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