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 <errno.h>
  12 #include <string.h>
  13 #include <sched.h>
  14 #include <sys/socket.h>
  15 #include <sys/poll.h>
  16 #include "init.h"
  17 #include "user.h"
  18 #include "kern_util.h"
  19 #include "user_util.h"
  20 #include "sigio.h"
  21 #include "os.h"
  22
  23 /* Protected by sigio_lock(), also used by sigio_cleanup, which is an
  24  * exitcall.
  25  */
  26 static int write_sigio_pid = -1;
  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
  34 static int write_sigio_fds[2] = SIGIO_FDS_INIT;
  35 static int sigio_private[2] = SIGIO_FDS_INIT;
  36
  37 struct pollfds {
  38         struct pollfd *poll;
  39         int size;
  40         int used;
  41 };
  42
  43 /* Protected by sigio_lock().  Used by the sigio thread, but the UML thread
  44  * synchronizes with it.
  45  */
  46 static struct pollfds current_poll;
  47 static struct pollfds next_poll;
  48 static struct pollfds all_sigio_fds;
  49
  50 static int write_sigio_thread(void *unused)
  51 {
  52         struct pollfds *fds, tmp;
  53         struct pollfd *p;
  54         int i, n, respond_fd;
  55         char c;
  56
  57         signal(SIGWINCH, SIG_IGN);
  58         fds = &current_poll;
  59         while(1){
  60                 n = poll(fds->poll, fds->used, -1);
  61                 if(n < 0){
  62                         if(errno == EINTR) continue;
  63                         printk("write_sigio_thread : poll returned %d, "
  64                                "errno = %d\n", n, errno);
  65                 }
  66                 for(i = 0; i < fds->used; i++){
  67                         p = &fds->poll[i];
  68                         if(p->revents == 0) continue;
  69                         if(p->fd == sigio_private[1]){
  70                                 n = os_read_file(sigio_private[1], &c, sizeof(c));
  71                                 if(n != sizeof(c))
  72                                         printk("write_sigio_thread : "
  73                                                "read on socket failed, "
  74                                                "err = %d\n", -n);
  75                                 tmp = current_poll;
  76                                 current_poll = next_poll;
  77                                 next_poll = tmp;
  78                                 respond_fd = sigio_private[1];
  79                         }
  80                         else {
  81                                 respond_fd = write_sigio_fds[1];
  82                                 fds->used--;
  83                                 memmove(&fds->poll[i], &fds->poll[i + 1],
  84                                         (fds->used - i) * sizeof(*fds->poll));
  85                         }
  86
  87                         n = os_write_file(respond_fd, &c, sizeof(c));
  88                         if(n != sizeof(c))
  89                                 printk("write_sigio_thread : write on socket "
  90                                        "failed, err = %d\n", -n);
  91                 }
  92         }
  93
  94         return 0;
  95 }
  96
  97 static int need_poll(struct pollfds *polls, int n)
  98 {
  99         if(n <= polls->size){
 100                 polls->used = n;
 101                 return 0;
 102         }
 103         kfree(polls->poll);
 104         polls->poll = um_kmalloc_atomic(n * sizeof(struct pollfd));
 105         if(polls->poll == NULL){
 106                 printk("need_poll : failed to allocate new pollfds\n");
 107                 polls->size = 0;
 108                 polls->used = 0;
 109                 return -ENOMEM;
 110         }
 111         polls->size = n;
 112         polls->used = n;
 113         return 0;
 114 }
 115
 116 /* Must be called with sigio_lock held, because it's needed by the marked
 117  * critical section.
 118  */
 119 static void update_thread(void)
 120 {
 121         unsigned long flags;
 122         int n;
 123         char c;
 124
 125         flags = set_signals(0);
 126         n = os_write_file(sigio_private[0], &c, sizeof(c));
 127         if(n != sizeof(c)){
 128                 printk("update_thread : write failed, err = %d\n", -n);
 129                 goto fail;
 130         }
 131
 132         n = os_read_file(sigio_private[0], &c, sizeof(c));
 133         if(n != sizeof(c)){
 134                 printk("update_thread : read failed, err = %d\n", -n);
 135                 goto fail;
 136         }
 137
 138         set_signals(flags);
 139         return;
 140  fail:
 141         /* Critical section start */
 142         if(write_sigio_pid != -1)
 143                 os_kill_process(write_sigio_pid, 1);
 144         write_sigio_pid = -1;
 145         close(sigio_private[0]);
 146         close(sigio_private[1]);
 147         close(write_sigio_fds[0]);
 148         close(write_sigio_fds[1]);
 149         /* Critical section end */
 150         set_signals(flags);
 151 }
 152
 153 int add_sigio_fd(int fd)
 154 {
 155         struct pollfd *p;
 156         int err = 0, i, n;
 157
 158         sigio_lock();
 159         for(i = 0; i < all_sigio_fds.used; i++){
 160                 if(all_sigio_fds.poll[i].fd == fd)
 161                         break;
 162         }
 163         if(i == all_sigio_fds.used)
 164                 goto out;
 165
 166         p = &all_sigio_fds.poll[i];
 167
 168         for(i = 0; i < current_poll.used; i++){
 169                 if(current_poll.poll[i].fd == fd)
 170                         goto out;
 171         }
 172
 173         n = current_poll.used + 1;
 174         err = need_poll(&next_poll, n);
 175         if(err)
 176                 goto out;
 177
 178         for(i = 0; i < current_poll.used; i++)
 179                 next_poll.poll[i] = current_poll.poll[i];
 180
 181         next_poll.poll[n - 1] = *p;
 182         update_thread();
 183  out:
 184         sigio_unlock();
 185         return err;
 186 }
 187
 188 int ignore_sigio_fd(int fd)
 189 {
 190         struct pollfd *p;
 191         int err = 0, i, n = 0;
 192
 193         /* This is called from exitcalls elsewhere in UML - if
 194          * sigio_cleanup has already run, then update_thread will hang
 195          * or fail because the thread is no longer running.
 196          */
 197         if(write_sigio_pid == -1)
 198                 return -EIO;
 199
 200         sigio_lock();
 201         for(i = 0; i < current_poll.used; i++){
 202                 if(current_poll.poll[i].fd == fd) break;
 203         }
 204         if(i == current_poll.used)
 205                 goto out;
 206
 207         err = need_poll(&next_poll, current_poll.used - 1);
 208         if(err)
 209                 goto out;
 210
 211         for(i = 0; i < current_poll.used; i++){
 212                 p = &current_poll.poll[i];
 213                 if(p->fd != fd)
 214                         next_poll.poll[n++] = *p;
 215         }
 216
 217         update_thread();
 218  out:
 219         sigio_unlock();
 220         return err;
 221 }
 222
 223 static struct pollfd *setup_initial_poll(int fd)
 224 {
 225         struct pollfd *p;
 226
 227         p = um_kmalloc(sizeof(struct pollfd));
 228         if (p == NULL) {
 229                 printk("setup_initial_poll : failed to allocate poll\n");
 230                 return NULL;
 231         }
 232         *p = ((struct pollfd) { .fd             = fd,
 233                                 .events         = POLLIN,
 234                                 .revents        = 0 });
 235         return p;
 236 }
 237
 238 static void write_sigio_workaround(void)
 239 {
 240         unsigned long stack;
 241         struct pollfd *p;
 242         int err;
 243         int l_write_sigio_fds[2];
 244         int l_sigio_private[2];
 245         int l_write_sigio_pid;
 246
 247         /* We call this *tons* of times - and most ones we must just fail. */
 248         sigio_lock();
 249         l_write_sigio_pid = write_sigio_pid;
 250         sigio_unlock();
 251
 252         if (l_write_sigio_pid != -1)
 253                 return;
 254
 255         err = os_pipe(l_write_sigio_fds, 1, 1);
 256         if(err < 0){
 257                 printk("write_sigio_workaround - os_pipe 1 failed, "
 258                        "err = %d\n", -err);
 259                 return;
 260         }
 261         err = os_pipe(l_sigio_private, 1, 1);
 262         if(err < 0){
 263                 printk("write_sigio_workaround - os_pipe 2 failed, "
 264                        "err = %d\n", -err);
 265                 goto out_close1;
 266         }
 267
 268         p = setup_initial_poll(l_sigio_private[1]);
 269         if(!p)
 270                 goto out_close2;
 271
 272         sigio_lock();
 273
 274         /* Did we race? Don't try to optimize this, please, it's not so likely
 275          * to happen, and no more than once at the boot. */
 276         if(write_sigio_pid != -1)
 277                 goto out_free;
 278
 279         current_poll = ((struct pollfds) { .poll        = p,
 280                                            .used        = 1,
 281                                            .size        = 1 });
 282
 283         if (write_sigio_irq(l_write_sigio_fds[0]))
 284                 goto out_clear_poll;
 285
 286         memcpy(write_sigio_fds, l_write_sigio_fds, sizeof(l_write_sigio_fds));
 287         memcpy(sigio_private, l_sigio_private, sizeof(l_sigio_private));
 288
 289         write_sigio_pid = run_helper_thread(write_sigio_thread, NULL,
 290                                             CLONE_FILES | CLONE_VM, &stack, 0);
 291
 292         if (write_sigio_pid < 0)
 293                 goto out_clear;
 294
 295         sigio_unlock();
 296         return;
 297
 298 out_clear:
 299         write_sigio_pid = -1;
 300         write_sigio_fds[0] = -1;
 301         write_sigio_fds[1] = -1;
 302         sigio_private[0] = -1;
 303         sigio_private[1] = -1;
 304 out_clear_poll:
 305         current_poll = ((struct pollfds) { .poll        = NULL,
 306                                            .size        = 0,
 307                                            .used        = 0 });
 308 out_free:
 309         sigio_unlock();
 310         kfree(p);
 311 out_close2:
 312         close(l_sigio_private[0]);
 313         close(l_sigio_private[1]);
 314 out_close1:
 315         close(l_write_sigio_fds[0]);
 316         close(l_write_sigio_fds[1]);
 317 }
 318
 319 void maybe_sigio_broken(int fd, int read)
 320 {
 321         int err;
 322
 323         if(!isatty(fd))
 324                 return;
 325
 326         if((read || pty_output_sigio) && (!read || pty_close_sigio))
 327                 return;
 328
 329         write_sigio_workaround();
 330
 331         sigio_lock();
 332         err = need_poll(&all_sigio_fds, all_sigio_fds.used + 1);
 333         if(err){
 334                 printk("maybe_sigio_broken - failed to add pollfd\n");
 335                 goto out;
 336         }
 337         all_sigio_fds.poll[all_sigio_fds.used++] =
 338                 ((struct pollfd) { .fd          = fd,
 339                                    .events      = read ? POLLIN : POLLOUT,
 340                                    .revents     = 0 });
 341 out:
 342         sigio_unlock();
 343 }
 344
 345 static void sigio_cleanup(void)
 346 {
 347         if(write_sigio_pid != -1){
 348                 os_kill_process(write_sigio_pid, 1);
 349                 write_sigio_pid = -1;
 350         }
 351 }
 352
 353 __uml_exitcall(sigio_cleanup);