1 //===- DWARF.cpp ----------------------------------------------------------===// 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 "lld/Common/DWARF.h" 10 #include "lld/Common/ErrorHandler.h" 11 12 using namespace llvm; 13 14 namespace lld { 15 16 DWARFCache::DWARFCache(std::unique_ptr<llvm::DWARFContext> d) 17 : dwarf(std::move(d)) { 18 for (std::unique_ptr<DWARFUnit> &cu : dwarf->compile_units()) { 19 auto report = [](Error err) { 20 handleAllErrors(std::move(err), 21 [](ErrorInfoBase &info) { warn(info.message()); }); 22 }; 23 Expected<const DWARFDebugLine::LineTable *> expectedLT = 24 dwarf->getLineTableForUnit(cu.get(), report); 25 const DWARFDebugLine::LineTable *lt = nullptr; 26 if (expectedLT) 27 lt = *expectedLT; 28 else 29 report(expectedLT.takeError()); 30 if (!lt) 31 continue; 32 lineTables.push_back(lt); 33 34 // Loop over variable records and insert them to variableLoc. 35 for (const auto &entry : cu->dies()) { 36 DWARFDie die(cu.get(), &entry); 37 // Skip all tags that are not variables. 38 if (die.getTag() != dwarf::DW_TAG_variable) 39 continue; 40 41 // Skip if a local variable because we don't need them for generating 42 // error messages. In general, only non-local symbols can fail to be 43 // linked. 44 if (!dwarf::toUnsigned(die.find(dwarf::DW_AT_external), 0)) 45 continue; 46 47 // Get the source filename index for the variable. 48 unsigned file = dwarf::toUnsigned(die.find(dwarf::DW_AT_decl_file), 0); 49 if (!lt->hasFileAtIndex(file)) 50 continue; 51 52 // Get the line number on which the variable is declared. 53 unsigned line = dwarf::toUnsigned(die.find(dwarf::DW_AT_decl_line), 0); 54 55 // Here we want to take the variable name to add it into variableLoc. 56 // Variable can have regular and linkage name associated. At first, we try 57 // to get linkage name as it can be different, for example when we have 58 // two variables in different namespaces of the same object. Use common 59 // name otherwise, but handle the case when it also absent in case if the 60 // input object file lacks some debug info. 61 StringRef name = 62 dwarf::toString(die.find(dwarf::DW_AT_linkage_name), 63 dwarf::toString(die.find(dwarf::DW_AT_name), "")); 64 if (!name.empty()) 65 variableLoc.insert({name, {lt, file, line}}); 66 } 67 } 68 } 69 70 // Returns the pair of file name and line number describing location of data 71 // object (variable, array, etc) definition. 72 std::optional<std::pair<std::string, unsigned>> 73 DWARFCache::getVariableLoc(StringRef name) { 74 // Return if we have no debug information about data object. 75 auto it = variableLoc.find(name); 76 if (it == variableLoc.end()) 77 return std::nullopt; 78 79 // Take file name string from line table. 80 std::string fileName; 81 if (!it->second.lt->getFileNameByIndex( 82 it->second.file, {}, 83 DILineInfoSpecifier::FileLineInfoKind::AbsoluteFilePath, fileName)) 84 return std::nullopt; 85 86 return std::make_pair(fileName, it->second.line); 87 } 88 89 // Returns source line information for a given offset 90 // using DWARF debug info. 91 std::optional<DILineInfo> DWARFCache::getDILineInfo(uint64_t offset, 92 uint64_t sectionIndex) { 93 DILineInfo info; 94 for (const llvm::DWARFDebugLine::LineTable *lt : lineTables) { 95 if (lt->getFileLineInfoForAddress( 96 {offset, sectionIndex}, nullptr, 97 DILineInfoSpecifier::FileLineInfoKind::AbsoluteFilePath, info)) 98 return info; 99 } 100 return std::nullopt; 101 } 102 103 } // namespace lld 104