1 /* 2 * Copyright (C) 2011 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 #ifndef ART_RUNTIME_MEMORY_REGION_H_ 18 #define ART_RUNTIME_MEMORY_REGION_H_ 19 20 #include <stdint.h> 21 #include <type_traits> 22 23 #include "arch/instruction_set.h" 24 #include "base/bit_utils.h" 25 #include "base/casts.h" 26 #include "base/logging.h" 27 #include "base/macros.h" 28 #include "base/value_object.h" 29 #include "globals.h" 30 31 namespace art { 32 33 // Memory regions are useful for accessing memory with bounds check in 34 // debug mode. They can be safely passed by value and do not assume ownership 35 // of the region. 36 class MemoryRegion FINAL : public ValueObject { 37 public: 38 MemoryRegion() : pointer_(nullptr), size_(0) {} 39 MemoryRegion(void* pointer_in, uintptr_t size_in) : pointer_(pointer_in), size_(size_in) {} 40 41 void* pointer() const { return pointer_; } 42 size_t size() const { return size_; } 43 size_t size_in_bits() const { return size_ * kBitsPerByte; } 44 45 static size_t pointer_offset() { 46 return OFFSETOF_MEMBER(MemoryRegion, pointer_); 47 } 48 49 uint8_t* start() const { return reinterpret_cast<uint8_t*>(pointer_); } 50 uint8_t* end() const { return start() + size_; } 51 52 // Load value of type `T` at `offset`. The memory address corresponding 53 // to `offset` should be word-aligned (on ARM, this is a requirement). 54 template<typename T> 55 ALWAYS_INLINE T Load(uintptr_t offset) const { 56 T* address = ComputeInternalPointer<T>(offset); 57 DCHECK(IsWordAligned(address)); 58 return *address; 59 } 60 61 // Store `value` (of type `T`) at `offset`. The memory address 62 // corresponding to `offset` should be word-aligned (on ARM, this is 63 // a requirement). 64 template<typename T> 65 ALWAYS_INLINE void Store(uintptr_t offset, T value) const { 66 T* address = ComputeInternalPointer<T>(offset); 67 DCHECK(IsWordAligned(address)); 68 *address = value; 69 } 70 71 // Load value of type `T` at `offset`. The memory address corresponding 72 // to `offset` does not need to be word-aligned. 73 template<typename T> 74 ALWAYS_INLINE T LoadUnaligned(uintptr_t offset) const { 75 // Equivalent unsigned integer type corresponding to T. 76 typedef typename std::make_unsigned<T>::type U; 77 U equivalent_unsigned_integer_value = 0; 78 // Read the value byte by byte in a little-endian fashion. 79 for (size_t i = 0; i < sizeof(U); ++i) { 80 equivalent_unsigned_integer_value += 81 *ComputeInternalPointer<uint8_t>(offset + i) << (i * kBitsPerByte); 82 } 83 return bit_cast<T, U>(equivalent_unsigned_integer_value); 84 } 85 86 // Store `value` (of type `T`) at `offset`. The memory address 87 // corresponding to `offset` does not need to be word-aligned. 88 template<typename T> 89 ALWAYS_INLINE void StoreUnaligned(uintptr_t offset, T value) const { 90 // Equivalent unsigned integer type corresponding to T. 91 typedef typename std::make_unsigned<T>::type U; 92 U equivalent_unsigned_integer_value = bit_cast<U, T>(value); 93 // Write the value byte by byte in a little-endian fashion. 94 for (size_t i = 0; i < sizeof(U); ++i) { 95 *ComputeInternalPointer<uint8_t>(offset + i) = 96 (equivalent_unsigned_integer_value >> (i * kBitsPerByte)) & 0xFF; 97 } 98 } 99 100 template<typename T> 101 ALWAYS_INLINE T* PointerTo(uintptr_t offset) const { 102 return ComputeInternalPointer<T>(offset); 103 } 104 105 // Load a single bit in the region. The bit at offset 0 is the least 106 // significant bit in the first byte. 107 ALWAYS_INLINE bool LoadBit(uintptr_t bit_offset) const { 108 uint8_t bit_mask; 109 uint8_t byte = *ComputeBitPointer(bit_offset, &bit_mask); 110 return byte & bit_mask; 111 } 112 113 ALWAYS_INLINE void StoreBit(uintptr_t bit_offset, bool value) const { 114 uint8_t bit_mask; 115 uint8_t* byte = ComputeBitPointer(bit_offset, &bit_mask); 116 if (value) { 117 *byte |= bit_mask; 118 } else { 119 *byte &= ~bit_mask; 120 } 121 } 122 123 // Load `length` bits from the region starting at bit offset `bit_offset`. 124 // The bit at the smallest offset is the least significant bit in the 125 // loaded value. `length` must not be larger than the number of bits 126 // contained in the return value (32). 127 uint32_t LoadBits(uintptr_t bit_offset, size_t length) const { 128 CHECK_LE(length, sizeof(uint32_t) * kBitsPerByte); 129 uint32_t value = 0u; 130 for (size_t i = 0; i < length; ++i) { 131 value |= LoadBit(bit_offset + i) << i; 132 } 133 return value; 134 } 135 136 // Store `value` on `length` bits in the region starting at bit offset 137 // `bit_offset`. The bit at the smallest offset is the least significant 138 // bit of the stored `value`. `value` must not be larger than `length` 139 // bits. 140 void StoreBits(uintptr_t bit_offset, uint32_t value, size_t length) { 141 CHECK_LE(value, MaxInt<uint32_t>(length)); 142 for (size_t i = 0; i < length; ++i) { 143 bool ith_bit = value & (1 << i); 144 StoreBit(bit_offset + i, ith_bit); 145 } 146 } 147 148 void CopyFrom(size_t offset, const MemoryRegion& from) const; 149 150 // Compute a sub memory region based on an existing one. 151 MemoryRegion Subregion(uintptr_t offset, uintptr_t size_in) const { 152 CHECK_GE(this->size(), size_in); 153 CHECK_LE(offset, this->size() - size_in); 154 return MemoryRegion(reinterpret_cast<void*>(start() + offset), size_in); 155 } 156 157 // Compute an extended memory region based on an existing one. 158 void Extend(const MemoryRegion& region, uintptr_t extra) { 159 pointer_ = region.pointer(); 160 size_ = (region.size() + extra); 161 } 162 163 private: 164 template<typename T> 165 ALWAYS_INLINE T* ComputeInternalPointer(size_t offset) const { 166 CHECK_GE(size(), sizeof(T)); 167 CHECK_LE(offset, size() - sizeof(T)); 168 return reinterpret_cast<T*>(start() + offset); 169 } 170 171 // Locate the bit with the given offset. Returns a pointer to the byte 172 // containing the bit, and sets bit_mask to the bit within that byte. 173 ALWAYS_INLINE uint8_t* ComputeBitPointer(uintptr_t bit_offset, uint8_t* bit_mask) const { 174 uintptr_t bit_remainder = (bit_offset & (kBitsPerByte - 1)); 175 *bit_mask = (1U << bit_remainder); 176 uintptr_t byte_offset = (bit_offset >> kBitsPerByteLog2); 177 return ComputeInternalPointer<uint8_t>(byte_offset); 178 } 179 180 // Is `address` aligned on a machine word? 181 template<typename T> static bool IsWordAligned(const T* address) { 182 // Word alignment in bytes. 183 size_t kWordAlignment = GetInstructionSetPointerSize(kRuntimeISA); 184 return IsAlignedParam(address, kWordAlignment); 185 } 186 187 void* pointer_; 188 size_t size_; 189 }; 190 191 } // namespace art 192 193 #endif // ART_RUNTIME_MEMORY_REGION_H_ 194
