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d353bf18 | 1 | /* Copyright (C) 2013-2015 Free Software Foundation, Inc. |
b710ec85 | 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" | |
9ef16211 | 138 | #include "backend.h" |
7c29e30e | 139 | #include "hard-reg-set.h" |
b20a8bb4 | 140 | #include "tree.h" |
9ef16211 | 141 | #include "gimple.h" |
7c29e30e | 142 | #include "tree-pass.h" |
9ef16211 | 143 | #include "ssa.h" |
7c29e30e | 144 | #include "alias.h" |
9ef16211 | 145 | #include "fold-const.h" |
bc61cadb | 146 | #include "internal-fn.h" |
dcf1a1ec | 147 | #include "gimple-iterator.h" |
b710ec85 | 148 | #include "cfgloop.h" |
149 | ||
150 | #include "vtable-verify.h" | |
151 | ||
152 | unsigned num_vtable_map_nodes = 0; | |
153 | int total_num_virtual_calls = 0; | |
154 | int total_num_verified_vcalls = 0; | |
155 | ||
156 | extern GTY(()) tree verify_vtbl_ptr_fndecl; | |
157 | tree verify_vtbl_ptr_fndecl = NULL_TREE; | |
158 | ||
159 | /* Keep track of whether or not any virtual call were verified. */ | |
160 | static bool any_verification_calls_generated = false; | |
161 | ||
162 | unsigned int vtable_verify_main (void); | |
163 | ||
164 | ||
165 | /* The following few functions are for the vtbl pointer hash table | |
166 | in the 'registered' field of the struct vtable_map_node. The hash | |
167 | table keeps track of which vtable pointers have been used in | |
168 | calls to __VLTRegisterPair with that particular vtable map variable. */ | |
169 | ||
170 | /* This function checks to see if a particular VTABLE_DECL and OFFSET are | |
171 | already in the 'registered' hash table for NODE. */ | |
172 | ||
173 | bool | |
174 | vtbl_map_node_registration_find (struct vtbl_map_node *node, | |
175 | tree vtable_decl, | |
176 | unsigned offset) | |
177 | { | |
178 | struct vtable_registration key; | |
179 | struct vtable_registration **slot; | |
180 | ||
c1f445d2 | 181 | gcc_assert (node && node->registered); |
b710ec85 | 182 | |
183 | key.vtable_decl = vtable_decl; | |
c1f445d2 | 184 | slot = node->registered->find_slot (&key, NO_INSERT); |
b710ec85 | 185 | |
186 | if (slot && (*slot)) | |
187 | { | |
188 | unsigned i; | |
9af5ce0c | 189 | for (i = 0; i < ((*slot)->offsets).length (); ++i) |
b710ec85 | 190 | if ((*slot)->offsets[i] == offset) |
191 | return true; | |
192 | } | |
193 | ||
194 | return false; | |
195 | } | |
196 | ||
197 | /* This function inserts VTABLE_DECL and OFFSET into the 'registered' | |
198 | hash table for NODE. It returns a boolean indicating whether or not | |
199 | it actually inserted anything. */ | |
200 | ||
201 | bool | |
202 | vtbl_map_node_registration_insert (struct vtbl_map_node *node, | |
203 | tree vtable_decl, | |
204 | unsigned offset) | |
205 | { | |
206 | struct vtable_registration key; | |
207 | struct vtable_registration **slot; | |
208 | bool inserted_something = false; | |
209 | ||
c1f445d2 | 210 | if (!node || !node->registered) |
b710ec85 | 211 | return false; |
212 | ||
213 | key.vtable_decl = vtable_decl; | |
c1f445d2 | 214 | slot = node->registered->find_slot (&key, INSERT); |
b710ec85 | 215 | |
216 | if (! *slot) | |
217 | { | |
218 | struct vtable_registration *node; | |
219 | node = XNEW (struct vtable_registration); | |
220 | node->vtable_decl = vtable_decl; | |
221 | ||
222 | (node->offsets).create (10); | |
223 | (node->offsets).safe_push (offset); | |
224 | *slot = node; | |
225 | inserted_something = true; | |
226 | } | |
227 | else | |
228 | { | |
229 | /* We found the vtable_decl slot; we need to see if it already | |
230 | contains the offset. If not, we need to add the offset. */ | |
231 | unsigned i; | |
232 | bool found = false; | |
9af5ce0c | 233 | for (i = 0; i < ((*slot)->offsets).length () && !found; ++i) |
b710ec85 | 234 | if ((*slot)->offsets[i] == offset) |
235 | found = true; | |
236 | ||
237 | if (!found) | |
238 | { | |
239 | ((*slot)->offsets).safe_push (offset); | |
240 | inserted_something = true; | |
241 | } | |
242 | } | |
243 | return inserted_something; | |
244 | } | |
245 | ||
246 | /* Hashtable functions for vtable_registration hashtables. */ | |
247 | ||
248 | inline hashval_t | |
9969c043 | 249 | registration_hasher::hash (const vtable_registration *p) |
b710ec85 | 250 | { |
251 | const struct vtable_registration *n = (const struct vtable_registration *) p; | |
252 | return (hashval_t) (DECL_UID (n->vtable_decl)); | |
253 | } | |
254 | ||
255 | inline bool | |
9969c043 | 256 | registration_hasher::equal (const vtable_registration *p1, |
257 | const vtable_registration *p2) | |
b710ec85 | 258 | { |
259 | const struct vtable_registration *n1 = | |
260 | (const struct vtable_registration *) p1; | |
261 | const struct vtable_registration *n2 = | |
262 | (const struct vtable_registration *) p2; | |
263 | return (DECL_UID (n1->vtable_decl) == DECL_UID (n2->vtable_decl)); | |
264 | } | |
265 | ||
266 | /* End of hashtable functions for "registered" hashtables. */ | |
267 | ||
268 | ||
269 | ||
270 | /* Hashtable definition and functions for vtbl_map_hash. */ | |
271 | ||
770ff93b | 272 | struct vtbl_map_hasher : nofree_ptr_hash <struct vtbl_map_node> |
b710ec85 | 273 | { |
9969c043 | 274 | static inline hashval_t hash (const vtbl_map_node *); |
275 | static inline bool equal (const vtbl_map_node *, const vtbl_map_node *); | |
b710ec85 | 276 | }; |
277 | ||
278 | /* Returns a hash code for P. */ | |
279 | ||
280 | inline hashval_t | |
9969c043 | 281 | vtbl_map_hasher::hash (const vtbl_map_node *p) |
b710ec85 | 282 | { |
283 | const struct vtbl_map_node n = *((const struct vtbl_map_node *) p); | |
284 | return (hashval_t) IDENTIFIER_HASH_VALUE (n.class_name); | |
285 | } | |
286 | ||
287 | /* Returns nonzero if P1 and P2 are equal. */ | |
288 | ||
289 | inline bool | |
9969c043 | 290 | vtbl_map_hasher::equal (const vtbl_map_node *p1, const vtbl_map_node *p2) |
b710ec85 | 291 | { |
292 | const struct vtbl_map_node n1 = *((const struct vtbl_map_node *) p1); | |
293 | const struct vtbl_map_node n2 = *((const struct vtbl_map_node *) p2); | |
294 | return (IDENTIFIER_HASH_VALUE (n1.class_name) == | |
295 | IDENTIFIER_HASH_VALUE (n2.class_name)); | |
296 | } | |
297 | ||
298 | /* Here are the two structures into which we insert vtable map nodes. | |
299 | We use two data structures because of the vastly different ways we need | |
300 | to find the nodes for various tasks (see comments in vtable-verify.h | |
301 | for more details. */ | |
302 | ||
c1f445d2 | 303 | typedef hash_table<vtbl_map_hasher> vtbl_map_table_type; |
b710ec85 | 304 | typedef vtbl_map_table_type::iterator vtbl_map_iterator_type; |
305 | ||
306 | /* Vtable map variable nodes stored in a hash table. */ | |
c1f445d2 | 307 | static vtbl_map_table_type *vtbl_map_hash; |
b710ec85 | 308 | |
309 | /* Vtable map variable nodes stored in a vector. */ | |
310 | vec<struct vtbl_map_node *> vtbl_map_nodes_vec; | |
311 | ||
68a98a70 | 312 | /* Vector of mangled names for anonymous classes. */ |
313 | extern GTY(()) vec<tree, va_gc> *vtbl_mangled_name_types; | |
314 | extern GTY(()) vec<tree, va_gc> *vtbl_mangled_name_ids; | |
315 | vec<tree, va_gc> *vtbl_mangled_name_types; | |
316 | vec<tree, va_gc> *vtbl_mangled_name_ids; | |
317 | ||
318 | /* Look up class_type (a type decl for record types) in the vtbl_mangled_names_* | |
319 | vectors. This is a linear lookup. Return the associated mangled name for | |
320 | the class type. This is for handling types from anonymous namespaces, whose | |
321 | DECL_ASSEMBLER_NAME ends up being "<anon>", which is useless for our | |
322 | purposes. | |
323 | ||
324 | We use two vectors of trees to keep track of the mangled names: One is a | |
325 | vector of class types and the other is a vector of the mangled names. The | |
326 | assumption is that these two vectors are kept in perfect lock-step so that | |
327 | vtbl_mangled_name_ids[i] is the mangled name for | |
328 | vtbl_mangled_name_types[i]. */ | |
329 | ||
330 | static tree | |
331 | vtbl_find_mangled_name (tree class_type) | |
332 | { | |
333 | tree result = NULL_TREE; | |
334 | unsigned i; | |
335 | ||
336 | if (!vtbl_mangled_name_types or !vtbl_mangled_name_ids) | |
337 | return result; | |
338 | ||
339 | if (vtbl_mangled_name_types->length() != vtbl_mangled_name_ids->length()) | |
340 | return result; | |
341 | ||
342 | for (i = 0; i < vtbl_mangled_name_types->length(); ++i) | |
343 | if ((*vtbl_mangled_name_types)[i] == class_type) | |
344 | { | |
345 | result = (*vtbl_mangled_name_ids)[i]; | |
346 | break; | |
347 | } | |
348 | ||
349 | return result; | |
350 | } | |
351 | ||
352 | /* Store a class type decl and its mangled name, for an anonymous RECORD_TYPE, | |
353 | in the vtbl_mangled_names vector. Make sure there is not already an | |
354 | entry for the class type before adding it. */ | |
355 | ||
356 | void | |
357 | vtbl_register_mangled_name (tree class_type, tree mangled_name) | |
358 | { | |
359 | if (!vtbl_mangled_name_types) | |
360 | vec_alloc (vtbl_mangled_name_types, 10); | |
361 | ||
362 | if (!vtbl_mangled_name_ids) | |
363 | vec_alloc (vtbl_mangled_name_ids, 10); | |
364 | ||
365 | gcc_assert (vtbl_mangled_name_types->length() == | |
366 | vtbl_mangled_name_ids->length()); | |
367 | ||
368 | ||
369 | if (vtbl_find_mangled_name (class_type) == NULL_TREE) | |
370 | { | |
371 | vec_safe_push (vtbl_mangled_name_types, class_type); | |
372 | vec_safe_push (vtbl_mangled_name_ids, mangled_name); | |
373 | } | |
374 | } | |
375 | ||
b710ec85 | 376 | /* Return vtbl_map node for CLASS_NAME without creating a new one. */ |
377 | ||
378 | struct vtbl_map_node * | |
379 | vtbl_map_get_node (tree class_type) | |
380 | { | |
381 | struct vtbl_map_node key; | |
382 | struct vtbl_map_node **slot; | |
383 | ||
384 | tree class_type_decl; | |
385 | tree class_name; | |
386 | unsigned int type_quals; | |
387 | ||
c1f445d2 | 388 | if (!vtbl_map_hash) |
b710ec85 | 389 | return NULL; |
390 | ||
391 | gcc_assert (TREE_CODE (class_type) == RECORD_TYPE); | |
392 | ||
393 | ||
394 | /* Find the TYPE_DECL for the class. */ | |
395 | class_type_decl = TYPE_NAME (class_type); | |
396 | ||
397 | /* Verify that there aren't any qualifiers on the type. */ | |
398 | type_quals = TYPE_QUALS (TREE_TYPE (class_type_decl)); | |
399 | gcc_assert (type_quals == TYPE_UNQUALIFIED); | |
400 | ||
401 | /* Get the mangled name for the unqualified type. */ | |
402 | gcc_assert (HAS_DECL_ASSEMBLER_NAME_P (class_type_decl)); | |
403 | class_name = DECL_ASSEMBLER_NAME (class_type_decl); | |
404 | ||
68a98a70 | 405 | if (strstr (IDENTIFIER_POINTER (class_name), "<anon>") != NULL) |
406 | class_name = vtbl_find_mangled_name (class_type_decl); | |
407 | ||
b710ec85 | 408 | key.class_name = class_name; |
c1f445d2 | 409 | slot = (struct vtbl_map_node **) vtbl_map_hash->find_slot (&key, NO_INSERT); |
b710ec85 | 410 | if (!slot) |
411 | return NULL; | |
412 | return *slot; | |
413 | } | |
414 | ||
415 | /* Return vtbl_map node assigned to BASE_CLASS_TYPE. Create new one | |
416 | when needed. */ | |
417 | ||
418 | struct vtbl_map_node * | |
419 | find_or_create_vtbl_map_node (tree base_class_type) | |
420 | { | |
421 | struct vtbl_map_node key; | |
422 | struct vtbl_map_node *node; | |
423 | struct vtbl_map_node **slot; | |
424 | tree class_type_decl; | |
425 | unsigned int type_quals; | |
426 | ||
c1f445d2 | 427 | if (!vtbl_map_hash) |
428 | vtbl_map_hash = new vtbl_map_table_type (10); | |
b710ec85 | 429 | |
430 | /* Find the TYPE_DECL for the class. */ | |
431 | class_type_decl = TYPE_NAME (base_class_type); | |
432 | ||
433 | /* Verify that there aren't any type qualifiers on type. */ | |
434 | type_quals = TYPE_QUALS (TREE_TYPE (class_type_decl)); | |
435 | gcc_assert (type_quals == TYPE_UNQUALIFIED); | |
436 | ||
437 | gcc_assert (HAS_DECL_ASSEMBLER_NAME_P (class_type_decl)); | |
438 | key.class_name = DECL_ASSEMBLER_NAME (class_type_decl); | |
68a98a70 | 439 | |
440 | if (strstr (IDENTIFIER_POINTER (key.class_name), "<anon>") != NULL) | |
441 | key.class_name = vtbl_find_mangled_name (class_type_decl); | |
442 | ||
c1f445d2 | 443 | slot = (struct vtbl_map_node **) vtbl_map_hash->find_slot (&key, INSERT); |
b710ec85 | 444 | |
445 | if (*slot) | |
446 | return *slot; | |
447 | ||
448 | node = XNEW (struct vtbl_map_node); | |
449 | node->vtbl_map_decl = NULL_TREE; | |
450 | node->class_name = key.class_name; | |
451 | node->uid = num_vtable_map_nodes++; | |
452 | ||
453 | node->class_info = XNEW (struct vtv_graph_node); | |
454 | node->class_info->class_type = base_class_type; | |
455 | node->class_info->class_uid = node->uid; | |
456 | node->class_info->num_processed_children = 0; | |
457 | ||
458 | (node->class_info->parents).create (4); | |
459 | (node->class_info->children).create (4); | |
460 | ||
c1f445d2 | 461 | node->registered = new register_table_type (16); |
b710ec85 | 462 | |
463 | node->is_used = false; | |
464 | ||
465 | vtbl_map_nodes_vec.safe_push (node); | |
466 | gcc_assert (vtbl_map_nodes_vec[node->uid] == node); | |
467 | ||
468 | *slot = node; | |
469 | return node; | |
470 | } | |
471 | ||
472 | /* End of hashtable functions for vtable_map variables hash table. */ | |
473 | ||
474 | /* Given a gimple STMT, this function checks to see if the statement | |
475 | is an assignment, the rhs of which is getting the vtable pointer | |
476 | value out of an object. (i.e. it's the value we need to verify | |
477 | because its the vtable pointer that will be used for a virtual | |
478 | call). */ | |
479 | ||
480 | static bool | |
42acab1c | 481 | is_vtable_assignment_stmt (gimple *stmt) |
b710ec85 | 482 | { |
483 | ||
484 | if (gimple_code (stmt) != GIMPLE_ASSIGN) | |
485 | return false; | |
486 | else | |
487 | { | |
488 | tree lhs = gimple_assign_lhs (stmt); | |
489 | tree rhs = gimple_assign_rhs1 (stmt); | |
490 | ||
491 | if (TREE_CODE (lhs) != SSA_NAME) | |
492 | return false; | |
493 | ||
494 | if (TREE_CODE (rhs) != COMPONENT_REF) | |
495 | return false; | |
496 | ||
497 | if (! (TREE_OPERAND (rhs, 1)) | |
498 | || (TREE_CODE (TREE_OPERAND (rhs, 1)) != FIELD_DECL)) | |
499 | return false; | |
500 | ||
501 | if (! DECL_VIRTUAL_P (TREE_OPERAND (rhs, 1))) | |
502 | return false; | |
503 | } | |
504 | ||
505 | return true; | |
506 | } | |
507 | ||
508 | /* This function attempts to recover the declared class of an object | |
509 | that is used in making a virtual call. We try to get the type from | |
510 | the type cast in the gimple assignment statement that extracts the | |
511 | vtable pointer from the object (DEF_STMT). The gimple statement | |
512 | usually looks something like this: | |
513 | ||
514 | D.2201_4 = MEM[(struct Event *)this_1(D)]._vptr.Event */ | |
515 | ||
516 | static tree | |
517 | extract_object_class_type (tree rhs) | |
518 | { | |
519 | tree result = NULL_TREE; | |
520 | ||
521 | /* Try to find and extract the type cast from that stmt. */ | |
522 | if (TREE_CODE (rhs) == COMPONENT_REF) | |
523 | { | |
524 | tree op0 = TREE_OPERAND (rhs, 0); | |
525 | tree op1 = TREE_OPERAND (rhs, 1); | |
526 | ||
527 | if (TREE_CODE (op1) == FIELD_DECL | |
528 | && DECL_VIRTUAL_P (op1)) | |
529 | { | |
530 | if (TREE_CODE (op0) == COMPONENT_REF | |
531 | && TREE_CODE (TREE_OPERAND (op0, 0)) == MEM_REF | |
532 | && TREE_CODE (TREE_TYPE (TREE_OPERAND (op0, 0)))== RECORD_TYPE) | |
533 | result = TREE_TYPE (TREE_OPERAND (op0, 0)); | |
534 | else | |
535 | result = TREE_TYPE (op0); | |
536 | } | |
537 | else if (TREE_CODE (op0) == COMPONENT_REF) | |
538 | { | |
539 | result = extract_object_class_type (op0); | |
540 | if (result == NULL_TREE | |
541 | && TREE_CODE (op1) == COMPONENT_REF) | |
542 | result = extract_object_class_type (op1); | |
543 | } | |
544 | } | |
545 | ||
546 | return result; | |
547 | } | |
548 | ||
549 | /* This function traces forward through the def-use chain of an SSA | |
550 | variable to see if it ever gets used in a virtual function call. It | |
551 | returns a boolean indicating whether or not it found a virtual call in | |
552 | the use chain. */ | |
553 | ||
554 | static bool | |
68a98a70 | 555 | var_is_used_for_virtual_call_p (tree lhs, int *mem_ref_depth, |
556 | int *recursion_depth) | |
b710ec85 | 557 | { |
558 | imm_use_iterator imm_iter; | |
559 | bool found_vcall = false; | |
560 | use_operand_p use_p; | |
561 | ||
562 | if (TREE_CODE (lhs) != SSA_NAME) | |
563 | return false; | |
564 | ||
565 | if (*mem_ref_depth > 2) | |
566 | return false; | |
567 | ||
68a98a70 | 568 | if (*recursion_depth > 25) |
569 | /* If we've recursed this far the chances are pretty good that | |
570 | we're not going to find what we're looking for, and that we've | |
571 | gone down a recursion black hole. Time to stop. */ | |
572 | return false; | |
573 | ||
574 | *recursion_depth = *recursion_depth + 1; | |
575 | ||
b710ec85 | 576 | /* Iterate through the immediate uses of the current variable. If |
577 | it's a virtual function call, we're done. Otherwise, if there's | |
578 | an LHS for the use stmt, add the ssa var to the work list | |
579 | (assuming it's not already in the list and is not a variable | |
580 | we've already examined. */ | |
581 | ||
582 | FOR_EACH_IMM_USE_FAST (use_p, imm_iter, lhs) | |
583 | { | |
42acab1c | 584 | gimple *stmt2 = USE_STMT (use_p); |
b710ec85 | 585 | |
475a6b35 | 586 | if (is_gimple_call (stmt2)) |
b710ec85 | 587 | { |
588 | tree fncall = gimple_call_fn (stmt2); | |
475a6b35 | 589 | if (fncall && TREE_CODE (fncall) == OBJ_TYPE_REF) |
b710ec85 | 590 | found_vcall = true; |
591 | else | |
592 | return false; | |
593 | } | |
594 | else if (gimple_code (stmt2) == GIMPLE_PHI) | |
595 | { | |
596 | found_vcall = var_is_used_for_virtual_call_p | |
597 | (gimple_phi_result (stmt2), | |
68a98a70 | 598 | mem_ref_depth, |
599 | recursion_depth); | |
b710ec85 | 600 | } |
475a6b35 | 601 | else if (is_gimple_assign (stmt2)) |
b710ec85 | 602 | { |
603 | tree rhs = gimple_assign_rhs1 (stmt2); | |
604 | if (TREE_CODE (rhs) == ADDR_EXPR | |
605 | || TREE_CODE (rhs) == MEM_REF) | |
606 | *mem_ref_depth = *mem_ref_depth + 1; | |
607 | ||
608 | if (TREE_CODE (rhs) == COMPONENT_REF) | |
609 | { | |
610 | while (TREE_CODE (TREE_OPERAND (rhs, 0)) == COMPONENT_REF) | |
611 | rhs = TREE_OPERAND (rhs, 0); | |
612 | ||
613 | if (TREE_CODE (TREE_OPERAND (rhs, 0)) == ADDR_EXPR | |
614 | || TREE_CODE (TREE_OPERAND (rhs, 0)) == MEM_REF) | |
615 | *mem_ref_depth = *mem_ref_depth + 1; | |
616 | } | |
617 | ||
618 | if (*mem_ref_depth < 3) | |
619 | found_vcall = var_is_used_for_virtual_call_p | |
620 | (gimple_assign_lhs (stmt2), | |
68a98a70 | 621 | mem_ref_depth, |
622 | recursion_depth); | |
b710ec85 | 623 | } |
624 | ||
625 | else | |
626 | break; | |
627 | ||
628 | if (found_vcall) | |
629 | return true; | |
630 | } | |
631 | ||
632 | return false; | |
633 | } | |
634 | ||
635 | /* Search through all the statements in a basic block (BB), searching | |
636 | for virtual method calls. For each virtual method dispatch, find | |
637 | the vptr value used, and the statically declared type of the | |
638 | object; retrieve the vtable map variable for the type of the | |
639 | object; generate a call to __VLTVerifyVtablePointer; and insert the | |
640 | generated call into the basic block, after the point where the vptr | |
641 | value is gotten out of the object and before the virtual method | |
642 | dispatch. Make the virtual method dispatch depend on the return | |
643 | value from the verification call, so that subsequent optimizations | |
644 | cannot reorder the two calls. */ | |
645 | ||
646 | static void | |
647 | verify_bb_vtables (basic_block bb) | |
648 | { | |
649 | gimple_seq stmts; | |
42acab1c | 650 | gimple *stmt = NULL; |
b710ec85 | 651 | gimple_stmt_iterator gsi_vtbl_assign; |
652 | gimple_stmt_iterator gsi_virtual_call; | |
653 | ||
654 | stmts = bb_seq (bb); | |
655 | gsi_virtual_call = gsi_start (stmts); | |
656 | for (; !gsi_end_p (gsi_virtual_call); gsi_next (&gsi_virtual_call)) | |
657 | { | |
658 | stmt = gsi_stmt (gsi_virtual_call); | |
659 | ||
660 | /* Count virtual calls. */ | |
0340f4fd | 661 | if (is_gimple_call (stmt)) |
b710ec85 | 662 | { |
663 | tree fncall = gimple_call_fn (stmt); | |
0340f4fd | 664 | if (fncall && TREE_CODE (fncall) == OBJ_TYPE_REF) |
b710ec85 | 665 | total_num_virtual_calls++; |
666 | } | |
667 | ||
668 | if (is_vtable_assignment_stmt (stmt)) | |
669 | { | |
670 | tree lhs = gimple_assign_lhs (stmt); | |
671 | tree vtbl_var_decl = NULL_TREE; | |
672 | struct vtbl_map_node *vtable_map_node; | |
673 | tree vtbl_decl = NULL_TREE; | |
1a91d914 | 674 | gcall *call_stmt; |
b710ec85 | 675 | const char *vtable_name = "<unknown>"; |
676 | tree tmp0; | |
677 | bool found; | |
678 | int mem_ref_depth = 0; | |
68a98a70 | 679 | int recursion_depth = 0; |
b710ec85 | 680 | |
681 | /* Make sure this vptr field access is for a virtual call. */ | |
68a98a70 | 682 | if (!var_is_used_for_virtual_call_p (lhs, &mem_ref_depth, |
683 | &recursion_depth)) | |
b710ec85 | 684 | continue; |
685 | ||
686 | /* Now we have found the virtual method dispatch and | |
687 | the preceding access of the _vptr.* field... Next | |
688 | we need to find the statically declared type of | |
689 | the object, so we can find and use the right | |
690 | vtable map variable in the verification call. */ | |
691 | tree class_type = extract_object_class_type | |
692 | (gimple_assign_rhs1 (stmt)); | |
693 | ||
694 | gsi_vtbl_assign = gsi_for_stmt (stmt); | |
695 | ||
696 | if (class_type | |
697 | && (TREE_CODE (class_type) == RECORD_TYPE) | |
698 | && TYPE_BINFO (class_type)) | |
699 | { | |
700 | /* Get the vtable VAR_DECL for the type. */ | |
701 | vtbl_var_decl = BINFO_VTABLE (TYPE_BINFO (class_type)); | |
702 | ||
703 | if (TREE_CODE (vtbl_var_decl) == POINTER_PLUS_EXPR) | |
704 | vtbl_var_decl = TREE_OPERAND (TREE_OPERAND (vtbl_var_decl, 0), | |
705 | 0); | |
706 | ||
707 | gcc_assert (vtbl_var_decl); | |
708 | ||
709 | vtbl_decl = vtbl_var_decl; | |
710 | vtable_map_node = vtbl_map_get_node | |
711 | (TYPE_MAIN_VARIANT (class_type)); | |
712 | ||
713 | gcc_assert (verify_vtbl_ptr_fndecl); | |
714 | ||
715 | /* Given the vtable pointer for the base class of the | |
716 | object, build the call to __VLTVerifyVtablePointer to | |
717 | verify that the object's vtable pointer (contained in | |
718 | lhs) is in the set of valid vtable pointers for the | |
719 | base class. */ | |
720 | ||
721 | if (vtable_map_node && vtable_map_node->vtbl_map_decl) | |
722 | { | |
b710ec85 | 723 | vtable_map_node->is_used = true; |
724 | vtbl_var_decl = vtable_map_node->vtbl_map_decl; | |
725 | ||
726 | if (TREE_CODE (vtbl_decl) == VAR_DECL) | |
727 | vtable_name = IDENTIFIER_POINTER (DECL_NAME (vtbl_decl)); | |
728 | ||
729 | /* Call different routines if we are interested in | |
730 | trace information to debug problems. */ | |
731 | if (flag_vtv_debug) | |
732 | { | |
733 | int len1 = IDENTIFIER_LENGTH | |
734 | (DECL_NAME (vtbl_var_decl)); | |
735 | int len2 = strlen (vtable_name); | |
736 | ||
737 | call_stmt = gimple_build_call | |
738 | (verify_vtbl_ptr_fndecl, 4, | |
739 | build1 (ADDR_EXPR, | |
740 | TYPE_POINTER_TO | |
741 | (TREE_TYPE (vtbl_var_decl)), | |
742 | vtbl_var_decl), | |
743 | lhs, | |
744 | build_string_literal | |
745 | (len1 + 1, | |
746 | IDENTIFIER_POINTER | |
747 | (DECL_NAME | |
748 | (vtbl_var_decl))), | |
749 | build_string_literal (len2 + 1, | |
750 | vtable_name)); | |
751 | } | |
752 | else | |
753 | call_stmt = gimple_build_call | |
754 | (verify_vtbl_ptr_fndecl, 2, | |
755 | build1 (ADDR_EXPR, | |
756 | TYPE_POINTER_TO | |
757 | (TREE_TYPE (vtbl_var_decl)), | |
758 | vtbl_var_decl), | |
759 | lhs); | |
760 | ||
761 | ||
762 | /* Create a new SSA_NAME var to hold the call's | |
763 | return value, and make the call_stmt use the | |
764 | variable for that purpose. */ | |
765 | tmp0 = make_temp_ssa_name (TREE_TYPE (lhs), NULL, "VTV"); | |
766 | gimple_call_set_lhs (call_stmt, tmp0); | |
767 | update_stmt (call_stmt); | |
768 | ||
754f4889 | 769 | /* Replace all uses of lhs with tmp0. */ |
b710ec85 | 770 | found = false; |
754f4889 | 771 | imm_use_iterator iterator; |
42acab1c | 772 | gimple *use_stmt; |
754f4889 | 773 | FOR_EACH_IMM_USE_STMT (use_stmt, iterator, lhs) |
b710ec85 | 774 | { |
754f4889 | 775 | use_operand_p use_p; |
776 | if (use_stmt == call_stmt) | |
777 | continue; | |
778 | FOR_EACH_IMM_USE_ON_STMT (use_p, iterator) | |
779 | SET_USE (use_p, tmp0); | |
780 | update_stmt (use_stmt); | |
781 | found = true; | |
b710ec85 | 782 | } |
754f4889 | 783 | |
b710ec85 | 784 | gcc_assert (found); |
785 | ||
786 | /* Insert the new verification call just after the | |
787 | statement that gets the vtable pointer out of the | |
788 | object. */ | |
754f4889 | 789 | gcc_assert (gsi_stmt (gsi_vtbl_assign) == stmt); |
b710ec85 | 790 | gsi_insert_after (&gsi_vtbl_assign, call_stmt, |
791 | GSI_NEW_STMT); | |
792 | ||
793 | any_verification_calls_generated = true; | |
794 | total_num_verified_vcalls++; | |
795 | } | |
796 | } | |
797 | } | |
798 | } | |
799 | } | |
800 | ||
b710ec85 | 801 | /* Definition of this optimization pass. */ |
802 | ||
7620bc82 | 803 | namespace { |
804 | ||
805 | const pass_data pass_data_vtable_verify = | |
b710ec85 | 806 | { |
807 | GIMPLE_PASS, /* type */ | |
808 | "vtable-verify", /* name */ | |
809 | OPTGROUP_NONE, /* optinfo_flags */ | |
b710ec85 | 810 | TV_VTABLE_VERIFICATION, /* tv_id */ |
811 | ( PROP_cfg | PROP_ssa ), /* properties_required */ | |
812 | 0, /* properties_provided */ | |
813 | 0, /* properties_destroyed */ | |
814 | 0, /* todo_flags_start */ | |
815 | TODO_update_ssa, /* todo_flags_finish */ | |
816 | }; | |
817 | ||
7620bc82 | 818 | class pass_vtable_verify : public gimple_opt_pass |
b710ec85 | 819 | { |
820 | public: | |
9af5ce0c | 821 | pass_vtable_verify (gcc::context *ctxt) |
822 | : gimple_opt_pass (pass_data_vtable_verify, ctxt) | |
b710ec85 | 823 | {} |
824 | ||
825 | /* opt_pass methods: */ | |
31315c24 | 826 | virtual bool gate (function *) { return (flag_vtable_verify); } |
65b0537f | 827 | virtual unsigned int execute (function *); |
b710ec85 | 828 | |
829 | }; // class pass_vtable_verify | |
830 | ||
65b0537f | 831 | /* Loop through all the basic blocks in the current function, passing them to |
832 | verify_bb_vtables, which searches for virtual calls, and inserts | |
833 | calls to __VLTVerifyVtablePointer. */ | |
834 | ||
835 | unsigned int | |
836 | pass_vtable_verify::execute (function *fun) | |
837 | { | |
838 | unsigned int ret = 1; | |
839 | basic_block bb; | |
840 | ||
841 | FOR_ALL_BB_FN (bb, fun) | |
842 | verify_bb_vtables (bb); | |
843 | ||
844 | return ret; | |
845 | } | |
846 | ||
7620bc82 | 847 | } // anon namespace |
848 | ||
b710ec85 | 849 | gimple_opt_pass * |
850 | make_pass_vtable_verify (gcc::context *ctxt) | |
851 | { | |
852 | return new pass_vtable_verify (ctxt); | |
853 | } | |
854 | ||
855 | #include "gt-vtable-verify.h" |