Linux-2.6.12-rc2
[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
26 #include <asm/uaccess.h>
27
28 #define ROUND_UP(x,y) (((x)+(y)-1)/(y))
29 #define DEFAULT_POLLMASK (POLLIN | POLLOUT | POLLRDNORM | POLLWRNORM)
30
31 struct poll_table_entry {
32         struct file * filp;
33         wait_queue_t wait;
34         wait_queue_head_t * wait_address;
35 };
36
37 struct poll_table_page {
38         struct poll_table_page * next;
39         struct poll_table_entry * entry;
40         struct poll_table_entry entries[0];
41 };
42
43 #define POLL_TABLE_FULL(table) \
44         ((unsigned long)((table)->entry+1) > PAGE_SIZE + (unsigned long)(table))
45
46 /*
47  * Ok, Peter made a complicated, but straightforward multiple_wait() function.
48  * I have rewritten this, taking some shortcuts: This code may not be easy to
49  * follow, but it should be free of race-conditions, and it's practical. If you
50  * understand what I'm doing here, then you understand how the linux
51  * sleep/wakeup mechanism works.
52  *
53  * Two very simple procedures, poll_wait() and poll_freewait() make all the
54  * work.  poll_wait() is an inline-function defined in <linux/poll.h>,
55  * as all select/poll functions have to call it to add an entry to the
56  * poll table.
57  */
58 void __pollwait(struct file *filp, wait_queue_head_t *wait_address, poll_table *p);
59
60 void poll_initwait(struct poll_wqueues *pwq)
61 {
62         init_poll_funcptr(&pwq->pt, __pollwait);
63         pwq->error = 0;
64         pwq->table = NULL;
65 }
66
67 EXPORT_SYMBOL(poll_initwait);
68
69 void poll_freewait(struct poll_wqueues *pwq)
70 {
71         struct poll_table_page * p = pwq->table;
72         while (p) {
73                 struct poll_table_entry * entry;
74                 struct poll_table_page *old;
75
76                 entry = p->entry;
77                 do {
78                         entry--;
79                         remove_wait_queue(entry->wait_address,&entry->wait);
80                         fput(entry->filp);
81                 } while (entry > p->entries);
82                 old = p;
83                 p = p->next;
84                 free_page((unsigned long) old);
85         }
86 }
87
88 EXPORT_SYMBOL(poll_freewait);
89
90 void __pollwait(struct file *filp, wait_queue_head_t *wait_address, poll_table *_p)
91 {
92         struct poll_wqueues *p = container_of(_p, struct poll_wqueues, pt);
93         struct poll_table_page *table = p->table;
94
95         if (!table || POLL_TABLE_FULL(table)) {
96                 struct poll_table_page *new_table;
97
98                 new_table = (struct poll_table_page *) __get_free_page(GFP_KERNEL);
99                 if (!new_table) {
100                         p->error = -ENOMEM;
101                         __set_current_state(TASK_RUNNING);
102                         return;
103                 }
104                 new_table->entry = new_table->entries;
105                 new_table->next = table;
106                 p->table = new_table;
107                 table = new_table;
108         }
109
110         /* Add a new entry */
111         {
112                 struct poll_table_entry * entry = table->entry;
113                 table->entry = entry+1;
114                 get_file(filp);
115                 entry->filp = filp;
116                 entry->wait_address = wait_address;
117                 init_waitqueue_entry(&entry->wait, current);
118                 add_wait_queue(wait_address,&entry->wait);
119         }
120 }
121
122 #define FDS_IN(fds, n)          (fds->in + n)
123 #define FDS_OUT(fds, n)         (fds->out + n)
124 #define FDS_EX(fds, n)          (fds->ex + n)
125
126 #define BITS(fds, n)    (*FDS_IN(fds, n)|*FDS_OUT(fds, n)|*FDS_EX(fds, n))
127
128 static int max_select_fd(unsigned long n, fd_set_bits *fds)
129 {
130         unsigned long *open_fds;
131         unsigned long set;
132         int max;
133
134         /* handle last in-complete long-word first */
135         set = ~(~0UL << (n & (__NFDBITS-1)));
136         n /= __NFDBITS;
137         open_fds = current->files->open_fds->fds_bits+n;
138         max = 0;
139         if (set) {
140                 set &= BITS(fds, n);
141                 if (set) {
142                         if (!(set & ~*open_fds))
143                                 goto get_max;
144                         return -EBADF;
145                 }
146         }
147         while (n) {
148                 open_fds--;
149                 n--;
150                 set = BITS(fds, n);
151                 if (!set)
152                         continue;
153                 if (set & ~*open_fds)
154                         return -EBADF;
155                 if (max)
156                         continue;
157 get_max:
158                 do {
159                         max++;
160                         set >>= 1;
161                 } while (set);
162                 max += n * __NFDBITS;
163         }
164
165         return max;
166 }
167
168 #define BIT(i)          (1UL << ((i)&(__NFDBITS-1)))
169 #define MEM(i,m)        ((m)+(unsigned)(i)/__NFDBITS)
170 #define ISSET(i,m)      (((i)&*(m)) != 0)
171 #define SET(i,m)        (*(m) |= (i))
172
173 #define POLLIN_SET (POLLRDNORM | POLLRDBAND | POLLIN | POLLHUP | POLLERR)
174 #define POLLOUT_SET (POLLWRBAND | POLLWRNORM | POLLOUT | POLLERR)
175 #define POLLEX_SET (POLLPRI)
176
177 int do_select(int n, fd_set_bits *fds, long *timeout)
178 {
179         struct poll_wqueues table;
180         poll_table *wait;
181         int retval, i;
182         long __timeout = *timeout;
183
184         spin_lock(&current->files->file_lock);
185         retval = max_select_fd(n, fds);
186         spin_unlock(&current->files->file_lock);
187
188         if (retval < 0)
189                 return retval;
190         n = retval;
191
192         poll_initwait(&table);
193         wait = &table.pt;
194         if (!__timeout)
195                 wait = NULL;
196         retval = 0;
197         for (;;) {
198                 unsigned long *rinp, *routp, *rexp, *inp, *outp, *exp;
199
200                 set_current_state(TASK_INTERRUPTIBLE);
201
202                 inp = fds->in; outp = fds->out; exp = fds->ex;
203                 rinp = fds->res_in; routp = fds->res_out; rexp = fds->res_ex;
204
205                 for (i = 0; i < n; ++rinp, ++routp, ++rexp) {
206                         unsigned long in, out, ex, all_bits, bit = 1, mask, j;
207                         unsigned long res_in = 0, res_out = 0, res_ex = 0;
208                         struct file_operations *f_op = NULL;
209                         struct file *file = NULL;
210
211                         in = *inp++; out = *outp++; ex = *exp++;
212                         all_bits = in | out | ex;
213                         if (all_bits == 0) {
214                                 i += __NFDBITS;
215                                 continue;
216                         }
217
218                         for (j = 0; j < __NFDBITS; ++j, ++i, bit <<= 1) {
219                                 if (i >= n)
220                                         break;
221                                 if (!(bit & all_bits))
222                                         continue;
223                                 file = fget(i);
224                                 if (file) {
225                                         f_op = file->f_op;
226                                         mask = DEFAULT_POLLMASK;
227                                         if (f_op && f_op->poll)
228                                                 mask = (*f_op->poll)(file, retval ? NULL : wait);
229                                         fput(file);
230                                         if ((mask & POLLIN_SET) && (in & bit)) {
231                                                 res_in |= bit;
232                                                 retval++;
233                                         }
234                                         if ((mask & POLLOUT_SET) && (out & bit)) {
235                                                 res_out |= bit;
236                                                 retval++;
237                                         }
238                                         if ((mask & POLLEX_SET) && (ex & bit)) {
239                                                 res_ex |= bit;
240                                                 retval++;
241                                         }
242                                 }
243                                 cond_resched();
244                         }
245                         if (res_in)
246                                 *rinp = res_in;
247                         if (res_out)
248                                 *routp = res_out;
249                         if (res_ex)
250                                 *rexp = res_ex;
251                 }
252                 wait = NULL;
253                 if (retval || !__timeout || signal_pending(current))
254                         break;
255                 if(table.error) {
256                         retval = table.error;
257                         break;
258                 }
259                 __timeout = schedule_timeout(__timeout);
260         }
261         __set_current_state(TASK_RUNNING);
262
263         poll_freewait(&table);
264
265         /*
266          * Up-to-date the caller timeout.
267          */
268         *timeout = __timeout;
269         return retval;
270 }
271
272 static void *select_bits_alloc(int size)
273 {
274         return kmalloc(6 * size, GFP_KERNEL);
275 }
276
277 static void select_bits_free(void *bits, int size)
278 {
279         kfree(bits);
280 }
281
282 /*
283  * We can actually return ERESTARTSYS instead of EINTR, but I'd
284  * like to be certain this leads to no problems. So I return
285  * EINTR just for safety.
286  *
287  * Update: ERESTARTSYS breaks at least the xview clock binary, so
288  * I'm trying ERESTARTNOHAND which restart only when you want to.
289  */
290 #define MAX_SELECT_SECONDS \
291         ((unsigned long) (MAX_SCHEDULE_TIMEOUT / HZ)-1)
292
293 asmlinkage long
294 sys_select(int n, fd_set __user *inp, fd_set __user *outp, fd_set __user *exp, struct timeval __user *tvp)
295 {
296         fd_set_bits fds;
297         char *bits;
298         long timeout;
299         int ret, size, max_fdset;
300
301         timeout = MAX_SCHEDULE_TIMEOUT;
302         if (tvp) {
303                 time_t sec, usec;
304
305                 if (!access_ok(VERIFY_READ, tvp, sizeof(*tvp))
306                     || __get_user(sec, &tvp->tv_sec)
307                     || __get_user(usec, &tvp->tv_usec)) {
308                         ret = -EFAULT;
309                         goto out_nofds;
310                 }
311
312                 ret = -EINVAL;
313                 if (sec < 0 || usec < 0)
314                         goto out_nofds;
315
316                 if ((unsigned long) sec < MAX_SELECT_SECONDS) {
317                         timeout = ROUND_UP(usec, 1000000/HZ);
318                         timeout += sec * (unsigned long) HZ;
319                 }
320         }
321
322         ret = -EINVAL;
323         if (n < 0)
324                 goto out_nofds;
325
326         /* max_fdset can increase, so grab it once to avoid race */
327         max_fdset = current->files->max_fdset;
328         if (n > max_fdset)
329                 n = max_fdset;
330
331         /*
332          * We need 6 bitmaps (in/out/ex for both incoming and outgoing),
333          * since we used fdset we need to allocate memory in units of
334          * long-words. 
335          */
336         ret = -ENOMEM;
337         size = FDS_BYTES(n);
338         bits = select_bits_alloc(size);
339         if (!bits)
340                 goto out_nofds;
341         fds.in      = (unsigned long *)  bits;
342         fds.out     = (unsigned long *) (bits +   size);
343         fds.ex      = (unsigned long *) (bits + 2*size);
344         fds.res_in  = (unsigned long *) (bits + 3*size);
345         fds.res_out = (unsigned long *) (bits + 4*size);
346         fds.res_ex  = (unsigned long *) (bits + 5*size);
347
348         if ((ret = get_fd_set(n, inp, fds.in)) ||
349             (ret = get_fd_set(n, outp, fds.out)) ||
350             (ret = get_fd_set(n, exp, fds.ex)))
351                 goto out;
352         zero_fd_set(n, fds.res_in);
353         zero_fd_set(n, fds.res_out);
354         zero_fd_set(n, fds.res_ex);
355
356         ret = do_select(n, &fds, &timeout);
357
358         if (tvp && !(current->personality & STICKY_TIMEOUTS)) {
359                 time_t sec = 0, usec = 0;
360                 if (timeout) {
361                         sec = timeout / HZ;
362                         usec = timeout % HZ;
363                         usec *= (1000000/HZ);
364                 }
365                 put_user(sec, &tvp->tv_sec);
366                 put_user(usec, &tvp->tv_usec);
367         }
368
369         if (ret < 0)
370                 goto out;
371         if (!ret) {
372                 ret = -ERESTARTNOHAND;
373                 if (signal_pending(current))
374                         goto out;
375                 ret = 0;
376         }
377
378         if (set_fd_set(n, inp, fds.res_in) ||
379             set_fd_set(n, outp, fds.res_out) ||
380             set_fd_set(n, exp, fds.res_ex))
381                 ret = -EFAULT;
382
383 out:
384         select_bits_free(bits, size);
385 out_nofds:
386         return ret;
387 }
388
389 struct poll_list {
390         struct poll_list *next;
391         int len;
392         struct pollfd entries[0];
393 };
394
395 #define POLLFD_PER_PAGE  ((PAGE_SIZE-sizeof(struct poll_list)) / sizeof(struct pollfd))
396
397 static void do_pollfd(unsigned int num, struct pollfd * fdpage,
398         poll_table ** pwait, int *count)
399 {
400         int i;
401
402         for (i = 0; i < num; i++) {
403                 int fd;
404                 unsigned int mask;
405                 struct pollfd *fdp;
406
407                 mask = 0;
408                 fdp = fdpage+i;
409                 fd = fdp->fd;
410                 if (fd >= 0) {
411                         struct file * file = fget(fd);
412                         mask = POLLNVAL;
413                         if (file != NULL) {
414                                 mask = DEFAULT_POLLMASK;
415                                 if (file->f_op && file->f_op->poll)
416                                         mask = file->f_op->poll(file, *pwait);
417                                 mask &= fdp->events | POLLERR | POLLHUP;
418                                 fput(file);
419                         }
420                         if (mask) {
421                                 *pwait = NULL;
422                                 (*count)++;
423                         }
424                 }
425                 fdp->revents = mask;
426         }
427 }
428
429 static int do_poll(unsigned int nfds,  struct poll_list *list,
430                         struct poll_wqueues *wait, long timeout)
431 {
432         int count = 0;
433         poll_table* pt = &wait->pt;
434
435         if (!timeout)
436                 pt = NULL;
437  
438         for (;;) {
439                 struct poll_list *walk;
440                 set_current_state(TASK_INTERRUPTIBLE);
441                 walk = list;
442                 while(walk != NULL) {
443                         do_pollfd( walk->len, walk->entries, &pt, &count);
444                         walk = walk->next;
445                 }
446                 pt = NULL;
447                 if (count || !timeout || signal_pending(current))
448                         break;
449                 count = wait->error;
450                 if (count)
451                         break;
452                 timeout = schedule_timeout(timeout);
453         }
454         __set_current_state(TASK_RUNNING);
455         return count;
456 }
457
458 asmlinkage long sys_poll(struct pollfd __user * ufds, unsigned int nfds, long timeout)
459 {
460         struct poll_wqueues table;
461         int fdcount, err;
462         unsigned int i;
463         struct poll_list *head;
464         struct poll_list *walk;
465
466         /* Do a sanity check on nfds ... */
467         if (nfds > current->files->max_fdset && nfds > OPEN_MAX)
468                 return -EINVAL;
469
470         if (timeout) {
471                 /* Careful about overflow in the intermediate values */
472                 if ((unsigned long) timeout < MAX_SCHEDULE_TIMEOUT / HZ)
473                         timeout = (unsigned long)(timeout*HZ+999)/1000+1;
474                 else /* Negative or overflow */
475                         timeout = MAX_SCHEDULE_TIMEOUT;
476         }
477
478         poll_initwait(&table);
479
480         head = NULL;
481         walk = NULL;
482         i = nfds;
483         err = -ENOMEM;
484         while(i!=0) {
485                 struct poll_list *pp;
486                 pp = kmalloc(sizeof(struct poll_list)+
487                                 sizeof(struct pollfd)*
488                                 (i>POLLFD_PER_PAGE?POLLFD_PER_PAGE:i),
489                                         GFP_KERNEL);
490                 if(pp==NULL)
491                         goto out_fds;
492                 pp->next=NULL;
493                 pp->len = (i>POLLFD_PER_PAGE?POLLFD_PER_PAGE:i);
494                 if (head == NULL)
495                         head = pp;
496                 else
497                         walk->next = pp;
498
499                 walk = pp;
500                 if (copy_from_user(pp->entries, ufds + nfds-i, 
501                                 sizeof(struct pollfd)*pp->len)) {
502                         err = -EFAULT;
503                         goto out_fds;
504                 }
505                 i -= pp->len;
506         }
507         fdcount = do_poll(nfds, head, &table, timeout);
508
509         /* OK, now copy the revents fields back to user space. */
510         walk = head;
511         err = -EFAULT;
512         while(walk != NULL) {
513                 struct pollfd *fds = walk->entries;
514                 int j;
515
516                 for (j=0; j < walk->len; j++, ufds++) {
517                         if(__put_user(fds[j].revents, &ufds->revents))
518                                 goto out_fds;
519                 }
520                 walk = walk->next;
521         }
522         err = fdcount;
523         if (!fdcount && signal_pending(current))
524                 err = -EINTR;
525 out_fds:
526         walk = head;
527         while(walk!=NULL) {
528                 struct poll_list *pp = walk->next;
529                 kfree(walk);
530                 walk = pp;
531         }
532         poll_freewait(&table);
533         return err;
534 }