1 /*
2  * Copyright 2014-2016 by Open Source Security, Inc., Brad Spengler <spender@grsecurity.net>
3  *                   and PaX Team <pageexec@freemail.hu>
4  * Licensed under the GPL v2
5  *
6  * Note: the choice of the license means that the compilation process is
7  *       NOT 'eligible' as defined by gcc's library exception to the GPL v3,
8  *       but for the kernel it doesn't matter since it doesn't link against
9  *       any of the gcc libraries
10  *
11  * Usage:
12  * $ # for 4.5/4.6/C based 4.7
13  * $ 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
14  * $ # for C++ based 4.7/4.8+
15  * $ 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
16  * $ gcc -fplugin=./randomize_layout_plugin.so test.c -O2
17  */
18 
19 #include "gcc-common.h"
20 #include "randomize_layout_seed.h"
21 
22 #if BUILDING_GCC_MAJOR < 4 || (BUILDING_GCC_MAJOR == 4 && BUILDING_GCC_MINOR < 7)
23 #error "The RANDSTRUCT plugin requires GCC 4.7 or newer."
24 #endif
25 
26 #define ORIG_TYPE_NAME(node) \
27 	(TYPE_NAME(TYPE_MAIN_VARIANT(node)) != NULL_TREE ? ((const unsigned char *)IDENTIFIER_POINTER(TYPE_NAME(TYPE_MAIN_VARIANT(node)))) : (const unsigned char *)"anonymous")
28 
29 #define INFORM(loc, msg, ...)	inform(loc, "randstruct: " msg, ##__VA_ARGS__)
30 #define MISMATCH(loc, how, ...)	INFORM(loc, "casting between randomized structure pointer types (" how "): %qT and %qT\n", __VA_ARGS__)
31 
32 __visible int plugin_is_GPL_compatible;
33 
34 static int performance_mode;
35 
36 static struct plugin_info randomize_layout_plugin_info = {
37 	.version	= "201402201816vanilla",
38 	.help		= "disable\t\t\tdo not activate plugin\n"
39 			  "performance-mode\tenable cacheline-aware layout randomization\n"
40 };
41 
42 struct whitelist_entry {
43 	const char *pathname;
44 	const char *lhs;
45 	const char *rhs;
46 };
47 
48 static const struct whitelist_entry whitelist[] = {
49 	/* NIU overloads mapping with page struct */
50 	{ "drivers/net/ethernet/sun/niu.c", "page", "address_space" },
51 	/* unix_skb_parms via UNIXCB() buffer */
52 	{ "net/unix/af_unix.c", "unix_skb_parms", "char" },
53 	/* big_key payload.data struct splashing */
54 	{ "security/keys/big_key.c", "path", "void *" },
55 	/* walk struct security_hook_heads as an array of struct hlist_head */
56 	{ "security/security.c", "hlist_head", "security_hook_heads" },
57 	{ }
58 };
59 
60 /* from old Linux dcache.h */
61 static inline unsigned long
62 partial_name_hash(unsigned long c, unsigned long prevhash)
63 {
64 	return (prevhash + (c << 4) + (c >> 4)) * 11;
65 }
66 static inline unsigned int
67 name_hash(const unsigned char *name)
68 {
69 	unsigned long hash = 0;
70 	unsigned int len = strlen((const char *)name);
71 	while (len--)
72 		hash = partial_name_hash(*name++, hash);
73 	return (unsigned int)hash;
74 }
75 
76 static tree handle_randomize_layout_attr(tree *node, tree name, tree args, int flags, bool *no_add_attrs)
77 {
78 	tree type;
79 
80 	*no_add_attrs = true;
81 	if (TREE_CODE(*node) == FUNCTION_DECL) {
82 		error("%qE attribute does not apply to functions (%qF)", name, *node);
83 		return NULL_TREE;
84 	}
85 
86 	if (TREE_CODE(*node) == PARM_DECL) {
87 		error("%qE attribute does not apply to function parameters (%qD)", name, *node);
88 		return NULL_TREE;
89 	}
90 
91 	if (TREE_CODE(*node) == VAR_DECL) {
92 		error("%qE attribute does not apply to variables (%qD)", name, *node);
93 		return NULL_TREE;
94 	}
95 
96 	if (TYPE_P(*node)) {
97 		type = *node;
98 	} else {
99 		gcc_assert(TREE_CODE(*node) == TYPE_DECL);
100 		type = TREE_TYPE(*node);
101 	}
102 
103 	if (TREE_CODE(type) != RECORD_TYPE) {
104 		error("%qE attribute used on %qT applies to struct types only", name, type);
105 		return NULL_TREE;
106 	}
107 
108 	if (lookup_attribute(IDENTIFIER_POINTER(name), TYPE_ATTRIBUTES(type))) {
109 		error("%qE attribute is already applied to the type %qT", name, type);
110 		return NULL_TREE;
111 	}
112 
113 	*no_add_attrs = false;
114 
115 	return NULL_TREE;
116 }
117 
118 /* set on complete types that we don't need to inspect further at all */
119 static tree handle_randomize_considered_attr(tree *node, tree name, tree args, int flags, bool *no_add_attrs)
120 {
121 	*no_add_attrs = false;
122 	return NULL_TREE;
123 }
124 
125 /*
126  * set on types that we've performed a shuffle on, to prevent re-shuffling
127  * this does not preclude us from inspecting its fields for potential shuffles
128  */
129 static tree handle_randomize_performed_attr(tree *node, tree name, tree args, int flags, bool *no_add_attrs)
130 {
131 	*no_add_attrs = false;
132 	return NULL_TREE;
133 }
134 
135 /*
136  * 64bit variant of Bob Jenkins' public domain PRNG
137  * 256 bits of internal state
138  */
139 
140 typedef unsigned long long u64;
141 
142 typedef struct ranctx { u64 a; u64 b; u64 c; u64 d; } ranctx;
143 
144 #define rot(x,k) (((x)<<(k))|((x)>>(64-(k))))
145 static u64 ranval(ranctx *x) {
146 	u64 e = x->a - rot(x->b, 7);
147 	x->a = x->b ^ rot(x->c, 13);
148 	x->b = x->c + rot(x->d, 37);
149 	x->c = x->d + e;
150 	x->d = e + x->a;
151 	return x->d;
152 }
153 
154 static void raninit(ranctx *x, u64 *seed) {
155 	int i;
156 
157 	x->a = seed[0];
158 	x->b = seed[1];
159 	x->c = seed[2];
160 	x->d = seed[3];
161 
162 	for (i=0; i < 30; ++i)
163 		(void)ranval(x);
164 }
165 
166 static u64 shuffle_seed[4];
167 
168 struct partition_group {
169 	tree tree_start;
170 	unsigned long start;
171 	unsigned long length;
172 };
173 
174 static void partition_struct(tree *fields, unsigned long length, struct partition_group *size_groups, unsigned long *num_groups)
175 {
176 	unsigned long i;
177 	unsigned long accum_size = 0;
178 	unsigned long accum_length = 0;
179 	unsigned long group_idx = 0;
180 
181 	gcc_assert(length < INT_MAX);
182 
183 	memset(size_groups, 0, sizeof(struct partition_group) * length);
184 
185 	for (i = 0; i < length; i++) {
186 		if (size_groups[group_idx].tree_start == NULL_TREE) {
187 			size_groups[group_idx].tree_start = fields[i];
188 			size_groups[group_idx].start = i;
189 			accum_length = 0;
190 			accum_size = 0;
191 		}
192 		accum_size += (unsigned long)int_size_in_bytes(TREE_TYPE(fields[i]));
193 		accum_length++;
194 		if (accum_size >= 64) {
195 			size_groups[group_idx].length = accum_length;
196 			accum_length = 0;
197 			group_idx++;
198 		}
199 	}
200 
201 	if (size_groups[group_idx].tree_start != NULL_TREE &&
202 	    !size_groups[group_idx].length) {
203 		size_groups[group_idx].length = accum_length;
204 		group_idx++;
205 	}
206 
207 	*num_groups = group_idx;
208 }
209 
210 static void performance_shuffle(tree *newtree, unsigned long length, ranctx *prng_state)
211 {
212 	unsigned long i, x;
213 	struct partition_group size_group[length];
214 	unsigned long num_groups = 0;
215 	unsigned long randnum;
216 
217 	partition_struct(newtree, length, (struct partition_group *)&size_group, &num_groups);
218 	for (i = num_groups - 1; i > 0; i--) {
219 		struct partition_group tmp;
220 		randnum = ranval(prng_state) % (i + 1);
221 		tmp = size_group[i];
222 		size_group[i] = size_group[randnum];
223 		size_group[randnum] = tmp;
224 	}
225 
226 	for (x = 0; x < num_groups; x++) {
227 		for (i = size_group[x].start + size_group[x].length - 1; i > size_group[x].start; i--) {
228 			tree tmp;
229 			if (DECL_BIT_FIELD_TYPE(newtree[i]))
230 				continue;
231 			randnum = ranval(prng_state) % (i + 1);
232 			// we could handle this case differently if desired
233 			if (DECL_BIT_FIELD_TYPE(newtree[randnum]))
234 				continue;
235 			tmp = newtree[i];
236 			newtree[i] = newtree[randnum];
237 			newtree[randnum] = tmp;
238 		}
239 	}
240 }
241 
242 static void full_shuffle(tree *newtree, unsigned long length, ranctx *prng_state)
243 {
244 	unsigned long i, randnum;
245 
246 	for (i = length - 1; i > 0; i--) {
247 		tree tmp;
248 		randnum = ranval(prng_state) % (i + 1);
249 		tmp = newtree[i];
250 		newtree[i] = newtree[randnum];
251 		newtree[randnum] = tmp;
252 	}
253 }
254 
255 /* modern in-place Fisher-Yates shuffle */
256 static void shuffle(const_tree type, tree *newtree, unsigned long length)
257 {
258 	unsigned long i;
259 	u64 seed[4];
260 	ranctx prng_state;
261 	const unsigned char *structname;
262 
263 	if (length == 0)
264 		return;
265 
266 	gcc_assert(TREE_CODE(type) == RECORD_TYPE);
267 
268 	structname = ORIG_TYPE_NAME(type);
269 
270 #ifdef __DEBUG_PLUGIN
271 	fprintf(stderr, "Shuffling struct %s %p\n", (const char *)structname, type);
272 #ifdef __DEBUG_VERBOSE
273 	debug_tree((tree)type);
274 #endif
275 #endif
276 
277 	for (i = 0; i < 4; i++) {
278 		seed[i] = shuffle_seed[i];
279 		seed[i] ^= name_hash(structname);
280 	}
281 
282 	raninit(&prng_state, (u64 *)&seed);
283 
284 	if (performance_mode)
285 		performance_shuffle(newtree, length, &prng_state);
286 	else
287 		full_shuffle(newtree, length, &prng_state);
288 }
289 
290 static bool is_flexible_array(const_tree field)
291 {
292 	const_tree fieldtype;
293 	const_tree typesize;
294 	const_tree elemtype;
295 	const_tree elemsize;
296 
297 	fieldtype = TREE_TYPE(field);
298 	typesize = TYPE_SIZE(fieldtype);
299 
300 	if (TREE_CODE(fieldtype) != ARRAY_TYPE)
301 		return false;
302 
303 	elemtype = TREE_TYPE(fieldtype);
304 	elemsize = TYPE_SIZE(elemtype);
305 
306 	/* size of type is represented in bits */
307 
308 	if (typesize == NULL_TREE && TYPE_DOMAIN(fieldtype) != NULL_TREE &&
309 	    TYPE_MAX_VALUE(TYPE_DOMAIN(fieldtype)) == NULL_TREE)
310 		return true;
311 
312 	if (typesize != NULL_TREE &&
313 	    (TREE_CONSTANT(typesize) && (!tree_to_uhwi(typesize) ||
314 	     tree_to_uhwi(typesize) == tree_to_uhwi(elemsize))))
315 		return true;
316 
317 	return false;
318 }
319 
320 static int relayout_struct(tree type)
321 {
322 	unsigned long num_fields = (unsigned long)list_length(TYPE_FIELDS(type));
323 	unsigned long shuffle_length = num_fields;
324 	tree field;
325 	tree newtree[num_fields];
326 	unsigned long i;
327 	tree list;
328 	tree variant;
329 	tree main_variant;
330 	expanded_location xloc;
331 	bool has_flexarray = false;
332 
333 	if (TYPE_FIELDS(type) == NULL_TREE)
334 		return 0;
335 
336 	if (num_fields < 2)
337 		return 0;
338 
339 	gcc_assert(TREE_CODE(type) == RECORD_TYPE);
340 
341 	gcc_assert(num_fields < INT_MAX);
342 
343 	if (lookup_attribute("randomize_performed", TYPE_ATTRIBUTES(type)) ||
344 	    lookup_attribute("no_randomize_layout", TYPE_ATTRIBUTES(TYPE_MAIN_VARIANT(type))))
345 		return 0;
346 
347 	/* Workaround for 3rd-party VirtualBox source that we can't modify ourselves */
348 	if (!strcmp((const char *)ORIG_TYPE_NAME(type), "INTNETTRUNKFACTORY") ||
349 	    !strcmp((const char *)ORIG_TYPE_NAME(type), "RAWPCIFACTORY"))
350 		return 0;
351 
352 	/* throw out any structs in uapi */
353 	xloc = expand_location(DECL_SOURCE_LOCATION(TYPE_FIELDS(type)));
354 
355 	if (strstr(xloc.file, "/uapi/"))
356 		error(G_("attempted to randomize userland API struct %s"), ORIG_TYPE_NAME(type));
357 
358 	for (field = TYPE_FIELDS(type), i = 0; field; field = TREE_CHAIN(field), i++) {
359 		gcc_assert(TREE_CODE(field) == FIELD_DECL);
360 		newtree[i] = field;
361 	}
362 
363 	/*
364 	 * enforce that we don't randomize the layout of the last
365 	 * element of a struct if it's a 0 or 1-length array
366 	 * or a proper flexible array
367 	 */
368 	if (is_flexible_array(newtree[num_fields - 1])) {
369 		has_flexarray = true;
370 		shuffle_length--;
371 	}
372 
373 	shuffle(type, (tree *)newtree, shuffle_length);
374 
375 	/*
376 	 * set up a bogus anonymous struct field designed to error out on unnamed struct initializers
377 	 * as gcc provides no other way to detect such code
378 	 */
379 	list = make_node(FIELD_DECL);
380 	TREE_CHAIN(list) = newtree[0];
381 	TREE_TYPE(list) = void_type_node;
382 	DECL_SIZE(list) = bitsize_zero_node;
383 	DECL_NONADDRESSABLE_P(list) = 1;
384 	DECL_FIELD_BIT_OFFSET(list) = bitsize_zero_node;
385 	DECL_SIZE_UNIT(list) = size_zero_node;
386 	DECL_FIELD_OFFSET(list) = size_zero_node;
387 	DECL_CONTEXT(list) = type;
388 	// to satisfy the constify plugin
389 	TREE_READONLY(list) = 1;
390 
391 	for (i = 0; i < num_fields - 1; i++)
392 		TREE_CHAIN(newtree[i]) = newtree[i+1];
393 	TREE_CHAIN(newtree[num_fields - 1]) = NULL_TREE;
394 
395 	main_variant = TYPE_MAIN_VARIANT(type);
396 	for (variant = main_variant; variant; variant = TYPE_NEXT_VARIANT(variant)) {
397 		TYPE_FIELDS(variant) = list;
398 		TYPE_ATTRIBUTES(variant) = copy_list(TYPE_ATTRIBUTES(variant));
399 		TYPE_ATTRIBUTES(variant) = tree_cons(get_identifier("randomize_performed"), NULL_TREE, TYPE_ATTRIBUTES(variant));
400 		TYPE_ATTRIBUTES(variant) = tree_cons(get_identifier("designated_init"), NULL_TREE, TYPE_ATTRIBUTES(variant));
401 		if (has_flexarray)
402 			TYPE_ATTRIBUTES(type) = tree_cons(get_identifier("has_flexarray"), NULL_TREE, TYPE_ATTRIBUTES(type));
403 	}
404 
405 	/*
406 	 * force a re-layout of the main variant
407 	 * the TYPE_SIZE for all variants will be recomputed
408 	 * by finalize_type_size()
409 	 */
410 	TYPE_SIZE(main_variant) = NULL_TREE;
411 	layout_type(main_variant);
412 	gcc_assert(TYPE_SIZE(main_variant) != NULL_TREE);
413 
414 	return 1;
415 }
416 
417 /* from constify plugin */
418 static const_tree get_field_type(const_tree field)
419 {
420 	return strip_array_types(TREE_TYPE(field));
421 }
422 
423 /* from constify plugin */
424 static bool is_fptr(const_tree fieldtype)
425 {
426 	if (TREE_CODE(fieldtype) != POINTER_TYPE)
427 		return false;
428 
429 	return TREE_CODE(TREE_TYPE(fieldtype)) == FUNCTION_TYPE;
430 }
431 
432 /* derived from constify plugin */
433 static int is_pure_ops_struct(const_tree node)
434 {
435 	const_tree field;
436 
437 	gcc_assert(TREE_CODE(node) == RECORD_TYPE || TREE_CODE(node) == UNION_TYPE);
438 
439 	for (field = TYPE_FIELDS(node); field; field = TREE_CHAIN(field)) {
440 		const_tree fieldtype = get_field_type(field);
441 		enum tree_code code = TREE_CODE(fieldtype);
442 
443 		if (node == fieldtype)
444 			continue;
445 
446 		if (code == RECORD_TYPE || code == UNION_TYPE) {
447 			if (!is_pure_ops_struct(fieldtype))
448 				return 0;
449 			continue;
450 		}
451 
452 		if (!is_fptr(fieldtype))
453 			return 0;
454 	}
455 
456 	return 1;
457 }
458 
459 static void randomize_type(tree type)
460 {
461 	tree variant;
462 
463 	gcc_assert(TREE_CODE(type) == RECORD_TYPE);
464 
465 	if (lookup_attribute("randomize_considered", TYPE_ATTRIBUTES(type)))
466 		return;
467 
468 	if (lookup_attribute("randomize_layout", TYPE_ATTRIBUTES(TYPE_MAIN_VARIANT(type))) || is_pure_ops_struct(type))
469 		relayout_struct(type);
470 
471 	for (variant = TYPE_MAIN_VARIANT(type); variant; variant = TYPE_NEXT_VARIANT(variant)) {
472 		TYPE_ATTRIBUTES(type) = copy_list(TYPE_ATTRIBUTES(type));
473 		TYPE_ATTRIBUTES(type) = tree_cons(get_identifier("randomize_considered"), NULL_TREE, TYPE_ATTRIBUTES(type));
474 	}
475 #ifdef __DEBUG_PLUGIN
476 	fprintf(stderr, "Marking randomize_considered on struct %s\n", ORIG_TYPE_NAME(type));
477 #ifdef __DEBUG_VERBOSE
478 	debug_tree(type);
479 #endif
480 #endif
481 }
482 
483 static void update_decl_size(tree decl)
484 {
485 	tree lastval, lastidx, field, init, type, flexsize;
486 	unsigned HOST_WIDE_INT len;
487 
488 	type = TREE_TYPE(decl);
489 
490 	if (!lookup_attribute("has_flexarray", TYPE_ATTRIBUTES(type)))
491 		return;
492 
493 	init = DECL_INITIAL(decl);
494 	if (init == NULL_TREE || init == error_mark_node)
495 		return;
496 
497 	if (TREE_CODE(init) != CONSTRUCTOR)
498 		return;
499 
500 	len = CONSTRUCTOR_NELTS(init);
501         if (!len)
502 		return;
503 
504 	lastval = CONSTRUCTOR_ELT(init, CONSTRUCTOR_NELTS(init) - 1)->value;
505 	lastidx = CONSTRUCTOR_ELT(init, CONSTRUCTOR_NELTS(init) - 1)->index;
506 
507 	for (field = TYPE_FIELDS(TREE_TYPE(decl)); TREE_CHAIN(field); field = TREE_CHAIN(field))
508 		;
509 
510 	if (lastidx != field)
511 		return;
512 
513 	if (TREE_CODE(lastval) != STRING_CST) {
514 		error("Only string constants are supported as initializers "
515 		      "for randomized structures with flexible arrays");
516 		return;
517 	}
518 
519 	flexsize = bitsize_int(TREE_STRING_LENGTH(lastval) *
520 		tree_to_uhwi(TYPE_SIZE(TREE_TYPE(TREE_TYPE(lastval)))));
521 
522 	DECL_SIZE(decl) = size_binop(PLUS_EXPR, TYPE_SIZE(type), flexsize);
523 
524 	return;
525 }
526 
527 
528 static void randomize_layout_finish_decl(void *event_data, void *data)
529 {
530 	tree decl = (tree)event_data;
531 	tree type;
532 
533 	if (decl == NULL_TREE || decl == error_mark_node)
534 		return;
535 
536 	type = TREE_TYPE(decl);
537 
538 	if (TREE_CODE(decl) != VAR_DECL)
539 		return;
540 
541 	if (TREE_CODE(type) != RECORD_TYPE && TREE_CODE(type) != UNION_TYPE)
542 		return;
543 
544 	if (!lookup_attribute("randomize_performed", TYPE_ATTRIBUTES(type)))
545 		return;
546 
547 	DECL_SIZE(decl) = 0;
548 	DECL_SIZE_UNIT(decl) = 0;
549 	SET_DECL_ALIGN(decl, 0);
550 	SET_DECL_MODE (decl, VOIDmode);
551 	SET_DECL_RTL(decl, 0);
552 	update_decl_size(decl);
553 	layout_decl(decl, 0);
554 }
555 
556 static void finish_type(void *event_data, void *data)
557 {
558 	tree type = (tree)event_data;
559 
560 	if (type == NULL_TREE || type == error_mark_node)
561 		return;
562 
563 	if (TREE_CODE(type) != RECORD_TYPE)
564 		return;
565 
566 	if (TYPE_FIELDS(type) == NULL_TREE)
567 		return;
568 
569 	if (lookup_attribute("randomize_considered", TYPE_ATTRIBUTES(type)))
570 		return;
571 
572 #ifdef __DEBUG_PLUGIN
573 	fprintf(stderr, "Calling randomize_type on %s\n", ORIG_TYPE_NAME(type));
574 #endif
575 #ifdef __DEBUG_VERBOSE
576 	debug_tree(type);
577 #endif
578 	randomize_type(type);
579 
580 	return;
581 }
582 
583 static struct attribute_spec randomize_layout_attr = { };
584 static struct attribute_spec no_randomize_layout_attr = { };
585 static struct attribute_spec randomize_considered_attr = { };
586 static struct attribute_spec randomize_performed_attr = { };
587 
588 static void register_attributes(void *event_data, void *data)
589 {
590 	randomize_layout_attr.name		= "randomize_layout";
591 	randomize_layout_attr.type_required	= true;
592 	randomize_layout_attr.handler		= handle_randomize_layout_attr;
593 	randomize_layout_attr.affects_type_identity = true;
594 
595 	no_randomize_layout_attr.name		= "no_randomize_layout";
596 	no_randomize_layout_attr.type_required	= true;
597 	no_randomize_layout_attr.handler	= handle_randomize_layout_attr;
598 	no_randomize_layout_attr.affects_type_identity = true;
599 
600 	randomize_considered_attr.name		= "randomize_considered";
601 	randomize_considered_attr.type_required	= true;
602 	randomize_considered_attr.handler	= handle_randomize_considered_attr;
603 
604 	randomize_performed_attr.name		= "randomize_performed";
605 	randomize_performed_attr.type_required	= true;
606 	randomize_performed_attr.handler	= handle_randomize_performed_attr;
607 
608 	register_attribute(&randomize_layout_attr);
609 	register_attribute(&no_randomize_layout_attr);
610 	register_attribute(&randomize_considered_attr);
611 	register_attribute(&randomize_performed_attr);
612 }
613 
614 static void check_bad_casts_in_constructor(tree var, tree init)
615 {
616 	unsigned HOST_WIDE_INT idx;
617 	tree field, val;
618 	tree field_type, val_type;
619 
620 	FOR_EACH_CONSTRUCTOR_ELT(CONSTRUCTOR_ELTS(init), idx, field, val) {
621 		if (TREE_CODE(val) == CONSTRUCTOR) {
622 			check_bad_casts_in_constructor(var, val);
623 			continue;
624 		}
625 
626 		/* pipacs' plugin creates franken-arrays that differ from those produced by
627 		   normal code which all have valid 'field' trees. work around this */
628 		if (field == NULL_TREE)
629 			continue;
630 		field_type = TREE_TYPE(field);
631 		val_type = TREE_TYPE(val);
632 
633 		if (TREE_CODE(field_type) != POINTER_TYPE || TREE_CODE(val_type) != POINTER_TYPE)
634 			continue;
635 
636 		if (field_type == val_type)
637 			continue;
638 
639 		field_type = TYPE_MAIN_VARIANT(strip_array_types(TYPE_MAIN_VARIANT(TREE_TYPE(field_type))));
640 		val_type = TYPE_MAIN_VARIANT(strip_array_types(TYPE_MAIN_VARIANT(TREE_TYPE(val_type))));
641 
642 		if (field_type == void_type_node)
643 			continue;
644 		if (field_type == val_type)
645 			continue;
646 		if (TREE_CODE(val_type) != RECORD_TYPE)
647 			continue;
648 
649 		if (!lookup_attribute("randomize_performed", TYPE_ATTRIBUTES(val_type)))
650 			continue;
651 		MISMATCH(DECL_SOURCE_LOCATION(var), "constructor\n", TYPE_MAIN_VARIANT(field_type), TYPE_MAIN_VARIANT(val_type));
652 	}
653 }
654 
655 /* derived from the constify plugin */
656 static void check_global_variables(void *event_data, void *data)
657 {
658 	struct varpool_node *node;
659 	tree init;
660 
661 	FOR_EACH_VARIABLE(node) {
662 		tree var = NODE_DECL(node);
663 		init = DECL_INITIAL(var);
664 		if (init == NULL_TREE)
665 			continue;
666 
667 		if (TREE_CODE(init) != CONSTRUCTOR)
668 			continue;
669 
670 		check_bad_casts_in_constructor(var, init);
671 	}
672 }
673 
674 static bool dominated_by_is_err(const_tree rhs, basic_block bb)
675 {
676 	basic_block dom;
677 	gimple dom_stmt;
678 	gimple call_stmt;
679 	const_tree dom_lhs;
680 	const_tree poss_is_err_cond;
681 	const_tree poss_is_err_func;
682 	const_tree is_err_arg;
683 
684 	dom = get_immediate_dominator(CDI_DOMINATORS, bb);
685 	if (!dom)
686 		return false;
687 
688 	dom_stmt = last_stmt(dom);
689 	if (!dom_stmt)
690 		return false;
691 
692 	if (gimple_code(dom_stmt) != GIMPLE_COND)
693 		return false;
694 
695 	if (gimple_cond_code(dom_stmt) != NE_EXPR)
696 		return false;
697 
698 	if (!integer_zerop(gimple_cond_rhs(dom_stmt)))
699 		return false;
700 
701 	poss_is_err_cond = gimple_cond_lhs(dom_stmt);
702 
703 	if (TREE_CODE(poss_is_err_cond) != SSA_NAME)
704 		return false;
705 
706 	call_stmt = SSA_NAME_DEF_STMT(poss_is_err_cond);
707 
708 	if (gimple_code(call_stmt) != GIMPLE_CALL)
709 		return false;
710 
711 	dom_lhs = gimple_get_lhs(call_stmt);
712 	poss_is_err_func = gimple_call_fndecl(call_stmt);
713 	if (!poss_is_err_func)
714 		return false;
715 	if (dom_lhs != poss_is_err_cond)
716 		return false;
717 	if (strcmp(DECL_NAME_POINTER(poss_is_err_func), "IS_ERR"))
718 		return false;
719 
720 	is_err_arg = gimple_call_arg(call_stmt, 0);
721 	if (!is_err_arg)
722 		return false;
723 
724 	if (is_err_arg != rhs)
725 		return false;
726 
727 	return true;
728 }
729 
730 static void handle_local_var_initializers(void)
731 {
732 	tree var;
733 	unsigned int i;
734 
735 	FOR_EACH_LOCAL_DECL(cfun, i, var) {
736 		tree init = DECL_INITIAL(var);
737 		if (!init)
738 			continue;
739 		if (TREE_CODE(init) != CONSTRUCTOR)
740 			continue;
741 		check_bad_casts_in_constructor(var, init);
742 	}
743 }
744 
745 static bool type_name_eq(gimple stmt, const_tree type_tree, const char *wanted_name)
746 {
747 	const char *type_name;
748 
749 	if (type_tree == NULL_TREE)
750 		return false;
751 
752 	switch (TREE_CODE(type_tree)) {
753 	case RECORD_TYPE:
754 		type_name = TYPE_NAME_POINTER(type_tree);
755 		break;
756 	case INTEGER_TYPE:
757 		if (TYPE_PRECISION(type_tree) == CHAR_TYPE_SIZE)
758 			type_name = "char";
759 		else {
760 			INFORM(gimple_location(stmt), "found non-char INTEGER_TYPE cast comparison: %qT\n", type_tree);
761 			debug_tree(type_tree);
762 			return false;
763 		}
764 		break;
765 	case POINTER_TYPE:
766 		if (TREE_CODE(TREE_TYPE(type_tree)) == VOID_TYPE) {
767 			type_name = "void *";
768 			break;
769 		} else {
770 			INFORM(gimple_location(stmt), "found non-void POINTER_TYPE cast comparison %qT\n", type_tree);
771 			debug_tree(type_tree);
772 			return false;
773 		}
774 	default:
775 		INFORM(gimple_location(stmt), "unhandled cast comparison: %qT\n", type_tree);
776 		debug_tree(type_tree);
777 		return false;
778 	}
779 
780 	return strcmp(type_name, wanted_name) == 0;
781 }
782 
783 static bool whitelisted_cast(gimple stmt, const_tree lhs_tree, const_tree rhs_tree)
784 {
785 	const struct whitelist_entry *entry;
786 	expanded_location xloc = expand_location(gimple_location(stmt));
787 
788 	for (entry = whitelist; entry->pathname; entry++) {
789 		if (!strstr(xloc.file, entry->pathname))
790 			continue;
791 
792 		if (type_name_eq(stmt, lhs_tree, entry->lhs) && type_name_eq(stmt, rhs_tree, entry->rhs))
793 			return true;
794 	}
795 
796 	return false;
797 }
798 
799 /*
800  * iterate over all statements to find "bad" casts:
801  * those where the address of the start of a structure is cast
802  * to a pointer of a structure of a different type, or a
803  * structure pointer type is cast to a different structure pointer type
804  */
805 static unsigned int find_bad_casts_execute(void)
806 {
807 	basic_block bb;
808 
809 	handle_local_var_initializers();
810 
811 	FOR_EACH_BB_FN(bb, cfun) {
812 		gimple_stmt_iterator gsi;
813 
814 		for (gsi = gsi_start_bb(bb); !gsi_end_p(gsi); gsi_next(&gsi)) {
815 			gimple stmt;
816 			const_tree lhs;
817 			const_tree lhs_type;
818 			const_tree rhs1;
819 			const_tree rhs_type;
820 			const_tree ptr_lhs_type;
821 			const_tree ptr_rhs_type;
822 			const_tree op0;
823 			const_tree op0_type;
824 			enum tree_code rhs_code;
825 
826 			stmt = gsi_stmt(gsi);
827 
828 #ifdef __DEBUG_PLUGIN
829 #ifdef __DEBUG_VERBOSE
830 			debug_gimple_stmt(stmt);
831 			debug_tree(gimple_get_lhs(stmt));
832 #endif
833 #endif
834 
835 			if (gimple_code(stmt) != GIMPLE_ASSIGN)
836 				continue;
837 
838 #ifdef __DEBUG_PLUGIN
839 #ifdef __DEBUG_VERBOSE
840 			debug_tree(gimple_assign_rhs1(stmt));
841 #endif
842 #endif
843 
844 
845 			rhs_code = gimple_assign_rhs_code(stmt);
846 
847 			if (rhs_code != ADDR_EXPR && rhs_code != SSA_NAME)
848 				continue;
849 
850 			lhs = gimple_get_lhs(stmt);
851 			lhs_type = TREE_TYPE(lhs);
852 			rhs1 = gimple_assign_rhs1(stmt);
853 			rhs_type = TREE_TYPE(rhs1);
854 
855 			if (TREE_CODE(rhs_type) != POINTER_TYPE ||
856 			    TREE_CODE(lhs_type) != POINTER_TYPE)
857 				continue;
858 
859 			ptr_lhs_type = TYPE_MAIN_VARIANT(strip_array_types(TYPE_MAIN_VARIANT(TREE_TYPE(lhs_type))));
860 			ptr_rhs_type = TYPE_MAIN_VARIANT(strip_array_types(TYPE_MAIN_VARIANT(TREE_TYPE(rhs_type))));
861 
862 			if (ptr_rhs_type == void_type_node)
863 				continue;
864 
865 			if (ptr_lhs_type == void_type_node)
866 				continue;
867 
868 			if (dominated_by_is_err(rhs1, bb))
869 				continue;
870 
871 			if (TREE_CODE(ptr_rhs_type) != RECORD_TYPE) {
872 #ifndef __DEBUG_PLUGIN
873 				if (lookup_attribute("randomize_performed", TYPE_ATTRIBUTES(ptr_lhs_type)))
874 #endif
875 				{
876 					if (!whitelisted_cast(stmt, ptr_lhs_type, ptr_rhs_type))
877 						MISMATCH(gimple_location(stmt), "rhs", ptr_lhs_type, ptr_rhs_type);
878 				}
879 				continue;
880 			}
881 
882 			if (rhs_code == SSA_NAME && ptr_lhs_type == ptr_rhs_type)
883 				continue;
884 
885 			if (rhs_code == ADDR_EXPR) {
886 				op0 = TREE_OPERAND(rhs1, 0);
887 
888 				if (op0 == NULL_TREE)
889 					continue;
890 
891 				if (TREE_CODE(op0) != VAR_DECL)
892 					continue;
893 
894 				op0_type = TYPE_MAIN_VARIANT(strip_array_types(TYPE_MAIN_VARIANT(TREE_TYPE(op0))));
895 				if (op0_type == ptr_lhs_type)
896 					continue;
897 
898 #ifndef __DEBUG_PLUGIN
899 				if (lookup_attribute("randomize_performed", TYPE_ATTRIBUTES(op0_type)))
900 #endif
901 				{
902 					if (!whitelisted_cast(stmt, ptr_lhs_type, op0_type))
903 						MISMATCH(gimple_location(stmt), "op0", ptr_lhs_type, op0_type);
904 				}
905 			} else {
906 				const_tree ssa_name_var = SSA_NAME_VAR(rhs1);
907 				/* skip bogus type casts introduced by container_of */
908 				if (ssa_name_var != NULL_TREE && DECL_NAME(ssa_name_var) &&
909 				    !strcmp((const char *)DECL_NAME_POINTER(ssa_name_var), "__mptr"))
910 					continue;
911 #ifndef __DEBUG_PLUGIN
912 				if (lookup_attribute("randomize_performed", TYPE_ATTRIBUTES(ptr_rhs_type)))
913 #endif
914 				{
915 					if (!whitelisted_cast(stmt, ptr_lhs_type, ptr_rhs_type))
916 						MISMATCH(gimple_location(stmt), "ssa", ptr_lhs_type, ptr_rhs_type);
917 				}
918 			}
919 
920 		}
921 	}
922 	return 0;
923 }
924 
925 #define PASS_NAME find_bad_casts
926 #define NO_GATE
927 #define TODO_FLAGS_FINISH TODO_dump_func
928 #include "gcc-generate-gimple-pass.h"
929 
930 __visible int plugin_init(struct plugin_name_args *plugin_info, struct plugin_gcc_version *version)
931 {
932 	int i;
933 	const char * const plugin_name = plugin_info->base_name;
934 	const int argc = plugin_info->argc;
935 	const struct plugin_argument * const argv = plugin_info->argv;
936 	bool enable = true;
937 	int obtained_seed = 0;
938 	struct register_pass_info find_bad_casts_pass_info;
939 
940 	find_bad_casts_pass_info.pass			= make_find_bad_casts_pass();
941 	find_bad_casts_pass_info.reference_pass_name	= "ssa";
942 	find_bad_casts_pass_info.ref_pass_instance_number	= 1;
943 	find_bad_casts_pass_info.pos_op			= PASS_POS_INSERT_AFTER;
944 
945 	if (!plugin_default_version_check(version, &gcc_version)) {
946 		error(G_("incompatible gcc/plugin versions"));
947 		return 1;
948 	}
949 
950 	if (strncmp(lang_hooks.name, "GNU C", 5) && !strncmp(lang_hooks.name, "GNU C+", 6)) {
951 		inform(UNKNOWN_LOCATION, G_("%s supports C only, not %s"), plugin_name, lang_hooks.name);
952 		enable = false;
953 	}
954 
955 	for (i = 0; i < argc; ++i) {
956 		if (!strcmp(argv[i].key, "disable")) {
957 			enable = false;
958 			continue;
959 		}
960 		if (!strcmp(argv[i].key, "performance-mode")) {
961 			performance_mode = 1;
962 			continue;
963 		}
964 		error(G_("unknown option '-fplugin-arg-%s-%s'"), plugin_name, argv[i].key);
965 	}
966 
967 	if (strlen(randstruct_seed) != 64) {
968 		error(G_("invalid seed value supplied for %s plugin"), plugin_name);
969 		return 1;
970 	}
971 	obtained_seed = sscanf(randstruct_seed, "%016llx%016llx%016llx%016llx",
972 		&shuffle_seed[0], &shuffle_seed[1], &shuffle_seed[2], &shuffle_seed[3]);
973 	if (obtained_seed != 4) {
974 		error(G_("Invalid seed supplied for %s plugin"), plugin_name);
975 		return 1;
976 	}
977 
978 	register_callback(plugin_name, PLUGIN_INFO, NULL, &randomize_layout_plugin_info);
979 	if (enable) {
980 		register_callback(plugin_name, PLUGIN_ALL_IPA_PASSES_START, check_global_variables, NULL);
981 		register_callback(plugin_name, PLUGIN_PASS_MANAGER_SETUP, NULL, &find_bad_casts_pass_info);
982 		register_callback(plugin_name, PLUGIN_FINISH_TYPE, finish_type, NULL);
983 		register_callback(plugin_name, PLUGIN_FINISH_DECL, randomize_layout_finish_decl, NULL);
984 	}
985 	register_callback(plugin_name, PLUGIN_ATTRIBUTES, register_attributes, NULL);
986 
987 	return 0;
988 }
989