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* Copyright (C) 2011 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
* Unless required by applicable law or agreed to in writing, software
* distributed under the License is distributed on an "AS IS" BASIS,
* See the License for the specific language governing permissions and
* limitations under the License.
#include <stdint.h>
#include "base/memory_tool.h"
#include <cstddef>
#include <memory>
#include <ostream>
#include <set>
#include <stack>
#include <string>
#include "art_method.h"
#include "base/bit_utils.h"
#include "base/dchecked_vector.h"
#include "base/enums.h"
#include "base/length_prefixed_array.h"
#include "base/macros.h"
#include "base/os.h"
#include "base/safe_map.h"
#include "base/utils.h"
#include "class_table.h"
#include "driver/compiler_driver.h"
#include "image.h"
#include "intern_table.h"
#include "lock_word.h"
#include "mem_map.h"
#include "mirror/dex_cache.h"
#include "oat_file.h"
#include "obj_ptr.h"
namespace art {
namespace gc {
namespace accounting {
template <size_t kAlignment> class SpaceBitmap;
typedef SpaceBitmap<kObjectAlignment> ContinuousSpaceBitmap;
} // namespace accounting
namespace space {
class ImageSpace;
} // namespace space
} // namespace gc
namespace mirror {
class ClassLoader;
} // namespace mirror
class ClassLoaderVisitor;
class ImTable;
class ImtConflictTable;
static constexpr int kInvalidFd = -1;
namespace linker {
// Write a Space built during compilation for use during execution.
class ImageWriter FINAL {
ImageWriter(const CompilerDriver& compiler_driver,
uintptr_t image_begin,
bool compile_pic,
bool compile_app_image,
ImageHeader::StorageMode image_storage_mode,
const std::vector<const char*>& oat_filenames,
const std::unordered_map<const DexFile*, size_t>& dex_file_oat_index_map,
const std::unordered_set<std::string>* dirty_image_objects);
bool PrepareImageAddressSpace();
bool IsImageAddressSpaceReady() const {
for (const ImageInfo& image_info : image_infos_) {
if (image_info.image_roots_address_ == 0u) {
return false;
return true;
ObjPtr<mirror::ClassLoader> GetClassLoader() {
CHECK_EQ(class_loaders_.size(), compile_app_image_ ? 1u : 0u);
return compile_app_image_ ? *class_loaders_.begin() : nullptr;
template <typename T>
T* GetImageAddress(T* object) const REQUIRES_SHARED(Locks::mutator_lock_) {
if (object == nullptr || IsInBootImage(object)) {
return object;
} else {
size_t oat_index = GetOatIndex(object);
const ImageInfo& image_info = GetImageInfo(oat_index);
return reinterpret_cast<T*>(image_info.image_begin_ + GetImageOffset(object));
ArtMethod* GetImageMethodAddress(ArtMethod* method) REQUIRES_SHARED(Locks::mutator_lock_);
size_t GetOatFileOffset(size_t oat_index) const {
return GetImageInfo(oat_index).oat_offset_;
const uint8_t* GetOatFileBegin(size_t oat_index) const {
return GetImageInfo(oat_index).oat_file_begin_;
// If image_fd is not kInvalidFd, then we use that for the image file. Otherwise we open
// the names in image_filenames.
// If oat_fd is not kInvalidFd, then we use that for the oat file. Otherwise we open
// the names in oat_filenames.
bool Write(int image_fd,
const std::vector<const char*>& image_filenames,
const std::vector<const char*>& oat_filenames)
uintptr_t GetOatDataBegin(size_t oat_index) {
return reinterpret_cast<uintptr_t>(GetImageInfo(oat_index).oat_data_begin_);
// Get the index of the oat file containing the dex file.
// This "oat_index" is used to retrieve information about the the memory layout
// of the oat file and its associated image file, needed for link-time patching
// of references to the image or across oat files.
size_t GetOatIndexForDexFile(const DexFile* dex_file) const;
// Get the index of the oat file containing the dex file served by the dex cache.
size_t GetOatIndexForDexCache(ObjPtr<mirror::DexCache> dex_cache) const
// Update the oat layout for the given oat file.
// This will make the oat_offset for the next oat file valid.
void UpdateOatFileLayout(size_t oat_index,
size_t oat_loaded_size,
size_t oat_data_offset,
size_t oat_data_size);
// Update information about the oat header, i.e. checksum and trampoline offsets.
void UpdateOatFileHeader(size_t oat_index, const OatHeader& oat_header);
using WorkStack = std::stack<std::pair<mirror::Object*, size_t>>;
bool AllocMemory();
// Mark the objects defined in this space in the given live bitmap.
void RecordImageAllocations() REQUIRES_SHARED(Locks::mutator_lock_);
// Classify different kinds of bins that objects end up getting packed into during image writing.
// Ordered from dirtiest to cleanest (until ArtMethods).
enum class Bin {
kKnownDirty, // Known dirty objects from --dirty-image-objects list
kMiscDirty, // Dex caches, object locks, etc...
kClassVerified, // Class verified, but initializers haven't been run
// Unknown mix of clean/dirty:
kClassInitialized, // Class initializers have been run
// All classes get their own bins since their fields often dirty
kClassInitializedFinalStatics, // Class initializers have been run, no non-final statics
// Likely-clean:
kString, // [String] Almost always immutable (except for obj header).
// Add more bins here if we add more segregation code.
// Non mirror fields must be below.
// ArtFields should be always clean.
// If the class is initialized, then the ArtMethods are probably clean.
// ArtMethods may be dirty if the class has native methods or a declaring class that isn't
// initialized.
// IMT (clean)
// Conflict tables (clean).
// Runtime methods (always clean, do not have a length prefix array).
// Dex cache arrays have a special slot for PC-relative addressing. Since they are
// huge, and as such their dirtiness is not important for the clean/dirty separation,
// we arbitrarily keep them at the end of the native data.
kDexCacheArray, // Arrays belonging to dex cache.
kLast = kDexCacheArray,
// Number of bins which are for mirror objects.
kMirrorCount = kArtField,
friend std::ostream& operator<<(std::ostream& stream, const Bin& bin);
enum class NativeObjectRelocationType {
friend std::ostream& operator<<(std::ostream& stream, const NativeObjectRelocationType& type);
enum class StubType {
kLast = kQuickToInterpreterBridge,
friend std::ostream& operator<<(std::ostream& stream, const StubType& stub_type);
static constexpr size_t kBinBits =
MinimumBitsToStore<uint32_t>(static_cast<size_t>(Bin::kMirrorCount) - 1);
// uint32 = typeof(lockword_)
// Subtract read barrier bits since we want these to remain 0, or else it may result in DCHECK
// failures due to invalid read barrier bits during object field reads.
static const size_t kBinShift = BitSizeOf<uint32_t>() - kBinBits - LockWord::kGCStateSize;
// 111000.....0
static const size_t kBinMask = ((static_cast<size_t>(1) << kBinBits) - 1) << kBinShift;
// Number of bins, including non-mirror bins.
static constexpr size_t kNumberOfBins = static_cast<size_t>(Bin::kLast) + 1u;
// Number of stub types.
static constexpr size_t kNumberOfStubTypes = static_cast<size_t>(StubType::kLast) + 1u;
// We use the lock word to store the bin # and bin index of the object in the image.
// The struct size must be exactly sizeof(LockWord), currently 32-bits, since this will end up
// stored in the lock word bit-for-bit when object forwarding addresses are being calculated.
struct BinSlot {
explicit BinSlot(uint32_t lockword);
BinSlot(Bin bin, uint32_t index);
// The bin an object belongs to, i.e. regular, class/verified, class/initialized, etc.
Bin GetBin() const;
// The offset in bytes from the beginning of the bin. Aligned to object size.
uint32_t GetIndex() const;
// Pack into a single uint32_t, for storing into a lock word.
uint32_t Uint32Value() const { return lockword_; }
// Comparison operator for map support
bool operator<(const BinSlot& other) const { return lockword_ < other.lockword_; }
// Must be the same size as LockWord, any larger and we would truncate the data.
const uint32_t lockword_;
struct ImageInfo {
ImageInfo(ImageInfo&&) = default;
// Create the image sections into the out sections variable, returns the size of the image
// excluding the bitmap.
size_t CreateImageSections(ImageSection* out_sections, bool app_image) const;
size_t GetStubOffset(StubType stub_type) const {
DCHECK_LT(static_cast<size_t>(stub_type), kNumberOfStubTypes);
return stub_offsets_[static_cast<size_t>(stub_type)];
void SetStubOffset(StubType stub_type, size_t offset) {
DCHECK_LT(static_cast<size_t>(stub_type), kNumberOfStubTypes);
stub_offsets_[static_cast<size_t>(stub_type)] = offset;
size_t GetBinSlotOffset(Bin bin) const {
DCHECK_LT(static_cast<size_t>(bin), kNumberOfBins);
return bin_slot_offsets_[static_cast<size_t>(bin)];
void IncrementBinSlotSize(Bin bin, size_t size_to_add) {
DCHECK_LT(static_cast<size_t>(bin), kNumberOfBins);
bin_slot_sizes_[static_cast<size_t>(bin)] += size_to_add;
size_t GetBinSlotSize(Bin bin) const {
DCHECK_LT(static_cast<size_t>(bin), kNumberOfBins);
return bin_slot_sizes_[static_cast<size_t>(bin)];
void IncrementBinSlotCount(Bin bin, size_t count_to_add) {
DCHECK_LT(static_cast<size_t>(bin), kNumberOfBins);
bin_slot_count_[static_cast<size_t>(bin)] += count_to_add;
// Calculate the sum total of the bin slot sizes in [0, up_to). Defaults to all bins.
size_t GetBinSizeSum(Bin up_to) const;
std::unique_ptr<MemMap> image_; // Memory mapped for generating the image.
// Target begin of this image. Notes: It is not valid to write here, this is the address
// of the target image, not necessarily where image_ is mapped. The address is only valid
// after layouting (otherwise null).
uint8_t* image_begin_ = nullptr;
// Offset to the free space in image_, initially size of image header.
size_t image_end_ = RoundUp(sizeof(ImageHeader), kObjectAlignment);
uint32_t image_roots_address_ = 0; // The image roots address in the image.
size_t image_offset_ = 0; // Offset of this image from the start of the first image.
// Image size is the *address space* covered by this image. As the live bitmap is aligned
// to the page size, the live bitmap will cover more address space than necessary. But live
// bitmaps may not overlap, so an image has a "shadow," which is accounted for in the size.
// The next image may only start at image_begin_ + image_size_ (which is guaranteed to be
// page-aligned).
size_t image_size_ = 0;
// Oat data.
// Offset of the oat file for this image from start of oat files. This is
// valid when the previous oat file has been written.
size_t oat_offset_ = 0;
// Layout of the loaded ELF file containing the oat file, valid after UpdateOatFileLayout().
const uint8_t* oat_file_begin_ = nullptr;
size_t oat_loaded_size_ = 0;
const uint8_t* oat_data_begin_ = nullptr;
size_t oat_size_ = 0; // Size of the corresponding oat data.
// The oat header checksum, valid after UpdateOatFileHeader().
uint32_t oat_checksum_ = 0u;
// Image bitmap which lets us know where the objects inside of the image reside.
std::unique_ptr<gc::accounting::ContinuousSpaceBitmap> image_bitmap_;
// The start offsets of the dex cache arrays.
SafeMap<const DexFile*, size_t> dex_cache_array_starts_;
// Offset from oat_data_begin_ to the stubs.
uint32_t stub_offsets_[kNumberOfStubTypes] = {};
// Bin slot tracking for dirty object packing.
size_t bin_slot_sizes_[kNumberOfBins] = {}; // Number of bytes in a bin.
size_t bin_slot_offsets_[kNumberOfBins] = {}; // Number of bytes in previous bins.
size_t bin_slot_count_[kNumberOfBins] = {}; // Number of objects in a bin.
// Cached size of the intern table for when we allocate memory.
size_t intern_table_bytes_ = 0;
// Number of image class table bytes.
size_t class_table_bytes_ = 0;
// Number of object fixup bytes.
size_t object_fixup_bytes_ = 0;
// Number of pointer fixup bytes.
size_t pointer_fixup_bytes_ = 0;
// Intern table associated with this image for serialization.
std::unique_ptr<InternTable> intern_table_;
// Class table associated with this image for serialization.
std::unique_ptr<ClassTable> class_table_;
// We use the lock word to store the offset of the object in the image.
void AssignImageOffset(mirror::Object* object, BinSlot bin_slot)
void SetImageOffset(mirror::Object* object, size_t offset)
bool IsImageOffsetAssigned(mirror::Object* object) const
size_t GetImageOffset(mirror::Object* object) const REQUIRES_SHARED(Locks::mutator_lock_);
void UpdateImageOffset(mirror::Object* obj, uintptr_t offset)
void PrepareDexCacheArraySlots() REQUIRES_SHARED(Locks::mutator_lock_);
void AssignImageBinSlot(mirror::Object* object, size_t oat_index)
mirror::Object* TryAssignBinSlot(WorkStack& work_stack, mirror::Object* obj, size_t oat_index)
void SetImageBinSlot(mirror::Object* object, BinSlot bin_slot)
bool IsImageBinSlotAssigned(mirror::Object* object) const
BinSlot GetImageBinSlot(mirror::Object* object) const REQUIRES_SHARED(Locks::mutator_lock_);
void AddDexCacheArrayRelocation(void* array, size_t offset, ObjPtr<mirror::DexCache> dex_cache)
void AddMethodPointerArray(mirror::PointerArray* arr) REQUIRES_SHARED(Locks::mutator_lock_);
static void* GetImageAddressCallback(void* writer, mirror::Object* obj)
REQUIRES_SHARED(Locks::mutator_lock_) {
return reinterpret_cast<ImageWriter*>(writer)->GetImageAddress(obj);
mirror::Object* GetLocalAddress(mirror::Object* object) const
REQUIRES_SHARED(Locks::mutator_lock_) {
size_t offset = GetImageOffset(object);
size_t oat_index = GetOatIndex(object);
const ImageInfo& image_info = GetImageInfo(oat_index);
uint8_t* dst = image_info.image_->Begin() + offset;
return reinterpret_cast<mirror::Object*>(dst);
// Returns the address in the boot image if we are compiling the app image.
const uint8_t* GetOatAddress(StubType type) const;
const uint8_t* GetOatAddressForOffset(uint32_t offset, const ImageInfo& image_info) const {
// With Quick, code is within the OatFile, as there are all in one
// .o ELF object. But interpret it as signed.
DCHECK_LE(static_cast<int32_t>(offset), static_cast<int32_t>(image_info.oat_size_));
DCHECK(image_info.oat_data_begin_ != nullptr);
return offset == 0u ? nullptr : image_info.oat_data_begin_ + static_cast<int32_t>(offset);
// Returns true if the class was in the original requested image classes list.
bool KeepClass(ObjPtr<mirror::Class> klass) REQUIRES_SHARED(Locks::mutator_lock_);
// Debug aid that list of requested image classes.
void DumpImageClasses();
// Preinitializes some otherwise lazy fields (such as Class name) to avoid runtime image dirtying.
void ComputeLazyFieldsForImageClasses()
// Visit all class loaders.
void VisitClassLoaders(ClassLoaderVisitor* visitor) REQUIRES_SHARED(Locks::mutator_lock_);
// Remove unwanted classes from various roots.
void PruneNonImageClasses() REQUIRES_SHARED(Locks::mutator_lock_);
// Remove unwanted classes from the DexCache roots and preload deterministic DexCache contents.
void PruneAndPreloadDexCache(ObjPtr<mirror::DexCache> dex_cache,
ObjPtr<mirror::ClassLoader> class_loader)
// Verify unwanted classes removed.
void CheckNonImageClassesRemoved() REQUIRES_SHARED(Locks::mutator_lock_);
// Lays out where the image objects will be at runtime.
void CalculateNewObjectOffsets()
void ProcessWorkStack(WorkStack* work_stack)
void CreateHeader(size_t oat_index)
mirror::ObjectArray<mirror::Object>* CreateImageRoots(size_t oat_index) const
void CalculateObjectBinSlots(mirror::Object* obj)
void UnbinObjectsIntoOffset(mirror::Object* obj)
// Creates the contiguous image in memory and adjusts pointers.
void CopyAndFixupNativeData(size_t oat_index) REQUIRES_SHARED(Locks::mutator_lock_);
void CopyAndFixupObjects() REQUIRES_SHARED(Locks::mutator_lock_);
void CopyAndFixupObject(mirror::Object* obj) REQUIRES_SHARED(Locks::mutator_lock_);
void CopyAndFixupMethod(ArtMethod* orig, ArtMethod* copy, const ImageInfo& image_info)
void CopyAndFixupImTable(ImTable* orig, ImTable* copy) REQUIRES_SHARED(Locks::mutator_lock_);
void CopyAndFixupImtConflictTable(ImtConflictTable* orig, ImtConflictTable* copy)
void FixupClass(mirror::Class* orig, mirror::Class* copy)
void FixupObject(mirror::Object* orig, mirror::Object* copy)
void FixupDexCache(mirror::DexCache* orig_dex_cache, mirror::DexCache* copy_dex_cache)
void FixupPointerArray(mirror::Object* dst,
mirror::PointerArray* arr,
mirror::Class* klass,
Bin array_type)
// Get quick code for non-resolution/imt_conflict/abstract method.
const uint8_t* GetQuickCode(ArtMethod* method,
const ImageInfo& image_info,
bool* quick_is_interpreted)
// Return true if a method is likely to be dirtied at runtime.
bool WillMethodBeDirty(ArtMethod* m) const REQUIRES_SHARED(Locks::mutator_lock_);
// Assign the offset for an ArtMethod.
void AssignMethodOffset(ArtMethod* method,
NativeObjectRelocationType type,
size_t oat_index)
// Return true if imt was newly inserted.
bool TryAssignImTableOffset(ImTable* imt, size_t oat_index) REQUIRES_SHARED(Locks::mutator_lock_);
// Assign the offset for an IMT conflict table. Does nothing if the table already has a native
// relocation.
void TryAssignConflictTableOffset(ImtConflictTable* table, size_t oat_index)
// Return true if klass is loaded by the boot class loader but not in the boot image.
bool IsBootClassLoaderNonImageClass(mirror::Class* klass) REQUIRES_SHARED(Locks::mutator_lock_);
// Return true if klass depends on a boot class loader non image class. We want to prune these
// classes since we do not want any boot class loader classes in the image. This means that
// we also cannot have any classes which refer to these boot class loader non image classes.
// PruneAppImageClass also prunes if klass depends on a non-image class according to the compiler
// driver.
bool PruneAppImageClass(ObjPtr<mirror::Class> klass)
// early_exit is true if we had a cyclic dependency anywhere down the chain.
bool PruneAppImageClassInternal(ObjPtr<mirror::Class> klass,
bool* early_exit,
std::unordered_set<mirror::Object*>* visited)
bool IsMultiImage() const {
return image_infos_.size() > 1;
static Bin BinTypeForNativeRelocationType(NativeObjectRelocationType type);
uintptr_t NativeOffsetInImage(void* obj) REQUIRES_SHARED(Locks::mutator_lock_);
// Location of where the object will be when the image is loaded at runtime.
template <typename T>
T* NativeLocationInImage(T* obj) REQUIRES_SHARED(Locks::mutator_lock_);
// Location of where the temporary copy of the object currently is.
template <typename T>
T* NativeCopyLocation(T* obj, mirror::DexCache* dex_cache) REQUIRES_SHARED(Locks::mutator_lock_);
// Return true of obj is inside of the boot image space. This may only return true if we are
// compiling an app image.
bool IsInBootImage(const void* obj) const;
// Return true if ptr is within the boot oat file.
bool IsInBootOatFile(const void* ptr) const;
// Get the index of the oat file associated with the object.
size_t GetOatIndex(mirror::Object* object) const REQUIRES_SHARED(Locks::mutator_lock_);
// The oat index for shared data in multi-image and all data in single-image compilation.
size_t GetDefaultOatIndex() const {
return 0u;
ImageInfo& GetImageInfo(size_t oat_index) {
return image_infos_[oat_index];
const ImageInfo& GetImageInfo(size_t oat_index) const {
return image_infos_[oat_index];
// Find an already strong interned string in the other images or in the boot image. Used to
// remove duplicates in the multi image and app image case.
mirror::String* FindInternedString(mirror::String* string) REQUIRES_SHARED(Locks::mutator_lock_);
// Return true if there already exists a native allocation for an object.
bool NativeRelocationAssigned(void* ptr) const;
void CopyReference(mirror::HeapReference<mirror::Object>* dest, ObjPtr<mirror::Object> src)
void CopyReference(mirror::CompressedReference<mirror::Object>* dest, ObjPtr<mirror::Object> src)
void CopyAndFixupPointer(void** target, void* value);
const CompilerDriver& compiler_driver_;
// Beginning target image address for the first image.
uint8_t* global_image_begin_;
// Offset from image_begin_ to where the first object is in image_.
size_t image_objects_offset_begin_;
// Pointer arrays that need to be updated. Since these are only some int and long arrays, we need
// to keep track. These include vtable arrays, iftable arrays, and dex caches.
std::unordered_map<mirror::PointerArray*, Bin> pointer_arrays_;
// Saved hash codes. We use these to restore lockwords which were temporarily used to have
// forwarding addresses as well as copying over hash codes.
std::unordered_map<mirror::Object*, uint32_t> saved_hashcode_map_;
// Oat index map for objects.
std::unordered_map<mirror::Object*, uint32_t> oat_index_map_;
// Boolean flags.
const bool compile_pic_;
const bool compile_app_image_;
// Size of pointers on the target architecture.
PointerSize target_ptr_size_;
// Image data indexed by the oat file index.
dchecked_vector<ImageInfo> image_infos_;
// ArtField, ArtMethod relocating map. These are allocated as array of structs but we want to
// have one entry per art field for convenience. ArtFields are placed right after the end of the
// image objects (aka sum of bin_slot_sizes_). ArtMethods are placed right after the ArtFields.
struct NativeObjectRelocation {
size_t oat_index;
uintptr_t offset;
NativeObjectRelocationType type;
bool IsArtMethodRelocation() const {
return type == NativeObjectRelocationType::kArtMethodClean ||
type == NativeObjectRelocationType::kArtMethodDirty ||
type == NativeObjectRelocationType::kRuntimeMethod;
std::unordered_map<void*, NativeObjectRelocation> native_object_relocations_;
// Runtime ArtMethods which aren't reachable from any Class but need to be copied into the image.
ArtMethod* image_methods_[ImageHeader::kImageMethodsCount];
// Counters for measurements, used for logging only.
uint64_t dirty_methods_;
uint64_t clean_methods_;
// Prune class memoization table to speed up ContainsBootClassLoaderNonImageClass.
std::unordered_map<mirror::Class*, bool> prune_class_memo_;
// Class loaders with a class table to write out. There should only be one class loader because
// dex2oat loads the dex files to be compiled into a single class loader. For the boot image,
// null is a valid entry.
std::unordered_set<mirror::ClassLoader*> class_loaders_;
// Which mode the image is stored as, see image.h
const ImageHeader::StorageMode image_storage_mode_;
// The file names of oat files.
const std::vector<const char*>& oat_filenames_;
// Map of dex files to the indexes of oat files that they were compiled into.
const std::unordered_map<const DexFile*, size_t>& dex_file_oat_index_map_;
// Set of objects known to be dirty in the image. Can be nullptr if there are none.
const std::unordered_set<std::string>* dirty_image_objects_;
class ComputeLazyFieldsForClassesVisitor;
class FixupClassVisitor;
class FixupRootVisitor;
class FixupVisitor;
class GetRootsVisitor;
class ImageAddressVisitorForDexCacheArray;
class NativeLocationVisitor;
class PruneClassesVisitor;
class PruneClassLoaderClassesVisitor;
class RegisterBootClassPathClassesVisitor;
class VisitReferencesVisitor;
class PruneObjectReferenceVisitor;
} // namespace linker
} // namespace art