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
20 using namespace llvm;
21 using namespace llvm::jitlink;
22
isMachOGOTSection(Section & S)23 static bool isMachOGOTSection(Section &S) { return S.getName() == "$__GOT"; }
24
isMachOStubsSection(Section & S)25 static bool isMachOStubsSection(Section &S) {
26 return S.getName() == "$__STUBS";
27 }
28
getFirstRelocationEdge(LinkGraph & G,Block & B)29 static Expected<Edge &> getFirstRelocationEdge(LinkGraph &G, Block &B) {
30 auto EItr =
31 llvm::find_if(B.edges(), [](Edge &E) { return E.isRelocation(); });
32 if (EItr == B.edges().end())
33 return make_error<StringError>("GOT entry in " + G.getName() + ", \"" +
34 B.getSection().getName() +
35 "\" has no relocations",
36 inconvertibleErrorCode());
37 return *EItr;
38 }
39
getMachOGOTTarget(LinkGraph & G,Block & B)40 static 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 "GOT entry in " + G.getName() + ", \"" +
48 TargetSym.getBlock().getSection().getName() +
49 "\" points to anonymous "
50 "symbol",
51 inconvertibleErrorCode());
52 return TargetSym;
53 }
54
getMachOStubTarget(LinkGraph & G,Block & B)55 static 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(GOTSym.getBlock().getSection()))
61 return make_error<StringError>(
62 "Stubs entry in " + G.getName() + ", \"" +
63 GOTSym.getBlock().getSection().getName() +
64 "\" does not point to GOT entry",
65 inconvertibleErrorCode());
66 return getMachOGOTTarget(G, GOTSym.getBlock());
67 }
68
69 namespace llvm {
70
registerMachOGraphInfo(Session & S,LinkGraph & G)71 Error registerMachOGraphInfo(Session &S, LinkGraph &G) {
72 auto FileName = sys::path::filename(G.getName());
73 if (S.FileInfos.count(FileName)) {
74 return make_error<StringError>("When -check is passed, file names must be "
75 "distinct (duplicate: \"" +
76 FileName + "\")",
77 inconvertibleErrorCode());
78 }
79
80 auto &FileInfo = S.FileInfos[FileName];
81 LLVM_DEBUG({
82 dbgs() << "Registering MachO file info for \"" << FileName << "\"\n";
83 });
84 for (auto &Sec : G.sections()) {
85 LLVM_DEBUG({
86 dbgs() << " Section \"" << Sec.getName() << "\": "
87 << (Sec.symbols().empty() ? "empty. skipping." : "processing...")
88 << "\n";
89 });
90
91 // Skip empty sections.
92 if (Sec.symbols().empty())
93 continue;
94
95 if (FileInfo.SectionInfos.count(Sec.getName()))
96 return make_error<StringError>("Encountered duplicate section name \"" +
97 Sec.getName() + "\" in \"" + FileName +
98 "\"",
99 inconvertibleErrorCode());
100
101 bool isGOTSection = isMachOGOTSection(Sec);
102 bool isStubsSection = isMachOStubsSection(Sec);
103
104 bool SectionContainsContent = false;
105 bool SectionContainsZeroFill = false;
106
107 auto *FirstSym = *Sec.symbols().begin();
108 auto *LastSym = FirstSym;
109 for (auto *Sym : Sec.symbols()) {
110 if (Sym->getAddress() < FirstSym->getAddress())
111 FirstSym = Sym;
112 if (Sym->getAddress() > LastSym->getAddress())
113 LastSym = Sym;
114 if (isGOTSection) {
115 if (Sym->isSymbolZeroFill())
116 return make_error<StringError>("zero-fill atom in GOT section",
117 inconvertibleErrorCode());
118
119 if (auto TS = getMachOGOTTarget(G, Sym->getBlock()))
120 FileInfo.GOTEntryInfos[TS->getName()] = {
121 Sym->getSymbolContent(), Sym->getAddress().getValue()};
122 else
123 return TS.takeError();
124 SectionContainsContent = true;
125 } else if (isStubsSection) {
126 if (Sym->isSymbolZeroFill())
127 return make_error<StringError>("zero-fill atom in Stub section",
128 inconvertibleErrorCode());
129
130 if (auto TS = getMachOStubTarget(G, Sym->getBlock()))
131 FileInfo.StubInfos[TS->getName()] = {Sym->getSymbolContent(),
132 Sym->getAddress().getValue()};
133 else
134 return TS.takeError();
135 SectionContainsContent = true;
136 } else if (Sym->hasName()) {
137 if (Sym->isSymbolZeroFill()) {
138 S.SymbolInfos[Sym->getName()] = {Sym->getSize(),
139 Sym->getAddress().getValue()};
140 SectionContainsZeroFill = true;
141 } else {
142 S.SymbolInfos[Sym->getName()] = {Sym->getSymbolContent(),
143 Sym->getAddress().getValue()};
144 SectionContainsContent = true;
145 }
146 }
147 }
148
149 auto SecAddr = FirstSym->getAddress();
150 auto SecSize =
151 (LastSym->getBlock().getAddress() + LastSym->getBlock().getSize()) -
152 SecAddr;
153
154 if (SectionContainsZeroFill && SectionContainsContent)
155 return make_error<StringError>("Mixed zero-fill and content sections not "
156 "supported yet",
157 inconvertibleErrorCode());
158 if (SectionContainsZeroFill)
159 FileInfo.SectionInfos[Sec.getName()] = {SecSize, SecAddr.getValue()};
160 else
161 FileInfo.SectionInfos[Sec.getName()] = {
162 ArrayRef<char>(FirstSym->getBlock().getContent().data(), SecSize),
163 SecAddr.getValue()};
164 }
165
166 return Error::success();
167 }
168
169 } // end namespace llvm
170