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 39 virtual ~MipsELFObjectWriter(); 40 41 virtual unsigned GetRelocType(const MCValue &Target, const MCFixup &Fixup, 42 bool IsPCRel, bool IsRelocWithSymbol, 43 int64_t Addend) const; 44 virtual unsigned getEFlags() 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 : MCELFObjectTargetWriter(_is64Bit, OSABI, ELF::EM_MIPS, 57 /*HasRelocationAddend*/ false) {} 58 59 MipsELFObjectWriter::~MipsELFObjectWriter() {} 60 61 // FIXME: get the real EABI Version from the Subtarget class. 62 unsigned MipsELFObjectWriter::getEFlags() const { 63 64 // FIXME: We can't tell if we are PIC (dynamic) or CPIC (static) 65 unsigned Flag = ELF::EF_MIPS_NOREORDER; 66 67 if (is64Bit()) 68 Flag |= ELF::EF_MIPS_ARCH_64R2; 69 else 70 Flag |= ELF::EF_MIPS_ARCH_32R2; 71 return Flag; 72 } 73 74 const MCSymbol *MipsELFObjectWriter::ExplicitRelSym(const MCAssembler &Asm, 75 const MCValue &Target, 76 const MCFragment &F, 77 const MCFixup &Fixup, 78 bool IsPCRel) const { 79 assert(Target.getSymA() && "SymA cannot be 0."); 80 const MCSymbol &Sym = Target.getSymA()->getSymbol().AliasedSymbol(); 81 82 if (Sym.getSection().getKind().isMergeableCString() || 83 Sym.getSection().getKind().isMergeableConst()) 84 return &Sym; 85 86 return NULL; 87 } 88 89 unsigned MipsELFObjectWriter::GetRelocType(const MCValue &Target, 90 const MCFixup &Fixup, 91 bool IsPCRel, 92 bool IsRelocWithSymbol, 93 int64_t Addend) const { 94 // determine the type of the relocation 95 unsigned Type = (unsigned)ELF::R_MIPS_NONE; 96 unsigned Kind = (unsigned)Fixup.getKind(); 97 98 switch (Kind) { 99 default: 100 llvm_unreachable("invalid fixup kind!"); 101 case FK_Data_4: 102 Type = ELF::R_MIPS_32; 103 break; 104 case FK_GPRel_4: 105 Type = ELF::R_MIPS_GPREL32; 106 break; 107 case Mips::fixup_Mips_GPREL16: 108 Type = ELF::R_MIPS_GPREL16; 109 break; 110 case Mips::fixup_Mips_26: 111 Type = ELF::R_MIPS_26; 112 break; 113 case Mips::fixup_Mips_CALL16: 114 Type = ELF::R_MIPS_CALL16; 115 break; 116 case Mips::fixup_Mips_GOT_Global: 117 case Mips::fixup_Mips_GOT_Local: 118 Type = ELF::R_MIPS_GOT16; 119 break; 120 case Mips::fixup_Mips_HI16: 121 Type = ELF::R_MIPS_HI16; 122 break; 123 case Mips::fixup_Mips_LO16: 124 Type = ELF::R_MIPS_LO16; 125 break; 126 case Mips::fixup_Mips_TLSGD: 127 Type = ELF::R_MIPS_TLS_GD; 128 break; 129 case Mips::fixup_Mips_GOTTPREL: 130 Type = ELF::R_MIPS_TLS_GOTTPREL; 131 break; 132 case Mips::fixup_Mips_TPREL_HI: 133 Type = ELF::R_MIPS_TLS_TPREL_HI16; 134 break; 135 case Mips::fixup_Mips_TPREL_LO: 136 Type = ELF::R_MIPS_TLS_TPREL_LO16; 137 break; 138 case Mips::fixup_Mips_TLSLDM: 139 Type = ELF::R_MIPS_TLS_LDM; 140 break; 141 case Mips::fixup_Mips_DTPREL_HI: 142 Type = ELF::R_MIPS_TLS_DTPREL_HI16; 143 break; 144 case Mips::fixup_Mips_DTPREL_LO: 145 Type = ELF::R_MIPS_TLS_DTPREL_LO16; 146 break; 147 case Mips::fixup_Mips_Branch_PCRel: 148 case Mips::fixup_Mips_PC16: 149 Type = ELF::R_MIPS_PC16; 150 break; 151 } 152 153 return Type; 154 } 155 156 // Return true if R is either a GOT16 against a local symbol or HI16. 157 static bool NeedsMatchingLo(const MCAssembler &Asm, const RelEntry &R) { 158 if (!R.Sym) 159 return false; 160 161 MCSymbolData &SD = Asm.getSymbolData(R.Sym->AliasedSymbol()); 162 163 return ((R.Reloc.Type == ELF::R_MIPS_GOT16) && !SD.isExternal()) || 164 (R.Reloc.Type == ELF::R_MIPS_HI16); 165 } 166 167 static bool HasMatchingLo(const MCAssembler &Asm, RelLsIter I, RelLsIter Last) { 168 if (I == Last) 169 return false; 170 171 RelLsIter Hi = I++; 172 173 return (I->Reloc.Type == ELF::R_MIPS_LO16) && (Hi->Sym == I->Sym) && 174 (Hi->Offset == I->Offset); 175 } 176 177 static bool HasSameSymbol(const RelEntry &R0, const RelEntry &R1) { 178 return R0.Sym == R1.Sym; 179 } 180 181 static int CompareOffset(const RelEntry &R0, const RelEntry &R1) { 182 return (R0.Offset > R1.Offset) ? 1 : ((R0.Offset == R1.Offset) ? 0 : -1); 183 } 184 185 void MipsELFObjectWriter::sortRelocs(const MCAssembler &Asm, 186 std::vector<ELFRelocationEntry> &Relocs) { 187 // Call the defualt function first. Relocations are sorted in descending 188 // order of r_offset. 189 MCELFObjectTargetWriter::sortRelocs(Asm, Relocs); 190 191 RelLs RelocLs; 192 std::vector<RelLsIter> Unmatched; 193 194 // Fill RelocLs. Traverse Relocs backwards so that relocations in RelocLs 195 // are in ascending order of r_offset. 196 for (std::vector<ELFRelocationEntry>::reverse_iterator R = Relocs.rbegin(); 197 R != Relocs.rend(); ++R) { 198 std::pair<const MCSymbolRefExpr*, int64_t> P = 199 MipsGetSymAndOffset(*R->Fixup); 200 RelocLs.push_back(RelEntry(*R, P.first ? &P.first->getSymbol() : 0, 201 P.second)); 202 } 203 204 // Get list of unmatched HI16 and GOT16. 205 for (RelLsIter R = RelocLs.begin(); R != RelocLs.end(); ++R) 206 if (NeedsMatchingLo(Asm, *R) && !HasMatchingLo(Asm, R, --RelocLs.end())) 207 Unmatched.push_back(R); 208 209 // Insert unmatched HI16 and GOT16 immediately before their matching LO16. 210 for (std::vector<RelLsIter>::iterator U = Unmatched.begin(); 211 U != Unmatched.end(); ++U) { 212 RelLsIter LoPos = RelocLs.end(), HiPos = *U; 213 bool MatchedLo = false; 214 215 for (RelLsIter R = RelocLs.begin(); R != RelocLs.end(); ++R) { 216 if ((R->Reloc.Type == ELF::R_MIPS_LO16) && HasSameSymbol(*HiPos, *R) && 217 (CompareOffset(*R, *HiPos) >= 0) && 218 ((LoPos == RelocLs.end()) || ((CompareOffset(*R, *LoPos) < 0)) || 219 (!MatchedLo && !CompareOffset(*R, *LoPos)))) 220 LoPos = R; 221 222 MatchedLo = NeedsMatchingLo(Asm, *R) && 223 HasMatchingLo(Asm, R, --RelocLs.end()); 224 } 225 226 // If a matching LoPos was found, move HiPos and insert it before LoPos. 227 // Make the offsets of HiPos and LoPos match. 228 if (LoPos != RelocLs.end()) { 229 HiPos->Offset = LoPos->Offset; 230 RelocLs.insert(LoPos, *HiPos); 231 RelocLs.erase(HiPos); 232 } 233 } 234 235 // Put the sorted list back in reverse order. 236 assert(Relocs.size() == RelocLs.size()); 237 unsigned I = RelocLs.size(); 238 239 for (RelLsIter R = RelocLs.begin(); R != RelocLs.end(); ++R) 240 Relocs[--I] = R->Reloc; 241 } 242 243 MCObjectWriter *llvm::createMipsELFObjectWriter(raw_ostream &OS, 244 uint8_t OSABI, 245 bool IsLittleEndian, 246 bool Is64Bit) { 247 MCELFObjectTargetWriter *MOTW = new MipsELFObjectWriter(Is64Bit, OSABI); 248 return createELFObjectWriter(MOTW, OS, IsLittleEndian); 249 } 250
