llvm/lib/Target/ARM/MCTargetDesc/ARMELFObjectWriter.cpp

   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 }