1//===-- llvm-jitlink-macho.cpp -- MachO parsing support for llvm-jitlink --===//
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// MachO parsing support for llvm-jitlink.
10//
11//===----------------------------------------------------------------------===//
12
13#include "llvm-jitlink.h"
14
15#include "llvm/Support/Error.h"
16#include "llvm/Support/Path.h"
17
18#define DEBUG_TYPE "llvm_jitlink"
19
20using namespace llvm;
21using namespace llvm::jitlink;
22
23static bool isMachOGOTSection(Section &S) { return S.getName() == "$__GOT"; }
24
25static bool isMachOStubsSection(Section &S) {
26 return S.getName() == "$__STUBS";
27}
28
29static Expected<Edge &> getFirstRelocationEdge(LinkGraph &G, Block &B) {
30 auto EItr =
31 llvm::find_if(Range: B.edges(), P: [](Edge &E) { return E.isRelocation(); });
32 if (EItr == B.edges().end())
33 return make_error<StringError>(Args: "GOT entry in " + G.getName() + ", \"" +
34 B.getSection().getName() +
35 "\" has no relocations",
36 Args: inconvertibleErrorCode());
37 return *EItr;
38}
39
40static Expected<Symbol &> getMachOGOTTarget(LinkGraph &G, Block &B) {
41 auto E = getFirstRelocationEdge(G, B);
42 if (!E)
43 return E.takeError();
44 auto &TargetSym = E->getTarget();
45 if (!TargetSym.hasName())
46 return make_error<StringError>(
47 Args: "GOT entry in " + G.getName() + ", \"" +
48 TargetSym.getBlock().getSection().getName() +
49 "\" points to anonymous "
50 "symbol",
51 Args: inconvertibleErrorCode());
52 return TargetSym;
53}
54
55static Expected<Symbol &> getMachOStubTarget(LinkGraph &G, Block &B) {
56 auto E = getFirstRelocationEdge(G, B);
57 if (!E)
58 return E.takeError();
59 auto &GOTSym = E->getTarget();
60 if (!GOTSym.isDefined() || !isMachOGOTSection(S&: GOTSym.getBlock().getSection()))
61 return make_error<StringError>(
62 Args: "Stubs entry in " + G.getName() + ", \"" +
63 GOTSym.getBlock().getSection().getName() +
64 "\" does not point to GOT entry",
65 Args: inconvertibleErrorCode());
66 return getMachOGOTTarget(G, B&: GOTSym.getBlock());
67}
68
69namespace llvm {
70
71Error registerMachOGraphInfo(Session &S, LinkGraph &G) {
72 std::lock_guard<std::mutex> Lock(S.M);
73
74 auto FileName = sys::path::filename(path: G.getName());
75 auto [It, Inserted] = S.FileInfos.try_emplace(Key: FileName);
76 if (!Inserted) {
77 return make_error<StringError>(Args: "When -check is passed, file names must be "
78 "distinct (duplicate: \"" +
79 FileName + "\")",
80 Args: inconvertibleErrorCode());
81 }
82
83 auto &FileInfo = It->second;
84 LLVM_DEBUG({
85 dbgs() << "Registering MachO file info for \"" << FileName << "\"\n";
86 });
87 for (auto &Sec : G.sections()) {
88 LLVM_DEBUG({
89 dbgs() << " Section \"" << Sec.getName() << "\": "
90 << (Sec.symbols().empty() ? "empty. skipping." : "processing...")
91 << "\n";
92 });
93
94 // Skip empty sections.
95 if (Sec.symbols().empty())
96 continue;
97
98 if (FileInfo.SectionInfos.count(Key: Sec.getName()))
99 return make_error<StringError>(Args: "Encountered duplicate section name \"" +
100 Sec.getName() + "\" in \"" + FileName +
101 "\"",
102 Args: inconvertibleErrorCode());
103
104 bool isGOTSection = isMachOGOTSection(S&: Sec);
105 bool isStubsSection = isMachOStubsSection(S&: Sec);
106
107 bool SectionContainsContent = false;
108 bool SectionContainsZeroFill = false;
109
110 auto *FirstSym = *Sec.symbols().begin();
111 auto *LastSym = FirstSym;
112 for (auto *Sym : Sec.symbols()) {
113 if (Sym->getAddress() < FirstSym->getAddress())
114 FirstSym = Sym;
115 if (Sym->getAddress() > LastSym->getAddress())
116 LastSym = Sym;
117 if (isGOTSection || isStubsSection) {
118 Error Err =
119 isGOTSection
120 ? FileInfo.registerGOTEntry(G, Sym&: *Sym, GetSymbolTarget: getMachOGOTTarget)
121 : FileInfo.registerStubEntry(G, Sym&: *Sym, GetSymbolTarget: getMachOStubTarget);
122 if (Err)
123 return Err;
124 SectionContainsContent = true;
125 } else if (Sym->hasName()) {
126 if (Sym->isSymbolZeroFill()) {
127 S.SymbolInfos[Sym->getName()] = {Sym->getSize(),
128 Sym->getAddress().getValue()};
129 SectionContainsZeroFill = true;
130 } else {
131 S.SymbolInfos[Sym->getName()] = {Sym->getSymbolContent(),
132 Sym->getAddress().getValue(),
133 Sym->getTargetFlags()};
134 SectionContainsContent = true;
135 }
136 }
137 }
138
139 auto SecAddr = FirstSym->getAddress();
140 auto SecSize =
141 (LastSym->getBlock().getAddress() + LastSym->getBlock().getSize()) -
142 SecAddr;
143
144 if (SectionContainsZeroFill && SectionContainsContent)
145 return make_error<StringError>(Args: "Mixed zero-fill and content sections not "
146 "supported yet",
147 Args: inconvertibleErrorCode());
148 if (SectionContainsZeroFill)
149 FileInfo.SectionInfos[Sec.getName()] = {SecSize, SecAddr.getValue()};
150 else
151 FileInfo.SectionInfos[Sec.getName()] = {
152 ArrayRef<char>(FirstSym->getBlock().getContent().data(), SecSize),
153 SecAddr.getValue(), FirstSym->getTargetFlags()};
154 }
155
156 return Error::success();
157}
158
159} // end namespace llvm
160