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 */