lib/Target/ARM/MCTargetDesc/ARMELFObjectWriter.cpp

   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     unsigned GetRelocType(const MCValue &Target, const MCFixup &Fixup,
  38                           bool IsPCRel) const override;
  39
  40     bool needsRelocateWithSymbol(const MCSymbolData &SD,
  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 MCSymbolData &SD,
  53                                                  unsigned Type) const {
  54   // FIXME: This is extremelly 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(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: llvm_unreachable("Unimplemented");
  85     case FK_Data_4:
  86       switch (Modifier) {
  87       default: llvm_unreachable("Unsupported Modifier");
  88       case MCSymbolRefExpr::VK_None:
  89         Type = ELF::R_ARM_REL32;
  90         break;
  91       case MCSymbolRefExpr::VK_TLSGD:
  92         llvm_unreachable("unimplemented");
  93       case MCSymbolRefExpr::VK_GOTTPOFF:
  94         Type = ELF::R_ARM_TLS_IE32;
  95         break;
  96       case MCSymbolRefExpr::VK_GOTPCREL:
  97         Type = ELF::R_ARM_GOT_PREL;
  98         break;
  99       }
 100       break;
 101     case ARM::fixup_arm_blx:
 102     case ARM::fixup_arm_uncondbl:
 103       switch (Modifier) {
 104       case MCSymbolRefExpr::VK_PLT:
 105         Type = ELF::R_ARM_CALL;
 106         break;
 107       case MCSymbolRefExpr::VK_ARM_TLSCALL:
 108         Type = ELF::R_ARM_TLS_CALL;
 109         break;
 110       default:
 111         Type = ELF::R_ARM_CALL;
 112         break;
 113       }
 114       break;
 115     case ARM::fixup_arm_condbl:
 116     case ARM::fixup_arm_condbranch:
 117     case ARM::fixup_arm_uncondbranch:
 118       Type = ELF::R_ARM_JUMP24;
 119       break;
 120     case ARM::fixup_t2_condbranch:
 121     case ARM::fixup_t2_uncondbranch:
 122       Type = ELF::R_ARM_THM_JUMP24;
 123       break;
 124     case ARM::fixup_arm_movt_hi16:
 125       Type = ELF::R_ARM_MOVT_PREL;
 126       break;
 127     case ARM::fixup_arm_movw_lo16:
 128       Type = ELF::R_ARM_MOVW_PREL_NC;
 129       break;
 130     case ARM::fixup_t2_movt_hi16:
 131       Type = ELF::R_ARM_THM_MOVT_PREL;
 132       break;
 133     case ARM::fixup_t2_movw_lo16:
 134       Type = ELF::R_ARM_THM_MOVW_PREL_NC;
 135       break;
 136     case ARM::fixup_arm_thumb_bl:
 137     case ARM::fixup_arm_thumb_blx:
 138       switch (Modifier) {
 139       case MCSymbolRefExpr::VK_ARM_TLSCALL:
 140         Type = ELF::R_ARM_THM_TLS_CALL;
 141         break;
 142       default:
 143         Type = ELF::R_ARM_THM_CALL;
 144         break;
 145       }
 146       break;
 147     }
 148   } else {
 149     switch ((unsigned)Fixup.getKind()) {
 150     default: llvm_unreachable("invalid fixup kind!");
 151     case FK_Data_4:
 152       switch (Modifier) {
 153       default: llvm_unreachable("Unsupported Modifier");
 154       case MCSymbolRefExpr::VK_ARM_NONE:
 155         Type = ELF::R_ARM_NONE;
 156         break;
 157       case MCSymbolRefExpr::VK_GOT:
 158         Type = ELF::R_ARM_GOT_BREL;
 159         break;
 160       case MCSymbolRefExpr::VK_TLSGD:
 161         Type = ELF::R_ARM_TLS_GD32;
 162         break;
 163       case MCSymbolRefExpr::VK_TPOFF:
 164         Type = ELF::R_ARM_TLS_LE32;
 165         break;
 166       case MCSymbolRefExpr::VK_GOTTPOFF:
 167         Type = ELF::R_ARM_TLS_IE32;
 168         break;
 169       case MCSymbolRefExpr::VK_None:
 170         Type = ELF::R_ARM_ABS32;
 171         break;
 172       case MCSymbolRefExpr::VK_GOTOFF:
 173         Type = ELF::R_ARM_GOTOFF32;
 174         break;
 175       case MCSymbolRefExpr::VK_GOTPCREL:
 176         Type = ELF::R_ARM_GOT_PREL;
 177         break;
 178       case MCSymbolRefExpr::VK_ARM_TARGET1:
 179         Type = ELF::R_ARM_TARGET1;
 180         break;
 181       case MCSymbolRefExpr::VK_ARM_TARGET2:
 182         Type = ELF::R_ARM_TARGET2;
 183         break;
 184       case MCSymbolRefExpr::VK_ARM_PREL31:
 185         Type = ELF::R_ARM_PREL31;
 186         break;
 187       case MCSymbolRefExpr::VK_ARM_TLSLDO:
 188         Type = ELF::R_ARM_TLS_LDO32;
 189         break;
 190       case MCSymbolRefExpr::VK_ARM_TLSCALL:
 191         Type = ELF::R_ARM_TLS_CALL;
 192         break;
 193       case MCSymbolRefExpr::VK_ARM_TLSDESC:
 194         Type = ELF::R_ARM_TLS_GOTDESC;
 195         break;
 196       case MCSymbolRefExpr::VK_ARM_TLSDESCSEQ:
 197         Type = ELF::R_ARM_TLS_DESCSEQ;
 198         break;
 199       }
 200       break;
 201     case ARM::fixup_arm_ldst_pcrel_12:
 202     case ARM::fixup_arm_pcrel_10:
 203     case ARM::fixup_arm_adr_pcrel_12:
 204     case ARM::fixup_arm_thumb_bl:
 205     case ARM::fixup_arm_thumb_cb:
 206     case ARM::fixup_arm_thumb_cp:
 207     case ARM::fixup_arm_thumb_br:
 208       llvm_unreachable("Unimplemented");
 209     case ARM::fixup_arm_condbranch:
 210     case ARM::fixup_arm_uncondbranch:
 211       Type = ELF::R_ARM_JUMP24;
 212       break;
 213     case ARM::fixup_arm_movt_hi16:
 214       Type = ELF::R_ARM_MOVT_ABS;
 215       break;
 216     case ARM::fixup_arm_movw_lo16:
 217       Type = ELF::R_ARM_MOVW_ABS_NC;
 218       break;
 219     case ARM::fixup_t2_movt_hi16:
 220       Type = ELF::R_ARM_THM_MOVT_ABS;
 221       break;
 222     case ARM::fixup_t2_movw_lo16:
 223       Type = ELF::R_ARM_THM_MOVW_ABS_NC;
 224       break;
 225     }
 226   }
 227
 228   return Type;
 229 }
 230
 231 MCObjectWriter *llvm::createARMELFObjectWriter(raw_ostream &OS,
 232                                                uint8_t OSABI,
 233                                                bool IsLittleEndian) {
 234   MCELFObjectTargetWriter *MOTW = new ARMELFObjectWriter(OSABI);
 235   return createELFObjectWriter(MOTW, OS, IsLittleEndian);
 236 }