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      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 <safe_iop.h>
     23 #include <stdlib.h>
     24 
     25 /*
     26  * Allocate and initialize a DexDataMap. Returns NULL on failure.
     27  */
     28 DexDataMap* dexDataMapAlloc(u4 maxCount) {
     29     /*
     30      * Allocate a single chunk for the DexDataMap per se as well as the
     31      * two arrays.
     32      */
     33     size_t size = 0;
     34     DexDataMap* map = NULL;
     35 
     36     /*
     37      * Avoiding pulling in safe_iop for safe_iopf.
     38      */
     39     const u4 sizeOfItems = (u4) (sizeof(u4) + sizeof(u2));
     40     if (!safe_mul(&size, maxCount, sizeOfItems) ||
     41         !safe_add(&size, size, sizeof(DexDataMap))) {
     42       return NULL;
     43     }
     44 
     45     map = (DexDataMap*) malloc(size);
     46 
     47     if (map == NULL) {
     48         return NULL;
     49     }
     50 
     51     map->count = 0;
     52     map->max = maxCount;
     53     map->offsets = (u4*) (map + 1);
     54     map->types = (u2*) (map->offsets + maxCount);
     55 
     56     return map;
     57 }
     58 
     59 /*
     60  * Free a DexDataMap.
     61  */
     62 void dexDataMapFree(DexDataMap* map) {
     63     /*
     64      * Since everything got allocated together, everything can be freed
     65      * in one fell swoop. Also, free(NULL) is a nop (per spec), so we
     66      * don't have to worry about an explicit test for that.
     67      */
     68     free(map);
     69 }
     70 
     71 /*
     72  * Add a new element to the map. The offset must be greater than the
     73  * all previously added offsets.
     74  */
     75 void dexDataMapAdd(DexDataMap* map, u4 offset, u2 type) {
     76     assert(map != NULL);
     77     assert(map->count < map->max);
     78 
     79     if ((map->count != 0) &&
     80             (map->offsets[map->count - 1] >= offset)) {
     81         ALOGE("Out-of-order data map offset: %#x then %#x",
     82                 map->offsets[map->count - 1], offset);
     83         return;
     84     }
     85 
     86     map->offsets[map->count] = offset;
     87     map->types[map->count] = type;
     88     map->count++;
     89 }
     90 
     91 /*
     92  * Get the type associated with the given offset. This returns -1 if
     93  * there is no entry for the given offset.
     94  */
     95 int dexDataMapGet(DexDataMap* map, u4 offset) {
     96     assert(map != NULL);
     97 
     98     // Note: Signed type is important for max and min.
     99     int min = 0;
    100     int max = map->count - 1;
    101     u4* offsets = map->offsets;
    102 
    103     while (max >= min) {
    104         int guessIdx = (min + max) >> 1;
    105         u4 guess = offsets[guessIdx];
    106 
    107         if (offset < guess) {
    108             max = guessIdx - 1;
    109         } else if (offset > guess) {
    110             min = guessIdx + 1;
    111         } else {
    112             // We have a winner!
    113             return map->types[guessIdx];
    114         }
    115     }
    116 
    117     // No match.
    118     return -1;
    119 }
    120 
    121 /*
    122  * Verify that there is an entry in the map, mapping the given offset to
    123  * the given type. This will return true if such an entry exists and
    124  * return false as well as log an error if not.
    125  */
    126 bool dexDataMapVerify(DexDataMap* map, u4 offset, u2 type) {
    127     int found = dexDataMapGet(map, offset);
    128 
    129     if (found == type) {
    130         return true;
    131     }
    132 
    133     if (found < 0) {
    134         ALOGE("No data map entry found @ %#x; expected %x",
    135                 offset, type);
    136     } else {
    137         ALOGE("Unexpected data map entry @ %#x: expected %x, found %x",
    138                 offset, type, found);
    139     }
    140 
    141     return false;
    142 }
    143