mem_map.h revision bddaea2b88b0a19d9cc7a4dea772af8e829323b3
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 "globals.h" 30 31namespace art { 32 33#if defined(__LP64__) && (!defined(__x86_64__) || defined(__APPLE__)) 34#define USE_ART_LOW_4G_ALLOCATOR 1 35#else 36#define USE_ART_LOW_4G_ALLOCATOR 0 37#endif 38 39#ifdef __linux__ 40static constexpr bool kMadviseZeroes = true; 41#else 42static constexpr bool kMadviseZeroes = false; 43#endif 44 45// Used to keep track of mmap segments. 46// 47// On 64b systems not supporting MAP_32BIT, the implementation of MemMap will do a linear scan 48// for free pages. For security, the start of this scan should be randomized. This requires a 49// dynamic initializer. 50// For this to work, it is paramount that there are no other static initializers that access MemMap. 51// Otherwise, calls might see uninitialized values. 52class MemMap { 53 public: 54 // Request an anonymous region of length 'byte_count' and a requested base address. 55 // Use NULL as the requested base address if you don't care. 56 // 57 // The word "anonymous" in this context means "not backed by a file". The supplied 58 // 'ashmem_name' will be used -- on systems that support it -- to give the mapping 59 // a name. 60 // 61 // On success, returns returns a MemMap instance. On failure, returns a NULL; 62 static MemMap* MapAnonymous(const char* ashmem_name, byte* addr, size_t byte_count, int prot, 63 bool low_4gb, std::string* error_msg); 64 65 // Map part of a file, taking care of non-page aligned offsets. The 66 // "start" offset is absolute, not relative. 67 // 68 // On success, returns returns a MemMap instance. On failure, returns a NULL; 69 static MemMap* MapFile(size_t byte_count, int prot, int flags, int fd, off_t start, 70 const char* filename, std::string* error_msg) { 71 return MapFileAtAddress(NULL, byte_count, prot, flags, fd, start, false, filename, error_msg); 72 } 73 74 // Map part of a file, taking care of non-page aligned offsets. The 75 // "start" offset is absolute, not relative. This version allows 76 // requesting a specific address for the base of the 77 // mapping. "reuse" allows us to create a view into an existing 78 // mapping where we do not take ownership of the memory. 79 // 80 // On success, returns returns a MemMap instance. On failure, returns a 81 // nullptr; 82 static MemMap* MapFileAtAddress(byte* addr, size_t byte_count, int prot, int flags, int fd, 83 off_t start, bool reuse, const char* filename, 84 std::string* error_msg); 85 86 // Releases the memory mapping 87 ~MemMap() LOCKS_EXCLUDED(Locks::mem_maps_lock_); 88 89 const std::string& GetName() const { 90 return name_; 91 } 92 93 bool Protect(int prot); 94 95 void MadviseDontNeedAndZero(); 96 97 int GetProtect() const { 98 return prot_; 99 } 100 101 byte* Begin() const { 102 return begin_; 103 } 104 105 size_t Size() const { 106 return size_; 107 } 108 109 byte* End() const { 110 return Begin() + Size(); 111 } 112 113 void* BaseBegin() const { 114 return base_begin_; 115 } 116 117 size_t BaseSize() const { 118 return base_size_; 119 } 120 121 void* BaseEnd() const { 122 return reinterpret_cast<byte*>(BaseBegin()) + BaseSize(); 123 } 124 125 bool HasAddress(const void* addr) const { 126 return Begin() <= addr && addr < End(); 127 } 128 129 // Unmap the pages at end and remap them to create another memory map. 130 MemMap* RemapAtEnd(byte* new_end, const char* tail_name, int tail_prot, 131 std::string* error_msg); 132 133 static bool CheckNoGaps(MemMap* begin_map, MemMap* end_map) 134 LOCKS_EXCLUDED(Locks::mem_maps_lock_); 135 static void DumpMaps(std::ostream& os) 136 LOCKS_EXCLUDED(Locks::mem_maps_lock_); 137 138 private: 139 MemMap(const std::string& name, byte* begin, size_t size, void* base_begin, size_t base_size, 140 int prot, bool reuse) LOCKS_EXCLUDED(Locks::mem_maps_lock_); 141 142 static void DumpMaps(std::ostream& os, const std::multimap<void*, MemMap*>& mem_maps) 143 LOCKS_EXCLUDED(Locks::mem_maps_lock_); 144 static void DumpMapsLocked(std::ostream& os, const std::multimap<void*, MemMap*>& mem_maps) 145 EXCLUSIVE_LOCKS_REQUIRED(Locks::mem_maps_lock_); 146 static bool HasMemMap(MemMap* map) 147 EXCLUSIVE_LOCKS_REQUIRED(Locks::mem_maps_lock_); 148 static MemMap* GetLargestMemMapAt(void* address) 149 EXCLUSIVE_LOCKS_REQUIRED(Locks::mem_maps_lock_); 150 151 const std::string name_; 152 byte* const begin_; // Start of data. 153 size_t size_; // Length of data. 154 155 void* const base_begin_; // Page-aligned base address. 156 size_t base_size_; // Length of mapping. May be changed by RemapAtEnd (ie Zygote). 157 int prot_; // Protection of the map. 158 159 // When reuse_ is true, this is just a view of an existing mapping 160 // and we do not take ownership and are not responsible for 161 // unmapping. 162 const bool reuse_; 163 164#if USE_ART_LOW_4G_ALLOCATOR 165 static uintptr_t next_mem_pos_; // Next memory location to check for low_4g extent. 166#endif 167 168 // All the non-empty MemMaps. Use a multimap as we do a reserve-and-divide (eg ElfMap::Load()). 169 static std::multimap<void*, MemMap*> maps_ GUARDED_BY(Locks::mem_maps_lock_); 170 171 friend class MemMapTest; // To allow access to base_begin_ and base_size_. 172}; 173std::ostream& operator<<(std::ostream& os, const MemMap& mem_map); 174 175} // namespace art 176 177#endif // ART_RUNTIME_MEM_MAP_H_ 178