1 //===-- MipsELFObjectWriter.cpp - Mips ELF Writer -------------------------===// 2 // 3 // The LLVM Compiler Infrastructure 4 // 5 // This file is distributed under the University of Illinois Open Source 6 // License. See LICENSE.TXT for details. 7 // 8 //===----------------------------------------------------------------------===// 9 10 #include "MCTargetDesc/MipsBaseInfo.h" 11 #include "MCTargetDesc/MipsFixupKinds.h" 12 #include "MCTargetDesc/MipsMCTargetDesc.h" 13 #include "llvm/MC/MCAssembler.h" 14 #include "llvm/MC/MCELFObjectWriter.h" 15 #include "llvm/MC/MCExpr.h" 16 #include "llvm/MC/MCSection.h" 17 #include "llvm/MC/MCValue.h" 18 #include "llvm/Support/ErrorHandling.h" 19 #include <list> 20 21 using namespace llvm; 22 23 namespace { 24 struct RelEntry { 25 RelEntry(const ELFRelocationEntry &R, const MCSymbol *S, int64_t O) : 26 Reloc(R), Sym(S), Offset(O) {} 27 ELFRelocationEntry Reloc; 28 const MCSymbol *Sym; 29 int64_t Offset; 30 }; 31 32 typedef std::list<RelEntry> RelLs; 33 typedef RelLs::iterator RelLsIter; 34 35 class MipsELFObjectWriter : public MCELFObjectTargetWriter { 36 public: 37 MipsELFObjectWriter(bool _is64Bit, uint8_t OSABI, 38 bool _isN64, bool IsLittleEndian); 39 40 virtual ~MipsELFObjectWriter(); 41 42 virtual unsigned GetRelocType(const MCValue &Target, const MCFixup &Fixup, 43 bool IsPCRel, bool IsRelocWithSymbol, 44 int64_t Addend) const; 45 virtual unsigned getEFlags() const; 46 virtual const MCSymbol *ExplicitRelSym(const MCAssembler &Asm, 47 const MCValue &Target, 48 const MCFragment &F, 49 const MCFixup &Fixup, 50 bool IsPCRel) const; 51 virtual void sortRelocs(const MCAssembler &Asm, 52 std::vector<ELFRelocationEntry> &Relocs); 53 }; 54 } 55 56 MipsELFObjectWriter::MipsELFObjectWriter(bool _is64Bit, uint8_t OSABI, 57 bool _isN64, bool IsLittleEndian) 58 : MCELFObjectTargetWriter(_is64Bit, OSABI, ELF::EM_MIPS, 59 /*HasRelocationAddend*/ (_isN64) ? true : false, 60 /*IsN64*/ _isN64) {} 61 62 MipsELFObjectWriter::~MipsELFObjectWriter() {} 63 64 // FIXME: get the real EABI Version from the Subtarget class. 65 unsigned MipsELFObjectWriter::getEFlags() const { 66 67 // FIXME: We can't tell if we are PIC (dynamic) or CPIC (static) 68 unsigned Flag = ELF::EF_MIPS_NOREORDER; 69 70 if (is64Bit()) 71 Flag |= ELF::EF_MIPS_ARCH_64R2; 72 else 73 Flag |= ELF::EF_MIPS_ARCH_32R2; 74 return Flag; 75 } 76 77 const MCSymbol *MipsELFObjectWriter::ExplicitRelSym(const MCAssembler &Asm, 78 const MCValue &Target, 79 const MCFragment &F, 80 const MCFixup &Fixup, 81 bool IsPCRel) const { 82 assert(Target.getSymA() && "SymA cannot be 0."); 83 const MCSymbol &Sym = Target.getSymA()->getSymbol().AliasedSymbol(); 84 85 if (Sym.getSection().getKind().isMergeableCString() || 86 Sym.getSection().getKind().isMergeableConst()) 87 return &Sym; 88 89 return NULL; 90 } 91 92 unsigned MipsELFObjectWriter::GetRelocType(const MCValue &Target, 93 const MCFixup &Fixup, 94 bool IsPCRel, 95 bool IsRelocWithSymbol, 96 int64_t Addend) const { 97 // determine the type of the relocation 98 unsigned Type = (unsigned)ELF::R_MIPS_NONE; 99 unsigned Kind = (unsigned)Fixup.getKind(); 100 101 switch (Kind) { 102 default: 103 llvm_unreachable("invalid fixup kind!"); 104 case FK_Data_4: 105 Type = ELF::R_MIPS_32; 106 break; 107 case FK_Data_8: 108 Type = ELF::R_MIPS_64; 109 break; 110 case FK_GPRel_4: 111 if (isN64()) { 112 Type = setRType((unsigned)ELF::R_MIPS_GPREL32, Type); 113 Type = setRType2((unsigned)ELF::R_MIPS_64, Type); 114 Type = setRType3((unsigned)ELF::R_MIPS_NONE, Type); 115 } 116 else 117 Type = ELF::R_MIPS_GPREL32; 118 break; 119 case Mips::fixup_Mips_GPREL16: 120 Type = ELF::R_MIPS_GPREL16; 121 break; 122 case Mips::fixup_Mips_26: 123 Type = ELF::R_MIPS_26; 124 break; 125 case Mips::fixup_Mips_CALL16: 126 Type = ELF::R_MIPS_CALL16; 127 break; 128 case Mips::fixup_Mips_GOT_Global: 129 case Mips::fixup_Mips_GOT_Local: 130 Type = ELF::R_MIPS_GOT16; 131 break; 132 case Mips::fixup_Mips_HI16: 133 Type = ELF::R_MIPS_HI16; 134 break; 135 case Mips::fixup_Mips_LO16: 136 Type = ELF::R_MIPS_LO16; 137 break; 138 case Mips::fixup_Mips_TLSGD: 139 Type = ELF::R_MIPS_TLS_GD; 140 break; 141 case Mips::fixup_Mips_GOTTPREL: 142 Type = ELF::R_MIPS_TLS_GOTTPREL; 143 break; 144 case Mips::fixup_Mips_TPREL_HI: 145 Type = ELF::R_MIPS_TLS_TPREL_HI16; 146 break; 147 case Mips::fixup_Mips_TPREL_LO: 148 Type = ELF::R_MIPS_TLS_TPREL_LO16; 149 break; 150 case Mips::fixup_Mips_TLSLDM: 151 Type = ELF::R_MIPS_TLS_LDM; 152 break; 153 case Mips::fixup_Mips_DTPREL_HI: 154 Type = ELF::R_MIPS_TLS_DTPREL_HI16; 155 break; 156 case Mips::fixup_Mips_DTPREL_LO: 157 Type = ELF::R_MIPS_TLS_DTPREL_LO16; 158 break; 159 case Mips::fixup_Mips_Branch_PCRel: 160 case Mips::fixup_Mips_PC16: 161 Type = ELF::R_MIPS_PC16; 162 break; 163 case Mips::fixup_Mips_GOT_PAGE: 164 Type = ELF::R_MIPS_GOT_PAGE; 165 break; 166 case Mips::fixup_Mips_GOT_OFST: 167 Type = ELF::R_MIPS_GOT_OFST; 168 break; 169 case Mips::fixup_Mips_GOT_DISP: 170 Type = ELF::R_MIPS_GOT_DISP; 171 break; 172 case Mips::fixup_Mips_GPOFF_HI: 173 Type = setRType((unsigned)ELF::R_MIPS_GPREL16, Type); 174 Type = setRType2((unsigned)ELF::R_MIPS_SUB, Type); 175 Type = setRType3((unsigned)ELF::R_MIPS_HI16, Type); 176 break; 177 case Mips::fixup_Mips_GPOFF_LO: 178 Type = setRType((unsigned)ELF::R_MIPS_GPREL16, Type); 179 Type = setRType2((unsigned)ELF::R_MIPS_SUB, Type); 180 Type = setRType3((unsigned)ELF::R_MIPS_LO16, Type); 181 break; 182 case Mips::fixup_Mips_HIGHER: 183 Type = ELF::R_MIPS_HIGHER; 184 break; 185 case Mips::fixup_Mips_HIGHEST: 186 Type = ELF::R_MIPS_HIGHEST; 187 break; 188 case Mips::fixup_Mips_GOT_HI16: 189 Type = ELF::R_MIPS_GOT_HI16; 190 break; 191 case Mips::fixup_Mips_GOT_LO16: 192 Type = ELF::R_MIPS_GOT_LO16; 193 break; 194 case Mips::fixup_Mips_CALL_HI16: 195 Type = ELF::R_MIPS_CALL_HI16; 196 break; 197 case Mips::fixup_Mips_CALL_LO16: 198 Type = ELF::R_MIPS_CALL_LO16; 199 break; 200 } 201 return Type; 202 } 203 204 // Return true if R is either a GOT16 against a local symbol or HI16. 205 static bool NeedsMatchingLo(const MCAssembler &Asm, const RelEntry &R) { 206 if (!R.Sym) 207 return false; 208 209 MCSymbolData &SD = Asm.getSymbolData(R.Sym->AliasedSymbol()); 210 211 return ((R.Reloc.Type == ELF::R_MIPS_GOT16) && !SD.isExternal()) || 212 (R.Reloc.Type == ELF::R_MIPS_HI16); 213 } 214 215 static bool HasMatchingLo(const MCAssembler &Asm, RelLsIter I, RelLsIter Last) { 216 if (I == Last) 217 return false; 218 219 RelLsIter Hi = I++; 220 221 return (I->Reloc.Type == ELF::R_MIPS_LO16) && (Hi->Sym == I->Sym) && 222 (Hi->Offset == I->Offset); 223 } 224 225 static bool HasSameSymbol(const RelEntry &R0, const RelEntry &R1) { 226 return R0.Sym == R1.Sym; 227 } 228 229 static int CompareOffset(const RelEntry &R0, const RelEntry &R1) { 230 return (R0.Offset > R1.Offset) ? 1 : ((R0.Offset == R1.Offset) ? 0 : -1); 231 } 232 233 void MipsELFObjectWriter::sortRelocs(const MCAssembler &Asm, 234 std::vector<ELFRelocationEntry> &Relocs) { 235 // Call the default function first. Relocations are sorted in descending 236 // order of r_offset. 237 MCELFObjectTargetWriter::sortRelocs(Asm, Relocs); 238 239 RelLs RelocLs; 240 std::vector<RelLsIter> Unmatched; 241 242 // Fill RelocLs. Traverse Relocs backwards so that relocations in RelocLs 243 // are in ascending order of r_offset. 244 for (std::vector<ELFRelocationEntry>::reverse_iterator R = Relocs.rbegin(); 245 R != Relocs.rend(); ++R) { 246 std::pair<const MCSymbolRefExpr*, int64_t> P = 247 MipsGetSymAndOffset(*R->Fixup); 248 RelocLs.push_back(RelEntry(*R, P.first ? &P.first->getSymbol() : 0, 249 P.second)); 250 } 251 252 // Get list of unmatched HI16 and GOT16. 253 for (RelLsIter R = RelocLs.begin(); R != RelocLs.end(); ++R) 254 if (NeedsMatchingLo(Asm, *R) && !HasMatchingLo(Asm, R, --RelocLs.end())) 255 Unmatched.push_back(R); 256 257 // Insert unmatched HI16 and GOT16 immediately before their matching LO16. 258 for (std::vector<RelLsIter>::iterator U = Unmatched.begin(); 259 U != Unmatched.end(); ++U) { 260 RelLsIter LoPos = RelocLs.end(), HiPos = *U; 261 bool MatchedLo = false; 262 263 for (RelLsIter R = RelocLs.begin(); R != RelocLs.end(); ++R) { 264 if ((R->Reloc.Type == ELF::R_MIPS_LO16) && HasSameSymbol(*HiPos, *R) && 265 (CompareOffset(*R, *HiPos) >= 0) && 266 ((LoPos == RelocLs.end()) || ((CompareOffset(*R, *LoPos) < 0)) || 267 (!MatchedLo && !CompareOffset(*R, *LoPos)))) 268 LoPos = R; 269 270 MatchedLo = NeedsMatchingLo(Asm, *R) && 271 HasMatchingLo(Asm, R, --RelocLs.end()); 272 } 273 274 // If a matching LoPos was found, move HiPos and insert it before LoPos. 275 // Make the offsets of HiPos and LoPos match. 276 if (LoPos != RelocLs.end()) { 277 HiPos->Offset = LoPos->Offset; 278 RelocLs.insert(LoPos, *HiPos); 279 RelocLs.erase(HiPos); 280 } 281 } 282 283 // Put the sorted list back in reverse order. 284 assert(Relocs.size() == RelocLs.size()); 285 unsigned I = RelocLs.size(); 286 287 for (RelLsIter R = RelocLs.begin(); R != RelocLs.end(); ++R) 288 Relocs[--I] = R->Reloc; 289 } 290 291 MCObjectWriter *llvm::createMipsELFObjectWriter(raw_ostream &OS, 292 uint8_t OSABI, 293 bool IsLittleEndian, 294 bool Is64Bit) { 295 MCELFObjectTargetWriter *MOTW = new MipsELFObjectWriter(Is64Bit, OSABI, 296 (Is64Bit) ? true : false, 297 IsLittleEndian); 298 return createELFObjectWriter(MOTW, OS, IsLittleEndian); 299 } 300