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/BinaryFormat/ELF.h" 13 #include "llvm/MC/MCContext.h" 14 #include "llvm/MC/MCELFObjectWriter.h" 15 #include "llvm/MC/MCExpr.h" 16 #include "llvm/MC/MCFixup.h" 17 #include "llvm/MC/MCObjectWriter.h" 18 #include "llvm/MC/MCValue.h" 19 #include "llvm/Support/ErrorHandling.h" 20 #include "llvm/Support/raw_ostream.h" 21 #include <cstdint> 22 23 using namespace llvm; 24 25 namespace { 26 27 class ARMELFObjectWriter : public MCELFObjectTargetWriter { 28 enum { DefaultEABIVersion = 0x05000000U }; 29 30 unsigned GetRelocTypeInner(const MCValue &Target, const MCFixup &Fixup, 31 bool IsPCRel, MCContext &Ctx) const; 32 33 public: 34 ARMELFObjectWriter(uint8_t OSABI); 35 36 ~ARMELFObjectWriter() override = default; 37 38 unsigned getRelocType(MCContext &Ctx, const MCValue &Target, 39 const MCFixup &Fixup, bool IsPCRel) const override; 40 41 bool needsRelocateWithSymbol(const MCSymbol &Sym, 42 unsigned Type) const override; 43 }; 44 45 } // end anonymous namespace 46 47 ARMELFObjectWriter::ARMELFObjectWriter(uint8_t OSABI) 48 : MCELFObjectTargetWriter(/*Is64Bit*/ false, OSABI, 49 ELF::EM_ARM, 50 /*HasRelocationAddend*/ false) {} 51 52 bool ARMELFObjectWriter::needsRelocateWithSymbol(const MCSymbol &Sym, 53 unsigned Type) const { 54 // FIXME: This is extremely conservative. This really needs to use a 55 // whitelist with a clear explanation for why each realocation needs to 56 // point to the symbol, not to the section. 57 switch (Type) { 58 default: 59 return true; 60 61 case ELF::R_ARM_PREL31: 62 case ELF::R_ARM_ABS32: 63 return false; 64 } 65 } 66 67 // Need to examine the Fixup when determining whether to 68 // emit the relocation as an explicit symbol or as a section relative 69 // offset 70 unsigned ARMELFObjectWriter::getRelocType(MCContext &Ctx, const MCValue &Target, 71 const MCFixup &Fixup, 72 bool IsPCRel) const { 73 return GetRelocTypeInner(Target, Fixup, IsPCRel, Ctx); 74 } 75 76 unsigned ARMELFObjectWriter::GetRelocTypeInner(const MCValue &Target, 77 const MCFixup &Fixup, 78 bool IsPCRel, 79 MCContext &Ctx) const { 80 MCSymbolRefExpr::VariantKind Modifier = Target.getAccessVariant(); 81 82 if (IsPCRel) { 83 switch ((unsigned)Fixup.getKind()) { 84 default: 85 Ctx.reportFatalError(Fixup.getLoc(), "unsupported relocation on symbol"); 86 return ELF::R_ARM_NONE; 87 case FK_Data_4: 88 switch (Modifier) { 89 default: 90 llvm_unreachable("Unsupported Modifier"); 91 case MCSymbolRefExpr::VK_None: 92 return ELF::R_ARM_REL32; 93 case MCSymbolRefExpr::VK_GOTTPOFF: 94 return ELF::R_ARM_TLS_IE32; 95 case MCSymbolRefExpr::VK_ARM_GOT_PREL: 96 return ELF::R_ARM_GOT_PREL; 97 case MCSymbolRefExpr::VK_ARM_PREL31: 98 return ELF::R_ARM_PREL31; 99 } 100 case ARM::fixup_arm_blx: 101 case ARM::fixup_arm_uncondbl: 102 switch (Modifier) { 103 case MCSymbolRefExpr::VK_PLT: 104 return ELF::R_ARM_CALL; 105 case MCSymbolRefExpr::VK_TLSCALL: 106 return ELF::R_ARM_TLS_CALL; 107 default: 108 return ELF::R_ARM_CALL; 109 } 110 case ARM::fixup_arm_condbl: 111 case ARM::fixup_arm_condbranch: 112 case ARM::fixup_arm_uncondbranch: 113 return ELF::R_ARM_JUMP24; 114 case ARM::fixup_t2_condbranch: 115 return ELF::R_ARM_THM_JUMP19; 116 case ARM::fixup_t2_uncondbranch: 117 return ELF::R_ARM_THM_JUMP24; 118 case ARM::fixup_arm_movt_hi16: 119 return ELF::R_ARM_MOVT_PREL; 120 case ARM::fixup_arm_movw_lo16: 121 return ELF::R_ARM_MOVW_PREL_NC; 122 case ARM::fixup_t2_movt_hi16: 123 return ELF::R_ARM_THM_MOVT_PREL; 124 case ARM::fixup_t2_movw_lo16: 125 return ELF::R_ARM_THM_MOVW_PREL_NC; 126 case ARM::fixup_arm_thumb_br: 127 return ELF::R_ARM_THM_JUMP11; 128 case ARM::fixup_arm_thumb_bcc: 129 return ELF::R_ARM_THM_JUMP8; 130 case ARM::fixup_arm_thumb_bl: 131 case ARM::fixup_arm_thumb_blx: 132 switch (Modifier) { 133 case MCSymbolRefExpr::VK_TLSCALL: 134 return ELF::R_ARM_THM_TLS_CALL; 135 default: 136 return ELF::R_ARM_THM_CALL; 137 } 138 } 139 } 140 switch ((unsigned)Fixup.getKind()) { 141 default: 142 Ctx.reportFatalError(Fixup.getLoc(), "unsupported relocation on symbol"); 143 return ELF::R_ARM_NONE; 144 case FK_Data_1: 145 switch (Modifier) { 146 default: 147 llvm_unreachable("unsupported Modifier"); 148 case MCSymbolRefExpr::VK_None: 149 return ELF::R_ARM_ABS8; 150 } 151 case FK_Data_2: 152 switch (Modifier) { 153 default: 154 llvm_unreachable("unsupported modifier"); 155 case MCSymbolRefExpr::VK_None: 156 return ELF::R_ARM_ABS16; 157 } 158 case FK_Data_4: 159 switch (Modifier) { 160 default: 161 llvm_unreachable("Unsupported Modifier"); 162 case MCSymbolRefExpr::VK_ARM_NONE: 163 return ELF::R_ARM_NONE; 164 case MCSymbolRefExpr::VK_GOT: 165 return ELF::R_ARM_GOT_BREL; 166 case MCSymbolRefExpr::VK_TLSGD: 167 return ELF::R_ARM_TLS_GD32; 168 case MCSymbolRefExpr::VK_TPOFF: 169 return ELF::R_ARM_TLS_LE32; 170 case MCSymbolRefExpr::VK_GOTTPOFF: 171 return ELF::R_ARM_TLS_IE32; 172 case MCSymbolRefExpr::VK_None: 173 return ELF::R_ARM_ABS32; 174 case MCSymbolRefExpr::VK_GOTOFF: 175 return ELF::R_ARM_GOTOFF32; 176 case MCSymbolRefExpr::VK_ARM_GOT_PREL: 177 return ELF::R_ARM_GOT_PREL; 178 case MCSymbolRefExpr::VK_ARM_TARGET1: 179 return ELF::R_ARM_TARGET1; 180 case MCSymbolRefExpr::VK_ARM_TARGET2: 181 return ELF::R_ARM_TARGET2; 182 case MCSymbolRefExpr::VK_ARM_PREL31: 183 return ELF::R_ARM_PREL31; 184 case MCSymbolRefExpr::VK_ARM_SBREL: 185 return ELF::R_ARM_SBREL32; 186 case MCSymbolRefExpr::VK_ARM_TLSLDO: 187 return ELF::R_ARM_TLS_LDO32; 188 case MCSymbolRefExpr::VK_TLSCALL: 189 return ELF::R_ARM_TLS_CALL; 190 case MCSymbolRefExpr::VK_TLSDESC: 191 return ELF::R_ARM_TLS_GOTDESC; 192 case MCSymbolRefExpr::VK_TLSLDM: 193 return ELF::R_ARM_TLS_LDM32; 194 case MCSymbolRefExpr::VK_ARM_TLSDESCSEQ: 195 return ELF::R_ARM_TLS_DESCSEQ; 196 } 197 case ARM::fixup_arm_condbranch: 198 case ARM::fixup_arm_uncondbranch: 199 return ELF::R_ARM_JUMP24; 200 case ARM::fixup_arm_movt_hi16: 201 switch (Modifier) { 202 default: 203 llvm_unreachable("Unsupported Modifier"); 204 case MCSymbolRefExpr::VK_None: 205 return ELF::R_ARM_MOVT_ABS; 206 case MCSymbolRefExpr::VK_ARM_SBREL: 207 return ELF::R_ARM_MOVT_BREL; 208 } 209 case ARM::fixup_arm_movw_lo16: 210 switch (Modifier) { 211 default: 212 llvm_unreachable("Unsupported Modifier"); 213 case MCSymbolRefExpr::VK_None: 214 return ELF::R_ARM_MOVW_ABS_NC; 215 case MCSymbolRefExpr::VK_ARM_SBREL: 216 return ELF::R_ARM_MOVW_BREL_NC; 217 } 218 case ARM::fixup_t2_movt_hi16: 219 switch (Modifier) { 220 default: 221 llvm_unreachable("Unsupported Modifier"); 222 case MCSymbolRefExpr::VK_None: 223 return ELF::R_ARM_THM_MOVT_ABS; 224 case MCSymbolRefExpr::VK_ARM_SBREL: 225 return ELF::R_ARM_THM_MOVT_BREL; 226 } 227 case ARM::fixup_t2_movw_lo16: 228 switch (Modifier) { 229 default: 230 llvm_unreachable("Unsupported Modifier"); 231 case MCSymbolRefExpr::VK_None: 232 return ELF::R_ARM_THM_MOVW_ABS_NC; 233 case MCSymbolRefExpr::VK_ARM_SBREL: 234 return ELF::R_ARM_THM_MOVW_BREL_NC; 235 } 236 } 237 } 238 239 std::unique_ptr<MCObjectTargetWriter> 240 llvm::createARMELFObjectWriter(uint8_t OSABI) { 241 return llvm::make_unique<ARMELFObjectWriter>(OSABI); 242 } 243
