ARMELFObjectWriter.cpp revision 34982576a43887e7f062ed0a3571af2cbab003f3
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/ARMFixupKinds.h" 11#include "MCTargetDesc/ARMMCTargetDesc.h" 12#include "llvm/Support/Debug.h" 13#include "llvm/Support/ErrorHandling.h" 14#include "llvm/ADT/Statistic.h" 15#include "llvm/ADT/StringSwitch.h" 16#include "llvm/MC/MCELFObjectWriter.h" 17#include "llvm/MC/MCExpr.h" 18#include "llvm/MC/MCSectionELF.h" 19#include "llvm/MC/MCValue.h" 20 21using namespace llvm; 22 23namespace { 24 class ARMELFObjectWriter : public MCELFObjectTargetWriter { 25 enum { DefaultEABIVersion = 0x05000000U }; 26 unsigned GetRelocTypeInner(const MCValue &Target, 27 const MCFixup &Fixup, 28 bool IsPCRel) const; 29 30 31 public: 32 ARMELFObjectWriter(uint8_t OSABI); 33 34 virtual ~ARMELFObjectWriter(); 35 36 virtual unsigned GetRelocType(const MCValue &Target, const MCFixup &Fixup, 37 bool IsPCRel, bool IsRelocWithSymbol, 38 int64_t Addend) const; 39 virtual unsigned getEFlags() const; 40 virtual const MCSymbol *ExplicitRelSym(const MCAssembler &Asm, 41 const MCValue &Target, 42 const MCFragment &F, 43 const MCFixup &Fixup, 44 bool IsPCRel) const; 45 }; 46} 47 48ARMELFObjectWriter::ARMELFObjectWriter(uint8_t OSABI) 49 : MCELFObjectTargetWriter(/*Is64Bit*/ false, OSABI, 50 ELF::EM_ARM, 51 /*HasRelocationAddend*/ false) {} 52 53ARMELFObjectWriter::~ARMELFObjectWriter() {} 54 55// FIXME: get the real EABI Version from the Triple. 56unsigned ARMELFObjectWriter::getEFlags() const { 57 return ELF::EF_ARM_EABIMASK & DefaultEABIVersion; 58} 59 60// In ARM, _MergedGlobals and other most symbols get emitted directly. 61// I.e. not as an offset to a section symbol. 62// This code is an approximation of what ARM/gcc does. 63 64STATISTIC(PCRelCount, "Total number of PIC Relocations"); 65STATISTIC(NonPCRelCount, "Total number of non-PIC relocations"); 66 67const MCSymbol *ARMELFObjectWriter::ExplicitRelSym(const MCAssembler &Asm, 68 const MCValue &Target, 69 const MCFragment &F, 70 const MCFixup &Fixup, 71 bool IsPCRel) const { 72 const MCSymbol &Symbol = Target.getSymA()->getSymbol(); 73 bool EmitThisSym = false; 74 75 const MCSectionELF &Section = 76 static_cast<const MCSectionELF&>(Symbol.getSection()); 77 bool InNormalSection = true; 78 unsigned RelocType = 0; 79 RelocType = GetRelocTypeInner(Target, Fixup, IsPCRel); 80 81 DEBUG( 82 const MCSymbolRefExpr::VariantKind Kind = Target.getSymA()->getKind(); 83 MCSymbolRefExpr::VariantKind Kind2; 84 Kind2 = Target.getSymB() ? Target.getSymB()->getKind() : 85 MCSymbolRefExpr::VK_None; 86 dbgs() << "considering symbol " 87 << Section.getSectionName() << "/" 88 << Symbol.getName() << "/" 89 << " Rel:" << (unsigned)RelocType 90 << " Kind: " << (int)Kind << "/" << (int)Kind2 91 << " Tmp:" 92 << Symbol.isAbsolute() << "/" << Symbol.isDefined() << "/" 93 << Symbol.isVariable() << "/" << Symbol.isTemporary() 94 << " Counts:" << PCRelCount << "/" << NonPCRelCount << "\n"); 95 96 if (IsPCRel) { ++PCRelCount; 97 switch (RelocType) { 98 default: 99 // Most relocation types are emitted as explicit symbols 100 InNormalSection = 101 StringSwitch<bool>(Section.getSectionName()) 102 .Case(".data.rel.ro.local", false) 103 .Case(".data.rel", false) 104 .Case(".bss", false) 105 .Default(true); 106 EmitThisSym = true; 107 break; 108 case ELF::R_ARM_ABS32: 109 // But things get strange with R_ARM_ABS32 110 // In this case, most things that go in .rodata show up 111 // as section relative relocations 112 InNormalSection = 113 StringSwitch<bool>(Section.getSectionName()) 114 .Case(".data.rel.ro.local", false) 115 .Case(".data.rel", false) 116 .Case(".rodata", false) 117 .Case(".bss", false) 118 .Default(true); 119 EmitThisSym = false; 120 break; 121 } 122 } else { 123 NonPCRelCount++; 124 InNormalSection = 125 StringSwitch<bool>(Section.getSectionName()) 126 .Case(".data.rel.ro.local", false) 127 .Case(".rodata", false) 128 .Case(".data.rel", false) 129 .Case(".bss", false) 130 .Default(true); 131 132 switch (RelocType) { 133 default: EmitThisSym = true; break; 134 case ELF::R_ARM_ABS32: EmitThisSym = false; break; 135 } 136 } 137 138 if (EmitThisSym) 139 return &Symbol; 140 if (! Symbol.isTemporary() && InNormalSection) { 141 return &Symbol; 142 } 143 return NULL; 144} 145 146// Need to examine the Fixup when determining whether to 147// emit the relocation as an explicit symbol or as a section relative 148// offset 149unsigned ARMELFObjectWriter::GetRelocType(const MCValue &Target, 150 const MCFixup &Fixup, 151 bool IsPCRel, 152 bool IsRelocWithSymbol, 153 int64_t Addend) const { 154 return GetRelocTypeInner(Target, Fixup, IsPCRel); 155} 156 157unsigned ARMELFObjectWriter::GetRelocTypeInner(const MCValue &Target, 158 const MCFixup &Fixup, 159 bool IsPCRel) const { 160 MCSymbolRefExpr::VariantKind Modifier = Target.isAbsolute() ? 161 MCSymbolRefExpr::VK_None : Target.getSymA()->getKind(); 162 163 unsigned Type = 0; 164 if (IsPCRel) { 165 switch ((unsigned)Fixup.getKind()) { 166 default: assert(0 && "Unimplemented"); 167 case FK_Data_4: 168 switch (Modifier) { 169 default: llvm_unreachable("Unsupported Modifier"); 170 case MCSymbolRefExpr::VK_None: 171 Type = ELF::R_ARM_REL32; 172 break; 173 case MCSymbolRefExpr::VK_ARM_TLSGD: 174 assert(0 && "unimplemented"); 175 break; 176 case MCSymbolRefExpr::VK_ARM_GOTTPOFF: 177 Type = ELF::R_ARM_TLS_IE32; 178 break; 179 } 180 break; 181 case ARM::fixup_arm_uncondbranch: 182 switch (Modifier) { 183 case MCSymbolRefExpr::VK_ARM_PLT: 184 Type = ELF::R_ARM_PLT32; 185 break; 186 default: 187 Type = ELF::R_ARM_CALL; 188 break; 189 } 190 break; 191 case ARM::fixup_arm_condbranch: 192 Type = ELF::R_ARM_JUMP24; 193 break; 194 case ARM::fixup_arm_movt_hi16: 195 case ARM::fixup_arm_movt_hi16_pcrel: 196 Type = ELF::R_ARM_MOVT_PREL; 197 break; 198 case ARM::fixup_arm_movw_lo16: 199 case ARM::fixup_arm_movw_lo16_pcrel: 200 Type = ELF::R_ARM_MOVW_PREL_NC; 201 break; 202 case ARM::fixup_t2_movt_hi16: 203 case ARM::fixup_t2_movt_hi16_pcrel: 204 Type = ELF::R_ARM_THM_MOVT_PREL; 205 break; 206 case ARM::fixup_t2_movw_lo16: 207 case ARM::fixup_t2_movw_lo16_pcrel: 208 Type = ELF::R_ARM_THM_MOVW_PREL_NC; 209 break; 210 case ARM::fixup_arm_thumb_bl: 211 case ARM::fixup_arm_thumb_blx: 212 Type = ELF::R_ARM_THM_CALL; 213 break; 214 } 215 } else { 216 switch ((unsigned)Fixup.getKind()) { 217 default: llvm_unreachable("invalid fixup kind!"); 218 case FK_Data_4: 219 switch (Modifier) { 220 default: llvm_unreachable("Unsupported Modifier"); 221 case MCSymbolRefExpr::VK_ARM_GOT: 222 Type = ELF::R_ARM_GOT_BREL; 223 break; 224 case MCSymbolRefExpr::VK_ARM_TLSGD: 225 Type = ELF::R_ARM_TLS_GD32; 226 break; 227 case MCSymbolRefExpr::VK_ARM_TPOFF: 228 Type = ELF::R_ARM_TLS_LE32; 229 break; 230 case MCSymbolRefExpr::VK_ARM_GOTTPOFF: 231 Type = ELF::R_ARM_TLS_IE32; 232 break; 233 case MCSymbolRefExpr::VK_None: 234 Type = ELF::R_ARM_ABS32; 235 break; 236 case MCSymbolRefExpr::VK_ARM_GOTOFF: 237 Type = ELF::R_ARM_GOTOFF32; 238 break; 239 case MCSymbolRefExpr::VK_ARM_TARGET1: 240 Type = ELF::R_ARM_TARGET1; 241 break; 242 } 243 break; 244 case ARM::fixup_arm_ldst_pcrel_12: 245 case ARM::fixup_arm_pcrel_10: 246 case ARM::fixup_arm_adr_pcrel_12: 247 case ARM::fixup_arm_thumb_bl: 248 case ARM::fixup_arm_thumb_cb: 249 case ARM::fixup_arm_thumb_cp: 250 case ARM::fixup_arm_thumb_br: 251 assert(0 && "Unimplemented"); 252 break; 253 case ARM::fixup_arm_uncondbranch: 254 Type = ELF::R_ARM_CALL; 255 break; 256 case ARM::fixup_arm_condbranch: 257 Type = ELF::R_ARM_JUMP24; 258 break; 259 case ARM::fixup_arm_movt_hi16: 260 Type = ELF::R_ARM_MOVT_ABS; 261 break; 262 case ARM::fixup_arm_movw_lo16: 263 Type = ELF::R_ARM_MOVW_ABS_NC; 264 break; 265 case ARM::fixup_t2_movt_hi16: 266 Type = ELF::R_ARM_THM_MOVT_ABS; 267 break; 268 case ARM::fixup_t2_movw_lo16: 269 Type = ELF::R_ARM_THM_MOVW_ABS_NC; 270 break; 271 } 272 } 273 274 return Type; 275} 276 277MCObjectWriter *llvm::createARMELFObjectWriter(raw_ostream &OS, 278 uint8_t OSABI) { 279 MCELFObjectTargetWriter *MOTW = new ARMELFObjectWriter(OSABI); 280 return createELFObjectWriter(MOTW, OS, /*IsLittleEndian=*/true); 281} 282