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 "opt_ktrace.h" 78 #include "opt_vm.h" 79 80 #include <sys/param.h> 81 #include <sys/systm.h> 82 #include <sys/kernel.h> 83 #include <sys/lock.h> 84 #include <sys/proc.h> 85 #include <sys/resourcevar.h> 86 #include <sys/rwlock.h> 87 #include <sys/sysctl.h> 88 #include <sys/vmmeter.h> 89 #include <sys/vnode.h> 90 #ifdef KTRACE 91 #include <sys/ktrace.h> 92 #endif 93 94 #include <vm/vm.h> 95 #include <vm/vm_param.h> 96 #include <vm/pmap.h> 97 #include <vm/vm_map.h> 98 #include <vm/vm_object.h> 99 #include <vm/vm_page.h> 100 #include <vm/vm_pageout.h> 101 #include <vm/vm_kern.h> 102 #include <vm/vm_pager.h> 103 #include <vm/vm_extern.h> 104 105 #define PFBAK 4 106 #define PFFOR 4 107 108 static int vm_fault_additional_pages(vm_page_t, int, int, vm_page_t *, int *); 109 110 #define VM_FAULT_READ_BEHIND 8 111 #define VM_FAULT_READ_MAX (1 + VM_FAULT_READ_AHEAD_MAX) 112 #define VM_FAULT_NINCR (VM_FAULT_READ_MAX / VM_FAULT_READ_BEHIND) 113 #define VM_FAULT_SUM (VM_FAULT_NINCR * (VM_FAULT_NINCR + 1) / 2) 114 #define VM_FAULT_CACHE_BEHIND (VM_FAULT_READ_BEHIND * VM_FAULT_SUM) 115 116 struct faultstate { 117 vm_page_t m; 118 vm_object_t object; 119 vm_pindex_t pindex; 120 vm_page_t first_m; 121 vm_object_t first_object; 122 vm_pindex_t first_pindex; 123 vm_map_t map; 124 vm_map_entry_t entry; 125 int lookup_still_valid; 126 struct vnode *vp; 127 }; 128 129 static void vm_fault_cache_behind(const struct faultstate *fs, int distance); 130 static void vm_fault_prefault(const struct faultstate *fs, vm_offset_t addra, 131 int faultcount, int reqpage); 132 133 static inline void 134 release_page(struct faultstate *fs) 135 { 136 137 vm_page_xunbusy(fs->m); 138 vm_page_lock(fs->m); 139 vm_page_deactivate(fs->m); 140 vm_page_unlock(fs->m); 141 fs->m = NULL; 142 } 143 144 static inline void 145 unlock_map(struct faultstate *fs) 146 { 147 148 if (fs->lookup_still_valid) { 149 vm_map_lookup_done(fs->map, fs->entry); 150 fs->lookup_still_valid = FALSE; 151 } 152 } 153 154 static void 155 unlock_and_deallocate(struct faultstate *fs) 156 { 157 158 vm_object_pip_wakeup(fs->object); 159 VM_OBJECT_WUNLOCK(fs->object); 160 if (fs->object != fs->first_object) { 161 VM_OBJECT_WLOCK(fs->first_object); 162 vm_page_lock(fs->first_m); 163 vm_page_free(fs->first_m); 164 vm_page_unlock(fs->first_m); 165 vm_object_pip_wakeup(fs->first_object); 166 VM_OBJECT_WUNLOCK(fs->first_object); 167 fs->first_m = NULL; 168 } 169 vm_object_deallocate(fs->first_object); 170 unlock_map(fs); 171 if (fs->vp != NULL) { 172 vput(fs->vp); 173 fs->vp = NULL; 174 } 175 } 176 177 static void 178 vm_fault_dirty(vm_map_entry_t entry, vm_page_t m, vm_prot_t prot, 179 vm_prot_t fault_type, int fault_flags, boolean_t set_wd) 180 { 181 boolean_t need_dirty; 182 183 if (((prot & VM_PROT_WRITE) == 0 && 184 (fault_flags & VM_FAULT_DIRTY) == 0) || 185 (m->oflags & VPO_UNMANAGED) != 0) 186 return; 187 188 VM_OBJECT_ASSERT_LOCKED(m->object); 189 190 need_dirty = ((fault_type & VM_PROT_WRITE) != 0 && 191 (fault_flags & VM_FAULT_CHANGE_WIRING) == 0) || 192 (fault_flags & VM_FAULT_DIRTY) != 0; 193 194 if (set_wd) 195 vm_object_set_writeable_dirty(m->object); 196 else 197 /* 198 * If two callers of vm_fault_dirty() with set_wd == 199 * FALSE, one for the map entry with MAP_ENTRY_NOSYNC 200 * flag set, other with flag clear, race, it is 201 * possible for the no-NOSYNC thread to see m->dirty 202 * != 0 and not clear VPO_NOSYNC. Take vm_page lock 203 * around manipulation of VPO_NOSYNC and 204 * vm_page_dirty() call, to avoid the race and keep 205 * m->oflags consistent. 206 */ 207 vm_page_lock(m); 208 209 /* 210 * If this is a NOSYNC mmap we do not want to set VPO_NOSYNC 211 * if the page is already dirty to prevent data written with 212 * the expectation of being synced from not being synced. 213 * Likewise if this entry does not request NOSYNC then make 214 * sure the page isn't marked NOSYNC. Applications sharing 215 * data should use the same flags to avoid ping ponging. 216 */ 217 if ((entry->eflags & MAP_ENTRY_NOSYNC) != 0) { 218 if (m->dirty == 0) { 219 m->oflags |= VPO_NOSYNC; 220 } 221 } else { 222 m->oflags &= ~VPO_NOSYNC; 223 } 224 225 /* 226 * If the fault is a write, we know that this page is being 227 * written NOW so dirty it explicitly to save on 228 * pmap_is_modified() calls later. 229 * 230 * Also tell the backing pager, if any, that it should remove 231 * any swap backing since the page is now dirty. 232 */ 233 if (need_dirty) 234 vm_page_dirty(m); 235 if (!set_wd) 236 vm_page_unlock(m); 237 if (need_dirty) 238 vm_pager_page_unswapped(m); 239 } 240 241 /* 242 * TRYPAGER - used by vm_fault to calculate whether the pager for the 243 * current object *might* contain the page. 244 * 245 * default objects are zero-fill, there is no real pager. 246 */ 247 #define TRYPAGER (fs.object->type != OBJT_DEFAULT && \ 248 ((fault_flags & VM_FAULT_CHANGE_WIRING) == 0 || wired)) 249 250 /* 251 * vm_fault: 252 * 253 * Handle a page fault occurring at the given address, 254 * requiring the given permissions, in the map specified. 255 * If successful, the page is inserted into the 256 * associated physical map. 257 * 258 * NOTE: the given address should be truncated to the 259 * proper page address. 260 * 261 * KERN_SUCCESS is returned if the page fault is handled; otherwise, 262 * a standard error specifying why the fault is fatal is returned. 263 * 264 * The map in question must be referenced, and remains so. 265 * Caller may hold no locks. 266 */ 267 int 268 vm_fault(vm_map_t map, vm_offset_t vaddr, vm_prot_t fault_type, 269 int fault_flags) 270 { 271 struct thread *td; 272 int result; 273 274 td = curthread; 275 if ((td->td_pflags & TDP_NOFAULTING) != 0) 276 return (KERN_PROTECTION_FAILURE); 277 #ifdef KTRACE 278 if (map != kernel_map && KTRPOINT(td, KTR_FAULT)) 279 ktrfault(vaddr, fault_type); 280 #endif 281 result = vm_fault_hold(map, trunc_page(vaddr), fault_type, fault_flags, 282 NULL); 283 #ifdef KTRACE 284 if (map != kernel_map && KTRPOINT(td, KTR_FAULTEND)) 285 ktrfaultend(result); 286 #endif 287 return (result); 288 } 289 290 int 291 vm_fault_hold(vm_map_t map, vm_offset_t vaddr, vm_prot_t fault_type, 292 int fault_flags, vm_page_t *m_hold) 293 { 294 vm_prot_t prot; 295 long ahead, behind; 296 int alloc_req, era, faultcount, nera, reqpage, result; 297 boolean_t growstack, is_first_object_locked, wired; 298 int map_generation; 299 vm_object_t next_object; 300 vm_page_t marray[VM_FAULT_READ_MAX]; 301 int hardfault; 302 struct faultstate fs; 303 struct vnode *vp; 304 vm_page_t m; 305 int locked, error; 306 307 hardfault = 0; 308 growstack = TRUE; 309 PCPU_INC(cnt.v_vm_faults); 310 fs.vp = NULL; 311 faultcount = reqpage = 0; 312 313 RetryFault:; 314 315 /* 316 * Find the backing store object and offset into it to begin the 317 * search. 318 */ 319 fs.map = map; 320 result = vm_map_lookup(&fs.map, vaddr, fault_type, &fs.entry, 321 &fs.first_object, &fs.first_pindex, &prot, &wired); 322 if (result != KERN_SUCCESS) { 323 if (growstack && result == KERN_INVALID_ADDRESS && 324 map != kernel_map) { 325 result = vm_map_growstack(curproc, vaddr); 326 if (result != KERN_SUCCESS) 327 return (KERN_FAILURE); 328 growstack = FALSE; 329 goto RetryFault; 330 } 331 return (result); 332 } 333 334 map_generation = fs.map->timestamp; 335 336 if (fs.entry->eflags & MAP_ENTRY_NOFAULT) { 337 if ((curthread->td_pflags & TDP_DEVMEMIO) != 0) { 338 vm_map_unlock_read(fs.map); 339 return (KERN_FAILURE); 340 } 341 panic("vm_fault: fault on nofault entry, addr: %lx", 342 (u_long)vaddr); 343 } 344 345 if (fs.entry->eflags & MAP_ENTRY_IN_TRANSITION && 346 fs.entry->wiring_thread != curthread) { 347 vm_map_unlock_read(fs.map); 348 vm_map_lock(fs.map); 349 if (vm_map_lookup_entry(fs.map, vaddr, &fs.entry) && 350 (fs.entry->eflags & MAP_ENTRY_IN_TRANSITION)) { 351 fs.entry->eflags |= MAP_ENTRY_NEEDS_WAKEUP; 352 vm_map_unlock_and_wait(fs.map, 0); 353 } else 354 vm_map_unlock(fs.map); 355 goto RetryFault; 356 } 357 358 if (wired) 359 fault_type = prot | (fault_type & VM_PROT_COPY); 360 361 if (fs.vp == NULL /* avoid locked vnode leak */ && 362 (fault_flags & (VM_FAULT_CHANGE_WIRING | VM_FAULT_DIRTY)) == 0 && 363 /* avoid calling vm_object_set_writeable_dirty() */ 364 ((prot & VM_PROT_WRITE) == 0 || 365 fs.first_object->type != OBJT_VNODE || 366 (fs.first_object->flags & OBJ_MIGHTBEDIRTY) != 0)) { 367 VM_OBJECT_RLOCK(fs.first_object); 368 if ((prot & VM_PROT_WRITE) != 0 && 369 fs.first_object->type == OBJT_VNODE && 370 (fs.first_object->flags & OBJ_MIGHTBEDIRTY) == 0) 371 goto fast_failed; 372 m = vm_page_lookup(fs.first_object, fs.first_pindex); 373 /* A busy page can be mapped for read|execute access. */ 374 if (m == NULL || ((prot & VM_PROT_WRITE) != 0 && 375 vm_page_busied(m)) || m->valid != VM_PAGE_BITS_ALL) 376 goto fast_failed; 377 result = pmap_enter(fs.map->pmap, vaddr, m, prot, 378 fault_type | PMAP_ENTER_NOSLEEP | (wired ? PMAP_ENTER_WIRED : 379 0), 0); 380 if (result != KERN_SUCCESS) 381 goto fast_failed; 382 if (m_hold != NULL) { 383 *m_hold = m; 384 vm_page_lock(m); 385 vm_page_hold(m); 386 vm_page_unlock(m); 387 } 388 vm_fault_dirty(fs.entry, m, prot, fault_type, fault_flags, 389 FALSE); 390 VM_OBJECT_RUNLOCK(fs.first_object); 391 if (!wired) 392 vm_fault_prefault(&fs, vaddr, 0, 0); 393 vm_map_lookup_done(fs.map, fs.entry); 394 curthread->td_ru.ru_minflt++; 395 return (KERN_SUCCESS); 396 fast_failed: 397 if (!VM_OBJECT_TRYUPGRADE(fs.first_object)) { 398 VM_OBJECT_RUNLOCK(fs.first_object); 399 VM_OBJECT_WLOCK(fs.first_object); 400 } 401 } else { 402 VM_OBJECT_WLOCK(fs.first_object); 403 } 404 405 /* 406 * Make a reference to this object to prevent its disposal while we 407 * are messing with it. Once we have the reference, the map is free 408 * to be diddled. Since objects reference their shadows (and copies), 409 * they will stay around as well. 410 * 411 * Bump the paging-in-progress count to prevent size changes (e.g. 412 * truncation operations) during I/O. This must be done after 413 * obtaining the vnode lock in order to avoid possible deadlocks. 414 */ 415 vm_object_reference_locked(fs.first_object); 416 vm_object_pip_add(fs.first_object, 1); 417 418 fs.lookup_still_valid = TRUE; 419 420 fs.first_m = NULL; 421 422 /* 423 * Search for the page at object/offset. 424 */ 425 fs.object = fs.first_object; 426 fs.pindex = fs.first_pindex; 427 while (TRUE) { 428 /* 429 * If the object is dead, we stop here 430 */ 431 if (fs.object->flags & OBJ_DEAD) { 432 unlock_and_deallocate(&fs); 433 return (KERN_PROTECTION_FAILURE); 434 } 435 436 /* 437 * See if page is resident 438 */ 439 fs.m = vm_page_lookup(fs.object, fs.pindex); 440 if (fs.m != NULL) { 441 /* 442 * Wait/Retry if the page is busy. We have to do this 443 * if the page is either exclusive or shared busy 444 * because the vm_pager may be using read busy for 445 * pageouts (and even pageins if it is the vnode 446 * pager), and we could end up trying to pagein and 447 * pageout the same page simultaneously. 448 * 449 * We can theoretically allow the busy case on a read 450 * fault if the page is marked valid, but since such 451 * pages are typically already pmap'd, putting that 452 * special case in might be more effort then it is 453 * worth. We cannot under any circumstances mess 454 * around with a shared busied page except, perhaps, 455 * to pmap it. 456 */ 457 if (vm_page_busied(fs.m)) { 458 /* 459 * Reference the page before unlocking and 460 * sleeping so that the page daemon is less 461 * likely to reclaim it. 462 */ 463 vm_page_aflag_set(fs.m, PGA_REFERENCED); 464 if (fs.object != fs.first_object) { 465 if (!VM_OBJECT_TRYWLOCK( 466 fs.first_object)) { 467 VM_OBJECT_WUNLOCK(fs.object); 468 VM_OBJECT_WLOCK(fs.first_object); 469 VM_OBJECT_WLOCK(fs.object); 470 } 471 vm_page_lock(fs.first_m); 472 vm_page_free(fs.first_m); 473 vm_page_unlock(fs.first_m); 474 vm_object_pip_wakeup(fs.first_object); 475 VM_OBJECT_WUNLOCK(fs.first_object); 476 fs.first_m = NULL; 477 } 478 unlock_map(&fs); 479 if (fs.m == vm_page_lookup(fs.object, 480 fs.pindex)) { 481 vm_page_sleep_if_busy(fs.m, "vmpfw"); 482 } 483 vm_object_pip_wakeup(fs.object); 484 VM_OBJECT_WUNLOCK(fs.object); 485 PCPU_INC(cnt.v_intrans); 486 vm_object_deallocate(fs.first_object); 487 goto RetryFault; 488 } 489 vm_page_lock(fs.m); 490 vm_page_remque(fs.m); 491 vm_page_unlock(fs.m); 492 493 /* 494 * Mark page busy for other processes, and the 495 * pagedaemon. If it still isn't completely valid 496 * (readable), jump to readrest, else break-out ( we 497 * found the page ). 498 */ 499 vm_page_xbusy(fs.m); 500 if (fs.m->valid != VM_PAGE_BITS_ALL) 501 goto readrest; 502 break; 503 } 504 505 /* 506 * Page is not resident, If this is the search termination 507 * or the pager might contain the page, allocate a new page. 508 */ 509 if (TRYPAGER || fs.object == fs.first_object) { 510 if (fs.pindex >= fs.object->size) { 511 unlock_and_deallocate(&fs); 512 return (KERN_PROTECTION_FAILURE); 513 } 514 515 /* 516 * Allocate a new page for this object/offset pair. 517 * 518 * Unlocked read of the p_flag is harmless. At 519 * worst, the P_KILLED might be not observed 520 * there, and allocation can fail, causing 521 * restart and new reading of the p_flag. 522 */ 523 fs.m = NULL; 524 if (!vm_page_count_severe() || P_KILLED(curproc)) { 525 #if VM_NRESERVLEVEL > 0 526 if ((fs.object->flags & OBJ_COLORED) == 0) { 527 fs.object->flags |= OBJ_COLORED; 528 fs.object->pg_color = atop(vaddr) - 529 fs.pindex; 530 } 531 #endif 532 alloc_req = P_KILLED(curproc) ? 533 VM_ALLOC_SYSTEM : VM_ALLOC_NORMAL; 534 if (fs.object->type != OBJT_VNODE && 535 fs.object->backing_object == NULL) 536 alloc_req |= VM_ALLOC_ZERO; 537 fs.m = vm_page_alloc(fs.object, fs.pindex, 538 alloc_req); 539 } 540 if (fs.m == NULL) { 541 unlock_and_deallocate(&fs); 542 VM_WAITPFAULT; 543 goto RetryFault; 544 } else if (fs.m->valid == VM_PAGE_BITS_ALL) 545 break; 546 } 547 548 readrest: 549 /* 550 * We have found a valid page or we have allocated a new page. 551 * The page thus may not be valid or may not be entirely 552 * valid. 553 * 554 * Attempt to fault-in the page if there is a chance that the 555 * pager has it, and potentially fault in additional pages 556 * at the same time. 557 */ 558 if (TRYPAGER) { 559 int rv; 560 u_char behavior = vm_map_entry_behavior(fs.entry); 561 562 if (behavior == MAP_ENTRY_BEHAV_RANDOM || 563 P_KILLED(curproc)) { 564 behind = 0; 565 ahead = 0; 566 } else if (behavior == MAP_ENTRY_BEHAV_SEQUENTIAL) { 567 behind = 0; 568 ahead = atop(fs.entry->end - vaddr) - 1; 569 if (ahead > VM_FAULT_READ_AHEAD_MAX) 570 ahead = VM_FAULT_READ_AHEAD_MAX; 571 if (fs.pindex == fs.entry->next_read) 572 vm_fault_cache_behind(&fs, 573 VM_FAULT_READ_MAX); 574 } else { 575 /* 576 * If this is a sequential page fault, then 577 * arithmetically increase the number of pages 578 * in the read-ahead window. Otherwise, reset 579 * the read-ahead window to its smallest size. 580 */ 581 behind = atop(vaddr - fs.entry->start); 582 if (behind > VM_FAULT_READ_BEHIND) 583 behind = VM_FAULT_READ_BEHIND; 584 ahead = atop(fs.entry->end - vaddr) - 1; 585 era = fs.entry->read_ahead; 586 if (fs.pindex == fs.entry->next_read) { 587 nera = era + behind; 588 if (nera > VM_FAULT_READ_AHEAD_MAX) 589 nera = VM_FAULT_READ_AHEAD_MAX; 590 behind = 0; 591 if (ahead > nera) 592 ahead = nera; 593 if (era == VM_FAULT_READ_AHEAD_MAX) 594 vm_fault_cache_behind(&fs, 595 VM_FAULT_CACHE_BEHIND); 596 } else if (ahead > VM_FAULT_READ_AHEAD_MIN) 597 ahead = VM_FAULT_READ_AHEAD_MIN; 598 if (era != ahead) 599 fs.entry->read_ahead = ahead; 600 } 601 602 /* 603 * Call the pager to retrieve the data, if any, after 604 * releasing the lock on the map. We hold a ref on 605 * fs.object and the pages are exclusive busied. 606 */ 607 unlock_map(&fs); 608 609 if (fs.object->type == OBJT_VNODE) { 610 vp = fs.object->handle; 611 if (vp == fs.vp) 612 goto vnode_locked; 613 else if (fs.vp != NULL) { 614 vput(fs.vp); 615 fs.vp = NULL; 616 } 617 locked = VOP_ISLOCKED(vp); 618 619 if (locked != LK_EXCLUSIVE) 620 locked = LK_SHARED; 621 /* Do not sleep for vnode lock while fs.m is busy */ 622 error = vget(vp, locked | LK_CANRECURSE | 623 LK_NOWAIT, curthread); 624 if (error != 0) { 625 vhold(vp); 626 release_page(&fs); 627 unlock_and_deallocate(&fs); 628 error = vget(vp, locked | LK_RETRY | 629 LK_CANRECURSE, curthread); 630 vdrop(vp); 631 fs.vp = vp; 632 KASSERT(error == 0, 633 ("vm_fault: vget failed")); 634 goto RetryFault; 635 } 636 fs.vp = vp; 637 } 638 vnode_locked: 639 KASSERT(fs.vp == NULL || !fs.map->system_map, 640 ("vm_fault: vnode-backed object mapped by system map")); 641 642 /* 643 * now we find out if any other pages should be paged 644 * in at this time this routine checks to see if the 645 * pages surrounding this fault reside in the same 646 * object as the page for this fault. If they do, 647 * then they are faulted in also into the object. The 648 * array "marray" returned contains an array of 649 * vm_page_t structs where one of them is the 650 * vm_page_t passed to the routine. The reqpage 651 * return value is the index into the marray for the 652 * vm_page_t passed to the routine. 653 * 654 * fs.m plus the additional pages are exclusive busied. 655 */ 656 faultcount = vm_fault_additional_pages( 657 fs.m, behind, ahead, marray, &reqpage); 658 659 rv = faultcount ? 660 vm_pager_get_pages(fs.object, marray, faultcount, 661 reqpage) : VM_PAGER_FAIL; 662 663 if (rv == VM_PAGER_OK) { 664 /* 665 * Found the page. Leave it busy while we play 666 * with it. 667 */ 668 669 /* 670 * Relookup in case pager changed page. Pager 671 * is responsible for disposition of old page 672 * if moved. 673 */ 674 fs.m = vm_page_lookup(fs.object, fs.pindex); 675 if (!fs.m) { 676 unlock_and_deallocate(&fs); 677 goto RetryFault; 678 } 679 680 hardfault++; 681 break; /* break to PAGE HAS BEEN FOUND */ 682 } 683 /* 684 * Remove the bogus page (which does not exist at this 685 * object/offset); before doing so, we must get back 686 * our object lock to preserve our invariant. 687 * 688 * Also wake up any other process that may want to bring 689 * in this page. 690 * 691 * If this is the top-level object, we must leave the 692 * busy page to prevent another process from rushing 693 * past us, and inserting the page in that object at 694 * the same time that we are. 695 */ 696 if (rv == VM_PAGER_ERROR) 697 printf("vm_fault: pager read error, pid %d (%s)\n", 698 curproc->p_pid, curproc->p_comm); 699 /* 700 * Data outside the range of the pager or an I/O error 701 */ 702 /* 703 * XXX - the check for kernel_map is a kludge to work 704 * around having the machine panic on a kernel space 705 * fault w/ I/O error. 706 */ 707 if (((fs.map != kernel_map) && (rv == VM_PAGER_ERROR)) || 708 (rv == VM_PAGER_BAD)) { 709 vm_page_lock(fs.m); 710 vm_page_free(fs.m); 711 vm_page_unlock(fs.m); 712 fs.m = NULL; 713 unlock_and_deallocate(&fs); 714 return ((rv == VM_PAGER_ERROR) ? KERN_FAILURE : KERN_PROTECTION_FAILURE); 715 } 716 if (fs.object != fs.first_object) { 717 vm_page_lock(fs.m); 718 vm_page_free(fs.m); 719 vm_page_unlock(fs.m); 720 fs.m = NULL; 721 /* 722 * XXX - we cannot just fall out at this 723 * point, m has been freed and is invalid! 724 */ 725 } 726 } 727 728 /* 729 * We get here if the object has default pager (or unwiring) 730 * or the pager doesn't have the page. 731 */ 732 if (fs.object == fs.first_object) 733 fs.first_m = fs.m; 734 735 /* 736 * Move on to the next object. Lock the next object before 737 * unlocking the current one. 738 */ 739 fs.pindex += OFF_TO_IDX(fs.object->backing_object_offset); 740 next_object = fs.object->backing_object; 741 if (next_object == NULL) { 742 /* 743 * If there's no object left, fill the page in the top 744 * object with zeros. 745 */ 746 if (fs.object != fs.first_object) { 747 vm_object_pip_wakeup(fs.object); 748 VM_OBJECT_WUNLOCK(fs.object); 749 750 fs.object = fs.first_object; 751 fs.pindex = fs.first_pindex; 752 fs.m = fs.first_m; 753 VM_OBJECT_WLOCK(fs.object); 754 } 755 fs.first_m = NULL; 756 757 /* 758 * Zero the page if necessary and mark it valid. 759 */ 760 if ((fs.m->flags & PG_ZERO) == 0) { 761 pmap_zero_page(fs.m); 762 } else { 763 PCPU_INC(cnt.v_ozfod); 764 } 765 PCPU_INC(cnt.v_zfod); 766 fs.m->valid = VM_PAGE_BITS_ALL; 767 /* Don't try to prefault neighboring pages. */ 768 faultcount = 1; 769 break; /* break to PAGE HAS BEEN FOUND */ 770 } else { 771 KASSERT(fs.object != next_object, 772 ("object loop %p", next_object)); 773 VM_OBJECT_WLOCK(next_object); 774 vm_object_pip_add(next_object, 1); 775 if (fs.object != fs.first_object) 776 vm_object_pip_wakeup(fs.object); 777 VM_OBJECT_WUNLOCK(fs.object); 778 fs.object = next_object; 779 } 780 } 781 782 vm_page_assert_xbusied(fs.m); 783 784 /* 785 * PAGE HAS BEEN FOUND. [Loop invariant still holds -- the object lock 786 * is held.] 787 */ 788 789 /* 790 * If the page is being written, but isn't already owned by the 791 * top-level object, we have to copy it into a new page owned by the 792 * top-level object. 793 */ 794 if (fs.object != fs.first_object) { 795 /* 796 * We only really need to copy if we want to write it. 797 */ 798 if ((fault_type & (VM_PROT_COPY | VM_PROT_WRITE)) != 0) { 799 /* 800 * This allows pages to be virtually copied from a 801 * backing_object into the first_object, where the 802 * backing object has no other refs to it, and cannot 803 * gain any more refs. Instead of a bcopy, we just 804 * move the page from the backing object to the 805 * first object. Note that we must mark the page 806 * dirty in the first object so that it will go out 807 * to swap when needed. 808 */ 809 is_first_object_locked = FALSE; 810 if ( 811 /* 812 * Only one shadow object 813 */ 814 (fs.object->shadow_count == 1) && 815 /* 816 * No COW refs, except us 817 */ 818 (fs.object->ref_count == 1) && 819 /* 820 * No one else can look this object up 821 */ 822 (fs.object->handle == NULL) && 823 /* 824 * No other ways to look the object up 825 */ 826 ((fs.object->type == OBJT_DEFAULT) || 827 (fs.object->type == OBJT_SWAP)) && 828 (is_first_object_locked = VM_OBJECT_TRYWLOCK(fs.first_object)) && 829 /* 830 * We don't chase down the shadow chain 831 */ 832 fs.object == fs.first_object->backing_object) { 833 /* 834 * get rid of the unnecessary page 835 */ 836 vm_page_lock(fs.first_m); 837 vm_page_free(fs.first_m); 838 vm_page_unlock(fs.first_m); 839 /* 840 * grab the page and put it into the 841 * process'es object. The page is 842 * automatically made dirty. 843 */ 844 if (vm_page_rename(fs.m, fs.first_object, 845 fs.first_pindex)) { 846 unlock_and_deallocate(&fs); 847 goto RetryFault; 848 } 849 vm_page_xbusy(fs.m); 850 fs.first_m = fs.m; 851 fs.m = NULL; 852 PCPU_INC(cnt.v_cow_optim); 853 } else { 854 /* 855 * Oh, well, lets copy it. 856 */ 857 pmap_copy_page(fs.m, fs.first_m); 858 fs.first_m->valid = VM_PAGE_BITS_ALL; 859 if (wired && (fault_flags & 860 VM_FAULT_CHANGE_WIRING) == 0) { 861 vm_page_lock(fs.first_m); 862 vm_page_wire(fs.first_m); 863 vm_page_unlock(fs.first_m); 864 865 vm_page_lock(fs.m); 866 vm_page_unwire(fs.m, PQ_INACTIVE); 867 vm_page_unlock(fs.m); 868 } 869 /* 870 * We no longer need the old page or object. 871 */ 872 release_page(&fs); 873 } 874 /* 875 * fs.object != fs.first_object due to above 876 * conditional 877 */ 878 vm_object_pip_wakeup(fs.object); 879 VM_OBJECT_WUNLOCK(fs.object); 880 /* 881 * Only use the new page below... 882 */ 883 fs.object = fs.first_object; 884 fs.pindex = fs.first_pindex; 885 fs.m = fs.first_m; 886 if (!is_first_object_locked) 887 VM_OBJECT_WLOCK(fs.object); 888 PCPU_INC(cnt.v_cow_faults); 889 curthread->td_cow++; 890 } else { 891 prot &= ~VM_PROT_WRITE; 892 } 893 } 894 895 /* 896 * We must verify that the maps have not changed since our last 897 * lookup. 898 */ 899 if (!fs.lookup_still_valid) { 900 vm_object_t retry_object; 901 vm_pindex_t retry_pindex; 902 vm_prot_t retry_prot; 903 904 if (!vm_map_trylock_read(fs.map)) { 905 release_page(&fs); 906 unlock_and_deallocate(&fs); 907 goto RetryFault; 908 } 909 fs.lookup_still_valid = TRUE; 910 if (fs.map->timestamp != map_generation) { 911 result = vm_map_lookup_locked(&fs.map, vaddr, fault_type, 912 &fs.entry, &retry_object, &retry_pindex, &retry_prot, &wired); 913 914 /* 915 * If we don't need the page any longer, put it on the inactive 916 * list (the easiest thing to do here). If no one needs it, 917 * pageout will grab it eventually. 918 */ 919 if (result != KERN_SUCCESS) { 920 release_page(&fs); 921 unlock_and_deallocate(&fs); 922 923 /* 924 * If retry of map lookup would have blocked then 925 * retry fault from start. 926 */ 927 if (result == KERN_FAILURE) 928 goto RetryFault; 929 return (result); 930 } 931 if ((retry_object != fs.first_object) || 932 (retry_pindex != fs.first_pindex)) { 933 release_page(&fs); 934 unlock_and_deallocate(&fs); 935 goto RetryFault; 936 } 937 938 /* 939 * Check whether the protection has changed or the object has 940 * been copied while we left the map unlocked. Changing from 941 * read to write permission is OK - we leave the page 942 * write-protected, and catch the write fault. Changing from 943 * write to read permission means that we can't mark the page 944 * write-enabled after all. 945 */ 946 prot &= retry_prot; 947 } 948 } 949 /* 950 * If the page was filled by a pager, update the map entry's 951 * last read offset. Since the pager does not return the 952 * actual set of pages that it read, this update is based on 953 * the requested set. Typically, the requested and actual 954 * sets are the same. 955 * 956 * XXX The following assignment modifies the map 957 * without holding a write lock on it. 958 */ 959 if (hardfault) 960 fs.entry->next_read = fs.pindex + faultcount - reqpage; 961 962 vm_fault_dirty(fs.entry, fs.m, prot, fault_type, fault_flags, TRUE); 963 vm_page_assert_xbusied(fs.m); 964 965 /* 966 * Page must be completely valid or it is not fit to 967 * map into user space. vm_pager_get_pages() ensures this. 968 */ 969 KASSERT(fs.m->valid == VM_PAGE_BITS_ALL, 970 ("vm_fault: page %p partially invalid", fs.m)); 971 VM_OBJECT_WUNLOCK(fs.object); 972 973 /* 974 * Put this page into the physical map. We had to do the unlock above 975 * because pmap_enter() may sleep. We don't put the page 976 * back on the active queue until later so that the pageout daemon 977 * won't find it (yet). 978 */ 979 pmap_enter(fs.map->pmap, vaddr, fs.m, prot, 980 fault_type | (wired ? PMAP_ENTER_WIRED : 0), 0); 981 if (faultcount != 1 && (fault_flags & VM_FAULT_CHANGE_WIRING) == 0 && 982 wired == 0) 983 vm_fault_prefault(&fs, vaddr, faultcount, reqpage); 984 VM_OBJECT_WLOCK(fs.object); 985 vm_page_lock(fs.m); 986 987 /* 988 * If the page is not wired down, then put it where the pageout daemon 989 * can find it. 990 */ 991 if (fault_flags & VM_FAULT_CHANGE_WIRING) { 992 if (wired) 993 vm_page_wire(fs.m); 994 else 995 vm_page_unwire(fs.m, PQ_ACTIVE); 996 } else 997 vm_page_activate(fs.m); 998 if (m_hold != NULL) { 999 *m_hold = fs.m; 1000 vm_page_hold(fs.m); 1001 } 1002 vm_page_unlock(fs.m); 1003 vm_page_xunbusy(fs.m); 1004 1005 /* 1006 * Unlock everything, and return 1007 */ 1008 unlock_and_deallocate(&fs); 1009 if (hardfault) { 1010 PCPU_INC(cnt.v_io_faults); 1011 curthread->td_ru.ru_majflt++; 1012 } else 1013 curthread->td_ru.ru_minflt++; 1014 1015 return (KERN_SUCCESS); 1016 } 1017 1018 /* 1019 * Speed up the reclamation of up to "distance" pages that precede the 1020 * faulting pindex within the first object of the shadow chain. 1021 */ 1022 static void 1023 vm_fault_cache_behind(const struct faultstate *fs, int distance) 1024 { 1025 vm_object_t first_object, object; 1026 vm_page_t m, m_prev; 1027 vm_pindex_t pindex; 1028 1029 object = fs->object; 1030 VM_OBJECT_ASSERT_WLOCKED(object); 1031 first_object = fs->first_object; 1032 if (first_object != object) { 1033 if (!VM_OBJECT_TRYWLOCK(first_object)) { 1034 VM_OBJECT_WUNLOCK(object); 1035 VM_OBJECT_WLOCK(first_object); 1036 VM_OBJECT_WLOCK(object); 1037 } 1038 } 1039 /* Neither fictitious nor unmanaged pages can be cached. */ 1040 if ((first_object->flags & (OBJ_FICTITIOUS | OBJ_UNMANAGED)) == 0) { 1041 if (fs->first_pindex < distance) 1042 pindex = 0; 1043 else 1044 pindex = fs->first_pindex - distance; 1045 if (pindex < OFF_TO_IDX(fs->entry->offset)) 1046 pindex = OFF_TO_IDX(fs->entry->offset); 1047 m = first_object != object ? fs->first_m : fs->m; 1048 vm_page_assert_xbusied(m); 1049 m_prev = vm_page_prev(m); 1050 while ((m = m_prev) != NULL && m->pindex >= pindex && 1051 m->valid == VM_PAGE_BITS_ALL) { 1052 m_prev = vm_page_prev(m); 1053 if (vm_page_busied(m)) 1054 continue; 1055 vm_page_lock(m); 1056 if (m->hold_count == 0 && m->wire_count == 0) { 1057 pmap_remove_all(m); 1058 vm_page_aflag_clear(m, PGA_REFERENCED); 1059 if (m->dirty != 0) 1060 vm_page_deactivate(m); 1061 else 1062 vm_page_cache(m); 1063 } 1064 vm_page_unlock(m); 1065 } 1066 } 1067 if (first_object != object) 1068 VM_OBJECT_WUNLOCK(first_object); 1069 } 1070 1071 /* 1072 * vm_fault_prefault provides a quick way of clustering 1073 * pagefaults into a processes address space. It is a "cousin" 1074 * of vm_map_pmap_enter, except it runs at page fault time instead 1075 * of mmap time. 1076 */ 1077 static void 1078 vm_fault_prefault(const struct faultstate *fs, vm_offset_t addra, 1079 int faultcount, int reqpage) 1080 { 1081 pmap_t pmap; 1082 vm_map_entry_t entry; 1083 vm_object_t backing_object, lobject; 1084 vm_offset_t addr, starta; 1085 vm_pindex_t pindex; 1086 vm_page_t m; 1087 int backward, forward, i; 1088 1089 pmap = fs->map->pmap; 1090 if (pmap != vmspace_pmap(curthread->td_proc->p_vmspace)) 1091 return; 1092 1093 if (faultcount > 0) { 1094 backward = reqpage; 1095 forward = faultcount - reqpage - 1; 1096 } else { 1097 backward = PFBAK; 1098 forward = PFFOR; 1099 } 1100 entry = fs->entry; 1101 1102 starta = addra - backward * PAGE_SIZE; 1103 if (starta < entry->start) { 1104 starta = entry->start; 1105 } else if (starta > addra) { 1106 starta = 0; 1107 } 1108 1109 /* 1110 * Generate the sequence of virtual addresses that are candidates for 1111 * prefaulting in an outward spiral from the faulting virtual address, 1112 * "addra". Specifically, the sequence is "addra - PAGE_SIZE", "addra 1113 * + PAGE_SIZE", "addra - 2 * PAGE_SIZE", "addra + 2 * PAGE_SIZE", ... 1114 * If the candidate address doesn't have a backing physical page, then 1115 * the loop immediately terminates. 1116 */ 1117 for (i = 0; i < 2 * imax(backward, forward); i++) { 1118 addr = addra + ((i >> 1) + 1) * ((i & 1) == 0 ? -PAGE_SIZE : 1119 PAGE_SIZE); 1120 if (addr > addra + forward * PAGE_SIZE) 1121 addr = 0; 1122 1123 if (addr < starta || addr >= entry->end) 1124 continue; 1125 1126 if (!pmap_is_prefaultable(pmap, addr)) 1127 continue; 1128 1129 pindex = ((addr - entry->start) + entry->offset) >> PAGE_SHIFT; 1130 lobject = entry->object.vm_object; 1131 VM_OBJECT_RLOCK(lobject); 1132 while ((m = vm_page_lookup(lobject, pindex)) == NULL && 1133 lobject->type == OBJT_DEFAULT && 1134 (backing_object = lobject->backing_object) != NULL) { 1135 KASSERT((lobject->backing_object_offset & PAGE_MASK) == 1136 0, ("vm_fault_prefault: unaligned object offset")); 1137 pindex += lobject->backing_object_offset >> PAGE_SHIFT; 1138 VM_OBJECT_RLOCK(backing_object); 1139 VM_OBJECT_RUNLOCK(lobject); 1140 lobject = backing_object; 1141 } 1142 if (m == NULL) { 1143 VM_OBJECT_RUNLOCK(lobject); 1144 break; 1145 } 1146 if (m->valid == VM_PAGE_BITS_ALL && 1147 (m->flags & PG_FICTITIOUS) == 0) 1148 pmap_enter_quick(pmap, addr, m, entry->protection); 1149 VM_OBJECT_RUNLOCK(lobject); 1150 } 1151 } 1152 1153 /* 1154 * Hold each of the physical pages that are mapped by the specified range of 1155 * virtual addresses, ["addr", "addr" + "len"), if those mappings are valid 1156 * and allow the specified types of access, "prot". If all of the implied 1157 * pages are successfully held, then the number of held pages is returned 1158 * together with pointers to those pages in the array "ma". However, if any 1159 * of the pages cannot be held, -1 is returned. 1160 */ 1161 int 1162 vm_fault_quick_hold_pages(vm_map_t map, vm_offset_t addr, vm_size_t len, 1163 vm_prot_t prot, vm_page_t *ma, int max_count) 1164 { 1165 vm_offset_t end, va; 1166 vm_page_t *mp; 1167 int count; 1168 boolean_t pmap_failed; 1169 1170 if (len == 0) 1171 return (0); 1172 end = round_page(addr + len); 1173 addr = trunc_page(addr); 1174 1175 /* 1176 * Check for illegal addresses. 1177 */ 1178 if (addr < vm_map_min(map) || addr > end || end > vm_map_max(map)) 1179 return (-1); 1180 1181 if (atop(end - addr) > max_count) 1182 panic("vm_fault_quick_hold_pages: count > max_count"); 1183 count = atop(end - addr); 1184 1185 /* 1186 * Most likely, the physical pages are resident in the pmap, so it is 1187 * faster to try pmap_extract_and_hold() first. 1188 */ 1189 pmap_failed = FALSE; 1190 for (mp = ma, va = addr; va < end; mp++, va += PAGE_SIZE) { 1191 *mp = pmap_extract_and_hold(map->pmap, va, prot); 1192 if (*mp == NULL) 1193 pmap_failed = TRUE; 1194 else if ((prot & VM_PROT_WRITE) != 0 && 1195 (*mp)->dirty != VM_PAGE_BITS_ALL) { 1196 /* 1197 * Explicitly dirty the physical page. Otherwise, the 1198 * caller's changes may go unnoticed because they are 1199 * performed through an unmanaged mapping or by a DMA 1200 * operation. 1201 * 1202 * The object lock is not held here. 1203 * See vm_page_clear_dirty_mask(). 1204 */ 1205 vm_page_dirty(*mp); 1206 } 1207 } 1208 if (pmap_failed) { 1209 /* 1210 * One or more pages could not be held by the pmap. Either no 1211 * page was mapped at the specified virtual address or that 1212 * mapping had insufficient permissions. Attempt to fault in 1213 * and hold these pages. 1214 */ 1215 for (mp = ma, va = addr; va < end; mp++, va += PAGE_SIZE) 1216 if (*mp == NULL && vm_fault_hold(map, va, prot, 1217 VM_FAULT_NORMAL, mp) != KERN_SUCCESS) 1218 goto error; 1219 } 1220 return (count); 1221 error: 1222 for (mp = ma; mp < ma + count; mp++) 1223 if (*mp != NULL) { 1224 vm_page_lock(*mp); 1225 vm_page_unhold(*mp); 1226 vm_page_unlock(*mp); 1227 } 1228 return (-1); 1229 } 1230 1231 /* 1232 * Routine: 1233 * vm_fault_copy_entry 1234 * Function: 1235 * Create new shadow object backing dst_entry with private copy of 1236 * all underlying pages. When src_entry is equal to dst_entry, 1237 * function implements COW for wired-down map entry. Otherwise, 1238 * it forks wired entry into dst_map. 1239 * 1240 * In/out conditions: 1241 * The source and destination maps must be locked for write. 1242 * The source map entry must be wired down (or be a sharing map 1243 * entry corresponding to a main map entry that is wired down). 1244 */ 1245 void 1246 vm_fault_copy_entry(vm_map_t dst_map, vm_map_t src_map, 1247 vm_map_entry_t dst_entry, vm_map_entry_t src_entry, 1248 vm_ooffset_t *fork_charge) 1249 { 1250 vm_object_t backing_object, dst_object, object, src_object; 1251 vm_pindex_t dst_pindex, pindex, src_pindex; 1252 vm_prot_t access, prot; 1253 vm_offset_t vaddr; 1254 vm_page_t dst_m; 1255 vm_page_t src_m; 1256 boolean_t upgrade; 1257 1258 #ifdef lint 1259 src_map++; 1260 #endif /* lint */ 1261 1262 upgrade = src_entry == dst_entry; 1263 access = prot = dst_entry->protection; 1264 1265 src_object = src_entry->object.vm_object; 1266 src_pindex = OFF_TO_IDX(src_entry->offset); 1267 1268 if (upgrade && (dst_entry->eflags & MAP_ENTRY_NEEDS_COPY) == 0) { 1269 dst_object = src_object; 1270 vm_object_reference(dst_object); 1271 } else { 1272 /* 1273 * Create the top-level object for the destination entry. (Doesn't 1274 * actually shadow anything - we copy the pages directly.) 1275 */ 1276 dst_object = vm_object_allocate(OBJT_DEFAULT, 1277 OFF_TO_IDX(dst_entry->end - dst_entry->start)); 1278 #if VM_NRESERVLEVEL > 0 1279 dst_object->flags |= OBJ_COLORED; 1280 dst_object->pg_color = atop(dst_entry->start); 1281 #endif 1282 } 1283 1284 VM_OBJECT_WLOCK(dst_object); 1285 KASSERT(upgrade || dst_entry->object.vm_object == NULL, 1286 ("vm_fault_copy_entry: vm_object not NULL")); 1287 if (src_object != dst_object) { 1288 dst_entry->object.vm_object = dst_object; 1289 dst_entry->offset = 0; 1290 dst_object->charge = dst_entry->end - dst_entry->start; 1291 } 1292 if (fork_charge != NULL) { 1293 KASSERT(dst_entry->cred == NULL, 1294 ("vm_fault_copy_entry: leaked swp charge")); 1295 dst_object->cred = curthread->td_ucred; 1296 crhold(dst_object->cred); 1297 *fork_charge += dst_object->charge; 1298 } else if (dst_object->cred == NULL) { 1299 KASSERT(dst_entry->cred != NULL, ("no cred for entry %p", 1300 dst_entry)); 1301 dst_object->cred = dst_entry->cred; 1302 dst_entry->cred = NULL; 1303 } 1304 1305 /* 1306 * If not an upgrade, then enter the mappings in the pmap as 1307 * read and/or execute accesses. Otherwise, enter them as 1308 * write accesses. 1309 * 1310 * A writeable large page mapping is only created if all of 1311 * the constituent small page mappings are modified. Marking 1312 * PTEs as modified on inception allows promotion to happen 1313 * without taking potentially large number of soft faults. 1314 */ 1315 if (!upgrade) 1316 access &= ~VM_PROT_WRITE; 1317 1318 /* 1319 * Loop through all of the virtual pages within the entry's 1320 * range, copying each page from the source object to the 1321 * destination object. Since the source is wired, those pages 1322 * must exist. In contrast, the destination is pageable. 1323 * Since the destination object does share any backing storage 1324 * with the source object, all of its pages must be dirtied, 1325 * regardless of whether they can be written. 1326 */ 1327 for (vaddr = dst_entry->start, dst_pindex = 0; 1328 vaddr < dst_entry->end; 1329 vaddr += PAGE_SIZE, dst_pindex++) { 1330 again: 1331 /* 1332 * Find the page in the source object, and copy it in. 1333 * Because the source is wired down, the page will be 1334 * in memory. 1335 */ 1336 if (src_object != dst_object) 1337 VM_OBJECT_RLOCK(src_object); 1338 object = src_object; 1339 pindex = src_pindex + dst_pindex; 1340 while ((src_m = vm_page_lookup(object, pindex)) == NULL && 1341 (backing_object = object->backing_object) != NULL) { 1342 /* 1343 * Unless the source mapping is read-only or 1344 * it is presently being upgraded from 1345 * read-only, the first object in the shadow 1346 * chain should provide all of the pages. In 1347 * other words, this loop body should never be 1348 * executed when the source mapping is already 1349 * read/write. 1350 */ 1351 KASSERT((src_entry->protection & VM_PROT_WRITE) == 0 || 1352 upgrade, 1353 ("vm_fault_copy_entry: main object missing page")); 1354 1355 VM_OBJECT_RLOCK(backing_object); 1356 pindex += OFF_TO_IDX(object->backing_object_offset); 1357 if (object != dst_object) 1358 VM_OBJECT_RUNLOCK(object); 1359 object = backing_object; 1360 } 1361 KASSERT(src_m != NULL, ("vm_fault_copy_entry: page missing")); 1362 1363 if (object != dst_object) { 1364 /* 1365 * Allocate a page in the destination object. 1366 */ 1367 dst_m = vm_page_alloc(dst_object, (src_object == 1368 dst_object ? src_pindex : 0) + dst_pindex, 1369 VM_ALLOC_NORMAL); 1370 if (dst_m == NULL) { 1371 VM_OBJECT_WUNLOCK(dst_object); 1372 VM_OBJECT_RUNLOCK(object); 1373 VM_WAIT; 1374 VM_OBJECT_WLOCK(dst_object); 1375 goto again; 1376 } 1377 pmap_copy_page(src_m, dst_m); 1378 VM_OBJECT_RUNLOCK(object); 1379 dst_m->valid = VM_PAGE_BITS_ALL; 1380 dst_m->dirty = VM_PAGE_BITS_ALL; 1381 } else { 1382 dst_m = src_m; 1383 if (vm_page_sleep_if_busy(dst_m, "fltupg")) 1384 goto again; 1385 vm_page_xbusy(dst_m); 1386 KASSERT(dst_m->valid == VM_PAGE_BITS_ALL, 1387 ("invalid dst page %p", dst_m)); 1388 } 1389 VM_OBJECT_WUNLOCK(dst_object); 1390 1391 /* 1392 * Enter it in the pmap. If a wired, copy-on-write 1393 * mapping is being replaced by a write-enabled 1394 * mapping, then wire that new mapping. 1395 */ 1396 pmap_enter(dst_map->pmap, vaddr, dst_m, prot, 1397 access | (upgrade ? PMAP_ENTER_WIRED : 0), 0); 1398 1399 /* 1400 * Mark it no longer busy, and put it on the active list. 1401 */ 1402 VM_OBJECT_WLOCK(dst_object); 1403 1404 if (upgrade) { 1405 if (src_m != dst_m) { 1406 vm_page_lock(src_m); 1407 vm_page_unwire(src_m, PQ_INACTIVE); 1408 vm_page_unlock(src_m); 1409 vm_page_lock(dst_m); 1410 vm_page_wire(dst_m); 1411 vm_page_unlock(dst_m); 1412 } else { 1413 KASSERT(dst_m->wire_count > 0, 1414 ("dst_m %p is not wired", dst_m)); 1415 } 1416 } else { 1417 vm_page_lock(dst_m); 1418 vm_page_activate(dst_m); 1419 vm_page_unlock(dst_m); 1420 } 1421 vm_page_xunbusy(dst_m); 1422 } 1423 VM_OBJECT_WUNLOCK(dst_object); 1424 if (upgrade) { 1425 dst_entry->eflags &= ~(MAP_ENTRY_COW | MAP_ENTRY_NEEDS_COPY); 1426 vm_object_deallocate(src_object); 1427 } 1428 } 1429 1430 1431 /* 1432 * This routine checks around the requested page for other pages that 1433 * might be able to be faulted in. This routine brackets the viable 1434 * pages for the pages to be paged in. 1435 * 1436 * Inputs: 1437 * m, rbehind, rahead 1438 * 1439 * Outputs: 1440 * marray (array of vm_page_t), reqpage (index of requested page) 1441 * 1442 * Return value: 1443 * number of pages in marray 1444 */ 1445 static int 1446 vm_fault_additional_pages(m, rbehind, rahead, marray, reqpage) 1447 vm_page_t m; 1448 int rbehind; 1449 int rahead; 1450 vm_page_t *marray; 1451 int *reqpage; 1452 { 1453 int i,j; 1454 vm_object_t object; 1455 vm_pindex_t pindex, startpindex, endpindex, tpindex; 1456 vm_page_t rtm; 1457 int cbehind, cahead; 1458 1459 VM_OBJECT_ASSERT_WLOCKED(m->object); 1460 1461 object = m->object; 1462 pindex = m->pindex; 1463 cbehind = cahead = 0; 1464 1465 /* 1466 * if the requested page is not available, then give up now 1467 */ 1468 if (!vm_pager_has_page(object, pindex, &cbehind, &cahead)) { 1469 return 0; 1470 } 1471 1472 if ((cbehind == 0) && (cahead == 0)) { 1473 *reqpage = 0; 1474 marray[0] = m; 1475 return 1; 1476 } 1477 1478 if (rahead > cahead) { 1479 rahead = cahead; 1480 } 1481 1482 if (rbehind > cbehind) { 1483 rbehind = cbehind; 1484 } 1485 1486 /* 1487 * scan backward for the read behind pages -- in memory 1488 */ 1489 if (pindex > 0) { 1490 if (rbehind > pindex) { 1491 rbehind = pindex; 1492 startpindex = 0; 1493 } else { 1494 startpindex = pindex - rbehind; 1495 } 1496 1497 if ((rtm = TAILQ_PREV(m, pglist, listq)) != NULL && 1498 rtm->pindex >= startpindex) 1499 startpindex = rtm->pindex + 1; 1500 1501 /* tpindex is unsigned; beware of numeric underflow. */ 1502 for (i = 0, tpindex = pindex - 1; tpindex >= startpindex && 1503 tpindex < pindex; i++, tpindex--) { 1504 1505 rtm = vm_page_alloc(object, tpindex, VM_ALLOC_NORMAL | 1506 VM_ALLOC_IFNOTCACHED); 1507 if (rtm == NULL) { 1508 /* 1509 * Shift the allocated pages to the 1510 * beginning of the array. 1511 */ 1512 for (j = 0; j < i; j++) { 1513 marray[j] = marray[j + tpindex + 1 - 1514 startpindex]; 1515 } 1516 break; 1517 } 1518 1519 marray[tpindex - startpindex] = rtm; 1520 } 1521 } else { 1522 startpindex = 0; 1523 i = 0; 1524 } 1525 1526 marray[i] = m; 1527 /* page offset of the required page */ 1528 *reqpage = i; 1529 1530 tpindex = pindex + 1; 1531 i++; 1532 1533 /* 1534 * scan forward for the read ahead pages 1535 */ 1536 endpindex = tpindex + rahead; 1537 if ((rtm = TAILQ_NEXT(m, listq)) != NULL && rtm->pindex < endpindex) 1538 endpindex = rtm->pindex; 1539 if (endpindex > object->size) 1540 endpindex = object->size; 1541 1542 for (; tpindex < endpindex; i++, tpindex++) { 1543 1544 rtm = vm_page_alloc(object, tpindex, VM_ALLOC_NORMAL | 1545 VM_ALLOC_IFNOTCACHED); 1546 if (rtm == NULL) { 1547 break; 1548 } 1549 1550 marray[i] = rtm; 1551 } 1552 1553 /* return number of pages */ 1554 return i; 1555 } 1556 1557 /* 1558 * Block entry into the machine-independent layer's page fault handler by 1559 * the calling thread. Subsequent calls to vm_fault() by that thread will 1560 * return KERN_PROTECTION_FAILURE. Enable machine-dependent handling of 1561 * spurious page faults. 1562 */ 1563 int 1564 vm_fault_disable_pagefaults(void) 1565 { 1566 1567 return (curthread_pflags_set(TDP_NOFAULTING | TDP_RESETSPUR)); 1568 } 1569 1570 void 1571 vm_fault_enable_pagefaults(int save) 1572 { 1573 1574 curthread_pflags_restore(save); 1575 } 1576