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llvm-project/lldb/source/Plugins/ObjectFile/JSON/ObjectFileJSON.h
Jason Molenda 2aa020f49b [lldb][NFC] Module, ModuleSpec, GetSectionData use DataExtractorSP (#178347)
In a PR last month I changed the ObjectFile CreateInstance etc methods
to accept an optional DataExtractorSP instead of a DataBufferSP, and
retain the extractor in a shared pointer internally in all of the
ObjectFile subclasses. This is laying the groundwork for using a
VirtualDataExtractor for some Mach-O binaries on macOS, where the
segments of the binary are out-of-order in actual memory, and we add a
lookup table to make it appear that the TEXT segment is at offset 0 in
the Extractor, etc. Working on the actual implementation, I realized we
were still using DataBufferSP's in ModuleSpec and Module, as well as in
ObjectFile::GetModuleSpecifications.

I originally was making a much larger NFC change where I had all
ObjectFile subclasses operating on DataExtractors throughout their
implementation, as well as in the DWARF parser. It was a very large
patchset. Many subclasses start with their DataExtractor, then create
smaller DataExtractors for parts of the binary image - the string table,
the symbol table, etc., for processing.

After consideration and discussion with Jonas, we agreed that a
segment/section of a binary will never require a lookup table to access
the bytes within it, so I changed
VirtualDataExtractor::GetSubsetExtractorSP to (1) require that the
Subset be contained within a single lookup table entry, and (2) return a
simple DataExtractor bounded on that byte range. By doing this, I was
able to remove all of my very-invasive changes to the ObjectFile
subclass internals; it's only when they are operating on the entire
binary image that care is needed.

One pattern that subclasses like ObjectFileBreakpad use is to take an
ArrayRef of the DataBuffer for a binary, then create a StringRef of
that, then look for strings in it. With a VirtualDataExtractor and
out-of-order binary segments, with gaps between them, this allows us to
search the entire buffer looking for a string, and segfault when it gets
to an unmapped region of the buffer. I added a
VirtualDataExtractor::GetSubsetExtractorSP(0) which gets the largest
contiguous memory region starting at offset 0 for this use case, and I
added a comment about what was being done there because I know it is not
obvious, and people not working on macOS wouldn't be familiar with the
requirement. (when we have a ModuleSpec with a DataExtractor, any of the
ObjectFile subclasses get a shot at Creating, so they all have to be
able to iterate on these)

rdar://148939795
2026-01-29 15:36:40 -08:00

131 lines
4.3 KiB
C++

//===-- ObjectFileJSON.h -------------------------------------- -*- C++ -*-===//
//
// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
// See https://llvm.org/LICENSE.txt for license information.
// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
//
//===----------------------------------------------------------------------===//
#ifndef LLDB_SOURCE_PLUGINS_OBJECTFILE_JSON_OBJECTFILEJSON_H
#define LLDB_SOURCE_PLUGINS_OBJECTFILE_JSON_OBJECTFILEJSON_H
#include "lldb/Symbol/ObjectFile.h"
#include "lldb/Utility/ArchSpec.h"
#include "llvm/Support/JSON.h"
namespace lldb_private {
class ObjectFileJSON : public ObjectFile {
public:
static void Initialize();
static void Terminate();
static llvm::StringRef GetPluginNameStatic() { return "JSON"; }
static const char *GetPluginDescriptionStatic() {
return "JSON object file reader.";
}
static ObjectFile *CreateInstance(const lldb::ModuleSP &module_sp,
lldb::DataExtractorSP extractor_sp,
lldb::offset_t data_offset,
const FileSpec *file,
lldb::offset_t file_offset,
lldb::offset_t length);
static ObjectFile *CreateMemoryInstance(const lldb::ModuleSP &module_sp,
lldb::WritableDataBufferSP data_sp,
const lldb::ProcessSP &process_sp,
lldb::addr_t header_addr);
static size_t GetModuleSpecifications(const FileSpec &file,
lldb::DataExtractorSP &extractor_sp,
lldb::offset_t data_offset,
lldb::offset_t file_offset,
lldb::offset_t length,
ModuleSpecList &specs);
llvm::StringRef GetPluginName() override { return GetPluginNameStatic(); }
// LLVM RTTI support
static char ID;
bool isA(const void *ClassID) const override {
return ClassID == &ID || ObjectFile::isA(ClassID);
}
static bool classof(const ObjectFile *obj) { return obj->isA(&ID); }
bool ParseHeader() override;
lldb::ByteOrder GetByteOrder() const override {
return m_arch.GetByteOrder();
}
bool IsExecutable() const override { return false; }
uint32_t GetAddressByteSize() const override {
return m_arch.GetAddressByteSize();
}
AddressClass GetAddressClass(lldb::addr_t file_addr) override {
return AddressClass::eInvalid;
}
void ParseSymtab(lldb_private::Symtab &symtab) override;
bool IsStripped() override { return false; }
void CreateSections(SectionList &unified_section_list) override;
void Dump(Stream *s) override {}
ArchSpec GetArchitecture() override { return m_arch; }
UUID GetUUID() override { return m_uuid; }
uint32_t GetDependentModules(FileSpecList &files) override { return 0; }
Type CalculateType() override { return m_type; }
Strata CalculateStrata() override { return eStrataUser; }
bool SetLoadAddress(Target &target, lldb::addr_t value,
bool value_is_offset) override;
static bool MagicBytesMatch(lldb::DataExtractorSP extractor_sp);
struct Header {
std::string triple;
std::string uuid;
std::optional<ObjectFile::Type> type;
};
struct Body {
std::vector<JSONSection> sections;
std::vector<JSONSymbol> symbols;
};
private:
ArchSpec m_arch;
UUID m_uuid;
ObjectFile::Type m_type;
std::optional<uint64_t> m_size;
std::vector<JSONSymbol> m_symbols;
std::vector<JSONSection> m_sections;
ObjectFileJSON(const lldb::ModuleSP &module_sp,
lldb::DataExtractorSP extractor_sp, lldb::offset_t data_offset,
const FileSpec *file, lldb::offset_t offset,
lldb::offset_t length, ArchSpec arch, UUID uuid, Type type,
std::vector<JSONSymbol> symbols,
std::vector<JSONSection> sections);
};
bool fromJSON(const llvm::json::Value &value, ObjectFileJSON::Header &header,
llvm::json::Path path);
bool fromJSON(const llvm::json::Value &value, ObjectFileJSON::Body &body,
llvm::json::Path path);
} // namespace lldb_private
#endif // LLDB_SOURCE_PLUGINS_OBJECTFILE_JSON_OBJECTFILEJSON_H