Root/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/module.h>
21#include <linux/slab.h>
22#include <linux/poll.h>
23#include <linux/personality.h> /* for STICKY_TIMEOUTS */
24#include <linux/file.h>
25#include <linux/fdtable.h>
26#include <linux/fs.h>
27#include <linux/rcupdate.h>
28#include <linux/hrtimer.h>
29
30#include <asm/uaccess.h>
31
32
33/*
34 * Estimate expected accuracy in ns from a timeval.
35 *
36 * After quite a bit of churning around, we've settled on
37 * a simple thing of taking 0.1% of the timeout as the
38 * slack, with a cap of 100 msec.
39 * "nice" tasks get a 0.5% slack instead.
40 *
41 * Consider this comment an open invitation to come up with even
42 * better solutions..
43 */
44
45#define MAX_SLACK (100 * NSEC_PER_MSEC)
46
47static long __estimate_accuracy(struct timespec *tv)
48{
49    long slack;
50    int divfactor = 1000;
51
52    if (tv->tv_sec < 0)
53        return 0;
54
55    if (task_nice(current) > 0)
56        divfactor = divfactor / 5;
57
58    if (tv->tv_sec > MAX_SLACK / (NSEC_PER_SEC/divfactor))
59        return MAX_SLACK;
60
61    slack = tv->tv_nsec / divfactor;
62    slack += tv->tv_sec * (NSEC_PER_SEC/divfactor);
63
64    if (slack > MAX_SLACK)
65        return MAX_SLACK;
66
67    return slack;
68}
69
70static long estimate_accuracy(struct timespec *tv)
71{
72    unsigned long ret;
73    struct timespec now;
74
75    /*
76     * Realtime tasks get a slack of 0 for obvious reasons.
77     */
78
79    if (rt_task(current))
80        return 0;
81
82    ktime_get_ts(&now);
83    now = timespec_sub(*tv, now);
84    ret = __estimate_accuracy(&now);
85    if (ret < current->timer_slack_ns)
86        return current->timer_slack_ns;
87    return ret;
88}
89
90
91
92struct poll_table_page {
93    struct poll_table_page * next;
94    struct poll_table_entry * entry;
95    struct poll_table_entry entries[0];
96};
97
98#define POLL_TABLE_FULL(table) \
99    ((unsigned long)((table)->entry+1) > PAGE_SIZE + (unsigned long)(table))
100
101/*
102 * Ok, Peter made a complicated, but straightforward multiple_wait() function.
103 * I have rewritten this, taking some shortcuts: This code may not be easy to
104 * follow, but it should be free of race-conditions, and it's practical. If you
105 * understand what I'm doing here, then you understand how the linux
106 * sleep/wakeup mechanism works.
107 *
108 * Two very simple procedures, poll_wait() and poll_freewait() make all the
109 * work. poll_wait() is an inline-function defined in <linux/poll.h>,
110 * as all select/poll functions have to call it to add an entry to the
111 * poll table.
112 */
113static void __pollwait(struct file *filp, wait_queue_head_t *wait_address,
114               poll_table *p);
115
116void poll_initwait(struct poll_wqueues *pwq)
117{
118    init_poll_funcptr(&pwq->pt, __pollwait);
119    pwq->polling_task = current;
120    pwq->triggered = 0;
121    pwq->error = 0;
122    pwq->table = NULL;
123    pwq->inline_index = 0;
124}
125EXPORT_SYMBOL(poll_initwait);
126
127static void free_poll_entry(struct poll_table_entry *entry)
128{
129    remove_wait_queue(entry->wait_address, &entry->wait);
130    fput(entry->filp);
131}
132
133void poll_freewait(struct poll_wqueues *pwq)
134{
135    struct poll_table_page * p = pwq->table;
136    int i;
137    for (i = 0; i < pwq->inline_index; i++)
138        free_poll_entry(pwq->inline_entries + i);
139    while (p) {
140        struct poll_table_entry * entry;
141        struct poll_table_page *old;
142
143        entry = p->entry;
144        do {
145            entry--;
146            free_poll_entry(entry);
147        } while (entry > p->entries);
148        old = p;
149        p = p->next;
150        free_page((unsigned long) old);
151    }
152}
153EXPORT_SYMBOL(poll_freewait);
154
155static struct poll_table_entry *poll_get_entry(struct poll_wqueues *p)
156{
157    struct poll_table_page *table = p->table;
158
159    if (p->inline_index < N_INLINE_POLL_ENTRIES)
160        return p->inline_entries + p->inline_index++;
161
162    if (!table || POLL_TABLE_FULL(table)) {
163        struct poll_table_page *new_table;
164
165        new_table = (struct poll_table_page *) __get_free_page(GFP_KERNEL);
166        if (!new_table) {
167            p->error = -ENOMEM;
168            return NULL;
169        }
170        new_table->entry = new_table->entries;
171        new_table->next = table;
172        p->table = new_table;
173        table = new_table;
174    }
175
176    return table->entry++;
177}
178
179static int __pollwake(wait_queue_t *wait, unsigned mode, int sync, void *key)
180{
181    struct poll_wqueues *pwq = wait->private;
182    DECLARE_WAITQUEUE(dummy_wait, pwq->polling_task);
183
184    /*
185     * Although this function is called under waitqueue lock, LOCK
186     * doesn't imply write barrier and the users expect write
187     * barrier semantics on wakeup functions. The following
188     * smp_wmb() is equivalent to smp_wmb() in try_to_wake_up()
189     * and is paired with set_mb() in poll_schedule_timeout.
190     */
191    smp_wmb();
192    pwq->triggered = 1;
193
194    /*
195     * Perform the default wake up operation using a dummy
196     * waitqueue.
197     *
198     * TODO: This is hacky but there currently is no interface to
199     * pass in @sync. @sync is scheduled to be removed and once
200     * that happens, wake_up_process() can be used directly.
201     */
202    return default_wake_function(&dummy_wait, mode, sync, key);
203}
204
205static int pollwake(wait_queue_t *wait, unsigned mode, int sync, void *key)
206{
207    struct poll_table_entry *entry;
208
209    entry = container_of(wait, struct poll_table_entry, wait);
210    if (key && !((unsigned long)key & entry->key))
211        return 0;
212    return __pollwake(wait, mode, sync, key);
213}
214
215/* Add a new entry */
216static void __pollwait(struct file *filp, wait_queue_head_t *wait_address,
217                poll_table *p)
218{
219    struct poll_wqueues *pwq = container_of(p, struct poll_wqueues, pt);
220    struct poll_table_entry *entry = poll_get_entry(pwq);
221    if (!entry)
222        return;
223    get_file(filp);
224    entry->filp = filp;
225    entry->wait_address = wait_address;
226    entry->key = p->key;
227    init_waitqueue_func_entry(&entry->wait, pollwake);
228    entry->wait.private = pwq;
229    add_wait_queue(wait_address, &entry->wait);
230}
231
232int poll_schedule_timeout(struct poll_wqueues *pwq, int state,
233              ktime_t *expires, unsigned long slack)
234{
235    int rc = -EINTR;
236
237    set_current_state(state);
238    if (!pwq->triggered)
239        rc = schedule_hrtimeout_range(expires, slack, HRTIMER_MODE_ABS);
240    __set_current_state(TASK_RUNNING);
241
242    /*
243     * Prepare for the next iteration.
244     *
245     * The following set_mb() serves two purposes. First, it's
246     * the counterpart rmb of the wmb in pollwake() such that data
247     * written before wake up is always visible after wake up.
248     * Second, the full barrier guarantees that triggered clearing
249     * doesn't pass event check of the next iteration. Note that
250     * this problem doesn't exist for the first iteration as
251     * add_wait_queue() has full barrier semantics.
252     */
253    set_mb(pwq->triggered, 0);
254
255    return rc;
256}
257EXPORT_SYMBOL(poll_schedule_timeout);
258
259/**
260 * poll_select_set_timeout - helper function to setup the timeout value
261 * @to: pointer to timespec variable for the final timeout
262 * @sec: seconds (from user space)
263 * @nsec: nanoseconds (from user space)
264 *
265 * Note, we do not use a timespec for the user space value here, That
266 * way we can use the function for timeval and compat interfaces as well.
267 *
268 * Returns -EINVAL if sec/nsec are not normalized. Otherwise 0.
269 */
270int poll_select_set_timeout(struct timespec *to, long sec, long nsec)
271{
272    struct timespec ts = {.tv_sec = sec, .tv_nsec = nsec};
273
274    if (!timespec_valid(&ts))
275        return -EINVAL;
276
277    /* Optimize for the zero timeout value here */
278    if (!sec && !nsec) {
279        to->tv_sec = to->tv_nsec = 0;
280    } else {
281        ktime_get_ts(to);
282        *to = timespec_add_safe(*to, ts);
283    }
284    return 0;
285}
286
287static int poll_select_copy_remaining(struct timespec *end_time, void __user *p,
288                      int timeval, int ret)
289{
290    struct timespec rts;
291    struct timeval rtv;
292
293    if (!p)
294        return ret;
295
296    if (current->personality & STICKY_TIMEOUTS)
297        goto sticky;
298
299    /* No update for zero timeout */
300    if (!end_time->tv_sec && !end_time->tv_nsec)
301        return ret;
302
303    ktime_get_ts(&rts);
304    rts = timespec_sub(*end_time, rts);
305    if (rts.tv_sec < 0)
306        rts.tv_sec = rts.tv_nsec = 0;
307
308    if (timeval) {
309        rtv.tv_sec = rts.tv_sec;
310        rtv.tv_usec = rts.tv_nsec / NSEC_PER_USEC;
311
312        if (!copy_to_user(p, &rtv, sizeof(rtv)))
313            return ret;
314
315    } else if (!copy_to_user(p, &rts, sizeof(rts)))
316        return ret;
317
318    /*
319     * If an application puts its timeval in read-only memory, we
320     * don't want the Linux-specific update to the timeval to
321     * cause a fault after the select has completed
322     * successfully. However, because we're not updating the
323     * timeval, we can't restart the system call.
324     */
325
326sticky:
327    if (ret == -ERESTARTNOHAND)
328        ret = -EINTR;
329    return ret;
330}
331
332#define FDS_IN(fds, n) (fds->in + n)
333#define FDS_OUT(fds, n) (fds->out + n)
334#define FDS_EX(fds, n) (fds->ex + n)
335
336#define BITS(fds, n) (*FDS_IN(fds, n)|*FDS_OUT(fds, n)|*FDS_EX(fds, n))
337
338static int max_select_fd(unsigned long n, fd_set_bits *fds)
339{
340    unsigned long *open_fds;
341    unsigned long set;
342    int max;
343    struct fdtable *fdt;
344
345    /* handle last in-complete long-word first */
346    set = ~(~0UL << (n & (__NFDBITS-1)));
347    n /= __NFDBITS;
348    fdt = files_fdtable(current->files);
349    open_fds = fdt->open_fds->fds_bits+n;
350    max = 0;
351    if (set) {
352        set &= BITS(fds, n);
353        if (set) {
354            if (!(set & ~*open_fds))
355                goto get_max;
356            return -EBADF;
357        }
358    }
359    while (n) {
360        open_fds--;
361        n--;
362        set = BITS(fds, n);
363        if (!set)
364            continue;
365        if (set & ~*open_fds)
366            return -EBADF;
367        if (max)
368            continue;
369get_max:
370        do {
371            max++;
372            set >>= 1;
373        } while (set);
374        max += n * __NFDBITS;
375    }
376
377    return max;
378}
379
380#define POLLIN_SET (POLLRDNORM | POLLRDBAND | POLLIN | POLLHUP | POLLERR)
381#define POLLOUT_SET (POLLWRBAND | POLLWRNORM | POLLOUT | POLLERR)
382#define POLLEX_SET (POLLPRI)
383
384static inline void wait_key_set(poll_table *wait, unsigned long in,
385                unsigned long out, unsigned long bit)
386{
387    if (wait) {
388        wait->key = POLLEX_SET;
389        if (in & bit)
390            wait->key |= POLLIN_SET;
391        if (out & bit)
392            wait->key |= POLLOUT_SET;
393    }
394}
395
396int do_select(int n, fd_set_bits *fds, struct timespec *end_time)
397{
398    ktime_t expire, *to = NULL;
399    struct poll_wqueues table;
400    poll_table *wait;
401    int retval, i, timed_out = 0;
402    unsigned long slack = 0;
403
404    rcu_read_lock();
405    retval = max_select_fd(n, fds);
406    rcu_read_unlock();
407
408    if (retval < 0)
409        return retval;
410    n = retval;
411
412    poll_initwait(&table);
413    wait = &table.pt;
414    if (end_time && !end_time->tv_sec && !end_time->tv_nsec) {
415        wait = NULL;
416        timed_out = 1;
417    }
418
419    if (end_time && !timed_out)
420        slack = estimate_accuracy(end_time);
421
422    retval = 0;
423    for (;;) {
424        unsigned long *rinp, *routp, *rexp, *inp, *outp, *exp;
425
426        inp = fds->in; outp = fds->out; exp = fds->ex;
427        rinp = fds->res_in; routp = fds->res_out; rexp = fds->res_ex;
428
429        for (i = 0; i < n; ++rinp, ++routp, ++rexp) {
430            unsigned long in, out, ex, all_bits, bit = 1, mask, j;
431            unsigned long res_in = 0, res_out = 0, res_ex = 0;
432            const struct file_operations *f_op = NULL;
433            struct file *file = NULL;
434
435            in = *inp++; out = *outp++; ex = *exp++;
436            all_bits = in | out | ex;
437            if (all_bits == 0) {
438                i += __NFDBITS;
439                continue;
440            }
441
442            for (j = 0; j < __NFDBITS; ++j, ++i, bit <<= 1) {
443                int fput_needed;
444                if (i >= n)
445                    break;
446                if (!(bit & all_bits))
447                    continue;
448                file = fget_light(i, &fput_needed);
449                if (file) {
450                    f_op = file->f_op;
451                    mask = DEFAULT_POLLMASK;
452                    if (f_op && f_op->poll) {
453                        wait_key_set(wait, in, out, bit);
454                        mask = (*f_op->poll)(file, wait);
455                    }
456                    fput_light(file, fput_needed);
457                    if ((mask & POLLIN_SET) && (in & bit)) {
458                        res_in |= bit;
459                        retval++;
460                        wait = NULL;
461                    }
462                    if ((mask & POLLOUT_SET) && (out & bit)) {
463                        res_out |= bit;
464                        retval++;
465                        wait = NULL;
466                    }
467                    if ((mask & POLLEX_SET) && (ex & bit)) {
468                        res_ex |= bit;
469                        retval++;
470                        wait = NULL;
471                    }
472                }
473            }
474            if (res_in)
475                *rinp = res_in;
476            if (res_out)
477                *routp = res_out;
478            if (res_ex)
479                *rexp = res_ex;
480            cond_resched();
481        }
482        wait = NULL;
483        if (retval || timed_out || signal_pending(current))
484            break;
485        if (table.error) {
486            retval = table.error;
487            break;
488        }
489
490        /*
491         * If this is the first loop and we have a timeout
492         * given, then we convert to ktime_t and set the to
493         * pointer to the expiry value.
494         */
495        if (end_time && !to) {
496            expire = timespec_to_ktime(*end_time);
497            to = &expire;
498        }
499
500        if (!poll_schedule_timeout(&table, TASK_INTERRUPTIBLE,
501                       to, slack))
502            timed_out = 1;
503    }
504
505    poll_freewait(&table);
506
507    return retval;
508}
509
510/*
511 * We can actually return ERESTARTSYS instead of EINTR, but I'd
512 * like to be certain this leads to no problems. So I return
513 * EINTR just for safety.
514 *
515 * Update: ERESTARTSYS breaks at least the xview clock binary, so
516 * I'm trying ERESTARTNOHAND which restart only when you want to.
517 */
518#define MAX_SELECT_SECONDS \
519    ((unsigned long) (MAX_SCHEDULE_TIMEOUT / HZ)-1)
520
521int core_sys_select(int n, fd_set __user *inp, fd_set __user *outp,
522               fd_set __user *exp, struct timespec *end_time)
523{
524    fd_set_bits fds;
525    void *bits;
526    int ret, max_fds;
527    unsigned int size;
528    struct fdtable *fdt;
529    /* Allocate small arguments on the stack to save memory and be faster */
530    long stack_fds[SELECT_STACK_ALLOC/sizeof(long)];
531
532    ret = -EINVAL;
533    if (n < 0)
534        goto out_nofds;
535
536    /* max_fds can increase, so grab it once to avoid race */
537    rcu_read_lock();
538    fdt = files_fdtable(current->files);
539    max_fds = fdt->max_fds;
540    rcu_read_unlock();
541    if (n > max_fds)
542        n = max_fds;
543
544    /*
545     * We need 6 bitmaps (in/out/ex for both incoming and outgoing),
546     * since we used fdset we need to allocate memory in units of
547     * long-words.
548     */
549    size = FDS_BYTES(n);
550    bits = stack_fds;
551    if (size > sizeof(stack_fds) / 6) {
552        /* Not enough space in on-stack array; must use kmalloc */
553        ret = -ENOMEM;
554        bits = kmalloc(6 * size, GFP_KERNEL);
555        if (!bits)
556            goto out_nofds;
557    }
558    fds.in = bits;
559    fds.out = bits + size;
560    fds.ex = bits + 2*size;
561    fds.res_in = bits + 3*size;
562    fds.res_out = bits + 4*size;
563    fds.res_ex = bits + 5*size;
564
565    if ((ret = get_fd_set(n, inp, fds.in)) ||
566        (ret = get_fd_set(n, outp, fds.out)) ||
567        (ret = get_fd_set(n, exp, fds.ex)))
568        goto out;
569    zero_fd_set(n, fds.res_in);
570    zero_fd_set(n, fds.res_out);
571    zero_fd_set(n, fds.res_ex);
572
573    ret = do_select(n, &fds, end_time);
574
575    if (ret < 0)
576        goto out;
577    if (!ret) {
578        ret = -ERESTARTNOHAND;
579        if (signal_pending(current))
580            goto out;
581        ret = 0;
582    }
583
584    if (set_fd_set(n, inp, fds.res_in) ||
585        set_fd_set(n, outp, fds.res_out) ||
586        set_fd_set(n, exp, fds.res_ex))
587        ret = -EFAULT;
588
589out:
590    if (bits != stack_fds)
591        kfree(bits);
592out_nofds:
593    return ret;
594}
595
596SYSCALL_DEFINE5(select, int, n, fd_set __user *, inp, fd_set __user *, outp,
597        fd_set __user *, exp, struct timeval __user *, tvp)
598{
599    struct timespec end_time, *to = NULL;
600    struct timeval tv;
601    int ret;
602
603    if (tvp) {
604        if (copy_from_user(&tv, tvp, sizeof(tv)))
605            return -EFAULT;
606
607        to = &end_time;
608        if (poll_select_set_timeout(to,
609                tv.tv_sec + (tv.tv_usec / USEC_PER_SEC),
610                (tv.tv_usec % USEC_PER_SEC) * NSEC_PER_USEC))
611            return -EINVAL;
612    }
613
614    ret = core_sys_select(n, inp, outp, exp, to);
615    ret = poll_select_copy_remaining(&end_time, tvp, 1, ret);
616
617    return ret;
618}
619
620#ifdef HAVE_SET_RESTORE_SIGMASK
621static long do_pselect(int n, fd_set __user *inp, fd_set __user *outp,
622               fd_set __user *exp, struct timespec __user *tsp,
623               const sigset_t __user *sigmask, size_t sigsetsize)
624{
625    sigset_t ksigmask, sigsaved;
626    struct timespec ts, end_time, *to = NULL;
627    int ret;
628
629    if (tsp) {
630        if (copy_from_user(&ts, tsp, sizeof(ts)))
631            return -EFAULT;
632
633        to = &end_time;
634        if (poll_select_set_timeout(to, ts.tv_sec, ts.tv_nsec))
635            return -EINVAL;
636    }
637
638    if (sigmask) {
639        /* XXX: Don't preclude handling different sized sigset_t's. */
640        if (sigsetsize != sizeof(sigset_t))
641            return -EINVAL;
642        if (copy_from_user(&ksigmask, sigmask, sizeof(ksigmask)))
643            return -EFAULT;
644
645        sigdelsetmask(&ksigmask, sigmask(SIGKILL)|sigmask(SIGSTOP));
646        sigprocmask(SIG_SETMASK, &ksigmask, &sigsaved);
647    }
648
649    ret = core_sys_select(n, inp, outp, exp, to);
650    ret = poll_select_copy_remaining(&end_time, tsp, 0, ret);
651
652    if (ret == -ERESTARTNOHAND) {
653        /*
654         * Don't restore the signal mask yet. Let do_signal() deliver
655         * the signal on the way back to userspace, before the signal
656         * mask is restored.
657         */
658        if (sigmask) {
659            memcpy(&current->saved_sigmask, &sigsaved,
660                    sizeof(sigsaved));
661            set_restore_sigmask();
662        }
663    } else if (sigmask)
664        sigprocmask(SIG_SETMASK, &sigsaved, NULL);
665
666    return ret;
667}
668
669/*
670 * Most architectures can't handle 7-argument syscalls. So we provide a
671 * 6-argument version where the sixth argument is a pointer to a structure
672 * which has a pointer to the sigset_t itself followed by a size_t containing
673 * the sigset size.
674 */
675SYSCALL_DEFINE6(pselect6, int, n, fd_set __user *, inp, fd_set __user *, outp,
676        fd_set __user *, exp, struct timespec __user *, tsp,
677        void __user *, sig)
678{
679    size_t sigsetsize = 0;
680    sigset_t __user *up = NULL;
681
682    if (sig) {
683        if (!access_ok(VERIFY_READ, sig, sizeof(void *)+sizeof(size_t))
684            || __get_user(up, (sigset_t __user * __user *)sig)
685            || __get_user(sigsetsize,
686                (size_t __user *)(sig+sizeof(void *))))
687            return -EFAULT;
688    }
689
690    return do_pselect(n, inp, outp, exp, tsp, up, sigsetsize);
691}
692#endif /* HAVE_SET_RESTORE_SIGMASK */
693
694#ifdef __ARCH_WANT_SYS_OLD_SELECT
695struct sel_arg_struct {
696    unsigned long n;
697    fd_set __user *inp, *outp, *exp;
698    struct timeval __user *tvp;
699};
700
701SYSCALL_DEFINE1(old_select, struct sel_arg_struct __user *, arg)
702{
703    struct sel_arg_struct a;
704
705    if (copy_from_user(&a, arg, sizeof(a)))
706        return -EFAULT;
707    return sys_select(a.n, a.inp, a.outp, a.exp, a.tvp);
708}
709#endif
710
711struct poll_list {
712    struct poll_list *next;
713    int len;
714    struct pollfd entries[0];
715};
716
717#define POLLFD_PER_PAGE ((PAGE_SIZE-sizeof(struct poll_list)) / sizeof(struct pollfd))
718
719/*
720 * Fish for pollable events on the pollfd->fd file descriptor. We're only
721 * interested in events matching the pollfd->events mask, and the result
722 * matching that mask is both recorded in pollfd->revents and returned. The
723 * pwait poll_table will be used by the fd-provided poll handler for waiting,
724 * if non-NULL.
725 */
726static inline unsigned int do_pollfd(struct pollfd *pollfd, poll_table *pwait)
727{
728    unsigned int mask;
729    int fd;
730
731    mask = 0;
732    fd = pollfd->fd;
733    if (fd >= 0) {
734        int fput_needed;
735        struct file * file;
736
737        file = fget_light(fd, &fput_needed);
738        mask = POLLNVAL;
739        if (file != NULL) {
740            mask = DEFAULT_POLLMASK;
741            if (file->f_op && file->f_op->poll) {
742                if (pwait)
743                    pwait->key = pollfd->events |
744                            POLLERR | POLLHUP;
745                mask = file->f_op->poll(file, pwait);
746            }
747            /* Mask out unneeded events. */
748            mask &= pollfd->events | POLLERR | POLLHUP;
749            fput_light(file, fput_needed);
750        }
751    }
752    pollfd->revents = mask;
753
754    return mask;
755}
756
757static int do_poll(unsigned int nfds, struct poll_list *list,
758           struct poll_wqueues *wait, struct timespec *end_time)
759{
760    poll_table* pt = &wait->pt;
761    ktime_t expire, *to = NULL;
762    int timed_out = 0, count = 0;
763    unsigned long slack = 0;
764
765    /* Optimise the no-wait case */
766    if (end_time && !end_time->tv_sec && !end_time->tv_nsec) {
767        pt = NULL;
768        timed_out = 1;
769    }
770
771    if (end_time && !timed_out)
772        slack = estimate_accuracy(end_time);
773
774    for (;;) {
775        struct poll_list *walk;
776
777        for (walk = list; walk != NULL; walk = walk->next) {
778            struct pollfd * pfd, * pfd_end;
779
780            pfd = walk->entries;
781            pfd_end = pfd + walk->len;
782            for (; pfd != pfd_end; pfd++) {
783                /*
784                 * Fish for events. If we found one, record it
785                 * and kill the poll_table, so we don't
786                 * needlessly register any other waiters after
787                 * this. They'll get immediately deregistered
788                 * when we break out and return.
789                 */
790                if (do_pollfd(pfd, pt)) {
791                    count++;
792                    pt = NULL;
793                }
794            }
795        }
796        /*
797         * All waiters have already been registered, so don't provide
798         * a poll_table to them on the next loop iteration.
799         */
800        pt = NULL;
801        if (!count) {
802            count = wait->error;
803            if (signal_pending(current))
804                count = -EINTR;
805        }
806        if (count || timed_out)
807            break;
808
809        /*
810         * If this is the first loop and we have a timeout
811         * given, then we convert to ktime_t and set the to
812         * pointer to the expiry value.
813         */
814        if (end_time && !to) {
815            expire = timespec_to_ktime(*end_time);
816            to = &expire;
817        }
818
819        if (!poll_schedule_timeout(wait, TASK_INTERRUPTIBLE, to, slack))
820            timed_out = 1;
821    }
822    return count;
823}
824
825#define N_STACK_PPS ((sizeof(stack_pps) - sizeof(struct poll_list)) / \
826            sizeof(struct pollfd))
827
828int do_sys_poll(struct pollfd __user *ufds, unsigned int nfds,
829        struct timespec *end_time)
830{
831    struct poll_wqueues table;
832     int err = -EFAULT, fdcount, len, size;
833    /* Allocate small arguments on the stack to save memory and be
834       faster - use long to make sure the buffer is aligned properly
835       on 64 bit archs to avoid unaligned access */
836    long stack_pps[POLL_STACK_ALLOC/sizeof(long)];
837    struct poll_list *const head = (struct poll_list *)stack_pps;
838     struct poll_list *walk = head;
839     unsigned long todo = nfds;
840
841    if (nfds > rlimit(RLIMIT_NOFILE))
842        return -EINVAL;
843
844    len = min_t(unsigned int, nfds, N_STACK_PPS);
845    for (;;) {
846        walk->next = NULL;
847        walk->len = len;
848        if (!len)
849            break;
850
851        if (copy_from_user(walk->entries, ufds + nfds-todo,
852                    sizeof(struct pollfd) * walk->len))
853            goto out_fds;
854
855        todo -= walk->len;
856        if (!todo)
857            break;
858
859        len = min(todo, POLLFD_PER_PAGE);
860        size = sizeof(struct poll_list) + sizeof(struct pollfd) * len;
861        walk = walk->next = kmalloc(size, GFP_KERNEL);
862        if (!walk) {
863            err = -ENOMEM;
864            goto out_fds;
865        }
866    }
867
868    poll_initwait(&table);
869    fdcount = do_poll(nfds, head, &table, end_time);
870    poll_freewait(&table);
871
872    for (walk = head; walk; walk = walk->next) {
873        struct pollfd *fds = walk->entries;
874        int j;
875
876        for (j = 0; j < walk->len; j++, ufds++)
877            if (__put_user(fds[j].revents, &ufds->revents))
878                goto out_fds;
879      }
880
881    err = fdcount;
882out_fds:
883    walk = head->next;
884    while (walk) {
885        struct poll_list *pos = walk;
886        walk = walk->next;
887        kfree(pos);
888    }
889
890    return err;
891}
892
893static long do_restart_poll(struct restart_block *restart_block)
894{
895    struct pollfd __user *ufds = restart_block->poll.ufds;
896    int nfds = restart_block->poll.nfds;
897    struct timespec *to = NULL, end_time;
898    int ret;
899
900    if (restart_block->poll.has_timeout) {
901        end_time.tv_sec = restart_block->poll.tv_sec;
902        end_time.tv_nsec = restart_block->poll.tv_nsec;
903        to = &end_time;
904    }
905
906    ret = do_sys_poll(ufds, nfds, to);
907
908    if (ret == -EINTR) {
909        restart_block->fn = do_restart_poll;
910        ret = -ERESTART_RESTARTBLOCK;
911    }
912    return ret;
913}
914
915SYSCALL_DEFINE3(poll, struct pollfd __user *, ufds, unsigned int, nfds,
916        long, timeout_msecs)
917{
918    struct timespec end_time, *to = NULL;
919    int ret;
920
921    if (timeout_msecs >= 0) {
922        to = &end_time;
923        poll_select_set_timeout(to, timeout_msecs / MSEC_PER_SEC,
924            NSEC_PER_MSEC * (timeout_msecs % MSEC_PER_SEC));
925    }
926
927    ret = do_sys_poll(ufds, nfds, to);
928
929    if (ret == -EINTR) {
930        struct restart_block *restart_block;
931
932        restart_block = &current_thread_info()->restart_block;
933        restart_block->fn = do_restart_poll;
934        restart_block->poll.ufds = ufds;
935        restart_block->poll.nfds = nfds;
936
937        if (timeout_msecs >= 0) {
938            restart_block->poll.tv_sec = end_time.tv_sec;
939            restart_block->poll.tv_nsec = end_time.tv_nsec;
940            restart_block->poll.has_timeout = 1;
941        } else
942            restart_block->poll.has_timeout = 0;
943
944        ret = -ERESTART_RESTARTBLOCK;
945    }
946    return ret;
947}
948
949#ifdef HAVE_SET_RESTORE_SIGMASK
950SYSCALL_DEFINE5(ppoll, struct pollfd __user *, ufds, unsigned int, nfds,
951        struct timespec __user *, tsp, const sigset_t __user *, sigmask,
952        size_t, sigsetsize)
953{
954    sigset_t ksigmask, sigsaved;
955    struct timespec ts, end_time, *to = NULL;
956    int ret;
957
958    if (tsp) {
959        if (copy_from_user(&ts, tsp, sizeof(ts)))
960            return -EFAULT;
961
962        to = &end_time;
963        if (poll_select_set_timeout(to, ts.tv_sec, ts.tv_nsec))
964            return -EINVAL;
965    }
966
967    if (sigmask) {
968        /* XXX: Don't preclude handling different sized sigset_t's. */
969        if (sigsetsize != sizeof(sigset_t))
970            return -EINVAL;
971        if (copy_from_user(&ksigmask, sigmask, sizeof(ksigmask)))
972            return -EFAULT;
973
974        sigdelsetmask(&ksigmask, sigmask(SIGKILL)|sigmask(SIGSTOP));
975        sigprocmask(SIG_SETMASK, &ksigmask, &sigsaved);
976    }
977
978    ret = do_sys_poll(ufds, nfds, to);
979
980    /* We can restart this syscall, usually */
981    if (ret == -EINTR) {
982        /*
983         * Don't restore the signal mask yet. Let do_signal() deliver
984         * the signal on the way back to userspace, before the signal
985         * mask is restored.
986         */
987        if (sigmask) {
988            memcpy(&current->saved_sigmask, &sigsaved,
989                    sizeof(sigsaved));
990            set_restore_sigmask();
991        }
992        ret = -ERESTARTNOHAND;
993    } else if (sigmask)
994        sigprocmask(SIG_SETMASK, &sigsaved, NULL);
995
996    ret = poll_select_copy_remaining(&end_time, tsp, 0, ret);
997
998    return ret;
999}
1000#endif /* HAVE_SET_RESTORE_SIGMASK */
1001

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