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
19using namespace llvm;
20using namespace llvm::orc;
21using namespace llvm::jitlink;
22
23namespace {
24static 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
33static 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(Val: &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(Content&: *Block, Offset: 0, Size: 0, IsCallable: false, IsLive: true);
45 else if (!PSym->isLive())
46 PSym->setLive(true);
47 }
48}
49
50static 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(first: SecBlocks.begin(), last: SecBlocks.end(), comp: [](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(N: SecData.size() + Block->getSize(), NV: 0);
63 else
64 SecData.append(in_start: Block->getContent().begin(), in_end: Block->getContent().end());
65 }
66 return SecData;
67}
68
69static 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
78Error llvm::orc::preserveDebugSections(LinkGraph &G) {
79 if (!G.getTargetTriple().isOSBinFormatELF()) {
80 return make_error<StringError>(
81 Args: "preserveDebugSections only supports ELF LinkGraphs!",
82 Args: inconvertibleErrorCode());
83 }
84 for (auto &Sec : G.sections()) {
85 if (DWARFSectionNames.count(V: 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
94Expected<std::pair<std::unique_ptr<DWARFContext>,
95 StringMap<std::unique_ptr<MemoryBuffer>>>>
96llvm::orc::createDWARFContext(LinkGraph &G) {
97 if (!G.getTargetTriple().isOSBinFormatELF()) {
98 return make_error<StringError>(
99 Args: "createDWARFContext only supports ELF LinkGraphs!",
100 Args: inconvertibleErrorCode());
101 }
102 StringMap<std::unique_ptr<MemoryBuffer>> DWARFSectionData;
103 for (auto &Sec : G.sections()) {
104 if (DWARFSectionNames.count(V: 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(Prefix: ".");
109 LLVM_DEBUG(dbgs() << "Creating DWARFContext section " << Name
110 << " with size " << SecData.size() << "\n");
111 DWARFSectionData[Name] =
112 std::make_unique<SmallVectorMemoryBuffer>(args: std::move(SecData));
113 }
114 }
115 auto Ctx =
116 DWARFContext::create(Sections: DWARFSectionData, AddrSize: G.getPointerSize(),
117 isLittleEndian: G.getEndianness() == llvm::endianness::little);
118 dumpDWARFContext(DC&: *Ctx);
119 return std::make_pair(x: std::move(Ctx), y: std::move(DWARFSectionData));
120}
121