linux/fs/select.c
<<
>>
Prefs
   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 = schedule_hrtimeout_range(expires, slack, HRTIMER_MODE_ABS);
 242        __set_current_state(TASK_RUNNING);
 243
 244        /*
 245         * Prepare for the next iteration.
 246         *
 247         * The following set_mb() serves two purposes.  First, it's
 248         * the counterpart rmb of the wmb in pollwake() such that data
 249         * written before wake up is always visible after wake up.
 250         * Second, the full barrier guarantees that triggered clearing
 251         * doesn't pass event check of the next iteration.  Note that
 252         * this problem doesn't exist for the first iteration as
 253         * add_wait_queue() has full barrier semantics.
 254         */
 255        set_mb(pwq->triggered, 0);
 256
 257        return rc;
 258}
 259EXPORT_SYMBOL(poll_schedule_timeout);
 260
 261/**
 262 * poll_select_set_timeout - helper function to setup the timeout value
 263 * @to:         pointer to timespec variable for the final timeout
 264 * @sec:        seconds (from user space)
 265 * @nsec:       nanoseconds (from user space)
 266 *
 267 * Note, we do not use a timespec for the user space value here, That
 268 * way we can use the function for timeval and compat interfaces as well.
 269 *
 270 * Returns -EINVAL if sec/nsec are not normalized. Otherwise 0.
 271 */
 272int poll_select_set_timeout(struct timespec *to, long sec, long nsec)
 273{
 274        struct timespec ts = {.tv_sec = sec, .tv_nsec = nsec};
 275
 276        if (!timespec_valid(&ts))
 277                return -EINVAL;
 278
 279        /* Optimize for the zero timeout value here */
 280        if (!sec && !nsec) {
 281                to->tv_sec = to->tv_nsec = 0;
 282        } else {
 283                ktime_get_ts(to);
 284                *to = timespec_add_safe(*to, ts);
 285        }
 286        return 0;
 287}
 288
 289static int poll_select_copy_remaining(struct timespec *end_time, void __user *p,
 290                                      int timeval, int ret)
 291{
 292        struct timespec rts;
 293        struct timeval rtv;
 294
 295        if (!p)
 296                return ret;
 297
 298        if (current->personality & STICKY_TIMEOUTS)
 299                goto sticky;
 300
 301        /* No update for zero timeout */
 302        if (!end_time->tv_sec && !end_time->tv_nsec)
 303                return ret;
 304
 305        ktime_get_ts(&rts);
 306        rts = timespec_sub(*end_time, rts);
 307        if (rts.tv_sec < 0)
 308                rts.tv_sec = rts.tv_nsec = 0;
 309
 310        if (timeval) {
 311                if (sizeof(rtv) > sizeof(rtv.tv_sec) + sizeof(rtv.tv_usec))
 312                        memset(&rtv, 0, sizeof(rtv));
 313                rtv.tv_sec = rts.tv_sec;
 314                rtv.tv_usec = rts.tv_nsec / NSEC_PER_USEC;
 315
 316                if (!copy_to_user(p, &rtv, sizeof(rtv)))
 317                        return ret;
 318
 319        } else if (!copy_to_user(p, &rts, sizeof(rts)))
 320                return ret;
 321
 322        /*
 323         * If an application puts its timeval in read-only memory, we
 324         * don't want the Linux-specific update to the timeval to
 325         * cause a fault after the select has completed
 326         * successfully. However, because we're not updating the
 327         * timeval, we can't restart the system call.
 328         */
 329
 330sticky:
 331        if (ret == -ERESTARTNOHAND)
 332                ret = -EINTR;
 333        return ret;
 334}
 335
 336#define FDS_IN(fds, n)          (fds->in + n)
 337#define FDS_OUT(fds, n)         (fds->out + n)
 338#define FDS_EX(fds, n)          (fds->ex + n)
 339
 340#define BITS(fds, n)    (*FDS_IN(fds, n)|*FDS_OUT(fds, n)|*FDS_EX(fds, n))
 341
 342static int max_select_fd(unsigned long n, fd_set_bits *fds)
 343{
 344        unsigned long *open_fds;
 345        unsigned long set;
 346        int max;
 347        struct fdtable *fdt;
 348
 349        /* handle last in-complete long-word first */
 350        set = ~(~0UL << (n & (BITS_PER_LONG-1)));
 351        n /= BITS_PER_LONG;
 352        fdt = files_fdtable(current->files);
 353        open_fds = fdt->open_fds + n;
 354        max = 0;
 355        if (set) {
 356                set &= BITS(fds, n);
 357                if (set) {
 358                        if (!(set & ~*open_fds))
 359                                goto get_max;
 360                        return -EBADF;
 361                }
 362        }
 363        while (n) {
 364                open_fds--;
 365                n--;
 366                set = BITS(fds, n);
 367                if (!set)
 368                        continue;
 369                if (set & ~*open_fds)
 370                        return -EBADF;
 371                if (max)
 372                        continue;
 373get_max:
 374                do {
 375                        max++;
 376                        set >>= 1;
 377                } while (set);
 378                max += n * BITS_PER_LONG;
 379        }
 380
 381        return max;
 382}
 383
 384#define POLLIN_SET (POLLRDNORM | POLLRDBAND | POLLIN | POLLHUP | POLLERR)
 385#define POLLOUT_SET (POLLWRBAND | POLLWRNORM | POLLOUT | POLLERR)
 386#define POLLEX_SET (POLLPRI)
 387
 388static inline void wait_key_set(poll_table *wait, unsigned long in,
 389                                unsigned long out, unsigned long bit,
 390                                unsigned int ll_flag)
 391{
 392        wait->_key = POLLEX_SET | ll_flag;
 393        if (in & bit)
 394                wait->_key |= POLLIN_SET;
 395        if (out & bit)
 396                wait->_key |= POLLOUT_SET;
 397}
 398
 399int do_select(int n, fd_set_bits *fds, struct timespec *end_time)
 400{
 401        ktime_t expire, *to = NULL;
 402        struct poll_wqueues table;
 403        poll_table *wait;
 404        int retval, i, timed_out = 0;
 405        unsigned long slack = 0;
 406        unsigned int busy_flag = net_busy_loop_on() ? POLL_BUSY_LOOP : 0;
 407        unsigned long busy_end = 0;
 408
 409        rcu_read_lock();
 410        retval = max_select_fd(n, fds);
 411        rcu_read_unlock();
 412
 413        if (retval < 0)
 414                return retval;
 415        n = retval;
 416
 417        poll_initwait(&table);
 418        wait = &table.pt;
 419        if (end_time && !end_time->tv_sec && !end_time->tv_nsec) {
 420                wait->_qproc = NULL;
 421                timed_out = 1;
 422        }
 423
 424        if (end_time && !timed_out)
 425                slack = select_estimate_accuracy(end_time);
 426
 427        retval = 0;
 428        for (;;) {
 429                unsigned long *rinp, *routp, *rexp, *inp, *outp, *exp;
 430                bool can_busy_loop = false;
 431
 432                inp = fds->in; outp = fds->out; exp = fds->ex;
 433                rinp = fds->res_in; routp = fds->res_out; rexp = fds->res_ex;
 434
 435                for (i = 0; i < n; ++rinp, ++routp, ++rexp) {
 436                        unsigned long in, out, ex, all_bits, bit = 1, mask, j;
 437                        unsigned long res_in = 0, res_out = 0, res_ex = 0;
 438
 439                        in = *inp++; out = *outp++; ex = *exp++;
 440                        all_bits = in | out | ex;
 441                        if (all_bits == 0) {
 442                                i += BITS_PER_LONG;
 443                                continue;
 444                        }
 445
 446                        for (j = 0; j < BITS_PER_LONG; ++j, ++i, bit <<= 1) {
 447                                struct fd f;
 448                                if (i >= n)
 449                                        break;
 450                                if (!(bit & all_bits))
 451                                        continue;
 452                                f = fdget(i);
 453                                if (f.file) {
 454                                        const struct file_operations *f_op;
 455                                        f_op = f.file->f_op;
 456                                        mask = DEFAULT_POLLMASK;
 457                                        if (f_op && f_op->poll) {
 458                                                wait_key_set(wait, in, out,
 459                                                             bit, busy_flag);
 460                                                mask = (*f_op->poll)(f.file, wait);
 461                                        }
 462                                        fdput(f);
 463                                        if ((mask & POLLIN_SET) && (in & bit)) {
 464                                                res_in |= bit;
 465                                                retval++;
 466                                                wait->_qproc = NULL;
 467                                        }
 468                                        if ((mask & POLLOUT_SET) && (out & bit)) {
 469                                                res_out |= bit;
 470                                                retval++;
 471                                                wait->_qproc = NULL;
 472                                        }
 473                                        if ((mask & POLLEX_SET) && (ex & bit)) {
 474                                                res_ex |= bit;
 475                                                retval++;
 476                                                wait->_qproc = NULL;
 477                                        }
 478                                        /* got something, stop busy polling */
 479                                        if (retval) {
 480                                                can_busy_loop = false;
 481                                                busy_flag = 0;
 482
 483                                        /*
 484                                         * only remember a returned
 485                                         * POLL_BUSY_LOOP if we asked for it
 486                                         */
 487                                        } else if (busy_flag & mask)
 488                                                can_busy_loop = true;
 489
 490                                }
 491                        }
 492                        if (res_in)
 493                                *rinp = res_in;
 494                        if (res_out)
 495                                *routp = res_out;
 496                        if (res_ex)
 497                                *rexp = res_ex;
 498                        cond_resched();
 499                }
 500                wait->_qproc = NULL;
 501                if (retval || timed_out || signal_pending(current))
 502                        break;
 503                if (table.error) {
 504                        retval = table.error;
 505                        break;
 506                }
 507
 508                /* only if found POLL_BUSY_LOOP sockets && not out of time */
 509                if (can_busy_loop && !need_resched()) {
 510                        if (!busy_end) {
 511                                busy_end = busy_loop_end_time();
 512                                continue;
 513                        }
 514                        if (!busy_loop_timeout(busy_end))
 515                                continue;
 516                }
 517                busy_flag = 0;
 518
 519                /*
 520                 * If this is the first loop and we have a timeout
 521                 * given, then we convert to ktime_t and set the to
 522                 * pointer to the expiry value.
 523                 */
 524                if (end_time && !to) {
 525                        expire = timespec_to_ktime(*end_time);
 526                        to = &expire;
 527                }
 528
 529                if (!poll_schedule_timeout(&table, TASK_INTERRUPTIBLE,
 530                                           to, slack))
 531                        timed_out = 1;
 532        }
 533
 534        poll_freewait(&table);
 535
 536        return retval;
 537}
 538
 539/*
 540 * We can actually return ERESTARTSYS instead of EINTR, but I'd
 541 * like to be certain this leads to no problems. So I return
 542 * EINTR just for safety.
 543 *
 544 * Update: ERESTARTSYS breaks at least the xview clock binary, so
 545 * I'm trying ERESTARTNOHAND which restart only when you want to.
 546 */
 547int core_sys_select(int n, fd_set __user *inp, fd_set __user *outp,
 548                           fd_set __user *exp, struct timespec *end_time)
 549{
 550        fd_set_bits fds;
 551        void *bits;
 552        int ret, max_fds;
 553        unsigned int size;
 554        struct fdtable *fdt;
 555        /* Allocate small arguments on the stack to save memory and be faster */
 556        long stack_fds[SELECT_STACK_ALLOC/sizeof(long)];
 557
 558        ret = -EINVAL;
 559        if (n < 0)
 560                goto out_nofds;
 561
 562        /* max_fds can increase, so grab it once to avoid race */
 563        rcu_read_lock();
 564        fdt = files_fdtable(current->files);
 565        max_fds = fdt->max_fds;
 566        rcu_read_unlock();
 567        if (n > max_fds)
 568                n = max_fds;
 569
 570        /*
 571         * We need 6 bitmaps (in/out/ex for both incoming and outgoing),
 572         * since we used fdset we need to allocate memory in units of
 573         * long-words. 
 574         */
 575        size = FDS_BYTES(n);
 576        bits = stack_fds;
 577        if (size > sizeof(stack_fds) / 6) {
 578                /* Not enough space in on-stack array; must use kmalloc */
 579                ret = -ENOMEM;
 580                bits = kmalloc(6 * size, GFP_KERNEL);
 581                if (!bits)
 582                        goto out_nofds;
 583        }
 584        fds.in      = bits;
 585        fds.out     = bits +   size;
 586        fds.ex      = bits + 2*size;
 587        fds.res_in  = bits + 3*size;
 588        fds.res_out = bits + 4*size;
 589        fds.res_ex  = bits + 5*size;
 590
 591        if ((ret = get_fd_set(n, inp, fds.in)) ||
 592            (ret = get_fd_set(n, outp, fds.out)) ||
 593            (ret = get_fd_set(n, exp, fds.ex)))
 594                goto out;
 595        zero_fd_set(n, fds.res_in);
 596        zero_fd_set(n, fds.res_out);
 597        zero_fd_set(n, fds.res_ex);
 598
 599        ret = do_select(n, &fds, end_time);
 600
 601        if (ret < 0)
 602                goto out;
 603        if (!ret) {
 604                ret = -ERESTARTNOHAND;
 605                if (signal_pending(current))
 606                        goto out;
 607                ret = 0;
 608        }
 609
 610        if (set_fd_set(n, inp, fds.res_in) ||
 611            set_fd_set(n, outp, fds.res_out) ||
 612            set_fd_set(n, exp, fds.res_ex))
 613                ret = -EFAULT;
 614
 615out:
 616        if (bits != stack_fds)
 617                kfree(bits);
 618out_nofds:
 619        return ret;
 620}
 621
 622SYSCALL_DEFINE5(select, int, n, fd_set __user *, inp, fd_set __user *, outp,
 623                fd_set __user *, exp, struct timeval __user *, tvp)
 624{
 625        struct timespec end_time, *to = NULL;
 626        struct timeval tv;
 627        int ret;
 628
 629        if (tvp) {
 630                if (copy_from_user(&tv, tvp, sizeof(tv)))
 631                        return -EFAULT;
 632
 633                to = &end_time;
 634                if (poll_select_set_timeout(to,
 635                                tv.tv_sec + (tv.tv_usec / USEC_PER_SEC),
 636                                (tv.tv_usec % USEC_PER_SEC) * NSEC_PER_USEC))
 637                        return -EINVAL;
 638        }
 639
 640        ret = core_sys_select(n, inp, outp, exp, to);
 641        ret = poll_select_copy_remaining(&end_time, tvp, 1, ret);
 642
 643        return ret;
 644}
 645
 646static long do_pselect(int n, fd_set __user *inp, fd_set __user *outp,
 647                       fd_set __user *exp, struct timespec __user *tsp,
 648                       const sigset_t __user *sigmask, size_t sigsetsize)
 649{
 650        sigset_t ksigmask, sigsaved;
 651        struct timespec ts, end_time, *to = NULL;
 652        int ret;
 653
 654        if (tsp) {
 655                if (copy_from_user(&ts, tsp, sizeof(ts)))
 656                        return -EFAULT;
 657
 658                to = &end_time;
 659                if (poll_select_set_timeout(to, ts.tv_sec, ts.tv_nsec))
 660                        return -EINVAL;
 661        }
 662
 663        if (sigmask) {
 664                /* XXX: Don't preclude handling different sized sigset_t's.  */
 665                if (sigsetsize != sizeof(sigset_t))
 666                        return -EINVAL;
 667                if (copy_from_user(&ksigmask, sigmask, sizeof(ksigmask)))
 668                        return -EFAULT;
 669
 670                sigdelsetmask(&ksigmask, sigmask(SIGKILL)|sigmask(SIGSTOP));
 671                sigprocmask(SIG_SETMASK, &ksigmask, &sigsaved);
 672        }
 673
 674        ret = core_sys_select(n, inp, outp, exp, to);
 675        ret = poll_select_copy_remaining(&end_time, tsp, 0, ret);
 676
 677        if (ret == -ERESTARTNOHAND) {
 678                /*
 679                 * Don't restore the signal mask yet. Let do_signal() deliver
 680                 * the signal on the way back to userspace, before the signal
 681                 * mask is restored.
 682                 */
 683                if (sigmask) {
 684                        memcpy(&current->saved_sigmask, &sigsaved,
 685                                        sizeof(sigsaved));
 686                        set_restore_sigmask();
 687                }
 688        } else if (sigmask)
 689                sigprocmask(SIG_SETMASK, &sigsaved, NULL);
 690
 691        return ret;
 692}
 693
 694/*
 695 * Most architectures can't handle 7-argument syscalls. So we provide a
 696 * 6-argument version where the sixth argument is a pointer to a structure
 697 * which has a pointer to the sigset_t itself followed by a size_t containing
 698 * the sigset size.
 699 */
 700SYSCALL_DEFINE6(pselect6, int, n, fd_set __user *, inp, fd_set __user *, outp,
 701                fd_set __user *, exp, struct timespec __user *, tsp,
 702                void __user *, sig)
 703{
 704        size_t sigsetsize = 0;
 705        sigset_t __user *up = NULL;
 706
 707        if (sig) {
 708                if (!access_ok(VERIFY_READ, sig, sizeof(void *)+sizeof(size_t))
 709                    || __get_user(up, (sigset_t __user * __user *)sig)
 710                    || __get_user(sigsetsize,
 711                                (size_t __user *)(sig+sizeof(void *))))
 712                        return -EFAULT;
 713        }
 714
 715        return do_pselect(n, inp, outp, exp, tsp, up, sigsetsize);
 716}
 717
 718#ifdef __ARCH_WANT_SYS_OLD_SELECT
 719struct sel_arg_struct {
 720        unsigned long n;
 721        fd_set __user *inp, *outp, *exp;
 722        struct timeval __user *tvp;
 723};
 724
 725SYSCALL_DEFINE1(old_select, struct sel_arg_struct __user *, arg)
 726{
 727        struct sel_arg_struct a;
 728
 729        if (copy_from_user(&a, arg, sizeof(a)))
 730                return -EFAULT;
 731        return sys_select(a.n, a.inp, a.outp, a.exp, a.tvp);
 732}
 733#endif
 734
 735struct poll_list {
 736        struct poll_list *next;
 737        int len;
 738        struct pollfd entries[0];
 739};
 740
 741#define POLLFD_PER_PAGE  ((PAGE_SIZE-sizeof(struct poll_list)) / sizeof(struct pollfd))
 742
 743/*
 744 * Fish for pollable events on the pollfd->fd file descriptor. We're only
 745 * interested in events matching the pollfd->events mask, and the result
 746 * matching that mask is both recorded in pollfd->revents and returned. The
 747 * pwait poll_table will be used by the fd-provided poll handler for waiting,
 748 * if pwait->_qproc is non-NULL.
 749 */
 750static inline unsigned int do_pollfd(struct pollfd *pollfd, poll_table *pwait,
 751                                     bool *can_busy_poll,
 752                                     unsigned int busy_flag)
 753{
 754        unsigned int mask;
 755        int fd;
 756
 757        mask = 0;
 758        fd = pollfd->fd;
 759        if (fd >= 0) {
 760                struct fd f = fdget(fd);
 761                mask = POLLNVAL;
 762                if (f.file) {
 763                        mask = DEFAULT_POLLMASK;
 764                        if (f.file->f_op && f.file->f_op->poll) {
 765                                pwait->_key = pollfd->events|POLLERR|POLLHUP;
 766                                pwait->_key |= busy_flag;
 767                                mask = f.file->f_op->poll(f.file, pwait);
 768                                if (mask & busy_flag)
 769                                        *can_busy_poll = true;
 770                        }
 771                        /* Mask out unneeded events. */
 772                        mask &= pollfd->events | POLLERR | POLLHUP;
 773                        fdput(f);
 774                }
 775        }
 776        pollfd->revents = mask;
 777
 778        return mask;
 779}
 780
 781static int do_poll(unsigned int nfds,  struct poll_list *list,
 782                   struct poll_wqueues *wait, struct timespec *end_time)
 783{
 784        poll_table* pt = &wait->pt;
 785        ktime_t expire, *to = NULL;
 786        int timed_out = 0, count = 0;
 787        unsigned long slack = 0;
 788        unsigned int busy_flag = net_busy_loop_on() ? POLL_BUSY_LOOP : 0;
 789        unsigned long busy_end = 0;
 790
 791        /* Optimise the no-wait case */
 792        if (end_time && !end_time->tv_sec && !end_time->tv_nsec) {
 793                pt->_qproc = NULL;
 794                timed_out = 1;
 795        }
 796
 797        if (end_time && !timed_out)
 798                slack = select_estimate_accuracy(end_time);
 799
 800        for (;;) {
 801                struct poll_list *walk;
 802                bool can_busy_loop = false;
 803
 804                for (walk = list; walk != NULL; walk = walk->next) {
 805                        struct pollfd * pfd, * pfd_end;
 806
 807                        pfd = walk->entries;
 808                        pfd_end = pfd + walk->len;
 809                        for (; pfd != pfd_end; pfd++) {
 810                                /*
 811                                 * Fish for events. If we found one, record it
 812                                 * and kill poll_table->_qproc, so we don't
 813                                 * needlessly register any other waiters after
 814                                 * this. They'll get immediately deregistered
 815                                 * when we break out and return.
 816                                 */
 817                                if (do_pollfd(pfd, pt, &can_busy_loop,
 818                                              busy_flag)) {
 819                                        count++;
 820                                        pt->_qproc = NULL;
 821                                        /* found something, stop busy polling */
 822                                        busy_flag = 0;
 823                                        can_busy_loop = false;
 824                                }
 825                        }
 826                }
 827                /*
 828                 * All waiters have already been registered, so don't provide
 829                 * a poll_table->_qproc to them on the next loop iteration.
 830                 */
 831                pt->_qproc = NULL;
 832                if (!count) {
 833                        count = wait->error;
 834                        if (signal_pending(current))
 835                                count = -EINTR;
 836                }
 837                if (count || timed_out)
 838                        break;
 839
 840                /* only if found POLL_BUSY_LOOP sockets && not out of time */
 841                if (can_busy_loop && !need_resched()) {
 842                        if (!busy_end) {
 843                                busy_end = busy_loop_end_time();
 844                                continue;
 845                        }
 846                        if (!busy_loop_timeout(busy_end))
 847                                continue;
 848                }
 849                busy_flag = 0;
 850
 851                /*
 852                 * If this is the first loop and we have a timeout
 853                 * given, then we convert to ktime_t and set the to
 854                 * pointer to the expiry value.
 855                 */
 856                if (end_time && !to) {
 857                        expire = timespec_to_ktime(*end_time);
 858                        to = &expire;
 859                }
 860
 861                if (!poll_schedule_timeout(wait, TASK_INTERRUPTIBLE, to, slack))
 862                        timed_out = 1;
 863        }
 864        return count;
 865}
 866
 867#define N_STACK_PPS ((sizeof(stack_pps) - sizeof(struct poll_list))  / \
 868                        sizeof(struct pollfd))
 869
 870int do_sys_poll(struct pollfd __user *ufds, unsigned int nfds,
 871                struct timespec *end_time)
 872{
 873        struct poll_wqueues table;
 874        int err = -EFAULT, fdcount, len, size;
 875        /* Allocate small arguments on the stack to save memory and be
 876           faster - use long to make sure the buffer is aligned properly
 877           on 64 bit archs to avoid unaligned access */
 878        long stack_pps[POLL_STACK_ALLOC/sizeof(long)];
 879        struct poll_list *const head = (struct poll_list *)stack_pps;
 880        struct poll_list *walk = head;
 881        unsigned long todo = nfds;
 882
 883        if (nfds > rlimit(RLIMIT_NOFILE))
 884                return -EINVAL;
 885
 886        len = min_t(unsigned int, nfds, N_STACK_PPS);
 887        for (;;) {
 888                walk->next = NULL;
 889                walk->len = len;
 890                if (!len)
 891                        break;
 892
 893                if (copy_from_user(walk->entries, ufds + nfds-todo,
 894                                        sizeof(struct pollfd) * walk->len))
 895                        goto out_fds;
 896
 897                todo -= walk->len;
 898                if (!todo)
 899                        break;
 900
 901                len = min(todo, POLLFD_PER_PAGE);
 902                size = sizeof(struct poll_list) + sizeof(struct pollfd) * len;
 903                walk = walk->next = kmalloc(size, GFP_KERNEL);
 904                if (!walk) {
 905                        err = -ENOMEM;
 906                        goto out_fds;
 907                }
 908        }
 909
 910        poll_initwait(&table);
 911        fdcount = do_poll(nfds, head, &table, end_time);
 912        poll_freewait(&table);
 913
 914        for (walk = head; walk; walk = walk->next) {
 915                struct pollfd *fds = walk->entries;
 916                int j;
 917
 918                for (j = 0; j < walk->len; j++, ufds++)
 919                        if (__put_user(fds[j].revents, &ufds->revents))
 920                                goto out_fds;
 921        }
 922
 923        err = fdcount;
 924out_fds:
 925        walk = head->next;
 926        while (walk) {
 927                struct poll_list *pos = walk;
 928                walk = walk->next;
 929                kfree(pos);
 930        }
 931
 932        return err;
 933}
 934
 935static long do_restart_poll(struct restart_block *restart_block)
 936{
 937        struct pollfd __user *ufds = restart_block->poll.ufds;
 938        int nfds = restart_block->poll.nfds;
 939        struct timespec *to = NULL, end_time;
 940        int ret;
 941
 942        if (restart_block->poll.has_timeout) {
 943                end_time.tv_sec = restart_block->poll.tv_sec;
 944                end_time.tv_nsec = restart_block->poll.tv_nsec;
 945                to = &end_time;
 946        }
 947
 948        ret = do_sys_poll(ufds, nfds, to);
 949
 950        if (ret == -EINTR) {
 951                restart_block->fn = do_restart_poll;
 952                ret = -ERESTART_RESTARTBLOCK;
 953        }
 954        return ret;
 955}
 956
 957SYSCALL_DEFINE3(poll, struct pollfd __user *, ufds, unsigned int, nfds,
 958                int, timeout_msecs)
 959{
 960        struct timespec end_time, *to = NULL;
 961        int ret;
 962
 963        if (timeout_msecs >= 0) {
 964                to = &end_time;
 965                poll_select_set_timeout(to, timeout_msecs / MSEC_PER_SEC,
 966                        NSEC_PER_MSEC * (timeout_msecs % MSEC_PER_SEC));
 967        }
 968
 969        ret = do_sys_poll(ufds, nfds, to);
 970
 971        if (ret == -EINTR) {
 972                struct restart_block *restart_block;
 973
 974                restart_block = &current_thread_info()->restart_block;
 975                restart_block->fn = do_restart_poll;
 976                restart_block->poll.ufds = ufds;
 977                restart_block->poll.nfds = nfds;
 978
 979                if (timeout_msecs >= 0) {
 980                        restart_block->poll.tv_sec = end_time.tv_sec;
 981                        restart_block->poll.tv_nsec = end_time.tv_nsec;
 982                        restart_block->poll.has_timeout = 1;
 983                } else
 984                        restart_block->poll.has_timeout = 0;
 985
 986                ret = -ERESTART_RESTARTBLOCK;
 987        }
 988        return ret;
 989}
 990
 991SYSCALL_DEFINE5(ppoll, struct pollfd __user *, ufds, unsigned int, nfds,
 992                struct timespec __user *, tsp, const sigset_t __user *, sigmask,
 993                size_t, sigsetsize)
 994{
 995        sigset_t ksigmask, sigsaved;
 996        struct timespec ts, end_time, *to = NULL;
 997        int ret;
 998
 999        if (tsp) {
1000                if (copy_from_user(&ts, tsp, sizeof(ts)))
1001                        return -EFAULT;
1002
1003                to = &end_time;
1004                if (poll_select_set_timeout(to, ts.tv_sec, ts.tv_nsec))
1005                        return -EINVAL;
1006        }
1007
1008        if (sigmask) {
1009                /* XXX: Don't preclude handling different sized sigset_t's.  */
1010                if (sigsetsize != sizeof(sigset_t))
1011                        return -EINVAL;
1012                if (copy_from_user(&ksigmask, sigmask, sizeof(ksigmask)))
1013                        return -EFAULT;
1014
1015                sigdelsetmask(&ksigmask, sigmask(SIGKILL)|sigmask(SIGSTOP));
1016                sigprocmask(SIG_SETMASK, &ksigmask, &sigsaved);
1017        }
1018
1019        ret = do_sys_poll(ufds, nfds, to);
1020
1021        /* We can restart this syscall, usually */
1022        if (ret == -EINTR) {
1023                /*
1024                 * Don't restore the signal mask yet. Let do_signal() deliver
1025                 * the signal on the way back to userspace, before the signal
1026                 * mask is restored.
1027                 */
1028                if (sigmask) {
1029                        memcpy(&current->saved_sigmask, &sigsaved,
1030                                        sizeof(sigsaved));
1031                        set_restore_sigmask();
1032                }
1033                ret = -ERESTARTNOHAND;
1034        } else if (sigmask)
1035                sigprocmask(SIG_SETMASK, &sigsaved, NULL);
1036
1037        ret = poll_select_copy_remaining(&end_time, tsp, 0, ret);
1038
1039        return ret;
1040}
1041
lxr.linux.no kindly hosted by Redpill Linpro AS, provider of Linux consulting and operations services since 1995.