1 /*
2 * Copyright (C) 2008 The Android Open Source Project
3 *
4 * Licensed under the Apache License, Version 2.0 (the "License");
5 * you may not use this file except in compliance with the License.
6 * You may obtain a copy of the License at
7 *
8 * http://www.apache.org/licenses/LICENSE-2.0
9 *
10 * Unless required by applicable law or agreed to in writing, software
11 * distributed under the License is distributed on an "AS IS" BASIS,
12 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
13 * See the License for the specific language governing permissions and
14 * limitations under the License.
15 */
16
17 /*
18 * Verification-time map of data section items
19 */
20
21 #include "DexDataMap.h"
22 #include <stdlib.h>
23
24 /*
25 * Allocate and initialize a DexDataMap. Returns NULL on failure.
26 */
dexDataMapAlloc(u4 maxCount)27 DexDataMap* dexDataMapAlloc(u4 maxCount) {
28 /*
29 * Allocate a single chunk for the DexDataMap itself as well as the
30 * two arrays.
31 */
32 size_t size = 0;
33 DexDataMap* map = NULL;
34
35 const u4 sizeOfItems = (u4) (sizeof(u4) + sizeof(u2));
36 if (__builtin_mul_overflow(maxCount, sizeOfItems, &size) ||
37 __builtin_add_overflow(size, sizeof(DexDataMap), &size)) {
38 return NULL;
39 }
40
41 map = (DexDataMap*) malloc(size);
42
43 if (map == NULL) {
44 return NULL;
45 }
46
47 map->count = 0;
48 map->max = maxCount;
49 map->offsets = (u4*) (map + 1);
50 map->types = (u2*) (map->offsets + maxCount);
51
52 return map;
53 }
54
55 /*
56 * Free a DexDataMap.
57 */
dexDataMapFree(DexDataMap * map)58 void dexDataMapFree(DexDataMap* map) {
59 /*
60 * Since everything got allocated together, everything can be freed
61 * in one fell swoop. Also, free(NULL) is a nop (per spec), so we
62 * don't have to worry about an explicit test for that.
63 */
64 free(map);
65 }
66
67 /*
68 * Add a new element to the map. The offset must be greater than the
69 * all previously added offsets.
70 */
dexDataMapAdd(DexDataMap * map,u4 offset,u2 type)71 void dexDataMapAdd(DexDataMap* map, u4 offset, u2 type) {
72 assert(map != NULL);
73 assert(map->count < map->max);
74
75 if ((map->count != 0) &&
76 (map->offsets[map->count - 1] >= offset)) {
77 ALOGE("Out-of-order data map offset: %#x then %#x",
78 map->offsets[map->count - 1], offset);
79 return;
80 }
81
82 map->offsets[map->count] = offset;
83 map->types[map->count] = type;
84 map->count++;
85 }
86
87 /*
88 * Get the type associated with the given offset. This returns -1 if
89 * there is no entry for the given offset.
90 */
dexDataMapGet(DexDataMap * map,u4 offset)91 int dexDataMapGet(DexDataMap* map, u4 offset) {
92 assert(map != NULL);
93
94 // Note: Signed type is important for max and min.
95 int min = 0;
96 int max = map->count - 1;
97 u4* offsets = map->offsets;
98
99 while (max >= min) {
100 int guessIdx = (min + max) >> 1;
101 u4 guess = offsets[guessIdx];
102
103 if (offset < guess) {
104 max = guessIdx - 1;
105 } else if (offset > guess) {
106 min = guessIdx + 1;
107 } else {
108 // We have a winner!
109 return map->types[guessIdx];
110 }
111 }
112
113 // No match.
114 return -1;
115 }
116
117 /*
118 * Verify that there is an entry in the map, mapping the given offset to
119 * the given type. This will return true if such an entry exists and
120 * return false as well as log an error if not.
121 */
dexDataMapVerify(DexDataMap * map,u4 offset,u2 type)122 bool dexDataMapVerify(DexDataMap* map, u4 offset, u2 type) {
123 int found = dexDataMapGet(map, offset);
124
125 if (found == type) {
126 return true;
127 }
128
129 if (found < 0) {
130 ALOGE("No data map entry found @ %#x; expected %x",
131 offset, type);
132 } else {
133 ALOGE("Unexpected data map entry @ %#x: expected %x, found %x",
134 offset, type, found);
135 }
136
137 return false;
138 }
139