int used;
42 };
43 
44 /*
45  * Protected by sigio_lock().  Used by the sigio thread, but the UML thread
46  * synchronizes with it.
47  */
48 static struct pollfds current_poll;
49 static struct pollfds next_poll;
50 static struct pollfds all_sigio_fds;
51 
write_sigio_thread(void * unused)52 static int write_sigio_thread(void *unused)
53 {
54 	struct pollfds *fds;
55 	struct pollfd *p;
56 	int i, n, respond_fd;
57 	char c;
58 
59 	os_fix_helper_signals();
60 	fds = &current_poll;
61 	while (1) {
62 		n = poll(fds->poll, fds->used, -1);
63 		if (n < 0) {
64 			if (errno == EINTR)
65 				continue;
66 			printk(UM_KERN_ERR "write_sigio_thread : poll returned "
67 			       "%d, errno = %d\n", n, errno);
68 		}
69 		for (i = 0; i < fds->used; i++) {
70 			p = &fds->poll[i];
71 			if (p->revents == 0)
72 				continue;
73 			if (p->fd == sigio_private[1]) {
74 				CATCH_EINTR(n = read(sigio_private[1], &c,
75 						     sizeof(c)));
76 				if (n != sizeof(c))
77 					printk(UM_KERN_ERR
78 					       "write_sigio_thread : "
79 					       "read on socket failed, "
80 					       "err = %d\n", errno);
81 				swap(current_poll, next_poll);
82 				respond_fd = sigio_private[1];
83 			}
84 			else {
85 				respond_fd = write_sigio_fds[1];
86 				fds->used--;
87 				memmove(&fds->poll[i], &fds->poll[i + 1],
88 					(fds->used - i) * sizeof(*fds->poll));
89 			}
90 
91 			CATCH_EINTR(n = write(respond_fd, &c, sizeof(c)));
92 			if (n != sizeof(c))
93 				printk(UM_KERN_ERR "write_sigio_thread : "
94 				       "write on socket failed, err = %d\n",
95 				       errno);
96 		}
97 	}
98 
99 	return 0;
100 }
101 
need_poll(struct pollfds * polls,int n)102 static int need_poll(struct pollfds *polls, int n)
103 {
104 	struct pollfd *new;
105 
106 	if (n <= polls->size)
107 		return 0;
108 
109 	new = uml_kmalloc(n * sizeof(struct pollfd), UM_GFP_ATOMIC);
110 	if (new == NULL) {
111 		printk(UM_KERN_ERR "need_poll : failed to allocate new "
112 		       "pollfds\n");
113 		return -ENOMEM;
114 	}
115 
116 	memcpy(new, polls->poll, polls->used * sizeof(struct pollfd));
117 	kfree(polls->poll);
118 
119 	polls->poll = new;
120 	polls->size = n;
121 	return 0;
122 }
123 
124 /*
125  * Must be called with sigio_lock held, because it's needed by the marked
126  * critical section.
127  */
update_thread(void)128 static void update_thread(void)
129 {
130 	unsigned long flags;
131 	int n;
132 	char c;
133 
134 	flags = um_set_signals_trace(0);
135 	CATCH_EINTR(n = write(sigio_private[0], &c, sizeof(c)));
136 	if (n != sizeof(c)) {
137 		printk(UM_KERN_ERR "update_thread : write failed, err = %d\n",
138 		       errno);
139 		goto fail;
140 	}
141 
142 	CATCH_EINTR(n = read(sigio_private[0], &c, sizeof(c)));
143 	if (n != sizeof(c)) {
144 		printk(UM_KERN_ERR "update_thread : read failed, err = %d\n",
145 		       errno);
146 		goto fail;
147 	}
148 
149 	um_set_signals_trace(flags);
150 	return;
151  fail:
152 	/* Critical section start */
153 	if (write_sigio_pid != -1) {
154 		os_kill_process(write_sigio_pid, 1);
155 		free_stack(write_sigio_stack, 0);
156 	}
157 	write_sigio_pid = -1;
158 	close(sigio_private[0]);
159 	close(sigio_private[1]);
160 	close(write_sigio_fds[0]);
161 	close(write_sigio_fds[1]);
162 	/* Critical section end */
163 	um_set_signals_trace(flags);
164 }
165 
__add_sigio_fd(int fd)166 int __add_sigio_fd(int fd)
167 {
168 	struct pollfd *p;
169 	int err, i, n;
170 
171 	for (i = 0; i < all_sigio_fds.used; i++) {
172 		if (all_sigio_fds.poll[i].fd == fd)
173 			break;
174 	}
175 	if (i == all_sigio_fds.used)
176 		return -ENOSPC;
177 
178 	p = &all_sigio_fds.poll[i];
179 
180 	for (i = 0; i < current_poll.used; i++) {
181 		if (current_poll.poll[i].fd == fd)
182 			return 0;
183 	}
184 
185 	n = current_poll.used;
186 	err = need_poll(&next_poll, n + 1);
187 	if (err)
188 		return err;
189 
190 	memcpy(next_poll.poll, current_poll.poll,
191 	       current_poll.used * sizeof(struct pollfd));
192 	next_poll.poll[n] = *p;
193 	next_poll.used = n + 1;
194 	update_thread();
195 
196 	return 0;
197 }
198 
199 
add_sigio_fd(int fd)200 int add_sigio_fd(int fd)
201 {
202 	int err;
203 
204 	sigio_lock();
205 	err = __add_sigio_fd(fd);
206 	sigio_unlock();
207 
208 	return err;
209 }
210 
__ignore_sigio_fd(int fd)211 int __ignore_sigio_fd(int fd)
212 {
213 	struct pollfd *p;
214 	int err, i, n = 0;
215 
216 	/*
217 	 * This is called from exitcalls elsewhere in UML - if
218 	 * sigio_cleanup has already run, then update_thread will hang
219 	 * or fail because the thread is no longer running.
220 	 */
221 	if (write_sigio_pid == -1)
222 		return -EIO;
223 
224 	for (i = 0; i < current_poll.used; i++) {
225 		if (current_poll.poll[i].fd == fd)
226 			break;
227 	}
228 	if (i == current_poll.used)
229 		return -ENOENT;
230 
231 	err = need_poll(&next_poll, current_poll.used - 1);
232 	if (err)
233 		return err;
234 
235 	for (i = 0; i < current_poll.used; i++) {
236 		p = &current_poll.poll[i];
237 		if (p->fd != fd)
238 			next_poll.poll[n++] = *p;
239 	}
240 	next_poll.used = current_poll.used - 1;
241 
242 	update_thread();
243 
244 	return 0;
245 }
246 
ignore_sigio_fd(int fd)247 int ignore_sigio_fd(int fd)
248 {
249 	int err;
250 
251 	sigio_lock();
252 	err = __ignore_sigio_fd(fd);
253 	sigio_unlock();
254 
255 	return err;
256 }
257 
setup_initial_poll(int fd)258 static struct pollfd *setup_initial_poll(int fd)
259 {
260 	struct pollfd *p;
261 
262 	p = uml_kmalloc(sizeof(struct pollfd), UM_GFP_KERNEL);
263 	if (p == NULL) {
264 		printk(UM_KERN_ERR "setup_initial_poll : failed to allocate "
265 		       "poll\n");
266 		return NULL;
267 	}
268 	*p = ((struct pollfd) { .fd		= fd,
269 				.events 	= POLLIN,
270 				.revents 	= 0 });
271 	return p;
272 }
273 
write_sigio_workaround(void)274 static void write_sigio_workaround(void)
275 {
276 	struct pollfd *p;
277 	int err;
278 	int l_write_sigio_fds[2];
279 	int l_sigio_private[2];
280 	int l_write_sigio_pid;
281 
282 	/* We call this *tons* of times - and most ones we must just fail. */
283 	sigio_lock();
284 	l_write_sigio_pid = write_sigio_pid;
285 	sigio_unlock();
286 
287 	if (l_write_sigio_pid != -1)
288 		return;
289 
290 	err = os_pipe(l_write_sigio_fds, 1, 1);
291 	if (err < 0) {
292 		printk(UM_KERN_ERR "write_sigio_workaround - os_pipe 1 failed, "
293 		       "err = %d\n", -err);
294 		return;
295 	}
296 	err = os_pipe(l_sigio_private, 1, 1);
297 	if (err < 0) {
298 		printk(UM_KERN_ERR "write_sigio_workaround - os_pipe 2 failed, "
299 		       "err = %d\n", -err);
300 		goto out_close1;
301 	}
302 
303 	p = setup_initial_poll(l_sigio_private[1]);
304 	if (!p)
305 		goto out_close2;
306 
307 	sigio_lock();
308 
309 	/*
310 	 * Did we race? Don't try to optimize this, please, it's not so likely
311 	 * to happen, and no more than once at the boot.
312 	 */
313 	if (write_sigio_pid != -1)
314 		goto out_free;
315 
316 	current_poll = ((struct pollfds) { .poll 	= p,
317 					   .used 	= 1,
318 					   .size 	= 1 });
319 
320 	if (write_sigio_irq(l_write_sigio_fds[0]))
321 		goto out_clear_poll;
322 
323 	memcpy(write_sigio_fds, l_write_sigio_fds, sizeof(l_write_sigio_fds));
324 	memcpy(sigio_private, l_sigio_private, sizeof(l_sigio_private));
325 
326 	write_sigio_pid = run_helper_thread(write_sigio_thread, NULL,
327 					    CLONE_FILES | CLONE_VM,
328 					    &write_sigio_stack);
329 
330 	if (write_sigio_pid < 0)
331 		goto out_clear;
332 
333 	sigio_unlock();
334 	return;
335 
336 out_clear:
337 	write_sigio_pid = -1;
338 	write_sigio_fds[0] = -1;
339 	write_sigio_fds[1] = -1;
340 	sigio_private[0] = -1;
341 	sigio_private[1] = -1;
342 out_clear_poll:
343 	current_poll = ((struct pollfds) { .poll	= NULL,
344 					   .size	= 0,
345 					   .used	= 0 });
346 out_free:
347 	sigio_unlock();
348 	kfree(p);
349 out_close2:
350 	close(l_sigio_private[0]);
351 	close(l_sigio_private[1]);
352 out_close1:
353 	close(l_write_sigio_fds[0]);
354 	close(l_write_sigio_fds[1]);
355 }
356 
sigio_broken(int fd)357 void sigio_broken(int fd)
358 {
359 	int err;
360 
361 	write_sigio_workaround();
362 
363 	sigio_lock();
364 	err = need_poll(&all_sigio_fds, all_sigio_fds.used + 1);
365 	if (err) {
366 		printk(UM_KERN_ERR "maybe_sigio_broken - failed to add pollfd "
367 		       "for descriptor %d\n", fd);
368 		goto out;
369 	}
370 
371 	all_sigio_fds.poll[all_sigio_fds.used++] =
372 		((struct pollfd) { .fd  	= fd,
373 				   .events 	= POLLIN,
374 				   .revents 	= 0 });
375 out:
376 	sigio_unlock();
377 }
378 
379 /* Changed during early boot */
380 static int pty_output_sigio;
381 
maybe_sigio_broken(int fd)382 void maybe_sigio_broken(int fd)
383 {
384 	if (!isatty(fd))
385 		return;
386 
387 	if (pty_output_sigio)
388 		return;
389 
390 	sigio_broken(fd);
391 }
392 
sigio_cleanup(void)393 static void sigio_cleanup(void)
394 {
395 	if (write_sigio_pid == -1)
396 		return;
397 
398 	os_kill_process(write_sigio_pid, 1);
399 	free_stack(write_sigio_stack, 0);
400 	write_sigio_pid = -1;
401 }
402 
403 __uml_exitcall(sigio_cleanup);
404 
405 /* Used as a flag during SIGIO testing early in boot */
406 static int got_sigio;
407 
handler(int sig)408 static void __init handler(int sig)
409 {
410 	got_sigio = 1;
411 }
412 
413 struct openpty_arg {
414 	int master;
415 	int slave;
416 	int err;
417 };
418 
openpty_cb(void * arg)419 static void openpty_cb(void *arg)
420 {
421 	struct openpty_arg *info = arg;
422 
423 	info->err = 0;
424 	if (openpty(&info->master, &info->slave, NULL, NULL, NULL))
425 		info->err = -errno;
426 }
427 
async_pty(int master,int slave)428 static int async_pty(int master, int slave)
429 {
430 	int flags;
431 
432 	flags = fcntl(master, F_GETFL);
433 	if (flags < 0)
434 		return -errno;
435 
436 	if ((fcntl(master, F_SETFL, flags | O_NONBLOCK | O_ASYNC) < 0) ||
437 	    (fcntl(master, F_SETOWN, os_getpid()) < 0))
438 		return -errno;
439 
440 	if ((fcntl(slave, F_SETFL, flags | O_NONBLOCK) < 0))
441 		return -errno;
442 
443 	return 0;
444 }
445 
check_one_sigio(void (* proc)(int,int))446 static void __init check_one_sigio(void (*proc)(int, int))
447 {
448 	struct sigaction old, new;
449 	struct openpty_arg pty = { .master = -1, .slave = -1 };
450 	int master, slave, err;
451 
452 	initial_thread_cb(openpty_cb, &pty);
453 	if (pty.err) {
454 		printk(UM_KERN_ERR "check_one_sigio failed, errno = %d\n",
455 		       -pty.err);
456 		return;
457 	}
458 
459 	master = pty.master;
460 	slave = pty.slave;
461 
462 	if ((master == -1) || (slave == -1)) {
463 		printk(UM_KERN_ERR "check_one_sigio failed to allocate a "
464 		       "pty\n");
465 		return;
466 	}
467 
468 	/* Not now, but complain so we now where we failed. */
469 	err = raw(master);
470 	if (err < 0) {
471 		printk(UM_KERN_ERR "check_one_sigio : raw failed, errno = %d\n",
472 		      -err);
473 		return;
474 	}
475 
476 	err = async_pty(master, slave);
477 	if (err < 0) {
478 		printk(UM_KERN_ERR "check_one_sigio : sigio_async failed, "
479 		       "err = %d\n", -err);
480 		return;
481 	}
482 
483 	if (sigaction(SIGIO, NULL, &old) < 0) {
484 		printk(UM_KERN_ERR "check_one_sigio : sigaction 1 failed, "
485 		       "errno = %d\n", errno);
486 		return;
487 	}
488 
489 	new = old;
490 	new.sa_handler = handler;
491 	if (sigaction(SIGIO, &new, NULL) < 0) {
492 		printk(UM_KERN_ERR "check_one_sigio : sigaction 2 failed, "
493 		       "errno = %d\n", errno);
494 		return;
495 	}
496 
497 	got_sigio = 0;
498 	(*proc)(master, slave);
499 
500 	close(master);
501 	close(slave);
502 
503 	if (sigaction(SIGIO, &old, NULL) < 0)
504 		printk(UM_KERN_ERR "check_one_sigio : sigaction 3 failed, "
505 		       "errno = %d\n", errno);
506 }
507 
tty_output(int master,int slave)508 static void tty_output(int master, int slave)
509 {
510 	int n;
511 	char buf[512];
512 
513 	printk(UM_KERN_INFO "Checking that host ptys support output SIGIO...");
514 
515 	memset(buf, 0, sizeof(buf));
516 
517 	while (write(master, buf, sizeof(buf)) > 0) ;
518 	if (errno != EAGAIN)
519 		printk(UM_KERN_ERR "tty_output : write failed, errno = %d\n",
520 		       errno);
521 	while (((n = read(slave, buf, sizeof(buf))) > 0) &&
522 	       !({ barrier(); got_sigio; }))
523 		;
524 
525 	if (got_sigio) {
526 		printk(UM_KERN_CONT "Yes\n");
527 		pty_output_sigio = 1;
528 	} else if (n == -EAGAIN)
529 		printk(UM_KERN_CONT "No, enabling workaround\n");
530 	else
531 		printk(UM_KERN_CONT "tty_output : read failed, err = %d\n", n);
532 }
533 
check_sigio(void)534 static void __init check_sigio(void)
535 {
536 	if ((access("/dev/ptmx", R_OK) < 0) &&
537 	    (access("/dev/ptyp0", R_OK) < 0)) {
538 		printk(UM_KERN_WARNING "No pseudo-terminals available - "
539 		       "skipping pty SIGIO check\n");
540 		return;
541 	}
542 	check_one_sigio(tty_output);
543 }
544 
545 /* Here because it only does the SIGIO testing for now */
os_check_bugs(void)546 void __init os_check_bugs(void)
547 {
548 	check_sigio();
549 }
550