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
Initialize(MCContext & Ctx,const TargetMachine & TM)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
getStaticBase() const58 MCRegister ARMElfTargetObjectFile::getStaticBase() const { return ARM::R9; }
59
getIndirectSymViaGOTPCRel(const GlobalValue * GV,const MCSymbol * Sym,const MCValue & MV,int64_t Offset,MachineModuleInfo * MMI,MCStreamer & Streamer) const60 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::
getIndirectSymViaRWPI(const MCSymbol * Sym) const71 getIndirectSymViaRWPI(const MCSymbol *Sym) const {
72 return MCSymbolRefExpr::create(Sym, MCSymbolRefExpr::VK_ARM_SBREL,
73 getContext());
74 }
75
getTTypeGlobalReference(const GlobalValue * GV,unsigned Encoding,const TargetMachine & TM,MachineModuleInfo * MMI,MCStreamer & Streamer) const76 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::
getDebugThreadLocalSymbol(const MCSymbol * Sym) const90 getDebugThreadLocalSymbol(const MCSymbol *Sym) const {
91 return MCSymbolRefExpr::create(Sym, MCSymbolRefExpr::VK_ARM_TLSLDO,
92 getContext());
93 }
94
isExecuteOnlyFunction(const GlobalObject * GO,SectionKind SK,const TargetMachine & TM)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
getExplicitSectionGlobal(const GlobalObject * GO,SectionKind SK,const TargetMachine & TM) const103 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
SelectSectionForGlobal(const GlobalObject * GO,SectionKind SK,const TargetMachine & TM) const112 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