1    :  // Copyright 2012 Google Inc.
   2    :  //
   3    :  // Licensed under the Apache License, Version 2.0 (the "License");
   4    :  // you may not use this file except in compliance with the License.
   5    :  // You may obtain a copy of the License at
   6    :  //
   7    :  //     http://www.apache.org/licenses/LICENSE-2.0
   8    :  //
   9    :  // Unless required by applicable law or agreed to in writing, software
  10    :  // distributed under the License is distributed on an "AS IS" BASIS,
  11    :  // WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
  12    :  // See the License for the specific language governing permissions and
  13    :  // limitations under the License.
  14    :  #include "syzygy/agent/asan/asan_shadow.h"
  15    :  
  16    :  #include "base/logging.h"
  17    :  
  18    :  namespace agent {
  19    :  namespace asan {
  20    :  
  21    :  uint8 Shadow::shadow_[kShadowSize];
  22    :  
  23  E :  void Shadow::Poison(const void* addr, size_t size) {
  24  E :    uintptr_t index = reinterpret_cast<uintptr_t>(addr);
  25  E :    uintptr_t start = index & 0x7;
  26  E :    DCHECK_EQ(0U, (index + size) & 0x7);
  27    :  
  28  E :    index >>= 3;
  29  E :    if (start)
  30  E :      shadow_[index++] = start;
  31    :  
  32  E :    size >>= 3;
  33  E :    DCHECK_GT(arraysize(shadow_), index + size);
  34  E :    memset(shadow_ + index, 0xFF, size);
  35  E :  }
  36    :  
  37  E :  void Shadow::Unpoison(const void* addr, size_t size) {
  38  E :    uintptr_t index = reinterpret_cast<uintptr_t>(addr);
  39  E :    DCHECK_EQ(0U, index & 0x7);
  40    :  
  41  E :    uint8 remainder = size & 0x7;
  42  E :    index >>= 3;
  43  E :    size >>= 3;
  44  E :    DCHECK_GT(arraysize(shadow_), index + size);
  45  E :    memset(shadow_ + index, 0, size);
  46    :  
  47  E :    if (remainder != 0)
  48  E :      shadow_[index + size] = remainder;
  49  E :  }
  50    :  
  51  E :  bool Shadow::IsAccessible(const void* addr) {
  52  E :    uintptr_t index = reinterpret_cast<uintptr_t>(addr);
  53  E :    uintptr_t start = index & 0x7;
  54    :  
  55  E :    index >>= 3;
  56    :  
  57  E :    DCHECK_GT(arraysize(shadow_), index);
  58  E :    uint8 shadow = shadow_[index];
  59  E :    if (shadow == 0)
  60  E :      return true;
  61    :  
  62  E :    if (shadow == 0xFF)
  63  E :      return false;
  64    :  
  65  E :    return start < shadow;
  66  E :  }
  67    :  
  68    :  }  // namespace asan
  69    :  }  // namespace agent