1 //===- GNULDBackend.h -----------------------------------------------------===// 2 // 3 // The MCLinker Project 4 // 5 // This file is distributed under the University of Illinois Open Source 6 // License. See LICENSE.TXT for details. 7 // 8 //===----------------------------------------------------------------------===// 9 #ifndef MCLD_TARGET_GNU_LDBACKEND_H 10 #define MCLD_TARGET_GNU_LDBACKEND_H 11 #ifdef ENABLE_UNITTEST 12 #include <gtest.h> 13 #endif 14 #include <mcld/Target/TargetLDBackend.h> 15 16 #include <llvm/Support/ELF.h> 17 #include <mcld/ADT/HashTable.h> 18 #include <mcld/ADT/HashEntry.h> 19 #include <mcld/LD/ELFDynObjFileFormat.h> 20 #include <mcld/LD/ELFExecFileFormat.h> 21 #include <mcld/LD/ELFObjectFileFormat.h> 22 #include <mcld/LD/GNUArchiveReader.h> 23 #include <mcld/LD/ELFObjectReader.h> 24 #include <mcld/LD/ELFDynObjReader.h> 25 #include <mcld/LD/ELFBinaryReader.h> 26 #include <mcld/LD/ELFObjectWriter.h> 27 #include <mcld/LD/ELFSegment.h> 28 #include <mcld/LD/ELFSegmentFactory.h> 29 #include <mcld/Target/ELFDynamic.h> 30 #include <mcld/Target/GNUInfo.h> 31 32 #include <mcld/Support/GCFactory.h> 33 #include <mcld/Module.h> 34 35 namespace mcld { 36 37 class Module; 38 class LinkerConfig; 39 class IRBuilder; 40 class Layout; 41 class EhFrameHdr; 42 class BranchIslandFactory; 43 class StubFactory; 44 class GNUInfo; 45 46 /** \class GNULDBackend 47 * \brief GNULDBackend provides a common interface for all GNU Unix-OS 48 * LDBackend. 49 */ 50 class GNULDBackend : public TargetLDBackend 51 { 52 protected: 53 GNULDBackend(const LinkerConfig& pConfig, GNUInfo* pInfo); 54 55 public: 56 virtual ~GNULDBackend(); 57 58 // ----- readers/writers ----- // 59 GNUArchiveReader* createArchiveReader(Module& pModule); 60 ELFObjectReader* createObjectReader(IRBuilder& pBuilder); 61 ELFDynObjReader* createDynObjReader(IRBuilder& pBuilder); 62 ELFBinaryReader* createBinaryReader(IRBuilder& pBuilder); 63 ELFObjectWriter* createWriter(); 64 65 // ----- output sections ----- // 66 /// initStdSections - initialize standard sections of the output file. 67 bool initStdSections(ObjectBuilder& pBuilder); 68 69 /// getOutputFormat - get the sections of the output file. 70 const ELFFileFormat* getOutputFormat() const; 71 ELFFileFormat* getOutputFormat(); 72 73 // ----- target symbols ----- // 74 /// initStandardSymbols - initialize standard symbols. 75 /// Some section symbols is undefined in input object, and linkers must set 76 /// up its value. Take __init_array_begin for example. This symbol is an 77 /// undefined symbol in input objects. ObjectLinker must finalize its value 78 /// to the begin of the .init_array section, then relocation enties to 79 /// __init_array_begin can be applied without emission of "undefined 80 /// reference to `__init_array_begin'". 81 bool initStandardSymbols(IRBuilder& pBuilder, Module& pModule); 82 83 /// finalizeSymbol - Linker checks pSymbol.reserved() if it's not zero, 84 /// then it will ask backend to finalize the symbol value. 85 /// @return ture - if backend set the symbol value sucessfully 86 /// @return false - if backend do not recognize the symbol 87 bool finalizeSymbols() { 88 return (finalizeStandardSymbols() && 89 finalizeTargetSymbols()); 90 } 91 92 /// finalizeStandardSymbols - set the value of standard symbols 93 virtual bool finalizeStandardSymbols(); 94 95 /// finalizeTargetSymbols - set the value of target symbols 96 virtual bool finalizeTargetSymbols() = 0; 97 98 /// finalizeTLSSymbol - set the value of a TLS symbol 99 virtual bool finalizeTLSSymbol(LDSymbol& pSymbol); 100 101 size_t sectionStartOffset() const; 102 103 const GNUInfo& getInfo() const { return *m_pInfo; } 104 GNUInfo& getInfo() { return *m_pInfo; } 105 106 bool hasTextRel() const { return m_bHasTextRel; } 107 108 bool hasStaticTLS() const { return m_bHasStaticTLS; } 109 110 /// getSegmentStartAddr - this function returns the start address of the segment 111 uint64_t getSegmentStartAddr(const LinkerScript& pScript) const; 112 113 /// sizeNamePools - compute the size of regular name pools 114 /// In ELF executable files, regular name pools are .symtab, .strtab., 115 /// .dynsym, .dynstr, and .hash 116 virtual void sizeNamePools(Module& pModule); 117 118 /// emitSectionData - emit target-dependent section data 119 virtual uint64_t emitSectionData(const LDSection& pSection, 120 MemoryRegion& pRegion) const = 0; 121 122 /// emitRegNamePools - emit regular name pools - .symtab, .strtab 123 virtual void emitRegNamePools(const Module& pModule, MemoryArea& pOutput); 124 125 /// emitNamePools - emit dynamic name pools - .dyntab, .dynstr, .hash 126 virtual void emitDynNamePools(Module& pModule, MemoryArea& pOutput); 127 128 /// emitELFHashTab - emit .hash 129 virtual void emitELFHashTab(const Module::SymbolTable& pSymtab, 130 MemoryArea& pOutput); 131 132 /// emitGNUHashTab - emit .gnu.hash 133 virtual void emitGNUHashTab(Module::SymbolTable& pSymtab, 134 MemoryArea& pOutput); 135 136 /// sizeInterp - compute the size of program interpreter's name 137 /// In ELF executables, this is the length of dynamic linker's path name 138 virtual void sizeInterp(); 139 140 /// emitInterp - emit the .interp 141 virtual void emitInterp(MemoryArea& pOutput); 142 143 /// hasEntryInStrTab - symbol has an entry in a .strtab 144 virtual bool hasEntryInStrTab(const LDSymbol& pSym) const; 145 146 /// orderSymbolTable - order symbol table before emitting 147 virtual void orderSymbolTable(Module& pModule); 148 149 void setHasStaticTLS(bool pVal = true) 150 { m_bHasStaticTLS = pVal; } 151 152 /// getSectionOrder - compute the layout order of the section 153 /// Layout calls this function to get the default order of the pSectHdr. 154 /// If the pSectHdr.type() is LDFileFormat::Target, then getSectionOrder() 155 /// will call getTargetSectionOrder(). 156 /// 157 /// If targets favors certain order for general sections, please override 158 /// this function. 159 /// 160 /// @see getTargetSectionOrder 161 virtual unsigned int getSectionOrder(const LDSection& pSectHdr) const; 162 163 /// getTargetSectionOrder - compute the layout order of target section 164 /// If the target favors certain order for the given gSectHdr, please 165 /// override this function. 166 /// 167 /// By default, this function returns the maximun order, and pSectHdr 168 /// will be the last section to be laid out. 169 virtual unsigned int getTargetSectionOrder(const LDSection& pSectHdr) const 170 { return (unsigned int)-1; } 171 172 /// numOfSegments - return the number of segments 173 /// if the target favors other ways to emit program header, please override 174 /// this function 175 size_t numOfSegments() const { return m_ELFSegmentTable.size(); } 176 177 /// elfSegmentTable - return the reference of the elf segment table 178 ELFSegmentFactory& elfSegmentTable() { return m_ELFSegmentTable; } 179 180 /// elfSegmentTable - return the reference of the elf segment table 181 const ELFSegmentFactory& elfSegmentTable() const { return m_ELFSegmentTable; } 182 183 /// commonPageSize - the common page size of the target machine 184 uint64_t commonPageSize() const; 185 186 /// abiPageSize - the abi page size of the target machine 187 uint64_t abiPageSize() const; 188 189 /// getSymbolIdx - get the symbol index of ouput symbol table 190 size_t getSymbolIdx(const LDSymbol* pSymbol) const; 191 192 /// allocateCommonSymbols - allocate common symbols in the corresponding 193 /// sections. 194 /// Different concrete target backend may overlap this function. 195 virtual bool allocateCommonSymbols(Module& pModule); 196 197 /// updateSectionFlags - update pTo's flags when merging pFrom 198 /// update the output section flags based on input section flags. 199 virtual bool updateSectionFlags(LDSection& pTo, const LDSection& pFrom); 200 201 /// symbolNeedsPLT - return whether the symbol needs a PLT entry 202 /// @ref Google gold linker, symtab.h:596 203 bool symbolNeedsPLT(const ResolveInfo& pSym) const; 204 205 /// symbolNeedsCopyReloc - return whether the symbol needs a copy relocation 206 bool symbolNeedsCopyReloc(const Relocation& pReloc, 207 const ResolveInfo& pSym) const; 208 209 /// symbolNeedsDynRel - return whether the symbol needs a dynamic relocation 210 /// @ref Google gold linker, symtab.h:645 211 bool symbolNeedsDynRel(const ResolveInfo& pSym, 212 bool pSymHasPLT, 213 bool isAbsReloc) const; 214 215 /// isSymbolPreemtible - whether the symbol can be preemted by other 216 /// link unit 217 /// @ref Google gold linker, symtab.h:551 218 bool isSymbolPreemptible(const ResolveInfo& pSym) const; 219 220 /// symbolHasFinalValue - return true if the symbol's value can be decided at 221 /// link time 222 bool symbolFinalValueIsKnown(const ResolveInfo& pSym) const; 223 224 /// isDynamicSymbol 225 /// @ref Google gold linker: symtab.cc:311 226 bool isDynamicSymbol(const LDSymbol& pSymbol); 227 228 /// isDynamicSymbol 229 /// @ref Google gold linker: symtab.cc:311 230 bool isDynamicSymbol(const ResolveInfo& pResolveInfo); 231 232 virtual ResolveInfo::Desc getSymDesc(uint16_t pShndx) const { 233 return ResolveInfo::Define; 234 } 235 236 bool hasTDATASymbol() const { return (NULL != f_pTDATA); } 237 bool hasTBSSSymbol() const { return (NULL != f_pTBSS); } 238 239 void setTDATASymbol(LDSymbol& pTDATA) { f_pTDATA = &pTDATA; } 240 void setTBSSSymbol(LDSymbol& pTBSS) { f_pTBSS = &pTBSS; } 241 242 // getTDATASymbol - get section symbol of .tdata 243 LDSymbol& getTDATASymbol(); 244 const LDSymbol& getTDATASymbol() const; 245 246 /// getTBSSSymbol - get section symbol of .tbss 247 LDSymbol& getTBSSSymbol(); 248 const LDSymbol& getTBSSSymbol() const; 249 250 // ----- relaxation ----- // 251 /// initBRIslandFactory - initialize the branch island factory for relaxation 252 bool initBRIslandFactory(); 253 254 /// initStubFactory - initialize the stub factory for relaxation 255 bool initStubFactory(); 256 257 /// getBRIslandFactory 258 BranchIslandFactory* getBRIslandFactory() { return m_pBRIslandFactory; } 259 260 /// getStubFactory 261 StubFactory* getStubFactory() { return m_pStubFactory; } 262 263 /// maxBranchOffset - return the max (forward) branch offset of the backend. 264 /// Target can override this function if needed. 265 virtual uint64_t maxBranchOffset() { return (uint64_t)-1; } 266 267 /// checkAndSetHasTextRel - check pSection flag to set HasTextRel 268 void checkAndSetHasTextRel(const LDSection& pSection); 269 270 protected: 271 uint64_t getSymbolSize(const LDSymbol& pSymbol) const; 272 273 uint64_t getSymbolInfo(const LDSymbol& pSymbol) const; 274 275 uint64_t getSymbolValue(const LDSymbol& pSymbol) const; 276 277 uint64_t getSymbolShndx(const LDSymbol& pSymbol) const; 278 279 /// isTemporary - Whether pSymbol is a local label. 280 virtual bool isTemporary(const LDSymbol& pSymbol) const; 281 282 /// getHashBucketCount - calculate hash bucket count. 283 /// @ref Google gold linker, dynobj.cc:791 284 static unsigned getHashBucketCount(unsigned pNumOfSymbols, bool pIsGNUStyle); 285 286 /// getGNUHashMaskbitslog2 - calculate the number of mask bits in log2 287 /// @ref binutils gold, dynobj.cc:1165 288 unsigned getGNUHashMaskbitslog2(unsigned pNumOfSymbols) const; 289 290 /// emitSymbol32 - emit an ELF32 symbol 291 void emitSymbol32(llvm::ELF::Elf32_Sym& pSym32, 292 LDSymbol& pSymbol, 293 char* pStrtab, 294 size_t pStrtabsize, 295 size_t pSymtabIdx); 296 297 /// emitSymbol64 - emit an ELF64 symbol 298 void emitSymbol64(llvm::ELF::Elf64_Sym& pSym64, 299 LDSymbol& pSymbol, 300 char* pStrtab, 301 size_t pStrtabsize, 302 size_t pSymtabIdx); 303 304 private: 305 /// createProgramHdrs - base on output sections to create the program headers 306 void createProgramHdrs(Module& pModule); 307 308 /// doCreateProgramHdrs - backend can implement this function to create the 309 /// target-dependent segments 310 virtual void doCreateProgramHdrs(Module& pModule) = 0; 311 312 /// setupProgramHdrs - set up the attributes of segments 313 /// (i.e., offset, addresses, file/mem size, flag, and alignment) 314 void setupProgramHdrs(const LinkerScript& pScript); 315 316 /// getSegmentFlag - give a section flag and return the corresponding segment 317 /// flag 318 inline uint32_t getSegmentFlag(const uint32_t pSectionFlag) 319 { 320 uint32_t flag = llvm::ELF::PF_R; 321 if (0 != (pSectionFlag & llvm::ELF::SHF_WRITE)) 322 flag |= llvm::ELF::PF_W; 323 if (0 != (pSectionFlag & llvm::ELF::SHF_EXECINSTR)) 324 flag |= llvm::ELF::PF_X; 325 return flag; 326 } 327 328 /// setupGNUStackInfo - setup the section flag of .note.GNU-stack in output 329 void setupGNUStackInfo(Module& pModule); 330 331 /// setupRelro - setup the offset constraint of PT_RELRO 332 void setupRelro(Module& pModule); 333 334 /// setOutputSectionOffset - helper function to set a group of output sections' 335 /// offset, and set pSectBegin to pStartOffset if pStartOffset is not -1U. 336 void setOutputSectionOffset(Module& pModule, 337 Module::iterator pSectBegin, 338 Module::iterator pSectEnd, 339 uint64_t pStartOffset = -1U); 340 341 /// setOutputSectionOffset - helper function to set output sections' address. 342 void setOutputSectionAddress(Module& pModule, 343 Module::iterator pSectBegin, 344 Module::iterator pSectEnd); 345 346 /// layout - layout method 347 void layout(Module& pModule); 348 349 /// preLayout - Backend can do any needed modification before layout 350 void preLayout(Module& pModule, IRBuilder& pBuilder); 351 352 /// postLayout -Backend can do any needed modification after layout 353 void postLayout(Module& pModule, IRBuilder& pBuilder); 354 355 /// preLayout - Backend can do any needed modification before layout 356 virtual void doPreLayout(IRBuilder& pBuilder) = 0; 357 358 /// postLayout -Backend can do any needed modification after layout 359 virtual void doPostLayout(Module& pModule, IRBuilder& pLinker) = 0; 360 361 /// postProcessing - Backend can do any needed modification in the final stage 362 void postProcessing(MemoryArea& pOutput); 363 364 /// dynamic - the dynamic section of the target machine. 365 virtual ELFDynamic& dynamic() = 0; 366 367 /// dynamic - the dynamic section of the target machine. 368 virtual const ELFDynamic& dynamic() const = 0; 369 370 /// relax - the relaxation pass 371 bool relax(Module& pModule, IRBuilder& pBuilder); 372 373 /// mayRelax - Backends should override this function if they need relaxation 374 virtual bool mayRelax() { return false; } 375 376 /// doRelax - Backend can orevride this function to add its relaxation 377 /// implementation. Return true if the output (e.g., .text) is "relaxed" 378 /// (i.e. layout is changed), and set pFinished to true if everything is fit, 379 /// otherwise set it to false. 380 virtual bool doRelax(Module& pModule, IRBuilder& pBuilder, bool& pFinished) 381 { return false; } 382 383 /// getRelEntrySize - the size in BYTE of rel type relocation 384 virtual size_t getRelEntrySize() = 0; 385 386 /// getRelEntrySize - the size in BYTE of rela type relocation 387 virtual size_t getRelaEntrySize() = 0; 388 389 protected: 390 // Based on Kind in LDFileFormat to define basic section orders for ELF, and 391 // refer gold linker to add more enumerations to handle Regular and BSS kind 392 enum SectionOrder { 393 SHO_INTERP = 1, // .interp 394 SHO_RO_NOTE, // .note.ABI-tag, .note.gnu.build-id 395 SHO_NAMEPOOL, // *.hash, .dynsym, .dynstr 396 SHO_RELOCATION, // .rel.*, .rela.* 397 SHO_REL_PLT, // .rel.plt should come after other .rel.* 398 SHO_INIT, // .init 399 SHO_PLT, // .plt 400 SHO_TEXT, // .text 401 SHO_FINI, // .fini 402 SHO_RO, // .rodata 403 SHO_EXCEPTION, // .eh_frame_hdr, .eh_frame, .gcc_except_table 404 SHO_TLS_DATA, // .tdata 405 SHO_TLS_BSS, // .tbss 406 SHO_RELRO_LOCAL, // .data.rel.ro.local 407 SHO_RELRO, // .data.rel.ro, 408 SHO_RELRO_LAST, // for x86 to adjust .got if needed 409 SHO_NON_RELRO_FIRST, // for x86 to adjust .got.plt if needed 410 SHO_DATA, // .data 411 SHO_LARGE_DATA, // .ldata 412 SHO_RW_NOTE, // 413 SHO_SMALL_DATA, // .sdata 414 SHO_SMALL_BSS, // .sbss 415 SHO_BSS, // .bss 416 SHO_LARGE_BSS, // .lbss 417 SHO_UNDEFINED, // default order 418 SHO_STRTAB // .strtab 419 }; 420 421 typedef std::pair<LDSection*, unsigned int> SHOEntry; 422 423 struct SHOCompare 424 { 425 bool operator()(const SHOEntry& X, const SHOEntry& Y) const 426 { return X.second < Y.second; } 427 }; 428 429 struct SymCompare 430 { 431 bool operator()(const LDSymbol* X, const LDSymbol* Y) const 432 { return (X==Y); } 433 }; 434 435 // for gnu style hash table 436 struct DynsymCompare 437 { 438 bool needGNUHash(const LDSymbol& X) const; 439 440 bool operator()(const LDSymbol* X, const LDSymbol* Y) const; 441 }; 442 443 struct SymPtrHash 444 { 445 size_t operator()(const LDSymbol* pKey) const 446 { 447 return (unsigned((uintptr_t)pKey) >> 4) ^ 448 (unsigned((uintptr_t)pKey) >> 9); 449 } 450 }; 451 452 typedef HashEntry<LDSymbol*, size_t, SymCompare> SymHashEntryType; 453 typedef HashTable<SymHashEntryType, 454 SymPtrHash, 455 EntryFactory<SymHashEntryType> > HashTableType; 456 457 458 protected: 459 ELFObjectReader* m_pObjectReader; 460 461 // ----- file formats ----- // 462 ELFDynObjFileFormat* m_pDynObjFileFormat; 463 ELFExecFileFormat* m_pExecFileFormat; 464 ELFObjectFileFormat* m_pObjectFileFormat; 465 466 // GNUInfo 467 GNUInfo* m_pInfo; 468 469 // ELF segment factory 470 ELFSegmentFactory m_ELFSegmentTable; 471 472 // branch island factory 473 BranchIslandFactory* m_pBRIslandFactory; 474 475 // stub factory 476 StubFactory* m_pStubFactory; 477 478 // map the LDSymbol to its index in the output symbol table 479 HashTableType* m_pSymIndexMap; 480 481 // section .eh_frame_hdr 482 EhFrameHdr* m_pEhFrameHdr; 483 484 // ----- dynamic flags ----- // 485 // DF_TEXTREL of DT_FLAGS 486 bool m_bHasTextRel; 487 488 // DF_STATIC_TLS of DT_FLAGS 489 bool m_bHasStaticTLS; 490 491 // ----- standard symbols ----- // 492 // section symbols 493 LDSymbol* f_pPreInitArrayStart; 494 LDSymbol* f_pPreInitArrayEnd; 495 LDSymbol* f_pInitArrayStart; 496 LDSymbol* f_pInitArrayEnd; 497 LDSymbol* f_pFiniArrayStart; 498 LDSymbol* f_pFiniArrayEnd; 499 LDSymbol* f_pStack; 500 LDSymbol* f_pDynamic; 501 502 // section symbols for .tdata and .tbss 503 LDSymbol* f_pTDATA; 504 LDSymbol* f_pTBSS; 505 506 // segment symbols 507 LDSymbol* f_pExecutableStart; 508 LDSymbol* f_pEText; 509 LDSymbol* f_p_EText; 510 LDSymbol* f_p__EText; 511 LDSymbol* f_pEData; 512 LDSymbol* f_p_EData; 513 LDSymbol* f_pBSSStart; 514 LDSymbol* f_pEnd; 515 LDSymbol* f_p_End; 516 }; 517 518 } // namespace of mcld 519 520 #endif 521 522
