1 //===- lib/MC/AArch64ELFStreamer.cpp - ELF Object Output for AArch64 ------===// 2 // 3 // Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions. 4 // See https://llvm.org/LICENSE.txt for license information. 5 // SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception 6 // 7 //===----------------------------------------------------------------------===// 8 // 9 // This file assembles .s files and emits AArch64 ELF .o object files. Different 10 // from generic ELF streamer in emitting mapping symbols ($x and $d) to delimit 11 // regions of data and code. 12 // 13 //===----------------------------------------------------------------------===// 14 15 #include "AArch64ELFStreamer.h" 16 #include "AArch64MCTargetDesc.h" 17 #include "AArch64TargetStreamer.h" 18 #include "AArch64WinCOFFStreamer.h" 19 #include "llvm/ADT/DenseMap.h" 20 #include "llvm/ADT/StringRef.h" 21 #include "llvm/ADT/Triple.h" 22 #include "llvm/ADT/Twine.h" 23 #include "llvm/BinaryFormat/ELF.h" 24 #include "llvm/MC/MCAsmBackend.h" 25 #include "llvm/MC/MCAssembler.h" 26 #include "llvm/MC/MCCodeEmitter.h" 27 #include "llvm/MC/MCContext.h" 28 #include "llvm/MC/MCELFStreamer.h" 29 #include "llvm/MC/MCExpr.h" 30 #include "llvm/MC/MCInst.h" 31 #include "llvm/MC/MCObjectWriter.h" 32 #include "llvm/MC/MCSection.h" 33 #include "llvm/MC/MCStreamer.h" 34 #include "llvm/MC/MCSubtargetInfo.h" 35 #include "llvm/MC/MCSymbolELF.h" 36 #include "llvm/MC/MCWinCOFFStreamer.h" 37 #include "llvm/Support/Casting.h" 38 #include "llvm/Support/FormattedStream.h" 39 #include "llvm/Support/raw_ostream.h" 40 41 using namespace llvm; 42 43 namespace { 44 45 class AArch64ELFStreamer; 46 47 class AArch64TargetAsmStreamer : public AArch64TargetStreamer { 48 formatted_raw_ostream &OS; 49 50 void emitInst(uint32_t Inst) override; 51 52 void emitDirectiveVariantPCS(MCSymbol *Symbol) override { 53 OS << "\t.variant_pcs\t" << Symbol->getName() << "\n"; 54 } 55 56 void emitARM64WinCFIAllocStack(unsigned Size) override { 57 OS << "\t.seh_stackalloc\t" << Size << "\n"; 58 } 59 void emitARM64WinCFISaveR19R20X(int Offset) override { 60 OS << "\t.seh_save_r19r20_x\t" << Offset << "\n"; 61 } 62 void emitARM64WinCFISaveFPLR(int Offset) override { 63 OS << "\t.seh_save_fplr\t" << Offset << "\n"; 64 } 65 void emitARM64WinCFISaveFPLRX(int Offset) override { 66 OS << "\t.seh_save_fplr_x\t" << Offset << "\n"; 67 } 68 void emitARM64WinCFISaveReg(unsigned Reg, int Offset) override { 69 OS << "\t.seh_save_reg\tx" << Reg << ", " << Offset << "\n"; 70 } 71 void emitARM64WinCFISaveRegX(unsigned Reg, int Offset) override { 72 OS << "\t.seh_save_reg_x\tx" << Reg << ", " << Offset << "\n"; 73 } 74 void emitARM64WinCFISaveRegP(unsigned Reg, int Offset) override { 75 OS << "\t.seh_save_regp\tx" << Reg << ", " << Offset << "\n"; 76 } 77 void emitARM64WinCFISaveRegPX(unsigned Reg, int Offset) override { 78 OS << "\t.seh_save_regp_x\tx" << Reg << ", " << Offset << "\n"; 79 } 80 void emitARM64WinCFISaveLRPair(unsigned Reg, int Offset) override { 81 OS << "\t.seh_save_lrpair\tx" << Reg << ", " << Offset << "\n"; 82 } 83 void emitARM64WinCFISaveFReg(unsigned Reg, int Offset) override { 84 OS << "\t.seh_save_freg\td" << Reg << ", " << Offset << "\n"; 85 } 86 void emitARM64WinCFISaveFRegX(unsigned Reg, int Offset) override { 87 OS << "\t.seh_save_freg_x\td" << Reg << ", " << Offset << "\n"; 88 } 89 void emitARM64WinCFISaveFRegP(unsigned Reg, int Offset) override { 90 OS << "\t.seh_save_fregp\td" << Reg << ", " << Offset << "\n"; 91 } 92 void emitARM64WinCFISaveFRegPX(unsigned Reg, int Offset) override { 93 OS << "\t.seh_save_fregp_x\td" << Reg << ", " << Offset << "\n"; 94 } 95 void emitARM64WinCFISetFP() override { OS << "\t.seh_set_fp\n"; } 96 void emitARM64WinCFIAddFP(unsigned Size) override { 97 OS << "\t.seh_add_fp\t" << Size << "\n"; 98 } 99 void emitARM64WinCFINop() override { OS << "\t.seh_nop\n"; } 100 void emitARM64WinCFISaveNext() override { OS << "\t.seh_save_next\n"; } 101 void emitARM64WinCFIPrologEnd() override { OS << "\t.seh_endprologue\n"; } 102 void emitARM64WinCFIEpilogStart() override { OS << "\t.seh_startepilogue\n"; } 103 void emitARM64WinCFIEpilogEnd() override { OS << "\t.seh_endepilogue\n"; } 104 void emitARM64WinCFITrapFrame() override { OS << "\t.seh_trap_frame\n"; } 105 void emitARM64WinCFIMachineFrame() override { OS << "\t.seh_pushframe\n"; } 106 void emitARM64WinCFIContext() override { OS << "\t.seh_context\n"; } 107 void emitARM64WinCFIClearUnwoundToCall() override { 108 OS << "\t.seh_clear_unwound_to_call\n"; 109 } 110 111 public: 112 AArch64TargetAsmStreamer(MCStreamer &S, formatted_raw_ostream &OS); 113 }; 114 115 AArch64TargetAsmStreamer::AArch64TargetAsmStreamer(MCStreamer &S, 116 formatted_raw_ostream &OS) 117 : AArch64TargetStreamer(S), OS(OS) {} 118 119 void AArch64TargetAsmStreamer::emitInst(uint32_t Inst) { 120 OS << "\t.inst\t0x" << Twine::utohexstr(Inst) << "\n"; 121 } 122 123 /// Extend the generic ELFStreamer class so that it can emit mapping symbols at 124 /// the appropriate points in the object files. These symbols are defined in the 125 /// AArch64 ELF ABI: 126 /// infocenter.arm.com/help/topic/com.arm.doc.ihi0056a/IHI0056A_aaelf64.pdf 127 /// 128 /// In brief: $x or $d should be emitted at the start of each contiguous region 129 /// of A64 code or data in a section. In practice, this emission does not rely 130 /// on explicit assembler directives but on inherent properties of the 131 /// directives doing the emission (e.g. ".byte" is data, "add x0, x0, x0" an 132 /// instruction). 133 /// 134 /// As a result this system is orthogonal to the DataRegion infrastructure used 135 /// by MachO. Beware! 136 class AArch64ELFStreamer : public MCELFStreamer { 137 public: 138 AArch64ELFStreamer(MCContext &Context, std::unique_ptr<MCAsmBackend> TAB, 139 std::unique_ptr<MCObjectWriter> OW, 140 std::unique_ptr<MCCodeEmitter> Emitter) 141 : MCELFStreamer(Context, std::move(TAB), std::move(OW), 142 std::move(Emitter)), 143 MappingSymbolCounter(0), LastEMS(EMS_None) {} 144 145 void changeSection(MCSection *Section, const MCExpr *Subsection) override { 146 // We have to keep track of the mapping symbol state of any sections we 147 // use. Each one should start off as EMS_None, which is provided as the 148 // default constructor by DenseMap::lookup. 149 LastMappingSymbols[getPreviousSection().first] = LastEMS; 150 LastEMS = LastMappingSymbols.lookup(Section); 151 152 MCELFStreamer::changeSection(Section, Subsection); 153 } 154 155 // Reset state between object emissions 156 void reset() override { 157 MappingSymbolCounter = 0; 158 MCELFStreamer::reset(); 159 LastMappingSymbols.clear(); 160 LastEMS = EMS_None; 161 } 162 163 /// This function is the one used to emit instruction data into the ELF 164 /// streamer. We override it to add the appropriate mapping symbol if 165 /// necessary. 166 void emitInstruction(const MCInst &Inst, 167 const MCSubtargetInfo &STI) override { 168 emitA64MappingSymbol(); 169 MCELFStreamer::emitInstruction(Inst, STI); 170 } 171 172 /// Emit a 32-bit value as an instruction. This is only used for the .inst 173 /// directive, EmitInstruction should be used in other cases. 174 void emitInst(uint32_t Inst) { 175 char Buffer[4]; 176 177 // We can't just use EmitIntValue here, as that will emit a data mapping 178 // symbol, and swap the endianness on big-endian systems (instructions are 179 // always little-endian). 180 for (char &C : Buffer) { 181 C = uint8_t(Inst); 182 Inst >>= 8; 183 } 184 185 emitA64MappingSymbol(); 186 MCELFStreamer::emitBytes(StringRef(Buffer, 4)); 187 } 188 189 /// This is one of the functions used to emit data into an ELF section, so the 190 /// AArch64 streamer overrides it to add the appropriate mapping symbol ($d) 191 /// if necessary. 192 void emitBytes(StringRef Data) override { 193 emitDataMappingSymbol(); 194 MCELFStreamer::emitBytes(Data); 195 } 196 197 /// This is one of the functions used to emit data into an ELF section, so the 198 /// AArch64 streamer overrides it to add the appropriate mapping symbol ($d) 199 /// if necessary. 200 void emitValueImpl(const MCExpr *Value, unsigned Size, SMLoc Loc) override { 201 emitDataMappingSymbol(); 202 MCELFStreamer::emitValueImpl(Value, Size, Loc); 203 } 204 205 void emitFill(const MCExpr &NumBytes, uint64_t FillValue, 206 SMLoc Loc) override { 207 emitDataMappingSymbol(); 208 MCObjectStreamer::emitFill(NumBytes, FillValue, Loc); 209 } 210 private: 211 enum ElfMappingSymbol { 212 EMS_None, 213 EMS_A64, 214 EMS_Data 215 }; 216 217 void emitDataMappingSymbol() { 218 if (LastEMS == EMS_Data) 219 return; 220 emitMappingSymbol("$d"); 221 LastEMS = EMS_Data; 222 } 223 224 void emitA64MappingSymbol() { 225 if (LastEMS == EMS_A64) 226 return; 227 emitMappingSymbol("$x"); 228 LastEMS = EMS_A64; 229 } 230 231 void emitMappingSymbol(StringRef Name) { 232 auto *Symbol = cast<MCSymbolELF>(getContext().getOrCreateSymbol( 233 Name + "." + Twine(MappingSymbolCounter++))); 234 emitLabel(Symbol); 235 Symbol->setType(ELF::STT_NOTYPE); 236 Symbol->setBinding(ELF::STB_LOCAL); 237 Symbol->setExternal(false); 238 } 239 240 int64_t MappingSymbolCounter; 241 242 DenseMap<const MCSection *, ElfMappingSymbol> LastMappingSymbols; 243 ElfMappingSymbol LastEMS; 244 }; 245 246 } // end anonymous namespace 247 248 AArch64ELFStreamer &AArch64TargetELFStreamer::getStreamer() { 249 return static_cast<AArch64ELFStreamer &>(Streamer); 250 } 251 252 void AArch64TargetELFStreamer::emitInst(uint32_t Inst) { 253 getStreamer().emitInst(Inst); 254 } 255 256 void AArch64TargetELFStreamer::emitDirectiveVariantPCS(MCSymbol *Symbol) { 257 getStreamer().getAssembler().registerSymbol(*Symbol); 258 cast<MCSymbolELF>(Symbol)->setOther(ELF::STO_AARCH64_VARIANT_PCS); 259 } 260 261 MCTargetStreamer * 262 llvm::createAArch64AsmTargetStreamer(MCStreamer &S, formatted_raw_ostream &OS, 263 MCInstPrinter *InstPrint, 264 bool isVerboseAsm) { 265 return new AArch64TargetAsmStreamer(S, OS); 266 } 267 268 MCELFStreamer *llvm::createAArch64ELFStreamer( 269 MCContext &Context, std::unique_ptr<MCAsmBackend> TAB, 270 std::unique_ptr<MCObjectWriter> OW, std::unique_ptr<MCCodeEmitter> Emitter, 271 bool RelaxAll) { 272 AArch64ELFStreamer *S = new AArch64ELFStreamer( 273 Context, std::move(TAB), std::move(OW), std::move(Emitter)); 274 if (RelaxAll) 275 S->getAssembler().setRelaxAll(true); 276 return S; 277 } 278