1 //===-- ARMELFObjectWriter.cpp - ARM 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/ARMFixupKinds.h" 11 #include "MCTargetDesc/ARMMCTargetDesc.h" 12 #include "llvm/Support/Debug.h" 13 #include "llvm/Support/ErrorHandling.h" 14 #include "llvm/Support/raw_ostream.h" 15 #include "llvm/ADT/Statistic.h" 16 #include "llvm/ADT/StringSwitch.h" 17 #include "llvm/MC/MCELFObjectWriter.h" 18 #include "llvm/MC/MCExpr.h" 19 #include "llvm/MC/MCSectionELF.h" 20 #include "llvm/MC/MCValue.h" 21 22 using namespace llvm; 23 24 namespace { 25 class ARMELFObjectWriter : public MCELFObjectTargetWriter { 26 enum { DefaultEABIVersion = 0x05000000U }; 27 unsigned GetRelocTypeInner(const MCValue &Target, 28 const MCFixup &Fixup, 29 bool IsPCRel) const; 30 31 32 public: 33 ARMELFObjectWriter(uint8_t OSABI); 34 35 virtual ~ARMELFObjectWriter(); 36 37 virtual unsigned GetRelocType(const MCValue &Target, const MCFixup &Fixup, 38 bool IsPCRel, bool IsRelocWithSymbol, 39 int64_t Addend) const; 40 virtual unsigned getEFlags() const; 41 virtual const MCSymbol *ExplicitRelSym(const MCAssembler &Asm, 42 const MCValue &Target, 43 const MCFragment &F, 44 const MCFixup &Fixup, 45 bool IsPCRel) const; 46 }; 47 } 48 49 ARMELFObjectWriter::ARMELFObjectWriter(uint8_t OSABI) 50 : MCELFObjectTargetWriter(/*Is64Bit*/ false, OSABI, 51 ELF::EM_ARM, 52 /*HasRelocationAddend*/ false) {} 53 54 ARMELFObjectWriter::~ARMELFObjectWriter() {} 55 56 // FIXME: get the real EABI Version from the Triple. 57 unsigned ARMELFObjectWriter::getEFlags() const { 58 return ELF::EF_ARM_EABIMASK & DefaultEABIVersion; 59 } 60 61 // In ARM, _MergedGlobals and other most symbols get emitted directly. 62 // I.e. not as an offset to a section symbol. 63 // This code is an approximation of what ARM/gcc does. 64 65 STATISTIC(PCRelCount, "Total number of PIC Relocations"); 66 STATISTIC(NonPCRelCount, "Total number of non-PIC relocations"); 67 68 const MCSymbol *ARMELFObjectWriter::ExplicitRelSym(const MCAssembler &Asm, 69 const MCValue &Target, 70 const MCFragment &F, 71 const MCFixup &Fixup, 72 bool IsPCRel) const { 73 const MCSymbol &Symbol = Target.getSymA()->getSymbol().AliasedSymbol(); 74 bool EmitThisSym = false; 75 76 const MCSectionELF &Section = 77 static_cast<const MCSectionELF&>(Symbol.getSection()); 78 bool InNormalSection = true; 79 unsigned RelocType = 0; 80 RelocType = GetRelocTypeInner(Target, Fixup, IsPCRel); 81 82 DEBUG( 83 const MCSymbolRefExpr::VariantKind Kind = Target.getSymA()->getKind(); 84 MCSymbolRefExpr::VariantKind Kind2; 85 Kind2 = Target.getSymB() ? Target.getSymB()->getKind() : 86 MCSymbolRefExpr::VK_None; 87 dbgs() << "considering symbol " 88 << Section.getSectionName() << "/" 89 << Symbol.getName() << "/" 90 << " Rel:" << (unsigned)RelocType 91 << " Kind: " << (int)Kind << "/" << (int)Kind2 92 << " Tmp:" 93 << Symbol.isAbsolute() << "/" << Symbol.isDefined() << "/" 94 << Symbol.isVariable() << "/" << Symbol.isTemporary() 95 << " Counts:" << PCRelCount << "/" << NonPCRelCount << "\n"); 96 97 if (IsPCRel) { ++PCRelCount; 98 switch (RelocType) { 99 default: 100 // Most relocation types are emitted as explicit symbols 101 InNormalSection = 102 StringSwitch<bool>(Section.getSectionName()) 103 .Case(".data.rel.ro.local", false) 104 .Case(".data.rel", false) 105 .Case(".bss", false) 106 .Default(true); 107 EmitThisSym = true; 108 break; 109 case ELF::R_ARM_ABS32: 110 // But things get strange with R_ARM_ABS32 111 // In this case, most things that go in .rodata show up 112 // as section relative relocations 113 InNormalSection = 114 StringSwitch<bool>(Section.getSectionName()) 115 .Case(".data.rel.ro.local", false) 116 .Case(".data.rel", false) 117 .Case(".rodata", false) 118 .Case(".bss", false) 119 .Default(true); 120 EmitThisSym = false; 121 break; 122 } 123 } else { 124 NonPCRelCount++; 125 InNormalSection = 126 StringSwitch<bool>(Section.getSectionName()) 127 .Case(".data.rel.ro.local", false) 128 .Case(".rodata", false) 129 .Case(".data.rel", false) 130 .Case(".bss", false) 131 .Default(true); 132 133 switch (RelocType) { 134 default: EmitThisSym = true; break; 135 case ELF::R_ARM_ABS32: EmitThisSym = false; break; 136 } 137 } 138 139 if (EmitThisSym) 140 return &Symbol; 141 if (! Symbol.isTemporary() && InNormalSection) { 142 return &Symbol; 143 } 144 return NULL; 145 } 146 147 // Need to examine the Fixup when determining whether to 148 // emit the relocation as an explicit symbol or as a section relative 149 // offset 150 unsigned ARMELFObjectWriter::GetRelocType(const MCValue &Target, 151 const MCFixup &Fixup, 152 bool IsPCRel, 153 bool IsRelocWithSymbol, 154 int64_t Addend) const { 155 return GetRelocTypeInner(Target, Fixup, IsPCRel); 156 } 157 158 unsigned ARMELFObjectWriter::GetRelocTypeInner(const MCValue &Target, 159 const MCFixup &Fixup, 160 bool IsPCRel) const { 161 MCSymbolRefExpr::VariantKind Modifier = Target.isAbsolute() ? 162 MCSymbolRefExpr::VK_None : Target.getSymA()->getKind(); 163 164 unsigned Type = 0; 165 if (IsPCRel) { 166 switch ((unsigned)Fixup.getKind()) { 167 default: llvm_unreachable("Unimplemented"); 168 case FK_Data_4: 169 switch (Modifier) { 170 default: llvm_unreachable("Unsupported Modifier"); 171 case MCSymbolRefExpr::VK_None: 172 Type = ELF::R_ARM_REL32; 173 break; 174 case MCSymbolRefExpr::VK_ARM_TLSGD: 175 llvm_unreachable("unimplemented"); 176 case MCSymbolRefExpr::VK_ARM_GOTTPOFF: 177 Type = ELF::R_ARM_TLS_IE32; 178 break; 179 } 180 break; 181 case ARM::fixup_arm_blx: 182 case ARM::fixup_arm_uncondbl: 183 switch (Modifier) { 184 case MCSymbolRefExpr::VK_ARM_PLT: 185 Type = ELF::R_ARM_PLT32; 186 break; 187 default: 188 Type = ELF::R_ARM_CALL; 189 break; 190 } 191 break; 192 case ARM::fixup_arm_condbl: 193 case ARM::fixup_arm_condbranch: 194 case ARM::fixup_arm_uncondbranch: 195 Type = ELF::R_ARM_JUMP24; 196 break; 197 case ARM::fixup_t2_condbranch: 198 case ARM::fixup_t2_uncondbranch: 199 Type = ELF::R_ARM_THM_JUMP24; 200 break; 201 case ARM::fixup_arm_movt_hi16: 202 case ARM::fixup_arm_movt_hi16_pcrel: 203 Type = ELF::R_ARM_MOVT_PREL; 204 break; 205 case ARM::fixup_arm_movw_lo16: 206 case ARM::fixup_arm_movw_lo16_pcrel: 207 Type = ELF::R_ARM_MOVW_PREL_NC; 208 break; 209 case ARM::fixup_t2_movt_hi16: 210 case ARM::fixup_t2_movt_hi16_pcrel: 211 Type = ELF::R_ARM_THM_MOVT_PREL; 212 break; 213 case ARM::fixup_t2_movw_lo16: 214 case ARM::fixup_t2_movw_lo16_pcrel: 215 Type = ELF::R_ARM_THM_MOVW_PREL_NC; 216 break; 217 case ARM::fixup_arm_thumb_bl: 218 case ARM::fixup_arm_thumb_blx: 219 Type = ELF::R_ARM_THM_CALL; 220 break; 221 } 222 } else { 223 switch ((unsigned)Fixup.getKind()) { 224 default: llvm_unreachable("invalid fixup kind!"); 225 case FK_Data_4: 226 switch (Modifier) { 227 default: llvm_unreachable("Unsupported Modifier"); 228 case MCSymbolRefExpr::VK_ARM_GOT: 229 Type = ELF::R_ARM_GOT_BREL; 230 break; 231 case MCSymbolRefExpr::VK_ARM_TLSGD: 232 Type = ELF::R_ARM_TLS_GD32; 233 break; 234 case MCSymbolRefExpr::VK_ARM_TPOFF: 235 Type = ELF::R_ARM_TLS_LE32; 236 break; 237 case MCSymbolRefExpr::VK_ARM_GOTTPOFF: 238 Type = ELF::R_ARM_TLS_IE32; 239 break; 240 case MCSymbolRefExpr::VK_None: 241 Type = ELF::R_ARM_ABS32; 242 break; 243 case MCSymbolRefExpr::VK_ARM_GOTOFF: 244 Type = ELF::R_ARM_GOTOFF32; 245 break; 246 case MCSymbolRefExpr::VK_ARM_TARGET1: 247 Type = ELF::R_ARM_TARGET1; 248 break; 249 } 250 break; 251 case ARM::fixup_arm_ldst_pcrel_12: 252 case ARM::fixup_arm_pcrel_10: 253 case ARM::fixup_arm_adr_pcrel_12: 254 case ARM::fixup_arm_thumb_bl: 255 case ARM::fixup_arm_thumb_cb: 256 case ARM::fixup_arm_thumb_cp: 257 case ARM::fixup_arm_thumb_br: 258 llvm_unreachable("Unimplemented"); 259 case ARM::fixup_arm_condbranch: 260 case ARM::fixup_arm_uncondbranch: 261 Type = ELF::R_ARM_JUMP24; 262 break; 263 case ARM::fixup_arm_movt_hi16: 264 Type = ELF::R_ARM_MOVT_ABS; 265 break; 266 case ARM::fixup_arm_movw_lo16: 267 Type = ELF::R_ARM_MOVW_ABS_NC; 268 break; 269 case ARM::fixup_t2_movt_hi16: 270 Type = ELF::R_ARM_THM_MOVT_ABS; 271 break; 272 case ARM::fixup_t2_movw_lo16: 273 Type = ELF::R_ARM_THM_MOVW_ABS_NC; 274 break; 275 } 276 } 277 278 return Type; 279 } 280 281 MCObjectWriter *llvm::createARMELFObjectWriter(raw_ostream &OS, 282 uint8_t OSABI) { 283 MCELFObjectTargetWriter *MOTW = new ARMELFObjectWriter(OSABI); 284 return createELFObjectWriter(MOTW, OS, /*IsLittleEndian=*/true); 285 } 286
