arch/um/os-Linux/sigio.c

   1 /*
   2  * Copyright (C) 2002 Jeff Dike (jdike@karaya.com)
   3  * Licensed under the GPL
   4  */
   5
   6 #include <unistd.h>
   7 #include <stdlib.h>
   8 #include <termios.h>
   9 #include <pty.h>
  10 #include <signal.h>
  11 #include <fcntl.h>
  12 #include <errno.h>
  13 #include <string.h>
  14 #include <sched.h>
  15 #include <sys/socket.h>
  16 #include <sys/poll.h>
  17 #include "init.h"
  18 #include "user.h"
  19 #include "kern_util.h"
  20 #include "sigio.h"
  21 #include "os.h"
  22 #include "um_malloc.h"
  23 #include "init.h"
  24
  25 /* Protected by sigio_lock(), also used by sigio_cleanup, which is an
  26  * exitcall.
  27  */
  28 static int write_sigio_pid = -1;
  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 /* Protected by sigio_lock().  Used by the sigio thread, but the UML thread
  46  * synchronizes with it.
  47  */
  48 static struct pollfds current_poll;
  49 static struct pollfds next_poll;
  50 static struct pollfds all_sigio_fds;
  51
  52 static int write_sigio_thread(void *unused)
  53 {
  54         struct pollfds *fds, tmp;
  55         struct pollfd *p;
  56         int i, n, respond_fd;
  57         char c;
  58
  59         signal(SIGWINCH, SIG_IGN);
  60         fds = &current_poll;
  61         while(1){
  62                 n = poll(fds->poll, fds->used, -1);
  63                 if(n < 0){
  64                         if(errno == EINTR) continue;
  65                         printk("write_sigio_thread : poll returned %d, "
  66                                "errno = %d\n", n, errno);
  67                 }
  68                 for(i = 0; i < fds->used; i++){
  69                         p = &fds->poll[i];
  70                         if(p->revents == 0) continue;
  71                         if(p->fd == sigio_private[1]){
  72                                 n = os_read_file(sigio_private[1], &c, sizeof(c));
  73                                 if(n != sizeof(c))
  74                                         printk("write_sigio_thread : "
  75                                                "read on socket failed, "
  76                                                "err = %d\n", -n);
  77                                 tmp = current_poll;
  78                                 current_poll = next_poll;
  79                                 next_poll = tmp;
  80                                 respond_fd = sigio_private[1];
  81                         }
  82                         else {
  83                                 respond_fd = write_sigio_fds[1];
  84                                 fds->used--;
  85                                 memmove(&fds->poll[i], &fds->poll[i + 1],
  86                                         (fds->used - i) * sizeof(*fds->poll));
  87                         }
  88
  89                         n = os_write_file(respond_fd, &c, sizeof(c));
  90                         if(n != sizeof(c))
  91                                 printk("write_sigio_thread : write on socket "
  92                                        "failed, err = %d\n", -n);
  93                 }
  94         }
  95
  96         return 0;
  97 }
  98
  99 static int need_poll(struct pollfds *polls, int n)
 100 {
 101         struct pollfd *new;
 102
 103         if(n <= polls->size)
 104                 return 0;
 105
 106         new = um_kmalloc_atomic(n * sizeof(struct pollfd));
 107         if(new == NULL){
 108                 printk("need_poll : failed to allocate new pollfds\n");
 109                 return -ENOMEM;
 110         }
 111
 112         memcpy(new, polls->poll, polls->used * sizeof(struct pollfd));
 113         kfree(polls->poll);
 114
 115         polls->poll = new;
 116         polls->size = n;
 117         return 0;
 118 }
 119
 120 /* Must be called with sigio_lock held, because it's needed by the marked
 121  * critical section.
 122  */
 123 static void update_thread(void)
 124 {
 125         unsigned long flags;
 126         int n;
 127         char c;
 128
 129         flags = set_signals(0);
 130         n = os_write_file(sigio_private[0], &c, sizeof(c));
 131         if(n != sizeof(c)){
 132                 printk("update_thread : write failed, err = %d\n", -n);
 133                 goto fail;
 134         }
 135
 136         n = os_read_file(sigio_private[0], &c, sizeof(c));
 137         if(n != sizeof(c)){
 138                 printk("update_thread : read failed, err = %d\n", -n);
 139                 goto fail;
 140         }
 141
 142         set_signals(flags);
 143         return;
 144  fail:
 145         /* Critical section start */
 146         if(write_sigio_pid != -1)
 147                 os_kill_process(write_sigio_pid, 1);
 148         write_sigio_pid = -1;
 149         close(sigio_private[0]);
 150         close(sigio_private[1]);
 151         close(write_sigio_fds[0]);
 152         close(write_sigio_fds[1]);
 153         /* Critical section end */
 154         set_signals(flags);
 155 }
 156
 157 int add_sigio_fd(int fd)
 158 {
 159         struct pollfd *p;
 160         int err = 0, i, n;
 161
 162         sigio_lock();
 163         for(i = 0; i < all_sigio_fds.used; i++){
 164                 if(all_sigio_fds.poll[i].fd == fd)
 165                         break;
 166         }
 167         if(i == all_sigio_fds.used)
 168                 goto out;
 169
 170         p = &all_sigio_fds.poll[i];
 171
 172         for(i = 0; i < current_poll.used; i++){
 173                 if(current_poll.poll[i].fd == fd)
 174                         goto out;
 175         }
 176
 177         n = current_poll.used;
 178         err = need_poll(&next_poll, n + 1);
 179         if(err)
 180                 goto out;
 181
 182         memcpy(next_poll.poll, current_poll.poll,
 183                current_poll.used * sizeof(struct pollfd));
 184         next_poll.poll[n] = *p;
 185         next_poll.used = n + 1;
 186         update_thread();
 187  out:
 188         sigio_unlock();
 189         return err;
 190 }
 191
 192 int ignore_sigio_fd(int fd)
 193 {
 194         struct pollfd *p;
 195         int err = 0, i, n = 0;
 196
 197         /* This is called from exitcalls elsewhere in UML - if
 198          * sigio_cleanup has already run, then update_thread will hang
 199          * or fail because the thread is no longer running.
 200          */
 201         if(write_sigio_pid == -1)
 202                 return -EIO;
 203
 204         sigio_lock();
 205         for(i = 0; i < current_poll.used; i++){
 206                 if(current_poll.poll[i].fd == fd) break;
 207         }
 208         if(i == current_poll.used)
 209                 goto out;
 210
 211         err = need_poll(&next_poll, current_poll.used - 1);
 212         if(err)
 213                 goto out;
 214
 215         for(i = 0; i < current_poll.used; i++){
 216                 p = &current_poll.poll[i];
 217                 if(p->fd != fd)
 218                         next_poll.poll[n++] = *p;
 219         }
 220         next_poll.used = current_poll.used - 1;
 221
 222         update_thread();
 223  out:
 224         sigio_unlock();
 225         return err;
 226 }
 227
 228 static struct pollfd *setup_initial_poll(int fd)
 229 {
 230         struct pollfd *p;
 231
 232         p = um_kmalloc(sizeof(struct pollfd));
 233         if (p == NULL) {
 234                 printk("setup_initial_poll : failed to allocate poll\n");
 235                 return NULL;
 236         }
 237         *p = ((struct pollfd) { .fd             = fd,
 238                                 .events         = POLLIN,
 239                                 .revents        = 0 });
 240         return p;
 241 }
 242
 243 static void write_sigio_workaround(void)
 244 {
 245         unsigned long stack;
 246         struct pollfd *p;
 247         int err;
 248         int l_write_sigio_fds[2];
 249         int l_sigio_private[2];
 250         int l_write_sigio_pid;
 251
 252         /* We call this *tons* of times - and most ones we must just fail. */
 253         sigio_lock();
 254         l_write_sigio_pid = write_sigio_pid;
 255         sigio_unlock();
 256
 257         if (l_write_sigio_pid != -1)
 258                 return;
 259
 260         err = os_pipe(l_write_sigio_fds, 1, 1);
 261         if(err < 0){
 262                 printk("write_sigio_workaround - os_pipe 1 failed, "
 263                        "err = %d\n", -err);
 264                 return;
 265         }
 266         err = os_pipe(l_sigio_private, 1, 1);
 267         if(err < 0){
 268                 printk("write_sigio_workaround - os_pipe 2 failed, "
 269                        "err = %d\n", -err);
 270                 goto out_close1;
 271         }
 272
 273         p = setup_initial_poll(l_sigio_private[1]);
 274         if(!p)
 275                 goto out_close2;
 276
 277         sigio_lock();
 278
 279         /* Did we race? Don't try to optimize this, please, it's not so likely
 280          * to happen, and no more than once at the boot. */
 281         if(write_sigio_pid != -1)
 282                 goto out_free;
 283
 284         current_poll = ((struct pollfds) { .poll        = p,
 285                                            .used        = 1,
 286                                            .size        = 1 });
 287
 288         if (write_sigio_irq(l_write_sigio_fds[0]))
 289                 goto out_clear_poll;
 290
 291         memcpy(write_sigio_fds, l_write_sigio_fds, sizeof(l_write_sigio_fds));
 292         memcpy(sigio_private, l_sigio_private, sizeof(l_sigio_private));
 293
 294         write_sigio_pid = run_helper_thread(write_sigio_thread, NULL,
 295                                             CLONE_FILES | CLONE_VM, &stack, 0);
 296
 297         if (write_sigio_pid < 0)
 298                 goto out_clear;
 299
 300         sigio_unlock();
 301         return;
 302
 303 out_clear:
 304         write_sigio_pid = -1;
 305         write_sigio_fds[0] = -1;
 306         write_sigio_fds[1] = -1;
 307         sigio_private[0] = -1;
 308         sigio_private[1] = -1;
 309 out_clear_poll:
 310         current_poll = ((struct pollfds) { .poll        = NULL,
 311                                            .size        = 0,
 312                                            .used        = 0 });
 313 out_free:
 314         sigio_unlock();
 315         kfree(p);
 316 out_close2:
 317         close(l_sigio_private[0]);
 318         close(l_sigio_private[1]);
 319 out_close1:
 320         close(l_write_sigio_fds[0]);
 321         close(l_write_sigio_fds[1]);
 322 }
 323
 324 /* Changed during early boot */
 325 static int pty_output_sigio = 0;
 326 static int pty_close_sigio = 0;
 327
 328 void maybe_sigio_broken(int fd, int read)
 329 {
 330         int err;
 331
 332         if(!isatty(fd))
 333                 return;
 334
 335         if((read || pty_output_sigio) && (!read || pty_close_sigio))
 336                 return;
 337
 338         write_sigio_workaround();
 339
 340         sigio_lock();
 341         err = need_poll(&all_sigio_fds, all_sigio_fds.used + 1);
 342         if(err){
 343                 printk("maybe_sigio_broken - failed to add pollfd for "
 344                        "descriptor %d\n", fd);
 345                 goto out;
 346         }
 347
 348         all_sigio_fds.poll[all_sigio_fds.used++] =
 349                 ((struct pollfd) { .fd          = fd,
 350                                    .events      = read ? POLLIN : POLLOUT,
 351                                    .revents     = 0 });
 352 out:
 353         sigio_unlock();
 354 }
 355
 356 static void sigio_cleanup(void)
 357 {
 358         if(write_sigio_pid != -1){
 359                 os_kill_process(write_sigio_pid, 1);
 360                 write_sigio_pid = -1;
 361         }
 362 }
 363
 364 __uml_exitcall(sigio_cleanup);
 365
 366 /* Used as a flag during SIGIO testing early in boot */
 367 static volatile int got_sigio = 0;
 368
 369 static void __init handler(int sig)
 370 {
 371         got_sigio = 1;
 372 }
 373
 374 struct openpty_arg {
 375         int master;
 376         int slave;
 377         int err;
 378 };
 379
 380 static void openpty_cb(void *arg)
 381 {
 382         struct openpty_arg *info = arg;
 383
 384         info->err = 0;
 385         if(openpty(&info->master, &info->slave, NULL, NULL, NULL))
 386                 info->err = -errno;
 387 }
 388
 389 static int async_pty(int master, int slave)
 390 {
 391         int flags;
 392
 393         flags = fcntl(master, F_GETFL);
 394         if(flags < 0)
 395                 return -errno;
 396
 397         if((fcntl(master, F_SETFL, flags | O_NONBLOCK | O_ASYNC) < 0) ||
 398            (fcntl(master, F_SETOWN, os_getpid()) < 0))
 399                 return -errno;
 400
 401         if((fcntl(slave, F_SETFL, flags | O_NONBLOCK) < 0))
 402                 return -errno;
 403
 404         return(0);
 405 }
 406
 407 static void __init check_one_sigio(void (*proc)(int, int))
 408 {
 409         struct sigaction old, new;
 410         struct openpty_arg pty = { .master = -1, .slave = -1 };
 411         int master, slave, err;
 412
 413         initial_thread_cb(openpty_cb, &pty);
 414         if(pty.err){
 415                 printk("openpty failed, errno = %d\n", -pty.err);
 416                 return;
 417         }
 418
 419         master = pty.master;
 420         slave = pty.slave;
 421
 422         if((master == -1) || (slave == -1)){
 423                 printk("openpty failed to allocate a pty\n");
 424                 return;
 425         }
 426
 427         /* Not now, but complain so we now where we failed. */
 428         err = raw(master);
 429         if (err < 0)
 430                 panic("check_sigio : __raw failed, errno = %d\n", -err);
 431
 432         err = async_pty(master, slave);
 433         if(err < 0)
 434                 panic("tty_fds : sigio_async failed, err = %d\n", -err);
 435
 436         if(sigaction(SIGIO, NULL, &old) < 0)
 437                 panic("check_sigio : sigaction 1 failed, errno = %d\n", errno);
 438         new = old;
 439         new.sa_handler = handler;
 440         if(sigaction(SIGIO, &new, NULL) < 0)
 441                 panic("check_sigio : sigaction 2 failed, errno = %d\n", errno);
 442
 443         got_sigio = 0;
 444         (*proc)(master, slave);
 445
 446         close(master);
 447         close(slave);
 448
 449         if(sigaction(SIGIO, &old, NULL) < 0)
 450                 panic("check_sigio : sigaction 3 failed, errno = %d\n", errno);
 451 }
 452
 453 static void tty_output(int master, int slave)
 454 {
 455         int n;
 456         char buf[512];
 457
 458         printk("Checking that host ptys support output SIGIO...");
 459
 460         memset(buf, 0, sizeof(buf));
 461
 462         while(os_write_file(master, buf, sizeof(buf)) > 0) ;
 463         if(errno != EAGAIN)
 464                 panic("check_sigio : write failed, errno = %d\n", errno);
 465         while(((n = os_read_file(slave, buf, sizeof(buf))) > 0) && !got_sigio) ;
 466
 467         if(got_sigio){
 468                 printk("Yes\n");
 469                 pty_output_sigio = 1;
 470         }
 471         else if(n == -EAGAIN) printk("No, enabling workaround\n");
 472         else panic("check_sigio : read failed, err = %d\n", n);
 473 }
 474
 475 static void tty_close(int master, int slave)
 476 {
 477         printk("Checking that host ptys support SIGIO on close...");
 478
 479         close(slave);
 480         if(got_sigio){
 481                 printk("Yes\n");
 482                 pty_close_sigio = 1;
 483         }
 484         else printk("No, enabling workaround\n");
 485 }
 486
 487 void __init check_sigio(void)
 488 {
 489         if((os_access("/dev/ptmx", OS_ACC_R_OK) < 0) &&
 490            (os_access("/dev/ptyp0", OS_ACC_R_OK) < 0)){
 491                 printk("No pseudo-terminals available - skipping pty SIGIO "
 492                        "check\n");
 493                 return;
 494         }
 495         check_one_sigio(tty_output);
 496         check_one_sigio(tty_close);
 497 }
 498
 499 /* Here because it only does the SIGIO testing for now */
 500 void __init os_check_bugs(void)
 501 {
 502         check_sigio();
 503 }