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Diffstat (limited to 'libartbase/base/mem_map.cc')
| -rw-r--r-- | libartbase/base/mem_map.cc | 1158 |
1 files changed, 1158 insertions, 0 deletions
diff --git a/libartbase/base/mem_map.cc b/libartbase/base/mem_map.cc new file mode 100644 index 00000000000..21634f86b69 --- /dev/null +++ b/libartbase/base/mem_map.cc @@ -0,0 +1,1158 @@ +/* + * Copyright (C) 2008 The Android Open Source Project + * + * Licensed under the Apache License, Version 2.0 (the "License"); + * you may not use this file except in compliance with the License. + * You may obtain a copy of the License at + * + * http://www.apache.org/licenses/LICENSE-2.0 + * + * Unless required by applicable law or agreed to in writing, software + * distributed under the License is distributed on an "AS IS" BASIS, + * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. + * See the License for the specific language governing permissions and + * limitations under the License. + */ + +#include "mem_map.h" + +#include <inttypes.h> +#include <stdlib.h> +#include <sys/mman.h> // For the PROT_* and MAP_* constants. +#ifndef ANDROID_OS +#include <sys/resource.h> +#endif + +#include <map> +#include <memory> +#include <sstream> + +#include "android-base/stringprintf.h" +#include "android-base/unique_fd.h" +#include "backtrace/BacktraceMap.h" +#include "cutils/ashmem.h" + +#include "base/allocator.h" +#include "base/bit_utils.h" +#include "base/globals.h" +#include "base/logging.h" // For VLOG_IS_ON. +#include "base/memory_tool.h" +#include "base/utils.h" + +#ifndef MAP_ANONYMOUS +#define MAP_ANONYMOUS MAP_ANON +#endif + +namespace art { + +using android::base::StringPrintf; +using android::base::unique_fd; + +template<class Key, class T, AllocatorTag kTag, class Compare = std::less<Key>> +using AllocationTrackingMultiMap = + std::multimap<Key, T, Compare, TrackingAllocator<std::pair<const Key, T>, kTag>>; + +using Maps = AllocationTrackingMultiMap<void*, MemMap*, kAllocatorTagMaps>; + +// All the non-empty MemMaps. Use a multimap as we do a reserve-and-divide (eg ElfMap::Load()). +static Maps* gMaps GUARDED_BY(MemMap::GetMemMapsLock()) = nullptr; + +static std::ostream& operator<<( + std::ostream& os, + std::pair<BacktraceMap::iterator, BacktraceMap::iterator> iters) { + for (BacktraceMap::iterator it = iters.first; it != iters.second; ++it) { + const backtrace_map_t* entry = *it; + os << StringPrintf("0x%08x-0x%08x %c%c%c %s\n", + static_cast<uint32_t>(entry->start), + static_cast<uint32_t>(entry->end), + (entry->flags & PROT_READ) ? 'r' : '-', + (entry->flags & PROT_WRITE) ? 'w' : '-', + (entry->flags & PROT_EXEC) ? 'x' : '-', entry->name.c_str()); + } + return os; +} + +std::ostream& operator<<(std::ostream& os, const Maps& mem_maps) { + os << "MemMap:" << std::endl; + for (auto it = mem_maps.begin(); it != mem_maps.end(); ++it) { + void* base = it->first; + MemMap* map = it->second; + CHECK_EQ(base, map->BaseBegin()); + os << *map << std::endl; + } + return os; +} + +std::mutex* MemMap::mem_maps_lock_ = nullptr; + +#if USE_ART_LOW_4G_ALLOCATOR +// Handling mem_map in 32b address range for 64b architectures that do not support MAP_32BIT. + +// The regular start of memory allocations. The first 64KB is protected by SELinux. +static constexpr uintptr_t LOW_MEM_START = 64 * KB; + +// Generate random starting position. +// To not interfere with image position, take the image's address and only place it below. Current +// formula (sketch): +// +// ART_BASE_ADDR = 0001XXXXXXXXXXXXXXX +// ---------------------------------------- +// = 0000111111111111111 +// & ~(kPageSize - 1) =~0000000000000001111 +// ---------------------------------------- +// mask = 0000111111111110000 +// & random data = YYYYYYYYYYYYYYYYYYY +// ----------------------------------- +// tmp = 0000YYYYYYYYYYY0000 +// + LOW_MEM_START = 0000000000001000000 +// -------------------------------------- +// start +// +// arc4random as an entropy source is exposed in Bionic, but not in glibc. When we +// do not have Bionic, simply start with LOW_MEM_START. + +// Function is standalone so it can be tested somewhat in mem_map_test.cc. +#ifdef __BIONIC__ +uintptr_t CreateStartPos(uint64_t input) { + CHECK_NE(0, ART_BASE_ADDRESS); + + // Start with all bits below highest bit in ART_BASE_ADDRESS. + constexpr size_t leading_zeros = CLZ(static_cast<uint32_t>(ART_BASE_ADDRESS)); + constexpr uintptr_t mask_ones = (1 << (31 - leading_zeros)) - 1; + + // Lowest (usually 12) bits are not used, as aligned by page size. + constexpr uintptr_t mask = mask_ones & ~(kPageSize - 1); + + // Mask input data. + return (input & mask) + LOW_MEM_START; +} +#endif + +static uintptr_t GenerateNextMemPos() { +#ifdef __BIONIC__ + uint64_t random_data; + arc4random_buf(&random_data, sizeof(random_data)); + return CreateStartPos(random_data); +#else + // No arc4random on host, see above. + return LOW_MEM_START; +#endif +} + +// Initialize linear scan to random position. +uintptr_t MemMap::next_mem_pos_ = GenerateNextMemPos(); +#endif + +// Return true if the address range is contained in a single memory map by either reading +// the gMaps variable or the /proc/self/map entry. +bool MemMap::ContainedWithinExistingMap(uint8_t* ptr, size_t size, std::string* error_msg) { + uintptr_t begin = reinterpret_cast<uintptr_t>(ptr); + uintptr_t end = begin + size; + + // There is a suspicion that BacktraceMap::Create is occasionally missing maps. TODO: Investigate + // further. + { + std::lock_guard<std::mutex> mu(*mem_maps_lock_); + for (auto& pair : *gMaps) { + MemMap* const map = pair.second; + if (begin >= reinterpret_cast<uintptr_t>(map->Begin()) && + end <= reinterpret_cast<uintptr_t>(map->End())) { + return true; + } + } + } + + std::unique_ptr<BacktraceMap> map(BacktraceMap::Create(getpid(), true)); + if (map == nullptr) { + if (error_msg != nullptr) { + *error_msg = StringPrintf("Failed to build process map"); + } + return false; + } + + ScopedBacktraceMapIteratorLock lock(map.get()); + for (BacktraceMap::iterator it = map->begin(); it != map->end(); ++it) { + const backtrace_map_t* entry = *it; + if ((begin >= entry->start && begin < entry->end) // start of new within old + && (end > entry->start && end <= entry->end)) { // end of new within old + return true; + } + } + if (error_msg != nullptr) { + PrintFileToLog("/proc/self/maps", LogSeverity::ERROR); + *error_msg = StringPrintf("Requested region 0x%08" PRIxPTR "-0x%08" PRIxPTR " does not overlap " + "any existing map. See process maps in the log.", begin, end); + } + return false; +} + +// Return true if the address range does not conflict with any /proc/self/maps entry. +static bool CheckNonOverlapping(uintptr_t begin, + uintptr_t end, + std::string* error_msg) { + std::unique_ptr<BacktraceMap> map(BacktraceMap::Create(getpid(), true)); + if (map.get() == nullptr) { + *error_msg = StringPrintf("Failed to build process map"); + return false; + } + ScopedBacktraceMapIteratorLock lock(map.get()); + for (BacktraceMap::iterator it = map->begin(); it != map->end(); ++it) { + const backtrace_map_t* entry = *it; + if ((begin >= entry->start && begin < entry->end) // start of new within old + || (end > entry->start && end < entry->end) // end of new within old + || (begin <= entry->start && end > entry->end)) { // start/end of new includes all of old + std::ostringstream map_info; + map_info << std::make_pair(it, map->end()); + *error_msg = StringPrintf("Requested region 0x%08" PRIxPTR "-0x%08" PRIxPTR " overlaps with " + "existing map 0x%08" PRIxPTR "-0x%08" PRIxPTR " (%s)\n%s", + begin, end, + static_cast<uintptr_t>(entry->start), + static_cast<uintptr_t>(entry->end), + entry->name.c_str(), + map_info.str().c_str()); + return false; + } + } + return true; +} + +// CheckMapRequest to validate a non-MAP_FAILED mmap result based on +// the expected value, calling munmap if validation fails, giving the +// reason in error_msg. +// +// If the expected_ptr is null, nothing is checked beyond the fact +// that the actual_ptr is not MAP_FAILED. However, if expected_ptr is +// non-null, we check that pointer is the actual_ptr == expected_ptr, +// and if not, report in error_msg what the conflict mapping was if +// found, or a generic error in other cases. +static bool CheckMapRequest(uint8_t* expected_ptr, void* actual_ptr, size_t byte_count, + std::string* error_msg) { + // Handled first by caller for more specific error messages. + CHECK(actual_ptr != MAP_FAILED); + + if (expected_ptr == nullptr) { + return true; + } + + uintptr_t actual = reinterpret_cast<uintptr_t>(actual_ptr); + uintptr_t expected = reinterpret_cast<uintptr_t>(expected_ptr); + uintptr_t limit = expected + byte_count; + + if (expected_ptr == actual_ptr) { + return true; + } + + // We asked for an address but didn't get what we wanted, all paths below here should fail. + int result = munmap(actual_ptr, byte_count); + if (result == -1) { + PLOG(WARNING) << StringPrintf("munmap(%p, %zd) failed", actual_ptr, byte_count); + } + + if (error_msg != nullptr) { + // We call this here so that we can try and generate a full error + // message with the overlapping mapping. There's no guarantee that + // that there will be an overlap though, since + // - The kernel is not *required* to honor expected_ptr unless MAP_FIXED is + // true, even if there is no overlap + // - There might have been an overlap at the point of mmap, but the + // overlapping region has since been unmapped. + std::string error_detail; + CheckNonOverlapping(expected, limit, &error_detail); + std::ostringstream os; + os << StringPrintf("Failed to mmap at expected address, mapped at " + "0x%08" PRIxPTR " instead of 0x%08" PRIxPTR, + actual, expected); + if (!error_detail.empty()) { + os << " : " << error_detail; + } + *error_msg = os.str(); + } + return false; +} + +#if USE_ART_LOW_4G_ALLOCATOR +static inline void* TryMemMapLow4GB(void* ptr, + size_t page_aligned_byte_count, + int prot, + int flags, + int fd, + off_t offset) { + void* actual = mmap(ptr, page_aligned_byte_count, prot, flags, fd, offset); + if (actual != MAP_FAILED) { + // Since we didn't use MAP_FIXED the kernel may have mapped it somewhere not in the low + // 4GB. If this is the case, unmap and retry. + if (reinterpret_cast<uintptr_t>(actual) + page_aligned_byte_count >= 4 * GB) { + munmap(actual, page_aligned_byte_count); + actual = MAP_FAILED; + } + } + return actual; +} +#endif + +MemMap* MemMap::MapAnonymous(const char* name, + uint8_t* expected_ptr, + size_t byte_count, + int prot, + bool low_4gb, + bool reuse, + std::string* error_msg, + bool use_ashmem) { +#ifndef __LP64__ + UNUSED(low_4gb); +#endif + use_ashmem = use_ashmem && !kIsTargetLinux; + if (byte_count == 0) { + return new MemMap(name, nullptr, 0, nullptr, 0, prot, false); + } + size_t page_aligned_byte_count = RoundUp(byte_count, kPageSize); + + int flags = MAP_PRIVATE | MAP_ANONYMOUS; + if (reuse) { + // reuse means it is okay that it overlaps an existing page mapping. + // Only use this if you actually made the page reservation yourself. + CHECK(expected_ptr != nullptr); + + DCHECK(ContainedWithinExistingMap(expected_ptr, byte_count, error_msg)) << *error_msg; + flags |= MAP_FIXED; + } + + if (use_ashmem) { + if (!kIsTargetBuild) { + // When not on Android (either host or assuming a linux target) ashmem is faked using + // files in /tmp. Ensure that such files won't fail due to ulimit restrictions. If they + // will then use a regular mmap. + struct rlimit rlimit_fsize; + CHECK_EQ(getrlimit(RLIMIT_FSIZE, &rlimit_fsize), 0); + use_ashmem = (rlimit_fsize.rlim_cur == RLIM_INFINITY) || + (page_aligned_byte_count < rlimit_fsize.rlim_cur); + } + } + + unique_fd fd; + + + if (use_ashmem) { + // android_os_Debug.cpp read_mapinfo assumes all ashmem regions associated with the VM are + // prefixed "dalvik-". + std::string debug_friendly_name("dalvik-"); + debug_friendly_name += name; + fd.reset(ashmem_create_region(debug_friendly_name.c_str(), page_aligned_byte_count)); + + if (fd.get() == -1) { + // We failed to create the ashmem region. Print a warning, but continue + // anyway by creating a true anonymous mmap with an fd of -1. It is + // better to use an unlabelled anonymous map than to fail to create a + // map at all. + PLOG(WARNING) << "ashmem_create_region failed for '" << name << "'"; + } else { + // We succeeded in creating the ashmem region. Use the created ashmem + // region as backing for the mmap. + flags &= ~MAP_ANONYMOUS; + } + } + + // We need to store and potentially set an error number for pretty printing of errors + int saved_errno = 0; + + void* actual = MapInternal(expected_ptr, + page_aligned_byte_count, + prot, + flags, + fd.get(), + 0, + low_4gb); + saved_errno = errno; + + if (actual == MAP_FAILED) { + if (error_msg != nullptr) { + if (kIsDebugBuild || VLOG_IS_ON(oat)) { + PrintFileToLog("/proc/self/maps", LogSeverity::WARNING); + } + + *error_msg = StringPrintf("Failed anonymous mmap(%p, %zd, 0x%x, 0x%x, %d, 0): %s. " + "See process maps in the log.", + expected_ptr, + page_aligned_byte_count, + prot, + flags, + fd.get(), + strerror(saved_errno)); + } + return nullptr; + } + if (!CheckMapRequest(expected_ptr, actual, page_aligned_byte_count, error_msg)) { + return nullptr; + } + return new MemMap(name, reinterpret_cast<uint8_t*>(actual), byte_count, actual, + page_aligned_byte_count, prot, reuse); +} + +MemMap* MemMap::MapDummy(const char* name, uint8_t* addr, size_t byte_count) { + if (byte_count == 0) { + return new MemMap(name, nullptr, 0, nullptr, 0, 0, false); + } + const size_t page_aligned_byte_count = RoundUp(byte_count, kPageSize); + return new MemMap(name, addr, byte_count, addr, page_aligned_byte_count, 0, true /* reuse */); +} + +template<typename A, typename B> +static ptrdiff_t PointerDiff(A* a, B* b) { + return static_cast<ptrdiff_t>(reinterpret_cast<intptr_t>(a) - reinterpret_cast<intptr_t>(b)); +} + +bool MemMap::ReplaceWith(MemMap** source_ptr, /*out*/std::string* error) { +#if !HAVE_MREMAP_SYSCALL + UNUSED(source_ptr); + *error = "Cannot perform atomic replace because we are missing the required mremap syscall"; + return false; +#else // !HAVE_MREMAP_SYSCALL + CHECK(source_ptr != nullptr); + CHECK(*source_ptr != nullptr); + if (!MemMap::kCanReplaceMapping) { + *error = "Unable to perform atomic replace due to runtime environment!"; + return false; + } + MemMap* source = *source_ptr; + // neither can be reuse. + if (source->reuse_ || reuse_) { + *error = "One or both mappings is not a real mmap!"; + return false; + } + // TODO Support redzones. + if (source->redzone_size_ != 0 || redzone_size_ != 0) { + *error = "source and dest have different redzone sizes"; + return false; + } + // Make sure they have the same offset from the actual mmap'd address + if (PointerDiff(BaseBegin(), Begin()) != PointerDiff(source->BaseBegin(), source->Begin())) { + *error = + "source starts at a different offset from the mmap. Cannot atomically replace mappings"; + return false; + } + // mremap doesn't allow the final [start, end] to overlap with the initial [start, end] (it's like + // memcpy but the check is explicit and actually done). + if (source->BaseBegin() > BaseBegin() && + reinterpret_cast<uint8_t*>(BaseBegin()) + source->BaseSize() > + reinterpret_cast<uint8_t*>(source->BaseBegin())) { + *error = "destination memory pages overlap with source memory pages"; + return false; + } + // Change the protection to match the new location. + int old_prot = source->GetProtect(); + if (!source->Protect(GetProtect())) { + *error = "Could not change protections for source to those required for dest."; + return false; + } + + // Do the mremap. + void* res = mremap(/*old_address*/source->BaseBegin(), + /*old_size*/source->BaseSize(), + /*new_size*/source->BaseSize(), + /*flags*/MREMAP_MAYMOVE | MREMAP_FIXED, + /*new_address*/BaseBegin()); + if (res == MAP_FAILED) { + int saved_errno = errno; + // Wasn't able to move mapping. Change the protection of source back to the original one and + // return. + source->Protect(old_prot); + *error = std::string("Failed to mremap source to dest. Error was ") + strerror(saved_errno); + return false; + } + CHECK(res == BaseBegin()); + + // The new base_size is all the pages of the 'source' plus any remaining dest pages. We will unmap + // them later. + size_t new_base_size = std::max(source->base_size_, base_size_); + + // Delete the old source, don't unmap it though (set reuse) since it is already gone. + *source_ptr = nullptr; + size_t source_size = source->size_; + source->already_unmapped_ = true; + delete source; + source = nullptr; + + size_ = source_size; + base_size_ = new_base_size; + // Reduce base_size if needed (this will unmap the extra pages). + SetSize(source_size); + + return true; +#endif // !HAVE_MREMAP_SYSCALL +} + +MemMap* MemMap::MapFileAtAddress(uint8_t* expected_ptr, + size_t byte_count, + int prot, + int flags, + int fd, + off_t start, + bool low_4gb, + bool reuse, + const char* filename, + std::string* error_msg) { + CHECK_NE(0, prot); + CHECK_NE(0, flags & (MAP_SHARED | MAP_PRIVATE)); + + // Note that we do not allow MAP_FIXED unless reuse == true, i.e we + // expect his mapping to be contained within an existing map. + if (reuse) { + // reuse means it is okay that it overlaps an existing page mapping. + // Only use this if you actually made the page reservation yourself. + CHECK(expected_ptr != nullptr); + DCHECK(error_msg != nullptr); + DCHECK(ContainedWithinExistingMap(expected_ptr, byte_count, error_msg)) + << ((error_msg != nullptr) ? *error_msg : std::string()); + flags |= MAP_FIXED; + } else { + CHECK_EQ(0, flags & MAP_FIXED); + // Don't bother checking for an overlapping region here. We'll + // check this if required after the fact inside CheckMapRequest. + } + + if (byte_count == 0) { + return new MemMap(filename, nullptr, 0, nullptr, 0, prot, false); + } + // Adjust 'offset' to be page-aligned as required by mmap. + int page_offset = start % kPageSize; + off_t page_aligned_offset = start - page_offset; + // Adjust 'byte_count' to be page-aligned as we will map this anyway. + size_t page_aligned_byte_count = RoundUp(byte_count + page_offset, kPageSize); + // The 'expected_ptr' is modified (if specified, ie non-null) to be page aligned to the file but + // not necessarily to virtual memory. mmap will page align 'expected' for us. + uint8_t* page_aligned_expected = + (expected_ptr == nullptr) ? nullptr : (expected_ptr - page_offset); + + size_t redzone_size = 0; + if (RUNNING_ON_MEMORY_TOOL && kMemoryToolAddsRedzones && expected_ptr == nullptr) { + redzone_size = kPageSize; + page_aligned_byte_count += redzone_size; + } + + uint8_t* actual = reinterpret_cast<uint8_t*>(MapInternal(page_aligned_expected, + page_aligned_byte_count, + prot, + flags, + fd, + page_aligned_offset, + low_4gb)); + if (actual == MAP_FAILED) { + if (error_msg != nullptr) { + auto saved_errno = errno; + + if (kIsDebugBuild || VLOG_IS_ON(oat)) { + PrintFileToLog("/proc/self/maps", LogSeverity::WARNING); + } + + *error_msg = StringPrintf("mmap(%p, %zd, 0x%x, 0x%x, %d, %" PRId64 + ") of file '%s' failed: %s. See process maps in the log.", + page_aligned_expected, page_aligned_byte_count, prot, flags, fd, + static_cast<int64_t>(page_aligned_offset), filename, + strerror(saved_errno)); + } + return nullptr; + } + if (!CheckMapRequest(expected_ptr, actual, page_aligned_byte_count, error_msg)) { + return nullptr; + } + if (redzone_size != 0) { + const uint8_t *real_start = actual + page_offset; + const uint8_t *real_end = actual + page_offset + byte_count; + const uint8_t *mapping_end = actual + page_aligned_byte_count; + + MEMORY_TOOL_MAKE_NOACCESS(actual, real_start - actual); + MEMORY_TOOL_MAKE_NOACCESS(real_end, mapping_end - real_end); + page_aligned_byte_count -= redzone_size; + } + + return new MemMap(filename, actual + page_offset, byte_count, actual, page_aligned_byte_count, + prot, reuse, redzone_size); +} + +MemMap::~MemMap() { + if (base_begin_ == nullptr && base_size_ == 0) { + return; + } + + // Unlike Valgrind, AddressSanitizer requires that all manually poisoned memory is unpoisoned + // before it is returned to the system. + if (redzone_size_ != 0) { + MEMORY_TOOL_MAKE_UNDEFINED( + reinterpret_cast<char*>(base_begin_) + base_size_ - redzone_size_, + redzone_size_); + } + + if (!reuse_) { + MEMORY_TOOL_MAKE_UNDEFINED(base_begin_, base_size_); + if (!already_unmapped_) { + int result = munmap(base_begin_, base_size_); + if (result == -1) { + PLOG(FATAL) << "munmap failed"; + } + } + } + + // Remove it from gMaps. + std::lock_guard<std::mutex> mu(*mem_maps_lock_); + bool found = false; + DCHECK(gMaps != nullptr); + for (auto it = gMaps->lower_bound(base_begin_), end = gMaps->end(); + it != end && it->first == base_begin_; ++it) { + if (it->second == this) { + found = true; + gMaps->erase(it); + break; + } + } + CHECK(found) << "MemMap not found"; +} + +MemMap::MemMap(const std::string& name, uint8_t* begin, size_t size, void* base_begin, + size_t base_size, int prot, bool reuse, size_t redzone_size) + : name_(name), begin_(begin), size_(size), base_begin_(base_begin), base_size_(base_size), + prot_(prot), reuse_(reuse), already_unmapped_(false), redzone_size_(redzone_size) { + if (size_ == 0) { + CHECK(begin_ == nullptr); + CHECK(base_begin_ == nullptr); + CHECK_EQ(base_size_, 0U); + } else { + CHECK(begin_ != nullptr); + CHECK(base_begin_ != nullptr); + CHECK_NE(base_size_, 0U); + + // Add it to gMaps. + std::lock_guard<std::mutex> mu(*mem_maps_lock_); + DCHECK(gMaps != nullptr); + gMaps->insert(std::make_pair(base_begin_, this)); + } +} + +MemMap* MemMap::RemapAtEnd(uint8_t* new_end, const char* tail_name, int tail_prot, + std::string* error_msg, bool use_ashmem) { + use_ashmem = use_ashmem && !kIsTargetLinux; + DCHECK_GE(new_end, Begin()); + DCHECK_LE(new_end, End()); + DCHECK_LE(begin_ + size_, reinterpret_cast<uint8_t*>(base_begin_) + base_size_); + DCHECK_ALIGNED(begin_, kPageSize); + DCHECK_ALIGNED(base_begin_, kPageSize); + DCHECK_ALIGNED(reinterpret_cast<uint8_t*>(base_begin_) + base_size_, kPageSize); + DCHECK_ALIGNED(new_end, kPageSize); + uint8_t* old_end = begin_ + size_; + uint8_t* old_base_end = reinterpret_cast<uint8_t*>(base_begin_) + base_size_; + uint8_t* new_base_end = new_end; + DCHECK_LE(new_base_end, old_base_end); + if (new_base_end == old_base_end) { + return new MemMap(tail_name, nullptr, 0, nullptr, 0, tail_prot, false); + } + size_ = new_end - reinterpret_cast<uint8_t*>(begin_); + base_size_ = new_base_end - reinterpret_cast<uint8_t*>(base_begin_); + DCHECK_LE(begin_ + size_, reinterpret_cast<uint8_t*>(base_begin_) + base_size_); + size_t tail_size = old_end - new_end; + uint8_t* tail_base_begin = new_base_end; + size_t tail_base_size = old_base_end - new_base_end; + DCHECK_EQ(tail_base_begin + tail_base_size, old_base_end); + DCHECK_ALIGNED(tail_base_size, kPageSize); + + unique_fd fd; + int flags = MAP_PRIVATE | MAP_ANONYMOUS; + if (use_ashmem) { + // android_os_Debug.cpp read_mapinfo assumes all ashmem regions associated with the VM are + // prefixed "dalvik-". + std::string debug_friendly_name("dalvik-"); + debug_friendly_name += tail_name; + fd.reset(ashmem_create_region(debug_friendly_name.c_str(), tail_base_size)); + flags = MAP_PRIVATE | MAP_FIXED; + if (fd.get() == -1) { + *error_msg = StringPrintf("ashmem_create_region failed for '%s': %s", + tail_name, strerror(errno)); + return nullptr; + } + } + + MEMORY_TOOL_MAKE_UNDEFINED(tail_base_begin, tail_base_size); + // Unmap/map the tail region. + int result = munmap(tail_base_begin, tail_base_size); + if (result == -1) { + PrintFileToLog("/proc/self/maps", LogSeverity::WARNING); + *error_msg = StringPrintf("munmap(%p, %zd) failed for '%s'. See process maps in the log.", + tail_base_begin, tail_base_size, name_.c_str()); + return nullptr; + } + // Don't cause memory allocation between the munmap and the mmap + // calls. Otherwise, libc (or something else) might take this memory + // region. Note this isn't perfect as there's no way to prevent + // other threads to try to take this memory region here. + uint8_t* actual = reinterpret_cast<uint8_t*>(mmap(tail_base_begin, + tail_base_size, + tail_prot, + flags, + fd.get(), + 0)); + if (actual == MAP_FAILED) { + PrintFileToLog("/proc/self/maps", LogSeverity::WARNING); + *error_msg = StringPrintf("anonymous mmap(%p, %zd, 0x%x, 0x%x, %d, 0) failed. See process " + "maps in the log.", tail_base_begin, tail_base_size, tail_prot, flags, + fd.get()); + return nullptr; + } + return new MemMap(tail_name, actual, tail_size, actual, tail_base_size, tail_prot, false); +} + +void MemMap::MadviseDontNeedAndZero() { + if (base_begin_ != nullptr || base_size_ != 0) { + if (!kMadviseZeroes) { + memset(base_begin_, 0, base_size_); + } + int result = madvise(base_begin_, base_size_, MADV_DONTNEED); + if (result == -1) { + PLOG(WARNING) << "madvise failed"; + } + } +} + +bool MemMap::Sync() { + bool result; + if (redzone_size_ != 0) { + // To avoid valgrind errors, temporarily lift the lower-end noaccess protection before passing + // it to msync() as it only accepts page-aligned base address, and exclude the higher-end + // noaccess protection from the msync range. b/27552451. + uint8_t* base_begin = reinterpret_cast<uint8_t*>(base_begin_); + MEMORY_TOOL_MAKE_DEFINED(base_begin, begin_ - base_begin); + result = msync(BaseBegin(), End() - base_begin, MS_SYNC) == 0; + MEMORY_TOOL_MAKE_NOACCESS(base_begin, begin_ - base_begin); + } else { + result = msync(BaseBegin(), BaseSize(), MS_SYNC) == 0; + } + return result; +} + +bool MemMap::Protect(int prot) { + if (base_begin_ == nullptr && base_size_ == 0) { + prot_ = prot; + return true; + } + + if (mprotect(base_begin_, base_size_, prot) == 0) { + prot_ = prot; + return true; + } + + PLOG(ERROR) << "mprotect(" << reinterpret_cast<void*>(base_begin_) << ", " << base_size_ << ", " + << prot << ") failed"; + return false; +} + +bool MemMap::CheckNoGaps(MemMap* begin_map, MemMap* end_map) { + std::lock_guard<std::mutex> mu(*mem_maps_lock_); + CHECK(begin_map != nullptr); + CHECK(end_map != nullptr); + CHECK(HasMemMap(begin_map)); + CHECK(HasMemMap(end_map)); + CHECK_LE(begin_map->BaseBegin(), end_map->BaseBegin()); + MemMap* map = begin_map; + while (map->BaseBegin() != end_map->BaseBegin()) { + MemMap* next_map = GetLargestMemMapAt(map->BaseEnd()); + if (next_map == nullptr) { + // Found a gap. + return false; + } + map = next_map; + } + return true; +} + +void MemMap::DumpMaps(std::ostream& os, bool terse) { + std::lock_guard<std::mutex> mu(*mem_maps_lock_); + DumpMapsLocked(os, terse); +} + +void MemMap::DumpMapsLocked(std::ostream& os, bool terse) { + const auto& mem_maps = *gMaps; + if (!terse) { + os << mem_maps; + return; + } + + // Terse output example: + // [MemMap: 0x409be000+0x20P~0x11dP+0x20P~0x61cP+0x20P prot=0x3 LinearAlloc] + // [MemMap: 0x451d6000+0x6bP(3) prot=0x3 large object space allocation] + // The details: + // "+0x20P" means 0x20 pages taken by a single mapping, + // "~0x11dP" means a gap of 0x11d pages, + // "+0x6bP(3)" means 3 mappings one after another, together taking 0x6b pages. + os << "MemMap:" << std::endl; + for (auto it = mem_maps.begin(), maps_end = mem_maps.end(); it != maps_end;) { + MemMap* map = it->second; + void* base = it->first; + CHECK_EQ(base, map->BaseBegin()); + os << "[MemMap: " << base; + ++it; + // Merge consecutive maps with the same protect flags and name. + constexpr size_t kMaxGaps = 9; + size_t num_gaps = 0; + size_t num = 1u; + size_t size = map->BaseSize(); + CHECK_ALIGNED(size, kPageSize); + void* end = map->BaseEnd(); + while (it != maps_end && + it->second->GetProtect() == map->GetProtect() && + it->second->GetName() == map->GetName() && + (it->second->BaseBegin() == end || num_gaps < kMaxGaps)) { + if (it->second->BaseBegin() != end) { + ++num_gaps; + os << "+0x" << std::hex << (size / kPageSize) << "P"; + if (num != 1u) { + os << "(" << std::dec << num << ")"; + } + size_t gap = + reinterpret_cast<uintptr_t>(it->second->BaseBegin()) - reinterpret_cast<uintptr_t>(end); + CHECK_ALIGNED(gap, kPageSize); + os << "~0x" << std::hex << (gap / kPageSize) << "P"; + num = 0u; + size = 0u; + } + CHECK_ALIGNED(it->second->BaseSize(), kPageSize); + ++num; + size += it->second->BaseSize(); + end = it->second->BaseEnd(); + ++it; + } + os << "+0x" << std::hex << (size / kPageSize) << "P"; + if (num != 1u) { + os << "(" << std::dec << num << ")"; + } + os << " prot=0x" << std::hex << map->GetProtect() << " " << map->GetName() << "]" << std::endl; + } +} + +bool MemMap::HasMemMap(MemMap* map) { + void* base_begin = map->BaseBegin(); + for (auto it = gMaps->lower_bound(base_begin), end = gMaps->end(); + it != end && it->first == base_begin; ++it) { + if (it->second == map) { + return true; + } + } + return false; +} + +MemMap* MemMap::GetLargestMemMapAt(void* address) { + size_t largest_size = 0; + MemMap* largest_map = nullptr; + DCHECK(gMaps != nullptr); + for (auto it = gMaps->lower_bound(address), end = gMaps->end(); + it != end && it->first == address; ++it) { + MemMap* map = it->second; + CHECK(map != nullptr); + if (largest_size < map->BaseSize()) { + largest_size = map->BaseSize(); + largest_map = map; + } + } + return largest_map; +} + +void MemMap::Init() { + if (mem_maps_lock_ != nullptr) { + // dex2oat calls MemMap::Init twice since its needed before the runtime is created. + return; + } + mem_maps_lock_ = new std::mutex(); + // Not for thread safety, but for the annotation that gMaps is GUARDED_BY(mem_maps_lock_). + std::lock_guard<std::mutex> mu(*mem_maps_lock_); + DCHECK(gMaps == nullptr); + gMaps = new Maps; +} + +void MemMap::Shutdown() { + if (mem_maps_lock_ == nullptr) { + // If MemMap::Shutdown is called more than once, there is no effect. + return; + } + { + // Not for thread safety, but for the annotation that gMaps is GUARDED_BY(mem_maps_lock_). + std::lock_guard<std::mutex> mu(*mem_maps_lock_); + DCHECK(gMaps != nullptr); + delete gMaps; + gMaps = nullptr; + } + delete mem_maps_lock_; + mem_maps_lock_ = nullptr; +} + +void MemMap::SetSize(size_t new_size) { + CHECK_LE(new_size, size_); + size_t new_base_size = RoundUp(new_size + static_cast<size_t>(PointerDiff(Begin(), BaseBegin())), + kPageSize); + if (new_base_size == base_size_) { + size_ = new_size; + return; + } + CHECK_LT(new_base_size, base_size_); + MEMORY_TOOL_MAKE_UNDEFINED( + reinterpret_cast<void*>(reinterpret_cast<uintptr_t>(BaseBegin()) + + new_base_size), + base_size_ - new_base_size); + CHECK_EQ(munmap(reinterpret_cast<void*>(reinterpret_cast<uintptr_t>(BaseBegin()) + new_base_size), + base_size_ - new_base_size), 0) << new_base_size << " " << base_size_; + base_size_ = new_base_size; + size_ = new_size; +} + +void* MemMap::MapInternalArtLow4GBAllocator(size_t length, + int prot, + int flags, + int fd, + off_t offset) { +#if USE_ART_LOW_4G_ALLOCATOR + void* actual = MAP_FAILED; + + bool first_run = true; + + std::lock_guard<std::mutex> mu(*mem_maps_lock_); + for (uintptr_t ptr = next_mem_pos_; ptr < 4 * GB; ptr += kPageSize) { + // Use gMaps as an optimization to skip over large maps. + // Find the first map which is address > ptr. + auto it = gMaps->upper_bound(reinterpret_cast<void*>(ptr)); + if (it != gMaps->begin()) { + auto before_it = it; + --before_it; + // Start at the end of the map before the upper bound. + ptr = std::max(ptr, reinterpret_cast<uintptr_t>(before_it->second->BaseEnd())); + CHECK_ALIGNED(ptr, kPageSize); + } + while (it != gMaps->end()) { + // How much space do we have until the next map? + size_t delta = reinterpret_cast<uintptr_t>(it->first) - ptr; + // If the space may be sufficient, break out of the loop. + if (delta >= length) { + break; + } + // Otherwise, skip to the end of the map. + ptr = reinterpret_cast<uintptr_t>(it->second->BaseEnd()); + CHECK_ALIGNED(ptr, kPageSize); + ++it; + } + + // Try to see if we get lucky with this address since none of the ART maps overlap. + actual = TryMemMapLow4GB(reinterpret_cast<void*>(ptr), length, prot, flags, fd, offset); + if (actual != MAP_FAILED) { + next_mem_pos_ = reinterpret_cast<uintptr_t>(actual) + length; + return actual; + } + + if (4U * GB - ptr < length) { + // Not enough memory until 4GB. + if (first_run) { + // Try another time from the bottom; + ptr = LOW_MEM_START - kPageSize; + first_run = false; + continue; + } else { + // Second try failed. + break; + } + } + + uintptr_t tail_ptr; + + // Check pages are free. + bool safe = true; + for (tail_ptr = ptr; tail_ptr < ptr + length; tail_ptr += kPageSize) { + if (msync(reinterpret_cast<void*>(tail_ptr), kPageSize, 0) == 0) { + safe = false; + break; + } else { + DCHECK_EQ(errno, ENOMEM); + } + } + + next_mem_pos_ = tail_ptr; // update early, as we break out when we found and mapped a region + + if (safe == true) { + actual = TryMemMapLow4GB(reinterpret_cast<void*>(ptr), length, prot, flags, fd, offset); + if (actual != MAP_FAILED) { + return actual; + } + } else { + // Skip over last page. + ptr = tail_ptr; + } + } + + if (actual == MAP_FAILED) { + LOG(ERROR) << "Could not find contiguous low-memory space."; + errno = ENOMEM; + } + return actual; +#else + UNUSED(length, prot, flags, fd, offset); + LOG(FATAL) << "Unreachable"; + UNREACHABLE(); +#endif +} + +void* MemMap::MapInternal(void* addr, + size_t length, + int prot, + int flags, + int fd, + off_t offset, + bool low_4gb) { +#ifdef __LP64__ + // When requesting low_4g memory and having an expectation, the requested range should fit into + // 4GB. + if (low_4gb && ( + // Start out of bounds. + (reinterpret_cast<uintptr_t>(addr) >> 32) != 0 || + // End out of bounds. For simplicity, this will fail for the last page of memory. + ((reinterpret_cast<uintptr_t>(addr) + length) >> 32) != 0)) { + LOG(ERROR) << "The requested address space (" << addr << ", " + << reinterpret_cast<void*>(reinterpret_cast<uintptr_t>(addr) + length) + << ") cannot fit in low_4gb"; + return MAP_FAILED; + } +#else + UNUSED(low_4gb); +#endif + DCHECK_ALIGNED(length, kPageSize); + // TODO: + // A page allocator would be a useful abstraction here, as + // 1) It is doubtful that MAP_32BIT on x86_64 is doing the right job for us + void* actual = MAP_FAILED; +#if USE_ART_LOW_4G_ALLOCATOR + // MAP_32BIT only available on x86_64. + if (low_4gb && addr == nullptr) { + // The linear-scan allocator has an issue when executable pages are denied (e.g., by selinux + // policies in sensitive processes). In that case, the error code will still be ENOMEM. So + // the allocator will scan all low 4GB twice, and still fail. This is *very* slow. + // + // To avoid the issue, always map non-executable first, and mprotect if necessary. + const int orig_prot = prot; + const int prot_non_exec = prot & ~PROT_EXEC; + actual = MapInternalArtLow4GBAllocator(length, prot_non_exec, flags, fd, offset); + + if (actual == MAP_FAILED) { + return MAP_FAILED; + } + + // See if we need to remap with the executable bit now. + if (orig_prot != prot_non_exec) { + if (mprotect(actual, length, orig_prot) != 0) { + PLOG(ERROR) << "Could not protect to requested prot: " << orig_prot; + munmap(actual, length); + errno = ENOMEM; + return MAP_FAILED; + } + } + return actual; + } + + actual = mmap(addr, length, prot, flags, fd, offset); +#else +#if defined(__LP64__) + if (low_4gb && addr == nullptr) { + flags |= MAP_32BIT; + } +#endif + actual = mmap(addr, length, prot, flags, fd, offset); +#endif + return actual; +} + +std::ostream& operator<<(std::ostream& os, const MemMap& mem_map) { + os << StringPrintf("[MemMap: %p-%p prot=0x%x %s]", + mem_map.BaseBegin(), mem_map.BaseEnd(), mem_map.GetProtect(), + mem_map.GetName().c_str()); + return os; +} + +void MemMap::TryReadable() { + if (base_begin_ == nullptr && base_size_ == 0) { + return; + } + CHECK_NE(prot_ & PROT_READ, 0); + volatile uint8_t* begin = reinterpret_cast<volatile uint8_t*>(base_begin_); + volatile uint8_t* end = begin + base_size_; + DCHECK(IsAligned<kPageSize>(begin)); + DCHECK(IsAligned<kPageSize>(end)); + // Read the first byte of each page. Use volatile to prevent the compiler from optimizing away the + // reads. + for (volatile uint8_t* ptr = begin; ptr < end; ptr += kPageSize) { + // This read could fault if protection wasn't set correctly. + uint8_t value = *ptr; + UNUSED(value); + } +} + +void ZeroAndReleasePages(void* address, size_t length) { + if (length == 0) { + return; + } + uint8_t* const mem_begin = reinterpret_cast<uint8_t*>(address); + uint8_t* const mem_end = mem_begin + length; + uint8_t* const page_begin = AlignUp(mem_begin, kPageSize); + uint8_t* const page_end = AlignDown(mem_end, kPageSize); + if (!kMadviseZeroes || page_begin >= page_end) { + // No possible area to madvise. + std::fill(mem_begin, mem_end, 0); + } else { + // Spans one or more pages. + DCHECK_LE(mem_begin, page_begin); + DCHECK_LE(page_begin, page_end); + DCHECK_LE(page_end, mem_end); + std::fill(mem_begin, page_begin, 0); + CHECK_NE(madvise(page_begin, page_end - page_begin, MADV_DONTNEED), -1) << "madvise failed"; + std::fill(page_end, mem_end, 0); + } +} + +void MemMap::AlignBy(size_t size) { + CHECK_EQ(begin_, base_begin_) << "Unsupported"; + CHECK_EQ(size_, base_size_) << "Unsupported"; + CHECK_GT(size, static_cast<size_t>(kPageSize)); + CHECK_ALIGNED(size, kPageSize); + if (IsAlignedParam(reinterpret_cast<uintptr_t>(base_begin_), size) && + IsAlignedParam(base_size_, size)) { + // Already aligned. + return; + } + uint8_t* base_begin = reinterpret_cast<uint8_t*>(base_begin_); + uint8_t* base_end = base_begin + base_size_; + uint8_t* aligned_base_begin = AlignUp(base_begin, size); + uint8_t* aligned_base_end = AlignDown(base_end, size); + CHECK_LE(base_begin, aligned_base_begin); + CHECK_LE(aligned_base_end, base_end); + size_t aligned_base_size = aligned_base_end - aligned_base_begin; + CHECK_LT(aligned_base_begin, aligned_base_end) + << "base_begin = " << reinterpret_cast<void*>(base_begin) + << " base_end = " << reinterpret_cast<void*>(base_end); + CHECK_GE(aligned_base_size, size); + // Unmap the unaligned parts. + if (base_begin < aligned_base_begin) { + MEMORY_TOOL_MAKE_UNDEFINED(base_begin, aligned_base_begin - base_begin); + CHECK_EQ(munmap(base_begin, aligned_base_begin - base_begin), 0) + << "base_begin=" << reinterpret_cast<void*>(base_begin) + << " aligned_base_begin=" << reinterpret_cast<void*>(aligned_base_begin); + } + if (aligned_base_end < base_end) { + MEMORY_TOOL_MAKE_UNDEFINED(aligned_base_end, base_end - aligned_base_end); + CHECK_EQ(munmap(aligned_base_end, base_end - aligned_base_end), 0) + << "base_end=" << reinterpret_cast<void*>(base_end) + << " aligned_base_end=" << reinterpret_cast<void*>(aligned_base_end); + } + std::lock_guard<std::mutex> mu(*mem_maps_lock_); + base_begin_ = aligned_base_begin; + base_size_ = aligned_base_size; + begin_ = aligned_base_begin; + size_ = aligned_base_size; + DCHECK(gMaps != nullptr); + if (base_begin < aligned_base_begin) { + auto it = gMaps->find(base_begin); + CHECK(it != gMaps->end()) << "MemMap not found"; + gMaps->erase(it); + gMaps->insert(std::make_pair(base_begin_, this)); + } +} + +} // namespace art |