/
uvm_fault.c
2502 lines (2130 loc) · 64.6 KB
/
uvm_fault.c
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
198
199
200
201
202
203
204
205
206
207
208
209
210
211
212
213
214
215
216
217
218
219
220
221
222
223
224
225
226
227
228
229
230
231
232
233
234
235
236
237
238
239
240
241
242
243
244
245
246
247
248
249
250
251
252
253
254
255
256
257
258
259
260
261
262
263
264
265
266
267
268
269
270
271
272
273
274
275
276
277
278
279
280
281
282
283
284
285
286
287
288
289
290
291
292
293
294
295
296
297
298
299
300
301
302
303
304
305
306
307
308
309
310
311
312
313
314
315
316
317
318
319
320
321
322
323
324
325
326
327
328
329
330
331
332
333
334
335
336
337
338
339
340
341
342
343
344
345
346
347
348
349
350
351
352
353
354
355
356
357
358
359
360
361
362
363
364
365
366
367
368
369
370
371
372
373
374
375
376
377
378
379
380
381
382
383
384
385
386
387
388
389
390
391
392
393
394
395
396
397
398
399
400
401
402
403
404
405
406
407
408
409
410
411
412
413
414
415
416
417
418
419
420
421
422
423
424
425
426
427
428
429
430
431
432
433
434
435
436
437
438
439
440
441
442
443
444
445
446
447
448
449
450
451
452
453
454
455
456
457
458
459
460
461
462
463
464
465
466
467
468
469
470
471
472
473
474
475
476
477
478
479
480
481
482
483
484
485
486
487
488
489
490
491
492
493
494
495
496
497
498
499
500
501
502
503
504
505
506
507
508
509
510
511
512
513
514
515
516
517
518
519
520
521
522
523
524
525
526
527
528
529
530
531
532
533
534
535
536
537
538
539
540
541
542
543
544
545
546
547
548
549
550
551
552
553
554
555
556
557
558
559
560
561
562
563
564
565
566
567
568
569
570
571
572
573
574
575
576
577
578
579
580
581
582
583
584
585
586
587
588
589
590
591
592
593
594
595
596
597
598
599
600
601
602
603
604
605
606
607
608
609
610
611
612
613
614
615
616
617
618
619
620
621
622
623
624
625
626
627
628
629
630
631
632
633
634
635
636
637
638
639
640
641
642
643
644
645
646
647
648
649
650
651
652
653
654
655
656
657
658
659
660
661
662
663
664
665
666
667
668
669
670
671
672
673
674
675
676
677
678
679
680
681
682
683
684
685
686
687
688
689
690
691
692
693
694
695
696
697
698
699
700
701
702
703
704
705
706
707
708
709
710
711
712
713
714
715
716
717
718
719
720
721
722
723
724
725
726
727
728
729
730
731
732
733
734
735
736
737
738
739
740
741
742
743
744
745
746
747
748
749
750
751
752
753
754
755
756
757
758
759
760
761
762
763
764
765
766
767
768
769
770
771
772
773
774
775
776
777
778
779
780
781
782
783
784
785
786
787
788
789
790
791
792
793
794
795
796
797
798
799
800
801
802
803
804
805
806
807
808
809
810
811
812
813
814
815
816
817
818
819
820
821
822
823
824
825
826
827
828
829
830
831
832
833
834
835
836
837
838
839
840
841
842
843
844
845
846
847
848
849
850
851
852
853
854
855
856
857
858
859
860
861
862
863
864
865
866
867
868
869
870
871
872
873
874
875
876
877
878
879
880
881
882
883
884
885
886
887
888
889
890
891
892
893
894
895
896
897
898
899
900
901
902
903
904
905
906
907
908
909
910
911
912
913
914
915
916
917
918
919
920
921
922
923
924
925
926
927
928
929
930
931
932
933
934
935
936
937
938
939
940
941
942
943
944
945
946
947
948
949
950
951
952
953
954
955
956
957
958
959
960
961
962
963
964
965
966
967
968
969
970
971
972
973
974
975
976
977
978
979
980
981
982
983
984
985
986
987
988
989
990
991
992
993
994
995
996
997
998
999
1000
/* $NetBSD: uvm_fault.c,v 1.206.2.3 2023/08/15 09:46:23 martin Exp $ */
/*
* Copyright (c) 1997 Charles D. Cranor and Washington University.
* All rights reserved.
*
* Redistribution and use in source and binary forms, with or without
* modification, are permitted provided that the following conditions
* are met:
* 1. Redistributions of source code must retain the above copyright
* notice, this list of conditions and the following disclaimer.
* 2. Redistributions in binary form must reproduce the above copyright
* notice, this list of conditions and the following disclaimer in the
* documentation and/or other materials provided with the distribution.
*
* THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS OR
* IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES
* OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED.
* IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY DIRECT, INDIRECT,
* INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT
* NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
* DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
* THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
* (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF
* THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
*
* from: Id: uvm_fault.c,v 1.1.2.23 1998/02/06 05:29:05 chs Exp
*/
/*
* uvm_fault.c: fault handler
*/
#include <sys/cdefs.h>
__KERNEL_RCSID(0, "$NetBSD: uvm_fault.c,v 1.206.2.3 2023/08/15 09:46:23 martin Exp $");
#include "opt_uvmhist.h"
#include <sys/param.h>
#include <sys/systm.h>
#include <sys/kernel.h>
#include <sys/mman.h>
#include <uvm/uvm.h>
/*
*
* a word on page faults:
*
* types of page faults we handle:
*
* CASE 1: upper layer faults CASE 2: lower layer faults
*
* CASE 1A CASE 1B CASE 2A CASE 2B
* read/write1 write>1 read/write +-cow_write/zero
* | | | |
* +--|--+ +--|--+ +-----+ + | + | +-----+
* amap | V | | ---------> new | | | | ^ |
* +-----+ +-----+ +-----+ + | + | +--|--+
* | | |
* +-----+ +-----+ +--|--+ | +--|--+
* uobj | d/c | | d/c | | V | +----+ |
* +-----+ +-----+ +-----+ +-----+
*
* d/c = don't care
*
* case [0]: layerless fault
* no amap or uobj is present. this is an error.
*
* case [1]: upper layer fault [anon active]
* 1A: [read] or [write with anon->an_ref == 1]
* I/O takes place in upper level anon and uobj is not touched.
* 1B: [write with anon->an_ref > 1]
* new anon is alloc'd and data is copied off ["COW"]
*
* case [2]: lower layer fault [uobj]
* 2A: [read on non-NULL uobj] or [write to non-copy_on_write area]
* I/O takes place directly in object.
* 2B: [write to copy_on_write] or [read on NULL uobj]
* data is "promoted" from uobj to a new anon.
* if uobj is null, then we zero fill.
*
* we follow the standard UVM locking protocol ordering:
*
* MAPS => AMAP => UOBJ => ANON => PAGE QUEUES (PQ)
* we hold a PG_BUSY page if we unlock for I/O
*
*
* the code is structured as follows:
*
* - init the "IN" params in the ufi structure
* ReFault: (ERESTART returned to the loop in uvm_fault_internal)
* - do lookups [locks maps], check protection, handle needs_copy
* - check for case 0 fault (error)
* - establish "range" of fault
* - if we have an amap lock it and extract the anons
* - if sequential advice deactivate pages behind us
* - at the same time check pmap for unmapped areas and anon for pages
* that we could map in (and do map it if found)
* - check object for resident pages that we could map in
* - if (case 2) goto Case2
* - >>> handle case 1
* - ensure source anon is resident in RAM
* - if case 1B alloc new anon and copy from source
* - map the correct page in
* Case2:
* - >>> handle case 2
* - ensure source page is resident (if uobj)
* - if case 2B alloc new anon and copy from source (could be zero
* fill if uobj == NULL)
* - map the correct page in
* - done!
*
* note on paging:
* if we have to do I/O we place a PG_BUSY page in the correct object,
* unlock everything, and do the I/O. when I/O is done we must reverify
* the state of the world before assuming that our data structures are
* valid. [because mappings could change while the map is unlocked]
*
* alternative 1: unbusy the page in question and restart the page fault
* from the top (ReFault). this is easy but does not take advantage
* of the information that we already have from our previous lookup,
* although it is possible that the "hints" in the vm_map will help here.
*
* alternative 2: the system already keeps track of a "version" number of
* a map. [i.e. every time you write-lock a map (e.g. to change a
* mapping) you bump the version number up by one...] so, we can save
* the version number of the map before we release the lock and start I/O.
* then when I/O is done we can relock and check the version numbers
* to see if anything changed. this might save us some over 1 because
* we don't have to unbusy the page and may be less compares(?).
*
* alternative 3: put in backpointers or a way to "hold" part of a map
* in place while I/O is in progress. this could be complex to
* implement (especially with structures like amap that can be referenced
* by multiple map entries, and figuring out what should wait could be
* complex as well...).
*
* we use alternative 2. given that we are multi-threaded now we may want
* to reconsider the choice.
*/
/*
* local data structures
*/
struct uvm_advice {
int advice;
int nback;
int nforw;
};
/*
* page range array:
* note: index in array must match "advice" value
* XXX: borrowed numbers from freebsd. do they work well for us?
*/
static const struct uvm_advice uvmadvice[] = {
{ UVM_ADV_NORMAL, 3, 4 },
{ UVM_ADV_RANDOM, 0, 0 },
{ UVM_ADV_SEQUENTIAL, 8, 7},
};
#define UVM_MAXRANGE 16 /* must be MAX() of nback+nforw+1 */
/*
* private prototypes
*/
/*
* externs from other modules
*/
extern int start_init_exec; /* Is init_main() done / init running? */
/*
* inline functions
*/
/*
* uvmfault_anonflush: try and deactivate pages in specified anons
*
* => does not have to deactivate page if it is busy
*/
static inline void
uvmfault_anonflush(struct vm_anon **anons, int n)
{
int lcv;
struct vm_page *pg;
for (lcv = 0; lcv < n; lcv++) {
if (anons[lcv] == NULL)
continue;
KASSERT(mutex_owned(anons[lcv]->an_lock));
pg = anons[lcv]->an_page;
if (pg && (pg->flags & PG_BUSY) == 0) {
mutex_enter(&uvm_pageqlock);
if (pg->wire_count == 0) {
uvm_pagedeactivate(pg);
}
mutex_exit(&uvm_pageqlock);
}
}
}
/*
* normal functions
*/
/*
* uvmfault_amapcopy: clear "needs_copy" in a map.
*
* => called with VM data structures unlocked (usually, see below)
* => we get a write lock on the maps and clear needs_copy for a VA
* => if we are out of RAM we sleep (waiting for more)
*/
static void
uvmfault_amapcopy(struct uvm_faultinfo *ufi)
{
for (;;) {
/*
* no mapping? give up.
*/
if (uvmfault_lookup(ufi, true) == false)
return;
/*
* copy if needed.
*/
if (UVM_ET_ISNEEDSCOPY(ufi->entry))
amap_copy(ufi->map, ufi->entry, AMAP_COPY_NOWAIT,
ufi->orig_rvaddr, ufi->orig_rvaddr + 1);
/*
* didn't work? must be out of RAM. unlock and sleep.
*/
if (UVM_ET_ISNEEDSCOPY(ufi->entry)) {
uvmfault_unlockmaps(ufi, true);
uvm_wait("fltamapcopy");
continue;
}
/*
* got it! unlock and return.
*/
uvmfault_unlockmaps(ufi, true);
return;
}
/*NOTREACHED*/
}
/*
* uvmfault_anonget: get data in an anon into a non-busy, non-released
* page in that anon.
*
* => Map, amap and thus anon should be locked by caller.
* => If we fail, we unlock everything and error is returned.
* => If we are successful, return with everything still locked.
* => We do not move the page on the queues [gets moved later]. If we
* allocate a new page [we_own], it gets put on the queues. Either way,
* the result is that the page is on the queues at return time
* => For pages which are on loan from a uvm_object (and thus are not owned
* by the anon): if successful, return with the owning object locked.
* The caller must unlock this object when it unlocks everything else.
*/
int
uvmfault_anonget(struct uvm_faultinfo *ufi, struct vm_amap *amap,
struct vm_anon *anon)
{
struct vm_page *pg;
int error;
UVMHIST_FUNC("uvmfault_anonget"); UVMHIST_CALLED(maphist);
KASSERT(mutex_owned(anon->an_lock));
KASSERT(anon->an_lock == amap->am_lock);
/* Increment the counters.*/
uvmexp.fltanget++;
if (anon->an_page) {
curlwp->l_ru.ru_minflt++;
} else {
curlwp->l_ru.ru_majflt++;
}
error = 0;
/*
* Loop until we get the anon data, or fail.
*/
for (;;) {
bool we_own, locked;
/*
* Note: 'we_own' will become true if we set PG_BUSY on a page.
*/
we_own = false;
pg = anon->an_page;
/*
* If there is a resident page and it is loaned, then anon
* may not own it. Call out to uvm_anon_lockloanpg() to
* identify and lock the real owner of the page.
*/
if (pg && pg->loan_count)
pg = uvm_anon_lockloanpg(anon);
/*
* Is page resident? Make sure it is not busy/released.
*/
if (pg) {
/*
* at this point, if the page has a uobject [meaning
* we have it on loan], then that uobject is locked
* by us! if the page is busy, we drop all the
* locks (including uobject) and try again.
*/
if ((pg->flags & PG_BUSY) == 0) {
UVMHIST_LOG(maphist, "<- OK",0,0,0,0);
return 0;
}
pg->flags |= PG_WANTED;
uvmexp.fltpgwait++;
/*
* The last unlock must be an atomic unlock and wait
* on the owner of page.
*/
if (pg->uobject) {
/* Owner of page is UVM object. */
uvmfault_unlockall(ufi, amap, NULL);
UVMHIST_LOG(maphist, " unlock+wait on uobj",0,
0,0,0);
UVM_UNLOCK_AND_WAIT(pg,
pg->uobject->vmobjlock,
false, "anonget1", 0);
} else {
/* Owner of page is anon. */
uvmfault_unlockall(ufi, NULL, NULL);
UVMHIST_LOG(maphist, " unlock+wait on anon",0,
0,0,0);
UVM_UNLOCK_AND_WAIT(pg, anon->an_lock,
false, "anonget2", 0);
}
} else {
#if defined(VMSWAP)
/*
* No page, therefore allocate one.
*/
pg = uvm_pagealloc(NULL,
ufi != NULL ? ufi->orig_rvaddr : 0,
anon, ufi != NULL ? UVM_FLAG_COLORMATCH : 0);
if (pg == NULL) {
/* Out of memory. Wait a little. */
uvmfault_unlockall(ufi, amap, NULL);
uvmexp.fltnoram++;
UVMHIST_LOG(maphist, " noram -- UVM_WAIT",0,
0,0,0);
if (!uvm_reclaimable()) {
return ENOMEM;
}
uvm_wait("flt_noram1");
} else {
/* PG_BUSY bit is set. */
we_own = true;
uvmfault_unlockall(ufi, amap, NULL);
/*
* Pass a PG_BUSY+PG_FAKE+PG_CLEAN page into
* the uvm_swap_get() function with all data
* structures unlocked. Note that it is OK
* to read an_swslot here, because we hold
* PG_BUSY on the page.
*/
uvmexp.pageins++;
error = uvm_swap_get(pg, anon->an_swslot,
PGO_SYNCIO);
/*
* We clean up after the I/O below in the
* 'we_own' case.
*/
}
#else
panic("%s: no page", __func__);
#endif /* defined(VMSWAP) */
}
/*
* Re-lock the map and anon.
*/
locked = uvmfault_relock(ufi);
if (locked || we_own) {
mutex_enter(anon->an_lock);
}
/*
* If we own the page (i.e. we set PG_BUSY), then we need
* to clean up after the I/O. There are three cases to
* consider:
*
* 1) Page was released during I/O: free anon and ReFault.
* 2) I/O not OK. Free the page and cause the fault to fail.
* 3) I/O OK! Activate the page and sync with the non-we_own
* case (i.e. drop anon lock if not locked).
*/
if (we_own) {
#if defined(VMSWAP)
if (pg->flags & PG_WANTED) {
wakeup(pg);
}
if (error) {
/*
* Remove the swap slot from the anon and
* mark the anon as having no real slot.
* Do not free the swap slot, thus preventing
* it from being used again.
*/
if (anon->an_swslot > 0) {
uvm_swap_markbad(anon->an_swslot, 1);
}
anon->an_swslot = SWSLOT_BAD;
if ((pg->flags & PG_RELEASED) != 0) {
goto released;
}
/*
* Note: page was never !PG_BUSY, so it
* cannot be mapped and thus no need to
* pmap_page_protect() it.
*/
mutex_enter(&uvm_pageqlock);
uvm_pagefree(pg);
mutex_exit(&uvm_pageqlock);
if (locked) {
uvmfault_unlockall(ufi, NULL, NULL);
}
mutex_exit(anon->an_lock);
UVMHIST_LOG(maphist, "<- ERROR", 0,0,0,0);
return error;
}
if ((pg->flags & PG_RELEASED) != 0) {
released:
KASSERT(anon->an_ref == 0);
/*
* Released while we had unlocked amap.
*/
if (locked) {
uvmfault_unlockall(ufi, NULL, NULL);
}
uvm_anon_release(anon);
if (error) {
UVMHIST_LOG(maphist,
"<- ERROR/RELEASED", 0,0,0,0);
return error;
}
UVMHIST_LOG(maphist, "<- RELEASED", 0,0,0,0);
return ERESTART;
}
/*
* We have successfully read the page, activate it.
*/
mutex_enter(&uvm_pageqlock);
uvm_pageactivate(pg);
mutex_exit(&uvm_pageqlock);
pg->flags &= ~(PG_WANTED|PG_BUSY|PG_FAKE);
UVM_PAGE_OWN(pg, NULL);
#else
panic("%s: we_own", __func__);
#endif /* defined(VMSWAP) */
}
/*
* We were not able to re-lock the map - restart the fault.
*/
if (!locked) {
if (we_own) {
mutex_exit(anon->an_lock);
}
UVMHIST_LOG(maphist, "<- REFAULT", 0,0,0,0);
return ERESTART;
}
/*
* Verify that no one has touched the amap and moved
* the anon on us.
*/
if (ufi != NULL && amap_lookup(&ufi->entry->aref,
ufi->orig_rvaddr - ufi->entry->start) != anon) {
uvmfault_unlockall(ufi, amap, NULL);
UVMHIST_LOG(maphist, "<- REFAULT", 0,0,0,0);
return ERESTART;
}
/*
* Retry..
*/
uvmexp.fltanretry++;
continue;
}
/*NOTREACHED*/
}
/*
* uvmfault_promote: promote data to a new anon. used for 1B and 2B.
*
* 1. allocate an anon and a page.
* 2. fill its contents.
* 3. put it into amap.
*
* => if we fail (result != 0) we unlock everything.
* => on success, return a new locked anon via 'nanon'.
* (*nanon)->an_page will be a resident, locked, dirty page.
* => it's caller's responsibility to put the promoted nanon->an_page to the
* page queue.
*/
static int
uvmfault_promote(struct uvm_faultinfo *ufi,
struct vm_anon *oanon,
struct vm_page *uobjpage,
struct vm_anon **nanon, /* OUT: allocated anon */
struct vm_anon **spare)
{
struct vm_amap *amap = ufi->entry->aref.ar_amap;
struct uvm_object *uobj;
struct vm_anon *anon;
struct vm_page *pg;
struct vm_page *opg;
int error;
UVMHIST_FUNC(__func__); UVMHIST_CALLED(maphist);
if (oanon) {
/* anon COW */
opg = oanon->an_page;
KASSERT(opg != NULL);
KASSERT(opg->uobject == NULL || opg->loan_count > 0);
} else if (uobjpage != PGO_DONTCARE) {
/* object-backed COW */
opg = uobjpage;
} else {
/* ZFOD */
opg = NULL;
}
if (opg != NULL) {
uobj = opg->uobject;
} else {
uobj = NULL;
}
KASSERT(amap != NULL);
KASSERT(uobjpage != NULL);
KASSERT(uobjpage == PGO_DONTCARE || (uobjpage->flags & PG_BUSY) != 0);
KASSERT(mutex_owned(amap->am_lock));
KASSERT(oanon == NULL || amap->am_lock == oanon->an_lock);
KASSERT(uobj == NULL || mutex_owned(uobj->vmobjlock));
if (*spare != NULL) {
anon = *spare;
*spare = NULL;
} else {
anon = uvm_analloc();
}
if (anon) {
/*
* The new anon is locked.
*
* if opg == NULL, we want a zero'd, dirty page,
* so have uvm_pagealloc() do that for us.
*/
KASSERT(anon->an_lock == NULL);
anon->an_lock = amap->am_lock;
pg = uvm_pagealloc(NULL, ufi->orig_rvaddr, anon,
UVM_FLAG_COLORMATCH | (opg == NULL ? UVM_PGA_ZERO : 0));
if (pg == NULL) {
anon->an_lock = NULL;
}
} else {
pg = NULL;
}
/*
* out of memory resources?
*/
if (pg == NULL) {
/* save anon for the next try. */
if (anon != NULL) {
*spare = anon;
}
/* unlock and fail ... */
uvm_page_unbusy(&uobjpage, 1);
uvmfault_unlockall(ufi, amap, uobj);
if (!uvm_reclaimable()) {
UVMHIST_LOG(maphist, "out of VM", 0,0,0,0);
uvmexp.fltnoanon++;
error = ENOMEM;
goto done;
}
UVMHIST_LOG(maphist, "out of RAM, waiting for more", 0,0,0,0);
uvmexp.fltnoram++;
uvm_wait("flt_noram5");
error = ERESTART;
goto done;
}
/*
* copy the page [pg now dirty]
*
* Remove the pmap entry now for the old page at this address
* so that no thread can modify the new page while any thread
* might still see the old page.
*/
if (opg) {
pmap_remove(vm_map_pmap(ufi->orig_map), ufi->orig_rvaddr,
ufi->orig_rvaddr + PAGE_SIZE);
pmap_update(vm_map_pmap(ufi->orig_map));
uvm_pagecopy(opg, pg);
}
amap_add(&ufi->entry->aref, ufi->orig_rvaddr - ufi->entry->start, anon,
oanon != NULL);
*nanon = anon;
error = 0;
done:
return error;
}
/*
* Update statistics after fault resolution.
* - maxrss
*/
void
uvmfault_update_stats(struct uvm_faultinfo *ufi)
{
struct vm_map *map;
struct vmspace *vm;
struct proc *p;
vsize_t res;
map = ufi->orig_map;
p = curproc;
KASSERT(p != NULL);
vm = p->p_vmspace;
if (&vm->vm_map != map)
return;
res = pmap_resident_count(map->pmap);
if (vm->vm_rssmax < res)
vm->vm_rssmax = res;
}
/*
* F A U L T - m a i n e n t r y p o i n t
*/
/*
* uvm_fault: page fault handler
*
* => called from MD code to resolve a page fault
* => VM data structures usually should be unlocked. however, it is
* possible to call here with the main map locked if the caller
* gets a write lock, sets it recusive, and then calls us (c.f.
* uvm_map_pageable). this should be avoided because it keeps
* the map locked off during I/O.
* => MUST NEVER BE CALLED IN INTERRUPT CONTEXT
*/
#define MASK(entry) (UVM_ET_ISCOPYONWRITE(entry) ? \
~VM_PROT_WRITE : VM_PROT_ALL)
/* fault_flag values passed from uvm_fault_wire to uvm_fault_internal */
#define UVM_FAULT_WIRE (1 << 0)
#define UVM_FAULT_MAXPROT (1 << 1)
struct uvm_faultctx {
/*
* the following members are set up by uvm_fault_check() and
* read-only after that.
*
* note that narrow is used by uvm_fault_check() to change
* the behaviour after ERESTART.
*
* most of them might change after RESTART if the underlying
* map entry has been changed behind us. an exception is
* wire_paging, which does never change.
*/
vm_prot_t access_type;
vaddr_t startva;
int npages;
int centeridx;
bool narrow; /* work on a single requested page only */
bool wire_mapping; /* request a PMAP_WIRED mapping
(UVM_FAULT_WIRE or VM_MAPENT_ISWIRED) */
bool wire_paging; /* request uvm_pagewire
(true for UVM_FAULT_WIRE) */
bool cow_now; /* VM_PROT_WRITE is actually requested
(ie. should break COW and page loaning) */
/*
* enter_prot is set up by uvm_fault_check() and clamped
* (ie. drop the VM_PROT_WRITE bit) in various places in case
* of !cow_now.
*/
vm_prot_t enter_prot; /* prot at which we want to enter pages in */
/*
* the following member is for uvmfault_promote() and ERESTART.
*/
struct vm_anon *anon_spare;
/*
* the folloing is actually a uvm_fault_lower() internal.
* it's here merely for debugging.
* (or due to the mechanical separation of the function?)
*/
bool promote;
};
static inline int uvm_fault_check(
struct uvm_faultinfo *, struct uvm_faultctx *,
struct vm_anon ***, bool);
static int uvm_fault_upper(
struct uvm_faultinfo *, struct uvm_faultctx *,
struct vm_anon **);
static inline int uvm_fault_upper_lookup(
struct uvm_faultinfo *, const struct uvm_faultctx *,
struct vm_anon **, struct vm_page **);
static inline void uvm_fault_upper_neighbor(
struct uvm_faultinfo *, const struct uvm_faultctx *,
vaddr_t, struct vm_page *, bool);
static inline int uvm_fault_upper_loan(
struct uvm_faultinfo *, struct uvm_faultctx *,
struct vm_anon *, struct uvm_object **);
static inline int uvm_fault_upper_promote(
struct uvm_faultinfo *, struct uvm_faultctx *,
struct uvm_object *, struct vm_anon *);
static inline int uvm_fault_upper_direct(
struct uvm_faultinfo *, struct uvm_faultctx *,
struct uvm_object *, struct vm_anon *);
static int uvm_fault_upper_enter(
struct uvm_faultinfo *, const struct uvm_faultctx *,
struct uvm_object *, struct vm_anon *,
struct vm_page *, struct vm_anon *);
static inline void uvm_fault_upper_done(
struct uvm_faultinfo *, const struct uvm_faultctx *,
struct vm_anon *, struct vm_page *);
static int uvm_fault_lower(
struct uvm_faultinfo *, struct uvm_faultctx *,
struct vm_page **);
static inline void uvm_fault_lower_lookup(
struct uvm_faultinfo *, const struct uvm_faultctx *,
struct vm_page **);
static inline void uvm_fault_lower_neighbor(
struct uvm_faultinfo *, const struct uvm_faultctx *,
vaddr_t, struct vm_page *, bool);
static inline int uvm_fault_lower_io(
struct uvm_faultinfo *, const struct uvm_faultctx *,
struct uvm_object **, struct vm_page **);
static inline int uvm_fault_lower_direct(
struct uvm_faultinfo *, struct uvm_faultctx *,
struct uvm_object *, struct vm_page *);
static inline int uvm_fault_lower_direct_loan(
struct uvm_faultinfo *, struct uvm_faultctx *,
struct uvm_object *, struct vm_page **,
struct vm_page **);
static inline int uvm_fault_lower_promote(
struct uvm_faultinfo *, struct uvm_faultctx *,
struct uvm_object *, struct vm_page *);
static int uvm_fault_lower_enter(
struct uvm_faultinfo *, const struct uvm_faultctx *,
struct uvm_object *,
struct vm_anon *, struct vm_page *);
static inline void uvm_fault_lower_done(
struct uvm_faultinfo *, const struct uvm_faultctx *,
struct uvm_object *, struct vm_page *);
int
uvm_fault_internal(struct vm_map *orig_map, vaddr_t vaddr,
vm_prot_t access_type, int fault_flag)
{
struct cpu_data *cd;
struct uvm_cpu *ucpu;
struct uvm_faultinfo ufi;
struct uvm_faultctx flt = {
.access_type = access_type,
/* don't look for neighborhood * pages on "wire" fault */
.narrow = (fault_flag & UVM_FAULT_WIRE) != 0,
/* "wire" fault causes wiring of both mapping and paging */
.wire_mapping = (fault_flag & UVM_FAULT_WIRE) != 0,
.wire_paging = (fault_flag & UVM_FAULT_WIRE) != 0,
};
const bool maxprot = (fault_flag & UVM_FAULT_MAXPROT) != 0;
struct vm_anon *anons_store[UVM_MAXRANGE], **anons;
struct vm_page *pages_store[UVM_MAXRANGE], **pages;
int error;
UVMHIST_FUNC("uvm_fault"); UVMHIST_CALLED(maphist);
UVMHIST_LOG(maphist, "(map=%#jx, vaddr=%#jx, at=%jd, ff=%jd)",
(uintptr_t)orig_map, vaddr, access_type, fault_flag);
cd = &(curcpu()->ci_data);
cd->cpu_nfault++;
ucpu = cd->cpu_uvm;
/* Don't flood RNG subsystem with samples. */
if (cd->cpu_nfault % 503)
goto norng;
/* Don't count anything until user interaction is possible */
if (__predict_true(start_init_exec)) {
kpreempt_disable();
rnd_add_uint32(&ucpu->rs,
sizeof(vaddr_t) == sizeof(uint32_t) ?
(uint32_t)vaddr : sizeof(vaddr_t) ==
sizeof(uint64_t) ?
(uint32_t)(vaddr & 0x00000000ffffffff) :
(uint32_t)(cd->cpu_nfault & 0x00000000ffffffff));
kpreempt_enable();
}
norng:
/*
* init the IN parameters in the ufi
*/
ufi.orig_map = orig_map;
ufi.orig_rvaddr = trunc_page(vaddr);
ufi.orig_size = PAGE_SIZE; /* can't get any smaller than this */
error = ERESTART;
while (error == ERESTART) { /* ReFault: */
anons = anons_store;
pages = pages_store;
error = uvm_fault_check(&ufi, &flt, &anons, maxprot);
if (error != 0)
continue;
error = uvm_fault_upper_lookup(&ufi, &flt, anons, pages);
if (error != 0)
continue;
if (pages[flt.centeridx] == PGO_DONTCARE)
error = uvm_fault_upper(&ufi, &flt, anons);
else {
struct uvm_object * const uobj =
ufi.entry->object.uvm_obj;
if (uobj && uobj->pgops->pgo_fault != NULL) {
/*
* invoke "special" fault routine.
*/
mutex_enter(uobj->vmobjlock);
/* locked: maps(read), amap(if there), uobj */
error = uobj->pgops->pgo_fault(&ufi,
flt.startva, pages, flt.npages,
flt.centeridx, flt.access_type,
PGO_LOCKED|PGO_SYNCIO);
/*
* locked: nothing, pgo_fault has unlocked
* everything
*/
/*
* object fault routine responsible for
* pmap_update().
*/
/*
* Wake up the pagedaemon if the fault method
* failed for lack of memory but some can be
* reclaimed.
*/
if (error == ENOMEM && uvm_reclaimable()) {
uvm_wait("pgo_fault");
error = ERESTART;
}
} else {
error = uvm_fault_lower(&ufi, &flt, pages);
}
}
}
if (flt.anon_spare != NULL) {
flt.anon_spare->an_ref--;
KASSERT(flt.anon_spare->an_ref == 0);
KASSERT(flt.anon_spare->an_lock == NULL);
uvm_anon_free(flt.anon_spare);
}
return error;
}
/*
* uvm_fault_check: check prot, handle needs-copy, etc.
*
* 1. lookup entry.
* 2. check protection.
* 3. adjust fault condition (mainly for simulated fault).
* 4. handle needs-copy (lazy amap copy).
* 5. establish range of interest for neighbor fault (aka pre-fault).
* 6. look up anons (if amap exists).
* 7. flush pages (if MADV_SEQUENTIAL)
*
* => called with nothing locked.
* => if we fail (result != 0) we unlock everything.
* => initialize/adjust many members of flt.
*/
static int
uvm_fault_check(
struct uvm_faultinfo *ufi, struct uvm_faultctx *flt,
struct vm_anon ***ranons, bool maxprot)
{
struct vm_amap *amap;
struct uvm_object *uobj;
vm_prot_t check_prot;
int nback, nforw;
UVMHIST_FUNC("uvm_fault_check"); UVMHIST_CALLED(maphist);
/*
* lookup and lock the maps
*/
if (uvmfault_lookup(ufi, false) == false) {
UVMHIST_LOG(maphist, "<- no mapping @ 0x%#jx", ufi->orig_rvaddr,
0,0,0);
return EFAULT;
}
/* locked: maps(read) */
#ifdef DIAGNOSTIC
if ((ufi->map->flags & VM_MAP_PAGEABLE) == 0) {
printf("Page fault on non-pageable map:\n");
printf("ufi->map = %p\n", ufi->map);
printf("ufi->orig_map = %p\n", ufi->orig_map);
printf("ufi->orig_rvaddr = 0x%lx\n", (u_long) ufi->orig_rvaddr);
panic("uvm_fault: (ufi->map->flags & VM_MAP_PAGEABLE) == 0");
}
#endif
/*
* check protection
*/
check_prot = maxprot ?
ufi->entry->max_protection : ufi->entry->protection;
if ((check_prot & flt->access_type) != flt->access_type) {
UVMHIST_LOG(maphist,
"<- protection failure (prot=%#jx, access=%#jx)",
ufi->entry->protection, flt->access_type, 0, 0);
uvmfault_unlockmaps(ufi, false);
return EFAULT;
}
/*