f10a10317d5494e0eb4995d9c016113a093f34ee
[linux-2.6.git] / 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/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 }