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(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 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(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_GOTPCREL:
  99         Type = ELF::R_ARM_GOT_PREL;
 100         break;
 101       }
 102       break;
 103     case ARM::fixup_arm_blx:
 104     case ARM::fixup_arm_uncondbl:
 105       switch (Modifier) {
 106       case MCSymbolRefExpr::VK_PLT:
 107         Type = ELF::R_ARM_CALL;
 108         break;
 109       case MCSymbolRefExpr::VK_ARM_TLSCALL:
 110         Type = ELF::R_ARM_TLS_CALL;
 111         break;
 112       default:
 113         Type = ELF::R_ARM_CALL;
 114         break;
 115       }
 116       break;
 117     case ARM::fixup_arm_condbl:
 118     case ARM::fixup_arm_condbranch:
 119     case ARM::fixup_arm_uncondbranch:
 120       Type = ELF::R_ARM_JUMP24;
 121       break;
 122     case ARM::fixup_t2_condbranch:
 123     case ARM::fixup_t2_uncondbranch:
 124       Type = ELF::R_ARM_THM_JUMP24;
 125       break;
 126     case ARM::fixup_arm_movt_hi16:
 127       Type = ELF::R_ARM_MOVT_PREL;
 128       break;
 129     case ARM::fixup_arm_movw_lo16:
 130       Type = ELF::R_ARM_MOVW_PREL_NC;
 131       break;
 132     case ARM::fixup_t2_movt_hi16:
 133       Type = ELF::R_ARM_THM_MOVT_PREL;
 134       break;
 135     case ARM::fixup_t2_movw_lo16:
 136       Type = ELF::R_ARM_THM_MOVW_PREL_NC;
 137       break;
 138     case ARM::fixup_arm_thumb_bl:
 139     case ARM::fixup_arm_thumb_blx:
 140       switch (Modifier) {
 141       case MCSymbolRefExpr::VK_ARM_TLSCALL:
 142         Type = ELF::R_ARM_THM_TLS_CALL;
 143         break;
 144       default:
 145         Type = ELF::R_ARM_THM_CALL;
 146         break;
 147       }
 148       break;
 149     }
 150   } else {
 151     switch ((unsigned)Fixup.getKind()) {
 152     default:
 153       report_fatal_error("unsupported relocation on symbol");
 154       return ELF::R_ARM_NONE;
 155     case FK_Data_1:
 156       switch (Modifier) {
 157       default: llvm_unreachable("unsupported Modifier");
 158       case MCSymbolRefExpr::VK_None:
 159         Type = ELF::R_ARM_ABS8;
 160         break;
 161       }
 162       break;
 163     case FK_Data_2:
 164       switch (Modifier) {
 165       default: llvm_unreachable("unsupported modifier");
 166       case MCSymbolRefExpr::VK_None:
 167         Type = ELF::R_ARM_ABS16;
 168         break;
 169       }
 170       break;
 171     case FK_Data_4:
 172       switch (Modifier) {
 173       default: llvm_unreachable("Unsupported Modifier");
 174       case MCSymbolRefExpr::VK_ARM_NONE:
 175         Type = ELF::R_ARM_NONE;
 176         break;
 177       case MCSymbolRefExpr::VK_GOT:
 178         Type = ELF::R_ARM_GOT_BREL;
 179         break;
 180       case MCSymbolRefExpr::VK_TLSGD:
 181         Type = ELF::R_ARM_TLS_GD32;
 182         break;
 183       case MCSymbolRefExpr::VK_TPOFF:
 184         Type = ELF::R_ARM_TLS_LE32;
 185         break;
 186       case MCSymbolRefExpr::VK_GOTTPOFF:
 187         Type = ELF::R_ARM_TLS_IE32;
 188         break;
 189       case MCSymbolRefExpr::VK_None:
 190         Type = ELF::R_ARM_ABS32;
 191         break;
 192       case MCSymbolRefExpr::VK_GOTOFF:
 193         Type = ELF::R_ARM_GOTOFF32;
 194         break;
 195       case MCSymbolRefExpr::VK_GOTPCREL:
 196         Type = ELF::R_ARM_GOT_PREL;
 197         break;
 198       case MCSymbolRefExpr::VK_ARM_TARGET1:
 199         Type = ELF::R_ARM_TARGET1;
 200         break;
 201       case MCSymbolRefExpr::VK_ARM_TARGET2:
 202         Type = ELF::R_ARM_TARGET2;
 203         break;
 204       case MCSymbolRefExpr::VK_ARM_PREL31:
 205         Type = ELF::R_ARM_PREL31;
 206         break;
 207       case MCSymbolRefExpr::VK_ARM_SBREL:
 208         Type = ELF::R_ARM_SBREL32;
 209         break;
 210       case MCSymbolRefExpr::VK_ARM_TLSLDO:
 211         Type = ELF::R_ARM_TLS_LDO32;
 212         break;
 213       case MCSymbolRefExpr::VK_ARM_TLSCALL:
 214         Type = ELF::R_ARM_TLS_CALL;
 215         break;
 216       case MCSymbolRefExpr::VK_ARM_TLSDESC:
 217         Type = ELF::R_ARM_TLS_GOTDESC;
 218         break;
 219       case MCSymbolRefExpr::VK_ARM_TLSDESCSEQ:
 220         Type = ELF::R_ARM_TLS_DESCSEQ;
 221         break;
 222       }
 223       break;
 224     case ARM::fixup_arm_ldst_pcrel_12:
 225     case ARM::fixup_arm_pcrel_10:
 226     case ARM::fixup_arm_adr_pcrel_12:
 227     case ARM::fixup_arm_thumb_bl:
 228     case ARM::fixup_arm_thumb_cb:
 229     case ARM::fixup_arm_thumb_cp:
 230     case ARM::fixup_arm_thumb_br:
 231       llvm_unreachable("Unimplemented");
 232     case ARM::fixup_arm_condbranch:
 233     case ARM::fixup_arm_uncondbranch:
 234       Type = ELF::R_ARM_JUMP24;
 235       break;
 236     case ARM::fixup_arm_movt_hi16:
 237       Type = ELF::R_ARM_MOVT_ABS;
 238       break;
 239     case ARM::fixup_arm_movw_lo16:
 240       Type = ELF::R_ARM_MOVW_ABS_NC;
 241       break;
 242     case ARM::fixup_t2_movt_hi16:
 243       Type = ELF::R_ARM_THM_MOVT_ABS;
 244       break;
 245     case ARM::fixup_t2_movw_lo16:
 246       Type = ELF::R_ARM_THM_MOVW_ABS_NC;
 247       break;
 248     }
 249   }
 250
 251   return Type;
 252 }
 253
 254 MCObjectWriter *llvm::createARMELFObjectWriter(raw_ostream &OS,
 255                                                uint8_t OSABI,
 256                                                bool IsLittleEndian) {
 257   MCELFObjectTargetWriter *MOTW = new ARMELFObjectWriter(OSABI);
 258   return createELFObjectWriter(MOTW, OS, IsLittleEndian);
 259 }