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TOMOYO Linux Cross Reference
Linux/arch/um/os-Linux/sigio.c

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  1 /*
  2  * Copyright (C) 2002 - 2008 Jeff Dike (jdike@{addtoit,linux.intel}.com)
  3  * Licensed under the GPL
  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 
 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 = &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 
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  */
129 static void update_thread(void)
130 {
131         unsigned long flags;
132         int n;
133         char c;
134 
135         flags = set_signals(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(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(flags);
165 }
166 
167 int 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 
202 int 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 
240 static 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 
256 static 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 
318 out_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;
324 out_clear_poll:
325         current_poll = ((struct pollfds) { .poll        = NULL,
326                                            .size        = 0,
327                                            .used        = 0 });
328 out_free:
329         sigio_unlock();
330         kfree(p);
331 out_close2:
332         close(l_sigio_private[0]);
333         close(l_sigio_private[1]);
334 out_close1:
335         close(l_write_sigio_fds[0]);
336         close(l_write_sigio_fds[1]);
337 }
338 
339 void 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 });
357 out:
358         sigio_unlock();
359 }
360 
361 /* Changed during early boot */
362 static int pty_output_sigio;
363 static int pty_close_sigio;
364 
365 void 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 
376 static 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 */
389 static int got_sigio;
390 
391 static void __init handler(int sig)
392 {
393         got_sigio = 1;
394 }
395 
396 struct openpty_arg {
397         int master;
398         int slave;
399         int err;
400 };
401 
402 static 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 
411 static 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 
429 static 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 
491 static 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 
517 static 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 
530 static 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 */
543 void __init os_check_bugs(void)
544 {
545         check_sigio();
546 }
547 

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