1 //===----------- Mangling.cpp -- Name Mangling Utilities for ORC ----------===//
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 #include "llvm/ExecutionEngine/Orc/Mangling.h"
10 #include "llvm/IR/Constants.h"
11 #include "llvm/IR/Mangler.h"
12 #include "llvm/Object/MachO.h"
13 #include "llvm/Object/ObjectFile.h"
14 #include "llvm/Support/Debug.h"
15 
16 #define DEBUG_TYPE "orc"
17 
18 namespace llvm {
19 namespace orc {
20 
21 MangleAndInterner::MangleAndInterner(ExecutionSession &ES, const DataLayout &DL)
22     : ES(ES), DL(DL) {}
23 
24 SymbolStringPtr MangleAndInterner::operator()(StringRef Name) {
25   std::string MangledName;
26   {
27     raw_string_ostream MangledNameStream(MangledName);
28     Mangler::getNameWithPrefix(MangledNameStream, Name, DL);
29   }
30   return ES.intern(MangledName);
31 }
32 
33 void IRSymbolMapper::add(ExecutionSession &ES, const ManglingOptions &MO,
34                          ArrayRef<GlobalValue *> GVs,
35                          SymbolFlagsMap &SymbolFlags,
36                          SymbolNameToDefinitionMap *SymbolToDefinition) {
37   if (GVs.empty())
38     return;
39 
40   MangleAndInterner Mangle(ES, GVs[0]->getParent()->getDataLayout());
41   for (auto *G : GVs) {
42     assert(G && "GVs cannot contain null elements");
43     if (!G->hasName() || G->isDeclaration() || G->hasLocalLinkage() ||
44         G->hasAvailableExternallyLinkage() || G->hasAppendingLinkage())
45       continue;
46 
47     if (G->isThreadLocal() && MO.EmulatedTLS) {
48       auto *GV = cast<GlobalVariable>(G);
49 
50       auto Flags = JITSymbolFlags::fromGlobalValue(*GV);
51 
52       auto EmuTLSV = Mangle(("__emutls_v." + GV->getName()).str());
53       SymbolFlags[EmuTLSV] = Flags;
54       if (SymbolToDefinition)
55         (*SymbolToDefinition)[EmuTLSV] = GV;
56 
57       // If this GV has a non-zero initializer we'll need to emit an
58       // __emutls.t symbol too.
59       if (GV->hasInitializer()) {
60         const auto *InitVal = GV->getInitializer();
61 
62         // Skip zero-initializers.
63         if (isa<ConstantAggregateZero>(InitVal))
64           continue;
65         const auto *InitIntValue = dyn_cast<ConstantInt>(InitVal);
66         if (InitIntValue && InitIntValue->isZero())
67           continue;
68 
69         auto EmuTLST = Mangle(("__emutls_t." + GV->getName()).str());
70         SymbolFlags[EmuTLST] = Flags;
71         if (SymbolToDefinition)
72           (*SymbolToDefinition)[EmuTLST] = GV;
73       }
74       continue;
75     }
76 
77     // Otherwise we just need a normal linker mangling.
78     auto MangledName = Mangle(G->getName());
79     SymbolFlags[MangledName] = JITSymbolFlags::fromGlobalValue(*G);
80     if (SymbolToDefinition)
81       (*SymbolToDefinition)[MangledName] = G;
82   }
83 }
84 
85 Expected<std::pair<SymbolFlagsMap, SymbolStringPtr>>
86 getObjectSymbolInfo(ExecutionSession &ES, MemoryBufferRef ObjBuffer) {
87   auto Obj = object::ObjectFile::createObjectFile(ObjBuffer);
88 
89   if (!Obj)
90     return Obj.takeError();
91 
92   bool IsMachO = isa<object::MachOObjectFile>(Obj->get());
93 
94   SymbolFlagsMap SymbolFlags;
95   for (auto &Sym : (*Obj)->symbols()) {
96     // Skip symbols not defined in this object file.
97     if (Sym.getFlags() & object::BasicSymbolRef::SF_Undefined)
98       continue;
99 
100     // Skip symbols that are not global.
101     if (!(Sym.getFlags() & object::BasicSymbolRef::SF_Global))
102       continue;
103 
104     // Skip symbols that have type SF_File.
105     if (auto SymType = Sym.getType()) {
106       if (*SymType == object::SymbolRef::ST_File)
107         continue;
108     } else
109       return SymType.takeError();
110 
111     auto Name = Sym.getName();
112     if (!Name)
113       return Name.takeError();
114     auto InternedName = ES.intern(*Name);
115     auto SymFlags = JITSymbolFlags::fromObjectSymbol(Sym);
116     if (!SymFlags)
117       return SymFlags.takeError();
118 
119     // Strip the 'exported' flag from MachO linker-private symbols.
120     if (IsMachO && Name->startswith("l"))
121       *SymFlags &= ~JITSymbolFlags::Exported;
122 
123     SymbolFlags[InternedName] = std::move(*SymFlags);
124   }
125 
126   SymbolStringPtr InitSymbol;
127 
128   if (IsMachO) {
129     auto &MachOObj = cast<object::MachOObjectFile>(*Obj->get());
130     for (auto &Sec : MachOObj.sections()) {
131       auto SecType = MachOObj.getSectionType(Sec);
132       if ((SecType & MachO::SECTION_TYPE) == MachO::S_MOD_INIT_FUNC_POINTERS) {
133         size_t Counter = 0;
134         while (true) {
135           std::string InitSymString;
136           raw_string_ostream(InitSymString)
137               << "$." << ObjBuffer.getBufferIdentifier() << ".__inits."
138               << Counter++;
139           InitSymbol = ES.intern(InitSymString);
140           if (SymbolFlags.count(InitSymbol))
141             continue;
142           SymbolFlags[InitSymbol] =
143               JITSymbolFlags::MaterializationSideEffectsOnly;
144           break;
145         }
146         break;
147       }
148     }
149   }
150 
151   return std::make_pair(std::move(SymbolFlags), std::move(InitSymbol));
152 }
153 
154 } // End namespace orc.
155 } // End namespace llvm.
156