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 auto FileName = sys::path::filename(path: G.getName());
73 if (S.FileInfos.count(Key: FileName)) {
74 return make_error<StringError>(Args: "When -check is passed, file names must be "
75 "distinct (duplicate: \"" +
76 FileName + "\")",
77 Args: 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(Key: Sec.getName()))
96 return make_error<StringError>(Args: "Encountered duplicate section name \"" +
97 Sec.getName() + "\" in \"" + FileName +
98 "\"",
99 Args: inconvertibleErrorCode());
100
101 bool isGOTSection = isMachOGOTSection(S&: Sec);
102 bool isStubsSection = isMachOStubsSection(S&: 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 || isStubsSection) {
115 Error Err =
116 isGOTSection
117 ? FileInfo.registerGOTEntry(G, Sym&: *Sym, GetSymbolTarget: getMachOGOTTarget)
118 : FileInfo.registerStubEntry(G, Sym&: *Sym, GetSymbolTarget: getMachOStubTarget);
119 if (Err)
120 return Err;
121 SectionContainsContent = true;
122 } else if (Sym->hasName()) {
123 if (Sym->isSymbolZeroFill()) {
124 S.SymbolInfos[Sym->getName()] = {Sym->getSize(),
125 Sym->getAddress().getValue()};
126 SectionContainsZeroFill = true;
127 } else {
128 S.SymbolInfos[Sym->getName()] = {Sym->getSymbolContent(),
129 Sym->getAddress().getValue(),
130 Sym->getTargetFlags()};
131 SectionContainsContent = true;
132 }
133 }
134 }
135
136 auto SecAddr = FirstSym->getAddress();
137 auto SecSize =
138 (LastSym->getBlock().getAddress() + LastSym->getBlock().getSize()) -
139 SecAddr;
140
141 if (SectionContainsZeroFill && SectionContainsContent)
142 return make_error<StringError>(Args: "Mixed zero-fill and content sections not "
143 "supported yet",
144 Args: inconvertibleErrorCode());
145 if (SectionContainsZeroFill)
146 FileInfo.SectionInfos[Sec.getName()] = {SecSize, SecAddr.getValue()};
147 else
148 FileInfo.SectionInfos[Sec.getName()] = {
149 ArrayRef<char>(FirstSym->getBlock().getContent().data(), SecSize),
150 SecAddr.getValue(), FirstSym->getTargetFlags()};
151 }
152
153 return Error::success();
154}
155
156} // end namespace llvm
157