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