1 /* 2 * Copyright (c) 1991, 1993 3 * The Regents of the University of California. All rights reserved. 4 * Copyright (c) 1994 John S. Dyson 5 * All rights reserved. 6 * Copyright (c) 1994 David Greenman 7 * All rights reserved. 8 * 9 * 10 * This code is derived from software contributed to Berkeley by 11 * The Mach Operating System project at Carnegie-Mellon University. 12 * 13 * Redistribution and use in source and binary forms, with or without 14 * modification, are permitted provided that the following conditions 15 * are met: 16 * 1. Redistributions of source code must retain the above copyright 17 * notice, this list of conditions and the following disclaimer. 18 * 2. Redistributions in binary form must reproduce the above copyright 19 * notice, this list of conditions and the following disclaimer in the 20 * documentation and/or other materials provided with the distribution. 21 * 3. All advertising materials mentioning features or use of this software 22 * must display the following acknowledgement: 23 * This product includes software developed by the University of 24 * California, Berkeley and its contributors. 25 * 4. Neither the name of the University nor the names of its contributors 26 * may be used to endorse or promote products derived from this software 27 * without specific prior written permission. 28 * 29 * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND 30 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE 31 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE 32 * ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE 33 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL 34 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS 35 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) 36 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT 37 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY 38 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF 39 * SUCH DAMAGE. 40 * 41 * from: @(#)vm_fault.c 8.4 (Berkeley) 1/12/94 42 * 43 * 44 * Copyright (c) 1987, 1990 Carnegie-Mellon University. 45 * All rights reserved. 46 * 47 * Authors: Avadis Tevanian, Jr., Michael Wayne Young 48 * 49 * Permission to use, copy, modify and distribute this software and 50 * its documentation is hereby granted, provided that both the copyright 51 * notice and this permission notice appear in all copies of the 52 * software, derivative works or modified versions, and any portions 53 * thereof, and that both notices appear in supporting documentation. 54 * 55 * CARNEGIE MELLON ALLOWS FREE USE OF THIS SOFTWARE IN ITS "AS IS" 56 * CONDITION. CARNEGIE MELLON DISCLAIMS ANY LIABILITY OF ANY KIND 57 * FOR ANY DAMAGES WHATSOEVER RESULTING FROM THE USE OF THIS SOFTWARE. 58 * 59 * Carnegie Mellon requests users of this software to return to 60 * 61 * Software Distribution Coordinator or Software.Distribution@CS.CMU.EDU 62 * School of Computer Science 63 * Carnegie Mellon University 64 * Pittsburgh PA 15213-3890 65 * 66 * any improvements or extensions that they make and grant Carnegie the 67 * rights to redistribute these changes. 68 */ 69 70 /* 71 * Page fault handling module. 72 */ 73 74 #include <sys/cdefs.h> 75 __FBSDID("$FreeBSD$"); 76 77 #include <sys/param.h> 78 #include <sys/systm.h> 79 #include <sys/kernel.h> 80 #include <sys/lock.h> 81 #include <sys/mutex.h> 82 #include <sys/proc.h> 83 #include <sys/resourcevar.h> 84 #include <sys/sysctl.h> 85 #include <sys/vmmeter.h> 86 #include <sys/vnode.h> 87 88 #include <vm/vm.h> 89 #include <vm/vm_param.h> 90 #include <vm/pmap.h> 91 #include <vm/vm_map.h> 92 #include <vm/vm_object.h> 93 #include <vm/vm_page.h> 94 #include <vm/vm_pageout.h> 95 #include <vm/vm_kern.h> 96 #include <vm/vm_pager.h> 97 #include <vm/vnode_pager.h> 98 #include <vm/vm_extern.h> 99 100 static int vm_fault_additional_pages(vm_page_t, int, int, vm_page_t *, int *); 101 102 #define VM_FAULT_READ_AHEAD 8 103 #define VM_FAULT_READ_BEHIND 7 104 #define VM_FAULT_READ (VM_FAULT_READ_AHEAD+VM_FAULT_READ_BEHIND+1) 105 106 struct faultstate { 107 vm_page_t m; 108 vm_object_t object; 109 vm_pindex_t pindex; 110 vm_page_t first_m; 111 vm_object_t first_object; 112 vm_pindex_t first_pindex; 113 vm_map_t map; 114 vm_map_entry_t entry; 115 int lookup_still_valid; 116 struct vnode *vp; 117 }; 118 119 static __inline void 120 release_page(struct faultstate *fs) 121 { 122 vm_page_lock_queues(); 123 vm_page_wakeup(fs->m); 124 vm_page_deactivate(fs->m); 125 vm_page_unlock_queues(); 126 fs->m = NULL; 127 } 128 129 static __inline void 130 unlock_map(struct faultstate *fs) 131 { 132 if (fs->lookup_still_valid) { 133 vm_map_lookup_done(fs->map, fs->entry); 134 fs->lookup_still_valid = FALSE; 135 } 136 } 137 138 static void 139 _unlock_things(struct faultstate *fs, int dealloc) 140 { 141 142 vm_object_pip_wakeup(fs->object); 143 VM_OBJECT_UNLOCK(fs->object); 144 if (fs->object != fs->first_object) { 145 VM_OBJECT_LOCK(fs->first_object); 146 vm_page_lock_queues(); 147 vm_page_free(fs->first_m); 148 vm_page_unlock_queues(); 149 vm_object_pip_wakeup(fs->first_object); 150 VM_OBJECT_UNLOCK(fs->first_object); 151 fs->first_m = NULL; 152 } 153 if (dealloc) { 154 vm_object_deallocate(fs->first_object); 155 } 156 unlock_map(fs); 157 if (fs->vp != NULL) { 158 vput(fs->vp); 159 fs->vp = NULL; 160 } 161 } 162 163 #define unlock_things(fs) _unlock_things(fs, 0) 164 #define unlock_and_deallocate(fs) _unlock_things(fs, 1) 165 166 /* 167 * TRYPAGER - used by vm_fault to calculate whether the pager for the 168 * current object *might* contain the page. 169 * 170 * default objects are zero-fill, there is no real pager. 171 */ 172 #define TRYPAGER (fs.object->type != OBJT_DEFAULT && \ 173 (((fault_flags & VM_FAULT_WIRE_MASK) == 0) || wired)) 174 175 /* 176 * vm_fault: 177 * 178 * Handle a page fault occurring at the given address, 179 * requiring the given permissions, in the map specified. 180 * If successful, the page is inserted into the 181 * associated physical map. 182 * 183 * NOTE: the given address should be truncated to the 184 * proper page address. 185 * 186 * KERN_SUCCESS is returned if the page fault is handled; otherwise, 187 * a standard error specifying why the fault is fatal is returned. 188 * 189 * 190 * The map in question must be referenced, and remains so. 191 * Caller may hold no locks. 192 */ 193 int 194 vm_fault(vm_map_t map, vm_offset_t vaddr, vm_prot_t fault_type, 195 int fault_flags) 196 { 197 vm_prot_t prot; 198 int is_first_object_locked, result; 199 boolean_t growstack, wired; 200 int map_generation; 201 vm_object_t next_object; 202 vm_page_t marray[VM_FAULT_READ]; 203 int hardfault; 204 int faultcount; 205 struct faultstate fs; 206 207 hardfault = 0; 208 growstack = TRUE; 209 atomic_add_int(&cnt.v_vm_faults, 1); 210 211 mtx_lock(&Giant); 212 RetryFault:; 213 214 /* 215 * Find the backing store object and offset into it to begin the 216 * search. 217 */ 218 fs.map = map; 219 result = vm_map_lookup(&fs.map, vaddr, fault_type, &fs.entry, 220 &fs.first_object, &fs.first_pindex, &prot, &wired); 221 if (result != KERN_SUCCESS) { 222 if (result != KERN_PROTECTION_FAILURE || 223 (fault_flags & VM_FAULT_WIRE_MASK) != VM_FAULT_USER_WIRE) { 224 if (growstack && result == KERN_INVALID_ADDRESS && 225 map != kernel_map && curproc != NULL) { 226 result = vm_map_growstack(curproc, vaddr); 227 if (result != KERN_SUCCESS) { 228 mtx_unlock(&Giant); 229 return (KERN_FAILURE); 230 } 231 growstack = FALSE; 232 goto RetryFault; 233 } 234 mtx_unlock(&Giant); 235 return (result); 236 } 237 238 /* 239 * If we are user-wiring a r/w segment, and it is COW, then 240 * we need to do the COW operation. Note that we don't COW 241 * currently RO sections now, because it is NOT desirable 242 * to COW .text. We simply keep .text from ever being COW'ed 243 * and take the heat that one cannot debug wired .text sections. 244 */ 245 result = vm_map_lookup(&fs.map, vaddr, 246 VM_PROT_READ|VM_PROT_WRITE|VM_PROT_OVERRIDE_WRITE, 247 &fs.entry, &fs.first_object, &fs.first_pindex, &prot, &wired); 248 if (result != KERN_SUCCESS) { 249 mtx_unlock(&Giant); 250 return (result); 251 } 252 253 /* 254 * If we don't COW now, on a user wire, the user will never 255 * be able to write to the mapping. If we don't make this 256 * restriction, the bookkeeping would be nearly impossible. 257 * 258 * XXX The following assignment modifies the map without 259 * holding a write lock on it. 260 */ 261 if ((fs.entry->protection & VM_PROT_WRITE) == 0) 262 fs.entry->max_protection &= ~VM_PROT_WRITE; 263 } 264 265 map_generation = fs.map->timestamp; 266 267 if (fs.entry->eflags & MAP_ENTRY_NOFAULT) { 268 panic("vm_fault: fault on nofault entry, addr: %lx", 269 (u_long)vaddr); 270 } 271 272 /* 273 * Make a reference to this object to prevent its disposal while we 274 * are messing with it. Once we have the reference, the map is free 275 * to be diddled. Since objects reference their shadows (and copies), 276 * they will stay around as well. 277 * 278 * Bump the paging-in-progress count to prevent size changes (e.g. 279 * truncation operations) during I/O. This must be done after 280 * obtaining the vnode lock in order to avoid possible deadlocks. 281 * 282 * XXX vnode_pager_lock() can block without releasing the map lock. 283 */ 284 vm_object_reference(fs.first_object); 285 VM_OBJECT_LOCK(fs.first_object); 286 fs.vp = vnode_pager_lock(fs.first_object); 287 vm_object_pip_add(fs.first_object, 1); 288 289 fs.lookup_still_valid = TRUE; 290 291 if (wired) 292 fault_type = prot; 293 294 fs.first_m = NULL; 295 296 /* 297 * Search for the page at object/offset. 298 */ 299 fs.object = fs.first_object; 300 fs.pindex = fs.first_pindex; 301 while (TRUE) { 302 /* 303 * If the object is dead, we stop here 304 */ 305 if (fs.object->flags & OBJ_DEAD) { 306 unlock_and_deallocate(&fs); 307 mtx_unlock(&Giant); 308 return (KERN_PROTECTION_FAILURE); 309 } 310 311 /* 312 * See if page is resident 313 */ 314 fs.m = vm_page_lookup(fs.object, fs.pindex); 315 if (fs.m != NULL) { 316 int queue, s; 317 318 /* 319 * check for page-based copy on write. 320 * We check fs.object == fs.first_object so 321 * as to ensure the legacy COW mechanism is 322 * used when the page in question is part of 323 * a shadow object. Otherwise, vm_page_cowfault() 324 * removes the page from the backing object, 325 * which is not what we want. 326 */ 327 vm_page_lock_queues(); 328 if ((fs.m->cow) && 329 (fault_type & VM_PROT_WRITE) && 330 (fs.object == fs.first_object)) { 331 s = splvm(); 332 vm_page_cowfault(fs.m); 333 splx(s); 334 vm_page_unlock_queues(); 335 unlock_and_deallocate(&fs); 336 goto RetryFault; 337 } 338 339 /* 340 * Wait/Retry if the page is busy. We have to do this 341 * if the page is busy via either PG_BUSY or 342 * vm_page_t->busy because the vm_pager may be using 343 * vm_page_t->busy for pageouts ( and even pageins if 344 * it is the vnode pager ), and we could end up trying 345 * to pagein and pageout the same page simultaneously. 346 * 347 * We can theoretically allow the busy case on a read 348 * fault if the page is marked valid, but since such 349 * pages are typically already pmap'd, putting that 350 * special case in might be more effort then it is 351 * worth. We cannot under any circumstances mess 352 * around with a vm_page_t->busy page except, perhaps, 353 * to pmap it. 354 */ 355 if ((fs.m->flags & PG_BUSY) || fs.m->busy) { 356 vm_page_unlock_queues(); 357 unlock_things(&fs); 358 vm_page_lock_queues(); 359 if (!vm_page_sleep_if_busy(fs.m, TRUE, "vmpfw")) 360 vm_page_unlock_queues(); 361 cnt.v_intrans++; 362 vm_object_deallocate(fs.first_object); 363 goto RetryFault; 364 } 365 queue = fs.m->queue; 366 367 s = splvm(); 368 vm_pageq_remove_nowakeup(fs.m); 369 splx(s); 370 371 if ((queue - fs.m->pc) == PQ_CACHE && vm_page_count_severe()) { 372 vm_page_activate(fs.m); 373 vm_page_unlock_queues(); 374 unlock_and_deallocate(&fs); 375 VM_WAITPFAULT; 376 goto RetryFault; 377 } 378 379 /* 380 * Mark page busy for other processes, and the 381 * pagedaemon. If it still isn't completely valid 382 * (readable), jump to readrest, else break-out ( we 383 * found the page ). 384 */ 385 vm_page_busy(fs.m); 386 vm_page_unlock_queues(); 387 if (((fs.m->valid & VM_PAGE_BITS_ALL) != VM_PAGE_BITS_ALL) && 388 fs.m->object != kernel_object && fs.m->object != kmem_object) { 389 goto readrest; 390 } 391 392 break; 393 } 394 395 /* 396 * Page is not resident, If this is the search termination 397 * or the pager might contain the page, allocate a new page. 398 */ 399 if (TRYPAGER || fs.object == fs.first_object) { 400 if (fs.pindex >= fs.object->size) { 401 unlock_and_deallocate(&fs); 402 mtx_unlock(&Giant); 403 return (KERN_PROTECTION_FAILURE); 404 } 405 406 /* 407 * Allocate a new page for this object/offset pair. 408 */ 409 fs.m = NULL; 410 if (!vm_page_count_severe()) { 411 fs.m = vm_page_alloc(fs.object, fs.pindex, 412 (fs.vp || fs.object->backing_object)? VM_ALLOC_NORMAL: VM_ALLOC_ZERO); 413 } 414 if (fs.m == NULL) { 415 unlock_and_deallocate(&fs); 416 VM_WAITPFAULT; 417 goto RetryFault; 418 } 419 } 420 421 readrest: 422 /* 423 * We have found a valid page or we have allocated a new page. 424 * The page thus may not be valid or may not be entirely 425 * valid. 426 * 427 * Attempt to fault-in the page if there is a chance that the 428 * pager has it, and potentially fault in additional pages 429 * at the same time. 430 */ 431 if (TRYPAGER) { 432 int rv; 433 int reqpage; 434 int ahead, behind; 435 u_char behavior = vm_map_entry_behavior(fs.entry); 436 437 if (behavior == MAP_ENTRY_BEHAV_RANDOM) { 438 ahead = 0; 439 behind = 0; 440 } else { 441 behind = (vaddr - fs.entry->start) >> PAGE_SHIFT; 442 if (behind > VM_FAULT_READ_BEHIND) 443 behind = VM_FAULT_READ_BEHIND; 444 445 ahead = ((fs.entry->end - vaddr) >> PAGE_SHIFT) - 1; 446 if (ahead > VM_FAULT_READ_AHEAD) 447 ahead = VM_FAULT_READ_AHEAD; 448 } 449 is_first_object_locked = FALSE; 450 if ((behavior == MAP_ENTRY_BEHAV_SEQUENTIAL || 451 (behavior != MAP_ENTRY_BEHAV_RANDOM && 452 fs.pindex >= fs.entry->lastr && 453 fs.pindex < fs.entry->lastr + VM_FAULT_READ)) && 454 (fs.first_object == fs.object || 455 (is_first_object_locked = VM_OBJECT_TRYLOCK(fs.first_object))) && 456 fs.first_object->type != OBJT_DEVICE) { 457 vm_pindex_t firstpindex, tmppindex; 458 459 if (fs.first_pindex < 2 * VM_FAULT_READ) 460 firstpindex = 0; 461 else 462 firstpindex = fs.first_pindex - 2 * VM_FAULT_READ; 463 464 vm_page_lock_queues(); 465 /* 466 * note: partially valid pages cannot be 467 * included in the lookahead - NFS piecemeal 468 * writes will barf on it badly. 469 */ 470 for (tmppindex = fs.first_pindex - 1; 471 tmppindex >= firstpindex; 472 --tmppindex) { 473 vm_page_t mt; 474 475 mt = vm_page_lookup(fs.first_object, tmppindex); 476 if (mt == NULL || (mt->valid != VM_PAGE_BITS_ALL)) 477 break; 478 if (mt->busy || 479 (mt->flags & (PG_BUSY | PG_FICTITIOUS | PG_UNMANAGED)) || 480 mt->hold_count || 481 mt->wire_count) 482 continue; 483 if (mt->dirty == 0) 484 vm_page_test_dirty(mt); 485 if (mt->dirty) { 486 pmap_remove_all(mt); 487 vm_page_deactivate(mt); 488 } else { 489 vm_page_cache(mt); 490 } 491 } 492 vm_page_unlock_queues(); 493 ahead += behind; 494 behind = 0; 495 } 496 if (is_first_object_locked) 497 VM_OBJECT_UNLOCK(fs.first_object); 498 /* 499 * now we find out if any other pages should be paged 500 * in at this time this routine checks to see if the 501 * pages surrounding this fault reside in the same 502 * object as the page for this fault. If they do, 503 * then they are faulted in also into the object. The 504 * array "marray" returned contains an array of 505 * vm_page_t structs where one of them is the 506 * vm_page_t passed to the routine. The reqpage 507 * return value is the index into the marray for the 508 * vm_page_t passed to the routine. 509 * 510 * fs.m plus the additional pages are PG_BUSY'd. 511 * 512 * XXX vm_fault_additional_pages() can block 513 * without releasing the map lock. 514 */ 515 faultcount = vm_fault_additional_pages( 516 fs.m, behind, ahead, marray, &reqpage); 517 518 /* 519 * update lastr imperfectly (we do not know how much 520 * getpages will actually read), but good enough. 521 * 522 * XXX The following assignment modifies the map 523 * without holding a write lock on it. 524 */ 525 fs.entry->lastr = fs.pindex + faultcount - behind; 526 527 /* 528 * Call the pager to retrieve the data, if any, after 529 * releasing the lock on the map. We hold a ref on 530 * fs.object and the pages are PG_BUSY'd. 531 */ 532 unlock_map(&fs); 533 534 rv = faultcount ? 535 vm_pager_get_pages(fs.object, marray, faultcount, 536 reqpage) : VM_PAGER_FAIL; 537 538 if (rv == VM_PAGER_OK) { 539 /* 540 * Found the page. Leave it busy while we play 541 * with it. 542 */ 543 544 /* 545 * Relookup in case pager changed page. Pager 546 * is responsible for disposition of old page 547 * if moved. 548 */ 549 fs.m = vm_page_lookup(fs.object, fs.pindex); 550 if (!fs.m) { 551 unlock_and_deallocate(&fs); 552 goto RetryFault; 553 } 554 555 hardfault++; 556 break; /* break to PAGE HAS BEEN FOUND */ 557 } 558 /* 559 * Remove the bogus page (which does not exist at this 560 * object/offset); before doing so, we must get back 561 * our object lock to preserve our invariant. 562 * 563 * Also wake up any other process that may want to bring 564 * in this page. 565 * 566 * If this is the top-level object, we must leave the 567 * busy page to prevent another process from rushing 568 * past us, and inserting the page in that object at 569 * the same time that we are. 570 */ 571 if (rv == VM_PAGER_ERROR) 572 printf("vm_fault: pager read error, pid %d (%s)\n", 573 curproc->p_pid, curproc->p_comm); 574 /* 575 * Data outside the range of the pager or an I/O error 576 */ 577 /* 578 * XXX - the check for kernel_map is a kludge to work 579 * around having the machine panic on a kernel space 580 * fault w/ I/O error. 581 */ 582 if (((fs.map != kernel_map) && (rv == VM_PAGER_ERROR)) || 583 (rv == VM_PAGER_BAD)) { 584 vm_page_lock_queues(); 585 vm_page_free(fs.m); 586 vm_page_unlock_queues(); 587 fs.m = NULL; 588 unlock_and_deallocate(&fs); 589 mtx_unlock(&Giant); 590 return ((rv == VM_PAGER_ERROR) ? KERN_FAILURE : KERN_PROTECTION_FAILURE); 591 } 592 if (fs.object != fs.first_object) { 593 vm_page_lock_queues(); 594 vm_page_free(fs.m); 595 vm_page_unlock_queues(); 596 fs.m = NULL; 597 /* 598 * XXX - we cannot just fall out at this 599 * point, m has been freed and is invalid! 600 */ 601 } 602 } 603 604 /* 605 * We get here if the object has default pager (or unwiring) 606 * or the pager doesn't have the page. 607 */ 608 if (fs.object == fs.first_object) 609 fs.first_m = fs.m; 610 611 /* 612 * Move on to the next object. Lock the next object before 613 * unlocking the current one. 614 */ 615 fs.pindex += OFF_TO_IDX(fs.object->backing_object_offset); 616 next_object = fs.object->backing_object; 617 if (next_object == NULL) { 618 /* 619 * If there's no object left, fill the page in the top 620 * object with zeros. 621 */ 622 if (fs.object != fs.first_object) { 623 vm_object_pip_wakeup(fs.object); 624 VM_OBJECT_UNLOCK(fs.object); 625 626 fs.object = fs.first_object; 627 fs.pindex = fs.first_pindex; 628 fs.m = fs.first_m; 629 VM_OBJECT_LOCK(fs.object); 630 } 631 fs.first_m = NULL; 632 633 /* 634 * Zero the page if necessary and mark it valid. 635 */ 636 if ((fs.m->flags & PG_ZERO) == 0) { 637 pmap_zero_page(fs.m); 638 } else { 639 cnt.v_ozfod++; 640 } 641 cnt.v_zfod++; 642 fs.m->valid = VM_PAGE_BITS_ALL; 643 break; /* break to PAGE HAS BEEN FOUND */ 644 } else { 645 KASSERT(fs.object != next_object, 646 ("object loop %p", next_object)); 647 VM_OBJECT_LOCK(next_object); 648 vm_object_pip_add(next_object, 1); 649 if (fs.object != fs.first_object) 650 vm_object_pip_wakeup(fs.object); 651 VM_OBJECT_UNLOCK(fs.object); 652 fs.object = next_object; 653 } 654 } 655 656 KASSERT((fs.m->flags & PG_BUSY) != 0, 657 ("vm_fault: not busy after main loop")); 658 659 /* 660 * PAGE HAS BEEN FOUND. [Loop invariant still holds -- the object lock 661 * is held.] 662 */ 663 664 /* 665 * If the page is being written, but isn't already owned by the 666 * top-level object, we have to copy it into a new page owned by the 667 * top-level object. 668 */ 669 if (fs.object != fs.first_object) { 670 /* 671 * We only really need to copy if we want to write it. 672 */ 673 if (fault_type & VM_PROT_WRITE) { 674 /* 675 * This allows pages to be virtually copied from a 676 * backing_object into the first_object, where the 677 * backing object has no other refs to it, and cannot 678 * gain any more refs. Instead of a bcopy, we just 679 * move the page from the backing object to the 680 * first object. Note that we must mark the page 681 * dirty in the first object so that it will go out 682 * to swap when needed. 683 */ 684 is_first_object_locked = FALSE; 685 if ( 686 /* 687 * Only one shadow object 688 */ 689 (fs.object->shadow_count == 1) && 690 /* 691 * No COW refs, except us 692 */ 693 (fs.object->ref_count == 1) && 694 /* 695 * No one else can look this object up 696 */ 697 (fs.object->handle == NULL) && 698 /* 699 * No other ways to look the object up 700 */ 701 ((fs.object->type == OBJT_DEFAULT) || 702 (fs.object->type == OBJT_SWAP)) && 703 (is_first_object_locked = VM_OBJECT_TRYLOCK(fs.first_object)) && 704 /* 705 * We don't chase down the shadow chain 706 */ 707 fs.object == fs.first_object->backing_object) { 708 vm_page_lock_queues(); 709 /* 710 * get rid of the unnecessary page 711 */ 712 pmap_remove_all(fs.first_m); 713 vm_page_free(fs.first_m); 714 /* 715 * grab the page and put it into the 716 * process'es object. The page is 717 * automatically made dirty. 718 */ 719 vm_page_rename(fs.m, fs.first_object, fs.first_pindex); 720 vm_page_busy(fs.m); 721 vm_page_unlock_queues(); 722 fs.first_m = fs.m; 723 fs.m = NULL; 724 cnt.v_cow_optim++; 725 } else { 726 /* 727 * Oh, well, lets copy it. 728 */ 729 vm_page_copy(fs.m, fs.first_m); 730 } 731 if (fs.m) { 732 /* 733 * We no longer need the old page or object. 734 */ 735 release_page(&fs); 736 } 737 /* 738 * fs.object != fs.first_object due to above 739 * conditional 740 */ 741 vm_object_pip_wakeup(fs.object); 742 VM_OBJECT_UNLOCK(fs.object); 743 /* 744 * Only use the new page below... 745 */ 746 fs.object = fs.first_object; 747 fs.pindex = fs.first_pindex; 748 fs.m = fs.first_m; 749 if (!is_first_object_locked) 750 VM_OBJECT_LOCK(fs.object); 751 cnt.v_cow_faults++; 752 } else { 753 prot &= ~VM_PROT_WRITE; 754 } 755 } 756 757 /* 758 * We must verify that the maps have not changed since our last 759 * lookup. 760 */ 761 if (!fs.lookup_still_valid && 762 (fs.map->timestamp != map_generation)) { 763 vm_object_t retry_object; 764 vm_pindex_t retry_pindex; 765 vm_prot_t retry_prot; 766 767 /* 768 * Since map entries may be pageable, make sure we can take a 769 * page fault on them. 770 */ 771 772 /* 773 * Unlock vnode before the lookup to avoid deadlock. E.G. 774 * avoid a deadlock between the inode and exec_map that can 775 * occur due to locks being obtained in different orders. 776 */ 777 if (fs.vp != NULL) { 778 vput(fs.vp); 779 fs.vp = NULL; 780 } 781 782 if (fs.map->infork) { 783 release_page(&fs); 784 unlock_and_deallocate(&fs); 785 goto RetryFault; 786 } 787 VM_OBJECT_UNLOCK(fs.object); 788 789 /* 790 * To avoid trying to write_lock the map while another process 791 * has it read_locked (in vm_map_pageable), we do not try for 792 * write permission. If the page is still writable, we will 793 * get write permission. If it is not, or has been marked 794 * needs_copy, we enter the mapping without write permission, 795 * and will merely take another fault. 796 */ 797 result = vm_map_lookup(&fs.map, vaddr, fault_type & ~VM_PROT_WRITE, 798 &fs.entry, &retry_object, &retry_pindex, &retry_prot, &wired); 799 map_generation = fs.map->timestamp; 800 801 VM_OBJECT_LOCK(fs.object); 802 /* 803 * If we don't need the page any longer, put it on the active 804 * list (the easiest thing to do here). If no one needs it, 805 * pageout will grab it eventually. 806 */ 807 if (result != KERN_SUCCESS) { 808 release_page(&fs); 809 unlock_and_deallocate(&fs); 810 mtx_unlock(&Giant); 811 return (result); 812 } 813 fs.lookup_still_valid = TRUE; 814 815 if ((retry_object != fs.first_object) || 816 (retry_pindex != fs.first_pindex)) { 817 release_page(&fs); 818 unlock_and_deallocate(&fs); 819 goto RetryFault; 820 } 821 /* 822 * Check whether the protection has changed or the object has 823 * been copied while we left the map unlocked. Changing from 824 * read to write permission is OK - we leave the page 825 * write-protected, and catch the write fault. Changing from 826 * write to read permission means that we can't mark the page 827 * write-enabled after all. 828 */ 829 prot &= retry_prot; 830 } 831 832 /* 833 * Put this page into the physical map. We had to do the unlock above 834 * because pmap_enter may cause other faults. We don't put the page 835 * back on the active queue until later so that the page-out daemon 836 * won't find us (yet). 837 */ 838 839 if (prot & VM_PROT_WRITE) { 840 vm_page_lock_queues(); 841 vm_page_flag_set(fs.m, PG_WRITEABLE); 842 vm_object_set_writeable_dirty(fs.m->object); 843 844 /* 845 * If the fault is a write, we know that this page is being 846 * written NOW so dirty it explicitly to save on 847 * pmap_is_modified() calls later. 848 * 849 * If this is a NOSYNC mmap we do not want to set PG_NOSYNC 850 * if the page is already dirty to prevent data written with 851 * the expectation of being synced from not being synced. 852 * Likewise if this entry does not request NOSYNC then make 853 * sure the page isn't marked NOSYNC. Applications sharing 854 * data should use the same flags to avoid ping ponging. 855 * 856 * Also tell the backing pager, if any, that it should remove 857 * any swap backing since the page is now dirty. 858 */ 859 if (fs.entry->eflags & MAP_ENTRY_NOSYNC) { 860 if (fs.m->dirty == 0) 861 vm_page_flag_set(fs.m, PG_NOSYNC); 862 } else { 863 vm_page_flag_clear(fs.m, PG_NOSYNC); 864 } 865 vm_page_unlock_queues(); 866 if (fault_flags & VM_FAULT_DIRTY) { 867 int s; 868 vm_page_dirty(fs.m); 869 s = splvm(); 870 vm_pager_page_unswapped(fs.m); 871 splx(s); 872 } 873 } 874 875 /* 876 * Page had better still be busy 877 */ 878 KASSERT(fs.m->flags & PG_BUSY, 879 ("vm_fault: page %p not busy!", fs.m)); 880 unlock_things(&fs); 881 882 /* 883 * Sanity check: page must be completely valid or it is not fit to 884 * map into user space. vm_pager_get_pages() ensures this. 885 */ 886 if (fs.m->valid != VM_PAGE_BITS_ALL) { 887 vm_page_zero_invalid(fs.m, TRUE); 888 printf("Warning: page %p partially invalid on fault\n", fs.m); 889 } 890 pmap_enter(fs.map->pmap, vaddr, fs.m, prot, wired); 891 if (((fault_flags & VM_FAULT_WIRE_MASK) == 0) && (wired == 0)) { 892 pmap_prefault(fs.map->pmap, vaddr, fs.entry); 893 } 894 vm_page_lock_queues(); 895 vm_page_flag_clear(fs.m, PG_ZERO); 896 vm_page_flag_set(fs.m, PG_REFERENCED); 897 898 /* 899 * If the page is not wired down, then put it where the pageout daemon 900 * can find it. 901 */ 902 if (fault_flags & VM_FAULT_WIRE_MASK) { 903 if (wired) 904 vm_page_wire(fs.m); 905 else 906 vm_page_unwire(fs.m, 1); 907 } else { 908 vm_page_activate(fs.m); 909 } 910 vm_page_wakeup(fs.m); 911 vm_page_unlock_queues(); 912 913 PROC_LOCK(curproc); 914 if ((curproc->p_sflag & PS_INMEM) && curproc->p_stats) { 915 if (hardfault) { 916 curproc->p_stats->p_ru.ru_majflt++; 917 } else { 918 curproc->p_stats->p_ru.ru_minflt++; 919 } 920 } 921 PROC_UNLOCK(curproc); 922 923 /* 924 * Unlock everything, and return 925 */ 926 vm_object_deallocate(fs.first_object); 927 mtx_unlock(&Giant); 928 return (KERN_SUCCESS); 929 } 930 931 /* 932 * vm_fault_quick: 933 * 934 * Ensure that the requested virtual address, which may be in userland, 935 * is valid. Fault-in the page if necessary. Return -1 on failure. 936 */ 937 int 938 vm_fault_quick(caddr_t v, int prot) 939 { 940 int r; 941 942 if (prot & VM_PROT_WRITE) 943 r = subyte(v, fubyte(v)); 944 else 945 r = fubyte(v); 946 return(r); 947 } 948 949 /* 950 * vm_fault_wire: 951 * 952 * Wire down a range of virtual addresses in a map. 953 */ 954 int 955 vm_fault_wire(map, start, end, user_wire) 956 vm_map_t map; 957 vm_offset_t start, end; 958 boolean_t user_wire; 959 { 960 vm_offset_t va; 961 int rv; 962 963 /* 964 * We simulate a fault to get the page and enter it in the physical 965 * map. For user wiring, we only ask for read access on currently 966 * read-only sections. 967 */ 968 for (va = start; va < end; va += PAGE_SIZE) { 969 rv = vm_fault(map, va, 970 user_wire ? VM_PROT_READ : VM_PROT_READ | VM_PROT_WRITE, 971 user_wire ? VM_FAULT_USER_WIRE : VM_FAULT_CHANGE_WIRING); 972 if (rv) { 973 if (va != start) 974 vm_fault_unwire(map, start, va); 975 return (rv); 976 } 977 } 978 return (KERN_SUCCESS); 979 } 980 981 /* 982 * vm_fault_unwire: 983 * 984 * Unwire a range of virtual addresses in a map. 985 */ 986 void 987 vm_fault_unwire(map, start, end) 988 vm_map_t map; 989 vm_offset_t start, end; 990 { 991 vm_paddr_t pa; 992 vm_offset_t va; 993 pmap_t pmap; 994 995 pmap = vm_map_pmap(map); 996 997 mtx_lock(&Giant); 998 /* 999 * Since the pages are wired down, we must be able to get their 1000 * mappings from the physical map system. 1001 */ 1002 for (va = start; va < end; va += PAGE_SIZE) { 1003 pa = pmap_extract(pmap, va); 1004 if (pa != 0) { 1005 pmap_change_wiring(pmap, va, FALSE); 1006 vm_page_lock_queues(); 1007 vm_page_unwire(PHYS_TO_VM_PAGE(pa), 1); 1008 vm_page_unlock_queues(); 1009 } 1010 } 1011 mtx_unlock(&Giant); 1012 } 1013 1014 /* 1015 * Routine: 1016 * vm_fault_copy_entry 1017 * Function: 1018 * Copy all of the pages from a wired-down map entry to another. 1019 * 1020 * In/out conditions: 1021 * The source and destination maps must be locked for write. 1022 * The source map entry must be wired down (or be a sharing map 1023 * entry corresponding to a main map entry that is wired down). 1024 */ 1025 void 1026 vm_fault_copy_entry(dst_map, src_map, dst_entry, src_entry) 1027 vm_map_t dst_map; 1028 vm_map_t src_map; 1029 vm_map_entry_t dst_entry; 1030 vm_map_entry_t src_entry; 1031 { 1032 vm_object_t dst_object; 1033 vm_object_t src_object; 1034 vm_ooffset_t dst_offset; 1035 vm_ooffset_t src_offset; 1036 vm_prot_t prot; 1037 vm_offset_t vaddr; 1038 vm_page_t dst_m; 1039 vm_page_t src_m; 1040 1041 #ifdef lint 1042 src_map++; 1043 #endif /* lint */ 1044 1045 src_object = src_entry->object.vm_object; 1046 src_offset = src_entry->offset; 1047 1048 /* 1049 * Create the top-level object for the destination entry. (Doesn't 1050 * actually shadow anything - we copy the pages directly.) 1051 */ 1052 dst_object = vm_object_allocate(OBJT_DEFAULT, 1053 (vm_size_t) OFF_TO_IDX(dst_entry->end - dst_entry->start)); 1054 1055 dst_entry->object.vm_object = dst_object; 1056 dst_entry->offset = 0; 1057 1058 prot = dst_entry->max_protection; 1059 1060 /* 1061 * Loop through all of the pages in the entry's range, copying each 1062 * one from the source object (it should be there) to the destination 1063 * object. 1064 */ 1065 for (vaddr = dst_entry->start, dst_offset = 0; 1066 vaddr < dst_entry->end; 1067 vaddr += PAGE_SIZE, dst_offset += PAGE_SIZE) { 1068 1069 /* 1070 * Allocate a page in the destination object 1071 */ 1072 do { 1073 dst_m = vm_page_alloc(dst_object, 1074 OFF_TO_IDX(dst_offset), VM_ALLOC_NORMAL); 1075 if (dst_m == NULL) { 1076 VM_WAIT; 1077 } 1078 } while (dst_m == NULL); 1079 1080 /* 1081 * Find the page in the source object, and copy it in. 1082 * (Because the source is wired down, the page will be in 1083 * memory.) 1084 */ 1085 VM_OBJECT_LOCK(src_object); 1086 src_m = vm_page_lookup(src_object, 1087 OFF_TO_IDX(dst_offset + src_offset)); 1088 VM_OBJECT_UNLOCK(src_object); 1089 if (src_m == NULL) 1090 panic("vm_fault_copy_wired: page missing"); 1091 1092 vm_page_copy(src_m, dst_m); 1093 1094 /* 1095 * Enter it in the pmap... 1096 */ 1097 pmap_enter(dst_map->pmap, vaddr, dst_m, prot, FALSE); 1098 vm_page_lock_queues(); 1099 vm_page_flag_set(dst_m, PG_WRITEABLE); 1100 1101 /* 1102 * Mark it no longer busy, and put it on the active list. 1103 */ 1104 vm_page_activate(dst_m); 1105 vm_page_wakeup(dst_m); 1106 vm_page_unlock_queues(); 1107 } 1108 } 1109 1110 1111 /* 1112 * This routine checks around the requested page for other pages that 1113 * might be able to be faulted in. This routine brackets the viable 1114 * pages for the pages to be paged in. 1115 * 1116 * Inputs: 1117 * m, rbehind, rahead 1118 * 1119 * Outputs: 1120 * marray (array of vm_page_t), reqpage (index of requested page) 1121 * 1122 * Return value: 1123 * number of pages in marray 1124 * 1125 * This routine can't block. 1126 */ 1127 static int 1128 vm_fault_additional_pages(m, rbehind, rahead, marray, reqpage) 1129 vm_page_t m; 1130 int rbehind; 1131 int rahead; 1132 vm_page_t *marray; 1133 int *reqpage; 1134 { 1135 int i,j; 1136 vm_object_t object; 1137 vm_pindex_t pindex, startpindex, endpindex, tpindex; 1138 vm_page_t rtm; 1139 int cbehind, cahead; 1140 1141 VM_OBJECT_LOCK_ASSERT(m->object, MA_OWNED); 1142 1143 object = m->object; 1144 pindex = m->pindex; 1145 1146 /* 1147 * we don't fault-ahead for device pager 1148 */ 1149 if (object->type == OBJT_DEVICE) { 1150 *reqpage = 0; 1151 marray[0] = m; 1152 return 1; 1153 } 1154 1155 /* 1156 * if the requested page is not available, then give up now 1157 */ 1158 if (!vm_pager_has_page(object, pindex, &cbehind, &cahead)) { 1159 return 0; 1160 } 1161 1162 if ((cbehind == 0) && (cahead == 0)) { 1163 *reqpage = 0; 1164 marray[0] = m; 1165 return 1; 1166 } 1167 1168 if (rahead > cahead) { 1169 rahead = cahead; 1170 } 1171 1172 if (rbehind > cbehind) { 1173 rbehind = cbehind; 1174 } 1175 1176 /* 1177 * try to do any readahead that we might have free pages for. 1178 */ 1179 if ((rahead + rbehind) > 1180 ((cnt.v_free_count + cnt.v_cache_count) - cnt.v_free_reserved)) { 1181 pagedaemon_wakeup(); 1182 marray[0] = m; 1183 *reqpage = 0; 1184 return 1; 1185 } 1186 1187 /* 1188 * scan backward for the read behind pages -- in memory 1189 */ 1190 if (pindex > 0) { 1191 if (rbehind > pindex) { 1192 rbehind = pindex; 1193 startpindex = 0; 1194 } else { 1195 startpindex = pindex - rbehind; 1196 } 1197 1198 for (tpindex = pindex - 1; tpindex >= startpindex; tpindex -= 1) { 1199 if (vm_page_lookup(object, tpindex)) { 1200 startpindex = tpindex + 1; 1201 break; 1202 } 1203 if (tpindex == 0) 1204 break; 1205 } 1206 1207 for (i = 0, tpindex = startpindex; tpindex < pindex; i++, tpindex++) { 1208 1209 rtm = vm_page_alloc(object, tpindex, VM_ALLOC_NORMAL); 1210 if (rtm == NULL) { 1211 vm_page_lock_queues(); 1212 for (j = 0; j < i; j++) { 1213 vm_page_free(marray[j]); 1214 } 1215 vm_page_unlock_queues(); 1216 marray[0] = m; 1217 *reqpage = 0; 1218 return 1; 1219 } 1220 1221 marray[i] = rtm; 1222 } 1223 } else { 1224 startpindex = 0; 1225 i = 0; 1226 } 1227 1228 marray[i] = m; 1229 /* page offset of the required page */ 1230 *reqpage = i; 1231 1232 tpindex = pindex + 1; 1233 i++; 1234 1235 /* 1236 * scan forward for the read ahead pages 1237 */ 1238 endpindex = tpindex + rahead; 1239 if (endpindex > object->size) 1240 endpindex = object->size; 1241 1242 for (; tpindex < endpindex; i++, tpindex++) { 1243 1244 if (vm_page_lookup(object, tpindex)) { 1245 break; 1246 } 1247 1248 rtm = vm_page_alloc(object, tpindex, VM_ALLOC_NORMAL); 1249 if (rtm == NULL) { 1250 break; 1251 } 1252 1253 marray[i] = rtm; 1254 } 1255 1256 /* return number of bytes of pages */ 1257 return i; 1258 } 1259