summaryrefslogtreecommitdiff
path: root/scripts/gcc-plugins/randomize_layout_plugin.c
blob: 6d5bbd31db7f2420fff6beb5ca71fc5dcf1eb493 (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
/*
 * Copyright 2014-2016 by Open Source Security, Inc., Brad Spengler <spender@grsecurity.net>
 *                   and PaX Team <pageexec@freemail.hu>
 * Licensed under the GPL v2
 *
 * Note: the choice of the license means that the compilation process is
 *       NOT 'eligible' as defined by gcc's library exception to the GPL v3,
 *       but for the kernel it doesn't matter since it doesn't link against
 *       any of the gcc libraries
 *
 * Usage:
 * $ # for 4.5/4.6/C based 4.7
 * $ gcc -I`gcc -print-file-name=plugin`/include -I`gcc -print-file-name=plugin`/include/c-family -fPIC -shared -O2 -o randomize_layout_plugin.so randomize_layout_plugin.c
 * $ # for C++ based 4.7/4.8+
 * $ g++ -I`g++ -print-file-name=plugin`/include -I`g++ -print-file-name=plugin`/include/c-family -fPIC -shared -O2 -o randomize_layout_plugin.so randomize_layout_plugin.c
 * $ gcc -fplugin=./randomize_layout_plugin.so test.c -O2
 */

#include "gcc-common.h"
#include "randomize_layout_seed.h"

#if BUILDING_GCC_MAJOR < 4 || (BUILDING_GCC_MAJOR == 4 && BUILDING_GCC_MINOR < 7)
#error "The RANDSTRUCT plugin requires GCC 4.7 or newer."
#endif

#define ORIG_TYPE_NAME(node) \
	(TYPE_NAME(TYPE_MAIN_VARIANT(node)) != NULL_TREE ? ((const unsigned char *)IDENTIFIER_POINTER(TYPE_NAME(TYPE_MAIN_VARIANT(node)))) : (const unsigned char *)"anonymous")

#define INFORM(loc, msg, ...)	inform(loc, "randstruct: " msg, ##__VA_ARGS__)
#define MISMATCH(loc, how, ...)	INFORM(loc, "casting between randomized structure pointer types (" how "): %qT and %qT\n", __VA_ARGS__)

__visible int plugin_is_GPL_compatible;

static int performance_mode;

static struct plugin_info randomize_layout_plugin_info = {
	.version	= "201402201816vanilla",
	.help		= "disable\t\t\tdo not activate plugin\n"
			  "performance-mode\tenable cacheline-aware layout randomization\n"
};

struct whitelist_entry {
	const char *pathname;
	const char *lhs;
	const char *rhs;
};

static const struct whitelist_entry whitelist[] = {
	/* NIU overloads mapping with page struct */
	{ "drivers/net/ethernet/sun/niu.c", "page", "address_space" },
	/* unix_skb_parms via UNIXCB() buffer */
	{ "net/unix/af_unix.c", "unix_skb_parms", "char" },
	/* big_key payload.data struct splashing */
	{ "security/keys/big_key.c", "path", "void *" },
	/* walk struct security_hook_heads as an array of struct hlist_head */
	{ "security/security.c", "hlist_head", "security_hook_heads" },
	{ }
};

/* from old Linux dcache.h */
static inline unsigned long
partial_name_hash(unsigned long c, unsigned long prevhash)
{
	return (prevhash + (c << 4) + (c >> 4)) * 11;
}
static inline unsigned int
name_hash(const unsigned char *name)
{
	unsigned long hash = 0;
	unsigned int len = strlen((const char *)name);
	while (len--)
		hash = partial_name_hash(*name++, hash);
	return (unsigned int)hash;
}

static tree handle_randomize_layout_attr(tree *node, tree name, tree args, int flags, bool *no_add_attrs)
{
	tree type;

	*no_add_attrs = true;
	if (TREE_CODE(*node) == FUNCTION_DECL) {
		error("%qE attribute does not apply to functions (%qF)", name, *node);
		return NULL_TREE;
	}

	if (TREE_CODE(*node) == PARM_DECL) {
		error("%qE attribute does not apply to function parameters (%qD)", name, *node);
		return NULL_TREE;
	}

	if (TREE_CODE(*node) == VAR_DECL) {
		error("%qE attribute does not apply to variables (%qD)", name, *node);
		return NULL_TREE;
	}

	if (TYPE_P(*node)) {
		type = *node;
	} else {
		gcc_assert(TREE_CODE(*node) == TYPE_DECL);
		type = TREE_TYPE(*node);
	}

	if (TREE_CODE(type) != RECORD_TYPE) {
		error("%qE attribute used on %qT applies to struct types only", name, type);
		return NULL_TREE;
	}

	if (lookup_attribute(IDENTIFIER_POINTER(name), TYPE_ATTRIBUTES(type))) {
		error("%qE attribute is already applied to the type %qT", name, type);
		return NULL_TREE;
	}

	*no_add_attrs = false;

	return NULL_TREE;
}

/* set on complete types that we don't need to inspect further at all */
static tree handle_randomize_considered_attr(tree *node, tree name, tree args, int flags, bool *no_add_attrs)
{
	*no_add_attrs = false;
	return NULL_TREE;
}

/*
 * set on types that we've performed a shuffle on, to prevent re-shuffling
 * this does not preclude us from inspecting its fields for potential shuffles
 */
static tree handle_randomize_performed_attr(tree *node, tree name, tree args, int flags, bool *no_add_attrs)
{
	*no_add_attrs = false;
	return NULL_TREE;
}

/*
 * 64bit variant of Bob Jenkins' public domain PRNG
 * 256 bits of internal state
 */

typedef unsigned long long u64;

typedef struct ranctx { u64 a; u64 b; u64 c; u64 d; } ranctx;

#define rot(x,k) (((x)<<(k))|((x)>>(64-(k))))
static u64 ranval(ranctx *x) {
	u64 e = x->a - rot(x->b, 7);
	x->a = x->b ^ rot(x->c, 13);
	x->b = x->c + rot(x->d, 37);
	x->c = x->d + e;
	x->d = e + x->a;
	return x->d;
}

static void raninit(ranctx *x, u64 *seed) {
	int i;

	x->a = seed[0];
	x->b = seed[1];
	x->c = seed[2];
	x->d = seed[3];

	for (i=0; i < 30; ++i)
		(void)ranval(x);
}

static u64 shuffle_seed[4];

struct partition_group {
	tree tree_start;
	unsigned long start;
	unsigned long length;
};

static void partition_struct(tree *fields, unsigned long length, struct partition_group *size_groups, unsigned long *num_groups)
{
	unsigned long i;
	unsigned long accum_size = 0;
	unsigned long accum_length = 0;
	unsigned long group_idx = 0;

	gcc_assert(length < INT_MAX);

	memset(size_groups, 0, sizeof(struct partition_group) * length);

	for (i = 0; i < length; i++) {
		if (size_groups[group_idx].tree_start == NULL_TREE) {
			size_groups[group_idx].tree_start = fields[i];
			size_groups[group_idx].start = i;
			accum_length = 0;
			accum_size = 0;
		}
		accum_size += (unsigned long)int_size_in_bytes(TREE_TYPE(fields[i]));
		accum_length++;
		if (accum_size >= 64) {
			size_groups[group_idx].length = accum_length;
			accum_length = 0;
			group_idx++;
		}
	}

	if (size_groups[group_idx].tree_start != NULL_TREE &&
	    !size_groups[group_idx].length) {
		size_groups[group_idx].length = accum_length;
		group_idx++;
	}

	*num_groups = group_idx;
}

static void performance_shuffle(tree *newtree, unsigned long length, ranctx *prng_state)
{
	unsigned long i, x;
	struct partition_group size_group[length];
	unsigned long num_groups = 0;
	unsigned long randnum;

	partition_struct(newtree, length, (struct partition_group *)&size_group, &num_groups);
	for (i = num_groups - 1; i > 0; i--) {
		struct partition_group tmp;
		randnum = ranval(prng_state) % (i + 1);
		tmp = size_group[i];
		size_group[i] = size_group[randnum];
		size_group[randnum] = tmp;
	}

	for (x = 0; x < num_groups; x++) {
		for (i = size_group[x].start + size_group[x].length - 1; i > size_group[x].start; i--) {
			tree tmp;
			if (DECL_BIT_FIELD_TYPE(newtree[i]))
				continue;
			randnum = ranval(prng_state) % (i + 1);
			// we could handle this case differently if desired
			if (DECL_BIT_FIELD_TYPE(newtree[randnum]))
				continue;
			tmp = newtree[i];
			newtree[i] = newtree[randnum];
			newtree[randnum] = tmp;
		}
	}
}

static void full_shuffle(tree *newtree, unsigned long length, ranctx *prng_state)
{
	unsigned long i, randnum;

	for (i = length - 1; i > 0; i--) {
		tree tmp;
		randnum = ranval(prng_state) % (i + 1);
		tmp = newtree[i];
		newtree[i] = newtree[randnum];
		newtree[randnum] = tmp;
	}
}

/* modern in-place Fisher-Yates shuffle */
static void shuffle(const_tree type, tree *newtree, unsigned long length)
{
	unsigned long i;
	u64 seed[4];
	ranctx prng_state;
	const unsigned char *structname;

	if (length == 0)
		return;

	gcc_assert(TREE_CODE(type) == RECORD_TYPE);

	structname = ORIG_TYPE_NAME(type);

#ifdef __DEBUG_PLUGIN
	fprintf(stderr, "Shuffling struct %s %p\n", (const char *)structname, type);
#ifdef __DEBUG_VERBOSE
	debug_tree((tree)type);
#endif
#endif

	for (i = 0; i < 4; i++) {
		seed[i] = shuffle_seed[i];
		seed[i] ^= name_hash(structname);
	}

	raninit(&prng_state, (u64 *)&seed);

	if (performance_mode)
		performance_shuffle(newtree, length, &prng_state);
	else
		full_shuffle(newtree, length, &prng_state);
}

static bool is_flexible_array(const_tree field)
{
	const_tree fieldtype;
	const_tree typesize;
	const_tree elemtype;
	const_tree elemsize;

	fieldtype = TREE_TYPE(field);
	typesize = TYPE_SIZE(fieldtype);

	if (TREE_CODE(fieldtype) != ARRAY_TYPE)
		return false;

	elemtype = TREE_TYPE(fieldtype);
	elemsize = TYPE_SIZE(elemtype);

	/* size of type is represented in bits */

	if (typesize == NULL_TREE && TYPE_DOMAIN(fieldtype) != NULL_TREE &&
	    TYPE_MAX_VALUE(TYPE_DOMAIN(fieldtype)) == NULL_TREE)
		return true;

	if (typesize != NULL_TREE &&
	    (TREE_CONSTANT(typesize) && (!tree_to_uhwi(typesize) ||
	     tree_to_uhwi(typesize) == tree_to_uhwi(elemsize))))
		return true;

	return false;
}

static int relayout_struct(tree type)
{
	unsigned long num_fields = (unsigned long)list_length(TYPE_FIELDS(type));
	unsigned long shuffle_length = num_fields;
	tree field;
	tree newtree[num_fields];
	unsigned long i;
	tree list;
	tree variant;
	tree main_variant;
	expanded_location xloc;
	bool has_flexarray = false;

	if (TYPE_FIELDS(type) == NULL_TREE)
		return 0;

	if (num_fields < 2)
		return 0;

	gcc_assert(TREE_CODE(type) == RECORD_TYPE);

	gcc_assert(num_fields < INT_MAX);

	if (lookup_attribute("randomize_performed", TYPE_ATTRIBUTES(type)) ||
	    lookup_attribute("no_randomize_layout", TYPE_ATTRIBUTES(TYPE_MAIN_VARIANT(type))))
		return 0;

	/* Workaround for 3rd-party VirtualBox source that we can't modify ourselves */
	if (!strcmp((const char *)ORIG_TYPE_NAME(type), "INTNETTRUNKFACTORY") ||
	    !strcmp((const char *)ORIG_TYPE_NAME(type), "RAWPCIFACTORY"))
		return 0;

	/* throw out any structs in uapi */
	xloc = expand_location(DECL_SOURCE_LOCATION(TYPE_FIELDS(type)));

	if (strstr(xloc.file, "/uapi/"))
		error(G_("attempted to randomize userland API struct %s"), ORIG_TYPE_NAME(type));

	for (field = TYPE_FIELDS(type), i = 0; field; field = TREE_CHAIN(field), i++) {
		gcc_assert(TREE_CODE(field) == FIELD_DECL);
		newtree[i] = field;
	}

	/*
	 * enforce that we don't randomize the layout of the last
	 * element of a struct if it's a 0 or 1-length array
	 * or a proper flexible array
	 */
	if (is_flexible_array(newtree[num_fields - 1])) {
		has_flexarray = true;
		shuffle_length--;
	}

	shuffle(type, (tree *)newtree, shuffle_length);

	/*
	 * set up a bogus anonymous struct field designed to error out on unnamed struct initializers
	 * as gcc provides no other way to detect such code
	 */
	list = make_node(FIELD_DECL);
	TREE_CHAIN(list) = newtree[0];
	TREE_TYPE(list) = void_type_node;
	DECL_SIZE(list) = bitsize_zero_node;
	DECL_NONADDRESSABLE_P(list) = 1;
	DECL_FIELD_BIT_OFFSET(list) = bitsize_zero_node;
	DECL_SIZE_UNIT(list) = size_zero_node;
	DECL_FIELD_OFFSET(list) = size_zero_node;
	DECL_CONTEXT(list) = type;
	// to satisfy the constify plugin
	TREE_READONLY(list) = 1;

	for (i = 0; i < num_fields - 1; i++)
		TREE_CHAIN(newtree[i]) = newtree[i+1];
	TREE_CHAIN(newtree[num_fields - 1]) = NULL_TREE;

	main_variant = TYPE_MAIN_VARIANT(type);
	for (variant = main_variant; variant; variant = TYPE_NEXT_VARIANT(variant)) {
		TYPE_FIELDS(variant) = list;
		TYPE_ATTRIBUTES(variant) = copy_list(TYPE_ATTRIBUTES(variant));
		TYPE_ATTRIBUTES(variant) = tree_cons(get_identifier("randomize_performed"), NULL_TREE, TYPE_ATTRIBUTES(variant));
		TYPE_ATTRIBUTES(variant) = tree_cons(get_identifier("designated_init"), NULL_TREE, TYPE_ATTRIBUTES(variant));
		if (has_flexarray)
			TYPE_ATTRIBUTES(type) = tree_cons(get_identifier("has_flexarray"), NULL_TREE, TYPE_ATTRIBUTES(type));
	}

	/*
	 * force a re-layout of the main variant
	 * the TYPE_SIZE for all variants will be recomputed
	 * by finalize_type_size()
	 */
	TYPE_SIZE(main_variant) = NULL_TREE;
	layout_type(main_variant);
	gcc_assert(TYPE_SIZE(main_variant) != NULL_TREE);

	return 1;
}

/* from constify plugin */
static const_tree get_field_type(const_tree field)
{
	return strip_array_types(TREE_TYPE(field));
}

/* from constify plugin */
static bool is_fptr(const_tree fieldtype)
{
	if (TREE_CODE(fieldtype) != POINTER_TYPE)
		return false;

	return TREE_CODE(TREE_TYPE(fieldtype)) == FUNCTION_TYPE;
}

/* derived from constify plugin */
static int is_pure_ops_struct(const_tree node)
{
	const_tree field;

	gcc_assert(TREE_CODE(node) == RECORD_TYPE || TREE_CODE(node) == UNION_TYPE);

	for (field = TYPE_FIELDS(node); field; field = TREE_CHAIN(field)) {
		const_tree fieldtype = get_field_type(field);
		enum tree_code code = TREE_CODE(fieldtype);

		if (node == fieldtype)
			continue;

		if (!is_fptr(fieldtype))
			return 0;

		if (code != RECORD_TYPE && code != UNION_TYPE)
			continue;

		if (!is_pure_ops_struct(fieldtype))
			return 0;
	}

	return 1;
}

static void randomize_type(tree type)
{
	tree variant;

	gcc_assert(TREE_CODE(type) == RECORD_TYPE);

	if (lookup_attribute("randomize_considered", TYPE_ATTRIBUTES(type)))
		return;

	if (lookup_attribute("randomize_layout", TYPE_ATTRIBUTES(TYPE_MAIN_VARIANT(type))) || is_pure_ops_struct(type))
		relayout_struct(type);

	for (variant = TYPE_MAIN_VARIANT(type); variant; variant = TYPE_NEXT_VARIANT(variant)) {
		TYPE_ATTRIBUTES(type) = copy_list(TYPE_ATTRIBUTES(type));
		TYPE_ATTRIBUTES(type) = tree_cons(get_identifier("randomize_considered"), NULL_TREE, TYPE_ATTRIBUTES(type));
	}
#ifdef __DEBUG_PLUGIN
	fprintf(stderr, "Marking randomize_considered on struct %s\n", ORIG_TYPE_NAME(type));
#ifdef __DEBUG_VERBOSE
	debug_tree(type);
#endif
#endif
}

static void update_decl_size(tree decl)
{
	tree lastval, lastidx, field, init, type, flexsize;
	unsigned HOST_WIDE_INT len;

	type = TREE_TYPE(decl);

	if (!lookup_attribute("has_flexarray", TYPE_ATTRIBUTES(type)))
		return;

	init = DECL_INITIAL(decl);
	if (init == NULL_TREE || init == error_mark_node)
		return;

	if (TREE_CODE(init) != CONSTRUCTOR)
		return;

	len = CONSTRUCTOR_NELTS(init);
        if (!len)
		return;

	lastval = CONSTRUCTOR_ELT(init, CONSTRUCTOR_NELTS(init) - 1)->value;
	lastidx = CONSTRUCTOR_ELT(init, CONSTRUCTOR_NELTS(init) - 1)->index;

	for (field = TYPE_FIELDS(TREE_TYPE(decl)); TREE_CHAIN(field); field = TREE_CHAIN(field))
		;

	if (lastidx != field)
		return;

	if (TREE_CODE(lastval) != STRING_CST) {
		error("Only string constants are supported as initializers "
		      "for randomized structures with flexible arrays");
		return;
	}

	flexsize = bitsize_int(TREE_STRING_LENGTH(lastval) *
		tree_to_uhwi(TYPE_SIZE(TREE_TYPE(TREE_TYPE(lastval)))));

	DECL_SIZE(decl) = size_binop(PLUS_EXPR, TYPE_SIZE(type), flexsize);

	return;
}


static void randomize_layout_finish_decl(void *event_data, void *data)
{
	tree decl = (tree)event_data;
	tree type;

	if (decl == NULL_TREE || decl == error_mark_node)
		return;

	type = TREE_TYPE(decl);

	if (TREE_CODE(decl) != VAR_DECL)
		return;

	if (TREE_CODE(type) != RECORD_TYPE && TREE_CODE(type) != UNION_TYPE)
		return;

	if (!lookup_attribute("randomize_performed", TYPE_ATTRIBUTES(type)))
		return;

	DECL_SIZE(decl) = 0;
	DECL_SIZE_UNIT(decl) = 0;
	SET_DECL_ALIGN(decl, 0);
	SET_DECL_MODE (decl, VOIDmode);
	SET_DECL_RTL(decl, 0);
	update_decl_size(decl);
	layout_decl(decl, 0);
}

static void finish_type(void *event_data, void *data)
{
	tree type = (tree)event_data;

	if (type == NULL_TREE || type == error_mark_node)
		return;

	if (TREE_CODE(type) != RECORD_TYPE)
		return;

	if (TYPE_FIELDS(type) == NULL_TREE)
		return;

	if (lookup_attribute("randomize_considered", TYPE_ATTRIBUTES(type)))
		return;

#ifdef __DEBUG_PLUGIN
	fprintf(stderr, "Calling randomize_type on %s\n", ORIG_TYPE_NAME(type));
#endif
#ifdef __DEBUG_VERBOSE
	debug_tree(type);
#endif
	randomize_type(type);

	return;
}

static struct attribute_spec randomize_layout_attr = { };
static struct attribute_spec no_randomize_layout_attr = { };
static struct attribute_spec randomize_considered_attr = { };
static struct attribute_spec randomize_performed_attr = { };

static void register_attributes(void *event_data, void *data)
{
	randomize_layout_attr.name		= "randomize_layout";
	randomize_layout_attr.type_required	= true;
	randomize_layout_attr.handler		= handle_randomize_layout_attr;
#if BUILDING_GCC_VERSION >= 4007
	randomize_layout_attr.affects_type_identity = true;
#endif

	no_randomize_layout_attr.name		= "no_randomize_layout";
	no_randomize_layout_attr.type_required	= true;
	no_randomize_layout_attr.handler	= handle_randomize_layout_attr;
#if BUILDING_GCC_VERSION >= 4007
	no_randomize_layout_attr.affects_type_identity = true;
#endif

	randomize_considered_attr.name		= "randomize_considered";
	randomize_considered_attr.type_required	= true;
	randomize_considered_attr.handler	= handle_randomize_considered_attr;

	randomize_performed_attr.name		= "randomize_performed";
	randomize_performed_attr.type_required	= true;
	randomize_performed_attr.handler	= handle_randomize_performed_attr;

	register_attribute(&randomize_layout_attr);
	register_attribute(&no_randomize_layout_attr);
	register_attribute(&randomize_considered_attr);
	register_attribute(&randomize_performed_attr);
}

static void check_bad_casts_in_constructor(tree var, tree init)
{
	unsigned HOST_WIDE_INT idx;
	tree field, val;
	tree field_type, val_type;

	FOR_EACH_CONSTRUCTOR_ELT(CONSTRUCTOR_ELTS(init), idx, field, val) {
		if (TREE_CODE(val) == CONSTRUCTOR) {
			check_bad_casts_in_constructor(var, val);
			continue;
		}

		/* pipacs' plugin creates franken-arrays that differ from those produced by
		   normal code which all have valid 'field' trees. work around this */
		if (field == NULL_TREE)
			continue;
		field_type = TREE_TYPE(field);
		val_type = TREE_TYPE(val);

		if (TREE_CODE(field_type) != POINTER_TYPE || TREE_CODE(val_type) != POINTER_TYPE)
			continue;

		if (field_type == val_type)
			continue;

		field_type = TYPE_MAIN_VARIANT(strip_array_types(TYPE_MAIN_VARIANT(TREE_TYPE(field_type))));
		val_type = TYPE_MAIN_VARIANT(strip_array_types(TYPE_MAIN_VARIANT(TREE_TYPE(val_type))));

		if (field_type == void_type_node)
			continue;
		if (field_type == val_type)
			continue;
		if (TREE_CODE(val_type) != RECORD_TYPE)
			continue;

		if (!lookup_attribute("randomize_performed", TYPE_ATTRIBUTES(val_type)))
			continue;
		MISMATCH(DECL_SOURCE_LOCATION(var), "constructor\n", TYPE_MAIN_VARIANT(field_type), TYPE_MAIN_VARIANT(val_type));
	}
}

/* derived from the constify plugin */
static void check_global_variables(void *event_data, void *data)
{
	struct varpool_node *node;
	tree init;

	FOR_EACH_VARIABLE(node) {
		tree var = NODE_DECL(node);
		init = DECL_INITIAL(var);
		if (init == NULL_TREE)
			continue;

		if (TREE_CODE(init) != CONSTRUCTOR)
			continue;

		check_bad_casts_in_constructor(var, init);
	}
}

static bool dominated_by_is_err(const_tree rhs, basic_block bb)
{
	basic_block dom;
	gimple dom_stmt;
	gimple call_stmt;
	const_tree dom_lhs;
	const_tree poss_is_err_cond;
	const_tree poss_is_err_func;
	const_tree is_err_arg;

	dom = get_immediate_dominator(CDI_DOMINATORS, bb);
	if (!dom)
		return false;

	dom_stmt = last_stmt(dom);
	if (!dom_stmt)
		return false;

	if (gimple_code(dom_stmt) != GIMPLE_COND)
		return false;

	if (gimple_cond_code(dom_stmt) != NE_EXPR)
		return false;

	if (!integer_zerop(gimple_cond_rhs(dom_stmt)))
		return false;

	poss_is_err_cond = gimple_cond_lhs(dom_stmt);

	if (TREE_CODE(poss_is_err_cond) != SSA_NAME)
		return false;

	call_stmt = SSA_NAME_DEF_STMT(poss_is_err_cond);

	if (gimple_code(call_stmt) != GIMPLE_CALL)
		return false;

	dom_lhs = gimple_get_lhs(call_stmt);
	poss_is_err_func = gimple_call_fndecl(call_stmt);
	if (!poss_is_err_func)
		return false;
	if (dom_lhs != poss_is_err_cond)
		return false;
	if (strcmp(DECL_NAME_POINTER(poss_is_err_func), "IS_ERR"))
		return false;

	is_err_arg = gimple_call_arg(call_stmt, 0);
	if (!is_err_arg)
		return false;

	if (is_err_arg != rhs)
		return false;

	return true;
}

static void handle_local_var_initializers(void)
{
	tree var;
	unsigned int i;

	FOR_EACH_LOCAL_DECL(cfun, i, var) {
		tree init = DECL_INITIAL(var);
		if (!init)
			continue;
		if (TREE_CODE(init) != CONSTRUCTOR)
			continue;
		check_bad_casts_in_constructor(var, init);
	}
}

static bool type_name_eq(gimple stmt, const_tree type_tree, const char *wanted_name)
{
	const char *type_name;

	if (type_tree == NULL_TREE)
		return false;

	switch (TREE_CODE(type_tree)) {
	case RECORD_TYPE:
		type_name = TYPE_NAME_POINTER(type_tree);
		break;
	case INTEGER_TYPE:
		if (TYPE_PRECISION(type_tree) == CHAR_TYPE_SIZE)
			type_name = "char";
		else {
			INFORM(gimple_location(stmt), "found non-char INTEGER_TYPE cast comparison: %qT\n", type_tree);
			debug_tree(type_tree);
			return false;
		}
		break;
	case POINTER_TYPE:
		if (TREE_CODE(TREE_TYPE(type_tree)) == VOID_TYPE) {
			type_name = "void *";
			break;
		} else {
			INFORM(gimple_location(stmt), "found non-void POINTER_TYPE cast comparison %qT\n", type_tree);
			debug_tree(type_tree);
			return false;
		}
	default:
		INFORM(gimple_location(stmt), "unhandled cast comparison: %qT\n", type_tree);
		debug_tree(type_tree);
		return false;
	}

	return strcmp(type_name, wanted_name) == 0;
}

static bool whitelisted_cast(gimple stmt, const_tree lhs_tree, const_tree rhs_tree)
{
	const struct whitelist_entry *entry;
	expanded_location xloc = expand_location(gimple_location(stmt));

	for (entry = whitelist; entry->pathname; entry++) {
		if (!strstr(xloc.file, entry->pathname))
			continue;

		if (type_name_eq(stmt, lhs_tree, entry->lhs) && type_name_eq(stmt, rhs_tree, entry->rhs))
			return true;
	}

	return false;
}

/*
 * iterate over all statements to find "bad" casts:
 * those where the address of the start of a structure is cast
 * to a pointer of a structure of a different type, or a
 * structure pointer type is cast to a different structure pointer type
 */
static unsigned int find_bad_casts_execute(void)
{
	basic_block bb;

	handle_local_var_initializers();

	FOR_EACH_BB_FN(bb, cfun) {
		gimple_stmt_iterator gsi;

		for (gsi = gsi_start_bb(bb); !gsi_end_p(gsi); gsi_next(&gsi)) {
			gimple stmt;
			const_tree lhs;
			const_tree lhs_type;
			const_tree rhs1;
			const_tree rhs_type;
			const_tree ptr_lhs_type;
			const_tree ptr_rhs_type;
			const_tree op0;
			const_tree op0_type;
			enum tree_code rhs_code;

			stmt = gsi_stmt(gsi);

#ifdef __DEBUG_PLUGIN
#ifdef __DEBUG_VERBOSE
			debug_gimple_stmt(stmt);
			debug_tree(gimple_get_lhs(stmt));
#endif
#endif

			if (gimple_code(stmt) != GIMPLE_ASSIGN)
				continue;

#ifdef __DEBUG_PLUGIN
#ifdef __DEBUG_VERBOSE
			debug_tree(gimple_assign_rhs1(stmt));
#endif
#endif


			rhs_code = gimple_assign_rhs_code(stmt);

			if (rhs_code != ADDR_EXPR && rhs_code != SSA_NAME)
				continue;

			lhs = gimple_get_lhs(stmt);
			lhs_type = TREE_TYPE(lhs);
			rhs1 = gimple_assign_rhs1(stmt);
			rhs_type = TREE_TYPE(rhs1);

			if (TREE_CODE(rhs_type) != POINTER_TYPE ||
			    TREE_CODE(lhs_type) != POINTER_TYPE)
				continue;

			ptr_lhs_type = TYPE_MAIN_VARIANT(strip_array_types(TYPE_MAIN_VARIANT(TREE_TYPE(lhs_type))));
			ptr_rhs_type = TYPE_MAIN_VARIANT(strip_array_types(TYPE_MAIN_VARIANT(TREE_TYPE(rhs_type))));

			if (ptr_rhs_type == void_type_node)
				continue;

			if (ptr_lhs_type == void_type_node)
				continue;

			if (dominated_by_is_err(rhs1, bb))
				continue;

			if (TREE_CODE(ptr_rhs_type) != RECORD_TYPE) {
#ifndef __DEBUG_PLUGIN
				if (lookup_attribute("randomize_performed", TYPE_ATTRIBUTES(ptr_lhs_type)))
#endif
				{
					if (!whitelisted_cast(stmt, ptr_lhs_type, ptr_rhs_type))
						MISMATCH(gimple_location(stmt), "rhs", ptr_lhs_type, ptr_rhs_type);
				}
				continue;
			}

			if (rhs_code == SSA_NAME && ptr_lhs_type == ptr_rhs_type)
				continue;

			if (rhs_code == ADDR_EXPR) {
				op0 = TREE_OPERAND(rhs1, 0);

				if (op0 == NULL_TREE)
					continue;

				if (TREE_CODE(op0) != VAR_DECL)
					continue;

				op0_type = TYPE_MAIN_VARIANT(strip_array_types(TYPE_MAIN_VARIANT(TREE_TYPE(op0))));
				if (op0_type == ptr_lhs_type)
					continue;

#ifndef __DEBUG_PLUGIN
				if (lookup_attribute("randomize_performed", TYPE_ATTRIBUTES(op0_type)))
#endif
				{
					if (!whitelisted_cast(stmt, ptr_lhs_type, op0_type))
						MISMATCH(gimple_location(stmt), "op0", ptr_lhs_type, op0_type);
				}
			} else {
				const_tree ssa_name_var = SSA_NAME_VAR(rhs1);
				/* skip bogus type casts introduced by container_of */
				if (ssa_name_var != NULL_TREE && DECL_NAME(ssa_name_var) && 
				    !strcmp((const char *)DECL_NAME_POINTER(ssa_name_var), "__mptr"))
					continue;
#ifndef __DEBUG_PLUGIN
				if (lookup_attribute("randomize_performed", TYPE_ATTRIBUTES(ptr_rhs_type)))
#endif
				{
					if (!whitelisted_cast(stmt, ptr_lhs_type, ptr_rhs_type))
						MISMATCH(gimple_location(stmt), "ssa", ptr_lhs_type, ptr_rhs_type);
				}
			}

		}
	}
	return 0;
}

#define PASS_NAME find_bad_casts
#define NO_GATE
#define TODO_FLAGS_FINISH TODO_dump_func
#include "gcc-generate-gimple-pass.h"

__visible int plugin_init(struct plugin_name_args *plugin_info, struct plugin_gcc_version *version)
{
	int i;
	const char * const plugin_name = plugin_info->base_name;
	const int argc = plugin_info->argc;
	const struct plugin_argument * const argv = plugin_info->argv;
	bool enable = true;
	int obtained_seed = 0;
	struct register_pass_info find_bad_casts_pass_info;

	find_bad_casts_pass_info.pass			= make_find_bad_casts_pass();
	find_bad_casts_pass_info.reference_pass_name	= "ssa";
	find_bad_casts_pass_info.ref_pass_instance_number	= 1;
	find_bad_casts_pass_info.pos_op			= PASS_POS_INSERT_AFTER;

	if (!plugin_default_version_check(version, &gcc_version)) {
		error(G_("incompatible gcc/plugin versions"));
		return 1;
	}

	if (strncmp(lang_hooks.name, "GNU C", 5) && !strncmp(lang_hooks.name, "GNU C+", 6)) {
		inform(UNKNOWN_LOCATION, G_("%s supports C only, not %s"), plugin_name, lang_hooks.name);
		enable = false;
	}

	for (i = 0; i < argc; ++i) {
		if (!strcmp(argv[i].key, "disable")) {
			enable = false;
			continue;
		}
		if (!strcmp(argv[i].key, "performance-mode")) {
			performance_mode = 1;
			continue;
		}
		error(G_("unknown option '-fplugin-arg-%s-%s'"), plugin_name, argv[i].key);
	}

	if (strlen(randstruct_seed) != 64) {
		error(G_("invalid seed value supplied for %s plugin"), plugin_name);
		return 1;
	}
	obtained_seed = sscanf(randstruct_seed, "%016llx%016llx%016llx%016llx",
		&shuffle_seed[0], &shuffle_seed[1], &shuffle_seed[2], &shuffle_seed[3]);
	if (obtained_seed != 4) {
		error(G_("Invalid seed supplied for %s plugin"), plugin_name);
		return 1;
	}

	register_callback(plugin_name, PLUGIN_INFO, NULL, &randomize_layout_plugin_info);
	if (enable) {
		register_callback(plugin_name, PLUGIN_ALL_IPA_PASSES_START, check_global_variables, NULL);
		register_callback(plugin_name, PLUGIN_PASS_MANAGER_SETUP, NULL, &find_bad_casts_pass_info);
		register_callback(plugin_name, PLUGIN_FINISH_TYPE, finish_type, NULL);
		register_callback(plugin_name, PLUGIN_FINISH_DECL, randomize_layout_finish_decl, NULL);
	}
	register_callback(plugin_name, PLUGIN_ATTRIBUTES, register_attributes, NULL);

	return 0;
}