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