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Summary: This is the first in a series of patches to enable LLDB debugging of WebAssembly targets. Current versions of Clang emit (partial) DWARF debug information in WebAssembly modules and we can leverage this debug information to give LLDB the ability to do source-level debugging of Wasm code that runs in a WebAssembly engine. A way to do this could be to use the remote debugging functionalities provided by LLDB via the GDB-remote protocol. Remote debugging can indeed be useful not only to connect a debugger to a process running on a remote machine, but also to connect the debugger to a managed VM or script engine that runs locally, provided that the engine implements a GDB-remote stub that offers the ability to access the engine runtime internal state. To make this work, the GDB-remote protocol would need to be extended with a few Wasm-specific custom query commands, used to access aspects of the Wasm engine state (like the Wasm memory, Wasm local and global variables, and so on). Furthermore, the DWARF format would need to be enriched with a few Wasm-specific extensions, here detailed: https://yurydelendik.github.io/webassembly-dwarf. This CL introduce classes **ObjectFileWasm**, a file plugin to represent a Wasm module loaded in a debuggee process. It knows how to parse Wasm modules and store the Code section and the DWARF-specific sections. Reviewers: jasonmolenda, clayborg, labath Tags: #lldb Differential Revision: https://reviews.llvm.org/D71575
139 lines
4.5 KiB
C++
139 lines
4.5 KiB
C++
//===-- ObjectFileWasm.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_PLUGINS_OBJECTFILE_WASM_OBJECTFILEWASM_H
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#define LLDB_PLUGINS_OBJECTFILE_WASM_OBJECTFILEWASM_H
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#include "lldb/Symbol/ObjectFile.h"
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#include "lldb/Utility/ArchSpec.h"
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namespace lldb_private {
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namespace wasm {
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/// Generic Wasm object file reader.
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///
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/// This class provides a generic wasm32 reader plugin implementing the
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/// ObjectFile protocol.
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class ObjectFileWasm : public ObjectFile {
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public:
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static void Initialize();
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static void Terminate();
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static ConstString GetPluginNameStatic();
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static const char *GetPluginDescriptionStatic() {
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return "WebAssembly object file reader.";
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}
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static ObjectFile *
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CreateInstance(const lldb::ModuleSP &module_sp, lldb::DataBufferSP &data_sp,
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lldb::offset_t data_offset, const FileSpec *file,
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lldb::offset_t file_offset, lldb::offset_t length);
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static ObjectFile *CreateMemoryInstance(const lldb::ModuleSP &module_sp,
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lldb::DataBufferSP &data_sp,
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const lldb::ProcessSP &process_sp,
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lldb::addr_t header_addr);
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static size_t GetModuleSpecifications(const FileSpec &file,
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lldb::DataBufferSP &data_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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ModuleSpecList &specs);
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/// PluginInterface protocol.
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/// \{
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ConstString GetPluginName() override { return GetPluginNameStatic(); }
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uint32_t GetPluginVersion() override { return 1; }
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/// \}
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/// ObjectFile Protocol.
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/// \{
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bool ParseHeader() override;
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lldb::ByteOrder GetByteOrder() const override {
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return m_arch.GetByteOrder();
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}
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bool IsExecutable() const override { return true; }
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uint32_t GetAddressByteSize() const override {
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return m_arch.GetAddressByteSize();
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}
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AddressClass GetAddressClass(lldb::addr_t file_addr) override {
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return AddressClass::eInvalid;
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}
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Symtab *GetSymtab() override;
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bool IsStripped() override { return true; }
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void CreateSections(SectionList &unified_section_list) override;
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void Dump(Stream *s) override;
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ArchSpec GetArchitecture() override { return m_arch; }
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UUID GetUUID() override { return m_uuid; }
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uint32_t GetDependentModules(FileSpecList &files) override { return 0; }
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Type CalculateType() override { return eTypeExecutable; }
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Strata CalculateStrata() override { return eStrataUser; }
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bool SetLoadAddress(lldb_private::Target &target, lldb::addr_t value,
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bool value_is_offset) override;
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lldb_private::Address GetBaseAddress() override {
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return IsInMemory() ? Address(m_memory_addr + m_code_section_offset)
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: Address(m_code_section_offset);
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}
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/// \}
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private:
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ObjectFileWasm(const lldb::ModuleSP &module_sp, lldb::DataBufferSP &data_sp,
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lldb::offset_t data_offset, const FileSpec *file,
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lldb::offset_t offset, lldb::offset_t length);
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ObjectFileWasm(const lldb::ModuleSP &module_sp,
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lldb::DataBufferSP &header_data_sp,
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const lldb::ProcessSP &process_sp, lldb::addr_t header_addr);
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/// Wasm section decoding routines.
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/// \{
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bool DecodeNextSection(lldb::offset_t *offset_ptr);
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bool DecodeSections();
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/// \}
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/// Read a range of bytes from the Wasm module.
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DataExtractor ReadImageData(uint64_t offset, size_t size);
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typedef struct section_info {
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lldb::offset_t offset;
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uint32_t size;
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uint32_t id;
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ConstString name;
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} section_info_t;
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/// Wasm section header dump routines.
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/// \{
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void DumpSectionHeader(llvm::raw_ostream &ostream, const section_info_t &sh);
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void DumpSectionHeaders(llvm::raw_ostream &ostream);
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/// \}
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std::vector<section_info_t> m_sect_infos;
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ArchSpec m_arch;
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UUID m_uuid;
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uint32_t m_code_section_offset;
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};
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} // namespace wasm
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} // namespace lldb_private
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#endif // LLDB_PLUGINS_OBJECTFILE_WASM_OBJECTFILEWASM_H
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