1 /* $NetBSD: uvm_fault.c,v 1.76 2002/03/25 01:56:48 chs 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 1.76 2002/03/25 01:56:48 chs 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 54 #include <uvm/uvm.h> 55 56 /* 57 * 58 * a word on page faults: 59 * 60 * types of page faults we handle: 61 * 62 * CASE 1: upper layer faults CASE 2: lower layer faults 63 * 64 * CASE 1A CASE 1B CASE 2A CASE 2B 65 * read/write1 write>1 read/write +-cow_write/zero 66 * | | | | 67 * +--|--+ +--|--+ +-----+ + | + | +-----+ 68 * amap | V | | ----------->new| | | | ^ | 69 * +-----+ +-----+ +-----+ + | + | +--|--+ 70 * | | | 71 * +-----+ +-----+ +--|--+ | +--|--+ 72 * uobj | d/c | | d/c | | V | +----| | 73 * +-----+ +-----+ +-----+ +-----+ 74 * 75 * d/c = don't care 76 * 77 * case [0]: layerless fault 78 * no amap or uobj is present. this is an error. 79 * 80 * case [1]: upper layer fault [anon active] 81 * 1A: [read] or [write with anon->an_ref == 1] 82 * I/O takes place in top level anon and uobj is not touched. 83 * 1B: [write with anon->an_ref > 1] 84 * new anon is alloc'd and data is copied off ["COW"] 85 * 86 * case [2]: lower layer fault [uobj] 87 * 2A: [read on non-NULL uobj] or [write to non-copy_on_write area] 88 * I/O takes place directly in object. 89 * 2B: [write to copy_on_write] or [read on NULL uobj] 90 * data is "promoted" from uobj to a new anon. 91 * if uobj is null, then we zero fill. 92 * 93 * we follow the standard UVM locking protocol ordering: 94 * 95 * MAPS => AMAP => UOBJ => ANON => PAGE QUEUES (PQ) 96 * we hold a PG_BUSY page if we unlock for I/O 97 * 98 * 99 * the code is structured as follows: 100 * 101 * - init the "IN" params in the ufi structure 102 * ReFault: 103 * - do lookups [locks maps], check protection, handle needs_copy 104 * - check for case 0 fault (error) 105 * - establish "range" of fault 106 * - if we have an amap lock it and extract the anons 107 * - if sequential advice deactivate pages behind us 108 * - at the same time check pmap for unmapped areas and anon for pages 109 * that we could map in (and do map it if found) 110 * - check object for resident pages that we could map in 111 * - if (case 2) goto Case2 112 * - >>> handle case 1 113 * - ensure source anon is resident in RAM 114 * - if case 1B alloc new anon and copy from source 115 * - map the correct page in 116 * Case2: 117 * - >>> handle case 2 118 * - ensure source page is resident (if uobj) 119 * - if case 2B alloc new anon and copy from source (could be zero 120 * fill if uobj == NULL) 121 * - map the correct page in 122 * - done! 123 * 124 * note on paging: 125 * if we have to do I/O we place a PG_BUSY page in the correct object, 126 * unlock everything, and do the I/O. when I/O is done we must reverify 127 * the state of the world before assuming that our data structures are 128 * valid. [because mappings could change while the map is unlocked] 129 * 130 * alternative 1: unbusy the page in question and restart the page fault 131 * from the top (ReFault). this is easy but does not take advantage 132 * of the information that we already have from our previous lookup, 133 * although it is possible that the "hints" in the vm_map will help here. 134 * 135 * alternative 2: the system already keeps track of a "version" number of 136 * a map. [i.e. every time you write-lock a map (e.g. to change a 137 * mapping) you bump the version number up by one...] so, we can save 138 * the version number of the map before we release the lock and start I/O. 139 * then when I/O is done we can relock and check the version numbers 140 * to see if anything changed. this might save us some over 1 because 141 * we don't have to unbusy the page and may be less compares(?). 142 * 143 * alternative 3: put in backpointers or a way to "hold" part of a map 144 * in place while I/O is in progress. this could be complex to 145 * implement (especially with structures like amap that can be referenced 146 * by multiple map entries, and figuring out what should wait could be 147 * complex as well...). 148 * 149 * given that we are not currently multiprocessor or multithreaded we might 150 * as well choose alternative 2 now. maybe alternative 3 would be useful 151 * in the future. XXX keep in mind for future consideration//rechecking. 152 */ 153 154 /* 155 * local data structures 156 */ 157 158 struct uvm_advice { 159 int advice; 160 int nback; 161 int nforw; 162 }; 163 164 /* 165 * page range array: 166 * note: index in array must match "advice" value 167 * XXX: borrowed numbers from freebsd. do they work well for us? 168 */ 169 170 static struct uvm_advice uvmadvice[] = { 171 { MADV_NORMAL, 3, 4 }, 172 { MADV_RANDOM, 0, 0 }, 173 { MADV_SEQUENTIAL, 8, 7}, 174 }; 175 176 #define UVM_MAXRANGE 16 /* must be MAX() of nback+nforw+1 */ 177 178 /* 179 * private prototypes 180 */ 181 182 static void uvmfault_amapcopy __P((struct uvm_faultinfo *)); 183 static __inline void uvmfault_anonflush __P((struct vm_anon **, int)); 184 185 /* 186 * inline functions 187 */ 188 189 /* 190 * uvmfault_anonflush: try and deactivate pages in specified anons 191 * 192 * => does not have to deactivate page if it is busy 193 */ 194 195 static __inline void 196 uvmfault_anonflush(anons, n) 197 struct vm_anon **anons; 198 int n; 199 { 200 int lcv; 201 struct vm_page *pg; 202 203 for (lcv = 0 ; lcv < n ; lcv++) { 204 if (anons[lcv] == NULL) 205 continue; 206 simple_lock(&anons[lcv]->an_lock); 207 pg = anons[lcv]->u.an_page; 208 if (pg && (pg->flags & PG_BUSY) == 0 && pg->loan_count == 0) { 209 uvm_lock_pageq(); 210 if (pg->wire_count == 0) { 211 pmap_clear_reference(pg); 212 uvm_pagedeactivate(pg); 213 } 214 uvm_unlock_pageq(); 215 } 216 simple_unlock(&anons[lcv]->an_lock); 217 } 218 } 219 220 /* 221 * normal functions 222 */ 223 224 /* 225 * uvmfault_amapcopy: clear "needs_copy" in a map. 226 * 227 * => called with VM data structures unlocked (usually, see below) 228 * => we get a write lock on the maps and clear needs_copy for a VA 229 * => if we are out of RAM we sleep (waiting for more) 230 */ 231 232 static void 233 uvmfault_amapcopy(ufi) 234 struct uvm_faultinfo *ufi; 235 { 236 for (;;) { 237 238 /* 239 * no mapping? give up. 240 */ 241 242 if (uvmfault_lookup(ufi, TRUE) == FALSE) 243 return; 244 245 /* 246 * copy if needed. 247 */ 248 249 if (UVM_ET_ISNEEDSCOPY(ufi->entry)) 250 amap_copy(ufi->map, ufi->entry, M_NOWAIT, TRUE, 251 ufi->orig_rvaddr, ufi->orig_rvaddr + 1); 252 253 /* 254 * didn't work? must be out of RAM. unlock and sleep. 255 */ 256 257 if (UVM_ET_ISNEEDSCOPY(ufi->entry)) { 258 uvmfault_unlockmaps(ufi, TRUE); 259 uvm_wait("fltamapcopy"); 260 continue; 261 } 262 263 /* 264 * got it! unlock and return. 265 */ 266 267 uvmfault_unlockmaps(ufi, TRUE); 268 return; 269 } 270 /*NOTREACHED*/ 271 } 272 273 /* 274 * uvmfault_anonget: get data in an anon into a non-busy, non-released 275 * page in that anon. 276 * 277 * => maps, amap, and anon locked by caller. 278 * => if we fail (result != 0) we unlock everything. 279 * => if we are successful, we return with everything still locked. 280 * => we don't move the page on the queues [gets moved later] 281 * => if we allocate a new page [we_own], it gets put on the queues. 282 * either way, the result is that the page is on the queues at return time 283 * => for pages which are on loan from a uvm_object (and thus are not 284 * owned by the anon): if successful, we return with the owning object 285 * locked. the caller must unlock this object when it unlocks everything 286 * else. 287 */ 288 289 int 290 uvmfault_anonget(ufi, amap, anon) 291 struct uvm_faultinfo *ufi; 292 struct vm_amap *amap; 293 struct vm_anon *anon; 294 { 295 boolean_t we_own; /* we own anon's page? */ 296 boolean_t locked; /* did we relock? */ 297 struct vm_page *pg; 298 int error; 299 UVMHIST_FUNC("uvmfault_anonget"); UVMHIST_CALLED(maphist); 300 301 LOCK_ASSERT(simple_lock_held(&anon->an_lock)); 302 303 error = 0; 304 uvmexp.fltanget++; 305 /* bump rusage counters */ 306 if (anon->u.an_page) 307 curproc->p_addr->u_stats.p_ru.ru_minflt++; 308 else 309 curproc->p_addr->u_stats.p_ru.ru_majflt++; 310 311 /* 312 * loop until we get it, or fail. 313 */ 314 315 for (;;) { 316 we_own = FALSE; /* TRUE if we set PG_BUSY on a page */ 317 pg = anon->u.an_page; 318 319 /* 320 * if there is a resident page and it is loaned, then anon 321 * may not own it. call out to uvm_anon_lockpage() to ensure 322 * the real owner of the page has been identified and locked. 323 */ 324 325 if (pg && pg->loan_count) 326 pg = uvm_anon_lockloanpg(anon); 327 328 /* 329 * page there? make sure it is not busy/released. 330 */ 331 332 if (pg) { 333 334 /* 335 * at this point, if the page has a uobject [meaning 336 * we have it on loan], then that uobject is locked 337 * by us! if the page is busy, we drop all the 338 * locks (including uobject) and try again. 339 */ 340 341 if ((pg->flags & PG_BUSY) == 0) { 342 UVMHIST_LOG(maphist, "<- OK",0,0,0,0); 343 return (0); 344 } 345 pg->flags |= PG_WANTED; 346 uvmexp.fltpgwait++; 347 348 /* 349 * the last unlock must be an atomic unlock+wait on 350 * the owner of page 351 */ 352 353 if (pg->uobject) { /* owner is uobject ? */ 354 uvmfault_unlockall(ufi, amap, NULL, anon); 355 UVMHIST_LOG(maphist, " unlock+wait on uobj",0, 356 0,0,0); 357 UVM_UNLOCK_AND_WAIT(pg, 358 &pg->uobject->vmobjlock, 359 FALSE, "anonget1",0); 360 } else { 361 /* anon owns page */ 362 uvmfault_unlockall(ufi, amap, NULL, NULL); 363 UVMHIST_LOG(maphist, " unlock+wait on anon",0, 364 0,0,0); 365 UVM_UNLOCK_AND_WAIT(pg,&anon->an_lock,0, 366 "anonget2",0); 367 } 368 } else { 369 370 /* 371 * no page, we must try and bring it in. 372 */ 373 374 pg = uvm_pagealloc(NULL, 0, anon, 0); 375 if (pg == NULL) { /* out of RAM. */ 376 uvmfault_unlockall(ufi, amap, NULL, anon); 377 uvmexp.fltnoram++; 378 UVMHIST_LOG(maphist, " noram -- UVM_WAIT",0, 379 0,0,0); 380 uvm_wait("flt_noram1"); 381 } else { 382 /* we set the PG_BUSY bit */ 383 we_own = TRUE; 384 uvmfault_unlockall(ufi, amap, NULL, anon); 385 386 /* 387 * we are passing a PG_BUSY+PG_FAKE+PG_CLEAN 388 * page into the uvm_swap_get function with 389 * all data structures unlocked. note that 390 * it is ok to read an_swslot here because 391 * we hold PG_BUSY on the page. 392 */ 393 uvmexp.pageins++; 394 error = uvm_swap_get(pg, anon->an_swslot, 395 PGO_SYNCIO); 396 397 /* 398 * we clean up after the i/o below in the 399 * "we_own" case 400 */ 401 } 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 (pg->flags & PG_WANTED) { 428 wakeup(pg); 429 } 430 if (error) { 431 /* remove page from anon */ 432 anon->u.an_page = NULL; 433 434 /* 435 * remove the swap slot from the anon 436 * and mark the anon as having no real slot. 437 * don't free the swap slot, thus preventing 438 * it from being used again. 439 */ 440 441 uvm_swap_markbad(anon->an_swslot, 1); 442 anon->an_swslot = SWSLOT_BAD; 443 444 /* 445 * note: page was never !PG_BUSY, so it 446 * can't be mapped and thus no need to 447 * pmap_page_protect it... 448 */ 449 450 uvm_lock_pageq(); 451 uvm_pagefree(pg); 452 uvm_unlock_pageq(); 453 454 if (locked) 455 uvmfault_unlockall(ufi, amap, NULL, 456 anon); 457 else 458 simple_unlock(&anon->an_lock); 459 UVMHIST_LOG(maphist, "<- ERROR", 0,0,0,0); 460 return error; 461 } 462 463 /* 464 * we've successfully read the page, activate it. 465 */ 466 467 uvm_lock_pageq(); 468 uvm_pageactivate(pg); 469 uvm_unlock_pageq(); 470 pg->flags &= ~(PG_WANTED|PG_BUSY|PG_FAKE); 471 UVM_PAGE_OWN(pg, NULL); 472 if (!locked) 473 simple_unlock(&anon->an_lock); 474 } 475 476 /* 477 * we were not able to relock. restart fault. 478 */ 479 480 if (!locked) { 481 UVMHIST_LOG(maphist, "<- REFAULT", 0,0,0,0); 482 return (ERESTART); 483 } 484 485 /* 486 * verify no one has touched the amap and moved the anon on us. 487 */ 488 489 if (ufi != NULL && 490 amap_lookup(&ufi->entry->aref, 491 ufi->orig_rvaddr - ufi->entry->start) != anon) { 492 493 uvmfault_unlockall(ufi, amap, NULL, anon); 494 UVMHIST_LOG(maphist, "<- REFAULT", 0,0,0,0); 495 return (ERESTART); 496 } 497 498 /* 499 * try it again! 500 */ 501 502 uvmexp.fltanretry++; 503 continue; 504 } 505 /*NOTREACHED*/ 506 } 507 508 /* 509 * F A U L T - m a i n e n t r y p o i n t 510 */ 511 512 /* 513 * uvm_fault: page fault handler 514 * 515 * => called from MD code to resolve a page fault 516 * => VM data structures usually should be unlocked. however, it is 517 * possible to call here with the main map locked if the caller 518 * gets a write lock, sets it recusive, and then calls us (c.f. 519 * uvm_map_pageable). this should be avoided because it keeps 520 * the map locked off during I/O. 521 * => MUST NEVER BE CALLED IN INTERRUPT CONTEXT 522 */ 523 524 #define MASK(entry) (UVM_ET_ISCOPYONWRITE(entry) ? \ 525 ~VM_PROT_WRITE : VM_PROT_ALL) 526 527 int 528 uvm_fault(orig_map, vaddr, fault_type, access_type) 529 struct vm_map *orig_map; 530 vaddr_t vaddr; 531 vm_fault_t fault_type; 532 vm_prot_t access_type; 533 { 534 struct uvm_faultinfo ufi; 535 vm_prot_t enter_prot, check_prot; 536 boolean_t wired, narrow, promote, locked, shadowed, wire_fault, cow_now; 537 int npages, nback, nforw, centeridx, error, lcv, gotpages; 538 vaddr_t startva, objaddr, currva, offset, uoff; 539 paddr_t pa; 540 struct vm_amap *amap; 541 struct uvm_object *uobj; 542 struct vm_anon *anons_store[UVM_MAXRANGE], **anons, *anon, *oanon; 543 struct vm_page *pages[UVM_MAXRANGE], *pg, *uobjpage; 544 UVMHIST_FUNC("uvm_fault"); UVMHIST_CALLED(maphist); 545 546 UVMHIST_LOG(maphist, "(map=0x%x, vaddr=0x%x, ft=%d, at=%d)", 547 orig_map, vaddr, fault_type, access_type); 548 549 anon = NULL; 550 pg = NULL; 551 552 uvmexp.faults++; /* XXX: locking? */ 553 554 /* 555 * init the IN parameters in the ufi 556 */ 557 558 ufi.orig_map = orig_map; 559 ufi.orig_rvaddr = trunc_page(vaddr); 560 ufi.orig_size = PAGE_SIZE; /* can't get any smaller than this */ 561 wire_fault = fault_type == VM_FAULT_WIRE || 562 fault_type == VM_FAULT_WIREMAX; 563 if (wire_fault) 564 narrow = TRUE; /* don't look for neighborhood 565 * pages on wire */ 566 else 567 narrow = FALSE; /* normal fault */ 568 569 /* 570 * "goto ReFault" means restart the page fault from ground zero. 571 */ 572 ReFault: 573 574 /* 575 * lookup and lock the maps 576 */ 577 578 if (uvmfault_lookup(&ufi, FALSE) == FALSE) { 579 UVMHIST_LOG(maphist, "<- no mapping @ 0x%x", vaddr, 0,0,0); 580 return (EFAULT); 581 } 582 /* locked: maps(read) */ 583 584 #ifdef DIAGNOSTIC 585 if ((ufi.map->flags & VM_MAP_PAGEABLE) == 0) { 586 printf("Page fault on non-pageable map:\n"); 587 printf("ufi.map = %p\n", ufi.map); 588 printf("ufi.orig_map = %p\n", ufi.orig_map); 589 printf("ufi.orig_rvaddr = 0x%lx\n", (u_long) ufi.orig_rvaddr); 590 panic("uvm_fault: (ufi.map->flags & VM_MAP_PAGEABLE) == 0"); 591 } 592 #endif 593 594 /* 595 * check protection 596 */ 597 598 check_prot = fault_type == VM_FAULT_WIREMAX ? 599 ufi.entry->max_protection : ufi.entry->protection; 600 if ((check_prot & access_type) != access_type) { 601 UVMHIST_LOG(maphist, 602 "<- protection failure (prot=0x%x, access=0x%x)", 603 ufi.entry->protection, access_type, 0, 0); 604 uvmfault_unlockmaps(&ufi, FALSE); 605 return EACCES; 606 } 607 608 /* 609 * "enter_prot" is the protection we want to enter the page in at. 610 * for certain pages (e.g. copy-on-write pages) this protection can 611 * be more strict than ufi.entry->protection. "wired" means either 612 * the entry is wired or we are fault-wiring the pg. 613 */ 614 615 enter_prot = ufi.entry->protection; 616 wired = VM_MAPENT_ISWIRED(ufi.entry) || wire_fault; 617 if (wired) { 618 access_type = enter_prot; /* full access for wired */ 619 cow_now = (check_prot & VM_PROT_WRITE) != 0; 620 } else { 621 cow_now = (access_type & VM_PROT_WRITE) != 0; 622 } 623 624 /* 625 * handle "needs_copy" case. if we need to copy the amap we will 626 * have to drop our readlock and relock it with a write lock. (we 627 * need a write lock to change anything in a map entry [e.g. 628 * needs_copy]). 629 */ 630 631 if (UVM_ET_ISNEEDSCOPY(ufi.entry)) { 632 KASSERT(fault_type != VM_FAULT_WIREMAX); 633 if (cow_now || (ufi.entry->object.uvm_obj == NULL)) { 634 /* need to clear */ 635 UVMHIST_LOG(maphist, 636 " need to clear needs_copy and refault",0,0,0,0); 637 uvmfault_unlockmaps(&ufi, FALSE); 638 uvmfault_amapcopy(&ufi); 639 uvmexp.fltamcopy++; 640 goto ReFault; 641 642 } else { 643 644 /* 645 * ensure that we pmap_enter page R/O since 646 * needs_copy is still true 647 */ 648 649 enter_prot &= ~VM_PROT_WRITE; 650 } 651 } 652 653 /* 654 * identify the players 655 */ 656 657 amap = ufi.entry->aref.ar_amap; /* top layer */ 658 uobj = ufi.entry->object.uvm_obj; /* bottom layer */ 659 660 /* 661 * check for a case 0 fault. if nothing backing the entry then 662 * error now. 663 */ 664 665 if (amap == NULL && uobj == NULL) { 666 uvmfault_unlockmaps(&ufi, FALSE); 667 UVMHIST_LOG(maphist,"<- no backing store, no overlay",0,0,0,0); 668 return (EFAULT); 669 } 670 671 /* 672 * establish range of interest based on advice from mapper 673 * and then clip to fit map entry. note that we only want 674 * to do this the first time through the fault. if we 675 * ReFault we will disable this by setting "narrow" to true. 676 */ 677 678 if (narrow == FALSE) { 679 680 /* wide fault (!narrow) */ 681 KASSERT(uvmadvice[ufi.entry->advice].advice == 682 ufi.entry->advice); 683 nback = MIN(uvmadvice[ufi.entry->advice].nback, 684 (ufi.orig_rvaddr - ufi.entry->start) >> PAGE_SHIFT); 685 startva = ufi.orig_rvaddr - (nback << PAGE_SHIFT); 686 nforw = MIN(uvmadvice[ufi.entry->advice].nforw, 687 ((ufi.entry->end - ufi.orig_rvaddr) >> 688 PAGE_SHIFT) - 1); 689 /* 690 * note: "-1" because we don't want to count the 691 * faulting page as forw 692 */ 693 npages = nback + nforw + 1; 694 centeridx = nback; 695 696 narrow = TRUE; /* ensure only once per-fault */ 697 698 } else { 699 700 /* narrow fault! */ 701 nback = nforw = 0; 702 startva = ufi.orig_rvaddr; 703 npages = 1; 704 centeridx = 0; 705 706 } 707 708 /* locked: maps(read) */ 709 UVMHIST_LOG(maphist, " narrow=%d, back=%d, forw=%d, startva=0x%x", 710 narrow, nback, nforw, startva); 711 UVMHIST_LOG(maphist, " entry=0x%x, amap=0x%x, obj=0x%x", ufi.entry, 712 amap, uobj, 0); 713 714 /* 715 * if we've got an amap, lock it and extract current anons. 716 */ 717 718 if (amap) { 719 amap_lock(amap); 720 anons = anons_store; 721 amap_lookups(&ufi.entry->aref, startva - ufi.entry->start, 722 anons, npages); 723 } else { 724 anons = NULL; /* to be safe */ 725 } 726 727 /* locked: maps(read), amap(if there) */ 728 729 /* 730 * for MADV_SEQUENTIAL mappings we want to deactivate the back pages 731 * now and then forget about them (for the rest of the fault). 732 */ 733 734 if (ufi.entry->advice == MADV_SEQUENTIAL && nback != 0) { 735 736 UVMHIST_LOG(maphist, " MADV_SEQUENTIAL: flushing backpages", 737 0,0,0,0); 738 /* flush back-page anons? */ 739 if (amap) 740 uvmfault_anonflush(anons, nback); 741 742 /* flush object? */ 743 if (uobj) { 744 objaddr = 745 (startva - ufi.entry->start) + ufi.entry->offset; 746 simple_lock(&uobj->vmobjlock); 747 (void) (uobj->pgops->pgo_put)(uobj, objaddr, objaddr + 748 (nback << PAGE_SHIFT), PGO_DEACTIVATE); 749 } 750 751 /* now forget about the backpages */ 752 if (amap) 753 anons += nback; 754 startva += (nback << PAGE_SHIFT); 755 npages -= nback; 756 nback = centeridx = 0; 757 } 758 759 /* locked: maps(read), amap(if there) */ 760 761 /* 762 * map in the backpages and frontpages we found in the amap in hopes 763 * of preventing future faults. we also init the pages[] array as 764 * we go. 765 */ 766 767 currva = startva; 768 shadowed = FALSE; 769 for (lcv = 0 ; lcv < npages ; lcv++, currva += PAGE_SIZE) { 770 771 /* 772 * dont play with VAs that are already mapped 773 * except for center) 774 */ 775 if (lcv != centeridx && 776 pmap_extract(ufi.orig_map->pmap, currva, &pa)) { 777 pages[lcv] = PGO_DONTCARE; 778 continue; 779 } 780 781 /* 782 * unmapped or center page. check if any anon at this level. 783 */ 784 if (amap == NULL || anons[lcv] == NULL) { 785 pages[lcv] = NULL; 786 continue; 787 } 788 789 /* 790 * check for present page and map if possible. re-activate it. 791 */ 792 793 pages[lcv] = PGO_DONTCARE; 794 if (lcv == centeridx) { /* save center for later! */ 795 shadowed = TRUE; 796 continue; 797 } 798 anon = anons[lcv]; 799 simple_lock(&anon->an_lock); 800 /* ignore loaned pages */ 801 if (anon->u.an_page && anon->u.an_page->loan_count == 0 && 802 (anon->u.an_page->flags & PG_BUSY) == 0) { 803 uvm_lock_pageq(); 804 uvm_pageactivate(anon->u.an_page); 805 uvm_unlock_pageq(); 806 UVMHIST_LOG(maphist, 807 " MAPPING: n anon: pm=0x%x, va=0x%x, pg=0x%x", 808 ufi.orig_map->pmap, currva, anon->u.an_page, 0); 809 uvmexp.fltnamap++; 810 811 /* 812 * Since this isn't the page that's actually faulting, 813 * ignore pmap_enter() failures; it's not critical 814 * that we enter these right now. 815 */ 816 817 (void) pmap_enter(ufi.orig_map->pmap, currva, 818 VM_PAGE_TO_PHYS(anon->u.an_page), 819 (anon->an_ref > 1) ? (enter_prot & ~VM_PROT_WRITE) : 820 enter_prot, 821 PMAP_CANFAIL | 822 (VM_MAPENT_ISWIRED(ufi.entry) ? PMAP_WIRED : 0)); 823 } 824 simple_unlock(&anon->an_lock); 825 pmap_update(ufi.orig_map->pmap); 826 } 827 828 /* locked: maps(read), amap(if there) */ 829 /* (shadowed == TRUE) if there is an anon at the faulting address */ 830 UVMHIST_LOG(maphist, " shadowed=%d, will_get=%d", shadowed, 831 (uobj && shadowed == FALSE),0,0); 832 833 /* 834 * note that if we are really short of RAM we could sleep in the above 835 * call to pmap_enter with everything locked. bad? 836 * 837 * XXX Actually, that is bad; pmap_enter() should just fail in that 838 * XXX case. --thorpej 839 */ 840 841 /* 842 * if the desired page is not shadowed by the amap and we have a 843 * backing object, then we check to see if the backing object would 844 * prefer to handle the fault itself (rather than letting us do it 845 * with the usual pgo_get hook). the backing object signals this by 846 * providing a pgo_fault routine. 847 */ 848 849 if (uobj && shadowed == FALSE && uobj->pgops->pgo_fault != NULL) { 850 simple_lock(&uobj->vmobjlock); 851 852 /* locked: maps(read), amap (if there), uobj */ 853 error = uobj->pgops->pgo_fault(&ufi, startva, pages, npages, 854 centeridx, fault_type, access_type, PGO_LOCKED|PGO_SYNCIO); 855 856 /* locked: nothing, pgo_fault has unlocked everything */ 857 858 if (error == ERESTART) 859 goto ReFault; /* try again! */ 860 /* 861 * object fault routine responsible for pmap_update(). 862 */ 863 return error; 864 } 865 866 /* 867 * now, if the desired page is not shadowed by the amap and we have 868 * a backing object that does not have a special fault routine, then 869 * we ask (with pgo_get) the object for resident pages that we care 870 * about and attempt to map them in. we do not let pgo_get block 871 * (PGO_LOCKED). 872 */ 873 874 if (uobj && shadowed == FALSE) { 875 simple_lock(&uobj->vmobjlock); 876 877 /* locked (!shadowed): maps(read), amap (if there), uobj */ 878 /* 879 * the following call to pgo_get does _not_ change locking state 880 */ 881 882 uvmexp.fltlget++; 883 gotpages = npages; 884 (void) uobj->pgops->pgo_get(uobj, ufi.entry->offset + 885 (startva - ufi.entry->start), 886 pages, &gotpages, centeridx, 887 access_type & MASK(ufi.entry), 888 ufi.entry->advice, PGO_LOCKED); 889 890 /* 891 * check for pages to map, if we got any 892 */ 893 894 uobjpage = NULL; 895 896 if (gotpages) { 897 currva = startva; 898 for (lcv = 0; lcv < npages; 899 lcv++, currva += PAGE_SIZE) { 900 if (pages[lcv] == NULL || 901 pages[lcv] == PGO_DONTCARE) { 902 continue; 903 } 904 905 /* 906 * if center page is resident and not 907 * PG_BUSY|PG_RELEASED then pgo_get 908 * made it PG_BUSY for us and gave 909 * us a handle to it. remember this 910 * page as "uobjpage." (for later use). 911 */ 912 913 if (lcv == centeridx) { 914 uobjpage = pages[lcv]; 915 UVMHIST_LOG(maphist, " got uobjpage " 916 "(0x%x) with locked get", 917 uobjpage, 0,0,0); 918 continue; 919 } 920 921 /* 922 * calling pgo_get with PGO_LOCKED returns us 923 * pages which are neither busy nor released, 924 * so we don't need to check for this. 925 * we can just directly enter the pages. 926 */ 927 928 uvm_lock_pageq(); 929 uvm_pageactivate(pages[lcv]); 930 uvm_unlock_pageq(); 931 UVMHIST_LOG(maphist, 932 " MAPPING: n obj: pm=0x%x, va=0x%x, pg=0x%x", 933 ufi.orig_map->pmap, currva, pages[lcv], 0); 934 uvmexp.fltnomap++; 935 936 /* 937 * Since this page isn't the page that's 938 * actually fauling, ignore pmap_enter() 939 * failures; it's not critical that we 940 * enter these right now. 941 */ 942 943 (void) pmap_enter(ufi.orig_map->pmap, currva, 944 VM_PAGE_TO_PHYS(pages[lcv]), 945 pages[lcv]->flags & PG_RDONLY ? 946 enter_prot & ~VM_PROT_WRITE : 947 enter_prot & MASK(ufi.entry), 948 PMAP_CANFAIL | 949 (wired ? PMAP_WIRED : 0)); 950 951 /* 952 * NOTE: page can't be PG_WANTED or PG_RELEASED 953 * because we've held the lock the whole time 954 * we've had the handle. 955 */ 956 957 pages[lcv]->flags &= ~(PG_BUSY); 958 UVM_PAGE_OWN(pages[lcv], NULL); 959 } 960 pmap_update(ufi.orig_map->pmap); 961 } 962 } else { 963 uobjpage = NULL; 964 } 965 966 /* locked (shadowed): maps(read), amap */ 967 /* locked (!shadowed): maps(read), amap(if there), 968 uobj(if !null), uobjpage(if !null) */ 969 970 /* 971 * note that at this point we are done with any front or back pages. 972 * we are now going to focus on the center page (i.e. the one we've 973 * faulted on). if we have faulted on the top (anon) layer 974 * [i.e. case 1], then the anon we want is anons[centeridx] (we have 975 * not touched it yet). if we have faulted on the bottom (uobj) 976 * layer [i.e. case 2] and the page was both present and available, 977 * then we've got a pointer to it as "uobjpage" and we've already 978 * made it BUSY. 979 */ 980 981 /* 982 * there are four possible cases we must address: 1A, 1B, 2A, and 2B 983 */ 984 985 /* 986 * redirect case 2: if we are not shadowed, go to case 2. 987 */ 988 989 if (shadowed == FALSE) 990 goto Case2; 991 992 /* locked: maps(read), amap */ 993 994 /* 995 * handle case 1: fault on an anon in our amap 996 */ 997 998 anon = anons[centeridx]; 999 UVMHIST_LOG(maphist, " case 1 fault: anon=0x%x", anon, 0,0,0); 1000 simple_lock(&anon->an_lock); 1001 1002 /* locked: maps(read), amap, anon */ 1003 1004 /* 1005 * no matter if we have case 1A or case 1B we are going to need to 1006 * have the anon's memory resident. ensure that now. 1007 */ 1008 1009 /* 1010 * let uvmfault_anonget do the dirty work. 1011 * if it fails (!OK) it will unlock everything for us. 1012 * if it succeeds, locks are still valid and locked. 1013 * also, if it is OK, then the anon's page is on the queues. 1014 * if the page is on loan from a uvm_object, then anonget will 1015 * lock that object for us if it does not fail. 1016 */ 1017 1018 error = uvmfault_anonget(&ufi, amap, anon); 1019 switch (error) { 1020 case 0: 1021 break; 1022 1023 case ERESTART: 1024 goto ReFault; 1025 1026 case EAGAIN: 1027 tsleep(&lbolt, PVM, "fltagain1", 0); 1028 goto ReFault; 1029 1030 default: 1031 return error; 1032 } 1033 1034 /* 1035 * uobj is non null if the page is on loan from an object (i.e. uobj) 1036 */ 1037 1038 uobj = anon->u.an_page->uobject; /* locked by anonget if !NULL */ 1039 1040 /* locked: maps(read), amap, anon, uobj(if one) */ 1041 1042 /* 1043 * special handling for loaned pages 1044 */ 1045 1046 if (anon->u.an_page->loan_count) { 1047 1048 if (!cow_now) { 1049 1050 /* 1051 * for read faults on loaned pages we just cap the 1052 * protection at read-only. 1053 */ 1054 1055 enter_prot = enter_prot & ~VM_PROT_WRITE; 1056 1057 } else { 1058 /* 1059 * note that we can't allow writes into a loaned page! 1060 * 1061 * if we have a write fault on a loaned page in an 1062 * anon then we need to look at the anon's ref count. 1063 * if it is greater than one then we are going to do 1064 * a normal copy-on-write fault into a new anon (this 1065 * is not a problem). however, if the reference count 1066 * is one (a case where we would normally allow a 1067 * write directly to the page) then we need to kill 1068 * the loan before we continue. 1069 */ 1070 1071 /* >1 case is already ok */ 1072 if (anon->an_ref == 1) { 1073 1074 /* get new un-owned replacement page */ 1075 pg = uvm_pagealloc(NULL, 0, NULL, 0); 1076 if (pg == NULL) { 1077 uvmfault_unlockall(&ufi, amap, uobj, 1078 anon); 1079 uvm_wait("flt_noram2"); 1080 goto ReFault; 1081 } 1082 1083 /* 1084 * copy data, kill loan, and drop uobj lock 1085 * (if any) 1086 */ 1087 /* copy old -> new */ 1088 uvm_pagecopy(anon->u.an_page, pg); 1089 1090 /* force reload */ 1091 pmap_page_protect(anon->u.an_page, 1092 VM_PROT_NONE); 1093 uvm_lock_pageq(); /* KILL loan */ 1094 if (uobj) 1095 /* if we were loaning */ 1096 anon->u.an_page->loan_count--; 1097 anon->u.an_page->uanon = NULL; 1098 /* in case we owned */ 1099 anon->u.an_page->pqflags &= ~PQ_ANON; 1100 uvm_unlock_pageq(); 1101 if (uobj) { 1102 simple_unlock(&uobj->vmobjlock); 1103 uobj = NULL; 1104 } 1105 1106 /* install new page in anon */ 1107 anon->u.an_page = pg; 1108 pg->uanon = anon; 1109 pg->pqflags |= PQ_ANON; 1110 pg->flags &= ~(PG_BUSY|PG_FAKE); 1111 UVM_PAGE_OWN(pg, NULL); 1112 1113 /* done! */ 1114 } /* ref == 1 */ 1115 } /* write fault */ 1116 } /* loan count */ 1117 1118 /* 1119 * if we are case 1B then we will need to allocate a new blank 1120 * anon to transfer the data into. note that we have a lock 1121 * on anon, so no one can busy or release the page until we are done. 1122 * also note that the ref count can't drop to zero here because 1123 * it is > 1 and we are only dropping one ref. 1124 * 1125 * in the (hopefully very rare) case that we are out of RAM we 1126 * will unlock, wait for more RAM, and refault. 1127 * 1128 * if we are out of anon VM we kill the process (XXX: could wait?). 1129 */ 1130 1131 if (cow_now && anon->an_ref > 1) { 1132 1133 UVMHIST_LOG(maphist, " case 1B: COW fault",0,0,0,0); 1134 uvmexp.flt_acow++; 1135 oanon = anon; /* oanon = old, locked anon */ 1136 anon = uvm_analloc(); 1137 if (anon) { 1138 /* new anon is locked! */ 1139 pg = uvm_pagealloc(NULL, 0, anon, 0); 1140 } 1141 1142 /* check for out of RAM */ 1143 if (anon == NULL || pg == NULL) { 1144 if (anon) { 1145 anon->an_ref--; 1146 simple_unlock(&anon->an_lock); 1147 uvm_anfree(anon); 1148 } 1149 uvmfault_unlockall(&ufi, amap, uobj, oanon); 1150 KASSERT(uvmexp.swpgonly <= uvmexp.swpages); 1151 if (anon == NULL || uvmexp.swpgonly == uvmexp.swpages) { 1152 UVMHIST_LOG(maphist, 1153 "<- failed. out of VM",0,0,0,0); 1154 uvmexp.fltnoanon++; 1155 return ENOMEM; 1156 } 1157 1158 uvmexp.fltnoram++; 1159 uvm_wait("flt_noram3"); /* out of RAM, wait for more */ 1160 goto ReFault; 1161 } 1162 1163 /* got all resources, replace anon with nanon */ 1164 uvm_pagecopy(oanon->u.an_page, pg); 1165 uvm_pageactivate(pg); 1166 pg->flags &= ~(PG_BUSY|PG_FAKE); 1167 UVM_PAGE_OWN(pg, NULL); 1168 amap_add(&ufi.entry->aref, ufi.orig_rvaddr - ufi.entry->start, 1169 anon, 1); 1170 1171 /* deref: can not drop to zero here by defn! */ 1172 oanon->an_ref--; 1173 1174 /* 1175 * note: oanon is still locked, as is the new anon. we 1176 * need to check for this later when we unlock oanon; if 1177 * oanon != anon, we'll have to unlock anon, too. 1178 */ 1179 1180 } else { 1181 1182 uvmexp.flt_anon++; 1183 oanon = anon; /* old, locked anon is same as anon */ 1184 pg = anon->u.an_page; 1185 if (anon->an_ref > 1) /* disallow writes to ref > 1 anons */ 1186 enter_prot = enter_prot & ~VM_PROT_WRITE; 1187 1188 } 1189 1190 /* locked: maps(read), amap, oanon, anon (if different from oanon) */ 1191 1192 /* 1193 * now map the page in. 1194 */ 1195 1196 UVMHIST_LOG(maphist, " MAPPING: anon: pm=0x%x, va=0x%x, pg=0x%x", 1197 ufi.orig_map->pmap, ufi.orig_rvaddr, pg, 0); 1198 if (pmap_enter(ufi.orig_map->pmap, ufi.orig_rvaddr, VM_PAGE_TO_PHYS(pg), 1199 enter_prot, access_type | PMAP_CANFAIL | (wired ? PMAP_WIRED : 0)) 1200 != 0) { 1201 1202 /* 1203 * No need to undo what we did; we can simply think of 1204 * this as the pmap throwing away the mapping information. 1205 * 1206 * We do, however, have to go through the ReFault path, 1207 * as the map may change while we're asleep. 1208 */ 1209 1210 if (anon != oanon) 1211 simple_unlock(&anon->an_lock); 1212 uvmfault_unlockall(&ufi, amap, uobj, oanon); 1213 KASSERT(uvmexp.swpgonly <= uvmexp.swpages); 1214 if (uvmexp.swpgonly == uvmexp.swpages) { 1215 UVMHIST_LOG(maphist, 1216 "<- failed. out of VM",0,0,0,0); 1217 /* XXX instrumentation */ 1218 return ENOMEM; 1219 } 1220 /* XXX instrumentation */ 1221 uvm_wait("flt_pmfail1"); 1222 goto ReFault; 1223 } 1224 1225 /* 1226 * ... update the page queues. 1227 */ 1228 1229 uvm_lock_pageq(); 1230 if (wire_fault) { 1231 uvm_pagewire(pg); 1232 1233 /* 1234 * since the now-wired page cannot be paged out, 1235 * release its swap resources for others to use. 1236 * since an anon with no swap cannot be PG_CLEAN, 1237 * clear its clean flag now. 1238 */ 1239 1240 pg->flags &= ~(PG_CLEAN); 1241 uvm_anon_dropswap(anon); 1242 } else { 1243 uvm_pageactivate(pg); 1244 } 1245 uvm_unlock_pageq(); 1246 1247 /* 1248 * done case 1! finish up by unlocking everything and returning success 1249 */ 1250 1251 if (anon != oanon) 1252 simple_unlock(&anon->an_lock); 1253 uvmfault_unlockall(&ufi, amap, uobj, oanon); 1254 pmap_update(ufi.orig_map->pmap); 1255 return 0; 1256 1257 Case2: 1258 /* 1259 * handle case 2: faulting on backing object or zero fill 1260 */ 1261 1262 /* 1263 * locked: 1264 * maps(read), amap(if there), uobj(if !null), uobjpage(if !null) 1265 */ 1266 1267 /* 1268 * note that uobjpage can not be PGO_DONTCARE at this point. we now 1269 * set uobjpage to PGO_DONTCARE if we are doing a zero fill. if we 1270 * have a backing object, check and see if we are going to promote 1271 * the data up to an anon during the fault. 1272 */ 1273 1274 if (uobj == NULL) { 1275 uobjpage = PGO_DONTCARE; 1276 promote = TRUE; /* always need anon here */ 1277 } else { 1278 KASSERT(uobjpage != PGO_DONTCARE); 1279 promote = cow_now && UVM_ET_ISCOPYONWRITE(ufi.entry); 1280 } 1281 UVMHIST_LOG(maphist, " case 2 fault: promote=%d, zfill=%d", 1282 promote, (uobj == NULL), 0,0); 1283 1284 /* 1285 * if uobjpage is not null then we do not need to do I/O to get the 1286 * uobjpage. 1287 * 1288 * if uobjpage is null, then we need to unlock and ask the pager to 1289 * get the data for us. once we have the data, we need to reverify 1290 * the state the world. we are currently not holding any resources. 1291 */ 1292 1293 if (uobjpage) { 1294 /* update rusage counters */ 1295 curproc->p_addr->u_stats.p_ru.ru_minflt++; 1296 } else { 1297 /* update rusage counters */ 1298 curproc->p_addr->u_stats.p_ru.ru_majflt++; 1299 1300 /* locked: maps(read), amap(if there), uobj */ 1301 uvmfault_unlockall(&ufi, amap, NULL, NULL); 1302 /* locked: uobj */ 1303 1304 uvmexp.fltget++; 1305 gotpages = 1; 1306 uoff = (ufi.orig_rvaddr - ufi.entry->start) + ufi.entry->offset; 1307 error = uobj->pgops->pgo_get(uobj, uoff, &uobjpage, &gotpages, 1308 0, access_type & MASK(ufi.entry), ufi.entry->advice, 1309 PGO_SYNCIO); 1310 /* locked: uobjpage(if no error) */ 1311 1312 /* 1313 * recover from I/O 1314 */ 1315 1316 if (error) { 1317 if (error == EAGAIN) { 1318 UVMHIST_LOG(maphist, 1319 " pgo_get says TRY AGAIN!",0,0,0,0); 1320 tsleep(&lbolt, PVM, "fltagain2", 0); 1321 goto ReFault; 1322 } 1323 1324 UVMHIST_LOG(maphist, "<- pgo_get failed (code %d)", 1325 error, 0,0,0); 1326 return error; 1327 } 1328 1329 /* locked: uobjpage */ 1330 1331 uvm_lock_pageq(); 1332 uvm_pageactivate(uobjpage); 1333 uvm_unlock_pageq(); 1334 1335 /* 1336 * re-verify the state of the world by first trying to relock 1337 * the maps. always relock the object. 1338 */ 1339 1340 locked = uvmfault_relock(&ufi); 1341 if (locked && amap) 1342 amap_lock(amap); 1343 simple_lock(&uobj->vmobjlock); 1344 1345 /* locked(locked): maps(read), amap(if !null), uobj, uobjpage */ 1346 /* locked(!locked): uobj, uobjpage */ 1347 1348 /* 1349 * verify that the page has not be released and re-verify 1350 * that amap slot is still free. if there is a problem, 1351 * we unlock and clean up. 1352 */ 1353 1354 if ((uobjpage->flags & PG_RELEASED) != 0 || 1355 (locked && amap && 1356 amap_lookup(&ufi.entry->aref, 1357 ufi.orig_rvaddr - ufi.entry->start))) { 1358 if (locked) 1359 uvmfault_unlockall(&ufi, amap, NULL, NULL); 1360 locked = FALSE; 1361 } 1362 1363 /* 1364 * didn't get the lock? release the page and retry. 1365 */ 1366 1367 if (locked == FALSE) { 1368 UVMHIST_LOG(maphist, 1369 " wasn't able to relock after fault: retry", 1370 0,0,0,0); 1371 if (uobjpage->flags & PG_WANTED) 1372 wakeup(uobjpage); 1373 if (uobjpage->flags & PG_RELEASED) { 1374 uvmexp.fltpgrele++; 1375 uvm_pagefree(uobjpage); 1376 goto ReFault; 1377 } 1378 uobjpage->flags &= ~(PG_BUSY|PG_WANTED); 1379 UVM_PAGE_OWN(uobjpage, NULL); 1380 simple_unlock(&uobj->vmobjlock); 1381 goto ReFault; 1382 } 1383 1384 /* 1385 * we have the data in uobjpage which is busy and 1386 * not released. we are holding object lock (so the page 1387 * can't be released on us). 1388 */ 1389 1390 /* locked: maps(read), amap(if !null), uobj, uobjpage */ 1391 } 1392 1393 /* 1394 * locked: 1395 * maps(read), amap(if !null), uobj(if !null), uobjpage(if uobj) 1396 */ 1397 1398 /* 1399 * notes: 1400 * - at this point uobjpage can not be NULL 1401 * - at this point uobjpage can not be PG_RELEASED (since we checked 1402 * for it above) 1403 * - at this point uobjpage could be PG_WANTED (handle later) 1404 */ 1405 1406 if (promote == FALSE) { 1407 1408 /* 1409 * we are not promoting. if the mapping is COW ensure that we 1410 * don't give more access than we should (e.g. when doing a read 1411 * fault on a COPYONWRITE mapping we want to map the COW page in 1412 * R/O even though the entry protection could be R/W). 1413 * 1414 * set "pg" to the page we want to map in (uobjpage, usually) 1415 */ 1416 1417 /* no anon in this case. */ 1418 anon = NULL; 1419 1420 uvmexp.flt_obj++; 1421 if (UVM_ET_ISCOPYONWRITE(ufi.entry)) 1422 enter_prot &= ~VM_PROT_WRITE; 1423 pg = uobjpage; /* map in the actual object */ 1424 1425 /* assert(uobjpage != PGO_DONTCARE) */ 1426 1427 /* 1428 * we are faulting directly on the page. be careful 1429 * about writing to loaned pages... 1430 */ 1431 1432 if (uobjpage->loan_count) { 1433 if (!cow_now) { 1434 /* read fault: cap the protection at readonly */ 1435 /* cap! */ 1436 enter_prot = enter_prot & ~VM_PROT_WRITE; 1437 } else { 1438 /* write fault: must break the loan here */ 1439 1440 /* alloc new un-owned page */ 1441 pg = uvm_pagealloc(NULL, 0, NULL, 0); 1442 1443 if (pg == NULL) { 1444 1445 /* 1446 * drop ownership of page, it can't 1447 * be released 1448 */ 1449 1450 if (uobjpage->flags & PG_WANTED) 1451 wakeup(uobjpage); 1452 uobjpage->flags &= ~(PG_BUSY|PG_WANTED); 1453 UVM_PAGE_OWN(uobjpage, NULL); 1454 1455 uvmfault_unlockall(&ufi, amap, uobj, 1456 NULL); 1457 UVMHIST_LOG(maphist, 1458 " out of RAM breaking loan, waiting", 1459 0,0,0,0); 1460 uvmexp.fltnoram++; 1461 uvm_wait("flt_noram4"); 1462 goto ReFault; 1463 } 1464 1465 /* 1466 * copy the data from the old page to the new 1467 * one and clear the fake/clean flags on the 1468 * new page (keep it busy). force a reload 1469 * of the old page by clearing it from all 1470 * pmaps. then lock the page queues to 1471 * rename the pages. 1472 */ 1473 1474 uvm_pagecopy(uobjpage, pg); /* old -> new */ 1475 pg->flags &= ~(PG_FAKE|PG_CLEAN); 1476 pmap_page_protect(uobjpage, VM_PROT_NONE); 1477 if (uobjpage->flags & PG_WANTED) 1478 wakeup(uobjpage); 1479 /* uobj still locked */ 1480 uobjpage->flags &= ~(PG_WANTED|PG_BUSY); 1481 UVM_PAGE_OWN(uobjpage, NULL); 1482 1483 uvm_lock_pageq(); 1484 offset = uobjpage->offset; 1485 uvm_pagerealloc(uobjpage, NULL, 0); 1486 1487 /* 1488 * at this point we have absolutely no 1489 * control over uobjpage 1490 */ 1491 1492 /* install new page */ 1493 uvm_pageactivate(pg); 1494 uvm_pagerealloc(pg, uobj, offset); 1495 uvm_unlock_pageq(); 1496 1497 /* 1498 * done! loan is broken and "pg" is 1499 * PG_BUSY. it can now replace uobjpage. 1500 */ 1501 1502 uobjpage = pg; 1503 } 1504 } 1505 } else { 1506 1507 /* 1508 * if we are going to promote the data to an anon we 1509 * allocate a blank anon here and plug it into our amap. 1510 */ 1511 #if DIAGNOSTIC 1512 if (amap == NULL) 1513 panic("uvm_fault: want to promote data, but no anon"); 1514 #endif 1515 1516 anon = uvm_analloc(); 1517 if (anon) { 1518 1519 /* 1520 * The new anon is locked. 1521 * 1522 * In `Fill in data...' below, if 1523 * uobjpage == PGO_DONTCARE, we want 1524 * a zero'd, dirty page, so have 1525 * uvm_pagealloc() do that for us. 1526 */ 1527 1528 pg = uvm_pagealloc(NULL, 0, anon, 1529 (uobjpage == PGO_DONTCARE) ? UVM_PGA_ZERO : 0); 1530 } 1531 1532 /* 1533 * out of memory resources? 1534 */ 1535 1536 if (anon == NULL || pg == NULL) { 1537 if (anon != NULL) { 1538 anon->an_ref--; 1539 simple_unlock(&anon->an_lock); 1540 uvm_anfree(anon); 1541 } 1542 1543 /* 1544 * arg! must unbusy our page and fail or sleep. 1545 */ 1546 1547 if (uobjpage != PGO_DONTCARE) { 1548 if (uobjpage->flags & PG_WANTED) 1549 /* still holding object lock */ 1550 wakeup(uobjpage); 1551 1552 uobjpage->flags &= ~(PG_BUSY|PG_WANTED); 1553 UVM_PAGE_OWN(uobjpage, NULL); 1554 } 1555 1556 /* unlock and fail ... */ 1557 uvmfault_unlockall(&ufi, amap, uobj, NULL); 1558 KASSERT(uvmexp.swpgonly <= uvmexp.swpages); 1559 if (anon == NULL || uvmexp.swpgonly == uvmexp.swpages) { 1560 UVMHIST_LOG(maphist, " promote: out of VM", 1561 0,0,0,0); 1562 uvmexp.fltnoanon++; 1563 return ENOMEM; 1564 } 1565 1566 UVMHIST_LOG(maphist, " out of RAM, waiting for more", 1567 0,0,0,0); 1568 uvmexp.fltnoram++; 1569 uvm_wait("flt_noram5"); 1570 goto ReFault; 1571 } 1572 1573 /* 1574 * fill in the data 1575 */ 1576 1577 if (uobjpage != PGO_DONTCARE) { 1578 uvmexp.flt_prcopy++; 1579 /* copy page [pg now dirty] */ 1580 uvm_pagecopy(uobjpage, pg); 1581 1582 /* 1583 * promote to shared amap? make sure all sharing 1584 * procs see it 1585 */ 1586 1587 if ((amap_flags(amap) & AMAP_SHARED) != 0) { 1588 pmap_page_protect(uobjpage, VM_PROT_NONE); 1589 /* 1590 * XXX: PAGE MIGHT BE WIRED! 1591 */ 1592 } 1593 1594 /* 1595 * dispose of uobjpage. it can't be PG_RELEASED 1596 * since we still hold the object lock. 1597 * drop handle to uobj as well. 1598 */ 1599 1600 if (uobjpage->flags & PG_WANTED) 1601 /* still have the obj lock */ 1602 wakeup(uobjpage); 1603 uobjpage->flags &= ~(PG_BUSY|PG_WANTED); 1604 UVM_PAGE_OWN(uobjpage, NULL); 1605 simple_unlock(&uobj->vmobjlock); 1606 uobj = NULL; 1607 1608 UVMHIST_LOG(maphist, 1609 " promote uobjpage 0x%x to anon/page 0x%x/0x%x", 1610 uobjpage, anon, pg, 0); 1611 1612 } else { 1613 uvmexp.flt_przero++; 1614 1615 /* 1616 * Page is zero'd and marked dirty by uvm_pagealloc() 1617 * above. 1618 */ 1619 1620 UVMHIST_LOG(maphist," zero fill anon/page 0x%x/0%x", 1621 anon, pg, 0, 0); 1622 } 1623 amap_add(&ufi.entry->aref, ufi.orig_rvaddr - ufi.entry->start, 1624 anon, 0); 1625 } 1626 1627 /* 1628 * locked: 1629 * maps(read), amap(if !null), uobj(if !null), uobjpage(if uobj), 1630 * anon(if !null), pg(if anon) 1631 * 1632 * note: pg is either the uobjpage or the new page in the new anon 1633 */ 1634 1635 /* 1636 * all resources are present. we can now map it in and free our 1637 * resources. 1638 */ 1639 1640 UVMHIST_LOG(maphist, 1641 " MAPPING: case2: pm=0x%x, va=0x%x, pg=0x%x, promote=%d", 1642 ufi.orig_map->pmap, ufi.orig_rvaddr, pg, promote); 1643 KASSERT((access_type & VM_PROT_WRITE) == 0 || 1644 (pg->flags & PG_RDONLY) == 0); 1645 if (pmap_enter(ufi.orig_map->pmap, ufi.orig_rvaddr, VM_PAGE_TO_PHYS(pg), 1646 pg->flags & PG_RDONLY ? enter_prot & ~VM_PROT_WRITE : enter_prot, 1647 access_type | PMAP_CANFAIL | (wired ? PMAP_WIRED : 0)) != 0) { 1648 1649 /* 1650 * No need to undo what we did; we can simply think of 1651 * this as the pmap throwing away the mapping information. 1652 * 1653 * We do, however, have to go through the ReFault path, 1654 * as the map may change while we're asleep. 1655 */ 1656 1657 if (pg->flags & PG_WANTED) 1658 wakeup(pg); 1659 1660 /* 1661 * note that pg can't be PG_RELEASED since we did not drop 1662 * the object lock since the last time we checked. 1663 */ 1664 1665 pg->flags &= ~(PG_BUSY|PG_FAKE|PG_WANTED); 1666 UVM_PAGE_OWN(pg, NULL); 1667 uvmfault_unlockall(&ufi, amap, uobj, anon); 1668 KASSERT(uvmexp.swpgonly <= uvmexp.swpages); 1669 if (uvmexp.swpgonly == uvmexp.swpages) { 1670 UVMHIST_LOG(maphist, 1671 "<- failed. out of VM",0,0,0,0); 1672 /* XXX instrumentation */ 1673 return ENOMEM; 1674 } 1675 /* XXX instrumentation */ 1676 uvm_wait("flt_pmfail2"); 1677 goto ReFault; 1678 } 1679 1680 uvm_lock_pageq(); 1681 if (wire_fault) { 1682 uvm_pagewire(pg); 1683 if (pg->pqflags & PQ_AOBJ) { 1684 1685 /* 1686 * since the now-wired page cannot be paged out, 1687 * release its swap resources for others to use. 1688 * since an aobj page with no swap cannot be PG_CLEAN, 1689 * clear its clean flag now. 1690 */ 1691 1692 pg->flags &= ~(PG_CLEAN); 1693 uao_dropswap(uobj, pg->offset >> PAGE_SHIFT); 1694 } 1695 } else { 1696 uvm_pageactivate(pg); 1697 } 1698 uvm_unlock_pageq(); 1699 if (pg->flags & PG_WANTED) 1700 wakeup(pg); 1701 1702 /* 1703 * note that pg can't be PG_RELEASED since we did not drop the object 1704 * lock since the last time we checked. 1705 */ 1706 1707 pg->flags &= ~(PG_BUSY|PG_FAKE|PG_WANTED); 1708 UVM_PAGE_OWN(pg, NULL); 1709 uvmfault_unlockall(&ufi, amap, uobj, anon); 1710 pmap_update(ufi.orig_map->pmap); 1711 UVMHIST_LOG(maphist, "<- done (SUCCESS!)",0,0,0,0); 1712 return 0; 1713 } 1714 1715 /* 1716 * uvm_fault_wire: wire down a range of virtual addresses in a map. 1717 * 1718 * => map may be read-locked by caller, but MUST NOT be write-locked. 1719 * => if map is read-locked, any operations which may cause map to 1720 * be write-locked in uvm_fault() must be taken care of by 1721 * the caller. See uvm_map_pageable(). 1722 */ 1723 1724 int 1725 uvm_fault_wire(map, start, end, fault_type, access_type) 1726 struct vm_map *map; 1727 vaddr_t start, end; 1728 vm_fault_t fault_type; 1729 vm_prot_t access_type; 1730 { 1731 vaddr_t va; 1732 int error; 1733 1734 /* 1735 * now fault it in a page at a time. if the fault fails then we have 1736 * to undo what we have done. note that in uvm_fault VM_PROT_NONE 1737 * is replaced with the max protection if fault_type is VM_FAULT_WIRE. 1738 */ 1739 1740 /* 1741 * XXX work around overflowing a vaddr_t. this prevents us from 1742 * wiring the last page in the address space, though. 1743 */ 1744 if (start > end) { 1745 return EFAULT; 1746 } 1747 1748 for (va = start ; va < end ; va += PAGE_SIZE) { 1749 error = uvm_fault(map, va, fault_type, access_type); 1750 if (error) { 1751 if (va != start) { 1752 uvm_fault_unwire(map, start, va); 1753 } 1754 return error; 1755 } 1756 } 1757 return 0; 1758 } 1759 1760 /* 1761 * uvm_fault_unwire(): unwire range of virtual space. 1762 */ 1763 1764 void 1765 uvm_fault_unwire(map, start, end) 1766 struct vm_map *map; 1767 vaddr_t start, end; 1768 { 1769 vm_map_lock_read(map); 1770 uvm_fault_unwire_locked(map, start, end); 1771 vm_map_unlock_read(map); 1772 } 1773 1774 /* 1775 * uvm_fault_unwire_locked(): the guts of uvm_fault_unwire(). 1776 * 1777 * => map must be at least read-locked. 1778 */ 1779 1780 void 1781 uvm_fault_unwire_locked(map, start, end) 1782 struct vm_map *map; 1783 vaddr_t start, end; 1784 { 1785 struct vm_map_entry *entry; 1786 pmap_t pmap = vm_map_pmap(map); 1787 vaddr_t va; 1788 paddr_t pa; 1789 struct vm_page *pg; 1790 1791 KASSERT((map->flags & VM_MAP_INTRSAFE) == 0); 1792 1793 /* 1794 * we assume that the area we are unwiring has actually been wired 1795 * in the first place. this means that we should be able to extract 1796 * the PAs from the pmap. we also lock out the page daemon so that 1797 * we can call uvm_pageunwire. 1798 */ 1799 1800 uvm_lock_pageq(); 1801 1802 /* 1803 * find the beginning map entry for the region. 1804 */ 1805 1806 KASSERT(start >= vm_map_min(map) && end <= vm_map_max(map)); 1807 if (uvm_map_lookup_entry(map, start, &entry) == FALSE) 1808 panic("uvm_fault_unwire_locked: address not in map"); 1809 1810 for (va = start; va < end; va += PAGE_SIZE) { 1811 if (pmap_extract(pmap, va, &pa) == FALSE) 1812 continue; 1813 1814 /* 1815 * find the map entry for the current address. 1816 */ 1817 1818 KASSERT(va >= entry->start); 1819 while (va >= entry->end) { 1820 KASSERT(entry->next != &map->header && 1821 entry->next->start <= entry->end); 1822 entry = entry->next; 1823 } 1824 1825 /* 1826 * if the entry is no longer wired, tell the pmap. 1827 */ 1828 1829 if (VM_MAPENT_ISWIRED(entry) == 0) 1830 pmap_unwire(pmap, va); 1831 1832 pg = PHYS_TO_VM_PAGE(pa); 1833 if (pg) 1834 uvm_pageunwire(pg); 1835 } 1836 1837 uvm_unlock_pageq(); 1838 } 1839