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/SectionKind.h" 20 #include "llvm/Target/TargetMachine.h" 21 #include <cassert> 22 23 using namespace llvm; 24 using namespace dwarf; 25 26 //===----------------------------------------------------------------------===// 27 // ELF Target 28 //===----------------------------------------------------------------------===// 29 30 void ARMElfTargetObjectFile::Initialize(MCContext &Ctx, 31 const TargetMachine &TM) { 32 const ARMBaseTargetMachine &ARM_TM = static_cast<const ARMBaseTargetMachine &>(TM); 33 bool isAAPCS_ABI = ARM_TM.TargetABI == ARMBaseTargetMachine::ARMABI::ARM_ABI_AAPCS; 34 bool genExecuteOnly = 35 ARM_TM.getMCSubtargetInfo()->hasFeature(ARM::FeatureExecuteOnly); 36 37 TargetLoweringObjectFileELF::Initialize(Ctx, TM); 38 InitializeELF(isAAPCS_ABI); 39 40 if (isAAPCS_ABI) { 41 LSDASection = nullptr; 42 } 43 44 // Make code section unreadable when in execute-only mode 45 if (genExecuteOnly) { 46 unsigned Type = ELF::SHT_PROGBITS; 47 unsigned Flags = 48 ELF::SHF_EXECINSTR | ELF::SHF_ALLOC | ELF::SHF_ARM_PURECODE; 49 // Since we cannot modify flags for an existing section, we create a new 50 // section with the right flags, and use 0 as the unique ID for 51 // execute-only text 52 TextSection = 53 Ctx.getELFSection(".text", Type, Flags, 0, "", false, 0U, nullptr); 54 } 55 } 56 57 const MCRegister ARMElfTargetObjectFile::getStaticBase() const { 58 return ARM::R9; 59 } 60 61 const MCExpr *ARMElfTargetObjectFile:: 62 getIndirectSymViaRWPI(const MCSymbol *Sym) const { 63 return MCSymbolRefExpr::create(Sym, MCSymbolRefExpr::VK_ARM_SBREL, 64 getContext()); 65 } 66 67 const MCExpr *ARMElfTargetObjectFile::getTTypeGlobalReference( 68 const GlobalValue *GV, unsigned Encoding, const TargetMachine &TM, 69 MachineModuleInfo *MMI, MCStreamer &Streamer) const { 70 if (TM.getMCAsmInfo()->getExceptionHandlingType() != ExceptionHandling::ARM) 71 return TargetLoweringObjectFileELF::getTTypeGlobalReference( 72 GV, Encoding, TM, MMI, Streamer); 73 74 assert(Encoding == DW_EH_PE_absptr && "Can handle absptr encoding only"); 75 76 return MCSymbolRefExpr::create(TM.getSymbol(GV), 77 MCSymbolRefExpr::VK_ARM_TARGET2, getContext()); 78 } 79 80 const MCExpr *ARMElfTargetObjectFile:: 81 getDebugThreadLocalSymbol(const MCSymbol *Sym) const { 82 return MCSymbolRefExpr::create(Sym, MCSymbolRefExpr::VK_ARM_TLSLDO, 83 getContext()); 84 } 85 86 static bool isExecuteOnlyFunction(const GlobalObject *GO, SectionKind SK, 87 const TargetMachine &TM) { 88 if (const Function *F = dyn_cast<Function>(GO)) 89 if (TM.getSubtarget<ARMSubtarget>(*F).genExecuteOnly() && SK.isText()) 90 return true; 91 return false; 92 } 93 94 MCSection *ARMElfTargetObjectFile::getExplicitSectionGlobal( 95 const GlobalObject *GO, SectionKind SK, const TargetMachine &TM) const { 96 // Set execute-only access for the explicit section 97 if (isExecuteOnlyFunction(GO, SK, TM)) 98 SK = SectionKind::getExecuteOnly(); 99 100 return TargetLoweringObjectFileELF::getExplicitSectionGlobal(GO, SK, TM); 101 } 102 103 MCSection *ARMElfTargetObjectFile::SelectSectionForGlobal( 104 const GlobalObject *GO, SectionKind SK, const TargetMachine &TM) const { 105 // Place the global in the execute-only text section 106 if (isExecuteOnlyFunction(GO, SK, TM)) 107 SK = SectionKind::getExecuteOnly(); 108 109 return TargetLoweringObjectFileELF::SelectSectionForGlobal(GO, SK, TM); 110 } 111