SAFE public projects git trees. - safe/jmp/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 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         struct fdtable *fdt;
 136
 137         /* handle last in-complete long-word first */
 138         set = ~(~0UL << (n & (__NFDBITS-1)));
 139         n /= __NFDBITS;
 140         fdt = files_fdtable(current->files);
 141         open_fds = fdt->open_fds->fds_bits+n;
 142         max = 0;
 143         if (set) {
 144                 set &= BITS(fds, n);
 145                 if (set) {
 146                         if (!(set & ~*open_fds))
 147                                 goto get_max;
 148                         return -EBADF;
 149                 }
 150         }
 151         while (n) {
 152                 open_fds--;
 153                 n--;
 154                 set = BITS(fds, n);
 155                 if (!set)
 156                         continue;
 157                 if (set & ~*open_fds)
 158                         return -EBADF;
 159                 if (max)
 160                         continue;
 161 get_max:
 162                 do {
 163                         max++;
 164                         set >>= 1;
 165                 } while (set);
 166                 max += n * __NFDBITS;
 167         }
 168
 169         return max;
 170 }
 171
 172 #define BIT(i)          (1UL << ((i)&(__NFDBITS-1)))
 173 #define MEM(i,m)        ((m)+(unsigned)(i)/__NFDBITS)
 174 #define ISSET(i,m)      (((i)&*(m)) != 0)
 175 #define SET(i,m)        (*(m) |= (i))
 176
 177 #define POLLIN_SET (POLLRDNORM | POLLRDBAND | POLLIN | POLLHUP | POLLERR)
 178 #define POLLOUT_SET (POLLWRBAND | POLLWRNORM | POLLOUT | POLLERR)
 179 #define POLLEX_SET (POLLPRI)
 180
 181 int do_select(int n, fd_set_bits *fds, long *timeout)
 182 {
 183         struct poll_wqueues table;
 184         poll_table *wait;
 185         int retval, i;
 186         long __timeout = *timeout;
 187
 188         spin_lock(&current->files->file_lock);
 189         retval = max_select_fd(n, fds);
 190         spin_unlock(&current->files->file_lock);
 191
 192         if (retval < 0)
 193                 return retval;
 194         n = retval;
 195
 196         poll_initwait(&table);
 197         wait = &table.pt;
 198         if (!__timeout)
 199                 wait = NULL;
 200         retval = 0;
 201         for (;;) {
 202                 unsigned long *rinp, *routp, *rexp, *inp, *outp, *exp;
 203
 204                 set_current_state(TASK_INTERRUPTIBLE);
 205
 206                 inp = fds->in; outp = fds->out; exp = fds->ex;
 207                 rinp = fds->res_in; routp = fds->res_out; rexp = fds->res_ex;
 208
 209                 for (i = 0; i < n; ++rinp, ++routp, ++rexp) {
 210                         unsigned long in, out, ex, all_bits, bit = 1, mask, j;
 211                         unsigned long res_in = 0, res_out = 0, res_ex = 0;
 212                         struct file_operations *f_op = NULL;
 213                         struct file *file = NULL;
 214
 215                         in = *inp++; out = *outp++; ex = *exp++;
 216                         all_bits = in | out | ex;
 217                         if (all_bits == 0) {
 218                                 i += __NFDBITS;
 219                                 continue;
 220                         }
 221
 222                         for (j = 0; j < __NFDBITS; ++j, ++i, bit <<= 1) {
 223                                 if (i >= n)
 224                                         break;
 225                                 if (!(bit & all_bits))
 226                                         continue;
 227                                 file = fget(i);
 228                                 if (file) {
 229                                         f_op = file->f_op;
 230                                         mask = DEFAULT_POLLMASK;
 231                                         if (f_op && f_op->poll)
 232                                                 mask = (*f_op->poll)(file, retval ? NULL : wait);
 233                                         fput(file);
 234                                         if ((mask & POLLIN_SET) && (in & bit)) {
 235                                                 res_in |= bit;
 236                                                 retval++;
 237                                         }
 238                                         if ((mask & POLLOUT_SET) && (out & bit)) {
 239                                                 res_out |= bit;
 240                                                 retval++;
 241                                         }
 242                                         if ((mask & POLLEX_SET) && (ex & bit)) {
 243                                                 res_ex |= bit;
 244                                                 retval++;
 245                                         }
 246                                 }
 247                                 cond_resched();
 248                         }
 249                         if (res_in)
 250                                 *rinp = res_in;
 251                         if (res_out)
 252                                 *routp = res_out;
 253                         if (res_ex)
 254                                 *rexp = res_ex;
 255                 }
 256                 wait = NULL;
 257                 if (retval || !__timeout || signal_pending(current))
 258                         break;
 259                 if(table.error) {
 260                         retval = table.error;
 261                         break;
 262                 }
 263                 __timeout = schedule_timeout(__timeout);
 264         }
 265         __set_current_state(TASK_RUNNING);
 266
 267         poll_freewait(&table);
 268
 269         /*
 270          * Up-to-date the caller timeout.
 271          */
 272         *timeout = __timeout;
 273         return retval;
 274 }
 275
 276 static void *select_bits_alloc(int size)
 277 {
 278         return kmalloc(6 * size, GFP_KERNEL);
 279 }
 280
 281 static void select_bits_free(void *bits, int size)
 282 {
 283         kfree(bits);
 284 }
 285
 286 /*
 287  * We can actually return ERESTARTSYS instead of EINTR, but I'd
 288  * like to be certain this leads to no problems. So I return
 289  * EINTR just for safety.
 290  *
 291  * Update: ERESTARTSYS breaks at least the xview clock binary, so
 292  * I'm trying ERESTARTNOHAND which restart only when you want to.
 293  */
 294 #define MAX_SELECT_SECONDS \
 295         ((unsigned long) (MAX_SCHEDULE_TIMEOUT / HZ)-1)
 296
 297 asmlinkage long
 298 sys_select(int n, fd_set __user *inp, fd_set __user *outp, fd_set __user *exp, struct timeval __user *tvp)
 299 {
 300         fd_set_bits fds;
 301         char *bits;
 302         long timeout;
 303         int ret, size, max_fdset;
 304         struct fdtable *fdt;
 305
 306         timeout = MAX_SCHEDULE_TIMEOUT;
 307         if (tvp) {
 308                 time_t sec, usec;
 309
 310                 if (!access_ok(VERIFY_READ, tvp, sizeof(*tvp))
 311                     || __get_user(sec, &tvp->tv_sec)
 312                     || __get_user(usec, &tvp->tv_usec)) {
 313                         ret = -EFAULT;
 314                         goto out_nofds;
 315                 }
 316
 317                 ret = -EINVAL;
 318                 if (sec < 0 || usec < 0)
 319                         goto out_nofds;
 320
 321                 if ((unsigned long) sec < MAX_SELECT_SECONDS) {
 322                         timeout = ROUND_UP(usec, 1000000/HZ);
 323                         timeout += sec * (unsigned long) HZ;
 324                 }
 325         }
 326
 327         ret = -EINVAL;
 328         if (n < 0)
 329                 goto out_nofds;
 330
 331         /* max_fdset can increase, so grab it once to avoid race */
 332         fdt = files_fdtable(current->files);
 333         max_fdset = fdt->max_fdset;
 334         if (n > max_fdset)
 335                 n = max_fdset;
 336
 337         /*
 338          * We need 6 bitmaps (in/out/ex for both incoming and outgoing),
 339          * since we used fdset we need to allocate memory in units of
 340          * long-words.
 341          */
 342         ret = -ENOMEM;
 343         size = FDS_BYTES(n);
 344         bits = select_bits_alloc(size);
 345         if (!bits)
 346                 goto out_nofds;
 347         fds.in      = (unsigned long *)  bits;
 348         fds.out     = (unsigned long *) (bits +   size);
 349         fds.ex      = (unsigned long *) (bits + 2*size);
 350         fds.res_in  = (unsigned long *) (bits + 3*size);
 351         fds.res_out = (unsigned long *) (bits + 4*size);
 352         fds.res_ex  = (unsigned long *) (bits + 5*size);
 353
 354         if ((ret = get_fd_set(n, inp, fds.in)) ||
 355             (ret = get_fd_set(n, outp, fds.out)) ||
 356             (ret = get_fd_set(n, exp, fds.ex)))
 357                 goto out;
 358         zero_fd_set(n, fds.res_in);
 359         zero_fd_set(n, fds.res_out);
 360         zero_fd_set(n, fds.res_ex);
 361
 362         ret = do_select(n, &fds, &timeout);
 363
 364         if (tvp && !(current->personality & STICKY_TIMEOUTS)) {
 365                 time_t sec = 0, usec = 0;
 366                 if (timeout) {
 367                         sec = timeout / HZ;
 368                         usec = timeout % HZ;
 369                         usec *= (1000000/HZ);
 370                 }
 371                 put_user(sec, &tvp->tv_sec);
 372                 put_user(usec, &tvp->tv_usec);
 373         }
 374
 375         if (ret < 0)
 376                 goto out;
 377         if (!ret) {
 378                 ret = -ERESTARTNOHAND;
 379                 if (signal_pending(current))
 380                         goto out;
 381                 ret = 0;
 382         }
 383
 384         if (set_fd_set(n, inp, fds.res_in) ||
 385             set_fd_set(n, outp, fds.res_out) ||
 386             set_fd_set(n, exp, fds.res_ex))
 387                 ret = -EFAULT;
 388
 389 out:
 390         select_bits_free(bits, size);
 391 out_nofds:
 392         return ret;
 393 }
 394
 395 struct poll_list {
 396         struct poll_list *next;
 397         int len;
 398         struct pollfd entries[0];
 399 };
 400
 401 #define POLLFD_PER_PAGE  ((PAGE_SIZE-sizeof(struct poll_list)) / sizeof(struct pollfd))
 402
 403 static void do_pollfd(unsigned int num, struct pollfd * fdpage,
 404         poll_table ** pwait, int *count)
 405 {
 406         int i;
 407
 408         for (i = 0; i < num; i++) {
 409                 int fd;
 410                 unsigned int mask;
 411                 struct pollfd *fdp;
 412
 413                 mask = 0;
 414                 fdp = fdpage+i;
 415                 fd = fdp->fd;
 416                 if (fd >= 0) {
 417                         struct file * file = fget(fd);
 418                         mask = POLLNVAL;
 419                         if (file != NULL) {
 420                                 mask = DEFAULT_POLLMASK;
 421                                 if (file->f_op && file->f_op->poll)
 422                                         mask = file->f_op->poll(file, *pwait);
 423                                 mask &= fdp->events | POLLERR | POLLHUP;
 424                                 fput(file);
 425                         }
 426                         if (mask) {
 427                                 *pwait = NULL;
 428                                 (*count)++;
 429                         }
 430                 }
 431                 fdp->revents = mask;
 432         }
 433 }
 434
 435 static int do_poll(unsigned int nfds,  struct poll_list *list,
 436                         struct poll_wqueues *wait, long timeout)
 437 {
 438         int count = 0;
 439         poll_table* pt = &wait->pt;
 440
 441         if (!timeout)
 442                 pt = NULL;
 443
 444         for (;;) {
 445                 struct poll_list *walk;
 446                 set_current_state(TASK_INTERRUPTIBLE);
 447                 walk = list;
 448                 while(walk != NULL) {
 449                         do_pollfd( walk->len, walk->entries, &pt, &count);
 450                         walk = walk->next;
 451                 }
 452                 pt = NULL;
 453                 if (count || !timeout || signal_pending(current))
 454                         break;
 455                 count = wait->error;
 456                 if (count)
 457                         break;
 458                 timeout = schedule_timeout(timeout);
 459         }
 460         __set_current_state(TASK_RUNNING);
 461         return count;
 462 }
 463
 464 asmlinkage long sys_poll(struct pollfd __user * ufds, unsigned int nfds, long timeout)
 465 {
 466         struct poll_wqueues table;
 467         int fdcount, err;
 468         unsigned int i;
 469         struct poll_list *head;
 470         struct poll_list *walk;
 471         struct fdtable *fdt;
 472
 473         /* Do a sanity check on nfds ... */
 474         fdt = files_fdtable(current->files);
 475         if (nfds > fdt->max_fdset && nfds > OPEN_MAX)
 476                 return -EINVAL;
 477
 478         if (timeout) {
 479                 /* Careful about overflow in the intermediate values */
 480                 if ((unsigned long) timeout < MAX_SCHEDULE_TIMEOUT / HZ)
 481                         timeout = (unsigned long)(timeout*HZ+999)/1000+1;
 482                 else /* Negative or overflow */
 483                         timeout = MAX_SCHEDULE_TIMEOUT;
 484         }
 485
 486         poll_initwait(&table);
 487
 488         head = NULL;
 489         walk = NULL;
 490         i = nfds;
 491         err = -ENOMEM;
 492         while(i!=0) {
 493                 struct poll_list *pp;
 494                 pp = kmalloc(sizeof(struct poll_list)+
 495                                 sizeof(struct pollfd)*
 496                                 (i>POLLFD_PER_PAGE?POLLFD_PER_PAGE:i),
 497                                         GFP_KERNEL);
 498                 if(pp==NULL)
 499                         goto out_fds;
 500                 pp->next=NULL;
 501                 pp->len = (i>POLLFD_PER_PAGE?POLLFD_PER_PAGE:i);
 502                 if (head == NULL)
 503                         head = pp;
 504                 else
 505                         walk->next = pp;
 506
 507                 walk = pp;
 508                 if (copy_from_user(pp->entries, ufds + nfds-i,
 509                                 sizeof(struct pollfd)*pp->len)) {
 510                         err = -EFAULT;
 511                         goto out_fds;
 512                 }
 513                 i -= pp->len;
 514         }
 515         fdcount = do_poll(nfds, head, &table, timeout);
 516
 517         /* OK, now copy the revents fields back to user space. */
 518         walk = head;
 519         err = -EFAULT;
 520         while(walk != NULL) {
 521                 struct pollfd *fds = walk->entries;
 522                 int j;
 523
 524                 for (j=0; j < walk->len; j++, ufds++) {
 525                         if(__put_user(fds[j].revents, &ufds->revents))
 526                                 goto out_fds;
 527                 }
 528                 walk = walk->next;
 529         }
 530         err = fdcount;
 531         if (!fdcount && signal_pending(current))
 532                 err = -EINTR;
 533 out_fds:
 534         walk = head;
 535         while(walk!=NULL) {
 536                 struct poll_list *pp = walk->next;
 537                 kfree(walk);
 538                 walk = pp;
 539         }
 540         poll_freewait(&table);
 541         return err;
 542 }