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 #ifndef ART_RUNTIME_MEM_MAP_H_ 18 #define ART_RUNTIME_MEM_MAP_H_ 19 20 #include "base/mutex.h" 21 22 #include <string> 23 #include <map> 24 25 #include <stddef.h> 26 #include <sys/mman.h> // For the PROT_* and MAP_* constants. 27 #include <sys/types.h> 28 29 #include "base/allocator.h" 30 #include "globals.h" 31 32 namespace art { 33 34 #if defined(__LP64__) && (!defined(__x86_64__) || defined(__APPLE__)) 35 #define USE_ART_LOW_4G_ALLOCATOR 1 36 #else 37 #define USE_ART_LOW_4G_ALLOCATOR 0 38 #endif 39 40 #ifdef __linux__ 41 static constexpr bool kMadviseZeroes = true; 42 #else 43 static constexpr bool kMadviseZeroes = false; 44 #endif 45 46 // Used to keep track of mmap segments. 47 // 48 // On 64b systems not supporting MAP_32BIT, the implementation of MemMap will do a linear scan 49 // for free pages. For security, the start of this scan should be randomized. This requires a 50 // dynamic initializer. 51 // For this to work, it is paramount that there are no other static initializers that access MemMap. 52 // Otherwise, calls might see uninitialized values. 53 class MemMap { 54 public: 55 // Request an anonymous region of length 'byte_count' and a requested base address. 56 // Use NULL as the requested base address if you don't care. 57 // 58 // The word "anonymous" in this context means "not backed by a file". The supplied 59 // 'ashmem_name' will be used -- on systems that support it -- to give the mapping 60 // a name. 61 // 62 // On success, returns returns a MemMap instance. On failure, returns a NULL; 63 static MemMap* MapAnonymous(const char* ashmem_name, byte* addr, size_t byte_count, int prot, 64 bool low_4gb, std::string* error_msg); 65 66 // Map part of a file, taking care of non-page aligned offsets. The 67 // "start" offset is absolute, not relative. 68 // 69 // On success, returns returns a MemMap instance. On failure, returns a NULL; 70 static MemMap* MapFile(size_t byte_count, int prot, int flags, int fd, off_t start, 71 const char* filename, std::string* error_msg) { 72 return MapFileAtAddress(NULL, byte_count, prot, flags, fd, start, false, filename, error_msg); 73 } 74 75 // Map part of a file, taking care of non-page aligned offsets. The 76 // "start" offset is absolute, not relative. This version allows 77 // requesting a specific address for the base of the 78 // mapping. "reuse" allows us to create a view into an existing 79 // mapping where we do not take ownership of the memory. 80 // 81 // On success, returns returns a MemMap instance. On failure, returns a 82 // nullptr; 83 static MemMap* MapFileAtAddress(byte* addr, size_t byte_count, int prot, int flags, int fd, 84 off_t start, bool reuse, const char* filename, 85 std::string* error_msg); 86 87 // Releases the memory mapping 88 ~MemMap() LOCKS_EXCLUDED(Locks::mem_maps_lock_); 89 90 const std::string& GetName() const { 91 return name_; 92 } 93 94 bool Protect(int prot); 95 96 void MadviseDontNeedAndZero(); 97 98 int GetProtect() const { 99 return prot_; 100 } 101 102 byte* Begin() const { 103 return begin_; 104 } 105 106 size_t Size() const { 107 return size_; 108 } 109 110 byte* End() const { 111 return Begin() + Size(); 112 } 113 114 void* BaseBegin() const { 115 return base_begin_; 116 } 117 118 size_t BaseSize() const { 119 return base_size_; 120 } 121 122 void* BaseEnd() const { 123 return reinterpret_cast<byte*>(BaseBegin()) + BaseSize(); 124 } 125 126 bool HasAddress(const void* addr) const { 127 return Begin() <= addr && addr < End(); 128 } 129 130 // Unmap the pages at end and remap them to create another memory map. 131 MemMap* RemapAtEnd(byte* new_end, const char* tail_name, int tail_prot, 132 std::string* error_msg); 133 134 static bool CheckNoGaps(MemMap* begin_map, MemMap* end_map) 135 LOCKS_EXCLUDED(Locks::mem_maps_lock_); 136 static void DumpMaps(std::ostream& os) 137 LOCKS_EXCLUDED(Locks::mem_maps_lock_); 138 139 typedef AllocationTrackingMultiMap<void*, MemMap*, kAllocatorTagMaps> Maps; 140 141 static void Init() LOCKS_EXCLUDED(Locks::mem_maps_lock_); 142 static void Shutdown() LOCKS_EXCLUDED(Locks::mem_maps_lock_); 143 144 private: 145 MemMap(const std::string& name, byte* begin, size_t size, void* base_begin, size_t base_size, 146 int prot, bool reuse) LOCKS_EXCLUDED(Locks::mem_maps_lock_); 147 148 static void DumpMapsLocked(std::ostream& os) 149 EXCLUSIVE_LOCKS_REQUIRED(Locks::mem_maps_lock_); 150 static bool HasMemMap(MemMap* map) 151 EXCLUSIVE_LOCKS_REQUIRED(Locks::mem_maps_lock_); 152 static MemMap* GetLargestMemMapAt(void* address) 153 EXCLUSIVE_LOCKS_REQUIRED(Locks::mem_maps_lock_); 154 155 const std::string name_; 156 byte* const begin_; // Start of data. 157 size_t size_; // Length of data. 158 159 void* const base_begin_; // Page-aligned base address. 160 size_t base_size_; // Length of mapping. May be changed by RemapAtEnd (ie Zygote). 161 int prot_; // Protection of the map. 162 163 // When reuse_ is true, this is just a view of an existing mapping 164 // and we do not take ownership and are not responsible for 165 // unmapping. 166 const bool reuse_; 167 168 #if USE_ART_LOW_4G_ALLOCATOR 169 static uintptr_t next_mem_pos_; // Next memory location to check for low_4g extent. 170 #endif 171 172 // All the non-empty MemMaps. Use a multimap as we do a reserve-and-divide (eg ElfMap::Load()). 173 static Maps* maps_ GUARDED_BY(Locks::mem_maps_lock_); 174 175 friend class MemMapTest; // To allow access to base_begin_ and base_size_. 176 }; 177 std::ostream& operator<<(std::ostream& os, const MemMap& mem_map); 178 179 } // namespace art 180 181 #endif // ART_RUNTIME_MEM_MAP_H_ 182
