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/ARMMCTargetDesc.h" 11 #include "MCTargetDesc/ARMFixupKinds.h" 12 #include "llvm/ADT/Statistic.h" 13 #include "llvm/ADT/StringSwitch.h" 14 #include "llvm/MC/MCELFObjectWriter.h" 15 #include "llvm/MC/MCExpr.h" 16 #include "llvm/MC/MCSectionELF.h" 17 #include "llvm/MC/MCValue.h" 18 #include "llvm/Support/Debug.h" 19 #include "llvm/Support/ErrorHandling.h" 20 #include "llvm/Support/raw_ostream.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 const MCSymbol *ExplicitRelSym(const MCAssembler &Asm, 41 const MCValue &Target, 42 const MCFragment &F, 43 const MCFixup &Fixup, 44 bool IsPCRel) const; 45 }; 46 } 47 48 ARMELFObjectWriter::ARMELFObjectWriter(uint8_t OSABI) 49 : MCELFObjectTargetWriter(/*Is64Bit*/ false, OSABI, 50 ELF::EM_ARM, 51 /*HasRelocationAddend*/ false) {} 52 53 ARMELFObjectWriter::~ARMELFObjectWriter() {} 54 55 // In ARM, _MergedGlobals and other most symbols get emitted directly. 56 // I.e. not as an offset to a section symbol. 57 // This code is an approximation of what ARM/gcc does. 58 59 STATISTIC(PCRelCount, "Total number of PIC Relocations"); 60 STATISTIC(NonPCRelCount, "Total number of non-PIC relocations"); 61 62 const MCSymbol *ARMELFObjectWriter::ExplicitRelSym(const MCAssembler &Asm, 63 const MCValue &Target, 64 const MCFragment &F, 65 const MCFixup &Fixup, 66 bool IsPCRel) const { 67 const MCSymbol &Symbol = Target.getSymA()->getSymbol().AliasedSymbol(); 68 bool EmitThisSym = false; 69 70 const MCSectionELF &Section = 71 static_cast<const MCSectionELF&>(Symbol.getSection()); 72 bool InNormalSection = true; 73 unsigned RelocType = 0; 74 RelocType = GetRelocTypeInner(Target, Fixup, IsPCRel); 75 76 DEBUG( 77 const MCSymbolRefExpr::VariantKind Kind = Target.getSymA()->getKind(); 78 MCSymbolRefExpr::VariantKind Kind2; 79 Kind2 = Target.getSymB() ? Target.getSymB()->getKind() : 80 MCSymbolRefExpr::VK_None; 81 dbgs() << "considering symbol " 82 << Section.getSectionName() << "/" 83 << Symbol.getName() << "/" 84 << " Rel:" << (unsigned)RelocType 85 << " Kind: " << (int)Kind << "/" << (int)Kind2 86 << " Tmp:" 87 << Symbol.isAbsolute() << "/" << Symbol.isDefined() << "/" 88 << Symbol.isVariable() << "/" << Symbol.isTemporary() 89 << " Counts:" << PCRelCount << "/" << NonPCRelCount << "\n"); 90 91 if (IsPCRel) { ++PCRelCount; 92 switch (RelocType) { 93 default: 94 // Most relocation types are emitted as explicit symbols 95 InNormalSection = 96 StringSwitch<bool>(Section.getSectionName()) 97 .Case(".data.rel.ro.local", false) 98 .Case(".data.rel", false) 99 .Case(".bss", false) 100 .Default(true); 101 EmitThisSym = true; 102 break; 103 case ELF::R_ARM_ABS32: 104 // But things get strange with R_ARM_ABS32 105 // In this case, most things that go in .rodata show up 106 // as section relative relocations 107 InNormalSection = 108 StringSwitch<bool>(Section.getSectionName()) 109 .Case(".data.rel.ro.local", false) 110 .Case(".data.rel", false) 111 .Case(".rodata", false) 112 .Case(".bss", false) 113 .Default(true); 114 EmitThisSym = false; 115 break; 116 } 117 } else { 118 NonPCRelCount++; 119 InNormalSection = 120 StringSwitch<bool>(Section.getSectionName()) 121 .Case(".data.rel.ro.local", false) 122 .Case(".rodata", false) 123 .Case(".data.rel", false) 124 .Case(".bss", false) 125 .Default(true); 126 127 switch (RelocType) { 128 default: EmitThisSym = true; break; 129 case ELF::R_ARM_ABS32: EmitThisSym = false; break; 130 case ELF::R_ARM_PREL31: EmitThisSym = false; break; 131 } 132 } 133 134 if (EmitThisSym) 135 return &Symbol; 136 if (! Symbol.isTemporary() && InNormalSection) { 137 return &Symbol; 138 } 139 return NULL; 140 } 141 142 // Need to examine the Fixup when determining whether to 143 // emit the relocation as an explicit symbol or as a section relative 144 // offset 145 unsigned ARMELFObjectWriter::GetRelocType(const MCValue &Target, 146 const MCFixup &Fixup, 147 bool IsPCRel, 148 bool IsRelocWithSymbol, 149 int64_t Addend) const { 150 return GetRelocTypeInner(Target, Fixup, IsPCRel); 151 } 152 153 unsigned ARMELFObjectWriter::GetRelocTypeInner(const MCValue &Target, 154 const MCFixup &Fixup, 155 bool IsPCRel) const { 156 MCSymbolRefExpr::VariantKind Modifier = Target.isAbsolute() ? 157 MCSymbolRefExpr::VK_None : Target.getSymA()->getKind(); 158 159 unsigned Type = 0; 160 if (IsPCRel) { 161 switch ((unsigned)Fixup.getKind()) { 162 default: llvm_unreachable("Unimplemented"); 163 case FK_Data_4: 164 switch (Modifier) { 165 default: llvm_unreachable("Unsupported Modifier"); 166 case MCSymbolRefExpr::VK_None: 167 Type = ELF::R_ARM_REL32; 168 break; 169 case MCSymbolRefExpr::VK_ARM_TLSGD: 170 llvm_unreachable("unimplemented"); 171 case MCSymbolRefExpr::VK_ARM_GOTTPOFF: 172 Type = ELF::R_ARM_TLS_IE32; 173 break; 174 } 175 break; 176 case ARM::fixup_arm_blx: 177 case ARM::fixup_arm_uncondbl: 178 switch (Modifier) { 179 case MCSymbolRefExpr::VK_ARM_PLT: 180 Type = ELF::R_ARM_PLT32; 181 break; 182 default: 183 Type = ELF::R_ARM_CALL; 184 break; 185 } 186 break; 187 case ARM::fixup_arm_condbl: 188 case ARM::fixup_arm_condbranch: 189 case ARM::fixup_arm_uncondbranch: 190 Type = ELF::R_ARM_JUMP24; 191 break; 192 case ARM::fixup_t2_condbranch: 193 case ARM::fixup_t2_uncondbranch: 194 Type = ELF::R_ARM_THM_JUMP24; 195 break; 196 case ARM::fixup_arm_movt_hi16: 197 case ARM::fixup_arm_movt_hi16_pcrel: 198 Type = ELF::R_ARM_MOVT_PREL; 199 break; 200 case ARM::fixup_arm_movw_lo16: 201 case ARM::fixup_arm_movw_lo16_pcrel: 202 Type = ELF::R_ARM_MOVW_PREL_NC; 203 break; 204 case ARM::fixup_t2_movt_hi16: 205 case ARM::fixup_t2_movt_hi16_pcrel: 206 Type = ELF::R_ARM_THM_MOVT_PREL; 207 break; 208 case ARM::fixup_t2_movw_lo16: 209 case ARM::fixup_t2_movw_lo16_pcrel: 210 Type = ELF::R_ARM_THM_MOVW_PREL_NC; 211 break; 212 case ARM::fixup_arm_thumb_bl: 213 case ARM::fixup_arm_thumb_blx: 214 Type = ELF::R_ARM_THM_CALL; 215 break; 216 } 217 } else { 218 switch ((unsigned)Fixup.getKind()) { 219 default: llvm_unreachable("invalid fixup kind!"); 220 case FK_Data_4: 221 switch (Modifier) { 222 default: llvm_unreachable("Unsupported Modifier"); 223 case MCSymbolRefExpr::VK_ARM_NONE: 224 Type = ELF::R_ARM_NONE; 225 break; 226 case MCSymbolRefExpr::VK_ARM_GOT: 227 Type = ELF::R_ARM_GOT_BREL; 228 break; 229 case MCSymbolRefExpr::VK_ARM_TLSGD: 230 Type = ELF::R_ARM_TLS_GD32; 231 break; 232 case MCSymbolRefExpr::VK_ARM_TPOFF: 233 Type = ELF::R_ARM_TLS_LE32; 234 break; 235 case MCSymbolRefExpr::VK_ARM_GOTTPOFF: 236 Type = ELF::R_ARM_TLS_IE32; 237 break; 238 case MCSymbolRefExpr::VK_None: 239 Type = ELF::R_ARM_ABS32; 240 break; 241 case MCSymbolRefExpr::VK_ARM_GOTOFF: 242 Type = ELF::R_ARM_GOTOFF32; 243 break; 244 case MCSymbolRefExpr::VK_ARM_TARGET1: 245 Type = ELF::R_ARM_TARGET1; 246 break; 247 case MCSymbolRefExpr::VK_ARM_TARGET2: 248 Type = ELF::R_ARM_TARGET2; 249 break; 250 case MCSymbolRefExpr::VK_ARM_PREL31: 251 Type = ELF::R_ARM_PREL31; 252 break; 253 } 254 break; 255 case ARM::fixup_arm_ldst_pcrel_12: 256 case ARM::fixup_arm_pcrel_10: 257 case ARM::fixup_arm_adr_pcrel_12: 258 case ARM::fixup_arm_thumb_bl: 259 case ARM::fixup_arm_thumb_cb: 260 case ARM::fixup_arm_thumb_cp: 261 case ARM::fixup_arm_thumb_br: 262 llvm_unreachable("Unimplemented"); 263 case ARM::fixup_arm_condbranch: 264 case ARM::fixup_arm_uncondbranch: 265 Type = ELF::R_ARM_JUMP24; 266 break; 267 case ARM::fixup_arm_movt_hi16: 268 Type = ELF::R_ARM_MOVT_ABS; 269 break; 270 case ARM::fixup_arm_movw_lo16: 271 Type = ELF::R_ARM_MOVW_ABS_NC; 272 break; 273 case ARM::fixup_t2_movt_hi16: 274 Type = ELF::R_ARM_THM_MOVT_ABS; 275 break; 276 case ARM::fixup_t2_movw_lo16: 277 Type = ELF::R_ARM_THM_MOVW_ABS_NC; 278 break; 279 } 280 } 281 282 return Type; 283 } 284 285 MCObjectWriter *llvm::createARMELFObjectWriter(raw_ostream &OS, 286 uint8_t OSABI) { 287 MCELFObjectTargetWriter *MOTW = new ARMELFObjectWriter(OSABI); 288 return createELFObjectWriter(MOTW, OS, /*IsLittleEndian=*/true); 289 } 290
