1 // SPDX-License-Identifier: GPL-2.0
2 /*
3 * Copyright (C) 2002 - 2008 Jeff Dike (jdike@{addtoit,linux.intel}.com)
4 */
5
6 #include <unistd.h>
7 #include <errno.h>
8 #include <fcntl.h>
9 #include <poll.h>
10 #include <pty.h>
11 #include <sched.h>
12 #include <signal.h>
13 #include <string.h>
14 #include <kern_util.h>
15 #include <init.h>
16 #include <os.h>
17 #include <sigio.h>
18 #include <um_malloc.h>
19
20 /*
21 * Protected by sigio_lock(), also used by sigio_cleanup, which is an
22 * exitcall.
23 */
24 static int write_sigio_pid = -1;
25 static unsigned long write_sigio_stack;
26
27 /*
28 * These arrays are initialized before the sigio thread is started, and
29 * the descriptors closed after it is killed. So, it can't see them change.
30 * On the UML side, they are changed under the sigio_lock.
31 */
32 #define SIGIO_FDS_INIT {-1, -1}
33
34 static int write_sigio_fds[2] = SIGIO_FDS_INIT;
35 static int sigio_private[2] = SIGIO_FDS_INIT;
36
37 struct pollfds {
38 struct pollfd *poll;
39 int size;
40 int used;
41 };
42
43 /*
44 * Protected by sigio_lock(). Used by the sigio thread, but the UML thread
45 * synchronizes with it.
46 */
47 static struct pollfds current_poll;
48 static struct pollfds next_poll;
49 static struct pollfds all_sigio_fds;
50
write_sigio_thread(void * unused)51 static int write_sigio_thread(void *unused)
52 {
53 struct pollfds *fds, tmp;
54 struct pollfd *p;
55 int i, n, respond_fd;
56 char c;
57
58 os_fix_helper_signals();
59 fds = ¤t_poll;
60 while (1) {
61 n = poll(fds->poll, fds->used, -1);
62 if (n < 0) {
63 if (errno == EINTR)
64 continue;
65 printk(UM_KERN_ERR "write_sigio_thread : poll returned "
66 "%d, errno = %d\n", n, errno);
67 }
68 for (i = 0; i < fds->used; i++) {
69 p = &fds->poll[i];
70 if (p->revents == 0)
71 continue;
72 if (p->fd == sigio_private[1]) {
73 CATCH_EINTR(n = read(sigio_private[1], &c,
74 sizeof(c)));
75 if (n != sizeof(c))
76 printk(UM_KERN_ERR
77 "write_sigio_thread : "
78 "read on socket failed, "
79 "err = %d\n", errno);
80 tmp = current_poll;
81 current_poll = next_poll;
82 next_poll = tmp;
83 respond_fd = sigio_private[1];
84 }
85 else {
86 respond_fd = write_sigio_fds[1];
87 fds->used--;
88 memmove(&fds->poll[i], &fds->poll[i + 1],
89 (fds->used - i) * sizeof(*fds->poll));
90 }
91
92 CATCH_EINTR(n = write(respond_fd, &c, sizeof(c)));
93 if (n != sizeof(c))
94 printk(UM_KERN_ERR "write_sigio_thread : "
95 "write on socket failed, err = %d\n",
96 errno);
97 }
98 }
99
100 return 0;
101 }
102
need_poll(struct pollfds * polls,int n)103 static int need_poll(struct pollfds *polls, int n)
104 {
105 struct pollfd *new;
106
107 if (n <= polls->size)
108 return 0;
109
110 new = uml_kmalloc(n * sizeof(struct pollfd), UM_GFP_ATOMIC);
111 if (new == NULL) {
112 printk(UM_KERN_ERR "need_poll : failed to allocate new "
113 "pollfds\n");
114 return -ENOMEM;
115 }
116
117 memcpy(new, polls->poll, polls->used * sizeof(struct pollfd));
118 kfree(polls->poll);
119
120 polls->poll = new;
121 polls->size = n;
122 return 0;
123 }
124
125 /*
126 * Must be called with sigio_lock held, because it's needed by the marked
127 * critical section.
128 */
update_thread(void)129 static void update_thread(void)
130 {
131 unsigned long flags;
132 int n;
133 char c;
134
135 flags = um_set_signals_trace(0);
136 CATCH_EINTR(n = write(sigio_private[0], &c, sizeof(c)));
137 if (n != sizeof(c)) {
138 printk(UM_KERN_ERR "update_thread : write failed, err = %d\n",
139 errno);
140 goto fail;
141 }
142
143 CATCH_EINTR(n = read(sigio_private[0], &c, sizeof(c)));
144 if (n != sizeof(c)) {
145 printk(UM_KERN_ERR "update_thread : read failed, err = %d\n",
146 errno);
147 goto fail;
148 }
149
150 um_set_signals_trace(flags);
151 return;
152 fail:
153 /* Critical section start */
154 if (write_sigio_pid != -1) {
155 os_kill_process(write_sigio_pid, 1);
156 free_stack(write_sigio_stack, 0);
157 }
158 write_sigio_pid = -1;
159 close(sigio_private[0]);
160 close(sigio_private[1]);
161 close(write_sigio_fds[0]);
162 close(write_sigio_fds[1]);
163 /* Critical section end */
164 um_set_signals_trace(flags);
165 }
166
__add_sigio_fd(int fd)167 int __add_sigio_fd(int fd)
168 {
169 struct pollfd *p;
170 int err, i, n;
171
172 for (i = 0; i < all_sigio_fds.used; i++) {
173 if (all_sigio_fds.poll[i].fd == fd)
174 break;
175 }
176 if (i == all_sigio_fds.used)
177 return -ENOSPC;
178
179 p = &all_sigio_fds.poll[i];
180
181 for (i = 0; i < current_poll.used; i++) {
182 if (current_poll.poll[i].fd == fd)
183 return 0;
184 }
185
186 n = current_poll.used;
187 err = need_poll(&next_poll, n + 1);
188 if (err)
189 return err;
190
191 memcpy(next_poll.poll, current_poll.poll,
192 current_poll.used * sizeof(struct pollfd));
193 next_poll.poll[n] = *p;
194 next_poll.used = n + 1;
195 update_thread();
196
197 return 0;
198 }
199
200
add_sigio_fd(int fd)201 int add_sigio_fd(int fd)
202 {
203 int err;
204
205 sigio_lock();
206 err = __add_sigio_fd(fd);
207 sigio_unlock();
208
209 return err;
210 }
211
__ignore_sigio_fd(int fd)212 int __ignore_sigio_fd(int fd)
213 {
214 struct pollfd *p;
215 int err, i, n = 0;
216
217 /*
218 * This is called from exitcalls elsewhere in UML - if
219 * sigio_cleanup has already run, then update_thread will hang
220 * or fail because the thread is no longer running.
221 */
222 if (write_sigio_pid == -1)
223 return -EIO;
224
225 for (i = 0; i < current_poll.used; i++) {
226 if (current_poll.poll[i].fd == fd)
227 break;
228 }
229 if (i == current_poll.used)
230 return -ENOENT;
231
232 err = need_poll(&next_poll, current_poll.used - 1);
233 if (err)
234 return err;
235
236 for (i = 0; i < current_poll.used; i++) {
237 p = ¤t_poll.poll[i];
238 if (p->fd != fd)
239 next_poll.poll[n++] = *p;
240 }
241 next_poll.used = current_poll.used - 1;
242
243 update_thread();
244
245 return 0;
246 }
247
ignore_sigio_fd(int fd)248 int ignore_sigio_fd(int fd)
249 {
250 int err;
251
252 sigio_lock();
253 err = __ignore_sigio_fd(fd);
254 sigio_unlock();
255
256 return err;
257 }
258
setup_initial_poll(int fd)259 static struct pollfd *setup_initial_poll(int fd)
260 {
261 struct pollfd *p;
262
263 p = uml_kmalloc(sizeof(struct pollfd), UM_GFP_KERNEL);
264 if (p == NULL) {
265 printk(UM_KERN_ERR "setup_initial_poll : failed to allocate "
266 "poll\n");
267 return NULL;
268 }
269 *p = ((struct pollfd) { .fd = fd,
270 .events = POLLIN,
271 .revents = 0 });
272 return p;
273 }
274
write_sigio_workaround(void)275 static void write_sigio_workaround(void)
276 {
277 struct pollfd *p;
278 int err;
279 int l_write_sigio_fds[2];
280 int l_sigio_private[2];
281 int l_write_sigio_pid;
282
283 /* We call this *tons* of times - and most ones we must just fail. */
284 sigio_lock();
285 l_write_sigio_pid = write_sigio_pid;
286 sigio_unlock();
287
288 if (l_write_sigio_pid != -1)
289 return;
290
291 err = os_pipe(l_write_sigio_fds, 1, 1);
292 if (err < 0) {
293 printk(UM_KERN_ERR "write_sigio_workaround - os_pipe 1 failed, "
294 "err = %d\n", -err);
295 return;
296 }
297 err = os_pipe(l_sigio_private, 1, 1);
298 if (err < 0) {
299 printk(UM_KERN_ERR "write_sigio_workaround - os_pipe 2 failed, "
300 "err = %d\n", -err);
301 goto out_close1;
302 }
303
304 p = setup_initial_poll(l_sigio_private[1]);
305 if (!p)
306 goto out_close2;
307
308 sigio_lock();
309
310 /*
311 * Did we race? Don't try to optimize this, please, it's not so likely
312 * to happen, and no more than once at the boot.
313 */
314 if (write_sigio_pid != -1)
315 goto out_free;
316
317 current_poll = ((struct pollfds) { .poll = p,
318 .used = 1,
319 .size = 1 });
320
321 if (write_sigio_irq(l_write_sigio_fds[0]))
322 goto out_clear_poll;
323
324 memcpy(write_sigio_fds, l_write_sigio_fds, sizeof(l_write_sigio_fds));
325 memcpy(sigio_private, l_sigio_private, sizeof(l_sigio_private));
326
327 write_sigio_pid = run_helper_thread(write_sigio_thread, NULL,
328 CLONE_FILES | CLONE_VM,
329 &write_sigio_stack);
330
331 if (write_sigio_pid < 0)
332 goto out_clear;
333
334 sigio_unlock();
335 return;
336
337 out_clear:
338 write_sigio_pid = -1;
339 write_sigio_fds[0] = -1;
340 write_sigio_fds[1] = -1;
341 sigio_private[0] = -1;
342 sigio_private[1] = -1;
343 out_clear_poll:
344 current_poll = ((struct pollfds) { .poll = NULL,
345 .size = 0,
346 .used = 0 });
347 out_free:
348 sigio_unlock();
349 kfree(p);
350 out_close2:
351 close(l_sigio_private[0]);
352 close(l_sigio_private[1]);
353 out_close1:
354 close(l_write_sigio_fds[0]);
355 close(l_write_sigio_fds[1]);
356 }
357
sigio_broken(int fd)358 void sigio_broken(int fd)
359 {
360 int err;
361
362 write_sigio_workaround();
363
364 sigio_lock();
365 err = need_poll(&all_sigio_fds, all_sigio_fds.used + 1);
366 if (err) {
367 printk(UM_KERN_ERR "maybe_sigio_broken - failed to add pollfd "
368 "for descriptor %d\n", fd);
369 goto out;
370 }
371
372 all_sigio_fds.poll[all_sigio_fds.used++] =
373 ((struct pollfd) { .fd = fd,
374 .events = POLLIN,
375 .revents = 0 });
376 out:
377 sigio_unlock();
378 }
379
380 /* Changed during early boot */
381 static int pty_output_sigio;
382
maybe_sigio_broken(int fd)383 void maybe_sigio_broken(int fd)
384 {
385 if (!isatty(fd))
386 return;
387
388 if (pty_output_sigio)
389 return;
390
391 sigio_broken(fd);
392 }
393
sigio_cleanup(void)394 static void sigio_cleanup(void)
395 {
396 if (write_sigio_pid == -1)
397 return;
398
399 os_kill_process(write_sigio_pid, 1);
400 free_stack(write_sigio_stack, 0);
401 write_sigio_pid = -1;
402 }
403
404 __uml_exitcall(sigio_cleanup);
405
406 /* Used as a flag during SIGIO testing early in boot */
407 static int got_sigio;
408
handler(int sig)409 static void __init handler(int sig)
410 {
411 got_sigio = 1;
412 }
413
414 struct openpty_arg {
415 int master;
416 int slave;
417 int err;
418 };
419
openpty_cb(void * arg)420 static void openpty_cb(void *arg)
421 {
422 struct openpty_arg *info = arg;
423
424 info->err = 0;
425 if (openpty(&info->master, &info->slave, NULL, NULL, NULL))
426 info->err = -errno;
427 }
428
async_pty(int master,int slave)429 static int async_pty(int master, int slave)
430 {
431 int flags;
432
433 flags = fcntl(master, F_GETFL);
434 if (flags < 0)
435 return -errno;
436
437 if ((fcntl(master, F_SETFL, flags | O_NONBLOCK | O_ASYNC) < 0) ||
438 (fcntl(master, F_SETOWN, os_getpid()) < 0))
439 return -errno;
440
441 if ((fcntl(slave, F_SETFL, flags | O_NONBLOCK) < 0))
442 return -errno;
443
444 return 0;
445 }
446
check_one_sigio(void (* proc)(int,int))447 static void __init check_one_sigio(void (*proc)(int, int))
448 {
449 struct sigaction old, new;
450 struct openpty_arg pty = { .master = -1, .slave = -1 };
451 int master, slave, err;
452
453 initial_thread_cb(openpty_cb, &pty);
454 if (pty.err) {
455 printk(UM_KERN_ERR "check_one_sigio failed, errno = %d\n",
456 -pty.err);
457 return;
458 }
459
460 master = pty.master;
461 slave = pty.slave;
462
463 if ((master == -1) || (slave == -1)) {
464 printk(UM_KERN_ERR "check_one_sigio failed to allocate a "
465 "pty\n");
466 return;
467 }
468
469 /* Not now, but complain so we now where we failed. */
470 err = raw(master);
471 if (err < 0) {
472 printk(UM_KERN_ERR "check_one_sigio : raw failed, errno = %d\n",
473 -err);
474 return;
475 }
476
477 err = async_pty(master, slave);
478 if (err < 0) {
479 printk(UM_KERN_ERR "check_one_sigio : sigio_async failed, "
480 "err = %d\n", -err);
481 return;
482 }
483
484 if (sigaction(SIGIO, NULL, &old) < 0) {
485 printk(UM_KERN_ERR "check_one_sigio : sigaction 1 failed, "
486 "errno = %d\n", errno);
487 return;
488 }
489
490 new = old;
491 new.sa_handler = handler;
492 if (sigaction(SIGIO, &new, NULL) < 0) {
493 printk(UM_KERN_ERR "check_one_sigio : sigaction 2 failed, "
494 "errno = %d\n", errno);
495 return;
496 }
497
498 got_sigio = 0;
499 (*proc)(master, slave);
500
501 close(master);
502 close(slave);
503
504 if (sigaction(SIGIO, &old, NULL) < 0)
505 printk(UM_KERN_ERR "check_one_sigio : sigaction 3 failed, "
506 "errno = %d\n", errno);
507 }
508
tty_output(int master,int slave)509 static void tty_output(int master, int slave)
510 {
511 int n;
512 char buf[512];
513
514 printk(UM_KERN_INFO "Checking that host ptys support output SIGIO...");
515
516 memset(buf, 0, sizeof(buf));
517
518 while (write(master, buf, sizeof(buf)) > 0) ;
519 if (errno != EAGAIN)
520 printk(UM_KERN_ERR "tty_output : write failed, errno = %d\n",
521 errno);
522 while (((n = read(slave, buf, sizeof(buf))) > 0) &&
523 !({ barrier(); got_sigio; }))
524 ;
525
526 if (got_sigio) {
527 printk(UM_KERN_CONT "Yes\n");
528 pty_output_sigio = 1;
529 } else if (n == -EAGAIN)
530 printk(UM_KERN_CONT "No, enabling workaround\n");
531 else
532 printk(UM_KERN_CONT "tty_output : read failed, err = %d\n", n);
533 }
534
check_sigio(void)535 static void __init check_sigio(void)
536 {
537 if ((access("/dev/ptmx", R_OK) < 0) &&
538 (access("/dev/ptyp0", R_OK) < 0)) {
539 printk(UM_KERN_WARNING "No pseudo-terminals available - "
540 "skipping pty SIGIO check\n");
541 return;
542 }
543 check_one_sigio(tty_output);
544 }
545
546 /* Here because it only does the SIGIO testing for now */
os_check_bugs(void)547 void __init os_check_bugs(void)
548 {
549 check_sigio();
550 }
551
