1 //===--- DebugInfoSupport.cpp -- Utils for debug info support ---*- C++ -*-===//
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 // Utilities to preserve and parse debug info from LinkGraphs.
10 //
11 //===----------------------------------------------------------------------===//
12
13 #include "llvm/ExecutionEngine/Orc/Debugging/DebugInfoSupport.h"
14
15 #include "llvm/Support/SmallVectorMemoryBuffer.h"
16
17 #define DEBUG_TYPE "orc"
18
19 using namespace llvm;
20 using namespace llvm::orc;
21 using namespace llvm::jitlink;
22
23 namespace {
24 static DenseSet<StringRef> DWARFSectionNames = {
25 #define HANDLE_DWARF_SECTION(ENUM_NAME, ELF_NAME, CMDLINE_NAME, OPTION) \
26 StringRef(ELF_NAME),
27 #include "llvm/BinaryFormat/Dwarf.def"
28 #undef HANDLE_DWARF_SECTION
29 };
30
31 // We might be able to drop relocations to symbols that do end up
32 // being pruned by the linker, but for now we just preserve all
preserveDWARFSection(LinkGraph & G,Section & Sec)33 static void preserveDWARFSection(LinkGraph &G, Section &Sec) {
34 DenseMap<Block *, Symbol *> Preserved;
35 for (auto Sym : Sec.symbols()) {
36 auto [It, Inserted] = Preserved.try_emplace(&Sym->getBlock());
37 if (Inserted || Sym->isLive())
38 It->second = Sym;
39 }
40 for (auto Block : Sec.blocks()) {
41 auto &PSym = Preserved[Block];
42 if (!PSym)
43 PSym = &G.addAnonymousSymbol(*Block, 0, 0, false, true);
44 else if (!PSym->isLive())
45 PSym->setLive(true);
46 }
47 }
48
getSectionData(Section & Sec)49 static SmallVector<char, 0> getSectionData(Section &Sec) {
50 SmallVector<char, 0> SecData;
51 SmallVector<Block *, 8> SecBlocks(Sec.blocks().begin(), Sec.blocks().end());
52 std::sort(SecBlocks.begin(), SecBlocks.end(), [](Block *LHS, Block *RHS) {
53 return LHS->getAddress() < RHS->getAddress();
54 });
55 // Convert back to what object file would have, one blob of section content
56 // Assumes all zerofill
57 // TODO handle alignment?
58 // TODO handle alignment offset?
59 for (auto *Block : SecBlocks) {
60 if (Block->isZeroFill())
61 SecData.resize(SecData.size() + Block->getSize(), 0);
62 else
63 SecData.append(Block->getContent().begin(), Block->getContent().end());
64 }
65 return SecData;
66 }
67
dumpDWARFContext(DWARFContext & DC)68 static void dumpDWARFContext(DWARFContext &DC) {
69 auto options = llvm::DIDumpOptions();
70 options.DumpType &= ~DIDT_UUID;
71 options.DumpType &= ~(1 << DIDT_ID_DebugFrame);
72 LLVM_DEBUG(DC.dump(dbgs(), options));
73 }
74
75 } // namespace
76
preserveDebugSections(LinkGraph & G)77 Error llvm::orc::preserveDebugSections(LinkGraph &G) {
78 if (!G.getTargetTriple().isOSBinFormatELF()) {
79 return make_error<StringError>(
80 "preserveDebugSections only supports ELF LinkGraphs!",
81 inconvertibleErrorCode());
82 }
83 for (auto &Sec : G.sections()) {
84 if (DWARFSectionNames.count(Sec.getName())) {
85 LLVM_DEBUG(dbgs() << "Preserving DWARF section " << Sec.getName()
86 << "\n");
87 preserveDWARFSection(G, Sec);
88 }
89 }
90 return Error::success();
91 }
92
93 Expected<std::pair<std::unique_ptr<DWARFContext>,
94 StringMap<std::unique_ptr<MemoryBuffer>>>>
createDWARFContext(LinkGraph & G)95 llvm::orc::createDWARFContext(LinkGraph &G) {
96 if (!G.getTargetTriple().isOSBinFormatELF()) {
97 return make_error<StringError>(
98 "createDWARFContext only supports ELF LinkGraphs!",
99 inconvertibleErrorCode());
100 }
101 StringMap<std::unique_ptr<MemoryBuffer>> DWARFSectionData;
102 for (auto &Sec : G.sections()) {
103 if (DWARFSectionNames.count(Sec.getName())) {
104 auto SecData = getSectionData(Sec);
105 auto Name = Sec.getName();
106 // DWARFContext expects the section name to not start with a dot
107 Name.consume_front(".");
108 LLVM_DEBUG(dbgs() << "Creating DWARFContext section " << Name
109 << " with size " << SecData.size() << "\n");
110 DWARFSectionData[Name] =
111 std::make_unique<SmallVectorMemoryBuffer>(std::move(SecData));
112 }
113 }
114 auto Ctx =
115 DWARFContext::create(DWARFSectionData, G.getPointerSize(),
116 G.getEndianness() == llvm::endianness::little);
117 dumpDWARFContext(*Ctx);
118 return std::make_pair(std::move(Ctx), std::move(DWARFSectionData));
119 }
120