1 //===-- llvm/Target/ARMTargetObjectFile.cpp - ARM Object Info Impl --------===//
2 //
3 // The LLVM Compiler Infrastructure
4 //
5 // This file is distributed under the University of Illinois Open Source
6 // License. See LICENSE.TXT for details.
7 //
8 //===----------------------------------------------------------------------===//
9
10 #include "ARMTargetObjectFile.h"
11 #include "ARMSubtarget.h"
12 #include "ARMTargetMachine.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/MCTargetOptions.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 = Ctx.getELFSection(".text", Type, Flags, 0, "", 0U);
54 }
55 }
56
getTTypeGlobalReference(const GlobalValue * GV,unsigned Encoding,const TargetMachine & TM,MachineModuleInfo * MMI,MCStreamer & Streamer) const57 const MCExpr *ARMElfTargetObjectFile::getTTypeGlobalReference(
58 const GlobalValue *GV, unsigned Encoding, const TargetMachine &TM,
59 MachineModuleInfo *MMI, MCStreamer &Streamer) const {
60 if (TM.getMCAsmInfo()->getExceptionHandlingType() != ExceptionHandling::ARM)
61 return TargetLoweringObjectFileELF::getTTypeGlobalReference(
62 GV, Encoding, TM, MMI, Streamer);
63
64 assert(Encoding == DW_EH_PE_absptr && "Can handle absptr encoding only");
65
66 return MCSymbolRefExpr::create(TM.getSymbol(GV),
67 MCSymbolRefExpr::VK_ARM_TARGET2, getContext());
68 }
69
70 const MCExpr *ARMElfTargetObjectFile::
getDebugThreadLocalSymbol(const MCSymbol * Sym) const71 getDebugThreadLocalSymbol(const MCSymbol *Sym) const {
72 return MCSymbolRefExpr::create(Sym, MCSymbolRefExpr::VK_ARM_TLSLDO,
73 getContext());
74 }
75
isExecuteOnlyFunction(const GlobalObject * GO,SectionKind SK,const TargetMachine & TM)76 static bool isExecuteOnlyFunction(const GlobalObject *GO, SectionKind SK,
77 const TargetMachine &TM) {
78 if (const Function *F = dyn_cast<Function>(GO))
79 if (TM.getSubtarget<ARMSubtarget>(*F).genExecuteOnly() && SK.isText())
80 return true;
81 return false;
82 }
83
getExplicitSectionGlobal(const GlobalObject * GO,SectionKind SK,const TargetMachine & TM) const84 MCSection *ARMElfTargetObjectFile::getExplicitSectionGlobal(
85 const GlobalObject *GO, SectionKind SK, const TargetMachine &TM) const {
86 // Set execute-only access for the explicit section
87 if (isExecuteOnlyFunction(GO, SK, TM))
88 SK = SectionKind::getExecuteOnly();
89
90 return TargetLoweringObjectFileELF::getExplicitSectionGlobal(GO, SK, TM);
91 }
92
SelectSectionForGlobal(const GlobalObject * GO,SectionKind SK,const TargetMachine & TM) const93 MCSection *ARMElfTargetObjectFile::SelectSectionForGlobal(
94 const GlobalObject *GO, SectionKind SK, const TargetMachine &TM) const {
95 // Place the global in the execute-only text section
96 if (isExecuteOnlyFunction(GO, SK, TM))
97 SK = SectionKind::getExecuteOnly();
98
99 return TargetLoweringObjectFileELF::SelectSectionForGlobal(GO, SK, TM);
100 }
101