1 /* $NetBSD: uvm_fault.c,v 1.109 2006/02/22 22:28:18 drochner Exp $ */ 2 3 /* 4 * 5 * Copyright (c) 1997 Charles D. Cranor and Washington University. 6 * All rights reserved. 7 * 8 * Redistribution and use in source and binary forms, with or without 9 * modification, are permitted provided that the following conditions 10 * are met: 11 * 1. Redistributions of source code must retain the above copyright 12 * notice, this list of conditions and the following disclaimer. 13 * 2. Redistributions in binary form must reproduce the above copyright 14 * notice, this list of conditions and the following disclaimer in the 15 * documentation and/or other materials provided with the distribution. 16 * 3. All advertising materials mentioning features or use of this software 17 * must display the following acknowledgement: 18 * This product includes software developed by Charles D. Cranor and 19 * Washington University. 20 * 4. The name of the author may not be used to endorse or promote products 21 * derived from this software without specific prior written permission. 22 * 23 * THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS OR 24 * IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES 25 * OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED. 26 * IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY DIRECT, INDIRECT, 27 * INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT 28 * NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, 29 * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY 30 * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT 31 * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF 32 * THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE. 33 * 34 * from: Id: uvm_fault.c,v 1.1.2.23 1998/02/06 05:29:05 chs Exp 35 */ 36 37 /* 38 * uvm_fault.c: fault handler 39 */ 40 41 #include <sys/cdefs.h> 42 __KERNEL_RCSID(0, "$NetBSD: uvm_fault.c,v 1.109 2006/02/22 22:28:18 drochner Exp $"); 43 44 #include "opt_uvmhist.h" 45 46 #include <sys/param.h> 47 #include <sys/systm.h> 48 #include <sys/kernel.h> 49 #include <sys/proc.h> 50 #include <sys/malloc.h> 51 #include <sys/mman.h> 52 #include <sys/user.h> 53 #include <sys/vnode.h> 54 55 #include <uvm/uvm.h> 56 57 /* 58 * 59 * a word on page faults: 60 * 61 * types of page faults we handle: 62 * 63 * CASE 1: upper layer faults CASE 2: lower layer faults 64 * 65 * CASE 1A CASE 1B CASE 2A CASE 2B 66 * read/write1 write>1 read/write +-cow_write/zero 67 * | | | | 68 * +--|--+ +--|--+ +-----+ + | + | +-----+ 69 * amap | V | | ----------->new| | | | ^ | 70 * +-----+ +-----+ +-----+ + | + | +--|--+ 71 * | | | 72 * +-----+ +-----+ +--|--+ | +--|--+ 73 * uobj | d/c | | d/c | | V | +----| | 74 * +-----+ +-----+ +-----+ +-----+ 75 * 76 * d/c = don't care 77 * 78 * case [0]: layerless fault 79 * no amap or uobj is present. this is an error. 80 * 81 * case [1]: upper layer fault [anon active] 82 * 1A: [read] or [write with anon->an_ref == 1] 83 * I/O takes place in top level anon and uobj is not touched. 84 * 1B: [write with anon->an_ref > 1] 85 * new anon is alloc'd and data is copied off ["COW"] 86 * 87 * case [2]: lower layer fault [uobj] 88 * 2A: [read on non-NULL uobj] or [write to non-copy_on_write area] 89 * I/O takes place directly in object. 90 * 2B: [write to copy_on_write] or [read on NULL uobj] 91 * data is "promoted" from uobj to a new anon. 92 * if uobj is null, then we zero fill. 93 * 94 * we follow the standard UVM locking protocol ordering: 95 * 96 * MAPS => AMAP => UOBJ => ANON => PAGE QUEUES (PQ) 97 * we hold a PG_BUSY page if we unlock for I/O 98 * 99 * 100 * the code is structured as follows: 101 * 102 * - init the "IN" params in the ufi structure 103 * ReFault: 104 * - do lookups [locks maps], check protection, handle needs_copy 105 * - check for case 0 fault (error) 106 * - establish "range" of fault 107 * - if we have an amap lock it and extract the anons 108 * - if sequential advice deactivate pages behind us 109 * - at the same time check pmap for unmapped areas and anon for pages 110 * that we could map in (and do map it if found) 111 * - check object for resident pages that we could map in 112 * - if (case 2) goto Case2 113 * - >>> handle case 1 114 * - ensure source anon is resident in RAM 115 * - if case 1B alloc new anon and copy from source 116 * - map the correct page in 117 * Case2: 118 * - >>> handle case 2 119 * - ensure source page is resident (if uobj) 120 * - if case 2B alloc new anon and copy from source (could be zero 121 * fill if uobj == NULL) 122 * - map the correct page in 123 * - done! 124 * 125 * note on paging: 126 * if we have to do I/O we place a PG_BUSY page in the correct object, 127 * unlock everything, and do the I/O. when I/O is done we must reverify 128 * the state of the world before assuming that our data structures are 129 * valid. [because mappings could change while the map is unlocked] 130 * 131 * alternative 1: unbusy the page in question and restart the page fault 132 * from the top (ReFault). this is easy but does not take advantage 133 * of the information that we already have from our previous lookup, 134 * although it is possible that the "hints" in the vm_map will help here. 135 * 136 * alternative 2: the system already keeps track of a "version" number of 137 * a map. [i.e. every time you write-lock a map (e.g. to change a 138 * mapping) you bump the version number up by one...] so, we can save 139 * the version number of the map before we release the lock and start I/O. 140 * then when I/O is done we can relock and check the version numbers 141 * to see if anything changed. this might save us some over 1 because 142 * we don't have to unbusy the page and may be less compares(?). 143 * 144 * alternative 3: put in backpointers or a way to "hold" part of a map 145 * in place while I/O is in progress. this could be complex to 146 * implement (especially with structures like amap that can be referenced 147 * by multiple map entries, and figuring out what should wait could be 148 * complex as well...). 149 * 150 * given that we are not currently multiprocessor or multithreaded we might 151 * as well choose alternative 2 now. maybe alternative 3 would be useful 152 * in the future. XXX keep in mind for future consideration//rechecking. 153 */ 154 155 /* 156 * local data structures 157 */ 158 159 struct uvm_advice { 160 int advice; 161 int nback; 162 int nforw; 163 }; 164 165 /* 166 * page range array: 167 * note: index in array must match "advice" value 168 * XXX: borrowed numbers from freebsd. do they work well for us? 169 */ 170 171 static const struct uvm_advice uvmadvice[] = { 172 { MADV_NORMAL, 3, 4 }, 173 { MADV_RANDOM, 0, 0 }, 174 { MADV_SEQUENTIAL, 8, 7}, 175 }; 176 177 #define UVM_MAXRANGE 16 /* must be MAX() of nback+nforw+1 */ 178 179 /* 180 * private prototypes 181 */ 182 183 /* 184 * inline functions 185 */ 186 187 /* 188 * uvmfault_anonflush: try and deactivate pages in specified anons 189 * 190 * => does not have to deactivate page if it is busy 191 */ 192 193 static inline void 194 uvmfault_anonflush(struct vm_anon **anons, int n) 195 { 196 int lcv; 197 struct vm_page *pg; 198 199 for (lcv = 0 ; lcv < n ; lcv++) { 200 if (anons[lcv] == NULL) 201 continue; 202 simple_lock(&anons[lcv]->an_lock); 203 pg = anons[lcv]->an_page; 204 if (pg && (pg->flags & PG_BUSY) == 0 && pg->loan_count == 0) { 205 uvm_lock_pageq(); 206 if (pg->wire_count == 0) { 207 pmap_clear_reference(pg); 208 uvm_pagedeactivate(pg); 209 } 210 uvm_unlock_pageq(); 211 } 212 simple_unlock(&anons[lcv]->an_lock); 213 } 214 } 215 216 /* 217 * normal functions 218 */ 219 220 /* 221 * uvmfault_amapcopy: clear "needs_copy" in a map. 222 * 223 * => called with VM data structures unlocked (usually, see below) 224 * => we get a write lock on the maps and clear needs_copy for a VA 225 * => if we are out of RAM we sleep (waiting for more) 226 */ 227 228 static void 229 uvmfault_amapcopy(struct uvm_faultinfo *ufi) 230 { 231 for (;;) { 232 233 /* 234 * no mapping? give up. 235 */ 236 237 if (uvmfault_lookup(ufi, TRUE) == FALSE) 238 return; 239 240 /* 241 * copy if needed. 242 */ 243 244 if (UVM_ET_ISNEEDSCOPY(ufi->entry)) 245 amap_copy(ufi->map, ufi->entry, AMAP_COPY_NOWAIT, 246 ufi->orig_rvaddr, ufi->orig_rvaddr + 1); 247 248 /* 249 * didn't work? must be out of RAM. unlock and sleep. 250 */ 251 252 if (UVM_ET_ISNEEDSCOPY(ufi->entry)) { 253 uvmfault_unlockmaps(ufi, TRUE); 254 uvm_wait("fltamapcopy"); 255 continue; 256 } 257 258 /* 259 * got it! unlock and return. 260 */ 261 262 uvmfault_unlockmaps(ufi, TRUE); 263 return; 264 } 265 /*NOTREACHED*/ 266 } 267 268 /* 269 * uvmfault_anonget: get data in an anon into a non-busy, non-released 270 * page in that anon. 271 * 272 * => maps, amap, and anon locked by caller. 273 * => if we fail (result != 0) we unlock everything. 274 * => if we are successful, we return with everything still locked. 275 * => we don't move the page on the queues [gets moved later] 276 * => if we allocate a new page [we_own], it gets put on the queues. 277 * either way, the result is that the page is on the queues at return time 278 * => for pages which are on loan from a uvm_object (and thus are not 279 * owned by the anon): if successful, we return with the owning object 280 * locked. the caller must unlock this object when it unlocks everything 281 * else. 282 */ 283 284 int 285 uvmfault_anonget(struct uvm_faultinfo *ufi, struct vm_amap *amap, 286 struct vm_anon *anon) 287 { 288 boolean_t we_own; /* we own anon's page? */ 289 boolean_t locked; /* did we relock? */ 290 struct vm_page *pg; 291 int error; 292 UVMHIST_FUNC("uvmfault_anonget"); UVMHIST_CALLED(maphist); 293 294 LOCK_ASSERT(simple_lock_held(&anon->an_lock)); 295 296 error = 0; 297 uvmexp.fltanget++; 298 /* bump rusage counters */ 299 if (anon->an_page) 300 curproc->p_stats->p_ru.ru_minflt++; 301 else 302 curproc->p_stats->p_ru.ru_majflt++; 303 304 /* 305 * loop until we get it, or fail. 306 */ 307 308 for (;;) { 309 we_own = FALSE; /* TRUE if we set PG_BUSY on a page */ 310 pg = anon->an_page; 311 312 /* 313 * if there is a resident page and it is loaned, then anon 314 * may not own it. call out to uvm_anon_lockpage() to ensure 315 * the real owner of the page has been identified and locked. 316 */ 317 318 if (pg && pg->loan_count) 319 pg = uvm_anon_lockloanpg(anon); 320 321 /* 322 * page there? make sure it is not busy/released. 323 */ 324 325 if (pg) { 326 327 /* 328 * at this point, if the page has a uobject [meaning 329 * we have it on loan], then that uobject is locked 330 * by us! if the page is busy, we drop all the 331 * locks (including uobject) and try again. 332 */ 333 334 if ((pg->flags & PG_BUSY) == 0) { 335 UVMHIST_LOG(maphist, "<- OK",0,0,0,0); 336 return (0); 337 } 338 pg->flags |= PG_WANTED; 339 uvmexp.fltpgwait++; 340 341 /* 342 * the last unlock must be an atomic unlock+wait on 343 * the owner of page 344 */ 345 346 if (pg->uobject) { /* owner is uobject ? */ 347 uvmfault_unlockall(ufi, amap, NULL, anon); 348 UVMHIST_LOG(maphist, " unlock+wait on uobj",0, 349 0,0,0); 350 UVM_UNLOCK_AND_WAIT(pg, 351 &pg->uobject->vmobjlock, 352 FALSE, "anonget1",0); 353 } else { 354 /* anon owns page */ 355 uvmfault_unlockall(ufi, amap, NULL, NULL); 356 UVMHIST_LOG(maphist, " unlock+wait on anon",0, 357 0,0,0); 358 UVM_UNLOCK_AND_WAIT(pg,&anon->an_lock,0, 359 "anonget2",0); 360 } 361 } else { 362 #if defined(VMSWAP) 363 364 /* 365 * no page, we must try and bring it in. 366 */ 367 368 pg = uvm_pagealloc(NULL, 0, anon, 0); 369 if (pg == NULL) { /* out of RAM. */ 370 uvmfault_unlockall(ufi, amap, NULL, anon); 371 uvmexp.fltnoram++; 372 UVMHIST_LOG(maphist, " noram -- UVM_WAIT",0, 373 0,0,0); 374 if (!uvm_reclaimable()) { 375 return ENOMEM; 376 } 377 uvm_wait("flt_noram1"); 378 } else { 379 /* we set the PG_BUSY bit */ 380 we_own = TRUE; 381 uvmfault_unlockall(ufi, amap, NULL, anon); 382 383 /* 384 * we are passing a PG_BUSY+PG_FAKE+PG_CLEAN 385 * page into the uvm_swap_get function with 386 * all data structures unlocked. note that 387 * it is ok to read an_swslot here because 388 * we hold PG_BUSY on the page. 389 */ 390 uvmexp.pageins++; 391 error = uvm_swap_get(pg, anon->an_swslot, 392 PGO_SYNCIO); 393 394 /* 395 * we clean up after the i/o below in the 396 * "we_own" case 397 */ 398 } 399 #else /* defined(VMSWAP) */ 400 panic("%s: no page", __func__); 401 #endif /* defined(VMSWAP) */ 402 } 403 404 /* 405 * now relock and try again 406 */ 407 408 locked = uvmfault_relock(ufi); 409 if (locked && amap != NULL) { 410 amap_lock(amap); 411 } 412 if (locked || we_own) 413 simple_lock(&anon->an_lock); 414 415 /* 416 * if we own the page (i.e. we set PG_BUSY), then we need 417 * to clean up after the I/O. there are three cases to 418 * consider: 419 * [1] page released during I/O: free anon and ReFault. 420 * [2] I/O not OK. free the page and cause the fault 421 * to fail. 422 * [3] I/O OK! activate the page and sync with the 423 * non-we_own case (i.e. drop anon lock if not locked). 424 */ 425 426 if (we_own) { 427 #if defined(VMSWAP) 428 if (pg->flags & PG_WANTED) { 429 wakeup(pg); 430 } 431 if (error) { 432 433 /* 434 * remove the swap slot from the anon 435 * and mark the anon as having no real slot. 436 * don't free the swap slot, thus preventing 437 * it from being used again. 438 */ 439 440 if (anon->an_swslot > 0) 441 uvm_swap_markbad(anon->an_swslot, 1); 442 anon->an_swslot = SWSLOT_BAD; 443 444 if ((pg->flags & PG_RELEASED) != 0) 445 goto released; 446 447 /* 448 * note: page was never !PG_BUSY, so it 449 * can't be mapped and thus no need to 450 * pmap_page_protect it... 451 */ 452 453 uvm_lock_pageq(); 454 uvm_pagefree(pg); 455 uvm_unlock_pageq(); 456 457 if (locked) 458 uvmfault_unlockall(ufi, amap, NULL, 459 anon); 460 else 461 simple_unlock(&anon->an_lock); 462 UVMHIST_LOG(maphist, "<- ERROR", 0,0,0,0); 463 return error; 464 } 465 466 if ((pg->flags & PG_RELEASED) != 0) { 467 released: 468 KASSERT(anon->an_ref == 0); 469 470 /* 471 * released while we unlocked amap. 472 */ 473 474 if (locked) 475 uvmfault_unlockall(ufi, amap, NULL, 476 NULL); 477 478 uvm_anon_release(anon); 479 480 if (error) { 481 UVMHIST_LOG(maphist, 482 "<- ERROR/RELEASED", 0,0,0,0); 483 return error; 484 } 485 486 UVMHIST_LOG(maphist, "<- RELEASED", 0,0,0,0); 487 return ERESTART; 488 } 489 490 /* 491 * we've successfully read the page, activate it. 492 */ 493 494 uvm_lock_pageq(); 495 uvm_pageactivate(pg); 496 uvm_unlock_pageq(); 497 pg->flags &= ~(PG_WANTED|PG_BUSY|PG_FAKE); 498 UVM_PAGE_OWN(pg, NULL); 499 if (!locked) 500 simple_unlock(&anon->an_lock); 501 #else /* defined(VMSWAP) */ 502 panic("%s: we_own", __func__); 503 #endif /* defined(VMSWAP) */ 504 } 505 506 /* 507 * we were not able to relock. restart fault. 508 */ 509 510 if (!locked) { 511 UVMHIST_LOG(maphist, "<- REFAULT", 0,0,0,0); 512 return (ERESTART); 513 } 514 515 /* 516 * verify no one has touched the amap and moved the anon on us. 517 */ 518 519 if (ufi != NULL && 520 amap_lookup(&ufi->entry->aref, 521 ufi->orig_rvaddr - ufi->entry->start) != anon) { 522 523 uvmfault_unlockall(ufi, amap, NULL, anon); 524 UVMHIST_LOG(maphist, "<- REFAULT", 0,0,0,0); 525 return (ERESTART); 526 } 527 528 /* 529 * try it again! 530 */ 531 532 uvmexp.fltanretry++; 533 continue; 534 } 535 /*NOTREACHED*/ 536 } 537 538 /* 539 * uvmfault_promote: promote data to a new anon. used for 1B and 2B. 540 * 541 * 1. allocate an anon and a page. 542 * 2. fill its contents. 543 * 3. put it into amap. 544 * 545 * => if we fail (result != 0) we unlock everything. 546 * => on success, return a new locked anon via 'nanon'. 547 * (*nanon)->an_page will be a resident, locked, dirty page. 548 */ 549 550 static int 551 uvmfault_promote(struct uvm_faultinfo *ufi, 552 struct vm_anon *oanon, 553 struct vm_page *uobjpage, 554 struct vm_anon **nanon, /* OUT: allocated anon */ 555 struct vm_anon **spare) 556 { 557 struct vm_amap *amap = ufi->entry->aref.ar_amap; 558 struct uvm_object *uobj; 559 struct vm_anon *anon; 560 struct vm_page *pg; 561 struct vm_page *opg; 562 int error; 563 UVMHIST_FUNC(__func__); UVMHIST_CALLED(maphist); 564 565 if (oanon) { 566 /* anon COW */ 567 opg = oanon->an_page; 568 KASSERT(opg != NULL); 569 KASSERT(opg->uobject == NULL || opg->loan_count > 0); 570 } else if (uobjpage != PGO_DONTCARE) { 571 /* object-backed COW */ 572 opg = uobjpage; 573 } else { 574 /* ZFOD */ 575 opg = NULL; 576 } 577 if (opg != NULL) { 578 uobj = opg->uobject; 579 } else { 580 uobj = NULL; 581 } 582 583 KASSERT(amap != NULL); 584 KASSERT(uobjpage != NULL); 585 KASSERT(uobjpage == PGO_DONTCARE || (uobjpage->flags & PG_BUSY) != 0); 586 LOCK_ASSERT(simple_lock_held(&amap->am_l)); 587 LOCK_ASSERT(oanon == NULL || simple_lock_held(&oanon->an_lock)); 588 LOCK_ASSERT(uobj == NULL || simple_lock_held(&uobj->vmobjlock)); 589 LOCK_ASSERT(*spare == NULL || !simple_lock_held(&(*spare)->an_lock)); 590 591 if (*spare != NULL) { 592 anon = *spare; 593 *spare = NULL; 594 simple_lock(&anon->an_lock); 595 } else if (ufi->map != kernel_map) { 596 anon = uvm_analloc(); 597 } else { 598 UVMHIST_LOG(maphist, "kernel_map, unlock and retry", 0,0,0,0); 599 600 /* 601 * we can't allocate anons with kernel_map locked. 602 */ 603 604 uvm_page_unbusy(&uobjpage, 1); 605 uvmfault_unlockall(ufi, amap, uobj, oanon); 606 607 *spare = uvm_analloc(); 608 if (*spare == NULL) { 609 goto nomem; 610 } 611 simple_unlock(&(*spare)->an_lock); 612 error = ERESTART; 613 goto done; 614 } 615 if (anon) { 616 617 /* 618 * The new anon is locked. 619 * 620 * if opg == NULL, we want a zero'd, dirty page, 621 * so have uvm_pagealloc() do that for us. 622 */ 623 624 pg = uvm_pagealloc(NULL, 0, anon, 625 (opg == NULL) ? UVM_PGA_ZERO : 0); 626 } else { 627 pg = NULL; 628 } 629 630 /* 631 * out of memory resources? 632 */ 633 634 if (pg == NULL) { 635 /* save anon for the next try. */ 636 if (anon != NULL) { 637 simple_unlock(&anon->an_lock); 638 *spare = anon; 639 } 640 641 /* unlock and fail ... */ 642 uvm_page_unbusy(&uobjpage, 1); 643 uvmfault_unlockall(ufi, amap, uobj, oanon); 644 nomem: 645 if (!uvm_reclaimable()) { 646 UVMHIST_LOG(maphist, "out of VM", 0,0,0,0); 647 uvmexp.fltnoanon++; 648 error = ENOMEM; 649 goto done; 650 } 651 652 UVMHIST_LOG(maphist, "out of RAM, waiting for more", 0,0,0,0); 653 uvmexp.fltnoram++; 654 uvm_wait("flt_noram5"); 655 error = ERESTART; 656 goto done; 657 } 658 659 /* copy page [pg now dirty] */ 660 if (opg) { 661 uvm_pagecopy(opg, pg); 662 } 663 664 amap_add(&ufi->entry->aref, ufi->orig_rvaddr - ufi->entry->start, anon, 665 oanon != NULL); 666 667 *nanon = anon; 668 error = 0; 669 done: 670 return error; 671 } 672 673 674 /* 675 * F A U L T - m a i n e n t r y p o i n t 676 */ 677 678 /* 679 * uvm_fault: page fault handler 680 * 681 * => called from MD code to resolve a page fault 682 * => VM data structures usually should be unlocked. however, it is 683 * possible to call here with the main map locked if the caller 684 * gets a write lock, sets it recusive, and then calls us (c.f. 685 * uvm_map_pageable). this should be avoided because it keeps 686 * the map locked off during I/O. 687 * => MUST NEVER BE CALLED IN INTERRUPT CONTEXT 688 */ 689 690 #define MASK(entry) (UVM_ET_ISCOPYONWRITE(entry) ? \ 691 ~VM_PROT_WRITE : VM_PROT_ALL) 692 693 int 694 uvm_fault(struct vm_map *orig_map, vaddr_t vaddr, vm_fault_t fault_type, 695 vm_prot_t access_type) 696 { 697 struct uvm_faultinfo ufi; 698 vm_prot_t enter_prot, check_prot; 699 boolean_t wired, narrow, promote, locked, shadowed, wire_fault, cow_now; 700 int npages, nback, nforw, centeridx, error, lcv, gotpages; 701 vaddr_t startva, currva; 702 voff_t uoff; 703 struct vm_amap *amap; 704 struct uvm_object *uobj; 705 struct vm_anon *anons_store[UVM_MAXRANGE], **anons, *anon, *oanon; 706 struct vm_anon *anon_spare; 707 struct vm_page *pages[UVM_MAXRANGE], *pg, *uobjpage; 708 UVMHIST_FUNC("uvm_fault"); UVMHIST_CALLED(maphist); 709 710 UVMHIST_LOG(maphist, "(map=0x%x, vaddr=0x%x, ft=%d, at=%d)", 711 orig_map, vaddr, fault_type, access_type); 712 713 anon = anon_spare = NULL; 714 pg = NULL; 715 716 uvmexp.faults++; /* XXX: locking? */ 717 718 /* 719 * init the IN parameters in the ufi 720 */ 721 722 ufi.orig_map = orig_map; 723 ufi.orig_rvaddr = trunc_page(vaddr); 724 ufi.orig_size = PAGE_SIZE; /* can't get any smaller than this */ 725 wire_fault = fault_type == VM_FAULT_WIRE || 726 fault_type == VM_FAULT_WIREMAX; 727 if (wire_fault) 728 narrow = TRUE; /* don't look for neighborhood 729 * pages on wire */ 730 else 731 narrow = FALSE; /* normal fault */ 732 733 /* 734 * "goto ReFault" means restart the page fault from ground zero. 735 */ 736 ReFault: 737 738 /* 739 * lookup and lock the maps 740 */ 741 742 if (uvmfault_lookup(&ufi, FALSE) == FALSE) { 743 UVMHIST_LOG(maphist, "<- no mapping @ 0x%x", vaddr, 0,0,0); 744 error = EFAULT; 745 goto done; 746 } 747 /* locked: maps(read) */ 748 749 #ifdef DIAGNOSTIC 750 if ((ufi.map->flags & VM_MAP_PAGEABLE) == 0) { 751 printf("Page fault on non-pageable map:\n"); 752 printf("ufi.map = %p\n", ufi.map); 753 printf("ufi.orig_map = %p\n", ufi.orig_map); 754 printf("ufi.orig_rvaddr = 0x%lx\n", (u_long) ufi.orig_rvaddr); 755 panic("uvm_fault: (ufi.map->flags & VM_MAP_PAGEABLE) == 0"); 756 } 757 #endif 758 759 /* 760 * check protection 761 */ 762 763 check_prot = fault_type == VM_FAULT_WIREMAX ? 764 ufi.entry->max_protection : ufi.entry->protection; 765 if ((check_prot & access_type) != access_type) { 766 UVMHIST_LOG(maphist, 767 "<- protection failure (prot=0x%x, access=0x%x)", 768 ufi.entry->protection, access_type, 0, 0); 769 uvmfault_unlockmaps(&ufi, FALSE); 770 error = EACCES; 771 goto done; 772 } 773 774 /* 775 * "enter_prot" is the protection we want to enter the page in at. 776 * for certain pages (e.g. copy-on-write pages) this protection can 777 * be more strict than ufi.entry->protection. "wired" means either 778 * the entry is wired or we are fault-wiring the pg. 779 */ 780 781 enter_prot = ufi.entry->protection; 782 wired = VM_MAPENT_ISWIRED(ufi.entry) || wire_fault; 783 if (wired) { 784 access_type = enter_prot; /* full access for wired */ 785 cow_now = (check_prot & VM_PROT_WRITE) != 0; 786 } else { 787 cow_now = (access_type & VM_PROT_WRITE) != 0; 788 } 789 790 /* 791 * handle "needs_copy" case. if we need to copy the amap we will 792 * have to drop our readlock and relock it with a write lock. (we 793 * need a write lock to change anything in a map entry [e.g. 794 * needs_copy]). 795 */ 796 797 if (UVM_ET_ISNEEDSCOPY(ufi.entry)) { 798 KASSERT(fault_type != VM_FAULT_WIREMAX); 799 if (cow_now || (ufi.entry->object.uvm_obj == NULL)) { 800 /* need to clear */ 801 UVMHIST_LOG(maphist, 802 " need to clear needs_copy and refault",0,0,0,0); 803 uvmfault_unlockmaps(&ufi, FALSE); 804 uvmfault_amapcopy(&ufi); 805 uvmexp.fltamcopy++; 806 goto ReFault; 807 808 } else { 809 810 /* 811 * ensure that we pmap_enter page R/O since 812 * needs_copy is still true 813 */ 814 815 enter_prot &= ~VM_PROT_WRITE; 816 } 817 } 818 819 /* 820 * identify the players 821 */ 822 823 amap = ufi.entry->aref.ar_amap; /* top layer */ 824 uobj = ufi.entry->object.uvm_obj; /* bottom layer */ 825 826 /* 827 * check for a case 0 fault. if nothing backing the entry then 828 * error now. 829 */ 830 831 if (amap == NULL && uobj == NULL) { 832 uvmfault_unlockmaps(&ufi, FALSE); 833 UVMHIST_LOG(maphist,"<- no backing store, no overlay",0,0,0,0); 834 error = EFAULT; 835 goto done; 836 } 837 838 /* 839 * establish range of interest based on advice from mapper 840 * and then clip to fit map entry. note that we only want 841 * to do this the first time through the fault. if we 842 * ReFault we will disable this by setting "narrow" to true. 843 */ 844 845 if (narrow == FALSE) { 846 847 /* wide fault (!narrow) */ 848 KASSERT(uvmadvice[ufi.entry->advice].advice == 849 ufi.entry->advice); 850 nback = MIN(uvmadvice[ufi.entry->advice].nback, 851 (ufi.orig_rvaddr - ufi.entry->start) >> PAGE_SHIFT); 852 startva = ufi.orig_rvaddr - (nback << PAGE_SHIFT); 853 nforw = MIN(uvmadvice[ufi.entry->advice].nforw, 854 ((ufi.entry->end - ufi.orig_rvaddr) >> 855 PAGE_SHIFT) - 1); 856 /* 857 * note: "-1" because we don't want to count the 858 * faulting page as forw 859 */ 860 npages = nback + nforw + 1; 861 centeridx = nback; 862 863 narrow = TRUE; /* ensure only once per-fault */ 864 865 } else { 866 867 /* narrow fault! */ 868 nback = nforw = 0; 869 startva = ufi.orig_rvaddr; 870 npages = 1; 871 centeridx = 0; 872 873 } 874 875 /* locked: maps(read) */ 876 UVMHIST_LOG(maphist, " narrow=%d, back=%d, forw=%d, startva=0x%x", 877 narrow, nback, nforw, startva); 878 UVMHIST_LOG(maphist, " entry=0x%x, amap=0x%x, obj=0x%x", ufi.entry, 879 amap, uobj, 0); 880 881 /* 882 * if we've got an amap, lock it and extract current anons. 883 */ 884 885 if (amap) { 886 amap_lock(amap); 887 anons = anons_store; 888 amap_lookups(&ufi.entry->aref, startva - ufi.entry->start, 889 anons, npages); 890 } else { 891 anons = NULL; /* to be safe */ 892 } 893 894 /* locked: maps(read), amap(if there) */ 895 896 /* 897 * for MADV_SEQUENTIAL mappings we want to deactivate the back pages 898 * now and then forget about them (for the rest of the fault). 899 */ 900 901 if (ufi.entry->advice == MADV_SEQUENTIAL && nback != 0) { 902 903 UVMHIST_LOG(maphist, " MADV_SEQUENTIAL: flushing backpages", 904 0,0,0,0); 905 /* flush back-page anons? */ 906 if (amap) 907 uvmfault_anonflush(anons, nback); 908 909 /* flush object? */ 910 if (uobj) { 911 uoff = (startva - ufi.entry->start) + ufi.entry->offset; 912 simple_lock(&uobj->vmobjlock); 913 (void) (uobj->pgops->pgo_put)(uobj, uoff, uoff + 914 (nback << PAGE_SHIFT), PGO_DEACTIVATE); 915 } 916 917 /* now forget about the backpages */ 918 if (amap) 919 anons += nback; 920 startva += (nback << PAGE_SHIFT); 921 npages -= nback; 922 nback = centeridx = 0; 923 } 924 925 /* locked: maps(read), amap(if there) */ 926 927 /* 928 * map in the backpages and frontpages we found in the amap in hopes 929 * of preventing future faults. we also init the pages[] array as 930 * we go. 931 */ 932 933 currva = startva; 934 shadowed = FALSE; 935 for (lcv = 0 ; lcv < npages ; lcv++, currva += PAGE_SIZE) { 936 937 /* 938 * dont play with VAs that are already mapped 939 * except for center) 940 */ 941 if (lcv != centeridx && 942 pmap_extract(ufi.orig_map->pmap, currva, NULL)) { 943 pages[lcv] = PGO_DONTCARE; 944 continue; 945 } 946 947 /* 948 * unmapped or center page. check if any anon at this level. 949 */ 950 if (amap == NULL || anons[lcv] == NULL) { 951 pages[lcv] = NULL; 952 continue; 953 } 954 955 /* 956 * check for present page and map if possible. re-activate it. 957 */ 958 959 pages[lcv] = PGO_DONTCARE; 960 if (lcv == centeridx) { /* save center for later! */ 961 shadowed = TRUE; 962 continue; 963 } 964 anon = anons[lcv]; 965 simple_lock(&anon->an_lock); 966 /* ignore loaned pages */ 967 if (anon->an_page && anon->an_page->loan_count == 0 && 968 (anon->an_page->flags & PG_BUSY) == 0) { 969 uvm_lock_pageq(); 970 uvm_pageactivate(anon->an_page); 971 uvm_unlock_pageq(); 972 UVMHIST_LOG(maphist, 973 " MAPPING: n anon: pm=0x%x, va=0x%x, pg=0x%x", 974 ufi.orig_map->pmap, currva, anon->an_page, 0); 975 uvmexp.fltnamap++; 976 977 /* 978 * Since this isn't the page that's actually faulting, 979 * ignore pmap_enter() failures; it's not critical 980 * that we enter these right now. 981 */ 982 983 (void) pmap_enter(ufi.orig_map->pmap, currva, 984 VM_PAGE_TO_PHYS(anon->an_page), 985 (anon->an_ref > 1) ? (enter_prot & ~VM_PROT_WRITE) : 986 enter_prot, 987 PMAP_CANFAIL | 988 (VM_MAPENT_ISWIRED(ufi.entry) ? PMAP_WIRED : 0)); 989 } 990 simple_unlock(&anon->an_lock); 991 pmap_update(ufi.orig_map->pmap); 992 } 993 994 /* locked: maps(read), amap(if there) */ 995 /* (shadowed == TRUE) if there is an anon at the faulting address */ 996 UVMHIST_LOG(maphist, " shadowed=%d, will_get=%d", shadowed, 997 (uobj && shadowed == FALSE),0,0); 998 999 /* 1000 * note that if we are really short of RAM we could sleep in the above 1001 * call to pmap_enter with everything locked. bad? 1002 * 1003 * XXX Actually, that is bad; pmap_enter() should just fail in that 1004 * XXX case. --thorpej 1005 */ 1006 1007 /* 1008 * if the desired page is not shadowed by the amap and we have a 1009 * backing object, then we check to see if the backing object would 1010 * prefer to handle the fault itself (rather than letting us do it 1011 * with the usual pgo_get hook). the backing object signals this by 1012 * providing a pgo_fault routine. 1013 */ 1014 1015 if (uobj && shadowed == FALSE && uobj->pgops->pgo_fault != NULL) { 1016 simple_lock(&uobj->vmobjlock); 1017 1018 /* locked: maps(read), amap (if there), uobj */ 1019 error = uobj->pgops->pgo_fault(&ufi, startva, pages, npages, 1020 centeridx, access_type, PGO_LOCKED|PGO_SYNCIO); 1021 1022 /* locked: nothing, pgo_fault has unlocked everything */ 1023 1024 if (error == ERESTART) 1025 goto ReFault; /* try again! */ 1026 /* 1027 * object fault routine responsible for pmap_update(). 1028 */ 1029 goto done; 1030 } 1031 1032 /* 1033 * now, if the desired page is not shadowed by the amap and we have 1034 * a backing object that does not have a special fault routine, then 1035 * we ask (with pgo_get) the object for resident pages that we care 1036 * about and attempt to map them in. we do not let pgo_get block 1037 * (PGO_LOCKED). 1038 */ 1039 1040 if (uobj && shadowed == FALSE) { 1041 simple_lock(&uobj->vmobjlock); 1042 1043 /* locked (!shadowed): maps(read), amap (if there), uobj */ 1044 /* 1045 * the following call to pgo_get does _not_ change locking state 1046 */ 1047 1048 uvmexp.fltlget++; 1049 gotpages = npages; 1050 (void) uobj->pgops->pgo_get(uobj, ufi.entry->offset + 1051 (startva - ufi.entry->start), 1052 pages, &gotpages, centeridx, 1053 access_type & MASK(ufi.entry), 1054 ufi.entry->advice, PGO_LOCKED); 1055 1056 /* 1057 * check for pages to map, if we got any 1058 */ 1059 1060 uobjpage = NULL; 1061 1062 if (gotpages) { 1063 currva = startva; 1064 for (lcv = 0; lcv < npages; 1065 lcv++, currva += PAGE_SIZE) { 1066 struct vm_page *curpg; 1067 boolean_t readonly; 1068 1069 curpg = pages[lcv]; 1070 if (curpg == NULL || curpg == PGO_DONTCARE) { 1071 continue; 1072 } 1073 KASSERT(curpg->uobject == uobj); 1074 1075 /* 1076 * if center page is resident and not 1077 * PG_BUSY|PG_RELEASED then pgo_get 1078 * made it PG_BUSY for us and gave 1079 * us a handle to it. remember this 1080 * page as "uobjpage." (for later use). 1081 */ 1082 1083 if (lcv == centeridx) { 1084 uobjpage = curpg; 1085 UVMHIST_LOG(maphist, " got uobjpage " 1086 "(0x%x) with locked get", 1087 uobjpage, 0,0,0); 1088 continue; 1089 } 1090 1091 /* 1092 * calling pgo_get with PGO_LOCKED returns us 1093 * pages which are neither busy nor released, 1094 * so we don't need to check for this. 1095 * we can just directly enter the pages. 1096 */ 1097 1098 uvm_lock_pageq(); 1099 uvm_pageactivate(curpg); 1100 uvm_unlock_pageq(); 1101 UVMHIST_LOG(maphist, 1102 " MAPPING: n obj: pm=0x%x, va=0x%x, pg=0x%x", 1103 ufi.orig_map->pmap, currva, curpg, 0); 1104 uvmexp.fltnomap++; 1105 1106 /* 1107 * Since this page isn't the page that's 1108 * actually faulting, ignore pmap_enter() 1109 * failures; it's not critical that we 1110 * enter these right now. 1111 */ 1112 KASSERT((curpg->flags & PG_PAGEOUT) == 0); 1113 KASSERT((curpg->flags & PG_RELEASED) == 0); 1114 KASSERT(!UVM_OBJ_IS_CLEAN(curpg->uobject) || 1115 (curpg->flags & PG_CLEAN) != 0); 1116 readonly = (curpg->flags & PG_RDONLY) 1117 || (curpg->loan_count > 0) 1118 || UVM_OBJ_NEEDS_WRITEFAULT(curpg->uobject); 1119 1120 (void) pmap_enter(ufi.orig_map->pmap, currva, 1121 VM_PAGE_TO_PHYS(curpg), 1122 readonly ? 1123 enter_prot & ~VM_PROT_WRITE : 1124 enter_prot & MASK(ufi.entry), 1125 PMAP_CANFAIL | 1126 (wired ? PMAP_WIRED : 0)); 1127 1128 /* 1129 * NOTE: page can't be PG_WANTED or PG_RELEASED 1130 * because we've held the lock the whole time 1131 * we've had the handle. 1132 */ 1133 1134 curpg->flags &= ~(PG_BUSY); 1135 UVM_PAGE_OWN(curpg, NULL); 1136 } 1137 pmap_update(ufi.orig_map->pmap); 1138 } 1139 } else { 1140 uobjpage = NULL; 1141 } 1142 1143 /* locked (shadowed): maps(read), amap */ 1144 /* locked (!shadowed): maps(read), amap(if there), 1145 uobj(if !null), uobjpage(if !null) */ 1146 1147 /* 1148 * note that at this point we are done with any front or back pages. 1149 * we are now going to focus on the center page (i.e. the one we've 1150 * faulted on). if we have faulted on the top (anon) layer 1151 * [i.e. case 1], then the anon we want is anons[centeridx] (we have 1152 * not touched it yet). if we have faulted on the bottom (uobj) 1153 * layer [i.e. case 2] and the page was both present and available, 1154 * then we've got a pointer to it as "uobjpage" and we've already 1155 * made it BUSY. 1156 */ 1157 1158 /* 1159 * there are four possible cases we must address: 1A, 1B, 2A, and 2B 1160 */ 1161 1162 /* 1163 * redirect case 2: if we are not shadowed, go to case 2. 1164 */ 1165 1166 if (shadowed == FALSE) 1167 goto Case2; 1168 1169 /* locked: maps(read), amap */ 1170 1171 /* 1172 * handle case 1: fault on an anon in our amap 1173 */ 1174 1175 anon = anons[centeridx]; 1176 UVMHIST_LOG(maphist, " case 1 fault: anon=0x%x", anon, 0,0,0); 1177 simple_lock(&anon->an_lock); 1178 1179 /* locked: maps(read), amap, anon */ 1180 1181 /* 1182 * no matter if we have case 1A or case 1B we are going to need to 1183 * have the anon's memory resident. ensure that now. 1184 */ 1185 1186 /* 1187 * let uvmfault_anonget do the dirty work. 1188 * if it fails (!OK) it will unlock everything for us. 1189 * if it succeeds, locks are still valid and locked. 1190 * also, if it is OK, then the anon's page is on the queues. 1191 * if the page is on loan from a uvm_object, then anonget will 1192 * lock that object for us if it does not fail. 1193 */ 1194 1195 error = uvmfault_anonget(&ufi, amap, anon); 1196 switch (error) { 1197 case 0: 1198 break; 1199 1200 case ERESTART: 1201 goto ReFault; 1202 1203 case EAGAIN: 1204 tsleep(&lbolt, PVM, "fltagain1", 0); 1205 goto ReFault; 1206 1207 default: 1208 goto done; 1209 } 1210 1211 /* 1212 * uobj is non null if the page is on loan from an object (i.e. uobj) 1213 */ 1214 1215 uobj = anon->an_page->uobject; /* locked by anonget if !NULL */ 1216 1217 /* locked: maps(read), amap, anon, uobj(if one) */ 1218 1219 /* 1220 * special handling for loaned pages 1221 */ 1222 1223 if (anon->an_page->loan_count) { 1224 1225 if (!cow_now) { 1226 1227 /* 1228 * for read faults on loaned pages we just cap the 1229 * protection at read-only. 1230 */ 1231 1232 enter_prot = enter_prot & ~VM_PROT_WRITE; 1233 1234 } else { 1235 /* 1236 * note that we can't allow writes into a loaned page! 1237 * 1238 * if we have a write fault on a loaned page in an 1239 * anon then we need to look at the anon's ref count. 1240 * if it is greater than one then we are going to do 1241 * a normal copy-on-write fault into a new anon (this 1242 * is not a problem). however, if the reference count 1243 * is one (a case where we would normally allow a 1244 * write directly to the page) then we need to kill 1245 * the loan before we continue. 1246 */ 1247 1248 /* >1 case is already ok */ 1249 if (anon->an_ref == 1) { 1250 1251 /* get new un-owned replacement page */ 1252 pg = uvm_pagealloc(NULL, 0, NULL, 0); 1253 if (pg == NULL) { 1254 uvmfault_unlockall(&ufi, amap, uobj, 1255 anon); 1256 uvm_wait("flt_noram2"); 1257 goto ReFault; 1258 } 1259 1260 /* 1261 * copy data, kill loan, and drop uobj lock 1262 * (if any) 1263 */ 1264 /* copy old -> new */ 1265 uvm_pagecopy(anon->an_page, pg); 1266 1267 /* force reload */ 1268 pmap_page_protect(anon->an_page, 1269 VM_PROT_NONE); 1270 uvm_lock_pageq(); /* KILL loan */ 1271 1272 anon->an_page->uanon = NULL; 1273 /* in case we owned */ 1274 anon->an_page->pqflags &= ~PQ_ANON; 1275 1276 if (uobj) { 1277 /* if we were receiver of loan */ 1278 anon->an_page->loan_count--; 1279 } else { 1280 /* 1281 * we were the lender (A->K); need 1282 * to remove the page from pageq's. 1283 */ 1284 uvm_pagedequeue(anon->an_page); 1285 } 1286 1287 uvm_pageactivate(pg); 1288 uvm_unlock_pageq(); 1289 if (uobj) { 1290 simple_unlock(&uobj->vmobjlock); 1291 uobj = NULL; 1292 } 1293 1294 /* install new page in anon */ 1295 anon->an_page = pg; 1296 pg->uanon = anon; 1297 pg->pqflags |= PQ_ANON; 1298 pg->flags &= ~(PG_BUSY|PG_FAKE); 1299 UVM_PAGE_OWN(pg, NULL); 1300 1301 /* done! */ 1302 } /* ref == 1 */ 1303 } /* write fault */ 1304 } /* loan count */ 1305 1306 /* 1307 * if we are case 1B then we will need to allocate a new blank 1308 * anon to transfer the data into. note that we have a lock 1309 * on anon, so no one can busy or release the page until we are done. 1310 * also note that the ref count can't drop to zero here because 1311 * it is > 1 and we are only dropping one ref. 1312 * 1313 * in the (hopefully very rare) case that we are out of RAM we 1314 * will unlock, wait for more RAM, and refault. 1315 * 1316 * if we are out of anon VM we kill the process (XXX: could wait?). 1317 */ 1318 1319 if (cow_now && anon->an_ref > 1) { 1320 1321 UVMHIST_LOG(maphist, " case 1B: COW fault",0,0,0,0); 1322 uvmexp.flt_acow++; 1323 oanon = anon; /* oanon = old, locked anon */ 1324 1325 error = uvmfault_promote(&ufi, oanon, PGO_DONTCARE, 1326 &anon, &anon_spare); 1327 switch (error) { 1328 case 0: 1329 break; 1330 case ERESTART: 1331 goto ReFault; 1332 default: 1333 goto done; 1334 } 1335 1336 pg = anon->an_page; 1337 uvm_lock_pageq(); 1338 uvm_pageactivate(pg); 1339 uvm_unlock_pageq(); 1340 pg->flags &= ~(PG_BUSY|PG_FAKE); 1341 UVM_PAGE_OWN(pg, NULL); 1342 1343 /* deref: can not drop to zero here by defn! */ 1344 oanon->an_ref--; 1345 1346 /* 1347 * note: oanon is still locked, as is the new anon. we 1348 * need to check for this later when we unlock oanon; if 1349 * oanon != anon, we'll have to unlock anon, too. 1350 */ 1351 1352 } else { 1353 1354 uvmexp.flt_anon++; 1355 oanon = anon; /* old, locked anon is same as anon */ 1356 pg = anon->an_page; 1357 if (anon->an_ref > 1) /* disallow writes to ref > 1 anons */ 1358 enter_prot = enter_prot & ~VM_PROT_WRITE; 1359 1360 } 1361 1362 /* locked: maps(read), amap, oanon, anon (if different from oanon) */ 1363 1364 /* 1365 * now map the page in. 1366 */ 1367 1368 UVMHIST_LOG(maphist, " MAPPING: anon: pm=0x%x, va=0x%x, pg=0x%x", 1369 ufi.orig_map->pmap, ufi.orig_rvaddr, pg, 0); 1370 if (pmap_enter(ufi.orig_map->pmap, ufi.orig_rvaddr, VM_PAGE_TO_PHYS(pg), 1371 enter_prot, access_type | PMAP_CANFAIL | (wired ? PMAP_WIRED : 0)) 1372 != 0) { 1373 1374 /* 1375 * No need to undo what we did; we can simply think of 1376 * this as the pmap throwing away the mapping information. 1377 * 1378 * We do, however, have to go through the ReFault path, 1379 * as the map may change while we're asleep. 1380 */ 1381 1382 if (anon != oanon) 1383 simple_unlock(&anon->an_lock); 1384 uvmfault_unlockall(&ufi, amap, uobj, oanon); 1385 if (!uvm_reclaimable()) { 1386 UVMHIST_LOG(maphist, 1387 "<- failed. out of VM",0,0,0,0); 1388 /* XXX instrumentation */ 1389 error = ENOMEM; 1390 goto done; 1391 } 1392 /* XXX instrumentation */ 1393 uvm_wait("flt_pmfail1"); 1394 goto ReFault; 1395 } 1396 1397 /* 1398 * ... update the page queues. 1399 */ 1400 1401 uvm_lock_pageq(); 1402 if (wire_fault) { 1403 uvm_pagewire(pg); 1404 1405 /* 1406 * since the now-wired page cannot be paged out, 1407 * release its swap resources for others to use. 1408 * since an anon with no swap cannot be PG_CLEAN, 1409 * clear its clean flag now. 1410 */ 1411 1412 pg->flags &= ~(PG_CLEAN); 1413 uvm_anon_dropswap(anon); 1414 } else { 1415 uvm_pageactivate(pg); 1416 } 1417 uvm_unlock_pageq(); 1418 1419 /* 1420 * done case 1! finish up by unlocking everything and returning success 1421 */ 1422 1423 if (anon != oanon) 1424 simple_unlock(&anon->an_lock); 1425 uvmfault_unlockall(&ufi, amap, uobj, oanon); 1426 pmap_update(ufi.orig_map->pmap); 1427 error = 0; 1428 goto done; 1429 1430 Case2: 1431 /* 1432 * handle case 2: faulting on backing object or zero fill 1433 */ 1434 1435 /* 1436 * locked: 1437 * maps(read), amap(if there), uobj(if !null), uobjpage(if !null) 1438 */ 1439 1440 /* 1441 * note that uobjpage can not be PGO_DONTCARE at this point. we now 1442 * set uobjpage to PGO_DONTCARE if we are doing a zero fill. if we 1443 * have a backing object, check and see if we are going to promote 1444 * the data up to an anon during the fault. 1445 */ 1446 1447 if (uobj == NULL) { 1448 uobjpage = PGO_DONTCARE; 1449 promote = TRUE; /* always need anon here */ 1450 } else { 1451 KASSERT(uobjpage != PGO_DONTCARE); 1452 promote = cow_now && UVM_ET_ISCOPYONWRITE(ufi.entry); 1453 } 1454 UVMHIST_LOG(maphist, " case 2 fault: promote=%d, zfill=%d", 1455 promote, (uobj == NULL), 0,0); 1456 1457 /* 1458 * if uobjpage is not null then we do not need to do I/O to get the 1459 * uobjpage. 1460 * 1461 * if uobjpage is null, then we need to unlock and ask the pager to 1462 * get the data for us. once we have the data, we need to reverify 1463 * the state the world. we are currently not holding any resources. 1464 */ 1465 1466 if (uobjpage) { 1467 /* update rusage counters */ 1468 curproc->p_stats->p_ru.ru_minflt++; 1469 } else { 1470 /* update rusage counters */ 1471 curproc->p_stats->p_ru.ru_majflt++; 1472 1473 /* locked: maps(read), amap(if there), uobj */ 1474 uvmfault_unlockall(&ufi, amap, NULL, NULL); 1475 /* locked: uobj */ 1476 1477 uvmexp.fltget++; 1478 gotpages = 1; 1479 uoff = (ufi.orig_rvaddr - ufi.entry->start) + ufi.entry->offset; 1480 error = uobj->pgops->pgo_get(uobj, uoff, &uobjpage, &gotpages, 1481 0, access_type & MASK(ufi.entry), ufi.entry->advice, 1482 PGO_SYNCIO); 1483 /* locked: uobjpage(if no error) */ 1484 1485 /* 1486 * recover from I/O 1487 */ 1488 1489 if (error) { 1490 if (error == EAGAIN) { 1491 UVMHIST_LOG(maphist, 1492 " pgo_get says TRY AGAIN!",0,0,0,0); 1493 tsleep(&lbolt, PVM, "fltagain2", 0); 1494 goto ReFault; 1495 } 1496 1497 UVMHIST_LOG(maphist, "<- pgo_get failed (code %d)", 1498 error, 0,0,0); 1499 goto done; 1500 } 1501 1502 /* locked: uobjpage */ 1503 1504 uvm_lock_pageq(); 1505 uvm_pageactivate(uobjpage); 1506 uvm_unlock_pageq(); 1507 1508 /* 1509 * re-verify the state of the world by first trying to relock 1510 * the maps. always relock the object. 1511 */ 1512 1513 locked = uvmfault_relock(&ufi); 1514 if (locked && amap) 1515 amap_lock(amap); 1516 uobj = uobjpage->uobject; 1517 simple_lock(&uobj->vmobjlock); 1518 1519 /* locked(locked): maps(read), amap(if !null), uobj, uobjpage */ 1520 /* locked(!locked): uobj, uobjpage */ 1521 1522 /* 1523 * verify that the page has not be released and re-verify 1524 * that amap slot is still free. if there is a problem, 1525 * we unlock and clean up. 1526 */ 1527 1528 if ((uobjpage->flags & PG_RELEASED) != 0 || 1529 (locked && amap && 1530 amap_lookup(&ufi.entry->aref, 1531 ufi.orig_rvaddr - ufi.entry->start))) { 1532 if (locked) 1533 uvmfault_unlockall(&ufi, amap, NULL, NULL); 1534 locked = FALSE; 1535 } 1536 1537 /* 1538 * didn't get the lock? release the page and retry. 1539 */ 1540 1541 if (locked == FALSE) { 1542 UVMHIST_LOG(maphist, 1543 " wasn't able to relock after fault: retry", 1544 0,0,0,0); 1545 if (uobjpage->flags & PG_WANTED) 1546 wakeup(uobjpage); 1547 if (uobjpage->flags & PG_RELEASED) { 1548 uvmexp.fltpgrele++; 1549 uvm_pagefree(uobjpage); 1550 goto ReFault; 1551 } 1552 uobjpage->flags &= ~(PG_BUSY|PG_WANTED); 1553 UVM_PAGE_OWN(uobjpage, NULL); 1554 simple_unlock(&uobj->vmobjlock); 1555 goto ReFault; 1556 } 1557 1558 /* 1559 * we have the data in uobjpage which is busy and 1560 * not released. we are holding object lock (so the page 1561 * can't be released on us). 1562 */ 1563 1564 /* locked: maps(read), amap(if !null), uobj, uobjpage */ 1565 } 1566 1567 /* 1568 * locked: 1569 * maps(read), amap(if !null), uobj(if !null), uobjpage(if uobj) 1570 */ 1571 1572 /* 1573 * notes: 1574 * - at this point uobjpage can not be NULL 1575 * - at this point uobjpage can not be PG_RELEASED (since we checked 1576 * for it above) 1577 * - at this point uobjpage could be PG_WANTED (handle later) 1578 */ 1579 1580 KASSERT(uobj == NULL || uobj == uobjpage->uobject); 1581 KASSERT(uobj == NULL || !UVM_OBJ_IS_CLEAN(uobjpage->uobject) || 1582 (uobjpage->flags & PG_CLEAN) != 0); 1583 if (promote == FALSE) { 1584 1585 /* 1586 * we are not promoting. if the mapping is COW ensure that we 1587 * don't give more access than we should (e.g. when doing a read 1588 * fault on a COPYONWRITE mapping we want to map the COW page in 1589 * R/O even though the entry protection could be R/W). 1590 * 1591 * set "pg" to the page we want to map in (uobjpage, usually) 1592 */ 1593 1594 /* no anon in this case. */ 1595 anon = NULL; 1596 1597 uvmexp.flt_obj++; 1598 if (UVM_ET_ISCOPYONWRITE(ufi.entry) || 1599 UVM_OBJ_NEEDS_WRITEFAULT(uobjpage->uobject)) 1600 enter_prot &= ~VM_PROT_WRITE; 1601 pg = uobjpage; /* map in the actual object */ 1602 1603 /* assert(uobjpage != PGO_DONTCARE) */ 1604 1605 /* 1606 * we are faulting directly on the page. be careful 1607 * about writing to loaned pages... 1608 */ 1609 1610 if (uobjpage->loan_count) { 1611 if (!cow_now) { 1612 /* read fault: cap the protection at readonly */ 1613 /* cap! */ 1614 enter_prot = enter_prot & ~VM_PROT_WRITE; 1615 } else { 1616 /* write fault: must break the loan here */ 1617 1618 pg = uvm_loanbreak(uobjpage); 1619 if (pg == NULL) { 1620 1621 /* 1622 * drop ownership of page, it can't 1623 * be released 1624 */ 1625 1626 if (uobjpage->flags & PG_WANTED) 1627 wakeup(uobjpage); 1628 uobjpage->flags &= ~(PG_BUSY|PG_WANTED); 1629 UVM_PAGE_OWN(uobjpage, NULL); 1630 1631 uvmfault_unlockall(&ufi, amap, uobj, 1632 NULL); 1633 UVMHIST_LOG(maphist, 1634 " out of RAM breaking loan, waiting", 1635 0,0,0,0); 1636 uvmexp.fltnoram++; 1637 uvm_wait("flt_noram4"); 1638 goto ReFault; 1639 } 1640 uobjpage = pg; 1641 } 1642 } 1643 } else { 1644 1645 /* 1646 * if we are going to promote the data to an anon we 1647 * allocate a blank anon here and plug it into our amap. 1648 */ 1649 #if DIAGNOSTIC 1650 if (amap == NULL) 1651 panic("uvm_fault: want to promote data, but no anon"); 1652 #endif 1653 error = uvmfault_promote(&ufi, NULL, uobjpage, 1654 &anon, &anon_spare); 1655 switch (error) { 1656 case 0: 1657 break; 1658 case ERESTART: 1659 goto ReFault; 1660 default: 1661 goto done; 1662 } 1663 1664 pg = anon->an_page; 1665 1666 /* 1667 * fill in the data 1668 */ 1669 1670 if (uobjpage != PGO_DONTCARE) { 1671 uvmexp.flt_prcopy++; 1672 1673 /* 1674 * promote to shared amap? make sure all sharing 1675 * procs see it 1676 */ 1677 1678 if ((amap_flags(amap) & AMAP_SHARED) != 0) { 1679 pmap_page_protect(uobjpage, VM_PROT_NONE); 1680 /* 1681 * XXX: PAGE MIGHT BE WIRED! 1682 */ 1683 } 1684 1685 /* 1686 * dispose of uobjpage. it can't be PG_RELEASED 1687 * since we still hold the object lock. 1688 * drop handle to uobj as well. 1689 */ 1690 1691 if (uobjpage->flags & PG_WANTED) 1692 /* still have the obj lock */ 1693 wakeup(uobjpage); 1694 uobjpage->flags &= ~(PG_BUSY|PG_WANTED); 1695 UVM_PAGE_OWN(uobjpage, NULL); 1696 simple_unlock(&uobj->vmobjlock); 1697 uobj = NULL; 1698 1699 UVMHIST_LOG(maphist, 1700 " promote uobjpage 0x%x to anon/page 0x%x/0x%x", 1701 uobjpage, anon, pg, 0); 1702 1703 } else { 1704 uvmexp.flt_przero++; 1705 1706 /* 1707 * Page is zero'd and marked dirty by 1708 * uvmfault_promote(). 1709 */ 1710 1711 UVMHIST_LOG(maphist," zero fill anon/page 0x%x/0%x", 1712 anon, pg, 0, 0); 1713 } 1714 } 1715 1716 /* 1717 * locked: 1718 * maps(read), amap(if !null), uobj(if !null), uobjpage(if uobj), 1719 * anon(if !null), pg(if anon) 1720 * 1721 * note: pg is either the uobjpage or the new page in the new anon 1722 */ 1723 1724 /* 1725 * all resources are present. we can now map it in and free our 1726 * resources. 1727 */ 1728 1729 UVMHIST_LOG(maphist, 1730 " MAPPING: case2: pm=0x%x, va=0x%x, pg=0x%x, promote=%d", 1731 ufi.orig_map->pmap, ufi.orig_rvaddr, pg, promote); 1732 KASSERT((access_type & VM_PROT_WRITE) == 0 || 1733 (pg->flags & PG_RDONLY) == 0); 1734 if (pmap_enter(ufi.orig_map->pmap, ufi.orig_rvaddr, VM_PAGE_TO_PHYS(pg), 1735 pg->flags & PG_RDONLY ? enter_prot & ~VM_PROT_WRITE : enter_prot, 1736 access_type | PMAP_CANFAIL | (wired ? PMAP_WIRED : 0)) != 0) { 1737 1738 /* 1739 * No need to undo what we did; we can simply think of 1740 * this as the pmap throwing away the mapping information. 1741 * 1742 * We do, however, have to go through the ReFault path, 1743 * as the map may change while we're asleep. 1744 */ 1745 1746 if (pg->flags & PG_WANTED) 1747 wakeup(pg); 1748 1749 /* 1750 * note that pg can't be PG_RELEASED since we did not drop 1751 * the object lock since the last time we checked. 1752 */ 1753 1754 pg->flags &= ~(PG_BUSY|PG_FAKE|PG_WANTED); 1755 UVM_PAGE_OWN(pg, NULL); 1756 uvmfault_unlockall(&ufi, amap, uobj, anon); 1757 if (!uvm_reclaimable()) { 1758 UVMHIST_LOG(maphist, 1759 "<- failed. out of VM",0,0,0,0); 1760 /* XXX instrumentation */ 1761 error = ENOMEM; 1762 goto done; 1763 } 1764 /* XXX instrumentation */ 1765 uvm_wait("flt_pmfail2"); 1766 goto ReFault; 1767 } 1768 1769 uvm_lock_pageq(); 1770 if (wire_fault) { 1771 uvm_pagewire(pg); 1772 if (pg->pqflags & PQ_AOBJ) { 1773 1774 /* 1775 * since the now-wired page cannot be paged out, 1776 * release its swap resources for others to use. 1777 * since an aobj page with no swap cannot be PG_CLEAN, 1778 * clear its clean flag now. 1779 */ 1780 1781 pg->flags &= ~(PG_CLEAN); 1782 uao_dropswap(uobj, pg->offset >> PAGE_SHIFT); 1783 } 1784 } else { 1785 uvm_pageactivate(pg); 1786 } 1787 uvm_unlock_pageq(); 1788 if (pg->flags & PG_WANTED) 1789 wakeup(pg); 1790 1791 /* 1792 * note that pg can't be PG_RELEASED since we did not drop the object 1793 * lock since the last time we checked. 1794 */ 1795 1796 pg->flags &= ~(PG_BUSY|PG_FAKE|PG_WANTED); 1797 UVM_PAGE_OWN(pg, NULL); 1798 uvmfault_unlockall(&ufi, amap, uobj, anon); 1799 pmap_update(ufi.orig_map->pmap); 1800 UVMHIST_LOG(maphist, "<- done (SUCCESS!)",0,0,0,0); 1801 error = 0; 1802 done: 1803 if (anon_spare != NULL) { 1804 anon_spare->an_ref--; 1805 uvm_anfree(anon_spare); 1806 } 1807 return error; 1808 } 1809 1810 /* 1811 * uvm_fault_wire: wire down a range of virtual addresses in a map. 1812 * 1813 * => map may be read-locked by caller, but MUST NOT be write-locked. 1814 * => if map is read-locked, any operations which may cause map to 1815 * be write-locked in uvm_fault() must be taken care of by 1816 * the caller. See uvm_map_pageable(). 1817 */ 1818 1819 int 1820 uvm_fault_wire(struct vm_map *map, vaddr_t start, vaddr_t end, 1821 vm_fault_t fault_type, vm_prot_t access_type) 1822 { 1823 vaddr_t va; 1824 int error; 1825 1826 /* 1827 * now fault it in a page at a time. if the fault fails then we have 1828 * to undo what we have done. note that in uvm_fault VM_PROT_NONE 1829 * is replaced with the max protection if fault_type is VM_FAULT_WIRE. 1830 */ 1831 1832 /* 1833 * XXX work around overflowing a vaddr_t. this prevents us from 1834 * wiring the last page in the address space, though. 1835 */ 1836 if (start > end) { 1837 return EFAULT; 1838 } 1839 1840 for (va = start ; va < end ; va += PAGE_SIZE) { 1841 error = uvm_fault(map, va, fault_type, access_type); 1842 if (error) { 1843 if (va != start) { 1844 uvm_fault_unwire(map, start, va); 1845 } 1846 return error; 1847 } 1848 } 1849 return 0; 1850 } 1851 1852 /* 1853 * uvm_fault_unwire(): unwire range of virtual space. 1854 */ 1855 1856 void 1857 uvm_fault_unwire(struct vm_map *map, vaddr_t start, vaddr_t end) 1858 { 1859 vm_map_lock_read(map); 1860 uvm_fault_unwire_locked(map, start, end); 1861 vm_map_unlock_read(map); 1862 } 1863 1864 /* 1865 * uvm_fault_unwire_locked(): the guts of uvm_fault_unwire(). 1866 * 1867 * => map must be at least read-locked. 1868 */ 1869 1870 void 1871 uvm_fault_unwire_locked(struct vm_map *map, vaddr_t start, vaddr_t end) 1872 { 1873 struct vm_map_entry *entry; 1874 pmap_t pmap = vm_map_pmap(map); 1875 vaddr_t va; 1876 paddr_t pa; 1877 struct vm_page *pg; 1878 1879 KASSERT((map->flags & VM_MAP_INTRSAFE) == 0); 1880 1881 /* 1882 * we assume that the area we are unwiring has actually been wired 1883 * in the first place. this means that we should be able to extract 1884 * the PAs from the pmap. we also lock out the page daemon so that 1885 * we can call uvm_pageunwire. 1886 */ 1887 1888 uvm_lock_pageq(); 1889 1890 /* 1891 * find the beginning map entry for the region. 1892 */ 1893 1894 KASSERT(start >= vm_map_min(map) && end <= vm_map_max(map)); 1895 if (uvm_map_lookup_entry(map, start, &entry) == FALSE) 1896 panic("uvm_fault_unwire_locked: address not in map"); 1897 1898 for (va = start; va < end; va += PAGE_SIZE) { 1899 if (pmap_extract(pmap, va, &pa) == FALSE) 1900 continue; 1901 1902 /* 1903 * find the map entry for the current address. 1904 */ 1905 1906 KASSERT(va >= entry->start); 1907 while (va >= entry->end) { 1908 KASSERT(entry->next != &map->header && 1909 entry->next->start <= entry->end); 1910 entry = entry->next; 1911 } 1912 1913 /* 1914 * if the entry is no longer wired, tell the pmap. 1915 */ 1916 1917 if (VM_MAPENT_ISWIRED(entry) == 0) 1918 pmap_unwire(pmap, va); 1919 1920 pg = PHYS_TO_VM_PAGE(pa); 1921 if (pg) 1922 uvm_pageunwire(pg); 1923 } 1924 1925 uvm_unlock_pageq(); 1926 } 1927