1 //===-- llvm/Target/ARMTargetObjectFile.cpp - ARM Object Info Impl --------===// 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 #include "ARMTargetObjectFile.h" 10 #include "ARMSubtarget.h" 11 #include "ARMTargetMachine.h" 12 #include "MCTargetDesc/ARMMCAsmInfo.h" 13 #include "llvm/BinaryFormat/Dwarf.h" 14 #include "llvm/BinaryFormat/ELF.h" 15 #include "llvm/MC/MCAsmInfo.h" 16 #include "llvm/MC/MCContext.h" 17 #include "llvm/MC/MCExpr.h" 18 #include "llvm/MC/MCSectionELF.h" 19 #include "llvm/MC/MCValue.h" 20 #include "llvm/MC/SectionKind.h" 21 #include "llvm/Target/TargetMachine.h" 22 #include <cassert> 23 24 using namespace llvm; 25 using namespace dwarf; 26 27 //===----------------------------------------------------------------------===// 28 // ELF Target 29 //===----------------------------------------------------------------------===// 30 31 ARMElfTargetObjectFile::ARMElfTargetObjectFile() { 32 PLTRelativeSpecifier = ARM::S_PREL31; 33 SupportIndirectSymViaGOTPCRel = true; 34 } 35 36 void ARMElfTargetObjectFile::Initialize(MCContext &Ctx, 37 const TargetMachine &TM) { 38 const ARMBaseTargetMachine &ARM_TM = static_cast<const ARMBaseTargetMachine &>(TM); 39 bool isAAPCS_ABI = ARM_TM.TargetABI == ARM::ARMABI::ARM_ABI_AAPCS; 40 bool genExecuteOnly = 41 ARM_TM.getMCSubtargetInfo()->hasFeature(ARM::FeatureExecuteOnly); 42 43 TargetLoweringObjectFileELF::Initialize(Ctx, TM); 44 InitializeELF(isAAPCS_ABI); 45 46 if (isAAPCS_ABI) { 47 LSDASection = nullptr; 48 } 49 50 // Make code section unreadable when in execute-only mode 51 if (genExecuteOnly) { 52 unsigned Type = ELF::SHT_PROGBITS; 53 unsigned Flags = 54 ELF::SHF_EXECINSTR | ELF::SHF_ALLOC | ELF::SHF_ARM_PURECODE; 55 // Since we cannot modify flags for an existing section, we create a new 56 // section with the right flags, and use 0 as the unique ID for 57 // execute-only text 58 TextSection = 59 Ctx.getELFSection(".text", Type, Flags, 0, "", false, 0U, nullptr); 60 } 61 } 62 63 MCRegister ARMElfTargetObjectFile::getStaticBase() const { return ARM::R9; } 64 65 const MCExpr *ARMElfTargetObjectFile::getIndirectSymViaGOTPCRel( 66 const GlobalValue *GV, const MCSymbol *Sym, const MCValue &MV, 67 int64_t Offset, MachineModuleInfo *MMI, MCStreamer &Streamer) const { 68 int64_t FinalOffset = Offset + MV.getConstant(); 69 const MCExpr *Res = 70 MCSymbolRefExpr::create(Sym, ARM::S_GOT_PREL, getContext()); 71 const MCExpr *Off = MCConstantExpr::create(FinalOffset, getContext()); 72 return MCBinaryExpr::createAdd(Res, Off, getContext()); 73 } 74 75 const MCExpr *ARMElfTargetObjectFile:: 76 getIndirectSymViaRWPI(const MCSymbol *Sym) const { 77 return MCSymbolRefExpr::create(Sym, ARM::S_SBREL, getContext()); 78 } 79 80 const MCExpr *ARMElfTargetObjectFile::getTTypeGlobalReference( 81 const GlobalValue *GV, unsigned Encoding, const TargetMachine &TM, 82 MachineModuleInfo *MMI, MCStreamer &Streamer) const { 83 if (TM.getMCAsmInfo()->getExceptionHandlingType() != ExceptionHandling::ARM) 84 return TargetLoweringObjectFileELF::getTTypeGlobalReference( 85 GV, Encoding, TM, MMI, Streamer); 86 87 assert(Encoding == DW_EH_PE_absptr && "Can handle absptr encoding only"); 88 89 return MCSymbolRefExpr::create(TM.getSymbol(GV), ARM::S_TARGET2, 90 getContext()); 91 } 92 93 const MCExpr *ARMElfTargetObjectFile:: 94 getDebugThreadLocalSymbol(const MCSymbol *Sym) const { 95 return MCSymbolRefExpr::create(Sym, ARM::S_TLSLDO, getContext()); 96 } 97 98 static bool isExecuteOnlyFunction(const GlobalObject *GO, SectionKind SK, 99 const TargetMachine &TM) { 100 if (const Function *F = dyn_cast<Function>(GO)) 101 if (TM.getSubtarget<ARMSubtarget>(*F).genExecuteOnly() && SK.isText()) 102 return true; 103 return false; 104 } 105 106 MCSection *ARMElfTargetObjectFile::getExplicitSectionGlobal( 107 const GlobalObject *GO, SectionKind SK, const TargetMachine &TM) const { 108 // Set execute-only access for the explicit section 109 if (isExecuteOnlyFunction(GO, SK, TM)) 110 SK = SectionKind::getExecuteOnly(); 111 112 return TargetLoweringObjectFileELF::getExplicitSectionGlobal(GO, SK, TM); 113 } 114 115 MCSection *ARMElfTargetObjectFile::SelectSectionForGlobal( 116 const GlobalObject *GO, SectionKind SK, const TargetMachine &TM) const { 117 // Place the global in the execute-only text section 118 if (isExecuteOnlyFunction(GO, SK, TM)) 119 SK = SectionKind::getExecuteOnly(); 120 121 return TargetLoweringObjectFileELF::SelectSectionForGlobal(GO, SK, TM); 122 } 123