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/slab.h>
18 #include <linux/smp_lock.h>
19 #include <linux/poll.h>
20 #include <linux/personality.h> /* for STICKY_TIMEOUTS */
21 #include <linux/file.h>
22
23 #include <asm/uaccess.h>
24
25 #define ROUND_UP(x,y) (((x)+(y)-1)/(y))
26 #define DEFAULT_POLLMASK (POLLIN | POLLOUT | POLLRDNORM | POLLWRNORM)
27
28 struct poll_table_entry {
29 struct file * filp;
30 wait_queue_t wait;
31 wait_queue_head_t * wait_address;
32 };
33
34 struct poll_table_page {
35 struct poll_table_page * next;
36 struct poll_table_entry * entry;
37 struct poll_table_entry entries[0];
38 };
39
40 #define POLL_TABLE_FULL(table) \
41 ((unsigned long)((table)->entry+1) > PAGE_SIZE + (unsigned long)(table))
42
43 /*
44 * Ok, Peter made a complicated, but straightforward multiple_wait() function.
45 * I have rewritten this, taking some shortcuts: This code may not be easy to
46 * follow, but it should be free of race-conditions, and it's practical. If you
47 * understand what I'm doing here, then you understand how the linux
48 * sleep/wakeup mechanism works.
49 *
50 * Two very simple procedures, poll_wait() and poll_freewait() make all the
51 * work. poll_wait() is an inline-function defined in <linux/poll.h>,
52 * as all select/poll functions have to call it to add an entry to the
53 * poll table.
54 */
55
poll_freewait(poll_table * pt)56 void poll_freewait(poll_table* pt)
57 {
58 struct poll_table_page * p = pt->table;
59 while (p) {
60 struct poll_table_entry * entry;
61 struct poll_table_page *old;
62
63 entry = p->entry;
64 do {
65 entry--;
66 remove_wait_queue(entry->wait_address,&entry->wait);
67 fput(entry->filp);
68 } while (entry > p->entries);
69 old = p;
70 p = p->next;
71 free_page((unsigned long) old);
72 }
73 }
74
__pollwait(struct file * filp,wait_queue_head_t * wait_address,poll_table * p)75 void __pollwait(struct file * filp, wait_queue_head_t * wait_address, poll_table *p)
76 {
77 struct poll_table_page *table = p->table;
78
79 if (!table || POLL_TABLE_FULL(table)) {
80 struct poll_table_page *new_table;
81
82 new_table = (struct poll_table_page *) __get_free_page(GFP_KERNEL);
83 if (!new_table) {
84 p->error = -ENOMEM;
85 __set_current_state(TASK_RUNNING);
86 return;
87 }
88 new_table->entry = new_table->entries;
89 new_table->next = table;
90 p->table = new_table;
91 table = new_table;
92 }
93
94 /* Add a new entry */
95 {
96 struct poll_table_entry * entry = table->entry;
97 table->entry = entry+1;
98 get_file(filp);
99 entry->filp = filp;
100 entry->wait_address = wait_address;
101 init_waitqueue_entry(&entry->wait, current);
102 add_wait_queue(wait_address,&entry->wait);
103 }
104 }
105
106 #define __IN(fds, n) (fds->in + n)
107 #define __OUT(fds, n) (fds->out + n)
108 #define __EX(fds, n) (fds->ex + n)
109 #define __RES_IN(fds, n) (fds->res_in + n)
110 #define __RES_OUT(fds, n) (fds->res_out + n)
111 #define __RES_EX(fds, n) (fds->res_ex + n)
112
113 #define BITS(fds, n) (*__IN(fds, n)|*__OUT(fds, n)|*__EX(fds, n))
114
max_select_fd(unsigned long n,fd_set_bits * fds)115 static int max_select_fd(unsigned long n, fd_set_bits *fds)
116 {
117 unsigned long *open_fds;
118 unsigned long set;
119 int max;
120
121 /* handle last in-complete long-word first */
122 set = ~(~0UL << (n & (__NFDBITS-1)));
123 n /= __NFDBITS;
124 open_fds = current->files->open_fds->fds_bits+n;
125 max = 0;
126 if (set) {
127 set &= BITS(fds, n);
128 if (set) {
129 if (!(set & ~*open_fds))
130 goto get_max;
131 return -EBADF;
132 }
133 }
134 while (n) {
135 open_fds--;
136 n--;
137 set = BITS(fds, n);
138 if (!set)
139 continue;
140 if (set & ~*open_fds)
141 return -EBADF;
142 if (max)
143 continue;
144 get_max:
145 do {
146 max++;
147 set >>= 1;
148 } while (set);
149 max += n * __NFDBITS;
150 }
151
152 return max;
153 }
154
155 #define BIT(i) (1UL << ((i)&(__NFDBITS-1)))
156 #define MEM(i,m) ((m)+(unsigned)(i)/__NFDBITS)
157 #define ISSET(i,m) (((i)&*(m)) != 0)
158 #define SET(i,m) (*(m) |= (i))
159
160 #define POLLIN_SET (POLLRDNORM | POLLRDBAND | POLLIN | POLLHUP | POLLERR)
161 #define POLLOUT_SET (POLLWRBAND | POLLWRNORM | POLLOUT | POLLERR)
162 #define POLLEX_SET (POLLPRI)
163
do_select(int n,fd_set_bits * fds,long * timeout)164 int do_select(int n, fd_set_bits *fds, long *timeout)
165 {
166 poll_table table, *wait;
167 int retval, i, off;
168 long __timeout = *timeout;
169
170 read_lock(¤t->files->file_lock);
171 retval = max_select_fd(n, fds);
172 read_unlock(¤t->files->file_lock);
173
174 if (retval < 0)
175 return retval;
176 n = retval;
177
178 poll_initwait(&table);
179 wait = &table;
180 if (!__timeout)
181 wait = NULL;
182 retval = 0;
183 for (;;) {
184 set_current_state(TASK_INTERRUPTIBLE);
185 for (i = 0 ; i < n; i++) {
186 unsigned long bit = BIT(i);
187 unsigned long mask;
188 struct file *file;
189
190 off = i / __NFDBITS;
191 if (!(bit & BITS(fds, off)))
192 continue;
193 file = fget(i);
194 mask = POLLNVAL;
195 if (file) {
196 mask = DEFAULT_POLLMASK;
197 if (file->f_op && file->f_op->poll)
198 mask = file->f_op->poll(file, wait);
199 fput(file);
200 }
201 if ((mask & POLLIN_SET) && ISSET(bit, __IN(fds,off))) {
202 SET(bit, __RES_IN(fds,off));
203 retval++;
204 wait = NULL;
205 }
206 if ((mask & POLLOUT_SET) && ISSET(bit, __OUT(fds,off))) {
207 SET(bit, __RES_OUT(fds,off));
208 retval++;
209 wait = NULL;
210 }
211 if ((mask & POLLEX_SET) && ISSET(bit, __EX(fds,off))) {
212 SET(bit, __RES_EX(fds,off));
213 retval++;
214 wait = NULL;
215 }
216 }
217 wait = NULL;
218 if (retval || !__timeout || signal_pending(current))
219 break;
220 if(table.error) {
221 retval = table.error;
222 break;
223 }
224 __timeout = schedule_timeout(__timeout);
225 }
226 current->state = TASK_RUNNING;
227
228 poll_freewait(&table);
229
230 /*
231 * Up-to-date the caller timeout.
232 */
233 *timeout = __timeout;
234 return retval;
235 }
236
select_bits_alloc(int size)237 static void *select_bits_alloc(int size)
238 {
239 return kmalloc(6 * size, GFP_KERNEL);
240 }
241
select_bits_free(void * bits,int size)242 static void select_bits_free(void *bits, int size)
243 {
244 kfree(bits);
245 }
246
247 /*
248 * We can actually return ERESTARTSYS instead of EINTR, but I'd
249 * like to be certain this leads to no problems. So I return
250 * EINTR just for safety.
251 *
252 * Update: ERESTARTSYS breaks at least the xview clock binary, so
253 * I'm trying ERESTARTNOHAND which restart only when you want to.
254 */
255 #define MAX_SELECT_SECONDS \
256 ((unsigned long) (MAX_SCHEDULE_TIMEOUT / HZ)-1)
257
258 asmlinkage long
sys_select(int n,fd_set * inp,fd_set * outp,fd_set * exp,struct timeval * tvp)259 sys_select(int n, fd_set *inp, fd_set *outp, fd_set *exp, struct timeval *tvp)
260 {
261 fd_set_bits fds;
262 char *bits;
263 long timeout;
264 int ret, size, max_fdset;
265
266 timeout = MAX_SCHEDULE_TIMEOUT;
267 if (tvp) {
268 time_t sec, usec;
269
270 if ((ret = verify_area(VERIFY_READ, tvp, sizeof(*tvp)))
271 || (ret = __get_user(sec, &tvp->tv_sec))
272 || (ret = __get_user(usec, &tvp->tv_usec)))
273 goto out_nofds;
274
275 ret = -EINVAL;
276 if (sec < 0 || usec < 0)
277 goto out_nofds;
278
279 if ((unsigned long) sec < MAX_SELECT_SECONDS) {
280 timeout = ROUND_UP(usec, 1000000/HZ);
281 timeout += sec * (unsigned long) HZ;
282 }
283 }
284
285 ret = -EINVAL;
286 if (n < 0)
287 goto out_nofds;
288
289 /* max_fdset can increase, so grab it once to avoid race */
290 max_fdset = current->files->max_fdset;
291 if (n > max_fdset)
292 n = max_fdset;
293
294 /*
295 * We need 6 bitmaps (in/out/ex for both incoming and outgoing),
296 * since we used fdset we need to allocate memory in units of
297 * long-words.
298 */
299 ret = -ENOMEM;
300 size = FDS_BYTES(n);
301 bits = select_bits_alloc(size);
302 if (!bits)
303 goto out_nofds;
304 fds.in = (unsigned long *) bits;
305 fds.out = (unsigned long *) (bits + size);
306 fds.ex = (unsigned long *) (bits + 2*size);
307 fds.res_in = (unsigned long *) (bits + 3*size);
308 fds.res_out = (unsigned long *) (bits + 4*size);
309 fds.res_ex = (unsigned long *) (bits + 5*size);
310
311 if ((ret = get_fd_set(n, inp, fds.in)) ||
312 (ret = get_fd_set(n, outp, fds.out)) ||
313 (ret = get_fd_set(n, exp, fds.ex)))
314 goto out;
315 zero_fd_set(n, fds.res_in);
316 zero_fd_set(n, fds.res_out);
317 zero_fd_set(n, fds.res_ex);
318
319 ret = do_select(n, &fds, &timeout);
320
321 if (tvp && !(current->personality & STICKY_TIMEOUTS)) {
322 time_t sec = 0, usec = 0;
323 if (timeout) {
324 sec = timeout / HZ;
325 usec = timeout % HZ;
326 usec *= (1000000/HZ);
327 }
328 put_user(sec, &tvp->tv_sec);
329 put_user(usec, &tvp->tv_usec);
330 }
331
332 if (ret < 0)
333 goto out;
334 if (!ret) {
335 ret = -ERESTARTNOHAND;
336 if (signal_pending(current))
337 goto out;
338 ret = 0;
339 }
340
341 set_fd_set(n, inp, fds.res_in);
342 set_fd_set(n, outp, fds.res_out);
343 set_fd_set(n, exp, fds.res_ex);
344
345 out:
346 select_bits_free(bits, size);
347 out_nofds:
348 return ret;
349 }
350
351 #define POLLFD_PER_PAGE ((PAGE_SIZE) / sizeof(struct pollfd))
352
do_pollfd(unsigned int num,struct pollfd * fdpage,poll_table ** pwait,int * count)353 static void do_pollfd(unsigned int num, struct pollfd * fdpage,
354 poll_table ** pwait, int *count)
355 {
356 int i;
357
358 for (i = 0; i < num; i++) {
359 int fd;
360 unsigned int mask;
361 struct pollfd *fdp;
362
363 mask = 0;
364 fdp = fdpage+i;
365 fd = fdp->fd;
366 if (fd >= 0) {
367 struct file * file = fget(fd);
368 mask = POLLNVAL;
369 if (file != NULL) {
370 mask = DEFAULT_POLLMASK;
371 if (file->f_op && file->f_op->poll)
372 mask = file->f_op->poll(file, *pwait);
373 mask &= fdp->events | POLLERR | POLLHUP;
374 fput(file);
375 }
376 if (mask) {
377 *pwait = NULL;
378 (*count)++;
379 }
380 }
381 fdp->revents = mask;
382 }
383 }
384
do_poll(unsigned int nfds,unsigned int nchunks,unsigned int nleft,struct pollfd * fds[],poll_table * wait,long timeout)385 static int do_poll(unsigned int nfds, unsigned int nchunks, unsigned int nleft,
386 struct pollfd *fds[], poll_table *wait, long timeout)
387 {
388 int count;
389 poll_table* pt = wait;
390
391 for (;;) {
392 unsigned int i;
393
394 set_current_state(TASK_INTERRUPTIBLE);
395 count = 0;
396 for (i=0; i < nchunks; i++)
397 do_pollfd(POLLFD_PER_PAGE, fds[i], &pt, &count);
398 if (nleft)
399 do_pollfd(nleft, fds[nchunks], &pt, &count);
400 pt = NULL;
401 if (count || !timeout || signal_pending(current))
402 break;
403 count = wait->error;
404 if (count)
405 break;
406 timeout = schedule_timeout(timeout);
407 }
408 current->state = TASK_RUNNING;
409 return count;
410 }
411
sys_poll(struct pollfd * ufds,unsigned int nfds,long timeout)412 asmlinkage long sys_poll(struct pollfd * ufds, unsigned int nfds, long timeout)
413 {
414 int i, j, fdcount, err;
415 struct pollfd **fds;
416 poll_table table, *wait;
417 int nchunks, nleft;
418
419 /* Do a sanity check on nfds ... */
420 if (nfds > current->files->max_fdset && nfds > OPEN_MAX)
421 return -EINVAL;
422
423 if (timeout) {
424 /* Careful about overflow in the intermediate values */
425 if ((unsigned long) timeout < MAX_SCHEDULE_TIMEOUT / HZ)
426 timeout = (unsigned long)(timeout*HZ+999)/1000+1;
427 else /* Negative or overflow */
428 timeout = MAX_SCHEDULE_TIMEOUT;
429 }
430
431 poll_initwait(&table);
432 wait = &table;
433 if (!timeout)
434 wait = NULL;
435
436 err = -ENOMEM;
437 fds = NULL;
438 if (nfds != 0) {
439 fds = (struct pollfd **)kmalloc(
440 (1 + (nfds - 1) / POLLFD_PER_PAGE) * sizeof(struct pollfd *),
441 GFP_KERNEL);
442 if (fds == NULL)
443 goto out;
444 }
445
446 nchunks = 0;
447 nleft = nfds;
448 while (nleft > POLLFD_PER_PAGE) { /* allocate complete PAGE_SIZE chunks */
449 fds[nchunks] = (struct pollfd *)__get_free_page(GFP_KERNEL);
450 if (fds[nchunks] == NULL)
451 goto out_fds;
452 nchunks++;
453 nleft -= POLLFD_PER_PAGE;
454 }
455 if (nleft) { /* allocate last PAGE_SIZE chunk, only nleft elements used */
456 fds[nchunks] = (struct pollfd *)__get_free_page(GFP_KERNEL);
457 if (fds[nchunks] == NULL)
458 goto out_fds;
459 }
460
461 err = -EFAULT;
462 for (i=0; i < nchunks; i++)
463 if (copy_from_user(fds[i], ufds + i*POLLFD_PER_PAGE, PAGE_SIZE))
464 goto out_fds1;
465 if (nleft) {
466 if (copy_from_user(fds[nchunks], ufds + nchunks*POLLFD_PER_PAGE,
467 nleft * sizeof(struct pollfd)))
468 goto out_fds1;
469 }
470
471 fdcount = do_poll(nfds, nchunks, nleft, fds, wait, timeout);
472
473 /* OK, now copy the revents fields back to user space. */
474 for(i=0; i < nchunks; i++)
475 for (j=0; j < POLLFD_PER_PAGE; j++, ufds++)
476 __put_user((fds[i] + j)->revents, &ufds->revents);
477 if (nleft)
478 for (j=0; j < nleft; j++, ufds++)
479 __put_user((fds[nchunks] + j)->revents, &ufds->revents);
480
481 err = fdcount;
482 if (!fdcount && signal_pending(current))
483 err = -EINTR;
484
485 out_fds1:
486 if (nleft)
487 free_page((unsigned long)(fds[nchunks]));
488 out_fds:
489 for (i=0; i < nchunks; i++)
490 free_page((unsigned long)(fds[i]));
491 if (nfds != 0)
492 kfree(fds);
493 out:
494 poll_freewait(&table);
495 return err;
496 }
497