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// Copyright (c) 2019, 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/allocation.h"
#include "vm/compiler/runtime_api.h"
#include "vm/datastream.h"
#include "vm/growable_array.h"
#include "vm/zone.h"
namespace dart {
class Dwarf;
class ElfWriteStream;
class Section;
class Segment;
class StringTable;
class SymbolTable;
class Elf : public ZoneAllocated {
enum class Type {
// A snapshot that should include segment contents.
// Separately compiled debugging information that should not include
// most segment contents.
Elf(Zone* zone, BaseWriteStream* stream, Type type, Dwarf* dwarf = nullptr);
static constexpr intptr_t kPageSize = 16 * KB;
static constexpr uword kNoSectionStart = 0;
bool IsStripped() const { return dwarf_ == nullptr; }
Zone* zone() { return zone_; }
const Dwarf* dwarf() const { return dwarf_; }
Dwarf* dwarf() { return dwarf_; }
// Returns the relocated address for the symbol with the given name or
// kNoSectionStart if the symbol was not found.
uword SymbolAddress(const char* name) const;
// What the next memory offset for an appropriately aligned section would be.
// Only used by AssemblyImageWriter and BlobImageWriter methods.
intptr_t NextMemoryOffset(intptr_t alignment) const;
intptr_t AddText(const char* name, const uint8_t* bytes, intptr_t size);
intptr_t AddROData(const char* name, const uint8_t* bytes, intptr_t size);
void AddDebug(const char* name, const uint8_t* bytes, intptr_t size);
// Adds a local symbol for the given offset and size in the "current" section,
// that is, the section index for the symbol is for the next added section.
void AddLocalSymbol(const char* name,
intptr_t type,
intptr_t offset,
intptr_t size);
void Finalize();
static constexpr const char* kBuildIdNoteName = "";
static Section* CreateBSS(Zone* zone, Type type, intptr_t size);
// Adds the section and also creates a PT_LOAD segment for the section if it
// is an allocated section.
// For allocated sections, if symbol_name is provided, a symbol for the
// section will be added to the dynamic table (if allocated) and static
// table (if not stripped) during finalization.
// Returns the memory offset if the section is allocated.
intptr_t AddSection(Section* section,
const char* name,
const char* symbol_name = nullptr);
// Replaces [old_section] with [new_section] in all appropriate places. If the
// section is allocated, the memory size of the section must be the same as
// the original to ensure any already-calculated memory offsets are unchanged.
void ReplaceSection(Section* old_section, Section* new_section);
void AddStaticSymbol(const char* name,
intptr_t binding,
intptr_t type,
intptr_t section_index,
intptr_t address,
intptr_t size);
void AddDynamicSymbol(const char* name,
intptr_t binding,
intptr_t type,
intptr_t section_index,
intptr_t address,
intptr_t size);
Segment* LastLoadSegment() const;
const Section* FindSectionForAddress(intptr_t address) const;
Section* CreateBuildIdNote(const void* description_bytes,
intptr_t description_length);
Section* GenerateFinalBuildId();
void AddSectionSymbols();
void FinalizeDwarfSections();
void FinalizeProgramTable();
void ComputeFileOffsets();
void FinalizeEhFrame();
void WriteHeader(ElfWriteStream* stream);
void WriteSectionTable(ElfWriteStream* stream);
void WriteProgramTable(ElfWriteStream* stream);
void WriteSections(ElfWriteStream* stream);
Zone* const zone_;
BaseWriteStream* const unwrapped_stream_;
const Type type_;
// If nullptr, then the ELF file should be stripped of static information like
// the static symbol table (and its corresponding string table).
Dwarf* const dwarf_;
// We always create a BSS section for all Elf files, though it may be NOBITS
// if this is separate debugging information.
Section* const bss_;
// All our strings would fit in a single page. However, we use separate
// .shstrtab and .dynstr to work around a bug in Android's strip utility.
StringTable* const shstrtab_;
StringTable* const dynstrtab_;
SymbolTable* const dynsym_;
// The static tables are lazily created when static symbols are added.
StringTable* strtab_ = nullptr;
SymbolTable* symtab_ = nullptr;
// We always create a GNU build ID for all Elf files. In order to create
// the appropriate offset to it in an InstructionsSection object, we create an
// initial build ID section as a placeholder and then replace that section
// during finalization once we have the information to calculate the real one.
Section* build_id_;
GrowableArray<Section*> sections_;
GrowableArray<Segment*> segments_;
intptr_t memory_offset_;
intptr_t section_table_file_offset_ = -1;
intptr_t section_table_file_size_ = -1;
intptr_t program_table_file_offset_ = -1;
intptr_t program_table_file_size_ = -1;
} // namespace dart
#endif // RUNTIME_VM_ELF_H_