aboutsummaryrefslogtreecommitdiff
path: root/arch/x86/mm/fault.c
blob: a530b230e7d7e3d71c5183edf4575c143ed914fe (plain)
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
1001
1002
1003
1004
1005
1006
1007
1008
1009
1010
1011
1012
1013
1014
1015
1016
1017
1018
1019
1020
1021
1022
1023
1024
1025
1026
1027
1028
1029
1030
1031
1032
1033
1034
1035
1036
1037
1038
1039
1040
1041
1042
1043
1044
1045
1046
1047
1048
1049
1050
1051
1052
1053
1054
1055
1056
1057
1058
1059
1060
1061
1062
1063
1064
1065
1066
1067
1068
1069
1070
1071
1072
1073
1074
1075
1076
1077
1078
1079
1080
1081
1082
1083
1084
1085
1086
1087
1088
1089
1090
1091
1092
1093
1094
1095
1096
1097
1098
1099
1100
1101
1102
1103
1104
1105
1106
1107
1108
1109
1110
1111
1112
1113
1114
1115
1116
1117
1118
1119
1120
1121
1122
1123
1124
1125
1126
1127
1128
1129
1130
1131
1132
1133
1134
1135
1136
1137
1138
1139
1140
1141
1142
1143
1144
1145
1146
1147
1148
1149
1150
1151
1152
1153
1154
1155
1156
1157
1158
1159
1160
1161
1162
1163
1164
1165
1166
1167
1168
1169
1170
1171
1172
1173
1174
1175
1176
1177
1178
1179
1180
1181
1182
1183
1184
1185
1186
1187
1188
1189
1190
1191
1192
1193
1194
1195
1196
1197
1198
1199
1200
1201
1202
1203
1204
1205
1206
1207
1208
1209
1210
1211
1212
1213
1214
1215
1216
1217
1218
1219
1220
1221
1222
1223
1224
1225
1226
1227
1228
1229
1230
1231
1232
1233
1234
1235
1236
1237
1238
/*
 *  Copyright (C) 1995  Linus Torvalds
 *  Copyright (C) 2001, 2002 Andi Kleen, SuSE Labs.
 *  Copyright (C) 2008-2009, Red Hat Inc., Ingo Molnar
 */
#include <linux/magic.h>		/* STACK_END_MAGIC		*/
#include <linux/sched.h>		/* test_thread_flag(), ...	*/
#include <linux/kdebug.h>		/* oops_begin/end, ...		*/
#include <linux/module.h>		/* search_exception_table	*/
#include <linux/bootmem.h>		/* max_low_pfn			*/
#include <linux/kprobes.h>		/* __kprobes, ...		*/
#include <linux/mmiotrace.h>		/* kmmio_handler, ...		*/
#include <linux/perf_event.h>		/* perf_sw_event		*/
#include <linux/hugetlb.h>		/* hstate_index_to_shift	*/
#include <linux/prefetch.h>		/* prefetchw			*/

#include <asm/traps.h>			/* dotraplinkage, ...		*/
#include <asm/pgalloc.h>		/* pgd_*(), ...			*/
#include <asm/kmemcheck.h>		/* kmemcheck_*(), ...		*/
#include <asm/fixmap.h>			/* VSYSCALL_START		*/
#include <asm/rcu.h>			/* exception_enter(), ...	*/

/*
 * Page fault error code bits:
 *
 *   bit 0 ==	 0: no page found	1: protection fault
 *   bit 1 ==	 0: read access		1: write access
 *   bit 2 ==	 0: kernel-mode access	1: user-mode access
 *   bit 3 ==				1: use of reserved bit detected
 *   bit 4 ==				1: fault was an instruction fetch
 */
enum x86_pf_error_code {

	PF_PROT		=		1 << 0,
	PF_WRITE	=		1 << 1,
	PF_USER		=		1 << 2,
	PF_RSVD		=		1 << 3,
	PF_INSTR	=		1 << 4,
};

/*
 * Returns 0 if mmiotrace is disabled, or if the fault is not
 * handled by mmiotrace:
 */
static inline int __kprobes
kmmio_fault(struct pt_regs *regs, unsigned long addr)
{
	if (unlikely(is_kmmio_active()))
		if (kmmio_handler(regs, addr) == 1)
			return -1;
	return 0;
}

static inline int __kprobes notify_page_fault(struct pt_regs *regs)
{
	int ret = 0;

	/* kprobe_running() needs smp_processor_id() */
	if (kprobes_built_in() && !user_mode_vm(regs)) {
		preempt_disable();
		if (kprobe_running() && kprobe_fault_handler(regs, 14))
			ret = 1;
		preempt_enable();
	}

	return ret;
}

/*
 * Prefetch quirks:
 *
 * 32-bit mode:
 *
 *   Sometimes AMD Athlon/Opteron CPUs report invalid exceptions on prefetch.
 *   Check that here and ignore it.
 *
 * 64-bit mode:
 *
 *   Sometimes the CPU reports invalid exceptions on prefetch.
 *   Check that here and ignore it.
 *
 * Opcode checker based on code by Richard Brunner.
 */
static inline int
check_prefetch_opcode(struct pt_regs *regs, unsigned char *instr,
		      unsigned char opcode, int *prefetch)
{
	unsigned char instr_hi = opcode & 0xf0;
	unsigned char instr_lo = opcode & 0x0f;

	switch (instr_hi) {
	case 0x20:
	case 0x30:
		/*
		 * Values 0x26,0x2E,0x36,0x3E are valid x86 prefixes.
		 * In X86_64 long mode, the CPU will signal invalid
		 * opcode if some of these prefixes are present so
		 * X86_64 will never get here anyway
		 */
		return ((instr_lo & 7) == 0x6);
#ifdef CONFIG_X86_64
	case 0x40:
		/*
		 * In AMD64 long mode 0x40..0x4F are valid REX prefixes
		 * Need to figure out under what instruction mode the
		 * instruction was issued. Could check the LDT for lm,
		 * but for now it's good enough to assume that long
		 * mode only uses well known segments or kernel.
		 */
		return (!user_mode(regs) || user_64bit_mode(regs));
#endif
	case 0x60:
		/* 0x64 thru 0x67 are valid prefixes in all modes. */
		return (instr_lo & 0xC) == 0x4;
	case 0xF0:
		/* 0xF0, 0xF2, 0xF3 are valid prefixes in all modes. */
		return !instr_lo || (instr_lo>>1) == 1;
	case 0x00:
		/* Prefetch instruction is 0x0F0D or 0x0F18 */
		if (probe_kernel_address(instr, opcode))
			return 0;

		*prefetch = (instr_lo == 0xF) &&
			(opcode == 0x0D || opcode == 0x18);
		return 0;
	default:
		return 0;
	}
}

static int
is_prefetch(struct pt_regs *regs, unsigned long error_code, unsigned long addr)
{
	unsigned char *max_instr;
	unsigned char *instr;
	int prefetch = 0;

	/*
	 * If it was a exec (instruction fetch) fault on NX page, then
	 * do not ignore the fault:
	 */
	if (error_code & PF_INSTR)
		return 0;

	instr = (void *)convert_ip_to_linear(current, regs);
	max_instr = instr + 15;

	if (user_mode(regs) && instr >= (unsigned char *)TASK_SIZE)
		return 0;

	while (instr < max_instr) {
		unsigned char opcode;

		if (probe_kernel_address(instr, opcode))
			break;

		instr++;

		if (!check_prefetch_opcode(regs, instr, opcode, &prefetch))
			break;
	}
	return prefetch;
}

static void
force_sig_info_fault(int si_signo, int si_code, unsigned long address,
		     struct task_struct *tsk, int fault)
{
	unsigned lsb = 0;
	siginfo_t info;

	info.si_signo	= si_signo;
	info.si_errno	= 0;
	info.si_code	= si_code;
	info.si_addr	= (void __user *)address;
	if (fault & VM_FAULT_HWPOISON_LARGE)
		lsb = hstate_index_to_shift(VM_FAULT_GET_HINDEX(fault)); 
	if (fault & VM_FAULT_HWPOISON)
		lsb = PAGE_SHIFT;
	info.si_addr_lsb = lsb;

	force_sig_info(si_signo, &info, tsk);
}

DEFINE_SPINLOCK(pgd_lock);
LIST_HEAD(pgd_list);

#ifdef CONFIG_X86_32
static inline pmd_t *vmalloc_sync_one(pgd_t *pgd, unsigned long address)
{
	unsigned index = pgd_index(address);
	pgd_t *pgd_k;
	pud_t *pud, *pud_k;
	pmd_t *pmd, *pmd_k;

	pgd += index;
	pgd_k = init_mm.pgd + index;

	if (!pgd_present(*pgd_k))
		return NULL;

	/*
	 * set_pgd(pgd, *pgd_k); here would be useless on PAE
	 * and redundant with the set_pmd() on non-PAE. As would
	 * set_pud.
	 */
	pud = pud_offset(pgd, address);
	pud_k = pud_offset(pgd_k, address);
	if (!pud_present(*pud_k))
		return NULL;

	pmd = pmd_offset(pud, address);
	pmd_k = pmd_offset(pud_k, address);
	if (!pmd_present(*pmd_k))
		return NULL;

	if (!pmd_present(*pmd))
		set_pmd(pmd, *pmd_k);
	else
		BUG_ON(pmd_page(*pmd) != pmd_page(*pmd_k));

	return pmd_k;
}

void vmalloc_sync_all(void)
{
	unsigned long address;

	if (SHARED_KERNEL_PMD)
		return;

	for (address = VMALLOC_START & PMD_MASK;
	     address >= TASK_SIZE && address < FIXADDR_TOP;
	     address += PMD_SIZE) {
		struct page *page;

		spin_lock(&pgd_lock);
		list_for_each_entry(page, &pgd_list, lru) {
			spinlock_t *pgt_lock;
			pmd_t *ret;

			/* the pgt_lock only for Xen */
			pgt_lock = &pgd_page_get_mm(page)->page_table_lock;

			spin_lock(pgt_lock);
			ret = vmalloc_sync_one(page_address(page), address);
			spin_unlock(pgt_lock);

			if (!ret)
				break;
		}
		spin_unlock(&pgd_lock);
	}
}

/*
 * 32-bit:
 *
 *   Handle a fault on the vmalloc or module mapping area
 */
static noinline __kprobes int vmalloc_fault(unsigned long address)
{
	unsigned long pgd_paddr;
	pmd_t *pmd_k;
	pte_t *pte_k;

	/* Make sure we are in vmalloc area: */
	if (!(address >= VMALLOC_START && address < VMALLOC_END))
		return -1;

	WARN_ON_ONCE(in_nmi());

	/*
	 * Synchronize this task's top level page-table
	 * with the 'reference' page table.
	 *
	 * Do _not_ use "current" here. We might be inside
	 * an interrupt in the middle of a task switch..
	 */
	pgd_paddr = read_cr3();
	pmd_k = vmalloc_sync_one(__va(pgd_paddr), address);
	if (!pmd_k)
		return -1;

	pte_k = pte_offset_kernel(pmd_k, address);
	if (!pte_present(*pte_k))
		return -1;

	return 0;
}

/*
 * Did it hit the DOS screen memory VA from vm86 mode?
 */
static inline void
check_v8086_mode(struct pt_regs *regs, unsigned long address,
		 struct task_struct *tsk)
{
	unsigned long bit;

	if (!v8086_mode(regs))
		return;

	bit = (address - 0xA0000) >> PAGE_SHIFT;
	if (bit < 32)
		tsk->thread.screen_bitmap |= 1 << bit;
}

static bool low_pfn(unsigned long pfn)
{
	return pfn < max_low_pfn;
}

static void dump_pagetable(unsigned long address)
{
	pgd_t *base = __va(read_cr3());
	pgd_t *pgd = &base[pgd_index(address)];
	pmd_t *pmd;
	pte_t *pte;

#ifdef CONFIG_X86_PAE
	printk("*pdpt = %016Lx ", pgd_val(*pgd));
	if (!low_pfn(pgd_val(*pgd) >> PAGE_SHIFT) || !pgd_present(*pgd))
		goto out;
#endif
	pmd = pmd_offset(pud_offset(pgd, address), address);
	printk(KERN_CONT "*pde = %0*Lx ", sizeof(*pmd) * 2, (u64)pmd_val(*pmd));

	/*
	 * We must not directly access the pte in the highpte
	 * case if the page table is located in highmem.
	 * And let's rather not kmap-atomic the pte, just in case
	 * it's allocated already:
	 */
	if (!low_pfn(pmd_pfn(*pmd)) || !pmd_present(*pmd) || pmd_large(*pmd))
		goto out;

	pte = pte_offset_kernel(pmd, address);
	printk("*pte = %0*Lx ", sizeof(*pte) * 2, (u64)pte_val(*pte));
out:
	printk("\n");
}

#else /* CONFIG_X86_64: */

void vmalloc_sync_all(void)
{
	sync_global_pgds(VMALLOC_START & PGDIR_MASK, VMALLOC_END);
}

/*
 * 64-bit:
 *
 *   Handle a fault on the vmalloc area
 *
 * This assumes no large pages in there.
 */
static noinline __kprobes int vmalloc_fault(unsigned long address)
{
	pgd_t *pgd, *pgd_ref;
	pud_t *pud, *pud_ref;
	pmd_t *pmd, *pmd_ref;
	pte_t *pte, *pte_ref;

	/* Make sure we are in vmalloc area: */
	if (!(address >= VMALLOC_START && address < VMALLOC_END))
		return -1;

	WARN_ON_ONCE(in_nmi());

	/*
	 * Copy kernel mappings over when needed. This can also
	 * happen within a race in page table update. In the later
	 * case just flush:
	 */
	pgd = pgd_offset(current->active_mm, address);
	pgd_ref = pgd_offset_k(address);
	if (pgd_none(*pgd_ref))
		return -1;

	if (pgd_none(*pgd))
		set_pgd(pgd, *pgd_ref);
	else
		BUG_ON(pgd_page_vaddr(*pgd) != pgd_page_vaddr(*pgd_ref));

	/*
	 * Below here mismatches are bugs because these lower tables
	 * are shared:
	 */

	pud = pud_offset(pgd, address);
	pud_ref = pud_offset(pgd_ref, address);
	if (pud_none(*pud_ref))
		return -1;

	if (pud_none(*pud) || pud_page_vaddr(*pud) != pud_page_vaddr(*pud_ref))
		BUG();

	pmd = pmd_offset(pud, address);
	pmd_ref = pmd_offset(pud_ref, address);
	if (pmd_none(*pmd_ref))
		return -1;

	if (pmd_none(*pmd) || pmd_page(*pmd) != pmd_page(*pmd_ref))
		BUG();

	pte_ref = pte_offset_kernel(pmd_ref, address);
	if (!pte_present(*pte_ref))
		return -1;

	pte = pte_offset_kernel(pmd, address);

	/*
	 * Don't use pte_page here, because the mappings can point
	 * outside mem_map, and the NUMA hash lookup cannot handle
	 * that:
	 */
	if (!pte_present(*pte) || pte_pfn(*pte) != pte_pfn(*pte_ref))
		BUG();

	return 0;
}

#ifdef CONFIG_CPU_SUP_AMD
static const char errata93_warning[] =
KERN_ERR 
"******* Your BIOS seems to not contain a fix for K8 errata #93\n"
"******* Working around it, but it may cause SEGVs or burn power.\n"
"******* Please consider a BIOS update.\n"
"******* Disabling USB legacy in the BIOS may also help.\n";
#endif

/*
 * No vm86 mode in 64-bit mode:
 */
static inline void
check_v8086_mode(struct pt_regs *regs, unsigned long address,
		 struct task_struct *tsk)
{
}

static int bad_address(void *p)
{
	unsigned long dummy;

	return probe_kernel_address((unsigned long *)p, dummy);
}

static void dump_pagetable(unsigned long address)
{
	pgd_t *base = __va(read_cr3() & PHYSICAL_PAGE_MASK);
	pgd_t *pgd = base + pgd_index(address);
	pud_t *pud;
	pmd_t *pmd;
	pte_t *pte;

	if (bad_address(pgd))
		goto bad;

	printk("PGD %lx ", pgd_val(*pgd));

	if (!pgd_present(*pgd))
		goto out;

	pud = pud_offset(pgd, address);
	if (bad_address(pud))
		goto bad;

	printk("PUD %lx ", pud_val(*pud));
	if (!pud_present(*pud) || pud_large(*pud))
		goto out;

	pmd = pmd_offset(pud, address);
	if (bad_address(pmd))
		goto bad;

	printk("PMD %lx ", pmd_val(*pmd));
	if (!pmd_present(*pmd) || pmd_large(*pmd))
		goto out;

	pte = pte_offset_kernel(pmd, address);
	if (bad_address(pte))
		goto bad;

	printk("PTE %lx", pte_val(*pte));
out:
	printk("\n");
	return;
bad:
	printk("BAD\n");
}

#endif /* CONFIG_X86_64 */

/*
 * Workaround for K8 erratum #93 & buggy BIOS.
 *
 * BIOS SMM functions are required to use a specific workaround
 * to avoid corruption of the 64bit RIP register on C stepping K8.
 *
 * A lot of BIOS that didn't get tested properly miss this.
 *
 * The OS sees this as a page fault with the upper 32bits of RIP cleared.
 * Try to work around it here.
 *
 * Note we only handle faults in kernel here.
 * Does nothing on 32-bit.
 */
static int is_errata93(struct pt_regs *regs, unsigned long address)
{
#if defined(CONFIG_X86_64) && defined(CONFIG_CPU_SUP_AMD)
	if (boot_cpu_data.x86_vendor != X86_VENDOR_AMD
	    || boot_cpu_data.x86 != 0xf)
		return 0;

	if (address != regs->ip)
		return 0;

	if ((address >> 32) != 0)
		return 0;

	address |= 0xffffffffUL << 32;
	if ((address >= (u64)_stext && address <= (u64)_etext) ||
	    (address >= MODULES_VADDR && address <= MODULES_END)) {
		printk_once(errata93_warning);
		regs->ip = address;
		return 1;
	}
#endif
	return 0;
}

/*
 * Work around K8 erratum #100 K8 in compat mode occasionally jumps
 * to illegal addresses >4GB.
 *
 * We catch this in the page fault handler because these addresses
 * are not reachable. Just detect this case and return.  Any code
 * segment in LDT is compatibility mode.
 */
static int is_errata100(struct pt_regs *regs, unsigned long address)
{
#ifdef CONFIG_X86_64
	if ((regs->cs == __USER32_CS || (regs->cs & (1<<2))) && (address >> 32))
		return 1;
#endif
	return 0;
}

static int is_f00f_bug(struct pt_regs *regs, unsigned long address)
{
#ifdef CONFIG_X86_F00F_BUG
	unsigned long nr;

	/*
	 * Pentium F0 0F C7 C8 bug workaround:
	 */
	if (boot_cpu_data.f00f_bug) {
		nr = (address - idt_descr.address) >> 3;

		if (nr == 6) {
			do_invalid_op(regs, 0);
			return 1;
		}
	}
#endif
	return 0;
}

static const char nx_warning[] = KERN_CRIT
"kernel tried to execute NX-protected page - exploit attempt? (uid: %d)\n";

static void
show_fault_oops(struct pt_regs *regs, unsigned long error_code,
		unsigned long address)
{
	if (!oops_may_print())
		return;

	if (error_code & PF_INSTR) {
		unsigned int level;

		pte_t *pte = lookup_address(address, &level);

		if (pte && pte_present(*pte) && !pte_exec(*pte))
			printk(nx_warning, from_kuid(&init_user_ns, current_uid()));
	}

	printk(KERN_ALERT "BUG: unable to handle kernel ");
	if (address < PAGE_SIZE)
		printk(KERN_CONT "NULL pointer dereference");
	else
		printk(KERN_CONT "paging request");

	printk(KERN_CONT " at %p\n", (void *) address);
	printk(KERN_ALERT "IP:");
	printk_address(regs->ip, 1);

	dump_pagetable(address);
}

static noinline void
pgtable_bad(struct pt_regs *regs, unsigned long error_code,
	    unsigned long address)
{
	struct task_struct *tsk;
	unsigned long flags;
	int sig;

	flags = oops_begin();
	tsk = current;
	sig = SIGKILL;

	printk(KERN_ALERT "%s: Corrupted page table at address %lx\n",
	       tsk->comm, address);
	dump_pagetable(address);

	tsk->thread.cr2		= address;
	tsk->thread.trap_nr	= X86_TRAP_PF;
	tsk->thread.error_code	= error_code;

	if (__die("Bad pagetable", regs, error_code))
		sig = 0;

	oops_end(flags, regs, sig);
}

static noinline void
no_context(struct pt_regs *regs, unsigned long error_code,
	   unsigned long address, int signal, int si_code)
{
	struct task_struct *tsk = current;
	unsigned long *stackend;
	unsigned long flags;
	int sig;

	/* Are we prepared to handle this kernel fault? */
	if (fixup_exception(regs)) {
		if (current_thread_info()->sig_on_uaccess_error && signal) {
			tsk->thread.trap_nr = X86_TRAP_PF;
			tsk->thread.error_code = error_code | PF_USER;
			tsk->thread.cr2 = address;

			/* XXX: hwpoison faults will set the wrong code. */
			force_sig_info_fault(signal, si_code, address, tsk, 0);
		}
		return;
	}

	/*
	 * 32-bit:
	 *
	 *   Valid to do another page fault here, because if this fault
	 *   had been triggered by is_prefetch fixup_exception would have
	 *   handled it.
	 *
	 * 64-bit:
	 *
	 *   Hall of shame of CPU/BIOS bugs.
	 */
	if (is_prefetch(regs, error_code, address))
		return;

	if (is_errata93(regs, address))
		return;

	/*
	 * Oops. The kernel tried to access some bad page. We'll have to
	 * terminate things with extreme prejudice:
	 */
	flags = oops_begin();

	show_fault_oops(regs, error_code, address);

	stackend = end_of_stack(tsk);
	if (tsk != &init_task && *stackend != STACK_END_MAGIC)
		printk(KERN_EMERG "Thread overran stack, or stack corrupted\n");

	tsk->thread.cr2		= address;
	tsk->thread.trap_nr	= X86_TRAP_PF;
	tsk->thread.error_code	= error_code;

	sig = SIGKILL;
	if (__die("Oops", regs, error_code))
		sig = 0;

	/* Executive summary in case the body of the oops scrolled away */
	printk(KERN_DEFAULT "CR2: %016lx\n", address);

	oops_end(flags, regs, sig);
}

/*
 * Print out info about fatal segfaults, if the show_unhandled_signals
 * sysctl is set:
 */
static inline void
show_signal_msg(struct pt_regs *regs, unsigned long error_code,
		unsigned long address, struct task_struct *tsk)
{
	if (!unhandled_signal(tsk, SIGSEGV))
		return;

	if (!printk_ratelimit())
		return;

	printk("%s%s[%d]: segfault at %lx ip %p sp %p error %lx",
		task_pid_nr(tsk) > 1 ? KERN_INFO : KERN_EMERG,
		tsk->comm, task_pid_nr(tsk), address,
		(void *)regs->ip, (void *)regs->sp, error_code);

	print_vma_addr(KERN_CONT " in ", regs->ip);

	printk(KERN_CONT "\n");
}

static void
__bad_area_nosemaphore(struct pt_regs *regs, unsigned long error_code,
		       unsigned long address, int si_code)
{
	struct task_struct *tsk = current;

	/* User mode accesses just cause a SIGSEGV */
	if (error_code & PF_USER) {
		/*
		 * It's possible to have interrupts off here:
		 */
		local_irq_enable();

		/*
		 * Valid to do another page fault here because this one came
		 * from user space:
		 */
		if (is_prefetch(regs, error_code, address))
			return;

		if (is_errata100(regs, address))
			return;

#ifdef CONFIG_X86_64
		/*
		 * Instruction fetch faults in the vsyscall page might need
		 * emulation.
		 */
		if (unlikely((error_code & PF_INSTR) &&
			     ((address & ~0xfff) == VSYSCALL_START))) {
			if (emulate_vsyscall(regs, address))
				return;
		}
#endif

		if (unlikely(show_unhandled_signals))
			show_signal_msg(regs, error_code, address, tsk);

		/* Kernel addresses are always protection faults: */
		tsk->thread.cr2		= address;
		tsk->thread.error_code	= error_code | (address >= TASK_SIZE);
		tsk->thread.trap_nr	= X86_TRAP_PF;

		force_sig_info_fault(SIGSEGV, si_code, address, tsk, 0);

		return;
	}

	if (is_f00f_bug(regs, address))
		return;

	no_context(regs, error_code, address, SIGSEGV, si_code);
}

static noinline void
bad_area_nosemaphore(struct pt_regs *regs, unsigned long error_code,
		     unsigned long address)
{
	__bad_area_nosemaphore(regs, error_code, address, SEGV_MAPERR);
}

static void
__bad_area(struct pt_regs *regs, unsigned long error_code,
	   unsigned long address, int si_code)
{
	struct mm_struct *mm = current->mm;

	/*
	 * Something tried to access memory that isn't in our memory map..
	 * Fix it, but check if it's kernel or user first..
	 */
	up_read(&mm->mmap_sem);

	__bad_area_nosemaphore(regs, error_code, address, si_code);
}

static noinline void
bad_area(struct pt_regs *regs, unsigned long error_code, unsigned long address)
{
	__bad_area(regs, error_code, address, SEGV_MAPERR);
}

static noinline void
bad_area_access_error(struct pt_regs *regs, unsigned long error_code,
		      unsigned long address)
{
	__bad_area(regs, error_code, address, SEGV_ACCERR);
}

/* TODO: fixup for "mm-invoke-oom-killer-from-page-fault.patch" */
static void
out_of_memory(struct pt_regs *regs, unsigned long error_code,
	      unsigned long address)
{
	/*
	 * We ran out of memory, call the OOM killer, and return the userspace
	 * (which will retry the fault, or kill us if we got oom-killed):
	 */
	up_read(&current->mm->mmap_sem);

	pagefault_out_of_memory();
}

static void
do_sigbus(struct pt_regs *regs, unsigned long error_code, unsigned long address,
	  unsigned int fault)
{
	struct task_struct *tsk = current;
	struct mm_struct *mm = tsk->mm;
	int code = BUS_ADRERR;

	up_read(&mm->mmap_sem);

	/* Kernel mode? Handle exceptions or die: */
	if (!(error_code & PF_USER)) {
		no_context(regs, error_code, address, SIGBUS, BUS_ADRERR);
		return;
	}

	/* User-space => ok to do another page fault: */
	if (is_prefetch(regs, error_code, address))
		return;

	tsk->thread.cr2		= address;
	tsk->thread.error_code	= error_code;
	tsk->thread.trap_nr	= X86_TRAP_PF;

#ifdef CONFIG_MEMORY_FAILURE
	if (fault & (VM_FAULT_HWPOISON|VM_FAULT_HWPOISON_LARGE)) {
		printk(KERN_ERR
	"MCE: Killing %s:%d due to hardware memory corruption fault at %lx\n",
			tsk->comm, tsk->pid, address);
		code = BUS_MCEERR_AR;
	}
#endif
	force_sig_info_fault(SIGBUS, code, address, tsk, fault);
}

static noinline int
mm_fault_error(struct pt_regs *regs, unsigned long error_code,
	       unsigned long address, unsigned int fault)
{
	/*
	 * Pagefault was interrupted by SIGKILL. We have no reason to
	 * continue pagefault.
	 */
	if (fatal_signal_pending(current)) {
		if (!(fault & VM_FAULT_RETRY))
			up_read(&current->mm->mmap_sem);
		if (!(error_code & PF_USER))
			no_context(regs, error_code, address, 0, 0);
		return 1;
	}
	if (!(fault & VM_FAULT_ERROR))
		return 0;

	if (fault & VM_FAULT_OOM) {
		/* Kernel mode? Handle exceptions or die: */
		if (!(error_code & PF_USER)) {
			up_read(&current->mm->mmap_sem);
			no_context(regs, error_code, address,
				   SIGSEGV, SEGV_MAPERR);
			return 1;
		}

		out_of_memory(regs, error_code, address);
	} else {
		if (fault & (VM_FAULT_SIGBUS|VM_FAULT_HWPOISON|
			     VM_FAULT_HWPOISON_LARGE))
			do_sigbus(regs, error_code, address, fault);
		else
			BUG();
	}
	return 1;
}

static int spurious_fault_check(unsigned long error_code, pte_t *pte)
{
	if ((error_code & PF_WRITE) && !pte_write(*pte))
		return 0;

	if ((error_code & PF_INSTR) && !pte_exec(*pte))
		return 0;

	return 1;
}

/*
 * Handle a spurious fault caused by a stale TLB entry.
 *
 * This allows us to lazily refresh the TLB when increasing the
 * permissions of a kernel page (RO -> RW or NX -> X).  Doing it
 * eagerly is very expensive since that implies doing a full
 * cross-processor TLB flush, even if no stale TLB entries exist
 * on other processors.
 *
 * There are no security implications to leaving a stale TLB when
 * increasing the permissions on a page.
 */
static noinline __kprobes int
spurious_fault(unsigned long error_code, unsigned long address)
{
	pgd_t *pgd;
	pud_t *pud;
	pmd_t *pmd;
	pte_t *pte;
	int ret;

	/* Reserved-bit violation or user access to kernel space? */
	if (error_code & (PF_USER | PF_RSVD))
		return 0;

	pgd = init_mm.pgd + pgd_index(address);
	if (!pgd_present(*pgd))
		return 0;

	pud = pud_offset(pgd, address);
	if (!pud_present(*pud))
		return 0;

	if (pud_large(*pud))
		return spurious_fault_check(error_code, (pte_t *) pud);

	pmd = pmd_offset(pud, address);
	if (!pmd_present(*pmd))
		return 0;

	if (pmd_large(*pmd))
		return spurious_fault_check(error_code, (pte_t *) pmd);

	/*
	 * Note: don't use pte_present() here, since it returns true
	 * if the _PAGE_PROTNONE bit is set.  However, this aliases the
	 * _PAGE_GLOBAL bit, which for kernel pages give false positives
	 * when CONFIG_DEBUG_PAGEALLOC is used.
	 */
	pte = pte_offset_kernel(pmd, address);
	if (!(pte_flags(*pte) & _PAGE_PRESENT))
		return 0;

	ret = spurious_fault_check(error_code, pte);
	if (!ret)
		return 0;

	/*
	 * Make sure we have permissions in PMD.
	 * If not, then there's a bug in the page tables:
	 */
	ret = spurious_fault_check(error_code, (pte_t *) pmd);
	WARN_ONCE(!ret, "PMD has incorrect permission bits\n");

	return ret;
}

int show_unhandled_signals = 1;

static inline int
access_error(unsigned long error_code, struct vm_area_struct *vma)
{
	if (error_code & PF_WRITE) {
		/* write, present and write, not present: */
		if (unlikely(!(vma->vm_flags & VM_WRITE)))
			return 1;
		return 0;
	}

	/* read, present: */
	if (unlikely(error_code & PF_PROT))
		return 1;

	/* read, not present: */
	if (unlikely(!(vma->vm_flags & (VM_READ | VM_EXEC | VM_WRITE))))
		return 1;

	return 0;
}

static int fault_in_kernel_space(unsigned long address)
{
	return address >= TASK_SIZE_MAX;
}

static inline bool smap_violation(int error_code, struct pt_regs *regs)
{
	if (error_code & PF_USER)
		return false;

	if (!user_mode_vm(regs) && (regs->flags & X86_EFLAGS_AC))
		return false;

	return true;
}

/*
 * This routine handles page faults.  It determines the address,
 * and the problem, and then passes it off to one of the appropriate
 * routines.
 */
static void __kprobes
__do_page_fault(struct pt_regs *regs, unsigned long error_code)
{
	struct vm_area_struct *vma;
	struct task_struct *tsk;
	unsigned long address;
	struct mm_struct *mm;
	int fault;
	int write = error_code & PF_WRITE;
	unsigned int flags = FAULT_FLAG_ALLOW_RETRY | FAULT_FLAG_KILLABLE |
					(write ? FAULT_FLAG_WRITE : 0);

	tsk = current;
	mm = tsk->mm;

	/* Get the faulting address: */
	address = read_cr2();

	/*
	 * Detect and handle instructions that would cause a page fault for
	 * both a tracked kernel page and a userspace page.
	 */
	if (kmemcheck_active(regs))
		kmemcheck_hide(regs);
	prefetchw(&mm->mmap_sem);

	if (unlikely(kmmio_fault(regs, address)))
		return;

	/*
	 * We fault-in kernel-space virtual memory on-demand. The
	 * 'reference' page table is init_mm.pgd.
	 *
	 * NOTE! We MUST NOT take any locks for this case. We may
	 * be in an interrupt or a critical region, and should
	 * only copy the information from the master page table,
	 * nothing more.
	 *
	 * This verifies that the fault happens in kernel space
	 * (error_code & 4) == 0, and that the fault was not a
	 * protection error (error_code & 9) == 0.
	 */
	if (unlikely(fault_in_kernel_space(address))) {
		if (!(error_code & (PF_RSVD | PF_USER | PF_PROT))) {
			if (vmalloc_fault(address) >= 0)
				return;

			if (kmemcheck_fault(regs, address, error_code))
				return;
		}

		/* Can handle a stale RO->RW TLB: */
		if (spurious_fault(error_code, address))
			return;

		/* kprobes don't want to hook the spurious faults: */
		if (notify_page_fault(regs))
			return;
		/*
		 * Don't take the mm semaphore here. If we fixup a prefetch
		 * fault we could otherwise deadlock:
		 */
		bad_area_nosemaphore(regs, error_code, address);

		return;
	}

	/* kprobes don't want to hook the spurious faults: */
	if (unlikely(notify_page_fault(regs)))
		return;
	/*
	 * It's safe to allow irq's after cr2 has been saved and the
	 * vmalloc fault has been handled.
	 *
	 * User-mode registers count as a user access even for any
	 * potential system fault or CPU buglet:
	 */
	if (user_mode_vm(regs)) {
		local_irq_enable();
		error_code |= PF_USER;
	} else {
		if (regs->flags & X86_EFLAGS_IF)
			local_irq_enable();
	}

	if (unlikely(error_code & PF_RSVD))
		pgtable_bad(regs, error_code, address);

	if (static_cpu_has(X86_FEATURE_SMAP)) {
		if (unlikely(smap_violation(error_code, regs))) {
			bad_area_nosemaphore(regs, error_code, address);
			return;
		}
	}

	perf_sw_event(PERF_COUNT_SW_PAGE_FAULTS, 1, regs, address);

	/*
	 * If we're in an interrupt, have no user context or are running
	 * in an atomic region then we must not take the fault:
	 */
	if (unlikely(in_atomic() || !mm)) {
		bad_area_nosemaphore(regs, error_code, address);
		return;
	}

	/*
	 * When running in the kernel we expect faults to occur only to
	 * addresses in user space.  All other faults represent errors in
	 * the kernel and should generate an OOPS.  Unfortunately, in the
	 * case of an erroneous fault occurring in a code path which already
	 * holds mmap_sem we will deadlock attempting to validate the fault
	 * against the address space.  Luckily the kernel only validly
	 * references user space from well defined areas of code, which are
	 * listed in the exceptions table.
	 *
	 * As the vast majority of faults will be valid we will only perform
	 * the source reference check when there is a possibility of a
	 * deadlock. Attempt to lock the address space, if we cannot we then
	 * validate the source. If this is invalid we can skip the address
	 * space check, thus avoiding the deadlock:
	 */
	if (unlikely(!down_read_trylock(&mm->mmap_sem))) {
		if ((error_code & PF_USER) == 0 &&
		    !search_exception_tables(regs->ip)) {
			bad_area_nosemaphore(regs, error_code, address);
			return;
		}
retry:
		down_read(&mm->mmap_sem);
	} else {
		/*
		 * The above down_read_trylock() might have succeeded in
		 * which case we'll have missed the might_sleep() from
		 * down_read():
		 */
		might_sleep();
	}

	vma = find_vma(mm, address);
	if (unlikely(!vma)) {
		bad_area(regs, error_code, address);
		return;
	}
	if (likely(vma->vm_start <= address))
		goto good_area;
	if (unlikely(!(vma->vm_flags & VM_GROWSDOWN))) {
		bad_area(regs, error_code, address);
		return;
	}
	if (error_code & PF_USER) {
		/*
		 * Accessing the stack below %sp is always a bug.
		 * The large cushion allows instructions like enter
		 * and pusha to work. ("enter $65535, $31" pushes
		 * 32 pointers and then decrements %sp by 65535.)
		 */
		if (unlikely(address + 65536 + 32 * sizeof(unsigned long) < regs->sp)) {
			bad_area(regs, error_code, address);
			return;
		}
	}
	if (unlikely(expand_stack(vma, address))) {
		bad_area(regs, error_code, address);
		return;
	}

	/*
	 * Ok, we have a good vm_area for this memory access, so
	 * we can handle it..
	 */
good_area:
	if (unlikely(access_error(error_code, vma))) {
		bad_area_access_error(regs, error_code, address);
		return;
	}

	/*
	 * If for any reason at all we couldn't handle the fault,
	 * make sure we exit gracefully rather than endlessly redo
	 * the fault:
	 */
	fault = handle_mm_fault(mm, vma, address, flags);

	if (unlikely(fault & (VM_FAULT_RETRY|VM_FAULT_ERROR))) {
		if (mm_fault_error(regs, error_code, address, fault))
			return;
	}

	/*
	 * Major/minor page fault accounting is only done on the
	 * initial attempt. If we go through a retry, it is extremely
	 * likely that the page will be found in page cache at that point.
	 */
	if (flags & FAULT_FLAG_ALLOW_RETRY) {
		if (fault & VM_FAULT_MAJOR) {
			tsk->maj_flt++;
			perf_sw_event(PERF_COUNT_SW_PAGE_FAULTS_MAJ, 1,
				      regs, address);
		} else {
			tsk->min_flt++;
			perf_sw_event(PERF_COUNT_SW_PAGE_FAULTS_MIN, 1,
				      regs, address);
		}
		if (fault & VM_FAULT_RETRY) {
			/* Clear FAULT_FLAG_ALLOW_RETRY to avoid any risk
			 * of starvation. */
			flags &= ~FAULT_FLAG_ALLOW_RETRY;
			goto retry;
		}
	}

	check_v8086_mode(regs, address, tsk);

	up_read(&mm->mmap_sem);
}

dotraplinkage void __kprobes
do_page_fault(struct pt_regs *regs, unsigned long error_code)
{
	exception_enter(regs);
	__do_page_fault(regs, error_code);
	exception_exit(regs);
}