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
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 = ¤t_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
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 */
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
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
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
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 = ¤t_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
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
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
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
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
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
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
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
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
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
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
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
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 */
546 void __init os_check_bugs(void)
547 {
548 check_sigio();
549 }
550
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