1/* UndefinedBehaviorSanitizer, undefined behavior detector.
2 Copyright (C) 2014-2017 Free Software Foundation, Inc.
3 Contributed by Jakub Jelinek <jakub@redhat.com>
4
5This file is part of GCC.
6
7GCC is free software; you can redistribute it and/or modify it under
8the terms of the GNU General Public License as published by the Free
9Software Foundation; either version 3, or (at your option) any later
10version.
11
12GCC is distributed in the hope that it will be useful, but WITHOUT ANY
13WARRANTY; without even the implied warranty of MERCHANTABILITY or
14FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License
15for more details.
16
17You should have received a copy of the GNU General Public License
18along with GCC; see the file COPYING3. If not see
19<http://www.gnu.org/licenses/>. */
20
21#include "config.h"
22#include "system.h"
23#include "coretypes.h"
24#include "cp-tree.h"
25#include "ubsan.h"
26#include "stringpool.h"
27#include "attribs.h"
28#include "asan.h"
29
30/* Test if we should instrument vptr access. */
31
32static bool
33cp_ubsan_instrument_vptr_p (tree type)
34{
35 if (!flag_rtti || flag_sanitize_undefined_trap_on_error)
36 return false;
37
38 if (!sanitize_flags_p (SANITIZE_VPTR))
39 return false;
40
41 if (current_function_decl == NULL_TREE)
42 return false;
43
44 if (type)
45 {
46 type = TYPE_MAIN_VARIANT (type);
47 if (!CLASS_TYPE_P (type) || !CLASSTYPE_VTABLES (type))
48 return false;
49 }
50
51 return true;
52}
53
54/* Helper function for
55 cp_ubsan_maybe_instrument_{member_{call,access},downcast}.
56 Instrument vptr access. */
57
58static tree
59cp_ubsan_instrument_vptr (location_t loc, tree op, tree type, bool is_addr,
60 enum ubsan_null_ckind ckind)
61{
62 type = TYPE_MAIN_VARIANT (type);
63 const char *mangled = mangle_type_string (type);
64 hashval_t str_hash1 = htab_hash_string (mangled);
65 hashval_t str_hash2 = iterative_hash (mangled, strlen (mangled), 0);
66 tree str_hash = wide_int_to_tree (uint64_type_node,
67 wi::uhwi (((uint64_t) str_hash1 << 32)
68 | str_hash2, 64));
69 if (!is_addr)
70 op = build_fold_addr_expr_loc (loc, op);
71 op = save_expr (op);
72 tree vptr = fold_build3_loc (loc, COMPONENT_REF,
73 TREE_TYPE (TYPE_VFIELD (type)),
74 build_fold_indirect_ref_loc (loc, op),
75 TYPE_VFIELD (type), NULL_TREE);
76 vptr = fold_convert_loc (loc, pointer_sized_int_node, vptr);
77 vptr = fold_convert_loc (loc, uint64_type_node, vptr);
78 if (ckind == UBSAN_DOWNCAST_POINTER)
79 {
80 tree cond = build2_loc (loc, NE_EXPR, boolean_type_node, op,
81 build_zero_cst (TREE_TYPE (op)));
82 /* This is a compiler generated comparison, don't emit
83 e.g. -Wnonnull-compare warning for it. */
84 TREE_NO_WARNING (cond) = 1;
85 vptr = build3_loc (loc, COND_EXPR, uint64_type_node, cond,
86 vptr, build_int_cst (uint64_type_node, 0));
87 }
88 tree ti_decl = get_tinfo_decl (type);
89 mark_used (ti_decl);
90 tree ptype = build_pointer_type (type);
91 tree call
92 = build_call_expr_internal_loc (loc, IFN_UBSAN_VPTR,
93 void_type_node, 5, op, vptr, str_hash,
94 build_address (ti_decl),
95 build_int_cst (ptype, ckind));
96 TREE_SIDE_EFFECTS (call) = 1;
97 return fold_build2 (COMPOUND_EXPR, TREE_TYPE (op), call, op);
98}
99
100/* Helper function for
101 cp_ubsan_maybe_instrument_{member_{call,access},downcast}.
102 Instrument vptr access if it should be instrumented, otherwise return
103 NULL_TREE. */
104
105static tree
106cp_ubsan_maybe_instrument_vptr (location_t loc, tree op, tree type,
107 bool is_addr, enum ubsan_null_ckind ckind)
108{
109 if (!cp_ubsan_instrument_vptr_p (type))
110 return NULL_TREE;
111 return cp_ubsan_instrument_vptr (loc, op, type, is_addr, ckind);
112}
113
114/* Instrument a member call (but not constructor call) if needed. */
115
116void
117cp_ubsan_maybe_instrument_member_call (tree stmt)
118{
119 if (call_expr_nargs (stmt) == 0)
120 return;
121 tree *opp = &CALL_EXPR_ARG (stmt, 0);
122 tree op = *opp;
123 if (op == error_mark_node
124 || !POINTER_TYPE_P (TREE_TYPE (op)))
125 return;
126 while (TREE_CODE (op) == COMPOUND_EXPR)
127 {
128 opp = &TREE_OPERAND (op, 1);
129 op = *opp;
130 }
131 op = cp_ubsan_maybe_instrument_vptr (EXPR_LOCATION (stmt), op,
132 TREE_TYPE (TREE_TYPE (op)),
133 true, UBSAN_MEMBER_CALL);
134 if (op)
135 *opp = op;
136}
137
138/* Data passed to cp_ubsan_check_member_access_r. */
139
140struct cp_ubsan_check_member_access_data
141{
142 hash_set<tree> *pset;
143 bool is_addr;
144};
145
146static tree cp_ubsan_check_member_access_r (tree *, int *, void *);
147
148/* Instrument a member access. */
149
150static bool
151cp_ubsan_maybe_instrument_member_access
152 (tree stmt, cp_ubsan_check_member_access_data *ucmd)
153{
154 if (DECL_ARTIFICIAL (TREE_OPERAND (stmt, 1)))
155 return false;
156
157 tree base = TREE_OPERAND (stmt, 0);
158 if (!cp_ubsan_instrument_vptr_p (TREE_TYPE (base)))
159 return false;
160
161 cp_walk_tree (&base, cp_ubsan_check_member_access_r, ucmd, ucmd->pset);
162
163 base = cp_ubsan_instrument_vptr (EXPR_LOCATION (stmt), base,
164 TREE_TYPE (base), false,
165 UBSAN_MEMBER_ACCESS);
166 TREE_OPERAND (stmt, 0)
167 = build_fold_indirect_ref_loc (EXPR_LOCATION (stmt), base);
168 return true;
169}
170
171/* Attempt to instrument member accesses inside of the function.
172 cp_ubsan_maybe_instrument_member_access should be called on COMPONENT_REFs
173 in the GENERIC IL, but only when the field is actually accessed, not
174 merely when it's address is taken. Therefore we track in is_addr field
175 whether in the current context we are processing address taken
176 handled components or not. E.g. for &x->y[w->z] we want to call
177 cp_ubsan_maybe_instrument_member_access on *w.z COMPONENT_REF, but
178 not on *x.y. */
179
180static tree
181cp_ubsan_check_member_access_r (tree *stmt_p, int *walk_subtrees, void *data)
182{
183 tree stmt = *stmt_p, t;
184 cp_ubsan_check_member_access_data *ucmd
185 = (cp_ubsan_check_member_access_data *) data;
186 switch (TREE_CODE (stmt))
187 {
188 case ADDR_EXPR:
189 t = TREE_OPERAND (stmt, 0);
190 while ((TREE_CODE (t) == MEM_REF || INDIRECT_REF_P (t))
191 && TREE_CODE (TREE_OPERAND (t, 0)) == ADDR_EXPR)
192 t = TREE_OPERAND (TREE_OPERAND (t, 0), 0);
193 if (handled_component_p (t))
194 {
195 *walk_subtrees = 0;
196 ucmd->is_addr = true;
197 cp_walk_tree (&t, cp_ubsan_check_member_access_r,
198 data, ucmd->pset);
199 ucmd->is_addr = false;
200 }
201 break;
202 case MEM_REF:
203 case INDIRECT_REF:
204 t = TREE_OPERAND (stmt, 0);
205 if (TREE_CODE (t) == ADDR_EXPR)
206 {
207 *walk_subtrees = 0;
208 t = TREE_OPERAND (t, 0);
209 cp_walk_tree (&t, cp_ubsan_check_member_access_r, data, ucmd->pset);
210 }
211 break;
212 case COMPONENT_REF:
213 if (!ucmd->is_addr && cp_ubsan_maybe_instrument_member_access (stmt, ucmd))
214 {
215 *walk_subtrees = 0;
216 break;
217 }
218 /* FALLTHRU */
219 default:
220 if (ucmd->is_addr && handled_component_p (stmt))
221 {
222 int i, len = TREE_OPERAND_LENGTH (stmt);
223 *walk_subtrees = 0;
224 if (!handled_component_p (TREE_OPERAND (stmt, 0)))
225 ucmd->is_addr = false;
226 for (i = 0; i < len; i++)
227 {
228 cp_walk_tree (&TREE_OPERAND (stmt, i),
229 cp_ubsan_check_member_access_r, data, ucmd->pset);
230 ucmd->is_addr = false;
231 }
232 ucmd->is_addr = true;
233 }
234 break;
235 }
236 return NULL_TREE;
237}
238
239/* Instrument all member accesses inside GENERIC *T_P. */
240
241void
242cp_ubsan_instrument_member_accesses (tree *t_p)
243{
244 if (cp_ubsan_instrument_vptr_p (NULL_TREE))
245 {
246 hash_set<tree> pset;
247 cp_ubsan_check_member_access_data ucmd;
248 ucmd.pset = &pset;
249 ucmd.is_addr = false;
250 cp_walk_tree (t_p, cp_ubsan_check_member_access_r, &ucmd, &pset);
251 }
252}
253
254/* Instrument downcast. */
255
256tree
257cp_ubsan_maybe_instrument_downcast (location_t loc, tree type,
258 tree intype, tree op)
259{
260 if (!POINTER_TYPE_P (type)
261 || !POINTER_TYPE_P (intype)
262 || !POINTER_TYPE_P (TREE_TYPE (op))
263 || !CLASS_TYPE_P (TREE_TYPE (TREE_TYPE (op)))
264 || !is_properly_derived_from (TREE_TYPE (type), TREE_TYPE (intype)))
265 return NULL_TREE;
266
267 return cp_ubsan_maybe_instrument_vptr (loc, op, TREE_TYPE (type), true,
268 TREE_CODE (type) == POINTER_TYPE
269 ? UBSAN_DOWNCAST_POINTER
270 : UBSAN_DOWNCAST_REFERENCE);
271}
272
273/* Instrument cast to virtual base. */
274
275tree
276cp_ubsan_maybe_instrument_cast_to_vbase (location_t loc, tree type, tree op)
277{
278 return cp_ubsan_maybe_instrument_vptr (loc, op, type, true,
279 UBSAN_CAST_TO_VBASE);
280}
281
282/* Called from initialize_vtbl_ptrs via dfs_walk. BINFO is the base
283 which we want to initialize the vtable pointer for, DATA is
284 TREE_LIST whose TREE_VALUE is the this ptr expression. */
285
286static tree
287cp_ubsan_dfs_initialize_vtbl_ptrs (tree binfo, void *data)
288{
289 if (!TYPE_CONTAINS_VPTR_P (BINFO_TYPE (binfo)))
290 return dfs_skip_bases;
291
292 if (!BINFO_PRIMARY_P (binfo))
293 {
294 tree base_ptr = TREE_VALUE ((tree) data);
295
296 base_ptr = build_base_path (PLUS_EXPR, base_ptr, binfo, /*nonnull=*/1,
297 tf_warning_or_error);
298
299 /* Compute the location of the vtpr. */
300 tree vtbl_ptr
301 = build_vfield_ref (cp_build_fold_indirect_ref (base_ptr),
302 TREE_TYPE (binfo));
303 gcc_assert (vtbl_ptr != error_mark_node);
304
305 /* Assign NULL to the vptr. */
306 tree vtbl = build_zero_cst (TREE_TYPE (vtbl_ptr));
307 tree stmt = cp_build_modify_expr (input_location, vtbl_ptr, NOP_EXPR,
308 vtbl, tf_warning_or_error);
309 if (vptr_via_virtual_p (binfo))
310 /* If this vptr comes from a virtual base of the complete object, only
311 clear it if we're in charge of virtual bases. */
312 stmt = build_if_in_charge (stmt);
313 finish_expr_stmt (stmt);
314 }
315
316 return NULL_TREE;
317}
318
319/* Initialize all the vtable pointers in the object pointed to by
320 ADDR to NULL, so that we catch invalid calls to methods before
321 mem-initializers are completed. */
322
323void
324cp_ubsan_maybe_initialize_vtbl_ptrs (tree addr)
325{
326 if (!cp_ubsan_instrument_vptr_p (NULL_TREE))
327 return;
328
329 tree type = TREE_TYPE (TREE_TYPE (addr));
330 tree list = build_tree_list (type, addr);
331 /* We cannot rely on the vtable being set up. We have to indirect via the
332 vtt_parm. */
333 int save_in_base_initializer = in_base_initializer;
334 in_base_initializer = 1;
335
336 /* Walk through the hierarchy, initializing the vptr in each base
337 class to NULL. */
338 dfs_walk_once (TYPE_BINFO (type), cp_ubsan_dfs_initialize_vtbl_ptrs,
339 NULL, list);
340
341 in_base_initializer = save_in_base_initializer;
342}
343