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