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 if (Sym->isLive())
37 Preserved[&Sym->getBlock()] = Sym;
38 else if (!Preserved.count(&Sym->getBlock()))
39 Preserved[&Sym->getBlock()] = Sym;
40 }
41 for (auto Block : Sec.blocks()) {
42 auto &PSym = Preserved[Block];
43 if (!PSym)
44 PSym = &G.addAnonymousSymbol(*Block, 0, 0, false, true);
45 else if (!PSym->isLive())
46 PSym->setLive(true);
47 }
48 }
49
getSectionData(Section & Sec)50 static SmallVector<char, 0> getSectionData(Section &Sec) {
51 SmallVector<char, 0> SecData;
52 SmallVector<Block *, 8> SecBlocks(Sec.blocks().begin(), Sec.blocks().end());
53 std::sort(SecBlocks.begin(), SecBlocks.end(), [](Block *LHS, Block *RHS) {
54 return LHS->getAddress() < RHS->getAddress();
55 });
56 // Convert back to what object file would have, one blob of section content
57 // Assumes all zerofill
58 // TODO handle alignment?
59 // TODO handle alignment offset?
60 for (auto *Block : SecBlocks) {
61 if (Block->isZeroFill())
62 SecData.resize(SecData.size() + Block->getSize(), 0);
63 else
64 SecData.append(Block->getContent().begin(), Block->getContent().end());
65 }
66 return SecData;
67 }
68
dumpDWARFContext(DWARFContext & DC)69 static void dumpDWARFContext(DWARFContext &DC) {
70 auto options = llvm::DIDumpOptions();
71 options.DumpType &= ~DIDT_UUID;
72 options.DumpType &= ~(1 << DIDT_ID_DebugFrame);
73 LLVM_DEBUG(DC.dump(dbgs(), options));
74 }
75
76 } // namespace
77
preserveDebugSections(LinkGraph & G)78 Error llvm::orc::preserveDebugSections(LinkGraph &G) {
79 if (!G.getTargetTriple().isOSBinFormatELF()) {
80 return make_error<StringError>(
81 "preserveDebugSections only supports ELF LinkGraphs!",
82 inconvertibleErrorCode());
83 }
84 for (auto &Sec : G.sections()) {
85 if (DWARFSectionNames.count(Sec.getName())) {
86 LLVM_DEBUG(dbgs() << "Preserving DWARF section " << Sec.getName()
87 << "\n");
88 preserveDWARFSection(G, Sec);
89 }
90 }
91 return Error::success();
92 }
93
94 Expected<std::pair<std::unique_ptr<DWARFContext>,
95 StringMap<std::unique_ptr<MemoryBuffer>>>>
createDWARFContext(LinkGraph & G)96 llvm::orc::createDWARFContext(LinkGraph &G) {
97 if (!G.getTargetTriple().isOSBinFormatELF()) {
98 return make_error<StringError>(
99 "createDWARFContext only supports ELF LinkGraphs!",
100 inconvertibleErrorCode());
101 }
102 StringMap<std::unique_ptr<MemoryBuffer>> DWARFSectionData;
103 for (auto &Sec : G.sections()) {
104 if (DWARFSectionNames.count(Sec.getName())) {
105 auto SecData = getSectionData(Sec);
106 auto Name = Sec.getName();
107 // DWARFContext expects the section name to not start with a dot
108 Name.consume_front(".");
109 LLVM_DEBUG(dbgs() << "Creating DWARFContext section " << Name
110 << " with size " << SecData.size() << "\n");
111 DWARFSectionData[Name] =
112 std::make_unique<SmallVectorMemoryBuffer>(std::move(SecData));
113 }
114 }
115 auto Ctx =
116 DWARFContext::create(DWARFSectionData, G.getPointerSize(),
117 G.getEndianness() == llvm::endianness::little);
118 dumpDWARFContext(*Ctx);
119 return std::make_pair(std::move(Ctx), std::move(DWARFSectionData));
120 }
121