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