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(unsigned Type) const override;
  41   };
  42 }
  43
  44 ARMELFObjectWriter::ARMELFObjectWriter(uint8_t OSABI)
  45   : MCELFObjectTargetWriter(/*Is64Bit*/ false, OSABI,
  46                             ELF::EM_ARM,
  47                             /*HasRelocationAddend*/ false) {}
  48
  49 ARMELFObjectWriter::~ARMELFObjectWriter() {}
  50
  51 bool ARMELFObjectWriter::needsRelocateWithSymbol(unsigned Type) const {
  52   // FIXME: This is extremelly conservative. This really needs to use a
  53   // whitelist with a clear explanation for why each realocation needs to
  54   // point to the symbol, not to the section.
  55   switch (Type) {
  56   default:
  57     return true;
  58
  59   case ELF::R_ARM_PREL31:
  60   case ELF::R_ARM_ABS32:
  61     return false;
  62   }
  63 }
  64
  65 // Need to examine the Fixup when determining whether to
  66 // emit the relocation as an explicit symbol or as a section relative
  67 // offset
  68 unsigned ARMELFObjectWriter::GetRelocType(const MCValue &Target,
  69                                           const MCFixup &Fixup,
  70                                           bool IsPCRel) const {
  71   return GetRelocTypeInner(Target, Fixup, IsPCRel);
  72 }
  73
  74 unsigned ARMELFObjectWriter::GetRelocTypeInner(const MCValue &Target,
  75                                                const MCFixup &Fixup,
  76                                                bool IsPCRel) const  {
  77   MCSymbolRefExpr::VariantKind Modifier = Target.getAccessVariant();
  78
  79   unsigned Type = 0;
  80   if (IsPCRel) {
  81     switch ((unsigned)Fixup.getKind()) {
  82     default: llvm_unreachable("Unimplemented");
  83     case FK_Data_4:
  84       switch (Modifier) {
  85       default: llvm_unreachable("Unsupported Modifier");
  86       case MCSymbolRefExpr::VK_None:
  87         Type = ELF::R_ARM_REL32;
  88         break;
  89       case MCSymbolRefExpr::VK_TLSGD:
  90         llvm_unreachable("unimplemented");
  91       case MCSymbolRefExpr::VK_GOTTPOFF:
  92         Type = ELF::R_ARM_TLS_IE32;
  93         break;
  94       case MCSymbolRefExpr::VK_GOTPCREL:
  95         Type = ELF::R_ARM_GOT_PREL;
  96         break;
  97       }
  98       break;
  99     case ARM::fixup_arm_blx:
 100     case ARM::fixup_arm_uncondbl:
 101       switch (Modifier) {
 102       case MCSymbolRefExpr::VK_PLT:
 103         Type = ELF::R_ARM_PLT32;
 104         break;
 105       case MCSymbolRefExpr::VK_ARM_TLSCALL:
 106         Type = ELF::R_ARM_TLS_CALL;
 107         break;
 108       default:
 109         Type = ELF::R_ARM_CALL;
 110         break;
 111       }
 112       break;
 113     case ARM::fixup_arm_condbl:
 114     case ARM::fixup_arm_condbranch:
 115     case ARM::fixup_arm_uncondbranch:
 116       Type = ELF::R_ARM_JUMP24;
 117       break;
 118     case ARM::fixup_t2_condbranch:
 119     case ARM::fixup_t2_uncondbranch:
 120       Type = ELF::R_ARM_THM_JUMP24;
 121       break;
 122     case ARM::fixup_arm_movt_hi16:
 123       Type = ELF::R_ARM_MOVT_PREL;
 124       break;
 125     case ARM::fixup_arm_movw_lo16:
 126       Type = ELF::R_ARM_MOVW_PREL_NC;
 127       break;
 128     case ARM::fixup_t2_movt_hi16:
 129       Type = ELF::R_ARM_THM_MOVT_PREL;
 130       break;
 131     case ARM::fixup_t2_movw_lo16:
 132       Type = ELF::R_ARM_THM_MOVW_PREL_NC;
 133       break;
 134     case ARM::fixup_arm_thumb_bl:
 135     case ARM::fixup_arm_thumb_blx:
 136       switch (Modifier) {
 137       case MCSymbolRefExpr::VK_ARM_TLSCALL:
 138         Type = ELF::R_ARM_THM_TLS_CALL;
 139         break;
 140       default:
 141         Type = ELF::R_ARM_THM_CALL;
 142         break;
 143       }
 144       break;
 145     }
 146   } else {
 147     switch ((unsigned)Fixup.getKind()) {
 148     default: llvm_unreachable("invalid fixup kind!");
 149     case FK_Data_4:
 150       switch (Modifier) {
 151       default: llvm_unreachable("Unsupported Modifier");
 152       case MCSymbolRefExpr::VK_ARM_NONE:
 153         Type = ELF::R_ARM_NONE;
 154         break;
 155       case MCSymbolRefExpr::VK_GOT:
 156         Type = ELF::R_ARM_GOT_BREL;
 157         break;
 158       case MCSymbolRefExpr::VK_TLSGD:
 159         Type = ELF::R_ARM_TLS_GD32;
 160         break;
 161       case MCSymbolRefExpr::VK_TPOFF:
 162         Type = ELF::R_ARM_TLS_LE32;
 163         break;
 164       case MCSymbolRefExpr::VK_GOTTPOFF:
 165         Type = ELF::R_ARM_TLS_IE32;
 166         break;
 167       case MCSymbolRefExpr::VK_None:
 168         Type = ELF::R_ARM_ABS32;
 169         break;
 170       case MCSymbolRefExpr::VK_GOTOFF:
 171         Type = ELF::R_ARM_GOTOFF32;
 172         break;
 173       case MCSymbolRefExpr::VK_GOTPCREL:
 174         Type = ELF::R_ARM_GOT_PREL;
 175         break;
 176       case MCSymbolRefExpr::VK_ARM_TARGET1:
 177         Type = ELF::R_ARM_TARGET1;
 178         break;
 179       case MCSymbolRefExpr::VK_ARM_TARGET2:
 180         Type = ELF::R_ARM_TARGET2;
 181         break;
 182       case MCSymbolRefExpr::VK_ARM_PREL31:
 183         Type = ELF::R_ARM_PREL31;
 184         break;
 185       case MCSymbolRefExpr::VK_ARM_TLSLDO:
 186         Type = ELF::R_ARM_TLS_LDO32;
 187         break;
 188       case MCSymbolRefExpr::VK_ARM_TLSCALL:
 189         Type = ELF::R_ARM_TLS_CALL;
 190         break;
 191       case MCSymbolRefExpr::VK_ARM_TLSDESC:
 192         Type = ELF::R_ARM_TLS_GOTDESC;
 193         break;
 194       case MCSymbolRefExpr::VK_ARM_TLSDESCSEQ:
 195         Type = ELF::R_ARM_TLS_DESCSEQ;
 196         break;
 197       }
 198       break;
 199     case ARM::fixup_arm_ldst_pcrel_12:
 200     case ARM::fixup_arm_pcrel_10:
 201     case ARM::fixup_arm_adr_pcrel_12:
 202     case ARM::fixup_arm_thumb_bl:
 203     case ARM::fixup_arm_thumb_cb:
 204     case ARM::fixup_arm_thumb_cp:
 205     case ARM::fixup_arm_thumb_br:
 206       llvm_unreachable("Unimplemented");
 207     case ARM::fixup_arm_condbranch:
 208     case ARM::fixup_arm_uncondbranch:
 209       Type = ELF::R_ARM_JUMP24;
 210       break;
 211     case ARM::fixup_arm_movt_hi16:
 212       Type = ELF::R_ARM_MOVT_ABS;
 213       break;
 214     case ARM::fixup_arm_movw_lo16:
 215       Type = ELF::R_ARM_MOVW_ABS_NC;
 216       break;
 217     case ARM::fixup_t2_movt_hi16:
 218       Type = ELF::R_ARM_THM_MOVT_ABS;
 219       break;
 220     case ARM::fixup_t2_movw_lo16:
 221       Type = ELF::R_ARM_THM_MOVW_ABS_NC;
 222       break;
 223     }
 224   }
 225
 226   return Type;
 227 }
 228
 229 MCObjectWriter *llvm::createARMELFObjectWriter(raw_ostream &OS,
 230                                                uint8_t OSABI,
 231                                                bool IsLittleEndian) {
 232   MCELFObjectTargetWriter *MOTW = new ARMELFObjectWriter(OSABI);
 233   return createELFObjectWriter(MOTW, OS, IsLittleEndian);
 234 }