1 //===-- ObjectFileELF.h --------------------------------------- -*- C++ -*-===//
2 //
3 // Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
4 // See https://llvm.org/LICENSE.txt for license information.
5 // SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
6 //
7 //===----------------------------------------------------------------------===//
8 
9 #ifndef LLDB_SOURCE_PLUGINS_OBJECTFILE_ELF_OBJECTFILEELF_H
10 #define LLDB_SOURCE_PLUGINS_OBJECTFILE_ELF_OBJECTFILEELF_H
11 
12 #include <cstdint>
13 
14 #include <vector>
15 
16 #include "lldb/Symbol/ObjectFile.h"
17 #include "lldb/Utility/ArchSpec.h"
18 #include "lldb/Utility/FileSpec.h"
19 #include "lldb/Utility/UUID.h"
20 #include "lldb/lldb-private.h"
21 
22 #include "ELFHeader.h"
23 
24 struct ELFNote {
25   elf::elf_word n_namesz = 0;
26   elf::elf_word n_descsz = 0;
27   elf::elf_word n_type = 0;
28 
29   std::string n_name;
30 
31   ELFNote() = default;
32 
33   /// Parse an ELFNote entry from the given DataExtractor starting at position
34   /// \p offset.
35   ///
36   /// \param[in] data
37   ///    The DataExtractor to read from.
38   ///
39   /// \param[in,out] offset
40   ///    Pointer to an offset in the data.  On return the offset will be
41   ///    advanced by the number of bytes read.
42   ///
43   /// \return
44   ///    True if the ELFRel entry was successfully read and false otherwise.
45   bool Parse(const lldb_private::DataExtractor &data, lldb::offset_t *offset);
46 
47   size_t GetByteSize() const {
48     return 12 + llvm::alignTo(n_namesz, 4) + llvm::alignTo(n_descsz, 4);
49   }
50 };
51 
52 /// \class ObjectFileELF
53 /// Generic ELF object file reader.
54 ///
55 /// This class provides a generic ELF (32/64 bit) reader plugin implementing
56 /// the ObjectFile protocol.
57 class ObjectFileELF : public lldb_private::ObjectFile {
58 public:
59   // Static Functions
60   static void Initialize();
61 
62   static void Terminate();
63 
64   static lldb_private::ConstString GetPluginNameStatic();
65 
66   static const char *GetPluginDescriptionStatic();
67 
68   static lldb_private::ObjectFile *
69   CreateInstance(const lldb::ModuleSP &module_sp, lldb::DataBufferSP &data_sp,
70                  lldb::offset_t data_offset, const lldb_private::FileSpec *file,
71                  lldb::offset_t file_offset, lldb::offset_t length);
72 
73   static lldb_private::ObjectFile *CreateMemoryInstance(
74       const lldb::ModuleSP &module_sp, lldb::DataBufferSP &data_sp,
75       const lldb::ProcessSP &process_sp, lldb::addr_t header_addr);
76 
77   static size_t GetModuleSpecifications(const lldb_private::FileSpec &file,
78                                         lldb::DataBufferSP &data_sp,
79                                         lldb::offset_t data_offset,
80                                         lldb::offset_t file_offset,
81                                         lldb::offset_t length,
82                                         lldb_private::ModuleSpecList &specs);
83 
84   static bool MagicBytesMatch(lldb::DataBufferSP &data_sp, lldb::addr_t offset,
85                               lldb::addr_t length);
86 
87   // PluginInterface protocol
88   lldb_private::ConstString GetPluginName() override;
89 
90   // LLVM RTTI support
91   static char ID;
92   bool isA(const void *ClassID) const override {
93     return ClassID == &ID || ObjectFile::isA(ClassID);
94   }
95   static bool classof(const ObjectFile *obj) { return obj->isA(&ID); }
96 
97   // ObjectFile Protocol.
98   bool ParseHeader() override;
99 
100   bool SetLoadAddress(lldb_private::Target &target, lldb::addr_t value,
101                       bool value_is_offset) override;
102 
103   lldb::ByteOrder GetByteOrder() const override;
104 
105   bool IsExecutable() const override;
106 
107   uint32_t GetAddressByteSize() const override;
108 
109   lldb_private::AddressClass GetAddressClass(lldb::addr_t file_addr) override;
110 
111   lldb_private::Symtab *GetSymtab() override;
112 
113   bool IsStripped() override;
114 
115   void CreateSections(lldb_private::SectionList &unified_section_list) override;
116 
117   void Dump(lldb_private::Stream *s) override;
118 
119   lldb_private::ArchSpec GetArchitecture() override;
120 
121   lldb_private::UUID GetUUID() override;
122 
123   /// Return the contents of the .gnu_debuglink section, if the object file
124   /// contains it.
125   llvm::Optional<lldb_private::FileSpec> GetDebugLink();
126 
127   uint32_t GetDependentModules(lldb_private::FileSpecList &files) override;
128 
129   lldb_private::Address
130   GetImageInfoAddress(lldb_private::Target *target) override;
131 
132   lldb_private::Address GetEntryPointAddress() override;
133 
134   lldb_private::Address GetBaseAddress() override;
135 
136   ObjectFile::Type CalculateType() override;
137 
138   ObjectFile::Strata CalculateStrata() override;
139 
140   size_t ReadSectionData(lldb_private::Section *section,
141                          lldb::offset_t section_offset, void *dst,
142                          size_t dst_len) override;
143 
144   size_t ReadSectionData(lldb_private::Section *section,
145                          lldb_private::DataExtractor &section_data) override;
146 
147   llvm::ArrayRef<elf::ELFProgramHeader> ProgramHeaders();
148   lldb_private::DataExtractor GetSegmentData(const elf::ELFProgramHeader &H);
149 
150   llvm::StringRef
151   StripLinkerSymbolAnnotations(llvm::StringRef symbol_name) const override;
152 
153   void RelocateSection(lldb_private::Section *section) override;
154 
155 protected:
156 
157   std::vector<LoadableData>
158   GetLoadableData(lldb_private::Target &target) override;
159 
160 private:
161   ObjectFileELF(const lldb::ModuleSP &module_sp, lldb::DataBufferSP &data_sp,
162                 lldb::offset_t data_offset, const lldb_private::FileSpec *file,
163                 lldb::offset_t offset, lldb::offset_t length);
164 
165   ObjectFileELF(const lldb::ModuleSP &module_sp,
166                 lldb::DataBufferSP &header_data_sp,
167                 const lldb::ProcessSP &process_sp, lldb::addr_t header_addr);
168 
169   typedef std::vector<elf::ELFProgramHeader> ProgramHeaderColl;
170 
171   struct ELFSectionHeaderInfo : public elf::ELFSectionHeader {
172     lldb_private::ConstString section_name;
173   };
174 
175   typedef std::vector<ELFSectionHeaderInfo> SectionHeaderColl;
176   typedef SectionHeaderColl::iterator SectionHeaderCollIter;
177   typedef SectionHeaderColl::const_iterator SectionHeaderCollConstIter;
178 
179   typedef std::vector<elf::ELFDynamic> DynamicSymbolColl;
180   typedef DynamicSymbolColl::iterator DynamicSymbolCollIter;
181   typedef DynamicSymbolColl::const_iterator DynamicSymbolCollConstIter;
182 
183   typedef std::map<lldb::addr_t, lldb_private::AddressClass>
184       FileAddressToAddressClassMap;
185 
186   /// Version of this reader common to all plugins based on this class.
187   static const uint32_t m_plugin_version = 1;
188   static const uint32_t g_core_uuid_magic;
189 
190   /// ELF file header.
191   elf::ELFHeader m_header;
192 
193   /// ELF build ID.
194   lldb_private::UUID m_uuid;
195 
196   /// ELF .gnu_debuglink file and crc data if available.
197   std::string m_gnu_debuglink_file;
198   uint32_t m_gnu_debuglink_crc = 0;
199 
200   /// Collection of program headers.
201   ProgramHeaderColl m_program_headers;
202 
203   /// Collection of section headers.
204   SectionHeaderColl m_section_headers;
205 
206   /// Collection of symbols from the dynamic table.
207   DynamicSymbolColl m_dynamic_symbols;
208 
209   /// Object file parsed from .gnu_debugdata section (\sa
210   /// GetGnuDebugDataObjectFile())
211   std::shared_ptr<ObjectFileELF> m_gnu_debug_data_object_file;
212 
213   /// List of file specifications corresponding to the modules (shared
214   /// libraries) on which this object file depends.
215   mutable std::unique_ptr<lldb_private::FileSpecList> m_filespec_up;
216 
217   /// Cached value of the entry point for this module.
218   lldb_private::Address m_entry_point_address;
219 
220   /// The architecture detected from parsing elf file contents.
221   lldb_private::ArchSpec m_arch_spec;
222 
223   /// The address class for each symbol in the elf file
224   FileAddressToAddressClassMap m_address_class_map;
225 
226   /// Returns the index of the given section header.
227   size_t SectionIndex(const SectionHeaderCollIter &I);
228 
229   /// Returns the index of the given section header.
230   size_t SectionIndex(const SectionHeaderCollConstIter &I) const;
231 
232   // Parses the ELF program headers.
233   static size_t GetProgramHeaderInfo(ProgramHeaderColl &program_headers,
234                                      lldb_private::DataExtractor &object_data,
235                                      const elf::ELFHeader &header);
236 
237   // Finds PT_NOTE segments and calculates their crc sum.
238   static uint32_t
239   CalculateELFNotesSegmentsCRC32(const ProgramHeaderColl &program_headers,
240                                  lldb_private::DataExtractor &data);
241 
242   /// Parses all section headers present in this object file and populates
243   /// m_program_headers.  This method will compute the header list only once.
244   /// Returns true iff the headers have been successfully parsed.
245   bool ParseProgramHeaders();
246 
247   /// Parses all section headers present in this object file and populates
248   /// m_section_headers.  This method will compute the header list only once.
249   /// Returns the number of headers parsed.
250   size_t ParseSectionHeaders();
251 
252   lldb::SectionType GetSectionType(const ELFSectionHeaderInfo &H) const;
253 
254   static void ParseARMAttributes(lldb_private::DataExtractor &data,
255                                  uint64_t length,
256                                  lldb_private::ArchSpec &arch_spec);
257 
258   /// Parses the elf section headers and returns the uuid, debug link name,
259   /// crc, archspec.
260   static size_t GetSectionHeaderInfo(SectionHeaderColl &section_headers,
261                                      lldb_private::DataExtractor &object_data,
262                                      const elf::ELFHeader &header,
263                                      lldb_private::UUID &uuid,
264                                      std::string &gnu_debuglink_file,
265                                      uint32_t &gnu_debuglink_crc,
266                                      lldb_private::ArchSpec &arch_spec);
267 
268   /// Scans the dynamic section and locates all dependent modules (shared
269   /// libraries) populating m_filespec_up.  This method will compute the
270   /// dependent module list only once.  Returns the number of dependent
271   /// modules parsed.
272   size_t ParseDependentModules();
273 
274   /// Parses the dynamic symbol table and populates m_dynamic_symbols.  The
275   /// vector retains the order as found in the object file.  Returns the
276   /// number of dynamic symbols parsed.
277   size_t ParseDynamicSymbols();
278 
279   /// Populates m_symtab_up will all non-dynamic linker symbols.  This method
280   /// will parse the symbols only once.  Returns the number of symbols parsed.
281   unsigned ParseSymbolTable(lldb_private::Symtab *symbol_table,
282                             lldb::user_id_t start_id,
283                             lldb_private::Section *symtab);
284 
285   /// Helper routine for ParseSymbolTable().
286   unsigned ParseSymbols(lldb_private::Symtab *symbol_table,
287                         lldb::user_id_t start_id,
288                         lldb_private::SectionList *section_list,
289                         const size_t num_symbols,
290                         const lldb_private::DataExtractor &symtab_data,
291                         const lldb_private::DataExtractor &strtab_data);
292 
293   /// Scans the relocation entries and adds a set of artificial symbols to the
294   /// given symbol table for each PLT slot.  Returns the number of symbols
295   /// added.
296   unsigned ParseTrampolineSymbols(lldb_private::Symtab *symbol_table,
297                                   lldb::user_id_t start_id,
298                                   const ELFSectionHeaderInfo *rela_hdr,
299                                   lldb::user_id_t section_id);
300 
301   void ParseUnwindSymbols(lldb_private::Symtab *symbol_table,
302                           lldb_private::DWARFCallFrameInfo *eh_frame);
303 
304   /// Relocates debug sections
305   unsigned RelocateDebugSections(const elf::ELFSectionHeader *rel_hdr,
306                                  lldb::user_id_t rel_id,
307                                  lldb_private::Symtab *thetab);
308 
309   unsigned ApplyRelocations(lldb_private::Symtab *symtab,
310                             const elf::ELFHeader *hdr,
311                             const elf::ELFSectionHeader *rel_hdr,
312                             const elf::ELFSectionHeader *symtab_hdr,
313                             const elf::ELFSectionHeader *debug_hdr,
314                             lldb_private::DataExtractor &rel_data,
315                             lldb_private::DataExtractor &symtab_data,
316                             lldb_private::DataExtractor &debug_data,
317                             lldb_private::Section *rel_section);
318 
319   /// Loads the section name string table into m_shstr_data.  Returns the
320   /// number of bytes constituting the table.
321   size_t GetSectionHeaderStringTable();
322 
323   /// Utility method for looking up a section given its name.  Returns the
324   /// index of the corresponding section or zero if no section with the given
325   /// name can be found (note that section indices are always 1 based, and so
326   /// section index 0 is never valid).
327   lldb::user_id_t GetSectionIndexByName(const char *name);
328 
329   /// Returns the section header with the given id or NULL.
330   const ELFSectionHeaderInfo *GetSectionHeaderByIndex(lldb::user_id_t id);
331 
332   /// \name  ELF header dump routines
333   //@{
334   static void DumpELFHeader(lldb_private::Stream *s,
335                             const elf::ELFHeader &header);
336 
337   static void DumpELFHeader_e_ident_EI_DATA(lldb_private::Stream *s,
338                                             unsigned char ei_data);
339 
340   static void DumpELFHeader_e_type(lldb_private::Stream *s,
341                                    elf::elf_half e_type);
342   //@}
343 
344   /// \name ELF program header dump routines
345   //@{
346   void DumpELFProgramHeaders(lldb_private::Stream *s);
347 
348   static void DumpELFProgramHeader(lldb_private::Stream *s,
349                                    const elf::ELFProgramHeader &ph);
350 
351   static void DumpELFProgramHeader_p_type(lldb_private::Stream *s,
352                                           elf::elf_word p_type);
353 
354   static void DumpELFProgramHeader_p_flags(lldb_private::Stream *s,
355                                            elf::elf_word p_flags);
356   //@}
357 
358   /// \name ELF section header dump routines
359   //@{
360   void DumpELFSectionHeaders(lldb_private::Stream *s);
361 
362   static void DumpELFSectionHeader(lldb_private::Stream *s,
363                                    const ELFSectionHeaderInfo &sh);
364 
365   static void DumpELFSectionHeader_sh_type(lldb_private::Stream *s,
366                                            elf::elf_word sh_type);
367 
368   static void DumpELFSectionHeader_sh_flags(lldb_private::Stream *s,
369                                             elf::elf_xword sh_flags);
370   //@}
371 
372   /// ELF dependent module dump routine.
373   void DumpDependentModules(lldb_private::Stream *s);
374 
375   const elf::ELFDynamic *FindDynamicSymbol(unsigned tag);
376 
377   unsigned PLTRelocationType();
378 
379   static lldb_private::Status
380   RefineModuleDetailsFromNote(lldb_private::DataExtractor &data,
381                               lldb_private::ArchSpec &arch_spec,
382                               lldb_private::UUID &uuid);
383 
384   bool AnySegmentHasPhysicalAddress();
385 
386   /// Takes the .gnu_debugdata and returns the decompressed object file that is
387   /// stored within that section.
388   ///
389   /// \returns either the decompressed object file stored within the
390   /// .gnu_debugdata section or \c nullptr if an error occured or if there's no
391   /// section with that name.
392   std::shared_ptr<ObjectFileELF> GetGnuDebugDataObjectFile();
393 };
394 
395 #endif // LLDB_SOURCE_PLUGINS_OBJECTFILE_ELF_OBJECTFILEELF_H
396