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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, index;
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
201 /* FIXME: this group shuffle is currently a no-op. */
202 for (i = num_groups - 1; i > 0; i--) {
203 struct partition_group tmp;
204 randnum = ranval(prng_state) % (i + 1);
205 tmp = size_group[i];
206 size_group[i] = size_group[randnum];
207 size_group[randnum] = tmp;
208 }
209
210 for (x = 0; x < num_groups; x++) {
211 for (index = size_group[x].length - 1; index > 0; index--) {
212 tree tmp;
213
214 i = size_group[x].start + index;
215 if (DECL_BIT_FIELD_TYPE(newtree[i]))
216 continue;
217 randnum = ranval(prng_state) % (index + 1);
218 randnum += size_group[x].start;
219 // we could handle this case differently if desired
220 if (DECL_BIT_FIELD_TYPE(newtree[randnum]))
221 continue;
222 tmp = newtree[i];
223 newtree[i] = newtree[randnum];
224 newtree[randnum] = tmp;
225 }
226 }
227}
228
229static void full_shuffle(tree *newtree, unsigned long length, ranctx *prng_state)
230{
231 unsigned long i, randnum;
232
233 for (i = length - 1; i > 0; i--) {
234 tree tmp;
235 randnum = ranval(prng_state) % (i + 1);
236 tmp = newtree[i];
237 newtree[i] = newtree[randnum];
238 newtree[randnum] = tmp;
239 }
240}
241
242/* modern in-place Fisher-Yates shuffle */
243static void shuffle(const_tree type, tree *newtree, unsigned long length)
244{
245 unsigned long i;
246 u64 seed[4];
247 ranctx prng_state;
248 const unsigned char *structname;
249
250 if (length == 0)
251 return;
252
253 gcc_assert(TREE_CODE(type) == RECORD_TYPE);
254
255 structname = ORIG_TYPE_NAME(type);
256
257#ifdef __DEBUG_PLUGIN
258 fprintf(stderr, "Shuffling struct %s %p\n", (const char *)structname, type);
259#ifdef __DEBUG_VERBOSE
260 debug_tree((tree)type);
261#endif
262#endif
263
264 for (i = 0; i < 4; i++) {
265 seed[i] = shuffle_seed[i];
266 seed[i] ^= name_hash(structname);
267 }
268
269 raninit(&prng_state, (u64 *)&seed);
270
271 if (performance_mode)
272 performance_shuffle(newtree, length, &prng_state);
273 else
274 full_shuffle(newtree, length, &prng_state);
275}
276
277static bool is_flexible_array(const_tree field)
278{
279 const_tree fieldtype;
280 const_tree typesize;
281
282 fieldtype = TREE_TYPE(field);
283 typesize = TYPE_SIZE(fieldtype);
284
285 if (TREE_CODE(fieldtype) != ARRAY_TYPE)
286 return false;
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 return false;
295}
296
297static int relayout_struct(tree type)
298{
299 unsigned long num_fields = (unsigned long)list_length(TYPE_FIELDS(type));
300 unsigned long shuffle_length = num_fields;
301 tree field;
302 tree newtree[num_fields];
303 unsigned long i;
304 tree list;
305 tree variant;
306 tree main_variant;
307 expanded_location xloc;
308 bool has_flexarray = false;
309
310 if (TYPE_FIELDS(type) == NULL_TREE)
311 return 0;
312
313 if (num_fields < 2)
314 return 0;
315
316 gcc_assert(TREE_CODE(type) == RECORD_TYPE);
317
318 gcc_assert(num_fields < INT_MAX);
319
320 if (lookup_attribute("randomize_performed", TYPE_ATTRIBUTES(type)) ||
321 lookup_attribute("no_randomize_layout", TYPE_ATTRIBUTES(TYPE_MAIN_VARIANT(type))))
322 return 0;
323
324 /* Workaround for 3rd-party VirtualBox source that we can't modify ourselves */
325 if (!strcmp((const char *)ORIG_TYPE_NAME(type), "INTNETTRUNKFACTORY") ||
326 !strcmp((const char *)ORIG_TYPE_NAME(type), "RAWPCIFACTORY"))
327 return 0;
328
329 /* throw out any structs in uapi */
330 xloc = expand_location(DECL_SOURCE_LOCATION(TYPE_FIELDS(type)));
331
332 if (strstr(xloc.file, "/uapi/"))
333 error(G_("attempted to randomize userland API struct %s"), ORIG_TYPE_NAME(type));
334
335 for (field = TYPE_FIELDS(type), i = 0; field; field = TREE_CHAIN(field), i++) {
336 gcc_assert(TREE_CODE(field) == FIELD_DECL);
337 newtree[i] = field;
338 }
339
340 /*
341 * enforce that we don't randomize the layout of the last
342 * element of a struct if it's a proper flexible array
343 */
344 if (is_flexible_array(newtree[num_fields - 1])) {
345 has_flexarray = true;
346 shuffle_length--;
347 }
348
349 shuffle(type, (tree *)newtree, shuffle_length);
350
351 /*
352 * set up a bogus anonymous struct field designed to error out on unnamed struct initializers
353 * as gcc provides no other way to detect such code
354 */
355 list = make_node(FIELD_DECL);
356 TREE_CHAIN(list) = newtree[0];
357 TREE_TYPE(list) = void_type_node;
358 DECL_SIZE(list) = bitsize_zero_node;
359 DECL_NONADDRESSABLE_P(list) = 1;
360 DECL_FIELD_BIT_OFFSET(list) = bitsize_zero_node;
361 DECL_SIZE_UNIT(list) = size_zero_node;
362 DECL_FIELD_OFFSET(list) = size_zero_node;
363 DECL_CONTEXT(list) = type;
364 // to satisfy the constify plugin
365 TREE_READONLY(list) = 1;
366
367 for (i = 0; i < num_fields - 1; i++)
368 TREE_CHAIN(newtree[i]) = newtree[i+1];
369 TREE_CHAIN(newtree[num_fields - 1]) = NULL_TREE;
370
371 main_variant = TYPE_MAIN_VARIANT(type);
372 for (variant = main_variant; variant; variant = TYPE_NEXT_VARIANT(variant)) {
373 TYPE_FIELDS(variant) = list;
374 TYPE_ATTRIBUTES(variant) = copy_list(TYPE_ATTRIBUTES(variant));
375 TYPE_ATTRIBUTES(variant) = tree_cons(get_identifier("randomize_performed"), NULL_TREE, TYPE_ATTRIBUTES(variant));
376 TYPE_ATTRIBUTES(variant) = tree_cons(get_identifier("designated_init"), NULL_TREE, TYPE_ATTRIBUTES(variant));
377 if (has_flexarray)
378 TYPE_ATTRIBUTES(type) = tree_cons(get_identifier("has_flexarray"), NULL_TREE, TYPE_ATTRIBUTES(type));
379 }
380
381 /*
382 * force a re-layout of the main variant
383 * the TYPE_SIZE for all variants will be recomputed
384 * by finalize_type_size()
385 */
386 TYPE_SIZE(main_variant) = NULL_TREE;
387 layout_type(main_variant);
388 gcc_assert(TYPE_SIZE(main_variant) != NULL_TREE);
389
390 return 1;
391}
392
393/* from constify plugin */
394static const_tree get_field_type(const_tree field)
395{
396 return strip_array_types(TREE_TYPE(field));
397}
398
399/* from constify plugin */
400static bool is_fptr(const_tree fieldtype)
401{
402 if (TREE_CODE(fieldtype) != POINTER_TYPE)
403 return false;
404
405 return TREE_CODE(TREE_TYPE(fieldtype)) == FUNCTION_TYPE;
406}
407
408/* derived from constify plugin */
409static int is_pure_ops_struct(const_tree node)
410{
411 const_tree field;
412
413 gcc_assert(TREE_CODE(node) == RECORD_TYPE || TREE_CODE(node) == UNION_TYPE);
414
415 for (field = TYPE_FIELDS(node); field; field = TREE_CHAIN(field)) {
416 const_tree fieldtype = get_field_type(field);
417 enum tree_code code = TREE_CODE(fieldtype);
418
419 if (node == fieldtype)
420 continue;
421
422 if (code == RECORD_TYPE || code == UNION_TYPE) {
423 if (!is_pure_ops_struct(fieldtype))
424 return 0;
425 continue;
426 }
427
428 if (!is_fptr(fieldtype))
429 return 0;
430 }
431
432 return 1;
433}
434
435static void randomize_type(tree type)
436{
437 tree variant;
438
439 gcc_assert(TREE_CODE(type) == RECORD_TYPE);
440
441 if (lookup_attribute("randomize_considered", TYPE_ATTRIBUTES(type)))
442 return;
443
444 if (lookup_attribute("randomize_layout", TYPE_ATTRIBUTES(TYPE_MAIN_VARIANT(type))) || is_pure_ops_struct(type))
445 relayout_struct(type);
446
447 for (variant = TYPE_MAIN_VARIANT(type); variant; variant = TYPE_NEXT_VARIANT(variant)) {
448 TYPE_ATTRIBUTES(type) = copy_list(TYPE_ATTRIBUTES(type));
449 TYPE_ATTRIBUTES(type) = tree_cons(get_identifier("randomize_considered"), NULL_TREE, TYPE_ATTRIBUTES(type));
450 }
451#ifdef __DEBUG_PLUGIN
452 fprintf(stderr, "Marking randomize_considered on struct %s\n", ORIG_TYPE_NAME(type));
453#ifdef __DEBUG_VERBOSE
454 debug_tree(type);
455#endif
456#endif
457}
458
459static void update_decl_size(tree decl)
460{
461 tree lastval, lastidx, field, init, type, flexsize;
462 unsigned HOST_WIDE_INT len;
463
464 type = TREE_TYPE(decl);
465
466 if (!lookup_attribute("has_flexarray", TYPE_ATTRIBUTES(type)))
467 return;
468
469 init = DECL_INITIAL(decl);
470 if (init == NULL_TREE || init == error_mark_node)
471 return;
472
473 if (TREE_CODE(init) != CONSTRUCTOR)
474 return;
475
476 len = CONSTRUCTOR_NELTS(init);
477 if (!len)
478 return;
479
480 lastval = CONSTRUCTOR_ELT(init, CONSTRUCTOR_NELTS(init) - 1)->value;
481 lastidx = CONSTRUCTOR_ELT(init, CONSTRUCTOR_NELTS(init) - 1)->index;
482
483 for (field = TYPE_FIELDS(TREE_TYPE(decl)); TREE_CHAIN(field); field = TREE_CHAIN(field))
484 ;
485
486 if (lastidx != field)
487 return;
488
489 if (TREE_CODE(lastval) != STRING_CST) {
490 error("Only string constants are supported as initializers "
491 "for randomized structures with flexible arrays");
492 return;
493 }
494
495 flexsize = bitsize_int(TREE_STRING_LENGTH(lastval) *
496 tree_to_uhwi(TYPE_SIZE(TREE_TYPE(TREE_TYPE(lastval)))));
497
498 DECL_SIZE(decl) = size_binop(PLUS_EXPR, TYPE_SIZE(type), flexsize);
499
500 return;
501}
502
503
504static void randomize_layout_finish_decl(void *event_data, void *data)
505{
506 tree decl = (tree)event_data;
507 tree type;
508
509 if (decl == NULL_TREE || decl == error_mark_node)
510 return;
511
512 type = TREE_TYPE(decl);
513
514 if (TREE_CODE(decl) != VAR_DECL)
515 return;
516
517 if (TREE_CODE(type) != RECORD_TYPE && TREE_CODE(type) != UNION_TYPE)
518 return;
519
520 if (!lookup_attribute("randomize_performed", TYPE_ATTRIBUTES(type)))
521 return;
522
523 DECL_SIZE(decl) = 0;
524 DECL_SIZE_UNIT(decl) = 0;
525 SET_DECL_ALIGN(decl, 0);
526 SET_DECL_MODE (decl, VOIDmode);
527 SET_DECL_RTL(decl, 0);
528 update_decl_size(decl);
529 layout_decl(decl, 0);
530}
531
532static void finish_type(void *event_data, void *data)
533{
534 tree type = (tree)event_data;
535
536 if (type == NULL_TREE || type == error_mark_node)
537 return;
538
539 if (TREE_CODE(type) != RECORD_TYPE)
540 return;
541
542 if (TYPE_FIELDS(type) == NULL_TREE)
543 return;
544
545 if (lookup_attribute("randomize_considered", TYPE_ATTRIBUTES(type)))
546 return;
547
548#ifdef __DEBUG_PLUGIN
549 fprintf(stderr, "Calling randomize_type on %s\n", ORIG_TYPE_NAME(type));
550#endif
551#ifdef __DEBUG_VERBOSE
552 debug_tree(type);
553#endif
554 randomize_type(type);
555
556 return;
557}
558
559static struct attribute_spec randomize_layout_attr = { };
560static struct attribute_spec no_randomize_layout_attr = { };
561static struct attribute_spec randomize_considered_attr = { };
562static struct attribute_spec randomize_performed_attr = { };
563
564static void register_attributes(void *event_data, void *data)
565{
566 randomize_layout_attr.name = "randomize_layout";
567 randomize_layout_attr.type_required = true;
568 randomize_layout_attr.handler = handle_randomize_layout_attr;
569 randomize_layout_attr.affects_type_identity = true;
570
571 no_randomize_layout_attr.name = "no_randomize_layout";
572 no_randomize_layout_attr.type_required = true;
573 no_randomize_layout_attr.handler = handle_randomize_layout_attr;
574 no_randomize_layout_attr.affects_type_identity = true;
575
576 randomize_considered_attr.name = "randomize_considered";
577 randomize_considered_attr.type_required = true;
578 randomize_considered_attr.handler = handle_randomize_considered_attr;
579
580 randomize_performed_attr.name = "randomize_performed";
581 randomize_performed_attr.type_required = true;
582 randomize_performed_attr.handler = handle_randomize_performed_attr;
583
584 register_attribute(&randomize_layout_attr);
585 register_attribute(&no_randomize_layout_attr);
586 register_attribute(&randomize_considered_attr);
587 register_attribute(&randomize_performed_attr);
588}
589
590static void check_bad_casts_in_constructor(tree var, tree init)
591{
592 unsigned HOST_WIDE_INT idx;
593 tree field, val;
594 tree field_type, val_type;
595
596 FOR_EACH_CONSTRUCTOR_ELT(CONSTRUCTOR_ELTS(init), idx, field, val) {
597 if (TREE_CODE(val) == CONSTRUCTOR) {
598 check_bad_casts_in_constructor(var, val);
599 continue;
600 }
601
602 /* pipacs' plugin creates franken-arrays that differ from those produced by
603 normal code which all have valid 'field' trees. work around this */
604 if (field == NULL_TREE)
605 continue;
606 field_type = TREE_TYPE(field);
607 val_type = TREE_TYPE(val);
608
609 if (TREE_CODE(field_type) != POINTER_TYPE || TREE_CODE(val_type) != POINTER_TYPE)
610 continue;
611
612 if (field_type == val_type)
613 continue;
614
615 field_type = TYPE_MAIN_VARIANT(strip_array_types(TYPE_MAIN_VARIANT(TREE_TYPE(field_type))));
616 val_type = TYPE_MAIN_VARIANT(strip_array_types(TYPE_MAIN_VARIANT(TREE_TYPE(val_type))));
617
618 if (field_type == void_type_node)
619 continue;
620 if (field_type == val_type)
621 continue;
622 if (TREE_CODE(val_type) != RECORD_TYPE)
623 continue;
624
625 if (!lookup_attribute("randomize_performed", TYPE_ATTRIBUTES(val_type)))
626 continue;
627 MISMATCH(DECL_SOURCE_LOCATION(var), "constructor\n", TYPE_MAIN_VARIANT(field_type), TYPE_MAIN_VARIANT(val_type));
628 }
629}
630
631/* derived from the constify plugin */
632static void check_global_variables(void *event_data, void *data)
633{
634 struct varpool_node *node;
635 tree init;
636
637 FOR_EACH_VARIABLE(node) {
638 tree var = NODE_DECL(node);
639 init = DECL_INITIAL(var);
640 if (init == NULL_TREE)
641 continue;
642
643 if (TREE_CODE(init) != CONSTRUCTOR)
644 continue;
645
646 check_bad_casts_in_constructor(var, init);
647 }
648}
649
650static bool dominated_by_is_err(const_tree rhs, basic_block bb)
651{
652 basic_block dom;
653 gimple dom_stmt;
654 gimple call_stmt;
655 const_tree dom_lhs;
656 const_tree poss_is_err_cond;
657 const_tree poss_is_err_func;
658 const_tree is_err_arg;
659
660 dom = get_immediate_dominator(CDI_DOMINATORS, bb);
661 if (!dom)
662 return false;
663
664 dom_stmt = last_stmt(dom);
665 if (!dom_stmt)
666 return false;
667
668 if (gimple_code(dom_stmt) != GIMPLE_COND)
669 return false;
670
671 if (gimple_cond_code(dom_stmt) != NE_EXPR)
672 return false;
673
674 if (!integer_zerop(gimple_cond_rhs(dom_stmt)))
675 return false;
676
677 poss_is_err_cond = gimple_cond_lhs(dom_stmt);
678
679 if (TREE_CODE(poss_is_err_cond) != SSA_NAME)
680 return false;
681
682 call_stmt = SSA_NAME_DEF_STMT(poss_is_err_cond);
683
684 if (gimple_code(call_stmt) != GIMPLE_CALL)
685 return false;
686
687 dom_lhs = gimple_get_lhs(call_stmt);
688 poss_is_err_func = gimple_call_fndecl(call_stmt);
689 if (!poss_is_err_func)
690 return false;
691 if (dom_lhs != poss_is_err_cond)
692 return false;
693 if (strcmp(DECL_NAME_POINTER(poss_is_err_func), "IS_ERR"))
694 return false;
695
696 is_err_arg = gimple_call_arg(call_stmt, 0);
697 if (!is_err_arg)
698 return false;
699
700 if (is_err_arg != rhs)
701 return false;
702
703 return true;
704}
705
706static void handle_local_var_initializers(void)
707{
708 tree var;
709 unsigned int i;
710
711 FOR_EACH_LOCAL_DECL(cfun, i, var) {
712 tree init = DECL_INITIAL(var);
713 if (!init)
714 continue;
715 if (TREE_CODE(init) != CONSTRUCTOR)
716 continue;
717 check_bad_casts_in_constructor(var, init);
718 }
719}
720
721/*
722 * iterate over all statements to find "bad" casts:
723 * those where the address of the start of a structure is cast
724 * to a pointer of a structure of a different type, or a
725 * structure pointer type is cast to a different structure pointer type
726 */
727static unsigned int find_bad_casts_execute(void)
728{
729 basic_block bb;
730
731 handle_local_var_initializers();
732
733 FOR_EACH_BB_FN(bb, cfun) {
734 gimple_stmt_iterator gsi;
735
736 for (gsi = gsi_start_bb(bb); !gsi_end_p(gsi); gsi_next(&gsi)) {
737 gimple stmt;
738 const_tree lhs;
739 const_tree lhs_type;
740 const_tree rhs1;
741 const_tree rhs_type;
742 const_tree ptr_lhs_type;
743 const_tree ptr_rhs_type;
744 const_tree op0;
745 const_tree op0_type;
746 enum tree_code rhs_code;
747
748 stmt = gsi_stmt(gsi);
749
750#ifdef __DEBUG_PLUGIN
751#ifdef __DEBUG_VERBOSE
752 debug_gimple_stmt(stmt);
753 debug_tree(gimple_get_lhs(stmt));
754#endif
755#endif
756
757 if (gimple_code(stmt) != GIMPLE_ASSIGN)
758 continue;
759
760#ifdef __DEBUG_PLUGIN
761#ifdef __DEBUG_VERBOSE
762 debug_tree(gimple_assign_rhs1(stmt));
763#endif
764#endif
765
766
767 rhs_code = gimple_assign_rhs_code(stmt);
768
769 if (rhs_code != ADDR_EXPR && rhs_code != SSA_NAME)
770 continue;
771
772 lhs = gimple_get_lhs(stmt);
773 lhs_type = TREE_TYPE(lhs);
774 rhs1 = gimple_assign_rhs1(stmt);
775 rhs_type = TREE_TYPE(rhs1);
776
777 if (TREE_CODE(rhs_type) != POINTER_TYPE ||
778 TREE_CODE(lhs_type) != POINTER_TYPE)
779 continue;
780
781 ptr_lhs_type = TYPE_MAIN_VARIANT(strip_array_types(TYPE_MAIN_VARIANT(TREE_TYPE(lhs_type))));
782 ptr_rhs_type = TYPE_MAIN_VARIANT(strip_array_types(TYPE_MAIN_VARIANT(TREE_TYPE(rhs_type))));
783
784 if (ptr_rhs_type == void_type_node)
785 continue;
786
787 if (ptr_lhs_type == void_type_node)
788 continue;
789
790 if (dominated_by_is_err(rhs1, bb))
791 continue;
792
793 if (TREE_CODE(ptr_rhs_type) != RECORD_TYPE) {
794#ifndef __DEBUG_PLUGIN
795 if (lookup_attribute("randomize_performed", TYPE_ATTRIBUTES(ptr_lhs_type)))
796#endif
797 MISMATCH(gimple_location(stmt), "rhs", ptr_lhs_type, ptr_rhs_type);
798 continue;
799 }
800
801 if (rhs_code == SSA_NAME && ptr_lhs_type == ptr_rhs_type)
802 continue;
803
804 if (rhs_code == ADDR_EXPR) {
805 op0 = TREE_OPERAND(rhs1, 0);
806
807 if (op0 == NULL_TREE)
808 continue;
809
810 if (TREE_CODE(op0) != VAR_DECL)
811 continue;
812
813 op0_type = TYPE_MAIN_VARIANT(strip_array_types(TYPE_MAIN_VARIANT(TREE_TYPE(op0))));
814 if (op0_type == ptr_lhs_type)
815 continue;
816
817#ifndef __DEBUG_PLUGIN
818 if (lookup_attribute("randomize_performed", TYPE_ATTRIBUTES(op0_type)))
819#endif
820 MISMATCH(gimple_location(stmt), "op0", ptr_lhs_type, op0_type);
821 } else {
822 const_tree ssa_name_var = SSA_NAME_VAR(rhs1);
823 /* skip bogus type casts introduced by container_of */
824 if (ssa_name_var != NULL_TREE && DECL_NAME(ssa_name_var) &&
825 !strcmp((const char *)DECL_NAME_POINTER(ssa_name_var), "__mptr"))
826 continue;
827#ifndef __DEBUG_PLUGIN
828 if (lookup_attribute("randomize_performed", TYPE_ATTRIBUTES(ptr_rhs_type)))
829#endif
830 MISMATCH(gimple_location(stmt), "ssa", ptr_lhs_type, ptr_rhs_type);
831 }
832
833 }
834 }
835 return 0;
836}
837
838#define PASS_NAME find_bad_casts
839#define NO_GATE
840#define TODO_FLAGS_FINISH TODO_dump_func
841#include "gcc-generate-gimple-pass.h"
842
843__visible int plugin_init(struct plugin_name_args *plugin_info, struct plugin_gcc_version *version)
844{
845 int i;
846 const char * const plugin_name = plugin_info->base_name;
847 const int argc = plugin_info->argc;
848 const struct plugin_argument * const argv = plugin_info->argv;
849 bool enable = true;
850 int obtained_seed = 0;
851 struct register_pass_info find_bad_casts_pass_info;
852
853 find_bad_casts_pass_info.pass = make_find_bad_casts_pass();
854 find_bad_casts_pass_info.reference_pass_name = "ssa";
855 find_bad_casts_pass_info.ref_pass_instance_number = 1;
856 find_bad_casts_pass_info.pos_op = PASS_POS_INSERT_AFTER;
857
858 if (!plugin_default_version_check(version, &gcc_version)) {
859 error(G_("incompatible gcc/plugin versions"));
860 return 1;
861 }
862
863 if (strncmp(lang_hooks.name, "GNU C", 5) && !strncmp(lang_hooks.name, "GNU C+", 6)) {
864 inform(UNKNOWN_LOCATION, G_("%s supports C only, not %s"), plugin_name, lang_hooks.name);
865 enable = false;
866 }
867
868 for (i = 0; i < argc; ++i) {
869 if (!strcmp(argv[i].key, "disable")) {
870 enable = false;
871 continue;
872 }
873 if (!strcmp(argv[i].key, "performance-mode")) {
874 performance_mode = 1;
875 continue;
876 }
877 error(G_("unknown option '-fplugin-arg-%s-%s'"), plugin_name, argv[i].key);
878 }
879
880 if (strlen(randstruct_seed) != 64) {
881 error(G_("invalid seed value supplied for %s plugin"), plugin_name);
882 return 1;
883 }
884 obtained_seed = sscanf(randstruct_seed, "%016llx%016llx%016llx%016llx",
885 &shuffle_seed[0], &shuffle_seed[1], &shuffle_seed[2], &shuffle_seed[3]);
886 if (obtained_seed != 4) {
887 error(G_("Invalid seed supplied for %s plugin"), plugin_name);
888 return 1;
889 }
890
891 register_callback(plugin_name, PLUGIN_INFO, NULL, &randomize_layout_plugin_info);
892 if (enable) {
893 register_callback(plugin_name, PLUGIN_ALL_IPA_PASSES_START, check_global_variables, NULL);
894 register_callback(plugin_name, PLUGIN_PASS_MANAGER_SETUP, NULL, &find_bad_casts_pass_info);
895 register_callback(plugin_name, PLUGIN_FINISH_TYPE, finish_type, NULL);
896 register_callback(plugin_name, PLUGIN_FINISH_DECL, randomize_layout_finish_decl, NULL);
897 }
898 register_callback(plugin_name, PLUGIN_ATTRIBUTES, register_attributes, NULL);
899
900 return 0;
901}
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#if BUILDING_GCC_VERSION >= 4007
594 randomize_layout_attr.affects_type_identity = true;
595#endif
596
597 no_randomize_layout_attr.name = "no_randomize_layout";
598 no_randomize_layout_attr.type_required = true;
599 no_randomize_layout_attr.handler = handle_randomize_layout_attr;
600#if BUILDING_GCC_VERSION >= 4007
601 no_randomize_layout_attr.affects_type_identity = true;
602#endif
603
604 randomize_considered_attr.name = "randomize_considered";
605 randomize_considered_attr.type_required = true;
606 randomize_considered_attr.handler = handle_randomize_considered_attr;
607
608 randomize_performed_attr.name = "randomize_performed";
609 randomize_performed_attr.type_required = true;
610 randomize_performed_attr.handler = handle_randomize_performed_attr;
611
612 register_attribute(&randomize_layout_attr);
613 register_attribute(&no_randomize_layout_attr);
614 register_attribute(&randomize_considered_attr);
615 register_attribute(&randomize_performed_attr);
616}
617
618static void check_bad_casts_in_constructor(tree var, tree init)
619{
620 unsigned HOST_WIDE_INT idx;
621 tree field, val;
622 tree field_type, val_type;
623
624 FOR_EACH_CONSTRUCTOR_ELT(CONSTRUCTOR_ELTS(init), idx, field, val) {
625 if (TREE_CODE(val) == CONSTRUCTOR) {
626 check_bad_casts_in_constructor(var, val);
627 continue;
628 }
629
630 /* pipacs' plugin creates franken-arrays that differ from those produced by
631 normal code which all have valid 'field' trees. work around this */
632 if (field == NULL_TREE)
633 continue;
634 field_type = TREE_TYPE(field);
635 val_type = TREE_TYPE(val);
636
637 if (TREE_CODE(field_type) != POINTER_TYPE || TREE_CODE(val_type) != POINTER_TYPE)
638 continue;
639
640 if (field_type == val_type)
641 continue;
642
643 field_type = TYPE_MAIN_VARIANT(strip_array_types(TYPE_MAIN_VARIANT(TREE_TYPE(field_type))));
644 val_type = TYPE_MAIN_VARIANT(strip_array_types(TYPE_MAIN_VARIANT(TREE_TYPE(val_type))));
645
646 if (field_type == void_type_node)
647 continue;
648 if (field_type == val_type)
649 continue;
650 if (TREE_CODE(val_type) != RECORD_TYPE)
651 continue;
652
653 if (!lookup_attribute("randomize_performed", TYPE_ATTRIBUTES(val_type)))
654 continue;
655 MISMATCH(DECL_SOURCE_LOCATION(var), "constructor\n", TYPE_MAIN_VARIANT(field_type), TYPE_MAIN_VARIANT(val_type));
656 }
657}
658
659/* derived from the constify plugin */
660static void check_global_variables(void *event_data, void *data)
661{
662 struct varpool_node *node;
663 tree init;
664
665 FOR_EACH_VARIABLE(node) {
666 tree var = NODE_DECL(node);
667 init = DECL_INITIAL(var);
668 if (init == NULL_TREE)
669 continue;
670
671 if (TREE_CODE(init) != CONSTRUCTOR)
672 continue;
673
674 check_bad_casts_in_constructor(var, init);
675 }
676}
677
678static bool dominated_by_is_err(const_tree rhs, basic_block bb)
679{
680 basic_block dom;
681 gimple dom_stmt;
682 gimple call_stmt;
683 const_tree dom_lhs;
684 const_tree poss_is_err_cond;
685 const_tree poss_is_err_func;
686 const_tree is_err_arg;
687
688 dom = get_immediate_dominator(CDI_DOMINATORS, bb);
689 if (!dom)
690 return false;
691
692 dom_stmt = last_stmt(dom);
693 if (!dom_stmt)
694 return false;
695
696 if (gimple_code(dom_stmt) != GIMPLE_COND)
697 return false;
698
699 if (gimple_cond_code(dom_stmt) != NE_EXPR)
700 return false;
701
702 if (!integer_zerop(gimple_cond_rhs(dom_stmt)))
703 return false;
704
705 poss_is_err_cond = gimple_cond_lhs(dom_stmt);
706
707 if (TREE_CODE(poss_is_err_cond) != SSA_NAME)
708 return false;
709
710 call_stmt = SSA_NAME_DEF_STMT(poss_is_err_cond);
711
712 if (gimple_code(call_stmt) != GIMPLE_CALL)
713 return false;
714
715 dom_lhs = gimple_get_lhs(call_stmt);
716 poss_is_err_func = gimple_call_fndecl(call_stmt);
717 if (!poss_is_err_func)
718 return false;
719 if (dom_lhs != poss_is_err_cond)
720 return false;
721 if (strcmp(DECL_NAME_POINTER(poss_is_err_func), "IS_ERR"))
722 return false;
723
724 is_err_arg = gimple_call_arg(call_stmt, 0);
725 if (!is_err_arg)
726 return false;
727
728 if (is_err_arg != rhs)
729 return false;
730
731 return true;
732}
733
734static void handle_local_var_initializers(void)
735{
736 tree var;
737 unsigned int i;
738
739 FOR_EACH_LOCAL_DECL(cfun, i, var) {
740 tree init = DECL_INITIAL(var);
741 if (!init)
742 continue;
743 if (TREE_CODE(init) != CONSTRUCTOR)
744 continue;
745 check_bad_casts_in_constructor(var, init);
746 }
747}
748
749static bool type_name_eq(gimple stmt, const_tree type_tree, const char *wanted_name)
750{
751 const char *type_name;
752
753 if (type_tree == NULL_TREE)
754 return false;
755
756 switch (TREE_CODE(type_tree)) {
757 case RECORD_TYPE:
758 type_name = TYPE_NAME_POINTER(type_tree);
759 break;
760 case INTEGER_TYPE:
761 if (TYPE_PRECISION(type_tree) == CHAR_TYPE_SIZE)
762 type_name = "char";
763 else {
764 INFORM(gimple_location(stmt), "found non-char INTEGER_TYPE cast comparison: %qT\n", type_tree);
765 debug_tree(type_tree);
766 return false;
767 }
768 break;
769 case POINTER_TYPE:
770 if (TREE_CODE(TREE_TYPE(type_tree)) == VOID_TYPE) {
771 type_name = "void *";
772 break;
773 } else {
774 INFORM(gimple_location(stmt), "found non-void POINTER_TYPE cast comparison %qT\n", type_tree);
775 debug_tree(type_tree);
776 return false;
777 }
778 default:
779 INFORM(gimple_location(stmt), "unhandled cast comparison: %qT\n", type_tree);
780 debug_tree(type_tree);
781 return false;
782 }
783
784 return strcmp(type_name, wanted_name) == 0;
785}
786
787static bool whitelisted_cast(gimple stmt, const_tree lhs_tree, const_tree rhs_tree)
788{
789 const struct whitelist_entry *entry;
790 expanded_location xloc = expand_location(gimple_location(stmt));
791
792 for (entry = whitelist; entry->pathname; entry++) {
793 if (!strstr(xloc.file, entry->pathname))
794 continue;
795
796 if (type_name_eq(stmt, lhs_tree, entry->lhs) && type_name_eq(stmt, rhs_tree, entry->rhs))
797 return true;
798 }
799
800 return false;
801}
802
803/*
804 * iterate over all statements to find "bad" casts:
805 * those where the address of the start of a structure is cast
806 * to a pointer of a structure of a different type, or a
807 * structure pointer type is cast to a different structure pointer type
808 */
809static unsigned int find_bad_casts_execute(void)
810{
811 basic_block bb;
812
813 handle_local_var_initializers();
814
815 FOR_EACH_BB_FN(bb, cfun) {
816 gimple_stmt_iterator gsi;
817
818 for (gsi = gsi_start_bb(bb); !gsi_end_p(gsi); gsi_next(&gsi)) {
819 gimple stmt;
820 const_tree lhs;
821 const_tree lhs_type;
822 const_tree rhs1;
823 const_tree rhs_type;
824 const_tree ptr_lhs_type;
825 const_tree ptr_rhs_type;
826 const_tree op0;
827 const_tree op0_type;
828 enum tree_code rhs_code;
829
830 stmt = gsi_stmt(gsi);
831
832#ifdef __DEBUG_PLUGIN
833#ifdef __DEBUG_VERBOSE
834 debug_gimple_stmt(stmt);
835 debug_tree(gimple_get_lhs(stmt));
836#endif
837#endif
838
839 if (gimple_code(stmt) != GIMPLE_ASSIGN)
840 continue;
841
842#ifdef __DEBUG_PLUGIN
843#ifdef __DEBUG_VERBOSE
844 debug_tree(gimple_assign_rhs1(stmt));
845#endif
846#endif
847
848
849 rhs_code = gimple_assign_rhs_code(stmt);
850
851 if (rhs_code != ADDR_EXPR && rhs_code != SSA_NAME)
852 continue;
853
854 lhs = gimple_get_lhs(stmt);
855 lhs_type = TREE_TYPE(lhs);
856 rhs1 = gimple_assign_rhs1(stmt);
857 rhs_type = TREE_TYPE(rhs1);
858
859 if (TREE_CODE(rhs_type) != POINTER_TYPE ||
860 TREE_CODE(lhs_type) != POINTER_TYPE)
861 continue;
862
863 ptr_lhs_type = TYPE_MAIN_VARIANT(strip_array_types(TYPE_MAIN_VARIANT(TREE_TYPE(lhs_type))));
864 ptr_rhs_type = TYPE_MAIN_VARIANT(strip_array_types(TYPE_MAIN_VARIANT(TREE_TYPE(rhs_type))));
865
866 if (ptr_rhs_type == void_type_node)
867 continue;
868
869 if (ptr_lhs_type == void_type_node)
870 continue;
871
872 if (dominated_by_is_err(rhs1, bb))
873 continue;
874
875 if (TREE_CODE(ptr_rhs_type) != RECORD_TYPE) {
876#ifndef __DEBUG_PLUGIN
877 if (lookup_attribute("randomize_performed", TYPE_ATTRIBUTES(ptr_lhs_type)))
878#endif
879 {
880 if (!whitelisted_cast(stmt, ptr_lhs_type, ptr_rhs_type))
881 MISMATCH(gimple_location(stmt), "rhs", ptr_lhs_type, ptr_rhs_type);
882 }
883 continue;
884 }
885
886 if (rhs_code == SSA_NAME && ptr_lhs_type == ptr_rhs_type)
887 continue;
888
889 if (rhs_code == ADDR_EXPR) {
890 op0 = TREE_OPERAND(rhs1, 0);
891
892 if (op0 == NULL_TREE)
893 continue;
894
895 if (TREE_CODE(op0) != VAR_DECL)
896 continue;
897
898 op0_type = TYPE_MAIN_VARIANT(strip_array_types(TYPE_MAIN_VARIANT(TREE_TYPE(op0))));
899 if (op0_type == ptr_lhs_type)
900 continue;
901
902#ifndef __DEBUG_PLUGIN
903 if (lookup_attribute("randomize_performed", TYPE_ATTRIBUTES(op0_type)))
904#endif
905 {
906 if (!whitelisted_cast(stmt, ptr_lhs_type, op0_type))
907 MISMATCH(gimple_location(stmt), "op0", ptr_lhs_type, op0_type);
908 }
909 } else {
910 const_tree ssa_name_var = SSA_NAME_VAR(rhs1);
911 /* skip bogus type casts introduced by container_of */
912 if (ssa_name_var != NULL_TREE && DECL_NAME(ssa_name_var) &&
913 !strcmp((const char *)DECL_NAME_POINTER(ssa_name_var), "__mptr"))
914 continue;
915#ifndef __DEBUG_PLUGIN
916 if (lookup_attribute("randomize_performed", TYPE_ATTRIBUTES(ptr_rhs_type)))
917#endif
918 {
919 if (!whitelisted_cast(stmt, ptr_lhs_type, ptr_rhs_type))
920 MISMATCH(gimple_location(stmt), "ssa", ptr_lhs_type, ptr_rhs_type);
921 }
922 }
923
924 }
925 }
926 return 0;
927}
928
929#define PASS_NAME find_bad_casts
930#define NO_GATE
931#define TODO_FLAGS_FINISH TODO_dump_func
932#include "gcc-generate-gimple-pass.h"
933
934__visible int plugin_init(struct plugin_name_args *plugin_info, struct plugin_gcc_version *version)
935{
936 int i;
937 const char * const plugin_name = plugin_info->base_name;
938 const int argc = plugin_info->argc;
939 const struct plugin_argument * const argv = plugin_info->argv;
940 bool enable = true;
941 int obtained_seed = 0;
942 struct register_pass_info find_bad_casts_pass_info;
943
944 find_bad_casts_pass_info.pass = make_find_bad_casts_pass();
945 find_bad_casts_pass_info.reference_pass_name = "ssa";
946 find_bad_casts_pass_info.ref_pass_instance_number = 1;
947 find_bad_casts_pass_info.pos_op = PASS_POS_INSERT_AFTER;
948
949 if (!plugin_default_version_check(version, &gcc_version)) {
950 error(G_("incompatible gcc/plugin versions"));
951 return 1;
952 }
953
954 if (strncmp(lang_hooks.name, "GNU C", 5) && !strncmp(lang_hooks.name, "GNU C+", 6)) {
955 inform(UNKNOWN_LOCATION, G_("%s supports C only, not %s"), plugin_name, lang_hooks.name);
956 enable = false;
957 }
958
959 for (i = 0; i < argc; ++i) {
960 if (!strcmp(argv[i].key, "disable")) {
961 enable = false;
962 continue;
963 }
964 if (!strcmp(argv[i].key, "performance-mode")) {
965 performance_mode = 1;
966 continue;
967 }
968 error(G_("unknown option '-fplugin-arg-%s-%s'"), plugin_name, argv[i].key);
969 }
970
971 if (strlen(randstruct_seed) != 64) {
972 error(G_("invalid seed value supplied for %s plugin"), plugin_name);
973 return 1;
974 }
975 obtained_seed = sscanf(randstruct_seed, "%016llx%016llx%016llx%016llx",
976 &shuffle_seed[0], &shuffle_seed[1], &shuffle_seed[2], &shuffle_seed[3]);
977 if (obtained_seed != 4) {
978 error(G_("Invalid seed supplied for %s plugin"), plugin_name);
979 return 1;
980 }
981
982 register_callback(plugin_name, PLUGIN_INFO, NULL, &randomize_layout_plugin_info);
983 if (enable) {
984 register_callback(plugin_name, PLUGIN_ALL_IPA_PASSES_START, check_global_variables, NULL);
985 register_callback(plugin_name, PLUGIN_PASS_MANAGER_SETUP, NULL, &find_bad_casts_pass_info);
986 register_callback(plugin_name, PLUGIN_FINISH_TYPE, finish_type, NULL);
987 register_callback(plugin_name, PLUGIN_FINISH_DECL, randomize_layout_finish_decl, NULL);
988 }
989 register_callback(plugin_name, PLUGIN_ATTRIBUTES, register_attributes, NULL);
990
991 return 0;
992}