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 "llvm/BinaryFormat/Dwarf.h" 13 #include "llvm/BinaryFormat/ELF.h" 14 #include "llvm/MC/MCAsmInfo.h" 15 #include "llvm/MC/MCContext.h" 16 #include "llvm/MC/MCExpr.h" 17 #include "llvm/MC/MCSectionELF.h" 18 #include "llvm/MC/MCTargetOptions.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 void ARMElfTargetObjectFile::Initialize(MCContext &Ctx, 32 const TargetMachine &TM) { 33 const ARMBaseTargetMachine &ARM_TM = static_cast<const ARMBaseTargetMachine &>(TM); 34 bool isAAPCS_ABI = ARM_TM.TargetABI == ARMBaseTargetMachine::ARMABI::ARM_ABI_AAPCS; 35 bool genExecuteOnly = 36 ARM_TM.getMCSubtargetInfo()->hasFeature(ARM::FeatureExecuteOnly); 37 38 TargetLoweringObjectFileELF::Initialize(Ctx, TM); 39 InitializeELF(isAAPCS_ABI); 40 41 if (isAAPCS_ABI) { 42 LSDASection = nullptr; 43 } 44 45 // Make code section unreadable when in execute-only mode 46 if (genExecuteOnly) { 47 unsigned Type = ELF::SHT_PROGBITS; 48 unsigned Flags = 49 ELF::SHF_EXECINSTR | ELF::SHF_ALLOC | ELF::SHF_ARM_PURECODE; 50 // Since we cannot modify flags for an existing section, we create a new 51 // section with the right flags, and use 0 as the unique ID for 52 // execute-only text 53 TextSection = 54 Ctx.getELFSection(".text", Type, Flags, 0, "", false, 0U, nullptr); 55 } 56 } 57 58 MCRegister ARMElfTargetObjectFile::getStaticBase() const { return ARM::R9; } 59 60 const MCExpr *ARMElfTargetObjectFile::getIndirectSymViaGOTPCRel( 61 const GlobalValue *GV, const MCSymbol *Sym, const MCValue &MV, 62 int64_t Offset, MachineModuleInfo *MMI, MCStreamer &Streamer) const { 63 int64_t FinalOffset = Offset + MV.getConstant(); 64 const MCExpr *Res = MCSymbolRefExpr::create( 65 Sym, MCSymbolRefExpr::VK_ARM_GOT_PREL, getContext()); 66 const MCExpr *Off = MCConstantExpr::create(FinalOffset, getContext()); 67 return MCBinaryExpr::createAdd(Res, Off, getContext()); 68 } 69 70 const MCExpr *ARMElfTargetObjectFile:: 71 getIndirectSymViaRWPI(const MCSymbol *Sym) const { 72 return MCSymbolRefExpr::create(Sym, MCSymbolRefExpr::VK_ARM_SBREL, 73 getContext()); 74 } 75 76 const MCExpr *ARMElfTargetObjectFile::getTTypeGlobalReference( 77 const GlobalValue *GV, unsigned Encoding, const TargetMachine &TM, 78 MachineModuleInfo *MMI, MCStreamer &Streamer) const { 79 if (TM.getMCAsmInfo()->getExceptionHandlingType() != ExceptionHandling::ARM) 80 return TargetLoweringObjectFileELF::getTTypeGlobalReference( 81 GV, Encoding, TM, MMI, Streamer); 82 83 assert(Encoding == DW_EH_PE_absptr && "Can handle absptr encoding only"); 84 85 return MCSymbolRefExpr::create(TM.getSymbol(GV), 86 MCSymbolRefExpr::VK_ARM_TARGET2, getContext()); 87 } 88 89 const MCExpr *ARMElfTargetObjectFile:: 90 getDebugThreadLocalSymbol(const MCSymbol *Sym) const { 91 return MCSymbolRefExpr::create(Sym, MCSymbolRefExpr::VK_ARM_TLSLDO, 92 getContext()); 93 } 94 95 static bool isExecuteOnlyFunction(const GlobalObject *GO, SectionKind SK, 96 const TargetMachine &TM) { 97 if (const Function *F = dyn_cast<Function>(GO)) 98 if (TM.getSubtarget<ARMSubtarget>(*F).genExecuteOnly() && SK.isText()) 99 return true; 100 return false; 101 } 102 103 MCSection *ARMElfTargetObjectFile::getExplicitSectionGlobal( 104 const GlobalObject *GO, SectionKind SK, const TargetMachine &TM) const { 105 // Set execute-only access for the explicit section 106 if (isExecuteOnlyFunction(GO, SK, TM)) 107 SK = SectionKind::getExecuteOnly(); 108 109 return TargetLoweringObjectFileELF::getExplicitSectionGlobal(GO, SK, TM); 110 } 111 112 MCSection *ARMElfTargetObjectFile::SelectSectionForGlobal( 113 const GlobalObject *GO, SectionKind SK, const TargetMachine &TM) const { 114 // Place the global in the execute-only text section 115 if (isExecuteOnlyFunction(GO, SK, TM)) 116 SK = SectionKind::getExecuteOnly(); 117 118 return TargetLoweringObjectFileELF::SelectSectionForGlobal(GO, SK, TM); 119 } 120