arch/um/kernel/sigio_user.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 "helper.h"
  22 #include "os.h"
  23
  24 /* Changed during early boot */
  25 int pty_output_sigio = 0;
  26 int pty_close_sigio = 0;
  27
  28 /* Used as a flag during SIGIO testing early in boot */
  29 static volatile int got_sigio = 0;
  30
  31 void __init handler(int sig)
  32 {
  33         got_sigio = 1;
  34 }
  35
  36 struct openpty_arg {
  37         int master;
  38         int slave;
  39         int err;
  40 };
  41
  42 static void openpty_cb(void *arg)
  43 {
  44         struct openpty_arg *info = arg;
  45
  46         info->err = 0;
  47         if(openpty(&info->master, &info->slave, NULL, NULL, NULL))
  48                 info->err = -errno;
  49 }
  50
  51 void __init check_one_sigio(void (*proc)(int, int))
  52 {
  53         struct sigaction old, new;
  54         struct openpty_arg pty = { .master = -1, .slave = -1 };
  55         int master, slave, err;
  56
  57         initial_thread_cb(openpty_cb, &pty);
  58         if(pty.err){
  59                 printk("openpty failed, errno = %d\n", -pty.err);
  60                 return;
  61         }
  62
  63         master = pty.master;
  64         slave = pty.slave;
  65
  66         if((master == -1) || (slave == -1)){
  67                 printk("openpty failed to allocate a pty\n");
  68                 return;
  69         }
  70
  71         /* Not now, but complain so we now where we failed. */
  72         err = raw(master);
  73         if (err < 0)
  74                 panic("check_sigio : __raw failed, errno = %d\n", -err);
  75
  76         err = os_sigio_async(master, slave);
  77         if(err < 0)
  78                 panic("tty_fds : sigio_async failed, err = %d\n", -err);
  79
  80         if(sigaction(SIGIO, NULL, &old) < 0)
  81                 panic("check_sigio : sigaction 1 failed, errno = %d\n", errno);
  82         new = old;
  83         new.sa_handler = handler;
  84         if(sigaction(SIGIO, &new, NULL) < 0)
  85                 panic("check_sigio : sigaction 2 failed, errno = %d\n", errno);
  86
  87         got_sigio = 0;
  88         (*proc)(master, slave);
  89
  90         os_close_file(master);
  91         os_close_file(slave);
  92
  93         if(sigaction(SIGIO, &old, NULL) < 0)
  94                 panic("check_sigio : sigaction 3 failed, errno = %d\n", errno);
  95 }
  96
  97 static void tty_output(int master, int slave)
  98 {
  99         int n;
 100         char buf[512];
 101
 102         printk("Checking that host ptys support output SIGIO...");
 103
 104         memset(buf, 0, sizeof(buf));
 105
 106         while(os_write_file(master, buf, sizeof(buf)) > 0) ;
 107         if(errno != EAGAIN)
 108                 panic("check_sigio : write failed, errno = %d\n", errno);
 109         while(((n = os_read_file(slave, buf, sizeof(buf))) > 0) && !got_sigio) ;
 110
 111         if (got_sigio) {
 112                 printk("Yes\n");
 113                 pty_output_sigio = 1;
 114         } else if (n == -EAGAIN) {
 115                 printk("No, enabling workaround\n");
 116         } else {
 117                 panic("check_sigio : read failed, err = %d\n", n);
 118         }
 119 }
 120
 121 static void tty_close(int master, int slave)
 122 {
 123         printk("Checking that host ptys support SIGIO on close...");
 124
 125         os_close_file(slave);
 126         if(got_sigio){
 127                 printk("Yes\n");
 128                 pty_close_sigio = 1;
 129         }
 130         else printk("No, enabling workaround\n");
 131 }
 132
 133 void __init check_sigio(void)
 134 {
 135         if((os_access("/dev/ptmx", OS_ACC_R_OK) < 0) &&
 136            (os_access("/dev/ptyp0", OS_ACC_R_OK) < 0)){
 137                 printk("No pseudo-terminals available - skipping pty SIGIO "
 138                        "check\n");
 139                 return;
 140         }
 141         check_one_sigio(tty_output);
 142         check_one_sigio(tty_close);
 143 }
 144
 145 /* Protected by sigio_lock(), also used by sigio_cleanup, which is an
 146  * exitcall.
 147  */
 148 static int write_sigio_pid = -1;
 149
 150 /* These arrays are initialized before the sigio thread is started, and
 151  * the descriptors closed after it is killed.  So, it can't see them change.
 152  * On the UML side, they are changed under the sigio_lock.
 153  */
 154 static int write_sigio_fds[2] = { -1, -1 };
 155 static int sigio_private[2] = { -1, -1 };
 156
 157 struct pollfds {
 158         struct pollfd *poll;
 159         int size;
 160         int used;
 161 };
 162
 163 /* Protected by sigio_lock().  Used by the sigio thread, but the UML thread
 164  * synchronizes with it.
 165  */
 166 struct pollfds current_poll = {
 167         .poll           = NULL,
 168         .size           = 0,
 169         .used           = 0
 170 };
 171
 172 struct pollfds next_poll = {
 173         .poll           = NULL,
 174         .size           = 0,
 175         .used           = 0
 176 };
 177
 178 static int write_sigio_thread(void *unused)
 179 {
 180         struct pollfds *fds, tmp;
 181         struct pollfd *p;
 182         int i, n, respond_fd;
 183         char c;
 184
 185         signal(SIGWINCH, SIG_IGN);
 186         fds = &current_poll;
 187         while(1){
 188                 n = poll(fds->poll, fds->used, -1);
 189                 if(n < 0){
 190                         if(errno == EINTR) continue;
 191                         printk("write_sigio_thread : poll returned %d, "
 192                                "errno = %d\n", n, errno);
 193                 }
 194                 for(i = 0; i < fds->used; i++){
 195                         p = &fds->poll[i];
 196                         if(p->revents == 0) continue;
 197                         if(p->fd == sigio_private[1]){
 198                                 n = os_read_file(sigio_private[1], &c, sizeof(c));
 199                                 if(n != sizeof(c))
 200                                         printk("write_sigio_thread : "
 201                                                "read failed, err = %d\n", -n);
 202                                 tmp = current_poll;
 203                                 current_poll = next_poll;
 204                                 next_poll = tmp;
 205                                 respond_fd = sigio_private[1];
 206                         }
 207                         else {
 208                                 respond_fd = write_sigio_fds[1];
 209                                 fds->used--;
 210                                 memmove(&fds->poll[i], &fds->poll[i + 1],
 211                                         (fds->used - i) * sizeof(*fds->poll));
 212                         }
 213
 214                         n = os_write_file(respond_fd, &c, sizeof(c));
 215                         if(n != sizeof(c))
 216                                 printk("write_sigio_thread : write failed, "
 217                                        "err = %d\n", -n);
 218                 }
 219         }
 220 }
 221
 222 static int need_poll(int n)
 223 {
 224         if(n <= next_poll.size){
 225                 next_poll.used = n;
 226                 return(0);
 227         }
 228         if(next_poll.poll != NULL) kfree(next_poll.poll);
 229         next_poll.poll = um_kmalloc_atomic(n * sizeof(struct pollfd));
 230         if(next_poll.poll == NULL){
 231                 printk("need_poll : failed to allocate new pollfds\n");
 232                 next_poll.size = 0;
 233                 next_poll.used = 0;
 234                 return(-1);
 235         }
 236         next_poll.size = n;
 237         next_poll.used = n;
 238         return(0);
 239 }
 240
 241 /* Must be called with sigio_lock held, because it's needed by the marked
 242  * critical section. */
 243 static void update_thread(void)
 244 {
 245         unsigned long flags;
 246         int n;
 247         char c;
 248
 249         flags = set_signals(0);
 250         n = os_write_file(sigio_private[0], &c, sizeof(c));
 251         if(n != sizeof(c)){
 252                 printk("update_thread : write failed, err = %d\n", -n);
 253                 goto fail;
 254         }
 255
 256         n = os_read_file(sigio_private[0], &c, sizeof(c));
 257         if(n != sizeof(c)){
 258                 printk("update_thread : read failed, err = %d\n", -n);
 259                 goto fail;
 260         }
 261
 262         set_signals(flags);
 263         return;
 264  fail:
 265         /* Critical section start */
 266         if(write_sigio_pid != -1)
 267                 os_kill_process(write_sigio_pid, 1);
 268         write_sigio_pid = -1;
 269         os_close_file(sigio_private[0]);
 270         os_close_file(sigio_private[1]);
 271         os_close_file(write_sigio_fds[0]);
 272         os_close_file(write_sigio_fds[1]);
 273         /* Critical section end */
 274         set_signals(flags);
 275 }
 276
 277 int add_sigio_fd(int fd, int read)
 278 {
 279         int err = 0, i, n, events;
 280
 281         sigio_lock();
 282         for(i = 0; i < current_poll.used; i++){
 283                 if(current_poll.poll[i].fd == fd)
 284                         goto out;
 285         }
 286
 287         n = current_poll.used + 1;
 288         err = need_poll(n);
 289         if(err)
 290                 goto out;
 291
 292         for(i = 0; i < current_poll.used; i++)
 293                 next_poll.poll[i] = current_poll.poll[i];
 294
 295         if(read) events = POLLIN;
 296         else events = POLLOUT;
 297
 298         next_poll.poll[n - 1] = ((struct pollfd) { .fd          = fd,
 299                                                    .events      = events,
 300                                                    .revents     = 0 });
 301         update_thread();
 302  out:
 303         sigio_unlock();
 304         return(err);
 305 }
 306
 307 int ignore_sigio_fd(int fd)
 308 {
 309         struct pollfd *p;
 310         int err = 0, i, n = 0;
 311
 312         sigio_lock();
 313         for(i = 0; i < current_poll.used; i++){
 314                 if(current_poll.poll[i].fd == fd) break;
 315         }
 316         if(i == current_poll.used)
 317                 goto out;
 318
 319         err = need_poll(current_poll.used - 1);
 320         if(err)
 321                 goto out;
 322
 323         for(i = 0; i < current_poll.used; i++){
 324                 p = &current_poll.poll[i];
 325                 if(p->fd != fd) next_poll.poll[n++] = current_poll.poll[i];
 326         }
 327         if(n == i){
 328                 printk("ignore_sigio_fd : fd %d not found\n", fd);
 329                 err = -1;
 330                 goto out;
 331         }
 332
 333         update_thread();
 334  out:
 335         sigio_unlock();
 336         return(err);
 337 }
 338
 339 static int setup_initial_poll(int fd)
 340 {
 341         struct pollfd *p;
 342
 343         p = um_kmalloc_atomic(sizeof(struct pollfd));
 344         if(p == NULL){
 345                 printk("setup_initial_poll : failed to allocate poll\n");
 346                 return(-1);
 347         }
 348         *p = ((struct pollfd) { .fd     = fd,
 349                                 .events         = POLLIN,
 350                                 .revents        = 0 });
 351         current_poll = ((struct pollfds) { .poll        = p,
 352                                            .used        = 1,
 353                                            .size        = 1 });
 354         return(0);
 355 }
 356
 357 void write_sigio_workaround(void)
 358 {
 359         unsigned long stack;
 360         int err;
 361
 362         sigio_lock();
 363         if(write_sigio_pid != -1)
 364                 goto out;
 365
 366         err = os_pipe(write_sigio_fds, 1, 1);
 367         if(err < 0){
 368                 printk("write_sigio_workaround - os_pipe 1 failed, "
 369                        "err = %d\n", -err);
 370                 goto out;
 371         }
 372         err = os_pipe(sigio_private, 1, 1);
 373         if(err < 0){
 374                 printk("write_sigio_workaround - os_pipe 2 failed, "
 375                        "err = %d\n", -err);
 376                 goto out_close1;
 377         }
 378         if(setup_initial_poll(sigio_private[1]))
 379                 goto out_close2;
 380
 381         write_sigio_pid = run_helper_thread(write_sigio_thread, NULL,
 382                                             CLONE_FILES | CLONE_VM, &stack, 0);
 383
 384         if(write_sigio_pid < 0) goto out_close2;
 385
 386         if(write_sigio_irq(write_sigio_fds[0]))
 387                 goto out_kill;
 388
 389  out:
 390         sigio_unlock();
 391         return;
 392
 393  out_kill:
 394         os_kill_process(write_sigio_pid, 1);
 395         write_sigio_pid = -1;
 396  out_close2:
 397         os_close_file(sigio_private[0]);
 398         os_close_file(sigio_private[1]);
 399  out_close1:
 400         os_close_file(write_sigio_fds[0]);
 401         os_close_file(write_sigio_fds[1]);
 402         sigio_unlock();
 403 }
 404
 405 int read_sigio_fd(int fd)
 406 {
 407         int n;
 408         char c;
 409
 410         n = os_read_file(fd, &c, sizeof(c));
 411         if(n != sizeof(c)){
 412                 if(n < 0) {
 413                         printk("read_sigio_fd - read failed, err = %d\n", -n);
 414                         return(n);
 415                 }
 416                 else {
 417                         printk("read_sigio_fd - short read, bytes = %d\n", n);
 418                         return(-EIO);
 419                 }
 420         }
 421         return(n);
 422 }
 423
 424 static void sigio_cleanup(void)
 425 {
 426         if (write_sigio_pid != -1) {
 427                 os_kill_process(write_sigio_pid, 1);
 428                 write_sigio_pid = -1;
 429         }
 430 }
 431
 432 __uml_exitcall(sigio_cleanup);