arch/um/os-Linux/sigio.c

   1 /*
   2  * Copyright (C) 2002 - 2007 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_constants.h"
  15 #include "kern_util.h"
  16 #include "init.h"
  17 #include "os.h"
  18 #include "sigio.h"
  19 #include "um_malloc.h"
  20 #include "user.h"
  21
  22 /*
  23  * Protected by sigio_lock(), also used by sigio_cleanup, which is an
  24  * exitcall.
  25  */
  26 static int write_sigio_pid = -1;
  27 static unsigned long write_sigio_stack;
  28
  29 /*
  30  * These arrays are initialized before the sigio thread is started, and
  31  * the descriptors closed after it is killed.  So, it can't see them change.
  32  * On the UML side, they are changed under the sigio_lock.
  33  */
  34 #define SIGIO_FDS_INIT {-1, -1}
  35
  36 static int write_sigio_fds[2] = SIGIO_FDS_INIT;
  37 static int sigio_private[2] = SIGIO_FDS_INIT;
  38
  39 struct pollfds {
  40         struct pollfd *poll;
  41         int size;
  42         int used;
  43 };
  44
  45 /*
  46  * Protected by sigio_lock().  Used by the sigio thread, but the UML thread
  47  * synchronizes with it.
  48  */
  49 static struct pollfds current_poll;
  50 static struct pollfds next_poll;
  51 static struct pollfds all_sigio_fds;
  52
  53 static int write_sigio_thread(void *unused)
  54 {
  55         struct pollfds *fds, tmp;
  56         struct pollfd *p;
  57         int i, n, respond_fd;
  58         char c;
  59
  60         signal(SIGWINCH, SIG_IGN);
  61         fds = &current_poll;
  62         while (1) {
  63                 n = poll(fds->poll, fds->used, -1);
  64                 if (n < 0) {
  65                         if (errno == EINTR)
  66                                 continue;
  67                         printk(UM_KERN_ERR "write_sigio_thread : poll returned "
  68                                "%d, errno = %d\n", n, errno);
  69                 }
  70                 for (i = 0; i < fds->used; i++) {
  71                         p = &fds->poll[i];
  72                         if (p->revents == 0)
  73                                 continue;
  74                         if (p->fd == sigio_private[1]) {
  75                                 CATCH_EINTR(n = read(sigio_private[1], &c,
  76                                                      sizeof(c)));
  77                                 if (n != sizeof(c))
  78                                         printk(UM_KERN_ERR
  79                                                "write_sigio_thread : "
  80                                                "read on socket failed, "
  81                                                "err = %d\n", errno);
  82                                 tmp = current_poll;
  83                                 current_poll = next_poll;
  84                                 next_poll = tmp;
  85                                 respond_fd = sigio_private[1];
  86                         }
  87                         else {
  88                                 respond_fd = write_sigio_fds[1];
  89                                 fds->used--;
  90                                 memmove(&fds->poll[i], &fds->poll[i + 1],
  91                                         (fds->used - i) * sizeof(*fds->poll));
  92                         }
  93
  94                         CATCH_EINTR(n = write(respond_fd, &c, sizeof(c)));
  95                         if (n != sizeof(c))
  96                                 printk(UM_KERN_ERR "write_sigio_thread : "
  97                                        "write on socket failed, err = %d\n",
  98                                        errno);
  99                 }
 100         }
 101
 102         return 0;
 103 }
 104
 105 static int need_poll(struct pollfds *polls, int n)
 106 {
 107         struct pollfd *new;
 108
 109         if (n <= polls->size)
 110                 return 0;
 111
 112         new = kmalloc(n * sizeof(struct pollfd), UM_GFP_ATOMIC);
 113         if (new == NULL) {
 114                 printk(UM_KERN_ERR "need_poll : failed to allocate new "
 115                        "pollfds\n");
 116                 return -ENOMEM;
 117         }
 118
 119         memcpy(new, polls->poll, polls->used * sizeof(struct pollfd));
 120         kfree(polls->poll);
 121
 122         polls->poll = new;
 123         polls->size = n;
 124         return 0;
 125 }
 126
 127 /*
 128  * Must be called with sigio_lock held, because it's needed by the marked
 129  * critical section.
 130  */
 131 static void update_thread(void)
 132 {
 133         unsigned long flags;
 134         int n;
 135         char c;
 136
 137         flags = set_signals(0);
 138         CATCH_EINTR(n = write(sigio_private[0], &c, sizeof(c)));
 139         if (n != sizeof(c)) {
 140                 printk(UM_KERN_ERR "update_thread : write failed, err = %d\n",
 141                        errno);
 142                 goto fail;
 143         }
 144
 145         CATCH_EINTR(n = read(sigio_private[0], &c, sizeof(c)));
 146         if (n != sizeof(c)) {
 147                 printk(UM_KERN_ERR "update_thread : read failed, err = %d\n",
 148                        errno);
 149                 goto fail;
 150         }
 151
 152         set_signals(flags);
 153         return;
 154  fail:
 155         /* Critical section start */
 156         if (write_sigio_pid != -1) {
 157                 os_kill_process(write_sigio_pid, 1);
 158                 free_stack(write_sigio_stack, 0);
 159         }
 160         write_sigio_pid = -1;
 161         close(sigio_private[0]);
 162         close(sigio_private[1]);
 163         close(write_sigio_fds[0]);
 164         close(write_sigio_fds[1]);
 165         /* Critical section end */
 166         set_signals(flags);
 167 }
 168
 169 int add_sigio_fd(int fd)
 170 {
 171         struct pollfd *p;
 172         int err = 0, i, n;
 173
 174         sigio_lock();
 175         for (i = 0; i < all_sigio_fds.used; i++) {
 176                 if (all_sigio_fds.poll[i].fd == fd)
 177                         break;
 178         }
 179         if (i == all_sigio_fds.used)
 180                 goto out;
 181
 182         p = &all_sigio_fds.poll[i];
 183
 184         for (i = 0; i < current_poll.used; i++) {
 185                 if (current_poll.poll[i].fd == fd)
 186                         goto out;
 187         }
 188
 189         n = current_poll.used;
 190         err = need_poll(&next_poll, n + 1);
 191         if (err)
 192                 goto out;
 193
 194         memcpy(next_poll.poll, current_poll.poll,
 195                current_poll.used * sizeof(struct pollfd));
 196         next_poll.poll[n] = *p;
 197         next_poll.used = n + 1;
 198         update_thread();
 199  out:
 200         sigio_unlock();
 201         return err;
 202 }
 203
 204 int ignore_sigio_fd(int fd)
 205 {
 206         struct pollfd *p;
 207         int err = 0, i, n = 0;
 208
 209         /*
 210          * This is called from exitcalls elsewhere in UML - if
 211          * sigio_cleanup has already run, then update_thread will hang
 212          * or fail because the thread is no longer running.
 213          */
 214         if (write_sigio_pid == -1)
 215                 return -EIO;
 216
 217         sigio_lock();
 218         for (i = 0; i < current_poll.used; i++) {
 219                 if (current_poll.poll[i].fd == fd)
 220                         break;
 221         }
 222         if (i == current_poll.used)
 223                 goto out;
 224
 225         err = need_poll(&next_poll, current_poll.used - 1);
 226         if (err)
 227                 goto out;
 228
 229         for (i = 0; i < current_poll.used; i++) {
 230                 p = &current_poll.poll[i];
 231                 if (p->fd != fd)
 232                         next_poll.poll[n++] = *p;
 233         }
 234         next_poll.used = current_poll.used - 1;
 235
 236         update_thread();
 237  out:
 238         sigio_unlock();
 239         return err;
 240 }
 241
 242 static struct pollfd *setup_initial_poll(int fd)
 243 {
 244         struct pollfd *p;
 245
 246         p = kmalloc(sizeof(struct pollfd), UM_GFP_KERNEL);
 247         if (p == NULL) {
 248                 printk(UM_KERN_ERR "setup_initial_poll : failed to allocate "
 249                        "poll\n");
 250                 return NULL;
 251         }
 252         *p = ((struct pollfd) { .fd             = fd,
 253                                 .events         = POLLIN,
 254                                 .revents        = 0 });
 255         return p;
 256 }
 257
 258 static void write_sigio_workaround(void)
 259 {
 260         struct pollfd *p;
 261         int err;
 262         int l_write_sigio_fds[2];
 263         int l_sigio_private[2];
 264         int l_write_sigio_pid;
 265
 266         /* We call this *tons* of times - and most ones we must just fail. */
 267         sigio_lock();
 268         l_write_sigio_pid = write_sigio_pid;
 269         sigio_unlock();
 270
 271         if (l_write_sigio_pid != -1)
 272                 return;
 273
 274         err = os_pipe(l_write_sigio_fds, 1, 1);
 275         if (err < 0) {
 276                 printk(UM_KERN_ERR "write_sigio_workaround - os_pipe 1 failed, "
 277                        "err = %d\n", -err);
 278                 return;
 279         }
 280         err = os_pipe(l_sigio_private, 1, 1);
 281         if (err < 0) {
 282                 printk(UM_KERN_ERR "write_sigio_workaround - os_pipe 2 failed, "
 283                        "err = %d\n", -err);
 284                 goto out_close1;
 285         }
 286
 287         p = setup_initial_poll(l_sigio_private[1]);
 288         if (!p)
 289                 goto out_close2;
 290
 291         sigio_lock();
 292
 293         /*
 294          * Did we race? Don't try to optimize this, please, it's not so likely
 295          * to happen, and no more than once at the boot.
 296          */
 297         if (write_sigio_pid != -1)
 298                 goto out_free;
 299
 300         current_poll = ((struct pollfds) { .poll        = p,
 301                                            .used        = 1,
 302                                            .size        = 1 });
 303
 304         if (write_sigio_irq(l_write_sigio_fds[0]))
 305                 goto out_clear_poll;
 306
 307         memcpy(write_sigio_fds, l_write_sigio_fds, sizeof(l_write_sigio_fds));
 308         memcpy(sigio_private, l_sigio_private, sizeof(l_sigio_private));
 309
 310         write_sigio_pid = run_helper_thread(write_sigio_thread, NULL,
 311                                             CLONE_FILES | CLONE_VM,
 312                                             &write_sigio_stack);
 313
 314         if (write_sigio_pid < 0)
 315                 goto out_clear;
 316
 317         sigio_unlock();
 318         return;
 319
 320 out_clear:
 321         write_sigio_pid = -1;
 322         write_sigio_fds[0] = -1;
 323         write_sigio_fds[1] = -1;
 324         sigio_private[0] = -1;
 325         sigio_private[1] = -1;
 326 out_clear_poll:
 327         current_poll = ((struct pollfds) { .poll        = NULL,
 328                                            .size        = 0,
 329                                            .used        = 0 });
 330 out_free:
 331         sigio_unlock();
 332         kfree(p);
 333 out_close2:
 334         close(l_sigio_private[0]);
 335         close(l_sigio_private[1]);
 336 out_close1:
 337         close(l_write_sigio_fds[0]);
 338         close(l_write_sigio_fds[1]);
 339 }
 340
 341 /* Changed during early boot */
 342 static int pty_output_sigio = 0;
 343 static int pty_close_sigio = 0;
 344
 345 void maybe_sigio_broken(int fd, int read)
 346 {
 347         int err;
 348
 349         if (!isatty(fd))
 350                 return;
 351
 352         if ((read || pty_output_sigio) && (!read || pty_close_sigio))
 353                 return;
 354
 355         write_sigio_workaround();
 356
 357         sigio_lock();
 358         err = need_poll(&all_sigio_fds, all_sigio_fds.used + 1);
 359         if (err) {
 360                 printk(UM_KERN_ERR "maybe_sigio_broken - failed to add pollfd "
 361                        "for descriptor %d\n", fd);
 362                 goto out;
 363         }
 364
 365         all_sigio_fds.poll[all_sigio_fds.used++] =
 366                 ((struct pollfd) { .fd          = fd,
 367                                    .events      = read ? POLLIN : POLLOUT,
 368                                    .revents     = 0 });
 369 out:
 370         sigio_unlock();
 371 }
 372
 373 static void sigio_cleanup(void)
 374 {
 375         if (write_sigio_pid == -1)
 376                 return;
 377
 378         os_kill_process(write_sigio_pid, 1);
 379         free_stack(write_sigio_stack, 0);
 380         write_sigio_pid = -1;
 381 }
 382
 383 __uml_exitcall(sigio_cleanup);
 384
 385 /* Used as a flag during SIGIO testing early in boot */
 386 static volatile int got_sigio = 0;
 387
 388 static void __init handler(int sig)
 389 {
 390         got_sigio = 1;
 391 }
 392
 393 struct openpty_arg {
 394         int master;
 395         int slave;
 396         int err;
 397 };
 398
 399 static void openpty_cb(void *arg)
 400 {
 401         struct openpty_arg *info = arg;
 402
 403         info->err = 0;
 404         if (openpty(&info->master, &info->slave, NULL, NULL, NULL))
 405                 info->err = -errno;
 406 }
 407
 408 static int async_pty(int master, int slave)
 409 {
 410         int flags;
 411
 412         flags = fcntl(master, F_GETFL);
 413         if (flags < 0)
 414                 return -errno;
 415
 416         if ((fcntl(master, F_SETFL, flags | O_NONBLOCK | O_ASYNC) < 0) ||
 417             (fcntl(master, F_SETOWN, os_getpid()) < 0))
 418                 return -errno;
 419
 420         if ((fcntl(slave, F_SETFL, flags | O_NONBLOCK) < 0))
 421                 return -errno;
 422
 423         return 0;
 424 }
 425
 426 static void __init check_one_sigio(void (*proc)(int, int))
 427 {
 428         struct sigaction old, new;
 429         struct openpty_arg pty = { .master = -1, .slave = -1 };
 430         int master, slave, err;
 431
 432         initial_thread_cb(openpty_cb, &pty);
 433         if (pty.err) {
 434                 printk(UM_KERN_ERR "check_one_sigio failed, errno = %d\n",
 435                        -pty.err);
 436                 return;
 437         }
 438
 439         master = pty.master;
 440         slave = pty.slave;
 441
 442         if ((master == -1) || (slave == -1)) {
 443                 printk(UM_KERN_ERR "check_one_sigio failed to allocate a "
 444                        "pty\n");
 445                 return;
 446         }
 447
 448         /* Not now, but complain so we now where we failed. */
 449         err = raw(master);
 450         if (err < 0) {
 451                 printk(UM_KERN_ERR "check_one_sigio : raw failed, errno = %d\n",
 452                       -err);
 453                 return;
 454         }
 455
 456         err = async_pty(master, slave);
 457         if (err < 0) {
 458                 printk(UM_KERN_ERR "check_one_sigio : sigio_async failed, "
 459                        "err = %d\n", -err);
 460                 return;
 461         }
 462
 463         if (sigaction(SIGIO, NULL, &old) < 0) {
 464                 printk(UM_KERN_ERR "check_one_sigio : sigaction 1 failed, "
 465                        "errno = %d\n", errno);
 466                 return;
 467         }
 468
 469         new = old;
 470         new.sa_handler = handler;
 471         if (sigaction(SIGIO, &new, NULL) < 0) {
 472                 printk(UM_KERN_ERR "check_one_sigio : sigaction 2 failed, "
 473                        "errno = %d\n", errno);
 474                 return;
 475         }
 476
 477         got_sigio = 0;
 478         (*proc)(master, slave);
 479
 480         close(master);
 481         close(slave);
 482
 483         if (sigaction(SIGIO, &old, NULL) < 0)
 484                 printk(UM_KERN_ERR "check_one_sigio : sigaction 3 failed, "
 485                        "errno = %d\n", errno);
 486 }
 487
 488 static void tty_output(int master, int slave)
 489 {
 490         int n;
 491         char buf[512];
 492
 493         printk(UM_KERN_INFO "Checking that host ptys support output SIGIO...");
 494
 495         memset(buf, 0, sizeof(buf));
 496
 497         while (write(master, buf, sizeof(buf)) > 0) ;
 498         if (errno != EAGAIN)
 499                 printk(UM_KERN_ERR "tty_output : write failed, errno = %d\n",
 500                        errno);
 501         while (((n = read(slave, buf, sizeof(buf))) > 0) && !got_sigio)
 502                 ;
 503
 504         if (got_sigio) {
 505                 printk(UM_KERN_CONT "Yes\n");
 506                 pty_output_sigio = 1;
 507         } else if (n == -EAGAIN)
 508                 printk(UM_KERN_CONT "No, enabling workaround\n");
 509         else
 510                 printk(UM_KERN_CONT "tty_output : read failed, err = %d\n", n);
 511 }
 512
 513 static void tty_close(int master, int slave)
 514 {
 515         printk(UM_KERN_INFO "Checking that host ptys support SIGIO on "
 516                "close...");
 517
 518         close(slave);
 519         if (got_sigio) {
 520                 printk(UM_KERN_CONT "Yes\n");
 521                 pty_close_sigio = 1;
 522         } else
 523                 printk(UM_KERN_CONT "No, enabling workaround\n");
 524 }
 525
 526 void __init check_sigio(void)
 527 {
 528         if ((access("/dev/ptmx", R_OK) < 0) &&
 529             (access("/dev/ptyp0", R_OK) < 0)) {
 530                 printk(UM_KERN_WARNING "No pseudo-terminals available - "
 531                        "skipping pty SIGIO check\n");
 532                 return;
 533         }
 534         check_one_sigio(tty_output);
 535         check_one_sigio(tty_close);
 536 }
 537
 538 /* Here because it only does the SIGIO testing for now */
 539 void __init os_check_bugs(void)
 540 {
 541         check_sigio();
 542 }