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dart / sdk / 0740566438c510835b87cad99f088c7302c5ed5d / . / runtime / vm / image_snapshot.cc
blob: 8318801648614b74920e2851f28972a252b86251 [file] [log] [blame]
// Copyright (c) 2017, the Dart project authors. Please see the AUTHORS file
// for details. All rights reserved. Use of this source code is governed by a
// BSD-style license that can be found in the LICENSE file.
#include "vm/image_snapshot.h"
#include "include/dart_api.h"
#include "platform/assert.h"
#include "platform/elf.h"
#include "vm/bss_relocs.h"
#include "vm/class_id.h"
#include "vm/compiler/runtime_api.h"
#include "vm/dwarf.h"
#include "vm/elf.h"
#include "vm/hash.h"
#include "vm/hash_map.h"
#include "vm/heap/heap.h"
#include "vm/instructions.h"
#include "vm/json_writer.h"
#include "vm/object.h"
#include "vm/object_store.h"
#include "vm/program_visitor.h"
#include "vm/stub_code.h"
#include "vm/timeline.h"
#include "vm/type_testing_stubs.h"
#if !defined(DART_PRECOMPILED_RUNTIME)
#include "vm/compiler/backend/code_statistics.h"
#endif // !defined(DART_PRECOMPILED_RUNTIME)
namespace dart {
#if defined(DART_PRECOMPILER)
DEFINE_FLAG(bool,
print_instruction_stats,
false,
"Print instruction statistics");
DEFINE_FLAG(charp,
print_instructions_sizes_to,
nullptr,
"Print sizes of all instruction objects to the given file");
#endif
const UntaggedInstructionsSection* Image::ExtraInfo(const uword raw_memory,
const uword size) {
#if defined(DART_PRECOMPILED_RUNTIME)
auto const raw_value =
FieldValue(raw_memory, HeaderField::InstructionsSectionOffset);
if (raw_value != kNoInstructionsSection) {
ASSERT(raw_value >= kHeaderSize);
ASSERT(raw_value <= size - InstructionsSection::HeaderSize());
auto const layout = reinterpret_cast<const UntaggedInstructionsSection*>(
raw_memory + raw_value);
// The instructions section is likely non-empty in bare instructions mode
// (unless splitting into multiple outputs and there are no Code objects
// in this particular output), but is guaranteed empty otherwise (the
// instructions follow the InstructionsSection object instead).
ASSERT(FLAG_use_bare_instructions || layout->payload_length_ == 0);
ASSERT(raw_value <=
size - InstructionsSection::InstanceSize(layout->payload_length_));
return layout;
}
#endif
return nullptr;
}
uword* Image::bss() const {
#if defined(DART_PRECOMPILED_RUNTIME)
ASSERT(extra_info_ != nullptr);
// There should always be a non-zero BSS offset.
ASSERT(extra_info_->bss_offset_ != 0);
// Returning a non-const uword* is safe because we're translating from
// the start of the instructions (read-only) to the start of the BSS
// (read-write).
return reinterpret_cast<uword*>(raw_memory_ + extra_info_->bss_offset_);
#else
return nullptr;
#endif
}
uword Image::instructions_relocated_address() const {
#if defined(DART_PRECOMPILED_RUNTIME)
ASSERT(extra_info_ != nullptr);
// For assembly snapshots, we need to retrieve this from the initialized BSS.
const uword address =
compiled_to_elf() ? extra_info_->instructions_relocated_address_
: bss()[BSS::RelocationIndex(
BSS::Relocation::InstructionsRelocatedAddress)];
ASSERT(address != kNoRelocatedAddress);
return address;
#else
return kNoRelocatedAddress;
#endif
}
const uint8_t* Image::build_id() const {
#if defined(DART_PRECOMPILED_RUNTIME)
ASSERT(extra_info_ != nullptr);
if (extra_info_->build_id_offset_ != kNoBuildId) {
auto const note = reinterpret_cast<elf::Note*>(
raw_memory_ + extra_info_->build_id_offset_);
// Check that we have a final build ID. A non-final build ID will either
// have a description length of 0 or an initial byte of 0.
auto const description = note->data + note->name_size;
auto const length = note->description_size;
if (length != 0 && description[0] != 0) {
return description;
}
}
#endif
return nullptr;
}
intptr_t Image::build_id_length() const {
#if defined(DART_PRECOMPILED_RUNTIME)
ASSERT(extra_info_ != nullptr);
if (extra_info_->build_id_offset_ != kNoBuildId) {
auto const note = reinterpret_cast<elf::Note*>(
raw_memory_ + extra_info_->build_id_offset_);
// Check that we have a final build ID. A non-final build ID will either
// have a description length of 0 or an initial byte of 0.
auto const description = note->data + note->name_size;
auto const length = note->description_size;
if (length != 0 && description[0] != 0) {
return length;
}
}
#endif
return 0;
}
bool Image::compiled_to_elf() const {
#if defined(DART_PRECOMPILED_RUNTIME)
ASSERT(extra_info_ != nullptr);
// Since assembly snapshots can't set up this field correctly (instead,
// it's initialized in BSS at snapshot load time), we use it to detect
// direct-to-ELF snapshots.
return extra_info_->instructions_relocated_address_ != kNoRelocatedAddress;
#else
return false;
#endif
}
uword ObjectOffsetTrait::Hash(Key key) {
ObjectPtr obj = key;
ASSERT(!obj->IsSmi());
uword body = UntaggedObject::ToAddr(obj) + sizeof(UntaggedObject);
uword end = UntaggedObject::ToAddr(obj) + obj->untag()->HeapSize();
uint32_t hash = obj->GetClassId();
// Don't include the header. Objects in the image are pre-marked, but objects
// in the current isolate are not.
for (uword cursor = body; cursor < end; cursor += sizeof(uint32_t)) {
hash = CombineHashes(hash, *reinterpret_cast<uint32_t*>(cursor));
}
return FinalizeHash(hash, 30);
}
bool ObjectOffsetTrait::IsKeyEqual(Pair pair, Key key) {
ObjectPtr a = pair.object;
ObjectPtr b = key;
ASSERT(!a->IsSmi());
ASSERT(!b->IsSmi());
if (a->GetClassId() != b->GetClassId()) {
return false;
}
intptr_t heap_size = a->untag()->HeapSize();
if (b->untag()->HeapSize() != heap_size) {
return false;
}
// Don't include the header. Objects in the image are pre-marked, but objects
// in the current isolate are not.
uword body_a = UntaggedObject::ToAddr(a) + sizeof(UntaggedObject);
uword body_b = UntaggedObject::ToAddr(b) + sizeof(UntaggedObject);
uword body_size = heap_size - sizeof(UntaggedObject);
return 0 == memcmp(reinterpret_cast<const void*>(body_a),
reinterpret_cast<const void*>(body_b), body_size);
}
#if !defined(DART_PRECOMPILED_RUNTIME)
ImageWriter::ImageWriter(Thread* t)
: heap_(t->heap()),
next_data_offset_(0),
next_text_offset_(0),
objects_(),
instructions_(),
image_type_(TagObjectTypeAsReadOnly(t->zone(), "Image")),
instructions_section_type_(
TagObjectTypeAsReadOnly(t->zone(), "InstructionsSection")),
instructions_type_(TagObjectTypeAsReadOnly(t->zone(), "Instructions")),
trampoline_type_(TagObjectTypeAsReadOnly(t->zone(), "Trampoline")) {
ResetOffsets();
}
void ImageWriter::PrepareForSerialization(
GrowableArray<ImageWriterCommand>* commands) {
if (commands != nullptr) {
const intptr_t initial_offset = next_text_offset_;
for (auto& inst : *commands) {
ASSERT((initial_offset + inst.expected_offset) == next_text_offset_);
switch (inst.op) {
case ImageWriterCommand::InsertInstructionOfCode: {
CodePtr code = inst.insert_instruction_of_code.code;
InstructionsPtr instructions = Code::InstructionsOf(code);
const intptr_t offset = next_text_offset_;
instructions_.Add(InstructionsData(instructions, code, offset));
next_text_offset_ += SizeInSnapshot(instructions);
ASSERT(heap_->GetObjectId(instructions) == 0);
heap_->SetObjectId(instructions, offset);
break;
}
case ImageWriterCommand::InsertBytesOfTrampoline: {
auto trampoline_bytes = inst.insert_trampoline_bytes.buffer;
auto trampoline_length = inst.insert_trampoline_bytes.buffer_length;
const intptr_t offset = next_text_offset_;
instructions_.Add(
InstructionsData(trampoline_bytes, trampoline_length, offset));
next_text_offset_ += trampoline_length;
break;
}
default:
UNREACHABLE();
}
}
}
}
int32_t ImageWriter::GetTextOffsetFor(InstructionsPtr instructions,
CodePtr code) {
intptr_t offset = heap_->GetObjectId(instructions);
if (offset != 0) {
return offset;
}
offset = next_text_offset_;
heap_->SetObjectId(instructions, offset);
next_text_offset_ += SizeInSnapshot(instructions);
instructions_.Add(InstructionsData(instructions, code, offset));
ASSERT(offset != 0);
return offset;
}
intptr_t ImageWriter::SizeInSnapshot(ObjectPtr raw_object) {
const classid_t cid = raw_object->GetClassId();
switch (cid) {
case kCompressedStackMapsCid: {
auto raw_maps = CompressedStackMaps::RawCast(raw_object);
return compiler::target::CompressedStackMaps::InstanceSize(
CompressedStackMaps::PayloadSizeOf(raw_maps));
}
case kCodeSourceMapCid: {
auto raw_map = CodeSourceMap::RawCast(raw_object);
return compiler::target::CodeSourceMap::InstanceSize(
raw_map->untag()->length_);
}
case kPcDescriptorsCid: {
auto raw_desc = PcDescriptors::RawCast(raw_object);
return compiler::target::PcDescriptors::InstanceSize(
raw_desc->untag()->length_);
}
case kInstructionsCid: {
auto raw_insns = Instructions::RawCast(raw_object);
return compiler::target::Instructions::InstanceSize(
Instructions::Size(raw_insns));
}
case kOneByteStringCid: {
auto raw_str = String::RawCast(raw_object);
return compiler::target::String::InstanceSize(
String::LengthOf(raw_str) * OneByteString::kBytesPerElement);
}
case kTwoByteStringCid: {
auto raw_str = String::RawCast(raw_object);
return compiler::target::String::InstanceSize(
String::LengthOf(raw_str) * TwoByteString::kBytesPerElement);
}
default: {
const Class& clazz = Class::Handle(Object::Handle(raw_object).clazz());
FATAL("Unsupported class %s in rodata section.\n", clazz.ToCString());
return 0;
}
}
}
uint32_t ImageWriter::GetDataOffsetFor(ObjectPtr raw_object) {
intptr_t snap_size = SizeInSnapshot(raw_object);
intptr_t offset = next_data_offset_;
next_data_offset_ += snap_size;
objects_.Add(ObjectData(raw_object));
return offset;
}
intptr_t ImageWriter::GetTextObjectCount() const {
return instructions_.length();
}
void ImageWriter::GetTrampolineInfo(intptr_t* count, intptr_t* size) const {
ASSERT(count != nullptr && size != nullptr);
*count = 0;
*size = 0;
for (auto const& data : instructions_) {
if (data.trampoline_length != 0) {
*count += 1;
*size += data.trampoline_length;
}
}
}
// Returns nullptr if there is no profile writer.
const char* ImageWriter::ObjectTypeForProfile(const Object& object) const {
if (profile_writer_ == nullptr) return nullptr;
ASSERT(IsROSpace());
Thread* thread = Thread::Current();
REUSABLE_CLASS_HANDLESCOPE(thread);
REUSABLE_STRING_HANDLESCOPE(thread);
Class& klass = thread->ClassHandle();
String& name = thread->StringHandle();
klass = object.clazz();
name = klass.UserVisibleName();
auto const name_str = name.ToCString();
return TagObjectTypeAsReadOnly(thread->zone(), name_str);
}
const char* ImageWriter::TagObjectTypeAsReadOnly(Zone* zone, const char* type) {
ASSERT(zone != nullptr && type != nullptr);
return OS::SCreate(zone, "(RO) %s", type);
}
#if defined(DART_PRECOMPILER)
void ImageWriter::DumpInstructionStats() {
std::unique_ptr<CombinedCodeStatistics> instruction_stats(
new CombinedCodeStatistics());
for (intptr_t i = 0; i < instructions_.length(); i++) {
auto& data = instructions_[i];
CodeStatistics* stats = data.insns_->stats();
if (stats != nullptr) {
stats->AppendTo(instruction_stats.get());
}
}
instruction_stats->DumpStatistics();
}
void ImageWriter::DumpInstructionsSizes() {
auto thread = Thread::Current();
auto zone = thread->zone();
auto& cls = Class::Handle(zone);
auto& lib = Library::Handle(zone);
auto& owner = Object::Handle(zone);
auto& url = String::Handle(zone);
auto& name = String::Handle(zone);
intptr_t trampolines_total_size = 0;
JSONWriter js;
js.OpenArray();
for (intptr_t i = 0; i < instructions_.length(); i++) {
auto& data = instructions_[i];
const bool is_trampoline = data.code_ == nullptr;
if (is_trampoline) {
trampolines_total_size += data.trampoline_length;
continue;
}
owner = WeakSerializationReference::Unwrap(data.code_->owner());
js.OpenObject();
if (owner.IsFunction()) {
cls = Function::Cast(owner).Owner();
name = cls.ScrubbedName();
lib = cls.library();
url = lib.url();
js.PrintPropertyStr("l", url);
js.PrintPropertyStr("c", name);
} else if (owner.IsClass()) {
cls ^= owner.ptr();
name = cls.ScrubbedName();
lib = cls.library();
url = lib.url();
js.PrintPropertyStr("l", url);
js.PrintPropertyStr("c", name);
}
js.PrintProperty("n",
data.code_->QualifiedName(
NameFormattingParams::DisambiguatedWithoutClassName(
Object::kInternalName)));
js.PrintProperty("s", SizeInSnapshot(data.insns_->ptr()));
js.CloseObject();
}
if (trampolines_total_size != 0) {
js.OpenObject();
js.PrintProperty("n", "[Stub] Trampoline");
js.PrintProperty("s", trampolines_total_size);
js.CloseObject();
}
js.CloseArray();
auto file_open = Dart::file_open_callback();
auto file_write = Dart::file_write_callback();
auto file_close = Dart::file_close_callback();
if ((file_open == nullptr) || (file_write == nullptr) ||
(file_close == nullptr)) {
return;
}
auto file = file_open(FLAG_print_instructions_sizes_to, /*write=*/true);
if (file == nullptr) {
OS::PrintErr("Failed to open file %s\n", FLAG_print_instructions_sizes_to);
return;
}
char* output = nullptr;
intptr_t output_length = 0;
js.Steal(&output, &output_length);
file_write(output, output_length, file);
free(output);
file_close(file);
}
void ImageWriter::DumpStatistics() {
if (FLAG_print_instruction_stats) {
DumpInstructionStats();
}
if (FLAG_print_instructions_sizes_to != nullptr) {
DumpInstructionsSizes();
}
}
#endif
void ImageWriter::Write(NonStreamingWriteStream* clustered_stream, bool vm) {
Thread* thread = Thread::Current();
Zone* zone = thread->zone();
Heap* heap = thread->isolate_group()->heap();
TIMELINE_DURATION(thread, Isolate, "WriteInstructions");
// Handlify collected raw pointers as building the names below
// will allocate on the Dart heap.
for (intptr_t i = 0; i < instructions_.length(); i++) {
InstructionsData& data = instructions_[i];
const bool is_trampoline = data.trampoline_bytes != nullptr;
if (is_trampoline) continue;
data.insns_ = &Instructions::Handle(zone, data.raw_insns_);
ASSERT(data.raw_code_ != nullptr);
data.code_ = &Code::Handle(zone, data.raw_code_);
// Reset object id as an isolate snapshot after a VM snapshot will not use
// the VM snapshot's text image.
heap->SetObjectId(data.insns_->ptr(), 0);
}
for (intptr_t i = 0; i < objects_.length(); i++) {
ObjectData& data = objects_[i];
data.obj_ = &Object::Handle(zone, data.raw_obj_);
}
// Needs to happen before WriteText, as we add information about the
// BSSsection in the text section as an initial InstructionsSection object.
WriteBss(vm);
offset_space_ = vm ? IdSpace::kVmText : IdSpace::kIsolateText;
WriteText(vm);
// Append the direct-mapped RO data objects after the clustered snapshot
// and then for ELF and assembly outputs, add appropriate sections with
// that combined data.
offset_space_ = vm ? IdSpace::kVmData : IdSpace::kIsolateData;
WriteROData(clustered_stream, vm);
}
void ImageWriter::WriteROData(NonStreamingWriteStream* stream, bool vm) {
#if defined(DART_PRECOMPILER)
const intptr_t start_position = stream->Position();
#endif
stream->Align(ImageWriter::kRODataAlignment);
// Heap page starts here.
intptr_t section_start = stream->Position();
stream->WriteWord(next_data_offset_); // Data length.
stream->WriteWord(Image::kNoInstructionsSection);
// Zero values for the rest of the Image object header bytes.
stream->Align(Image::kHeaderSize);
ASSERT_EQUAL(stream->Position() - section_start, Image::kHeaderSize);
#if defined(DART_PRECOMPILER)
if (profile_writer_ != nullptr) {
const intptr_t end_position = stream->Position();
profile_writer_->AttributeBytesTo(
V8SnapshotProfileWriter::kArtificialRootId,
end_position - start_position);
}
#endif
// Heap page objects start here.
for (intptr_t i = 0; i < objects_.length(); i++) {
const Object& obj = *objects_[i].obj_;
#if defined(DART_PRECOMPILER)
AutoTraceImage(obj, section_start, stream);
#endif
auto const object_start = stream->Position();
NoSafepointScope no_safepoint;
// Write object header with the mark and read-only bits set.
stream->WriteTargetWord(GetMarkedTags(obj));
if (obj.IsCompressedStackMaps()) {
const CompressedStackMaps& map = CompressedStackMaps::Cast(obj);
const intptr_t payload_size = map.payload_size();
stream->WriteTargetWord(map.ptr()->untag()->flags_and_size_);
ASSERT_EQUAL(stream->Position() - object_start,
compiler::target::CompressedStackMaps::HeaderSize());
stream->WriteBytes(map.ptr()->untag()->data(), payload_size);
} else if (obj.IsCodeSourceMap()) {
const CodeSourceMap& map = CodeSourceMap::Cast(obj);
stream->WriteTargetWord(map.Length());
ASSERT_EQUAL(stream->Position() - object_start,
compiler::target::CodeSourceMap::HeaderSize());
stream->WriteBytes(map.Data(), map.Length());
} else if (obj.IsPcDescriptors()) {
const PcDescriptors& desc = PcDescriptors::Cast(obj);
stream->WriteTargetWord(desc.Length());
ASSERT_EQUAL(stream->Position() - object_start,
compiler::target::PcDescriptors::HeaderSize());
stream->WriteBytes(desc.ptr()->untag()->data(), desc.Length());
} else if (obj.IsString()) {
const String& str = String::Cast(obj);
RELEASE_ASSERT(String::GetCachedHash(str.ptr()) != 0);
RELEASE_ASSERT(str.IsOneByteString() || str.IsTwoByteString());
stream->WriteTargetWord(static_cast<uword>(str.ptr()->untag()->length()));
#if !defined(HASH_IN_OBJECT_HEADER)
stream->WriteTargetWord(static_cast<uword>(str.ptr()->untag()->hash()));
#endif
ASSERT_EQUAL(stream->Position() - object_start,
compiler::target::String::InstanceSize());
stream->WriteBytes(
str.IsOneByteString()
? static_cast<const void*>(OneByteString::DataStart(str))
: static_cast<const void*>(TwoByteString::DataStart(str)),
str.Length() * (str.IsOneByteString()
? OneByteString::kBytesPerElement
: TwoByteString::kBytesPerElement));
} else {
const Class& clazz = Class::Handle(obj.clazz());
FATAL("Unsupported class %s in rodata section.\n", clazz.ToCString());
}
stream->Align(compiler::target::ObjectAlignment::kObjectAlignment);
ASSERT_EQUAL(stream->Position() - object_start, SizeInSnapshot(obj));
}
}
static constexpr uword kReadOnlyGCBits =
UntaggedObject::OldBit::encode(true) |
UntaggedObject::OldAndNotMarkedBit::encode(false) |
UntaggedObject::OldAndNotRememberedBit::encode(true) |
UntaggedObject::NewBit::encode(false);
uword ImageWriter::GetMarkedTags(classid_t cid,
intptr_t size,
bool is_canonical /* = false */) {
// UntaggedObject::SizeTag expects a size divisible by kObjectAlignment and
// checks this in debug mode, but the size on the target machine may not be
// divisible by the host machine's object alignment if they differ.
//
// We define [adjusted_size] as [size] * m, where m is the host alignment
// divided by the target alignment. This means [adjusted_size] encodes on the
// host machine to the same bits that decode to [size] on the target machine.
// That is,
// [adjusted_size] / host align ==
// [size] * (host align / target align) / host align ==
// [size] / target align
//
// Since alignments are always powers of 2, we use shifts and logs.
const intptr_t adjusted_size =
size << (kObjectAlignmentLog2 -
compiler::target::ObjectAlignment::kObjectAlignmentLog2);
return kReadOnlyGCBits | UntaggedObject::ClassIdTag::encode(cid) |
UntaggedObject::SizeTag::encode(adjusted_size) |
UntaggedObject::CanonicalBit::encode(is_canonical);
}
uword ImageWriter::GetMarkedTags(const Object& obj) {
uword tags = GetMarkedTags(obj.ptr()->untag()->GetClassId(),
SizeInSnapshot(obj), obj.IsCanonical());
#if defined(HASH_IN_OBJECT_HEADER)
tags = UntaggedObject::HashTag::update(obj.ptr()->untag()->GetHeaderHash(),
tags);
#endif
return tags;
}
const char* ImageWriter::SectionSymbol(ProgramSection section, bool vm) const {
switch (section) {
case ProgramSection::Text:
return vm ? kVmSnapshotInstructionsAsmSymbol
: kIsolateSnapshotInstructionsAsmSymbol;
case ProgramSection::Data:
return vm ? kVmSnapshotDataAsmSymbol : kIsolateSnapshotDataAsmSymbol;
case ProgramSection::Bss:
return vm ? kVmSnapshotBssAsmSymbol : kIsolateSnapshotBssAsmSymbol;
case ProgramSection::BuildId:
return kSnapshotBuildIdAsmSymbol;
}
return nullptr;
}
void ImageWriter::WriteText(bool vm) {
Zone* zone = Thread::Current()->zone();
const bool bare_instruction_payloads =
FLAG_precompiled_mode && FLAG_use_bare_instructions;
// Start snapshot at page boundary.
ASSERT(ImageWriter::kTextAlignment >= VirtualMemory::PageSize());
if (!EnterSection(ProgramSection::Text, vm, ImageWriter::kTextAlignment)) {
return;
}
intptr_t text_offset = 0;
#if defined(DART_PRECOMPILER)
// Parent used for later profile objects. Starts off as the Image. When
// writing bare instructions payloads, this is later updated with the
// InstructionsSection object which contains all the bare payloads.
V8SnapshotProfileWriter::ObjectId parent_id(offset_space_, text_offset);
#endif
// This head also provides the gap to make the instructions snapshot
// look like a OldPage.
const intptr_t image_size = Utils::RoundUp(
next_text_offset_, compiler::target::ObjectAlignment::kObjectAlignment);
text_offset += WriteTargetWord(image_size);
// Output the offset to the InstructionsSection object from the start of the
// image, if any.
text_offset +=
WriteTargetWord(FLAG_precompiled_mode ? Image::kHeaderSize
: Image::kNoInstructionsSection);
// Zero values for the rest of the Image object header bytes.
text_offset += Align(Image::kHeaderSize, text_offset);
ASSERT_EQUAL(text_offset, Image::kHeaderSize);
#if defined(DART_PRECOMPILER)
const char* instructions_symbol = SectionSymbol(ProgramSection::Text, vm);
ASSERT(instructions_symbol != nullptr);
const char* bss_symbol = SectionSymbol(ProgramSection::Bss, vm);
ASSERT(bss_symbol != nullptr);
if (profile_writer_ != nullptr) {
profile_writer_->SetObjectTypeAndName(parent_id, image_type_,
instructions_symbol);
profile_writer_->AttributeBytesTo(parent_id, Image::kHeaderSize);
profile_writer_->AddRoot(parent_id);
}
if (FLAG_precompiled_mode) {
const intptr_t section_header_length =
compiler::target::InstructionsSection::HeaderSize();
// Calculated using next_text_offset_, which doesn't include post-payload
// padding to object alignment. Note that if not in bare instructions mode,
// the section has no contents, instead the instructions objects follow it.
const intptr_t section_payload_length =
bare_instruction_payloads
? next_text_offset_ - text_offset - section_header_length
: 0;
const intptr_t section_size =
compiler::target::InstructionsSection::InstanceSize(
section_payload_length);
const V8SnapshotProfileWriter::ObjectId id(offset_space_, text_offset);
if (profile_writer_ != nullptr) {
profile_writer_->SetObjectTypeAndName(id, instructions_section_type_,
instructions_symbol);
profile_writer_->AttributeBytesTo(id,
section_size - section_payload_length);
const intptr_t element_offset = id.nonce() - parent_id.nonce();
profile_writer_->AttributeReferenceTo(
parent_id,
V8SnapshotProfileWriter::Reference::Element(element_offset), id);
// Later objects will have the InstructionsSection as a parent if in
// bare instructions mode, otherwise the image.
if (bare_instruction_payloads) {
parent_id = id;
}
}
// Add the RawInstructionsSection header.
text_offset +=
WriteTargetWord(GetMarkedTags(kInstructionsSectionCid, section_size));
// An InstructionsSection has five fields:
// 1) The length of the payload.
text_offset += WriteTargetWord(section_payload_length);
// 2) The BSS offset from this section.
text_offset += Relocation(text_offset, instructions_symbol, bss_symbol);
// 3) The relocated address of the instructions.
text_offset += WriteTargetWord(RelocatedAddress(instructions_symbol));
// 4) The GNU build ID note offset from this section.
text_offset += Relocation(text_offset, instructions_symbol,
SectionSymbol(ProgramSection::BuildId, vm));
const intptr_t section_contents_alignment =
bare_instruction_payloads
? compiler::target::Instructions::kBarePayloadAlignment
: compiler::target::ObjectAlignment::kObjectAlignment;
const intptr_t expected_size =
bare_instruction_payloads
? compiler::target::InstructionsSection::HeaderSize()
: compiler::target::InstructionsSection::InstanceSize(0);
text_offset += Align(section_contents_alignment, text_offset);
ASSERT_EQUAL(text_offset - id.nonce(), expected_size);
}
#endif
FrameUnwindPrologue();
PcDescriptors& descriptors = PcDescriptors::Handle(zone);
#if defined(DART_PRECOMPILER)
SnapshotTextObjectNamer namer(zone);
#endif
ASSERT(offset_space_ != IdSpace::kSnapshot);
for (intptr_t i = 0; i < instructions_.length(); i++) {
auto& data = instructions_[i];
const bool is_trampoline = data.trampoline_bytes != nullptr;
ASSERT_EQUAL(data.text_offset_, text_offset);
#if defined(DART_PRECOMPILER)
// We won't add trampolines as symbols, so their name need not be unique
// across different WriteText() calls.
const char* object_name = namer.SnapshotNameFor(
is_trampoline ? i : unique_symbol_counter_++, data);
if (profile_writer_ != nullptr) {
const V8SnapshotProfileWriter::ObjectId id(offset_space_, text_offset);
auto const type = is_trampoline ? trampoline_type_ : instructions_type_;
const intptr_t size = is_trampoline ? data.trampoline_length
: SizeInSnapshot(data.insns_->ptr());
profile_writer_->SetObjectTypeAndName(id, type, object_name);
profile_writer_->AttributeBytesTo(id, size);
const intptr_t element_offset = id.nonce() - parent_id.nonce();
profile_writer_->AttributeReferenceTo(
parent_id,
V8SnapshotProfileWriter::Reference::Element(element_offset), id);
}
#endif
if (is_trampoline) {
text_offset += WriteBytes(data.trampoline_bytes, data.trampoline_length);
delete[] data.trampoline_bytes;
data.trampoline_bytes = nullptr;
continue;
}
const intptr_t instr_start = text_offset;
const auto& code = *data.code_;
const auto& insns = *data.insns_;
// 1. Write from the object start to the payload start. This includes the
// object header and the fixed fields. Not written for AOT snapshots using
// bare instructions.
if (!bare_instruction_payloads) {
NoSafepointScope no_safepoint;
// Write Instructions with the mark and read-only bits set.
text_offset += WriteTargetWord(GetMarkedTags(insns));
text_offset += WriteFixed(insns.untag()->size_and_flags_);
text_offset +=
Align(compiler::target::Instructions::kNonBarePayloadAlignment,
text_offset);
}
ASSERT_EQUAL(text_offset - instr_start,
compiler::target::Instructions::HeaderSize());
#if defined(DART_PRECOMPILER)
// 2. Add a symbol for the code at the entry point in precompiled snapshots.
// Linux's perf uses these labels.
AddCodeSymbol(code, object_name, text_offset);
#endif
{
NoSafepointScope no_safepoint;
// 3. Write from the payload start to payload end. For AOT snapshots
// with bare instructions, this is the only part serialized other than
// any padding needed for alignment.
auto const payload_start =
reinterpret_cast<const uint8_t*>(insns.PayloadStart());
// Double-check the payload alignment, since we will load and write
// target-sized words starting from that address.
ASSERT(Utils::IsAligned(payload_start, compiler::target::kWordSize));
const uword payload_size = insns.Size();
descriptors = code.pc_descriptors();
PcDescriptors::Iterator iterator(
descriptors, /*kind_mask=*/UntaggedPcDescriptors::kBSSRelocation);
auto const payload_end = payload_start + payload_size;
auto cursor = payload_start;
while (iterator.MoveNext()) {
ASSERT(FLAG_precompiled_mode);
auto const next_reloc_offset = iterator.PcOffset();
auto const next_reloc_address = payload_start + next_reloc_offset;
// We only generate BSS relocations that are target word-sized and at
// target word-aligned offsets in the payload. Double-check this..
ASSERT(
Utils::IsAligned(next_reloc_address, compiler::target::kWordSize));
text_offset += WriteBytes(cursor, next_reloc_address - cursor);
#if defined(DART_PRECOMPILER)
// The instruction stream at the relocation position holds an offset
// into BSS corresponding to the symbol being resolved. This addend is
// factored into the relocation.
const auto addend = *reinterpret_cast<const compiler::target::word*>(
next_reloc_address);
text_offset += Relocation(text_offset, instructions_symbol, text_offset,
bss_symbol, /*target_offset=*/0, addend);
#endif
cursor = next_reloc_address + compiler::target::kWordSize;
}
text_offset += WriteBytes(cursor, payload_end - cursor);
}
// 4. Add appropriate padding. Note we can't simply copy from the object
// because the host object may have less alignment filler than the target
// object in the cross-word case.
const intptr_t alignment =
bare_instruction_payloads
? compiler::target::Instructions::kBarePayloadAlignment
: compiler::target::ObjectAlignment::kObjectAlignment;
text_offset += AlignWithBreakInstructions(alignment, text_offset);
ASSERT_EQUAL(text_offset - instr_start, SizeInSnapshot(insns.ptr()));
}
// Should be a no-op unless writing bare instruction payloads, in which case
// we need to add post-payload padding for the InstructionsSection object.
// Since this follows instructions, we'll use break instructions for padding.
ASSERT(bare_instruction_payloads ||
Utils::IsAligned(text_offset,
compiler::target::ObjectAlignment::kObjectAlignment));
text_offset += AlignWithBreakInstructions(
compiler::target::ObjectAlignment::kObjectAlignment, text_offset);
ASSERT_EQUAL(text_offset, image_size);
FrameUnwindEpilogue();
ExitSection(ProgramSection::Text, vm, text_offset);
}
intptr_t ImageWriter::AlignWithBreakInstructions(intptr_t alignment,
intptr_t offset) {
intptr_t bytes_written = 0;
uword remaining;
for (remaining = Utils::RoundUp(offset, alignment) - offset;
remaining >= compiler::target::kWordSize;
remaining -= compiler::target::kWordSize) {
bytes_written += WriteTargetWord(kBreakInstructionFiller);
}
#if defined(TARGET_ARCH_ARM)
// All instructions are 4 bytes long on ARM architectures, so on 32-bit ARM
// there won't be any padding.
ASSERT_EQUAL(remaining, 0);
#elif defined(TARGET_ARCH_ARM64)
// All instructions are 4 bytes long on ARM architectures, so on 64-bit ARM
// there is only 0 or 4 bytes of padding.
if (remaining != 0) {
ASSERT_EQUAL(remaining, 4);
bytes_written += WriteBytes(&kBreakInstructionFiller, remaining);
}
#elif defined(TARGET_ARCH_X64) || defined(TARGET_ARCH_IA32)
// The break instruction is a single byte, repeated to fill a word.
bytes_written += WriteBytes(&kBreakInstructionFiller, remaining);
#else
#error Unexpected architecture.
#endif
ASSERT_EQUAL(bytes_written, Utils::RoundUp(offset, alignment) - offset);
return bytes_written;
}
#if defined(DART_PRECOMPILER)
// Indices are log2(size in bytes).
static constexpr const char* kSizeDirectives[] = {".byte", ".2byte", ".long",
".quad"};
static constexpr const char* kWordDirective =
kSizeDirectives[compiler::target::kWordSizeLog2];
class DwarfAssemblyStream : public DwarfWriteStream {
public:
explicit DwarfAssemblyStream(BaseWriteStream* stream)
: stream_(ASSERT_NOTNULL(stream)) {}
void sleb128(intptr_t value) { stream_->Printf(".sleb128 %" Pd "\n", value); }
void uleb128(uintptr_t value) {
stream_->Printf(".uleb128 %" Pd "\n", value);
}
void u1(uint8_t value) {
stream_->Printf("%s %u\n", kSizeDirectives[kInt8SizeLog2], value);
}
void u2(uint16_t value) {
stream_->Printf("%s %u\n", kSizeDirectives[kInt16SizeLog2], value);
}
void u4(uint32_t value) {
stream_->Printf("%s %" Pu32 "\n", kSizeDirectives[kInt32SizeLog2], value);
}
void u8(uint64_t value) {
stream_->Printf("%s %" Pu64 "\n", kSizeDirectives[kInt64SizeLog2], value);
}
void string(const char* cstr) { // NOLINT
stream_->Printf(".string \"%s\"\n", cstr); // NOLINT
}
// Uses labels, so doesn't output to start or return a useful fixup position.
intptr_t ReserveSize(const char* prefix, intptr_t* start) {
// Assignment to temp works around buggy Mac assembler.
stream_->Printf("L%s_size = .L%s_end - .L%s_start\n", prefix, prefix,
prefix);
stream_->Printf("%s L%s_size\n", kSizeDirectives[kInt32SizeLog2], prefix);
stream_->Printf(".L%s_start:\n", prefix);
return -1;
}
// Just need to label the end so the assembler can calculate the size, so
// start and the fixup position is unused.
void SetSize(intptr_t fixup, const char* prefix, intptr_t start) {
stream_->Printf(".L%s_end:\n", prefix);
}
void OffsetFromSymbol(const char* symbol, intptr_t offset) {
if (offset == 0) {
PrintNamedAddress(symbol);
} else {
PrintNamedAddressWithOffset(symbol, offset);
}
}
void DistanceBetweenSymbolOffsets(const char* symbol1,
intptr_t offset1,
const char* symbol2,
intptr_t offset2) {
stream_->Printf(".uleb128 %s - %s + %" Pd "\n", symbol1, symbol2,
offset1 - offset2);
}
// No-op, we'll be using labels.
void InitializeAbstractOrigins(intptr_t size) {}
void RegisterAbstractOrigin(intptr_t index) {
// Label for DW_AT_abstract_origin references
stream_->Printf(".Lfunc%" Pd ":\n", index);
}
void AbstractOrigin(intptr_t index) {
// Assignment to temp works around buggy Mac assembler.
stream_->Printf("Ltemp%" Pd " = .Lfunc%" Pd " - %s\n", temp_, index,
kDebugInfoLabel);
stream_->Printf("%s Ltemp%" Pd "\n", kSizeDirectives[kInt32SizeLog2],
temp_);
temp_++;
}
// Methods for writing the assembly prologues for various DWARF sections.
void AbbreviationsPrologue() {
#if defined(TARGET_OS_MACOS) || defined(TARGET_OS_MACOS_IOS)
stream_->WriteString(".section __DWARF,__debug_abbrev,regular,debug\n");
#elif defined(TARGET_OS_LINUX) || defined(TARGET_OS_ANDROID) || \
defined(TARGET_OS_FUCHSIA)
stream_->WriteString(".section .debug_abbrev,\"\"\n");
#else
UNIMPLEMENTED();
#endif
}
void DebugInfoPrologue() {
#if defined(TARGET_OS_MACOS) || defined(TARGET_OS_MACOS_IOS)
stream_->WriteString(".section __DWARF,__debug_info,regular,debug\n");
#elif defined(TARGET_OS_LINUX) || defined(TARGET_OS_ANDROID) || \
defined(TARGET_OS_FUCHSIA)
stream_->WriteString(".section .debug_info,\"\"\n");
#else
UNIMPLEMENTED();
#endif
// Used to calculate abstract origin values.
stream_->Printf("%s:\n", kDebugInfoLabel);
}
void LineNumberProgramPrologue() {
#if defined(TARGET_OS_MACOS) || defined(TARGET_OS_MACOS_IOS)
stream_->WriteString(".section __DWARF,__debug_line,regular,debug\n");
#elif defined(TARGET_OS_LINUX) || defined(TARGET_OS_ANDROID) || \
defined(TARGET_OS_FUCHSIA)
stream_->WriteString(".section .debug_line,\"\"\n");
#else
UNIMPLEMENTED();
#endif
}
private:
static constexpr const char* kDebugInfoLabel = ".Ldebug_info";
void PrintNamedAddress(const char* name) {
stream_->Printf("%s %s\n", kWordDirective, name);
}
void PrintNamedAddressWithOffset(const char* name, intptr_t offset) {
stream_->Printf("%s %s + %" Pd "\n", kWordDirective, name, offset);
}
BaseWriteStream* const stream_;
intptr_t temp_ = 0;
DISALLOW_COPY_AND_ASSIGN(DwarfAssemblyStream);
};
static inline Dwarf* AddDwarfIfUnstripped(Zone* zone, bool strip, Elf* elf) {
if (!strip) {
if (elf != nullptr) {
// Reuse the existing DWARF object.
ASSERT(elf->dwarf() != nullptr);
return elf->dwarf();
}
return new (zone) Dwarf(zone);
}
return nullptr;
}
AssemblyImageWriter::AssemblyImageWriter(Thread* thread,
BaseWriteStream* stream,
bool strip,
Elf* debug_elf)
: ImageWriter(thread),
assembly_stream_(stream),
assembly_dwarf_(AddDwarfIfUnstripped(thread->zone(), strip, debug_elf)),
debug_elf_(debug_elf) {}
void AssemblyImageWriter::Finalize() {
if (assembly_dwarf_ != nullptr) {
DwarfAssemblyStream dwarf_stream(assembly_stream_);
dwarf_stream.AbbreviationsPrologue();
assembly_dwarf_->WriteAbbreviations(&dwarf_stream);
dwarf_stream.DebugInfoPrologue();
assembly_dwarf_->WriteDebugInfo(&dwarf_stream);
dwarf_stream.LineNumberProgramPrologue();
assembly_dwarf_->WriteLineNumberProgram(&dwarf_stream);
}
if (debug_elf_ != nullptr) {
debug_elf_->Finalize();
}
}
static void EnsureAssemblerIdentifier(char* label) {
for (char c = *label; c != '\0'; c = *++label) {
if (((c >= 'a') && (c <= 'z')) || ((c >= 'A') && (c <= 'Z')) ||
((c >= '0') && (c <= '9'))) {
continue;
}
*label = '_';
}
}
const char* SnapshotTextObjectNamer::SnapshotNameFor(intptr_t code_index,
const Code& code) {
ASSERT(!code.IsNull());
const char* prefix = FLAG_precompiled_mode ? "Precompiled_" : "";
owner_ = code.owner();
if (owner_.IsNull()) {
insns_ = code.instructions();
const char* name = StubCode::NameOfStub(insns_.EntryPoint());
ASSERT(name != nullptr);
return OS::SCreate(zone_, "%sStub_%s", prefix, name);
}
// The weak reference to the Code's owner should never have been removed via
// an intermediate serialization, since WSRs are only introduced during
// precompilation.
owner_ = WeakSerializationReference::Unwrap(owner_);
ASSERT(!owner_.IsNull());
if (owner_.IsClass()) {
string_ = Class::Cast(owner_).Name();
const char* name = string_.ToCString();
EnsureAssemblerIdentifier(const_cast<char*>(name));
return OS::SCreate(zone_, "%sAllocationStub_%s_%" Pd, prefix, name,
code_index);
} else if (owner_.IsAbstractType()) {
const char* name = namer_.StubNameForType(AbstractType::Cast(owner_));
return OS::SCreate(zone_, "%s%s_%" Pd, prefix, name, code_index);
} else if (owner_.IsFunction()) {
const char* name = Function::Cast(owner_).ToQualifiedCString();
EnsureAssemblerIdentifier(const_cast<char*>(name));
return OS::SCreate(zone_, "%s%s_%" Pd, prefix, name, code_index);
} else {
UNREACHABLE();
}
}
const char* SnapshotTextObjectNamer::SnapshotNameFor(
intptr_t index,
const ImageWriter::InstructionsData& data) {
if (data.trampoline_bytes != nullptr) {
return OS::SCreate(zone_, "Trampoline_%" Pd "", index);
}
return SnapshotNameFor(index, *data.code_);
}
void AssemblyImageWriter::WriteBss(bool vm) {
EnterSection(ProgramSection::Bss, vm, ImageWriter::kBssAlignment);
auto const entry_count = vm ? BSS::kVmEntryCount : BSS::kIsolateEntryCount;
for (intptr_t i = 0; i < entry_count; i++) {
// All bytes in the .bss section must be zero.
WriteTargetWord(0);
}
ExitSection(ProgramSection::Bss, vm,
entry_count * compiler::target::kWordSize);
}
void AssemblyImageWriter::WriteROData(NonStreamingWriteStream* clustered_stream,
bool vm) {
ImageWriter::WriteROData(clustered_stream, vm);
if (!EnterSection(ProgramSection::Data, vm, ImageWriter::kRODataAlignment)) {
return;
}
WriteBytes(clustered_stream->buffer(), clustered_stream->bytes_written());
ExitSection(ProgramSection::Data, vm, clustered_stream->bytes_written());
}
bool AssemblyImageWriter::EnterSection(ProgramSection section,
bool vm,
intptr_t alignment) {
ASSERT(FLAG_precompiled_mode);
ASSERT(current_section_symbol_ == nullptr);
bool global_symbol = false;
switch (section) {
case ProgramSection::Text:
assembly_stream_->WriteString(".text\n");
global_symbol = true;
break;
case ProgramSection::Data:
#if defined(TARGET_OS_LINUX) || defined(TARGET_OS_ANDROID) || \
defined(TARGET_OS_FUCHSIA)
assembly_stream_->WriteString(".section .rodata\n");
#elif defined(TARGET_OS_MACOS) || defined(TARGET_OS_MACOS_IOS)
assembly_stream_->WriteString(".const\n");
#else
UNIMPLEMENTED();
#endif
global_symbol = true;
break;
case ProgramSection::Bss:
assembly_stream_->WriteString(".bss\n");
break;
case ProgramSection::BuildId:
break;
}
current_section_symbol_ = SectionSymbol(section, vm);
ASSERT(current_section_symbol_ != nullptr);
if (global_symbol) {
assembly_stream_->Printf(".globl %s\n", current_section_symbol_);
}
Align(alignment);
assembly_stream_->Printf("%s:\n", current_section_symbol_);
return true;
}
static void ElfAddSection(Elf* elf,
ImageWriter::ProgramSection section,
const char* symbol,
const uint8_t* bytes,
intptr_t size) {
if (elf == nullptr) return;
switch (section) {
case ImageWriter::ProgramSection::Text:
elf->AddText(symbol, bytes, size);
break;
case ImageWriter::ProgramSection::Data:
elf->AddROData(symbol, bytes, size);
break;
default:
// Other sections are handled by the Elf object internally.
break;
}
}
void AssemblyImageWriter::ExitSection(ProgramSection name,
bool vm,
intptr_t size) {
// We should still be in the same section as the last EnterSection.
ASSERT(current_section_symbol_ != nullptr);
ASSERT_EQUAL(strcmp(SectionSymbol(name, vm), current_section_symbol_), 0);
// We need to generate a text segment of the appropriate size in the ELF
// for two reasons:
//
// * We need unique virtual addresses for each text section in the DWARF
// file and that the virtual addresses for payloads within those sections
// do not overlap.
//
// * Our tools for converting DWARF stack traces back to "normal" Dart
// stack traces calculate an offset into the appropriate instructions
// section, and then add that offset to the virtual address of the
// corresponding segment to get the virtual address for the frame.
//
// Since we don't want to add the actual contents of the segment in the
// separate debugging information, we pass nullptr for the bytes, which
// creates an appropriate NOBITS section instead of PROGBITS.
ElfAddSection(debug_elf_, name, current_section_symbol_, /*bytes=*/nullptr,
size);
current_section_symbol_ = nullptr;
}
intptr_t AssemblyImageWriter::WriteTargetWord(word value) {
ASSERT(compiler::target::kBitsPerWord == kBitsPerWord ||
Utils::IsAbsoluteUint(compiler::target::kBitsPerWord, value));
// Padding is helpful for comparing the .S with --disassemble.
assembly_stream_->Printf("%s 0x%.*" Px "\n", kWordDirective,
2 * compiler::target::kWordSize, value);
return compiler::target::kWordSize;
}
intptr_t AssemblyImageWriter::Relocation(intptr_t section_offset,
const char* source_symbol,
intptr_t source_offset,
const char* target_symbol,
intptr_t target_offset,
intptr_t target_addend) {
ASSERT(source_symbol != nullptr);
ASSERT(target_symbol != nullptr);
// TODO(dartbug.com/43274): Remove once we generate consistent build IDs
// between assembly snapshots and their debugging information.
const char* build_id_symbol =
SectionSymbol(ProgramSection::BuildId, /*vm=*/false);
if (strcmp(target_symbol, build_id_symbol) == 0) {
return WriteTargetWord(Image::kNoBuildId);
}
// All relocations are word-sized.
assembly_stream_->Printf("%s ", kWordDirective);
if (strcmp(target_symbol, current_section_symbol_) == 0 &&
target_offset == section_offset) {
assembly_stream_->WriteString("(.)");
} else {
assembly_stream_->Printf("%s", target_symbol);
if (target_offset != 0) {
assembly_stream_->Printf(" + %" Pd "", target_offset);
}
}
if (target_addend != 0) {
assembly_stream_->Printf(" + %" Pd "", target_addend);
}
if (strcmp(source_symbol, current_section_symbol_) == 0 &&
source_offset == section_offset) {
assembly_stream_->WriteString(" - (.)");
} else {
assembly_stream_->Printf(" - %s", source_symbol);
if (source_offset != 0) {
assembly_stream_->Printf(" - %" Pd "", source_offset);
}
}
assembly_stream_->WriteString("\n");
return compiler::target::kWordSize;
}
void AssemblyImageWriter::AddCodeSymbol(const Code& code,
const char* symbol,
intptr_t offset) {
if (assembly_dwarf_ != nullptr) {
assembly_dwarf_->AddCode(code, symbol);
}
if (debug_elf_ != nullptr) {
debug_elf_->dwarf()->AddCode(code, symbol);
debug_elf_->AddLocalSymbol(symbol, elf::STT_FUNC, offset, code.Size());
}
assembly_stream_->Printf("%s:\n", symbol);
}
void AssemblyImageWriter::FrameUnwindPrologue() {
// Creates DWARF's .debug_frame
// CFI = Call frame information
// CFA = Canonical frame address
assembly_stream_->WriteString(".cfi_startproc\n");
#if defined(TARGET_ARCH_X64)
assembly_stream_->WriteString(".cfi_def_cfa rbp, 0\n"); // CFA is fp+0
assembly_stream_->WriteString(
".cfi_offset rbp, 0\n"); // saved fp is *(CFA+0)
assembly_stream_->WriteString(
".cfi_offset rip, 8\n"); // saved pc is *(CFA+8)
// saved sp is CFA+16
// Would prefer to use ".cfi_value_offset sp, 16", but this requires gcc
// newer than late 2016. Can't emit .cfi_value_offset using .cfi_scape
// because DW_CFA_val_offset uses scaled operand and we don't know what
// data alignment factor will be choosen by the assembler when emitting CIE.
// DW_CFA_expression 0x10
// uleb128 register (rsp) 7 (DWARF register number)
// uleb128 size of operation 2
// DW_OP_plus_uconst 0x23
// uleb128 addend 16
assembly_stream_->WriteString(".cfi_escape 0x10, 31, 2, 0x23, 16\n");
#elif defined(TARGET_ARCH_ARM64)
COMPILE_ASSERT(R29 == FP);
COMPILE_ASSERT(R30 == LINK_REGISTER);
assembly_stream_->WriteString(".cfi_def_cfa x29, 0\n"); // CFA is fp+0
assembly_stream_->WriteString(
".cfi_offset x29, 0\n"); // saved fp is *(CFA+0)
assembly_stream_->WriteString(
".cfi_offset x30, 8\n"); // saved pc is *(CFA+8)
// saved sp is CFA+16
// Would prefer to use ".cfi_value_offset sp, 16", but this requires gcc
// newer than late 2016. Can't emit .cfi_value_offset using .cfi_scape
// because DW_CFA_val_offset uses scaled operand and we don't know what
// data alignment factor will be choosen by the assembler when emitting CIE.
#if defined(TARGET_OS_ANDROID)
// On Android libunwindstack has a bug (b/191113792): it does not push
// CFA value to the expression stack before evaluating expression given
// to DW_CFA_expression. We have to workaround this bug by manually pushing
// CFA (R11) to the stack using DW_OP_breg29 0.
// DW_CFA_expression 0x10
// uleb128 register (x31) 31
// uleb128 size of operation 4
// DW_OP_breg11 0x8d (0x70 + 29)
// sleb128 offset 0
// DW_OP_plus_uconst 0x23
// uleb128 addend 16
assembly_stream_->WriteString(".cfi_escape 0x10, 31, 4, 0x8d, 0, 0x23, 16\n");
#else
// DW_CFA_expression 0x10
// uleb128 register (x31) 31
// uleb128 size of operation 2
// DW_OP_plus_uconst 0x23
// uleb128 addend 16
assembly_stream_->WriteString(".cfi_escape 0x10, 31, 2, 0x23, 16\n");
#endif
#elif defined(TARGET_ARCH_ARM)
#if defined(TARGET_OS_MACOS) || defined(TARGET_OS_MACOS_IOS)
COMPILE_ASSERT(FP == R7);
assembly_stream_->WriteString(".cfi_def_cfa r7, 0\n"); // CFA is fp+0
assembly_stream_->WriteString(".cfi_offset r7, 0\n"); // saved fp is *(CFA+0)
#else
COMPILE_ASSERT(FP == R11);
assembly_stream_->WriteString(".cfi_def_cfa r11, 0\n"); // CFA is fp+0
assembly_stream_->WriteString(
".cfi_offset r11, 0\n"); // saved fp is *(CFA+0)
#endif
assembly_stream_->WriteString(".cfi_offset lr, 4\n"); // saved pc is *(CFA+4)
// saved sp is CFA+8
// Would prefer to use ".cfi_value_offset sp, 16", but this requires gcc
// newer than late 2016. Can't emit .cfi_value_offset using .cfi_scape
// because DW_CFA_val_offset uses scaled operand and we don't know what
// data alignment factor will be choosen by the assembler when emitting CIE.
#if defined(TARGET_OS_ANDROID)
// On Android libunwindstack has a bug (b/191113792): it does not push
// CFA value to the expression stack before evaluating expression given
// to DW_CFA_expression. We have to workaround this bug by manually pushing
// CFA (R11) to the stack using DW_OP_breg11 0.
// DW_CFA_expression 0x10
// uleb128 register (sp) 13
// uleb128 size of operation 4
// DW_OP_breg11 0x7b (0x70 + 11)
// sleb128 offset 0
// DW_OP_plus_uconst 0x23
// uleb128 addend 8
assembly_stream_->WriteString(".cfi_escape 0x10, 31, 4, 0x7b, 0, 0x23, 16\n");
#else
// DW_CFA_expression 0x10
// uleb128 register (sp) 13
// uleb128 size of operation 2
// DW_OP_plus_uconst 0x23
// uleb128 addend 8
assembly_stream_->WriteString(".cfi_escape 0x10, 13, 2, 0x23, 8\n");
#endif
// libunwind on ARM may use .ARM.exidx instead of .debug_frame
#if !defined(TARGET_OS_MACOS) && !defined(TARGET_OS_MACOS_IOS)
COMPILE_ASSERT(FP == R11);
assembly_stream_->WriteString(".fnstart\n");
assembly_stream_->WriteString(".save {r11, lr}\n");
assembly_stream_->WriteString(".setfp r11, sp, #0\n");
#endif
#endif
}
void AssemblyImageWriter::FrameUnwindEpilogue() {
#if defined(TARGET_ARCH_ARM)
#if !defined(TARGET_OS_MACOS) && !defined(TARGET_OS_MACOS_IOS)
assembly_stream_->WriteString(".fnend\n");
#endif
#endif
assembly_stream_->WriteString(".cfi_endproc\n");
}
intptr_t AssemblyImageWriter::WriteBytes(const void* bytes, intptr_t size) {
ASSERT(size >= 0);
auto const start = reinterpret_cast<const uint8_t*>(bytes);
auto const end_of_words =
start + Utils::RoundDown(size, compiler::target::kWordSize);
for (auto cursor = reinterpret_cast<const compiler::target::word*>(start);
cursor < reinterpret_cast<const compiler::target::word*>(end_of_words);
cursor++) {
WriteTargetWord(*cursor);
}
auto const end = start + size;
if (end != end_of_words) {
assembly_stream_->WriteString(kSizeDirectives[kInt8SizeLog2]);
for (auto cursor = end_of_words; cursor < end; cursor++) {
assembly_stream_->Printf("%s 0x%.2x", cursor != end_of_words ? "," : "",
*cursor);
}
assembly_stream_->WriteString("\n");
}
return size;
}
intptr_t AssemblyImageWriter::Align(intptr_t alignment, intptr_t position) {
const intptr_t next_position = Utils::RoundUp(position, alignment);
assembly_stream_->Printf(".balign %" Pd ", 0\n", alignment);
return next_position - position;
}
#endif // defined(DART_PRECOMPILER)
BlobImageWriter::BlobImageWriter(Thread* thread,
NonStreamingWriteStream* vm_instructions,
NonStreamingWriteStream* isolate_instructions,
Elf* debug_elf,
Elf* elf)
: ImageWriter(thread),
vm_instructions_(vm_instructions),
isolate_instructions_(isolate_instructions),
elf_(elf),
debug_elf_(debug_elf) {
#if defined(DART_PRECOMPILER)
ASSERT_EQUAL(FLAG_precompiled_mode, elf_ != nullptr);
ASSERT(debug_elf_ == nullptr || debug_elf_->dwarf() != nullptr);
#else
RELEASE_ASSERT(elf_ == nullptr);
#endif
}
intptr_t BlobImageWriter::WriteBytes(const void* bytes, intptr_t size) {
current_section_stream_->WriteBytes(bytes, size);
return size;
}
void BlobImageWriter::WriteBss(bool vm) {
#if defined(DART_PRECOMPILER)
// We don't actually write a BSS segment, it's created as part of the
// Elf constructor, but make sure it has an non-zero start.
ASSERT(elf_ == nullptr ||
elf_->SymbolAddress(vm ? kVmSnapshotBssAsmSymbol
: kIsolateSnapshotBssAsmSymbol) != 0);
#endif
}
void BlobImageWriter::WriteROData(NonStreamingWriteStream* clustered_stream,
bool vm) {
ImageWriter::WriteROData(clustered_stream, vm);
current_section_stream_ = clustered_stream;
if (!EnterSection(ProgramSection::Data, vm, ImageWriter::kRODataAlignment)) {
return;
}
ExitSection(ProgramSection::Data, vm, clustered_stream->bytes_written());
}
bool BlobImageWriter::EnterSection(ProgramSection section,
bool vm,
intptr_t alignment) {
#if defined(DART_PRECOMPILER)
ASSERT_EQUAL(elf_ != nullptr, FLAG_precompiled_mode);
#endif
// For now, we set current_section_stream_ in ::WriteData.
ASSERT(section == ProgramSection::Data || current_section_stream_ == nullptr);
ASSERT(current_section_symbol_ == nullptr);
switch (section) {
case ProgramSection::Text:
current_section_stream_ =
ASSERT_NOTNULL(vm ? vm_instructions_ : isolate_instructions_);
break;
case ProgramSection::Data:
break;
case ProgramSection::Bss:
// The BSS section is pre-made in the Elf object for precompiled snapshots
// and unused otherwise, so there's no work that needs doing here.
return false;
case ProgramSection::BuildId:
// The GNU build ID is handled specially in the Elf object, and does not
// get used for non-precompiled snapshots.
return false;
}
current_section_symbol_ = SectionSymbol(section, vm);
current_section_stream_->Align(alignment);
return true;
}
void BlobImageWriter::ExitSection(ProgramSection name, bool vm, intptr_t size) {
// We should still be in the same section as the last EnterSection.
ASSERT(current_section_symbol_ != nullptr);
ASSERT_EQUAL(strcmp(SectionSymbol(name, vm), current_section_symbol_), 0);
#if defined(DART_PRECOMPILER)
ElfAddSection(elf_, name, current_section_symbol_,
current_section_stream_->buffer(), size);
// We create the corresponding segment in the debugging information as well,
// since it needs the contents to create the correct build ID.
ElfAddSection(debug_elf_, name, current_section_symbol_,
current_section_stream_->buffer(), size);
#endif
current_section_symbol_ = nullptr;
current_section_stream_ = nullptr;
}
intptr_t BlobImageWriter::WriteTargetWord(word value) {
current_section_stream_->WriteTargetWord(value);
return compiler::target::kWordSize;
}
intptr_t BlobImageWriter::Align(intptr_t alignment, intptr_t offset) {
const intptr_t stream_padding = current_section_stream_->Align(alignment);
// Double-check that the offset has the same alignment.
ASSERT_EQUAL(Utils::RoundUp(offset, alignment) - offset, stream_padding);
return stream_padding;
}
#if defined(DART_PRECOMPILER)
intptr_t BlobImageWriter::Relocation(intptr_t section_offset,
const char* source_symbol,
intptr_t source_offset,
const char* target_symbol,
intptr_t target_offset,
intptr_t target_addend) {
ASSERT(FLAG_precompiled_mode);
const uword source_address = RelocatedAddress(source_symbol) + source_offset;
const uword target_address = RelocatedAddress(target_symbol) + target_offset;
return WriteTargetWord(target_address + target_addend - source_address);
}
uword BlobImageWriter::RelocatedAddress(const char* symbol) {
ASSERT(FLAG_precompiled_mode);
ASSERT(symbol != nullptr);
if (strcmp(symbol, current_section_symbol_) == 0) {
// Cheating a bit here, assuming that the current section will go into its
// own load segment (and that the load segment alignment is the same as
// the text section alignment).
return elf_->NextMemoryOffset(ImageWriter::kTextAlignment);
}
const uword start = elf_->SymbolAddress(symbol);
ASSERT(start != Elf::kNoSectionStart);
return start;
}
void BlobImageWriter::AddCodeSymbol(const Code& code,
const char* symbol,
intptr_t offset) {
if (elf_ != nullptr && elf_->dwarf() != nullptr) {
elf_->dwarf()->AddCode(code, symbol);
elf_->AddLocalSymbol(symbol, elf::STT_FUNC, offset, code.Size());
}
if (debug_elf_ != nullptr) {
debug_elf_->dwarf()->AddCode(code, symbol);
debug_elf_->AddLocalSymbol(symbol, elf::STT_FUNC, offset, code.Size());
}
}
#endif // defined(DART_PRECOMPILER)
#endif // !defined(DART_PRECOMPILED_RUNTIME)
ImageReader::ImageReader(const uint8_t* data_image,
const uint8_t* instructions_image)
: data_image_(ASSERT_NOTNULL(data_image)),
instructions_image_(ASSERT_NOTNULL(instructions_image)) {}
ApiErrorPtr ImageReader::VerifyAlignment() const {
if (!Utils::IsAligned(data_image_, kObjectAlignment) ||
!Utils::IsAligned(instructions_image_, kMaxObjectAlignment)) {
return ApiError::New(
String::Handle(String::New("Snapshot is misaligned", Heap::kOld)),
Heap::kOld);
}
return ApiError::null();
}
#if defined(DART_PRECOMPILED_RUNTIME)
uword ImageReader::GetBareInstructionsAt(uint32_t offset) const {
ASSERT(FLAG_use_bare_instructions);
ASSERT(Utils::IsAligned(offset, Instructions::kBarePayloadAlignment));
return reinterpret_cast<uword>(instructions_image_) + offset;
}
uword ImageReader::GetBareInstructionsEnd() const {
ASSERT(FLAG_use_bare_instructions);
Image image(instructions_image_);
return reinterpret_cast<uword>(image.object_start()) + image.object_size();
}
#endif
InstructionsPtr ImageReader::GetInstructionsAt(uint32_t offset) const {
ASSERT(!FLAG_precompiled_mode || !FLAG_use_bare_instructions);
ASSERT(Utils::IsAligned(offset, kObjectAlignment));
ObjectPtr result = UntaggedObject::FromAddr(
reinterpret_cast<uword>(instructions_image_) + offset);
ASSERT(result->IsInstructions());
ASSERT(result->untag()->IsMarked());
return Instructions::RawCast(result);
}
ObjectPtr ImageReader::GetObjectAt(uint32_t offset) const {
ASSERT(Utils::IsAligned(offset, kObjectAlignment));
ObjectPtr result =
UntaggedObject::FromAddr(reinterpret_cast<uword>(data_image_) + offset);
ASSERT(result->untag()->IsMarked());
return result;
}
} // namespace dart