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