Line data Source code
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 0 : 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 0 : os_fix_helper_signals();
60 0 : fds = ¤t_poll;
61 : while (1) {
62 0 : n = poll(fds->poll, fds->used, -1);
63 0 : if (n < 0) {
64 0 : if (errno == EINTR)
65 0 : continue;
66 0 : printk(UM_KERN_ERR "write_sigio_thread : poll returned "
67 : "%d, errno = %d\n", n, errno);
68 : }
69 0 : for (i = 0; i < fds->used; i++) {
70 0 : p = &fds->poll[i];
71 0 : if (p->revents == 0)
72 0 : continue;
73 0 : if (p->fd == sigio_private[1]) {
74 0 : CATCH_EINTR(n = read(sigio_private[1], &c,
75 : sizeof(c)));
76 0 : if (n != sizeof(c))
77 0 : printk(UM_KERN_ERR
78 : "write_sigio_thread : "
79 : "read on socket failed, "
80 : "err = %d\n", errno);
81 0 : swap(current_poll, next_poll);
82 0 : respond_fd = sigio_private[1];
83 : }
84 : else {
85 0 : respond_fd = write_sigio_fds[1];
86 0 : fds->used--;
87 0 : memmove(&fds->poll[i], &fds->poll[i + 1],
88 0 : (fds->used - i) * sizeof(*fds->poll));
89 : }
90 :
91 0 : CATCH_EINTR(n = write(respond_fd, &c, sizeof(c)));
92 0 : if (n != sizeof(c))
93 0 : 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 0 : static int need_poll(struct pollfds *polls, int n)
103 : {
104 : struct pollfd *new;
105 :
106 0 : if (n <= polls->size)
107 : return 0;
108 :
109 0 : new = uml_kmalloc(n * sizeof(struct pollfd), UM_GFP_ATOMIC);
110 0 : if (new == NULL) {
111 0 : printk(UM_KERN_ERR "need_poll : failed to allocate new "
112 : "pollfds\n");
113 0 : return -ENOMEM;
114 : }
115 :
116 0 : memcpy(new, polls->poll, polls->used * sizeof(struct pollfd));
117 0 : kfree(polls->poll);
118 :
119 0 : polls->poll = new;
120 0 : polls->size = n;
121 0 : 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 0 : static void update_thread(void)
129 : {
130 : unsigned long flags;
131 : int n;
132 : char c;
133 :
134 0 : flags = um_set_signals_trace(0);
135 0 : CATCH_EINTR(n = write(sigio_private[0], &c, sizeof(c)));
136 0 : if (n != sizeof(c)) {
137 0 : printk(UM_KERN_ERR "update_thread : write failed, err = %d\n",
138 : errno);
139 0 : goto fail;
140 : }
141 :
142 0 : CATCH_EINTR(n = read(sigio_private[0], &c, sizeof(c)));
143 0 : if (n != sizeof(c)) {
144 0 : printk(UM_KERN_ERR "update_thread : read failed, err = %d\n",
145 : errno);
146 0 : goto fail;
147 : }
148 :
149 0 : um_set_signals_trace(flags);
150 0 : return;
151 : fail:
152 : /* Critical section start */
153 0 : if (write_sigio_pid != -1) {
154 0 : os_kill_process(write_sigio_pid, 1);
155 0 : free_stack(write_sigio_stack, 0);
156 : }
157 0 : write_sigio_pid = -1;
158 0 : close(sigio_private[0]);
159 0 : close(sigio_private[1]);
160 0 : close(write_sigio_fds[0]);
161 0 : close(write_sigio_fds[1]);
162 : /* Critical section end */
163 0 : um_set_signals_trace(flags);
164 : }
165 :
166 0 : int __add_sigio_fd(int fd)
167 : {
168 : struct pollfd *p;
169 : int err, i, n;
170 :
171 0 : for (i = 0; i < all_sigio_fds.used; i++) {
172 0 : if (all_sigio_fds.poll[i].fd == fd)
173 : break;
174 : }
175 0 : if (i == all_sigio_fds.used)
176 : return -ENOSPC;
177 :
178 0 : p = &all_sigio_fds.poll[i];
179 :
180 0 : for (i = 0; i < current_poll.used; i++) {
181 0 : if (current_poll.poll[i].fd == fd)
182 : return 0;
183 : }
184 :
185 0 : n = current_poll.used;
186 0 : err = need_poll(&next_poll, n + 1);
187 0 : if (err)
188 : return err;
189 :
190 0 : memcpy(next_poll.poll, current_poll.poll,
191 0 : current_poll.used * sizeof(struct pollfd));
192 0 : next_poll.poll[n] = *p;
193 0 : next_poll.used = n + 1;
194 0 : update_thread();
195 :
196 0 : return 0;
197 : }
198 :
199 :
200 0 : int add_sigio_fd(int fd)
201 : {
202 : int err;
203 :
204 0 : sigio_lock();
205 0 : err = __add_sigio_fd(fd);
206 0 : sigio_unlock();
207 :
208 0 : return err;
209 : }
210 :
211 0 : int __ignore_sigio_fd(int fd)
212 : {
213 : struct pollfd *p;
214 0 : 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 0 : if (write_sigio_pid == -1)
222 : return -EIO;
223 :
224 0 : for (i = 0; i < current_poll.used; i++) {
225 0 : if (current_poll.poll[i].fd == fd)
226 : break;
227 : }
228 0 : if (i == current_poll.used)
229 : return -ENOENT;
230 :
231 0 : err = need_poll(&next_poll, current_poll.used - 1);
232 0 : if (err)
233 : return err;
234 :
235 0 : for (i = 0; i < current_poll.used; i++) {
236 0 : p = ¤t_poll.poll[i];
237 0 : if (p->fd != fd)
238 0 : next_poll.poll[n++] = *p;
239 : }
240 0 : next_poll.used = current_poll.used - 1;
241 :
242 0 : update_thread();
243 :
244 0 : return 0;
245 : }
246 :
247 0 : int ignore_sigio_fd(int fd)
248 : {
249 : int err;
250 :
251 0 : sigio_lock();
252 0 : err = __ignore_sigio_fd(fd);
253 0 : sigio_unlock();
254 :
255 0 : return err;
256 : }
257 :
258 0 : static struct pollfd *setup_initial_poll(int fd)
259 : {
260 : struct pollfd *p;
261 :
262 0 : p = uml_kmalloc(sizeof(struct pollfd), UM_GFP_KERNEL);
263 0 : if (p == NULL) {
264 0 : printk(UM_KERN_ERR "setup_initial_poll : failed to allocate "
265 : "poll\n");
266 0 : return NULL;
267 : }
268 0 : *p = ((struct pollfd) { .fd = fd,
269 : .events = POLLIN,
270 : .revents = 0 });
271 0 : return p;
272 : }
273 :
274 0 : 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 0 : sigio_lock();
284 0 : l_write_sigio_pid = write_sigio_pid;
285 0 : sigio_unlock();
286 :
287 0 : if (l_write_sigio_pid != -1)
288 0 : return;
289 :
290 0 : err = os_pipe(l_write_sigio_fds, 1, 1);
291 0 : if (err < 0) {
292 0 : printk(UM_KERN_ERR "write_sigio_workaround - os_pipe 1 failed, "
293 : "err = %d\n", -err);
294 0 : return;
295 : }
296 0 : err = os_pipe(l_sigio_private, 1, 1);
297 0 : if (err < 0) {
298 0 : printk(UM_KERN_ERR "write_sigio_workaround - os_pipe 2 failed, "
299 : "err = %d\n", -err);
300 0 : goto out_close1;
301 : }
302 :
303 0 : p = setup_initial_poll(l_sigio_private[1]);
304 0 : if (!p)
305 : goto out_close2;
306 :
307 0 : 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 0 : if (write_sigio_pid != -1)
314 : goto out_free;
315 :
316 0 : current_poll = ((struct pollfds) { .poll = p,
317 : .used = 1,
318 : .size = 1 });
319 :
320 0 : if (write_sigio_irq(l_write_sigio_fds[0]))
321 : goto out_clear_poll;
322 :
323 0 : memcpy(write_sigio_fds, l_write_sigio_fds, sizeof(l_write_sigio_fds));
324 0 : memcpy(sigio_private, l_sigio_private, sizeof(l_sigio_private));
325 :
326 0 : write_sigio_pid = run_helper_thread(write_sigio_thread, NULL,
327 : CLONE_FILES | CLONE_VM,
328 : &write_sigio_stack);
329 :
330 0 : if (write_sigio_pid < 0)
331 : goto out_clear;
332 :
333 0 : sigio_unlock();
334 0 : return;
335 :
336 : out_clear:
337 0 : write_sigio_pid = -1;
338 0 : write_sigio_fds[0] = -1;
339 0 : write_sigio_fds[1] = -1;
340 0 : sigio_private[0] = -1;
341 0 : sigio_private[1] = -1;
342 : out_clear_poll:
343 0 : current_poll = ((struct pollfds) { .poll = NULL,
344 : .size = 0,
345 : .used = 0 });
346 : out_free:
347 0 : sigio_unlock();
348 0 : kfree(p);
349 : out_close2:
350 0 : close(l_sigio_private[0]);
351 0 : close(l_sigio_private[1]);
352 : out_close1:
353 0 : close(l_write_sigio_fds[0]);
354 0 : close(l_write_sigio_fds[1]);
355 : }
356 :
357 0 : void sigio_broken(int fd)
358 : {
359 : int err;
360 :
361 0 : write_sigio_workaround();
362 :
363 0 : sigio_lock();
364 0 : err = need_poll(&all_sigio_fds, all_sigio_fds.used + 1);
365 0 : if (err) {
366 0 : printk(UM_KERN_ERR "maybe_sigio_broken - failed to add pollfd "
367 : "for descriptor %d\n", fd);
368 0 : goto out;
369 : }
370 :
371 0 : all_sigio_fds.poll[all_sigio_fds.used++] =
372 : ((struct pollfd) { .fd = fd,
373 : .events = POLLIN,
374 : .revents = 0 });
375 : out:
376 0 : sigio_unlock();
377 0 : }
378 :
379 : /* Changed during early boot */
380 : static int pty_output_sigio;
381 :
382 1 : void maybe_sigio_broken(int fd)
383 : {
384 1 : if (!isatty(fd))
385 : return;
386 :
387 0 : if (pty_output_sigio)
388 : return;
389 :
390 0 : sigio_broken(fd);
391 : }
392 :
393 1 : static void sigio_cleanup(void)
394 : {
395 1 : if (write_sigio_pid == -1)
396 : return;
397 :
398 0 : os_kill_process(write_sigio_pid, 1);
399 0 : free_stack(write_sigio_stack, 0);
400 0 : 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 1 : static void __init handler(int sig)
409 : {
410 1 : got_sigio = 1;
411 1 : }
412 :
413 : struct openpty_arg {
414 : int master;
415 : int slave;
416 : int err;
417 : };
418 :
419 1 : static void openpty_cb(void *arg)
420 : {
421 1 : struct openpty_arg *info = arg;
422 :
423 1 : info->err = 0;
424 1 : if (openpty(&info->master, &info->slave, NULL, NULL, NULL))
425 0 : info->err = -errno;
426 1 : }
427 :
428 1 : static int async_pty(int master, int slave)
429 : {
430 : int flags;
431 :
432 1 : flags = fcntl(master, F_GETFL);
433 1 : if (flags < 0)
434 0 : return -errno;
435 :
436 2 : if ((fcntl(master, F_SETFL, flags | O_NONBLOCK | O_ASYNC) < 0) ||
437 1 : (fcntl(master, F_SETOWN, os_getpid()) < 0))
438 0 : return -errno;
439 :
440 1 : if ((fcntl(slave, F_SETFL, flags | O_NONBLOCK) < 0))
441 0 : return -errno;
442 :
443 : return 0;
444 : }
445 :
446 1 : static void __init check_one_sigio(void (*proc)(int, int))
447 : {
448 : struct sigaction old, new;
449 1 : struct openpty_arg pty = { .master = -1, .slave = -1 };
450 : int master, slave, err;
451 :
452 1 : initial_thread_cb(openpty_cb, &pty);
453 1 : if (pty.err) {
454 0 : printk(UM_KERN_ERR "check_one_sigio failed, errno = %d\n",
455 : -pty.err);
456 0 : return;
457 : }
458 :
459 1 : master = pty.master;
460 1 : slave = pty.slave;
461 :
462 1 : if ((master == -1) || (slave == -1)) {
463 0 : printk(UM_KERN_ERR "check_one_sigio failed to allocate a "
464 : "pty\n");
465 0 : return;
466 : }
467 :
468 : /* Not now, but complain so we now where we failed. */
469 1 : err = raw(master);
470 1 : if (err < 0) {
471 0 : printk(UM_KERN_ERR "check_one_sigio : raw failed, errno = %d\n",
472 : -err);
473 0 : return;
474 : }
475 :
476 1 : err = async_pty(master, slave);
477 1 : if (err < 0) {
478 0 : printk(UM_KERN_ERR "check_one_sigio : sigio_async failed, "
479 : "err = %d\n", -err);
480 0 : return;
481 : }
482 :
483 1 : if (sigaction(SIGIO, NULL, &old) < 0) {
484 0 : printk(UM_KERN_ERR "check_one_sigio : sigaction 1 failed, "
485 : "errno = %d\n", errno);
486 0 : return;
487 : }
488 :
489 1 : new = old;
490 1 : new.sa_handler = handler;
491 1 : if (sigaction(SIGIO, &new, NULL) < 0) {
492 0 : printk(UM_KERN_ERR "check_one_sigio : sigaction 2 failed, "
493 : "errno = %d\n", errno);
494 0 : return;
495 : }
496 :
497 1 : got_sigio = 0;
498 1 : (*proc)(master, slave);
499 :
500 1 : close(master);
501 1 : close(slave);
502 :
503 1 : if (sigaction(SIGIO, &old, NULL) < 0)
504 0 : printk(UM_KERN_ERR "check_one_sigio : sigaction 3 failed, "
505 : "errno = %d\n", errno);
506 : }
507 :
508 1 : static void tty_output(int master, int slave)
509 : {
510 : int n;
511 : char buf[512];
512 :
513 1 : printk(UM_KERN_INFO "Checking that host ptys support output SIGIO...");
514 :
515 1 : memset(buf, 0, sizeof(buf));
516 :
517 1 : while (write(master, buf, sizeof(buf)) > 0) ;
518 1 : if (errno != EAGAIN)
519 0 : printk(UM_KERN_ERR "tty_output : write failed, errno = %d\n",
520 : errno);
521 80 : while (((n = read(slave, buf, sizeof(buf))) > 0) &&
522 40 : !({ barrier(); got_sigio; }))
523 : ;
524 :
525 1 : if (got_sigio) {
526 1 : printk(UM_KERN_CONT "Yes\n");
527 1 : pty_output_sigio = 1;
528 0 : } else if (n == -EAGAIN)
529 0 : printk(UM_KERN_CONT "No, enabling workaround\n");
530 : else
531 0 : printk(UM_KERN_CONT "tty_output : read failed, err = %d\n", n);
532 1 : }
533 :
534 1 : static void __init check_sigio(void)
535 : {
536 1 : if ((access("/dev/ptmx", R_OK) < 0) &&
537 0 : (access("/dev/ptyp0", R_OK) < 0)) {
538 0 : printk(UM_KERN_WARNING "No pseudo-terminals available - "
539 : "skipping pty SIGIO check\n");
540 0 : return;
541 : }
542 1 : check_one_sigio(tty_output);
543 : }
544 :
545 : /* Here because it only does the SIGIO testing for now */
546 1 : void __init os_check_bugs(void)
547 : {
548 1 : check_sigio();
549 1 : }
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