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
Initialize(MCContext & Ctx,const TargetMachine & TM)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 = Ctx.getELFSection(".text", Type, Flags, 0, "", 0U, nullptr);
53 }
54 }
55
getTTypeGlobalReference(const GlobalValue * GV,unsigned Encoding,const TargetMachine & TM,MachineModuleInfo * MMI,MCStreamer & Streamer) const56 const MCExpr *ARMElfTargetObjectFile::getTTypeGlobalReference(
57 const GlobalValue *GV, unsigned Encoding, const TargetMachine &TM,
58 MachineModuleInfo *MMI, MCStreamer &Streamer) const {
59 if (TM.getMCAsmInfo()->getExceptionHandlingType() != ExceptionHandling::ARM)
60 return TargetLoweringObjectFileELF::getTTypeGlobalReference(
61 GV, Encoding, TM, MMI, Streamer);
62
63 assert(Encoding == DW_EH_PE_absptr && "Can handle absptr encoding only");
64
65 return MCSymbolRefExpr::create(TM.getSymbol(GV),
66 MCSymbolRefExpr::VK_ARM_TARGET2, getContext());
67 }
68
69 const MCExpr *ARMElfTargetObjectFile::
getDebugThreadLocalSymbol(const MCSymbol * Sym) const70 getDebugThreadLocalSymbol(const MCSymbol *Sym) const {
71 return MCSymbolRefExpr::create(Sym, MCSymbolRefExpr::VK_ARM_TLSLDO,
72 getContext());
73 }
74
isExecuteOnlyFunction(const GlobalObject * GO,SectionKind SK,const TargetMachine & TM)75 static bool isExecuteOnlyFunction(const GlobalObject *GO, SectionKind SK,
76 const TargetMachine &TM) {
77 if (const Function *F = dyn_cast<Function>(GO))
78 if (TM.getSubtarget<ARMSubtarget>(*F).genExecuteOnly() && SK.isText())
79 return true;
80 return false;
81 }
82
getExplicitSectionGlobal(const GlobalObject * GO,SectionKind SK,const TargetMachine & TM) const83 MCSection *ARMElfTargetObjectFile::getExplicitSectionGlobal(
84 const GlobalObject *GO, SectionKind SK, const TargetMachine &TM) const {
85 // Set execute-only access for the explicit section
86 if (isExecuteOnlyFunction(GO, SK, TM))
87 SK = SectionKind::getExecuteOnly();
88
89 return TargetLoweringObjectFileELF::getExplicitSectionGlobal(GO, SK, TM);
90 }
91
SelectSectionForGlobal(const GlobalObject * GO,SectionKind SK,const TargetMachine & TM) const92 MCSection *ARMElfTargetObjectFile::SelectSectionForGlobal(
93 const GlobalObject *GO, SectionKind SK, const TargetMachine &TM) const {
94 // Place the global in the execute-only text section
95 if (isExecuteOnlyFunction(GO, SK, TM))
96 SK = SectionKind::getExecuteOnly();
97
98 return TargetLoweringObjectFileELF::SelectSectionForGlobal(GO, SK, TM);
99 }
100