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/arch/um/os-Linux/sigio.c

http://github.com/mirrors/linux
C | 546 lines | 421 code | 88 blank | 37 comment | 86 complexity | 51210c5daf3ae3c15639328f7c5ce580 MD5 | raw file
  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 */
 24static int write_sigio_pid = -1;
 25static 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
 34static int write_sigio_fds[2] = SIGIO_FDS_INIT;
 35static int sigio_private[2] = SIGIO_FDS_INIT;
 36
 37struct 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 */
 47static struct pollfds current_poll;
 48static struct pollfds next_poll;
 49static struct pollfds all_sigio_fds;
 50
 51static 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 = &current_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
103static 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 */
129static void update_thread(void)
130{
131	unsigned long flags;
132	int n;
133	char c;
134
135	flags = 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	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	set_signals_trace(flags);
165}
166
167int add_sigio_fd(int fd)
168{
169	struct pollfd *p;
170	int err = 0, i, n;
171
172	sigio_lock();
173	for (i = 0; i < all_sigio_fds.used; i++) {
174		if (all_sigio_fds.poll[i].fd == fd)
175			break;
176	}
177	if (i == all_sigio_fds.used)
178		goto out;
179
180	p = &all_sigio_fds.poll[i];
181
182	for (i = 0; i < current_poll.used; i++) {
183		if (current_poll.poll[i].fd == fd)
184			goto out;
185	}
186
187	n = current_poll.used;
188	err = need_poll(&next_poll, n + 1);
189	if (err)
190		goto out;
191
192	memcpy(next_poll.poll, current_poll.poll,
193	       current_poll.used * sizeof(struct pollfd));
194	next_poll.poll[n] = *p;
195	next_poll.used = n + 1;
196	update_thread();
197 out:
198	sigio_unlock();
199	return err;
200}
201
202int ignore_sigio_fd(int fd)
203{
204	struct pollfd *p;
205	int err = 0, i, n = 0;
206
207	/*
208	 * This is called from exitcalls elsewhere in UML - if
209	 * sigio_cleanup has already run, then update_thread will hang
210	 * or fail because the thread is no longer running.
211	 */
212	if (write_sigio_pid == -1)
213		return -EIO;
214
215	sigio_lock();
216	for (i = 0; i < current_poll.used; i++) {
217		if (current_poll.poll[i].fd == fd)
218			break;
219	}
220	if (i == current_poll.used)
221		goto out;
222
223	err = need_poll(&next_poll, current_poll.used - 1);
224	if (err)
225		goto out;
226
227	for (i = 0; i < current_poll.used; i++) {
228		p = &current_poll.poll[i];
229		if (p->fd != fd)
230			next_poll.poll[n++] = *p;
231	}
232	next_poll.used = current_poll.used - 1;
233
234	update_thread();
235 out:
236	sigio_unlock();
237	return err;
238}
239
240static struct pollfd *setup_initial_poll(int fd)
241{
242	struct pollfd *p;
243
244	p = uml_kmalloc(sizeof(struct pollfd), UM_GFP_KERNEL);
245	if (p == NULL) {
246		printk(UM_KERN_ERR "setup_initial_poll : failed to allocate "
247		       "poll\n");
248		return NULL;
249	}
250	*p = ((struct pollfd) { .fd		= fd,
251				.events 	= POLLIN,
252				.revents 	= 0 });
253	return p;
254}
255
256static void write_sigio_workaround(void)
257{
258	struct pollfd *p;
259	int err;
260	int l_write_sigio_fds[2];
261	int l_sigio_private[2];
262	int l_write_sigio_pid;
263
264	/* We call this *tons* of times - and most ones we must just fail. */
265	sigio_lock();
266	l_write_sigio_pid = write_sigio_pid;
267	sigio_unlock();
268
269	if (l_write_sigio_pid != -1)
270		return;
271
272	err = os_pipe(l_write_sigio_fds, 1, 1);
273	if (err < 0) {
274		printk(UM_KERN_ERR "write_sigio_workaround - os_pipe 1 failed, "
275		       "err = %d\n", -err);
276		return;
277	}
278	err = os_pipe(l_sigio_private, 1, 1);
279	if (err < 0) {
280		printk(UM_KERN_ERR "write_sigio_workaround - os_pipe 2 failed, "
281		       "err = %d\n", -err);
282		goto out_close1;
283	}
284
285	p = setup_initial_poll(l_sigio_private[1]);
286	if (!p)
287		goto out_close2;
288
289	sigio_lock();
290
291	/*
292	 * Did we race? Don't try to optimize this, please, it's not so likely
293	 * to happen, and no more than once at the boot.
294	 */
295	if (write_sigio_pid != -1)
296		goto out_free;
297
298	current_poll = ((struct pollfds) { .poll 	= p,
299					   .used 	= 1,
300					   .size 	= 1 });
301
302	if (write_sigio_irq(l_write_sigio_fds[0]))
303		goto out_clear_poll;
304
305	memcpy(write_sigio_fds, l_write_sigio_fds, sizeof(l_write_sigio_fds));
306	memcpy(sigio_private, l_sigio_private, sizeof(l_sigio_private));
307
308	write_sigio_pid = run_helper_thread(write_sigio_thread, NULL,
309					    CLONE_FILES | CLONE_VM,
310					    &write_sigio_stack);
311
312	if (write_sigio_pid < 0)
313		goto out_clear;
314
315	sigio_unlock();
316	return;
317
318out_clear:
319	write_sigio_pid = -1;
320	write_sigio_fds[0] = -1;
321	write_sigio_fds[1] = -1;
322	sigio_private[0] = -1;
323	sigio_private[1] = -1;
324out_clear_poll:
325	current_poll = ((struct pollfds) { .poll	= NULL,
326					   .size	= 0,
327					   .used	= 0 });
328out_free:
329	sigio_unlock();
330	kfree(p);
331out_close2:
332	close(l_sigio_private[0]);
333	close(l_sigio_private[1]);
334out_close1:
335	close(l_write_sigio_fds[0]);
336	close(l_write_sigio_fds[1]);
337}
338
339void sigio_broken(int fd, int read)
340{
341	int err;
342
343	write_sigio_workaround();
344
345	sigio_lock();
346	err = need_poll(&all_sigio_fds, all_sigio_fds.used + 1);
347	if (err) {
348		printk(UM_KERN_ERR "maybe_sigio_broken - failed to add pollfd "
349		       "for descriptor %d\n", fd);
350		goto out;
351	}
352
353	all_sigio_fds.poll[all_sigio_fds.used++] =
354		((struct pollfd) { .fd  	= fd,
355				   .events 	= read ? POLLIN : POLLOUT,
356				   .revents 	= 0 });
357out:
358	sigio_unlock();
359}
360
361/* Changed during early boot */
362static int pty_output_sigio;
363static int pty_close_sigio;
364
365void maybe_sigio_broken(int fd, int read)
366{
367	if (!isatty(fd))
368		return;
369
370	if ((read || pty_output_sigio) && (!read || pty_close_sigio))
371		return;
372
373	sigio_broken(fd, read);
374}
375
376static void sigio_cleanup(void)
377{
378	if (write_sigio_pid == -1)
379		return;
380
381	os_kill_process(write_sigio_pid, 1);
382	free_stack(write_sigio_stack, 0);
383	write_sigio_pid = -1;
384}
385
386__uml_exitcall(sigio_cleanup);
387
388/* Used as a flag during SIGIO testing early in boot */
389static int got_sigio;
390
391static void __init handler(int sig)
392{
393	got_sigio = 1;
394}
395
396struct openpty_arg {
397	int master;
398	int slave;
399	int err;
400};
401
402static void openpty_cb(void *arg)
403{
404	struct openpty_arg *info = arg;
405
406	info->err = 0;
407	if (openpty(&info->master, &info->slave, NULL, NULL, NULL))
408		info->err = -errno;
409}
410
411static int async_pty(int master, int slave)
412{
413	int flags;
414
415	flags = fcntl(master, F_GETFL);
416	if (flags < 0)
417		return -errno;
418
419	if ((fcntl(master, F_SETFL, flags | O_NONBLOCK | O_ASYNC) < 0) ||
420	    (fcntl(master, F_SETOWN, os_getpid()) < 0))
421		return -errno;
422
423	if ((fcntl(slave, F_SETFL, flags | O_NONBLOCK) < 0))
424		return -errno;
425
426	return 0;
427}
428
429static void __init check_one_sigio(void (*proc)(int, int))
430{
431	struct sigaction old, new;
432	struct openpty_arg pty = { .master = -1, .slave = -1 };
433	int master, slave, err;
434
435	initial_thread_cb(openpty_cb, &pty);
436	if (pty.err) {
437		printk(UM_KERN_ERR "check_one_sigio failed, errno = %d\n",
438		       -pty.err);
439		return;
440	}
441
442	master = pty.master;
443	slave = pty.slave;
444
445	if ((master == -1) || (slave == -1)) {
446		printk(UM_KERN_ERR "check_one_sigio failed to allocate a "
447		       "pty\n");
448		return;
449	}
450
451	/* Not now, but complain so we now where we failed. */
452	err = raw(master);
453	if (err < 0) {
454		printk(UM_KERN_ERR "check_one_sigio : raw failed, errno = %d\n",
455		      -err);
456		return;
457	}
458
459	err = async_pty(master, slave);
460	if (err < 0) {
461		printk(UM_KERN_ERR "check_one_sigio : sigio_async failed, "
462		       "err = %d\n", -err);
463		return;
464	}
465
466	if (sigaction(SIGIO, NULL, &old) < 0) {
467		printk(UM_KERN_ERR "check_one_sigio : sigaction 1 failed, "
468		       "errno = %d\n", errno);
469		return;
470	}
471
472	new = old;
473	new.sa_handler = handler;
474	if (sigaction(SIGIO, &new, NULL) < 0) {
475		printk(UM_KERN_ERR "check_one_sigio : sigaction 2 failed, "
476		       "errno = %d\n", errno);
477		return;
478	}
479
480	got_sigio = 0;
481	(*proc)(master, slave);
482
483	close(master);
484	close(slave);
485
486	if (sigaction(SIGIO, &old, NULL) < 0)
487		printk(UM_KERN_ERR "check_one_sigio : sigaction 3 failed, "
488		       "errno = %d\n", errno);
489}
490
491static void tty_output(int master, int slave)
492{
493	int n;
494	char buf[512];
495
496	printk(UM_KERN_INFO "Checking that host ptys support output SIGIO...");
497
498	memset(buf, 0, sizeof(buf));
499
500	while (write(master, buf, sizeof(buf)) > 0) ;
501	if (errno != EAGAIN)
502		printk(UM_KERN_ERR "tty_output : write failed, errno = %d\n",
503		       errno);
504	while (((n = read(slave, buf, sizeof(buf))) > 0) &&
505	       !({ barrier(); got_sigio; }))
506		;
507
508	if (got_sigio) {
509		printk(UM_KERN_CONT "Yes\n");
510		pty_output_sigio = 1;
511	} else if (n == -EAGAIN)
512		printk(UM_KERN_CONT "No, enabling workaround\n");
513	else
514		printk(UM_KERN_CONT "tty_output : read failed, err = %d\n", n);
515}
516
517static void tty_close(int master, int slave)
518{
519	printk(UM_KERN_INFO "Checking that host ptys support SIGIO on "
520	       "close...");
521
522	close(slave);
523	if (got_sigio) {
524		printk(UM_KERN_CONT "Yes\n");
525		pty_close_sigio = 1;
526	} else
527		printk(UM_KERN_CONT "No, enabling workaround\n");
528}
529
530static void __init check_sigio(void)
531{
532	if ((access("/dev/ptmx", R_OK) < 0) &&
533	    (access("/dev/ptyp0", R_OK) < 0)) {
534		printk(UM_KERN_WARNING "No pseudo-terminals available - "
535		       "skipping pty SIGIO check\n");
536		return;
537	}
538	check_one_sigio(tty_output);
539	check_one_sigio(tty_close);
540}
541
542/* Here because it only does the SIGIO testing for now */
543void __init os_check_bugs(void)
544{
545	check_sigio();
546}