fs/select.c

   1 /*
   2  * This file contains the procedures for the handling of select and poll
   3  *
   4  * Created for Linux based loosely upon Mathius Lattner's minix
   5  * patches by Peter MacDonald. Heavily edited by Linus.
   6  *
   7  *  4 February 1994
   8  *     COFF/ELF binary emulation. If the process has the STICKY_TIMEOUTS
   9  *     flag set in its personality we do *not* modify the given timeout
  10  *     parameter to reflect time remaining.
  11  *
  12  *  24 January 2000
  13  *     Changed sys_poll()/do_poll() to use PAGE_SIZE chunk-based allocation
  14  *     of fds to overcome nfds < 16390 descriptors limit (Tigran Aivazian).
  15  */
  16
  17 #include <linux/kernel.h>
  18 #include <linux/sched.h>
  19 #include <linux/syscalls.h>
  20 #include <linux/export.h>
  21 #include <linux/slab.h>
  22 #include <linux/poll.h>
  23 #include <linux/personality.h> /* for STICKY_TIMEOUTS */
  24 #include <linux/file.h>
  25 #include <linux/fdtable.h>
  26 #include <linux/fs.h>
  27 #include <linux/rcupdate.h>
  28 #include <linux/hrtimer.h>
  29 #include <linux/sched/rt.h>
  30 #include <linux/freezer.h>
  31 #include <net/busy_poll.h>
  32
  33 #include <asm/uaccess.h>
  34
  35
  36 /*
  37  * Estimate expected accuracy in ns from a timeval.
  38  *
  39  * After quite a bit of churning around, we've settled on
  40  * a simple thing of taking 0.1% of the timeout as the
  41  * slack, with a cap of 100 msec.
  42  * "nice" tasks get a 0.5% slack instead.
  43  *
  44  * Consider this comment an open invitation to come up with even
  45  * better solutions..
  46  */
  47
  48 #define MAX_SLACK       (100 * NSEC_PER_MSEC)
  49
  50 static long __estimate_accuracy(struct timespec64 *tv)
  51 {
  52         long slack;
  53         int divfactor = 1000;
  54
  55         if (tv->tv_sec < 0)
  56                 return 0;
  57
  58         if (task_nice(current) > 0)
  59                 divfactor = divfactor / 5;
  60
  61         if (tv->tv_sec > MAX_SLACK / (NSEC_PER_SEC/divfactor))
  62                 return MAX_SLACK;
  63
  64         slack = tv->tv_nsec / divfactor;
  65         slack += tv->tv_sec * (NSEC_PER_SEC/divfactor);
  66
  67         if (slack > MAX_SLACK)
  68                 return MAX_SLACK;
  69
  70         return slack;
  71 }
  72
  73 u64 select_estimate_accuracy(struct timespec64 *tv)
  74 {
  75         u64 ret;
  76         struct timespec64 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_ts64(&now);
  86         now = timespec64_sub(*tv, now);
  87         ret = __estimate_accuracy(&now);
  88         if (ret < current->timer_slack_ns)
  89                 return current->timer_slack_ns;
  90         return ret;
  91 }
  92
  93
  94
  95 struct poll_table_page {
  96         struct poll_table_page * next;
  97         struct poll_table_entry * entry;
  98         struct poll_table_entry entries[0];
  99 };
 100
 101 #define POLL_TABLE_FULL(table) \
 102         ((unsigned long)((table)->entry+1) > PAGE_SIZE + (unsigned long)(table))
 103
 104 /*
 105  * Ok, Peter made a complicated, but straightforward multiple_wait() function.
 106  * I have rewritten this, taking some shortcuts: This code may not be easy to
 107  * follow, but it should be free of race-conditions, and it's practical. If you
 108  * understand what I'm doing here, then you understand how the linux
 109  * sleep/wakeup mechanism works.
 110  *
 111  * Two very simple procedures, poll_wait() and poll_freewait() make all the
 112  * work.  poll_wait() is an inline-function defined in <linux/poll.h>,
 113  * as all select/poll functions have to call it to add an entry to the
 114  * poll table.
 115  */
 116 static void __pollwait(struct file *filp, wait_queue_head_t *wait_address,
 117                        poll_table *p);
 118
 119 void poll_initwait(struct poll_wqueues *pwq)
 120 {
 121         init_poll_funcptr(&pwq->pt, __pollwait);
 122         pwq->polling_task = current;
 123         pwq->triggered = 0;
 124         pwq->error = 0;
 125         pwq->table = NULL;
 126         pwq->inline_index = 0;
 127 }
 128 EXPORT_SYMBOL(poll_initwait);
 129
 130 static void free_poll_entry(struct poll_table_entry *entry)
 131 {
 132         remove_wait_queue(entry->wait_address, &entry->wait);
 133         fput(entry->filp);
 134 }
 135
 136 void poll_freewait(struct poll_wqueues *pwq)
 137 {
 138         struct poll_table_page * p = pwq->table;
 139         int i;
 140         for (i = 0; i < pwq->inline_index; i++)
 141                 free_poll_entry(pwq->inline_entries + i);
 142         while (p) {
 143                 struct poll_table_entry * entry;
 144                 struct poll_table_page *old;
 145
 146                 entry = p->entry;
 147                 do {
 148                         entry--;
 149                         free_poll_entry(entry);
 150                 } while (entry > p->entries);
 151                 old = p;
 152                 p = p->next;
 153                 free_page((unsigned long) old);
 154         }
 155 }
 156 EXPORT_SYMBOL(poll_freewait);
 157
 158 static struct poll_table_entry *poll_get_entry(struct poll_wqueues *p)
 159 {
 160         struct poll_table_page *table = p->table;
 161
 162         if (p->inline_index < N_INLINE_POLL_ENTRIES)
 163                 return p->inline_entries + p->inline_index++;
 164
 165         if (!table || POLL_TABLE_FULL(table)) {
 166                 struct poll_table_page *new_table;
 167
 168                 new_table = (struct poll_table_page *) __get_free_page(GFP_KERNEL);
 169                 if (!new_table) {
 170                         p->error = -ENOMEM;
 171                         return NULL;
 172                 }
 173                 new_table->entry = new_table->entries;
 174                 new_table->next = table;
 175                 p->table = new_table;
 176                 table = new_table;
 177         }
 178
 179         return table->entry++;
 180 }
 181
 182 static int __pollwake(wait_queue_t *wait, unsigned mode, int sync, void *key)
 183 {
 184         struct poll_wqueues *pwq = wait->private;
 185         DECLARE_WAITQUEUE(dummy_wait, pwq->polling_task);
 186
 187         /*
 188          * Although this function is called under waitqueue lock, LOCK
 189          * doesn't imply write barrier and the users expect write
 190          * barrier semantics on wakeup functions.  The following
 191          * smp_wmb() is equivalent to smp_wmb() in try_to_wake_up()
 192          * and is paired with smp_store_mb() in poll_schedule_timeout.
 193          */
 194         smp_wmb();
 195         pwq->triggered = 1;
 196
 197         /*
 198          * Perform the default wake up operation using a dummy
 199          * waitqueue.
 200          *
 201          * TODO: This is hacky but there currently is no interface to
 202          * pass in @sync.  @sync is scheduled to be removed and once
 203          * that happens, wake_up_process() can be used directly.
 204          */
 205         return default_wake_function(&dummy_wait, mode, sync, key);
 206 }
 207
 208 static int pollwake(wait_queue_t *wait, unsigned mode, int sync, void *key)
 209 {
 210         struct poll_table_entry *entry;
 211
 212         entry = container_of(wait, struct poll_table_entry, wait);
 213         if (key && !((unsigned long)key & entry->key))
 214                 return 0;
 215         return __pollwake(wait, mode, sync, key);
 216 }
 217
 218 /* Add a new entry */
 219 static void __pollwait(struct file *filp, wait_queue_head_t *wait_address,
 220                                 poll_table *p)
 221 {
 222         struct poll_wqueues *pwq = container_of(p, struct poll_wqueues, pt);
 223         struct poll_table_entry *entry = poll_get_entry(pwq);
 224         if (!entry)
 225                 return;
 226         entry->filp = get_file(filp);
 227         entry->wait_address = wait_address;
 228         entry->key = p->_key;
 229         init_waitqueue_func_entry(&entry->wait, pollwake);
 230         entry->wait.private = pwq;
 231         add_wait_queue(wait_address, &entry->wait);
 232 }
 233
 234 int poll_schedule_timeout(struct poll_wqueues *pwq, int state,
 235                           ktime_t *expires, unsigned long slack)
 236 {
 237         int rc = -EINTR;
 238
 239         set_current_state(state);
 240         if (!pwq->triggered)
 241                 rc = schedule_hrtimeout_range(expires, slack, HRTIMER_MODE_ABS);
 242         __set_current_state(TASK_RUNNING);
 243
 244         /*
 245          * Prepare for the next iteration.
 246          *
 247          * The following smp_store_mb() serves two purposes.  First, it's
 248          * the counterpart rmb of the wmb in pollwake() such that data
 249          * written before wake up is always visible after wake up.
 250          * Second, the full barrier guarantees that triggered clearing
 251          * doesn't pass event check of the next iteration.  Note that
 252          * this problem doesn't exist for the first iteration as
 253          * add_wait_queue() has full barrier semantics.
 254          */
 255         smp_store_mb(pwq->triggered, 0);
 256
 257         return rc;
 258 }
 259 EXPORT_SYMBOL(poll_schedule_timeout);
 260
 261 /**
 262  * poll_select_set_timeout - helper function to setup the timeout value
 263  * @to:         pointer to timespec64 variable for the final timeout
 264  * @sec:        seconds (from user space)
 265  * @nsec:       nanoseconds (from user space)
 266  *
 267  * Note, we do not use a timespec for the user space value here, That
 268  * way we can use the function for timeval and compat interfaces as well.
 269  *
 270  * Returns -EINVAL if sec/nsec are not normalized. Otherwise 0.
 271  */
 272 int poll_select_set_timeout(struct timespec64 *to, time64_t sec, long nsec)
 273 {
 274         struct timespec64 ts = {.tv_sec = sec, .tv_nsec = nsec};
 275
 276         if (!timespec64_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_ts64(to);
 284                 *to = timespec64_add_safe(*to, ts);
 285         }
 286         return 0;
 287 }
 288
 289 static int poll_select_copy_remaining(struct timespec64 *end_time,
 290                                       void __user *p,
 291                                       int timeval, int ret)
 292 {
 293         struct timespec64 rts64;
 294         struct timespec rts;
 295         struct timeval rtv;
 296
 297         if (!p)
 298                 return ret;
 299
 300         if (current->personality & STICKY_TIMEOUTS)
 301                 goto sticky;
 302
 303         /* No update for zero timeout */
 304         if (!end_time->tv_sec && !end_time->tv_nsec)
 305                 return ret;
 306
 307         ktime_get_ts64(&rts64);
 308         rts64 = timespec64_sub(*end_time, rts64);
 309         if (rts64.tv_sec < 0)
 310                 rts64.tv_sec = rts64.tv_nsec = 0;
 311
 312         rts = timespec64_to_timespec(rts64);
 313
 314         if (timeval) {
 315                 if (sizeof(rtv) > sizeof(rtv.tv_sec) + sizeof(rtv.tv_usec))
 316                         memset(&rtv, 0, sizeof(rtv));
 317                 rtv.tv_sec = rts64.tv_sec;
 318                 rtv.tv_usec = rts64.tv_nsec / NSEC_PER_USEC;
 319
 320                 if (!copy_to_user(p, &rtv, sizeof(rtv)))
 321                         return ret;
 322
 323         } else if (!copy_to_user(p, &rts, sizeof(rts)))
 324                 return ret;
 325
 326         /*
 327          * If an application puts its timeval in read-only memory, we
 328          * don't want the Linux-specific update to the timeval to
 329          * cause a fault after the select has completed
 330          * successfully. However, because we're not updating the
 331          * timeval, we can't restart the system call.
 332          */
 333
 334 sticky:
 335         if (ret == -ERESTARTNOHAND)
 336                 ret = -EINTR;
 337         return ret;
 338 }
 339
 340 #define FDS_IN(fds, n)          (fds->in + n)
 341 #define FDS_OUT(fds, n)         (fds->out + n)
 342 #define FDS_EX(fds, n)          (fds->ex + n)
 343
 344 #define BITS(fds, n)    (*FDS_IN(fds, n)|*FDS_OUT(fds, n)|*FDS_EX(fds, n))
 345
 346 static int max_select_fd(unsigned long n, fd_set_bits *fds)
 347 {
 348         unsigned long *open_fds;
 349         unsigned long set;
 350         int max;
 351         struct fdtable *fdt;
 352
 353         /* handle last in-complete long-word first */
 354         set = ~(~0UL << (n & (BITS_PER_LONG-1)));
 355         n /= BITS_PER_LONG;
 356         fdt = files_fdtable(current->files);
 357         open_fds = fdt->open_fds + n;
 358         max = 0;
 359         if (set) {
 360                 set &= BITS(fds, n);
 361                 if (set) {
 362                         if (!(set & ~*open_fds))
 363                                 goto get_max;
 364                         return -EBADF;
 365                 }
 366         }
 367         while (n) {
 368                 open_fds--;
 369                 n--;
 370                 set = BITS(fds, n);
 371                 if (!set)
 372                         continue;
 373                 if (set & ~*open_fds)
 374                         return -EBADF;
 375                 if (max)
 376                         continue;
 377 get_max:
 378                 do {
 379                         max++;
 380                         set >>= 1;
 381                 } while (set);
 382                 max += n * BITS_PER_LONG;
 383         }
 384
 385         return max;
 386 }
 387
 388 #define POLLIN_SET (POLLRDNORM | POLLRDBAND | POLLIN | POLLHUP | POLLERR)
 389 #define POLLOUT_SET (POLLWRBAND | POLLWRNORM | POLLOUT | POLLERR)
 390 #define POLLEX_SET (POLLPRI)
 391
 392 static inline void wait_key_set(poll_table *wait, unsigned long in,
 393                                 unsigned long out, unsigned long bit,
 394                                 unsigned int ll_flag)
 395 {
 396         wait->_key = POLLEX_SET | ll_flag;
 397         if (in & bit)
 398                 wait->_key |= POLLIN_SET;
 399         if (out & bit)
 400                 wait->_key |= POLLOUT_SET;
 401 }
 402
 403 int do_select(int n, fd_set_bits *fds, struct timespec64 *end_time)
 404 {
 405         ktime_t expire, *to = NULL;
 406         struct poll_wqueues table;
 407         poll_table *wait;
 408         int retval, i, timed_out = 0;
 409         u64 slack = 0;
 410         unsigned int busy_flag = net_busy_loop_on() ? POLL_BUSY_LOOP : 0;
 411         unsigned long busy_end = 0;
 412
 413         rcu_read_lock();
 414         retval = max_select_fd(n, fds);
 415         rcu_read_unlock();
 416
 417         if (retval < 0)
 418                 return retval;
 419         n = retval;
 420
 421         poll_initwait(&table);
 422         wait = &table.pt;
 423         if (end_time && !end_time->tv_sec && !end_time->tv_nsec) {
 424                 wait->_qproc = NULL;
 425                 timed_out = 1;
 426         }
 427
 428         if (end_time && !timed_out)
 429                 slack = select_estimate_accuracy(end_time);
 430
 431         retval = 0;
 432         for (;;) {
 433                 unsigned long *rinp, *routp, *rexp, *inp, *outp, *exp;
 434                 bool can_busy_loop = false;
 435
 436                 inp = fds->in; outp = fds->out; exp = fds->ex;
 437                 rinp = fds->res_in; routp = fds->res_out; rexp = fds->res_ex;
 438
 439                 for (i = 0; i < n; ++rinp, ++routp, ++rexp) {
 440                         unsigned long in, out, ex, all_bits, bit = 1, mask, j;
 441                         unsigned long res_in = 0, res_out = 0, res_ex = 0;
 442
 443                         in = *inp++; out = *outp++; ex = *exp++;
 444                         all_bits = in | out | ex;
 445                         if (all_bits == 0) {
 446                                 i += BITS_PER_LONG;
 447                                 continue;
 448                         }
 449
 450                         for (j = 0; j < BITS_PER_LONG; ++j, ++i, bit <<= 1) {
 451                                 struct fd f;
 452                                 if (i >= n)
 453                                         break;
 454                                 if (!(bit & all_bits))
 455                                         continue;
 456                                 f = fdget(i);
 457                                 if (f.file) {
 458                                         const struct file_operations *f_op;
 459                                         f_op = f.file->f_op;
 460                                         mask = DEFAULT_POLLMASK;
 461                                         if (f_op->poll) {
 462                                                 wait_key_set(wait, in, out,
 463                                                              bit, busy_flag);
 464                                                 mask = (*f_op->poll)(f.file, wait);
 465                                         }
 466                                         fdput(f);
 467                                         if ((mask & POLLIN_SET) && (in & bit)) {
 468                                                 res_in |= bit;
 469                                                 retval++;
 470                                                 wait->_qproc = NULL;
 471                                         }
 472                                         if ((mask & POLLOUT_SET) && (out & bit)) {
 473                                                 res_out |= bit;
 474                                                 retval++;
 475                                                 wait->_qproc = NULL;
 476                                         }
 477                                         if ((mask & POLLEX_SET) && (ex & bit)) {
 478                                                 res_ex |= bit;
 479                                                 retval++;
 480                                                 wait->_qproc = NULL;
 481                                         }
 482                                         /* got something, stop busy polling */
 483                                         if (retval) {
 484                                                 can_busy_loop = false;
 485                                                 busy_flag = 0;
 486
 487                                         /*
 488                                          * only remember a returned
 489                                          * POLL_BUSY_LOOP if we asked for it
 490                                          */
 491                                         } else if (busy_flag & mask)
 492                                                 can_busy_loop = true;
 493
 494                                 }
 495                         }
 496                         if (res_in)
 497                                 *rinp = res_in;
 498                         if (res_out)
 499                                 *routp = res_out;
 500                         if (res_ex)
 501                                 *rexp = res_ex;
 502                         cond_resched();
 503                 }
 504                 wait->_qproc = NULL;
 505                 if (retval || timed_out || signal_pending(current))
 506                         break;
 507                 if (table.error) {
 508                         retval = table.error;
 509                         break;
 510                 }
 511
 512                 /* only if found POLL_BUSY_LOOP sockets && not out of time */
 513                 if (can_busy_loop && !need_resched()) {
 514                         if (!busy_end) {
 515                                 busy_end = busy_loop_end_time();
 516                                 continue;
 517                         }
 518                         if (!busy_loop_timeout(busy_end))
 519                                 continue;
 520                 }
 521                 busy_flag = 0;
 522
 523                 /*
 524                  * If this is the first loop and we have a timeout
 525                  * given, then we convert to ktime_t and set the to
 526                  * pointer to the expiry value.
 527                  */
 528                 if (end_time && !to) {
 529                         expire = timespec64_to_ktime(*end_time);
 530                         to = &expire;
 531                 }
 532
 533                 if (!poll_schedule_timeout(&table, TASK_INTERRUPTIBLE,
 534                                            to, slack))
 535                         timed_out = 1;
 536         }
 537
 538         poll_freewait(&table);
 539
 540         return retval;
 541 }
 542
 543 /*
 544  * We can actually return ERESTARTSYS instead of EINTR, but I'd
 545  * like to be certain this leads to no problems. So I return
 546  * EINTR just for safety.
 547  *
 548  * Update: ERESTARTSYS breaks at least the xview clock binary, so
 549  * I'm trying ERESTARTNOHAND which restart only when you want to.
 550  */
 551 int core_sys_select(int n, fd_set __user *inp, fd_set __user *outp,
 552                            fd_set __user *exp, struct timespec64 *end_time)
 553 {
 554         fd_set_bits fds;
 555         void *bits;
 556         int ret, max_fds;
 557         unsigned int size;
 558         struct fdtable *fdt;
 559         /* Allocate small arguments on the stack to save memory and be faster */
 560         long stack_fds[SELECT_STACK_ALLOC/sizeof(long)];
 561
 562         ret = -EINVAL;
 563         if (n < 0)
 564                 goto out_nofds;
 565
 566         /* max_fds can increase, so grab it once to avoid race */
 567         rcu_read_lock();
 568         fdt = files_fdtable(current->files);
 569         max_fds = fdt->max_fds;
 570         rcu_read_unlock();
 571         if (n > max_fds)
 572                 n = max_fds;
 573
 574         /*
 575          * We need 6 bitmaps (in/out/ex for both incoming and outgoing),
 576          * since we used fdset we need to allocate memory in units of
 577          * long-words.
 578          */
 579         size = FDS_BYTES(n);
 580         bits = stack_fds;
 581         if (size > sizeof(stack_fds) / 6) {
 582                 /* Not enough space in on-stack array; must use kmalloc */
 583                 ret = -ENOMEM;
 584                 bits = kmalloc(6 * size, GFP_KERNEL);
 585                 if (!bits)
 586                         goto out_nofds;
 587         }
 588         fds.in      = bits;
 589         fds.out     = bits +   size;
 590         fds.ex      = bits + 2*size;
 591         fds.res_in  = bits + 3*size;
 592         fds.res_out = bits + 4*size;
 593         fds.res_ex  = bits + 5*size;
 594
 595         if ((ret = get_fd_set(n, inp, fds.in)) ||
 596             (ret = get_fd_set(n, outp, fds.out)) ||
 597             (ret = get_fd_set(n, exp, fds.ex)))
 598                 goto out;
 599         zero_fd_set(n, fds.res_in);
 600         zero_fd_set(n, fds.res_out);
 601         zero_fd_set(n, fds.res_ex);
 602
 603         ret = do_select(n, &fds, end_time);
 604
 605         if (ret < 0)
 606                 goto out;
 607         if (!ret) {
 608                 ret = -ERESTARTNOHAND;
 609                 if (signal_pending(current))
 610                         goto out;
 611                 ret = 0;
 612         }
 613
 614         if (set_fd_set(n, inp, fds.res_in) ||
 615             set_fd_set(n, outp, fds.res_out) ||
 616             set_fd_set(n, exp, fds.res_ex))
 617                 ret = -EFAULT;
 618
 619 out:
 620         if (bits != stack_fds)
 621                 kfree(bits);
 622 out_nofds:
 623         return ret;
 624 }
 625
 626 SYSCALL_DEFINE5(select, int, n, fd_set __user *, inp, fd_set __user *, outp,
 627                 fd_set __user *, exp, struct timeval __user *, tvp)
 628 {
 629         struct timespec64 end_time, *to = NULL;
 630         struct timeval tv;
 631         int ret;
 632
 633         if (tvp) {
 634                 if (copy_from_user(&tv, tvp, sizeof(tv)))
 635                         return -EFAULT;
 636
 637                 to = &end_time;
 638                 if (poll_select_set_timeout(to,
 639                                 tv.tv_sec + (tv.tv_usec / USEC_PER_SEC),
 640                                 (tv.tv_usec % USEC_PER_SEC) * NSEC_PER_USEC))
 641                         return -EINVAL;
 642         }
 643
 644         ret = core_sys_select(n, inp, outp, exp, to);
 645         ret = poll_select_copy_remaining(&end_time, tvp, 1, ret);
 646
 647         return ret;
 648 }
 649
 650 static long do_pselect(int n, fd_set __user *inp, fd_set __user *outp,
 651                        fd_set __user *exp, struct timespec __user *tsp,
 652                        const sigset_t __user *sigmask, size_t sigsetsize)
 653 {
 654         sigset_t ksigmask, sigsaved;
 655         struct timespec ts;
 656         struct timespec64 ts64, end_time, *to = NULL;
 657         int ret;
 658
 659         if (tsp) {
 660                 if (copy_from_user(&ts, tsp, sizeof(ts)))
 661                         return -EFAULT;
 662                 ts64 = timespec_to_timespec64(ts);
 663
 664                 to = &end_time;
 665                 if (poll_select_set_timeout(to, ts64.tv_sec, ts64.tv_nsec))
 666                         return -EINVAL;
 667         }
 668
 669         if (sigmask) {
 670                 /* XXX: Don't preclude handling different sized sigset_t's.  */
 671                 if (sigsetsize != sizeof(sigset_t))
 672                         return -EINVAL;
 673                 if (copy_from_user(&ksigmask, sigmask, sizeof(ksigmask)))
 674                         return -EFAULT;
 675
 676                 sigdelsetmask(&ksigmask, sigmask(SIGKILL)|sigmask(SIGSTOP));
 677                 sigprocmask(SIG_SETMASK, &ksigmask, &sigsaved);
 678         }
 679
 680         ret = core_sys_select(n, inp, outp, exp, to);
 681         ret = poll_select_copy_remaining(&end_time, tsp, 0, ret);
 682
 683         if (ret == -ERESTARTNOHAND) {
 684                 /*
 685                  * Don't restore the signal mask yet. Let do_signal() deliver
 686                  * the signal on the way back to userspace, before the signal
 687                  * mask is restored.
 688                  */
 689                 if (sigmask) {
 690                         memcpy(&current->saved_sigmask, &sigsaved,
 691                                         sizeof(sigsaved));
 692                         set_restore_sigmask();
 693                 }
 694         } else if (sigmask)
 695                 sigprocmask(SIG_SETMASK, &sigsaved, NULL);
 696
 697         return ret;
 698 }
 699
 700 /*
 701  * Most architectures can't handle 7-argument syscalls. So we provide a
 702  * 6-argument version where the sixth argument is a pointer to a structure
 703  * which has a pointer to the sigset_t itself followed by a size_t containing
 704  * the sigset size.
 705  */
 706 SYSCALL_DEFINE6(pselect6, int, n, fd_set __user *, inp, fd_set __user *, outp,
 707                 fd_set __user *, exp, struct timespec __user *, tsp,
 708                 void __user *, sig)
 709 {
 710         size_t sigsetsize = 0;
 711         sigset_t __user *up = NULL;
 712
 713         if (sig) {
 714                 if (!access_ok(VERIFY_READ, sig, sizeof(void *)+sizeof(size_t))
 715                     || __get_user(up, (sigset_t __user * __user *)sig)
 716                     || __get_user(sigsetsize,
 717                                 (size_t __user *)(sig+sizeof(void *))))
 718                         return -EFAULT;
 719         }
 720
 721         return do_pselect(n, inp, outp, exp, tsp, up, sigsetsize);
 722 }
 723
 724 #ifdef __ARCH_WANT_SYS_OLD_SELECT
 725 struct sel_arg_struct {
 726         unsigned long n;
 727         fd_set __user *inp, *outp, *exp;
 728         struct timeval __user *tvp;
 729 };
 730
 731 SYSCALL_DEFINE1(old_select, struct sel_arg_struct __user *, arg)
 732 {
 733         struct sel_arg_struct a;
 734
 735         if (copy_from_user(&a, arg, sizeof(a)))
 736                 return -EFAULT;
 737         return sys_select(a.n, a.inp, a.outp, a.exp, a.tvp);
 738 }
 739 #endif
 740
 741 struct poll_list {
 742         struct poll_list *next;
 743         int len;
 744         struct pollfd entries[0];
 745 };
 746
 747 #define POLLFD_PER_PAGE  ((PAGE_SIZE-sizeof(struct poll_list)) / sizeof(struct pollfd))
 748
 749 /*
 750  * Fish for pollable events on the pollfd->fd file descriptor. We're only
 751  * interested in events matching the pollfd->events mask, and the result
 752  * matching that mask is both recorded in pollfd->revents and returned. The
 753  * pwait poll_table will be used by the fd-provided poll handler for waiting,
 754  * if pwait->_qproc is non-NULL.
 755  */
 756 static inline unsigned int do_pollfd(struct pollfd *pollfd, poll_table *pwait,
 757                                      bool *can_busy_poll,
 758                                      unsigned int busy_flag)
 759 {
 760         unsigned int mask;
 761         int fd;
 762
 763         mask = 0;
 764         fd = pollfd->fd;
 765         if (fd >= 0) {
 766                 struct fd f = fdget(fd);
 767                 mask = POLLNVAL;
 768                 if (f.file) {
 769                         mask = DEFAULT_POLLMASK;
 770                         if (f.file->f_op->poll) {
 771                                 pwait->_key = pollfd->events|POLLERR|POLLHUP;
 772                                 pwait->_key |= busy_flag;
 773                                 mask = f.file->f_op->poll(f.file, pwait);
 774                                 if (mask & busy_flag)
 775                                         *can_busy_poll = true;
 776                         }
 777                         /* Mask out unneeded events. */
 778                         mask &= pollfd->events | POLLERR | POLLHUP;
 779                         fdput(f);
 780                 }
 781         }
 782         pollfd->revents = mask;
 783
 784         return mask;
 785 }
 786
 787 static int do_poll(struct poll_list *list, struct poll_wqueues *wait,
 788                    struct timespec64 *end_time)
 789 {
 790         poll_table* pt = &wait->pt;
 791         ktime_t expire, *to = NULL;
 792         int timed_out = 0, count = 0;
 793         u64 slack = 0;
 794         unsigned int busy_flag = net_busy_loop_on() ? POLL_BUSY_LOOP : 0;
 795         unsigned long busy_end = 0;
 796
 797         /* Optimise the no-wait case */
 798         if (end_time && !end_time->tv_sec && !end_time->tv_nsec) {
 799                 pt->_qproc = NULL;
 800                 timed_out = 1;
 801         }
 802
 803         if (end_time && !timed_out)
 804                 slack = select_estimate_accuracy(end_time);
 805
 806         for (;;) {
 807                 struct poll_list *walk;
 808                 bool can_busy_loop = false;
 809
 810                 for (walk = list; walk != NULL; walk = walk->next) {
 811                         struct pollfd * pfd, * pfd_end;
 812
 813                         pfd = walk->entries;
 814                         pfd_end = pfd + walk->len;
 815                         for (; pfd != pfd_end; pfd++) {
 816                                 /*
 817                                  * Fish for events. If we found one, record it
 818                                  * and kill poll_table->_qproc, so we don't
 819                                  * needlessly register any other waiters after
 820                                  * this. They'll get immediately deregistered
 821                                  * when we break out and return.
 822                                  */
 823                                 if (do_pollfd(pfd, pt, &can_busy_loop,
 824                                               busy_flag)) {
 825                                         count++;
 826                                         pt->_qproc = NULL;
 827                                         /* found something, stop busy polling */
 828                                         busy_flag = 0;
 829                                         can_busy_loop = false;
 830                                 }
 831                         }
 832                 }
 833                 /*
 834                  * All waiters have already been registered, so don't provide
 835                  * a poll_table->_qproc to them on the next loop iteration.
 836                  */
 837                 pt->_qproc = NULL;
 838                 if (!count) {
 839                         count = wait->error;
 840                         if (signal_pending(current))
 841                                 count = -EINTR;
 842                 }
 843                 if (count || timed_out)
 844                         break;
 845
 846                 /* only if found POLL_BUSY_LOOP sockets && not out of time */
 847                 if (can_busy_loop && !need_resched()) {
 848                         if (!busy_end) {
 849                                 busy_end = busy_loop_end_time();
 850                                 continue;
 851                         }
 852                         if (!busy_loop_timeout(busy_end))
 853                                 continue;
 854                 }
 855                 busy_flag = 0;
 856
 857                 /*
 858                  * If this is the first loop and we have a timeout
 859                  * given, then we convert to ktime_t and set the to
 860                  * pointer to the expiry value.
 861                  */
 862                 if (end_time && !to) {
 863                         expire = timespec64_to_ktime(*end_time);
 864                         to = &expire;
 865                 }
 866
 867                 if (!poll_schedule_timeout(wait, TASK_INTERRUPTIBLE, to, slack))
 868                         timed_out = 1;
 869         }
 870         return count;
 871 }
 872
 873 #define N_STACK_PPS ((sizeof(stack_pps) - sizeof(struct poll_list))  / \
 874                         sizeof(struct pollfd))
 875
 876 int do_sys_poll(struct pollfd __user *ufds, unsigned int nfds,
 877                 struct timespec64 *end_time)
 878 {
 879         struct poll_wqueues table;
 880         int err = -EFAULT, fdcount, len, size;
 881         /* Allocate small arguments on the stack to save memory and be
 882            faster - use long to make sure the buffer is aligned properly
 883            on 64 bit archs to avoid unaligned access */
 884         long stack_pps[POLL_STACK_ALLOC/sizeof(long)];
 885         struct poll_list *const head = (struct poll_list *)stack_pps;
 886         struct poll_list *walk = head;
 887         unsigned long todo = nfds;
 888
 889         if (nfds > rlimit(RLIMIT_NOFILE))
 890                 return -EINVAL;
 891
 892         len = min_t(unsigned int, nfds, N_STACK_PPS);
 893         for (;;) {
 894                 walk->next = NULL;
 895                 walk->len = len;
 896                 if (!len)
 897                         break;
 898
 899                 if (copy_from_user(walk->entries, ufds + nfds-todo,
 900                                         sizeof(struct pollfd) * walk->len))
 901                         goto out_fds;
 902
 903                 todo -= walk->len;
 904                 if (!todo)
 905                         break;
 906
 907                 len = min(todo, POLLFD_PER_PAGE);
 908                 size = sizeof(struct poll_list) + sizeof(struct pollfd) * len;
 909                 walk = walk->next = kmalloc(size, GFP_KERNEL);
 910                 if (!walk) {
 911                         err = -ENOMEM;
 912                         goto out_fds;
 913                 }
 914         }
 915
 916         poll_initwait(&table);
 917         fdcount = do_poll(head, &table, end_time);
 918         poll_freewait(&table);
 919
 920         for (walk = head; walk; walk = walk->next) {
 921                 struct pollfd *fds = walk->entries;
 922                 int j;
 923
 924                 for (j = 0; j < walk->len; j++, ufds++)
 925                         if (__put_user(fds[j].revents, &ufds->revents))
 926                                 goto out_fds;
 927         }
 928
 929         err = fdcount;
 930 out_fds:
 931         walk = head->next;
 932         while (walk) {
 933                 struct poll_list *pos = walk;
 934                 walk = walk->next;
 935                 kfree(pos);
 936         }
 937
 938         return err;
 939 }
 940
 941 static long do_restart_poll(struct restart_block *restart_block)
 942 {
 943         struct pollfd __user *ufds = restart_block->poll.ufds;
 944         int nfds = restart_block->poll.nfds;
 945         struct timespec64 *to = NULL, end_time;
 946         int ret;
 947
 948         if (restart_block->poll.has_timeout) {
 949                 end_time.tv_sec = restart_block->poll.tv_sec;
 950                 end_time.tv_nsec = restart_block->poll.tv_nsec;
 951                 to = &end_time;
 952         }
 953
 954         ret = do_sys_poll(ufds, nfds, to);
 955
 956         if (ret == -EINTR) {
 957                 restart_block->fn = do_restart_poll;
 958                 ret = -ERESTART_RESTARTBLOCK;
 959         }
 960         return ret;
 961 }
 962
 963 SYSCALL_DEFINE3(poll, struct pollfd __user *, ufds, unsigned int, nfds,
 964                 int, timeout_msecs)
 965 {
 966         struct timespec64 end_time, *to = NULL;
 967         int ret;
 968
 969         if (timeout_msecs >= 0) {
 970                 to = &end_time;
 971                 poll_select_set_timeout(to, timeout_msecs / MSEC_PER_SEC,
 972                         NSEC_PER_MSEC * (timeout_msecs % MSEC_PER_SEC));
 973         }
 974
 975         ret = do_sys_poll(ufds, nfds, to);
 976
 977         if (ret == -EINTR) {
 978                 struct restart_block *restart_block;
 979
 980                 restart_block = &current->restart_block;
 981                 restart_block->fn = do_restart_poll;
 982                 restart_block->poll.ufds = ufds;
 983                 restart_block->poll.nfds = nfds;
 984
 985                 if (timeout_msecs >= 0) {
 986                         restart_block->poll.tv_sec = end_time.tv_sec;
 987                         restart_block->poll.tv_nsec = end_time.tv_nsec;
 988                         restart_block->poll.has_timeout = 1;
 989                 } else
 990                         restart_block->poll.has_timeout = 0;
 991
 992                 ret = -ERESTART_RESTARTBLOCK;
 993         }
 994         return ret;
 995 }
 996
 997 SYSCALL_DEFINE5(ppoll, struct pollfd __user *, ufds, unsigned int, nfds,
 998                 struct timespec __user *, tsp, const sigset_t __user *, sigmask,
 999                 size_t, sigsetsize)
1000 {
1001         sigset_t ksigmask, sigsaved;
1002         struct timespec ts;
1003         struct timespec64 end_time, *to = NULL;
1004         int ret;
1005
1006         if (tsp) {
1007                 if (copy_from_user(&ts, tsp, sizeof(ts)))
1008                         return -EFAULT;
1009
1010                 to = &end_time;
1011                 if (poll_select_set_timeout(to, ts.tv_sec, ts.tv_nsec))
1012                         return -EINVAL;
1013         }
1014
1015         if (sigmask) {
1016                 /* XXX: Don't preclude handling different sized sigset_t's.  */
1017                 if (sigsetsize != sizeof(sigset_t))
1018                         return -EINVAL;
1019                 if (copy_from_user(&ksigmask, sigmask, sizeof(ksigmask)))
1020                         return -EFAULT;
1021
1022                 sigdelsetmask(&ksigmask, sigmask(SIGKILL)|sigmask(SIGSTOP));
1023                 sigprocmask(SIG_SETMASK, &ksigmask, &sigsaved);
1024         }
1025
1026         ret = do_sys_poll(ufds, nfds, to);
1027
1028         /* We can restart this syscall, usually */
1029         if (ret == -EINTR) {
1030                 /*
1031                  * Don't restore the signal mask yet. Let do_signal() deliver
1032                  * the signal on the way back to userspace, before the signal
1033                  * mask is restored.
1034                  */
1035                 if (sigmask) {
1036                         memcpy(&current->saved_sigmask, &sigsaved,
1037                                         sizeof(sigsaved));
1038                         set_restore_sigmask();
1039                 }
1040                 ret = -ERESTARTNOHAND;
1041         } else if (sigmask)
1042                 sigprocmask(SIG_SETMASK, &sigsaved, NULL);
1043
1044         ret = poll_select_copy_remaining(&end_time, tsp, 0, ret);
1045
1046         return ret;
1047 }