xref: /openbmc/linux/fs/select.c (revision d5cb9783536a41df9f9cba5b0a1d78047ed787f7)
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/syscalls.h>
18 #include <linux/module.h>
19 #include <linux/slab.h>
20 #include <linux/smp_lock.h>
21 #include <linux/poll.h>
22 #include <linux/personality.h> /* for STICKY_TIMEOUTS */
23 #include <linux/file.h>
24 #include <linux/fs.h>
25 #include <linux/rcupdate.h>
26 
27 #include <asm/uaccess.h>
28 
29 #define ROUND_UP(x,y) (((x)+(y)-1)/(y))
30 #define DEFAULT_POLLMASK (POLLIN | POLLOUT | POLLRDNORM | POLLWRNORM)
31 
32 struct poll_table_entry {
33 	struct file * filp;
34 	wait_queue_t wait;
35 	wait_queue_head_t * wait_address;
36 };
37 
38 struct poll_table_page {
39 	struct poll_table_page * next;
40 	struct poll_table_entry * entry;
41 	struct poll_table_entry entries[0];
42 };
43 
44 #define POLL_TABLE_FULL(table) \
45 	((unsigned long)((table)->entry+1) > PAGE_SIZE + (unsigned long)(table))
46 
47 /*
48  * Ok, Peter made a complicated, but straightforward multiple_wait() function.
49  * I have rewritten this, taking some shortcuts: This code may not be easy to
50  * follow, but it should be free of race-conditions, and it's practical. If you
51  * understand what I'm doing here, then you understand how the linux
52  * sleep/wakeup mechanism works.
53  *
54  * Two very simple procedures, poll_wait() and poll_freewait() make all the
55  * work.  poll_wait() is an inline-function defined in <linux/poll.h>,
56  * as all select/poll functions have to call it to add an entry to the
57  * poll table.
58  */
59 static void __pollwait(struct file *filp, wait_queue_head_t *wait_address,
60 		       poll_table *p);
61 
62 void poll_initwait(struct poll_wqueues *pwq)
63 {
64 	init_poll_funcptr(&pwq->pt, __pollwait);
65 	pwq->error = 0;
66 	pwq->table = NULL;
67 }
68 
69 EXPORT_SYMBOL(poll_initwait);
70 
71 void poll_freewait(struct poll_wqueues *pwq)
72 {
73 	struct poll_table_page * p = pwq->table;
74 	while (p) {
75 		struct poll_table_entry * entry;
76 		struct poll_table_page *old;
77 
78 		entry = p->entry;
79 		do {
80 			entry--;
81 			remove_wait_queue(entry->wait_address,&entry->wait);
82 			fput(entry->filp);
83 		} while (entry > p->entries);
84 		old = p;
85 		p = p->next;
86 		free_page((unsigned long) old);
87 	}
88 }
89 
90 EXPORT_SYMBOL(poll_freewait);
91 
92 static void __pollwait(struct file *filp, wait_queue_head_t *wait_address,
93 		       poll_table *_p)
94 {
95 	struct poll_wqueues *p = container_of(_p, struct poll_wqueues, pt);
96 	struct poll_table_page *table = p->table;
97 
98 	if (!table || POLL_TABLE_FULL(table)) {
99 		struct poll_table_page *new_table;
100 
101 		new_table = (struct poll_table_page *) __get_free_page(GFP_KERNEL);
102 		if (!new_table) {
103 			p->error = -ENOMEM;
104 			__set_current_state(TASK_RUNNING);
105 			return;
106 		}
107 		new_table->entry = new_table->entries;
108 		new_table->next = table;
109 		p->table = new_table;
110 		table = new_table;
111 	}
112 
113 	/* Add a new entry */
114 	{
115 		struct poll_table_entry * entry = table->entry;
116 		table->entry = entry+1;
117 	 	get_file(filp);
118 	 	entry->filp = filp;
119 		entry->wait_address = wait_address;
120 		init_waitqueue_entry(&entry->wait, current);
121 		add_wait_queue(wait_address,&entry->wait);
122 	}
123 }
124 
125 #define FDS_IN(fds, n)		(fds->in + n)
126 #define FDS_OUT(fds, n)		(fds->out + n)
127 #define FDS_EX(fds, n)		(fds->ex + n)
128 
129 #define BITS(fds, n)	(*FDS_IN(fds, n)|*FDS_OUT(fds, n)|*FDS_EX(fds, n))
130 
131 static int max_select_fd(unsigned long n, fd_set_bits *fds)
132 {
133 	unsigned long *open_fds;
134 	unsigned long set;
135 	int max;
136 	struct fdtable *fdt;
137 
138 	/* handle last in-complete long-word first */
139 	set = ~(~0UL << (n & (__NFDBITS-1)));
140 	n /= __NFDBITS;
141 	fdt = files_fdtable(current->files);
142 	open_fds = fdt->open_fds->fds_bits+n;
143 	max = 0;
144 	if (set) {
145 		set &= BITS(fds, n);
146 		if (set) {
147 			if (!(set & ~*open_fds))
148 				goto get_max;
149 			return -EBADF;
150 		}
151 	}
152 	while (n) {
153 		open_fds--;
154 		n--;
155 		set = BITS(fds, n);
156 		if (!set)
157 			continue;
158 		if (set & ~*open_fds)
159 			return -EBADF;
160 		if (max)
161 			continue;
162 get_max:
163 		do {
164 			max++;
165 			set >>= 1;
166 		} while (set);
167 		max += n * __NFDBITS;
168 	}
169 
170 	return max;
171 }
172 
173 #define BIT(i)		(1UL << ((i)&(__NFDBITS-1)))
174 #define MEM(i,m)	((m)+(unsigned)(i)/__NFDBITS)
175 #define ISSET(i,m)	(((i)&*(m)) != 0)
176 #define SET(i,m)	(*(m) |= (i))
177 
178 #define POLLIN_SET (POLLRDNORM | POLLRDBAND | POLLIN | POLLHUP | POLLERR)
179 #define POLLOUT_SET (POLLWRBAND | POLLWRNORM | POLLOUT | POLLERR)
180 #define POLLEX_SET (POLLPRI)
181 
182 int do_select(int n, fd_set_bits *fds, long *timeout)
183 {
184 	struct poll_wqueues table;
185 	poll_table *wait;
186 	int retval, i;
187 	long __timeout = *timeout;
188 
189 	rcu_read_lock();
190 	retval = max_select_fd(n, fds);
191 	rcu_read_unlock();
192 
193 	if (retval < 0)
194 		return retval;
195 	n = retval;
196 
197 	poll_initwait(&table);
198 	wait = &table.pt;
199 	if (!__timeout)
200 		wait = NULL;
201 	retval = 0;
202 	for (;;) {
203 		unsigned long *rinp, *routp, *rexp, *inp, *outp, *exp;
204 
205 		set_current_state(TASK_INTERRUPTIBLE);
206 
207 		inp = fds->in; outp = fds->out; exp = fds->ex;
208 		rinp = fds->res_in; routp = fds->res_out; rexp = fds->res_ex;
209 
210 		for (i = 0; i < n; ++rinp, ++routp, ++rexp) {
211 			unsigned long in, out, ex, all_bits, bit = 1, mask, j;
212 			unsigned long res_in = 0, res_out = 0, res_ex = 0;
213 			struct file_operations *f_op = NULL;
214 			struct file *file = NULL;
215 
216 			in = *inp++; out = *outp++; ex = *exp++;
217 			all_bits = in | out | ex;
218 			if (all_bits == 0) {
219 				i += __NFDBITS;
220 				continue;
221 			}
222 
223 			for (j = 0; j < __NFDBITS; ++j, ++i, bit <<= 1) {
224 				if (i >= n)
225 					break;
226 				if (!(bit & all_bits))
227 					continue;
228 				file = fget(i);
229 				if (file) {
230 					f_op = file->f_op;
231 					mask = DEFAULT_POLLMASK;
232 					if (f_op && f_op->poll)
233 						mask = (*f_op->poll)(file, retval ? NULL : wait);
234 					fput(file);
235 					if ((mask & POLLIN_SET) && (in & bit)) {
236 						res_in |= bit;
237 						retval++;
238 					}
239 					if ((mask & POLLOUT_SET) && (out & bit)) {
240 						res_out |= bit;
241 						retval++;
242 					}
243 					if ((mask & POLLEX_SET) && (ex & bit)) {
244 						res_ex |= bit;
245 						retval++;
246 					}
247 				}
248 				cond_resched();
249 			}
250 			if (res_in)
251 				*rinp = res_in;
252 			if (res_out)
253 				*routp = res_out;
254 			if (res_ex)
255 				*rexp = res_ex;
256 		}
257 		wait = NULL;
258 		if (retval || !__timeout || signal_pending(current))
259 			break;
260 		if(table.error) {
261 			retval = table.error;
262 			break;
263 		}
264 		__timeout = schedule_timeout(__timeout);
265 	}
266 	__set_current_state(TASK_RUNNING);
267 
268 	poll_freewait(&table);
269 
270 	/*
271 	 * Up-to-date the caller timeout.
272 	 */
273 	*timeout = __timeout;
274 	return retval;
275 }
276 
277 static void *select_bits_alloc(int size)
278 {
279 	return kmalloc(6 * size, GFP_KERNEL);
280 }
281 
282 static void select_bits_free(void *bits, int size)
283 {
284 	kfree(bits);
285 }
286 
287 /*
288  * We can actually return ERESTARTSYS instead of EINTR, but I'd
289  * like to be certain this leads to no problems. So I return
290  * EINTR just for safety.
291  *
292  * Update: ERESTARTSYS breaks at least the xview clock binary, so
293  * I'm trying ERESTARTNOHAND which restart only when you want to.
294  */
295 #define MAX_SELECT_SECONDS \
296 	((unsigned long) (MAX_SCHEDULE_TIMEOUT / HZ)-1)
297 
298 asmlinkage long
299 sys_select(int n, fd_set __user *inp, fd_set __user *outp, fd_set __user *exp, struct timeval __user *tvp)
300 {
301 	fd_set_bits fds;
302 	char *bits;
303 	long timeout;
304 	int ret, size, max_fdset;
305 	struct fdtable *fdt;
306 
307 	timeout = MAX_SCHEDULE_TIMEOUT;
308 	if (tvp) {
309 		time_t sec, usec;
310 
311 		if (!access_ok(VERIFY_READ, tvp, sizeof(*tvp))
312 		    || __get_user(sec, &tvp->tv_sec)
313 		    || __get_user(usec, &tvp->tv_usec)) {
314 			ret = -EFAULT;
315 			goto out_nofds;
316 		}
317 
318 		ret = -EINVAL;
319 		if (sec < 0 || usec < 0)
320 			goto out_nofds;
321 
322 		if ((unsigned long) sec < MAX_SELECT_SECONDS) {
323 			timeout = ROUND_UP(usec, 1000000/HZ);
324 			timeout += sec * (unsigned long) HZ;
325 		}
326 	}
327 
328 	ret = -EINVAL;
329 	if (n < 0)
330 		goto out_nofds;
331 
332 	/* max_fdset can increase, so grab it once to avoid race */
333 	rcu_read_lock();
334 	fdt = files_fdtable(current->files);
335 	max_fdset = fdt->max_fdset;
336 	rcu_read_unlock();
337 	if (n > max_fdset)
338 		n = max_fdset;
339 
340 	/*
341 	 * We need 6 bitmaps (in/out/ex for both incoming and outgoing),
342 	 * since we used fdset we need to allocate memory in units of
343 	 * long-words.
344 	 */
345 	ret = -ENOMEM;
346 	size = FDS_BYTES(n);
347 	bits = select_bits_alloc(size);
348 	if (!bits)
349 		goto out_nofds;
350 	fds.in      = (unsigned long *)  bits;
351 	fds.out     = (unsigned long *) (bits +   size);
352 	fds.ex      = (unsigned long *) (bits + 2*size);
353 	fds.res_in  = (unsigned long *) (bits + 3*size);
354 	fds.res_out = (unsigned long *) (bits + 4*size);
355 	fds.res_ex  = (unsigned long *) (bits + 5*size);
356 
357 	if ((ret = get_fd_set(n, inp, fds.in)) ||
358 	    (ret = get_fd_set(n, outp, fds.out)) ||
359 	    (ret = get_fd_set(n, exp, fds.ex)))
360 		goto out;
361 	zero_fd_set(n, fds.res_in);
362 	zero_fd_set(n, fds.res_out);
363 	zero_fd_set(n, fds.res_ex);
364 
365 	ret = do_select(n, &fds, &timeout);
366 
367 	if (tvp && !(current->personality & STICKY_TIMEOUTS)) {
368 		time_t sec = 0, usec = 0;
369 		if (timeout) {
370 			sec = timeout / HZ;
371 			usec = timeout % HZ;
372 			usec *= (1000000/HZ);
373 		}
374 		put_user(sec, &tvp->tv_sec);
375 		put_user(usec, &tvp->tv_usec);
376 	}
377 
378 	if (ret < 0)
379 		goto out;
380 	if (!ret) {
381 		ret = -ERESTARTNOHAND;
382 		if (signal_pending(current))
383 			goto out;
384 		ret = 0;
385 	}
386 
387 	if (set_fd_set(n, inp, fds.res_in) ||
388 	    set_fd_set(n, outp, fds.res_out) ||
389 	    set_fd_set(n, exp, fds.res_ex))
390 		ret = -EFAULT;
391 
392 out:
393 	select_bits_free(bits, size);
394 out_nofds:
395 	return ret;
396 }
397 
398 struct poll_list {
399 	struct poll_list *next;
400 	int len;
401 	struct pollfd entries[0];
402 };
403 
404 #define POLLFD_PER_PAGE  ((PAGE_SIZE-sizeof(struct poll_list)) / sizeof(struct pollfd))
405 
406 static void do_pollfd(unsigned int num, struct pollfd * fdpage,
407 	poll_table ** pwait, int *count)
408 {
409 	int i;
410 
411 	for (i = 0; i < num; i++) {
412 		int fd;
413 		unsigned int mask;
414 		struct pollfd *fdp;
415 
416 		mask = 0;
417 		fdp = fdpage+i;
418 		fd = fdp->fd;
419 		if (fd >= 0) {
420 			struct file * file = fget(fd);
421 			mask = POLLNVAL;
422 			if (file != NULL) {
423 				mask = DEFAULT_POLLMASK;
424 				if (file->f_op && file->f_op->poll)
425 					mask = file->f_op->poll(file, *pwait);
426 				mask &= fdp->events | POLLERR | POLLHUP;
427 				fput(file);
428 			}
429 			if (mask) {
430 				*pwait = NULL;
431 				(*count)++;
432 			}
433 		}
434 		fdp->revents = mask;
435 	}
436 }
437 
438 static int do_poll(unsigned int nfds,  struct poll_list *list,
439 			struct poll_wqueues *wait, long timeout)
440 {
441 	int count = 0;
442 	poll_table* pt = &wait->pt;
443 
444 	if (!timeout)
445 		pt = NULL;
446 
447 	for (;;) {
448 		struct poll_list *walk;
449 		set_current_state(TASK_INTERRUPTIBLE);
450 		walk = list;
451 		while(walk != NULL) {
452 			do_pollfd( walk->len, walk->entries, &pt, &count);
453 			walk = walk->next;
454 		}
455 		pt = NULL;
456 		if (count || !timeout || signal_pending(current))
457 			break;
458 		count = wait->error;
459 		if (count)
460 			break;
461 		timeout = schedule_timeout(timeout);
462 	}
463 	__set_current_state(TASK_RUNNING);
464 	return count;
465 }
466 
467 asmlinkage long sys_poll(struct pollfd __user * ufds, unsigned int nfds, long timeout)
468 {
469 	struct poll_wqueues table;
470  	int fdcount, err;
471  	unsigned int i;
472 	struct poll_list *head;
473  	struct poll_list *walk;
474 	struct fdtable *fdt;
475 	int max_fdset;
476 
477 	/* Do a sanity check on nfds ... */
478 	rcu_read_lock();
479 	fdt = files_fdtable(current->files);
480 	max_fdset = fdt->max_fdset;
481 	rcu_read_unlock();
482 	if (nfds > max_fdset && nfds > OPEN_MAX)
483 		return -EINVAL;
484 
485 	if (timeout) {
486 		/* Careful about overflow in the intermediate values */
487 		if ((unsigned long) timeout < MAX_SCHEDULE_TIMEOUT / HZ)
488 			timeout = (unsigned long)(timeout*HZ+999)/1000+1;
489 		else /* Negative or overflow */
490 			timeout = MAX_SCHEDULE_TIMEOUT;
491 	}
492 
493 	poll_initwait(&table);
494 
495 	head = NULL;
496 	walk = NULL;
497 	i = nfds;
498 	err = -ENOMEM;
499 	while(i!=0) {
500 		struct poll_list *pp;
501 		pp = kmalloc(sizeof(struct poll_list)+
502 				sizeof(struct pollfd)*
503 				(i>POLLFD_PER_PAGE?POLLFD_PER_PAGE:i),
504 					GFP_KERNEL);
505 		if(pp==NULL)
506 			goto out_fds;
507 		pp->next=NULL;
508 		pp->len = (i>POLLFD_PER_PAGE?POLLFD_PER_PAGE:i);
509 		if (head == NULL)
510 			head = pp;
511 		else
512 			walk->next = pp;
513 
514 		walk = pp;
515 		if (copy_from_user(pp->entries, ufds + nfds-i,
516 				sizeof(struct pollfd)*pp->len)) {
517 			err = -EFAULT;
518 			goto out_fds;
519 		}
520 		i -= pp->len;
521 	}
522 	fdcount = do_poll(nfds, head, &table, timeout);
523 
524 	/* OK, now copy the revents fields back to user space. */
525 	walk = head;
526 	err = -EFAULT;
527 	while(walk != NULL) {
528 		struct pollfd *fds = walk->entries;
529 		int j;
530 
531 		for (j=0; j < walk->len; j++, ufds++) {
532 			if(__put_user(fds[j].revents, &ufds->revents))
533 				goto out_fds;
534 		}
535 		walk = walk->next;
536   	}
537 	err = fdcount;
538 	if (!fdcount && signal_pending(current))
539 		err = -EINTR;
540 out_fds:
541 	walk = head;
542 	while(walk!=NULL) {
543 		struct poll_list *pp = walk->next;
544 		kfree(walk);
545 		walk = pp;
546 	}
547 	poll_freewait(&table);
548 	return err;
549 }
550