1 /*- 2 * SPDX-License-Identifier: (BSD-4-Clause AND MIT-CMU) 3 * 4 * Copyright (c) 1991, 1993 5 * The Regents of the University of California. All rights reserved. 6 * Copyright (c) 1994 John S. Dyson 7 * All rights reserved. 8 * Copyright (c) 1994 David Greenman 9 * All rights reserved. 10 * 11 * 12 * This code is derived from software contributed to Berkeley by 13 * The Mach Operating System project at Carnegie-Mellon University. 14 * 15 * Redistribution and use in source and binary forms, with or without 16 * modification, are permitted provided that the following conditions 17 * are met: 18 * 1. Redistributions of source code must retain the above copyright 19 * notice, this list of conditions and the following disclaimer. 20 * 2. Redistributions in binary form must reproduce the above copyright 21 * notice, this list of conditions and the following disclaimer in the 22 * documentation and/or other materials provided with the distribution. 23 * 3. All advertising materials mentioning features or use of this software 24 * must display the following acknowledgement: 25 * This product includes software developed by the University of 26 * California, Berkeley and its contributors. 27 * 4. Neither the name of the University nor the names of its contributors 28 * may be used to endorse or promote products derived from this software 29 * without specific prior written permission. 30 * 31 * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND 32 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE 33 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE 34 * ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE 35 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL 36 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS 37 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) 38 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT 39 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY 40 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF 41 * SUCH DAMAGE. 42 * 43 * from: @(#)vm_fault.c 8.4 (Berkeley) 1/12/94 44 * 45 * 46 * Copyright (c) 1987, 1990 Carnegie-Mellon University. 47 * All rights reserved. 48 * 49 * Authors: Avadis Tevanian, Jr., Michael Wayne Young 50 * 51 * Permission to use, copy, modify and distribute this software and 52 * its documentation is hereby granted, provided that both the copyright 53 * notice and this permission notice appear in all copies of the 54 * software, derivative works or modified versions, and any portions 55 * thereof, and that both notices appear in supporting documentation. 56 * 57 * CARNEGIE MELLON ALLOWS FREE USE OF THIS SOFTWARE IN ITS "AS IS" 58 * CONDITION. CARNEGIE MELLON DISCLAIMS ANY LIABILITY OF ANY KIND 59 * FOR ANY DAMAGES WHATSOEVER RESULTING FROM THE USE OF THIS SOFTWARE. 60 * 61 * Carnegie Mellon requests users of this software to return to 62 * 63 * Software Distribution Coordinator or Software.Distribution@CS.CMU.EDU 64 * School of Computer Science 65 * Carnegie Mellon University 66 * Pittsburgh PA 15213-3890 67 * 68 * any improvements or extensions that they make and grant Carnegie the 69 * rights to redistribute these changes. 70 */ 71 72 /* 73 * Page fault handling module. 74 */ 75 76 #include <sys/cdefs.h> 77 __FBSDID("$FreeBSD$"); 78 79 #include "opt_ktrace.h" 80 #include "opt_vm.h" 81 82 #include <sys/param.h> 83 #include <sys/systm.h> 84 #include <sys/kernel.h> 85 #include <sys/lock.h> 86 #include <sys/mman.h> 87 #include <sys/mutex.h> 88 #include <sys/proc.h> 89 #include <sys/racct.h> 90 #include <sys/refcount.h> 91 #include <sys/resourcevar.h> 92 #include <sys/rwlock.h> 93 #include <sys/signalvar.h> 94 #include <sys/sysctl.h> 95 #include <sys/sysent.h> 96 #include <sys/vmmeter.h> 97 #include <sys/vnode.h> 98 #ifdef KTRACE 99 #include <sys/ktrace.h> 100 #endif 101 102 #include <vm/vm.h> 103 #include <vm/vm_param.h> 104 #include <vm/pmap.h> 105 #include <vm/vm_map.h> 106 #include <vm/vm_object.h> 107 #include <vm/vm_page.h> 108 #include <vm/vm_pageout.h> 109 #include <vm/vm_kern.h> 110 #include <vm/vm_pager.h> 111 #include <vm/vm_extern.h> 112 #include <vm/vm_reserv.h> 113 114 #define PFBAK 4 115 #define PFFOR 4 116 117 #define VM_FAULT_READ_DEFAULT (1 + VM_FAULT_READ_AHEAD_INIT) 118 119 #define VM_FAULT_DONTNEED_MIN 1048576 120 121 struct faultstate { 122 /* Fault parameters. */ 123 vm_offset_t vaddr; 124 vm_page_t *m_hold; 125 vm_prot_t fault_type; 126 vm_prot_t prot; 127 int fault_flags; 128 int oom; 129 boolean_t wired; 130 131 /* Page reference for cow. */ 132 vm_page_t m_cow; 133 134 /* Current object. */ 135 vm_object_t object; 136 vm_pindex_t pindex; 137 vm_page_t m; 138 139 /* Top-level map object. */ 140 vm_object_t first_object; 141 vm_pindex_t first_pindex; 142 vm_page_t first_m; 143 144 /* Map state. */ 145 vm_map_t map; 146 vm_map_entry_t entry; 147 int map_generation; 148 bool lookup_still_valid; 149 150 /* Vnode if locked. */ 151 struct vnode *vp; 152 }; 153 154 static void vm_fault_dontneed(const struct faultstate *fs, vm_offset_t vaddr, 155 int ahead); 156 static void vm_fault_prefault(const struct faultstate *fs, vm_offset_t addra, 157 int backward, int forward, bool obj_locked); 158 159 static int vm_pfault_oom_attempts = 3; 160 SYSCTL_INT(_vm, OID_AUTO, pfault_oom_attempts, CTLFLAG_RWTUN, 161 &vm_pfault_oom_attempts, 0, 162 "Number of page allocation attempts in page fault handler before it " 163 "triggers OOM handling"); 164 165 static int vm_pfault_oom_wait = 10; 166 SYSCTL_INT(_vm, OID_AUTO, pfault_oom_wait, CTLFLAG_RWTUN, 167 &vm_pfault_oom_wait, 0, 168 "Number of seconds to wait for free pages before retrying " 169 "the page fault handler"); 170 171 static inline void 172 fault_page_release(vm_page_t *mp) 173 { 174 vm_page_t m; 175 176 m = *mp; 177 if (m != NULL) { 178 /* 179 * We are likely to loop around again and attempt to busy 180 * this page. Deactivating it leaves it available for 181 * pageout while optimizing fault restarts. 182 */ 183 vm_page_deactivate(m); 184 vm_page_xunbusy(m); 185 *mp = NULL; 186 } 187 } 188 189 static inline void 190 fault_page_free(vm_page_t *mp) 191 { 192 vm_page_t m; 193 194 m = *mp; 195 if (m != NULL) { 196 VM_OBJECT_ASSERT_WLOCKED(m->object); 197 if (!vm_page_wired(m)) 198 vm_page_free(m); 199 else 200 vm_page_xunbusy(m); 201 *mp = NULL; 202 } 203 } 204 205 static inline void 206 unlock_map(struct faultstate *fs) 207 { 208 209 if (fs->lookup_still_valid) { 210 vm_map_lookup_done(fs->map, fs->entry); 211 fs->lookup_still_valid = false; 212 } 213 } 214 215 static void 216 unlock_vp(struct faultstate *fs) 217 { 218 219 if (fs->vp != NULL) { 220 vput(fs->vp); 221 fs->vp = NULL; 222 } 223 } 224 225 static void 226 fault_deallocate(struct faultstate *fs) 227 { 228 229 fault_page_release(&fs->m_cow); 230 fault_page_release(&fs->m); 231 vm_object_pip_wakeup(fs->object); 232 if (fs->object != fs->first_object) { 233 VM_OBJECT_WLOCK(fs->first_object); 234 fault_page_free(&fs->first_m); 235 VM_OBJECT_WUNLOCK(fs->first_object); 236 vm_object_pip_wakeup(fs->first_object); 237 } 238 vm_object_deallocate(fs->first_object); 239 unlock_map(fs); 240 unlock_vp(fs); 241 } 242 243 static void 244 unlock_and_deallocate(struct faultstate *fs) 245 { 246 247 VM_OBJECT_WUNLOCK(fs->object); 248 fault_deallocate(fs); 249 } 250 251 static void 252 vm_fault_dirty(struct faultstate *fs, vm_page_t m) 253 { 254 bool need_dirty; 255 256 if (((fs->prot & VM_PROT_WRITE) == 0 && 257 (fs->fault_flags & VM_FAULT_DIRTY) == 0) || 258 (m->oflags & VPO_UNMANAGED) != 0) 259 return; 260 261 VM_PAGE_OBJECT_BUSY_ASSERT(m); 262 263 need_dirty = ((fs->fault_type & VM_PROT_WRITE) != 0 && 264 (fs->fault_flags & VM_FAULT_WIRE) == 0) || 265 (fs->fault_flags & VM_FAULT_DIRTY) != 0; 266 267 vm_object_set_writeable_dirty(m->object); 268 269 /* 270 * If the fault is a write, we know that this page is being 271 * written NOW so dirty it explicitly to save on 272 * pmap_is_modified() calls later. 273 * 274 * Also, since the page is now dirty, we can possibly tell 275 * the pager to release any swap backing the page. 276 */ 277 if (need_dirty && vm_page_set_dirty(m) == 0) { 278 /* 279 * If this is a NOSYNC mmap we do not want to set PGA_NOSYNC 280 * if the page is already dirty to prevent data written with 281 * the expectation of being synced from not being synced. 282 * Likewise if this entry does not request NOSYNC then make 283 * sure the page isn't marked NOSYNC. Applications sharing 284 * data should use the same flags to avoid ping ponging. 285 */ 286 if ((fs->entry->eflags & MAP_ENTRY_NOSYNC) != 0) 287 vm_page_aflag_set(m, PGA_NOSYNC); 288 else 289 vm_page_aflag_clear(m, PGA_NOSYNC); 290 } 291 292 } 293 294 /* 295 * Unlocks fs.first_object and fs.map on success. 296 */ 297 static int 298 vm_fault_soft_fast(struct faultstate *fs) 299 { 300 vm_page_t m, m_map; 301 #if VM_NRESERVLEVEL > 0 302 vm_page_t m_super; 303 int flags; 304 #endif 305 int psind, rv; 306 vm_offset_t vaddr; 307 308 MPASS(fs->vp == NULL); 309 vaddr = fs->vaddr; 310 vm_object_busy(fs->first_object); 311 m = vm_page_lookup(fs->first_object, fs->first_pindex); 312 /* A busy page can be mapped for read|execute access. */ 313 if (m == NULL || ((fs->prot & VM_PROT_WRITE) != 0 && 314 vm_page_busied(m)) || !vm_page_all_valid(m)) { 315 rv = KERN_FAILURE; 316 goto out; 317 } 318 m_map = m; 319 psind = 0; 320 #if VM_NRESERVLEVEL > 0 321 if ((m->flags & PG_FICTITIOUS) == 0 && 322 (m_super = vm_reserv_to_superpage(m)) != NULL && 323 rounddown2(vaddr, pagesizes[m_super->psind]) >= fs->entry->start && 324 roundup2(vaddr + 1, pagesizes[m_super->psind]) <= fs->entry->end && 325 (vaddr & (pagesizes[m_super->psind] - 1)) == (VM_PAGE_TO_PHYS(m) & 326 (pagesizes[m_super->psind] - 1)) && !fs->wired && 327 pmap_ps_enabled(fs->map->pmap)) { 328 flags = PS_ALL_VALID; 329 if ((fs->prot & VM_PROT_WRITE) != 0) { 330 /* 331 * Create a superpage mapping allowing write access 332 * only if none of the constituent pages are busy and 333 * all of them are already dirty (except possibly for 334 * the page that was faulted on). 335 */ 336 flags |= PS_NONE_BUSY; 337 if ((fs->first_object->flags & OBJ_UNMANAGED) == 0) 338 flags |= PS_ALL_DIRTY; 339 } 340 if (vm_page_ps_test(m_super, flags, m)) { 341 m_map = m_super; 342 psind = m_super->psind; 343 vaddr = rounddown2(vaddr, pagesizes[psind]); 344 /* Preset the modified bit for dirty superpages. */ 345 if ((flags & PS_ALL_DIRTY) != 0) 346 fs->fault_type |= VM_PROT_WRITE; 347 } 348 } 349 #endif 350 rv = pmap_enter(fs->map->pmap, vaddr, m_map, fs->prot, fs->fault_type | 351 PMAP_ENTER_NOSLEEP | (fs->wired ? PMAP_ENTER_WIRED : 0), psind); 352 if (rv != KERN_SUCCESS) 353 goto out; 354 if (fs->m_hold != NULL) { 355 (*fs->m_hold) = m; 356 vm_page_wire(m); 357 } 358 if (psind == 0 && !fs->wired) 359 vm_fault_prefault(fs, vaddr, PFBAK, PFFOR, true); 360 VM_OBJECT_RUNLOCK(fs->first_object); 361 vm_fault_dirty(fs, m); 362 vm_map_lookup_done(fs->map, fs->entry); 363 curthread->td_ru.ru_minflt++; 364 365 out: 366 vm_object_unbusy(fs->first_object); 367 return (rv); 368 } 369 370 static void 371 vm_fault_restore_map_lock(struct faultstate *fs) 372 { 373 374 VM_OBJECT_ASSERT_WLOCKED(fs->first_object); 375 MPASS(blockcount_read(&fs->first_object->paging_in_progress) > 0); 376 377 if (!vm_map_trylock_read(fs->map)) { 378 VM_OBJECT_WUNLOCK(fs->first_object); 379 vm_map_lock_read(fs->map); 380 VM_OBJECT_WLOCK(fs->first_object); 381 } 382 fs->lookup_still_valid = true; 383 } 384 385 static void 386 vm_fault_populate_check_page(vm_page_t m) 387 { 388 389 /* 390 * Check each page to ensure that the pager is obeying the 391 * interface: the page must be installed in the object, fully 392 * valid, and exclusively busied. 393 */ 394 MPASS(m != NULL); 395 MPASS(vm_page_all_valid(m)); 396 MPASS(vm_page_xbusied(m)); 397 } 398 399 static void 400 vm_fault_populate_cleanup(vm_object_t object, vm_pindex_t first, 401 vm_pindex_t last) 402 { 403 vm_page_t m; 404 vm_pindex_t pidx; 405 406 VM_OBJECT_ASSERT_WLOCKED(object); 407 MPASS(first <= last); 408 for (pidx = first, m = vm_page_lookup(object, pidx); 409 pidx <= last; pidx++, m = vm_page_next(m)) { 410 vm_fault_populate_check_page(m); 411 vm_page_deactivate(m); 412 vm_page_xunbusy(m); 413 } 414 } 415 416 static int 417 vm_fault_populate(struct faultstate *fs) 418 { 419 vm_offset_t vaddr; 420 vm_page_t m; 421 vm_pindex_t map_first, map_last, pager_first, pager_last, pidx; 422 int bdry_idx, i, npages, psind, rv; 423 424 MPASS(fs->object == fs->first_object); 425 VM_OBJECT_ASSERT_WLOCKED(fs->first_object); 426 MPASS(blockcount_read(&fs->first_object->paging_in_progress) > 0); 427 MPASS(fs->first_object->backing_object == NULL); 428 MPASS(fs->lookup_still_valid); 429 430 pager_first = OFF_TO_IDX(fs->entry->offset); 431 pager_last = pager_first + atop(fs->entry->end - fs->entry->start) - 1; 432 unlock_map(fs); 433 unlock_vp(fs); 434 435 /* 436 * Call the pager (driver) populate() method. 437 * 438 * There is no guarantee that the method will be called again 439 * if the current fault is for read, and a future fault is 440 * for write. Report the entry's maximum allowed protection 441 * to the driver. 442 */ 443 rv = vm_pager_populate(fs->first_object, fs->first_pindex, 444 fs->fault_type, fs->entry->max_protection, &pager_first, 445 &pager_last); 446 447 VM_OBJECT_ASSERT_WLOCKED(fs->first_object); 448 if (rv == VM_PAGER_BAD) { 449 /* 450 * VM_PAGER_BAD is the backdoor for a pager to request 451 * normal fault handling. 452 */ 453 vm_fault_restore_map_lock(fs); 454 if (fs->map->timestamp != fs->map_generation) 455 return (KERN_RESTART); 456 return (KERN_NOT_RECEIVER); 457 } 458 if (rv != VM_PAGER_OK) 459 return (KERN_FAILURE); /* AKA SIGSEGV */ 460 461 /* Ensure that the driver is obeying the interface. */ 462 MPASS(pager_first <= pager_last); 463 MPASS(fs->first_pindex <= pager_last); 464 MPASS(fs->first_pindex >= pager_first); 465 MPASS(pager_last < fs->first_object->size); 466 467 vm_fault_restore_map_lock(fs); 468 bdry_idx = (fs->entry->eflags & MAP_ENTRY_SPLIT_BOUNDARY_MASK) >> 469 MAP_ENTRY_SPLIT_BOUNDARY_SHIFT; 470 if (fs->map->timestamp != fs->map_generation) { 471 if (bdry_idx == 0) { 472 vm_fault_populate_cleanup(fs->first_object, pager_first, 473 pager_last); 474 } else { 475 m = vm_page_lookup(fs->first_object, pager_first); 476 if (m != fs->m) 477 vm_page_xunbusy(m); 478 } 479 return (KERN_RESTART); 480 } 481 482 /* 483 * The map is unchanged after our last unlock. Process the fault. 484 * 485 * First, the special case of largepage mappings, where 486 * populate only busies the first page in superpage run. 487 */ 488 if (bdry_idx != 0) { 489 KASSERT(PMAP_HAS_LARGEPAGES, 490 ("missing pmap support for large pages")); 491 m = vm_page_lookup(fs->first_object, pager_first); 492 vm_fault_populate_check_page(m); 493 VM_OBJECT_WUNLOCK(fs->first_object); 494 vaddr = fs->entry->start + IDX_TO_OFF(pager_first) - 495 fs->entry->offset; 496 /* assert alignment for entry */ 497 KASSERT((vaddr & (pagesizes[bdry_idx] - 1)) == 0, 498 ("unaligned superpage start %#jx pager_first %#jx offset %#jx vaddr %#jx", 499 (uintmax_t)fs->entry->start, (uintmax_t)pager_first, 500 (uintmax_t)fs->entry->offset, (uintmax_t)vaddr)); 501 KASSERT((VM_PAGE_TO_PHYS(m) & (pagesizes[bdry_idx] - 1)) == 0, 502 ("unaligned superpage m %p %#jx", m, 503 (uintmax_t)VM_PAGE_TO_PHYS(m))); 504 rv = pmap_enter(fs->map->pmap, vaddr, m, fs->prot, 505 fs->fault_type | (fs->wired ? PMAP_ENTER_WIRED : 0) | 506 PMAP_ENTER_LARGEPAGE, bdry_idx); 507 VM_OBJECT_WLOCK(fs->first_object); 508 vm_page_xunbusy(m); 509 if (rv != KERN_SUCCESS) 510 goto out; 511 if ((fs->fault_flags & VM_FAULT_WIRE) != 0) { 512 for (i = 0; i < atop(pagesizes[bdry_idx]); i++) 513 vm_page_wire(m + i); 514 } 515 if (fs->m_hold != NULL) { 516 *fs->m_hold = m + (fs->first_pindex - pager_first); 517 vm_page_wire(*fs->m_hold); 518 } 519 goto out; 520 } 521 522 /* 523 * The range [pager_first, pager_last] that is given to the 524 * pager is only a hint. The pager may populate any range 525 * within the object that includes the requested page index. 526 * In case the pager expanded the range, clip it to fit into 527 * the map entry. 528 */ 529 map_first = OFF_TO_IDX(fs->entry->offset); 530 if (map_first > pager_first) { 531 vm_fault_populate_cleanup(fs->first_object, pager_first, 532 map_first - 1); 533 pager_first = map_first; 534 } 535 map_last = map_first + atop(fs->entry->end - fs->entry->start) - 1; 536 if (map_last < pager_last) { 537 vm_fault_populate_cleanup(fs->first_object, map_last + 1, 538 pager_last); 539 pager_last = map_last; 540 } 541 for (pidx = pager_first, m = vm_page_lookup(fs->first_object, pidx); 542 pidx <= pager_last; 543 pidx += npages, m = vm_page_next(&m[npages - 1])) { 544 vaddr = fs->entry->start + IDX_TO_OFF(pidx) - fs->entry->offset; 545 #if defined(__aarch64__) || defined(__amd64__) || (defined(__arm__) && \ 546 __ARM_ARCH >= 6) || defined(__i386__) || defined(__riscv) || \ 547 defined(__powerpc64__) 548 psind = m->psind; 549 if (psind > 0 && ((vaddr & (pagesizes[psind] - 1)) != 0 || 550 pidx + OFF_TO_IDX(pagesizes[psind]) - 1 > pager_last || 551 !pmap_ps_enabled(fs->map->pmap) || fs->wired)) 552 psind = 0; 553 #else 554 psind = 0; 555 #endif 556 npages = atop(pagesizes[psind]); 557 for (i = 0; i < npages; i++) { 558 vm_fault_populate_check_page(&m[i]); 559 vm_fault_dirty(fs, &m[i]); 560 } 561 VM_OBJECT_WUNLOCK(fs->first_object); 562 rv = pmap_enter(fs->map->pmap, vaddr, m, fs->prot, fs->fault_type | 563 (fs->wired ? PMAP_ENTER_WIRED : 0), psind); 564 #if defined(__amd64__) 565 if (psind > 0 && rv == KERN_FAILURE) { 566 for (i = 0; i < npages; i++) { 567 rv = pmap_enter(fs->map->pmap, vaddr + ptoa(i), 568 &m[i], fs->prot, fs->fault_type | 569 (fs->wired ? PMAP_ENTER_WIRED : 0), 0); 570 MPASS(rv == KERN_SUCCESS); 571 } 572 } 573 #else 574 MPASS(rv == KERN_SUCCESS); 575 #endif 576 VM_OBJECT_WLOCK(fs->first_object); 577 for (i = 0; i < npages; i++) { 578 if ((fs->fault_flags & VM_FAULT_WIRE) != 0) 579 vm_page_wire(&m[i]); 580 else 581 vm_page_activate(&m[i]); 582 if (fs->m_hold != NULL && m[i].pindex == fs->first_pindex) { 583 (*fs->m_hold) = &m[i]; 584 vm_page_wire(&m[i]); 585 } 586 vm_page_xunbusy(&m[i]); 587 } 588 } 589 out: 590 curthread->td_ru.ru_majflt++; 591 return (rv); 592 } 593 594 static int prot_fault_translation; 595 SYSCTL_INT(_machdep, OID_AUTO, prot_fault_translation, CTLFLAG_RWTUN, 596 &prot_fault_translation, 0, 597 "Control signal to deliver on protection fault"); 598 599 /* compat definition to keep common code for signal translation */ 600 #define UCODE_PAGEFLT 12 601 #ifdef T_PAGEFLT 602 _Static_assert(UCODE_PAGEFLT == T_PAGEFLT, "T_PAGEFLT"); 603 #endif 604 605 /* 606 * vm_fault_trap: 607 * 608 * Handle a page fault occurring at the given address, 609 * requiring the given permissions, in the map specified. 610 * If successful, the page is inserted into the 611 * associated physical map. 612 * 613 * NOTE: the given address should be truncated to the 614 * proper page address. 615 * 616 * KERN_SUCCESS is returned if the page fault is handled; otherwise, 617 * a standard error specifying why the fault is fatal is returned. 618 * 619 * The map in question must be referenced, and remains so. 620 * Caller may hold no locks. 621 */ 622 int 623 vm_fault_trap(vm_map_t map, vm_offset_t vaddr, vm_prot_t fault_type, 624 int fault_flags, int *signo, int *ucode) 625 { 626 int result; 627 628 MPASS(signo == NULL || ucode != NULL); 629 #ifdef KTRACE 630 if (map != kernel_map && KTRPOINT(curthread, KTR_FAULT)) 631 ktrfault(vaddr, fault_type); 632 #endif 633 result = vm_fault(map, trunc_page(vaddr), fault_type, fault_flags, 634 NULL); 635 KASSERT(result == KERN_SUCCESS || result == KERN_FAILURE || 636 result == KERN_INVALID_ADDRESS || 637 result == KERN_RESOURCE_SHORTAGE || 638 result == KERN_PROTECTION_FAILURE || 639 result == KERN_OUT_OF_BOUNDS, 640 ("Unexpected Mach error %d from vm_fault()", result)); 641 #ifdef KTRACE 642 if (map != kernel_map && KTRPOINT(curthread, KTR_FAULTEND)) 643 ktrfaultend(result); 644 #endif 645 if (result != KERN_SUCCESS && signo != NULL) { 646 switch (result) { 647 case KERN_FAILURE: 648 case KERN_INVALID_ADDRESS: 649 *signo = SIGSEGV; 650 *ucode = SEGV_MAPERR; 651 break; 652 case KERN_RESOURCE_SHORTAGE: 653 *signo = SIGBUS; 654 *ucode = BUS_OOMERR; 655 break; 656 case KERN_OUT_OF_BOUNDS: 657 *signo = SIGBUS; 658 *ucode = BUS_OBJERR; 659 break; 660 case KERN_PROTECTION_FAILURE: 661 if (prot_fault_translation == 0) { 662 /* 663 * Autodetect. This check also covers 664 * the images without the ABI-tag ELF 665 * note. 666 */ 667 if (SV_CURPROC_ABI() == SV_ABI_FREEBSD && 668 curproc->p_osrel >= P_OSREL_SIGSEGV) { 669 *signo = SIGSEGV; 670 *ucode = SEGV_ACCERR; 671 } else { 672 *signo = SIGBUS; 673 *ucode = UCODE_PAGEFLT; 674 } 675 } else if (prot_fault_translation == 1) { 676 /* Always compat mode. */ 677 *signo = SIGBUS; 678 *ucode = UCODE_PAGEFLT; 679 } else { 680 /* Always SIGSEGV mode. */ 681 *signo = SIGSEGV; 682 *ucode = SEGV_ACCERR; 683 } 684 break; 685 default: 686 KASSERT(0, ("Unexpected Mach error %d from vm_fault()", 687 result)); 688 break; 689 } 690 } 691 return (result); 692 } 693 694 static int 695 vm_fault_lock_vnode(struct faultstate *fs, bool objlocked) 696 { 697 struct vnode *vp; 698 int error, locked; 699 700 if (fs->object->type != OBJT_VNODE) 701 return (KERN_SUCCESS); 702 vp = fs->object->handle; 703 if (vp == fs->vp) { 704 ASSERT_VOP_LOCKED(vp, "saved vnode is not locked"); 705 return (KERN_SUCCESS); 706 } 707 708 /* 709 * Perform an unlock in case the desired vnode changed while 710 * the map was unlocked during a retry. 711 */ 712 unlock_vp(fs); 713 714 locked = VOP_ISLOCKED(vp); 715 if (locked != LK_EXCLUSIVE) 716 locked = LK_SHARED; 717 718 /* 719 * We must not sleep acquiring the vnode lock while we have 720 * the page exclusive busied or the object's 721 * paging-in-progress count incremented. Otherwise, we could 722 * deadlock. 723 */ 724 error = vget(vp, locked | LK_CANRECURSE | LK_NOWAIT); 725 if (error == 0) { 726 fs->vp = vp; 727 return (KERN_SUCCESS); 728 } 729 730 vhold(vp); 731 if (objlocked) 732 unlock_and_deallocate(fs); 733 else 734 fault_deallocate(fs); 735 error = vget(vp, locked | LK_RETRY | LK_CANRECURSE); 736 vdrop(vp); 737 fs->vp = vp; 738 KASSERT(error == 0, ("vm_fault: vget failed %d", error)); 739 return (KERN_RESOURCE_SHORTAGE); 740 } 741 742 /* 743 * Calculate the desired readahead. Handle drop-behind. 744 * 745 * Returns the number of readahead blocks to pass to the pager. 746 */ 747 static int 748 vm_fault_readahead(struct faultstate *fs) 749 { 750 int era, nera; 751 u_char behavior; 752 753 KASSERT(fs->lookup_still_valid, ("map unlocked")); 754 era = fs->entry->read_ahead; 755 behavior = vm_map_entry_behavior(fs->entry); 756 if (behavior == MAP_ENTRY_BEHAV_RANDOM) { 757 nera = 0; 758 } else if (behavior == MAP_ENTRY_BEHAV_SEQUENTIAL) { 759 nera = VM_FAULT_READ_AHEAD_MAX; 760 if (fs->vaddr == fs->entry->next_read) 761 vm_fault_dontneed(fs, fs->vaddr, nera); 762 } else if (fs->vaddr == fs->entry->next_read) { 763 /* 764 * This is a sequential fault. Arithmetically 765 * increase the requested number of pages in 766 * the read-ahead window. The requested 767 * number of pages is "# of sequential faults 768 * x (read ahead min + 1) + read ahead min" 769 */ 770 nera = VM_FAULT_READ_AHEAD_MIN; 771 if (era > 0) { 772 nera += era + 1; 773 if (nera > VM_FAULT_READ_AHEAD_MAX) 774 nera = VM_FAULT_READ_AHEAD_MAX; 775 } 776 if (era == VM_FAULT_READ_AHEAD_MAX) 777 vm_fault_dontneed(fs, fs->vaddr, nera); 778 } else { 779 /* 780 * This is a non-sequential fault. 781 */ 782 nera = 0; 783 } 784 if (era != nera) { 785 /* 786 * A read lock on the map suffices to update 787 * the read ahead count safely. 788 */ 789 fs->entry->read_ahead = nera; 790 } 791 792 return (nera); 793 } 794 795 static int 796 vm_fault_lookup(struct faultstate *fs) 797 { 798 int result; 799 800 KASSERT(!fs->lookup_still_valid, 801 ("vm_fault_lookup: Map already locked.")); 802 result = vm_map_lookup(&fs->map, fs->vaddr, fs->fault_type | 803 VM_PROT_FAULT_LOOKUP, &fs->entry, &fs->first_object, 804 &fs->first_pindex, &fs->prot, &fs->wired); 805 if (result != KERN_SUCCESS) { 806 unlock_vp(fs); 807 return (result); 808 } 809 810 fs->map_generation = fs->map->timestamp; 811 812 if (fs->entry->eflags & MAP_ENTRY_NOFAULT) { 813 panic("%s: fault on nofault entry, addr: %#lx", 814 __func__, (u_long)fs->vaddr); 815 } 816 817 if (fs->entry->eflags & MAP_ENTRY_IN_TRANSITION && 818 fs->entry->wiring_thread != curthread) { 819 vm_map_unlock_read(fs->map); 820 vm_map_lock(fs->map); 821 if (vm_map_lookup_entry(fs->map, fs->vaddr, &fs->entry) && 822 (fs->entry->eflags & MAP_ENTRY_IN_TRANSITION)) { 823 unlock_vp(fs); 824 fs->entry->eflags |= MAP_ENTRY_NEEDS_WAKEUP; 825 vm_map_unlock_and_wait(fs->map, 0); 826 } else 827 vm_map_unlock(fs->map); 828 return (KERN_RESOURCE_SHORTAGE); 829 } 830 831 MPASS((fs->entry->eflags & MAP_ENTRY_GUARD) == 0); 832 833 if (fs->wired) 834 fs->fault_type = fs->prot | (fs->fault_type & VM_PROT_COPY); 835 else 836 KASSERT((fs->fault_flags & VM_FAULT_WIRE) == 0, 837 ("!fs->wired && VM_FAULT_WIRE")); 838 fs->lookup_still_valid = true; 839 840 return (KERN_SUCCESS); 841 } 842 843 static int 844 vm_fault_relookup(struct faultstate *fs) 845 { 846 vm_object_t retry_object; 847 vm_pindex_t retry_pindex; 848 vm_prot_t retry_prot; 849 int result; 850 851 if (!vm_map_trylock_read(fs->map)) 852 return (KERN_RESTART); 853 854 fs->lookup_still_valid = true; 855 if (fs->map->timestamp == fs->map_generation) 856 return (KERN_SUCCESS); 857 858 result = vm_map_lookup_locked(&fs->map, fs->vaddr, fs->fault_type, 859 &fs->entry, &retry_object, &retry_pindex, &retry_prot, 860 &fs->wired); 861 if (result != KERN_SUCCESS) { 862 /* 863 * If retry of map lookup would have blocked then 864 * retry fault from start. 865 */ 866 if (result == KERN_FAILURE) 867 return (KERN_RESTART); 868 return (result); 869 } 870 if (retry_object != fs->first_object || 871 retry_pindex != fs->first_pindex) 872 return (KERN_RESTART); 873 874 /* 875 * Check whether the protection has changed or the object has 876 * been copied while we left the map unlocked. Changing from 877 * read to write permission is OK - we leave the page 878 * write-protected, and catch the write fault. Changing from 879 * write to read permission means that we can't mark the page 880 * write-enabled after all. 881 */ 882 fs->prot &= retry_prot; 883 fs->fault_type &= retry_prot; 884 if (fs->prot == 0) 885 return (KERN_RESTART); 886 887 /* Reassert because wired may have changed. */ 888 KASSERT(fs->wired || (fs->fault_flags & VM_FAULT_WIRE) == 0, 889 ("!wired && VM_FAULT_WIRE")); 890 891 return (KERN_SUCCESS); 892 } 893 894 static void 895 vm_fault_cow(struct faultstate *fs) 896 { 897 bool is_first_object_locked; 898 899 /* 900 * This allows pages to be virtually copied from a backing_object 901 * into the first_object, where the backing object has no other 902 * refs to it, and cannot gain any more refs. Instead of a bcopy, 903 * we just move the page from the backing object to the first 904 * object. Note that we must mark the page dirty in the first 905 * object so that it will go out to swap when needed. 906 */ 907 is_first_object_locked = false; 908 if ( 909 /* 910 * Only one shadow object and no other refs. 911 */ 912 fs->object->shadow_count == 1 && fs->object->ref_count == 1 && 913 /* 914 * No other ways to look the object up 915 */ 916 fs->object->handle == NULL && (fs->object->flags & OBJ_ANON) != 0 && 917 /* 918 * We don't chase down the shadow chain and we can acquire locks. 919 */ 920 (is_first_object_locked = VM_OBJECT_TRYWLOCK(fs->first_object)) && 921 fs->object == fs->first_object->backing_object && 922 VM_OBJECT_TRYWLOCK(fs->object)) { 923 /* 924 * Remove but keep xbusy for replace. fs->m is moved into 925 * fs->first_object and left busy while fs->first_m is 926 * conditionally freed. 927 */ 928 vm_page_remove_xbusy(fs->m); 929 vm_page_replace(fs->m, fs->first_object, fs->first_pindex, 930 fs->first_m); 931 vm_page_dirty(fs->m); 932 #if VM_NRESERVLEVEL > 0 933 /* 934 * Rename the reservation. 935 */ 936 vm_reserv_rename(fs->m, fs->first_object, fs->object, 937 OFF_TO_IDX(fs->first_object->backing_object_offset)); 938 #endif 939 VM_OBJECT_WUNLOCK(fs->object); 940 VM_OBJECT_WUNLOCK(fs->first_object); 941 fs->first_m = fs->m; 942 fs->m = NULL; 943 VM_CNT_INC(v_cow_optim); 944 } else { 945 if (is_first_object_locked) 946 VM_OBJECT_WUNLOCK(fs->first_object); 947 /* 948 * Oh, well, lets copy it. 949 */ 950 pmap_copy_page(fs->m, fs->first_m); 951 vm_page_valid(fs->first_m); 952 if (fs->wired && (fs->fault_flags & VM_FAULT_WIRE) == 0) { 953 vm_page_wire(fs->first_m); 954 vm_page_unwire(fs->m, PQ_INACTIVE); 955 } 956 /* 957 * Save the cow page to be released after 958 * pmap_enter is complete. 959 */ 960 fs->m_cow = fs->m; 961 fs->m = NULL; 962 } 963 /* 964 * fs->object != fs->first_object due to above 965 * conditional 966 */ 967 vm_object_pip_wakeup(fs->object); 968 969 /* 970 * Only use the new page below... 971 */ 972 fs->object = fs->first_object; 973 fs->pindex = fs->first_pindex; 974 fs->m = fs->first_m; 975 VM_CNT_INC(v_cow_faults); 976 curthread->td_cow++; 977 } 978 979 static bool 980 vm_fault_next(struct faultstate *fs) 981 { 982 vm_object_t next_object; 983 984 /* 985 * The requested page does not exist at this object/ 986 * offset. Remove the invalid page from the object, 987 * waking up anyone waiting for it, and continue on to 988 * the next object. However, if this is the top-level 989 * object, we must leave the busy page in place to 990 * prevent another process from rushing past us, and 991 * inserting the page in that object at the same time 992 * that we are. 993 */ 994 if (fs->object == fs->first_object) { 995 fs->first_m = fs->m; 996 fs->m = NULL; 997 } else 998 fault_page_free(&fs->m); 999 1000 /* 1001 * Move on to the next object. Lock the next object before 1002 * unlocking the current one. 1003 */ 1004 VM_OBJECT_ASSERT_WLOCKED(fs->object); 1005 next_object = fs->object->backing_object; 1006 if (next_object == NULL) 1007 return (false); 1008 MPASS(fs->first_m != NULL); 1009 KASSERT(fs->object != next_object, ("object loop %p", next_object)); 1010 VM_OBJECT_WLOCK(next_object); 1011 vm_object_pip_add(next_object, 1); 1012 if (fs->object != fs->first_object) 1013 vm_object_pip_wakeup(fs->object); 1014 fs->pindex += OFF_TO_IDX(fs->object->backing_object_offset); 1015 VM_OBJECT_WUNLOCK(fs->object); 1016 fs->object = next_object; 1017 1018 return (true); 1019 } 1020 1021 static void 1022 vm_fault_zerofill(struct faultstate *fs) 1023 { 1024 1025 /* 1026 * If there's no object left, fill the page in the top 1027 * object with zeros. 1028 */ 1029 if (fs->object != fs->first_object) { 1030 vm_object_pip_wakeup(fs->object); 1031 fs->object = fs->first_object; 1032 fs->pindex = fs->first_pindex; 1033 } 1034 MPASS(fs->first_m != NULL); 1035 MPASS(fs->m == NULL); 1036 fs->m = fs->first_m; 1037 fs->first_m = NULL; 1038 1039 /* 1040 * Zero the page if necessary and mark it valid. 1041 */ 1042 if ((fs->m->flags & PG_ZERO) == 0) { 1043 pmap_zero_page(fs->m); 1044 } else { 1045 VM_CNT_INC(v_ozfod); 1046 } 1047 VM_CNT_INC(v_zfod); 1048 vm_page_valid(fs->m); 1049 } 1050 1051 /* 1052 * Allocate a page directly or via the object populate method. 1053 */ 1054 static int 1055 vm_fault_allocate(struct faultstate *fs) 1056 { 1057 struct domainset *dset; 1058 int alloc_req; 1059 int rv; 1060 1061 if ((fs->object->flags & OBJ_SIZEVNLOCK) != 0) { 1062 rv = vm_fault_lock_vnode(fs, true); 1063 MPASS(rv == KERN_SUCCESS || rv == KERN_RESOURCE_SHORTAGE); 1064 if (rv == KERN_RESOURCE_SHORTAGE) 1065 return (rv); 1066 } 1067 1068 if (fs->pindex >= fs->object->size) 1069 return (KERN_OUT_OF_BOUNDS); 1070 1071 if (fs->object == fs->first_object && 1072 (fs->first_object->flags & OBJ_POPULATE) != 0 && 1073 fs->first_object->shadow_count == 0) { 1074 rv = vm_fault_populate(fs); 1075 switch (rv) { 1076 case KERN_SUCCESS: 1077 case KERN_FAILURE: 1078 case KERN_PROTECTION_FAILURE: 1079 case KERN_RESTART: 1080 return (rv); 1081 case KERN_NOT_RECEIVER: 1082 /* 1083 * Pager's populate() method 1084 * returned VM_PAGER_BAD. 1085 */ 1086 break; 1087 default: 1088 panic("inconsistent return codes"); 1089 } 1090 } 1091 1092 /* 1093 * Allocate a new page for this object/offset pair. 1094 * 1095 * Unlocked read of the p_flag is harmless. At worst, the P_KILLED 1096 * might be not observed there, and allocation can fail, causing 1097 * restart and new reading of the p_flag. 1098 */ 1099 dset = fs->object->domain.dr_policy; 1100 if (dset == NULL) 1101 dset = curthread->td_domain.dr_policy; 1102 if (!vm_page_count_severe_set(&dset->ds_mask) || P_KILLED(curproc)) { 1103 #if VM_NRESERVLEVEL > 0 1104 vm_object_color(fs->object, atop(fs->vaddr) - fs->pindex); 1105 #endif 1106 alloc_req = P_KILLED(curproc) ? 1107 VM_ALLOC_SYSTEM : VM_ALLOC_NORMAL; 1108 if (fs->object->type != OBJT_VNODE && 1109 fs->object->backing_object == NULL) 1110 alloc_req |= VM_ALLOC_ZERO; 1111 fs->m = vm_page_alloc(fs->object, fs->pindex, alloc_req); 1112 } 1113 if (fs->m == NULL) { 1114 unlock_and_deallocate(fs); 1115 if (vm_pfault_oom_attempts < 0 || 1116 fs->oom < vm_pfault_oom_attempts) { 1117 fs->oom++; 1118 vm_waitpfault(dset, vm_pfault_oom_wait * hz); 1119 } else { 1120 if (bootverbose) 1121 printf( 1122 "proc %d (%s) failed to alloc page on fault, starting OOM\n", 1123 curproc->p_pid, curproc->p_comm); 1124 vm_pageout_oom(VM_OOM_MEM_PF); 1125 fs->oom = 0; 1126 } 1127 return (KERN_RESOURCE_SHORTAGE); 1128 } 1129 fs->oom = 0; 1130 1131 return (KERN_NOT_RECEIVER); 1132 } 1133 1134 /* 1135 * Call the pager to retrieve the page if there is a chance 1136 * that the pager has it, and potentially retrieve additional 1137 * pages at the same time. 1138 */ 1139 static int 1140 vm_fault_getpages(struct faultstate *fs, int nera, int *behindp, int *aheadp) 1141 { 1142 vm_offset_t e_end, e_start; 1143 int ahead, behind, cluster_offset, rv; 1144 u_char behavior; 1145 1146 /* 1147 * Prepare for unlocking the map. Save the map 1148 * entry's start and end addresses, which are used to 1149 * optimize the size of the pager operation below. 1150 * Even if the map entry's addresses change after 1151 * unlocking the map, using the saved addresses is 1152 * safe. 1153 */ 1154 e_start = fs->entry->start; 1155 e_end = fs->entry->end; 1156 behavior = vm_map_entry_behavior(fs->entry); 1157 1158 /* 1159 * Release the map lock before locking the vnode or 1160 * sleeping in the pager. (If the current object has 1161 * a shadow, then an earlier iteration of this loop 1162 * may have already unlocked the map.) 1163 */ 1164 unlock_map(fs); 1165 1166 rv = vm_fault_lock_vnode(fs, false); 1167 MPASS(rv == KERN_SUCCESS || rv == KERN_RESOURCE_SHORTAGE); 1168 if (rv == KERN_RESOURCE_SHORTAGE) 1169 return (rv); 1170 KASSERT(fs->vp == NULL || !fs->map->system_map, 1171 ("vm_fault: vnode-backed object mapped by system map")); 1172 1173 /* 1174 * Page in the requested page and hint the pager, 1175 * that it may bring up surrounding pages. 1176 */ 1177 if (nera == -1 || behavior == MAP_ENTRY_BEHAV_RANDOM || 1178 P_KILLED(curproc)) { 1179 behind = 0; 1180 ahead = 0; 1181 } else { 1182 /* Is this a sequential fault? */ 1183 if (nera > 0) { 1184 behind = 0; 1185 ahead = nera; 1186 } else { 1187 /* 1188 * Request a cluster of pages that is 1189 * aligned to a VM_FAULT_READ_DEFAULT 1190 * page offset boundary within the 1191 * object. Alignment to a page offset 1192 * boundary is more likely to coincide 1193 * with the underlying file system 1194 * block than alignment to a virtual 1195 * address boundary. 1196 */ 1197 cluster_offset = fs->pindex % VM_FAULT_READ_DEFAULT; 1198 behind = ulmin(cluster_offset, 1199 atop(fs->vaddr - e_start)); 1200 ahead = VM_FAULT_READ_DEFAULT - 1 - cluster_offset; 1201 } 1202 ahead = ulmin(ahead, atop(e_end - fs->vaddr) - 1); 1203 } 1204 *behindp = behind; 1205 *aheadp = ahead; 1206 rv = vm_pager_get_pages(fs->object, &fs->m, 1, behindp, aheadp); 1207 if (rv == VM_PAGER_OK) 1208 return (KERN_SUCCESS); 1209 if (rv == VM_PAGER_ERROR) 1210 printf("vm_fault: pager read error, pid %d (%s)\n", 1211 curproc->p_pid, curproc->p_comm); 1212 /* 1213 * If an I/O error occurred or the requested page was 1214 * outside the range of the pager, clean up and return 1215 * an error. 1216 */ 1217 if (rv == VM_PAGER_ERROR || rv == VM_PAGER_BAD) 1218 return (KERN_OUT_OF_BOUNDS); 1219 return (KERN_NOT_RECEIVER); 1220 } 1221 1222 /* 1223 * Wait/Retry if the page is busy. We have to do this if the page is 1224 * either exclusive or shared busy because the vm_pager may be using 1225 * read busy for pageouts (and even pageins if it is the vnode pager), 1226 * and we could end up trying to pagein and pageout the same page 1227 * simultaneously. 1228 * 1229 * We can theoretically allow the busy case on a read fault if the page 1230 * is marked valid, but since such pages are typically already pmap'd, 1231 * putting that special case in might be more effort then it is worth. 1232 * We cannot under any circumstances mess around with a shared busied 1233 * page except, perhaps, to pmap it. 1234 */ 1235 static void 1236 vm_fault_busy_sleep(struct faultstate *fs) 1237 { 1238 /* 1239 * Reference the page before unlocking and 1240 * sleeping so that the page daemon is less 1241 * likely to reclaim it. 1242 */ 1243 vm_page_aflag_set(fs->m, PGA_REFERENCED); 1244 if (fs->object != fs->first_object) { 1245 fault_page_release(&fs->first_m); 1246 vm_object_pip_wakeup(fs->first_object); 1247 } 1248 vm_object_pip_wakeup(fs->object); 1249 unlock_map(fs); 1250 if (fs->m == vm_page_lookup(fs->object, fs->pindex)) 1251 vm_page_busy_sleep(fs->m, "vmpfw", false); 1252 else 1253 VM_OBJECT_WUNLOCK(fs->object); 1254 VM_CNT_INC(v_intrans); 1255 vm_object_deallocate(fs->first_object); 1256 } 1257 1258 int 1259 vm_fault(vm_map_t map, vm_offset_t vaddr, vm_prot_t fault_type, 1260 int fault_flags, vm_page_t *m_hold) 1261 { 1262 struct faultstate fs; 1263 int ahead, behind, faultcount; 1264 int nera, result, rv; 1265 bool dead, hardfault; 1266 1267 VM_CNT_INC(v_vm_faults); 1268 1269 if ((curthread->td_pflags & TDP_NOFAULTING) != 0) 1270 return (KERN_PROTECTION_FAILURE); 1271 1272 fs.vp = NULL; 1273 fs.vaddr = vaddr; 1274 fs.m_hold = m_hold; 1275 fs.fault_flags = fault_flags; 1276 fs.map = map; 1277 fs.lookup_still_valid = false; 1278 fs.oom = 0; 1279 faultcount = 0; 1280 nera = -1; 1281 hardfault = false; 1282 1283 RetryFault: 1284 fs.fault_type = fault_type; 1285 1286 /* 1287 * Find the backing store object and offset into it to begin the 1288 * search. 1289 */ 1290 result = vm_fault_lookup(&fs); 1291 if (result != KERN_SUCCESS) { 1292 if (result == KERN_RESOURCE_SHORTAGE) 1293 goto RetryFault; 1294 return (result); 1295 } 1296 1297 /* 1298 * Try to avoid lock contention on the top-level object through 1299 * special-case handling of some types of page faults, specifically, 1300 * those that are mapping an existing page from the top-level object. 1301 * Under this condition, a read lock on the object suffices, allowing 1302 * multiple page faults of a similar type to run in parallel. 1303 */ 1304 if (fs.vp == NULL /* avoid locked vnode leak */ && 1305 (fs.entry->eflags & MAP_ENTRY_SPLIT_BOUNDARY_MASK) == 0 && 1306 (fs.fault_flags & (VM_FAULT_WIRE | VM_FAULT_DIRTY)) == 0) { 1307 VM_OBJECT_RLOCK(fs.first_object); 1308 rv = vm_fault_soft_fast(&fs); 1309 if (rv == KERN_SUCCESS) 1310 return (rv); 1311 if (!VM_OBJECT_TRYUPGRADE(fs.first_object)) { 1312 VM_OBJECT_RUNLOCK(fs.first_object); 1313 VM_OBJECT_WLOCK(fs.first_object); 1314 } 1315 } else { 1316 VM_OBJECT_WLOCK(fs.first_object); 1317 } 1318 1319 /* 1320 * Make a reference to this object to prevent its disposal while we 1321 * are messing with it. Once we have the reference, the map is free 1322 * to be diddled. Since objects reference their shadows (and copies), 1323 * they will stay around as well. 1324 * 1325 * Bump the paging-in-progress count to prevent size changes (e.g. 1326 * truncation operations) during I/O. 1327 */ 1328 vm_object_reference_locked(fs.first_object); 1329 vm_object_pip_add(fs.first_object, 1); 1330 1331 fs.m_cow = fs.m = fs.first_m = NULL; 1332 1333 /* 1334 * Search for the page at object/offset. 1335 */ 1336 fs.object = fs.first_object; 1337 fs.pindex = fs.first_pindex; 1338 1339 if ((fs.entry->eflags & MAP_ENTRY_SPLIT_BOUNDARY_MASK) != 0) { 1340 rv = vm_fault_allocate(&fs); 1341 switch (rv) { 1342 case KERN_RESTART: 1343 unlock_and_deallocate(&fs); 1344 /* FALLTHROUGH */ 1345 case KERN_RESOURCE_SHORTAGE: 1346 goto RetryFault; 1347 case KERN_SUCCESS: 1348 case KERN_FAILURE: 1349 case KERN_PROTECTION_FAILURE: 1350 case KERN_OUT_OF_BOUNDS: 1351 unlock_and_deallocate(&fs); 1352 return (rv); 1353 case KERN_NOT_RECEIVER: 1354 break; 1355 default: 1356 panic("vm_fault: Unhandled rv %d", rv); 1357 } 1358 } 1359 1360 while (TRUE) { 1361 KASSERT(fs.m == NULL, 1362 ("page still set %p at loop start", fs.m)); 1363 /* 1364 * If the object is marked for imminent termination, 1365 * we retry here, since the collapse pass has raced 1366 * with us. Otherwise, if we see terminally dead 1367 * object, return fail. 1368 */ 1369 if ((fs.object->flags & OBJ_DEAD) != 0) { 1370 dead = fs.object->type == OBJT_DEAD; 1371 unlock_and_deallocate(&fs); 1372 if (dead) 1373 return (KERN_PROTECTION_FAILURE); 1374 pause("vmf_de", 1); 1375 goto RetryFault; 1376 } 1377 1378 /* 1379 * See if page is resident 1380 */ 1381 fs.m = vm_page_lookup(fs.object, fs.pindex); 1382 if (fs.m != NULL) { 1383 if (vm_page_tryxbusy(fs.m) == 0) { 1384 vm_fault_busy_sleep(&fs); 1385 goto RetryFault; 1386 } 1387 1388 /* 1389 * The page is marked busy for other processes and the 1390 * pagedaemon. If it still is completely valid we 1391 * are done. 1392 */ 1393 if (vm_page_all_valid(fs.m)) { 1394 VM_OBJECT_WUNLOCK(fs.object); 1395 break; /* break to PAGE HAS BEEN FOUND. */ 1396 } 1397 } 1398 VM_OBJECT_ASSERT_WLOCKED(fs.object); 1399 1400 /* 1401 * Page is not resident. If the pager might contain the page 1402 * or this is the beginning of the search, allocate a new 1403 * page. (Default objects are zero-fill, so there is no real 1404 * pager for them.) 1405 */ 1406 if (fs.m == NULL && (fs.object->type != OBJT_DEFAULT || 1407 fs.object == fs.first_object)) { 1408 rv = vm_fault_allocate(&fs); 1409 switch (rv) { 1410 case KERN_RESTART: 1411 unlock_and_deallocate(&fs); 1412 /* FALLTHROUGH */ 1413 case KERN_RESOURCE_SHORTAGE: 1414 goto RetryFault; 1415 case KERN_SUCCESS: 1416 case KERN_FAILURE: 1417 case KERN_PROTECTION_FAILURE: 1418 case KERN_OUT_OF_BOUNDS: 1419 unlock_and_deallocate(&fs); 1420 return (rv); 1421 case KERN_NOT_RECEIVER: 1422 break; 1423 default: 1424 panic("vm_fault: Unhandled rv %d", rv); 1425 } 1426 } 1427 1428 /* 1429 * Default objects have no pager so no exclusive busy exists 1430 * to protect this page in the chain. Skip to the next 1431 * object without dropping the lock to preserve atomicity of 1432 * shadow faults. 1433 */ 1434 if (fs.object->type != OBJT_DEFAULT) { 1435 /* 1436 * At this point, we have either allocated a new page 1437 * or found an existing page that is only partially 1438 * valid. 1439 * 1440 * We hold a reference on the current object and the 1441 * page is exclusive busied. The exclusive busy 1442 * prevents simultaneous faults and collapses while 1443 * the object lock is dropped. 1444 */ 1445 VM_OBJECT_WUNLOCK(fs.object); 1446 1447 /* 1448 * If the pager for the current object might have 1449 * the page, then determine the number of additional 1450 * pages to read and potentially reprioritize 1451 * previously read pages for earlier reclamation. 1452 * These operations should only be performed once per 1453 * page fault. Even if the current pager doesn't 1454 * have the page, the number of additional pages to 1455 * read will apply to subsequent objects in the 1456 * shadow chain. 1457 */ 1458 if (nera == -1 && !P_KILLED(curproc)) 1459 nera = vm_fault_readahead(&fs); 1460 1461 rv = vm_fault_getpages(&fs, nera, &behind, &ahead); 1462 if (rv == KERN_SUCCESS) { 1463 faultcount = behind + 1 + ahead; 1464 hardfault = true; 1465 break; /* break to PAGE HAS BEEN FOUND. */ 1466 } 1467 if (rv == KERN_RESOURCE_SHORTAGE) 1468 goto RetryFault; 1469 VM_OBJECT_WLOCK(fs.object); 1470 if (rv == KERN_OUT_OF_BOUNDS) { 1471 fault_page_free(&fs.m); 1472 unlock_and_deallocate(&fs); 1473 return (rv); 1474 } 1475 } 1476 1477 /* 1478 * The page was not found in the current object. Try to 1479 * traverse into a backing object or zero fill if none is 1480 * found. 1481 */ 1482 if (vm_fault_next(&fs)) 1483 continue; 1484 if ((fs.fault_flags & VM_FAULT_NOFILL) != 0) { 1485 if (fs.first_object == fs.object) 1486 fault_page_free(&fs.first_m); 1487 unlock_and_deallocate(&fs); 1488 return (KERN_OUT_OF_BOUNDS); 1489 } 1490 VM_OBJECT_WUNLOCK(fs.object); 1491 vm_fault_zerofill(&fs); 1492 /* Don't try to prefault neighboring pages. */ 1493 faultcount = 1; 1494 break; /* break to PAGE HAS BEEN FOUND. */ 1495 } 1496 1497 /* 1498 * PAGE HAS BEEN FOUND. A valid page has been found and exclusively 1499 * busied. The object lock must no longer be held. 1500 */ 1501 vm_page_assert_xbusied(fs.m); 1502 VM_OBJECT_ASSERT_UNLOCKED(fs.object); 1503 1504 /* 1505 * If the page is being written, but isn't already owned by the 1506 * top-level object, we have to copy it into a new page owned by the 1507 * top-level object. 1508 */ 1509 if (fs.object != fs.first_object) { 1510 /* 1511 * We only really need to copy if we want to write it. 1512 */ 1513 if ((fs.fault_type & (VM_PROT_COPY | VM_PROT_WRITE)) != 0) { 1514 vm_fault_cow(&fs); 1515 /* 1516 * We only try to prefault read-only mappings to the 1517 * neighboring pages when this copy-on-write fault is 1518 * a hard fault. In other cases, trying to prefault 1519 * is typically wasted effort. 1520 */ 1521 if (faultcount == 0) 1522 faultcount = 1; 1523 1524 } else { 1525 fs.prot &= ~VM_PROT_WRITE; 1526 } 1527 } 1528 1529 /* 1530 * We must verify that the maps have not changed since our last 1531 * lookup. 1532 */ 1533 if (!fs.lookup_still_valid) { 1534 result = vm_fault_relookup(&fs); 1535 if (result != KERN_SUCCESS) { 1536 fault_deallocate(&fs); 1537 if (result == KERN_RESTART) 1538 goto RetryFault; 1539 return (result); 1540 } 1541 } 1542 VM_OBJECT_ASSERT_UNLOCKED(fs.object); 1543 1544 /* 1545 * If the page was filled by a pager, save the virtual address that 1546 * should be faulted on next under a sequential access pattern to the 1547 * map entry. A read lock on the map suffices to update this address 1548 * safely. 1549 */ 1550 if (hardfault) 1551 fs.entry->next_read = vaddr + ptoa(ahead) + PAGE_SIZE; 1552 1553 /* 1554 * Page must be completely valid or it is not fit to 1555 * map into user space. vm_pager_get_pages() ensures this. 1556 */ 1557 vm_page_assert_xbusied(fs.m); 1558 KASSERT(vm_page_all_valid(fs.m), 1559 ("vm_fault: page %p partially invalid", fs.m)); 1560 1561 vm_fault_dirty(&fs, fs.m); 1562 1563 /* 1564 * Put this page into the physical map. We had to do the unlock above 1565 * because pmap_enter() may sleep. We don't put the page 1566 * back on the active queue until later so that the pageout daemon 1567 * won't find it (yet). 1568 */ 1569 pmap_enter(fs.map->pmap, vaddr, fs.m, fs.prot, 1570 fs.fault_type | (fs.wired ? PMAP_ENTER_WIRED : 0), 0); 1571 if (faultcount != 1 && (fs.fault_flags & VM_FAULT_WIRE) == 0 && 1572 fs.wired == 0) 1573 vm_fault_prefault(&fs, vaddr, 1574 faultcount > 0 ? behind : PFBAK, 1575 faultcount > 0 ? ahead : PFFOR, false); 1576 1577 /* 1578 * If the page is not wired down, then put it where the pageout daemon 1579 * can find it. 1580 */ 1581 if ((fs.fault_flags & VM_FAULT_WIRE) != 0) 1582 vm_page_wire(fs.m); 1583 else 1584 vm_page_activate(fs.m); 1585 if (fs.m_hold != NULL) { 1586 (*fs.m_hold) = fs.m; 1587 vm_page_wire(fs.m); 1588 } 1589 vm_page_xunbusy(fs.m); 1590 fs.m = NULL; 1591 1592 /* 1593 * Unlock everything, and return 1594 */ 1595 fault_deallocate(&fs); 1596 if (hardfault) { 1597 VM_CNT_INC(v_io_faults); 1598 curthread->td_ru.ru_majflt++; 1599 #ifdef RACCT 1600 if (racct_enable && fs.object->type == OBJT_VNODE) { 1601 PROC_LOCK(curproc); 1602 if ((fs.fault_type & (VM_PROT_COPY | VM_PROT_WRITE)) != 0) { 1603 racct_add_force(curproc, RACCT_WRITEBPS, 1604 PAGE_SIZE + behind * PAGE_SIZE); 1605 racct_add_force(curproc, RACCT_WRITEIOPS, 1); 1606 } else { 1607 racct_add_force(curproc, RACCT_READBPS, 1608 PAGE_SIZE + ahead * PAGE_SIZE); 1609 racct_add_force(curproc, RACCT_READIOPS, 1); 1610 } 1611 PROC_UNLOCK(curproc); 1612 } 1613 #endif 1614 } else 1615 curthread->td_ru.ru_minflt++; 1616 1617 return (KERN_SUCCESS); 1618 } 1619 1620 /* 1621 * Speed up the reclamation of pages that precede the faulting pindex within 1622 * the first object of the shadow chain. Essentially, perform the equivalent 1623 * to madvise(..., MADV_DONTNEED) on a large cluster of pages that precedes 1624 * the faulting pindex by the cluster size when the pages read by vm_fault() 1625 * cross a cluster-size boundary. The cluster size is the greater of the 1626 * smallest superpage size and VM_FAULT_DONTNEED_MIN. 1627 * 1628 * When "fs->first_object" is a shadow object, the pages in the backing object 1629 * that precede the faulting pindex are deactivated by vm_fault(). So, this 1630 * function must only be concerned with pages in the first object. 1631 */ 1632 static void 1633 vm_fault_dontneed(const struct faultstate *fs, vm_offset_t vaddr, int ahead) 1634 { 1635 vm_map_entry_t entry; 1636 vm_object_t first_object, object; 1637 vm_offset_t end, start; 1638 vm_page_t m, m_next; 1639 vm_pindex_t pend, pstart; 1640 vm_size_t size; 1641 1642 object = fs->object; 1643 VM_OBJECT_ASSERT_UNLOCKED(object); 1644 first_object = fs->first_object; 1645 /* Neither fictitious nor unmanaged pages can be reclaimed. */ 1646 if ((first_object->flags & (OBJ_FICTITIOUS | OBJ_UNMANAGED)) == 0) { 1647 VM_OBJECT_RLOCK(first_object); 1648 size = VM_FAULT_DONTNEED_MIN; 1649 if (MAXPAGESIZES > 1 && size < pagesizes[1]) 1650 size = pagesizes[1]; 1651 end = rounddown2(vaddr, size); 1652 if (vaddr - end >= size - PAGE_SIZE - ptoa(ahead) && 1653 (entry = fs->entry)->start < end) { 1654 if (end - entry->start < size) 1655 start = entry->start; 1656 else 1657 start = end - size; 1658 pmap_advise(fs->map->pmap, start, end, MADV_DONTNEED); 1659 pstart = OFF_TO_IDX(entry->offset) + atop(start - 1660 entry->start); 1661 m_next = vm_page_find_least(first_object, pstart); 1662 pend = OFF_TO_IDX(entry->offset) + atop(end - 1663 entry->start); 1664 while ((m = m_next) != NULL && m->pindex < pend) { 1665 m_next = TAILQ_NEXT(m, listq); 1666 if (!vm_page_all_valid(m) || 1667 vm_page_busied(m)) 1668 continue; 1669 1670 /* 1671 * Don't clear PGA_REFERENCED, since it would 1672 * likely represent a reference by a different 1673 * process. 1674 * 1675 * Typically, at this point, prefetched pages 1676 * are still in the inactive queue. Only 1677 * pages that triggered page faults are in the 1678 * active queue. The test for whether the page 1679 * is in the inactive queue is racy; in the 1680 * worst case we will requeue the page 1681 * unnecessarily. 1682 */ 1683 if (!vm_page_inactive(m)) 1684 vm_page_deactivate(m); 1685 } 1686 } 1687 VM_OBJECT_RUNLOCK(first_object); 1688 } 1689 } 1690 1691 /* 1692 * vm_fault_prefault provides a quick way of clustering 1693 * pagefaults into a processes address space. It is a "cousin" 1694 * of vm_map_pmap_enter, except it runs at page fault time instead 1695 * of mmap time. 1696 */ 1697 static void 1698 vm_fault_prefault(const struct faultstate *fs, vm_offset_t addra, 1699 int backward, int forward, bool obj_locked) 1700 { 1701 pmap_t pmap; 1702 vm_map_entry_t entry; 1703 vm_object_t backing_object, lobject; 1704 vm_offset_t addr, starta; 1705 vm_pindex_t pindex; 1706 vm_page_t m; 1707 int i; 1708 1709 pmap = fs->map->pmap; 1710 if (pmap != vmspace_pmap(curthread->td_proc->p_vmspace)) 1711 return; 1712 1713 entry = fs->entry; 1714 1715 if (addra < backward * PAGE_SIZE) { 1716 starta = entry->start; 1717 } else { 1718 starta = addra - backward * PAGE_SIZE; 1719 if (starta < entry->start) 1720 starta = entry->start; 1721 } 1722 1723 /* 1724 * Generate the sequence of virtual addresses that are candidates for 1725 * prefaulting in an outward spiral from the faulting virtual address, 1726 * "addra". Specifically, the sequence is "addra - PAGE_SIZE", "addra 1727 * + PAGE_SIZE", "addra - 2 * PAGE_SIZE", "addra + 2 * PAGE_SIZE", ... 1728 * If the candidate address doesn't have a backing physical page, then 1729 * the loop immediately terminates. 1730 */ 1731 for (i = 0; i < 2 * imax(backward, forward); i++) { 1732 addr = addra + ((i >> 1) + 1) * ((i & 1) == 0 ? -PAGE_SIZE : 1733 PAGE_SIZE); 1734 if (addr > addra + forward * PAGE_SIZE) 1735 addr = 0; 1736 1737 if (addr < starta || addr >= entry->end) 1738 continue; 1739 1740 if (!pmap_is_prefaultable(pmap, addr)) 1741 continue; 1742 1743 pindex = ((addr - entry->start) + entry->offset) >> PAGE_SHIFT; 1744 lobject = entry->object.vm_object; 1745 if (!obj_locked) 1746 VM_OBJECT_RLOCK(lobject); 1747 while ((m = vm_page_lookup(lobject, pindex)) == NULL && 1748 lobject->type == OBJT_DEFAULT && 1749 (backing_object = lobject->backing_object) != NULL) { 1750 KASSERT((lobject->backing_object_offset & PAGE_MASK) == 1751 0, ("vm_fault_prefault: unaligned object offset")); 1752 pindex += lobject->backing_object_offset >> PAGE_SHIFT; 1753 VM_OBJECT_RLOCK(backing_object); 1754 if (!obj_locked || lobject != entry->object.vm_object) 1755 VM_OBJECT_RUNLOCK(lobject); 1756 lobject = backing_object; 1757 } 1758 if (m == NULL) { 1759 if (!obj_locked || lobject != entry->object.vm_object) 1760 VM_OBJECT_RUNLOCK(lobject); 1761 break; 1762 } 1763 if (vm_page_all_valid(m) && 1764 (m->flags & PG_FICTITIOUS) == 0) 1765 pmap_enter_quick(pmap, addr, m, entry->protection); 1766 if (!obj_locked || lobject != entry->object.vm_object) 1767 VM_OBJECT_RUNLOCK(lobject); 1768 } 1769 } 1770 1771 /* 1772 * Hold each of the physical pages that are mapped by the specified range of 1773 * virtual addresses, ["addr", "addr" + "len"), if those mappings are valid 1774 * and allow the specified types of access, "prot". If all of the implied 1775 * pages are successfully held, then the number of held pages is returned 1776 * together with pointers to those pages in the array "ma". However, if any 1777 * of the pages cannot be held, -1 is returned. 1778 */ 1779 int 1780 vm_fault_quick_hold_pages(vm_map_t map, vm_offset_t addr, vm_size_t len, 1781 vm_prot_t prot, vm_page_t *ma, int max_count) 1782 { 1783 vm_offset_t end, va; 1784 vm_page_t *mp; 1785 int count; 1786 boolean_t pmap_failed; 1787 1788 if (len == 0) 1789 return (0); 1790 end = round_page(addr + len); 1791 addr = trunc_page(addr); 1792 1793 if (!vm_map_range_valid(map, addr, end)) 1794 return (-1); 1795 1796 if (atop(end - addr) > max_count) 1797 panic("vm_fault_quick_hold_pages: count > max_count"); 1798 count = atop(end - addr); 1799 1800 /* 1801 * Most likely, the physical pages are resident in the pmap, so it is 1802 * faster to try pmap_extract_and_hold() first. 1803 */ 1804 pmap_failed = FALSE; 1805 for (mp = ma, va = addr; va < end; mp++, va += PAGE_SIZE) { 1806 *mp = pmap_extract_and_hold(map->pmap, va, prot); 1807 if (*mp == NULL) 1808 pmap_failed = TRUE; 1809 else if ((prot & VM_PROT_WRITE) != 0 && 1810 (*mp)->dirty != VM_PAGE_BITS_ALL) { 1811 /* 1812 * Explicitly dirty the physical page. Otherwise, the 1813 * caller's changes may go unnoticed because they are 1814 * performed through an unmanaged mapping or by a DMA 1815 * operation. 1816 * 1817 * The object lock is not held here. 1818 * See vm_page_clear_dirty_mask(). 1819 */ 1820 vm_page_dirty(*mp); 1821 } 1822 } 1823 if (pmap_failed) { 1824 /* 1825 * One or more pages could not be held by the pmap. Either no 1826 * page was mapped at the specified virtual address or that 1827 * mapping had insufficient permissions. Attempt to fault in 1828 * and hold these pages. 1829 * 1830 * If vm_fault_disable_pagefaults() was called, 1831 * i.e., TDP_NOFAULTING is set, we must not sleep nor 1832 * acquire MD VM locks, which means we must not call 1833 * vm_fault(). Some (out of tree) callers mark 1834 * too wide a code area with vm_fault_disable_pagefaults() 1835 * already, use the VM_PROT_QUICK_NOFAULT flag to request 1836 * the proper behaviour explicitly. 1837 */ 1838 if ((prot & VM_PROT_QUICK_NOFAULT) != 0 && 1839 (curthread->td_pflags & TDP_NOFAULTING) != 0) 1840 goto error; 1841 for (mp = ma, va = addr; va < end; mp++, va += PAGE_SIZE) 1842 if (*mp == NULL && vm_fault(map, va, prot, 1843 VM_FAULT_NORMAL, mp) != KERN_SUCCESS) 1844 goto error; 1845 } 1846 return (count); 1847 error: 1848 for (mp = ma; mp < ma + count; mp++) 1849 if (*mp != NULL) 1850 vm_page_unwire(*mp, PQ_INACTIVE); 1851 return (-1); 1852 } 1853 1854 /* 1855 * Routine: 1856 * vm_fault_copy_entry 1857 * Function: 1858 * Create new shadow object backing dst_entry with private copy of 1859 * all underlying pages. When src_entry is equal to dst_entry, 1860 * function implements COW for wired-down map entry. Otherwise, 1861 * it forks wired entry into dst_map. 1862 * 1863 * In/out conditions: 1864 * The source and destination maps must be locked for write. 1865 * The source map entry must be wired down (or be a sharing map 1866 * entry corresponding to a main map entry that is wired down). 1867 */ 1868 void 1869 vm_fault_copy_entry(vm_map_t dst_map, vm_map_t src_map, 1870 vm_map_entry_t dst_entry, vm_map_entry_t src_entry, 1871 vm_ooffset_t *fork_charge) 1872 { 1873 vm_object_t backing_object, dst_object, object, src_object; 1874 vm_pindex_t dst_pindex, pindex, src_pindex; 1875 vm_prot_t access, prot; 1876 vm_offset_t vaddr; 1877 vm_page_t dst_m; 1878 vm_page_t src_m; 1879 boolean_t upgrade; 1880 1881 #ifdef lint 1882 src_map++; 1883 #endif /* lint */ 1884 1885 upgrade = src_entry == dst_entry; 1886 access = prot = dst_entry->protection; 1887 1888 src_object = src_entry->object.vm_object; 1889 src_pindex = OFF_TO_IDX(src_entry->offset); 1890 1891 if (upgrade && (dst_entry->eflags & MAP_ENTRY_NEEDS_COPY) == 0) { 1892 dst_object = src_object; 1893 vm_object_reference(dst_object); 1894 } else { 1895 /* 1896 * Create the top-level object for the destination entry. 1897 * Doesn't actually shadow anything - we copy the pages 1898 * directly. 1899 */ 1900 dst_object = vm_object_allocate_anon(atop(dst_entry->end - 1901 dst_entry->start), NULL, NULL, 0); 1902 #if VM_NRESERVLEVEL > 0 1903 dst_object->flags |= OBJ_COLORED; 1904 dst_object->pg_color = atop(dst_entry->start); 1905 #endif 1906 dst_object->domain = src_object->domain; 1907 dst_object->charge = dst_entry->end - dst_entry->start; 1908 } 1909 1910 VM_OBJECT_WLOCK(dst_object); 1911 KASSERT(upgrade || dst_entry->object.vm_object == NULL, 1912 ("vm_fault_copy_entry: vm_object not NULL")); 1913 if (src_object != dst_object) { 1914 dst_entry->object.vm_object = dst_object; 1915 dst_entry->offset = 0; 1916 dst_entry->eflags &= ~MAP_ENTRY_VN_EXEC; 1917 } 1918 if (fork_charge != NULL) { 1919 KASSERT(dst_entry->cred == NULL, 1920 ("vm_fault_copy_entry: leaked swp charge")); 1921 dst_object->cred = curthread->td_ucred; 1922 crhold(dst_object->cred); 1923 *fork_charge += dst_object->charge; 1924 } else if ((dst_object->type == OBJT_DEFAULT || 1925 dst_object->type == OBJT_SWAP) && 1926 dst_object->cred == NULL) { 1927 KASSERT(dst_entry->cred != NULL, ("no cred for entry %p", 1928 dst_entry)); 1929 dst_object->cred = dst_entry->cred; 1930 dst_entry->cred = NULL; 1931 } 1932 1933 /* 1934 * If not an upgrade, then enter the mappings in the pmap as 1935 * read and/or execute accesses. Otherwise, enter them as 1936 * write accesses. 1937 * 1938 * A writeable large page mapping is only created if all of 1939 * the constituent small page mappings are modified. Marking 1940 * PTEs as modified on inception allows promotion to happen 1941 * without taking potentially large number of soft faults. 1942 */ 1943 if (!upgrade) 1944 access &= ~VM_PROT_WRITE; 1945 1946 /* 1947 * Loop through all of the virtual pages within the entry's 1948 * range, copying each page from the source object to the 1949 * destination object. Since the source is wired, those pages 1950 * must exist. In contrast, the destination is pageable. 1951 * Since the destination object doesn't share any backing storage 1952 * with the source object, all of its pages must be dirtied, 1953 * regardless of whether they can be written. 1954 */ 1955 for (vaddr = dst_entry->start, dst_pindex = 0; 1956 vaddr < dst_entry->end; 1957 vaddr += PAGE_SIZE, dst_pindex++) { 1958 again: 1959 /* 1960 * Find the page in the source object, and copy it in. 1961 * Because the source is wired down, the page will be 1962 * in memory. 1963 */ 1964 if (src_object != dst_object) 1965 VM_OBJECT_RLOCK(src_object); 1966 object = src_object; 1967 pindex = src_pindex + dst_pindex; 1968 while ((src_m = vm_page_lookup(object, pindex)) == NULL && 1969 (backing_object = object->backing_object) != NULL) { 1970 /* 1971 * Unless the source mapping is read-only or 1972 * it is presently being upgraded from 1973 * read-only, the first object in the shadow 1974 * chain should provide all of the pages. In 1975 * other words, this loop body should never be 1976 * executed when the source mapping is already 1977 * read/write. 1978 */ 1979 KASSERT((src_entry->protection & VM_PROT_WRITE) == 0 || 1980 upgrade, 1981 ("vm_fault_copy_entry: main object missing page")); 1982 1983 VM_OBJECT_RLOCK(backing_object); 1984 pindex += OFF_TO_IDX(object->backing_object_offset); 1985 if (object != dst_object) 1986 VM_OBJECT_RUNLOCK(object); 1987 object = backing_object; 1988 } 1989 KASSERT(src_m != NULL, ("vm_fault_copy_entry: page missing")); 1990 1991 if (object != dst_object) { 1992 /* 1993 * Allocate a page in the destination object. 1994 */ 1995 dst_m = vm_page_alloc(dst_object, (src_object == 1996 dst_object ? src_pindex : 0) + dst_pindex, 1997 VM_ALLOC_NORMAL); 1998 if (dst_m == NULL) { 1999 VM_OBJECT_WUNLOCK(dst_object); 2000 VM_OBJECT_RUNLOCK(object); 2001 vm_wait(dst_object); 2002 VM_OBJECT_WLOCK(dst_object); 2003 goto again; 2004 } 2005 pmap_copy_page(src_m, dst_m); 2006 VM_OBJECT_RUNLOCK(object); 2007 dst_m->dirty = dst_m->valid = src_m->valid; 2008 } else { 2009 dst_m = src_m; 2010 if (vm_page_busy_acquire(dst_m, VM_ALLOC_WAITFAIL) == 0) 2011 goto again; 2012 if (dst_m->pindex >= dst_object->size) { 2013 /* 2014 * We are upgrading. Index can occur 2015 * out of bounds if the object type is 2016 * vnode and the file was truncated. 2017 */ 2018 vm_page_xunbusy(dst_m); 2019 break; 2020 } 2021 } 2022 VM_OBJECT_WUNLOCK(dst_object); 2023 2024 /* 2025 * Enter it in the pmap. If a wired, copy-on-write 2026 * mapping is being replaced by a write-enabled 2027 * mapping, then wire that new mapping. 2028 * 2029 * The page can be invalid if the user called 2030 * msync(MS_INVALIDATE) or truncated the backing vnode 2031 * or shared memory object. In this case, do not 2032 * insert it into pmap, but still do the copy so that 2033 * all copies of the wired map entry have similar 2034 * backing pages. 2035 */ 2036 if (vm_page_all_valid(dst_m)) { 2037 pmap_enter(dst_map->pmap, vaddr, dst_m, prot, 2038 access | (upgrade ? PMAP_ENTER_WIRED : 0), 0); 2039 } 2040 2041 /* 2042 * Mark it no longer busy, and put it on the active list. 2043 */ 2044 VM_OBJECT_WLOCK(dst_object); 2045 2046 if (upgrade) { 2047 if (src_m != dst_m) { 2048 vm_page_unwire(src_m, PQ_INACTIVE); 2049 vm_page_wire(dst_m); 2050 } else { 2051 KASSERT(vm_page_wired(dst_m), 2052 ("dst_m %p is not wired", dst_m)); 2053 } 2054 } else { 2055 vm_page_activate(dst_m); 2056 } 2057 vm_page_xunbusy(dst_m); 2058 } 2059 VM_OBJECT_WUNLOCK(dst_object); 2060 if (upgrade) { 2061 dst_entry->eflags &= ~(MAP_ENTRY_COW | MAP_ENTRY_NEEDS_COPY); 2062 vm_object_deallocate(src_object); 2063 } 2064 } 2065 2066 /* 2067 * Block entry into the machine-independent layer's page fault handler by 2068 * the calling thread. Subsequent calls to vm_fault() by that thread will 2069 * return KERN_PROTECTION_FAILURE. Enable machine-dependent handling of 2070 * spurious page faults. 2071 */ 2072 int 2073 vm_fault_disable_pagefaults(void) 2074 { 2075 2076 return (curthread_pflags_set(TDP_NOFAULTING | TDP_RESETSPUR)); 2077 } 2078 2079 void 2080 vm_fault_enable_pagefaults(int save) 2081 { 2082 2083 curthread_pflags_restore(save); 2084 } 2085