1 //===-- CodeGen/AsmPrinter/DwarfException.cpp - Dwarf Exception 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 // This file contains support for writing DWARF exception info into asm files. 10 // 11 //===----------------------------------------------------------------------===// 12 13 #include "DwarfException.h" 14 #include "llvm/ADT/Twine.h" 15 #include "llvm/BinaryFormat/Dwarf.h" 16 #include "llvm/CodeGen/AsmPrinter.h" 17 #include "llvm/CodeGen/MachineFunction.h" 18 #include "llvm/CodeGen/MachineModuleInfo.h" 19 #include "llvm/IR/DataLayout.h" 20 #include "llvm/IR/Mangler.h" 21 #include "llvm/IR/Module.h" 22 #include "llvm/MC/MCAsmInfo.h" 23 #include "llvm/MC/MCContext.h" 24 #include "llvm/MC/MCExpr.h" 25 #include "llvm/MC/MCSection.h" 26 #include "llvm/MC/MCStreamer.h" 27 #include "llvm/MC/MCSymbol.h" 28 #include "llvm/MC/MachineLocation.h" 29 #include "llvm/Support/ErrorHandling.h" 30 #include "llvm/Support/FormattedStream.h" 31 #include "llvm/Target/TargetLoweringObjectFile.h" 32 #include "llvm/Target/TargetMachine.h" 33 #include "llvm/Target/TargetOptions.h" 34 using namespace llvm; 35 36 DwarfCFIExceptionBase::DwarfCFIExceptionBase(AsmPrinter *A) 37 : EHStreamer(A), shouldEmitCFI(false), hasEmittedCFISections(false) {} 38 39 void DwarfCFIExceptionBase::markFunctionEnd() { 40 endFragment(); 41 42 // Map all labels and get rid of any dead landing pads. 43 if (!Asm->MF->getLandingPads().empty()) { 44 MachineFunction *NonConstMF = const_cast<MachineFunction*>(Asm->MF); 45 NonConstMF->tidyLandingPads(); 46 } 47 } 48 49 void DwarfCFIExceptionBase::endFragment() { 50 if (shouldEmitCFI && !Asm->MF->hasBBSections()) 51 Asm->OutStreamer->emitCFIEndProc(); 52 } 53 54 DwarfCFIException::DwarfCFIException(AsmPrinter *A) 55 : DwarfCFIExceptionBase(A), shouldEmitPersonality(false), 56 forceEmitPersonality(false), shouldEmitLSDA(false) {} 57 58 DwarfCFIException::~DwarfCFIException() {} 59 60 /// endModule - Emit all exception information that should come after the 61 /// content. 62 void DwarfCFIException::endModule() { 63 // SjLj uses this pass and it doesn't need this info. 64 if (!Asm->MAI->usesCFIForEH()) 65 return; 66 67 const TargetLoweringObjectFile &TLOF = Asm->getObjFileLowering(); 68 69 unsigned PerEncoding = TLOF.getPersonalityEncoding(); 70 71 if ((PerEncoding & 0x80) != dwarf::DW_EH_PE_indirect) 72 return; 73 74 // Emit references to all used personality functions 75 for (const Function *Personality : MMI->getPersonalities()) { 76 if (!Personality) 77 continue; 78 MCSymbol *Sym = Asm->getSymbol(Personality); 79 TLOF.emitPersonalityValue(*Asm->OutStreamer, Asm->getDataLayout(), Sym); 80 } 81 } 82 83 static MCSymbol *getExceptionSym(AsmPrinter *Asm, 84 const MachineBasicBlock *MBB) { 85 return Asm->getMBBExceptionSym(*MBB); 86 } 87 88 void DwarfCFIException::beginFunction(const MachineFunction *MF) { 89 shouldEmitPersonality = shouldEmitLSDA = false; 90 const Function &F = MF->getFunction(); 91 92 // If any landing pads survive, we need an EH table. 93 bool hasLandingPads = !MF->getLandingPads().empty(); 94 95 // See if we need frame move info. 96 bool shouldEmitMoves = 97 Asm->getFunctionCFISectionType(*MF) != AsmPrinter::CFISection::None; 98 99 const TargetLoweringObjectFile &TLOF = Asm->getObjFileLowering(); 100 unsigned PerEncoding = TLOF.getPersonalityEncoding(); 101 const Function *Per = nullptr; 102 if (F.hasPersonalityFn()) 103 Per = dyn_cast<Function>(F.getPersonalityFn()->stripPointerCasts()); 104 105 // Emit a personality function even when there are no landing pads 106 forceEmitPersonality = 107 // ...if a personality function is explicitly specified 108 F.hasPersonalityFn() && 109 // ... and it's not known to be a noop in the absence of invokes 110 !isNoOpWithoutInvoke(classifyEHPersonality(Per)) && 111 // ... and we're not explicitly asked not to emit it 112 F.needsUnwindTableEntry(); 113 114 shouldEmitPersonality = 115 (forceEmitPersonality || 116 (hasLandingPads && PerEncoding != dwarf::DW_EH_PE_omit)) && 117 Per; 118 119 unsigned LSDAEncoding = TLOF.getLSDAEncoding(); 120 shouldEmitLSDA = shouldEmitPersonality && 121 LSDAEncoding != dwarf::DW_EH_PE_omit; 122 123 const MCAsmInfo &MAI = *MF->getMMI().getContext().getAsmInfo(); 124 if (MAI.getExceptionHandlingType() != ExceptionHandling::None) 125 shouldEmitCFI = 126 MAI.usesCFIForEH() && (shouldEmitPersonality || shouldEmitMoves); 127 else 128 shouldEmitCFI = Asm->needsCFIForDebug() && shouldEmitMoves; 129 130 beginFragment(&*MF->begin(), getExceptionSym); 131 } 132 133 void DwarfCFIException::beginFragment(const MachineBasicBlock *MBB, 134 ExceptionSymbolProvider ESP) { 135 if (!shouldEmitCFI) 136 return; 137 138 if (!hasEmittedCFISections) { 139 AsmPrinter::CFISection CFISecType = Asm->getModuleCFISectionType(); 140 // If we don't say anything it implies `.cfi_sections .eh_frame`, so we 141 // chose not to be verbose in that case. And with `ForceDwarfFrameSection`, 142 // we should always emit .debug_frame. 143 if (CFISecType == AsmPrinter::CFISection::Debug || 144 Asm->TM.Options.ForceDwarfFrameSection) 145 Asm->OutStreamer->emitCFISections( 146 CFISecType == AsmPrinter::CFISection::EH, true); 147 hasEmittedCFISections = true; 148 } 149 150 Asm->OutStreamer->emitCFIStartProc(/*IsSimple=*/false); 151 152 // Indicate personality routine, if any. 153 if (!shouldEmitPersonality) 154 return; 155 156 auto &F = MBB->getParent()->getFunction(); 157 auto *P = dyn_cast<Function>(F.getPersonalityFn()->stripPointerCasts()); 158 assert(P && "Expected personality function"); 159 160 // If we are forced to emit this personality, make sure to record 161 // it because it might not appear in any landingpad 162 if (forceEmitPersonality) 163 MMI->addPersonality(P); 164 165 const TargetLoweringObjectFile &TLOF = Asm->getObjFileLowering(); 166 unsigned PerEncoding = TLOF.getPersonalityEncoding(); 167 const MCSymbol *Sym = TLOF.getCFIPersonalitySymbol(P, Asm->TM, MMI); 168 Asm->OutStreamer->emitCFIPersonality(Sym, PerEncoding); 169 170 // Provide LSDA information. 171 if (shouldEmitLSDA) 172 Asm->OutStreamer->emitCFILsda(ESP(Asm, MBB), TLOF.getLSDAEncoding()); 173 } 174 175 /// endFunction - Gather and emit post-function exception information. 176 /// 177 void DwarfCFIException::endFunction(const MachineFunction *MF) { 178 if (!shouldEmitPersonality) 179 return; 180 181 emitExceptionTable(); 182 } 183 184 void DwarfCFIException::beginBasicBlock(const MachineBasicBlock &MBB) { 185 beginFragment(&MBB, getExceptionSym); 186 } 187 188 void DwarfCFIException::endBasicBlock(const MachineBasicBlock &MBB) { 189 if (shouldEmitCFI) 190 Asm->OutStreamer->emitCFIEndProc(); 191 } 192