git.oblomov.eu Git - linux-2.6/blob - 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 void __pollwait(struct file *filp, wait_queue_head_t *wait_address, poll_table *p);
  59
  60 void poll_initwait(struct poll_wqueues *pwq)
  61 {
  62         init_poll_funcptr(&pwq->pt, __pollwait);
  63         pwq->error = 0;
  64         pwq->table = NULL;
  65 }
  66
  67 EXPORT_SYMBOL(poll_initwait);
  68
  69 void poll_freewait(struct poll_wqueues *pwq)
  70 {
  71         struct poll_table_page * p = pwq->table;
  72         while (p) {
  73                 struct poll_table_entry * entry;
  74                 struct poll_table_page *old;
  75
  76                 entry = p->entry;
  77                 do {
  78                         entry--;
  79                         remove_wait_queue(entry->wait_address,&entry->wait);
  80                         fput(entry->filp);
  81                 } while (entry > p->entries);
  82                 old = p;
  83                 p = p->next;
  84                 free_page((unsigned long) old);
  85         }
  86 }
  87
  88 EXPORT_SYMBOL(poll_freewait);
  89
  90 void __pollwait(struct file *filp, wait_queue_head_t *wait_address, poll_table *_p)
  91 {
  92         struct poll_wqueues *p = container_of(_p, struct poll_wqueues, pt);
  93         struct poll_table_page *table = p->table;
  94
  95         if (!table || POLL_TABLE_FULL(table)) {
  96                 struct poll_table_page *new_table;
  97
  98                 new_table = (struct poll_table_page *) __get_free_page(GFP_KERNEL);
  99                 if (!new_table) {
 100                         p->error = -ENOMEM;
 101                         __set_current_state(TASK_RUNNING);
 102                         return;
 103                 }
 104                 new_table->entry = new_table->entries;
 105                 new_table->next = table;
 106                 p->table = new_table;
 107                 table = new_table;
 108         }
 109
 110         /* Add a new entry */
 111         {
 112                 struct poll_table_entry * entry = table->entry;
 113                 table->entry = entry+1;
 114                 get_file(filp);
 115                 entry->filp = filp;
 116                 entry->wait_address = wait_address;
 117                 init_waitqueue_entry(&entry->wait, current);
 118                 add_wait_queue(wait_address,&entry->wait);
 119         }
 120 }
 121
 122 #define FDS_IN(fds, n)          (fds->in + n)
 123 #define FDS_OUT(fds, n)         (fds->out + n)
 124 #define FDS_EX(fds, n)          (fds->ex + n)
 125
 126 #define BITS(fds, n)    (*FDS_IN(fds, n)|*FDS_OUT(fds, n)|*FDS_EX(fds, n))
 127
 128 static int max_select_fd(unsigned long n, fd_set_bits *fds)
 129 {
 130         unsigned long *open_fds;
 131         unsigned long set;
 132         int max;
 133
 134         /* handle last in-complete long-word first */
 135         set = ~(~0UL << (n & (__NFDBITS-1)));
 136         n /= __NFDBITS;
 137         open_fds = current->files->open_fds->fds_bits+n;
 138         max = 0;
 139         if (set) {
 140                 set &= BITS(fds, n);
 141                 if (set) {
 142                         if (!(set & ~*open_fds))
 143                                 goto get_max;
 144                         return -EBADF;
 145                 }
 146         }
 147         while (n) {
 148                 open_fds--;
 149                 n--;
 150                 set = BITS(fds, n);
 151                 if (!set)
 152                         continue;
 153                 if (set & ~*open_fds)
 154                         return -EBADF;
 155                 if (max)
 156                         continue;
 157 get_max:
 158                 do {
 159                         max++;
 160                         set >>= 1;
 161                 } while (set);
 162                 max += n * __NFDBITS;
 163         }
 164
 165         return max;
 166 }
 167
 168 #define BIT(i)          (1UL << ((i)&(__NFDBITS-1)))
 169 #define MEM(i,m)        ((m)+(unsigned)(i)/__NFDBITS)
 170 #define ISSET(i,m)      (((i)&*(m)) != 0)
 171 #define SET(i,m)        (*(m) |= (i))
 172
 173 #define POLLIN_SET (POLLRDNORM | POLLRDBAND | POLLIN | POLLHUP | POLLERR)
 174 #define POLLOUT_SET (POLLWRBAND | POLLWRNORM | POLLOUT | POLLERR)
 175 #define POLLEX_SET (POLLPRI)
 176
 177 int do_select(int n, fd_set_bits *fds, long *timeout)
 178 {
 179         struct poll_wqueues table;
 180         poll_table *wait;
 181         int retval, i;
 182         long __timeout = *timeout;
 183
 184         spin_lock(&current->files->file_lock);
 185         retval = max_select_fd(n, fds);
 186         spin_unlock(&current->files->file_lock);
 187
 188         if (retval < 0)
 189                 return retval;
 190         n = retval;
 191
 192         poll_initwait(&table);
 193         wait = &table.pt;
 194         if (!__timeout)
 195                 wait = NULL;
 196         retval = 0;
 197         for (;;) {
 198                 unsigned long *rinp, *routp, *rexp, *inp, *outp, *exp;
 199
 200                 set_current_state(TASK_INTERRUPTIBLE);
 201
 202                 inp = fds->in; outp = fds->out; exp = fds->ex;
 203                 rinp = fds->res_in; routp = fds->res_out; rexp = fds->res_ex;
 204
 205                 for (i = 0; i < n; ++rinp, ++routp, ++rexp) {
 206                         unsigned long in, out, ex, all_bits, bit = 1, mask, j;
 207                         unsigned long res_in = 0, res_out = 0, res_ex = 0;
 208                         struct file_operations *f_op = NULL;
 209                         struct file *file = NULL;
 210
 211                         in = *inp++; out = *outp++; ex = *exp++;
 212                         all_bits = in | out | ex;
 213                         if (all_bits == 0) {
 214                                 i += __NFDBITS;
 215                                 continue;
 216                         }
 217
 218                         for (j = 0; j < __NFDBITS; ++j, ++i, bit <<= 1) {
 219                                 if (i >= n)
 220                                         break;
 221                                 if (!(bit & all_bits))
 222                                         continue;
 223                                 file = fget(i);
 224                                 if (file) {
 225                                         f_op = file->f_op;
 226                                         mask = DEFAULT_POLLMASK;
 227                                         if (f_op && f_op->poll)
 228                                                 mask = (*f_op->poll)(file, retval ? NULL : wait);
 229                                         fput(file);
 230                                         if ((mask & POLLIN_SET) && (in & bit)) {
 231                                                 res_in |= bit;
 232                                                 retval++;
 233                                         }
 234                                         if ((mask & POLLOUT_SET) && (out & bit)) {
 235                                                 res_out |= bit;
 236                                                 retval++;
 237                                         }
 238                                         if ((mask & POLLEX_SET) && (ex & bit)) {
 239                                                 res_ex |= bit;
 240                                                 retval++;
 241                                         }
 242                                 }
 243                                 cond_resched();
 244                         }
 245                         if (res_in)
 246                                 *rinp = res_in;
 247                         if (res_out)
 248                                 *routp = res_out;
 249                         if (res_ex)
 250                                 *rexp = res_ex;
 251                 }
 252                 wait = NULL;
 253                 if (retval || !__timeout || signal_pending(current))
 254                         break;
 255                 if(table.error) {
 256                         retval = table.error;
 257                         break;
 258                 }
 259                 __timeout = schedule_timeout(__timeout);
 260         }
 261         __set_current_state(TASK_RUNNING);
 262
 263         poll_freewait(&table);
 264
 265         /*
 266          * Up-to-date the caller timeout.
 267          */
 268         *timeout = __timeout;
 269         return retval;
 270 }
 271
 272 static void *select_bits_alloc(int size)
 273 {
 274         return kmalloc(6 * size, GFP_KERNEL);
 275 }
 276
 277 static void select_bits_free(void *bits, int size)
 278 {
 279         kfree(bits);
 280 }
 281
 282 /*
 283  * We can actually return ERESTARTSYS instead of EINTR, but I'd
 284  * like to be certain this leads to no problems. So I return
 285  * EINTR just for safety.
 286  *
 287  * Update: ERESTARTSYS breaks at least the xview clock binary, so
 288  * I'm trying ERESTARTNOHAND which restart only when you want to.
 289  */
 290 #define MAX_SELECT_SECONDS \
 291         ((unsigned long) (MAX_SCHEDULE_TIMEOUT / HZ)-1)
 292
 293 asmlinkage long
 294 sys_select(int n, fd_set __user *inp, fd_set __user *outp, fd_set __user *exp, struct timeval __user *tvp)
 295 {
 296         fd_set_bits fds;
 297         char *bits;
 298         long timeout;
 299         int ret, size, max_fdset;
 300
 301         timeout = MAX_SCHEDULE_TIMEOUT;
 302         if (tvp) {
 303                 time_t sec, usec;
 304
 305                 if (!access_ok(VERIFY_READ, tvp, sizeof(*tvp))
 306                     || __get_user(sec, &tvp->tv_sec)
 307                     || __get_user(usec, &tvp->tv_usec)) {
 308                         ret = -EFAULT;
 309                         goto out_nofds;
 310                 }
 311
 312                 ret = -EINVAL;
 313                 if (sec < 0 || usec < 0)
 314                         goto out_nofds;
 315
 316                 if ((unsigned long) sec < MAX_SELECT_SECONDS) {
 317                         timeout = ROUND_UP(usec, 1000000/HZ);
 318                         timeout += sec * (unsigned long) HZ;
 319                 }
 320         }
 321
 322         ret = -EINVAL;
 323         if (n < 0)
 324                 goto out_nofds;
 325
 326         /* max_fdset can increase, so grab it once to avoid race */
 327         max_fdset = current->files->max_fdset;
 328         if (n > max_fdset)
 329                 n = max_fdset;
 330
 331         /*
 332          * We need 6 bitmaps (in/out/ex for both incoming and outgoing),
 333          * since we used fdset we need to allocate memory in units of
 334          * long-words.
 335          */
 336         ret = -ENOMEM;
 337         size = FDS_BYTES(n);
 338         bits = select_bits_alloc(size);
 339         if (!bits)
 340                 goto out_nofds;
 341         fds.in      = (unsigned long *)  bits;
 342         fds.out     = (unsigned long *) (bits +   size);
 343         fds.ex      = (unsigned long *) (bits + 2*size);
 344         fds.res_in  = (unsigned long *) (bits + 3*size);
 345         fds.res_out = (unsigned long *) (bits + 4*size);
 346         fds.res_ex  = (unsigned long *) (bits + 5*size);
 347
 348         if ((ret = get_fd_set(n, inp, fds.in)) ||
 349             (ret = get_fd_set(n, outp, fds.out)) ||
 350             (ret = get_fd_set(n, exp, fds.ex)))
 351                 goto out;
 352         zero_fd_set(n, fds.res_in);
 353         zero_fd_set(n, fds.res_out);
 354         zero_fd_set(n, fds.res_ex);
 355
 356         ret = do_select(n, &fds, &timeout);
 357
 358         if (tvp && !(current->personality & STICKY_TIMEOUTS)) {
 359                 time_t sec = 0, usec = 0;
 360                 if (timeout) {
 361                         sec = timeout / HZ;
 362                         usec = timeout % HZ;
 363                         usec *= (1000000/HZ);
 364                 }
 365                 put_user(sec, &tvp->tv_sec);
 366                 put_user(usec, &tvp->tv_usec);
 367         }
 368
 369         if (ret < 0)
 370                 goto out;
 371         if (!ret) {
 372                 ret = -ERESTARTNOHAND;
 373                 if (signal_pending(current))
 374                         goto out;
 375                 ret = 0;
 376         }
 377
 378         if (set_fd_set(n, inp, fds.res_in) ||
 379             set_fd_set(n, outp, fds.res_out) ||
 380             set_fd_set(n, exp, fds.res_ex))
 381                 ret = -EFAULT;
 382
 383 out:
 384         select_bits_free(bits, size);
 385 out_nofds:
 386         return ret;
 387 }
 388
 389 struct poll_list {
 390         struct poll_list *next;
 391         int len;
 392         struct pollfd entries[0];
 393 };
 394
 395 #define POLLFD_PER_PAGE  ((PAGE_SIZE-sizeof(struct poll_list)) / sizeof(struct pollfd))
 396
 397 static void do_pollfd(unsigned int num, struct pollfd * fdpage,
 398         poll_table ** pwait, int *count)
 399 {
 400         int i;
 401
 402         for (i = 0; i < num; i++) {
 403                 int fd;
 404                 unsigned int mask;
 405                 struct pollfd *fdp;
 406
 407                 mask = 0;
 408                 fdp = fdpage+i;
 409                 fd = fdp->fd;
 410                 if (fd >= 0) {
 411                         struct file * file = fget(fd);
 412                         mask = POLLNVAL;
 413                         if (file != NULL) {
 414                                 mask = DEFAULT_POLLMASK;
 415                                 if (file->f_op && file->f_op->poll)
 416                                         mask = file->f_op->poll(file, *pwait);
 417                                 mask &= fdp->events | POLLERR | POLLHUP;
 418                                 fput(file);
 419                         }
 420                         if (mask) {
 421                                 *pwait = NULL;
 422                                 (*count)++;
 423                         }
 424                 }
 425                 fdp->revents = mask;
 426         }
 427 }
 428
 429 static int do_poll(unsigned int nfds,  struct poll_list *list,
 430                         struct poll_wqueues *wait, long timeout)
 431 {
 432         int count = 0;
 433         poll_table* pt = &wait->pt;
 434
 435         if (!timeout)
 436                 pt = NULL;
 437
 438         for (;;) {
 439                 struct poll_list *walk;
 440                 set_current_state(TASK_INTERRUPTIBLE);
 441                 walk = list;
 442                 while(walk != NULL) {
 443                         do_pollfd( walk->len, walk->entries, &pt, &count);
 444                         walk = walk->next;
 445                 }
 446                 pt = NULL;
 447                 if (count || !timeout || signal_pending(current))
 448                         break;
 449                 count = wait->error;
 450                 if (count)
 451                         break;
 452                 timeout = schedule_timeout(timeout);
 453         }
 454         __set_current_state(TASK_RUNNING);
 455         return count;
 456 }
 457
 458 asmlinkage long sys_poll(struct pollfd __user * ufds, unsigned int nfds, long timeout)
 459 {
 460         struct poll_wqueues table;
 461         int fdcount, err;
 462         unsigned int i;
 463         struct poll_list *head;
 464         struct poll_list *walk;
 465
 466         /* Do a sanity check on nfds ... */
 467         if (nfds > current->files->max_fdset && nfds > OPEN_MAX)
 468                 return -EINVAL;
 469
 470         if (timeout) {
 471                 /* Careful about overflow in the intermediate values */
 472                 if ((unsigned long) timeout < MAX_SCHEDULE_TIMEOUT / HZ)
 473                         timeout = (unsigned long)(timeout*HZ+999)/1000+1;
 474                 else /* Negative or overflow */
 475                         timeout = MAX_SCHEDULE_TIMEOUT;
 476         }
 477
 478         poll_initwait(&table);
 479
 480         head = NULL;
 481         walk = NULL;
 482         i = nfds;
 483         err = -ENOMEM;
 484         while(i!=0) {
 485                 struct poll_list *pp;
 486                 pp = kmalloc(sizeof(struct poll_list)+
 487                                 sizeof(struct pollfd)*
 488                                 (i>POLLFD_PER_PAGE?POLLFD_PER_PAGE:i),
 489                                         GFP_KERNEL);
 490                 if(pp==NULL)
 491                         goto out_fds;
 492                 pp->next=NULL;
 493                 pp->len = (i>POLLFD_PER_PAGE?POLLFD_PER_PAGE:i);
 494                 if (head == NULL)
 495                         head = pp;
 496                 else
 497                         walk->next = pp;
 498
 499                 walk = pp;
 500                 if (copy_from_user(pp->entries, ufds + nfds-i,
 501                                 sizeof(struct pollfd)*pp->len)) {
 502                         err = -EFAULT;
 503                         goto out_fds;
 504                 }
 505                 i -= pp->len;
 506         }
 507         fdcount = do_poll(nfds, head, &table, timeout);
 508
 509         /* OK, now copy the revents fields back to user space. */
 510         walk = head;
 511         err = -EFAULT;
 512         while(walk != NULL) {
 513                 struct pollfd *fds = walk->entries;
 514                 int j;
 515
 516                 for (j=0; j < walk->len; j++, ufds++) {
 517                         if(__put_user(fds[j].revents, &ufds->revents))
 518                                 goto out_fds;
 519                 }
 520                 walk = walk->next;
 521         }
 522         err = fdcount;
 523         if (!fdcount && signal_pending(current))
 524                 err = -EINTR;
 525 out_fds:
 526         walk = head;
 527         while(walk!=NULL) {
 528                 struct poll_list *pp = walk->next;
 529                 kfree(walk);
 530                 walk = pp;
 531         }
 532         poll_freewait(&table);
 533         return err;
 534 }