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