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 */
  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        signal(SIGWINCH, SIG_IGN);
  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(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
 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}
 547
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