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/mman.h> 85 #include <sys/proc.h> 86 #include <sys/resourcevar.h> 87 #include <sys/rwlock.h> 88 #include <sys/sysctl.h> 89 #include <sys/vmmeter.h> 90 #include <sys/vnode.h> 91 #ifdef KTRACE 92 #include <sys/ktrace.h> 93 #endif 94 95 #include <vm/vm.h> 96 #include <vm/vm_param.h> 97 #include <vm/pmap.h> 98 #include <vm/vm_map.h> 99 #include <vm/vm_object.h> 100 #include <vm/vm_page.h> 101 #include <vm/vm_pageout.h> 102 #include <vm/vm_kern.h> 103 #include <vm/vm_pager.h> 104 #include <vm/vm_extern.h> 105 #include <vm/vm_reserv.h> 106 107 #define PFBAK 4 108 #define PFFOR 4 109 110 #define VM_FAULT_READ_DEFAULT (1 + VM_FAULT_READ_AHEAD_INIT) 111 #define VM_FAULT_READ_MAX (1 + VM_FAULT_READ_AHEAD_MAX) 112 113 #define VM_FAULT_DONTNEED_MIN 1048576 114 115 struct faultstate { 116 vm_page_t m; 117 vm_object_t object; 118 vm_pindex_t pindex; 119 vm_page_t first_m; 120 vm_object_t first_object; 121 vm_pindex_t first_pindex; 122 vm_map_t map; 123 vm_map_entry_t entry; 124 int lookup_still_valid; 125 struct vnode *vp; 126 }; 127 128 static void vm_fault_dontneed(const struct faultstate *fs, vm_offset_t vaddr, 129 int ahead); 130 static void vm_fault_prefault(const struct faultstate *fs, vm_offset_t addra, 131 int backward, int forward); 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_WIRE) == 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 * vm_fault: 243 * 244 * Handle a page fault occurring at the given address, 245 * requiring the given permissions, in the map specified. 246 * If successful, the page is inserted into the 247 * associated physical map. 248 * 249 * NOTE: the given address should be truncated to the 250 * proper page address. 251 * 252 * KERN_SUCCESS is returned if the page fault is handled; otherwise, 253 * a standard error specifying why the fault is fatal is returned. 254 * 255 * The map in question must be referenced, and remains so. 256 * Caller may hold no locks. 257 */ 258 int 259 vm_fault(vm_map_t map, vm_offset_t vaddr, vm_prot_t fault_type, 260 int fault_flags) 261 { 262 struct thread *td; 263 int result; 264 265 td = curthread; 266 if ((td->td_pflags & TDP_NOFAULTING) != 0) 267 return (KERN_PROTECTION_FAILURE); 268 #ifdef KTRACE 269 if (map != kernel_map && KTRPOINT(td, KTR_FAULT)) 270 ktrfault(vaddr, fault_type); 271 #endif 272 result = vm_fault_hold(map, trunc_page(vaddr), fault_type, fault_flags, 273 NULL); 274 #ifdef KTRACE 275 if (map != kernel_map && KTRPOINT(td, KTR_FAULTEND)) 276 ktrfaultend(result); 277 #endif 278 return (result); 279 } 280 281 int 282 vm_fault_hold(vm_map_t map, vm_offset_t vaddr, vm_prot_t fault_type, 283 int fault_flags, vm_page_t *m_hold) 284 { 285 vm_prot_t prot; 286 int alloc_req, era, faultcount, nera, result; 287 boolean_t growstack, is_first_object_locked, wired; 288 int map_generation; 289 vm_object_t next_object; 290 int hardfault; 291 struct faultstate fs; 292 struct vnode *vp; 293 vm_page_t m; 294 int ahead, behind, cluster_offset, error, locked; 295 296 hardfault = 0; 297 growstack = TRUE; 298 PCPU_INC(cnt.v_vm_faults); 299 fs.vp = NULL; 300 faultcount = 0; 301 302 RetryFault:; 303 304 /* 305 * Find the backing store object and offset into it to begin the 306 * search. 307 */ 308 fs.map = map; 309 result = vm_map_lookup(&fs.map, vaddr, fault_type, &fs.entry, 310 &fs.first_object, &fs.first_pindex, &prot, &wired); 311 if (result != KERN_SUCCESS) { 312 if (growstack && result == KERN_INVALID_ADDRESS && 313 map != kernel_map) { 314 result = vm_map_growstack(curproc, vaddr); 315 if (result != KERN_SUCCESS) 316 return (KERN_FAILURE); 317 growstack = FALSE; 318 goto RetryFault; 319 } 320 return (result); 321 } 322 323 map_generation = fs.map->timestamp; 324 325 if (fs.entry->eflags & MAP_ENTRY_NOFAULT) { 326 panic("vm_fault: fault on nofault entry, addr: %lx", 327 (u_long)vaddr); 328 } 329 330 if (fs.entry->eflags & MAP_ENTRY_IN_TRANSITION && 331 fs.entry->wiring_thread != curthread) { 332 vm_map_unlock_read(fs.map); 333 vm_map_lock(fs.map); 334 if (vm_map_lookup_entry(fs.map, vaddr, &fs.entry) && 335 (fs.entry->eflags & MAP_ENTRY_IN_TRANSITION)) { 336 if (fs.vp != NULL) { 337 vput(fs.vp); 338 fs.vp = NULL; 339 } 340 fs.entry->eflags |= MAP_ENTRY_NEEDS_WAKEUP; 341 vm_map_unlock_and_wait(fs.map, 0); 342 } else 343 vm_map_unlock(fs.map); 344 goto RetryFault; 345 } 346 347 if (wired) 348 fault_type = prot | (fault_type & VM_PROT_COPY); 349 else 350 KASSERT((fault_flags & VM_FAULT_WIRE) == 0, 351 ("!wired && VM_FAULT_WIRE")); 352 353 if (fs.vp == NULL /* avoid locked vnode leak */ && 354 (fault_flags & (VM_FAULT_WIRE | VM_FAULT_DIRTY)) == 0 && 355 /* avoid calling vm_object_set_writeable_dirty() */ 356 ((prot & VM_PROT_WRITE) == 0 || 357 (fs.first_object->type != OBJT_VNODE && 358 (fs.first_object->flags & OBJ_TMPFS_NODE) == 0) || 359 (fs.first_object->flags & OBJ_MIGHTBEDIRTY) != 0)) { 360 VM_OBJECT_RLOCK(fs.first_object); 361 if ((prot & VM_PROT_WRITE) != 0 && 362 (fs.first_object->type == OBJT_VNODE || 363 (fs.first_object->flags & OBJ_TMPFS_NODE) != 0) && 364 (fs.first_object->flags & OBJ_MIGHTBEDIRTY) == 0) 365 goto fast_failed; 366 m = vm_page_lookup(fs.first_object, fs.first_pindex); 367 /* A busy page can be mapped for read|execute access. */ 368 if (m == NULL || ((prot & VM_PROT_WRITE) != 0 && 369 vm_page_busied(m)) || m->valid != VM_PAGE_BITS_ALL) 370 goto fast_failed; 371 result = pmap_enter(fs.map->pmap, vaddr, m, prot, 372 fault_type | PMAP_ENTER_NOSLEEP | (wired ? PMAP_ENTER_WIRED : 373 0), 0); 374 if (result != KERN_SUCCESS) 375 goto fast_failed; 376 if (m_hold != NULL) { 377 *m_hold = m; 378 vm_page_lock(m); 379 vm_page_hold(m); 380 vm_page_unlock(m); 381 } 382 vm_fault_dirty(fs.entry, m, prot, fault_type, fault_flags, 383 FALSE); 384 VM_OBJECT_RUNLOCK(fs.first_object); 385 if (!wired) 386 vm_fault_prefault(&fs, vaddr, PFBAK, PFFOR); 387 vm_map_lookup_done(fs.map, fs.entry); 388 curthread->td_ru.ru_minflt++; 389 return (KERN_SUCCESS); 390 fast_failed: 391 if (!VM_OBJECT_TRYUPGRADE(fs.first_object)) { 392 VM_OBJECT_RUNLOCK(fs.first_object); 393 VM_OBJECT_WLOCK(fs.first_object); 394 } 395 } else { 396 VM_OBJECT_WLOCK(fs.first_object); 397 } 398 399 /* 400 * Make a reference to this object to prevent its disposal while we 401 * are messing with it. Once we have the reference, the map is free 402 * to be diddled. Since objects reference their shadows (and copies), 403 * they will stay around as well. 404 * 405 * Bump the paging-in-progress count to prevent size changes (e.g. 406 * truncation operations) during I/O. This must be done after 407 * obtaining the vnode lock in order to avoid possible deadlocks. 408 */ 409 vm_object_reference_locked(fs.first_object); 410 vm_object_pip_add(fs.first_object, 1); 411 412 fs.lookup_still_valid = TRUE; 413 414 fs.first_m = NULL; 415 416 /* 417 * Search for the page at object/offset. 418 */ 419 fs.object = fs.first_object; 420 fs.pindex = fs.first_pindex; 421 while (TRUE) { 422 /* 423 * If the object is dead, we stop here 424 */ 425 if (fs.object->flags & OBJ_DEAD) { 426 unlock_and_deallocate(&fs); 427 return (KERN_PROTECTION_FAILURE); 428 } 429 430 /* 431 * See if page is resident 432 */ 433 fs.m = vm_page_lookup(fs.object, fs.pindex); 434 if (fs.m != NULL) { 435 /* 436 * Wait/Retry if the page is busy. We have to do this 437 * if the page is either exclusive or shared busy 438 * because the vm_pager may be using read busy for 439 * pageouts (and even pageins if it is the vnode 440 * pager), and we could end up trying to pagein and 441 * pageout the same page simultaneously. 442 * 443 * We can theoretically allow the busy case on a read 444 * fault if the page is marked valid, but since such 445 * pages are typically already pmap'd, putting that 446 * special case in might be more effort then it is 447 * worth. We cannot under any circumstances mess 448 * around with a shared busied page except, perhaps, 449 * to pmap it. 450 */ 451 if (vm_page_busied(fs.m)) { 452 /* 453 * Reference the page before unlocking and 454 * sleeping so that the page daemon is less 455 * likely to reclaim it. 456 */ 457 vm_page_aflag_set(fs.m, PGA_REFERENCED); 458 if (fs.object != fs.first_object) { 459 if (!VM_OBJECT_TRYWLOCK( 460 fs.first_object)) { 461 VM_OBJECT_WUNLOCK(fs.object); 462 VM_OBJECT_WLOCK(fs.first_object); 463 VM_OBJECT_WLOCK(fs.object); 464 } 465 vm_page_lock(fs.first_m); 466 vm_page_free(fs.first_m); 467 vm_page_unlock(fs.first_m); 468 vm_object_pip_wakeup(fs.first_object); 469 VM_OBJECT_WUNLOCK(fs.first_object); 470 fs.first_m = NULL; 471 } 472 unlock_map(&fs); 473 if (fs.m == vm_page_lookup(fs.object, 474 fs.pindex)) { 475 vm_page_sleep_if_busy(fs.m, "vmpfw"); 476 } 477 vm_object_pip_wakeup(fs.object); 478 VM_OBJECT_WUNLOCK(fs.object); 479 PCPU_INC(cnt.v_intrans); 480 vm_object_deallocate(fs.first_object); 481 goto RetryFault; 482 } 483 vm_page_lock(fs.m); 484 vm_page_remque(fs.m); 485 vm_page_unlock(fs.m); 486 487 /* 488 * Mark page busy for other processes, and the 489 * pagedaemon. If it still isn't completely valid 490 * (readable), jump to readrest, else break-out ( we 491 * found the page ). 492 */ 493 vm_page_xbusy(fs.m); 494 if (fs.m->valid != VM_PAGE_BITS_ALL) 495 goto readrest; 496 break; 497 } 498 499 /* 500 * Page is not resident. If this is the search termination 501 * or the pager might contain the page, allocate a new page. 502 * Default objects are zero-fill, there is no real pager. 503 */ 504 if (fs.object->type != OBJT_DEFAULT || 505 fs.object == fs.first_object) { 506 if (fs.pindex >= fs.object->size) { 507 unlock_and_deallocate(&fs); 508 return (KERN_PROTECTION_FAILURE); 509 } 510 511 /* 512 * Allocate a new page for this object/offset pair. 513 * 514 * Unlocked read of the p_flag is harmless. At 515 * worst, the P_KILLED might be not observed 516 * there, and allocation can fail, causing 517 * restart and new reading of the p_flag. 518 */ 519 fs.m = NULL; 520 if (!vm_page_count_severe() || P_KILLED(curproc)) { 521 #if VM_NRESERVLEVEL > 0 522 vm_object_color(fs.object, atop(vaddr) - 523 fs.pindex); 524 #endif 525 alloc_req = P_KILLED(curproc) ? 526 VM_ALLOC_SYSTEM : VM_ALLOC_NORMAL; 527 if (fs.object->type != OBJT_VNODE && 528 fs.object->backing_object == NULL) 529 alloc_req |= VM_ALLOC_ZERO; 530 fs.m = vm_page_alloc(fs.object, fs.pindex, 531 alloc_req); 532 } 533 if (fs.m == NULL) { 534 unlock_and_deallocate(&fs); 535 VM_WAITPFAULT; 536 goto RetryFault; 537 } else if (fs.m->valid == VM_PAGE_BITS_ALL) 538 break; 539 } 540 541 readrest: 542 /* 543 * We have found a valid page or we have allocated a new page. 544 * The page thus may not be valid or may not be entirely 545 * valid. 546 * 547 * Attempt to fault-in the page if there is a chance that the 548 * pager has it, and potentially fault in additional pages 549 * at the same time. For default objects simply provide 550 * zero-filled pages. 551 */ 552 if (fs.object->type != OBJT_DEFAULT) { 553 int rv; 554 u_char behavior = vm_map_entry_behavior(fs.entry); 555 556 era = fs.entry->read_ahead; 557 if (behavior == MAP_ENTRY_BEHAV_RANDOM || 558 P_KILLED(curproc)) { 559 behind = 0; 560 nera = 0; 561 ahead = 0; 562 } else if (behavior == MAP_ENTRY_BEHAV_SEQUENTIAL) { 563 behind = 0; 564 nera = VM_FAULT_READ_AHEAD_MAX; 565 ahead = nera; 566 if (fs.pindex == fs.entry->next_read) 567 vm_fault_dontneed(&fs, vaddr, ahead); 568 } else if (fs.pindex == fs.entry->next_read) { 569 /* 570 * This is a sequential fault. Arithmetically 571 * increase the requested number of pages in 572 * the read-ahead window. The requested 573 * number of pages is "# of sequential faults 574 * x (read ahead min + 1) + read ahead min" 575 */ 576 behind = 0; 577 nera = VM_FAULT_READ_AHEAD_MIN; 578 if (era > 0) { 579 nera += era + 1; 580 if (nera > VM_FAULT_READ_AHEAD_MAX) 581 nera = VM_FAULT_READ_AHEAD_MAX; 582 } 583 ahead = nera; 584 if (era == VM_FAULT_READ_AHEAD_MAX) 585 vm_fault_dontneed(&fs, vaddr, ahead); 586 } else { 587 /* 588 * This is a non-sequential fault. Request a 589 * cluster of pages that is aligned to a 590 * VM_FAULT_READ_DEFAULT page offset boundary 591 * within the object. Alignment to a page 592 * offset boundary is more likely to coincide 593 * with the underlying file system block than 594 * alignment to a virtual address boundary. 595 */ 596 cluster_offset = fs.pindex % 597 VM_FAULT_READ_DEFAULT; 598 behind = ulmin(cluster_offset, 599 atop(vaddr - fs.entry->start)); 600 nera = 0; 601 ahead = VM_FAULT_READ_DEFAULT - 1 - 602 cluster_offset; 603 } 604 ahead = ulmin(ahead, atop(fs.entry->end - vaddr) - 1); 605 if (era != nera) 606 fs.entry->read_ahead = nera; 607 608 /* 609 * Call the pager to retrieve the data, if any, after 610 * releasing the lock on the map. We hold a ref on 611 * fs.object and the pages are exclusive busied. 612 */ 613 unlock_map(&fs); 614 615 if (fs.object->type == OBJT_VNODE) { 616 vp = fs.object->handle; 617 if (vp == fs.vp) 618 goto vnode_locked; 619 else if (fs.vp != NULL) { 620 vput(fs.vp); 621 fs.vp = NULL; 622 } 623 locked = VOP_ISLOCKED(vp); 624 625 if (locked != LK_EXCLUSIVE) 626 locked = LK_SHARED; 627 /* Do not sleep for vnode lock while fs.m is busy */ 628 error = vget(vp, locked | LK_CANRECURSE | 629 LK_NOWAIT, curthread); 630 if (error != 0) { 631 vhold(vp); 632 release_page(&fs); 633 unlock_and_deallocate(&fs); 634 error = vget(vp, locked | LK_RETRY | 635 LK_CANRECURSE, curthread); 636 vdrop(vp); 637 fs.vp = vp; 638 KASSERT(error == 0, 639 ("vm_fault: vget failed")); 640 goto RetryFault; 641 } 642 fs.vp = vp; 643 } 644 vnode_locked: 645 KASSERT(fs.vp == NULL || !fs.map->system_map, 646 ("vm_fault: vnode-backed object mapped by system map")); 647 648 /* 649 * Page in the requested page and hint the pager, 650 * that it may bring up surrounding pages. 651 */ 652 rv = vm_pager_get_pages(fs.object, &fs.m, 1, 653 &behind, &ahead); 654 if (rv == VM_PAGER_OK) { 655 faultcount = behind + 1 + ahead; 656 hardfault++; 657 break; /* break to PAGE HAS BEEN FOUND */ 658 } 659 /* 660 * Remove the bogus page (which does not exist at this 661 * object/offset); before doing so, we must get back 662 * our object lock to preserve our invariant. 663 * 664 * Also wake up any other process that may want to bring 665 * in this page. 666 * 667 * If this is the top-level object, we must leave the 668 * busy page to prevent another process from rushing 669 * past us, and inserting the page in that object at 670 * the same time that we are. 671 */ 672 if (rv == VM_PAGER_ERROR) 673 printf("vm_fault: pager read error, pid %d (%s)\n", 674 curproc->p_pid, curproc->p_comm); 675 /* 676 * Data outside the range of the pager or an I/O error 677 */ 678 /* 679 * XXX - the check for kernel_map is a kludge to work 680 * around having the machine panic on a kernel space 681 * fault w/ I/O error. 682 */ 683 if (((fs.map != kernel_map) && (rv == VM_PAGER_ERROR)) || 684 (rv == VM_PAGER_BAD)) { 685 vm_page_lock(fs.m); 686 vm_page_free(fs.m); 687 vm_page_unlock(fs.m); 688 fs.m = NULL; 689 unlock_and_deallocate(&fs); 690 return ((rv == VM_PAGER_ERROR) ? KERN_FAILURE : KERN_PROTECTION_FAILURE); 691 } 692 if (fs.object != fs.first_object) { 693 vm_page_lock(fs.m); 694 vm_page_free(fs.m); 695 vm_page_unlock(fs.m); 696 fs.m = NULL; 697 /* 698 * XXX - we cannot just fall out at this 699 * point, m has been freed and is invalid! 700 */ 701 } 702 } 703 704 /* 705 * We get here if the object has default pager (or unwiring) 706 * or the pager doesn't have the page. 707 */ 708 if (fs.object == fs.first_object) 709 fs.first_m = fs.m; 710 711 /* 712 * Move on to the next object. Lock the next object before 713 * unlocking the current one. 714 */ 715 fs.pindex += OFF_TO_IDX(fs.object->backing_object_offset); 716 next_object = fs.object->backing_object; 717 if (next_object == NULL) { 718 /* 719 * If there's no object left, fill the page in the top 720 * object with zeros. 721 */ 722 if (fs.object != fs.first_object) { 723 vm_object_pip_wakeup(fs.object); 724 VM_OBJECT_WUNLOCK(fs.object); 725 726 fs.object = fs.first_object; 727 fs.pindex = fs.first_pindex; 728 fs.m = fs.first_m; 729 VM_OBJECT_WLOCK(fs.object); 730 } 731 fs.first_m = NULL; 732 733 /* 734 * Zero the page if necessary and mark it valid. 735 */ 736 if ((fs.m->flags & PG_ZERO) == 0) { 737 pmap_zero_page(fs.m); 738 } else { 739 PCPU_INC(cnt.v_ozfod); 740 } 741 PCPU_INC(cnt.v_zfod); 742 fs.m->valid = VM_PAGE_BITS_ALL; 743 /* Don't try to prefault neighboring pages. */ 744 faultcount = 1; 745 break; /* break to PAGE HAS BEEN FOUND */ 746 } else { 747 KASSERT(fs.object != next_object, 748 ("object loop %p", next_object)); 749 VM_OBJECT_WLOCK(next_object); 750 vm_object_pip_add(next_object, 1); 751 if (fs.object != fs.first_object) 752 vm_object_pip_wakeup(fs.object); 753 VM_OBJECT_WUNLOCK(fs.object); 754 fs.object = next_object; 755 } 756 } 757 758 vm_page_assert_xbusied(fs.m); 759 760 /* 761 * PAGE HAS BEEN FOUND. [Loop invariant still holds -- the object lock 762 * is held.] 763 */ 764 765 /* 766 * If the page is being written, but isn't already owned by the 767 * top-level object, we have to copy it into a new page owned by the 768 * top-level object. 769 */ 770 if (fs.object != fs.first_object) { 771 /* 772 * We only really need to copy if we want to write it. 773 */ 774 if ((fault_type & (VM_PROT_COPY | VM_PROT_WRITE)) != 0) { 775 /* 776 * This allows pages to be virtually copied from a 777 * backing_object into the first_object, where the 778 * backing object has no other refs to it, and cannot 779 * gain any more refs. Instead of a bcopy, we just 780 * move the page from the backing object to the 781 * first object. Note that we must mark the page 782 * dirty in the first object so that it will go out 783 * to swap when needed. 784 */ 785 is_first_object_locked = FALSE; 786 if ( 787 /* 788 * Only one shadow object 789 */ 790 (fs.object->shadow_count == 1) && 791 /* 792 * No COW refs, except us 793 */ 794 (fs.object->ref_count == 1) && 795 /* 796 * No one else can look this object up 797 */ 798 (fs.object->handle == NULL) && 799 /* 800 * No other ways to look the object up 801 */ 802 ((fs.object->type == OBJT_DEFAULT) || 803 (fs.object->type == OBJT_SWAP)) && 804 (is_first_object_locked = VM_OBJECT_TRYWLOCK(fs.first_object)) && 805 /* 806 * We don't chase down the shadow chain 807 */ 808 fs.object == fs.first_object->backing_object) { 809 /* 810 * get rid of the unnecessary page 811 */ 812 vm_page_lock(fs.first_m); 813 vm_page_remove(fs.first_m); 814 vm_page_unlock(fs.first_m); 815 /* 816 * grab the page and put it into the 817 * process'es object. The page is 818 * automatically made dirty. 819 */ 820 if (vm_page_rename(fs.m, fs.first_object, 821 fs.first_pindex)) { 822 VM_OBJECT_WUNLOCK(fs.first_object); 823 unlock_and_deallocate(&fs); 824 goto RetryFault; 825 } 826 vm_page_lock(fs.first_m); 827 vm_page_free(fs.first_m); 828 vm_page_unlock(fs.first_m); 829 #if VM_NRESERVLEVEL > 0 830 /* 831 * Rename the reservation. 832 */ 833 vm_reserv_rename(fs.m, fs.first_object, 834 fs.object, OFF_TO_IDX( 835 fs.first_object->backing_object_offset)); 836 #endif 837 vm_page_xbusy(fs.m); 838 fs.first_m = fs.m; 839 fs.m = NULL; 840 PCPU_INC(cnt.v_cow_optim); 841 } else { 842 /* 843 * Oh, well, lets copy it. 844 */ 845 pmap_copy_page(fs.m, fs.first_m); 846 fs.first_m->valid = VM_PAGE_BITS_ALL; 847 if (wired && (fault_flags & 848 VM_FAULT_WIRE) == 0) { 849 vm_page_lock(fs.first_m); 850 vm_page_wire(fs.first_m); 851 vm_page_unlock(fs.first_m); 852 853 vm_page_lock(fs.m); 854 vm_page_unwire(fs.m, PQ_INACTIVE); 855 vm_page_unlock(fs.m); 856 } 857 /* 858 * We no longer need the old page or object. 859 */ 860 release_page(&fs); 861 } 862 /* 863 * fs.object != fs.first_object due to above 864 * conditional 865 */ 866 vm_object_pip_wakeup(fs.object); 867 VM_OBJECT_WUNLOCK(fs.object); 868 /* 869 * Only use the new page below... 870 */ 871 fs.object = fs.first_object; 872 fs.pindex = fs.first_pindex; 873 fs.m = fs.first_m; 874 if (!is_first_object_locked) 875 VM_OBJECT_WLOCK(fs.object); 876 PCPU_INC(cnt.v_cow_faults); 877 curthread->td_cow++; 878 } else { 879 prot &= ~VM_PROT_WRITE; 880 } 881 } 882 883 /* 884 * We must verify that the maps have not changed since our last 885 * lookup. 886 */ 887 if (!fs.lookup_still_valid) { 888 vm_object_t retry_object; 889 vm_pindex_t retry_pindex; 890 vm_prot_t retry_prot; 891 892 if (!vm_map_trylock_read(fs.map)) { 893 release_page(&fs); 894 unlock_and_deallocate(&fs); 895 goto RetryFault; 896 } 897 fs.lookup_still_valid = TRUE; 898 if (fs.map->timestamp != map_generation) { 899 result = vm_map_lookup_locked(&fs.map, vaddr, fault_type, 900 &fs.entry, &retry_object, &retry_pindex, &retry_prot, &wired); 901 902 /* 903 * If we don't need the page any longer, put it on the inactive 904 * list (the easiest thing to do here). If no one needs it, 905 * pageout will grab it eventually. 906 */ 907 if (result != KERN_SUCCESS) { 908 release_page(&fs); 909 unlock_and_deallocate(&fs); 910 911 /* 912 * If retry of map lookup would have blocked then 913 * retry fault from start. 914 */ 915 if (result == KERN_FAILURE) 916 goto RetryFault; 917 return (result); 918 } 919 if ((retry_object != fs.first_object) || 920 (retry_pindex != fs.first_pindex)) { 921 release_page(&fs); 922 unlock_and_deallocate(&fs); 923 goto RetryFault; 924 } 925 926 /* 927 * Check whether the protection has changed or the object has 928 * been copied while we left the map unlocked. Changing from 929 * read to write permission is OK - we leave the page 930 * write-protected, and catch the write fault. Changing from 931 * write to read permission means that we can't mark the page 932 * write-enabled after all. 933 */ 934 prot &= retry_prot; 935 } 936 } 937 /* 938 * If the page was filled by a pager, update the map entry's 939 * last read offset. 940 * 941 * XXX The following assignment modifies the map 942 * without holding a write lock on it. 943 */ 944 if (hardfault) 945 fs.entry->next_read = fs.pindex + ahead + 1; 946 947 vm_fault_dirty(fs.entry, fs.m, prot, fault_type, fault_flags, TRUE); 948 vm_page_assert_xbusied(fs.m); 949 950 /* 951 * Page must be completely valid or it is not fit to 952 * map into user space. vm_pager_get_pages() ensures this. 953 */ 954 KASSERT(fs.m->valid == VM_PAGE_BITS_ALL, 955 ("vm_fault: page %p partially invalid", fs.m)); 956 VM_OBJECT_WUNLOCK(fs.object); 957 958 /* 959 * Put this page into the physical map. We had to do the unlock above 960 * because pmap_enter() may sleep. We don't put the page 961 * back on the active queue until later so that the pageout daemon 962 * won't find it (yet). 963 */ 964 pmap_enter(fs.map->pmap, vaddr, fs.m, prot, 965 fault_type | (wired ? PMAP_ENTER_WIRED : 0), 0); 966 if (faultcount != 1 && (fault_flags & VM_FAULT_WIRE) == 0 && 967 wired == 0) 968 vm_fault_prefault(&fs, vaddr, 969 faultcount > 0 ? behind : PFBAK, 970 faultcount > 0 ? ahead : PFFOR); 971 VM_OBJECT_WLOCK(fs.object); 972 vm_page_lock(fs.m); 973 974 /* 975 * If the page is not wired down, then put it where the pageout daemon 976 * can find it. 977 */ 978 if ((fault_flags & VM_FAULT_WIRE) != 0) { 979 KASSERT(wired, ("VM_FAULT_WIRE && !wired")); 980 vm_page_wire(fs.m); 981 } else 982 vm_page_activate(fs.m); 983 if (m_hold != NULL) { 984 *m_hold = fs.m; 985 vm_page_hold(fs.m); 986 } 987 vm_page_unlock(fs.m); 988 vm_page_xunbusy(fs.m); 989 990 /* 991 * Unlock everything, and return 992 */ 993 unlock_and_deallocate(&fs); 994 if (hardfault) { 995 PCPU_INC(cnt.v_io_faults); 996 curthread->td_ru.ru_majflt++; 997 } else 998 curthread->td_ru.ru_minflt++; 999 1000 return (KERN_SUCCESS); 1001 } 1002 1003 /* 1004 * Speed up the reclamation of pages that precede the faulting pindex within 1005 * the first object of the shadow chain. Essentially, perform the equivalent 1006 * to madvise(..., MADV_DONTNEED) on a large cluster of pages that precedes 1007 * the faulting pindex by the cluster size when the pages read by vm_fault() 1008 * cross a cluster-size boundary. The cluster size is the greater of the 1009 * smallest superpage size and VM_FAULT_DONTNEED_MIN. 1010 * 1011 * When "fs->first_object" is a shadow object, the pages in the backing object 1012 * that precede the faulting pindex are deactivated by vm_fault(). So, this 1013 * function must only be concerned with pages in the first object. 1014 */ 1015 static void 1016 vm_fault_dontneed(const struct faultstate *fs, vm_offset_t vaddr, int ahead) 1017 { 1018 vm_map_entry_t entry; 1019 vm_object_t first_object, object; 1020 vm_offset_t end, start; 1021 vm_page_t m, m_next; 1022 vm_pindex_t pend, pstart; 1023 vm_size_t size; 1024 1025 object = fs->object; 1026 VM_OBJECT_ASSERT_WLOCKED(object); 1027 first_object = fs->first_object; 1028 if (first_object != object) { 1029 if (!VM_OBJECT_TRYWLOCK(first_object)) { 1030 VM_OBJECT_WUNLOCK(object); 1031 VM_OBJECT_WLOCK(first_object); 1032 VM_OBJECT_WLOCK(object); 1033 } 1034 } 1035 /* Neither fictitious nor unmanaged pages can be reclaimed. */ 1036 if ((first_object->flags & (OBJ_FICTITIOUS | OBJ_UNMANAGED)) == 0) { 1037 size = VM_FAULT_DONTNEED_MIN; 1038 if (MAXPAGESIZES > 1 && size < pagesizes[1]) 1039 size = pagesizes[1]; 1040 end = rounddown2(vaddr, size); 1041 if (vaddr - end >= size - PAGE_SIZE - ptoa(ahead) && 1042 (entry = fs->entry)->start < end) { 1043 if (end - entry->start < size) 1044 start = entry->start; 1045 else 1046 start = end - size; 1047 pmap_advise(fs->map->pmap, start, end, MADV_DONTNEED); 1048 pstart = OFF_TO_IDX(entry->offset) + atop(start - 1049 entry->start); 1050 m_next = vm_page_find_least(first_object, pstart); 1051 pend = OFF_TO_IDX(entry->offset) + atop(end - 1052 entry->start); 1053 while ((m = m_next) != NULL && m->pindex < pend) { 1054 m_next = TAILQ_NEXT(m, listq); 1055 if (m->valid != VM_PAGE_BITS_ALL || 1056 vm_page_busied(m)) 1057 continue; 1058 1059 /* 1060 * Don't clear PGA_REFERENCED, since it would 1061 * likely represent a reference by a different 1062 * process. 1063 * 1064 * Typically, at this point, prefetched pages 1065 * are still in the inactive queue. Only 1066 * pages that triggered page faults are in the 1067 * active queue. 1068 */ 1069 vm_page_lock(m); 1070 vm_page_deactivate(m); 1071 vm_page_unlock(m); 1072 } 1073 } 1074 } 1075 if (first_object != object) 1076 VM_OBJECT_WUNLOCK(first_object); 1077 } 1078 1079 /* 1080 * vm_fault_prefault provides a quick way of clustering 1081 * pagefaults into a processes address space. It is a "cousin" 1082 * of vm_map_pmap_enter, except it runs at page fault time instead 1083 * of mmap time. 1084 */ 1085 static void 1086 vm_fault_prefault(const struct faultstate *fs, vm_offset_t addra, 1087 int backward, int forward) 1088 { 1089 pmap_t pmap; 1090 vm_map_entry_t entry; 1091 vm_object_t backing_object, lobject; 1092 vm_offset_t addr, starta; 1093 vm_pindex_t pindex; 1094 vm_page_t m; 1095 int i; 1096 1097 pmap = fs->map->pmap; 1098 if (pmap != vmspace_pmap(curthread->td_proc->p_vmspace)) 1099 return; 1100 1101 entry = fs->entry; 1102 1103 starta = addra - backward * PAGE_SIZE; 1104 if (starta < entry->start) { 1105 starta = entry->start; 1106 } else if (starta > addra) { 1107 starta = 0; 1108 } 1109 1110 /* 1111 * Generate the sequence of virtual addresses that are candidates for 1112 * prefaulting in an outward spiral from the faulting virtual address, 1113 * "addra". Specifically, the sequence is "addra - PAGE_SIZE", "addra 1114 * + PAGE_SIZE", "addra - 2 * PAGE_SIZE", "addra + 2 * PAGE_SIZE", ... 1115 * If the candidate address doesn't have a backing physical page, then 1116 * the loop immediately terminates. 1117 */ 1118 for (i = 0; i < 2 * imax(backward, forward); i++) { 1119 addr = addra + ((i >> 1) + 1) * ((i & 1) == 0 ? -PAGE_SIZE : 1120 PAGE_SIZE); 1121 if (addr > addra + forward * PAGE_SIZE) 1122 addr = 0; 1123 1124 if (addr < starta || addr >= entry->end) 1125 continue; 1126 1127 if (!pmap_is_prefaultable(pmap, addr)) 1128 continue; 1129 1130 pindex = ((addr - entry->start) + entry->offset) >> PAGE_SHIFT; 1131 lobject = entry->object.vm_object; 1132 VM_OBJECT_RLOCK(lobject); 1133 while ((m = vm_page_lookup(lobject, pindex)) == NULL && 1134 lobject->type == OBJT_DEFAULT && 1135 (backing_object = lobject->backing_object) != NULL) { 1136 KASSERT((lobject->backing_object_offset & PAGE_MASK) == 1137 0, ("vm_fault_prefault: unaligned object offset")); 1138 pindex += lobject->backing_object_offset >> PAGE_SHIFT; 1139 VM_OBJECT_RLOCK(backing_object); 1140 VM_OBJECT_RUNLOCK(lobject); 1141 lobject = backing_object; 1142 } 1143 if (m == NULL) { 1144 VM_OBJECT_RUNLOCK(lobject); 1145 break; 1146 } 1147 if (m->valid == VM_PAGE_BITS_ALL && 1148 (m->flags & PG_FICTITIOUS) == 0) 1149 pmap_enter_quick(pmap, addr, m, entry->protection); 1150 VM_OBJECT_RUNLOCK(lobject); 1151 } 1152 } 1153 1154 /* 1155 * Hold each of the physical pages that are mapped by the specified range of 1156 * virtual addresses, ["addr", "addr" + "len"), if those mappings are valid 1157 * and allow the specified types of access, "prot". If all of the implied 1158 * pages are successfully held, then the number of held pages is returned 1159 * together with pointers to those pages in the array "ma". However, if any 1160 * of the pages cannot be held, -1 is returned. 1161 */ 1162 int 1163 vm_fault_quick_hold_pages(vm_map_t map, vm_offset_t addr, vm_size_t len, 1164 vm_prot_t prot, vm_page_t *ma, int max_count) 1165 { 1166 vm_offset_t end, va; 1167 vm_page_t *mp; 1168 int count; 1169 boolean_t pmap_failed; 1170 1171 if (len == 0) 1172 return (0); 1173 end = round_page(addr + len); 1174 addr = trunc_page(addr); 1175 1176 /* 1177 * Check for illegal addresses. 1178 */ 1179 if (addr < vm_map_min(map) || addr > end || end > vm_map_max(map)) 1180 return (-1); 1181 1182 if (atop(end - addr) > max_count) 1183 panic("vm_fault_quick_hold_pages: count > max_count"); 1184 count = atop(end - addr); 1185 1186 /* 1187 * Most likely, the physical pages are resident in the pmap, so it is 1188 * faster to try pmap_extract_and_hold() first. 1189 */ 1190 pmap_failed = FALSE; 1191 for (mp = ma, va = addr; va < end; mp++, va += PAGE_SIZE) { 1192 *mp = pmap_extract_and_hold(map->pmap, va, prot); 1193 if (*mp == NULL) 1194 pmap_failed = TRUE; 1195 else if ((prot & VM_PROT_WRITE) != 0 && 1196 (*mp)->dirty != VM_PAGE_BITS_ALL) { 1197 /* 1198 * Explicitly dirty the physical page. Otherwise, the 1199 * caller's changes may go unnoticed because they are 1200 * performed through an unmanaged mapping or by a DMA 1201 * operation. 1202 * 1203 * The object lock is not held here. 1204 * See vm_page_clear_dirty_mask(). 1205 */ 1206 vm_page_dirty(*mp); 1207 } 1208 } 1209 if (pmap_failed) { 1210 /* 1211 * One or more pages could not be held by the pmap. Either no 1212 * page was mapped at the specified virtual address or that 1213 * mapping had insufficient permissions. Attempt to fault in 1214 * and hold these pages. 1215 */ 1216 for (mp = ma, va = addr; va < end; mp++, va += PAGE_SIZE) 1217 if (*mp == NULL && vm_fault_hold(map, va, prot, 1218 VM_FAULT_NORMAL, mp) != KERN_SUCCESS) 1219 goto error; 1220 } 1221 return (count); 1222 error: 1223 for (mp = ma; mp < ma + count; mp++) 1224 if (*mp != NULL) { 1225 vm_page_lock(*mp); 1226 vm_page_unhold(*mp); 1227 vm_page_unlock(*mp); 1228 } 1229 return (-1); 1230 } 1231 1232 /* 1233 * Routine: 1234 * vm_fault_copy_entry 1235 * Function: 1236 * Create new shadow object backing dst_entry with private copy of 1237 * all underlying pages. When src_entry is equal to dst_entry, 1238 * function implements COW for wired-down map entry. Otherwise, 1239 * it forks wired entry into dst_map. 1240 * 1241 * In/out conditions: 1242 * The source and destination maps must be locked for write. 1243 * The source map entry must be wired down (or be a sharing map 1244 * entry corresponding to a main map entry that is wired down). 1245 */ 1246 void 1247 vm_fault_copy_entry(vm_map_t dst_map, vm_map_t src_map, 1248 vm_map_entry_t dst_entry, vm_map_entry_t src_entry, 1249 vm_ooffset_t *fork_charge) 1250 { 1251 vm_object_t backing_object, dst_object, object, src_object; 1252 vm_pindex_t dst_pindex, pindex, src_pindex; 1253 vm_prot_t access, prot; 1254 vm_offset_t vaddr; 1255 vm_page_t dst_m; 1256 vm_page_t src_m; 1257 boolean_t upgrade; 1258 1259 #ifdef lint 1260 src_map++; 1261 #endif /* lint */ 1262 1263 upgrade = src_entry == dst_entry; 1264 access = prot = dst_entry->protection; 1265 1266 src_object = src_entry->object.vm_object; 1267 src_pindex = OFF_TO_IDX(src_entry->offset); 1268 1269 if (upgrade && (dst_entry->eflags & MAP_ENTRY_NEEDS_COPY) == 0) { 1270 dst_object = src_object; 1271 vm_object_reference(dst_object); 1272 } else { 1273 /* 1274 * Create the top-level object for the destination entry. (Doesn't 1275 * actually shadow anything - we copy the pages directly.) 1276 */ 1277 dst_object = vm_object_allocate(OBJT_DEFAULT, 1278 OFF_TO_IDX(dst_entry->end - dst_entry->start)); 1279 #if VM_NRESERVLEVEL > 0 1280 dst_object->flags |= OBJ_COLORED; 1281 dst_object->pg_color = atop(dst_entry->start); 1282 #endif 1283 } 1284 1285 VM_OBJECT_WLOCK(dst_object); 1286 KASSERT(upgrade || dst_entry->object.vm_object == NULL, 1287 ("vm_fault_copy_entry: vm_object not NULL")); 1288 if (src_object != dst_object) { 1289 dst_entry->object.vm_object = dst_object; 1290 dst_entry->offset = 0; 1291 dst_object->charge = dst_entry->end - dst_entry->start; 1292 } 1293 if (fork_charge != NULL) { 1294 KASSERT(dst_entry->cred == NULL, 1295 ("vm_fault_copy_entry: leaked swp charge")); 1296 dst_object->cred = curthread->td_ucred; 1297 crhold(dst_object->cred); 1298 *fork_charge += dst_object->charge; 1299 } else if (dst_object->cred == NULL) { 1300 KASSERT(dst_entry->cred != NULL, ("no cred for entry %p", 1301 dst_entry)); 1302 dst_object->cred = dst_entry->cred; 1303 dst_entry->cred = NULL; 1304 } 1305 1306 /* 1307 * If not an upgrade, then enter the mappings in the pmap as 1308 * read and/or execute accesses. Otherwise, enter them as 1309 * write accesses. 1310 * 1311 * A writeable large page mapping is only created if all of 1312 * the constituent small page mappings are modified. Marking 1313 * PTEs as modified on inception allows promotion to happen 1314 * without taking potentially large number of soft faults. 1315 */ 1316 if (!upgrade) 1317 access &= ~VM_PROT_WRITE; 1318 1319 /* 1320 * Loop through all of the virtual pages within the entry's 1321 * range, copying each page from the source object to the 1322 * destination object. Since the source is wired, those pages 1323 * must exist. In contrast, the destination is pageable. 1324 * Since the destination object does share any backing storage 1325 * with the source object, all of its pages must be dirtied, 1326 * regardless of whether they can be written. 1327 */ 1328 for (vaddr = dst_entry->start, dst_pindex = 0; 1329 vaddr < dst_entry->end; 1330 vaddr += PAGE_SIZE, dst_pindex++) { 1331 again: 1332 /* 1333 * Find the page in the source object, and copy it in. 1334 * Because the source is wired down, the page will be 1335 * in memory. 1336 */ 1337 if (src_object != dst_object) 1338 VM_OBJECT_RLOCK(src_object); 1339 object = src_object; 1340 pindex = src_pindex + dst_pindex; 1341 while ((src_m = vm_page_lookup(object, pindex)) == NULL && 1342 (backing_object = object->backing_object) != NULL) { 1343 /* 1344 * Unless the source mapping is read-only or 1345 * it is presently being upgraded from 1346 * read-only, the first object in the shadow 1347 * chain should provide all of the pages. In 1348 * other words, this loop body should never be 1349 * executed when the source mapping is already 1350 * read/write. 1351 */ 1352 KASSERT((src_entry->protection & VM_PROT_WRITE) == 0 || 1353 upgrade, 1354 ("vm_fault_copy_entry: main object missing page")); 1355 1356 VM_OBJECT_RLOCK(backing_object); 1357 pindex += OFF_TO_IDX(object->backing_object_offset); 1358 if (object != dst_object) 1359 VM_OBJECT_RUNLOCK(object); 1360 object = backing_object; 1361 } 1362 KASSERT(src_m != NULL, ("vm_fault_copy_entry: page missing")); 1363 1364 if (object != dst_object) { 1365 /* 1366 * Allocate a page in the destination object. 1367 */ 1368 dst_m = vm_page_alloc(dst_object, (src_object == 1369 dst_object ? src_pindex : 0) + dst_pindex, 1370 VM_ALLOC_NORMAL); 1371 if (dst_m == NULL) { 1372 VM_OBJECT_WUNLOCK(dst_object); 1373 VM_OBJECT_RUNLOCK(object); 1374 VM_WAIT; 1375 VM_OBJECT_WLOCK(dst_object); 1376 goto again; 1377 } 1378 pmap_copy_page(src_m, dst_m); 1379 VM_OBJECT_RUNLOCK(object); 1380 dst_m->valid = VM_PAGE_BITS_ALL; 1381 dst_m->dirty = VM_PAGE_BITS_ALL; 1382 } else { 1383 dst_m = src_m; 1384 if (vm_page_sleep_if_busy(dst_m, "fltupg")) 1385 goto again; 1386 vm_page_xbusy(dst_m); 1387 KASSERT(dst_m->valid == VM_PAGE_BITS_ALL, 1388 ("invalid dst page %p", dst_m)); 1389 } 1390 VM_OBJECT_WUNLOCK(dst_object); 1391 1392 /* 1393 * Enter it in the pmap. If a wired, copy-on-write 1394 * mapping is being replaced by a write-enabled 1395 * mapping, then wire that new mapping. 1396 */ 1397 pmap_enter(dst_map->pmap, vaddr, dst_m, prot, 1398 access | (upgrade ? PMAP_ENTER_WIRED : 0), 0); 1399 1400 /* 1401 * Mark it no longer busy, and put it on the active list. 1402 */ 1403 VM_OBJECT_WLOCK(dst_object); 1404 1405 if (upgrade) { 1406 if (src_m != dst_m) { 1407 vm_page_lock(src_m); 1408 vm_page_unwire(src_m, PQ_INACTIVE); 1409 vm_page_unlock(src_m); 1410 vm_page_lock(dst_m); 1411 vm_page_wire(dst_m); 1412 vm_page_unlock(dst_m); 1413 } else { 1414 KASSERT(dst_m->wire_count > 0, 1415 ("dst_m %p is not wired", dst_m)); 1416 } 1417 } else { 1418 vm_page_lock(dst_m); 1419 vm_page_activate(dst_m); 1420 vm_page_unlock(dst_m); 1421 } 1422 vm_page_xunbusy(dst_m); 1423 } 1424 VM_OBJECT_WUNLOCK(dst_object); 1425 if (upgrade) { 1426 dst_entry->eflags &= ~(MAP_ENTRY_COW | MAP_ENTRY_NEEDS_COPY); 1427 vm_object_deallocate(src_object); 1428 } 1429 } 1430 1431 /* 1432 * Block entry into the machine-independent layer's page fault handler by 1433 * the calling thread. Subsequent calls to vm_fault() by that thread will 1434 * return KERN_PROTECTION_FAILURE. Enable machine-dependent handling of 1435 * spurious page faults. 1436 */ 1437 int 1438 vm_fault_disable_pagefaults(void) 1439 { 1440 1441 return (curthread_pflags_set(TDP_NOFAULTING | TDP_RESETSPUR)); 1442 } 1443 1444 void 1445 vm_fault_enable_pagefaults(int save) 1446 { 1447 1448 curthread_pflags_restore(save); 1449 } 1450