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 ~ARMELFObjectWriter() override; 36 37 unsigned getRelocType(MCContext &Ctx, const MCValue &Target, 38 const MCFixup &Fixup, bool IsPCRel) const override; 39 40 bool needsRelocateWithSymbol(const MCSymbol &Sym, 41 unsigned Type) const override; 42 }; 43 } 44 45 ARMELFObjectWriter::ARMELFObjectWriter(uint8_t OSABI) 46 : MCELFObjectTargetWriter(/*Is64Bit*/ false, OSABI, 47 ELF::EM_ARM, 48 /*HasRelocationAddend*/ false) {} 49 50 ARMELFObjectWriter::~ARMELFObjectWriter() {} 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); 74 } 75 76 unsigned ARMELFObjectWriter::GetRelocTypeInner(const MCValue &Target, 77 const MCFixup &Fixup, 78 bool IsPCRel) const { 79 MCSymbolRefExpr::VariantKind Modifier = Target.getAccessVariant(); 80 81 unsigned Type = 0; 82 if (IsPCRel) { 83 switch ((unsigned)Fixup.getKind()) { 84 default: 85 report_fatal_error("unsupported relocation on symbol"); 86 return ELF::R_ARM_NONE; 87 case FK_Data_4: 88 switch (Modifier) { 89 default: llvm_unreachable("Unsupported Modifier"); 90 case MCSymbolRefExpr::VK_None: 91 Type = ELF::R_ARM_REL32; 92 break; 93 case MCSymbolRefExpr::VK_TLSGD: 94 llvm_unreachable("unimplemented"); 95 case MCSymbolRefExpr::VK_GOTTPOFF: 96 Type = ELF::R_ARM_TLS_IE32; 97 break; 98 case MCSymbolRefExpr::VK_ARM_GOT_PREL: 99 Type = ELF::R_ARM_GOT_PREL; 100 break; 101 case MCSymbolRefExpr::VK_ARM_PREL31: 102 Type = ELF::R_ARM_PREL31; 103 break; 104 } 105 break; 106 case ARM::fixup_arm_blx: 107 case ARM::fixup_arm_uncondbl: 108 switch (Modifier) { 109 case MCSymbolRefExpr::VK_PLT: 110 Type = ELF::R_ARM_CALL; 111 break; 112 case MCSymbolRefExpr::VK_ARM_TLSCALL: 113 Type = ELF::R_ARM_TLS_CALL; 114 break; 115 default: 116 Type = ELF::R_ARM_CALL; 117 break; 118 } 119 break; 120 case ARM::fixup_arm_condbl: 121 case ARM::fixup_arm_condbranch: 122 case ARM::fixup_arm_uncondbranch: 123 Type = ELF::R_ARM_JUMP24; 124 break; 125 case ARM::fixup_t2_condbranch: 126 case ARM::fixup_t2_uncondbranch: 127 Type = ELF::R_ARM_THM_JUMP24; 128 break; 129 case ARM::fixup_arm_movt_hi16: 130 Type = ELF::R_ARM_MOVT_PREL; 131 break; 132 case ARM::fixup_arm_movw_lo16: 133 Type = ELF::R_ARM_MOVW_PREL_NC; 134 break; 135 case ARM::fixup_t2_movt_hi16: 136 Type = ELF::R_ARM_THM_MOVT_PREL; 137 break; 138 case ARM::fixup_t2_movw_lo16: 139 Type = ELF::R_ARM_THM_MOVW_PREL_NC; 140 break; 141 case ARM::fixup_arm_thumb_bl: 142 case ARM::fixup_arm_thumb_blx: 143 switch (Modifier) { 144 case MCSymbolRefExpr::VK_ARM_TLSCALL: 145 Type = ELF::R_ARM_THM_TLS_CALL; 146 break; 147 default: 148 Type = ELF::R_ARM_THM_CALL; 149 break; 150 } 151 break; 152 } 153 } else { 154 switch ((unsigned)Fixup.getKind()) { 155 default: 156 report_fatal_error("unsupported relocation on symbol"); 157 return ELF::R_ARM_NONE; 158 case FK_Data_1: 159 switch (Modifier) { 160 default: llvm_unreachable("unsupported Modifier"); 161 case MCSymbolRefExpr::VK_None: 162 Type = ELF::R_ARM_ABS8; 163 break; 164 } 165 break; 166 case FK_Data_2: 167 switch (Modifier) { 168 default: llvm_unreachable("unsupported modifier"); 169 case MCSymbolRefExpr::VK_None: 170 Type = ELF::R_ARM_ABS16; 171 break; 172 } 173 break; 174 case FK_Data_4: 175 switch (Modifier) { 176 default: llvm_unreachable("Unsupported Modifier"); 177 case MCSymbolRefExpr::VK_ARM_NONE: 178 Type = ELF::R_ARM_NONE; 179 break; 180 case MCSymbolRefExpr::VK_GOT: 181 Type = ELF::R_ARM_GOT_BREL; 182 break; 183 case MCSymbolRefExpr::VK_TLSGD: 184 Type = ELF::R_ARM_TLS_GD32; 185 break; 186 case MCSymbolRefExpr::VK_TPOFF: 187 Type = ELF::R_ARM_TLS_LE32; 188 break; 189 case MCSymbolRefExpr::VK_GOTTPOFF: 190 Type = ELF::R_ARM_TLS_IE32; 191 break; 192 case MCSymbolRefExpr::VK_None: 193 Type = ELF::R_ARM_ABS32; 194 break; 195 case MCSymbolRefExpr::VK_GOTOFF: 196 Type = ELF::R_ARM_GOTOFF32; 197 break; 198 case MCSymbolRefExpr::VK_ARM_GOT_PREL: 199 Type = ELF::R_ARM_GOT_PREL; 200 break; 201 case MCSymbolRefExpr::VK_ARM_TARGET1: 202 Type = ELF::R_ARM_TARGET1; 203 break; 204 case MCSymbolRefExpr::VK_ARM_TARGET2: 205 Type = ELF::R_ARM_TARGET2; 206 break; 207 case MCSymbolRefExpr::VK_ARM_PREL31: 208 Type = ELF::R_ARM_PREL31; 209 break; 210 case MCSymbolRefExpr::VK_ARM_SBREL: 211 Type = ELF::R_ARM_SBREL32; 212 break; 213 case MCSymbolRefExpr::VK_ARM_TLSLDO: 214 Type = ELF::R_ARM_TLS_LDO32; 215 break; 216 case MCSymbolRefExpr::VK_ARM_TLSCALL: 217 Type = ELF::R_ARM_TLS_CALL; 218 break; 219 case MCSymbolRefExpr::VK_ARM_TLSDESC: 220 Type = ELF::R_ARM_TLS_GOTDESC; 221 break; 222 case MCSymbolRefExpr::VK_ARM_TLSDESCSEQ: 223 Type = ELF::R_ARM_TLS_DESCSEQ; 224 break; 225 } 226 break; 227 case ARM::fixup_arm_ldst_pcrel_12: 228 case ARM::fixup_arm_pcrel_10: 229 case ARM::fixup_arm_adr_pcrel_12: 230 case ARM::fixup_arm_thumb_bl: 231 case ARM::fixup_arm_thumb_cb: 232 case ARM::fixup_arm_thumb_cp: 233 case ARM::fixup_arm_thumb_br: 234 llvm_unreachable("Unimplemented"); 235 case ARM::fixup_arm_condbranch: 236 case ARM::fixup_arm_uncondbranch: 237 Type = ELF::R_ARM_JUMP24; 238 break; 239 case ARM::fixup_arm_movt_hi16: 240 Type = ELF::R_ARM_MOVT_ABS; 241 break; 242 case ARM::fixup_arm_movw_lo16: 243 Type = ELF::R_ARM_MOVW_ABS_NC; 244 break; 245 case ARM::fixup_t2_movt_hi16: 246 Type = ELF::R_ARM_THM_MOVT_ABS; 247 break; 248 case ARM::fixup_t2_movw_lo16: 249 Type = ELF::R_ARM_THM_MOVW_ABS_NC; 250 break; 251 } 252 } 253 254 return Type; 255 } 256 257 MCObjectWriter *llvm::createARMELFObjectWriter(raw_pwrite_stream &OS, 258 uint8_t OSABI, 259 bool IsLittleEndian) { 260 MCELFObjectTargetWriter *MOTW = new ARMELFObjectWriter(OSABI); 261 return createELFObjectWriter(MOTW, OS, IsLittleEndian); 262 } 263