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