1 //===-- ARMELFObjectWriter.cpp - ARM ELF Writer ---------------------------===// 2 // 3 // Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions. 4 // See https://llvm.org/LICENSE.txt for license information. 5 // SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception 6 // 7 //===----------------------------------------------------------------------===// 8 9 #include "MCTargetDesc/ARMFixupKinds.h" 10 #include "MCTargetDesc/ARMMCTargetDesc.h" 11 #include "llvm/BinaryFormat/ELF.h" 12 #include "llvm/MC/MCContext.h" 13 #include "llvm/MC/MCELFObjectWriter.h" 14 #include "llvm/MC/MCExpr.h" 15 #include "llvm/MC/MCFixup.h" 16 #include "llvm/MC/MCObjectFileInfo.h" 17 #include "llvm/MC/MCObjectWriter.h" 18 #include "llvm/MC/MCValue.h" 19 #include "llvm/Object/ELF.h" 20 #include "llvm/Support/ErrorHandling.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 MCValue &Val, 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 MCValue &, 53 const MCSymbol &, 54 unsigned Type) const { 55 // FIXME: This is extremely conservative. This really needs to use an 56 // explicit list with a clear explanation for why each realocation needs to 57 // point to the symbol, not to the section. 58 switch (Type) { 59 default: 60 return true; 61 62 case ELF::R_ARM_PREL31: 63 case ELF::R_ARM_ABS32: 64 return false; 65 } 66 } 67 68 // Need to examine the Fixup when determining whether to 69 // emit the relocation as an explicit symbol or as a section relative 70 // offset 71 unsigned ARMELFObjectWriter::getRelocType(MCContext &Ctx, const MCValue &Target, 72 const MCFixup &Fixup, 73 bool IsPCRel) const { 74 return GetRelocTypeInner(Target, Fixup, IsPCRel, Ctx); 75 } 76 77 unsigned ARMELFObjectWriter::GetRelocTypeInner(const MCValue &Target, 78 const MCFixup &Fixup, 79 bool IsPCRel, 80 MCContext &Ctx) const { 81 unsigned Kind = Fixup.getTargetKind(); 82 if (Kind >= FirstLiteralRelocationKind) 83 return Kind - FirstLiteralRelocationKind; 84 MCSymbolRefExpr::VariantKind Modifier = Target.getAccessVariant(); 85 auto CheckFDPIC = [&](uint32_t Type) { 86 if (getOSABI() != ELF::ELFOSABI_ARM_FDPIC) 87 Ctx.reportError(Fixup.getLoc(), 88 "relocation " + 89 object::getELFRelocationTypeName(ELF::EM_ARM, Type) + 90 " only supported in FDPIC mode"); 91 return Type; 92 }; 93 94 if (IsPCRel) { 95 switch (Fixup.getTargetKind()) { 96 default: 97 Ctx.reportError(Fixup.getLoc(), "unsupported relocation type"); 98 return ELF::R_ARM_NONE; 99 case FK_Data_4: 100 switch (Modifier) { 101 default: 102 Ctx.reportError(Fixup.getLoc(), 103 "invalid fixup for 4-byte pc-relative data relocation"); 104 return ELF::R_ARM_NONE; 105 case MCSymbolRefExpr::VK_None: { 106 if (const MCSymbolRefExpr *SymRef = Target.getSymA()) { 107 // For GNU AS compatibility expressions such as 108 // _GLOBAL_OFFSET_TABLE_ - label emit a R_ARM_BASE_PREL relocation. 109 if (SymRef->getSymbol().getName() == "_GLOBAL_OFFSET_TABLE_") 110 return ELF::R_ARM_BASE_PREL; 111 } 112 return ELF::R_ARM_REL32; 113 } 114 case MCSymbolRefExpr::VK_GOTTPOFF: 115 return ELF::R_ARM_TLS_IE32; 116 case MCSymbolRefExpr::VK_ARM_GOT_PREL: 117 return ELF::R_ARM_GOT_PREL; 118 case MCSymbolRefExpr::VK_ARM_PREL31: 119 return ELF::R_ARM_PREL31; 120 } 121 case ARM::fixup_arm_blx: 122 case ARM::fixup_arm_uncondbl: 123 switch (Modifier) { 124 case MCSymbolRefExpr::VK_PLT: 125 return ELF::R_ARM_CALL; 126 case MCSymbolRefExpr::VK_TLSCALL: 127 return ELF::R_ARM_TLS_CALL; 128 default: 129 return ELF::R_ARM_CALL; 130 } 131 case ARM::fixup_arm_condbl: 132 case ARM::fixup_arm_condbranch: 133 case ARM::fixup_arm_uncondbranch: 134 return ELF::R_ARM_JUMP24; 135 case ARM::fixup_t2_condbranch: 136 return ELF::R_ARM_THM_JUMP19; 137 case ARM::fixup_t2_uncondbranch: 138 return ELF::R_ARM_THM_JUMP24; 139 case ARM::fixup_arm_movt_hi16: 140 return ELF::R_ARM_MOVT_PREL; 141 case ARM::fixup_arm_movw_lo16: 142 return ELF::R_ARM_MOVW_PREL_NC; 143 case ARM::fixup_t2_movt_hi16: 144 return ELF::R_ARM_THM_MOVT_PREL; 145 case ARM::fixup_t2_movw_lo16: 146 return ELF::R_ARM_THM_MOVW_PREL_NC; 147 case ARM::fixup_arm_thumb_upper_8_15: 148 return ELF::R_ARM_THM_ALU_ABS_G3; 149 case ARM::fixup_arm_thumb_upper_0_7: 150 return ELF::R_ARM_THM_ALU_ABS_G2_NC; 151 case ARM::fixup_arm_thumb_lower_8_15: 152 return ELF::R_ARM_THM_ALU_ABS_G1_NC; 153 case ARM::fixup_arm_thumb_lower_0_7: 154 return ELF::R_ARM_THM_ALU_ABS_G0_NC; 155 case ARM::fixup_arm_thumb_br: 156 return ELF::R_ARM_THM_JUMP11; 157 case ARM::fixup_arm_thumb_bcc: 158 return ELF::R_ARM_THM_JUMP8; 159 case ARM::fixup_arm_thumb_bl: 160 case ARM::fixup_arm_thumb_blx: 161 switch (Modifier) { 162 case MCSymbolRefExpr::VK_TLSCALL: 163 return ELF::R_ARM_THM_TLS_CALL; 164 default: 165 return ELF::R_ARM_THM_CALL; 166 } 167 case ARM::fixup_arm_ldst_pcrel_12: 168 return ELF::R_ARM_LDR_PC_G0; 169 case ARM::fixup_arm_pcrel_10_unscaled: 170 return ELF::R_ARM_LDRS_PC_G0; 171 case ARM::fixup_t2_ldst_pcrel_12: 172 return ELF::R_ARM_THM_PC12; 173 case ARM::fixup_arm_adr_pcrel_12: 174 return ELF::R_ARM_ALU_PC_G0; 175 case ARM::fixup_thumb_adr_pcrel_10: 176 return ELF::R_ARM_THM_PC8; 177 case ARM::fixup_t2_adr_pcrel_12: 178 return ELF::R_ARM_THM_ALU_PREL_11_0; 179 case ARM::fixup_bf_target: 180 return ELF::R_ARM_THM_BF16; 181 case ARM::fixup_bfc_target: 182 return ELF::R_ARM_THM_BF12; 183 case ARM::fixup_bfl_target: 184 return ELF::R_ARM_THM_BF18; 185 } 186 } 187 switch (Kind) { 188 default: 189 Ctx.reportError(Fixup.getLoc(), "unsupported relocation type"); 190 return ELF::R_ARM_NONE; 191 case FK_Data_1: 192 switch (Modifier) { 193 default: 194 Ctx.reportError(Fixup.getLoc(), 195 "invalid fixup for 1-byte data relocation"); 196 return ELF::R_ARM_NONE; 197 case MCSymbolRefExpr::VK_None: 198 return ELF::R_ARM_ABS8; 199 } 200 case FK_Data_2: 201 switch (Modifier) { 202 default: 203 Ctx.reportError(Fixup.getLoc(), 204 "invalid fixup for 2-byte data relocation"); 205 return ELF::R_ARM_NONE; 206 case MCSymbolRefExpr::VK_None: 207 return ELF::R_ARM_ABS16; 208 } 209 case FK_Data_4: 210 switch (Modifier) { 211 default: 212 Ctx.reportError(Fixup.getLoc(), 213 "invalid fixup for 4-byte data relocation"); 214 return ELF::R_ARM_NONE; 215 case MCSymbolRefExpr::VK_ARM_NONE: 216 return ELF::R_ARM_NONE; 217 case MCSymbolRefExpr::VK_GOT: 218 return ELF::R_ARM_GOT_BREL; 219 case MCSymbolRefExpr::VK_TLSGD: 220 return ELF::R_ARM_TLS_GD32; 221 case MCSymbolRefExpr::VK_TPOFF: 222 return ELF::R_ARM_TLS_LE32; 223 case MCSymbolRefExpr::VK_GOTTPOFF: 224 return ELF::R_ARM_TLS_IE32; 225 case MCSymbolRefExpr::VK_None: 226 return ELF::R_ARM_ABS32; 227 case MCSymbolRefExpr::VK_GOTOFF: 228 return ELF::R_ARM_GOTOFF32; 229 case MCSymbolRefExpr::VK_ARM_GOT_PREL: 230 return ELF::R_ARM_GOT_PREL; 231 case MCSymbolRefExpr::VK_ARM_TARGET1: 232 return ELF::R_ARM_TARGET1; 233 case MCSymbolRefExpr::VK_ARM_TARGET2: 234 return ELF::R_ARM_TARGET2; 235 case MCSymbolRefExpr::VK_ARM_PREL31: 236 return ELF::R_ARM_PREL31; 237 case MCSymbolRefExpr::VK_ARM_SBREL: 238 return ELF::R_ARM_SBREL32; 239 case MCSymbolRefExpr::VK_ARM_TLSLDO: 240 return ELF::R_ARM_TLS_LDO32; 241 case MCSymbolRefExpr::VK_TLSCALL: 242 return ELF::R_ARM_TLS_CALL; 243 case MCSymbolRefExpr::VK_TLSDESC: 244 return ELF::R_ARM_TLS_GOTDESC; 245 case MCSymbolRefExpr::VK_TLSLDM: 246 return ELF::R_ARM_TLS_LDM32; 247 case MCSymbolRefExpr::VK_ARM_TLSDESCSEQ: 248 return ELF::R_ARM_TLS_DESCSEQ; 249 case MCSymbolRefExpr::VK_FUNCDESC: 250 return CheckFDPIC(ELF::R_ARM_FUNCDESC); 251 case MCSymbolRefExpr::VK_GOTFUNCDESC: 252 return CheckFDPIC(ELF::R_ARM_GOTFUNCDESC); 253 case MCSymbolRefExpr::VK_GOTOFFFUNCDESC: 254 return CheckFDPIC(ELF::R_ARM_GOTOFFFUNCDESC); 255 case MCSymbolRefExpr::VK_TLSGD_FDPIC: 256 return CheckFDPIC(ELF::R_ARM_TLS_GD32_FDPIC); 257 case MCSymbolRefExpr::VK_TLSLDM_FDPIC: 258 return CheckFDPIC(ELF::R_ARM_TLS_LDM32_FDPIC); 259 case MCSymbolRefExpr::VK_GOTTPOFF_FDPIC: 260 return CheckFDPIC(ELF::R_ARM_TLS_IE32_FDPIC); 261 } 262 case ARM::fixup_arm_condbranch: 263 case ARM::fixup_arm_uncondbranch: 264 return ELF::R_ARM_JUMP24; 265 case ARM::fixup_arm_movt_hi16: 266 switch (Modifier) { 267 default: 268 Ctx.reportError(Fixup.getLoc(), "invalid fixup for ARM MOVT instruction"); 269 return ELF::R_ARM_NONE; 270 case MCSymbolRefExpr::VK_None: 271 return ELF::R_ARM_MOVT_ABS; 272 case MCSymbolRefExpr::VK_ARM_SBREL: 273 return ELF::R_ARM_MOVT_BREL; 274 } 275 case ARM::fixup_arm_movw_lo16: 276 switch (Modifier) { 277 default: 278 Ctx.reportError(Fixup.getLoc(), "invalid fixup for ARM MOVW instruction"); 279 return ELF::R_ARM_NONE; 280 case MCSymbolRefExpr::VK_None: 281 return ELF::R_ARM_MOVW_ABS_NC; 282 case MCSymbolRefExpr::VK_ARM_SBREL: 283 return ELF::R_ARM_MOVW_BREL_NC; 284 } 285 case ARM::fixup_t2_movt_hi16: 286 switch (Modifier) { 287 default: 288 Ctx.reportError(Fixup.getLoc(), 289 "invalid fixup for Thumb MOVT instruction"); 290 return ELF::R_ARM_NONE; 291 case MCSymbolRefExpr::VK_None: 292 return ELF::R_ARM_THM_MOVT_ABS; 293 case MCSymbolRefExpr::VK_ARM_SBREL: 294 return ELF::R_ARM_THM_MOVT_BREL; 295 } 296 case ARM::fixup_t2_movw_lo16: 297 switch (Modifier) { 298 default: 299 Ctx.reportError(Fixup.getLoc(), 300 "invalid fixup for Thumb MOVW instruction"); 301 return ELF::R_ARM_NONE; 302 case MCSymbolRefExpr::VK_None: 303 return ELF::R_ARM_THM_MOVW_ABS_NC; 304 case MCSymbolRefExpr::VK_ARM_SBREL: 305 return ELF::R_ARM_THM_MOVW_BREL_NC; 306 } 307 308 case ARM::fixup_arm_thumb_upper_8_15: 309 return ELF::R_ARM_THM_ALU_ABS_G3; 310 case ARM::fixup_arm_thumb_upper_0_7: 311 return ELF::R_ARM_THM_ALU_ABS_G2_NC; 312 case ARM::fixup_arm_thumb_lower_8_15: 313 return ELF::R_ARM_THM_ALU_ABS_G1_NC; 314 case ARM::fixup_arm_thumb_lower_0_7: 315 return ELF::R_ARM_THM_ALU_ABS_G0_NC; 316 } 317 } 318 319 std::unique_ptr<MCObjectTargetWriter> 320 llvm::createARMELFObjectWriter(uint8_t OSABI) { 321 return std::make_unique<ARMELFObjectWriter>(OSABI); 322 } 323