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
DWARFCache(std::unique_ptr<llvm::DWARFContext> d)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>>
getVariableLoc(StringRef name)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.
getDILineInfo(uint64_t offset,uint64_t sectionIndex)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