lld/ELF/InputFiles.h

   1 //===- InputFiles.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 LLD_ELF_INPUT_FILES_H
  10 #define LLD_ELF_INPUT_FILES_H
  11
  12 #include "Config.h"
  13 #include "Symbols.h"
  14 #include "lld/Common/ErrorHandler.h"
  15 #include "lld/Common/LLVM.h"
  16 #include "lld/Common/Reproduce.h"
  17 #include "llvm/ADT/DenseSet.h"
  18 #include "llvm/BinaryFormat/Magic.h"
  19 #include "llvm/Object/ELF.h"
  20 #include "llvm/Support/MemoryBufferRef.h"
  21 #include "llvm/Support/Threading.h"
  22
  23 namespace llvm {
  24 struct DILineInfo;
  25 class TarWriter;
  26 namespace lto {
  27 class InputFile;
  28 }
  29 } // namespace llvm
  30
  31 namespace lld {
  32 class DWARFCache;
  33
  34 // Returns "<internal>", "foo.a(bar.o)" or "baz.o".
  35 std::string toString(const elf::InputFile *f);
  36
  37 namespace elf {
  38
  39 class InputSection;
  40 class Symbol;
  41
  42 // If --reproduce is specified, all input files are written to this tar archive.
  43 extern std::unique_ptr<llvm::TarWriter> tar;
  44
  45 // Opens a given file.
  46 std::optional<MemoryBufferRef> readFile(StringRef path);
  47
  48 // Add symbols in File to the symbol table.
  49 void parseFile(InputFile *file);
  50 void parseFiles(const std::vector<InputFile *> &files,
  51                 InputFile *armCmseImpLib);
  52
  53 // The root class of input files.
  54 class InputFile {
  55 protected:
  56   std::unique_ptr<Symbol *[]> symbols;
  57   uint32_t numSymbols = 0;
  58   SmallVector<InputSectionBase *, 0> sections;
  59
  60 public:
  61   enum Kind : uint8_t {
  62     ObjKind,
  63     SharedKind,
  64     BitcodeKind,
  65     BinaryKind,
  66     InternalKind,
  67   };
  68
  69   InputFile(Kind k, MemoryBufferRef m);
  70   Kind kind() const { return fileKind; }
  71
  72   bool isElf() const {
  73     Kind k = kind();
  74     return k == ObjKind || k == SharedKind;
  75   }
  76   bool isInternal() const { return kind() == InternalKind; }
  77
  78   StringRef getName() const { return mb.getBufferIdentifier(); }
  79   MemoryBufferRef mb;
  80
  81   // Returns sections. It is a runtime error to call this function
  82   // on files that don't have the notion of sections.
  83   ArrayRef<InputSectionBase *> getSections() const {
  84     assert(fileKind == ObjKind || fileKind == BinaryKind);
  85     return sections;
  86   }
  87   void cacheDecodedCrel(size_t i, InputSectionBase *s) { sections[i] = s; }
  88
  89   // Returns object file symbols. It is a runtime error to call this
  90   // function on files of other types.
  91   ArrayRef<Symbol *> getSymbols() const {
  92     assert(fileKind == BinaryKind || fileKind == ObjKind ||
  93            fileKind == BitcodeKind);
  94     return {symbols.get(), numSymbols};
  95   }
  96
  97   MutableArrayRef<Symbol *> getMutableSymbols() {
  98     assert(fileKind == BinaryKind || fileKind == ObjKind ||
  99            fileKind == BitcodeKind);
 100     return {symbols.get(), numSymbols};
 101   }
 102
 103   Symbol &getSymbol(uint32_t symbolIndex) const {
 104     assert(fileKind == ObjKind);
 105     if (symbolIndex >= numSymbols)
 106       fatal(toString(this) + ": invalid symbol index");
 107     return *this->symbols[symbolIndex];
 108   }
 109
 110   template <typename RelT> Symbol &getRelocTargetSym(const RelT &rel) const {
 111     uint32_t symIndex = rel.getSymbol(config->isMips64EL);
 112     return getSymbol(symIndex);
 113   }
 114
 115   // Get filename to use for linker script processing.
 116   StringRef getNameForScript() const;
 117
 118   // Check if a non-common symbol should be extracted to override a common
 119   // definition.
 120   bool shouldExtractForCommon(StringRef name) const;
 121
 122   // .got2 in the current file. This is used by PPC32 -fPIC/-fPIE to compute
 123   // offsets in PLT call stubs.
 124   InputSection *ppc32Got2 = nullptr;
 125
 126   // Index of MIPS GOT built for this file.
 127   uint32_t mipsGotIndex = -1;
 128
 129   // groupId is used for --warn-backrefs which is an optional error
 130   // checking feature. All files within the same --{start,end}-group or
 131   // --{start,end}-lib get the same group ID. Otherwise, each file gets a new
 132   // group ID. For more info, see checkDependency() in SymbolTable.cpp.
 133   uint32_t groupId;
 134   static bool isInGroup;
 135   static uint32_t nextGroupId;
 136
 137   // If this is an architecture-specific file, the following members
 138   // have ELF type (i.e. ELF{32,64}{LE,BE}) and target machine type.
 139   uint16_t emachine = llvm::ELF::EM_NONE;
 140   const Kind fileKind;
 141   ELFKind ekind = ELFNoneKind;
 142   uint8_t osabi = 0;
 143   uint8_t abiVersion = 0;
 144
 145   // True if this is a relocatable object file/bitcode file in an ar archive
 146   // or between --start-lib and --end-lib.
 147   bool lazy = false;
 148
 149   // True if this is an argument for --just-symbols. Usually false.
 150   bool justSymbols = false;
 151
 152   std::string getSrcMsg(const Symbol &sym, const InputSectionBase &sec,
 153                         uint64_t offset);
 154
 155   // On PPC64 we need to keep track of which files contain small code model
 156   // relocations that access the .toc section. To minimize the chance of a
 157   // relocation overflow, files that do contain said relocations should have
 158   // their .toc sections sorted closer to the .got section than files that do
 159   // not contain any small code model relocations. Thats because the toc-pointer
 160   // is defined to point at .got + 0x8000 and the instructions used with small
 161   // code model relocations support immediates in the range [-0x8000, 0x7FFC],
 162   // making the addressable range relative to the toc pointer
 163   // [.got, .got + 0xFFFC].
 164   bool ppc64SmallCodeModelTocRelocs = false;
 165
 166   // True if the file has TLSGD/TLSLD GOT relocations without R_PPC64_TLSGD or
 167   // R_PPC64_TLSLD. Disable TLS relaxation to avoid bad code generation.
 168   bool ppc64DisableTLSRelax = false;
 169
 170 public:
 171   // If not empty, this stores the name of the archive containing this file.
 172   // We use this string for creating error messages.
 173   SmallString<0> archiveName;
 174   // Cache for toString(). Only toString() should use this member.
 175   mutable SmallString<0> toStringCache;
 176
 177 private:
 178   // Cache for getNameForScript().
 179   mutable SmallString<0> nameForScriptCache;
 180 };
 181
 182 class ELFFileBase : public InputFile {
 183 public:
 184   ELFFileBase(Kind k, ELFKind ekind, MemoryBufferRef m);
 185   static bool classof(const InputFile *f) { return f->isElf(); }
 186
 187   void init();
 188   template <typename ELFT> llvm::object::ELFFile<ELFT> getObj() const {
 189     return check(llvm::object::ELFFile<ELFT>::create(mb.getBuffer()));
 190   }
 191
 192   StringRef getStringTable() const { return stringTable; }
 193
 194   ArrayRef<Symbol *> getLocalSymbols() {
 195     if (numSymbols == 0)
 196       return {};
 197     return llvm::ArrayRef(symbols.get() + 1, firstGlobal - 1);
 198   }
 199   ArrayRef<Symbol *> getGlobalSymbols() {
 200     return llvm::ArrayRef(symbols.get() + firstGlobal,
 201                           numSymbols - firstGlobal);
 202   }
 203   MutableArrayRef<Symbol *> getMutableGlobalSymbols() {
 204     return llvm::MutableArrayRef(symbols.get() + firstGlobal,
 205                                      numSymbols - firstGlobal);
 206   }
 207
 208   template <typename ELFT> typename ELFT::ShdrRange getELFShdrs() const {
 209     return typename ELFT::ShdrRange(
 210         reinterpret_cast<const typename ELFT::Shdr *>(elfShdrs), numELFShdrs);
 211   }
 212   template <typename ELFT> typename ELFT::SymRange getELFSyms() const {
 213     return typename ELFT::SymRange(
 214         reinterpret_cast<const typename ELFT::Sym *>(elfSyms), numELFSyms);
 215   }
 216   template <typename ELFT> typename ELFT::SymRange getGlobalELFSyms() const {
 217     return getELFSyms<ELFT>().slice(firstGlobal);
 218   }
 219
 220 protected:
 221   // Initializes this class's member variables.
 222   template <typename ELFT> void init(InputFile::Kind k);
 223
 224   StringRef stringTable;
 225   const void *elfShdrs = nullptr;
 226   const void *elfSyms = nullptr;
 227   uint32_t numELFShdrs = 0;
 228   uint32_t numELFSyms = 0;
 229   uint32_t firstGlobal = 0;
 230
 231 public:
 232   uint32_t andFeatures = 0;
 233   bool hasCommonSyms = false;
 234   ArrayRef<uint8_t> aarch64PauthAbiCoreInfo;
 235 };
 236
 237 // .o file.
 238 template <class ELFT> class ObjFile : public ELFFileBase {
 239   LLVM_ELF_IMPORT_TYPES_ELFT(ELFT)
 240
 241 public:
 242   static bool classof(const InputFile *f) { return f->kind() == ObjKind; }
 243
 244   llvm::object::ELFFile<ELFT> getObj() const {
 245     return this->ELFFileBase::getObj<ELFT>();
 246   }
 247
 248   ObjFile(ELFKind ekind, MemoryBufferRef m, StringRef archiveName)
 249       : ELFFileBase(ObjKind, ekind, m) {
 250     this->archiveName = archiveName;
 251   }
 252
 253   void parse(bool ignoreComdats = false);
 254   void parseLazy();
 255
 256   StringRef getShtGroupSignature(ArrayRef<Elf_Shdr> sections,
 257                                  const Elf_Shdr &sec);
 258
 259   uint32_t getSectionIndex(const Elf_Sym &sym) const;
 260
 261   std::optional<llvm::DILineInfo> getDILineInfo(const InputSectionBase *,
 262                                                 uint64_t);
 263   std::optional<std::pair<std::string, unsigned>>
 264   getVariableLoc(StringRef name);
 265
 266   // Name of source file obtained from STT_FILE symbol value,
 267   // or empty string if there is no such symbol in object file
 268   // symbol table.
 269   StringRef sourceFile;
 270
 271   // Pointer to this input file's .llvm_addrsig section, if it has one.
 272   const Elf_Shdr *addrsigSec = nullptr;
 273
 274   // SHT_LLVM_CALL_GRAPH_PROFILE section index.
 275   uint32_t cgProfileSectionIndex = 0;
 276
 277   // MIPS GP0 value defined by this file. This value represents the gp value
 278   // used to create the relocatable object and required to support
 279   // R_MIPS_GPREL16 / R_MIPS_GPREL32 relocations.
 280   uint32_t mipsGp0 = 0;
 281
 282   // True if the file defines functions compiled with
 283   // -fsplit-stack. Usually false.
 284   bool splitStack = false;
 285
 286   // True if the file defines functions compiled with -fsplit-stack,
 287   // but had one or more functions with the no_split_stack attribute.
 288   bool someNoSplitStack = false;
 289
 290   // Get cached DWARF information.
 291   DWARFCache *getDwarf();
 292
 293   void initSectionsAndLocalSyms(bool ignoreComdats);
 294   void postParse();
 295   void importCmseSymbols();
 296
 297 private:
 298   void initializeSections(bool ignoreComdats,
 299                           const llvm::object::ELFFile<ELFT> &obj);
 300   void initializeSymbols(const llvm::object::ELFFile<ELFT> &obj);
 301   void initializeJustSymbols();
 302
 303   InputSectionBase *getRelocTarget(uint32_t idx, uint32_t info);
 304   InputSectionBase *createInputSection(uint32_t idx, const Elf_Shdr &sec,
 305                                        StringRef name);
 306
 307   bool shouldMerge(const Elf_Shdr &sec, StringRef name);
 308
 309   // Each ELF symbol contains a section index which the symbol belongs to.
 310   // However, because the number of bits dedicated for that is limited, a
 311   // symbol can directly point to a section only when the section index is
 312   // equal to or smaller than 65280.
 313   //
 314   // If an object file contains more than 65280 sections, the file must
 315   // contain .symtab_shndx section. The section contains an array of
 316   // 32-bit integers whose size is the same as the number of symbols.
 317   // Nth symbol's section index is in the Nth entry of .symtab_shndx.
 318   //
 319   // The following variable contains the contents of .symtab_shndx.
 320   // If the section does not exist (which is common), the array is empty.
 321   ArrayRef<Elf_Word> shndxTable;
 322
 323   // Debugging information to retrieve source file and line for error
 324   // reporting. Linker may find reasonable number of errors in a
 325   // single object file, so we cache debugging information in order to
 326   // parse it only once for each object file we link.
 327   std::unique_ptr<DWARFCache> dwarf;
 328   llvm::once_flag initDwarf;
 329 };
 330
 331 class BitcodeFile : public InputFile {
 332 public:
 333   BitcodeFile(MemoryBufferRef m, StringRef archiveName,
 334               uint64_t offsetInArchive, bool lazy);
 335   static bool classof(const InputFile *f) { return f->kind() == BitcodeKind; }
 336   void parse();
 337   void parseLazy();
 338   void postParse();
 339   std::unique_ptr<llvm::lto::InputFile> obj;
 340   std::vector<bool> keptComdats;
 341 };
 342
 343 // .so file.
 344 class SharedFile : public ELFFileBase {
 345 public:
 346   SharedFile(MemoryBufferRef m, StringRef defaultSoName);
 347
 348   // This is actually a vector of Elf_Verdef pointers.
 349   SmallVector<const void *, 0> verdefs;
 350
 351   // If the output file needs Elf_Verneed data structures for this file, this is
 352   // a vector of Elf_Vernaux version identifiers that map onto the entries in
 353   // Verdefs, otherwise it is empty.
 354   SmallVector<uint32_t, 0> vernauxs;
 355
 356   static unsigned vernauxNum;
 357
 358   SmallVector<StringRef, 0> dtNeeded;
 359   StringRef soName;
 360
 361   static bool classof(const InputFile *f) { return f->kind() == SharedKind; }
 362
 363   template <typename ELFT> void parse();
 364
 365   // Used for --as-needed
 366   bool isNeeded;
 367
 368   // Non-weak undefined symbols which are not yet resolved when the SO is
 369   // parsed. Only filled for `--no-allow-shlib-undefined`.
 370   SmallVector<Symbol *, 0> requiredSymbols;
 371
 372 private:
 373   template <typename ELFT>
 374   std::vector<uint32_t> parseVerneed(const llvm::object::ELFFile<ELFT> &obj,
 375                                      const typename ELFT::Shdr *sec);
 376 };
 377
 378 class BinaryFile : public InputFile {
 379 public:
 380   explicit BinaryFile(MemoryBufferRef m) : InputFile(BinaryKind, m) {}
 381   static bool classof(const InputFile *f) { return f->kind() == BinaryKind; }
 382   void parse();
 383 };
 384
 385 InputFile *createInternalFile(StringRef name);
 386 ELFFileBase *createObjFile(MemoryBufferRef mb, StringRef archiveName = "",
 387                            bool lazy = false);
 388
 389 std::string replaceThinLTOSuffix(StringRef path);
 390
 391 } // namespace elf
 392 } // namespace lld
 393
 394 #endif