1 //===----- MachOLinkGraphBuilder.h - MachO LinkGraph builder ----*- 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 // Generic MachO LinkGraph building code.
10 //
11 //===----------------------------------------------------------------------===//
12 
13 #ifndef LIB_EXECUTIONENGINE_JITLINK_MACHOLINKGRAPHBUILDER_H
14 #define LIB_EXECUTIONENGINE_JITLINK_MACHOLINKGRAPHBUILDER_H
15 
16 #include "llvm/ADT/DenseMap.h"
17 #include "llvm/ADT/StringMap.h"
18 #include "llvm/ExecutionEngine/JITLink/JITLink.h"
19 #include "llvm/Object/MachO.h"
20 
21 #include "EHFrameSupportImpl.h"
22 #include "JITLinkGeneric.h"
23 
24 #include <list>
25 
26 namespace llvm {
27 namespace jitlink {
28 
29 class MachOLinkGraphBuilder {
30 public:
31   virtual ~MachOLinkGraphBuilder();
32   Expected<std::unique_ptr<LinkGraph>> buildGraph();
33 
34 protected:
35 
36   struct NormalizedSymbol {
37     friend class MachOLinkGraphBuilder;
38 
39   private:
40     NormalizedSymbol(Optional<StringRef> Name, uint64_t Value, uint8_t Type,
41                      uint8_t Sect, uint16_t Desc, Linkage L, Scope S)
42         : Name(Name), Value(Value), Type(Type), Sect(Sect), Desc(Desc), L(L),
43           S(S) {
44       assert((!Name || !Name->empty()) && "Name must be none or non-empty");
45     }
46 
47   public:
48     NormalizedSymbol(const NormalizedSymbol &) = delete;
49     NormalizedSymbol &operator=(const NormalizedSymbol &) = delete;
50     NormalizedSymbol(NormalizedSymbol &&) = delete;
51     NormalizedSymbol &operator=(NormalizedSymbol &&) = delete;
52 
53     Optional<StringRef> Name;
54     uint64_t Value = 0;
55     uint8_t Type = 0;
56     uint8_t Sect = 0;
57     uint16_t Desc = 0;
58     Linkage L = Linkage::Strong;
59     Scope S = Scope::Default;
60     Symbol *GraphSymbol = nullptr;
61   };
62 
63   // Normalized section representation. Section and segment names are guaranteed
64   // to be null-terminated, hence the extra bytes on SegName and SectName.
65   class NormalizedSection {
66     friend class MachOLinkGraphBuilder;
67 
68   private:
69     NormalizedSection() = default;
70 
71   public:
72     char SectName[17];
73     char SegName[17];
74     orc::ExecutorAddr Address;
75     uint64_t Size = 0;
76     uint64_t Alignment = 0;
77     uint32_t Flags = 0;
78     const char *Data = nullptr;
79     Section *GraphSection = nullptr;
80     std::map<orc::ExecutorAddr, Symbol *> CanonicalSymbols;
81   };
82 
83   using SectionParserFunction = std::function<Error(NormalizedSection &S)>;
84 
85   MachOLinkGraphBuilder(const object::MachOObjectFile &Obj, Triple TT,
86                         LinkGraph::GetEdgeKindNameFunction GetEdgeKindName);
87 
88   LinkGraph &getGraph() const { return *G; }
89 
90   const object::MachOObjectFile &getObject() const { return Obj; }
91 
92   void addCustomSectionParser(StringRef SectionName,
93                               SectionParserFunction Parse);
94 
95   virtual Error addRelocations() = 0;
96 
97   /// Create a symbol.
98   template <typename... ArgTs>
99   NormalizedSymbol &createNormalizedSymbol(ArgTs &&... Args) {
100     NormalizedSymbol *Sym = reinterpret_cast<NormalizedSymbol *>(
101         Allocator.Allocate<NormalizedSymbol>());
102     new (Sym) NormalizedSymbol(std::forward<ArgTs>(Args)...);
103     return *Sym;
104   }
105 
106   /// Index is zero-based (MachO section indexes are usually one-based) and
107   /// assumed to be in-range. Client is responsible for checking.
108   NormalizedSection &getSectionByIndex(unsigned Index) {
109     auto I = IndexToSection.find(Index);
110     assert(I != IndexToSection.end() && "No section recorded at index");
111     return I->second;
112   }
113 
114   /// Try to get the section at the given index. Will return an error if the
115   /// given index is out of range, or if no section has been added for the given
116   /// index.
117   Expected<NormalizedSection &> findSectionByIndex(unsigned Index) {
118     auto I = IndexToSection.find(Index);
119     if (I == IndexToSection.end())
120       return make_error<JITLinkError>("No section recorded for index " +
121                                       formatv("{0:d}", Index));
122     return I->second;
123   }
124 
125   /// Try to get the symbol at the given index. Will return an error if the
126   /// given index is out of range, or if no symbol has been added for the given
127   /// index.
128   Expected<NormalizedSymbol &> findSymbolByIndex(uint64_t Index) {
129     auto I = IndexToSymbol.find(Index);
130     if (I == IndexToSymbol.end())
131       return make_error<JITLinkError>("No symbol at index " +
132                                       formatv("{0:d}", Index));
133     assert(I->second && "Null symbol at index");
134     return *I->second;
135   }
136 
137   /// Returns the symbol with the highest address not greater than the search
138   /// address, or null if no such symbol exists.
139   Symbol *getSymbolByAddress(NormalizedSection &NSec,
140                              orc::ExecutorAddr Address) {
141     auto I = NSec.CanonicalSymbols.upper_bound(Address);
142     if (I == NSec.CanonicalSymbols.begin())
143       return nullptr;
144     return std::prev(I)->second;
145   }
146 
147   /// Returns the symbol with the highest address not greater than the search
148   /// address, or an error if no such symbol exists.
149   Expected<Symbol &> findSymbolByAddress(NormalizedSection &NSec,
150                                          orc::ExecutorAddr Address) {
151     auto *Sym = getSymbolByAddress(NSec, Address);
152     if (Sym)
153       if (Address <= Sym->getAddress() + Sym->getSize())
154         return *Sym;
155     return make_error<JITLinkError>("No symbol covering address " +
156                                     formatv("{0:x16}", Address));
157   }
158 
159   static Linkage getLinkage(uint16_t Desc);
160   static Scope getScope(StringRef Name, uint8_t Type);
161   static bool isAltEntry(const NormalizedSymbol &NSym);
162 
163   static bool isDebugSection(const NormalizedSection &NSec);
164   static bool isZeroFillSection(const NormalizedSection &NSec);
165 
166   MachO::relocation_info
167   getRelocationInfo(const object::relocation_iterator RelItr) {
168     MachO::any_relocation_info ARI =
169         getObject().getRelocation(RelItr->getRawDataRefImpl());
170     MachO::relocation_info RI;
171     RI.r_address = ARI.r_word0;
172     RI.r_symbolnum = ARI.r_word1 & 0xffffff;
173     RI.r_pcrel = (ARI.r_word1 >> 24) & 1;
174     RI.r_length = (ARI.r_word1 >> 25) & 3;
175     RI.r_extern = (ARI.r_word1 >> 27) & 1;
176     RI.r_type = (ARI.r_word1 >> 28);
177     return RI;
178   }
179 
180 private:
181   static unsigned getPointerSize(const object::MachOObjectFile &Obj);
182   static support::endianness getEndianness(const object::MachOObjectFile &Obj);
183 
184   void setCanonicalSymbol(NormalizedSection &NSec, Symbol &Sym) {
185     auto *&CanonicalSymEntry = NSec.CanonicalSymbols[Sym.getAddress()];
186     // There should be no symbol at this address, or, if there is,
187     // it should be a zero-sized symbol from an empty section (which
188     // we can safely override).
189     assert((!CanonicalSymEntry || CanonicalSymEntry->getSize() == 0) &&
190            "Duplicate canonical symbol at address");
191     CanonicalSymEntry = &Sym;
192   }
193 
194   Section &getCommonSection();
195   void addSectionStartSymAndBlock(unsigned SecIndex, Section &GraphSec,
196                                   orc::ExecutorAddr Address, const char *Data,
197                                   orc::ExecutorAddrDiff Size,
198                                   uint32_t Alignment, bool IsLive);
199 
200   Error createNormalizedSections();
201   Error createNormalizedSymbols();
202 
203   /// Create graph blocks and symbols for externals, absolutes, commons and
204   /// all defined symbols in sections without custom parsers.
205   Error graphifyRegularSymbols();
206 
207   /// Create and return a graph symbol for the given normalized symbol.
208   ///
209   /// NSym's GraphSymbol member will be updated to point at the newly created
210   /// symbol.
211   Symbol &createStandardGraphSymbol(NormalizedSymbol &Sym, Block &B,
212                                     size_t Size, bool IsText,
213                                     bool IsNoDeadStrip, bool IsCanonical);
214 
215   /// Create graph blocks and symbols for all sections.
216   Error graphifySectionsWithCustomParsers();
217 
218   /// Graphify cstring section.
219   Error graphifyCStringSection(NormalizedSection &NSec,
220                                std::vector<NormalizedSymbol *> NSyms);
221 
222   // Put the BumpPtrAllocator first so that we don't free any of the underlying
223   // memory until the Symbol/Addressable destructors have been run.
224   BumpPtrAllocator Allocator;
225 
226   const object::MachOObjectFile &Obj;
227   std::unique_ptr<LinkGraph> G;
228 
229   DenseMap<unsigned, NormalizedSection> IndexToSection;
230   Section *CommonSection = nullptr;
231 
232   DenseMap<uint32_t, NormalizedSymbol *> IndexToSymbol;
233   StringMap<SectionParserFunction> CustomSectionParserFunctions;
234 };
235 
236 /// A pass to split up __LD,__compact_unwind sections.
237 class CompactUnwindSplitter {
238 public:
239   CompactUnwindSplitter(StringRef CompactUnwindSectionName)
240       : CompactUnwindSectionName(CompactUnwindSectionName) {}
241   Error operator()(LinkGraph &G);
242 
243 private:
244   StringRef CompactUnwindSectionName;
245 };
246 
247 } // end namespace jitlink
248 } // end namespace llvm
249 
250 #endif // LIB_EXECUTIONENGINE_JITLINK_MACHOLINKGRAPHBUILDER_H
251