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23a5b65a | 1 | /* Copyright (C) 2013-2014 Free Software Foundation, Inc. |
2077db1b CT |
2 | |
3 | This file is part of GCC. | |
4 | ||
5 | GCC is free software; you can redistribute it and/or modify it under | |
6 | the terms of the GNU General Public License as published by the Free | |
7 | Software Foundation; either version 3, or (at your option) any later | |
8 | version. | |
9 | ||
10 | GCC is distributed in the hope that it will be useful, but WITHOUT ANY | |
11 | WARRANTY; without even the implied warranty of MERCHANTABILITY or | |
12 | FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License | |
13 | for more details. | |
14 | ||
15 | You should have received a copy of the GNU General Public License | |
16 | along with GCC; see the file COPYING3. If not see | |
17 | <http://www.gnu.org/licenses/>. */ | |
18 | ||
19 | /* Virtual Table Pointer Security Pass - Detect corruption of vtable pointers | |
20 | before using them for virtual method dispatches. */ | |
21 | ||
22 | /* This file is part of the vtable security feature implementation. | |
23 | The vtable security feature is designed to detect when a virtual | |
24 | call is about to be made through an invalid vtable pointer | |
25 | (possibly due to data corruption or malicious attacks). The | |
26 | compiler finds every virtual call, and inserts a verification call | |
27 | before the virtual call. The verification call takes the actual | |
28 | vtable pointer value in the object through which the virtual call | |
29 | is being made, and compares the vtable pointer against a set of all | |
30 | valid vtable pointers that the object could contain (this set is | |
31 | based on the declared type of the object). If the pointer is in | |
32 | the valid set, execution is allowed to continue; otherwise the | |
33 | program is halted. | |
34 | ||
35 | There are several pieces needed in order to make this work: 1. For | |
36 | every virtual class in the program (i.e. a class that contains | |
37 | virtual methods), we need to build the set of all possible valid | |
38 | vtables that an object of that class could point to. This includes | |
39 | vtables for any class(es) that inherit from the class under | |
40 | consideration. 2. For every such data set we build up, we need a | |
41 | way to find and reference the data set. This is complicated by the | |
42 | fact that the real vtable addresses are not known until runtime, | |
43 | when the program is loaded into memory, but we need to reference the | |
44 | sets at compile time when we are inserting verification calls into | |
45 | the program. 3. We need to find every virtual call in the program, | |
46 | and insert the verification call (with the appropriate arguments) | |
47 | before the virtual call. 4. We need some runtime library pieces: | |
48 | the code to build up the data sets at runtime; the code to actually | |
49 | perform the verification using the data sets; and some code to set | |
50 | protections on the data sets, so they themselves do not become | |
51 | hacker targets. | |
52 | ||
53 | To find and reference the set of valid vtable pointers for any given | |
54 | virtual class, we create a special global variable for each virtual | |
55 | class. We refer to this as the "vtable map variable" for that | |
56 | class. The vtable map variable has the type "void *", and is | |
57 | initialized by the compiler to NULL. At runtime when the set of | |
58 | valid vtable pointers for a virtual class, e.g. class Foo, is built, | |
59 | the vtable map variable for class Foo is made to point to the set. | |
60 | During compile time, when the compiler is inserting verification | |
61 | calls into the program, it passes the vtable map variable for the | |
62 | appropriate class to the verification call, so that at runtime the | |
63 | verification call can find the appropriate data set. | |
64 | ||
65 | The actual set of valid vtable pointers for a virtual class, | |
66 | e.g. class Foo, cannot be built until runtime, when the vtables get | |
67 | loaded into memory and their addresses are known. But the knowledge | |
68 | about which vtables belong in which class' hierarchy is only known | |
69 | at compile time. Therefore at compile time we collect class | |
70 | hierarchy and vtable information about every virtual class, and we | |
71 | generate calls to build up the data sets at runtime. To build the | |
72 | data sets, we call one of the functions we add to the runtime | |
73 | library, __VLTRegisterPair. __VLTRegisterPair takes two arguments, | |
74 | a vtable map variable and the address of a vtable. If the vtable | |
75 | map variable is currently NULL, it creates a new data set (hash | |
76 | table), makes the vtable map variable point to the new data set, and | |
77 | inserts the vtable address into the data set. If the vtable map | |
78 | variable is not NULL, it just inserts the vtable address into the | |
79 | data set. In order to make sure that our data sets are built before | |
80 | any verification calls happen, we create a special constructor | |
81 | initialization function for each compilation unit, give it a very | |
82 | high initialization priority, and insert all of our calls to | |
83 | __VLTRegisterPair into our special constructor initialization | |
84 | function. | |
85 | ||
86 | The vtable verification feature is controlled by the flag | |
87 | '-fvtable-verify='. There are three flavors of this: | |
88 | '-fvtable-verify=std', '-fvtable-verify=preinit', and | |
89 | '-fvtable-verify=none'. If the option '-fvtable-verfy=preinit' is | |
90 | used, then our constructor initialization function gets put into the | |
91 | preinit array. This is necessary if there are data sets that need | |
92 | to be built very early in execution. If the constructor | |
93 | initialization function gets put into the preinit array, the we also | |
94 | add calls to __VLTChangePermission at the beginning and end of the | |
95 | function. The call at the beginning sets the permissions on the | |
96 | data sets and vtable map variables to read/write, and the one at the | |
97 | end makes them read-only. If the '-fvtable-verify=std' option is | |
98 | used, the constructor initialization functions are executed at their | |
99 | normal time, and the __VLTChangePermission calls are handled | |
100 | differently (see the comments in libstdc++-v3/libsupc++/vtv_rts.cc). | |
101 | The option '-fvtable-verify=none' turns off vtable verification. | |
102 | ||
103 | This file contains code for the tree pass that goes through all the | |
104 | statements in each basic block, looking for virtual calls, and | |
105 | inserting a call to __VLTVerifyVtablePointer (with appropriate | |
106 | arguments) before each one. It also contains the hash table | |
107 | functions for the data structures used for collecting the class | |
108 | hierarchy data and building/maintaining the vtable map variable data | |
109 | are defined in gcc/vtable-verify.h. These data structures are | |
110 | shared with the code in the C++ front end that collects the class | |
111 | hierarchy & vtable information and generates the vtable map | |
112 | variables (see cp/vtable-class-hierarchy.c). This tree pass should | |
113 | run just before the gimple is converted to RTL. | |
114 | ||
115 | Some implementation details for this pass: | |
116 | ||
117 | To find all of the virtual calls, we iterate through all the | |
118 | gimple statements in each basic block, looking for any call | |
119 | statement with the code "OBJ_TYPE_REF". Once we have found the | |
120 | virtual call, we need to find the vtable pointer through which the | |
121 | call is being made, and the type of the object containing the | |
122 | pointer (to find the appropriate vtable map variable). We then use | |
123 | these to build a call to __VLTVerifyVtablePointer, passing the | |
124 | vtable map variable, and the vtable pointer. We insert the | |
125 | verification call just after the gimple statement that gets the | |
126 | vtable pointer out of the object, and we update the next | |
127 | statement to depend on the result returned from | |
128 | __VLTVerifyVtablePointer (the vtable pointer value), to ensure | |
129 | subsequent compiler phases don't remove or reorder the call (it's no | |
130 | good to have the verification occur after the virtual call, for | |
131 | example). To find the vtable pointer being used (and the type of | |
132 | the object) we search backwards through the def_stmts chain from the | |
133 | virtual call (see verify_bb_vtables for more details). */ | |
134 | ||
135 | #include "config.h" | |
136 | #include "system.h" | |
137 | #include "coretypes.h" | |
138 | #include "tree.h" | |
60393bbc AM |
139 | #include "predict.h" |
140 | #include "vec.h" | |
141 | #include "hashtab.h" | |
142 | #include "hash-set.h" | |
143 | #include "machmode.h" | |
144 | #include "tm.h" | |
145 | #include "hard-reg-set.h" | |
146 | #include "input.h" | |
147 | #include "function.h" | |
148 | #include "dominance.h" | |
149 | #include "cfg.h" | |
2077db1b | 150 | #include "basic-block.h" |
2fb9a547 AM |
151 | #include "tree-ssa-alias.h" |
152 | #include "internal-fn.h" | |
153 | #include "gimple-expr.h" | |
154 | #include "is-a.h" | |
442b4905 | 155 | #include "gimple.h" |
5be5c238 | 156 | #include "gimple-iterator.h" |
442b4905 AM |
157 | #include "gimple-ssa.h" |
158 | #include "tree-phinodes.h" | |
159 | #include "ssa-iterators.h" | |
d8a2d370 | 160 | #include "stringpool.h" |
442b4905 | 161 | #include "tree-ssanames.h" |
2077db1b CT |
162 | #include "tree-pass.h" |
163 | #include "cfgloop.h" | |
164 | ||
165 | #include "vtable-verify.h" | |
166 | ||
167 | unsigned num_vtable_map_nodes = 0; | |
168 | int total_num_virtual_calls = 0; | |
169 | int total_num_verified_vcalls = 0; | |
170 | ||
171 | extern GTY(()) tree verify_vtbl_ptr_fndecl; | |
172 | tree verify_vtbl_ptr_fndecl = NULL_TREE; | |
173 | ||
174 | /* Keep track of whether or not any virtual call were verified. */ | |
175 | static bool any_verification_calls_generated = false; | |
176 | ||
177 | unsigned int vtable_verify_main (void); | |
178 | ||
179 | ||
180 | /* The following few functions are for the vtbl pointer hash table | |
181 | in the 'registered' field of the struct vtable_map_node. The hash | |
182 | table keeps track of which vtable pointers have been used in | |
183 | calls to __VLTRegisterPair with that particular vtable map variable. */ | |
184 | ||
185 | /* This function checks to see if a particular VTABLE_DECL and OFFSET are | |
186 | already in the 'registered' hash table for NODE. */ | |
187 | ||
188 | bool | |
189 | vtbl_map_node_registration_find (struct vtbl_map_node *node, | |
190 | tree vtable_decl, | |
191 | unsigned offset) | |
192 | { | |
193 | struct vtable_registration key; | |
194 | struct vtable_registration **slot; | |
195 | ||
c203e8a7 | 196 | gcc_assert (node && node->registered); |
2077db1b CT |
197 | |
198 | key.vtable_decl = vtable_decl; | |
c203e8a7 | 199 | slot = node->registered->find_slot (&key, NO_INSERT); |
2077db1b CT |
200 | |
201 | if (slot && (*slot)) | |
202 | { | |
203 | unsigned i; | |
c3284718 | 204 | for (i = 0; i < ((*slot)->offsets).length (); ++i) |
2077db1b CT |
205 | if ((*slot)->offsets[i] == offset) |
206 | return true; | |
207 | } | |
208 | ||
209 | return false; | |
210 | } | |
211 | ||
212 | /* This function inserts VTABLE_DECL and OFFSET into the 'registered' | |
213 | hash table for NODE. It returns a boolean indicating whether or not | |
214 | it actually inserted anything. */ | |
215 | ||
216 | bool | |
217 | vtbl_map_node_registration_insert (struct vtbl_map_node *node, | |
218 | tree vtable_decl, | |
219 | unsigned offset) | |
220 | { | |
221 | struct vtable_registration key; | |
222 | struct vtable_registration **slot; | |
223 | bool inserted_something = false; | |
224 | ||
c203e8a7 | 225 | if (!node || !node->registered) |
2077db1b CT |
226 | return false; |
227 | ||
228 | key.vtable_decl = vtable_decl; | |
c203e8a7 | 229 | slot = node->registered->find_slot (&key, INSERT); |
2077db1b CT |
230 | |
231 | if (! *slot) | |
232 | { | |
233 | struct vtable_registration *node; | |
234 | node = XNEW (struct vtable_registration); | |
235 | node->vtable_decl = vtable_decl; | |
236 | ||
237 | (node->offsets).create (10); | |
238 | (node->offsets).safe_push (offset); | |
239 | *slot = node; | |
240 | inserted_something = true; | |
241 | } | |
242 | else | |
243 | { | |
244 | /* We found the vtable_decl slot; we need to see if it already | |
245 | contains the offset. If not, we need to add the offset. */ | |
246 | unsigned i; | |
247 | bool found = false; | |
c3284718 | 248 | for (i = 0; i < ((*slot)->offsets).length () && !found; ++i) |
2077db1b CT |
249 | if ((*slot)->offsets[i] == offset) |
250 | found = true; | |
251 | ||
252 | if (!found) | |
253 | { | |
254 | ((*slot)->offsets).safe_push (offset); | |
255 | inserted_something = true; | |
256 | } | |
257 | } | |
258 | return inserted_something; | |
259 | } | |
260 | ||
261 | /* Hashtable functions for vtable_registration hashtables. */ | |
262 | ||
263 | inline hashval_t | |
264 | registration_hasher::hash (const value_type *p) | |
265 | { | |
266 | const struct vtable_registration *n = (const struct vtable_registration *) p; | |
267 | return (hashval_t) (DECL_UID (n->vtable_decl)); | |
268 | } | |
269 | ||
270 | inline bool | |
271 | registration_hasher::equal (const value_type *p1, const compare_type *p2) | |
272 | { | |
273 | const struct vtable_registration *n1 = | |
274 | (const struct vtable_registration *) p1; | |
275 | const struct vtable_registration *n2 = | |
276 | (const struct vtable_registration *) p2; | |
277 | return (DECL_UID (n1->vtable_decl) == DECL_UID (n2->vtable_decl)); | |
278 | } | |
279 | ||
280 | /* End of hashtable functions for "registered" hashtables. */ | |
281 | ||
282 | ||
283 | ||
284 | /* Hashtable definition and functions for vtbl_map_hash. */ | |
285 | ||
286 | struct vtbl_map_hasher : typed_noop_remove <struct vtbl_map_node> | |
287 | { | |
288 | typedef struct vtbl_map_node value_type; | |
289 | typedef struct vtbl_map_node compare_type; | |
290 | static inline hashval_t hash (const value_type *); | |
291 | static inline bool equal (const value_type *, const compare_type *); | |
292 | }; | |
293 | ||
294 | /* Returns a hash code for P. */ | |
295 | ||
296 | inline hashval_t | |
297 | vtbl_map_hasher::hash (const value_type *p) | |
298 | { | |
299 | const struct vtbl_map_node n = *((const struct vtbl_map_node *) p); | |
300 | return (hashval_t) IDENTIFIER_HASH_VALUE (n.class_name); | |
301 | } | |
302 | ||
303 | /* Returns nonzero if P1 and P2 are equal. */ | |
304 | ||
305 | inline bool | |
306 | vtbl_map_hasher::equal (const value_type *p1, const compare_type *p2) | |
307 | { | |
308 | const struct vtbl_map_node n1 = *((const struct vtbl_map_node *) p1); | |
309 | const struct vtbl_map_node n2 = *((const struct vtbl_map_node *) p2); | |
310 | return (IDENTIFIER_HASH_VALUE (n1.class_name) == | |
311 | IDENTIFIER_HASH_VALUE (n2.class_name)); | |
312 | } | |
313 | ||
314 | /* Here are the two structures into which we insert vtable map nodes. | |
315 | We use two data structures because of the vastly different ways we need | |
316 | to find the nodes for various tasks (see comments in vtable-verify.h | |
317 | for more details. */ | |
318 | ||
c203e8a7 | 319 | typedef hash_table<vtbl_map_hasher> vtbl_map_table_type; |
2077db1b CT |
320 | typedef vtbl_map_table_type::iterator vtbl_map_iterator_type; |
321 | ||
322 | /* Vtable map variable nodes stored in a hash table. */ | |
c203e8a7 | 323 | static vtbl_map_table_type *vtbl_map_hash; |
2077db1b CT |
324 | |
325 | /* Vtable map variable nodes stored in a vector. */ | |
326 | vec<struct vtbl_map_node *> vtbl_map_nodes_vec; | |
327 | ||
328 | /* Return vtbl_map node for CLASS_NAME without creating a new one. */ | |
329 | ||
330 | struct vtbl_map_node * | |
331 | vtbl_map_get_node (tree class_type) | |
332 | { | |
333 | struct vtbl_map_node key; | |
334 | struct vtbl_map_node **slot; | |
335 | ||
336 | tree class_type_decl; | |
337 | tree class_name; | |
338 | unsigned int type_quals; | |
339 | ||
c203e8a7 | 340 | if (!vtbl_map_hash) |
2077db1b CT |
341 | return NULL; |
342 | ||
343 | gcc_assert (TREE_CODE (class_type) == RECORD_TYPE); | |
344 | ||
345 | ||
346 | /* Find the TYPE_DECL for the class. */ | |
347 | class_type_decl = TYPE_NAME (class_type); | |
348 | ||
349 | /* Verify that there aren't any qualifiers on the type. */ | |
350 | type_quals = TYPE_QUALS (TREE_TYPE (class_type_decl)); | |
351 | gcc_assert (type_quals == TYPE_UNQUALIFIED); | |
352 | ||
353 | /* Get the mangled name for the unqualified type. */ | |
354 | gcc_assert (HAS_DECL_ASSEMBLER_NAME_P (class_type_decl)); | |
355 | class_name = DECL_ASSEMBLER_NAME (class_type_decl); | |
356 | ||
357 | key.class_name = class_name; | |
c203e8a7 | 358 | slot = (struct vtbl_map_node **) vtbl_map_hash->find_slot (&key, NO_INSERT); |
2077db1b CT |
359 | if (!slot) |
360 | return NULL; | |
361 | return *slot; | |
362 | } | |
363 | ||
364 | /* Return vtbl_map node assigned to BASE_CLASS_TYPE. Create new one | |
365 | when needed. */ | |
366 | ||
367 | struct vtbl_map_node * | |
368 | find_or_create_vtbl_map_node (tree base_class_type) | |
369 | { | |
370 | struct vtbl_map_node key; | |
371 | struct vtbl_map_node *node; | |
372 | struct vtbl_map_node **slot; | |
373 | tree class_type_decl; | |
374 | unsigned int type_quals; | |
375 | ||
c203e8a7 TS |
376 | if (!vtbl_map_hash) |
377 | vtbl_map_hash = new vtbl_map_table_type (10); | |
2077db1b CT |
378 | |
379 | /* Find the TYPE_DECL for the class. */ | |
380 | class_type_decl = TYPE_NAME (base_class_type); | |
381 | ||
382 | /* Verify that there aren't any type qualifiers on type. */ | |
383 | type_quals = TYPE_QUALS (TREE_TYPE (class_type_decl)); | |
384 | gcc_assert (type_quals == TYPE_UNQUALIFIED); | |
385 | ||
386 | gcc_assert (HAS_DECL_ASSEMBLER_NAME_P (class_type_decl)); | |
387 | key.class_name = DECL_ASSEMBLER_NAME (class_type_decl); | |
c203e8a7 | 388 | slot = (struct vtbl_map_node **) vtbl_map_hash->find_slot (&key, INSERT); |
2077db1b CT |
389 | |
390 | if (*slot) | |
391 | return *slot; | |
392 | ||
393 | node = XNEW (struct vtbl_map_node); | |
394 | node->vtbl_map_decl = NULL_TREE; | |
395 | node->class_name = key.class_name; | |
396 | node->uid = num_vtable_map_nodes++; | |
397 | ||
398 | node->class_info = XNEW (struct vtv_graph_node); | |
399 | node->class_info->class_type = base_class_type; | |
400 | node->class_info->class_uid = node->uid; | |
401 | node->class_info->num_processed_children = 0; | |
402 | ||
403 | (node->class_info->parents).create (4); | |
404 | (node->class_info->children).create (4); | |
405 | ||
c203e8a7 | 406 | node->registered = new register_table_type (16); |
2077db1b CT |
407 | |
408 | node->is_used = false; | |
409 | ||
410 | vtbl_map_nodes_vec.safe_push (node); | |
411 | gcc_assert (vtbl_map_nodes_vec[node->uid] == node); | |
412 | ||
413 | *slot = node; | |
414 | return node; | |
415 | } | |
416 | ||
417 | /* End of hashtable functions for vtable_map variables hash table. */ | |
418 | ||
419 | /* Given a gimple STMT, this function checks to see if the statement | |
420 | is an assignment, the rhs of which is getting the vtable pointer | |
421 | value out of an object. (i.e. it's the value we need to verify | |
422 | because its the vtable pointer that will be used for a virtual | |
423 | call). */ | |
424 | ||
425 | static bool | |
426 | is_vtable_assignment_stmt (gimple stmt) | |
427 | { | |
428 | ||
429 | if (gimple_code (stmt) != GIMPLE_ASSIGN) | |
430 | return false; | |
431 | else | |
432 | { | |
433 | tree lhs = gimple_assign_lhs (stmt); | |
434 | tree rhs = gimple_assign_rhs1 (stmt); | |
435 | ||
436 | if (TREE_CODE (lhs) != SSA_NAME) | |
437 | return false; | |
438 | ||
439 | if (TREE_CODE (rhs) != COMPONENT_REF) | |
440 | return false; | |
441 | ||
442 | if (! (TREE_OPERAND (rhs, 1)) | |
443 | || (TREE_CODE (TREE_OPERAND (rhs, 1)) != FIELD_DECL)) | |
444 | return false; | |
445 | ||
446 | if (! DECL_VIRTUAL_P (TREE_OPERAND (rhs, 1))) | |
447 | return false; | |
448 | } | |
449 | ||
450 | return true; | |
451 | } | |
452 | ||
453 | /* This function attempts to recover the declared class of an object | |
454 | that is used in making a virtual call. We try to get the type from | |
455 | the type cast in the gimple assignment statement that extracts the | |
456 | vtable pointer from the object (DEF_STMT). The gimple statement | |
457 | usually looks something like this: | |
458 | ||
459 | D.2201_4 = MEM[(struct Event *)this_1(D)]._vptr.Event */ | |
460 | ||
461 | static tree | |
462 | extract_object_class_type (tree rhs) | |
463 | { | |
464 | tree result = NULL_TREE; | |
465 | ||
466 | /* Try to find and extract the type cast from that stmt. */ | |
467 | if (TREE_CODE (rhs) == COMPONENT_REF) | |
468 | { | |
469 | tree op0 = TREE_OPERAND (rhs, 0); | |
470 | tree op1 = TREE_OPERAND (rhs, 1); | |
471 | ||
472 | if (TREE_CODE (op1) == FIELD_DECL | |
473 | && DECL_VIRTUAL_P (op1)) | |
474 | { | |
475 | if (TREE_CODE (op0) == COMPONENT_REF | |
476 | && TREE_CODE (TREE_OPERAND (op0, 0)) == MEM_REF | |
477 | && TREE_CODE (TREE_TYPE (TREE_OPERAND (op0, 0)))== RECORD_TYPE) | |
478 | result = TREE_TYPE (TREE_OPERAND (op0, 0)); | |
479 | else | |
480 | result = TREE_TYPE (op0); | |
481 | } | |
482 | else if (TREE_CODE (op0) == COMPONENT_REF) | |
483 | { | |
484 | result = extract_object_class_type (op0); | |
485 | if (result == NULL_TREE | |
486 | && TREE_CODE (op1) == COMPONENT_REF) | |
487 | result = extract_object_class_type (op1); | |
488 | } | |
489 | } | |
490 | ||
491 | return result; | |
492 | } | |
493 | ||
494 | /* This function traces forward through the def-use chain of an SSA | |
495 | variable to see if it ever gets used in a virtual function call. It | |
496 | returns a boolean indicating whether or not it found a virtual call in | |
497 | the use chain. */ | |
498 | ||
499 | static bool | |
500 | var_is_used_for_virtual_call_p (tree lhs, int *mem_ref_depth) | |
501 | { | |
502 | imm_use_iterator imm_iter; | |
503 | bool found_vcall = false; | |
504 | use_operand_p use_p; | |
505 | ||
506 | if (TREE_CODE (lhs) != SSA_NAME) | |
507 | return false; | |
508 | ||
509 | if (*mem_ref_depth > 2) | |
510 | return false; | |
511 | ||
512 | /* Iterate through the immediate uses of the current variable. If | |
513 | it's a virtual function call, we're done. Otherwise, if there's | |
514 | an LHS for the use stmt, add the ssa var to the work list | |
515 | (assuming it's not already in the list and is not a variable | |
516 | we've already examined. */ | |
517 | ||
518 | FOR_EACH_IMM_USE_FAST (use_p, imm_iter, lhs) | |
519 | { | |
520 | gimple stmt2 = USE_STMT (use_p); | |
521 | ||
ed9e19a4 | 522 | if (is_gimple_call (stmt2)) |
2077db1b CT |
523 | { |
524 | tree fncall = gimple_call_fn (stmt2); | |
ed9e19a4 | 525 | if (fncall && TREE_CODE (fncall) == OBJ_TYPE_REF) |
2077db1b CT |
526 | found_vcall = true; |
527 | else | |
528 | return false; | |
529 | } | |
530 | else if (gimple_code (stmt2) == GIMPLE_PHI) | |
531 | { | |
532 | found_vcall = var_is_used_for_virtual_call_p | |
533 | (gimple_phi_result (stmt2), | |
534 | mem_ref_depth); | |
535 | } | |
ed9e19a4 | 536 | else if (is_gimple_assign (stmt2)) |
2077db1b CT |
537 | { |
538 | tree rhs = gimple_assign_rhs1 (stmt2); | |
539 | if (TREE_CODE (rhs) == ADDR_EXPR | |
540 | || TREE_CODE (rhs) == MEM_REF) | |
541 | *mem_ref_depth = *mem_ref_depth + 1; | |
542 | ||
543 | if (TREE_CODE (rhs) == COMPONENT_REF) | |
544 | { | |
545 | while (TREE_CODE (TREE_OPERAND (rhs, 0)) == COMPONENT_REF) | |
546 | rhs = TREE_OPERAND (rhs, 0); | |
547 | ||
548 | if (TREE_CODE (TREE_OPERAND (rhs, 0)) == ADDR_EXPR | |
549 | || TREE_CODE (TREE_OPERAND (rhs, 0)) == MEM_REF) | |
550 | *mem_ref_depth = *mem_ref_depth + 1; | |
551 | } | |
552 | ||
553 | if (*mem_ref_depth < 3) | |
554 | found_vcall = var_is_used_for_virtual_call_p | |
555 | (gimple_assign_lhs (stmt2), | |
556 | mem_ref_depth); | |
557 | } | |
558 | ||
559 | else | |
560 | break; | |
561 | ||
562 | if (found_vcall) | |
563 | return true; | |
564 | } | |
565 | ||
566 | return false; | |
567 | } | |
568 | ||
569 | /* Search through all the statements in a basic block (BB), searching | |
570 | for virtual method calls. For each virtual method dispatch, find | |
571 | the vptr value used, and the statically declared type of the | |
572 | object; retrieve the vtable map variable for the type of the | |
573 | object; generate a call to __VLTVerifyVtablePointer; and insert the | |
574 | generated call into the basic block, after the point where the vptr | |
575 | value is gotten out of the object and before the virtual method | |
576 | dispatch. Make the virtual method dispatch depend on the return | |
577 | value from the verification call, so that subsequent optimizations | |
578 | cannot reorder the two calls. */ | |
579 | ||
580 | static void | |
581 | verify_bb_vtables (basic_block bb) | |
582 | { | |
583 | gimple_seq stmts; | |
584 | gimple stmt = NULL; | |
585 | gimple_stmt_iterator gsi_vtbl_assign; | |
586 | gimple_stmt_iterator gsi_virtual_call; | |
587 | ||
588 | stmts = bb_seq (bb); | |
589 | gsi_virtual_call = gsi_start (stmts); | |
590 | for (; !gsi_end_p (gsi_virtual_call); gsi_next (&gsi_virtual_call)) | |
591 | { | |
592 | stmt = gsi_stmt (gsi_virtual_call); | |
593 | ||
594 | /* Count virtual calls. */ | |
fe46e7aa | 595 | if (is_gimple_call (stmt)) |
2077db1b CT |
596 | { |
597 | tree fncall = gimple_call_fn (stmt); | |
fe46e7aa | 598 | if (fncall && TREE_CODE (fncall) == OBJ_TYPE_REF) |
2077db1b CT |
599 | total_num_virtual_calls++; |
600 | } | |
601 | ||
602 | if (is_vtable_assignment_stmt (stmt)) | |
603 | { | |
604 | tree lhs = gimple_assign_lhs (stmt); | |
605 | tree vtbl_var_decl = NULL_TREE; | |
606 | struct vtbl_map_node *vtable_map_node; | |
607 | tree vtbl_decl = NULL_TREE; | |
538dd0b7 | 608 | gcall *call_stmt; |
2077db1b CT |
609 | const char *vtable_name = "<unknown>"; |
610 | tree tmp0; | |
611 | bool found; | |
612 | int mem_ref_depth = 0; | |
613 | ||
614 | /* Make sure this vptr field access is for a virtual call. */ | |
615 | if (!var_is_used_for_virtual_call_p (lhs, &mem_ref_depth)) | |
616 | continue; | |
617 | ||
618 | /* Now we have found the virtual method dispatch and | |
619 | the preceding access of the _vptr.* field... Next | |
620 | we need to find the statically declared type of | |
621 | the object, so we can find and use the right | |
622 | vtable map variable in the verification call. */ | |
623 | tree class_type = extract_object_class_type | |
624 | (gimple_assign_rhs1 (stmt)); | |
625 | ||
626 | gsi_vtbl_assign = gsi_for_stmt (stmt); | |
627 | ||
628 | if (class_type | |
629 | && (TREE_CODE (class_type) == RECORD_TYPE) | |
630 | && TYPE_BINFO (class_type)) | |
631 | { | |
632 | /* Get the vtable VAR_DECL for the type. */ | |
633 | vtbl_var_decl = BINFO_VTABLE (TYPE_BINFO (class_type)); | |
634 | ||
635 | if (TREE_CODE (vtbl_var_decl) == POINTER_PLUS_EXPR) | |
636 | vtbl_var_decl = TREE_OPERAND (TREE_OPERAND (vtbl_var_decl, 0), | |
637 | 0); | |
638 | ||
639 | gcc_assert (vtbl_var_decl); | |
640 | ||
641 | vtbl_decl = vtbl_var_decl; | |
642 | vtable_map_node = vtbl_map_get_node | |
643 | (TYPE_MAIN_VARIANT (class_type)); | |
644 | ||
645 | gcc_assert (verify_vtbl_ptr_fndecl); | |
646 | ||
647 | /* Given the vtable pointer for the base class of the | |
648 | object, build the call to __VLTVerifyVtablePointer to | |
649 | verify that the object's vtable pointer (contained in | |
650 | lhs) is in the set of valid vtable pointers for the | |
651 | base class. */ | |
652 | ||
653 | if (vtable_map_node && vtable_map_node->vtbl_map_decl) | |
654 | { | |
2077db1b CT |
655 | vtable_map_node->is_used = true; |
656 | vtbl_var_decl = vtable_map_node->vtbl_map_decl; | |
657 | ||
658 | if (TREE_CODE (vtbl_decl) == VAR_DECL) | |
659 | vtable_name = IDENTIFIER_POINTER (DECL_NAME (vtbl_decl)); | |
660 | ||
661 | /* Call different routines if we are interested in | |
662 | trace information to debug problems. */ | |
663 | if (flag_vtv_debug) | |
664 | { | |
665 | int len1 = IDENTIFIER_LENGTH | |
666 | (DECL_NAME (vtbl_var_decl)); | |
667 | int len2 = strlen (vtable_name); | |
668 | ||
669 | call_stmt = gimple_build_call | |
670 | (verify_vtbl_ptr_fndecl, 4, | |
671 | build1 (ADDR_EXPR, | |
672 | TYPE_POINTER_TO | |
673 | (TREE_TYPE (vtbl_var_decl)), | |
674 | vtbl_var_decl), | |
675 | lhs, | |
676 | build_string_literal | |
677 | (len1 + 1, | |
678 | IDENTIFIER_POINTER | |
679 | (DECL_NAME | |
680 | (vtbl_var_decl))), | |
681 | build_string_literal (len2 + 1, | |
682 | vtable_name)); | |
683 | } | |
684 | else | |
685 | call_stmt = gimple_build_call | |
686 | (verify_vtbl_ptr_fndecl, 2, | |
687 | build1 (ADDR_EXPR, | |
688 | TYPE_POINTER_TO | |
689 | (TREE_TYPE (vtbl_var_decl)), | |
690 | vtbl_var_decl), | |
691 | lhs); | |
692 | ||
693 | ||
694 | /* Create a new SSA_NAME var to hold the call's | |
695 | return value, and make the call_stmt use the | |
696 | variable for that purpose. */ | |
697 | tmp0 = make_temp_ssa_name (TREE_TYPE (lhs), NULL, "VTV"); | |
698 | gimple_call_set_lhs (call_stmt, tmp0); | |
699 | update_stmt (call_stmt); | |
700 | ||
31226750 | 701 | /* Replace all uses of lhs with tmp0. */ |
2077db1b | 702 | found = false; |
31226750 CT |
703 | imm_use_iterator iterator; |
704 | gimple use_stmt; | |
705 | FOR_EACH_IMM_USE_STMT (use_stmt, iterator, lhs) | |
2077db1b | 706 | { |
31226750 CT |
707 | use_operand_p use_p; |
708 | if (use_stmt == call_stmt) | |
709 | continue; | |
710 | FOR_EACH_IMM_USE_ON_STMT (use_p, iterator) | |
711 | SET_USE (use_p, tmp0); | |
712 | update_stmt (use_stmt); | |
713 | found = true; | |
2077db1b | 714 | } |
31226750 | 715 | |
2077db1b CT |
716 | gcc_assert (found); |
717 | ||
718 | /* Insert the new verification call just after the | |
719 | statement that gets the vtable pointer out of the | |
720 | object. */ | |
31226750 | 721 | gcc_assert (gsi_stmt (gsi_vtbl_assign) == stmt); |
2077db1b CT |
722 | gsi_insert_after (&gsi_vtbl_assign, call_stmt, |
723 | GSI_NEW_STMT); | |
724 | ||
725 | any_verification_calls_generated = true; | |
726 | total_num_verified_vcalls++; | |
727 | } | |
728 | } | |
729 | } | |
730 | } | |
731 | } | |
732 | ||
2077db1b CT |
733 | /* Definition of this optimization pass. */ |
734 | ||
735 | namespace { | |
736 | ||
737 | const pass_data pass_data_vtable_verify = | |
738 | { | |
739 | GIMPLE_PASS, /* type */ | |
740 | "vtable-verify", /* name */ | |
741 | OPTGROUP_NONE, /* optinfo_flags */ | |
2077db1b CT |
742 | TV_VTABLE_VERIFICATION, /* tv_id */ |
743 | ( PROP_cfg | PROP_ssa ), /* properties_required */ | |
744 | 0, /* properties_provided */ | |
745 | 0, /* properties_destroyed */ | |
746 | 0, /* todo_flags_start */ | |
747 | TODO_update_ssa, /* todo_flags_finish */ | |
748 | }; | |
749 | ||
750 | class pass_vtable_verify : public gimple_opt_pass | |
751 | { | |
752 | public: | |
c3284718 RS |
753 | pass_vtable_verify (gcc::context *ctxt) |
754 | : gimple_opt_pass (pass_data_vtable_verify, ctxt) | |
2077db1b CT |
755 | {} |
756 | ||
757 | /* opt_pass methods: */ | |
1a3d085c | 758 | virtual bool gate (function *) { return (flag_vtable_verify); } |
be55bfe6 | 759 | virtual unsigned int execute (function *); |
2077db1b CT |
760 | |
761 | }; // class pass_vtable_verify | |
762 | ||
be55bfe6 TS |
763 | /* Loop through all the basic blocks in the current function, passing them to |
764 | verify_bb_vtables, which searches for virtual calls, and inserts | |
765 | calls to __VLTVerifyVtablePointer. */ | |
766 | ||
767 | unsigned int | |
768 | pass_vtable_verify::execute (function *fun) | |
769 | { | |
770 | unsigned int ret = 1; | |
771 | basic_block bb; | |
772 | ||
773 | FOR_ALL_BB_FN (bb, fun) | |
774 | verify_bb_vtables (bb); | |
775 | ||
776 | return ret; | |
777 | } | |
778 | ||
2077db1b CT |
779 | } // anon namespace |
780 | ||
781 | gimple_opt_pass * | |
782 | make_pass_vtable_verify (gcc::context *ctxt) | |
783 | { | |
784 | return new pass_vtable_verify (ctxt); | |
785 | } | |
786 | ||
787 | #include "gt-vtable-verify.h" |