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