contrib/llvm/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     ~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_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       Type = ELF::R_ARM_THM_JUMP19;
 127       break;
 128     case ARM::fixup_t2_uncondbranch:
 129       Type = ELF::R_ARM_THM_JUMP24;
 130       break;
 131     case ARM::fixup_arm_movt_hi16:
 132       Type = ELF::R_ARM_MOVT_PREL;
 133       break;
 134     case ARM::fixup_arm_movw_lo16:
 135       Type = ELF::R_ARM_MOVW_PREL_NC;
 136       break;
 137     case ARM::fixup_t2_movt_hi16:
 138       Type = ELF::R_ARM_THM_MOVT_PREL;
 139       break;
 140     case ARM::fixup_t2_movw_lo16:
 141       Type = ELF::R_ARM_THM_MOVW_PREL_NC;
 142       break;
 143     case ARM::fixup_arm_thumb_bl:
 144     case ARM::fixup_arm_thumb_blx:
 145       switch (Modifier) {
 146       case MCSymbolRefExpr::VK_TLSCALL:
 147         Type = ELF::R_ARM_THM_TLS_CALL;
 148         break;
 149       default:
 150         Type = ELF::R_ARM_THM_CALL;
 151         break;
 152       }
 153       break;
 154     }
 155   } else {
 156     switch ((unsigned)Fixup.getKind()) {
 157     default:
 158       report_fatal_error("unsupported relocation on symbol");
 159       return ELF::R_ARM_NONE;
 160     case FK_Data_1:
 161       switch (Modifier) {
 162       default: llvm_unreachable("unsupported Modifier");
 163       case MCSymbolRefExpr::VK_None:
 164         Type = ELF::R_ARM_ABS8;
 165         break;
 166       }
 167       break;
 168     case FK_Data_2:
 169       switch (Modifier) {
 170       default: llvm_unreachable("unsupported modifier");
 171       case MCSymbolRefExpr::VK_None:
 172         Type = ELF::R_ARM_ABS16;
 173         break;
 174       }
 175       break;
 176     case FK_Data_4:
 177       switch (Modifier) {
 178       default: llvm_unreachable("Unsupported Modifier");
 179       case MCSymbolRefExpr::VK_ARM_NONE:
 180         Type = ELF::R_ARM_NONE;
 181         break;
 182       case MCSymbolRefExpr::VK_GOT:
 183         Type = ELF::R_ARM_GOT_BREL;
 184         break;
 185       case MCSymbolRefExpr::VK_TLSGD:
 186         Type = ELF::R_ARM_TLS_GD32;
 187         break;
 188       case MCSymbolRefExpr::VK_TPOFF:
 189         Type = ELF::R_ARM_TLS_LE32;
 190         break;
 191       case MCSymbolRefExpr::VK_GOTTPOFF:
 192         Type = ELF::R_ARM_TLS_IE32;
 193         break;
 194       case MCSymbolRefExpr::VK_None:
 195         Type = ELF::R_ARM_ABS32;
 196         break;
 197       case MCSymbolRefExpr::VK_GOTOFF:
 198         Type = ELF::R_ARM_GOTOFF32;
 199         break;
 200       case MCSymbolRefExpr::VK_ARM_GOT_PREL:
 201         Type = ELF::R_ARM_GOT_PREL;
 202         break;
 203       case MCSymbolRefExpr::VK_ARM_TARGET1:
 204         Type = ELF::R_ARM_TARGET1;
 205         break;
 206       case MCSymbolRefExpr::VK_ARM_TARGET2:
 207         Type = ELF::R_ARM_TARGET2;
 208         break;
 209       case MCSymbolRefExpr::VK_ARM_PREL31:
 210         Type = ELF::R_ARM_PREL31;
 211         break;
 212       case MCSymbolRefExpr::VK_ARM_SBREL:
 213         Type = ELF::R_ARM_SBREL32;
 214         break;
 215       case MCSymbolRefExpr::VK_ARM_TLSLDO:
 216         Type = ELF::R_ARM_TLS_LDO32;
 217         break;
 218       case MCSymbolRefExpr::VK_TLSCALL:
 219         Type = ELF::R_ARM_TLS_CALL;
 220         break;
 221       case MCSymbolRefExpr::VK_TLSDESC:
 222         Type = ELF::R_ARM_TLS_GOTDESC;
 223         break;
 224       case MCSymbolRefExpr::VK_ARM_TLSDESCSEQ:
 225         Type = ELF::R_ARM_TLS_DESCSEQ;
 226         break;
 227       }
 228       break;
 229     case ARM::fixup_arm_ldst_pcrel_12:
 230     case ARM::fixup_arm_pcrel_10:
 231     case ARM::fixup_arm_adr_pcrel_12:
 232     case ARM::fixup_arm_thumb_bl:
 233     case ARM::fixup_arm_thumb_cb:
 234     case ARM::fixup_arm_thumb_cp:
 235     case ARM::fixup_arm_thumb_br:
 236       llvm_unreachable("Unimplemented");
 237     case ARM::fixup_arm_condbranch:
 238     case ARM::fixup_arm_uncondbranch:
 239       Type = ELF::R_ARM_JUMP24;
 240       break;
 241     case ARM::fixup_arm_movt_hi16:
 242       Type = ELF::R_ARM_MOVT_ABS;
 243       break;
 244     case ARM::fixup_arm_movw_lo16:
 245       Type = ELF::R_ARM_MOVW_ABS_NC;
 246       break;
 247     case ARM::fixup_t2_movt_hi16:
 248       Type = ELF::R_ARM_THM_MOVT_ABS;
 249       break;
 250     case ARM::fixup_t2_movw_lo16:
 251       Type = ELF::R_ARM_THM_MOVW_ABS_NC;
 252       break;
 253     }
 254   }
 255
 256   return Type;
 257 }
 258
 259 MCObjectWriter *llvm::createARMELFObjectWriter(raw_pwrite_stream &OS,
 260                                                uint8_t OSABI,
 261                                                bool IsLittleEndian) {
 262   MCELFObjectTargetWriter *MOTW = new ARMELFObjectWriter(OSABI);
 263   return createELFObjectWriter(MOTW, OS, IsLittleEndian);
 264 }