1 //===- ExecutionUtils.h - Utilities for executing code in Orc ---*- 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 // Contains utilities for executing code in Orc.
10 //
11 //===----------------------------------------------------------------------===//
12 
13 #ifndef LLVM_EXECUTIONENGINE_ORC_EXECUTIONUTILS_H
14 #define LLVM_EXECUTIONENGINE_ORC_EXECUTIONUTILS_H
15 
16 #include "llvm/ADT/StringMap.h"
17 #include "llvm/ADT/iterator_range.h"
18 #include "llvm/ExecutionEngine/JITSymbol.h"
19 #include "llvm/ExecutionEngine/Orc/Core.h"
20 #include "llvm/ExecutionEngine/Orc/Mangling.h"
21 #include "llvm/ExecutionEngine/Orc/Shared/OrcError.h"
22 #include "llvm/ExecutionEngine/RuntimeDyld.h"
23 #include "llvm/Object/Archive.h"
24 #include "llvm/Support/DynamicLibrary.h"
25 #include <algorithm>
26 #include <cstdint>
27 #include <utility>
28 #include <vector>
29 
30 namespace llvm {
31 
32 class ConstantArray;
33 class GlobalVariable;
34 class Function;
35 class Module;
36 class TargetMachine;
37 class Value;
38 
39 namespace orc {
40 
41 class ObjectLayer;
42 
43 /// This iterator provides a convenient way to iterate over the elements
44 ///        of an llvm.global_ctors/llvm.global_dtors instance.
45 ///
46 ///   The easiest way to get hold of instances of this class is to use the
47 /// getConstructors/getDestructors functions.
48 class CtorDtorIterator {
49 public:
50   /// Accessor for an element of the global_ctors/global_dtors array.
51   ///
52   ///   This class provides a read-only view of the element with any casts on
53   /// the function stripped away.
54   struct Element {
55     Element(unsigned Priority, Function *Func, Value *Data)
56       : Priority(Priority), Func(Func), Data(Data) {}
57 
58     unsigned Priority;
59     Function *Func;
60     Value *Data;
61   };
62 
63   /// Construct an iterator instance. If End is true then this iterator
64   ///        acts as the end of the range, otherwise it is the beginning.
65   CtorDtorIterator(const GlobalVariable *GV, bool End);
66 
67   /// Test iterators for equality.
68   bool operator==(const CtorDtorIterator &Other) const;
69 
70   /// Test iterators for inequality.
71   bool operator!=(const CtorDtorIterator &Other) const;
72 
73   /// Pre-increment iterator.
74   CtorDtorIterator& operator++();
75 
76   /// Post-increment iterator.
77   CtorDtorIterator operator++(int);
78 
79   /// Dereference iterator. The resulting value provides a read-only view
80   ///        of this element of the global_ctors/global_dtors list.
81   Element operator*() const;
82 
83 private:
84   const ConstantArray *InitList;
85   unsigned I;
86 };
87 
88 /// Create an iterator range over the entries of the llvm.global_ctors
89 ///        array.
90 iterator_range<CtorDtorIterator> getConstructors(const Module &M);
91 
92 /// Create an iterator range over the entries of the llvm.global_ctors
93 ///        array.
94 iterator_range<CtorDtorIterator> getDestructors(const Module &M);
95 
96 /// This iterator provides a convenient way to iterate over GlobalValues that
97 /// have initialization effects.
98 class StaticInitGVIterator {
99 public:
100   StaticInitGVIterator() = default;
101 
102   StaticInitGVIterator(Module &M)
103       : I(M.global_values().begin()), E(M.global_values().end()),
104         ObjFmt(Triple(M.getTargetTriple()).getObjectFormat()) {
105     if (I != E) {
106       if (!isStaticInitGlobal(*I))
107         moveToNextStaticInitGlobal();
108     } else
109       I = E = Module::global_value_iterator();
110   }
111 
112   bool operator==(const StaticInitGVIterator &O) const { return I == O.I; }
113   bool operator!=(const StaticInitGVIterator &O) const { return I != O.I; }
114 
115   StaticInitGVIterator &operator++() {
116     assert(I != E && "Increment past end of range");
117     moveToNextStaticInitGlobal();
118     return *this;
119   }
120 
121   GlobalValue &operator*() { return *I; }
122 
123 private:
124   bool isStaticInitGlobal(GlobalValue &GV);
125   void moveToNextStaticInitGlobal() {
126     ++I;
127     while (I != E && !isStaticInitGlobal(*I))
128       ++I;
129     if (I == E)
130       I = E = Module::global_value_iterator();
131   }
132 
133   Module::global_value_iterator I, E;
134   Triple::ObjectFormatType ObjFmt;
135 };
136 
137 /// Create an iterator range over the GlobalValues that contribute to static
138 /// initialization.
139 inline iterator_range<StaticInitGVIterator> getStaticInitGVs(Module &M) {
140   return make_range(StaticInitGVIterator(M), StaticInitGVIterator());
141 }
142 
143 class CtorDtorRunner {
144 public:
145   CtorDtorRunner(JITDylib &JD) : JD(JD) {}
146   void add(iterator_range<CtorDtorIterator> CtorDtors);
147   Error run();
148 
149 private:
150   using CtorDtorList = std::vector<SymbolStringPtr>;
151   using CtorDtorPriorityMap = std::map<unsigned, CtorDtorList>;
152 
153   JITDylib &JD;
154   CtorDtorPriorityMap CtorDtorsByPriority;
155 };
156 
157 /// Support class for static dtor execution. For hosted (in-process) JITs
158 ///        only!
159 ///
160 ///   If a __cxa_atexit function isn't found C++ programs that use static
161 /// destructors will fail to link. However, we don't want to use the host
162 /// process's __cxa_atexit, because it will schedule JIT'd destructors to run
163 /// after the JIT has been torn down, which is no good. This class makes it easy
164 /// to override __cxa_atexit (and the related __dso_handle).
165 ///
166 ///   To use, clients should manually call searchOverrides from their symbol
167 /// resolver. This should generally be done after attempting symbol resolution
168 /// inside the JIT, but before searching the host process's symbol table. When
169 /// the client determines that destructors should be run (generally at JIT
170 /// teardown or after a return from main), the runDestructors method should be
171 /// called.
172 class LocalCXXRuntimeOverridesBase {
173 public:
174   /// Run any destructors recorded by the overriden __cxa_atexit function
175   /// (CXAAtExitOverride).
176   void runDestructors();
177 
178 protected:
179   template <typename PtrTy> JITTargetAddress toTargetAddress(PtrTy *P) {
180     return static_cast<JITTargetAddress>(reinterpret_cast<uintptr_t>(P));
181   }
182 
183   using DestructorPtr = void (*)(void *);
184   using CXXDestructorDataPair = std::pair<DestructorPtr, void *>;
185   using CXXDestructorDataPairList = std::vector<CXXDestructorDataPair>;
186   CXXDestructorDataPairList DSOHandleOverride;
187   static int CXAAtExitOverride(DestructorPtr Destructor, void *Arg,
188                                void *DSOHandle);
189 };
190 
191 class LocalCXXRuntimeOverrides : public LocalCXXRuntimeOverridesBase {
192 public:
193   Error enable(JITDylib &JD, MangleAndInterner &Mangler);
194 };
195 
196 /// An interface for Itanium __cxa_atexit interposer implementations.
197 class ItaniumCXAAtExitSupport {
198 public:
199   struct AtExitRecord {
200     void (*F)(void *);
201     void *Ctx;
202   };
203 
204   void registerAtExit(void (*F)(void *), void *Ctx, void *DSOHandle);
205   void runAtExits(void *DSOHandle);
206 
207 private:
208   std::mutex AtExitsMutex;
209   DenseMap<void *, std::vector<AtExitRecord>> AtExitRecords;
210 };
211 
212 /// A utility class to expose symbols found via dlsym to the JIT.
213 ///
214 /// If an instance of this class is attached to a JITDylib as a fallback
215 /// definition generator, then any symbol found in the given DynamicLibrary that
216 /// passes the 'Allow' predicate will be added to the JITDylib.
217 class DynamicLibrarySearchGenerator : public DefinitionGenerator {
218 public:
219   using SymbolPredicate = std::function<bool(const SymbolStringPtr &)>;
220 
221   /// Create a DynamicLibrarySearchGenerator that searches for symbols in the
222   /// given sys::DynamicLibrary.
223   ///
224   /// If the Allow predicate is given then only symbols matching the predicate
225   /// will be searched for. If the predicate is not given then all symbols will
226   /// be searched for.
227   DynamicLibrarySearchGenerator(sys::DynamicLibrary Dylib, char GlobalPrefix,
228                                 SymbolPredicate Allow = SymbolPredicate());
229 
230   /// Permanently loads the library at the given path and, on success, returns
231   /// a DynamicLibrarySearchGenerator that will search it for symbol definitions
232   /// in the library. On failure returns the reason the library failed to load.
233   static Expected<std::unique_ptr<DynamicLibrarySearchGenerator>>
234   Load(const char *FileName, char GlobalPrefix,
235        SymbolPredicate Allow = SymbolPredicate());
236 
237   /// Creates a DynamicLibrarySearchGenerator that searches for symbols in
238   /// the current process.
239   static Expected<std::unique_ptr<DynamicLibrarySearchGenerator>>
240   GetForCurrentProcess(char GlobalPrefix,
241                        SymbolPredicate Allow = SymbolPredicate()) {
242     return Load(nullptr, GlobalPrefix, std::move(Allow));
243   }
244 
245   Error tryToGenerate(LookupState &LS, LookupKind K, JITDylib &JD,
246                       JITDylibLookupFlags JDLookupFlags,
247                       const SymbolLookupSet &Symbols) override;
248 
249 private:
250   sys::DynamicLibrary Dylib;
251   SymbolPredicate Allow;
252   char GlobalPrefix;
253 };
254 
255 /// A utility class to expose symbols from a static library.
256 ///
257 /// If an instance of this class is attached to a JITDylib as a fallback
258 /// definition generator, then any symbol found in the archive will result in
259 /// the containing object being added to the JITDylib.
260 class StaticLibraryDefinitionGenerator : public DefinitionGenerator {
261 public:
262   /// Try to create a StaticLibraryDefinitionGenerator from the given path.
263   ///
264   /// This call will succeed if the file at the given path is a static library
265   /// is a valid archive, otherwise it will return an error.
266   static Expected<std::unique_ptr<StaticLibraryDefinitionGenerator>>
267   Load(ObjectLayer &L, const char *FileName);
268 
269   /// Try to create a StaticLibraryDefinitionGenerator from the given path.
270   ///
271   /// This call will succeed if the file at the given path is a static library
272   /// or a MachO universal binary containing a static library that is compatible
273   /// with the given triple. Otherwise it will return an error.
274   static Expected<std::unique_ptr<StaticLibraryDefinitionGenerator>>
275   Load(ObjectLayer &L, const char *FileName, const Triple &TT);
276 
277   /// Try to create a StaticLibrarySearchGenerator from the given memory buffer.
278   /// This call will succeed if the buffer contains a valid archive, otherwise
279   /// it will return an error.
280   static Expected<std::unique_ptr<StaticLibraryDefinitionGenerator>>
281   Create(ObjectLayer &L, std::unique_ptr<MemoryBuffer> ArchiveBuffer);
282 
283   Error tryToGenerate(LookupState &LS, LookupKind K, JITDylib &JD,
284                       JITDylibLookupFlags JDLookupFlags,
285                       const SymbolLookupSet &Symbols) override;
286 
287 private:
288   StaticLibraryDefinitionGenerator(ObjectLayer &L,
289                                    std::unique_ptr<MemoryBuffer> ArchiveBuffer,
290                                    Error &Err);
291 
292   ObjectLayer &L;
293   std::unique_ptr<MemoryBuffer> ArchiveBuffer;
294   std::unique_ptr<object::Archive> Archive;
295 };
296 
297 } // end namespace orc
298 } // end namespace llvm
299 
300 #endif // LLVM_EXECUTIONENGINE_ORC_EXECUTIONUTILS_H
301