ARMELFObjectWriter.cpp revision 234285
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/Support/raw_ostream.h" 15#include "llvm/ADT/Statistic.h" 16#include "llvm/ADT/StringSwitch.h" 17#include "llvm/MC/MCELFObjectWriter.h" 18#include "llvm/MC/MCExpr.h" 19#include "llvm/MC/MCSectionELF.h" 20#include "llvm/MC/MCValue.h" 21 22using namespace llvm; 23 24namespace { 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 virtual unsigned GetRelocType(const MCValue &Target, const MCFixup &Fixup, 38 bool IsPCRel, bool IsRelocWithSymbol, 39 int64_t Addend) const; 40 virtual unsigned getEFlags() const; 41 virtual const MCSymbol *ExplicitRelSym(const MCAssembler &Asm, 42 const MCValue &Target, 43 const MCFragment &F, 44 const MCFixup &Fixup, 45 bool IsPCRel) const; 46 }; 47} 48 49ARMELFObjectWriter::ARMELFObjectWriter(uint8_t OSABI) 50 : MCELFObjectTargetWriter(/*Is64Bit*/ false, OSABI, 51 ELF::EM_ARM, 52 /*HasRelocationAddend*/ false) {} 53 54ARMELFObjectWriter::~ARMELFObjectWriter() {} 55 56// FIXME: get the real EABI Version from the Triple. 57unsigned ARMELFObjectWriter::getEFlags() const { 58 return ELF::EF_ARM_EABIMASK & DefaultEABIVersion; 59} 60 61// In ARM, _MergedGlobals and other most symbols get emitted directly. 62// I.e. not as an offset to a section symbol. 63// This code is an approximation of what ARM/gcc does. 64 65STATISTIC(PCRelCount, "Total number of PIC Relocations"); 66STATISTIC(NonPCRelCount, "Total number of non-PIC relocations"); 67 68const MCSymbol *ARMELFObjectWriter::ExplicitRelSym(const MCAssembler &Asm, 69 const MCValue &Target, 70 const MCFragment &F, 71 const MCFixup &Fixup, 72 bool IsPCRel) const { 73 const MCSymbol &Symbol = Target.getSymA()->getSymbol().AliasedSymbol(); 74 bool EmitThisSym = false; 75 76 const MCSectionELF &Section = 77 static_cast<const MCSectionELF&>(Symbol.getSection()); 78 bool InNormalSection = true; 79 unsigned RelocType = 0; 80 RelocType = GetRelocTypeInner(Target, Fixup, IsPCRel); 81 82 DEBUG( 83 const MCSymbolRefExpr::VariantKind Kind = Target.getSymA()->getKind(); 84 MCSymbolRefExpr::VariantKind Kind2; 85 Kind2 = Target.getSymB() ? Target.getSymB()->getKind() : 86 MCSymbolRefExpr::VK_None; 87 dbgs() << "considering symbol " 88 << Section.getSectionName() << "/" 89 << Symbol.getName() << "/" 90 << " Rel:" << (unsigned)RelocType 91 << " Kind: " << (int)Kind << "/" << (int)Kind2 92 << " Tmp:" 93 << Symbol.isAbsolute() << "/" << Symbol.isDefined() << "/" 94 << Symbol.isVariable() << "/" << Symbol.isTemporary() 95 << " Counts:" << PCRelCount << "/" << NonPCRelCount << "\n"); 96 97 if (IsPCRel) { ++PCRelCount; 98 switch (RelocType) { 99 default: 100 // Most relocation types are emitted as explicit symbols 101 InNormalSection = 102 StringSwitch<bool>(Section.getSectionName()) 103 .Case(".data.rel.ro.local", false) 104 .Case(".data.rel", false) 105 .Case(".bss", false) 106 .Default(true); 107 EmitThisSym = true; 108 break; 109 case ELF::R_ARM_ABS32: 110 // But things get strange with R_ARM_ABS32 111 // In this case, most things that go in .rodata show up 112 // as section relative relocations 113 InNormalSection = 114 StringSwitch<bool>(Section.getSectionName()) 115 .Case(".data.rel.ro.local", false) 116 .Case(".data.rel", false) 117 .Case(".rodata", false) 118 .Case(".bss", false) 119 .Default(true); 120 EmitThisSym = false; 121 break; 122 } 123 } else { 124 NonPCRelCount++; 125 InNormalSection = 126 StringSwitch<bool>(Section.getSectionName()) 127 .Case(".data.rel.ro.local", false) 128 .Case(".rodata", false) 129 .Case(".data.rel", false) 130 .Case(".bss", false) 131 .Default(true); 132 133 switch (RelocType) { 134 default: EmitThisSym = true; break; 135 case ELF::R_ARM_ABS32: EmitThisSym = false; break; 136 } 137 } 138 139 if (EmitThisSym) 140 return &Symbol; 141 if (! Symbol.isTemporary() && InNormalSection) { 142 return &Symbol; 143 } 144 return NULL; 145} 146 147// Need to examine the Fixup when determining whether to 148// emit the relocation as an explicit symbol or as a section relative 149// offset 150unsigned ARMELFObjectWriter::GetRelocType(const MCValue &Target, 151 const MCFixup &Fixup, 152 bool IsPCRel, 153 bool IsRelocWithSymbol, 154 int64_t Addend) const { 155 return GetRelocTypeInner(Target, Fixup, IsPCRel); 156} 157 158unsigned ARMELFObjectWriter::GetRelocTypeInner(const MCValue &Target, 159 const MCFixup &Fixup, 160 bool IsPCRel) const { 161 MCSymbolRefExpr::VariantKind Modifier = Target.isAbsolute() ? 162 MCSymbolRefExpr::VK_None : Target.getSymA()->getKind(); 163 164 unsigned Type = 0; 165 if (IsPCRel) { 166 switch ((unsigned)Fixup.getKind()) { 167 default: llvm_unreachable("Unimplemented"); 168 case FK_Data_4: 169 switch (Modifier) { 170 default: llvm_unreachable("Unsupported Modifier"); 171 case MCSymbolRefExpr::VK_None: 172 Type = ELF::R_ARM_REL32; 173 break; 174 case MCSymbolRefExpr::VK_ARM_TLSGD: 175 llvm_unreachable("unimplemented"); 176 case MCSymbolRefExpr::VK_ARM_GOTTPOFF: 177 Type = ELF::R_ARM_TLS_IE32; 178 break; 179 } 180 break; 181 case ARM::fixup_arm_uncondbl: 182 case ARM::fixup_arm_blx: 183 case ARM::fixup_arm_uncondbranch: 184 switch (Modifier) { 185 case MCSymbolRefExpr::VK_ARM_PLT: 186 Type = ELF::R_ARM_PLT32; 187 break; 188 default: 189 Type = ELF::R_ARM_CALL; 190 break; 191 } 192 break; 193 case ARM::fixup_arm_condbl: 194 case ARM::fixup_arm_condbranch: 195 Type = ELF::R_ARM_JUMP24; 196 break; 197 case ARM::fixup_arm_movt_hi16: 198 case ARM::fixup_arm_movt_hi16_pcrel: 199 Type = ELF::R_ARM_MOVT_PREL; 200 break; 201 case ARM::fixup_arm_movw_lo16: 202 case ARM::fixup_arm_movw_lo16_pcrel: 203 Type = ELF::R_ARM_MOVW_PREL_NC; 204 break; 205 case ARM::fixup_t2_movt_hi16: 206 case ARM::fixup_t2_movt_hi16_pcrel: 207 Type = ELF::R_ARM_THM_MOVT_PREL; 208 break; 209 case ARM::fixup_t2_movw_lo16: 210 case ARM::fixup_t2_movw_lo16_pcrel: 211 Type = ELF::R_ARM_THM_MOVW_PREL_NC; 212 break; 213 case ARM::fixup_arm_thumb_bl: 214 case ARM::fixup_arm_thumb_blx: 215 Type = ELF::R_ARM_THM_CALL; 216 break; 217 } 218 } else { 219 switch ((unsigned)Fixup.getKind()) { 220 default: llvm_unreachable("invalid fixup kind!"); 221 case FK_Data_4: 222 switch (Modifier) { 223 default: llvm_unreachable("Unsupported Modifier"); 224 case MCSymbolRefExpr::VK_ARM_GOT: 225 Type = ELF::R_ARM_GOT_BREL; 226 break; 227 case MCSymbolRefExpr::VK_ARM_TLSGD: 228 Type = ELF::R_ARM_TLS_GD32; 229 break; 230 case MCSymbolRefExpr::VK_ARM_TPOFF: 231 Type = ELF::R_ARM_TLS_LE32; 232 break; 233 case MCSymbolRefExpr::VK_ARM_GOTTPOFF: 234 Type = ELF::R_ARM_TLS_IE32; 235 break; 236 case MCSymbolRefExpr::VK_None: 237 Type = ELF::R_ARM_ABS32; 238 break; 239 case MCSymbolRefExpr::VK_ARM_GOTOFF: 240 Type = ELF::R_ARM_GOTOFF32; 241 break; 242 case MCSymbolRefExpr::VK_ARM_TARGET1: 243 Type = ELF::R_ARM_TARGET1; 244 break; 245 } 246 break; 247 case ARM::fixup_arm_ldst_pcrel_12: 248 case ARM::fixup_arm_pcrel_10: 249 case ARM::fixup_arm_adr_pcrel_12: 250 case ARM::fixup_arm_thumb_bl: 251 case ARM::fixup_arm_thumb_cb: 252 case ARM::fixup_arm_thumb_cp: 253 case ARM::fixup_arm_thumb_br: 254 llvm_unreachable("Unimplemented"); 255 case ARM::fixup_arm_uncondbranch: 256 Type = ELF::R_ARM_CALL; 257 break; 258 case ARM::fixup_arm_condbranch: 259 Type = ELF::R_ARM_JUMP24; 260 break; 261 case ARM::fixup_arm_movt_hi16: 262 Type = ELF::R_ARM_MOVT_ABS; 263 break; 264 case ARM::fixup_arm_movw_lo16: 265 Type = ELF::R_ARM_MOVW_ABS_NC; 266 break; 267 case ARM::fixup_t2_movt_hi16: 268 Type = ELF::R_ARM_THM_MOVT_ABS; 269 break; 270 case ARM::fixup_t2_movw_lo16: 271 Type = ELF::R_ARM_THM_MOVW_ABS_NC; 272 break; 273 } 274 } 275 276 return Type; 277} 278 279MCObjectWriter *llvm::createARMELFObjectWriter(raw_ostream &OS, 280 uint8_t OSABI) { 281 MCELFObjectTargetWriter *MOTW = new ARMELFObjectWriter(OSABI); 282 return createELFObjectWriter(MOTW, OS, /*IsLittleEndian=*/true); 283} 284