summaryrefslogtreecommitdiffstats
path: root/arch/x86/kernel/cpu/sgx/encl.c
blob: d5f76b996795fd75820607be83265391d66aca46 (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
1239
1240
1241
1242
1243
1244
1245
1246
1247
1248
1249
1250
1251
1252
1253
1254
1255
1256
1257
1258
1259
1260
1261
1262
1263
1264
1265
1266
1267
1268
1269
1270
1271
1272
1273
1274
1275
1276
1277
1278
1279
1280
1281
1282
1283
1284
1285
1286
1287
1288
1289
1290
1291
1292
1293
1294
1295
1296
1297
1298
1299
1300
1301
1302
1303
1304
1305
1306
1307
1308
1309
1310
1311
1312
1313
1314
1315
1316
1317
1318
1319
1320
1321
1322
1323
// SPDX-License-Identifier: GPL-2.0
/*  Copyright(c) 2016-20 Intel Corporation. */

#include <linux/lockdep.h>
#include <linux/mm.h>
#include <linux/mman.h>
#include <linux/shmem_fs.h>
#include <linux/suspend.h>
#include <linux/sched/mm.h>
#include <asm/sgx.h>
#include "encl.h"
#include "encls.h"
#include "sgx.h"

static int sgx_encl_lookup_backing(struct sgx_encl *encl, unsigned long page_index,
			    struct sgx_backing *backing);

#define PCMDS_PER_PAGE (PAGE_SIZE / sizeof(struct sgx_pcmd))
/*
 * 32 PCMD entries share a PCMD page. PCMD_FIRST_MASK is used to
 * determine the page index associated with the first PCMD entry
 * within a PCMD page.
 */
#define PCMD_FIRST_MASK GENMASK(4, 0)

/**
 * reclaimer_writing_to_pcmd() - Query if any enclave page associated with
 *                               a PCMD page is in process of being reclaimed.
 * @encl:        Enclave to which PCMD page belongs
 * @start_addr:  Address of enclave page using first entry within the PCMD page
 *
 * When an enclave page is reclaimed some Paging Crypto MetaData (PCMD) is
 * stored. The PCMD data of a reclaimed enclave page contains enough
 * information for the processor to verify the page at the time
 * it is loaded back into the Enclave Page Cache (EPC).
 *
 * The backing storage to which enclave pages are reclaimed is laid out as
 * follows:
 * Encrypted enclave pages:SECS page:PCMD pages
 *
 * Each PCMD page contains the PCMD metadata of
 * PAGE_SIZE/sizeof(struct sgx_pcmd) enclave pages.
 *
 * A PCMD page can only be truncated if it is (a) empty, and (b) not in the
 * process of getting data (and thus soon being non-empty). (b) is tested with
 * a check if an enclave page sharing the PCMD page is in the process of being
 * reclaimed.
 *
 * The reclaimer sets the SGX_ENCL_PAGE_BEING_RECLAIMED flag when it
 * intends to reclaim that enclave page - it means that the PCMD page
 * associated with that enclave page is about to get some data and thus
 * even if the PCMD page is empty, it should not be truncated.
 *
 * Context: Enclave mutex (&sgx_encl->lock) must be held.
 * Return: 1 if the reclaimer is about to write to the PCMD page
 *         0 if the reclaimer has no intention to write to the PCMD page
 */
static int reclaimer_writing_to_pcmd(struct sgx_encl *encl,
				     unsigned long start_addr)
{
	int reclaimed = 0;
	int i;

	/*
	 * PCMD_FIRST_MASK is based on number of PCMD entries within
	 * PCMD page being 32.
	 */
	BUILD_BUG_ON(PCMDS_PER_PAGE != 32);

	for (i = 0; i < PCMDS_PER_PAGE; i++) {
		struct sgx_encl_page *entry;
		unsigned long addr;

		addr = start_addr + i * PAGE_SIZE;

		/*
		 * Stop when reaching the SECS page - it does not
		 * have a page_array entry and its reclaim is
		 * started and completed with enclave mutex held so
		 * it does not use the SGX_ENCL_PAGE_BEING_RECLAIMED
		 * flag.
		 */
		if (addr == encl->base + encl->size)
			break;

		entry = xa_load(&encl->page_array, PFN_DOWN(addr));
		if (!entry)
			continue;

		/*
		 * VA page slot ID uses same bit as the flag so it is important
		 * to ensure that the page is not already in backing store.
		 */
		if (entry->epc_page &&
		    (entry->desc & SGX_ENCL_PAGE_BEING_RECLAIMED)) {
			reclaimed = 1;
			break;
		}
	}

	return reclaimed;
}

/*
 * Calculate byte offset of a PCMD struct associated with an enclave page. PCMD's
 * follow right after the EPC data in the backing storage. In addition to the
 * visible enclave pages, there's one extra page slot for SECS, before PCMD
 * structs.
 */
static inline pgoff_t sgx_encl_get_backing_page_pcmd_offset(struct sgx_encl *encl,
							    unsigned long page_index)
{
	pgoff_t epc_end_off = encl->size + sizeof(struct sgx_secs);

	return epc_end_off + page_index * sizeof(struct sgx_pcmd);
}

/*
 * Free a page from the backing storage in the given page index.
 */
static inline void sgx_encl_truncate_backing_page(struct sgx_encl *encl, unsigned long page_index)
{
	struct inode *inode = file_inode(encl->backing);

	shmem_truncate_range(inode, PFN_PHYS(page_index), PFN_PHYS(page_index) + PAGE_SIZE - 1);
}

/*
 * ELDU: Load an EPC page as unblocked. For more info, see "OS Management of EPC
 * Pages" in the SDM.
 */
static int __sgx_encl_eldu(struct sgx_encl_page *encl_page,
			   struct sgx_epc_page *epc_page,
			   struct sgx_epc_page *secs_page)
{
	unsigned long va_offset = encl_page->desc & SGX_ENCL_PAGE_VA_OFFSET_MASK;
	struct sgx_encl *encl = encl_page->encl;
	pgoff_t page_index, page_pcmd_off;
	unsigned long pcmd_first_page;
	struct sgx_pageinfo pginfo;
	struct sgx_backing b;
	bool pcmd_page_empty;
	u8 *pcmd_page;
	int ret;

	if (secs_page)
		page_index = PFN_DOWN(encl_page->desc - encl_page->encl->base);
	else
		page_index = PFN_DOWN(encl->size);

	/*
	 * Address of enclave page using the first entry within the PCMD page.
	 */
	pcmd_first_page = PFN_PHYS(page_index & ~PCMD_FIRST_MASK) + encl->base;

	page_pcmd_off = sgx_encl_get_backing_page_pcmd_offset(encl, page_index);

	ret = sgx_encl_lookup_backing(encl, page_index, &b);
	if (ret)
		return ret;

	pginfo.addr = encl_page->desc & PAGE_MASK;
	pginfo.contents = (unsigned long)kmap_atomic(b.contents);
	pcmd_page = kmap_atomic(b.pcmd);
	pginfo.metadata = (unsigned long)pcmd_page + b.pcmd_offset;

	if (secs_page)
		pginfo.secs = (u64)sgx_get_epc_virt_addr(secs_page);
	else
		pginfo.secs = 0;

	ret = __eldu(&pginfo, sgx_get_epc_virt_addr(epc_page),
		     sgx_get_epc_virt_addr(encl_page->va_page->epc_page) + va_offset);
	if (ret) {
		if (encls_failed(ret))
			ENCLS_WARN(ret, "ELDU");

		ret = -EFAULT;
	}

	memset(pcmd_page + b.pcmd_offset, 0, sizeof(struct sgx_pcmd));
	set_page_dirty(b.pcmd);

	/*
	 * The area for the PCMD in the page was zeroed above.  Check if the
	 * whole page is now empty meaning that all PCMD's have been zeroed:
	 */
	pcmd_page_empty = !memchr_inv(pcmd_page, 0, PAGE_SIZE);

	kunmap_atomic(pcmd_page);
	kunmap_atomic((void *)(unsigned long)pginfo.contents);

	get_page(b.pcmd);
	sgx_encl_put_backing(&b);

	sgx_encl_truncate_backing_page(encl, page_index);

	if (pcmd_page_empty && !reclaimer_writing_to_pcmd(encl, pcmd_first_page)) {
		sgx_encl_truncate_backing_page(encl, PFN_DOWN(page_pcmd_off));
		pcmd_page = kmap_atomic(b.pcmd);
		if (memchr_inv(pcmd_page, 0, PAGE_SIZE))
			pr_warn("PCMD page not empty after truncate.\n");
		kunmap_atomic(pcmd_page);
	}

	put_page(b.pcmd);

	return ret;
}

static struct sgx_epc_page *sgx_encl_eldu(struct sgx_encl_page *encl_page,
					  struct sgx_epc_page *secs_page)
{

	unsigned long va_offset = encl_page->desc & SGX_ENCL_PAGE_VA_OFFSET_MASK;
	struct sgx_encl *encl = encl_page->encl;
	struct sgx_epc_page *epc_page;
	int ret;

	epc_page = sgx_alloc_epc_page(encl_page, false);
	if (IS_ERR(epc_page))
		return epc_page;

	ret = __sgx_encl_eldu(encl_page, epc_page, secs_page);
	if (ret) {
		sgx_encl_free_epc_page(epc_page);
		return ERR_PTR(ret);
	}

	sgx_free_va_slot(encl_page->va_page, va_offset);
	list_move(&encl_page->va_page->list, &encl->va_pages);
	encl_page->desc &= ~SGX_ENCL_PAGE_VA_OFFSET_MASK;
	encl_page->epc_page = epc_page;

	return epc_page;
}

/*
 * Ensure the SECS page is not swapped out.  Must be called with encl->lock
 * to protect the enclave states including SECS and ensure the SECS page is
 * not swapped out again while being used.
 */
static struct sgx_epc_page *sgx_encl_load_secs(struct sgx_encl *encl)
{
	struct sgx_epc_page *epc_page = encl->secs.epc_page;

	if (!epc_page)
		epc_page = sgx_encl_eldu(&encl->secs, NULL);

	return epc_page;
}

static struct sgx_encl_page *__sgx_encl_load_page(struct sgx_encl *encl,
						  struct sgx_encl_page *entry)
{
	struct sgx_epc_page *epc_page;

	/* Entry successfully located. */
	if (entry->epc_page) {
		if (entry->desc & SGX_ENCL_PAGE_BEING_RECLAIMED)
			return ERR_PTR(-EBUSY);

		return entry;
	}

	epc_page = sgx_encl_load_secs(encl);
	if (IS_ERR(epc_page))
		return ERR_CAST(epc_page);

	epc_page = sgx_encl_eldu(entry, encl->secs.epc_page);
	if (IS_ERR(epc_page))
		return ERR_CAST(epc_page);

	encl->secs_child_cnt++;
	sgx_mark_page_reclaimable(entry->epc_page);

	return entry;
}

static struct sgx_encl_page *sgx_encl_load_page_in_vma(struct sgx_encl *encl,
						       unsigned long addr,
						       unsigned long vm_flags)
{
	unsigned long vm_prot_bits = vm_flags & (VM_READ | VM_WRITE | VM_EXEC);
	struct sgx_encl_page *entry;

	entry = xa_load(&encl->page_array, PFN_DOWN(addr));
	if (!entry)
		return ERR_PTR(-EFAULT);

	/*
	 * Verify that the page has equal or higher build time
	 * permissions than the VMA permissions (i.e. the subset of {VM_READ,
	 * VM_WRITE, VM_EXECUTE} in vma->vm_flags).
	 */
	if ((entry->vm_max_prot_bits & vm_prot_bits) != vm_prot_bits)
		return ERR_PTR(-EFAULT);

	return __sgx_encl_load_page(encl, entry);
}

struct sgx_encl_page *sgx_encl_load_page(struct sgx_encl *encl,
					 unsigned long addr)
{
	struct sgx_encl_page *entry;

	entry = xa_load(&encl->page_array, PFN_DOWN(addr));
	if (!entry)
		return ERR_PTR(-EFAULT);

	return __sgx_encl_load_page(encl, entry);
}

/**
 * sgx_encl_eaug_page() - Dynamically add page to initialized enclave
 * @vma:	VMA obtained from fault info from where page is accessed
 * @encl:	enclave accessing the page
 * @addr:	address that triggered the page fault
 *
 * When an initialized enclave accesses a page with no backing EPC page
 * on a SGX2 system then the EPC can be added dynamically via the SGX2
 * ENCLS[EAUG] instruction.
 *
 * Returns: Appropriate vm_fault_t: VM_FAULT_NOPAGE when PTE was installed
 * successfully, VM_FAULT_SIGBUS or VM_FAULT_OOM as error otherwise.
 */
static vm_fault_t sgx_encl_eaug_page(struct vm_area_struct *vma,
				     struct sgx_encl *encl, unsigned long addr)
{
	vm_fault_t vmret = VM_FAULT_SIGBUS;
	struct sgx_pageinfo pginfo = {0};
	struct sgx_encl_page *encl_page;
	struct sgx_epc_page *epc_page;
	struct sgx_va_page *va_page;
	unsigned long phys_addr;
	u64 secinfo_flags;
	int ret;

	if (!test_bit(SGX_ENCL_INITIALIZED, &encl->flags))
		return VM_FAULT_SIGBUS;

	/*
	 * Ignore internal permission checking for dynamically added pages.
	 * They matter only for data added during the pre-initialization
	 * phase. The enclave decides the permissions by the means of
	 * EACCEPT, EACCEPTCOPY and EMODPE.
	 */
	secinfo_flags = SGX_SECINFO_R | SGX_SECINFO_W | SGX_SECINFO_X;
	encl_page = sgx_encl_page_alloc(encl, addr - encl->base, secinfo_flags);
	if (IS_ERR(encl_page))
		return VM_FAULT_OOM;

	mutex_lock(&encl->lock);

	epc_page = sgx_encl_load_secs(encl);
	if (IS_ERR(epc_page)) {
		if (PTR_ERR(epc_page) == -EBUSY)
			vmret = VM_FAULT_NOPAGE;
		goto err_out_unlock;
	}

	epc_page = sgx_alloc_epc_page(encl_page, false);
	if (IS_ERR(epc_page)) {
		if (PTR_ERR(epc_page) == -EBUSY)
			vmret =  VM_FAULT_NOPAGE;
		goto err_out_unlock;
	}

	va_page = sgx_encl_grow(encl, false);
	if (IS_ERR(va_page)) {
		if (PTR_ERR(va_page) == -EBUSY)
			vmret = VM_FAULT_NOPAGE;
		goto err_out_epc;
	}

	if (va_page)
		list_add(&va_page->list, &encl->va_pages);

	ret = xa_insert(&encl->page_array, PFN_DOWN(encl_page->desc),
			encl_page, GFP_KERNEL);
	/*
	 * If ret == -EBUSY then page was created in another flow while
	 * running without encl->lock
	 */
	if (ret)
		goto err_out_shrink;

	pginfo.secs = (unsigned long)sgx_get_epc_virt_addr(encl->secs.epc_page);
	pginfo.addr = encl_page->desc & PAGE_MASK;
	pginfo.metadata = 0;

	ret = __eaug(&pginfo, sgx_get_epc_virt_addr(epc_page));
	if (ret)
		goto err_out;

	encl_page->encl = encl;
	encl_page->epc_page = epc_page;
	encl_page->type = SGX_PAGE_TYPE_REG;
	encl->secs_child_cnt++;

	sgx_mark_page_reclaimable(encl_page->epc_page);

	phys_addr = sgx_get_epc_phys_addr(epc_page);
	/*
	 * Do not undo everything when creating PTE entry fails - next #PF
	 * would find page ready for a PTE.
	 */
	vmret = vmf_insert_pfn(vma, addr, PFN_DOWN(phys_addr));
	if (vmret != VM_FAULT_NOPAGE) {
		mutex_unlock(&encl->lock);
		return VM_FAULT_SIGBUS;
	}
	mutex_unlock(&encl->lock);
	return VM_FAULT_NOPAGE;

err_out:
	xa_erase(&encl->page_array, PFN_DOWN(encl_page->desc));

err_out_shrink:
	sgx_encl_shrink(encl, va_page);
err_out_epc:
	sgx_encl_free_epc_page(epc_page);
err_out_unlock:
	mutex_unlock(&encl->lock);
	kfree(encl_page);

	return vmret;
}

static vm_fault_t sgx_vma_fault(struct vm_fault *vmf)
{
	unsigned long addr = (unsigned long)vmf->address;
	struct vm_area_struct *vma = vmf->vma;
	struct sgx_encl_page *entry;
	unsigned long phys_addr;
	struct sgx_encl *encl;
	vm_fault_t ret;

	encl = vma->vm_private_data;

	/*
	 * It's very unlikely but possible that allocating memory for the
	 * mm_list entry of a forked process failed in sgx_vma_open(). When
	 * this happens, vm_private_data is set to NULL.
	 */
	if (unlikely(!encl))
		return VM_FAULT_SIGBUS;

	/*
	 * The page_array keeps track of all enclave pages, whether they
	 * are swapped out or not. If there is no entry for this page and
	 * the system supports SGX2 then it is possible to dynamically add
	 * a new enclave page. This is only possible for an initialized
	 * enclave that will be checked for right away.
	 */
	if (cpu_feature_enabled(X86_FEATURE_SGX2) &&
	    (!xa_load(&encl->page_array, PFN_DOWN(addr))))
		return sgx_encl_eaug_page(vma, encl, addr);

	mutex_lock(&encl->lock);

	entry = sgx_encl_load_page_in_vma(encl, addr, vma->vm_flags);
	if (IS_ERR(entry)) {
		mutex_unlock(&encl->lock);

		if (PTR_ERR(entry) == -EBUSY)
			return VM_FAULT_NOPAGE;

		return VM_FAULT_SIGBUS;
	}

	phys_addr = sgx_get_epc_phys_addr(entry->epc_page);

	ret = vmf_insert_pfn(vma, addr, PFN_DOWN(phys_addr));
	if (ret != VM_FAULT_NOPAGE) {
		mutex_unlock(&encl->lock);

		return VM_FAULT_SIGBUS;
	}

	sgx_encl_test_and_clear_young(vma->vm_mm, entry);
	mutex_unlock(&encl->lock);

	return VM_FAULT_NOPAGE;
}

static void sgx_vma_open(struct vm_area_struct *vma)
{
	struct sgx_encl *encl = vma->vm_private_data;

	/*
	 * It's possible but unlikely that vm_private_data is NULL. This can
	 * happen in a grandchild of a process, when sgx_encl_mm_add() had
	 * failed to allocate memory in this callback.
	 */
	if (unlikely(!encl))
		return;

	if (sgx_encl_mm_add(encl, vma->vm_mm))
		vma->vm_private_data = NULL;
}


/**
 * sgx_encl_may_map() - Check if a requested VMA mapping is allowed
 * @encl:		an enclave pointer
 * @start:		lower bound of the address range, inclusive
 * @end:		upper bound of the address range, exclusive
 * @vm_flags:		VMA flags
 *
 * Iterate through the enclave pages contained within [@start, @end) to verify
 * that the permissions requested by a subset of {VM_READ, VM_WRITE, VM_EXEC}
 * do not contain any permissions that are not contained in the build time
 * permissions of any of the enclave pages within the given address range.
 *
 * An enclave creator must declare the strongest permissions that will be
 * needed for each enclave page. This ensures that mappings have the identical
 * or weaker permissions than the earlier declared permissions.
 *
 * Return: 0 on success, -EACCES otherwise
 */
int sgx_encl_may_map(struct sgx_encl *encl, unsigned long start,
		     unsigned long end, unsigned long vm_flags)
{
	unsigned long vm_prot_bits = vm_flags & (VM_READ | VM_WRITE | VM_EXEC);
	struct sgx_encl_page *page;
	unsigned long count = 0;
	int ret = 0;

	XA_STATE(xas, &encl->page_array, PFN_DOWN(start));

	/* Disallow mapping outside enclave's address range. */
	if (test_bit(SGX_ENCL_INITIALIZED, &encl->flags) &&
	    (start < encl->base || end > encl->base + encl->size))
		return -EACCES;

	/*
	 * Disallow READ_IMPLIES_EXEC tasks as their VMA permissions might
	 * conflict with the enclave page permissions.
	 */
	if (current->personality & READ_IMPLIES_EXEC)
		return -EACCES;

	mutex_lock(&encl->lock);
	xas_lock(&xas);
	xas_for_each(&xas, page, PFN_DOWN(end - 1)) {
		if (~page->vm_max_prot_bits & vm_prot_bits) {
			ret = -EACCES;
			break;
		}

		/* Reschedule on every XA_CHECK_SCHED iteration. */
		if (!(++count % XA_CHECK_SCHED)) {
			xas_pause(&xas);
			xas_unlock(&xas);
			mutex_unlock(&encl->lock);

			cond_resched();

			mutex_lock(&encl->lock);
			xas_lock(&xas);
		}
	}
	xas_unlock(&xas);
	mutex_unlock(&encl->lock);

	return ret;
}

static int sgx_vma_mprotect(struct vm_area_struct *vma, unsigned long start,
			    unsigned long end, unsigned long newflags)
{
	return sgx_encl_may_map(vma->vm_private_data, start, end, newflags);
}

static int sgx_encl_debug_read(struct sgx_encl *encl, struct sgx_encl_page *page,
			       unsigned long addr, void *data)
{
	unsigned long offset = addr & ~PAGE_MASK;
	int ret;


	ret = __edbgrd(sgx_get_epc_virt_addr(page->epc_page) + offset, data);
	if (ret)
		return -EIO;

	return 0;
}

static int sgx_encl_debug_write(struct sgx_encl *encl, struct sgx_encl_page *page,
				unsigned long addr, void *data)
{
	unsigned long offset = addr & ~PAGE_MASK;
	int ret;

	ret = __edbgwr(sgx_get_epc_virt_addr(page->epc_page) + offset, data);
	if (ret)
		return -EIO;

	return 0;
}

/*
 * Load an enclave page to EPC if required, and take encl->lock.
 */
static struct sgx_encl_page *sgx_encl_reserve_page(struct sgx_encl *encl,
						   unsigned long addr,
						   unsigned long vm_flags)
{
	struct sgx_encl_page *entry;

	for ( ; ; ) {
		mutex_lock(&encl->lock);

		entry = sgx_encl_load_page_in_vma(encl, addr, vm_flags);
		if (PTR_ERR(entry) != -EBUSY)
			break;

		mutex_unlock(&encl->lock);
	}

	if (IS_ERR(entry))
		mutex_unlock(&encl->lock);

	return entry;
}

static int sgx_vma_access(struct vm_area_struct *vma, unsigned long addr,
			  void *buf, int len, int write)
{
	struct sgx_encl *encl = vma->vm_private_data;
	struct sgx_encl_page *entry = NULL;
	char data[sizeof(unsigned long)];
	unsigned long align;
	int offset;
	int cnt;
	int ret = 0;
	int i;

	/*
	 * If process was forked, VMA is still there but vm_private_data is set
	 * to NULL.
	 */
	if (!encl)
		return -EFAULT;

	if (!test_bit(SGX_ENCL_DEBUG, &encl->flags))
		return -EFAULT;

	for (i = 0; i < len; i += cnt) {
		entry = sgx_encl_reserve_page(encl, (addr + i) & PAGE_MASK,
					      vma->vm_flags);
		if (IS_ERR(entry)) {
			ret = PTR_ERR(entry);
			break;
		}

		align = ALIGN_DOWN(addr + i, sizeof(unsigned long));
		offset = (addr + i) & (sizeof(unsigned long) - 1);
		cnt = sizeof(unsigned long) - offset;
		cnt = min(cnt, len - i);

		ret = sgx_encl_debug_read(encl, entry, align, data);
		if (ret)
			goto out;

		if (write) {
			memcpy(data + offset, buf + i, cnt);
			ret = sgx_encl_debug_write(encl, entry, align, data);
			if (ret)
				goto out;
		} else {
			memcpy(buf + i, data + offset, cnt);
		}

out:
		mutex_unlock(&encl->lock);

		if (ret)
			break;
	}

	return ret < 0 ? ret : i;
}

const struct vm_operations_struct sgx_vm_ops = {
	.fault = sgx_vma_fault,
	.mprotect = sgx_vma_mprotect,
	.open = sgx_vma_open,
	.access = sgx_vma_access,
};

/**
 * sgx_encl_release - Destroy an enclave instance
 * @ref:	address of a kref inside &sgx_encl
 *
 * Used together with kref_put(). Frees all the resources associated with the
 * enclave and the instance itself.
 */
void sgx_encl_release(struct kref *ref)
{
	struct sgx_encl *encl = container_of(ref, struct sgx_encl, refcount);
	unsigned long max_page_index = PFN_DOWN(encl->base + encl->size - 1);
	struct sgx_va_page *va_page;
	struct sgx_encl_page *entry;
	unsigned long count = 0;

	XA_STATE(xas, &encl->page_array, PFN_DOWN(encl->base));

	xas_lock(&xas);
	xas_for_each(&xas, entry, max_page_index) {
		if (entry->epc_page) {
			/*
			 * The page and its radix tree entry cannot be freed
			 * if the page is being held by the reclaimer.
			 */
			if (sgx_unmark_page_reclaimable(entry->epc_page))
				continue;

			sgx_encl_free_epc_page(entry->epc_page);
			encl->secs_child_cnt--;
			entry->epc_page = NULL;
		}

		kfree(entry);
		/*
		 * Invoke scheduler on every XA_CHECK_SCHED iteration
		 * to prevent soft lockups.
		 */
		if (!(++count % XA_CHECK_SCHED)) {
			xas_pause(&xas);
			xas_unlock(&xas);

			cond_resched();

			xas_lock(&xas);
		}
	}
	xas_unlock(&xas);

	xa_destroy(&encl->page_array);

	if (!encl->secs_child_cnt && encl->secs.epc_page) {
		sgx_encl_free_epc_page(encl->secs.epc_page);
		encl->secs.epc_page = NULL;
	}

	while (!list_empty(&encl->va_pages)) {
		va_page = list_first_entry(&encl->va_pages, struct sgx_va_page,
					   list);
		list_del(&va_page->list);
		sgx_encl_free_epc_page(va_page->epc_page);
		kfree(va_page);
	}

	if (encl->backing)
		fput(encl->backing);

	cleanup_srcu_struct(&encl->srcu);

	WARN_ON_ONCE(!list_empty(&encl->mm_list));

	/* Detect EPC page leak's. */
	WARN_ON_ONCE(encl->secs_child_cnt);
	WARN_ON_ONCE(encl->secs.epc_page);

	kfree(encl);
}

/*
 * 'mm' is exiting and no longer needs mmu notifications.
 */
static void sgx_mmu_notifier_release(struct mmu_notifier *mn,
				     struct mm_struct *mm)
{
	struct sgx_encl_mm *encl_mm = container_of(mn, struct sgx_encl_mm, mmu_notifier);
	struct sgx_encl_mm *tmp = NULL;

	/*
	 * The enclave itself can remove encl_mm.  Note, objects can't be moved
	 * off an RCU protected list, but deletion is ok.
	 */
	spin_lock(&encl_mm->encl->mm_lock);
	list_for_each_entry(tmp, &encl_mm->encl->mm_list, list) {
		if (tmp == encl_mm) {
			list_del_rcu(&encl_mm->list);
			break;
		}
	}
	spin_unlock(&encl_mm->encl->mm_lock);

	if (tmp == encl_mm) {
		synchronize_srcu(&encl_mm->encl->srcu);
		mmu_notifier_put(mn);
	}
}

static void sgx_mmu_notifier_free(struct mmu_notifier *mn)
{
	struct sgx_encl_mm *encl_mm = container_of(mn, struct sgx_encl_mm, mmu_notifier);

	/* 'encl_mm' is going away, put encl_mm->encl reference: */
	kref_put(&encl_mm->encl->refcount, sgx_encl_release);

	kfree(encl_mm);
}

static const struct mmu_notifier_ops sgx_mmu_notifier_ops = {
	.release		= sgx_mmu_notifier_release,
	.free_notifier		= sgx_mmu_notifier_free,
};

static struct sgx_encl_mm *sgx_encl_find_mm(struct sgx_encl *encl,
					    struct mm_struct *mm)
{
	struct sgx_encl_mm *encl_mm = NULL;
	struct sgx_encl_mm *tmp;
	int idx;

	idx = srcu_read_lock(&encl->srcu);

	list_for_each_entry_rcu(tmp, &encl->mm_list, list) {
		if (tmp->mm == mm) {
			encl_mm = tmp;
			break;
		}
	}

	srcu_read_unlock(&encl->srcu, idx);

	return encl_mm;
}

int sgx_encl_mm_add(struct sgx_encl *encl, struct mm_struct *mm)
{
	struct sgx_encl_mm *encl_mm;
	int ret;

	/*
	 * Even though a single enclave may be mapped into an mm more than once,
	 * each 'mm' only appears once on encl->mm_list. This is guaranteed by
	 * holding the mm's mmap lock for write before an mm can be added or
	 * remove to an encl->mm_list.
	 */
	mmap_assert_write_locked(mm);

	/*
	 * It's possible that an entry already exists in the mm_list, because it
	 * is removed only on VFS release or process exit.
	 */
	if (sgx_encl_find_mm(encl, mm))
		return 0;

	encl_mm = kzalloc(sizeof(*encl_mm), GFP_KERNEL);
	if (!encl_mm)
		return -ENOMEM;

	/* Grab a refcount for the encl_mm->encl reference: */
	kref_get(&encl->refcount);
	encl_mm->encl = encl;
	encl_mm->mm = mm;
	encl_mm->mmu_notifier.ops = &sgx_mmu_notifier_ops;

	ret = __mmu_notifier_register(&encl_mm->mmu_notifier, mm);
	if (ret) {
		kfree(encl_mm);
		return ret;
	}

	spin_lock(&encl->mm_lock);
	list_add_rcu(&encl_mm->list, &encl->mm_list);
	/* Pairs with smp_rmb() in sgx_zap_enclave_ptes(). */
	smp_wmb();
	encl->mm_list_version++;
	spin_unlock(&encl->mm_lock);

	return 0;
}

/**
 * sgx_encl_cpumask() - Query which CPUs might be accessing the enclave
 * @encl: the enclave
 *
 * Some SGX functions require that no cached linear-to-physical address
 * mappings are present before they can succeed. For example, ENCLS[EWB]
 * copies a page from the enclave page cache to regular main memory but
 * it fails if it cannot ensure that there are no cached
 * linear-to-physical address mappings referring to the page.
 *
 * SGX hardware flushes all cached linear-to-physical mappings on a CPU
 * when an enclave is exited via ENCLU[EEXIT] or an Asynchronous Enclave
 * Exit (AEX). Exiting an enclave will thus ensure cached linear-to-physical
 * address mappings are cleared but coordination with the tracking done within
 * the SGX hardware is needed to support the SGX functions that depend on this
 * cache clearing.
 *
 * When the ENCLS[ETRACK] function is issued on an enclave the hardware
 * tracks threads operating inside the enclave at that time. The SGX
 * hardware tracking require that all the identified threads must have
 * exited the enclave in order to flush the mappings before a function such
 * as ENCLS[EWB] will be permitted
 *
 * The following flow is used to support SGX functions that require that
 * no cached linear-to-physical address mappings are present:
 * 1) Execute ENCLS[ETRACK] to initiate hardware tracking.
 * 2) Use this function (sgx_encl_cpumask()) to query which CPUs might be
 *    accessing the enclave.
 * 3) Send IPI to identified CPUs, kicking them out of the enclave and
 *    thus flushing all locally cached linear-to-physical address mappings.
 * 4) Execute SGX function.
 *
 * Context: It is required to call this function after ENCLS[ETRACK].
 *          This will ensure that if any new mm appears (racing with
 *          sgx_encl_mm_add()) then the new mm will enter into the
 *          enclave with fresh linear-to-physical address mappings.
 *
 *          It is required that all IPIs are completed before a new
 *          ENCLS[ETRACK] is issued so be sure to protect steps 1 to 3
 *          of the above flow with the enclave's mutex.
 *
 * Return: cpumask of CPUs that might be accessing @encl
 */
const cpumask_t *sgx_encl_cpumask(struct sgx_encl *encl)
{
	cpumask_t *cpumask = &encl->cpumask;
	struct sgx_encl_mm *encl_mm;
	int idx;

	cpumask_clear(cpumask);

	idx = srcu_read_lock(&encl->srcu);

	list_for_each_entry_rcu(encl_mm, &encl->mm_list, list) {
		if (!mmget_not_zero(encl_mm->mm))
			continue;

		cpumask_or(cpumask, cpumask, mm_cpumask(encl_mm->mm));

		mmput_async(encl_mm->mm);
	}

	srcu_read_unlock(&encl->srcu, idx);

	return cpumask;
}

static struct page *sgx_encl_get_backing_page(struct sgx_encl *encl,
					      pgoff_t index)
{
	struct address_space *mapping = encl->backing->f_mapping;
	gfp_t gfpmask = mapping_gfp_mask(mapping);

	return shmem_read_mapping_page_gfp(mapping, index, gfpmask);
}

/**
 * __sgx_encl_get_backing() - Pin the backing storage
 * @encl:	an enclave pointer
 * @page_index:	enclave page index
 * @backing:	data for accessing backing storage for the page
 *
 * Pin the backing storage pages for storing the encrypted contents and Paging
 * Crypto MetaData (PCMD) of an enclave page.
 *
 * Return:
 *   0 on success,
 *   -errno otherwise.
 */
static int __sgx_encl_get_backing(struct sgx_encl *encl, unsigned long page_index,
			 struct sgx_backing *backing)
{
	pgoff_t page_pcmd_off = sgx_encl_get_backing_page_pcmd_offset(encl, page_index);
	struct page *contents;
	struct page *pcmd;

	contents = sgx_encl_get_backing_page(encl, page_index);
	if (IS_ERR(contents))
		return PTR_ERR(contents);

	pcmd = sgx_encl_get_backing_page(encl, PFN_DOWN(page_pcmd_off));
	if (IS_ERR(pcmd)) {
		put_page(contents);
		return PTR_ERR(pcmd);
	}

	backing->contents = contents;
	backing->pcmd = pcmd;
	backing->pcmd_offset = page_pcmd_off & (PAGE_SIZE - 1);

	return 0;
}

/*
 * When called from ksgxd, returns the mem_cgroup of a struct mm stored
 * in the enclave's mm_list. When not called from ksgxd, just returns
 * the mem_cgroup of the current task.
 */
static struct mem_cgroup *sgx_encl_get_mem_cgroup(struct sgx_encl *encl)
{
	struct mem_cgroup *memcg = NULL;
	struct sgx_encl_mm *encl_mm;
	int idx;

	/*
	 * If called from normal task context, return the mem_cgroup
	 * of the current task's mm. The remainder of the handling is for
	 * ksgxd.
	 */
	if (!current_is_ksgxd())
		return get_mem_cgroup_from_mm(current->mm);

	/*
	 * Search the enclave's mm_list to find an mm associated with
	 * this enclave to charge the allocation to.
	 */
	idx = srcu_read_lock(&encl->srcu);

	list_for_each_entry_rcu(encl_mm, &encl->mm_list, list) {
		if (!mmget_not_zero(encl_mm->mm))
			continue;

		memcg = get_mem_cgroup_from_mm(encl_mm->mm);

		mmput_async(encl_mm->mm);

		break;
	}

	srcu_read_unlock(&encl->srcu, idx);

	/*
	 * In the rare case that there isn't an mm associated with
	 * the enclave, set memcg to the current active mem_cgroup.
	 * This will be the root mem_cgroup if there is no active
	 * mem_cgroup.
	 */
	if (!memcg)
		return get_mem_cgroup_from_mm(NULL);

	return memcg;
}

/**
 * sgx_encl_alloc_backing() - create a new backing storage page
 * @encl:	an enclave pointer
 * @page_index:	enclave page index
 * @backing:	data for accessing backing storage for the page
 *
 * When called from ksgxd, sets the active memcg from one of the
 * mms in the enclave's mm_list prior to any backing page allocation,
 * in order to ensure that shmem page allocations are charged to the
 * enclave.  Create a backing page for loading data back into an EPC page with
 * ELDU.  This function takes a reference on a new backing page which
 * must be dropped with a corresponding call to sgx_encl_put_backing().
 *
 * Return:
 *   0 on success,
 *   -errno otherwise.
 */
int sgx_encl_alloc_backing(struct sgx_encl *encl, unsigned long page_index,
			   struct sgx_backing *backing)
{
	struct mem_cgroup *encl_memcg = sgx_encl_get_mem_cgroup(encl);
	struct mem_cgroup *memcg = set_active_memcg(encl_memcg);
	int ret;

	ret = __sgx_encl_get_backing(encl, page_index, backing);

	set_active_memcg(memcg);
	mem_cgroup_put(encl_memcg);

	return ret;
}

/**
 * sgx_encl_lookup_backing() - retrieve an existing backing storage page
 * @encl:	an enclave pointer
 * @page_index:	enclave page index
 * @backing:	data for accessing backing storage for the page
 *
 * Retrieve a backing page for loading data back into an EPC page with ELDU.
 * It is the caller's responsibility to ensure that it is appropriate to use
 * sgx_encl_lookup_backing() rather than sgx_encl_alloc_backing(). If lookup is
 * not used correctly, this will cause an allocation which is not accounted for.
 * This function takes a reference on an existing backing page which must be
 * dropped with a corresponding call to sgx_encl_put_backing().
 *
 * Return:
 *   0 on success,
 *   -errno otherwise.
 */
static int sgx_encl_lookup_backing(struct sgx_encl *encl, unsigned long page_index,
			   struct sgx_backing *backing)
{
	return __sgx_encl_get_backing(encl, page_index, backing);
}

/**
 * sgx_encl_put_backing() - Unpin the backing storage
 * @backing:	data for accessing backing storage for the page
 */
void sgx_encl_put_backing(struct sgx_backing *backing)
{
	put_page(backing->pcmd);
	put_page(backing->contents);
}

static int sgx_encl_test_and_clear_young_cb(pte_t *ptep, unsigned long addr,
					    void *data)
{
	pte_t pte;
	int ret;

	ret = pte_young(*ptep);
	if (ret) {
		pte = pte_mkold(*ptep);
		set_pte_at((struct mm_struct *)data, addr, ptep, pte);
	}

	return ret;
}

/**
 * sgx_encl_test_and_clear_young() - Test and reset the accessed bit
 * @mm:		mm_struct that is checked
 * @page:	enclave page to be tested for recent access
 *
 * Checks the Access (A) bit from the PTE corresponding to the enclave page and
 * clears it.
 *
 * Return: 1 if the page has been recently accessed and 0 if not.
 */
int sgx_encl_test_and_clear_young(struct mm_struct *mm,
				  struct sgx_encl_page *page)
{
	unsigned long addr = page->desc & PAGE_MASK;
	struct sgx_encl *encl = page->encl;
	struct vm_area_struct *vma;
	int ret;

	ret = sgx_encl_find(mm, addr, &vma);
	if (ret)
		return 0;

	if (encl != vma->vm_private_data)
		return 0;

	ret = apply_to_page_range(vma->vm_mm, addr, PAGE_SIZE,
				  sgx_encl_test_and_clear_young_cb, vma->vm_mm);
	if (ret < 0)
		return 0;

	return ret;
}

struct sgx_encl_page *sgx_encl_page_alloc(struct sgx_encl *encl,
					  unsigned long offset,
					  u64 secinfo_flags)
{
	struct sgx_encl_page *encl_page;
	unsigned long prot;

	encl_page = kzalloc(sizeof(*encl_page), GFP_KERNEL);
	if (!encl_page)
		return ERR_PTR(-ENOMEM);

	encl_page->desc = encl->base + offset;
	encl_page->encl = encl;

	prot = _calc_vm_trans(secinfo_flags, SGX_SECINFO_R, PROT_READ)  |
	       _calc_vm_trans(secinfo_flags, SGX_SECINFO_W, PROT_WRITE) |
	       _calc_vm_trans(secinfo_flags, SGX_SECINFO_X, PROT_EXEC);

	/*
	 * TCS pages must always RW set for CPU access while the SECINFO
	 * permissions are *always* zero - the CPU ignores the user provided
	 * values and silently overwrites them with zero permissions.
	 */
	if ((secinfo_flags & SGX_SECINFO_PAGE_TYPE_MASK) == SGX_SECINFO_TCS)
		prot |= PROT_READ | PROT_WRITE;

	/* Calculate maximum of the VM flags for the page. */
	encl_page->vm_max_prot_bits = calc_vm_prot_bits(prot, 0);

	return encl_page;
}

/**
 * sgx_zap_enclave_ptes() - remove PTEs mapping the address from enclave
 * @encl: the enclave
 * @addr: page aligned pointer to single page for which PTEs will be removed
 *
 * Multiple VMAs may have an enclave page mapped. Remove the PTE mapping
 * @addr from each VMA. Ensure that page fault handler is ready to handle
 * new mappings of @addr before calling this function.
 */
void sgx_zap_enclave_ptes(struct sgx_encl *encl, unsigned long addr)
{
	unsigned long mm_list_version;
	struct sgx_encl_mm *encl_mm;
	struct vm_area_struct *vma;
	int idx, ret;

	do {
		mm_list_version = encl->mm_list_version;

		/* Pairs with smp_wmb() in sgx_encl_mm_add(). */
		smp_rmb();

		idx = srcu_read_lock(&encl->srcu);

		list_for_each_entry_rcu(encl_mm, &encl->mm_list, list) {
			if (!mmget_not_zero(encl_mm->mm))
				continue;

			mmap_read_lock(encl_mm->mm);

			ret = sgx_encl_find(encl_mm->mm, addr, &vma);
			if (!ret && encl == vma->vm_private_data)
				zap_vma_ptes(vma, addr, PAGE_SIZE);

			mmap_read_unlock(encl_mm->mm);

			mmput_async(encl_mm->mm);
		}

		srcu_read_unlock(&encl->srcu, idx);
	} while (unlikely(encl->mm_list_version != mm_list_version));
}

/**
 * sgx_alloc_va_page() - Allocate a Version Array (VA) page
 * @reclaim: Reclaim EPC pages directly if none available. Enclave
 *           mutex should not be held if this is set.
 *
 * Allocate a free EPC page and convert it to a Version Array (VA) page.
 *
 * Return:
 *   a VA page,
 *   -errno otherwise
 */
struct sgx_epc_page *sgx_alloc_va_page(bool reclaim)
{
	struct sgx_epc_page *epc_page;
	int ret;

	epc_page = sgx_alloc_epc_page(NULL, reclaim);
	if (IS_ERR(epc_page))
		return ERR_CAST(epc_page);

	ret = __epa(sgx_get_epc_virt_addr(epc_page));
	if (ret) {
		WARN_ONCE(1, "EPA returned %d (0x%x)", ret, ret);
		sgx_encl_free_epc_page(epc_page);
		return ERR_PTR(-EFAULT);
	}

	return epc_page;
}

/**
 * sgx_alloc_va_slot - allocate a VA slot
 * @va_page:	a &struct sgx_va_page instance
 *
 * Allocates a slot from a &struct sgx_va_page instance.
 *
 * Return: offset of the slot inside the VA page
 */
unsigned int sgx_alloc_va_slot(struct sgx_va_page *va_page)
{
	int slot = find_first_zero_bit(va_page->slots, SGX_VA_SLOT_COUNT);

	if (slot < SGX_VA_SLOT_COUNT)
		set_bit(slot, va_page->slots);

	return slot << 3;
}

/**
 * sgx_free_va_slot - free a VA slot
 * @va_page:	a &struct sgx_va_page instance
 * @offset:	offset of the slot inside the VA page
 *
 * Frees a slot from a &struct sgx_va_page instance.
 */
void sgx_free_va_slot(struct sgx_va_page *va_page, unsigned int offset)
{
	clear_bit(offset >> 3, va_page->slots);
}

/**
 * sgx_va_page_full - is the VA page full?
 * @va_page:	a &struct sgx_va_page instance
 *
 * Return: true if all slots have been taken
 */
bool sgx_va_page_full(struct sgx_va_page *va_page)
{
	int slot = find_first_zero_bit(va_page->slots, SGX_VA_SLOT_COUNT);

	return slot == SGX_VA_SLOT_COUNT;
}

/**
 * sgx_encl_free_epc_page - free an EPC page assigned to an enclave
 * @page:	EPC page to be freed
 *
 * Free an EPC page assigned to an enclave. It does EREMOVE for the page, and
 * only upon success, it puts the page back to free page list.  Otherwise, it
 * gives a WARNING to indicate page is leaked.
 */
void sgx_encl_free_epc_page(struct sgx_epc_page *page)
{
	int ret;

	WARN_ON_ONCE(page->flags & SGX_EPC_PAGE_RECLAIMER_TRACKED);

	ret = __eremove(sgx_get_epc_virt_addr(page));
	if (WARN_ONCE(ret, EREMOVE_ERROR_MESSAGE, ret, ret))
		return;

	sgx_free_epc_page(page);
}