runtime/vdex_file.cc - LeafOS-Project/android_art - Gitiles

 /*
  * Copyright (C) 2016 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 "vdex_file.h"

 #include <sys/mman.h>  // For the PROT_* and MAP_* constants.
 #include <sys/stat.h>  // for mkdir()

 #include <memory>
 #include <unordered_set>

 #include <android-base/logging.h>
 #include <android-base/stringprintf.h>
 #include <log/log.h>

 #include "base/bit_utils.h"
 #include "base/leb128.h"
 #include "base/stl_util.h"
 #include "base/systrace.h"
 #include "base/unix_file/fd_file.h"
 #include "base/zip_archive.h"
 #include "class_linker.h"
 #include "class_loader_context.h"
 #include "dex/art_dex_file_loader.h"
 #include "dex/class_accessor-inl.h"
 #include "dex/dex_file_loader.h"
 #include "gc/heap.h"
 #include "gc/space/image_space.h"
 #include "mirror/class-inl.h"
 #include "handle_scope-inl.h"
 #include "runtime.h"
 #include "verifier/verifier_deps.h"

 namespace art HIDDEN {

 using android::base::StringPrintf;

 bool VdexFile::VdexFileHeader::IsMagicValid() const {
   return (memcmp(magic_, kVdexMagic, sizeof(kVdexMagic)) == 0);
 }

 bool VdexFile::VdexFileHeader::IsVdexVersionValid() const {
   return (memcmp(vdex_version_, kVdexVersion, sizeof(kVdexVersion)) == 0);
 }

 VdexFile::VdexFileHeader::VdexFileHeader([[maybe_unused]] bool has_dex_section)
     : number_of_sections_(static_cast<uint32_t>(VdexSection::kNumberOfSections)) {
   memcpy(magic_, kVdexMagic, sizeof(kVdexMagic));
   memcpy(vdex_version_, kVdexVersion, sizeof(kVdexVersion));
   DCHECK(IsMagicValid());
   DCHECK(IsVdexVersionValid());
 }

 std::unique_ptr<VdexFile> VdexFile::OpenAtAddress(uint8_t* mmap_addr,
                                                   size_t mmap_size,
                                                   bool mmap_reuse,
                                                   const std::string& vdex_filename,
                                                   bool writable,
                                                   bool low_4gb,
                                                   std::string* error_msg) {
   ScopedTrace trace(("VdexFile::OpenAtAddress " + vdex_filename).c_str());
   if (!OS::FileExists(vdex_filename.c_str())) {
     *error_msg = "File " + vdex_filename + " does not exist.";
     return nullptr;
   }

   std::unique_ptr<File> vdex_file;
   if (writable) {
     vdex_file.reset(OS::OpenFileReadWrite(vdex_filename.c_str()));
   } else {
     vdex_file.reset(OS::OpenFileForReading(vdex_filename.c_str()));
   }
   if (vdex_file == nullptr) {
     *error_msg = "Could not open file " + vdex_filename +
                  (writable ? " for read/write" : "for reading");
     return nullptr;
   }

   int64_t vdex_length = vdex_file->GetLength();
   if (vdex_length == -1) {
     *error_msg = "Could not read the length of file " + vdex_filename;
     return nullptr;
   }

   return OpenAtAddress(mmap_addr,
                        mmap_size,
                        mmap_reuse,
                        vdex_file->Fd(),
                        vdex_length,
                        vdex_filename,
                        writable,
                        low_4gb,
                        error_msg);
 }

 std::unique_ptr<VdexFile> VdexFile::OpenAtAddress(uint8_t* mmap_addr,
                                                   size_t mmap_size,
                                                   bool mmap_reuse,
                                                   int file_fd,
                                                   size_t vdex_length,
                                                   const std::string& vdex_filename,
                                                   bool writable,
                                                   bool low_4gb,
                                                   std::string* error_msg) {
   if (mmap_addr != nullptr && mmap_size < vdex_length) {
     *error_msg = StringPrintf("Insufficient pre-allocated space to mmap vdex: %zu and %zu",
                               mmap_size,
                               vdex_length);
     return nullptr;
   }
   CHECK_IMPLIES(mmap_reuse, mmap_addr != nullptr);
   // Start as PROT_WRITE so we can mprotect back to it if we want to.
   MemMap mmap = MemMap::MapFileAtAddress(
       mmap_addr,
       vdex_length,
       PROT_READ | PROT_WRITE,
       writable ? MAP_SHARED : MAP_PRIVATE,
       file_fd,
       /* start= */ 0u,
       low_4gb,
       vdex_filename.c_str(),
       mmap_reuse,
       /* reservation= */ nullptr,
       error_msg);
   if (!mmap.IsValid()) {
     *error_msg = "Failed to mmap file " + vdex_filename + " : " + *error_msg;
     return nullptr;
   }

   std::unique_ptr<VdexFile> vdex(new VdexFile(std::move(mmap)));
   if (!vdex->IsValid()) {
     *error_msg = "Vdex file is not valid";
     return nullptr;
   }

   return vdex;
 }

 std::unique_ptr<VdexFile> VdexFile::OpenFromDm(const std::string& filename,
                                                const ZipArchive& archive) {
   std::string error_msg;
   std::unique_ptr<ZipEntry> zip_entry(archive.Find(VdexFile::kVdexNameInDmFile, &error_msg));
   if (zip_entry == nullptr) {
     LOG(INFO) << "No " << VdexFile::kVdexNameInDmFile << " file in DexMetadata archive. "
               << "Not doing fast verification.";
     return nullptr;
   }
   MemMap input_file = zip_entry->MapDirectlyOrExtract(
       filename.c_str(),
       VdexFile::kVdexNameInDmFile,
       &error_msg,
       alignof(VdexFile));
   if (!input_file.IsValid()) {
     LOG(WARNING) << "Could not open vdex file in DexMetadata archive: " << error_msg;
     return nullptr;
   }
   std::unique_ptr<VdexFile> vdex_file = std::make_unique<VdexFile>(std::move(input_file));
   if (!vdex_file->IsValid()) {
     LOG(WARNING) << "The dex metadata .vdex is not valid. Ignoring it.";
     return nullptr;
   }
   if (vdex_file->HasDexSection()) {
     LOG(ERROR) << "The dex metadata is not allowed to contain dex files";
     android_errorWriteLog(0x534e4554, "178055795");  // Report to SafetyNet.
     return nullptr;
   }
   return vdex_file;
 }

 const uint8_t* VdexFile::GetNextDexFileData(const uint8_t* cursor, uint32_t dex_file_index) const {
   DCHECK(cursor == nullptr || (cursor > Begin() && cursor <= End()));
   if (cursor == nullptr) {
     // Beginning of the iteration, return the first dex file if there is one.
     return HasDexSection() ? DexBegin() : nullptr;
   } else if (dex_file_index >= GetNumberOfDexFiles()) {
     return nullptr;
   } else {
     // Fetch the next dex file. Return null if there is none.
     const uint8_t* data = cursor + reinterpret_cast<const DexFile::Header*>(cursor)->file_size_;
     // Dex files are required to be 4 byte aligned. the OatWriter makes sure they are, see
     // OatWriter::SeekToDexFiles.
     return AlignUp(data, 4);
   }
 }

 const uint8_t* VdexFile::GetNextTypeLookupTableData(const uint8_t* cursor,
                                                     uint32_t dex_file_index) const {
   if (cursor == nullptr) {
     // Beginning of the iteration, return the first dex file if there is one.
     return HasTypeLookupTableSection() ? TypeLookupTableDataBegin() : nullptr;
   } else if (dex_file_index >= GetNumberOfDexFiles()) {
     return nullptr;
   } else {
     const uint8_t* data = cursor + sizeof(uint32_t) + reinterpret_cast<const uint32_t*>(cursor)[0];
     // TypeLookupTables are required to be 4 byte aligned. the OatWriter makes sure they are.
     // We don't check this here to be defensive against corrupted vdex files.
     // Callers should check the returned value matches their expectations.
     return data;
   }
 }

 bool VdexFile::OpenAllDexFiles(std::vector<std::unique_ptr<const DexFile>>* dex_files,
                                std::string* error_msg) const {
   size_t i = 0;
   auto dex_file_container = std::make_shared<MemoryDexFileContainer>(Begin(), End());
   for (const uint8_t* dex_file_start = GetNextDexFileData(nullptr, i);
        dex_file_start != nullptr;
        dex_file_start = GetNextDexFileData(dex_file_start, ++i)) {
     // TODO: Supply the location information for a vdex file.
     static constexpr char kVdexLocation[] = "";
     std::string location = DexFileLoader::GetMultiDexLocation(i, kVdexLocation);
     ArtDexFileLoader dex_file_loader(dex_file_container, location);
     std::unique_ptr<const DexFile> dex(dex_file_loader.OpenOne(dex_file_start - Begin(),
                                                                GetLocationChecksum(i),
                                                                /*oat_dex_file=*/nullptr,
                                                                /*verify=*/false,
                                                                /*verify_checksum=*/false,
                                                                error_msg));
     if (dex == nullptr) {
       return false;
     }
     dex_files->push_back(std::move(dex));
   }
   return true;
 }

 static bool CreateDirectories(const std::string& child_path, /* out */ std::string* error_msg) {
   size_t last_slash_pos = child_path.find_last_of('/');
   CHECK_NE(last_slash_pos, std::string::npos) << "Invalid path: " << child_path;
   std::string parent_path = child_path.substr(0, last_slash_pos);
   if (OS::DirectoryExists(parent_path.c_str())) {
     return true;
   } else if (CreateDirectories(parent_path, error_msg)) {
     if (mkdir(parent_path.c_str(), 0700) == 0) {
       return true;
     }
     *error_msg = "Could not create directory " + parent_path;
     return false;
   } else {
     return false;
   }
 }

 bool VdexFile::WriteToDisk(const std::string& path,
                            const std::vector<const DexFile*>& dex_files,
                            const verifier::VerifierDeps& verifier_deps,
                            std::string* error_msg) {
   std::vector<uint8_t> verifier_deps_data;
   verifier_deps.Encode(dex_files, &verifier_deps_data);
   uint32_t verifier_deps_size = verifier_deps_data.size();
   // Add padding so the type lookup tables are 4 byte aligned.
   uint32_t verifier_deps_with_padding_size = RoundUp(verifier_deps_data.size(), 4);
   DCHECK_GE(verifier_deps_with_padding_size, verifier_deps_data.size());
   verifier_deps_data.resize(verifier_deps_with_padding_size, 0);

   size_t type_lookup_table_size = 0u;
   for (const DexFile* dex_file : dex_files) {
     type_lookup_table_size +=
         sizeof(uint32_t) + TypeLookupTable::RawDataLength(dex_file->NumClassDefs());
   }

   VdexFile::VdexFileHeader vdex_header(/* has_dex_section= */ false);
   VdexFile::VdexSectionHeader sections[static_cast<uint32_t>(VdexSection::kNumberOfSections)];

   // Set checksum section.
   sections[VdexSection::kChecksumSection].section_kind = VdexSection::kChecksumSection;
   sections[VdexSection::kChecksumSection].section_offset = GetChecksumsOffset();
   sections[VdexSection::kChecksumSection].section_size =
       sizeof(VdexFile::VdexChecksum) * dex_files.size();

   // Set dex section.
   sections[VdexSection::kDexFileSection].section_kind = VdexSection::kDexFileSection;
   sections[VdexSection::kDexFileSection].section_offset = 0u;
   sections[VdexSection::kDexFileSection].section_size = 0u;

   // Set VerifierDeps section.
   sections[VdexSection::kVerifierDepsSection].section_kind = VdexSection::kVerifierDepsSection;
   sections[VdexSection::kVerifierDepsSection].section_offset =
       GetChecksumsOffset() + sections[kChecksumSection].section_size;
   sections[VdexSection::kVerifierDepsSection].section_size = verifier_deps_size;

   // Set TypeLookupTable section.
   sections[VdexSection::kTypeLookupTableSection].section_kind =
       VdexSection::kTypeLookupTableSection;
   sections[VdexSection::kTypeLookupTableSection].section_offset =
       sections[VdexSection::kVerifierDepsSection].section_offset + verifier_deps_with_padding_size;
   sections[VdexSection::kTypeLookupTableSection].section_size = type_lookup_table_size;

   if (!CreateDirectories(path, error_msg)) {
     return false;
   }

   std::unique_ptr<File> out(OS::CreateEmptyFileWriteOnly(path.c_str()));
   if (out == nullptr) {
     *error_msg = "Could not open " + path + " for writing";
     return false;
   }

   // Write header.
   if (!out->WriteFully(reinterpret_cast<const char*>(&vdex_header), sizeof(vdex_header))) {
     *error_msg = "Could not write vdex header to " + path;
     out->Unlink();
     return false;
   }

   // Write section infos.
   if (!out->WriteFully(reinterpret_cast<const char*>(&sections), sizeof(sections))) {
     *error_msg = "Could not write vdex sections to " + path;
     out->Unlink();
     return false;
   }

   // Write checksum section.
   for (const DexFile* dex_file : dex_files) {
     uint32_t checksum = dex_file->GetLocationChecksum();
     const uint32_t* checksum_ptr = &checksum;
     static_assert(sizeof(*checksum_ptr) == sizeof(VdexFile::VdexChecksum));
     if (!out->WriteFully(reinterpret_cast<const char*>(checksum_ptr),
                          sizeof(VdexFile::VdexChecksum))) {
       *error_msg = "Could not write dex checksums to " + path;
       out->Unlink();
       return false;
     }
   }

   if (!out->WriteFully(reinterpret_cast<const char*>(verifier_deps_data.data()),
                        verifier_deps_with_padding_size)) {
     *error_msg = "Could not write verifier deps to " + path;
     out->Unlink();
     return false;
   }

   size_t written_type_lookup_table_size = 0;
   for (const DexFile* dex_file : dex_files) {
     TypeLookupTable type_lookup_table = TypeLookupTable::Create(*dex_file);
     uint32_t size = type_lookup_table.RawDataLength();
     DCHECK_ALIGNED(size, 4);
     if (!out->WriteFully(reinterpret_cast<const char*>(&size), sizeof(uint32_t)) ||
         !out->WriteFully(reinterpret_cast<const char*>(type_lookup_table.RawData()), size)) {
       *error_msg = "Could not write type lookup table " + path;
       out->Unlink();
       return false;
     }
     written_type_lookup_table_size += sizeof(uint32_t) + size;
   }
   DCHECK_EQ(written_type_lookup_table_size, type_lookup_table_size);

   if (out->FlushClose() != 0) {
     *error_msg = "Could not flush and close " + path;
     out->Unlink();
     return false;
   }

   return true;
 }

 bool VdexFile::MatchesDexFileChecksums(const std::vector<const DexFile::Header*>& dex_headers)
     const {
   if (dex_headers.size() != GetNumberOfDexFiles()) {
     LOG(WARNING) << "Mismatch of number of dex files in vdex (expected="
         << GetNumberOfDexFiles() << ", actual=" << dex_headers.size() << ")";
     return false;
   }
   const VdexChecksum* checksums = GetDexChecksumsArray();
   for (size_t i = 0; i < dex_headers.size(); ++i) {
     if (checksums[i] != dex_headers[i]->checksum_) {
       LOG(WARNING) << "Mismatch of dex file checksum in vdex (index=" << i << ")";
       return false;
     }
   }
   return true;
 }

 bool VdexFile::HasOnlyStandardDexFiles() const {
   // All are the same so it's enough to check the first one.
   const uint8_t* dex_file_start = GetNextDexFileData(nullptr, 0);
   return dex_file_start == nullptr || StandardDexFile::IsMagicValid(dex_file_start);
 }

 static ObjPtr<mirror::Class> FindClassAndClearException(ClassLinker* class_linker,
                                                         Thread* self,
                                                         const char* name,
                                                         Handle<mirror::ClassLoader> class_loader)
     REQUIRES_SHARED(Locks::mutator_lock_) {
   ObjPtr<mirror::Class> result = class_linker->FindClass(self, name, class_loader);
   if (result == nullptr) {
     DCHECK(self->IsExceptionPending());
     self->ClearException();
   }
   return result;
 }

 static const char* GetStringFromId(const DexFile& dex_file,
                                    dex::StringIndex string_id,
                                    uint32_t number_of_extra_strings,
                                    const uint32_t* extra_strings_offsets,
                                    const uint8_t* verifier_deps) {
   uint32_t num_ids_in_dex = dex_file.NumStringIds();
   if (string_id.index_ < num_ids_in_dex) {
     return dex_file.StringDataByIdx(string_id);
   } else {
     CHECK_LT(string_id.index_ - num_ids_in_dex, number_of_extra_strings);
     uint32_t offset = extra_strings_offsets[string_id.index_ - num_ids_in_dex];
     return reinterpret_cast<const char*>(verifier_deps) + offset;
   }
 }

 // Returns an array of offsets where the assignability checks for each class
 // definition are stored.
 static const uint32_t* GetDexFileClassDefs(const uint8_t* verifier_deps, uint32_t index) {
   uint32_t dex_file_offset = reinterpret_cast<const uint32_t*>(verifier_deps)[index];
   return reinterpret_cast<const uint32_t*>(verifier_deps + dex_file_offset);
 }

 // Returns an array of offsets where extra strings are stored.
 static const uint32_t* GetExtraStringsOffsets(const DexFile& dex_file,
                                               const uint8_t* verifier_deps,
                                               const uint32_t* dex_file_class_defs,
                                               /*out*/ uint32_t* number_of_extra_strings) {
   // The information for strings is right after dex_file_class_defs, 4-byte
   // aligned
   uint32_t end_of_assignability_types = dex_file_class_defs[dex_file.NumClassDefs()];
   const uint8_t* strings_data_start =
       AlignUp(verifier_deps + end_of_assignability_types, sizeof(uint32_t));
   // First entry is the number of extra strings for this dex file.
   *number_of_extra_strings = *reinterpret_cast<const uint32_t*>(strings_data_start);
   // Then an array of offsets in `verifier_deps` for the extra strings.
   return reinterpret_cast<const uint32_t*>(strings_data_start + sizeof(uint32_t));
 }

 ClassStatus VdexFile::ComputeClassStatus(Thread* self, Handle<mirror::Class> cls) const {
   const DexFile& dex_file = cls->GetDexFile();
   uint16_t class_def_index = cls->GetDexClassDefIndex();

   // Find which dex file index from within the vdex file.
   uint32_t index = 0;
   for (; index < GetNumberOfDexFiles(); ++index) {
     if (dex_file.GetLocationChecksum() == GetLocationChecksum(index)) {
       break;
     }
   }

   DCHECK_NE(index, GetNumberOfDexFiles());

   const uint8_t* verifier_deps = GetVerifierDepsData().data();
   const uint32_t* dex_file_class_defs = GetDexFileClassDefs(verifier_deps, index);

   // Fetch type checks offsets.
   uint32_t class_def_offset = dex_file_class_defs[class_def_index];
   if (class_def_offset == verifier::VerifierDeps::kNotVerifiedMarker) {
     // Return a status that needs re-verification.
     return ClassStatus::kResolved;
   }
   // End offset for this class's type checks. We know there is one and the loop
   // will terminate.
   uint32_t end_offset = verifier::VerifierDeps::kNotVerifiedMarker;
   for (uint32_t i = class_def_index + 1; i < dex_file.NumClassDefs() + 1; ++i) {
     end_offset = dex_file_class_defs[i];
     if (end_offset != verifier::VerifierDeps::kNotVerifiedMarker) {
       break;
     }
   }
   DCHECK_NE(end_offset, verifier::VerifierDeps::kNotVerifiedMarker);

   uint32_t number_of_extra_strings = 0;
   // Offset where extra strings are stored.
   const uint32_t* extra_strings_offsets = GetExtraStringsOffsets(dex_file,
                                                                  verifier_deps,
                                                                  dex_file_class_defs,
                                                                  &number_of_extra_strings);

   // Loop over and perform each assignability check.
   StackHandleScope<3> hs(self);
   ClassLinker* class_linker = Runtime::Current()->GetClassLinker();
   Handle<mirror::ClassLoader> class_loader(hs.NewHandle(cls->GetClassLoader()));
   MutableHandle<mirror::Class> source(hs.NewHandle<mirror::Class>(nullptr));
   MutableHandle<mirror::Class> destination(hs.NewHandle<mirror::Class>(nullptr));

   const uint8_t* cursor = verifier_deps + class_def_offset;
   const uint8_t* end = verifier_deps + end_offset;
   while (cursor < end) {
     uint32_t destination_index;
     uint32_t source_index;
     if (UNLIKELY(!DecodeUnsignedLeb128Checked(&cursor, end, &destination_index) ||
                  !DecodeUnsignedLeb128Checked(&cursor, end, &source_index))) {
       // Error parsing the data, just return that we are not verified.
       return ClassStatus::kResolved;
     }
     const char* destination_desc = GetStringFromId(dex_file,
                                                    dex::StringIndex(destination_index),
                                                    number_of_extra_strings,
                                                    extra_strings_offsets,
                                                    verifier_deps);
     destination.Assign(
         FindClassAndClearException(class_linker, self, destination_desc, class_loader));

     const char* source_desc = GetStringFromId(dex_file,
                                               dex::StringIndex(source_index),
                                               number_of_extra_strings,
                                               extra_strings_offsets,
                                               verifier_deps);
     source.Assign(FindClassAndClearException(class_linker, self, source_desc, class_loader));

     if (destination == nullptr || source == nullptr) {
       // The interpreter / compiler can handle a missing class.
       continue;
     }

     DCHECK(destination->IsResolved() && source->IsResolved());
     if (!destination->IsAssignableFrom(source.Get())) {
       VLOG(verifier) << "Vdex checking failed for " << cls->PrettyClass()
                      << ": expected " << destination->PrettyClass()
                      << " to be assignable from " << source->PrettyClass();
       // An implicit assignability check is failing in the code, return that the
       // class is not verified.
       return ClassStatus::kResolved;
     }
   }

   return ClassStatus::kVerifiedNeedsAccessChecks;
 }

 }  // namespace art
	/*
	* Copyright (C) 2016 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 "vdex_file.h"

	#include <sys/mman.h> // For the PROT_* and MAP_* constants.
	#include <sys/stat.h> // for mkdir()

	#include <memory>
	#include <unordered_set>

	#include <android-base/logging.h>
	#include <android-base/stringprintf.h>
	#include <log/log.h>

	#include "base/bit_utils.h"
	#include "base/leb128.h"
	#include "base/stl_util.h"
	#include "base/systrace.h"
	#include "base/unix_file/fd_file.h"
	#include "base/zip_archive.h"
	#include "class_linker.h"
	#include "class_loader_context.h"
	#include "dex/art_dex_file_loader.h"
	#include "dex/class_accessor-inl.h"
	#include "dex/dex_file_loader.h"
	#include "gc/heap.h"
	#include "gc/space/image_space.h"
	#include "mirror/class-inl.h"
	#include "handle_scope-inl.h"
	#include "runtime.h"
	#include "verifier/verifier_deps.h"

	namespace art HIDDEN {

	using android::base::StringPrintf;

	bool VdexFile::VdexFileHeader::IsMagicValid() const {
	return (memcmp(magic_, kVdexMagic, sizeof(kVdexMagic)) == 0);
	}

	bool VdexFile::VdexFileHeader::IsVdexVersionValid() const {
	return (memcmp(vdex_version_, kVdexVersion, sizeof(kVdexVersion)) == 0);
	}

	VdexFile::VdexFileHeader::VdexFileHeader([[maybe_unused]] bool has_dex_section)
	: number_of_sections_(static_cast<uint32_t>(VdexSection::kNumberOfSections)) {
	memcpy(magic_, kVdexMagic, sizeof(kVdexMagic));
	memcpy(vdex_version_, kVdexVersion, sizeof(kVdexVersion));
	DCHECK(IsMagicValid());
	DCHECK(IsVdexVersionValid());
	}

	std::unique_ptr<VdexFile> VdexFile::OpenAtAddress(uint8_t* mmap_addr,
	size_t mmap_size,
	bool mmap_reuse,
	const std::string& vdex_filename,
	bool writable,
	bool low_4gb,
	std::string* error_msg) {
	ScopedTrace trace(("VdexFile::OpenAtAddress " + vdex_filename).c_str());
	if (!OS::FileExists(vdex_filename.c_str())) {
	*error_msg = "File " + vdex_filename + " does not exist.";
	return nullptr;
	}

	std::unique_ptr<File> vdex_file;
	if (writable) {
	vdex_file.reset(OS::OpenFileReadWrite(vdex_filename.c_str()));
	} else {
	vdex_file.reset(OS::OpenFileForReading(vdex_filename.c_str()));
	}
	if (vdex_file == nullptr) {
	*error_msg = "Could not open file " + vdex_filename +
	(writable ? " for read/write" : "for reading");
	return nullptr;
	}

	int64_t vdex_length = vdex_file->GetLength();
	if (vdex_length == -1) {
	*error_msg = "Could not read the length of file " + vdex_filename;
	return nullptr;
	}

	return OpenAtAddress(mmap_addr,
	mmap_size,
	mmap_reuse,
	vdex_file->Fd(),
	vdex_length,
	vdex_filename,
	writable,
	low_4gb,
	error_msg);
	}

	std::unique_ptr<VdexFile> VdexFile::OpenAtAddress(uint8_t* mmap_addr,
	size_t mmap_size,
	bool mmap_reuse,
	int file_fd,
	size_t vdex_length,
	const std::string& vdex_filename,
	bool writable,
	bool low_4gb,
	std::string* error_msg) {
	if (mmap_addr != nullptr && mmap_size < vdex_length) {
	*error_msg = StringPrintf("Insufficient pre-allocated space to mmap vdex: %zu and %zu",
	mmap_size,
	vdex_length);
	return nullptr;
	}
	CHECK_IMPLIES(mmap_reuse, mmap_addr != nullptr);
	// Start as PROT_WRITE so we can mprotect back to it if we want to.
	MemMap mmap = MemMap::MapFileAtAddress(
	mmap_addr,
	vdex_length,
	PROT_READ \| PROT_WRITE,
	writable ? MAP_SHARED : MAP_PRIVATE,
	file_fd,
	/* start= */ 0u,
	low_4gb,
	vdex_filename.c_str(),
	mmap_reuse,
	/* reservation= */ nullptr,
	error_msg);
	if (!mmap.IsValid()) {
	error_msg = "Failed to mmap file " + vdex_filename + " : " + error_msg;
	return nullptr;
	}

	std::unique_ptr<VdexFile> vdex(new VdexFile(std::move(mmap)));
	if (!vdex->IsValid()) {
	*error_msg = "Vdex file is not valid";
	return nullptr;
	}

	return vdex;
	}

	std::unique_ptr<VdexFile> VdexFile::OpenFromDm(const std::string& filename,
	const ZipArchive& archive) {
	std::string error_msg;
	std::unique_ptr<ZipEntry> zip_entry(archive.Find(VdexFile::kVdexNameInDmFile, &error_msg));
	if (zip_entry == nullptr) {
	LOG(INFO) << "No " << VdexFile::kVdexNameInDmFile << " file in DexMetadata archive. "
	<< "Not doing fast verification.";
	return nullptr;
	}
	MemMap input_file = zip_entry->MapDirectlyOrExtract(
	filename.c_str(),
	VdexFile::kVdexNameInDmFile,
	&error_msg,
	alignof(VdexFile));
	if (!input_file.IsValid()) {
	LOG(WARNING) << "Could not open vdex file in DexMetadata archive: " << error_msg;
	return nullptr;
	}
	std::unique_ptr<VdexFile> vdex_file = std::make_unique<VdexFile>(std::move(input_file));
	if (!vdex_file->IsValid()) {
	LOG(WARNING) << "The dex metadata .vdex is not valid. Ignoring it.";
	return nullptr;
	}
	if (vdex_file->HasDexSection()) {
	LOG(ERROR) << "The dex metadata is not allowed to contain dex files";
	android_errorWriteLog(0x534e4554, "178055795"); // Report to SafetyNet.
	return nullptr;
	}
	return vdex_file;
	}

	const uint8_t* VdexFile::GetNextDexFileData(const uint8_t* cursor, uint32_t dex_file_index) const {
	DCHECK(cursor == nullptr \|\| (cursor > Begin() && cursor <= End()));
	if (cursor == nullptr) {
	// Beginning of the iteration, return the first dex file if there is one.
	return HasDexSection() ? DexBegin() : nullptr;
	} else if (dex_file_index >= GetNumberOfDexFiles()) {
	return nullptr;
	} else {
	// Fetch the next dex file. Return null if there is none.
	const uint8_t* data = cursor + reinterpret_cast<const DexFile::Header*>(cursor)->file_size_;
	// Dex files are required to be 4 byte aligned. the OatWriter makes sure they are, see
	// OatWriter::SeekToDexFiles.
	return AlignUp(data, 4);
	}
	}

	const uint8_t* VdexFile::GetNextTypeLookupTableData(const uint8_t* cursor,
	uint32_t dex_file_index) const {
	if (cursor == nullptr) {
	// Beginning of the iteration, return the first dex file if there is one.
	return HasTypeLookupTableSection() ? TypeLookupTableDataBegin() : nullptr;
	} else if (dex_file_index >= GetNumberOfDexFiles()) {
	return nullptr;
	} else {
	const uint8_t* data = cursor + sizeof(uint32_t) + reinterpret_cast<const uint32_t*>(cursor)[0];
	// TypeLookupTables are required to be 4 byte aligned. the OatWriter makes sure they are.
	// We don't check this here to be defensive against corrupted vdex files.
	// Callers should check the returned value matches their expectations.
	return data;
	}
	}

	bool VdexFile::OpenAllDexFiles(std::vector<std::unique_ptr<const DexFile>>* dex_files,
	std::string* error_msg) const {
	size_t i = 0;
	auto dex_file_container = std::make_shared<MemoryDexFileContainer>(Begin(), End());
	for (const uint8_t* dex_file_start = GetNextDexFileData(nullptr, i);
	dex_file_start != nullptr;
	dex_file_start = GetNextDexFileData(dex_file_start, ++i)) {
	// TODO: Supply the location information for a vdex file.
	static constexpr char kVdexLocation[] = "";
	std::string location = DexFileLoader::GetMultiDexLocation(i, kVdexLocation);
	ArtDexFileLoader dex_file_loader(dex_file_container, location);
	std::unique_ptr<const DexFile> dex(dex_file_loader.OpenOne(dex_file_start - Begin(),
	GetLocationChecksum(i),
	/oat_dex_file=/nullptr,
	/verify=/false,
	/verify_checksum=/false,
	error_msg));
	if (dex == nullptr) {
	return false;
	}
	dex_files->push_back(std::move(dex));
	}
	return true;
	}

	static bool CreateDirectories(const std::string& child_path, /* out / std::string error_msg) {
	size_t last_slash_pos = child_path.find_last_of('/');
	CHECK_NE(last_slash_pos, std::string::npos) << "Invalid path: " << child_path;
	std::string parent_path = child_path.substr(0, last_slash_pos);
	if (OS::DirectoryExists(parent_path.c_str())) {
	return true;
	} else if (CreateDirectories(parent_path, error_msg)) {
	if (mkdir(parent_path.c_str(), 0700) == 0) {
	return true;
	}
	*error_msg = "Could not create directory " + parent_path;
	return false;
	} else {
	return false;
	}
	}

	bool VdexFile::WriteToDisk(const std::string& path,
	const std::vector<const DexFile*>& dex_files,
	const verifier::VerifierDeps& verifier_deps,
	std::string* error_msg) {
	std::vector<uint8_t> verifier_deps_data;
	verifier_deps.Encode(dex_files, &verifier_deps_data);
	uint32_t verifier_deps_size = verifier_deps_data.size();
	// Add padding so the type lookup tables are 4 byte aligned.
	uint32_t verifier_deps_with_padding_size = RoundUp(verifier_deps_data.size(), 4);
	DCHECK_GE(verifier_deps_with_padding_size, verifier_deps_data.size());
	verifier_deps_data.resize(verifier_deps_with_padding_size, 0);

	size_t type_lookup_table_size = 0u;
	for (const DexFile* dex_file : dex_files) {
	type_lookup_table_size +=
	sizeof(uint32_t) + TypeLookupTable::RawDataLength(dex_file->NumClassDefs());
	}

	VdexFile::VdexFileHeader vdex_header(/* has_dex_section= */ false);
	VdexFile::VdexSectionHeader sections[static_cast<uint32_t>(VdexSection::kNumberOfSections)];

	// Set checksum section.
	sections[VdexSection::kChecksumSection].section_kind = VdexSection::kChecksumSection;
	sections[VdexSection::kChecksumSection].section_offset = GetChecksumsOffset();
	sections[VdexSection::kChecksumSection].section_size =
	sizeof(VdexFile::VdexChecksum) * dex_files.size();

	// Set dex section.
	sections[VdexSection::kDexFileSection].section_kind = VdexSection::kDexFileSection;
	sections[VdexSection::kDexFileSection].section_offset = 0u;
	sections[VdexSection::kDexFileSection].section_size = 0u;

	// Set VerifierDeps section.
	sections[VdexSection::kVerifierDepsSection].section_kind = VdexSection::kVerifierDepsSection;
	sections[VdexSection::kVerifierDepsSection].section_offset =
	GetChecksumsOffset() + sections[kChecksumSection].section_size;
	sections[VdexSection::kVerifierDepsSection].section_size = verifier_deps_size;

	// Set TypeLookupTable section.
	sections[VdexSection::kTypeLookupTableSection].section_kind =
	VdexSection::kTypeLookupTableSection;
	sections[VdexSection::kTypeLookupTableSection].section_offset =
	sections[VdexSection::kVerifierDepsSection].section_offset + verifier_deps_with_padding_size;
	sections[VdexSection::kTypeLookupTableSection].section_size = type_lookup_table_size;

	if (!CreateDirectories(path, error_msg)) {
	return false;
	}

	std::unique_ptr<File> out(OS::CreateEmptyFileWriteOnly(path.c_str()));
	if (out == nullptr) {
	*error_msg = "Could not open " + path + " for writing";
	return false;
	}

	// Write header.
	if (!out->WriteFully(reinterpret_cast<const char*>(&vdex_header), sizeof(vdex_header))) {
	*error_msg = "Could not write vdex header to " + path;
	out->Unlink();
	return false;
	}

	// Write section infos.
	if (!out->WriteFully(reinterpret_cast<const char*>(&sections), sizeof(sections))) {
	*error_msg = "Could not write vdex sections to " + path;
	out->Unlink();
	return false;
	}

	// Write checksum section.
	for (const DexFile* dex_file : dex_files) {
	uint32_t checksum = dex_file->GetLocationChecksum();
	const uint32_t* checksum_ptr = &checksum;
	static_assert(sizeof(*checksum_ptr) == sizeof(VdexFile::VdexChecksum));
	if (!out->WriteFully(reinterpret_cast<const char*>(checksum_ptr),
	sizeof(VdexFile::VdexChecksum))) {
	*error_msg = "Could not write dex checksums to " + path;
	out->Unlink();
	return false;
	}
	}

	if (!out->WriteFully(reinterpret_cast<const char*>(verifier_deps_data.data()),
	verifier_deps_with_padding_size)) {
	*error_msg = "Could not write verifier deps to " + path;
	out->Unlink();
	return false;
	}

	size_t written_type_lookup_table_size = 0;
	for (const DexFile* dex_file : dex_files) {
	TypeLookupTable type_lookup_table = TypeLookupTable::Create(*dex_file);
	uint32_t size = type_lookup_table.RawDataLength();
	DCHECK_ALIGNED(size, 4);
	if (!out->WriteFully(reinterpret_cast<const char*>(&size), sizeof(uint32_t)) \|\|
	!out->WriteFully(reinterpret_cast<const char*>(type_lookup_table.RawData()), size)) {
	*error_msg = "Could not write type lookup table " + path;
	out->Unlink();
	return false;
	}
	written_type_lookup_table_size += sizeof(uint32_t) + size;
	}
	DCHECK_EQ(written_type_lookup_table_size, type_lookup_table_size);

	if (out->FlushClose() != 0) {
	*error_msg = "Could not flush and close " + path;
	out->Unlink();
	return false;
	}

	return true;
	}

	bool VdexFile::MatchesDexFileChecksums(const std::vector<const DexFile::Header*>& dex_headers)
	const {
	if (dex_headers.size() != GetNumberOfDexFiles()) {
	LOG(WARNING) << "Mismatch of number of dex files in vdex (expected="
	<< GetNumberOfDexFiles() << ", actual=" << dex_headers.size() << ")";
	return false;
	}
	const VdexChecksum* checksums = GetDexChecksumsArray();
	for (size_t i = 0; i < dex_headers.size(); ++i) {
	if (checksums[i] != dex_headers[i]->checksum_) {
	LOG(WARNING) << "Mismatch of dex file checksum in vdex (index=" << i << ")";
	return false;
	}
	}
	return true;
	}

	bool VdexFile::HasOnlyStandardDexFiles() const {
	// All are the same so it's enough to check the first one.
	const uint8_t* dex_file_start = GetNextDexFileData(nullptr, 0);
	return dex_file_start == nullptr \|\| StandardDexFile::IsMagicValid(dex_file_start);
	}

	static ObjPtr<mirror::Class> FindClassAndClearException(ClassLinker* class_linker,
	Thread* self,
	const char* name,
	Handle<mirror::ClassLoader> class_loader)
	REQUIRES_SHARED(Locks::mutator_lock_) {
	ObjPtr<mirror::Class> result = class_linker->FindClass(self, name, class_loader);
	if (result == nullptr) {
	DCHECK(self->IsExceptionPending());
	self->ClearException();
	}
	return result;
	}

	static const char* GetStringFromId(const DexFile& dex_file,
	dex::StringIndex string_id,
	uint32_t number_of_extra_strings,
	const uint32_t* extra_strings_offsets,
	const uint8_t* verifier_deps) {
	uint32_t num_ids_in_dex = dex_file.NumStringIds();
	if (string_id.index_ < num_ids_in_dex) {
	return dex_file.StringDataByIdx(string_id);
	} else {
	CHECK_LT(string_id.index_ - num_ids_in_dex, number_of_extra_strings);
	uint32_t offset = extra_strings_offsets[string_id.index_ - num_ids_in_dex];
	return reinterpret_cast<const char*>(verifier_deps) + offset;
	}
	}

	// Returns an array of offsets where the assignability checks for each class
	// definition are stored.
	static const uint32_t* GetDexFileClassDefs(const uint8_t* verifier_deps, uint32_t index) {
	uint32_t dex_file_offset = reinterpret_cast<const uint32_t*>(verifier_deps)[index];
	return reinterpret_cast<const uint32_t*>(verifier_deps + dex_file_offset);
	}

	// Returns an array of offsets where extra strings are stored.
	static const uint32_t* GetExtraStringsOffsets(const DexFile& dex_file,
	const uint8_t* verifier_deps,
	const uint32_t* dex_file_class_defs,
	/out/ uint32_t* number_of_extra_strings) {
	// The information for strings is right after dex_file_class_defs, 4-byte
	// aligned
	uint32_t end_of_assignability_types = dex_file_class_defs[dex_file.NumClassDefs()];
	const uint8_t* strings_data_start =
	AlignUp(verifier_deps + end_of_assignability_types, sizeof(uint32_t));
	// First entry is the number of extra strings for this dex file.
	number_of_extra_strings = reinterpret_cast<const uint32_t*>(strings_data_start);
	// Then an array of offsets in `verifier_deps` for the extra strings.
	return reinterpret_cast<const uint32_t*>(strings_data_start + sizeof(uint32_t));
	}

	ClassStatus VdexFile::ComputeClassStatus(Thread* self, Handle<mirror::Class> cls) const {
	const DexFile& dex_file = cls->GetDexFile();
	uint16_t class_def_index = cls->GetDexClassDefIndex();

	// Find which dex file index from within the vdex file.
	uint32_t index = 0;
	for (; index < GetNumberOfDexFiles(); ++index) {
	if (dex_file.GetLocationChecksum() == GetLocationChecksum(index)) {
	break;
	}
	}

	DCHECK_NE(index, GetNumberOfDexFiles());

	const uint8_t* verifier_deps = GetVerifierDepsData().data();
	const uint32_t* dex_file_class_defs = GetDexFileClassDefs(verifier_deps, index);

	// Fetch type checks offsets.
	uint32_t class_def_offset = dex_file_class_defs[class_def_index];
	if (class_def_offset == verifier::VerifierDeps::kNotVerifiedMarker) {
	// Return a status that needs re-verification.
	return ClassStatus::kResolved;
	}
	// End offset for this class's type checks. We know there is one and the loop
	// will terminate.
	uint32_t end_offset = verifier::VerifierDeps::kNotVerifiedMarker;
	for (uint32_t i = class_def_index + 1; i < dex_file.NumClassDefs() + 1; ++i) {
	end_offset = dex_file_class_defs[i];
	if (end_offset != verifier::VerifierDeps::kNotVerifiedMarker) {
	break;
	}
	}
	DCHECK_NE(end_offset, verifier::VerifierDeps::kNotVerifiedMarker);

	uint32_t number_of_extra_strings = 0;
	// Offset where extra strings are stored.
	const uint32_t* extra_strings_offsets = GetExtraStringsOffsets(dex_file,
	verifier_deps,
	dex_file_class_defs,
	&number_of_extra_strings);

	// Loop over and perform each assignability check.
	StackHandleScope<3> hs(self);
	ClassLinker* class_linker = Runtime::Current()->GetClassLinker();
	Handle<mirror::ClassLoader> class_loader(hs.NewHandle(cls->GetClassLoader()));
	MutableHandle<mirror::Class> source(hs.NewHandle<mirror::Class>(nullptr));
	MutableHandle<mirror::Class> destination(hs.NewHandle<mirror::Class>(nullptr));

	const uint8_t* cursor = verifier_deps + class_def_offset;
	const uint8_t* end = verifier_deps + end_offset;
	while (cursor < end) {
	uint32_t destination_index;
	uint32_t source_index;
	if (UNLIKELY(!DecodeUnsignedLeb128Checked(&cursor, end, &destination_index) \|\|
	!DecodeUnsignedLeb128Checked(&cursor, end, &source_index))) {
	// Error parsing the data, just return that we are not verified.
	return ClassStatus::kResolved;
	}
	const char* destination_desc = GetStringFromId(dex_file,
	dex::StringIndex(destination_index),
	number_of_extra_strings,
	extra_strings_offsets,
	verifier_deps);
	destination.Assign(
	FindClassAndClearException(class_linker, self, destination_desc, class_loader));

	const char* source_desc = GetStringFromId(dex_file,
	dex::StringIndex(source_index),
	number_of_extra_strings,
	extra_strings_offsets,
	verifier_deps);
	source.Assign(FindClassAndClearException(class_linker, self, source_desc, class_loader));

	if (destination == nullptr \|\| source == nullptr) {
	// The interpreter / compiler can handle a missing class.
	continue;
	}

	DCHECK(destination->IsResolved() && source->IsResolved());
	if (!destination->IsAssignableFrom(source.Get())) {
	VLOG(verifier) << "Vdex checking failed for " << cls->PrettyClass()
	<< ": expected " << destination->PrettyClass()
	<< " to be assignable from " << source->PrettyClass();
	// An implicit assignability check is failing in the code, return that the
	// class is not verified.
	return ClassStatus::kResolved;
	}
	}

	return ClassStatus::kVerifiedNeedsAccessChecks;
	}

	} // namespace art