fs/select.c

   1 /*
   2  * This file contains the procedures for the handling of select and poll
   3  *
   4  * Created for Linux based loosely upon Mathius Lattner's minix
   5  * patches by Peter MacDonald. Heavily edited by Linus.
   6  *
   7  *  4 February 1994
   8  *     COFF/ELF binary emulation. If the process has the STICKY_TIMEOUTS
   9  *     flag set in its personality we do *not* modify the given timeout
  10  *     parameter to reflect time remaining.
  11  *
  12  *  24 January 2000
  13  *     Changed sys_poll()/do_poll() to use PAGE_SIZE chunk-based allocation
  14  *     of fds to overcome nfds < 16390 descriptors limit (Tigran Aivazian).
  15  */
  16
  17 #include <linux/syscalls.h>
  18 #include <linux/module.h>
  19 #include <linux/slab.h>
  20 #include <linux/smp_lock.h>
  21 #include <linux/poll.h>
  22 #include <linux/personality.h> /* for STICKY_TIMEOUTS */
  23 #include <linux/file.h>
  24 #include <linux/fs.h>
  25
  26 #include <asm/uaccess.h>
  27
  28 #define ROUND_UP(x,y) (((x)+(y)-1)/(y))
  29 #define DEFAULT_POLLMASK (POLLIN | POLLOUT | POLLRDNORM | POLLWRNORM)
  30
  31 struct poll_table_entry {
  32         struct file * filp;
  33         wait_queue_t wait;
  34         wait_queue_head_t * wait_address;
  35 };
  36
  37 struct poll_table_page {
  38         struct poll_table_page * next;
  39         struct poll_table_entry * entry;
  40         struct poll_table_entry entries[0];
  41 };
  42
  43 #define POLL_TABLE_FULL(table) \
  44         ((unsigned long)((table)->entry+1) > PAGE_SIZE + (unsigned long)(table))
  45
  46 /*
  47  * Ok, Peter made a complicated, but straightforward multiple_wait() function.
  48  * I have rewritten this, taking some shortcuts: This code may not be easy to
  49  * follow, but it should be free of race-conditions, and it's practical. If you
  50  * understand what I'm doing here, then you understand how the linux
  51  * sleep/wakeup mechanism works.
  52  *
  53  * Two very simple procedures, poll_wait() and poll_freewait() make all the
  54  * work.  poll_wait() is an inline-function defined in <linux/poll.h>,
  55  * as all select/poll functions have to call it to add an entry to the
  56  * poll table.
  57  */
  58 static void __pollwait(struct file *filp, wait_queue_head_t *wait_address,
  59                        poll_table *p);
  60
  61 void poll_initwait(struct poll_wqueues *pwq)
  62 {
  63         init_poll_funcptr(&pwq->pt, __pollwait);
  64         pwq->error = 0;
  65         pwq->table = NULL;
  66 }
  67
  68 EXPORT_SYMBOL(poll_initwait);
  69
  70 void poll_freewait(struct poll_wqueues *pwq)
  71 {
  72         struct poll_table_page * p = pwq->table;
  73         while (p) {
  74                 struct poll_table_entry * entry;
  75                 struct poll_table_page *old;
  76
  77                 entry = p->entry;
  78                 do {
  79                         entry--;
  80                         remove_wait_queue(entry->wait_address,&entry->wait);
  81                         fput(entry->filp);
  82                 } while (entry > p->entries);
  83                 old = p;
  84                 p = p->next;
  85                 free_page((unsigned long) old);
  86         }
  87 }
  88
  89 EXPORT_SYMBOL(poll_freewait);
  90
  91 static void __pollwait(struct file *filp, wait_queue_head_t *wait_address,
  92                        poll_table *_p)
  93 {
  94         struct poll_wqueues *p = container_of(_p, struct poll_wqueues, pt);
  95         struct poll_table_page *table = p->table;
  96
  97         if (!table || POLL_TABLE_FULL(table)) {
  98                 struct poll_table_page *new_table;
  99
 100                 new_table = (struct poll_table_page *) __get_free_page(GFP_KERNEL);
 101                 if (!new_table) {
 102                         p->error = -ENOMEM;
 103                         __set_current_state(TASK_RUNNING);
 104                         return;
 105                 }
 106                 new_table->entry = new_table->entries;
 107                 new_table->next = table;
 108                 p->table = new_table;
 109                 table = new_table;
 110         }
 111
 112         /* Add a new entry */
 113         {
 114                 struct poll_table_entry * entry = table->entry;
 115                 table->entry = entry+1;
 116                 get_file(filp);
 117                 entry->filp = filp;
 118                 entry->wait_address = wait_address;
 119                 init_waitqueue_entry(&entry->wait, current);
 120                 add_wait_queue(wait_address,&entry->wait);
 121         }
 122 }
 123
 124 #define FDS_IN(fds, n)          (fds->in + n)
 125 #define FDS_OUT(fds, n)         (fds->out + n)
 126 #define FDS_EX(fds, n)          (fds->ex + n)
 127
 128 #define BITS(fds, n)    (*FDS_IN(fds, n)|*FDS_OUT(fds, n)|*FDS_EX(fds, n))
 129
 130 static int max_select_fd(unsigned long n, fd_set_bits *fds)
 131 {
 132         unsigned long *open_fds;
 133         unsigned long set;
 134         int max;
 135
 136         /* handle last in-complete long-word first */
 137         set = ~(~0UL << (n & (__NFDBITS-1)));
 138         n /= __NFDBITS;
 139         open_fds = current->files->open_fds->fds_bits+n;
 140         max = 0;
 141         if (set) {
 142                 set &= BITS(fds, n);
 143                 if (set) {
 144                         if (!(set & ~*open_fds))
 145                                 goto get_max;
 146                         return -EBADF;
 147                 }
 148         }
 149         while (n) {
 150                 open_fds--;
 151                 n--;
 152                 set = BITS(fds, n);
 153                 if (!set)
 154                         continue;
 155                 if (set & ~*open_fds)
 156                         return -EBADF;
 157                 if (max)
 158                         continue;
 159 get_max:
 160                 do {
 161                         max++;
 162                         set >>= 1;
 163                 } while (set);
 164                 max += n * __NFDBITS;
 165         }
 166
 167         return max;
 168 }
 169
 170 #define BIT(i)          (1UL << ((i)&(__NFDBITS-1)))
 171 #define MEM(i,m)        ((m)+(unsigned)(i)/__NFDBITS)
 172 #define ISSET(i,m)      (((i)&*(m)) != 0)
 173 #define SET(i,m)        (*(m) |= (i))
 174
 175 #define POLLIN_SET (POLLRDNORM | POLLRDBAND | POLLIN | POLLHUP | POLLERR)
 176 #define POLLOUT_SET (POLLWRBAND | POLLWRNORM | POLLOUT | POLLERR)
 177 #define POLLEX_SET (POLLPRI)
 178
 179 int do_select(int n, fd_set_bits *fds, long *timeout)
 180 {
 181         struct poll_wqueues table;
 182         poll_table *wait;
 183         int retval, i;
 184         long __timeout = *timeout;
 185
 186         spin_lock(&current->files->file_lock);
 187         retval = max_select_fd(n, fds);
 188         spin_unlock(&current->files->file_lock);
 189
 190         if (retval < 0)
 191                 return retval;
 192         n = retval;
 193
 194         poll_initwait(&table);
 195         wait = &table.pt;
 196         if (!__timeout)
 197                 wait = NULL;
 198         retval = 0;
 199         for (;;) {
 200                 unsigned long *rinp, *routp, *rexp, *inp, *outp, *exp;
 201
 202                 set_current_state(TASK_INTERRUPTIBLE);
 203
 204                 inp = fds->in; outp = fds->out; exp = fds->ex;
 205                 rinp = fds->res_in; routp = fds->res_out; rexp = fds->res_ex;
 206
 207                 for (i = 0; i < n; ++rinp, ++routp, ++rexp) {
 208                         unsigned long in, out, ex, all_bits, bit = 1, mask, j;
 209                         unsigned long res_in = 0, res_out = 0, res_ex = 0;
 210                         struct file_operations *f_op = NULL;
 211                         struct file *file = NULL;
 212
 213                         in = *inp++; out = *outp++; ex = *exp++;
 214                         all_bits = in | out | ex;
 215                         if (all_bits == 0) {
 216                                 i += __NFDBITS;
 217                                 continue;
 218                         }
 219
 220                         for (j = 0; j < __NFDBITS; ++j, ++i, bit <<= 1) {
 221                                 if (i >= n)
 222                                         break;
 223                                 if (!(bit & all_bits))
 224                                         continue;
 225                                 file = fget(i);
 226                                 if (file) {
 227                                         f_op = file->f_op;
 228                                         mask = DEFAULT_POLLMASK;
 229                                         if (f_op && f_op->poll)
 230                                                 mask = (*f_op->poll)(file, retval ? NULL : wait);
 231                                         fput(file);
 232                                         if ((mask & POLLIN_SET) && (in & bit)) {
 233                                                 res_in |= bit;
 234                                                 retval++;
 235                                         }
 236                                         if ((mask & POLLOUT_SET) && (out & bit)) {
 237                                                 res_out |= bit;
 238                                                 retval++;
 239                                         }
 240                                         if ((mask & POLLEX_SET) && (ex & bit)) {
 241                                                 res_ex |= bit;
 242                                                 retval++;
 243                                         }
 244                                 }
 245                                 cond_resched();
 246                         }
 247                         if (res_in)
 248                                 *rinp = res_in;
 249                         if (res_out)
 250                                 *routp = res_out;
 251                         if (res_ex)
 252                                 *rexp = res_ex;
 253                 }
 254                 wait = NULL;
 255                 if (retval || !__timeout || signal_pending(current))
 256                         break;
 257                 if(table.error) {
 258                         retval = table.error;
 259                         break;
 260                 }
 261                 __timeout = schedule_timeout(__timeout);
 262         }
 263         __set_current_state(TASK_RUNNING);
 264
 265         poll_freewait(&table);
 266
 267         /*
 268          * Up-to-date the caller timeout.
 269          */
 270         *timeout = __timeout;
 271         return retval;
 272 }
 273
 274 static void *select_bits_alloc(int size)
 275 {
 276         return kmalloc(6 * size, GFP_KERNEL);
 277 }
 278
 279 static void select_bits_free(void *bits, int size)
 280 {
 281         kfree(bits);
 282 }
 283
 284 /*
 285  * We can actually return ERESTARTSYS instead of EINTR, but I'd
 286  * like to be certain this leads to no problems. So I return
 287  * EINTR just for safety.
 288  *
 289  * Update: ERESTARTSYS breaks at least the xview clock binary, so
 290  * I'm trying ERESTARTNOHAND which restart only when you want to.
 291  */
 292 #define MAX_SELECT_SECONDS \
 293         ((unsigned long) (MAX_SCHEDULE_TIMEOUT / HZ)-1)
 294
 295 asmlinkage long
 296 sys_select(int n, fd_set __user *inp, fd_set __user *outp, fd_set __user *exp, struct timeval __user *tvp)
 297 {
 298         fd_set_bits fds;
 299         char *bits;
 300         long timeout;
 301         int ret, size, max_fdset;
 302
 303         timeout = MAX_SCHEDULE_TIMEOUT;
 304         if (tvp) {
 305                 time_t sec, usec;
 306
 307                 if (!access_ok(VERIFY_READ, tvp, sizeof(*tvp))
 308                     || __get_user(sec, &tvp->tv_sec)
 309                     || __get_user(usec, &tvp->tv_usec)) {
 310                         ret = -EFAULT;
 311                         goto out_nofds;
 312                 }
 313
 314                 ret = -EINVAL;
 315                 if (sec < 0 || usec < 0)
 316                         goto out_nofds;
 317
 318                 if ((unsigned long) sec < MAX_SELECT_SECONDS) {
 319                         timeout = ROUND_UP(usec, 1000000/HZ);
 320                         timeout += sec * (unsigned long) HZ;
 321                 }
 322         }
 323
 324         ret = -EINVAL;
 325         if (n < 0)
 326                 goto out_nofds;
 327
 328         /* max_fdset can increase, so grab it once to avoid race */
 329         max_fdset = current->files->max_fdset;
 330         if (n > max_fdset)
 331                 n = max_fdset;
 332
 333         /*
 334          * We need 6 bitmaps (in/out/ex for both incoming and outgoing),
 335          * since we used fdset we need to allocate memory in units of
 336          * long-words.
 337          */
 338         ret = -ENOMEM;
 339         size = FDS_BYTES(n);
 340         bits = select_bits_alloc(size);
 341         if (!bits)
 342                 goto out_nofds;
 343         fds.in      = (unsigned long *)  bits;
 344         fds.out     = (unsigned long *) (bits +   size);
 345         fds.ex      = (unsigned long *) (bits + 2*size);
 346         fds.res_in  = (unsigned long *) (bits + 3*size);
 347         fds.res_out = (unsigned long *) (bits + 4*size);
 348         fds.res_ex  = (unsigned long *) (bits + 5*size);
 349
 350         if ((ret = get_fd_set(n, inp, fds.in)) ||
 351             (ret = get_fd_set(n, outp, fds.out)) ||
 352             (ret = get_fd_set(n, exp, fds.ex)))
 353                 goto out;
 354         zero_fd_set(n, fds.res_in);
 355         zero_fd_set(n, fds.res_out);
 356         zero_fd_set(n, fds.res_ex);
 357
 358         ret = do_select(n, &fds, &timeout);
 359
 360         if (tvp && !(current->personality & STICKY_TIMEOUTS)) {
 361                 time_t sec = 0, usec = 0;
 362                 if (timeout) {
 363                         sec = timeout / HZ;
 364                         usec = timeout % HZ;
 365                         usec *= (1000000/HZ);
 366                 }
 367                 put_user(sec, &tvp->tv_sec);
 368                 put_user(usec, &tvp->tv_usec);
 369         }
 370
 371         if (ret < 0)
 372                 goto out;
 373         if (!ret) {
 374                 ret = -ERESTARTNOHAND;
 375                 if (signal_pending(current))
 376                         goto out;
 377                 ret = 0;
 378         }
 379
 380         if (set_fd_set(n, inp, fds.res_in) ||
 381             set_fd_set(n, outp, fds.res_out) ||
 382             set_fd_set(n, exp, fds.res_ex))
 383                 ret = -EFAULT;
 384
 385 out:
 386         select_bits_free(bits, size);
 387 out_nofds:
 388         return ret;
 389 }
 390
 391 struct poll_list {
 392         struct poll_list *next;
 393         int len;
 394         struct pollfd entries[0];
 395 };
 396
 397 #define POLLFD_PER_PAGE  ((PAGE_SIZE-sizeof(struct poll_list)) / sizeof(struct pollfd))
 398
 399 static void do_pollfd(unsigned int num, struct pollfd * fdpage,
 400         poll_table ** pwait, int *count)
 401 {
 402         int i;
 403
 404         for (i = 0; i < num; i++) {
 405                 int fd;
 406                 unsigned int mask;
 407                 struct pollfd *fdp;
 408
 409                 mask = 0;
 410                 fdp = fdpage+i;
 411                 fd = fdp->fd;
 412                 if (fd >= 0) {
 413                         struct file * file = fget(fd);
 414                         mask = POLLNVAL;
 415                         if (file != NULL) {
 416                                 mask = DEFAULT_POLLMASK;
 417                                 if (file->f_op && file->f_op->poll)
 418                                         mask = file->f_op->poll(file, *pwait);
 419                                 mask &= fdp->events | POLLERR | POLLHUP;
 420                                 fput(file);
 421                         }
 422                         if (mask) {
 423                                 *pwait = NULL;
 424                                 (*count)++;
 425                         }
 426                 }
 427                 fdp->revents = mask;
 428         }
 429 }
 430
 431 static int do_poll(unsigned int nfds,  struct poll_list *list,
 432                         struct poll_wqueues *wait, long timeout)
 433 {
 434         int count = 0;
 435         poll_table* pt = &wait->pt;
 436
 437         if (!timeout)
 438                 pt = NULL;
 439
 440         for (;;) {
 441                 struct poll_list *walk;
 442                 set_current_state(TASK_INTERRUPTIBLE);
 443                 walk = list;
 444                 while(walk != NULL) {
 445                         do_pollfd( walk->len, walk->entries, &pt, &count);
 446                         walk = walk->next;
 447                 }
 448                 pt = NULL;
 449                 if (count || !timeout || signal_pending(current))
 450                         break;
 451                 count = wait->error;
 452                 if (count)
 453                         break;
 454                 timeout = schedule_timeout(timeout);
 455         }
 456         __set_current_state(TASK_RUNNING);
 457         return count;
 458 }
 459
 460 asmlinkage long sys_poll(struct pollfd __user * ufds, unsigned int nfds, long timeout)
 461 {
 462         struct poll_wqueues table;
 463         int fdcount, err;
 464         unsigned int i;
 465         struct poll_list *head;
 466         struct poll_list *walk;
 467
 468         /* Do a sanity check on nfds ... */
 469         if (nfds > current->files->max_fdset && nfds > OPEN_MAX)
 470                 return -EINVAL;
 471
 472         if (timeout) {
 473                 /* Careful about overflow in the intermediate values */
 474                 if ((unsigned long) timeout < MAX_SCHEDULE_TIMEOUT / HZ)
 475                         timeout = (unsigned long)(timeout*HZ+999)/1000+1;
 476                 else /* Negative or overflow */
 477                         timeout = MAX_SCHEDULE_TIMEOUT;
 478         }
 479
 480         poll_initwait(&table);
 481
 482         head = NULL;
 483         walk = NULL;
 484         i = nfds;
 485         err = -ENOMEM;
 486         while(i!=0) {
 487                 struct poll_list *pp;
 488                 pp = kmalloc(sizeof(struct poll_list)+
 489                                 sizeof(struct pollfd)*
 490                                 (i>POLLFD_PER_PAGE?POLLFD_PER_PAGE:i),
 491                                         GFP_KERNEL);
 492                 if(pp==NULL)
 493                         goto out_fds;
 494                 pp->next=NULL;
 495                 pp->len = (i>POLLFD_PER_PAGE?POLLFD_PER_PAGE:i);
 496                 if (head == NULL)
 497                         head = pp;
 498                 else
 499                         walk->next = pp;
 500
 501                 walk = pp;
 502                 if (copy_from_user(pp->entries, ufds + nfds-i,
 503                                 sizeof(struct pollfd)*pp->len)) {
 504                         err = -EFAULT;
 505                         goto out_fds;
 506                 }
 507                 i -= pp->len;
 508         }
 509         fdcount = do_poll(nfds, head, &table, timeout);
 510
 511         /* OK, now copy the revents fields back to user space. */
 512         walk = head;
 513         err = -EFAULT;
 514         while(walk != NULL) {
 515                 struct pollfd *fds = walk->entries;
 516                 int j;
 517
 518                 for (j=0; j < walk->len; j++, ufds++) {
 519                         if(__put_user(fds[j].revents, &ufds->revents))
 520                                 goto out_fds;
 521                 }
 522                 walk = walk->next;
 523         }
 524         err = fdcount;
 525         if (!fdcount && signal_pending(current))
 526                 err = -EINTR;
 527 out_fds:
 528         walk = head;
 529         while(walk!=NULL) {
 530                 struct poll_list *pp = walk->next;
 531                 kfree(walk);
 532                 walk = pp;
 533         }
 534         poll_freewait(&table);
 535         return err;
 536 }