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
partial_name_hash(unsigned long c,unsigned long prevhash)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
name_hash(const unsigned char * name)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
handle_randomize_layout_attr(tree * node,tree name,tree args,int flags,bool * no_add_attrs)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 */
handle_randomize_considered_attr(tree * node,tree name,tree args,int flags,bool * no_add_attrs)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 */
handle_randomize_performed_attr(tree * node,tree name,tree args,int flags,bool * no_add_attrs)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))))
ranval(ranctx * x)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
raninit(ranctx * x,u64 * seed)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
partition_struct(tree * fields,unsigned long length,struct partition_group * size_groups,unsigned long * num_groups)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
performance_shuffle(tree * newtree,unsigned long length,ranctx * prng_state)210 static void performance_shuffle(tree *newtree, unsigned long length, ranctx *prng_state)
211 {
212 unsigned long i, x, index;
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
219 /* FIXME: this group shuffle is currently a no-op. */
220 for (i = num_groups - 1; i > 0; i--) {
221 struct partition_group tmp;
222 randnum = ranval(prng_state) % (i + 1);
223 tmp = size_group[i];
224 size_group[i] = size_group[randnum];
225 size_group[randnum] = tmp;
226 }
227
228 for (x = 0; x < num_groups; x++) {
229 for (index = size_group[x].length - 1; index > 0; index--) {
230 tree tmp;
231
232 i = size_group[x].start + index;
233 if (DECL_BIT_FIELD_TYPE(newtree[i]))
234 continue;
235 randnum = ranval(prng_state) % (index + 1);
236 randnum += size_group[x].start;
237 // we could handle this case differently if desired
238 if (DECL_BIT_FIELD_TYPE(newtree[randnum]))
239 continue;
240 tmp = newtree[i];
241 newtree[i] = newtree[randnum];
242 newtree[randnum] = tmp;
243 }
244 }
245 }
246
full_shuffle(tree * newtree,unsigned long length,ranctx * prng_state)247 static void full_shuffle(tree *newtree, unsigned long length, ranctx *prng_state)
248 {
249 unsigned long i, randnum;
250
251 for (i = length - 1; i > 0; i--) {
252 tree tmp;
253 randnum = ranval(prng_state) % (i + 1);
254 tmp = newtree[i];
255 newtree[i] = newtree[randnum];
256 newtree[randnum] = tmp;
257 }
258 }
259
260 /* modern in-place Fisher-Yates shuffle */
shuffle(const_tree type,tree * newtree,unsigned long length)261 static void shuffle(const_tree type, tree *newtree, unsigned long length)
262 {
263 unsigned long i;
264 u64 seed[4];
265 ranctx prng_state;
266 const unsigned char *structname;
267
268 if (length == 0)
269 return;
270
271 gcc_assert(TREE_CODE(type) == RECORD_TYPE);
272
273 structname = ORIG_TYPE_NAME(type);
274
275 #ifdef __DEBUG_PLUGIN
276 fprintf(stderr, "Shuffling struct %s %p\n", (const char *)structname, type);
277 #ifdef __DEBUG_VERBOSE
278 debug_tree((tree)type);
279 #endif
280 #endif
281
282 for (i = 0; i < 4; i++) {
283 seed[i] = shuffle_seed[i];
284 seed[i] ^= name_hash(structname);
285 }
286
287 raninit(&prng_state, (u64 *)&seed);
288
289 if (performance_mode)
290 performance_shuffle(newtree, length, &prng_state);
291 else
292 full_shuffle(newtree, length, &prng_state);
293 }
294
is_flexible_array(const_tree field)295 static bool is_flexible_array(const_tree field)
296 {
297 const_tree fieldtype;
298 const_tree typesize;
299 const_tree elemtype;
300 const_tree elemsize;
301
302 fieldtype = TREE_TYPE(field);
303 typesize = TYPE_SIZE(fieldtype);
304
305 if (TREE_CODE(fieldtype) != ARRAY_TYPE)
306 return false;
307
308 elemtype = TREE_TYPE(fieldtype);
309 elemsize = TYPE_SIZE(elemtype);
310
311 /* size of type is represented in bits */
312
313 if (typesize == NULL_TREE && TYPE_DOMAIN(fieldtype) != NULL_TREE &&
314 TYPE_MAX_VALUE(TYPE_DOMAIN(fieldtype)) == NULL_TREE)
315 return true;
316
317 if (typesize != NULL_TREE &&
318 (TREE_CONSTANT(typesize) && (!tree_to_uhwi(typesize) ||
319 tree_to_uhwi(typesize) == tree_to_uhwi(elemsize))))
320 return true;
321
322 return false;
323 }
324
relayout_struct(tree type)325 static int relayout_struct(tree type)
326 {
327 unsigned long num_fields = (unsigned long)list_length(TYPE_FIELDS(type));
328 unsigned long shuffle_length = num_fields;
329 tree field;
330 tree newtree[num_fields];
331 unsigned long i;
332 tree list;
333 tree variant;
334 tree main_variant;
335 expanded_location xloc;
336 bool has_flexarray = false;
337
338 if (TYPE_FIELDS(type) == NULL_TREE)
339 return 0;
340
341 if (num_fields < 2)
342 return 0;
343
344 gcc_assert(TREE_CODE(type) == RECORD_TYPE);
345
346 gcc_assert(num_fields < INT_MAX);
347
348 if (lookup_attribute("randomize_performed", TYPE_ATTRIBUTES(type)) ||
349 lookup_attribute("no_randomize_layout", TYPE_ATTRIBUTES(TYPE_MAIN_VARIANT(type))))
350 return 0;
351
352 /* Workaround for 3rd-party VirtualBox source that we can't modify ourselves */
353 if (!strcmp((const char *)ORIG_TYPE_NAME(type), "INTNETTRUNKFACTORY") ||
354 !strcmp((const char *)ORIG_TYPE_NAME(type), "RAWPCIFACTORY"))
355 return 0;
356
357 /* throw out any structs in uapi */
358 xloc = expand_location(DECL_SOURCE_LOCATION(TYPE_FIELDS(type)));
359
360 if (strstr(xloc.file, "/uapi/"))
361 error(G_("attempted to randomize userland API struct %s"), ORIG_TYPE_NAME(type));
362
363 for (field = TYPE_FIELDS(type), i = 0; field; field = TREE_CHAIN(field), i++) {
364 gcc_assert(TREE_CODE(field) == FIELD_DECL);
365 newtree[i] = field;
366 }
367
368 /*
369 * enforce that we don't randomize the layout of the last
370 * element of a struct if it's a 0 or 1-length array
371 * or a proper flexible array
372 */
373 if (is_flexible_array(newtree[num_fields - 1])) {
374 has_flexarray = true;
375 shuffle_length--;
376 }
377
378 shuffle(type, (tree *)newtree, shuffle_length);
379
380 /*
381 * set up a bogus anonymous struct field designed to error out on unnamed struct initializers
382 * as gcc provides no other way to detect such code
383 */
384 list = make_node(FIELD_DECL);
385 TREE_CHAIN(list) = newtree[0];
386 TREE_TYPE(list) = void_type_node;
387 DECL_SIZE(list) = bitsize_zero_node;
388 DECL_NONADDRESSABLE_P(list) = 1;
389 DECL_FIELD_BIT_OFFSET(list) = bitsize_zero_node;
390 DECL_SIZE_UNIT(list) = size_zero_node;
391 DECL_FIELD_OFFSET(list) = size_zero_node;
392 DECL_CONTEXT(list) = type;
393 // to satisfy the constify plugin
394 TREE_READONLY(list) = 1;
395
396 for (i = 0; i < num_fields - 1; i++)
397 TREE_CHAIN(newtree[i]) = newtree[i+1];
398 TREE_CHAIN(newtree[num_fields - 1]) = NULL_TREE;
399
400 main_variant = TYPE_MAIN_VARIANT(type);
401 for (variant = main_variant; variant; variant = TYPE_NEXT_VARIANT(variant)) {
402 TYPE_FIELDS(variant) = list;
403 TYPE_ATTRIBUTES(variant) = copy_list(TYPE_ATTRIBUTES(variant));
404 TYPE_ATTRIBUTES(variant) = tree_cons(get_identifier("randomize_performed"), NULL_TREE, TYPE_ATTRIBUTES(variant));
405 TYPE_ATTRIBUTES(variant) = tree_cons(get_identifier("designated_init"), NULL_TREE, TYPE_ATTRIBUTES(variant));
406 if (has_flexarray)
407 TYPE_ATTRIBUTES(type) = tree_cons(get_identifier("has_flexarray"), NULL_TREE, TYPE_ATTRIBUTES(type));
408 }
409
410 /*
411 * force a re-layout of the main variant
412 * the TYPE_SIZE for all variants will be recomputed
413 * by finalize_type_size()
414 */
415 TYPE_SIZE(main_variant) = NULL_TREE;
416 layout_type(main_variant);
417 gcc_assert(TYPE_SIZE(main_variant) != NULL_TREE);
418
419 return 1;
420 }
421
422 /* from constify plugin */
get_field_type(const_tree field)423 static const_tree get_field_type(const_tree field)
424 {
425 return strip_array_types(TREE_TYPE(field));
426 }
427
428 /* from constify plugin */
is_fptr(const_tree fieldtype)429 static bool is_fptr(const_tree fieldtype)
430 {
431 if (TREE_CODE(fieldtype) != POINTER_TYPE)
432 return false;
433
434 return TREE_CODE(TREE_TYPE(fieldtype)) == FUNCTION_TYPE;
435 }
436
437 /* derived from constify plugin */
is_pure_ops_struct(const_tree node)438 static int is_pure_ops_struct(const_tree node)
439 {
440 const_tree field;
441
442 gcc_assert(TREE_CODE(node) == RECORD_TYPE || TREE_CODE(node) == UNION_TYPE);
443
444 for (field = TYPE_FIELDS(node); field; field = TREE_CHAIN(field)) {
445 const_tree fieldtype = get_field_type(field);
446 enum tree_code code = TREE_CODE(fieldtype);
447
448 if (node == fieldtype)
449 continue;
450
451 if (code == RECORD_TYPE || code == UNION_TYPE) {
452 if (!is_pure_ops_struct(fieldtype))
453 return 0;
454 continue;
455 }
456
457 if (!is_fptr(fieldtype))
458 return 0;
459 }
460
461 return 1;
462 }
463
randomize_type(tree type)464 static void randomize_type(tree type)
465 {
466 tree variant;
467
468 gcc_assert(TREE_CODE(type) == RECORD_TYPE);
469
470 if (lookup_attribute("randomize_considered", TYPE_ATTRIBUTES(type)))
471 return;
472
473 if (lookup_attribute("randomize_layout", TYPE_ATTRIBUTES(TYPE_MAIN_VARIANT(type))) || is_pure_ops_struct(type))
474 relayout_struct(type);
475
476 for (variant = TYPE_MAIN_VARIANT(type); variant; variant = TYPE_NEXT_VARIANT(variant)) {
477 TYPE_ATTRIBUTES(type) = copy_list(TYPE_ATTRIBUTES(type));
478 TYPE_ATTRIBUTES(type) = tree_cons(get_identifier("randomize_considered"), NULL_TREE, TYPE_ATTRIBUTES(type));
479 }
480 #ifdef __DEBUG_PLUGIN
481 fprintf(stderr, "Marking randomize_considered on struct %s\n", ORIG_TYPE_NAME(type));
482 #ifdef __DEBUG_VERBOSE
483 debug_tree(type);
484 #endif
485 #endif
486 }
487
update_decl_size(tree decl)488 static void update_decl_size(tree decl)
489 {
490 tree lastval, lastidx, field, init, type, flexsize;
491 unsigned HOST_WIDE_INT len;
492
493 type = TREE_TYPE(decl);
494
495 if (!lookup_attribute("has_flexarray", TYPE_ATTRIBUTES(type)))
496 return;
497
498 init = DECL_INITIAL(decl);
499 if (init == NULL_TREE || init == error_mark_node)
500 return;
501
502 if (TREE_CODE(init) != CONSTRUCTOR)
503 return;
504
505 len = CONSTRUCTOR_NELTS(init);
506 if (!len)
507 return;
508
509 lastval = CONSTRUCTOR_ELT(init, CONSTRUCTOR_NELTS(init) - 1)->value;
510 lastidx = CONSTRUCTOR_ELT(init, CONSTRUCTOR_NELTS(init) - 1)->index;
511
512 for (field = TYPE_FIELDS(TREE_TYPE(decl)); TREE_CHAIN(field); field = TREE_CHAIN(field))
513 ;
514
515 if (lastidx != field)
516 return;
517
518 if (TREE_CODE(lastval) != STRING_CST) {
519 error("Only string constants are supported as initializers "
520 "for randomized structures with flexible arrays");
521 return;
522 }
523
524 flexsize = bitsize_int(TREE_STRING_LENGTH(lastval) *
525 tree_to_uhwi(TYPE_SIZE(TREE_TYPE(TREE_TYPE(lastval)))));
526
527 DECL_SIZE(decl) = size_binop(PLUS_EXPR, TYPE_SIZE(type), flexsize);
528
529 return;
530 }
531
532
randomize_layout_finish_decl(void * event_data,void * data)533 static void randomize_layout_finish_decl(void *event_data, void *data)
534 {
535 tree decl = (tree)event_data;
536 tree type;
537
538 if (decl == NULL_TREE || decl == error_mark_node)
539 return;
540
541 type = TREE_TYPE(decl);
542
543 if (TREE_CODE(decl) != VAR_DECL)
544 return;
545
546 if (TREE_CODE(type) != RECORD_TYPE && TREE_CODE(type) != UNION_TYPE)
547 return;
548
549 if (!lookup_attribute("randomize_performed", TYPE_ATTRIBUTES(type)))
550 return;
551
552 DECL_SIZE(decl) = 0;
553 DECL_SIZE_UNIT(decl) = 0;
554 SET_DECL_ALIGN(decl, 0);
555 SET_DECL_MODE (decl, VOIDmode);
556 SET_DECL_RTL(decl, 0);
557 update_decl_size(decl);
558 layout_decl(decl, 0);
559 }
560
finish_type(void * event_data,void * data)561 static void finish_type(void *event_data, void *data)
562 {
563 tree type = (tree)event_data;
564
565 if (type == NULL_TREE || type == error_mark_node)
566 return;
567
568 if (TREE_CODE(type) != RECORD_TYPE)
569 return;
570
571 if (TYPE_FIELDS(type) == NULL_TREE)
572 return;
573
574 if (lookup_attribute("randomize_considered", TYPE_ATTRIBUTES(type)))
575 return;
576
577 #ifdef __DEBUG_PLUGIN
578 fprintf(stderr, "Calling randomize_type on %s\n", ORIG_TYPE_NAME(type));
579 #endif
580 #ifdef __DEBUG_VERBOSE
581 debug_tree(type);
582 #endif
583 randomize_type(type);
584
585 return;
586 }
587
588 static struct attribute_spec randomize_layout_attr = { };
589 static struct attribute_spec no_randomize_layout_attr = { };
590 static struct attribute_spec randomize_considered_attr = { };
591 static struct attribute_spec randomize_performed_attr = { };
592
register_attributes(void * event_data,void * data)593 static void register_attributes(void *event_data, void *data)
594 {
595 randomize_layout_attr.name = "randomize_layout";
596 randomize_layout_attr.type_required = true;
597 randomize_layout_attr.handler = handle_randomize_layout_attr;
598 randomize_layout_attr.affects_type_identity = true;
599
600 no_randomize_layout_attr.name = "no_randomize_layout";
601 no_randomize_layout_attr.type_required = true;
602 no_randomize_layout_attr.handler = handle_randomize_layout_attr;
603 no_randomize_layout_attr.affects_type_identity = true;
604
605 randomize_considered_attr.name = "randomize_considered";
606 randomize_considered_attr.type_required = true;
607 randomize_considered_attr.handler = handle_randomize_considered_attr;
608
609 randomize_performed_attr.name = "randomize_performed";
610 randomize_performed_attr.type_required = true;
611 randomize_performed_attr.handler = handle_randomize_performed_attr;
612
613 register_attribute(&randomize_layout_attr);
614 register_attribute(&no_randomize_layout_attr);
615 register_attribute(&randomize_considered_attr);
616 register_attribute(&randomize_performed_attr);
617 }
618
check_bad_casts_in_constructor(tree var,tree init)619 static void check_bad_casts_in_constructor(tree var, tree init)
620 {
621 unsigned HOST_WIDE_INT idx;
622 tree field, val;
623 tree field_type, val_type;
624
625 FOR_EACH_CONSTRUCTOR_ELT(CONSTRUCTOR_ELTS(init), idx, field, val) {
626 if (TREE_CODE(val) == CONSTRUCTOR) {
627 check_bad_casts_in_constructor(var, val);
628 continue;
629 }
630
631 /* pipacs' plugin creates franken-arrays that differ from those produced by
632 normal code which all have valid 'field' trees. work around this */
633 if (field == NULL_TREE)
634 continue;
635 field_type = TREE_TYPE(field);
636 val_type = TREE_TYPE(val);
637
638 if (TREE_CODE(field_type) != POINTER_TYPE || TREE_CODE(val_type) != POINTER_TYPE)
639 continue;
640
641 if (field_type == val_type)
642 continue;
643
644 field_type = TYPE_MAIN_VARIANT(strip_array_types(TYPE_MAIN_VARIANT(TREE_TYPE(field_type))));
645 val_type = TYPE_MAIN_VARIANT(strip_array_types(TYPE_MAIN_VARIANT(TREE_TYPE(val_type))));
646
647 if (field_type == void_type_node)
648 continue;
649 if (field_type == val_type)
650 continue;
651 if (TREE_CODE(val_type) != RECORD_TYPE)
652 continue;
653
654 if (!lookup_attribute("randomize_performed", TYPE_ATTRIBUTES(val_type)))
655 continue;
656 MISMATCH(DECL_SOURCE_LOCATION(var), "constructor\n", TYPE_MAIN_VARIANT(field_type), TYPE_MAIN_VARIANT(val_type));
657 }
658 }
659
660 /* derived from the constify plugin */
check_global_variables(void * event_data,void * data)661 static void check_global_variables(void *event_data, void *data)
662 {
663 struct varpool_node *node;
664 tree init;
665
666 FOR_EACH_VARIABLE(node) {
667 tree var = NODE_DECL(node);
668 init = DECL_INITIAL(var);
669 if (init == NULL_TREE)
670 continue;
671
672 if (TREE_CODE(init) != CONSTRUCTOR)
673 continue;
674
675 check_bad_casts_in_constructor(var, init);
676 }
677 }
678
dominated_by_is_err(const_tree rhs,basic_block bb)679 static bool dominated_by_is_err(const_tree rhs, basic_block bb)
680 {
681 basic_block dom;
682 gimple dom_stmt;
683 gimple call_stmt;
684 const_tree dom_lhs;
685 const_tree poss_is_err_cond;
686 const_tree poss_is_err_func;
687 const_tree is_err_arg;
688
689 dom = get_immediate_dominator(CDI_DOMINATORS, bb);
690 if (!dom)
691 return false;
692
693 dom_stmt = last_stmt(dom);
694 if (!dom_stmt)
695 return false;
696
697 if (gimple_code(dom_stmt) != GIMPLE_COND)
698 return false;
699
700 if (gimple_cond_code(dom_stmt) != NE_EXPR)
701 return false;
702
703 if (!integer_zerop(gimple_cond_rhs(dom_stmt)))
704 return false;
705
706 poss_is_err_cond = gimple_cond_lhs(dom_stmt);
707
708 if (TREE_CODE(poss_is_err_cond) != SSA_NAME)
709 return false;
710
711 call_stmt = SSA_NAME_DEF_STMT(poss_is_err_cond);
712
713 if (gimple_code(call_stmt) != GIMPLE_CALL)
714 return false;
715
716 dom_lhs = gimple_get_lhs(call_stmt);
717 poss_is_err_func = gimple_call_fndecl(call_stmt);
718 if (!poss_is_err_func)
719 return false;
720 if (dom_lhs != poss_is_err_cond)
721 return false;
722 if (strcmp(DECL_NAME_POINTER(poss_is_err_func), "IS_ERR"))
723 return false;
724
725 is_err_arg = gimple_call_arg(call_stmt, 0);
726 if (!is_err_arg)
727 return false;
728
729 if (is_err_arg != rhs)
730 return false;
731
732 return true;
733 }
734
handle_local_var_initializers(void)735 static void handle_local_var_initializers(void)
736 {
737 tree var;
738 unsigned int i;
739
740 FOR_EACH_LOCAL_DECL(cfun, i, var) {
741 tree init = DECL_INITIAL(var);
742 if (!init)
743 continue;
744 if (TREE_CODE(init) != CONSTRUCTOR)
745 continue;
746 check_bad_casts_in_constructor(var, init);
747 }
748 }
749
type_name_eq(gimple stmt,const_tree type_tree,const char * wanted_name)750 static bool type_name_eq(gimple stmt, const_tree type_tree, const char *wanted_name)
751 {
752 const char *type_name;
753
754 if (type_tree == NULL_TREE)
755 return false;
756
757 switch (TREE_CODE(type_tree)) {
758 case RECORD_TYPE:
759 type_name = TYPE_NAME_POINTER(type_tree);
760 break;
761 case INTEGER_TYPE:
762 if (TYPE_PRECISION(type_tree) == CHAR_TYPE_SIZE)
763 type_name = "char";
764 else {
765 INFORM(gimple_location(stmt), "found non-char INTEGER_TYPE cast comparison: %qT\n", type_tree);
766 debug_tree(type_tree);
767 return false;
768 }
769 break;
770 case POINTER_TYPE:
771 if (TREE_CODE(TREE_TYPE(type_tree)) == VOID_TYPE) {
772 type_name = "void *";
773 break;
774 } else {
775 INFORM(gimple_location(stmt), "found non-void POINTER_TYPE cast comparison %qT\n", type_tree);
776 debug_tree(type_tree);
777 return false;
778 }
779 default:
780 INFORM(gimple_location(stmt), "unhandled cast comparison: %qT\n", type_tree);
781 debug_tree(type_tree);
782 return false;
783 }
784
785 return strcmp(type_name, wanted_name) == 0;
786 }
787
whitelisted_cast(gimple stmt,const_tree lhs_tree,const_tree rhs_tree)788 static bool whitelisted_cast(gimple stmt, const_tree lhs_tree, const_tree rhs_tree)
789 {
790 const struct whitelist_entry *entry;
791 expanded_location xloc = expand_location(gimple_location(stmt));
792
793 for (entry = whitelist; entry->pathname; entry++) {
794 if (!strstr(xloc.file, entry->pathname))
795 continue;
796
797 if (type_name_eq(stmt, lhs_tree, entry->lhs) && type_name_eq(stmt, rhs_tree, entry->rhs))
798 return true;
799 }
800
801 return false;
802 }
803
804 /*
805 * iterate over all statements to find "bad" casts:
806 * those where the address of the start of a structure is cast
807 * to a pointer of a structure of a different type, or a
808 * structure pointer type is cast to a different structure pointer type
809 */
find_bad_casts_execute(void)810 static unsigned int find_bad_casts_execute(void)
811 {
812 basic_block bb;
813
814 handle_local_var_initializers();
815
816 FOR_EACH_BB_FN(bb, cfun) {
817 gimple_stmt_iterator gsi;
818
819 for (gsi = gsi_start_bb(bb); !gsi_end_p(gsi); gsi_next(&gsi)) {
820 gimple stmt;
821 const_tree lhs;
822 const_tree lhs_type;
823 const_tree rhs1;
824 const_tree rhs_type;
825 const_tree ptr_lhs_type;
826 const_tree ptr_rhs_type;
827 const_tree op0;
828 const_tree op0_type;
829 enum tree_code rhs_code;
830
831 stmt = gsi_stmt(gsi);
832
833 #ifdef __DEBUG_PLUGIN
834 #ifdef __DEBUG_VERBOSE
835 debug_gimple_stmt(stmt);
836 debug_tree(gimple_get_lhs(stmt));
837 #endif
838 #endif
839
840 if (gimple_code(stmt) != GIMPLE_ASSIGN)
841 continue;
842
843 #ifdef __DEBUG_PLUGIN
844 #ifdef __DEBUG_VERBOSE
845 debug_tree(gimple_assign_rhs1(stmt));
846 #endif
847 #endif
848
849
850 rhs_code = gimple_assign_rhs_code(stmt);
851
852 if (rhs_code != ADDR_EXPR && rhs_code != SSA_NAME)
853 continue;
854
855 lhs = gimple_get_lhs(stmt);
856 lhs_type = TREE_TYPE(lhs);
857 rhs1 = gimple_assign_rhs1(stmt);
858 rhs_type = TREE_TYPE(rhs1);
859
860 if (TREE_CODE(rhs_type) != POINTER_TYPE ||
861 TREE_CODE(lhs_type) != POINTER_TYPE)
862 continue;
863
864 ptr_lhs_type = TYPE_MAIN_VARIANT(strip_array_types(TYPE_MAIN_VARIANT(TREE_TYPE(lhs_type))));
865 ptr_rhs_type = TYPE_MAIN_VARIANT(strip_array_types(TYPE_MAIN_VARIANT(TREE_TYPE(rhs_type))));
866
867 if (ptr_rhs_type == void_type_node)
868 continue;
869
870 if (ptr_lhs_type == void_type_node)
871 continue;
872
873 if (dominated_by_is_err(rhs1, bb))
874 continue;
875
876 if (TREE_CODE(ptr_rhs_type) != RECORD_TYPE) {
877 #ifndef __DEBUG_PLUGIN
878 if (lookup_attribute("randomize_performed", TYPE_ATTRIBUTES(ptr_lhs_type)))
879 #endif
880 {
881 if (!whitelisted_cast(stmt, ptr_lhs_type, ptr_rhs_type))
882 MISMATCH(gimple_location(stmt), "rhs", ptr_lhs_type, ptr_rhs_type);
883 }
884 continue;
885 }
886
887 if (rhs_code == SSA_NAME && ptr_lhs_type == ptr_rhs_type)
888 continue;
889
890 if (rhs_code == ADDR_EXPR) {
891 op0 = TREE_OPERAND(rhs1, 0);
892
893 if (op0 == NULL_TREE)
894 continue;
895
896 if (TREE_CODE(op0) != VAR_DECL)
897 continue;
898
899 op0_type = TYPE_MAIN_VARIANT(strip_array_types(TYPE_MAIN_VARIANT(TREE_TYPE(op0))));
900 if (op0_type == ptr_lhs_type)
901 continue;
902
903 #ifndef __DEBUG_PLUGIN
904 if (lookup_attribute("randomize_performed", TYPE_ATTRIBUTES(op0_type)))
905 #endif
906 {
907 if (!whitelisted_cast(stmt, ptr_lhs_type, op0_type))
908 MISMATCH(gimple_location(stmt), "op0", ptr_lhs_type, op0_type);
909 }
910 } else {
911 const_tree ssa_name_var = SSA_NAME_VAR(rhs1);
912 /* skip bogus type casts introduced by container_of */
913 if (ssa_name_var != NULL_TREE && DECL_NAME(ssa_name_var) &&
914 !strcmp((const char *)DECL_NAME_POINTER(ssa_name_var), "__mptr"))
915 continue;
916 #ifndef __DEBUG_PLUGIN
917 if (lookup_attribute("randomize_performed", TYPE_ATTRIBUTES(ptr_rhs_type)))
918 #endif
919 {
920 if (!whitelisted_cast(stmt, ptr_lhs_type, ptr_rhs_type))
921 MISMATCH(gimple_location(stmt), "ssa", ptr_lhs_type, ptr_rhs_type);
922 }
923 }
924
925 }
926 }
927 return 0;
928 }
929
930 #define PASS_NAME find_bad_casts
931 #define NO_GATE
932 #define TODO_FLAGS_FINISH TODO_dump_func
933 #include "gcc-generate-gimple-pass.h"
934
plugin_init(struct plugin_name_args * plugin_info,struct plugin_gcc_version * version)935 __visible int plugin_init(struct plugin_name_args *plugin_info, struct plugin_gcc_version *version)
936 {
937 int i;
938 const char * const plugin_name = plugin_info->base_name;
939 const int argc = plugin_info->argc;
940 const struct plugin_argument * const argv = plugin_info->argv;
941 bool enable = true;
942 int obtained_seed = 0;
943 struct register_pass_info find_bad_casts_pass_info;
944
945 find_bad_casts_pass_info.pass = make_find_bad_casts_pass();
946 find_bad_casts_pass_info.reference_pass_name = "ssa";
947 find_bad_casts_pass_info.ref_pass_instance_number = 1;
948 find_bad_casts_pass_info.pos_op = PASS_POS_INSERT_AFTER;
949
950 if (!plugin_default_version_check(version, &gcc_version)) {
951 error(G_("incompatible gcc/plugin versions"));
952 return 1;
953 }
954
955 if (strncmp(lang_hooks.name, "GNU C", 5) && !strncmp(lang_hooks.name, "GNU C+", 6)) {
956 inform(UNKNOWN_LOCATION, G_("%s supports C only, not %s"), plugin_name, lang_hooks.name);
957 enable = false;
958 }
959
960 for (i = 0; i < argc; ++i) {
961 if (!strcmp(argv[i].key, "disable")) {
962 enable = false;
963 continue;
964 }
965 if (!strcmp(argv[i].key, "performance-mode")) {
966 performance_mode = 1;
967 continue;
968 }
969 error(G_("unknown option '-fplugin-arg-%s-%s'"), plugin_name, argv[i].key);
970 }
971
972 if (strlen(randstruct_seed) != 64) {
973 error(G_("invalid seed value supplied for %s plugin"), plugin_name);
974 return 1;
975 }
976 obtained_seed = sscanf(randstruct_seed, "%016llx%016llx%016llx%016llx",
977 &shuffle_seed[0], &shuffle_seed[1], &shuffle_seed[2], &shuffle_seed[3]);
978 if (obtained_seed != 4) {
979 error(G_("Invalid seed supplied for %s plugin"), plugin_name);
980 return 1;
981 }
982
983 register_callback(plugin_name, PLUGIN_INFO, NULL, &randomize_layout_plugin_info);
984 if (enable) {
985 register_callback(plugin_name, PLUGIN_ALL_IPA_PASSES_START, check_global_variables, NULL);
986 register_callback(plugin_name, PLUGIN_PASS_MANAGER_SETUP, NULL, &find_bad_casts_pass_info);
987 register_callback(plugin_name, PLUGIN_FINISH_TYPE, finish_type, NULL);
988 register_callback(plugin_name, PLUGIN_FINISH_DECL, randomize_layout_finish_decl, NULL);
989 }
990 register_callback(plugin_name, PLUGIN_ATTRIBUTES, register_attributes, NULL);
991
992 return 0;
993 }
994