llvm/lib/Target/ARM/ARMTargetObjectFile.cpp

   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 }