1 /*
2 * Copyright (C) 2015 Oracle.
3 *
4 * This program is free software; you can redistribute it and/or
5 * modify it under the terms of the GNU General Public License
6 * as published by the Free Software Foundation; either version 2
7 * of the License, or (at your option) any later version.
8 *
9 * This program is distributed in the hope that it will be useful,
10 * but WITHOUT ANY WARRANTY; without even the implied warranty of
11 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
12 * GNU General Public License for more details.
13 *
14 * You should have received a copy of the GNU General Public License
15 * along with this program; if not, see http://www.gnu.org/copyleft/gpl.txt
16 */
17
18 #include "smatch.h"
19 #include "smatch_slist.h"
20 #include "smatch_extra.h"
21
22 static bool is_non_null_array(struct expression *expr)
23 {
24 struct symbol *type;
25 struct symbol *sym;
26 struct symbol *tmp;
27 int i;
28
29 type = get_type(expr);
30 if (!type || type->type != SYM_ARRAY)
31 return 0;
32 if (expr->type == EXPR_SYMBOL)
33 return 1;
34 if (implied_not_equal(expr, 0))
35 return 1;
36
37 /* verify that it's not the first member of the struct */
38 if (expr->type != EXPR_DEREF || !expr->member)
39 return 0;
40 sym = expr_to_sym(expr);
41 if (!sym)
42 return 0;
43 type = get_real_base_type(sym);
44 if (!type || type->type != SYM_PTR)
45 return 0;
46 type = get_real_base_type(type);
47 if (type->type != SYM_STRUCT)
48 return 0;
49
50 i = 0;
51 FOR_EACH_PTR(type->symbol_list, tmp) {
52 i++;
53 if (!tmp->ident)
54 continue;
55 if (strcmp(expr->member->name, tmp->ident->name) == 0) {
56 if (i == 1)
57 return 0;
58 return 1;
59 }
60 } END_FOR_EACH_PTR(tmp);
61
62 return 0;
63 }
64
65 static bool matches_anonymous_union(struct symbol *sym, const char *member_name)
66 {
67 struct symbol *type, *tmp;
68
69 if (sym->ident)
70 return false;
71 type = get_real_base_type(sym);
72 if (!type || type->type != SYM_UNION)
73 return false;
74
75 FOR_EACH_PTR(type->symbol_list, tmp) {
76 if (tmp->ident &&
77 strcmp(member_name, tmp->ident->name) == 0) {
78 return true;
79 }
80 } END_FOR_EACH_PTR(tmp);
81
82 return false;
83 }
84
85 int get_member_offset(struct symbol *type, const char *member_name)
86 {
87 struct symbol *tmp;
88 int offset;
89 int bits;
90
91 if (!type || type->type != SYM_STRUCT)
92 return -1;
93
94 bits = 0;
95 offset = 0;
96 FOR_EACH_PTR(type->symbol_list, tmp) {
97 if (bits_to_bytes(bits + type_bits(tmp)) > tmp->ctype.alignment) {
98 offset += bits_to_bytes(bits);
99 bits = 0;
100 }
101 offset = ALIGN(offset, tmp->ctype.alignment);
102 if (tmp->ident &&
103 strcmp(member_name, tmp->ident->name) == 0) {
104 return offset;
105 }
106 if (matches_anonymous_union(tmp, member_name))
107 return offset;
108 if (!(type_bits(tmp) % 8) && type_bits(tmp) / 8 == type_bytes(tmp))
109 offset += type_bytes(tmp);
110 else
111 bits += type_bits(tmp);
112 } END_FOR_EACH_PTR(tmp);
113 return -1;
114 }
115
116 int get_member_offset_from_deref(struct expression *expr)
117 {
118 struct symbol *type;
119 struct ident *member;
120 int offset;
121
122 if (expr->type != EXPR_DEREF) /* hopefully, this doesn't happen */
123 return -1;
124
125 if (expr->member_offset >= 0)
126 return expr->member_offset;
127
128 member = expr->member;
129 if (!member)
130 return -1;
131
132 type = get_type(expr->deref);
133 if (type_is_ptr(type))
134 type = get_real_base_type(type);
135 if (!type || type->type != SYM_STRUCT)
136 return -1;
137
138 offset = get_member_offset(type, member->name);
139 if (offset >= 0)
140 expr->member_offset = offset;
141 return offset;
142 }
143
144 static void add_offset_to_pointer(struct range_list **rl, int offset)
145 {
146 sval_t min, max, remove, sval;
147 struct range_list *orig = *rl;
148
149 /*
150 * Ha ha. Treating zero as a special case means I'm correct at least a
151 * tiny fraction of the time. Which is better than nothing.
152 *
153 */
154 if (offset == 0)
155 return;
156
157 if (is_unknown_ptr(orig))
158 return;
159
160 /*
161 * This function doesn't necessarily work how you might expect...
162 *
163 * Say you have s64min-(-1),1-s64max and you add 8 then I guess what
164 * we want to say is maybe something like 9-s64max. This shows that the
165 * min it could be is 9 which is potentially useful information. But
166 * if we start with (-12),5000000-57777777 and we add 8 then we'd want
167 * the result to be (-4),5000008-57777777 but (-4),5000000-57777777 is
168 * also probably acceptable. If you start with s64min-s64max then the
169 * result should be 8-s64max.
170 *
171 */
172
173 /* We do the math on void pointer type, because this isn't "&v + 16" it
174 * is &v->sixteenth_byte.
175 */
176 orig = cast_rl(&ptr_ctype, orig);
177 min = sval_type_min(&ptr_ctype);
178 min.value = offset;
179 max = sval_type_max(&ptr_ctype);
180
181 if (!orig || is_whole_rl(orig)) {
182 *rl = alloc_rl(min, max);
183 return;
184 }
185
186 /* no wrap around */
187 max.uvalue = rl_max(orig).uvalue;
188 if (max.uvalue > sval_type_max(&ptr_ctype).uvalue - offset) {
189 remove = sval_type_max(&ptr_ctype);
190 remove.uvalue -= offset;
191 orig = remove_range(orig, remove, max);
192 }
193
194 sval.type = &int_ctype;
195 sval.value = offset;
196
197 *rl = rl_binop(orig, '+', alloc_rl(sval, sval));
198 }
199
200 static struct range_list *where_allocated_rl(struct symbol *sym)
201 {
202 if (!sym)
203 return NULL;
204
205 return alloc_rl(valid_ptr_min_sval, valid_ptr_max_sval);
206 }
207
208 int get_address_rl(struct expression *expr, struct range_list **rl)
209 {
210 struct expression *unop;
211
212 expr = strip_expr(expr);
213 if (!expr)
214 return 0;
215
216 if (expr->type == EXPR_STRING) {
217 *rl = alloc_rl(valid_ptr_min_sval, valid_ptr_max_sval);
218 return 1;
219 }
220
221 if (expr->type == EXPR_PREOP && expr->op == '&')
222 expr = strip_expr(expr->unop);
223 else {
224 struct symbol *type;
225
226 type = get_type(expr);
227 if (!type || type->type != SYM_ARRAY)
228 return 0;
229 }
230
231 if (expr->type == EXPR_SYMBOL) {
232 *rl = where_allocated_rl(expr->symbol);
233 return 1;
234 }
235
236 if (is_array(expr)) {
237 struct expression *array;
238 struct expression *offset_expr;
239 struct range_list *array_rl, *offset_rl, *bytes_rl, *res;
240 struct symbol *type;
241 sval_t bytes;
242
243 array = get_array_base(expr);
244 offset_expr = get_array_offset(expr);
245
246 type = get_type(array);
247 type = get_real_base_type(type);
248 bytes.type = ssize_t_ctype;
249 bytes.uvalue = type_bytes(type);
250 bytes_rl = alloc_rl(bytes, bytes);
251
252 get_absolute_rl(array, &array_rl);
253 get_absolute_rl(offset_expr, &offset_rl);
254
255 if (type_bytes(type)) {
256 res = rl_binop(offset_rl, '*', bytes_rl);
257 res = rl_binop(res, '+', array_rl);
258 *rl = res;
259 return true;
260 }
261
262 if (implied_not_equal(array, 0) ||
263 implied_not_equal(offset_expr, 0)) {
264 *rl = alloc_rl(valid_ptr_min_sval, valid_ptr_max_sval);
265 return 1;
266 }
267
268 return 0;
269 }
270
271 if (expr->type == EXPR_DEREF && expr->member) {
272 struct range_list *unop_rl;
273 int offset;
274
275 offset = get_member_offset_from_deref(expr);
276 unop = strip_expr(expr->unop);
277 if (unop->type == EXPR_PREOP && unop->op == '*')
278 unop = strip_expr(unop->unop);
279
280 if (offset >= 0 &&
281 get_implied_rl(unop, &unop_rl) &&
282 !is_whole_rl(unop_rl)) {
283 *rl = unop_rl;
284 add_offset_to_pointer(rl, offset);
285 return 1;
286 }
287
288 if (implied_not_equal(unop, 0) || offset > 0) {
289 *rl = alloc_rl(valid_ptr_min_sval, valid_ptr_max_sval);
290 return 1;
291 }
292
293 return 0;
294 }
295
296 if (is_non_null_array(expr)) {
297 *rl = alloc_rl(array_min_sval, array_max_sval);
298 return 1;
299 }
300
301 return 0;
302 }