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