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_constants.h"
  15 #include "kern_util.h"
  16 #include "init.h"
  17 #include "os.h"
  18 #include "process.h"
  19 #include "sigio.h"
  20 #include "um_malloc.h"
  21 #include "user.h"
  22
  23 /*
  24  * Protected by sigio_lock(), also used by sigio_cleanup, which is an
  25  * exitcall.
  26  */
  27 static int write_sigio_pid = -1;
  28 static unsigned long write_sigio_stack;
  29
  30 /*
  31  * These arrays are initialized before the sigio thread is started, and
  32  * the descriptors closed after it is killed.  So, it can't see them change.
  33  * On the UML side, they are changed under the sigio_lock.
  34  */
  35 #define SIGIO_FDS_INIT {-1, -1}
  36
  37 static int write_sigio_fds[2] = SIGIO_FDS_INIT;
  38 static int sigio_private[2] = SIGIO_FDS_INIT;
  39
  40 struct pollfds {
  41         struct pollfd *poll;
  42         int size;
  43         int used;
  44 };
  45
  46 /*
  47  * Protected by sigio_lock().  Used by the sigio thread, but the UML thread
  48  * synchronizes with it.
  49  */
  50 static struct pollfds current_poll;
  51 static struct pollfds next_poll;
  52 static struct pollfds all_sigio_fds;
  53
  54 static int write_sigio_thread(void *unused)
  55 {
  56         struct pollfds *fds, tmp;
  57         struct pollfd *p;
  58         int i, n, respond_fd;
  59         char c;
  60
  61         signal(SIGWINCH, SIG_IGN);
  62         fds = &current_poll;
  63         while (1) {
  64                 n = poll(fds->poll, fds->used, -1);
  65                 if (n < 0) {
  66                         if (errno == EINTR)
  67                                 continue;
  68                         printk(UM_KERN_ERR "write_sigio_thread : poll returned "
  69                                "%d, errno = %d\n", n, errno);
  70                 }
  71                 for (i = 0; i < fds->used; i++) {
  72                         p = &fds->poll[i];
  73                         if (p->revents == 0)
  74                                 continue;
  75                         if (p->fd == sigio_private[1]) {
  76                                 CATCH_EINTR(n = read(sigio_private[1], &c,
  77                                                      sizeof(c)));
  78                                 if (n != sizeof(c))
  79                                         printk(UM_KERN_ERR
  80                                                "write_sigio_thread : "
  81                                                "read on socket failed, "
  82                                                "err = %d\n", errno);
  83                                 tmp = current_poll;
  84                                 current_poll = next_poll;
  85                                 next_poll = tmp;
  86                                 respond_fd = sigio_private[1];
  87                         }
  88                         else {
  89                                 respond_fd = write_sigio_fds[1];
  90                                 fds->used--;
  91                                 memmove(&fds->poll[i], &fds->poll[i + 1],
  92                                         (fds->used - i) * sizeof(*fds->poll));
  93                         }
  94
  95                         CATCH_EINTR(n = write(respond_fd, &c, sizeof(c)));
  96                         if (n != sizeof(c))
  97                                 printk(UM_KERN_ERR "write_sigio_thread : "
  98                                        "write on socket failed, err = %d\n",
  99                                        errno);
 100                 }
 101         }
 102
 103         return 0;
 104 }
 105
 106 static int need_poll(struct pollfds *polls, int n)
 107 {
 108         struct pollfd *new;
 109
 110         if (n <= polls->size)
 111                 return 0;
 112
 113         new = uml_kmalloc(n * sizeof(struct pollfd), UM_GFP_ATOMIC);
 114         if (new == NULL) {
 115                 printk(UM_KERN_ERR "need_poll : failed to allocate new "
 116                        "pollfds\n");
 117                 return -ENOMEM;
 118         }
 119
 120         memcpy(new, polls->poll, polls->used * sizeof(struct pollfd));
 121         kfree(polls->poll);
 122
 123         polls->poll = new;
 124         polls->size = n;
 125         return 0;
 126 }
 127
 128 /*
 129  * Must be called with sigio_lock held, because it's needed by the marked
 130  * critical section.
 131  */
 132 static void update_thread(void)
 133 {
 134         unsigned long flags;
 135         int n;
 136         char c;
 137
 138         flags = set_signals(0);
 139         CATCH_EINTR(n = write(sigio_private[0], &c, sizeof(c)));
 140         if (n != sizeof(c)) {
 141                 printk(UM_KERN_ERR "update_thread : write failed, err = %d\n",
 142                        errno);
 143                 goto fail;
 144         }
 145
 146         CATCH_EINTR(n = read(sigio_private[0], &c, sizeof(c)));
 147         if (n != sizeof(c)) {
 148                 printk(UM_KERN_ERR "update_thread : read failed, err = %d\n",
 149                        errno);
 150                 goto fail;
 151         }
 152
 153         set_signals(flags);
 154         return;
 155  fail:
 156         /* Critical section start */
 157         if (write_sigio_pid != -1) {
 158                 os_kill_process(write_sigio_pid, 1);
 159                 free_stack(write_sigio_stack, 0);
 160         }
 161         write_sigio_pid = -1;
 162         close(sigio_private[0]);
 163         close(sigio_private[1]);
 164         close(write_sigio_fds[0]);
 165         close(write_sigio_fds[1]);
 166         /* Critical section end */
 167         set_signals(flags);
 168 }
 169
 170 int add_sigio_fd(int fd)
 171 {
 172         struct pollfd *p;
 173         int err = 0, i, n;
 174
 175         sigio_lock();
 176         for (i = 0; i < all_sigio_fds.used; i++) {
 177                 if (all_sigio_fds.poll[i].fd == fd)
 178                         break;
 179         }
 180         if (i == all_sigio_fds.used)
 181                 goto out;
 182
 183         p = &all_sigio_fds.poll[i];
 184
 185         for (i = 0; i < current_poll.used; i++) {
 186                 if (current_poll.poll[i].fd == fd)
 187                         goto out;
 188         }
 189
 190         n = current_poll.used;
 191         err = need_poll(&next_poll, n + 1);
 192         if (err)
 193                 goto out;
 194
 195         memcpy(next_poll.poll, current_poll.poll,
 196                current_poll.used * sizeof(struct pollfd));
 197         next_poll.poll[n] = *p;
 198         next_poll.used = n + 1;
 199         update_thread();
 200  out:
 201         sigio_unlock();
 202         return err;
 203 }
 204
 205 int ignore_sigio_fd(int fd)
 206 {
 207         struct pollfd *p;
 208         int err = 0, i, n = 0;
 209
 210         /*
 211          * This is called from exitcalls elsewhere in UML - if
 212          * sigio_cleanup has already run, then update_thread will hang
 213          * or fail because the thread is no longer running.
 214          */
 215         if (write_sigio_pid == -1)
 216                 return -EIO;
 217
 218         sigio_lock();
 219         for (i = 0; i < current_poll.used; i++) {
 220                 if (current_poll.poll[i].fd == fd)
 221                         break;
 222         }
 223         if (i == current_poll.used)
 224                 goto out;
 225
 226         err = need_poll(&next_poll, current_poll.used - 1);
 227         if (err)
 228                 goto out;
 229
 230         for (i = 0; i < current_poll.used; i++) {
 231                 p = &current_poll.poll[i];
 232                 if (p->fd != fd)
 233                         next_poll.poll[n++] = *p;
 234         }
 235         next_poll.used = current_poll.used - 1;
 236
 237         update_thread();
 238  out:
 239         sigio_unlock();
 240         return err;
 241 }
 242
 243 static struct pollfd *setup_initial_poll(int fd)
 244 {
 245         struct pollfd *p;
 246
 247         p = uml_kmalloc(sizeof(struct pollfd), UM_GFP_KERNEL);
 248         if (p == NULL) {
 249                 printk(UM_KERN_ERR "setup_initial_poll : failed to allocate "
 250                        "poll\n");
 251                 return NULL;
 252         }
 253         *p = ((struct pollfd) { .fd             = fd,
 254                                 .events         = POLLIN,
 255                                 .revents        = 0 });
 256         return p;
 257 }
 258
 259 static void write_sigio_workaround(void)
 260 {
 261         struct pollfd *p;
 262         int err;
 263         int l_write_sigio_fds[2];
 264         int l_sigio_private[2];
 265         int l_write_sigio_pid;
 266
 267         /* We call this *tons* of times - and most ones we must just fail. */
 268         sigio_lock();
 269         l_write_sigio_pid = write_sigio_pid;
 270         sigio_unlock();
 271
 272         if (l_write_sigio_pid != -1)
 273                 return;
 274
 275         err = os_pipe(l_write_sigio_fds, 1, 1);
 276         if (err < 0) {
 277                 printk(UM_KERN_ERR "write_sigio_workaround - os_pipe 1 failed, "
 278                        "err = %d\n", -err);
 279                 return;
 280         }
 281         err = os_pipe(l_sigio_private, 1, 1);
 282         if (err < 0) {
 283                 printk(UM_KERN_ERR "write_sigio_workaround - os_pipe 2 failed, "
 284                        "err = %d\n", -err);
 285                 goto out_close1;
 286         }
 287
 288         p = setup_initial_poll(l_sigio_private[1]);
 289         if (!p)
 290                 goto out_close2;
 291
 292         sigio_lock();
 293
 294         /*
 295          * Did we race? Don't try to optimize this, please, it's not so likely
 296          * to happen, and no more than once at the boot.
 297          */
 298         if (write_sigio_pid != -1)
 299                 goto out_free;
 300
 301         current_poll = ((struct pollfds) { .poll        = p,
 302                                            .used        = 1,
 303                                            .size        = 1 });
 304
 305         if (write_sigio_irq(l_write_sigio_fds[0]))
 306                 goto out_clear_poll;
 307
 308         memcpy(write_sigio_fds, l_write_sigio_fds, sizeof(l_write_sigio_fds));
 309         memcpy(sigio_private, l_sigio_private, sizeof(l_sigio_private));
 310
 311         write_sigio_pid = run_helper_thread(write_sigio_thread, NULL,
 312                                             CLONE_FILES | CLONE_VM,
 313                                             &write_sigio_stack);
 314
 315         if (write_sigio_pid < 0)
 316                 goto out_clear;
 317
 318         sigio_unlock();
 319         return;
 320
 321 out_clear:
 322         write_sigio_pid = -1;
 323         write_sigio_fds[0] = -1;
 324         write_sigio_fds[1] = -1;
 325         sigio_private[0] = -1;
 326         sigio_private[1] = -1;
 327 out_clear_poll:
 328         current_poll = ((struct pollfds) { .poll        = NULL,
 329                                            .size        = 0,
 330                                            .used        = 0 });
 331 out_free:
 332         sigio_unlock();
 333         kfree(p);
 334 out_close2:
 335         close(l_sigio_private[0]);
 336         close(l_sigio_private[1]);
 337 out_close1:
 338         close(l_write_sigio_fds[0]);
 339         close(l_write_sigio_fds[1]);
 340 }
 341
 342 void sigio_broken(int fd, int read)
 343 {
 344         int err;
 345
 346         write_sigio_workaround();
 347
 348         sigio_lock();
 349         err = need_poll(&all_sigio_fds, all_sigio_fds.used + 1);
 350         if (err) {
 351                 printk(UM_KERN_ERR "maybe_sigio_broken - failed to add pollfd "
 352                        "for descriptor %d\n", fd);
 353                 goto out;
 354         }
 355
 356         all_sigio_fds.poll[all_sigio_fds.used++] =
 357                 ((struct pollfd) { .fd          = fd,
 358                                    .events      = read ? POLLIN : POLLOUT,
 359                                    .revents     = 0 });
 360 out:
 361         sigio_unlock();
 362 }
 363
 364 /* Changed during early boot */
 365 static int pty_output_sigio;
 366 static int pty_close_sigio;
 367
 368 void maybe_sigio_broken(int fd, int read)
 369 {
 370         if (!isatty(fd))
 371                 return;
 372
 373         if ((read || pty_output_sigio) && (!read || pty_close_sigio))
 374                 return;
 375
 376         sigio_broken(fd, read);
 377 }
 378
 379 static void sigio_cleanup(void)
 380 {
 381         if (write_sigio_pid == -1)
 382                 return;
 383
 384         os_kill_process(write_sigio_pid, 1);
 385         free_stack(write_sigio_stack, 0);
 386         write_sigio_pid = -1;
 387 }
 388
 389 __uml_exitcall(sigio_cleanup);
 390
 391 /* Used as a flag during SIGIO testing early in boot */
 392 static int got_sigio;
 393
 394 static void __init handler(int sig)
 395 {
 396         got_sigio = 1;
 397 }
 398
 399 struct openpty_arg {
 400         int master;
 401         int slave;
 402         int err;
 403 };
 404
 405 static void openpty_cb(void *arg)
 406 {
 407         struct openpty_arg *info = arg;
 408
 409         info->err = 0;
 410         if (openpty(&info->master, &info->slave, NULL, NULL, NULL))
 411                 info->err = -errno;
 412 }
 413
 414 static int async_pty(int master, int slave)
 415 {
 416         int flags;
 417
 418         flags = fcntl(master, F_GETFL);
 419         if (flags < 0)
 420                 return -errno;
 421
 422         if ((fcntl(master, F_SETFL, flags | O_NONBLOCK | O_ASYNC) < 0) ||
 423             (fcntl(master, F_SETOWN, os_getpid()) < 0))
 424                 return -errno;
 425
 426         if ((fcntl(slave, F_SETFL, flags | O_NONBLOCK) < 0))
 427                 return -errno;
 428
 429         return 0;
 430 }
 431
 432 static void __init check_one_sigio(void (*proc)(int, int))
 433 {
 434         struct sigaction old, new;
 435         struct openpty_arg pty = { .master = -1, .slave = -1 };
 436         int master, slave, err;
 437
 438         initial_thread_cb(openpty_cb, &pty);
 439         if (pty.err) {
 440                 printk(UM_KERN_ERR "check_one_sigio failed, errno = %d\n",
 441                        -pty.err);
 442                 return;
 443         }
 444
 445         master = pty.master;
 446         slave = pty.slave;
 447
 448         if ((master == -1) || (slave == -1)) {
 449                 printk(UM_KERN_ERR "check_one_sigio failed to allocate a "
 450                        "pty\n");
 451                 return;
 452         }
 453
 454         /* Not now, but complain so we now where we failed. */
 455         err = raw(master);
 456         if (err < 0) {
 457                 printk(UM_KERN_ERR "check_one_sigio : raw failed, errno = %d\n",
 458                       -err);
 459                 return;
 460         }
 461
 462         err = async_pty(master, slave);
 463         if (err < 0) {
 464                 printk(UM_KERN_ERR "check_one_sigio : sigio_async failed, "
 465                        "err = %d\n", -err);
 466                 return;
 467         }
 468
 469         if (sigaction(SIGIO, NULL, &old) < 0) {
 470                 printk(UM_KERN_ERR "check_one_sigio : sigaction 1 failed, "
 471                        "errno = %d\n", errno);
 472                 return;
 473         }
 474
 475         new = old;
 476         new.sa_handler = handler;
 477         if (sigaction(SIGIO, &new, NULL) < 0) {
 478                 printk(UM_KERN_ERR "check_one_sigio : sigaction 2 failed, "
 479                        "errno = %d\n", errno);
 480                 return;
 481         }
 482
 483         got_sigio = 0;
 484         (*proc)(master, slave);
 485
 486         close(master);
 487         close(slave);
 488
 489         if (sigaction(SIGIO, &old, NULL) < 0)
 490                 printk(UM_KERN_ERR "check_one_sigio : sigaction 3 failed, "
 491                        "errno = %d\n", errno);
 492 }
 493
 494 static void tty_output(int master, int slave)
 495 {
 496         int n;
 497         char buf[512];
 498
 499         printk(UM_KERN_INFO "Checking that host ptys support output SIGIO...");
 500
 501         memset(buf, 0, sizeof(buf));
 502
 503         while (write(master, buf, sizeof(buf)) > 0) ;
 504         if (errno != EAGAIN)
 505                 printk(UM_KERN_ERR "tty_output : write failed, errno = %d\n",
 506                        errno);
 507         while (((n = read(slave, buf, sizeof(buf))) > 0) &&
 508                !({ barrier(); got_sigio; }))
 509                 ;
 510
 511         if (got_sigio) {
 512                 printk(UM_KERN_CONT "Yes\n");
 513                 pty_output_sigio = 1;
 514         } else if (n == -EAGAIN)
 515                 printk(UM_KERN_CONT "No, enabling workaround\n");
 516         else
 517                 printk(UM_KERN_CONT "tty_output : read failed, err = %d\n", n);
 518 }
 519
 520 static void tty_close(int master, int slave)
 521 {
 522         printk(UM_KERN_INFO "Checking that host ptys support SIGIO on "
 523                "close...");
 524
 525         close(slave);
 526         if (got_sigio) {
 527                 printk(UM_KERN_CONT "Yes\n");
 528                 pty_close_sigio = 1;
 529         } else
 530                 printk(UM_KERN_CONT "No, enabling workaround\n");
 531 }
 532
 533 static void __init check_sigio(void)
 534 {
 535         if ((access("/dev/ptmx", R_OK) < 0) &&
 536             (access("/dev/ptyp0", R_OK) < 0)) {
 537                 printk(UM_KERN_WARNING "No pseudo-terminals available - "
 538                        "skipping pty SIGIO check\n");
 539                 return;
 540         }
 541         check_one_sigio(tty_output);
 542         check_one_sigio(tty_close);
 543 }
 544
 545 /* Here because it only does the SIGIO testing for now */
 546 void __init os_check_bugs(void)
 547 {
 548         check_sigio();
 549 }