]>
Commit | Line | Data |
---|---|---|
2077db1b CT |
1 | /* Copyright (C) 2013 |
2 | Free Software Foundation, Inc. | |
3 | ||
4 | This file is part of GCC. | |
5 | ||
6 | GCC is free software; you can redistribute it and/or modify it under | |
7 | the terms of the GNU General Public License as published by the Free | |
8 | Software Foundation; either version 3, or (at your option) any later | |
9 | version. | |
10 | ||
11 | GCC is distributed in the hope that it will be useful, but WITHOUT ANY | |
12 | WARRANTY; without even the implied warranty of MERCHANTABILITY or | |
13 | FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License | |
14 | for more details. | |
15 | ||
16 | You should have received a copy of the GNU General Public License | |
17 | along with GCC; see the file COPYING3. If not see | |
18 | <http://www.gnu.org/licenses/>. */ | |
19 | ||
20 | /* Virtual Table Pointer Security Pass - Detect corruption of vtable pointers | |
21 | before using them for virtual method dispatches. */ | |
22 | ||
23 | /* This file is part of the vtable security feature implementation. | |
24 | The vtable security feature is designed to detect when a virtual | |
25 | call is about to be made through an invalid vtable pointer | |
26 | (possibly due to data corruption or malicious attacks). The | |
27 | compiler finds every virtual call, and inserts a verification call | |
28 | before the virtual call. The verification call takes the actual | |
29 | vtable pointer value in the object through which the virtual call | |
30 | is being made, and compares the vtable pointer against a set of all | |
31 | valid vtable pointers that the object could contain (this set is | |
32 | based on the declared type of the object). If the pointer is in | |
33 | the valid set, execution is allowed to continue; otherwise the | |
34 | program is halted. | |
35 | ||
36 | There are several pieces needed in order to make this work: 1. For | |
37 | every virtual class in the program (i.e. a class that contains | |
38 | virtual methods), we need to build the set of all possible valid | |
39 | vtables that an object of that class could point to. This includes | |
40 | vtables for any class(es) that inherit from the class under | |
41 | consideration. 2. For every such data set we build up, we need a | |
42 | way to find and reference the data set. This is complicated by the | |
43 | fact that the real vtable addresses are not known until runtime, | |
44 | when the program is loaded into memory, but we need to reference the | |
45 | sets at compile time when we are inserting verification calls into | |
46 | the program. 3. We need to find every virtual call in the program, | |
47 | and insert the verification call (with the appropriate arguments) | |
48 | before the virtual call. 4. We need some runtime library pieces: | |
49 | the code to build up the data sets at runtime; the code to actually | |
50 | perform the verification using the data sets; and some code to set | |
51 | protections on the data sets, so they themselves do not become | |
52 | hacker targets. | |
53 | ||
54 | To find and reference the set of valid vtable pointers for any given | |
55 | virtual class, we create a special global variable for each virtual | |
56 | class. We refer to this as the "vtable map variable" for that | |
57 | class. The vtable map variable has the type "void *", and is | |
58 | initialized by the compiler to NULL. At runtime when the set of | |
59 | valid vtable pointers for a virtual class, e.g. class Foo, is built, | |
60 | the vtable map variable for class Foo is made to point to the set. | |
61 | During compile time, when the compiler is inserting verification | |
62 | calls into the program, it passes the vtable map variable for the | |
63 | appropriate class to the verification call, so that at runtime the | |
64 | verification call can find the appropriate data set. | |
65 | ||
66 | The actual set of valid vtable pointers for a virtual class, | |
67 | e.g. class Foo, cannot be built until runtime, when the vtables get | |
68 | loaded into memory and their addresses are known. But the knowledge | |
69 | about which vtables belong in which class' hierarchy is only known | |
70 | at compile time. Therefore at compile time we collect class | |
71 | hierarchy and vtable information about every virtual class, and we | |
72 | generate calls to build up the data sets at runtime. To build the | |
73 | data sets, we call one of the functions we add to the runtime | |
74 | library, __VLTRegisterPair. __VLTRegisterPair takes two arguments, | |
75 | a vtable map variable and the address of a vtable. If the vtable | |
76 | map variable is currently NULL, it creates a new data set (hash | |
77 | table), makes the vtable map variable point to the new data set, and | |
78 | inserts the vtable address into the data set. If the vtable map | |
79 | variable is not NULL, it just inserts the vtable address into the | |
80 | data set. In order to make sure that our data sets are built before | |
81 | any verification calls happen, we create a special constructor | |
82 | initialization function for each compilation unit, give it a very | |
83 | high initialization priority, and insert all of our calls to | |
84 | __VLTRegisterPair into our special constructor initialization | |
85 | function. | |
86 | ||
87 | The vtable verification feature is controlled by the flag | |
88 | '-fvtable-verify='. There are three flavors of this: | |
89 | '-fvtable-verify=std', '-fvtable-verify=preinit', and | |
90 | '-fvtable-verify=none'. If the option '-fvtable-verfy=preinit' is | |
91 | used, then our constructor initialization function gets put into the | |
92 | preinit array. This is necessary if there are data sets that need | |
93 | to be built very early in execution. If the constructor | |
94 | initialization function gets put into the preinit array, the we also | |
95 | add calls to __VLTChangePermission at the beginning and end of the | |
96 | function. The call at the beginning sets the permissions on the | |
97 | data sets and vtable map variables to read/write, and the one at the | |
98 | end makes them read-only. If the '-fvtable-verify=std' option is | |
99 | used, the constructor initialization functions are executed at their | |
100 | normal time, and the __VLTChangePermission calls are handled | |
101 | differently (see the comments in libstdc++-v3/libsupc++/vtv_rts.cc). | |
102 | The option '-fvtable-verify=none' turns off vtable verification. | |
103 | ||
104 | This file contains code for the tree pass that goes through all the | |
105 | statements in each basic block, looking for virtual calls, and | |
106 | inserting a call to __VLTVerifyVtablePointer (with appropriate | |
107 | arguments) before each one. It also contains the hash table | |
108 | functions for the data structures used for collecting the class | |
109 | hierarchy data and building/maintaining the vtable map variable data | |
110 | are defined in gcc/vtable-verify.h. These data structures are | |
111 | shared with the code in the C++ front end that collects the class | |
112 | hierarchy & vtable information and generates the vtable map | |
113 | variables (see cp/vtable-class-hierarchy.c). This tree pass should | |
114 | run just before the gimple is converted to RTL. | |
115 | ||
116 | Some implementation details for this pass: | |
117 | ||
118 | To find all of the virtual calls, we iterate through all the | |
119 | gimple statements in each basic block, looking for any call | |
120 | statement with the code "OBJ_TYPE_REF". Once we have found the | |
121 | virtual call, we need to find the vtable pointer through which the | |
122 | call is being made, and the type of the object containing the | |
123 | pointer (to find the appropriate vtable map variable). We then use | |
124 | these to build a call to __VLTVerifyVtablePointer, passing the | |
125 | vtable map variable, and the vtable pointer. We insert the | |
126 | verification call just after the gimple statement that gets the | |
127 | vtable pointer out of the object, and we update the next | |
128 | statement to depend on the result returned from | |
129 | __VLTVerifyVtablePointer (the vtable pointer value), to ensure | |
130 | subsequent compiler phases don't remove or reorder the call (it's no | |
131 | good to have the verification occur after the virtual call, for | |
132 | example). To find the vtable pointer being used (and the type of | |
133 | the object) we search backwards through the def_stmts chain from the | |
134 | virtual call (see verify_bb_vtables for more details). */ | |
135 | ||
136 | #include "config.h" | |
137 | #include "system.h" | |
138 | #include "coretypes.h" | |
139 | #include "tree.h" | |
140 | #include "basic-block.h" | |
7a300452 | 141 | #include "tree-ssa.h" |
2077db1b CT |
142 | #include "tree-pass.h" |
143 | #include "cfgloop.h" | |
144 | ||
145 | #include "vtable-verify.h" | |
146 | ||
147 | unsigned num_vtable_map_nodes = 0; | |
148 | int total_num_virtual_calls = 0; | |
149 | int total_num_verified_vcalls = 0; | |
150 | ||
151 | extern GTY(()) tree verify_vtbl_ptr_fndecl; | |
152 | tree verify_vtbl_ptr_fndecl = NULL_TREE; | |
153 | ||
154 | /* Keep track of whether or not any virtual call were verified. */ | |
155 | static bool any_verification_calls_generated = false; | |
156 | ||
157 | unsigned int vtable_verify_main (void); | |
158 | ||
159 | ||
160 | /* The following few functions are for the vtbl pointer hash table | |
161 | in the 'registered' field of the struct vtable_map_node. The hash | |
162 | table keeps track of which vtable pointers have been used in | |
163 | calls to __VLTRegisterPair with that particular vtable map variable. */ | |
164 | ||
165 | /* This function checks to see if a particular VTABLE_DECL and OFFSET are | |
166 | already in the 'registered' hash table for NODE. */ | |
167 | ||
168 | bool | |
169 | vtbl_map_node_registration_find (struct vtbl_map_node *node, | |
170 | tree vtable_decl, | |
171 | unsigned offset) | |
172 | { | |
173 | struct vtable_registration key; | |
174 | struct vtable_registration **slot; | |
175 | ||
176 | gcc_assert (node && node->registered.is_created()); | |
177 | ||
178 | key.vtable_decl = vtable_decl; | |
179 | slot = (struct vtable_registration **) node->registered.find_slot (&key, | |
180 | NO_INSERT); | |
181 | ||
182 | if (slot && (*slot)) | |
183 | { | |
184 | unsigned i; | |
185 | for (i = 0; i < ((*slot)->offsets).length(); ++i) | |
186 | if ((*slot)->offsets[i] == offset) | |
187 | return true; | |
188 | } | |
189 | ||
190 | return false; | |
191 | } | |
192 | ||
193 | /* This function inserts VTABLE_DECL and OFFSET into the 'registered' | |
194 | hash table for NODE. It returns a boolean indicating whether or not | |
195 | it actually inserted anything. */ | |
196 | ||
197 | bool | |
198 | vtbl_map_node_registration_insert (struct vtbl_map_node *node, | |
199 | tree vtable_decl, | |
200 | unsigned offset) | |
201 | { | |
202 | struct vtable_registration key; | |
203 | struct vtable_registration **slot; | |
204 | bool inserted_something = false; | |
205 | ||
206 | if (!node || !node->registered.is_created()) | |
207 | return false; | |
208 | ||
209 | key.vtable_decl = vtable_decl; | |
210 | slot = (struct vtable_registration **) node->registered.find_slot (&key, | |
211 | INSERT); | |
212 | ||
213 | if (! *slot) | |
214 | { | |
215 | struct vtable_registration *node; | |
216 | node = XNEW (struct vtable_registration); | |
217 | node->vtable_decl = vtable_decl; | |
218 | ||
219 | (node->offsets).create (10); | |
220 | (node->offsets).safe_push (offset); | |
221 | *slot = node; | |
222 | inserted_something = true; | |
223 | } | |
224 | else | |
225 | { | |
226 | /* We found the vtable_decl slot; we need to see if it already | |
227 | contains the offset. If not, we need to add the offset. */ | |
228 | unsigned i; | |
229 | bool found = false; | |
230 | for (i = 0; i < ((*slot)->offsets).length() && !found; ++i) | |
231 | if ((*slot)->offsets[i] == offset) | |
232 | found = true; | |
233 | ||
234 | if (!found) | |
235 | { | |
236 | ((*slot)->offsets).safe_push (offset); | |
237 | inserted_something = true; | |
238 | } | |
239 | } | |
240 | return inserted_something; | |
241 | } | |
242 | ||
243 | /* Hashtable functions for vtable_registration hashtables. */ | |
244 | ||
245 | inline hashval_t | |
246 | registration_hasher::hash (const value_type *p) | |
247 | { | |
248 | const struct vtable_registration *n = (const struct vtable_registration *) p; | |
249 | return (hashval_t) (DECL_UID (n->vtable_decl)); | |
250 | } | |
251 | ||
252 | inline bool | |
253 | registration_hasher::equal (const value_type *p1, const compare_type *p2) | |
254 | { | |
255 | const struct vtable_registration *n1 = | |
256 | (const struct vtable_registration *) p1; | |
257 | const struct vtable_registration *n2 = | |
258 | (const struct vtable_registration *) p2; | |
259 | return (DECL_UID (n1->vtable_decl) == DECL_UID (n2->vtable_decl)); | |
260 | } | |
261 | ||
262 | /* End of hashtable functions for "registered" hashtables. */ | |
263 | ||
264 | ||
265 | ||
266 | /* Hashtable definition and functions for vtbl_map_hash. */ | |
267 | ||
268 | struct vtbl_map_hasher : typed_noop_remove <struct vtbl_map_node> | |
269 | { | |
270 | typedef struct vtbl_map_node value_type; | |
271 | typedef struct vtbl_map_node compare_type; | |
272 | static inline hashval_t hash (const value_type *); | |
273 | static inline bool equal (const value_type *, const compare_type *); | |
274 | }; | |
275 | ||
276 | /* Returns a hash code for P. */ | |
277 | ||
278 | inline hashval_t | |
279 | vtbl_map_hasher::hash (const value_type *p) | |
280 | { | |
281 | const struct vtbl_map_node n = *((const struct vtbl_map_node *) p); | |
282 | return (hashval_t) IDENTIFIER_HASH_VALUE (n.class_name); | |
283 | } | |
284 | ||
285 | /* Returns nonzero if P1 and P2 are equal. */ | |
286 | ||
287 | inline bool | |
288 | vtbl_map_hasher::equal (const value_type *p1, const compare_type *p2) | |
289 | { | |
290 | const struct vtbl_map_node n1 = *((const struct vtbl_map_node *) p1); | |
291 | const struct vtbl_map_node n2 = *((const struct vtbl_map_node *) p2); | |
292 | return (IDENTIFIER_HASH_VALUE (n1.class_name) == | |
293 | IDENTIFIER_HASH_VALUE (n2.class_name)); | |
294 | } | |
295 | ||
296 | /* Here are the two structures into which we insert vtable map nodes. | |
297 | We use two data structures because of the vastly different ways we need | |
298 | to find the nodes for various tasks (see comments in vtable-verify.h | |
299 | for more details. */ | |
300 | ||
301 | typedef hash_table <vtbl_map_hasher> vtbl_map_table_type; | |
302 | typedef vtbl_map_table_type::iterator vtbl_map_iterator_type; | |
303 | ||
304 | /* Vtable map variable nodes stored in a hash table. */ | |
305 | static vtbl_map_table_type vtbl_map_hash; | |
306 | ||
307 | /* Vtable map variable nodes stored in a vector. */ | |
308 | vec<struct vtbl_map_node *> vtbl_map_nodes_vec; | |
309 | ||
310 | /* Return vtbl_map node for CLASS_NAME without creating a new one. */ | |
311 | ||
312 | struct vtbl_map_node * | |
313 | vtbl_map_get_node (tree class_type) | |
314 | { | |
315 | struct vtbl_map_node key; | |
316 | struct vtbl_map_node **slot; | |
317 | ||
318 | tree class_type_decl; | |
319 | tree class_name; | |
320 | unsigned int type_quals; | |
321 | ||
322 | if (!vtbl_map_hash.is_created()) | |
323 | return NULL; | |
324 | ||
325 | gcc_assert (TREE_CODE (class_type) == RECORD_TYPE); | |
326 | ||
327 | ||
328 | /* Find the TYPE_DECL for the class. */ | |
329 | class_type_decl = TYPE_NAME (class_type); | |
330 | ||
331 | /* Verify that there aren't any qualifiers on the type. */ | |
332 | type_quals = TYPE_QUALS (TREE_TYPE (class_type_decl)); | |
333 | gcc_assert (type_quals == TYPE_UNQUALIFIED); | |
334 | ||
335 | /* Get the mangled name for the unqualified type. */ | |
336 | gcc_assert (HAS_DECL_ASSEMBLER_NAME_P (class_type_decl)); | |
337 | class_name = DECL_ASSEMBLER_NAME (class_type_decl); | |
338 | ||
339 | key.class_name = class_name; | |
340 | slot = (struct vtbl_map_node **) vtbl_map_hash.find_slot (&key, | |
341 | NO_INSERT); | |
342 | if (!slot) | |
343 | return NULL; | |
344 | return *slot; | |
345 | } | |
346 | ||
347 | /* Return vtbl_map node assigned to BASE_CLASS_TYPE. Create new one | |
348 | when needed. */ | |
349 | ||
350 | struct vtbl_map_node * | |
351 | find_or_create_vtbl_map_node (tree base_class_type) | |
352 | { | |
353 | struct vtbl_map_node key; | |
354 | struct vtbl_map_node *node; | |
355 | struct vtbl_map_node **slot; | |
356 | tree class_type_decl; | |
357 | unsigned int type_quals; | |
358 | ||
359 | if (!vtbl_map_hash.is_created()) | |
360 | vtbl_map_hash.create (10); | |
361 | ||
362 | /* Find the TYPE_DECL for the class. */ | |
363 | class_type_decl = TYPE_NAME (base_class_type); | |
364 | ||
365 | /* Verify that there aren't any type qualifiers on type. */ | |
366 | type_quals = TYPE_QUALS (TREE_TYPE (class_type_decl)); | |
367 | gcc_assert (type_quals == TYPE_UNQUALIFIED); | |
368 | ||
369 | gcc_assert (HAS_DECL_ASSEMBLER_NAME_P (class_type_decl)); | |
370 | key.class_name = DECL_ASSEMBLER_NAME (class_type_decl); | |
371 | slot = (struct vtbl_map_node **) vtbl_map_hash.find_slot (&key, | |
372 | INSERT); | |
373 | ||
374 | if (*slot) | |
375 | return *slot; | |
376 | ||
377 | node = XNEW (struct vtbl_map_node); | |
378 | node->vtbl_map_decl = NULL_TREE; | |
379 | node->class_name = key.class_name; | |
380 | node->uid = num_vtable_map_nodes++; | |
381 | ||
382 | node->class_info = XNEW (struct vtv_graph_node); | |
383 | node->class_info->class_type = base_class_type; | |
384 | node->class_info->class_uid = node->uid; | |
385 | node->class_info->num_processed_children = 0; | |
386 | ||
387 | (node->class_info->parents).create (4); | |
388 | (node->class_info->children).create (4); | |
389 | ||
390 | node->registered.create (16); | |
391 | ||
392 | node->is_used = false; | |
393 | ||
394 | vtbl_map_nodes_vec.safe_push (node); | |
395 | gcc_assert (vtbl_map_nodes_vec[node->uid] == node); | |
396 | ||
397 | *slot = node; | |
398 | return node; | |
399 | } | |
400 | ||
401 | /* End of hashtable functions for vtable_map variables hash table. */ | |
402 | ||
403 | /* Given a gimple STMT, this function checks to see if the statement | |
404 | is an assignment, the rhs of which is getting the vtable pointer | |
405 | value out of an object. (i.e. it's the value we need to verify | |
406 | because its the vtable pointer that will be used for a virtual | |
407 | call). */ | |
408 | ||
409 | static bool | |
410 | is_vtable_assignment_stmt (gimple stmt) | |
411 | { | |
412 | ||
413 | if (gimple_code (stmt) != GIMPLE_ASSIGN) | |
414 | return false; | |
415 | else | |
416 | { | |
417 | tree lhs = gimple_assign_lhs (stmt); | |
418 | tree rhs = gimple_assign_rhs1 (stmt); | |
419 | ||
420 | if (TREE_CODE (lhs) != SSA_NAME) | |
421 | return false; | |
422 | ||
423 | if (TREE_CODE (rhs) != COMPONENT_REF) | |
424 | return false; | |
425 | ||
426 | if (! (TREE_OPERAND (rhs, 1)) | |
427 | || (TREE_CODE (TREE_OPERAND (rhs, 1)) != FIELD_DECL)) | |
428 | return false; | |
429 | ||
430 | if (! DECL_VIRTUAL_P (TREE_OPERAND (rhs, 1))) | |
431 | return false; | |
432 | } | |
433 | ||
434 | return true; | |
435 | } | |
436 | ||
437 | /* This function attempts to recover the declared class of an object | |
438 | that is used in making a virtual call. We try to get the type from | |
439 | the type cast in the gimple assignment statement that extracts the | |
440 | vtable pointer from the object (DEF_STMT). The gimple statement | |
441 | usually looks something like this: | |
442 | ||
443 | D.2201_4 = MEM[(struct Event *)this_1(D)]._vptr.Event */ | |
444 | ||
445 | static tree | |
446 | extract_object_class_type (tree rhs) | |
447 | { | |
448 | tree result = NULL_TREE; | |
449 | ||
450 | /* Try to find and extract the type cast from that stmt. */ | |
451 | if (TREE_CODE (rhs) == COMPONENT_REF) | |
452 | { | |
453 | tree op0 = TREE_OPERAND (rhs, 0); | |
454 | tree op1 = TREE_OPERAND (rhs, 1); | |
455 | ||
456 | if (TREE_CODE (op1) == FIELD_DECL | |
457 | && DECL_VIRTUAL_P (op1)) | |
458 | { | |
459 | if (TREE_CODE (op0) == COMPONENT_REF | |
460 | && TREE_CODE (TREE_OPERAND (op0, 0)) == MEM_REF | |
461 | && TREE_CODE (TREE_TYPE (TREE_OPERAND (op0, 0)))== RECORD_TYPE) | |
462 | result = TREE_TYPE (TREE_OPERAND (op0, 0)); | |
463 | else | |
464 | result = TREE_TYPE (op0); | |
465 | } | |
466 | else if (TREE_CODE (op0) == COMPONENT_REF) | |
467 | { | |
468 | result = extract_object_class_type (op0); | |
469 | if (result == NULL_TREE | |
470 | && TREE_CODE (op1) == COMPONENT_REF) | |
471 | result = extract_object_class_type (op1); | |
472 | } | |
473 | } | |
474 | ||
475 | return result; | |
476 | } | |
477 | ||
478 | /* This function traces forward through the def-use chain of an SSA | |
479 | variable to see if it ever gets used in a virtual function call. It | |
480 | returns a boolean indicating whether or not it found a virtual call in | |
481 | the use chain. */ | |
482 | ||
483 | static bool | |
484 | var_is_used_for_virtual_call_p (tree lhs, int *mem_ref_depth) | |
485 | { | |
486 | imm_use_iterator imm_iter; | |
487 | bool found_vcall = false; | |
488 | use_operand_p use_p; | |
489 | ||
490 | if (TREE_CODE (lhs) != SSA_NAME) | |
491 | return false; | |
492 | ||
493 | if (*mem_ref_depth > 2) | |
494 | return false; | |
495 | ||
496 | /* Iterate through the immediate uses of the current variable. If | |
497 | it's a virtual function call, we're done. Otherwise, if there's | |
498 | an LHS for the use stmt, add the ssa var to the work list | |
499 | (assuming it's not already in the list and is not a variable | |
500 | we've already examined. */ | |
501 | ||
502 | FOR_EACH_IMM_USE_FAST (use_p, imm_iter, lhs) | |
503 | { | |
504 | gimple stmt2 = USE_STMT (use_p); | |
505 | ||
506 | if (gimple_code (stmt2) == GIMPLE_CALL) | |
507 | { | |
508 | tree fncall = gimple_call_fn (stmt2); | |
509 | if (TREE_CODE (fncall) == OBJ_TYPE_REF) | |
510 | found_vcall = true; | |
511 | else | |
512 | return false; | |
513 | } | |
514 | else if (gimple_code (stmt2) == GIMPLE_PHI) | |
515 | { | |
516 | found_vcall = var_is_used_for_virtual_call_p | |
517 | (gimple_phi_result (stmt2), | |
518 | mem_ref_depth); | |
519 | } | |
520 | else if (gimple_code (stmt2) == GIMPLE_ASSIGN) | |
521 | { | |
522 | tree rhs = gimple_assign_rhs1 (stmt2); | |
523 | if (TREE_CODE (rhs) == ADDR_EXPR | |
524 | || TREE_CODE (rhs) == MEM_REF) | |
525 | *mem_ref_depth = *mem_ref_depth + 1; | |
526 | ||
527 | if (TREE_CODE (rhs) == COMPONENT_REF) | |
528 | { | |
529 | while (TREE_CODE (TREE_OPERAND (rhs, 0)) == COMPONENT_REF) | |
530 | rhs = TREE_OPERAND (rhs, 0); | |
531 | ||
532 | if (TREE_CODE (TREE_OPERAND (rhs, 0)) == ADDR_EXPR | |
533 | || TREE_CODE (TREE_OPERAND (rhs, 0)) == MEM_REF) | |
534 | *mem_ref_depth = *mem_ref_depth + 1; | |
535 | } | |
536 | ||
537 | if (*mem_ref_depth < 3) | |
538 | found_vcall = var_is_used_for_virtual_call_p | |
539 | (gimple_assign_lhs (stmt2), | |
540 | mem_ref_depth); | |
541 | } | |
542 | ||
543 | else | |
544 | break; | |
545 | ||
546 | if (found_vcall) | |
547 | return true; | |
548 | } | |
549 | ||
550 | return false; | |
551 | } | |
552 | ||
553 | /* Search through all the statements in a basic block (BB), searching | |
554 | for virtual method calls. For each virtual method dispatch, find | |
555 | the vptr value used, and the statically declared type of the | |
556 | object; retrieve the vtable map variable for the type of the | |
557 | object; generate a call to __VLTVerifyVtablePointer; and insert the | |
558 | generated call into the basic block, after the point where the vptr | |
559 | value is gotten out of the object and before the virtual method | |
560 | dispatch. Make the virtual method dispatch depend on the return | |
561 | value from the verification call, so that subsequent optimizations | |
562 | cannot reorder the two calls. */ | |
563 | ||
564 | static void | |
565 | verify_bb_vtables (basic_block bb) | |
566 | { | |
567 | gimple_seq stmts; | |
568 | gimple stmt = NULL; | |
569 | gimple_stmt_iterator gsi_vtbl_assign; | |
570 | gimple_stmt_iterator gsi_virtual_call; | |
571 | ||
572 | stmts = bb_seq (bb); | |
573 | gsi_virtual_call = gsi_start (stmts); | |
574 | for (; !gsi_end_p (gsi_virtual_call); gsi_next (&gsi_virtual_call)) | |
575 | { | |
576 | stmt = gsi_stmt (gsi_virtual_call); | |
577 | ||
578 | /* Count virtual calls. */ | |
579 | if (gimple_code (stmt) == GIMPLE_CALL) | |
580 | { | |
581 | tree fncall = gimple_call_fn (stmt); | |
582 | if (TREE_CODE (fncall) == OBJ_TYPE_REF) | |
583 | total_num_virtual_calls++; | |
584 | } | |
585 | ||
586 | if (is_vtable_assignment_stmt (stmt)) | |
587 | { | |
588 | tree lhs = gimple_assign_lhs (stmt); | |
589 | tree vtbl_var_decl = NULL_TREE; | |
590 | struct vtbl_map_node *vtable_map_node; | |
591 | tree vtbl_decl = NULL_TREE; | |
592 | gimple call_stmt; | |
593 | const char *vtable_name = "<unknown>"; | |
594 | tree tmp0; | |
595 | bool found; | |
596 | int mem_ref_depth = 0; | |
597 | ||
598 | /* Make sure this vptr field access is for a virtual call. */ | |
599 | if (!var_is_used_for_virtual_call_p (lhs, &mem_ref_depth)) | |
600 | continue; | |
601 | ||
602 | /* Now we have found the virtual method dispatch and | |
603 | the preceding access of the _vptr.* field... Next | |
604 | we need to find the statically declared type of | |
605 | the object, so we can find and use the right | |
606 | vtable map variable in the verification call. */ | |
607 | tree class_type = extract_object_class_type | |
608 | (gimple_assign_rhs1 (stmt)); | |
609 | ||
610 | gsi_vtbl_assign = gsi_for_stmt (stmt); | |
611 | ||
612 | if (class_type | |
613 | && (TREE_CODE (class_type) == RECORD_TYPE) | |
614 | && TYPE_BINFO (class_type)) | |
615 | { | |
616 | /* Get the vtable VAR_DECL for the type. */ | |
617 | vtbl_var_decl = BINFO_VTABLE (TYPE_BINFO (class_type)); | |
618 | ||
619 | if (TREE_CODE (vtbl_var_decl) == POINTER_PLUS_EXPR) | |
620 | vtbl_var_decl = TREE_OPERAND (TREE_OPERAND (vtbl_var_decl, 0), | |
621 | 0); | |
622 | ||
623 | gcc_assert (vtbl_var_decl); | |
624 | ||
625 | vtbl_decl = vtbl_var_decl; | |
626 | vtable_map_node = vtbl_map_get_node | |
627 | (TYPE_MAIN_VARIANT (class_type)); | |
628 | ||
629 | gcc_assert (verify_vtbl_ptr_fndecl); | |
630 | ||
631 | /* Given the vtable pointer for the base class of the | |
632 | object, build the call to __VLTVerifyVtablePointer to | |
633 | verify that the object's vtable pointer (contained in | |
634 | lhs) is in the set of valid vtable pointers for the | |
635 | base class. */ | |
636 | ||
637 | if (vtable_map_node && vtable_map_node->vtbl_map_decl) | |
638 | { | |
639 | use_operand_p use_p; | |
640 | ssa_op_iter iter; | |
641 | ||
642 | vtable_map_node->is_used = true; | |
643 | vtbl_var_decl = vtable_map_node->vtbl_map_decl; | |
644 | ||
645 | if (TREE_CODE (vtbl_decl) == VAR_DECL) | |
646 | vtable_name = IDENTIFIER_POINTER (DECL_NAME (vtbl_decl)); | |
647 | ||
648 | /* Call different routines if we are interested in | |
649 | trace information to debug problems. */ | |
650 | if (flag_vtv_debug) | |
651 | { | |
652 | int len1 = IDENTIFIER_LENGTH | |
653 | (DECL_NAME (vtbl_var_decl)); | |
654 | int len2 = strlen (vtable_name); | |
655 | ||
656 | call_stmt = gimple_build_call | |
657 | (verify_vtbl_ptr_fndecl, 4, | |
658 | build1 (ADDR_EXPR, | |
659 | TYPE_POINTER_TO | |
660 | (TREE_TYPE (vtbl_var_decl)), | |
661 | vtbl_var_decl), | |
662 | lhs, | |
663 | build_string_literal | |
664 | (len1 + 1, | |
665 | IDENTIFIER_POINTER | |
666 | (DECL_NAME | |
667 | (vtbl_var_decl))), | |
668 | build_string_literal (len2 + 1, | |
669 | vtable_name)); | |
670 | } | |
671 | else | |
672 | call_stmt = gimple_build_call | |
673 | (verify_vtbl_ptr_fndecl, 2, | |
674 | build1 (ADDR_EXPR, | |
675 | TYPE_POINTER_TO | |
676 | (TREE_TYPE (vtbl_var_decl)), | |
677 | vtbl_var_decl), | |
678 | lhs); | |
679 | ||
680 | ||
681 | /* Create a new SSA_NAME var to hold the call's | |
682 | return value, and make the call_stmt use the | |
683 | variable for that purpose. */ | |
684 | tmp0 = make_temp_ssa_name (TREE_TYPE (lhs), NULL, "VTV"); | |
685 | gimple_call_set_lhs (call_stmt, tmp0); | |
686 | update_stmt (call_stmt); | |
687 | ||
688 | /* Find the next stmt, after the vptr assignment | |
689 | statememt, which should use the result of the | |
690 | vptr assignment statement value. */ | |
691 | gsi_next (&gsi_vtbl_assign); | |
692 | gimple next_stmt = gsi_stmt (gsi_vtbl_assign); | |
693 | ||
694 | if (!next_stmt) | |
695 | return; | |
696 | ||
697 | /* Find any/all uses of 'lhs' in next_stmt, and | |
698 | replace them with 'tmp0'. */ | |
699 | found = false; | |
700 | FOR_EACH_PHI_OR_STMT_USE (use_p, next_stmt, iter, | |
701 | SSA_OP_ALL_USES) | |
702 | { | |
703 | tree op = USE_FROM_PTR (use_p); | |
704 | if (op == lhs) | |
705 | { | |
706 | SET_USE (use_p, tmp0); | |
707 | found = true; | |
708 | } | |
709 | } | |
710 | update_stmt (next_stmt); | |
711 | gcc_assert (found); | |
712 | ||
713 | /* Insert the new verification call just after the | |
714 | statement that gets the vtable pointer out of the | |
715 | object. */ | |
716 | gsi_vtbl_assign = gsi_for_stmt (stmt); | |
717 | gsi_insert_after (&gsi_vtbl_assign, call_stmt, | |
718 | GSI_NEW_STMT); | |
719 | ||
720 | any_verification_calls_generated = true; | |
721 | total_num_verified_vcalls++; | |
722 | } | |
723 | } | |
724 | } | |
725 | } | |
726 | } | |
727 | ||
728 | /* Main function, called from pass->excute(). Loop through all the | |
729 | basic blocks in the current function, passing them to | |
730 | verify_bb_vtables, which searches for virtual calls, and inserts | |
731 | calls to __VLTVerifyVtablePointer. */ | |
732 | ||
733 | unsigned int | |
734 | vtable_verify_main (void) | |
735 | { | |
736 | unsigned int ret = 1; | |
737 | basic_block bb; | |
738 | ||
739 | FOR_ALL_BB (bb) | |
740 | verify_bb_vtables (bb); | |
741 | ||
742 | return ret; | |
743 | } | |
744 | ||
745 | /* Gate function for the pass. */ | |
746 | ||
747 | static bool | |
748 | gate_tree_vtable_verify (void) | |
749 | { | |
750 | return (flag_vtable_verify); | |
751 | } | |
752 | ||
753 | /* Definition of this optimization pass. */ | |
754 | ||
755 | namespace { | |
756 | ||
757 | const pass_data pass_data_vtable_verify = | |
758 | { | |
759 | GIMPLE_PASS, /* type */ | |
760 | "vtable-verify", /* name */ | |
761 | OPTGROUP_NONE, /* optinfo_flags */ | |
762 | true, /* has_gate */ | |
763 | true, /* has_execute */ | |
764 | TV_VTABLE_VERIFICATION, /* tv_id */ | |
765 | ( PROP_cfg | PROP_ssa ), /* properties_required */ | |
766 | 0, /* properties_provided */ | |
767 | 0, /* properties_destroyed */ | |
768 | 0, /* todo_flags_start */ | |
769 | TODO_update_ssa, /* todo_flags_finish */ | |
770 | }; | |
771 | ||
772 | class pass_vtable_verify : public gimple_opt_pass | |
773 | { | |
774 | public: | |
775 | pass_vtable_verify(gcc::context *ctxt) | |
776 | : gimple_opt_pass(pass_data_vtable_verify, ctxt) | |
777 | {} | |
778 | ||
779 | /* opt_pass methods: */ | |
780 | bool gate () { return gate_tree_vtable_verify (); } | |
781 | unsigned int execute () { return vtable_verify_main (); } | |
782 | ||
783 | }; // class pass_vtable_verify | |
784 | ||
785 | } // anon namespace | |
786 | ||
787 | gimple_opt_pass * | |
788 | make_pass_vtable_verify (gcc::context *ctxt) | |
789 | { | |
790 | return new pass_vtable_verify (ctxt); | |
791 | } | |
792 | ||
793 | #include "gt-vtable-verify.h" |