Line data Source code
1 : /* UndefinedBehaviorSanitizer, undefined behavior detector.
2 : Copyright (C) 2014-2026 Free Software Foundation, Inc.
3 : Contributed by Jakub Jelinek <jakub@redhat.com>
4 :
5 : This file is part of GCC.
6 :
7 : GCC is free software; you can redistribute it and/or modify it under
8 : the terms of the GNU General Public License as published by the Free
9 : Software Foundation; either version 3, or (at your option) any later
10 : version.
11 :
12 : GCC is distributed in the hope that it will be useful, but WITHOUT ANY
13 : WARRANTY; without even the implied warranty of MERCHANTABILITY or
14 : FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License
15 : for more details.
16 :
17 : You should have received a copy of the GNU General Public License
18 : along 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 :
32 : static bool
33 13805 : cp_ubsan_instrument_vptr_p (tree type)
34 : {
35 13805 : if (!flag_rtti || (flag_sanitize_trap & SANITIZE_VPTR))
36 : return false;
37 :
38 13715 : if (!sanitize_flags_p (SANITIZE_VPTR))
39 : return false;
40 :
41 13715 : if (current_function_decl == NULL_TREE)
42 : return false;
43 :
44 13715 : if (type)
45 : {
46 7647 : type = TYPE_MAIN_VARIANT (type);
47 7647 : 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 :
58 : static tree
59 1537 : cp_ubsan_instrument_vptr (location_t loc, tree op, tree type, bool is_addr,
60 : enum ubsan_null_ckind ckind)
61 : {
62 1537 : type = TYPE_MAIN_VARIANT (type);
63 1537 : const char *mangled = mangle_type_string (type);
64 1537 : hashval_t str_hash1 = htab_hash_string (mangled);
65 1537 : hashval_t str_hash2 = iterative_hash (mangled, strlen (mangled), 0);
66 4611 : tree str_hash = wide_int_to_tree (uint64_type_node,
67 1537 : wi::uhwi (((uint64_t) str_hash1 << 32)
68 1537 : | str_hash2, 64));
69 1537 : if (!is_addr)
70 511 : op = build_fold_addr_expr_loc (loc, op);
71 1537 : op = save_expr (op);
72 3074 : tree vptr = fold_build3_loc (loc, COMPONENT_REF,
73 1537 : TREE_TYPE (TYPE_VFIELD (type)),
74 : build_fold_indirect_ref_loc (loc, op),
75 1537 : TYPE_VFIELD (type), NULL_TREE);
76 1537 : vptr = fold_convert_loc (loc, pointer_sized_int_node, vptr);
77 1537 : vptr = fold_convert_loc (loc, uint64_type_node, vptr);
78 1537 : if (ckind == UBSAN_DOWNCAST_POINTER)
79 : {
80 41 : tree cond = build2_loc (loc, NE_EXPR, boolean_type_node, op,
81 41 : 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 41 : suppress_warning (cond, OPT_Wnonnull_compare);
85 41 : vptr = build3_loc (loc, COND_EXPR, uint64_type_node, cond,
86 : vptr, build_int_cst (uint64_type_node, 0));
87 : }
88 1537 : tree ti_decl = get_tinfo_decl (type);
89 1537 : mark_used (ti_decl);
90 1537 : tree ptype = build_pointer_type (type);
91 1537 : tree call
92 1537 : = build_call_expr_internal_loc (loc, IFN_UBSAN_VPTR,
93 : void_type_node, 5, op, vptr, str_hash,
94 : build_address (ti_decl),
95 1537 : build_int_cst (ptype, ckind));
96 1537 : TREE_SIDE_EFFECTS (call) = 1;
97 1537 : 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 :
105 : static tree
106 4709 : cp_ubsan_maybe_instrument_vptr (location_t loc, tree op, tree type,
107 : bool is_addr, enum ubsan_null_ckind ckind)
108 : {
109 4709 : if (!cp_ubsan_instrument_vptr_p (type))
110 : return NULL_TREE;
111 1026 : 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 :
116 : void
117 4622 : cp_ubsan_maybe_instrument_member_call (tree stmt)
118 : {
119 4622 : if (call_expr_nargs (stmt) == 0)
120 : return;
121 4622 : tree op, *opp;
122 :
123 4622 : tree fn = CALL_EXPR_FN (stmt);
124 4622 : if (fn && TREE_CODE (fn) == OBJ_TYPE_REF)
125 : {
126 : /* Virtual function call: Sanitize the use of the object pointer in the
127 : OBJ_TYPE_REF, since the vtable reference will SEGV otherwise (95221).
128 : OBJ_TYPE_REF_EXPR is ptr->vptr[N] and OBJ_TYPE_REF_OBJECT is ptr. But
129 : we can't be sure of finding OBJ_TYPE_REF_OBJECT in OBJ_TYPE_REF_EXPR
130 : if the latter has been optimized, so we use a COMPOUND_EXPR below. */
131 115 : opp = &OBJ_TYPE_REF_EXPR (fn);
132 115 : op = OBJ_TYPE_REF_OBJECT (fn);
133 : }
134 : else
135 : {
136 : /* Non-virtual call: Sanitize the 'this' argument. */
137 4507 : opp = &CALL_EXPR_ARG (stmt, 0);
138 4507 : if (*opp == error_mark_node
139 4507 : || !INDIRECT_TYPE_P (TREE_TYPE (*opp)))
140 : return;
141 7259 : while (TREE_CODE (*opp) == COMPOUND_EXPR)
142 2752 : opp = &TREE_OPERAND (*opp, 1);
143 : op = *opp;
144 : }
145 4622 : op = cp_ubsan_maybe_instrument_vptr (EXPR_LOCATION (stmt), op,
146 4622 : TREE_TYPE (TREE_TYPE (op)),
147 : true, UBSAN_MEMBER_CALL);
148 4622 : if (!op)
149 : /* No change. */;
150 941 : else if (fn && TREE_CODE (fn) == OBJ_TYPE_REF)
151 115 : *opp = cp_build_compound_expr (op, *opp, tf_none);
152 : else
153 826 : *opp = op;
154 : }
155 :
156 : /* Data passed to cp_ubsan_check_member_access_r. */
157 :
158 : struct cp_ubsan_check_member_access_data
159 : {
160 : hash_set<tree> *pset;
161 : bool is_addr;
162 : };
163 :
164 : static tree cp_ubsan_check_member_access_r (tree *, int *, void *);
165 :
166 : /* Instrument a member access. */
167 :
168 : static bool
169 5865 : cp_ubsan_maybe_instrument_member_access
170 : (tree stmt, cp_ubsan_check_member_access_data *ucmd)
171 : {
172 5865 : if (DECL_ARTIFICIAL (TREE_OPERAND (stmt, 1)))
173 : return false;
174 :
175 2938 : tree base = TREE_OPERAND (stmt, 0);
176 2938 : if (!cp_ubsan_instrument_vptr_p (TREE_TYPE (base)))
177 : return false;
178 :
179 511 : cp_walk_tree (&base, cp_ubsan_check_member_access_r, ucmd, ucmd->pset);
180 :
181 511 : base = cp_ubsan_instrument_vptr (EXPR_LOCATION (stmt), base,
182 511 : TREE_TYPE (base), false,
183 : UBSAN_MEMBER_ACCESS);
184 511 : TREE_OPERAND (stmt, 0)
185 511 : = build_fold_indirect_ref_loc (EXPR_LOCATION (stmt), base);
186 511 : return true;
187 : }
188 :
189 : /* Attempt to instrument member accesses inside of the function.
190 : cp_ubsan_maybe_instrument_member_access should be called on COMPONENT_REFs
191 : in the GENERIC IL, but only when the field is actually accessed, not
192 : merely when it's address is taken. Therefore we track in is_addr field
193 : whether in the current context we are processing address taken
194 : handled components or not. E.g. for &x->y[w->z] we want to call
195 : cp_ubsan_maybe_instrument_member_access on *w.z COMPONENT_REF, but
196 : not on *x.y. */
197 :
198 : static tree
199 206475 : cp_ubsan_check_member_access_r (tree *stmt_p, int *walk_subtrees, void *data)
200 : {
201 206475 : tree stmt = *stmt_p, t;
202 206475 : cp_ubsan_check_member_access_data *ucmd
203 : = (cp_ubsan_check_member_access_data *) data;
204 206475 : switch (TREE_CODE (stmt))
205 : {
206 16872 : case ADDR_EXPR:
207 16872 : t = TREE_OPERAND (stmt, 0);
208 33744 : while ((TREE_CODE (t) == MEM_REF || INDIRECT_REF_P (t))
209 16872 : && TREE_CODE (TREE_OPERAND (t, 0)) == ADDR_EXPR)
210 0 : t = TREE_OPERAND (TREE_OPERAND (t, 0), 0);
211 16872 : if (handled_component_p (t))
212 : {
213 1610 : *walk_subtrees = 0;
214 1610 : ucmd->is_addr = true;
215 1610 : cp_walk_tree (&t, cp_ubsan_check_member_access_r,
216 : data, ucmd->pset);
217 1610 : ucmd->is_addr = false;
218 : }
219 : break;
220 6747 : case MEM_REF:
221 6747 : case INDIRECT_REF:
222 6747 : t = TREE_OPERAND (stmt, 0);
223 6747 : if (TREE_CODE (t) == ADDR_EXPR)
224 : {
225 29 : *walk_subtrees = 0;
226 29 : t = TREE_OPERAND (t, 0);
227 29 : cp_walk_tree (&t, cp_ubsan_check_member_access_r, data, ucmd->pset);
228 : }
229 : break;
230 8095 : case COMPONENT_REF:
231 8095 : if (!ucmd->is_addr && cp_ubsan_maybe_instrument_member_access (stmt, ucmd))
232 : {
233 511 : *walk_subtrees = 0;
234 511 : break;
235 : }
236 : /* FALLTHRU */
237 182345 : default:
238 182345 : if (ucmd->is_addr && handled_component_p (stmt))
239 : {
240 2254 : int i, len = TREE_OPERAND_LENGTH (stmt);
241 2254 : *walk_subtrees = 0;
242 2254 : if (!handled_component_p (TREE_OPERAND (stmt, 0)))
243 1607 : ucmd->is_addr = false;
244 9040 : for (i = 0; i < len; i++)
245 : {
246 6786 : cp_walk_tree (&TREE_OPERAND (stmt, i),
247 : cp_ubsan_check_member_access_r, data, ucmd->pset);
248 6786 : ucmd->is_addr = false;
249 : }
250 2254 : ucmd->is_addr = true;
251 : }
252 : break;
253 : }
254 206475 : return NULL_TREE;
255 : }
256 :
257 : /* Instrument all member accesses inside GENERIC *T_P. */
258 :
259 : void
260 5678 : cp_ubsan_instrument_member_accesses (tree *t_p)
261 : {
262 5678 : if (cp_ubsan_instrument_vptr_p (NULL_TREE))
263 : {
264 5588 : hash_set<tree> pset;
265 5588 : cp_ubsan_check_member_access_data ucmd;
266 5588 : ucmd.pset = &pset;
267 5588 : ucmd.is_addr = false;
268 5588 : cp_walk_tree (t_p, cp_ubsan_check_member_access_r, &ucmd, &pset);
269 5588 : }
270 5678 : }
271 :
272 : /* Instrument downcast. */
273 :
274 : tree
275 530 : cp_ubsan_maybe_instrument_downcast (location_t loc, tree type,
276 : tree intype, tree op)
277 : {
278 530 : if (!INDIRECT_TYPE_P (type)
279 530 : || !INDIRECT_TYPE_P (intype)
280 43 : || !INDIRECT_TYPE_P (TREE_TYPE (op))
281 43 : || !CLASS_TYPE_P (TREE_TYPE (TREE_TYPE (op)))
282 573 : || !is_properly_derived_from (TREE_TYPE (type), TREE_TYPE (intype)))
283 487 : return NULL_TREE;
284 :
285 43 : return cp_ubsan_maybe_instrument_vptr (loc, op, TREE_TYPE (type), true,
286 43 : TYPE_PTR_P (type)
287 : ? UBSAN_DOWNCAST_POINTER
288 43 : : UBSAN_DOWNCAST_REFERENCE);
289 : }
290 :
291 : /* Instrument cast to virtual base. */
292 :
293 : tree
294 44 : cp_ubsan_maybe_instrument_cast_to_vbase (location_t loc, tree type, tree op)
295 : {
296 44 : return cp_ubsan_maybe_instrument_vptr (loc, op, type, true,
297 44 : UBSAN_CAST_TO_VBASE);
298 : }
299 :
300 : /* Called from initialize_vtbl_ptrs via dfs_walk. BINFO is the base
301 : which we want to initialize the vtable pointer for, DATA is
302 : TREE_LIST whose TREE_VALUE is the this ptr expression. */
303 :
304 : static tree
305 686 : cp_ubsan_dfs_initialize_vtbl_ptrs (tree binfo, void *data)
306 : {
307 686 : if (!TYPE_CONTAINS_VPTR_P (BINFO_TYPE (binfo)))
308 : return dfs_skip_bases;
309 :
310 345 : if (!BINFO_PRIMARY_P (binfo))
311 : {
312 167 : tree base_ptr = TREE_VALUE ((tree) data);
313 :
314 167 : base_ptr = build_base_path (PLUS_EXPR, base_ptr, binfo, /*nonnull=*/1,
315 : tf_warning_or_error);
316 :
317 : /* Compute the location of the vtpr. */
318 167 : tree vtbl_ptr
319 167 : = build_vfield_ref (cp_build_fold_indirect_ref (base_ptr),
320 167 : TREE_TYPE (binfo));
321 167 : gcc_assert (vtbl_ptr != error_mark_node);
322 :
323 : /* Assign NULL to the vptr. */
324 167 : tree vtbl = build_zero_cst (TREE_TYPE (vtbl_ptr));
325 167 : tree stmt = cp_build_modify_expr (input_location, vtbl_ptr, NOP_EXPR,
326 : vtbl, tf_warning_or_error);
327 167 : if (vptr_via_virtual_p (binfo))
328 : /* If this vptr comes from a virtual base of the complete object, only
329 : clear it if we're in charge of virtual bases. */
330 12 : stmt = build_if_in_charge (stmt);
331 167 : finish_expr_stmt (stmt);
332 : }
333 :
334 : return NULL_TREE;
335 : }
336 :
337 : /* Initialize all the vtable pointers in the object pointed to by
338 : ADDR to NULL, so that we catch invalid calls to methods before
339 : mem-initializers are completed. */
340 :
341 : void
342 480 : cp_ubsan_maybe_initialize_vtbl_ptrs (tree addr)
343 : {
344 480 : if (!cp_ubsan_instrument_vptr_p (NULL_TREE))
345 : return;
346 :
347 480 : tree type = TREE_TYPE (TREE_TYPE (addr));
348 480 : tree list = build_tree_list (type, addr);
349 : /* We cannot rely on the vtable being set up. We have to indirect via the
350 : vtt_parm. */
351 480 : int save_in_base_initializer = in_base_initializer;
352 480 : in_base_initializer = 1;
353 :
354 : /* Walk through the hierarchy, initializing the vptr in each base
355 : class to NULL. */
356 480 : dfs_walk_once (TYPE_BINFO (type), cp_ubsan_dfs_initialize_vtbl_ptrs,
357 : NULL, list);
358 :
359 480 : in_base_initializer = save_in_base_initializer;
360 : }
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