mem_map.cc revision ef7d42fca18c16fbaf103822ad16f23246e2905d
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#include "mem_map.h" 18 19#include <inttypes.h> 20#include <backtrace/BacktraceMap.h> 21 22#include "UniquePtr.h" 23#include "base/stringprintf.h" 24#include "ScopedFd.h" 25#include "utils.h" 26 27#define USE_ASHMEM 1 28 29#ifdef USE_ASHMEM 30#include <cutils/ashmem.h> 31#endif 32 33namespace art { 34 35#if !defined(NDEBUG) 36 37static std::ostream& operator<<( 38 std::ostream& os, 39 std::pair<BacktraceMap::const_iterator, BacktraceMap::const_iterator> iters) { 40 for (BacktraceMap::const_iterator it = iters.first; it != iters.second; ++it) { 41 os << StringPrintf("0x%08x-0x%08x %c%c%c %s\n", 42 static_cast<uint32_t>(it->start), 43 static_cast<uint32_t>(it->end), 44 (it->flags & PROT_READ) ? 'r' : '-', 45 (it->flags & PROT_WRITE) ? 'w' : '-', 46 (it->flags & PROT_EXEC) ? 'x' : '-', it->name.c_str()); 47 } 48 return os; 49} 50 51static void CheckMapRequest(byte* addr, size_t byte_count) { 52 if (addr == NULL) { 53 return; 54 } 55 56 uintptr_t base = reinterpret_cast<uintptr_t>(addr); 57 uintptr_t limit = base + byte_count; 58 59 UniquePtr<BacktraceMap> map(BacktraceMap::Create(getpid())); 60 if (!map->Build()) { 61 PLOG(WARNING) << "Failed to build process map"; 62 return; 63 } 64 for (BacktraceMap::const_iterator it = map->begin(); it != map->end(); ++it) { 65 CHECK(!(base >= it->start && base < it->end) // start of new within old 66 && !(limit > it->start && limit < it->end) // end of new within old 67 && !(base <= it->start && limit > it->end)) // start/end of new includes all of old 68 << StringPrintf("Requested region 0x%08" PRIxPTR "-0x%08" PRIxPTR " overlaps with " 69 "existing map 0x%08" PRIxPTR "-0x%08" PRIxPTR " (%s)\n", 70 base, limit, 71 static_cast<uintptr_t>(it->start), static_cast<uintptr_t>(it->end), 72 it->name.c_str()) 73 << std::make_pair(it, map->end()); 74 } 75} 76 77#else 78static void CheckMapRequest(byte*, size_t) { } 79#endif 80 81MemMap* MemMap::MapAnonymous(const char* name, byte* addr, size_t byte_count, int prot, 82 bool low_4gb, std::string* error_msg) { 83 if (byte_count == 0) { 84 return new MemMap(name, NULL, 0, NULL, 0, prot); 85 } 86 size_t page_aligned_byte_count = RoundUp(byte_count, kPageSize); 87 CheckMapRequest(addr, page_aligned_byte_count); 88 89#ifdef USE_ASHMEM 90 // android_os_Debug.cpp read_mapinfo assumes all ashmem regions associated with the VM are 91 // prefixed "dalvik-". 92 std::string debug_friendly_name("dalvik-"); 93 debug_friendly_name += name; 94 ScopedFd fd(ashmem_create_region(debug_friendly_name.c_str(), page_aligned_byte_count)); 95 int flags = MAP_PRIVATE; 96 if (fd.get() == -1) { 97 *error_msg = StringPrintf("ashmem_create_region failed for '%s': %s", name, strerror(errno)); 98 return nullptr; 99 } 100#else 101 ScopedFd fd(-1); 102 int flags = MAP_PRIVATE | MAP_ANONYMOUS; 103#endif 104#ifdef __LP64__ 105 if (low_4gb) { 106 flags |= MAP_32BIT; 107 } 108#endif 109 byte* actual = reinterpret_cast<byte*>(mmap(addr, page_aligned_byte_count, prot, flags, fd.get(), 0)); 110 if (actual == MAP_FAILED) { 111 std::string maps; 112 ReadFileToString("/proc/self/maps", &maps); 113 *error_msg = StringPrintf("anonymous mmap(%p, %zd, %x, %x, %d, 0) failed\n%s", 114 addr, page_aligned_byte_count, prot, flags, fd.get(), 115 maps.c_str()); 116 return nullptr; 117 } 118 return new MemMap(name, actual, byte_count, actual, page_aligned_byte_count, prot); 119} 120 121MemMap* MemMap::MapFileAtAddress(byte* addr, size_t byte_count, int prot, int flags, int fd, 122 off_t start, bool reuse, const char* filename, 123 std::string* error_msg) { 124 CHECK_NE(0, prot); 125 CHECK_NE(0, flags & (MAP_SHARED | MAP_PRIVATE)); 126 if (byte_count == 0) { 127 return new MemMap(filename, NULL, 0, NULL, 0, prot); 128 } 129 // Adjust 'offset' to be page-aligned as required by mmap. 130 int page_offset = start % kPageSize; 131 off_t page_aligned_offset = start - page_offset; 132 // Adjust 'byte_count' to be page-aligned as we will map this anyway. 133 size_t page_aligned_byte_count = RoundUp(byte_count + page_offset, kPageSize); 134 // The 'addr' is modified (if specified, ie non-null) to be page aligned to the file but not 135 // necessarily to virtual memory. mmap will page align 'addr' for us. 136 byte* page_aligned_addr = (addr == NULL) ? NULL : (addr - page_offset); 137 if (!reuse) { 138 // reuse means it is okay that it overlaps an existing page mapping. 139 // Only use this if you actually made the page reservation yourself. 140 CheckMapRequest(page_aligned_addr, page_aligned_byte_count); 141 } else { 142 CHECK(addr != NULL); 143 } 144 byte* actual = reinterpret_cast<byte*>(mmap(page_aligned_addr, 145 page_aligned_byte_count, 146 prot, 147 flags, 148 fd, 149 page_aligned_offset)); 150 if (actual == MAP_FAILED) { 151 std::string strerr(strerror(errno)); 152 std::string maps; 153 ReadFileToString("/proc/self/maps", &maps); 154 *error_msg = StringPrintf("mmap(%p, %zd, %x, %x, %d, %" PRId64 ") of file '%s' failed: %s\n%s", 155 page_aligned_addr, page_aligned_byte_count, prot, flags, fd, 156 static_cast<int64_t>(page_aligned_offset), filename, strerr.c_str(), 157 maps.c_str()); 158 return NULL; 159 } 160 return new MemMap(filename, actual + page_offset, byte_count, actual, page_aligned_byte_count, 161 prot); 162} 163 164MemMap::~MemMap() { 165 if (base_begin_ == NULL && base_size_ == 0) { 166 return; 167 } 168 int result = munmap(base_begin_, base_size_); 169 if (result == -1) { 170 PLOG(FATAL) << "munmap failed"; 171 } 172} 173 174MemMap::MemMap(const std::string& name, byte* begin, size_t size, void* base_begin, 175 size_t base_size, int prot) 176 : name_(name), begin_(begin), size_(size), base_begin_(base_begin), base_size_(base_size), 177 prot_(prot) { 178 if (size_ == 0) { 179 CHECK(begin_ == NULL); 180 CHECK(base_begin_ == NULL); 181 CHECK_EQ(base_size_, 0U); 182 } else { 183 CHECK(begin_ != NULL); 184 CHECK(base_begin_ != NULL); 185 CHECK_NE(base_size_, 0U); 186 } 187}; 188 189MemMap* MemMap::RemapAtEnd(byte* new_end, const char* tail_name, int tail_prot, 190 std::string* error_msg) { 191 DCHECK_GE(new_end, Begin()); 192 DCHECK_LE(new_end, End()); 193 DCHECK_LE(begin_ + size_, reinterpret_cast<byte*>(base_begin_) + base_size_); 194 DCHECK(IsAligned<kPageSize>(begin_)); 195 DCHECK(IsAligned<kPageSize>(base_begin_)); 196 DCHECK(IsAligned<kPageSize>(reinterpret_cast<byte*>(base_begin_) + base_size_)); 197 DCHECK(IsAligned<kPageSize>(new_end)); 198 byte* old_end = begin_ + size_; 199 byte* old_base_end = reinterpret_cast<byte*>(base_begin_) + base_size_; 200 byte* new_base_end = new_end; 201 DCHECK_LE(new_base_end, old_base_end); 202 if (new_base_end == old_base_end) { 203 return new MemMap(tail_name, NULL, 0, NULL, 0, tail_prot); 204 } 205 size_ = new_end - reinterpret_cast<byte*>(begin_); 206 base_size_ = new_base_end - reinterpret_cast<byte*>(base_begin_); 207 DCHECK_LE(begin_ + size_, reinterpret_cast<byte*>(base_begin_) + base_size_); 208 size_t tail_size = old_end - new_end; 209 byte* tail_base_begin = new_base_end; 210 size_t tail_base_size = old_base_end - new_base_end; 211 DCHECK_EQ(tail_base_begin + tail_base_size, old_base_end); 212 DCHECK(IsAligned<kPageSize>(tail_base_size)); 213 214#ifdef USE_ASHMEM 215 // android_os_Debug.cpp read_mapinfo assumes all ashmem regions associated with the VM are 216 // prefixed "dalvik-". 217 std::string debug_friendly_name("dalvik-"); 218 debug_friendly_name += tail_name; 219 ScopedFd fd(ashmem_create_region(debug_friendly_name.c_str(), tail_base_size)); 220 int flags = MAP_PRIVATE; 221 if (fd.get() == -1) { 222 *error_msg = StringPrintf("ashmem_create_region failed for '%s': %s", 223 tail_name, strerror(errno)); 224 return nullptr; 225 } 226#else 227 ScopedFd fd(-1); 228 int flags = MAP_PRIVATE | MAP_ANONYMOUS; 229#endif 230 231 // Unmap/map the tail region. 232 int result = munmap(tail_base_begin, tail_base_size); 233 if (result == -1) { 234 std::string maps; 235 ReadFileToString("/proc/self/maps", &maps); 236 *error_msg = StringPrintf("munmap(%p, %zd) failed for '%s'\n%s", 237 tail_base_begin, tail_base_size, name_.c_str(), 238 maps.c_str()); 239 return nullptr; 240 } 241 // Don't cause memory allocation between the munmap and the mmap 242 // calls. Otherwise, libc (or something else) might take this memory 243 // region. Note this isn't perfect as there's no way to prevent 244 // other threads to try to take this memory region here. 245 byte* actual = reinterpret_cast<byte*>(mmap(tail_base_begin, tail_base_size, tail_prot, 246 flags, fd.get(), 0)); 247 if (actual == MAP_FAILED) { 248 std::string maps; 249 ReadFileToString("/proc/self/maps", &maps); 250 *error_msg = StringPrintf("anonymous mmap(%p, %zd, %x, %x, %d, 0) failed\n%s", 251 tail_base_begin, tail_base_size, tail_prot, flags, fd.get(), 252 maps.c_str()); 253 return nullptr; 254 } 255 return new MemMap(tail_name, actual, tail_size, actual, tail_base_size, tail_prot); 256} 257 258bool MemMap::Protect(int prot) { 259 if (base_begin_ == NULL && base_size_ == 0) { 260 prot_ = prot; 261 return true; 262 } 263 264 if (mprotect(base_begin_, base_size_, prot) == 0) { 265 prot_ = prot; 266 return true; 267 } 268 269 PLOG(ERROR) << "mprotect(" << reinterpret_cast<void*>(base_begin_) << ", " << base_size_ << ", " 270 << prot << ") failed"; 271 return false; 272} 273 274std::ostream& operator<<(std::ostream& os, const MemMap& mem_map) { 275 os << StringPrintf("[MemMap: %s prot=%x %p-%p]", 276 mem_map.GetName().c_str(), mem_map.GetProtect(), 277 mem_map.BaseBegin(), mem_map.BaseEnd()); 278 return os; 279} 280 281} // namespace art 282