2aa020f49b
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
120 lines
4.2 KiB
C++
120 lines
4.2 KiB
C++
//===-- ObjectFileCOFF.h -------------------------------------- -*- C++ -*-===//
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//
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// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
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// See https://llvm.org/LICENSE.txt for license information.
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// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
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//
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//===----------------------------------------------------------------------===//
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#ifndef LLDB_SOURCE_PLUGINS_OBJECTFILE_COFF_OBJECTFILECOFF_H
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#define LLDB_SOURCE_PLUGINS_OBJECTFILE_COFF_OBJECTFILECOFF_H
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#include "lldb/Symbol/ObjectFile.h"
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#include "llvm/Object/COFF.h"
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/// \class ObjectFileELF
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/// Generic COFF object file reader.
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///
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/// This class provides a generic COFF reader plugin implementing the ObjectFile
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/// protocol. Assumes that the COFF object format is a Microsoft style COFF
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/// rather than the full generality afforded by it.
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class ObjectFileCOFF : public lldb_private::ObjectFile {
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std::unique_ptr<llvm::object::COFFObjectFile> m_object;
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lldb_private::UUID m_uuid;
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ObjectFileCOFF(std::unique_ptr<llvm::object::COFFObjectFile> object,
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const lldb::ModuleSP &module_sp,
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lldb::DataExtractorSP extractor_sp, lldb::offset_t data_offset,
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const lldb_private::FileSpec *file, lldb::offset_t file_offset,
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lldb::offset_t length)
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: ObjectFile(module_sp, file, file_offset, length, extractor_sp,
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data_offset),
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m_object(std::move(object)) {}
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public:
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~ObjectFileCOFF() override;
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static void Initialize();
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static void Terminate();
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static llvm::StringRef GetPluginNameStatic() { return "COFF"; }
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static llvm::StringRef GetPluginDescriptionStatic() {
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return "COFF Object File Reader";
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}
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static lldb_private::ObjectFile *
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CreateInstance(const lldb::ModuleSP &module_sp,
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lldb::DataExtractorSP extractor_sp, lldb::offset_t data_offset,
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const lldb_private::FileSpec *file, lldb::offset_t file_offset,
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lldb::offset_t length);
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static lldb_private::ObjectFile *
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CreateMemoryInstance(const lldb::ModuleSP &module_sp,
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lldb::WritableDataBufferSP data_sp,
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const lldb::ProcessSP &process_sp, lldb::addr_t header);
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static size_t GetModuleSpecifications(const lldb_private::FileSpec &file,
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lldb::DataExtractorSP &extractor_sp,
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lldb::offset_t data_offset,
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lldb::offset_t file_offset,
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lldb::offset_t length,
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lldb_private::ModuleSpecList &specs);
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// LLVM RTTI support
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static char ID;
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bool isA(const void *ClassID) const override {
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return ClassID == &ID || ObjectFile::isA(ClassID);
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}
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static bool classof(const ObjectFile *obj) { return obj->isA(&ID); }
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// PluginInterface protocol
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llvm::StringRef GetPluginName() override { return GetPluginNameStatic(); }
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// ObjectFile protocol
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void Dump(lldb_private::Stream *stream) override;
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uint32_t GetAddressByteSize() const override;
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uint32_t GetDependentModules(lldb_private::FileSpecList &specs) override {
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return 0;
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}
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bool IsExecutable() const override {
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// COFF is an object file format only, it cannot host an executable.
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return false;
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}
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lldb_private::ArchSpec GetArchitecture() override;
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void CreateSections(lldb_private::SectionList &) override;
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void ParseSymtab(lldb_private::Symtab &) override;
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bool IsStripped() override {
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// FIXME see if there is a good way to identify a /Z7 v /Zi or /ZI build.
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return false;
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}
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lldb_private::UUID GetUUID() override { return m_uuid; }
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lldb::ByteOrder GetByteOrder() const override {
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// Microsoft always uses little endian.
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return lldb::ByteOrder::eByteOrderLittle;
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}
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bool ParseHeader() override;
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lldb_private::ObjectFile::Type CalculateType() override {
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// COFF is an object file format only, it cannot host an executable.
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return lldb_private::ObjectFile::eTypeObjectFile;
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}
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lldb_private::ObjectFile::Strata CalculateStrata() override {
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// FIXME the object file may correspond to a kernel image.
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return lldb_private::ObjectFile::eStrataUser;
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}
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};
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#endif
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