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sdk/runtime/vm/image_snapshot.cc
T
Vyacheslav Egorov b97e8ecf72 [vm/snapshots] Write strings as ROData in root snapshot 
This partially undoes changes from acbd51c08
because they are now known to increate RSS of AOT
compiled applications.

This CL also removes length adjustment code from *String::InstanceSize
which tried to ensure that external string fits into a non-external
string. This code is no longer necessary because APIs for
string externalization were removed.

TEST=covered by the existing tests

Cq-Include-Trybots: luci.dart.try:app-kernel-linux-release-x64-try,app-kernel-linux-debug-x64-try,vm-kernel-nnbd-linux-debug-x64-try,vm-kernel-linux-debug-x64-try,vm-kernel-precomp-linux-debug-x64-try,vm-kernel-precomp-nnbd-linux-debug-x64-try
Change-Id: Ife4f16d6939d98bb7966121b5899cef9f0121220
Reviewed-on: https://dart-review.googlesource.com/c/sdk/+/170080
Commit-Queue: Vyacheslav Egorov <vegorov@google.com>
Reviewed-by: Ryan Macnak <rmacnak@google.com>
2020-11-02 21:11:50 +00:00

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// 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 InstructionsSectionLayout* 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 InstructionsSectionLayout*>(
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
}
intptr_t ObjectOffsetTrait::Hashcode(Key key) {
ObjectPtr obj = key;
ASSERT(!obj->IsSmi());
uword body = ObjectLayout::ToAddr(obj) + sizeof(ObjectLayout);
uword end = ObjectLayout::ToAddr(obj) + obj->ptr()->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->ptr()->HeapSize();
if (b->ptr()->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 = ObjectLayout::ToAddr(a) + sizeof(ObjectLayout);
uword body_b = ObjectLayout::ToAddr(b) + sizeof(ObjectLayout);
uword body_size = heap_size - sizeof(ObjectLayout);
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->ptr()->length_);
}
case kPcDescriptorsCid: {
auto raw_desc = PcDescriptors::RawCast(raw_object);
return compiler::target::PcDescriptors::InstanceSize(
raw_desc->ptr()->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.raw();
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_->raw()));
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()->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_->raw(), 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 ? V8SnapshotProfileWriter::kVmText
: V8SnapshotProfileWriter::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 ? V8SnapshotProfileWriter::kVmData
: V8SnapshotProfileWriter::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::ArtificialRootId(),
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->WriteFixed<uint32_t>(map.raw()->ptr()->flags_and_size_);
ASSERT_EQUAL(stream->Position() - object_start,
compiler::target::CompressedStackMaps::HeaderSize());
stream->WriteBytes(map.raw()->ptr()->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.raw()->ptr()->data(), desc.Length());
} else if (obj.IsString()) {
const String& str = String::Cast(obj);
RELEASE_ASSERT(String::GetCachedHash(str.raw()) != 0);
RELEASE_ASSERT(str.IsOneByteString() || str.IsTwoByteString());
stream->WriteTargetWord(static_cast<uword>(str.raw()->ptr()->length_));
#if !defined(HASH_IN_OBJECT_HEADER)
stream->WriteTargetWord(static_cast<uword>(str.raw()->ptr()->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 UNLESS_DEBUG(constexpr) const uword kReadOnlyGCBits =
ObjectLayout::OldBit::encode(true) |
ObjectLayout::OldAndNotMarkedBit::encode(false) |
ObjectLayout::OldAndNotRememberedBit::encode(true) |
ObjectLayout::NewBit::encode(false);
uword ImageWriter::GetMarkedTags(classid_t cid,
intptr_t size,
bool is_canonical /* = false */) {
// ObjectLayout::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 | ObjectLayout::ClassIdTag::encode(cid) |
ObjectLayout::SizeTag::encode(adjusted_size) |
ObjectLayout::CanonicalBit::encode(is_canonical);
}
uword ImageWriter::GetMarkedTags(const Object& obj) {
return
#if defined(HASH_IN_OBJECT_HEADER)
static_cast<uword>(obj.raw()->ptr()->hash_) << kBitsPerInt32 |
#endif
GetMarkedTags(obj.raw()->GetClassId(), SizeInSnapshot(obj),
obj.IsCanonical());
}
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 (FLAG_precompiled_mode) {
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);
}
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.second - parent_id.second;
profile_writer_->AttributeReferenceTo(
parent_id,
{id, V8SnapshotProfileWriter::Reference::kElement, element_offset});
// 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.second, expected_size);
}
#endif
FrameUnwindPrologue();
PcDescriptors& descriptors = PcDescriptors::Handle(zone);
#if defined(DART_PRECOMPILER)
SnapshotTextObjectNamer namer(zone);
#endif
ASSERT(offset_space_ != V8SnapshotProfileWriter::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_->raw());
profile_writer_->SetObjectTypeAndName(id, type, object_name);
profile_writer_->AttributeBytesTo(id, size);
const intptr_t element_offset = id.second - parent_id.second;
profile_writer_->AttributeReferenceTo(
parent_id,
{id, V8SnapshotProfileWriter::Reference::kElement, element_offset});
}
#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.raw_ptr()->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=*/PcDescriptorsLayout::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.raw()));
}
// 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%0.*" 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
// Should be ".cfi_value_offset rsp, 16", but requires gcc newer than late
// 2016 and not supported by Android's libunwind.
// 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(FP == R29);
COMPILE_ASSERT(LR == R30);
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
// Should be ".cfi_value_offset sp, 16", but requires gcc newer than late
// 2016 and not supported by Android's libunwind.
// 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");
#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+j0
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
// Should be ".cfi_value_offset sp, 8", but requires gcc newer than late
// 2016 and not supported by Android's libunwind.
// 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");
// 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%0.2x", 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 = ObjectLayout::FromAddr(
reinterpret_cast<uword>(instructions_image_) + offset);
ASSERT(result->IsInstructions());
ASSERT(result->ptr()->IsMarked());
return Instructions::RawCast(result);
}
ObjectPtr ImageReader::GetObjectAt(uint32_t offset) const {
ASSERT(Utils::IsAligned(offset, kObjectAlignment));
ObjectPtr result =
ObjectLayout::FromAddr(reinterpret_cast<uword>(data_image_) + offset);
ASSERT(result->ptr()->IsMarked());
return result;
}
} // namespace dart
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