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, bool _isN64); 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 bool _isN64) 57 : MCELFObjectTargetWriter(_is64Bit, OSABI, ELF::EM_MIPS, 58 /*HasRelocationAddend*/ false, 59 /*IsN64*/ _isN64) {} 60 61 MipsELFObjectWriter::~MipsELFObjectWriter() {} 62 63 // FIXME: get the real EABI Version from the Subtarget class. 64 unsigned MipsELFObjectWriter::getEFlags() const { 65 66 // FIXME: We can't tell if we are PIC (dynamic) or CPIC (static) 67 unsigned Flag = ELF::EF_MIPS_NOREORDER; 68 69 if (is64Bit()) 70 Flag |= ELF::EF_MIPS_ARCH_64R2; 71 else 72 Flag |= ELF::EF_MIPS_ARCH_32R2; 73 return Flag; 74 } 75 76 const MCSymbol *MipsELFObjectWriter::ExplicitRelSym(const MCAssembler &Asm, 77 const MCValue &Target, 78 const MCFragment &F, 79 const MCFixup &Fixup, 80 bool IsPCRel) const { 81 assert(Target.getSymA() && "SymA cannot be 0."); 82 const MCSymbol &Sym = Target.getSymA()->getSymbol().AliasedSymbol(); 83 84 if (Sym.getSection().getKind().isMergeableCString() || 85 Sym.getSection().getKind().isMergeableConst()) 86 return &Sym; 87 88 return NULL; 89 } 90 91 unsigned MipsELFObjectWriter::GetRelocType(const MCValue &Target, 92 const MCFixup &Fixup, 93 bool IsPCRel, 94 bool IsRelocWithSymbol, 95 int64_t Addend) const { 96 // determine the type of the relocation 97 unsigned Type = (unsigned)ELF::R_MIPS_NONE; 98 unsigned Kind = (unsigned)Fixup.getKind(); 99 100 switch (Kind) { 101 default: 102 llvm_unreachable("invalid fixup kind!"); 103 case FK_Data_4: 104 Type = ELF::R_MIPS_32; 105 break; 106 case FK_GPRel_4: 107 Type = ELF::R_MIPS_GPREL32; 108 break; 109 case Mips::fixup_Mips_GPREL16: 110 Type = ELF::R_MIPS_GPREL16; 111 break; 112 case Mips::fixup_Mips_26: 113 Type = ELF::R_MIPS_26; 114 break; 115 case Mips::fixup_Mips_CALL16: 116 Type = ELF::R_MIPS_CALL16; 117 break; 118 case Mips::fixup_Mips_GOT_Global: 119 case Mips::fixup_Mips_GOT_Local: 120 Type = ELF::R_MIPS_GOT16; 121 break; 122 case Mips::fixup_Mips_HI16: 123 Type = ELF::R_MIPS_HI16; 124 break; 125 case Mips::fixup_Mips_LO16: 126 Type = ELF::R_MIPS_LO16; 127 break; 128 case Mips::fixup_Mips_TLSGD: 129 Type = ELF::R_MIPS_TLS_GD; 130 break; 131 case Mips::fixup_Mips_GOTTPREL: 132 Type = ELF::R_MIPS_TLS_GOTTPREL; 133 break; 134 case Mips::fixup_Mips_TPREL_HI: 135 Type = ELF::R_MIPS_TLS_TPREL_HI16; 136 break; 137 case Mips::fixup_Mips_TPREL_LO: 138 Type = ELF::R_MIPS_TLS_TPREL_LO16; 139 break; 140 case Mips::fixup_Mips_TLSLDM: 141 Type = ELF::R_MIPS_TLS_LDM; 142 break; 143 case Mips::fixup_Mips_DTPREL_HI: 144 Type = ELF::R_MIPS_TLS_DTPREL_HI16; 145 break; 146 case Mips::fixup_Mips_DTPREL_LO: 147 Type = ELF::R_MIPS_TLS_DTPREL_LO16; 148 break; 149 case Mips::fixup_Mips_Branch_PCRel: 150 case Mips::fixup_Mips_PC16: 151 Type = ELF::R_MIPS_PC16; 152 break; 153 case Mips::fixup_Mips_GOT_PAGE: 154 Type = ELF::R_MIPS_GOT_PAGE; 155 break; 156 case Mips::fixup_Mips_GOT_OFST: 157 Type = ELF::R_MIPS_GOT_OFST; 158 break; 159 case Mips::fixup_Mips_GOT_DISP: 160 Type = ELF::R_MIPS_GOT_DISP; 161 break; 162 case Mips::fixup_Mips_GPOFF_HI: 163 Type = setRType((unsigned)ELF::R_MIPS_GPREL16, Type); 164 Type = setRType2((unsigned)ELF::R_MIPS_SUB, Type); 165 Type = setRType3((unsigned)ELF::R_MIPS_HI16, Type); 166 break; 167 case Mips::fixup_Mips_GPOFF_LO: 168 Type = setRType((unsigned)ELF::R_MIPS_GPREL16, Type); 169 Type = setRType2((unsigned)ELF::R_MIPS_SUB, Type); 170 Type = setRType3((unsigned)ELF::R_MIPS_LO16, Type); 171 break; 172 } 173 return Type; 174 } 175 176 // Return true if R is either a GOT16 against a local symbol or HI16. 177 static bool NeedsMatchingLo(const MCAssembler &Asm, const RelEntry &R) { 178 if (!R.Sym) 179 return false; 180 181 MCSymbolData &SD = Asm.getSymbolData(R.Sym->AliasedSymbol()); 182 183 return ((R.Reloc.Type == ELF::R_MIPS_GOT16) && !SD.isExternal()) || 184 (R.Reloc.Type == ELF::R_MIPS_HI16); 185 } 186 187 static bool HasMatchingLo(const MCAssembler &Asm, RelLsIter I, RelLsIter Last) { 188 if (I == Last) 189 return false; 190 191 RelLsIter Hi = I++; 192 193 return (I->Reloc.Type == ELF::R_MIPS_LO16) && (Hi->Sym == I->Sym) && 194 (Hi->Offset == I->Offset); 195 } 196 197 static bool HasSameSymbol(const RelEntry &R0, const RelEntry &R1) { 198 return R0.Sym == R1.Sym; 199 } 200 201 static int CompareOffset(const RelEntry &R0, const RelEntry &R1) { 202 return (R0.Offset > R1.Offset) ? 1 : ((R0.Offset == R1.Offset) ? 0 : -1); 203 } 204 205 void MipsELFObjectWriter::sortRelocs(const MCAssembler &Asm, 206 std::vector<ELFRelocationEntry> &Relocs) { 207 // Call the default function first. Relocations are sorted in descending 208 // order of r_offset. 209 MCELFObjectTargetWriter::sortRelocs(Asm, Relocs); 210 211 RelLs RelocLs; 212 std::vector<RelLsIter> Unmatched; 213 214 // Fill RelocLs. Traverse Relocs backwards so that relocations in RelocLs 215 // are in ascending order of r_offset. 216 for (std::vector<ELFRelocationEntry>::reverse_iterator R = Relocs.rbegin(); 217 R != Relocs.rend(); ++R) { 218 std::pair<const MCSymbolRefExpr*, int64_t> P = 219 MipsGetSymAndOffset(*R->Fixup); 220 RelocLs.push_back(RelEntry(*R, P.first ? &P.first->getSymbol() : 0, 221 P.second)); 222 } 223 224 // Get list of unmatched HI16 and GOT16. 225 for (RelLsIter R = RelocLs.begin(); R != RelocLs.end(); ++R) 226 if (NeedsMatchingLo(Asm, *R) && !HasMatchingLo(Asm, R, --RelocLs.end())) 227 Unmatched.push_back(R); 228 229 // Insert unmatched HI16 and GOT16 immediately before their matching LO16. 230 for (std::vector<RelLsIter>::iterator U = Unmatched.begin(); 231 U != Unmatched.end(); ++U) { 232 RelLsIter LoPos = RelocLs.end(), HiPos = *U; 233 bool MatchedLo = false; 234 235 for (RelLsIter R = RelocLs.begin(); R != RelocLs.end(); ++R) { 236 if ((R->Reloc.Type == ELF::R_MIPS_LO16) && HasSameSymbol(*HiPos, *R) && 237 (CompareOffset(*R, *HiPos) >= 0) && 238 ((LoPos == RelocLs.end()) || ((CompareOffset(*R, *LoPos) < 0)) || 239 (!MatchedLo && !CompareOffset(*R, *LoPos)))) 240 LoPos = R; 241 242 MatchedLo = NeedsMatchingLo(Asm, *R) && 243 HasMatchingLo(Asm, R, --RelocLs.end()); 244 } 245 246 // If a matching LoPos was found, move HiPos and insert it before LoPos. 247 // Make the offsets of HiPos and LoPos match. 248 if (LoPos != RelocLs.end()) { 249 HiPos->Offset = LoPos->Offset; 250 RelocLs.insert(LoPos, *HiPos); 251 RelocLs.erase(HiPos); 252 } 253 } 254 255 // Put the sorted list back in reverse order. 256 assert(Relocs.size() == RelocLs.size()); 257 unsigned I = RelocLs.size(); 258 259 for (RelLsIter R = RelocLs.begin(); R != RelocLs.end(); ++R) 260 Relocs[--I] = R->Reloc; 261 } 262 263 MCObjectWriter *llvm::createMipsELFObjectWriter(raw_ostream &OS, 264 uint8_t OSABI, 265 bool IsLittleEndian, 266 bool Is64Bit) { 267 MCELFObjectTargetWriter *MOTW = new MipsELFObjectWriter(Is64Bit, OSABI, 268 (Is64Bit) ? true : false); 269 return createELFObjectWriter(MOTW, OS, IsLittleEndian); 270 } 271