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#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
  50static 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
  73long 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
  95struct 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 */
 116static void __pollwait(struct file *filp, wait_queue_head_t *wait_address,
 117                       poll_table *p);
 118
 119void 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}
 128EXPORT_SYMBOL(poll_initwait);
 129
 130static 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
 136void 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}
 156EXPORT_SYMBOL(poll_freewait);
 157
 158static 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
 182static 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 set_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
 208static 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 */
 219static 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
 234int 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 = freezable_schedule_hrtimeout_range(expires, slack,
 242                                                        HRTIMER_MODE_ABS);
 243        __set_current_state(TASK_RUNNING);
 244
 245        /*
 246         * Prepare for the next iteration.
 247         *
 248         * The following set_mb() serves two purposes.  First, it's
 249         * the counterpart rmb of the wmb in pollwake() such that data
 250         * written before wake up is always visible after wake up.
 251         * Second, the full barrier guarantees that triggered clearing
 252         * doesn't pass event check of the next iteration.  Note that
 253         * this problem doesn't exist for the first iteration as
 254         * add_wait_queue() has full barrier semantics.
 255         */
 256        set_mb(pwq->triggered, 0);
 257
 258        return rc;
 259}
 260EXPORT_SYMBOL(poll_schedule_timeout);
 261
 262/**
 263 * poll_select_set_timeout - helper function to setup the timeout value
 264 * @to:         pointer to timespec variable for the final timeout
 265 * @sec:        seconds (from user space)
 266 * @nsec:       nanoseconds (from user space)
 267 *
 268 * Note, we do not use a timespec for the user space value here, That
 269 * way we can use the function for timeval and compat interfaces as well.
 270 *
 271 * Returns -EINVAL if sec/nsec are not normalized. Otherwise 0.
 272 */
 273int poll_select_set_timeout(struct timespec *to, long sec, long nsec)
 274{
 275        struct timespec ts = {.tv_sec = sec, .tv_nsec = nsec};
 276
 277        if (!timespec_valid(&ts))
 278                return -EINVAL;
 279
 280        /* Optimize for the zero timeout value here */
 281        if (!sec && !nsec) {
 282                to->tv_sec = to->tv_nsec = 0;
 283        } else {
 284                ktime_get_ts(to);
 285                *to = timespec_add_safe(*to, ts);
 286        }
 287        return 0;
 288}
 289
 290static int poll_select_copy_remaining(struct timespec *end_time, void __user *p,
 291                                      int timeval, int ret)
 292{
 293        struct timespec rts;
 294        struct timeval rtv;
 295
 296        if (!p)
 297                return ret;
 298
 299        if (current->personality & STICKY_TIMEOUTS)
 300                goto sticky;
 301
 302        /* No update for zero timeout */
 303        if (!end_time->tv_sec && !end_time->tv_nsec)
 304                return ret;
 305
 306        ktime_get_ts(&rts);
 307        rts = timespec_sub(*end_time, rts);
 308        if (rts.tv_sec < 0)
 309                rts.tv_sec = rts.tv_nsec = 0;
 310
 311        if (timeval) {
 312                if (sizeof(rtv) > sizeof(rtv.tv_sec) + sizeof(rtv.tv_usec))
 313                        memset(&rtv, 0, sizeof(rtv));
 314                rtv.tv_sec = rts.tv_sec;
 315                rtv.tv_usec = rts.tv_nsec / NSEC_PER_USEC;
 316
 317                if (!copy_to_user(p, &rtv, sizeof(rtv)))
 318                        return ret;
 319
 320        } else if (!copy_to_user(p, &rts, sizeof(rts)))
 321                return ret;
 322
 323        /*
 324         * If an application puts its timeval in read-only memory, we
 325         * don't want the Linux-specific update to the timeval to
 326         * cause a fault after the select has completed
 327         * successfully. However, because we're not updating the
 328         * timeval, we can't restart the system call.
 329         */
 330
 331sticky:
 332        if (ret == -ERESTARTNOHAND)
 333                ret = -EINTR;
 334        return ret;
 335}
 336
 337#define FDS_IN(fds, n)          (fds->in + n)
 338#define FDS_OUT(fds, n)         (fds->out + n)
 339#define FDS_EX(fds, n)          (fds->ex + n)
 340
 341#define BITS(fds, n)    (*FDS_IN(fds, n)|*FDS_OUT(fds, n)|*FDS_EX(fds, n))
 342
 343static int max_select_fd(unsigned long n, fd_set_bits *fds)
 344{
 345        unsigned long *open_fds;
 346        unsigned long set;
 347        int max;
 348        struct fdtable *fdt;
 349
 350        /* handle last in-complete long-word first */
 351        set = ~(~0UL << (n & (BITS_PER_LONG-1)));
 352        n /= BITS_PER_LONG;
 353        fdt = files_fdtable(current->files);
 354        open_fds = fdt->open_fds + n;
 355        max = 0;
 356        if (set) {
 357                set &= BITS(fds, n);
 358                if (set) {
 359                        if (!(set & ~*open_fds))
 360                                goto get_max;
 361                        return -EBADF;
 362                }
 363        }
 364        while (n) {
 365                open_fds--;
 366                n--;
 367                set = BITS(fds, n);
 368                if (!set)
 369                        continue;
 370                if (set & ~*open_fds)
 371                        return -EBADF;
 372                if (max)
 373                        continue;
 374get_max:
 375                do {
 376                        max++;
 377                        set >>= 1;
 378                } while (set);
 379                max += n * BITS_PER_LONG;
 380        }
 381
 382        return max;
 383}
 384
 385#define POLLIN_SET (POLLRDNORM | POLLRDBAND | POLLIN | POLLHUP | POLLERR)
 386#define POLLOUT_SET (POLLWRBAND | POLLWRNORM | POLLOUT | POLLERR)
 387#define POLLEX_SET (POLLPRI)
 388
 389static inline void wait_key_set(poll_table *wait, unsigned long in,
 390                                unsigned long out, unsigned long bit,
 391                                unsigned int ll_flag)
 392{
 393        wait->_key = POLLEX_SET | ll_flag;
 394        if (in & bit)
 395                wait->_key |= POLLIN_SET;
 396        if (out & bit)
 397                wait->_key |= POLLOUT_SET;
 398}
 399
 400int do_select(int n, fd_set_bits *fds, struct timespec *end_time)
 401{
 402        ktime_t expire, *to = NULL;
 403        struct poll_wqueues table;
 404        poll_table *wait;
 405        int retval, i, timed_out = 0;
 406        unsigned long slack = 0;
 407        unsigned int busy_flag = net_busy_loop_on() ? POLL_BUSY_LOOP : 0;
 408        unsigned long busy_end = 0;
 409
 410        rcu_read_lock();
 411        retval = max_select_fd(n, fds);
 412        rcu_read_unlock();
 413
 414        if (retval < 0)
 415                return retval;
 416        n = retval;
 417
 418        poll_initwait(&table);
 419        wait = &table.pt;
 420        if (end_time && !end_time->tv_sec && !end_time->tv_nsec) {
 421                wait->_qproc = NULL;
 422                timed_out = 1;
 423        }
 424
 425        if (end_time && !timed_out)
 426                slack = select_estimate_accuracy(end_time);
 427
 428        retval = 0;
 429        for (;;) {
 430                unsigned long *rinp, *routp, *rexp, *inp, *outp, *exp;
 431                bool can_busy_loop = false;
 432
 433                inp = fds->in; outp = fds->out; exp = fds->ex;
 434                rinp = fds->res_in; routp = fds->res_out; rexp = fds->res_ex;
 435
 436                for (i = 0; i < n; ++rinp, ++routp, ++rexp) {
 437                        unsigned long in, out, ex, all_bits, bit = 1, mask, j;
 438                        unsigned long res_in = 0, res_out = 0, res_ex = 0;
 439
 440                        in = *inp++; out = *outp++; ex = *exp++;
 441                        all_bits = in | out | ex;
 442                        if (all_bits == 0) {
 443                                i += BITS_PER_LONG;
 444                                continue;
 445                        }
 446
 447                        for (j = 0; j < BITS_PER_LONG; ++j, ++i, bit <<= 1) {
 448                                struct fd f;
 449                                if (i >= n)
 450                                        break;
 451                                if (!(bit & all_bits))
 452                                        continue;
 453                                f = fdget(i);
 454                                if (f.file) {
 455                                        const struct file_operations *f_op;
 456                                        f_op = f.file->f_op;
 457                                        mask = DEFAULT_POLLMASK;
 458                                        if (f_op && f_op->poll) {
 459                                                wait_key_set(wait, in, out,
 460                                                             bit, busy_flag);
 461                                                mask = (*f_op->poll)(f.file, wait);
 462                                        }
 463                                        fdput(f);
 464                                        if ((mask & POLLIN_SET) && (in & bit)) {
 465                                                res_in |= bit;
 466                                                retval++;
 467                                                wait->_qproc = NULL;
 468                                        }
 469                                        if ((mask & POLLOUT_SET) && (out & bit)) {
 470                                                res_out |= bit;
 471                                                retval++;
 472                                                wait->_qproc = NULL;
 473                                        }
 474                                        if ((mask & POLLEX_SET) && (ex & bit)) {
 475                                                res_ex |= bit;
 476                                                retval++;
 477                                                wait->_qproc = NULL;
 478                                        }
 479                                        /* got something, stop busy polling */
 480                                        if (retval) {
 481                                                can_busy_loop = false;
 482                                                busy_flag = 0;
 483
 484                                        /*
 485                                         * only remember a returned
 486                                         * POLL_BUSY_LOOP if we asked for it
 487                                         */
 488                                        } else if (busy_flag & mask)
 489                                                can_busy_loop = true;
 490
 491                                }
 492                        }
 493                        if (res_in)
 494                                *rinp = res_in;
 495                        if (res_out)
 496                                *routp = res_out;
 497                        if (res_ex)
 498                                *rexp = res_ex;
 499                        cond_resched();
 500                }
 501                wait->_qproc = NULL;
 502                if (retval || timed_out || signal_pending(current))
 503                        break;
 504                if (table.error) {
 505                        retval = table.error;
 506                        break;
 507                }
 508
 509                /* only if found POLL_BUSY_LOOP sockets && not out of time */
 510                if (can_busy_loop && !need_resched()) {
 511                        if (!busy_end) {
 512                                busy_end = busy_loop_end_time();
 513                                continue;
 514                        }
 515                        if (!busy_loop_timeout(busy_end))
 516                                continue;
 517                }
 518                busy_flag = 0;
 519
 520                /*
 521                 * If this is the first loop and we have a timeout
 522                 * given, then we convert to ktime_t and set the to
 523                 * pointer to the expiry value.
 524                 */
 525                if (end_time && !to) {
 526                        expire = timespec_to_ktime(*end_time);
 527                        to = &expire;
 528                }
 529
 530                if (!poll_schedule_timeout(&table, TASK_INTERRUPTIBLE,
 531                                           to, slack))
 532                        timed_out = 1;
 533        }
 534
 535        poll_freewait(&table);
 536
 537        return retval;
 538}
 539
 540/*
 541 * We can actually return ERESTARTSYS instead of EINTR, but I'd
 542 * like to be certain this leads to no problems. So I return
 543 * EINTR just for safety.
 544 *
 545 * Update: ERESTARTSYS breaks at least the xview clock binary, so
 546 * I'm trying ERESTARTNOHAND which restart only when you want to.
 547 */
 548int core_sys_select(int n, fd_set __user *inp, fd_set __user *outp,
 549                           fd_set __user *exp, struct timespec *end_time)
 550{
 551        fd_set_bits fds;
 552        void *bits;
 553        int ret, max_fds;
 554        unsigned int size;
 555        struct fdtable *fdt;
 556        /* Allocate small arguments on the stack to save memory and be faster */
 557        long stack_fds[SELECT_STACK_ALLOC/sizeof(long)];
 558
 559        ret = -EINVAL;
 560        if (n < 0)
 561                goto out_nofds;
 562
 563        /* max_fds can increase, so grab it once to avoid race */
 564        rcu_read_lock();
 565        fdt = files_fdtable(current->files);
 566        max_fds = fdt->max_fds;
 567        rcu_read_unlock();
 568        if (n > max_fds)
 569                n = max_fds;
 570
 571        /*
 572         * We need 6 bitmaps (in/out/ex for both incoming and outgoing),
 573         * since we used fdset we need to allocate memory in units of
 574         * long-words. 
 575         */
 576        size = FDS_BYTES(n);
 577        bits = stack_fds;
 578        if (size > sizeof(stack_fds) / 6) {
 579                /* Not enough space in on-stack array; must use kmalloc */
 580                ret = -ENOMEM;
 581                bits = kmalloc(6 * size, GFP_KERNEL);
 582                if (!bits)
 583                        goto out_nofds;
 584        }
 585        fds.in      = bits;
 586        fds.out     = bits +   size;
 587        fds.ex      = bits + 2*size;
 588        fds.res_in  = bits + 3*size;
 589        fds.res_out = bits + 4*size;
 590        fds.res_ex  = bits + 5*size;
 591
 592        if ((ret = get_fd_set(n, inp, fds.in)) ||
 593            (ret = get_fd_set(n, outp, fds.out)) ||
 594            (ret = get_fd_set(n, exp, fds.ex)))
 595                goto out;
 596        zero_fd_set(n, fds.res_in);
 597        zero_fd_set(n, fds.res_out);
 598        zero_fd_set(n, fds.res_ex);
 599
 600        ret = do_select(n, &fds, end_time);
 601
 602        if (ret < 0)
 603                goto out;
 604        if (!ret) {
 605                ret = -ERESTARTNOHAND;
 606                if (signal_pending(current))
 607                        goto out;
 608                ret = 0;
 609        }
 610
 611        if (set_fd_set(n, inp, fds.res_in) ||
 612            set_fd_set(n, outp, fds.res_out) ||
 613            set_fd_set(n, exp, fds.res_ex))
 614                ret = -EFAULT;
 615
 616out:
 617        if (bits != stack_fds)
 618                kfree(bits);
 619out_nofds:
 620        return ret;
 621}
 622
 623SYSCALL_DEFINE5(select, int, n, fd_set __user *, inp, fd_set __user *, outp,
 624                fd_set __user *, exp, struct timeval __user *, tvp)
 625{
 626        struct timespec end_time, *to = NULL;
 627        struct timeval tv;
 628        int ret;
 629
 630        if (tvp) {
 631                if (copy_from_user(&tv, tvp, sizeof(tv)))
 632                        return -EFAULT;
 633
 634                to = &end_time;
 635                if (poll_select_set_timeout(to,
 636                                tv.tv_sec + (tv.tv_usec / USEC_PER_SEC),
 637                                (tv.tv_usec % USEC_PER_SEC) * NSEC_PER_USEC))
 638                        return -EINVAL;
 639        }
 640
 641        ret = core_sys_select(n, inp, outp, exp, to);
 642        ret = poll_select_copy_remaining(&end_time, tvp, 1, ret);
 643
 644        return ret;
 645}
 646
 647static long do_pselect(int n, fd_set __user *inp, fd_set __user *outp,
 648                       fd_set __user *exp, struct timespec __user *tsp,
 649                       const sigset_t __user *sigmask, size_t sigsetsize)
 650{
 651        sigset_t ksigmask, sigsaved;
 652        struct timespec ts, end_time, *to = NULL;
 653        int ret;
 654
 655        if (tsp) {
 656                if (copy_from_user(&ts, tsp, sizeof(ts)))
 657                        return -EFAULT;
 658
 659                to = &end_time;
 660                if (poll_select_set_timeout(to, ts.tv_sec, ts.tv_nsec))
 661                        return -EINVAL;
 662        }
 663
 664        if (sigmask) {
 665                /* XXX: Don't preclude handling different sized sigset_t's.  */
 666                if (sigsetsize != sizeof(sigset_t))
 667                        return -EINVAL;
 668                if (copy_from_user(&ksigmask, sigmask, sizeof(ksigmask)))
 669                        return -EFAULT;
 670
 671                sigdelsetmask(&ksigmask, sigmask(SIGKILL)|sigmask(SIGSTOP));
 672                sigprocmask(SIG_SETMASK, &ksigmask, &sigsaved);
 673        }
 674
 675        ret = core_sys_select(n, inp, outp, exp, to);
 676        ret = poll_select_copy_remaining(&end_time, tsp, 0, ret);
 677
 678        if (ret == -ERESTARTNOHAND) {
 679                /*
 680                 * Don't restore the signal mask yet. Let do_signal() deliver
 681                 * the signal on the way back to userspace, before the signal
 682                 * mask is restored.
 683                 */
 684                if (sigmask) {
 685                        memcpy(&current->saved_sigmask, &sigsaved,
 686                                        sizeof(sigsaved));
 687                        set_restore_sigmask();
 688                }
 689        } else if (sigmask)
 690                sigprocmask(SIG_SETMASK, &sigsaved, NULL);
 691
 692        return ret;
 693}
 694
 695/*
 696 * Most architectures can't handle 7-argument syscalls. So we provide a
 697 * 6-argument version where the sixth argument is a pointer to a structure
 698 * which has a pointer to the sigset_t itself followed by a size_t containing
 699 * the sigset size.
 700 */
 701SYSCALL_DEFINE6(pselect6, int, n, fd_set __user *, inp, fd_set __user *, outp,
 702                fd_set __user *, exp, struct timespec __user *, tsp,
 703                void __user *, sig)
 704{
 705        size_t sigsetsize = 0;
 706        sigset_t __user *up = NULL;
 707
 708        if (sig) {
 709                if (!access_ok(VERIFY_READ, sig, sizeof(void *)+sizeof(size_t))
 710                    || __get_user(up, (sigset_t __user * __user *)sig)
 711                    || __get_user(sigsetsize,
 712                                (size_t __user *)(sig+sizeof(void *))))
 713                        return -EFAULT;
 714        }
 715
 716        return do_pselect(n, inp, outp, exp, tsp, up, sigsetsize);
 717}
 718
 719#ifdef __ARCH_WANT_SYS_OLD_SELECT
 720struct sel_arg_struct {
 721        unsigned long n;
 722        fd_set __user *inp, *outp, *exp;
 723        struct timeval __user *tvp;
 724};
 725
 726SYSCALL_DEFINE1(old_select, struct sel_arg_struct __user *, arg)
 727{
 728        struct sel_arg_struct a;
 729
 730        if (copy_from_user(&a, arg, sizeof(a)))
 731                return -EFAULT;
 732        return sys_select(a.n, a.inp, a.outp, a.exp, a.tvp);
 733}
 734#endif
 735
 736struct poll_list {
 737        struct poll_list *next;
 738        int len;
 739        struct pollfd entries[0];
 740};
 741
 742#define POLLFD_PER_PAGE  ((PAGE_SIZE-sizeof(struct poll_list)) / sizeof(struct pollfd))
 743
 744/*
 745 * Fish for pollable events on the pollfd->fd file descriptor. We're only
 746 * interested in events matching the pollfd->events mask, and the result
 747 * matching that mask is both recorded in pollfd->revents and returned. The
 748 * pwait poll_table will be used by the fd-provided poll handler for waiting,
 749 * if pwait->_qproc is non-NULL.
 750 */
 751static inline unsigned int do_pollfd(struct pollfd *pollfd, poll_table *pwait,
 752                                     bool *can_busy_poll,
 753                                     unsigned int busy_flag)
 754{
 755        unsigned int mask;
 756        int fd;
 757
 758        mask = 0;
 759        fd = pollfd->fd;
 760        if (fd >= 0) {
 761                struct fd f = fdget(fd);
 762                mask = POLLNVAL;
 763                if (f.file) {
 764                        mask = DEFAULT_POLLMASK;
 765                        if (f.file->f_op && f.file->f_op->poll) {
 766                                pwait->_key = pollfd->events|POLLERR|POLLHUP;
 767                                pwait->_key |= busy_flag;
 768                                mask = f.file->f_op->poll(f.file, pwait);
 769                                if (mask & busy_flag)
 770                                        *can_busy_poll = true;
 771                        }
 772                        /* Mask out unneeded events. */
 773                        mask &= pollfd->events | POLLERR | POLLHUP;
 774                        fdput(f);
 775                }
 776        }
 777        pollfd->revents = mask;
 778
 779        return mask;
 780}
 781
 782static int do_poll(unsigned int nfds,  struct poll_list *list,
 783                   struct poll_wqueues *wait, struct timespec *end_time)
 784{
 785        poll_table* pt = &wait->pt;
 786        ktime_t expire, *to = NULL;
 787        int timed_out = 0, count = 0;
 788        unsigned long slack = 0;
 789        unsigned int busy_flag = net_busy_loop_on() ? POLL_BUSY_LOOP : 0;
 790        unsigned long busy_end = 0;
 791
 792        /* Optimise the no-wait case */
 793        if (end_time && !end_time->tv_sec && !end_time->tv_nsec) {
 794                pt->_qproc = NULL;
 795                timed_out = 1;
 796        }
 797
 798        if (end_time && !timed_out)
 799                slack = select_estimate_accuracy(end_time);
 800
 801        for (;;) {
 802                struct poll_list *walk;
 803                bool can_busy_loop = false;
 804
 805                for (walk = list; walk != NULL; walk = walk->next) {
 806                        struct pollfd * pfd, * pfd_end;
 807
 808                        pfd = walk->entries;
 809                        pfd_end = pfd + walk->len;
 810                        for (; pfd != pfd_end; pfd++) {
 811                                /*
 812                                 * Fish for events. If we found one, record it
 813                                 * and kill poll_table->_qproc, so we don't
 814                                 * needlessly register any other waiters after
 815                                 * this. They'll get immediately deregistered
 816                                 * when we break out and return.
 817                                 */
 818                                if (do_pollfd(pfd, pt, &can_busy_loop,
 819                                              busy_flag)) {
 820                                        count++;
 821                                        pt->_qproc = NULL;
 822                                        /* found something, stop busy polling */
 823                                        busy_flag = 0;
 824                                        can_busy_loop = false;
 825                                }
 826                        }
 827                }
 828                /*
 829                 * All waiters have already been registered, so don't provide
 830                 * a poll_table->_qproc to them on the next loop iteration.
 831                 */
 832                pt->_qproc = NULL;
 833                if (!count) {
 834                        count = wait->error;
 835                        if (signal_pending(current))
 836                                count = -EINTR;
 837                }
 838                if (count || timed_out)
 839                        break;
 840
 841                /* only if found POLL_BUSY_LOOP sockets && not out of time */
 842                if (can_busy_loop && !need_resched()) {
 843                        if (!busy_end) {
 844                                busy_end = busy_loop_end_time();
 845                                continue;
 846                        }
 847                        if (!busy_loop_timeout(busy_end))
 848                                continue;
 849                }
 850                busy_flag = 0;
 851
 852                /*
 853                 * If this is the first loop and we have a timeout
 854                 * given, then we convert to ktime_t and set the to
 855                 * pointer to the expiry value.
 856                 */
 857                if (end_time && !to) {
 858                        expire = timespec_to_ktime(*end_time);
 859                        to = &expire;
 860                }
 861
 862                if (!poll_schedule_timeout(wait, TASK_INTERRUPTIBLE, to, slack))
 863                        timed_out = 1;
 864        }
 865        return count;
 866}
 867
 868#define N_STACK_PPS ((sizeof(stack_pps) - sizeof(struct poll_list))  / \
 869                        sizeof(struct pollfd))
 870
 871int do_sys_poll(struct pollfd __user *ufds, unsigned int nfds,
 872                struct timespec *end_time)
 873{
 874        struct poll_wqueues table;
 875        int err = -EFAULT, fdcount, len, size;
 876        /* Allocate small arguments on the stack to save memory and be
 877           faster - use long to make sure the buffer is aligned properly
 878           on 64 bit archs to avoid unaligned access */
 879        long stack_pps[POLL_STACK_ALLOC/sizeof(long)];
 880        struct poll_list *const head = (struct poll_list *)stack_pps;
 881        struct poll_list *walk = head;
 882        unsigned long todo = nfds;
 883
 884        if (nfds > rlimit(RLIMIT_NOFILE))
 885                return -EINVAL;
 886
 887        len = min_t(unsigned int, nfds, N_STACK_PPS);
 888        for (;;) {
 889                walk->next = NULL;
 890                walk->len = len;
 891                if (!len)
 892                        break;
 893
 894                if (copy_from_user(walk->entries, ufds + nfds-todo,
 895                                        sizeof(struct pollfd) * walk->len))
 896                        goto out_fds;
 897
 898                todo -= walk->len;
 899                if (!todo)
 900                        break;
 901
 902                len = min(todo, POLLFD_PER_PAGE);
 903                size = sizeof(struct poll_list) + sizeof(struct pollfd) * len;
 904                walk = walk->next = kmalloc(size, GFP_KERNEL);
 905                if (!walk) {
 906                        err = -ENOMEM;
 907                        goto out_fds;
 908                }
 909        }
 910
 911        poll_initwait(&table);
 912        fdcount = do_poll(nfds, head, &table, end_time);
 913        poll_freewait(&table);
 914
 915        for (walk = head; walk; walk = walk->next) {
 916                struct pollfd *fds = walk->entries;
 917                int j;
 918
 919                for (j = 0; j < walk->len; j++, ufds++)
 920                        if (__put_user(fds[j].revents, &ufds->revents))
 921                                goto out_fds;
 922        }
 923
 924        err = fdcount;
 925out_fds:
 926        walk = head->next;
 927        while (walk) {
 928                struct poll_list *pos = walk;
 929                walk = walk->next;
 930                kfree(pos);
 931        }
 932
 933        return err;
 934}
 935
 936static long do_restart_poll(struct restart_block *restart_block)
 937{
 938        struct pollfd __user *ufds = restart_block->poll.ufds;
 939        int nfds = restart_block->poll.nfds;
 940        struct timespec *to = NULL, end_time;
 941        int ret;
 942
 943        if (restart_block->poll.has_timeout) {
 944                end_time.tv_sec = restart_block->poll.tv_sec;
 945                end_time.tv_nsec = restart_block->poll.tv_nsec;
 946                to = &end_time;
 947        }
 948
 949        ret = do_sys_poll(ufds, nfds, to);
 950
 951        if (ret == -EINTR) {
 952                restart_block->fn = do_restart_poll;
 953                ret = -ERESTART_RESTARTBLOCK;
 954        }
 955        return ret;
 956}
 957
 958SYSCALL_DEFINE3(poll, struct pollfd __user *, ufds, unsigned int, nfds,
 959                int, timeout_msecs)
 960{
 961        struct timespec end_time, *to = NULL;
 962        int ret;
 963
 964        if (timeout_msecs >= 0) {
 965                to = &end_time;
 966                poll_select_set_timeout(to, timeout_msecs / MSEC_PER_SEC,
 967                        NSEC_PER_MSEC * (timeout_msecs % MSEC_PER_SEC));
 968        }
 969
 970        ret = do_sys_poll(ufds, nfds, to);
 971
 972        if (ret == -EINTR) {
 973                struct restart_block *restart_block;
 974
 975                restart_block = &current_thread_info()->restart_block;
 976                restart_block->fn = do_restart_poll;
 977                restart_block->poll.ufds = ufds;
 978                restart_block->poll.nfds = nfds;
 979
 980                if (timeout_msecs >= 0) {
 981                        restart_block->poll.tv_sec = end_time.tv_sec;
 982                        restart_block->poll.tv_nsec = end_time.tv_nsec;
 983                        restart_block->poll.has_timeout = 1;
 984                } else
 985                        restart_block->poll.has_timeout = 0;
 986
 987                ret = -ERESTART_RESTARTBLOCK;
 988        }
 989        return ret;
 990}
 991
 992SYSCALL_DEFINE5(ppoll, struct pollfd __user *, ufds, unsigned int, nfds,
 993                struct timespec __user *, tsp, const sigset_t __user *, sigmask,
 994                size_t, sigsetsize)
 995{
 996        sigset_t ksigmask, sigsaved;
 997        struct timespec ts, end_time, *to = NULL;
 998        int ret;
 999
1000        if (tsp) {
1001                if (copy_from_user(&ts, tsp, sizeof(ts)))
1002                        return -EFAULT;
1003
1004                to = &end_time;
1005                if (poll_select_set_timeout(to, ts.tv_sec, ts.tv_nsec))
1006                        return -EINVAL;
1007        }
1008
1009        if (sigmask) {
1010                /* XXX: Don't preclude handling different sized sigset_t's.  */
1011                if (sigsetsize != sizeof(sigset_t))
1012                        return -EINVAL;
1013                if (copy_from_user(&ksigmask, sigmask, sizeof(ksigmask)))
1014                        return -EFAULT;
1015
1016                sigdelsetmask(&ksigmask, sigmask(SIGKILL)|sigmask(SIGSTOP));
1017                sigprocmask(SIG_SETMASK, &ksigmask, &sigsaved);
1018        }
1019
1020        ret = do_sys_poll(ufds, nfds, to);
1021
1022        /* We can restart this syscall, usually */
1023        if (ret == -EINTR) {
1024                /*
1025                 * Don't restore the signal mask yet. Let do_signal() deliver
1026                 * the signal on the way back to userspace, before the signal
1027                 * mask is restored.
1028                 */
1029                if (sigmask) {
1030                        memcpy(&current->saved_sigmask, &sigsaved,
1031                                        sizeof(sigsaved));
1032                        set_restore_sigmask();
1033                }
1034                ret = -ERESTARTNOHAND;
1035        } else if (sigmask)
1036                sigprocmask(SIG_SETMASK, &sigsaved, NULL);
1037
1038        ret = poll_select_copy_remaining(&end_time, tsp, 0, ret);
1039
1040        return ret;
1041}
1042
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