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/kernel.h>
  18 #include <linux/sched.h>
  19 #include <linux/syscalls.h>
  20 #include <linux/export.h>
  21 #include <linux/slab.h>
  22 #include <linux/poll.h>
  23 #include <linux/personality.h> /* for STICKY_TIMEOUTS */
  24 #include <linux/file.h>
  25 #include <linux/fdtable.h>
  26 #include <linux/fs.h>
  27 #include <linux/rcupdate.h>
  28 #include <linux/hrtimer.h>
  29 #include <linux/sched/rt.h>
  30 #include <linux/freezer.h>
  31 #include <net/busy_poll.h>
  32
  33 #include <asm/uaccess.h>
  34
  35
  36 /*
  37  * Estimate expected accuracy in ns from a timeval.
  38  *
  39  * After quite a bit of churning around, we've settled on
  40  * a simple thing of taking 0.1% of the timeout as the
  41  * slack, with a cap of 100 msec.
  42  * "nice" tasks get a 0.5% slack instead.
  43  *
  44  * Consider this comment an open invitation to come up with even
  45  * better solutions..
  46  */
  47
  48 #define MAX_SLACK       (100 * NSEC_PER_MSEC)
  49
  50 static long __estimate_accuracy(struct timespec *tv)
  51 {
  52         long slack;
  53         int divfactor = 1000;
  54
  55         if (tv->tv_sec < 0)
  56                 return 0;
  57
  58         if (task_nice(current) > 0)
  59                 divfactor = divfactor / 5;
  60
  61         if (tv->tv_sec > MAX_SLACK / (NSEC_PER_SEC/divfactor))
  62                 return MAX_SLACK;
  63
  64         slack = tv->tv_nsec / divfactor;
  65         slack += tv->tv_sec * (NSEC_PER_SEC/divfactor);
  66
  67         if (slack > MAX_SLACK)
  68                 return MAX_SLACK;
  69
  70         return slack;
  71 }
  72
  73 long select_estimate_accuracy(struct timespec *tv)
  74 {
  75         unsigned long ret;
  76         struct timespec now;
  77
  78         /*
  79          * Realtime tasks get a slack of 0 for obvious reasons.
  80          */
  81
  82         if (rt_task(current))
  83                 return 0;
  84
  85         ktime_get_ts(&now);
  86         now = timespec_sub(*tv, now);
  87         ret = __estimate_accuracy(&now);
  88         if (ret < current->timer_slack_ns)
  89                 return current->timer_slack_ns;
  90         return ret;
  91 }
  92
  93
  94
  95 struct poll_table_page {
  96         struct poll_table_page * next;
  97         struct poll_table_entry * entry;
  98         struct poll_table_entry entries[0];
  99 };
 100
 101 #define POLL_TABLE_FULL(table) \
 102         ((unsigned long)((table)->entry+1) > PAGE_SIZE + (unsigned long)(table))
 103
 104 /*
 105  * Ok, Peter made a complicated, but straightforward multiple_wait() function.
 106  * I have rewritten this, taking some shortcuts: This code may not be easy to
 107  * follow, but it should be free of race-conditions, and it's practical. If you
 108  * understand what I'm doing here, then you understand how the linux
 109  * sleep/wakeup mechanism works.
 110  *
 111  * Two very simple procedures, poll_wait() and poll_freewait() make all the
 112  * work.  poll_wait() is an inline-function defined in <linux/poll.h>,
 113  * as all select/poll functions have to call it to add an entry to the
 114  * poll table.
 115  */
 116 static void __pollwait(struct file *filp, wait_queue_head_t *wait_address,
 117                        poll_table *p);
 118
 119 void poll_initwait(struct poll_wqueues *pwq)
 120 {
 121         init_poll_funcptr(&pwq->pt, __pollwait);
 122         pwq->polling_task = current;
 123         pwq->triggered = 0;
 124         pwq->error = 0;
 125         pwq->table = NULL;
 126         pwq->inline_index = 0;
 127 }
 128 EXPORT_SYMBOL(poll_initwait);
 129
 130 static void free_poll_entry(struct poll_table_entry *entry)
 131 {
 132         remove_wait_queue(entry->wait_address, &entry->wait);
 133         fput(entry->filp);
 134 }
 135
 136 void poll_freewait(struct poll_wqueues *pwq)
 137 {
 138         struct poll_table_page * p = pwq->table;
 139         int i;
 140         for (i = 0; i < pwq->inline_index; i++)
 141                 free_poll_entry(pwq->inline_entries + i);
 142         while (p) {
 143                 struct poll_table_entry * entry;
 144                 struct poll_table_page *old;
 145
 146                 entry = p->entry;
 147                 do {
 148                         entry--;
 149                         free_poll_entry(entry);
 150                 } while (entry > p->entries);
 151                 old = p;
 152                 p = p->next;
 153                 free_page((unsigned long) old);
 154         }
 155 }
 156 EXPORT_SYMBOL(poll_freewait);
 157
 158 static struct poll_table_entry *poll_get_entry(struct poll_wqueues *p)
 159 {
 160         struct poll_table_page *table = p->table;
 161
 162         if (p->inline_index < N_INLINE_POLL_ENTRIES)
 163                 return p->inline_entries + p->inline_index++;
 164
 165         if (!table || POLL_TABLE_FULL(table)) {
 166                 struct poll_table_page *new_table;
 167
 168                 new_table = (struct poll_table_page *) __get_free_page(GFP_KERNEL);
 169                 if (!new_table) {
 170                         p->error = -ENOMEM;
 171                         return NULL;
 172                 }
 173                 new_table->entry = new_table->entries;
 174                 new_table->next = table;
 175                 p->table = new_table;
 176                 table = new_table;
 177         }
 178
 179         return table->entry++;
 180 }
 181
 182 static int __pollwake(wait_queue_t *wait, unsigned mode, int sync, void *key)
 183 {
 184         struct poll_wqueues *pwq = wait->private;
 185         DECLARE_WAITQUEUE(dummy_wait, pwq->polling_task);
 186
 187         /*
 188          * Although this function is called under waitqueue lock, LOCK
 189          * doesn't imply write barrier and the users expect write
 190          * barrier semantics on wakeup functions.  The following
 191          * smp_wmb() is equivalent to smp_wmb() in try_to_wake_up()
 192          * and is paired with smp_store_mb() in poll_schedule_timeout.
 193          */
 194         smp_wmb();
 195         pwq->triggered = 1;
 196
 197         /*
 198          * Perform the default wake up operation using a dummy
 199          * waitqueue.
 200          *
 201          * TODO: This is hacky but there currently is no interface to
 202          * pass in @sync.  @sync is scheduled to be removed and once
 203          * that happens, wake_up_process() can be used directly.
 204          */
 205         return default_wake_function(&dummy_wait, mode, sync, key);
 206 }
 207
 208 static int pollwake(wait_queue_t *wait, unsigned mode, int sync, void *key)
 209 {
 210         struct poll_table_entry *entry;
 211
 212         entry = container_of(wait, struct poll_table_entry, wait);
 213         if (key && !((unsigned long)key & entry->key))
 214                 return 0;
 215         return __pollwake(wait, mode, sync, key);
 216 }
 217
 218 /* Add a new entry */
 219 static void __pollwait(struct file *filp, wait_queue_head_t *wait_address,
 220                                 poll_table *p)
 221 {
 222         struct poll_wqueues *pwq = container_of(p, struct poll_wqueues, pt);
 223         struct poll_table_entry *entry = poll_get_entry(pwq);
 224         if (!entry)
 225                 return;
 226         entry->filp = get_file(filp);
 227         entry->wait_address = wait_address;
 228         entry->key = p->_key;
 229         init_waitqueue_func_entry(&entry->wait, pollwake);
 230         entry->wait.private = pwq;
 231         add_wait_queue(wait_address, &entry->wait);
 232 }
 233
 234 int poll_schedule_timeout(struct poll_wqueues *pwq, int state,
 235                           ktime_t *expires, unsigned long slack)
 236 {
 237         int rc = -EINTR;
 238
 239         set_current_state(state);
 240         if (!pwq->triggered)
 241                 rc = schedule_hrtimeout_range(expires, slack, HRTIMER_MODE_ABS);
 242         __set_current_state(TASK_RUNNING);
 243
 244         /*
 245          * Prepare for the next iteration.
 246          *
 247          * The following smp_store_mb() serves two purposes.  First, it's
 248          * the counterpart rmb of the wmb in pollwake() such that data
 249          * written before wake up is always visible after wake up.
 250          * Second, the full barrier guarantees that triggered clearing
 251          * doesn't pass event check of the next iteration.  Note that
 252          * this problem doesn't exist for the first iteration as
 253          * add_wait_queue() has full barrier semantics.
 254          */
 255         smp_store_mb(pwq->triggered, 0);
 256
 257         return rc;
 258 }
 259 EXPORT_SYMBOL(poll_schedule_timeout);
 260
 261 /**
 262  * poll_select_set_timeout - helper function to setup the timeout value
 263  * @to:         pointer to timespec variable for the final timeout
 264  * @sec:        seconds (from user space)
 265  * @nsec:       nanoseconds (from user space)
 266  *
 267  * Note, we do not use a timespec for the user space value here, That
 268  * way we can use the function for timeval and compat interfaces as well.
 269  *
 270  * Returns -EINVAL if sec/nsec are not normalized. Otherwise 0.
 271  */
 272 int poll_select_set_timeout(struct timespec *to, long sec, long nsec)
 273 {
 274         struct timespec ts = {.tv_sec = sec, .tv_nsec = nsec};
 275
 276         if (!timespec_valid(&ts))
 277                 return -EINVAL;
 278
 279         /* Optimize for the zero timeout value here */
 280         if (!sec && !nsec) {
 281                 to->tv_sec = to->tv_nsec = 0;
 282         } else {
 283                 ktime_get_ts(to);
 284                 *to = timespec_add_safe(*to, ts);
 285         }
 286         return 0;
 287 }
 288
 289 static int poll_select_copy_remaining(struct timespec *end_time, void __user *p,
 290                                       int timeval, int ret)
 291 {
 292         struct timespec rts;
 293         struct timeval rtv;
 294
 295         if (!p)
 296                 return ret;
 297
 298         if (current->personality & STICKY_TIMEOUTS)
 299                 goto sticky;
 300
 301         /* No update for zero timeout */
 302         if (!end_time->tv_sec && !end_time->tv_nsec)
 303                 return ret;
 304
 305         ktime_get_ts(&rts);
 306         rts = timespec_sub(*end_time, rts);
 307         if (rts.tv_sec < 0)
 308                 rts.tv_sec = rts.tv_nsec = 0;
 309
 310         if (timeval) {
 311                 if (sizeof(rtv) > sizeof(rtv.tv_sec) + sizeof(rtv.tv_usec))
 312                         memset(&rtv, 0, sizeof(rtv));
 313                 rtv.tv_sec = rts.tv_sec;
 314                 rtv.tv_usec = rts.tv_nsec / NSEC_PER_USEC;
 315
 316                 if (!copy_to_user(p, &rtv, sizeof(rtv)))
 317                         return ret;
 318
 319         } else if (!copy_to_user(p, &rts, sizeof(rts)))
 320                 return ret;
 321
 322         /*
 323          * If an application puts its timeval in read-only memory, we
 324          * don't want the Linux-specific update to the timeval to
 325          * cause a fault after the select has completed
 326          * successfully. However, because we're not updating the
 327          * timeval, we can't restart the system call.
 328          */
 329
 330 sticky:
 331         if (ret == -ERESTARTNOHAND)
 332                 ret = -EINTR;
 333         return ret;
 334 }
 335
 336 #define FDS_IN(fds, n)          (fds->in + n)
 337 #define FDS_OUT(fds, n)         (fds->out + n)
 338 #define FDS_EX(fds, n)          (fds->ex + n)
 339
 340 #define BITS(fds, n)    (*FDS_IN(fds, n)|*FDS_OUT(fds, n)|*FDS_EX(fds, n))
 341
 342 static int max_select_fd(unsigned long n, fd_set_bits *fds)
 343 {
 344         unsigned long *open_fds;
 345         unsigned long set;
 346         int max;
 347         struct fdtable *fdt;
 348
 349         /* handle last in-complete long-word first */
 350         set = ~(~0UL << (n & (BITS_PER_LONG-1)));
 351         n /= BITS_PER_LONG;
 352         fdt = files_fdtable(current->files);
 353         open_fds = fdt->open_fds + n;
 354         max = 0;
 355         if (set) {
 356                 set &= BITS(fds, n);
 357                 if (set) {
 358                         if (!(set & ~*open_fds))
 359                                 goto get_max;
 360                         return -EBADF;
 361                 }
 362         }
 363         while (n) {
 364                 open_fds--;
 365                 n--;
 366                 set = BITS(fds, n);
 367                 if (!set)
 368                         continue;
 369                 if (set & ~*open_fds)
 370                         return -EBADF;
 371                 if (max)
 372                         continue;
 373 get_max:
 374                 do {
 375                         max++;
 376                         set >>= 1;
 377                 } while (set);
 378                 max += n * BITS_PER_LONG;
 379         }
 380
 381         return max;
 382 }
 383
 384 #define POLLIN_SET (POLLRDNORM | POLLRDBAND | POLLIN | POLLHUP | POLLERR)
 385 #define POLLOUT_SET (POLLWRBAND | POLLWRNORM | POLLOUT | POLLERR)
 386 #define POLLEX_SET (POLLPRI)
 387
 388 static inline void wait_key_set(poll_table *wait, unsigned long in,
 389                                 unsigned long out, unsigned long bit,
 390                                 unsigned int ll_flag)
 391 {
 392         wait->_key = POLLEX_SET | ll_flag;
 393         if (in & bit)
 394                 wait->_key |= POLLIN_SET;
 395         if (out & bit)
 396                 wait->_key |= POLLOUT_SET;
 397 }
 398
 399 int do_select(int n, fd_set_bits *fds, struct timespec *end_time)
 400 {
 401         ktime_t expire, *to = NULL;
 402         struct poll_wqueues table;
 403         poll_table *wait;
 404         int retval, i, timed_out = 0;
 405         unsigned long slack = 0;
 406         unsigned int busy_flag = net_busy_loop_on() ? POLL_BUSY_LOOP : 0;
 407         unsigned long busy_end = 0;
 408
 409         rcu_read_lock();
 410         retval = max_select_fd(n, fds);
 411         rcu_read_unlock();
 412
 413         if (retval < 0)
 414                 return retval;
 415         n = retval;
 416
 417         poll_initwait(&table);
 418         wait = &table.pt;
 419         if (end_time && !end_time->tv_sec && !end_time->tv_nsec) {
 420                 wait->_qproc = NULL;
 421                 timed_out = 1;
 422         }
 423
 424         if (end_time && !timed_out)
 425                 slack = select_estimate_accuracy(end_time);
 426
 427         retval = 0;
 428         for (;;) {
 429                 unsigned long *rinp, *routp, *rexp, *inp, *outp, *exp;
 430                 bool can_busy_loop = false;
 431
 432                 inp = fds->in; outp = fds->out; exp = fds->ex;
 433                 rinp = fds->res_in; routp = fds->res_out; rexp = fds->res_ex;
 434
 435                 for (i = 0; i < n; ++rinp, ++routp, ++rexp) {
 436                         unsigned long in, out, ex, all_bits, bit = 1, mask, j;
 437                         unsigned long res_in = 0, res_out = 0, res_ex = 0;
 438
 439                         in = *inp++; out = *outp++; ex = *exp++;
 440                         all_bits = in | out | ex;
 441                         if (all_bits == 0) {
 442                                 i += BITS_PER_LONG;
 443                                 continue;
 444                         }
 445
 446                         for (j = 0; j < BITS_PER_LONG; ++j, ++i, bit <<= 1) {
 447                                 struct fd f;
 448                                 if (i >= n)
 449                                         break;
 450                                 if (!(bit & all_bits))
 451                                         continue;
 452                                 f = fdget(i);
 453                                 if (f.file) {
 454                                         const struct file_operations *f_op;
 455                                         f_op = f.file->f_op;
 456                                         mask = DEFAULT_POLLMASK;
 457                                         if (f_op->poll) {
 458                                                 wait_key_set(wait, in, out,
 459                                                              bit, busy_flag);
 460                                                 mask = (*f_op->poll)(f.file, wait);
 461                                         }
 462                                         fdput(f);
 463                                         if ((mask & POLLIN_SET) && (in & bit)) {
 464                                                 res_in |= bit;
 465                                                 retval++;
 466                                                 wait->_qproc = NULL;
 467                                         }
 468                                         if ((mask & POLLOUT_SET) && (out & bit)) {
 469                                                 res_out |= bit;
 470                                                 retval++;
 471                                                 wait->_qproc = NULL;
 472                                         }
 473                                         if ((mask & POLLEX_SET) && (ex & bit)) {
 474                                                 res_ex |= bit;
 475                                                 retval++;
 476                                                 wait->_qproc = NULL;
 477                                         }
 478                                         /* got something, stop busy polling */
 479                                         if (retval) {
 480                                                 can_busy_loop = false;
 481                                                 busy_flag = 0;
 482
 483                                         /*
 484                                          * only remember a returned
 485                                          * POLL_BUSY_LOOP if we asked for it
 486                                          */
 487                                         } else if (busy_flag & mask)
 488                                                 can_busy_loop = true;
 489
 490                                 }
 491                         }
 492                         if (res_in)
 493                                 *rinp = res_in;
 494                         if (res_out)
 495                                 *routp = res_out;
 496                         if (res_ex)
 497                                 *rexp = res_ex;
 498                         cond_resched();
 499                 }
 500                 wait->_qproc = NULL;
 501                 if (retval || timed_out || signal_pending(current))
 502                         break;
 503                 if (table.error) {
 504                         retval = table.error;
 505                         break;
 506                 }
 507
 508                 /* only if found POLL_BUSY_LOOP sockets && not out of time */
 509                 if (can_busy_loop && !need_resched()) {
 510                         if (!busy_end) {
 511                                 busy_end = busy_loop_end_time();
 512                                 continue;
 513                         }
 514                         if (!busy_loop_timeout(busy_end))
 515                                 continue;
 516                 }
 517                 busy_flag = 0;
 518
 519                 /*
 520                  * If this is the first loop and we have a timeout
 521                  * given, then we convert to ktime_t and set the to
 522                  * pointer to the expiry value.
 523                  */
 524                 if (end_time && !to) {
 525                         expire = timespec_to_ktime(*end_time);
 526                         to = &expire;
 527                 }
 528
 529                 if (!poll_schedule_timeout(&table, TASK_INTERRUPTIBLE,
 530                                            to, slack))
 531                         timed_out = 1;
 532         }
 533
 534         poll_freewait(&table);
 535
 536         return retval;
 537 }
 538
 539 /*
 540  * We can actually return ERESTARTSYS instead of EINTR, but I'd
 541  * like to be certain this leads to no problems. So I return
 542  * EINTR just for safety.
 543  *
 544  * Update: ERESTARTSYS breaks at least the xview clock binary, so
 545  * I'm trying ERESTARTNOHAND which restart only when you want to.
 546  */
 547 int core_sys_select(int n, fd_set __user *inp, fd_set __user *outp,
 548                            fd_set __user *exp, struct timespec *end_time)
 549 {
 550         fd_set_bits fds;
 551         void *bits;
 552         int ret, max_fds;
 553         unsigned int size;
 554         struct fdtable *fdt;
 555         /* Allocate small arguments on the stack to save memory and be faster */
 556         long stack_fds[SELECT_STACK_ALLOC/sizeof(long)];
 557
 558         ret = -EINVAL;
 559         if (n < 0)
 560                 goto out_nofds;
 561
 562         /* max_fds can increase, so grab it once to avoid race */
 563         rcu_read_lock();
 564         fdt = files_fdtable(current->files);
 565         max_fds = fdt->max_fds;
 566         rcu_read_unlock();
 567         if (n > max_fds)
 568                 n = max_fds;
 569
 570         /*
 571          * We need 6 bitmaps (in/out/ex for both incoming and outgoing),
 572          * since we used fdset we need to allocate memory in units of
 573          * long-words.
 574          */
 575         size = FDS_BYTES(n);
 576         bits = stack_fds;
 577         if (size > sizeof(stack_fds) / 6) {
 578                 /* Not enough space in on-stack array; must use kmalloc */
 579                 ret = -ENOMEM;
 580                 bits = kmalloc(6 * size, GFP_KERNEL);
 581                 if (!bits)
 582                         goto out_nofds;
 583         }
 584         fds.in      = bits;
 585         fds.out     = bits +   size;
 586         fds.ex      = bits + 2*size;
 587         fds.res_in  = bits + 3*size;
 588         fds.res_out = bits + 4*size;
 589         fds.res_ex  = bits + 5*size;
 590
 591         if ((ret = get_fd_set(n, inp, fds.in)) ||
 592             (ret = get_fd_set(n, outp, fds.out)) ||
 593             (ret = get_fd_set(n, exp, fds.ex)))
 594                 goto out;
 595         zero_fd_set(n, fds.res_in);
 596         zero_fd_set(n, fds.res_out);
 597         zero_fd_set(n, fds.res_ex);
 598
 599         ret = do_select(n, &fds, end_time);
 600
 601         if (ret < 0)
 602                 goto out;
 603         if (!ret) {
 604                 ret = -ERESTARTNOHAND;
 605                 if (signal_pending(current))
 606                         goto out;
 607                 ret = 0;
 608         }
 609
 610         if (set_fd_set(n, inp, fds.res_in) ||
 611             set_fd_set(n, outp, fds.res_out) ||
 612             set_fd_set(n, exp, fds.res_ex))
 613                 ret = -EFAULT;
 614
 615 out:
 616         if (bits != stack_fds)
 617                 kfree(bits);
 618 out_nofds:
 619         return ret;
 620 }
 621
 622 SYSCALL_DEFINE5(select, int, n, fd_set __user *, inp, fd_set __user *, outp,
 623                 fd_set __user *, exp, struct timeval __user *, tvp)
 624 {
 625         struct timespec end_time, *to = NULL;
 626         struct timeval tv;
 627         int ret;
 628
 629         if (tvp) {
 630                 if (copy_from_user(&tv, tvp, sizeof(tv)))
 631                         return -EFAULT;
 632
 633                 to = &end_time;
 634                 if (poll_select_set_timeout(to,
 635                                 tv.tv_sec + (tv.tv_usec / USEC_PER_SEC),
 636                                 (tv.tv_usec % USEC_PER_SEC) * NSEC_PER_USEC))
 637                         return -EINVAL;
 638         }
 639
 640         ret = core_sys_select(n, inp, outp, exp, to);
 641         ret = poll_select_copy_remaining(&end_time, tvp, 1, ret);
 642
 643         return ret;
 644 }
 645
 646 static long do_pselect(int n, fd_set __user *inp, fd_set __user *outp,
 647                        fd_set __user *exp, struct timespec __user *tsp,
 648                        const sigset_t __user *sigmask, size_t sigsetsize)
 649 {
 650         sigset_t ksigmask, sigsaved;
 651         struct timespec ts, end_time, *to = NULL;
 652         int ret;
 653
 654         if (tsp) {
 655                 if (copy_from_user(&ts, tsp, sizeof(ts)))
 656                         return -EFAULT;
 657
 658                 to = &end_time;
 659                 if (poll_select_set_timeout(to, ts.tv_sec, ts.tv_nsec))
 660                         return -EINVAL;
 661         }
 662
 663         if (sigmask) {
 664                 /* XXX: Don't preclude handling different sized sigset_t's.  */
 665                 if (sigsetsize != sizeof(sigset_t))
 666                         return -EINVAL;
 667                 if (copy_from_user(&ksigmask, sigmask, sizeof(ksigmask)))
 668                         return -EFAULT;
 669
 670                 sigdelsetmask(&ksigmask, sigmask(SIGKILL)|sigmask(SIGSTOP));
 671                 sigprocmask(SIG_SETMASK, &ksigmask, &sigsaved);
 672         }
 673
 674         ret = core_sys_select(n, inp, outp, exp, to);
 675         ret = poll_select_copy_remaining(&end_time, tsp, 0, ret);
 676
 677         if (ret == -ERESTARTNOHAND) {
 678                 /*
 679                  * Don't restore the signal mask yet. Let do_signal() deliver
 680                  * the signal on the way back to userspace, before the signal
 681                  * mask is restored.
 682                  */
 683                 if (sigmask) {
 684                         memcpy(&current->saved_sigmask, &sigsaved,
 685                                         sizeof(sigsaved));
 686                         set_restore_sigmask();
 687                 }
 688         } else if (sigmask)
 689                 sigprocmask(SIG_SETMASK, &sigsaved, NULL);
 690
 691         return ret;
 692 }
 693
 694 /*
 695  * Most architectures can't handle 7-argument syscalls. So we provide a
 696  * 6-argument version where the sixth argument is a pointer to a structure
 697  * which has a pointer to the sigset_t itself followed by a size_t containing
 698  * the sigset size.
 699  */
 700 SYSCALL_DEFINE6(pselect6, int, n, fd_set __user *, inp, fd_set __user *, outp,
 701                 fd_set __user *, exp, struct timespec __user *, tsp,
 702                 void __user *, sig)
 703 {
 704         size_t sigsetsize = 0;
 705         sigset_t __user *up = NULL;
 706
 707         if (sig) {
 708                 if (!access_ok(VERIFY_READ, sig, sizeof(void *)+sizeof(size_t))
 709                     || __get_user(up, (sigset_t __user * __user *)sig)
 710                     || __get_user(sigsetsize,
 711                                 (size_t __user *)(sig+sizeof(void *))))
 712                         return -EFAULT;
 713         }
 714
 715         return do_pselect(n, inp, outp, exp, tsp, up, sigsetsize);
 716 }
 717
 718 #ifdef __ARCH_WANT_SYS_OLD_SELECT
 719 struct sel_arg_struct {
 720         unsigned long n;
 721         fd_set __user *inp, *outp, *exp;
 722         struct timeval __user *tvp;
 723 };
 724
 725 SYSCALL_DEFINE1(old_select, struct sel_arg_struct __user *, arg)
 726 {
 727         struct sel_arg_struct a;
 728
 729         if (copy_from_user(&a, arg, sizeof(a)))
 730                 return -EFAULT;
 731         return sys_select(a.n, a.inp, a.outp, a.exp, a.tvp);
 732 }
 733 #endif
 734
 735 struct poll_list {
 736         struct poll_list *next;
 737         int len;
 738         struct pollfd entries[0];
 739 };
 740
 741 #define POLLFD_PER_PAGE  ((PAGE_SIZE-sizeof(struct poll_list)) / sizeof(struct pollfd))
 742
 743 /*
 744  * Fish for pollable events on the pollfd->fd file descriptor. We're only
 745  * interested in events matching the pollfd->events mask, and the result
 746  * matching that mask is both recorded in pollfd->revents and returned. The
 747  * pwait poll_table will be used by the fd-provided poll handler for waiting,
 748  * if pwait->_qproc is non-NULL.
 749  */
 750 static inline unsigned int do_pollfd(struct pollfd *pollfd, poll_table *pwait,
 751                                      bool *can_busy_poll,
 752                                      unsigned int busy_flag)
 753 {
 754         unsigned int mask;
 755         int fd;
 756
 757         mask = 0;
 758         fd = pollfd->fd;
 759         if (fd >= 0) {
 760                 struct fd f = fdget(fd);
 761                 mask = POLLNVAL;
 762                 if (f.file) {
 763                         mask = DEFAULT_POLLMASK;
 764                         if (f.file->f_op->poll) {
 765                                 pwait->_key = pollfd->events|POLLERR|POLLHUP;
 766                                 pwait->_key |= busy_flag;
 767                                 mask = f.file->f_op->poll(f.file, pwait);
 768                                 if (mask & busy_flag)
 769                                         *can_busy_poll = true;
 770                         }
 771                         /* Mask out unneeded events. */
 772                         mask &= pollfd->events | POLLERR | POLLHUP;
 773                         fdput(f);
 774                 }
 775         }
 776         pollfd->revents = mask;
 777
 778         return mask;
 779 }
 780
 781 static int do_poll(struct poll_list *list, struct poll_wqueues *wait,
 782                    struct timespec *end_time)
 783 {
 784         poll_table* pt = &wait->pt;
 785         ktime_t expire, *to = NULL;
 786         int timed_out = 0, count = 0;
 787         unsigned long slack = 0;
 788         unsigned int busy_flag = net_busy_loop_on() ? POLL_BUSY_LOOP : 0;
 789         unsigned long busy_end = 0;
 790
 791         /* Optimise the no-wait case */
 792         if (end_time && !end_time->tv_sec && !end_time->tv_nsec) {
 793                 pt->_qproc = NULL;
 794                 timed_out = 1;
 795         }
 796
 797         if (end_time && !timed_out)
 798                 slack = select_estimate_accuracy(end_time);
 799
 800         for (;;) {
 801                 struct poll_list *walk;
 802                 bool can_busy_loop = false;
 803
 804                 for (walk = list; walk != NULL; walk = walk->next) {
 805                         struct pollfd * pfd, * pfd_end;
 806
 807                         pfd = walk->entries;
 808                         pfd_end = pfd + walk->len;
 809                         for (; pfd != pfd_end; pfd++) {
 810                                 /*
 811                                  * Fish for events. If we found one, record it
 812                                  * and kill poll_table->_qproc, so we don't
 813                                  * needlessly register any other waiters after
 814                                  * this. They'll get immediately deregistered
 815                                  * when we break out and return.
 816                                  */
 817                                 if (do_pollfd(pfd, pt, &can_busy_loop,
 818                                               busy_flag)) {
 819                                         count++;
 820                                         pt->_qproc = NULL;
 821                                         /* found something, stop busy polling */
 822                                         busy_flag = 0;
 823                                         can_busy_loop = false;
 824                                 }
 825                         }
 826                 }
 827                 /*
 828                  * All waiters have already been registered, so don't provide
 829                  * a poll_table->_qproc to them on the next loop iteration.
 830                  */
 831                 pt->_qproc = NULL;
 832                 if (!count) {
 833                         count = wait->error;
 834                         if (signal_pending(current))
 835                                 count = -EINTR;
 836                 }
 837                 if (count || timed_out)
 838                         break;
 839
 840                 /* only if found POLL_BUSY_LOOP sockets && not out of time */
 841                 if (can_busy_loop && !need_resched()) {
 842                         if (!busy_end) {
 843                                 busy_end = busy_loop_end_time();
 844                                 continue;
 845                         }
 846                         if (!busy_loop_timeout(busy_end))
 847                                 continue;
 848                 }
 849                 busy_flag = 0;
 850
 851                 /*
 852                  * If this is the first loop and we have a timeout
 853                  * given, then we convert to ktime_t and set the to
 854                  * pointer to the expiry value.
 855                  */
 856                 if (end_time && !to) {
 857                         expire = timespec_to_ktime(*end_time);
 858                         to = &expire;
 859                 }
 860
 861                 if (!poll_schedule_timeout(wait, TASK_INTERRUPTIBLE, to, slack))
 862                         timed_out = 1;
 863         }
 864         return count;
 865 }
 866
 867 #define N_STACK_PPS ((sizeof(stack_pps) - sizeof(struct poll_list))  / \
 868                         sizeof(struct pollfd))
 869
 870 int do_sys_poll(struct pollfd __user *ufds, unsigned int nfds,
 871                 struct timespec *end_time)
 872 {
 873         struct poll_wqueues table;
 874         int err = -EFAULT, fdcount, len, size;
 875         /* Allocate small arguments on the stack to save memory and be
 876            faster - use long to make sure the buffer is aligned properly
 877            on 64 bit archs to avoid unaligned access */
 878         long stack_pps[POLL_STACK_ALLOC/sizeof(long)];
 879         struct poll_list *const head = (struct poll_list *)stack_pps;
 880         struct poll_list *walk = head;
 881         unsigned long todo = nfds;
 882
 883         if (nfds > rlimit(RLIMIT_NOFILE))
 884                 return -EINVAL;
 885
 886         len = min_t(unsigned int, nfds, N_STACK_PPS);
 887         for (;;) {
 888                 walk->next = NULL;
 889                 walk->len = len;
 890                 if (!len)
 891                         break;
 892
 893                 if (copy_from_user(walk->entries, ufds + nfds-todo,
 894                                         sizeof(struct pollfd) * walk->len))
 895                         goto out_fds;
 896
 897                 todo -= walk->len;
 898                 if (!todo)
 899                         break;
 900
 901                 len = min(todo, POLLFD_PER_PAGE);
 902                 size = sizeof(struct poll_list) + sizeof(struct pollfd) * len;
 903                 walk = walk->next = kmalloc(size, GFP_KERNEL);
 904                 if (!walk) {
 905                         err = -ENOMEM;
 906                         goto out_fds;
 907                 }
 908         }
 909
 910         poll_initwait(&table);
 911         fdcount = do_poll(head, &table, end_time);
 912         poll_freewait(&table);
 913
 914         for (walk = head; walk; walk = walk->next) {
 915                 struct pollfd *fds = walk->entries;
 916                 int j;
 917
 918                 for (j = 0; j < walk->len; j++, ufds++)
 919                         if (__put_user(fds[j].revents, &ufds->revents))
 920                                 goto out_fds;
 921         }
 922
 923         err = fdcount;
 924 out_fds:
 925         walk = head->next;
 926         while (walk) {
 927                 struct poll_list *pos = walk;
 928                 walk = walk->next;
 929                 kfree(pos);
 930         }
 931
 932         return err;
 933 }
 934
 935 static long do_restart_poll(struct restart_block *restart_block)
 936 {
 937         struct pollfd __user *ufds = restart_block->poll.ufds;
 938         int nfds = restart_block->poll.nfds;
 939         struct timespec *to = NULL, end_time;
 940         int ret;
 941
 942         if (restart_block->poll.has_timeout) {
 943                 end_time.tv_sec = restart_block->poll.tv_sec;
 944                 end_time.tv_nsec = restart_block->poll.tv_nsec;
 945                 to = &end_time;
 946         }
 947
 948         ret = do_sys_poll(ufds, nfds, to);
 949
 950         if (ret == -EINTR) {
 951                 restart_block->fn = do_restart_poll;
 952                 ret = -ERESTART_RESTARTBLOCK;
 953         }
 954         return ret;
 955 }
 956
 957 SYSCALL_DEFINE3(poll, struct pollfd __user *, ufds, unsigned int, nfds,
 958                 int, timeout_msecs)
 959 {
 960         struct timespec end_time, *to = NULL;
 961         int ret;
 962
 963         if (timeout_msecs >= 0) {
 964                 to = &end_time;
 965                 poll_select_set_timeout(to, timeout_msecs / MSEC_PER_SEC,
 966                         NSEC_PER_MSEC * (timeout_msecs % MSEC_PER_SEC));
 967         }
 968
 969         ret = do_sys_poll(ufds, nfds, to);
 970
 971         if (ret == -EINTR) {
 972                 struct restart_block *restart_block;
 973
 974                 restart_block = &current->restart_block;
 975                 restart_block->fn = do_restart_poll;
 976                 restart_block->poll.ufds = ufds;
 977                 restart_block->poll.nfds = nfds;
 978
 979                 if (timeout_msecs >= 0) {
 980                         restart_block->poll.tv_sec = end_time.tv_sec;
 981                         restart_block->poll.tv_nsec = end_time.tv_nsec;
 982                         restart_block->poll.has_timeout = 1;
 983                 } else
 984                         restart_block->poll.has_timeout = 0;
 985
 986                 ret = -ERESTART_RESTARTBLOCK;
 987         }
 988         return ret;
 989 }
 990
 991 SYSCALL_DEFINE5(ppoll, struct pollfd __user *, ufds, unsigned int, nfds,
 992                 struct timespec __user *, tsp, const sigset_t __user *, sigmask,
 993                 size_t, sigsetsize)
 994 {
 995         sigset_t ksigmask, sigsaved;
 996         struct timespec ts, end_time, *to = NULL;
 997         int ret;
 998
 999         if (tsp) {
1000                 if (copy_from_user(&ts, tsp, sizeof(ts)))
1001                         return -EFAULT;
1002
1003                 to = &end_time;
1004                 if (poll_select_set_timeout(to, ts.tv_sec, ts.tv_nsec))
1005                         return -EINVAL;
1006         }
1007
1008         if (sigmask) {
1009                 /* XXX: Don't preclude handling different sized sigset_t's.  */
1010                 if (sigsetsize != sizeof(sigset_t))
1011                         return -EINVAL;
1012                 if (copy_from_user(&ksigmask, sigmask, sizeof(ksigmask)))
1013                         return -EFAULT;
1014
1015                 sigdelsetmask(&ksigmask, sigmask(SIGKILL)|sigmask(SIGSTOP));
1016                 sigprocmask(SIG_SETMASK, &ksigmask, &sigsaved);
1017         }
1018
1019         ret = do_sys_poll(ufds, nfds, to);
1020
1021         /* We can restart this syscall, usually */
1022         if (ret == -EINTR) {
1023                 /*
1024                  * Don't restore the signal mask yet. Let do_signal() deliver
1025                  * the signal on the way back to userspace, before the signal
1026                  * mask is restored.
1027                  */
1028                 if (sigmask) {
1029                         memcpy(&current->saved_sigmask, &sigsaved,
1030                                         sizeof(sigsaved));
1031                         set_restore_sigmask();
1032                 }
1033                 ret = -ERESTARTNOHAND;
1034         } else if (sigmask)
1035                 sigprocmask(SIG_SETMASK, &sigsaved, NULL);
1036
1037         ret = poll_select_copy_remaining(&end_time, tsp, 0, ret);
1038
1039         return ret;
1040 }