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

   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 }