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TOMOYO Linux Cross Reference
Linux/scripts/gcc-plugins/randomize_layout_plugin.c

Version: ~ [ linux-5.1-rc5 ] ~ [ linux-5.0.7 ] ~ [ linux-4.20.17 ] ~ [ linux-4.19.34 ] ~ [ linux-4.18.20 ] ~ [ linux-4.17.19 ] ~ [ linux-4.16.18 ] ~ [ linux-4.15.18 ] ~ [ linux-4.14.111 ] ~ [ linux-4.13.16 ] ~ [ linux-4.12.14 ] ~ [ linux-4.11.12 ] ~ [ linux-4.10.17 ] ~ [ linux-4.9.168 ] ~ [ linux-4.8.17 ] ~ [ linux-4.7.10 ] ~ [ linux-4.6.7 ] ~ [ linux-4.5.7 ] ~ [ linux-4.4.178 ] ~ [ linux-4.3.6 ] ~ [ linux-4.2.8 ] ~ [ linux-4.1.52 ] ~ [ linux-4.0.9 ] ~ [ linux-3.19.8 ] ~ [ linux-3.18.138 ] ~ [ linux-3.17.8 ] ~ [ linux-3.16.65 ] ~ [ linux-3.15.10 ] ~ [ linux-3.14.79 ] ~ [ linux-3.13.11 ] ~ [ linux-3.12.74 ] ~ [ linux-3.11.10 ] ~ [ linux-3.10.108 ] ~ [ linux-3.9.11 ] ~ [ linux-3.8.13 ] ~ [ linux-3.7.10 ] ~ [ linux-3.6.11 ] ~ [ linux-3.5.7 ] ~ [ linux-3.4.113 ] ~ [ linux-3.3.8 ] ~ [ linux-3.2.102 ] ~ [ linux-3.1.10 ] ~ [ linux-3.0.101 ] ~ [ linux-2.6.39.4 ] ~ [ linux-2.6.38.8 ] ~ [ linux-2.6.37.6 ] ~ [ linux-2.6.36.4 ] ~ [ linux-2.6.35.14 ] ~ [ linux-2.6.34.15 ] ~ [ linux-2.6.33.20 ] ~ [ linux-2.6.32.71 ] ~ [ linux-2.6.0 ] ~ [ linux-2.4.37.11 ] ~ [ unix-v6-master ] ~ [ ccs-tools-1.8.5 ] ~ [ policy-sample ] ~
Architecture: ~ [ i386 ] ~ [ alpha ] ~ [ m68k ] ~ [ mips ] ~ [ ppc ] ~ [ sparc ] ~ [ sparc64 ] ~

  1 /*
  2  * Copyright 2014-2016 by Open Source Security, Inc., Brad Spengler <spender@grsecurity.net>
  3  *                   and PaX Team <pageexec@freemail.hu>
  4  * Licensed under the GPL v2
  5  *
  6  * Note: the choice of the license means that the compilation process is
  7  *       NOT 'eligible' as defined by gcc's library exception to the GPL v3,
  8  *       but for the kernel it doesn't matter since it doesn't link against
  9  *       any of the gcc libraries
 10  *
 11  * Usage:
 12  * $ # for 4.5/4.6/C based 4.7
 13  * $ gcc -I`gcc -print-file-name=plugin`/include -I`gcc -print-file-name=plugin`/include/c-family -fPIC -shared -O2 -o randomize_layout_plugin.so randomize_layout_plugin.c
 14  * $ # for C++ based 4.7/4.8+
 15  * $ g++ -I`g++ -print-file-name=plugin`/include -I`g++ -print-file-name=plugin`/include/c-family -fPIC -shared -O2 -o randomize_layout_plugin.so randomize_layout_plugin.c
 16  * $ gcc -fplugin=./randomize_layout_plugin.so test.c -O2
 17  */
 18 
 19 #include "gcc-common.h"
 20 #include "randomize_layout_seed.h"
 21 
 22 #if BUILDING_GCC_MAJOR < 4 || (BUILDING_GCC_MAJOR == 4 && BUILDING_GCC_MINOR < 7)
 23 #error "The RANDSTRUCT plugin requires GCC 4.7 or newer."
 24 #endif
 25 
 26 #define ORIG_TYPE_NAME(node) \
 27         (TYPE_NAME(TYPE_MAIN_VARIANT(node)) != NULL_TREE ? ((const unsigned char *)IDENTIFIER_POINTER(TYPE_NAME(TYPE_MAIN_VARIANT(node)))) : (const unsigned char *)"anonymous")
 28 
 29 #define INFORM(loc, msg, ...)   inform(loc, "randstruct: " msg, ##__VA_ARGS__)
 30 #define MISMATCH(loc, how, ...) INFORM(loc, "casting between randomized structure pointer types (" how "): %qT and %qT\n", __VA_ARGS__)
 31 
 32 __visible int plugin_is_GPL_compatible;
 33 
 34 static int performance_mode;
 35 
 36 static struct plugin_info randomize_layout_plugin_info = {
 37         .version        = "201402201816vanilla",
 38         .help           = "disable\t\t\tdo not activate plugin\n"
 39                           "performance-mode\tenable cacheline-aware layout randomization\n"
 40 };
 41 
 42 struct whitelist_entry {
 43         const char *pathname;
 44         const char *lhs;
 45         const char *rhs;
 46 };
 47 
 48 static const struct whitelist_entry whitelist[] = {
 49         /* NIU overloads mapping with page struct */
 50         { "drivers/net/ethernet/sun/niu.c", "page", "address_space" },
 51         /* unix_skb_parms via UNIXCB() buffer */
 52         { "net/unix/af_unix.c", "unix_skb_parms", "char" },
 53         /* big_key payload.data struct splashing */
 54         { "security/keys/big_key.c", "path", "void *" },
 55         /* walk struct security_hook_heads as an array of struct hlist_head */
 56         { "security/security.c", "hlist_head", "security_hook_heads" },
 57         { }
 58 };
 59 
 60 /* from old Linux dcache.h */
 61 static inline unsigned long
 62 partial_name_hash(unsigned long c, unsigned long prevhash)
 63 {
 64         return (prevhash + (c << 4) + (c >> 4)) * 11;
 65 }
 66 static inline unsigned int
 67 name_hash(const unsigned char *name)
 68 {
 69         unsigned long hash = 0;
 70         unsigned int len = strlen((const char *)name);
 71         while (len--)
 72                 hash = partial_name_hash(*name++, hash);
 73         return (unsigned int)hash;
 74 }
 75 
 76 static tree handle_randomize_layout_attr(tree *node, tree name, tree args, int flags, bool *no_add_attrs)
 77 {
 78         tree type;
 79 
 80         *no_add_attrs = true;
 81         if (TREE_CODE(*node) == FUNCTION_DECL) {
 82                 error("%qE attribute does not apply to functions (%qF)", name, *node);
 83                 return NULL_TREE;
 84         }
 85 
 86         if (TREE_CODE(*node) == PARM_DECL) {
 87                 error("%qE attribute does not apply to function parameters (%qD)", name, *node);
 88                 return NULL_TREE;
 89         }
 90 
 91         if (TREE_CODE(*node) == VAR_DECL) {
 92                 error("%qE attribute does not apply to variables (%qD)", name, *node);
 93                 return NULL_TREE;
 94         }
 95 
 96         if (TYPE_P(*node)) {
 97                 type = *node;
 98         } else {
 99                 gcc_assert(TREE_CODE(*node) == TYPE_DECL);
100                 type = TREE_TYPE(*node);
101         }
102 
103         if (TREE_CODE(type) != RECORD_TYPE) {
104                 error("%qE attribute used on %qT applies to struct types only", name, type);
105                 return NULL_TREE;
106         }
107 
108         if (lookup_attribute(IDENTIFIER_POINTER(name), TYPE_ATTRIBUTES(type))) {
109                 error("%qE attribute is already applied to the type %qT", name, type);
110                 return NULL_TREE;
111         }
112 
113         *no_add_attrs = false;
114 
115         return NULL_TREE;
116 }
117 
118 /* set on complete types that we don't need to inspect further at all */
119 static tree handle_randomize_considered_attr(tree *node, tree name, tree args, int flags, bool *no_add_attrs)
120 {
121         *no_add_attrs = false;
122         return NULL_TREE;
123 }
124 
125 /*
126  * set on types that we've performed a shuffle on, to prevent re-shuffling
127  * this does not preclude us from inspecting its fields for potential shuffles
128  */
129 static tree handle_randomize_performed_attr(tree *node, tree name, tree args, int flags, bool *no_add_attrs)
130 {
131         *no_add_attrs = false;
132         return NULL_TREE;
133 }
134 
135 /*
136  * 64bit variant of Bob Jenkins' public domain PRNG
137  * 256 bits of internal state
138  */
139 
140 typedef unsigned long long u64;
141 
142 typedef struct ranctx { u64 a; u64 b; u64 c; u64 d; } ranctx;
143 
144 #define rot(x,k) (((x)<<(k))|((x)>>(64-(k))))
145 static u64 ranval(ranctx *x) {
146         u64 e = x->a - rot(x->b, 7);
147         x->a = x->b ^ rot(x->c, 13);
148         x->b = x->c + rot(x->d, 37);
149         x->c = x->d + e;
150         x->d = e + x->a;
151         return x->d;
152 }
153 
154 static void raninit(ranctx *x, u64 *seed) {
155         int i;
156 
157         x->a = seed[0];
158         x->b = seed[1];
159         x->c = seed[2];
160         x->d = seed[3];
161 
162         for (i=0; i < 30; ++i)
163                 (void)ranval(x);
164 }
165 
166 static u64 shuffle_seed[4];
167 
168 struct partition_group {
169         tree tree_start;
170         unsigned long start;
171         unsigned long length;
172 };
173 
174 static void partition_struct(tree *fields, unsigned long length, struct partition_group *size_groups, unsigned long *num_groups)
175 {
176         unsigned long i;
177         unsigned long accum_size = 0;
178         unsigned long accum_length = 0;
179         unsigned long group_idx = 0;
180 
181         gcc_assert(length < INT_MAX);
182 
183         memset(size_groups, 0, sizeof(struct partition_group) * length);
184 
185         for (i = 0; i < length; i++) {
186                 if (size_groups[group_idx].tree_start == NULL_TREE) {
187                         size_groups[group_idx].tree_start = fields[i];
188                         size_groups[group_idx].start = i;
189                         accum_length = 0;
190                         accum_size = 0;
191                 }
192                 accum_size += (unsigned long)int_size_in_bytes(TREE_TYPE(fields[i]));
193                 accum_length++;
194                 if (accum_size >= 64) {
195                         size_groups[group_idx].length = accum_length;
196                         accum_length = 0;
197                         group_idx++;
198                 }
199         }
200 
201         if (size_groups[group_idx].tree_start != NULL_TREE &&
202             !size_groups[group_idx].length) {
203                 size_groups[group_idx].length = accum_length;
204                 group_idx++;
205         }
206 
207         *num_groups = group_idx;
208 }
209 
210 static void performance_shuffle(tree *newtree, unsigned long length, ranctx *prng_state)
211 {
212         unsigned long i, x;
213         struct partition_group size_group[length];
214         unsigned long num_groups = 0;
215         unsigned long randnum;
216 
217         partition_struct(newtree, length, (struct partition_group *)&size_group, &num_groups);
218         for (i = num_groups - 1; i > 0; i--) {
219                 struct partition_group tmp;
220                 randnum = ranval(prng_state) % (i + 1);
221                 tmp = size_group[i];
222                 size_group[i] = size_group[randnum];
223                 size_group[randnum] = tmp;
224         }
225 
226         for (x = 0; x < num_groups; x++) {
227                 for (i = size_group[x].start + size_group[x].length - 1; i > size_group[x].start; i--) {
228                         tree tmp;
229                         if (DECL_BIT_FIELD_TYPE(newtree[i]))
230                                 continue;
231                         randnum = ranval(prng_state) % (i + 1);
232                         // we could handle this case differently if desired
233                         if (DECL_BIT_FIELD_TYPE(newtree[randnum]))
234                                 continue;
235                         tmp = newtree[i];
236                         newtree[i] = newtree[randnum];
237                         newtree[randnum] = tmp;
238                 }
239         }
240 }
241 
242 static void full_shuffle(tree *newtree, unsigned long length, ranctx *prng_state)
243 {
244         unsigned long i, randnum;
245 
246         for (i = length - 1; i > 0; i--) {
247                 tree tmp;
248                 randnum = ranval(prng_state) % (i + 1);
249                 tmp = newtree[i];
250                 newtree[i] = newtree[randnum];
251                 newtree[randnum] = tmp;
252         }
253 }
254 
255 /* modern in-place Fisher-Yates shuffle */
256 static void shuffle(const_tree type, tree *newtree, unsigned long length)
257 {
258         unsigned long i;
259         u64 seed[4];
260         ranctx prng_state;
261         const unsigned char *structname;
262 
263         if (length == 0)
264                 return;
265 
266         gcc_assert(TREE_CODE(type) == RECORD_TYPE);
267 
268         structname = ORIG_TYPE_NAME(type);
269 
270 #ifdef __DEBUG_PLUGIN
271         fprintf(stderr, "Shuffling struct %s %p\n", (const char *)structname, type);
272 #ifdef __DEBUG_VERBOSE
273         debug_tree((tree)type);
274 #endif
275 #endif
276 
277         for (i = 0; i < 4; i++) {
278                 seed[i] = shuffle_seed[i];
279                 seed[i] ^= name_hash(structname);
280         }
281 
282         raninit(&prng_state, (u64 *)&seed);
283 
284         if (performance_mode)
285                 performance_shuffle(newtree, length, &prng_state);
286         else
287                 full_shuffle(newtree, length, &prng_state);
288 }
289 
290 static bool is_flexible_array(const_tree field)
291 {
292         const_tree fieldtype;
293         const_tree typesize;
294         const_tree elemtype;
295         const_tree elemsize;
296 
297         fieldtype = TREE_TYPE(field);
298         typesize = TYPE_SIZE(fieldtype);
299 
300         if (TREE_CODE(fieldtype) != ARRAY_TYPE)
301                 return false;
302 
303         elemtype = TREE_TYPE(fieldtype);
304         elemsize = TYPE_SIZE(elemtype);
305 
306         /* size of type is represented in bits */
307 
308         if (typesize == NULL_TREE && TYPE_DOMAIN(fieldtype) != NULL_TREE &&
309             TYPE_MAX_VALUE(TYPE_DOMAIN(fieldtype)) == NULL_TREE)
310                 return true;
311 
312         if (typesize != NULL_TREE &&
313             (TREE_CONSTANT(typesize) && (!tree_to_uhwi(typesize) ||
314              tree_to_uhwi(typesize) == tree_to_uhwi(elemsize))))
315                 return true;
316 
317         return false;
318 }
319 
320 static int relayout_struct(tree type)
321 {
322         unsigned long num_fields = (unsigned long)list_length(TYPE_FIELDS(type));
323         unsigned long shuffle_length = num_fields;
324         tree field;
325         tree newtree[num_fields];
326         unsigned long i;
327         tree list;
328         tree variant;
329         tree main_variant;
330         expanded_location xloc;
331         bool has_flexarray = false;
332 
333         if (TYPE_FIELDS(type) == NULL_TREE)
334                 return 0;
335 
336         if (num_fields < 2)
337                 return 0;
338 
339         gcc_assert(TREE_CODE(type) == RECORD_TYPE);
340 
341         gcc_assert(num_fields < INT_MAX);
342 
343         if (lookup_attribute("randomize_performed", TYPE_ATTRIBUTES(type)) ||
344             lookup_attribute("no_randomize_layout", TYPE_ATTRIBUTES(TYPE_MAIN_VARIANT(type))))
345                 return 0;
346 
347         /* Workaround for 3rd-party VirtualBox source that we can't modify ourselves */
348         if (!strcmp((const char *)ORIG_TYPE_NAME(type), "INTNETTRUNKFACTORY") ||
349             !strcmp((const char *)ORIG_TYPE_NAME(type), "RAWPCIFACTORY"))
350                 return 0;
351 
352         /* throw out any structs in uapi */
353         xloc = expand_location(DECL_SOURCE_LOCATION(TYPE_FIELDS(type)));
354 
355         if (strstr(xloc.file, "/uapi/"))
356                 error(G_("attempted to randomize userland API struct %s"), ORIG_TYPE_NAME(type));
357 
358         for (field = TYPE_FIELDS(type), i = 0; field; field = TREE_CHAIN(field), i++) {
359                 gcc_assert(TREE_CODE(field) == FIELD_DECL);
360                 newtree[i] = field;
361         }
362 
363         /*
364          * enforce that we don't randomize the layout of the last
365          * element of a struct if it's a 0 or 1-length array
366          * or a proper flexible array
367          */
368         if (is_flexible_array(newtree[num_fields - 1])) {
369                 has_flexarray = true;
370                 shuffle_length--;
371         }
372 
373         shuffle(type, (tree *)newtree, shuffle_length);
374 
375         /*
376          * set up a bogus anonymous struct field designed to error out on unnamed struct initializers
377          * as gcc provides no other way to detect such code
378          */
379         list = make_node(FIELD_DECL);
380         TREE_CHAIN(list) = newtree[0];
381         TREE_TYPE(list) = void_type_node;
382         DECL_SIZE(list) = bitsize_zero_node;
383         DECL_NONADDRESSABLE_P(list) = 1;
384         DECL_FIELD_BIT_OFFSET(list) = bitsize_zero_node;
385         DECL_SIZE_UNIT(list) = size_zero_node;
386         DECL_FIELD_OFFSET(list) = size_zero_node;
387         DECL_CONTEXT(list) = type;
388         // to satisfy the constify plugin
389         TREE_READONLY(list) = 1;
390 
391         for (i = 0; i < num_fields - 1; i++)
392                 TREE_CHAIN(newtree[i]) = newtree[i+1];
393         TREE_CHAIN(newtree[num_fields - 1]) = NULL_TREE;
394 
395         main_variant = TYPE_MAIN_VARIANT(type);
396         for (variant = main_variant; variant; variant = TYPE_NEXT_VARIANT(variant)) {
397                 TYPE_FIELDS(variant) = list;
398                 TYPE_ATTRIBUTES(variant) = copy_list(TYPE_ATTRIBUTES(variant));
399                 TYPE_ATTRIBUTES(variant) = tree_cons(get_identifier("randomize_performed"), NULL_TREE, TYPE_ATTRIBUTES(variant));
400                 TYPE_ATTRIBUTES(variant) = tree_cons(get_identifier("designated_init"), NULL_TREE, TYPE_ATTRIBUTES(variant));
401                 if (has_flexarray)
402                         TYPE_ATTRIBUTES(type) = tree_cons(get_identifier("has_flexarray"), NULL_TREE, TYPE_ATTRIBUTES(type));
403         }
404 
405         /*
406          * force a re-layout of the main variant
407          * the TYPE_SIZE for all variants will be recomputed
408          * by finalize_type_size()
409          */
410         TYPE_SIZE(main_variant) = NULL_TREE;
411         layout_type(main_variant);
412         gcc_assert(TYPE_SIZE(main_variant) != NULL_TREE);
413 
414         return 1;
415 }
416 
417 /* from constify plugin */
418 static const_tree get_field_type(const_tree field)
419 {
420         return strip_array_types(TREE_TYPE(field));
421 }
422 
423 /* from constify plugin */
424 static bool is_fptr(const_tree fieldtype)
425 {
426         if (TREE_CODE(fieldtype) != POINTER_TYPE)
427                 return false;
428 
429         return TREE_CODE(TREE_TYPE(fieldtype)) == FUNCTION_TYPE;
430 }
431 
432 /* derived from constify plugin */
433 static int is_pure_ops_struct(const_tree node)
434 {
435         const_tree field;
436 
437         gcc_assert(TREE_CODE(node) == RECORD_TYPE || TREE_CODE(node) == UNION_TYPE);
438 
439         for (field = TYPE_FIELDS(node); field; field = TREE_CHAIN(field)) {
440                 const_tree fieldtype = get_field_type(field);
441                 enum tree_code code = TREE_CODE(fieldtype);
442 
443                 if (node == fieldtype)
444                         continue;
445 
446                 if (!is_fptr(fieldtype))
447                         return 0;
448 
449                 if (code != RECORD_TYPE && code != UNION_TYPE)
450                         continue;
451 
452                 if (!is_pure_ops_struct(fieldtype))
453                         return 0;
454         }
455 
456         return 1;
457 }
458 
459 static void randomize_type(tree type)
460 {
461         tree variant;
462 
463         gcc_assert(TREE_CODE(type) == RECORD_TYPE);
464 
465         if (lookup_attribute("randomize_considered", TYPE_ATTRIBUTES(type)))
466                 return;
467 
468         if (lookup_attribute("randomize_layout", TYPE_ATTRIBUTES(TYPE_MAIN_VARIANT(type))) || is_pure_ops_struct(type))
469                 relayout_struct(type);
470 
471         for (variant = TYPE_MAIN_VARIANT(type); variant; variant = TYPE_NEXT_VARIANT(variant)) {
472                 TYPE_ATTRIBUTES(type) = copy_list(TYPE_ATTRIBUTES(type));
473                 TYPE_ATTRIBUTES(type) = tree_cons(get_identifier("randomize_considered"), NULL_TREE, TYPE_ATTRIBUTES(type));
474         }
475 #ifdef __DEBUG_PLUGIN
476         fprintf(stderr, "Marking randomize_considered on struct %s\n", ORIG_TYPE_NAME(type));
477 #ifdef __DEBUG_VERBOSE
478         debug_tree(type);
479 #endif
480 #endif
481 }
482 
483 static void update_decl_size(tree decl)
484 {
485         tree lastval, lastidx, field, init, type, flexsize;
486         unsigned HOST_WIDE_INT len;
487 
488         type = TREE_TYPE(decl);
489 
490         if (!lookup_attribute("has_flexarray", TYPE_ATTRIBUTES(type)))
491                 return;
492 
493         init = DECL_INITIAL(decl);
494         if (init == NULL_TREE || init == error_mark_node)
495                 return;
496 
497         if (TREE_CODE(init) != CONSTRUCTOR)
498                 return;
499 
500         len = CONSTRUCTOR_NELTS(init);
501         if (!len)
502                 return;
503 
504         lastval = CONSTRUCTOR_ELT(init, CONSTRUCTOR_NELTS(init) - 1)->value;
505         lastidx = CONSTRUCTOR_ELT(init, CONSTRUCTOR_NELTS(init) - 1)->index;
506 
507         for (field = TYPE_FIELDS(TREE_TYPE(decl)); TREE_CHAIN(field); field = TREE_CHAIN(field))
508                 ;
509 
510         if (lastidx != field)
511                 return;
512 
513         if (TREE_CODE(lastval) != STRING_CST) {
514                 error("Only string constants are supported as initializers "
515                       "for randomized structures with flexible arrays");
516                 return;
517         }
518 
519         flexsize = bitsize_int(TREE_STRING_LENGTH(lastval) *
520                 tree_to_uhwi(TYPE_SIZE(TREE_TYPE(TREE_TYPE(lastval)))));
521 
522         DECL_SIZE(decl) = size_binop(PLUS_EXPR, TYPE_SIZE(type), flexsize);
523 
524         return;
525 }
526 
527 
528 static void randomize_layout_finish_decl(void *event_data, void *data)
529 {
530         tree decl = (tree)event_data;
531         tree type;
532 
533         if (decl == NULL_TREE || decl == error_mark_node)
534                 return;
535 
536         type = TREE_TYPE(decl);
537 
538         if (TREE_CODE(decl) != VAR_DECL)
539                 return;
540 
541         if (TREE_CODE(type) != RECORD_TYPE && TREE_CODE(type) != UNION_TYPE)
542                 return;
543 
544         if (!lookup_attribute("randomize_performed", TYPE_ATTRIBUTES(type)))
545                 return;
546 
547         DECL_SIZE(decl) = 0;
548         DECL_SIZE_UNIT(decl) = 0;
549         SET_DECL_ALIGN(decl, 0);
550         SET_DECL_MODE (decl, VOIDmode);
551         SET_DECL_RTL(decl, 0);
552         update_decl_size(decl);
553         layout_decl(decl, 0);
554 }
555 
556 static void finish_type(void *event_data, void *data)
557 {
558         tree type = (tree)event_data;
559 
560         if (type == NULL_TREE || type == error_mark_node)
561                 return;
562 
563         if (TREE_CODE(type) != RECORD_TYPE)
564                 return;
565 
566         if (TYPE_FIELDS(type) == NULL_TREE)
567                 return;
568 
569         if (lookup_attribute("randomize_considered", TYPE_ATTRIBUTES(type)))
570                 return;
571 
572 #ifdef __DEBUG_PLUGIN
573         fprintf(stderr, "Calling randomize_type on %s\n", ORIG_TYPE_NAME(type));
574 #endif
575 #ifdef __DEBUG_VERBOSE
576         debug_tree(type);
577 #endif
578         randomize_type(type);
579 
580         return;
581 }
582 
583 static struct attribute_spec randomize_layout_attr = { };
584 static struct attribute_spec no_randomize_layout_attr = { };
585 static struct attribute_spec randomize_considered_attr = { };
586 static struct attribute_spec randomize_performed_attr = { };
587 
588 static void register_attributes(void *event_data, void *data)
589 {
590         randomize_layout_attr.name              = "randomize_layout";
591         randomize_layout_attr.type_required     = true;
592         randomize_layout_attr.handler           = handle_randomize_layout_attr;
593 #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 
618 static 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 */
660 static 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 
678 static 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 
734 static 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 
749 static 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 
787 static 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  */
809 static 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 }
993 

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