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fe83270ee9
SHF_ARM_PURECODE flag when being built with the -mexecute-only flag. All code sections of an ELF must have the flag set for the final .text section to be execute-only, otherwise the flag gets removed. A HasData flag is added to MCSection to aid in the determination that the section is empty. A virtual setTargetSectionFlags is added to MCELFObjectTargetWriter to allow subclasses to set target specific section flags to be added to sections which we then use in the ARM backend to set SHF_ARM_PURECODE. Patch by Ivan Lozano! Reviewed By: echristo Differential Revision: https://reviews.llvm.org/D48792 llvm-svn: 341593
101 lines
3.7 KiB
C++
101 lines
3.7 KiB
C++
//===-- llvm/Target/ARMTargetObjectFile.cpp - ARM Object Info Impl --------===//
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//
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// The LLVM Compiler Infrastructure
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//
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// This file is distributed under the University of Illinois Open Source
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// License. See LICENSE.TXT for details.
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//
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//===----------------------------------------------------------------------===//
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#include "ARMTargetObjectFile.h"
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#include "ARMSubtarget.h"
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#include "ARMTargetMachine.h"
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#include "llvm/BinaryFormat/Dwarf.h"
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#include "llvm/BinaryFormat/ELF.h"
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#include "llvm/MC/MCAsmInfo.h"
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#include "llvm/MC/MCContext.h"
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#include "llvm/MC/MCExpr.h"
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#include "llvm/MC/MCSectionELF.h"
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#include "llvm/MC/MCTargetOptions.h"
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#include "llvm/MC/SectionKind.h"
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#include "llvm/Target/TargetMachine.h"
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#include <cassert>
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using namespace llvm;
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using namespace dwarf;
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//===----------------------------------------------------------------------===//
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// ELF Target
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//===----------------------------------------------------------------------===//
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void ARMElfTargetObjectFile::Initialize(MCContext &Ctx,
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const TargetMachine &TM) {
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const ARMBaseTargetMachine &ARM_TM = static_cast<const ARMBaseTargetMachine &>(TM);
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bool isAAPCS_ABI = ARM_TM.TargetABI == ARMBaseTargetMachine::ARMABI::ARM_ABI_AAPCS;
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bool genExecuteOnly =
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ARM_TM.getMCSubtargetInfo()->hasFeature(ARM::FeatureExecuteOnly);
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TargetLoweringObjectFileELF::Initialize(Ctx, TM);
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InitializeELF(isAAPCS_ABI);
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if (isAAPCS_ABI) {
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LSDASection = nullptr;
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}
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// Make code section unreadable when in execute-only mode
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if (genExecuteOnly) {
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unsigned Type = ELF::SHT_PROGBITS;
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unsigned Flags =
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ELF::SHF_EXECINSTR | ELF::SHF_ALLOC | ELF::SHF_ARM_PURECODE;
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// Since we cannot modify flags for an existing section, we create a new
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// section with the right flags, and use 0 as the unique ID for
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// execute-only text
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TextSection = Ctx.getELFSection(".text", Type, Flags, 0, "", 0U);
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}
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}
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const MCExpr *ARMElfTargetObjectFile::getTTypeGlobalReference(
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const GlobalValue *GV, unsigned Encoding, const TargetMachine &TM,
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MachineModuleInfo *MMI, MCStreamer &Streamer) const {
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if (TM.getMCAsmInfo()->getExceptionHandlingType() != ExceptionHandling::ARM)
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return TargetLoweringObjectFileELF::getTTypeGlobalReference(
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GV, Encoding, TM, MMI, Streamer);
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assert(Encoding == DW_EH_PE_absptr && "Can handle absptr encoding only");
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return MCSymbolRefExpr::create(TM.getSymbol(GV),
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MCSymbolRefExpr::VK_ARM_TARGET2, getContext());
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}
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const MCExpr *ARMElfTargetObjectFile::
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getDebugThreadLocalSymbol(const MCSymbol *Sym) const {
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return MCSymbolRefExpr::create(Sym, MCSymbolRefExpr::VK_ARM_TLSLDO,
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getContext());
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}
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static bool isExecuteOnlyFunction(const GlobalObject *GO, SectionKind SK,
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const TargetMachine &TM) {
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if (const Function *F = dyn_cast<Function>(GO))
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if (TM.getSubtarget<ARMSubtarget>(*F).genExecuteOnly() && SK.isText())
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return true;
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return false;
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}
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MCSection *ARMElfTargetObjectFile::getExplicitSectionGlobal(
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const GlobalObject *GO, SectionKind SK, const TargetMachine &TM) const {
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// Set execute-only access for the explicit section
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if (isExecuteOnlyFunction(GO, SK, TM))
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SK = SectionKind::getExecuteOnly();
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return TargetLoweringObjectFileELF::getExplicitSectionGlobal(GO, SK, TM);
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}
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MCSection *ARMElfTargetObjectFile::SelectSectionForGlobal(
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const GlobalObject *GO, SectionKind SK, const TargetMachine &TM) const {
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// Place the global in the execute-only text section
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if (isExecuteOnlyFunction(GO, SK, TM))
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SK = SectionKind::getExecuteOnly();
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return TargetLoweringObjectFileELF::SelectSectionForGlobal(GO, SK, TM);
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}
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