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(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(uint8_t OSABI) 56 : MCELFObjectTargetWriter(/*Is64Bit*/ false, OSABI, ELF::EM_MIPS, 57 /*HasRelocationAddend*/ false) {} 58 59 MipsELFObjectWriter::~MipsELFObjectWriter() {} 60 61 // FIXME: get the real EABI Version from the Triple. 62 unsigned MipsELFObjectWriter::getEFlags() const { 63 return ELF::EF_MIPS_NOREORDER | ELF::EF_MIPS_ARCH_32R2; 64 } 65 66 const MCSymbol *MipsELFObjectWriter::ExplicitRelSym(const MCAssembler &Asm, 67 const MCValue &Target, 68 const MCFragment &F, 69 const MCFixup &Fixup, 70 bool IsPCRel) const { 71 assert(Target.getSymA() && "SymA cannot be 0."); 72 const MCSymbol &Sym = Target.getSymA()->getSymbol().AliasedSymbol(); 73 74 if (Sym.getSection().getKind().isMergeableCString() || 75 Sym.getSection().getKind().isMergeableConst()) 76 return &Sym; 77 78 return NULL; 79 } 80 81 unsigned MipsELFObjectWriter::GetRelocType(const MCValue &Target, 82 const MCFixup &Fixup, 83 bool IsPCRel, 84 bool IsRelocWithSymbol, 85 int64_t Addend) const { 86 // determine the type of the relocation 87 unsigned Type = (unsigned)ELF::R_MIPS_NONE; 88 unsigned Kind = (unsigned)Fixup.getKind(); 89 90 switch (Kind) { 91 default: 92 llvm_unreachable("invalid fixup kind!"); 93 case FK_Data_4: 94 Type = ELF::R_MIPS_32; 95 break; 96 case FK_GPRel_4: 97 Type = ELF::R_MIPS_GPREL32; 98 break; 99 case Mips::fixup_Mips_GPREL16: 100 Type = ELF::R_MIPS_GPREL16; 101 break; 102 case Mips::fixup_Mips_26: 103 Type = ELF::R_MIPS_26; 104 break; 105 case Mips::fixup_Mips_CALL16: 106 Type = ELF::R_MIPS_CALL16; 107 break; 108 case Mips::fixup_Mips_GOT_Global: 109 case Mips::fixup_Mips_GOT_Local: 110 Type = ELF::R_MIPS_GOT16; 111 break; 112 case Mips::fixup_Mips_HI16: 113 Type = ELF::R_MIPS_HI16; 114 break; 115 case Mips::fixup_Mips_LO16: 116 Type = ELF::R_MIPS_LO16; 117 break; 118 case Mips::fixup_Mips_TLSGD: 119 Type = ELF::R_MIPS_TLS_GD; 120 break; 121 case Mips::fixup_Mips_GOTTPREL: 122 Type = ELF::R_MIPS_TLS_GOTTPREL; 123 break; 124 case Mips::fixup_Mips_TPREL_HI: 125 Type = ELF::R_MIPS_TLS_TPREL_HI16; 126 break; 127 case Mips::fixup_Mips_TPREL_LO: 128 Type = ELF::R_MIPS_TLS_TPREL_LO16; 129 break; 130 case Mips::fixup_Mips_TLSLDM: 131 Type = ELF::R_MIPS_TLS_LDM; 132 break; 133 case Mips::fixup_Mips_DTPREL_HI: 134 Type = ELF::R_MIPS_TLS_DTPREL_HI16; 135 break; 136 case Mips::fixup_Mips_DTPREL_LO: 137 Type = ELF::R_MIPS_TLS_DTPREL_LO16; 138 break; 139 case Mips::fixup_Mips_Branch_PCRel: 140 case Mips::fixup_Mips_PC16: 141 Type = ELF::R_MIPS_PC16; 142 break; 143 } 144 145 return Type; 146 } 147 148 // Return true if R is either a GOT16 against a local symbol or HI16. 149 static bool NeedsMatchingLo(const MCAssembler &Asm, const RelEntry &R) { 150 if (!R.Sym) 151 return false; 152 153 MCSymbolData &SD = Asm.getSymbolData(R.Sym->AliasedSymbol()); 154 155 return ((R.Reloc.Type == ELF::R_MIPS_GOT16) && !SD.isExternal()) || 156 (R.Reloc.Type == ELF::R_MIPS_HI16); 157 } 158 159 static bool HasMatchingLo(const MCAssembler &Asm, RelLsIter I, RelLsIter Last) { 160 if (I == Last) 161 return false; 162 163 RelLsIter Hi = I++; 164 165 return (I->Reloc.Type == ELF::R_MIPS_LO16) && (Hi->Sym == I->Sym) && 166 (Hi->Offset == I->Offset); 167 } 168 169 static bool HasSameSymbol(const RelEntry &R0, const RelEntry &R1) { 170 return R0.Sym == R1.Sym; 171 } 172 173 static int CompareOffset(const RelEntry &R0, const RelEntry &R1) { 174 return (R0.Offset > R1.Offset) ? 1 : ((R0.Offset == R1.Offset) ? 0 : -1); 175 } 176 177 void MipsELFObjectWriter::sortRelocs(const MCAssembler &Asm, 178 std::vector<ELFRelocationEntry> &Relocs) { 179 // Call the defualt function first. Relocations are sorted in descending 180 // order of r_offset. 181 MCELFObjectTargetWriter::sortRelocs(Asm, Relocs); 182 183 RelLs RelocLs; 184 std::vector<RelLsIter> Unmatched; 185 186 // Fill RelocLs. Traverse Relocs backwards so that relocations in RelocLs 187 // are in ascending order of r_offset. 188 for (std::vector<ELFRelocationEntry>::reverse_iterator R = Relocs.rbegin(); 189 R != Relocs.rend(); ++R) { 190 std::pair<const MCSymbolRefExpr*, int64_t> P = 191 MipsGetSymAndOffset(*R->Fixup); 192 RelocLs.push_back(RelEntry(*R, P.first ? &P.first->getSymbol() : 0, 193 P.second)); 194 } 195 196 // Get list of unmatched HI16 and GOT16. 197 for (RelLsIter R = RelocLs.begin(); R != RelocLs.end(); ++R) 198 if (NeedsMatchingLo(Asm, *R) && !HasMatchingLo(Asm, R, --RelocLs.end())) 199 Unmatched.push_back(R); 200 201 // Insert unmatched HI16 and GOT16 immediately before their matching LO16. 202 for (std::vector<RelLsIter>::iterator U = Unmatched.begin(); 203 U != Unmatched.end(); ++U) { 204 RelLsIter LoPos = RelocLs.end(), HiPos = *U; 205 bool MatchedLo = false; 206 207 for (RelLsIter R = RelocLs.begin(); R != RelocLs.end(); ++R) { 208 if ((R->Reloc.Type == ELF::R_MIPS_LO16) && HasSameSymbol(*HiPos, *R) && 209 (CompareOffset(*R, *HiPos) >= 0) && 210 ((LoPos == RelocLs.end()) || ((CompareOffset(*R, *LoPos) < 0)) || 211 (!MatchedLo && !CompareOffset(*R, *LoPos)))) 212 LoPos = R; 213 214 MatchedLo = NeedsMatchingLo(Asm, *R) && 215 HasMatchingLo(Asm, R, --RelocLs.end()); 216 } 217 218 // If a matching LoPos was found, move HiPos and insert it before LoPos. 219 // Make the offsets of HiPos and LoPos match. 220 if (LoPos != RelocLs.end()) { 221 HiPos->Offset = LoPos->Offset; 222 RelocLs.insert(LoPos, *HiPos); 223 RelocLs.erase(HiPos); 224 } 225 } 226 227 // Put the sorted list back in reverse order. 228 assert(Relocs.size() == RelocLs.size()); 229 unsigned I = RelocLs.size(); 230 231 for (RelLsIter R = RelocLs.begin(); R != RelocLs.end(); ++R) 232 Relocs[--I] = R->Reloc; 233 } 234 235 MCObjectWriter *llvm::createMipsELFObjectWriter(raw_ostream &OS, uint8_t OSABI, 236 bool IsLittleEndian) { 237 MCELFObjectTargetWriter *MOTW = new MipsELFObjectWriter(OSABI); 238 return createELFObjectWriter(MOTW, OS, IsLittleEndian); 239 } 240