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
70long select_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        if (sizeof(rtv) > sizeof(rtv.tv_sec) + sizeof(rtv.tv_usec))
310            memset(&rtv, 0, sizeof(rtv));
311        rtv.tv_sec = rts.tv_sec;
312        rtv.tv_usec = rts.tv_nsec / NSEC_PER_USEC;
313
314        if (!copy_to_user(p, &rtv, sizeof(rtv)))
315            return ret;
316
317    } else if (!copy_to_user(p, &rts, sizeof(rts)))
318        return ret;
319
320    /*
321     * If an application puts its timeval in read-only memory, we
322     * don't want the Linux-specific update to the timeval to
323     * cause a fault after the select has completed
324     * successfully. However, because we're not updating the
325     * timeval, we can't restart the system call.
326     */
327
328sticky:
329    if (ret == -ERESTARTNOHAND)
330        ret = -EINTR;
331    return ret;
332}
333
334#define FDS_IN(fds, n) (fds->in + n)
335#define FDS_OUT(fds, n) (fds->out + n)
336#define FDS_EX(fds, n) (fds->ex + n)
337
338#define BITS(fds, n) (*FDS_IN(fds, n)|*FDS_OUT(fds, n)|*FDS_EX(fds, n))
339
340static int max_select_fd(unsigned long n, fd_set_bits *fds)
341{
342    unsigned long *open_fds;
343    unsigned long set;
344    int max;
345    struct fdtable *fdt;
346
347    /* handle last in-complete long-word first */
348    set = ~(~0UL << (n & (__NFDBITS-1)));
349    n /= __NFDBITS;
350    fdt = files_fdtable(current->files);
351    open_fds = fdt->open_fds->fds_bits+n;
352    max = 0;
353    if (set) {
354        set &= BITS(fds, n);
355        if (set) {
356            if (!(set & ~*open_fds))
357                goto get_max;
358            return -EBADF;
359        }
360    }
361    while (n) {
362        open_fds--;
363        n--;
364        set = BITS(fds, n);
365        if (!set)
366            continue;
367        if (set & ~*open_fds)
368            return -EBADF;
369        if (max)
370            continue;
371get_max:
372        do {
373            max++;
374            set >>= 1;
375        } while (set);
376        max += n * __NFDBITS;
377    }
378
379    return max;
380}
381
382#define POLLIN_SET (POLLRDNORM | POLLRDBAND | POLLIN | POLLHUP | POLLERR)
383#define POLLOUT_SET (POLLWRBAND | POLLWRNORM | POLLOUT | POLLERR)
384#define POLLEX_SET (POLLPRI)
385
386static inline void wait_key_set(poll_table *wait, unsigned long in,
387                unsigned long out, unsigned long bit)
388{
389    if (wait) {
390        wait->key = POLLEX_SET;
391        if (in & bit)
392            wait->key |= POLLIN_SET;
393        if (out & bit)
394            wait->key |= POLLOUT_SET;
395    }
396}
397
398int do_select(int n, fd_set_bits *fds, struct timespec *end_time)
399{
400    ktime_t expire, *to = NULL;
401    struct poll_wqueues table;
402    poll_table *wait;
403    int retval, i, timed_out = 0;
404    unsigned long slack = 0;
405
406    rcu_read_lock();
407    retval = max_select_fd(n, fds);
408    rcu_read_unlock();
409
410    if (retval < 0)
411        return retval;
412    n = retval;
413
414    poll_initwait(&table);
415    wait = &table.pt;
416    if (end_time && !end_time->tv_sec && !end_time->tv_nsec) {
417        wait = NULL;
418        timed_out = 1;
419    }
420
421    if (end_time && !timed_out)
422        slack = select_estimate_accuracy(end_time);
423
424    retval = 0;
425    for (;;) {
426        unsigned long *rinp, *routp, *rexp, *inp, *outp, *exp;
427
428        inp = fds->in; outp = fds->out; exp = fds->ex;
429        rinp = fds->res_in; routp = fds->res_out; rexp = fds->res_ex;
430
431        for (i = 0; i < n; ++rinp, ++routp, ++rexp) {
432            unsigned long in, out, ex, all_bits, bit = 1, mask, j;
433            unsigned long res_in = 0, res_out = 0, res_ex = 0;
434            const struct file_operations *f_op = NULL;
435            struct file *file = NULL;
436
437            in = *inp++; out = *outp++; ex = *exp++;
438            all_bits = in | out | ex;
439            if (all_bits == 0) {
440                i += __NFDBITS;
441                continue;
442            }
443
444            for (j = 0; j < __NFDBITS; ++j, ++i, bit <<= 1) {
445                int fput_needed;
446                if (i >= n)
447                    break;
448                if (!(bit & all_bits))
449                    continue;
450                file = fget_light(i, &fput_needed);
451                if (file) {
452                    f_op = file->f_op;
453                    mask = DEFAULT_POLLMASK;
454                    if (f_op && f_op->poll) {
455                        wait_key_set(wait, in, out, bit);
456                        mask = (*f_op->poll)(file, wait);
457                    }
458                    fput_light(file, fput_needed);
459                    if ((mask & POLLIN_SET) && (in & bit)) {
460                        res_in |= bit;
461                        retval++;
462                        wait = NULL;
463                    }
464                    if ((mask & POLLOUT_SET) && (out & bit)) {
465                        res_out |= bit;
466                        retval++;
467                        wait = NULL;
468                    }
469                    if ((mask & POLLEX_SET) && (ex & bit)) {
470                        res_ex |= bit;
471                        retval++;
472                        wait = NULL;
473                    }
474                }
475            }
476            if (res_in)
477                *rinp = res_in;
478            if (res_out)
479                *routp = res_out;
480            if (res_ex)
481                *rexp = res_ex;
482            cond_resched();
483        }
484        wait = NULL;
485        if (retval || timed_out || signal_pending(current))
486            break;
487        if (table.error) {
488            retval = table.error;
489            break;
490        }
491
492        /*
493         * If this is the first loop and we have a timeout
494         * given, then we convert to ktime_t and set the to
495         * pointer to the expiry value.
496         */
497        if (end_time && !to) {
498            expire = timespec_to_ktime(*end_time);
499            to = &expire;
500        }
501
502        if (!poll_schedule_timeout(&table, TASK_INTERRUPTIBLE,
503                       to, slack))
504            timed_out = 1;
505    }
506
507    poll_freewait(&table);
508
509    return retval;
510}
511
512/*
513 * We can actually return ERESTARTSYS instead of EINTR, but I'd
514 * like to be certain this leads to no problems. So I return
515 * EINTR just for safety.
516 *
517 * Update: ERESTARTSYS breaks at least the xview clock binary, so
518 * I'm trying ERESTARTNOHAND which restart only when you want to.
519 */
520int core_sys_select(int n, fd_set __user *inp, fd_set __user *outp,
521               fd_set __user *exp, struct timespec *end_time)
522{
523    fd_set_bits fds;
524    void *bits;
525    int ret, max_fds;
526    unsigned int size;
527    struct fdtable *fdt;
528    /* Allocate small arguments on the stack to save memory and be faster */
529    long stack_fds[SELECT_STACK_ALLOC/sizeof(long)];
530
531    ret = -EINVAL;
532    if (n < 0)
533        goto out_nofds;
534
535    /* max_fds can increase, so grab it once to avoid race */
536    rcu_read_lock();
537    fdt = files_fdtable(current->files);
538    max_fds = fdt->max_fds;
539    rcu_read_unlock();
540    if (n > max_fds)
541        n = max_fds;
542
543    /*
544     * We need 6 bitmaps (in/out/ex for both incoming and outgoing),
545     * since we used fdset we need to allocate memory in units of
546     * long-words.
547     */
548    size = FDS_BYTES(n);
549    bits = stack_fds;
550    if (size > sizeof(stack_fds) / 6) {
551        /* Not enough space in on-stack array; must use kmalloc */
552        ret = -ENOMEM;
553        bits = kmalloc(6 * size, GFP_KERNEL);
554        if (!bits)
555            goto out_nofds;
556    }
557    fds.in = bits;
558    fds.out = bits + size;
559    fds.ex = bits + 2*size;
560    fds.res_in = bits + 3*size;
561    fds.res_out = bits + 4*size;
562    fds.res_ex = bits + 5*size;
563
564    if ((ret = get_fd_set(n, inp, fds.in)) ||
565        (ret = get_fd_set(n, outp, fds.out)) ||
566        (ret = get_fd_set(n, exp, fds.ex)))
567        goto out;
568    zero_fd_set(n, fds.res_in);
569    zero_fd_set(n, fds.res_out);
570    zero_fd_set(n, fds.res_ex);
571
572    ret = do_select(n, &fds, end_time);
573
574    if (ret < 0)
575        goto out;
576    if (!ret) {
577        ret = -ERESTARTNOHAND;
578        if (signal_pending(current))
579            goto out;
580        ret = 0;
581    }
582
583    if (set_fd_set(n, inp, fds.res_in) ||
584        set_fd_set(n, outp, fds.res_out) ||
585        set_fd_set(n, exp, fds.res_ex))
586        ret = -EFAULT;
587
588out:
589    if (bits != stack_fds)
590        kfree(bits);
591out_nofds:
592    return ret;
593}
594
595SYSCALL_DEFINE5(select, int, n, fd_set __user *, inp, fd_set __user *, outp,
596        fd_set __user *, exp, struct timeval __user *, tvp)
597{
598    struct timespec end_time, *to = NULL;
599    struct timeval tv;
600    int ret;
601
602    if (tvp) {
603        if (copy_from_user(&tv, tvp, sizeof(tv)))
604            return -EFAULT;
605
606        to = &end_time;
607        if (poll_select_set_timeout(to,
608                tv.tv_sec + (tv.tv_usec / USEC_PER_SEC),
609                (tv.tv_usec % USEC_PER_SEC) * NSEC_PER_USEC))
610            return -EINVAL;
611    }
612
613    ret = core_sys_select(n, inp, outp, exp, to);
614    ret = poll_select_copy_remaining(&end_time, tvp, 1, ret);
615
616    return ret;
617}
618
619#ifdef HAVE_SET_RESTORE_SIGMASK
620static long do_pselect(int n, fd_set __user *inp, fd_set __user *outp,
621               fd_set __user *exp, struct timespec __user *tsp,
622               const sigset_t __user *sigmask, size_t sigsetsize)
623{
624    sigset_t ksigmask, sigsaved;
625    struct timespec ts, end_time, *to = NULL;
626    int ret;
627
628    if (tsp) {
629        if (copy_from_user(&ts, tsp, sizeof(ts)))
630            return -EFAULT;
631
632        to = &end_time;
633        if (poll_select_set_timeout(to, ts.tv_sec, ts.tv_nsec))
634            return -EINVAL;
635    }
636
637    if (sigmask) {
638        /* XXX: Don't preclude handling different sized sigset_t's. */
639        if (sigsetsize != sizeof(sigset_t))
640            return -EINVAL;
641        if (copy_from_user(&ksigmask, sigmask, sizeof(ksigmask)))
642            return -EFAULT;
643
644        sigdelsetmask(&ksigmask, sigmask(SIGKILL)|sigmask(SIGSTOP));
645        sigprocmask(SIG_SETMASK, &ksigmask, &sigsaved);
646    }
647
648    ret = core_sys_select(n, inp, outp, exp, to);
649    ret = poll_select_copy_remaining(&end_time, tsp, 0, ret);
650
651    if (ret == -ERESTARTNOHAND) {
652        /*
653         * Don't restore the signal mask yet. Let do_signal() deliver
654         * the signal on the way back to userspace, before the signal
655         * mask is restored.
656         */
657        if (sigmask) {
658            memcpy(&current->saved_sigmask, &sigsaved,
659                    sizeof(sigsaved));
660            set_restore_sigmask();
661        }
662    } else if (sigmask)
663        sigprocmask(SIG_SETMASK, &sigsaved, NULL);
664
665    return ret;
666}
667
668/*
669 * Most architectures can't handle 7-argument syscalls. So we provide a
670 * 6-argument version where the sixth argument is a pointer to a structure
671 * which has a pointer to the sigset_t itself followed by a size_t containing
672 * the sigset size.
673 */
674SYSCALL_DEFINE6(pselect6, int, n, fd_set __user *, inp, fd_set __user *, outp,
675        fd_set __user *, exp, struct timespec __user *, tsp,
676        void __user *, sig)
677{
678    size_t sigsetsize = 0;
679    sigset_t __user *up = NULL;
680
681    if (sig) {
682        if (!access_ok(VERIFY_READ, sig, sizeof(void *)+sizeof(size_t))
683            || __get_user(up, (sigset_t __user * __user *)sig)
684            || __get_user(sigsetsize,
685                (size_t __user *)(sig+sizeof(void *))))
686            return -EFAULT;
687    }
688
689    return do_pselect(n, inp, outp, exp, tsp, up, sigsetsize);
690}
691#endif /* HAVE_SET_RESTORE_SIGMASK */
692
693#ifdef __ARCH_WANT_SYS_OLD_SELECT
694struct sel_arg_struct {
695    unsigned long n;
696    fd_set __user *inp, *outp, *exp;
697    struct timeval __user *tvp;
698};
699
700SYSCALL_DEFINE1(old_select, struct sel_arg_struct __user *, arg)
701{
702    struct sel_arg_struct a;
703
704    if (copy_from_user(&a, arg, sizeof(a)))
705        return -EFAULT;
706    return sys_select(a.n, a.inp, a.outp, a.exp, a.tvp);
707}
708#endif
709
710struct poll_list {
711    struct poll_list *next;
712    int len;
713    struct pollfd entries[0];
714};
715
716#define POLLFD_PER_PAGE ((PAGE_SIZE-sizeof(struct poll_list)) / sizeof(struct pollfd))
717
718/*
719 * Fish for pollable events on the pollfd->fd file descriptor. We're only
720 * interested in events matching the pollfd->events mask, and the result
721 * matching that mask is both recorded in pollfd->revents and returned. The
722 * pwait poll_table will be used by the fd-provided poll handler for waiting,
723 * if non-NULL.
724 */
725static inline unsigned int do_pollfd(struct pollfd *pollfd, poll_table *pwait)
726{
727    unsigned int mask;
728    int fd;
729
730    mask = 0;
731    fd = pollfd->fd;
732    if (fd >= 0) {
733        int fput_needed;
734        struct file * file;
735
736        file = fget_light(fd, &fput_needed);
737        mask = POLLNVAL;
738        if (file != NULL) {
739            mask = DEFAULT_POLLMASK;
740            if (file->f_op && file->f_op->poll) {
741                if (pwait)
742                    pwait->key = pollfd->events |
743                            POLLERR | POLLHUP;
744                mask = file->f_op->poll(file, pwait);
745            }
746            /* Mask out unneeded events. */
747            mask &= pollfd->events | POLLERR | POLLHUP;
748            fput_light(file, fput_needed);
749        }
750    }
751    pollfd->revents = mask;
752
753    return mask;
754}
755
756static int do_poll(unsigned int nfds, struct poll_list *list,
757           struct poll_wqueues *wait, struct timespec *end_time)
758{
759    poll_table* pt = &wait->pt;
760    ktime_t expire, *to = NULL;
761    int timed_out = 0, count = 0;
762    unsigned long slack = 0;
763
764    /* Optimise the no-wait case */
765    if (end_time && !end_time->tv_sec && !end_time->tv_nsec) {
766        pt = NULL;
767        timed_out = 1;
768    }
769
770    if (end_time && !timed_out)
771        slack = select_estimate_accuracy(end_time);
772
773    for (;;) {
774        struct poll_list *walk;
775
776        for (walk = list; walk != NULL; walk = walk->next) {
777            struct pollfd * pfd, * pfd_end;
778
779            pfd = walk->entries;
780            pfd_end = pfd + walk->len;
781            for (; pfd != pfd_end; pfd++) {
782                /*
783                 * Fish for events. If we found one, record it
784                 * and kill the poll_table, so we don't
785                 * needlessly register any other waiters after
786                 * this. They'll get immediately deregistered
787                 * when we break out and return.
788                 */
789                if (do_pollfd(pfd, pt)) {
790                    count++;
791                    pt = NULL;
792                }
793            }
794        }
795        /*
796         * All waiters have already been registered, so don't provide
797         * a poll_table to them on the next loop iteration.
798         */
799        pt = NULL;
800        if (!count) {
801            count = wait->error;
802            if (signal_pending(current))
803                count = -EINTR;
804        }
805        if (count || timed_out)
806            break;
807
808        /*
809         * If this is the first loop and we have a timeout
810         * given, then we convert to ktime_t and set the to
811         * pointer to the expiry value.
812         */
813        if (end_time && !to) {
814            expire = timespec_to_ktime(*end_time);
815            to = &expire;
816        }
817
818        if (!poll_schedule_timeout(wait, TASK_INTERRUPTIBLE, to, slack))
819            timed_out = 1;
820    }
821    return count;
822}
823
824#define N_STACK_PPS ((sizeof(stack_pps) - sizeof(struct poll_list)) / \
825            sizeof(struct pollfd))
826
827int do_sys_poll(struct pollfd __user *ufds, unsigned int nfds,
828        struct timespec *end_time)
829{
830    struct poll_wqueues table;
831     int err = -EFAULT, fdcount, len, size;
832    /* Allocate small arguments on the stack to save memory and be
833       faster - use long to make sure the buffer is aligned properly
834       on 64 bit archs to avoid unaligned access */
835    long stack_pps[POLL_STACK_ALLOC/sizeof(long)];
836    struct poll_list *const head = (struct poll_list *)stack_pps;
837     struct poll_list *walk = head;
838     unsigned long todo = nfds;
839
840    if (nfds > rlimit(RLIMIT_NOFILE))
841        return -EINVAL;
842
843    len = min_t(unsigned int, nfds, N_STACK_PPS);
844    for (;;) {
845        walk->next = NULL;
846        walk->len = len;
847        if (!len)
848            break;
849
850        if (copy_from_user(walk->entries, ufds + nfds-todo,
851                    sizeof(struct pollfd) * walk->len))
852            goto out_fds;
853
854        todo -= walk->len;
855        if (!todo)
856            break;
857
858        len = min(todo, POLLFD_PER_PAGE);
859        size = sizeof(struct poll_list) + sizeof(struct pollfd) * len;
860        walk = walk->next = kmalloc(size, GFP_KERNEL);
861        if (!walk) {
862            err = -ENOMEM;
863            goto out_fds;
864        }
865    }
866
867    poll_initwait(&table);
868    fdcount = do_poll(nfds, head, &table, end_time);
869    poll_freewait(&table);
870
871    for (walk = head; walk; walk = walk->next) {
872        struct pollfd *fds = walk->entries;
873        int j;
874
875        for (j = 0; j < walk->len; j++, ufds++)
876            if (__put_user(fds[j].revents, &ufds->revents))
877                goto out_fds;
878      }
879
880    err = fdcount;
881out_fds:
882    walk = head->next;
883    while (walk) {
884        struct poll_list *pos = walk;
885        walk = walk->next;
886        kfree(pos);
887    }
888
889    return err;
890}
891
892static long do_restart_poll(struct restart_block *restart_block)
893{
894    struct pollfd __user *ufds = restart_block->poll.ufds;
895    int nfds = restart_block->poll.nfds;
896    struct timespec *to = NULL, end_time;
897    int ret;
898
899    if (restart_block->poll.has_timeout) {
900        end_time.tv_sec = restart_block->poll.tv_sec;
901        end_time.tv_nsec = restart_block->poll.tv_nsec;
902        to = &end_time;
903    }
904
905    ret = do_sys_poll(ufds, nfds, to);
906
907    if (ret == -EINTR) {
908        restart_block->fn = do_restart_poll;
909        ret = -ERESTART_RESTARTBLOCK;
910    }
911    return ret;
912}
913
914SYSCALL_DEFINE3(poll, struct pollfd __user *, ufds, unsigned int, nfds,
915        long, timeout_msecs)
916{
917    struct timespec end_time, *to = NULL;
918    int ret;
919
920    if (timeout_msecs >= 0) {
921        to = &end_time;
922        poll_select_set_timeout(to, timeout_msecs / MSEC_PER_SEC,
923            NSEC_PER_MSEC * (timeout_msecs % MSEC_PER_SEC));
924    }
925
926    ret = do_sys_poll(ufds, nfds, to);
927
928    if (ret == -EINTR) {
929        struct restart_block *restart_block;
930
931        restart_block = &current_thread_info()->restart_block;
932        restart_block->fn = do_restart_poll;
933        restart_block->poll.ufds = ufds;
934        restart_block->poll.nfds = nfds;
935
936        if (timeout_msecs >= 0) {
937            restart_block->poll.tv_sec = end_time.tv_sec;
938            restart_block->poll.tv_nsec = end_time.tv_nsec;
939            restart_block->poll.has_timeout = 1;
940        } else
941            restart_block->poll.has_timeout = 0;
942
943        ret = -ERESTART_RESTARTBLOCK;
944    }
945    return ret;
946}
947
948#ifdef HAVE_SET_RESTORE_SIGMASK
949SYSCALL_DEFINE5(ppoll, struct pollfd __user *, ufds, unsigned int, nfds,
950        struct timespec __user *, tsp, const sigset_t __user *, sigmask,
951        size_t, sigsetsize)
952{
953    sigset_t ksigmask, sigsaved;
954    struct timespec ts, end_time, *to = NULL;
955    int ret;
956
957    if (tsp) {
958        if (copy_from_user(&ts, tsp, sizeof(ts)))
959            return -EFAULT;
960
961        to = &end_time;
962        if (poll_select_set_timeout(to, ts.tv_sec, ts.tv_nsec))
963            return -EINVAL;
964    }
965
966    if (sigmask) {
967        /* XXX: Don't preclude handling different sized sigset_t's. */
968        if (sigsetsize != sizeof(sigset_t))
969            return -EINVAL;
970        if (copy_from_user(&ksigmask, sigmask, sizeof(ksigmask)))
971            return -EFAULT;
972
973        sigdelsetmask(&ksigmask, sigmask(SIGKILL)|sigmask(SIGSTOP));
974        sigprocmask(SIG_SETMASK, &ksigmask, &sigsaved);
975    }
976
977    ret = do_sys_poll(ufds, nfds, to);
978
979    /* We can restart this syscall, usually */
980    if (ret == -EINTR) {
981        /*
982         * Don't restore the signal mask yet. Let do_signal() deliver
983         * the signal on the way back to userspace, before the signal
984         * mask is restored.
985         */
986        if (sigmask) {
987            memcpy(&current->saved_sigmask, &sigsaved,
988                    sizeof(sigsaved));
989            set_restore_sigmask();
990        }
991        ret = -ERESTARTNOHAND;
992    } else if (sigmask)
993        sigprocmask(SIG_SETMASK, &sigsaved, NULL);
994
995    ret = poll_select_copy_remaining(&end_time, tsp, 0, ret);
996
997    return ret;
998}
999#endif /* HAVE_SET_RESTORE_SIGMASK */
1000

Archive Download this file



interactive