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