1 //===- RuntimeDyld.h - Run-time dynamic linker for MC-JIT -------*- 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 // Interface for the runtime dynamic linker facilities of the MC-JIT.
10 //
11 //===----------------------------------------------------------------------===//
12 
13 #ifndef LLVM_EXECUTIONENGINE_RUNTIMEDYLD_H
14 #define LLVM_EXECUTIONENGINE_RUNTIMEDYLD_H
15 
16 #include "llvm/ADT/FunctionExtras.h"
17 #include "llvm/ADT/STLExtras.h"
18 #include "llvm/ADT/StringRef.h"
19 #include "llvm/DebugInfo/DIContext.h"
20 #include "llvm/ExecutionEngine/JITSymbol.h"
21 #include "llvm/Object/ObjectFile.h"
22 #include "llvm/Support/Error.h"
23 #include <algorithm>
24 #include <cassert>
25 #include <cstddef>
26 #include <cstdint>
27 #include <map>
28 #include <memory>
29 #include <string>
30 #include <system_error>
31 
32 namespace llvm {
33 
34 namespace object {
35 
36 template <typename T> class OwningBinary;
37 
38 } // end namespace object
39 
40 /// Base class for errors originating in RuntimeDyld, e.g. missing relocation
41 /// support.
42 class RuntimeDyldError : public ErrorInfo<RuntimeDyldError> {
43 public:
44   static char ID;
45 
46   RuntimeDyldError(std::string ErrMsg) : ErrMsg(std::move(ErrMsg)) {}
47 
48   void log(raw_ostream &OS) const override;
49   const std::string &getErrorMessage() const { return ErrMsg; }
50   std::error_code convertToErrorCode() const override;
51 
52 private:
53   std::string ErrMsg;
54 };
55 
56 class RuntimeDyldImpl;
57 
58 class RuntimeDyld {
59 public:
60   // Change the address associated with a section when resolving relocations.
61   // Any relocations already associated with the symbol will be re-resolved.
62   void reassignSectionAddress(unsigned SectionID, uint64_t Addr);
63 
64   using NotifyStubEmittedFunction = std::function<void(
65       StringRef FileName, StringRef SectionName, StringRef SymbolName,
66       unsigned SectionID, uint32_t StubOffset)>;
67 
68   /// Information about the loaded object.
69   class LoadedObjectInfo : public llvm::LoadedObjectInfo {
70     friend class RuntimeDyldImpl;
71 
72   public:
73     using ObjSectionToIDMap = std::map<object::SectionRef, unsigned>;
74 
75     LoadedObjectInfo(RuntimeDyldImpl &RTDyld, ObjSectionToIDMap ObjSecToIDMap)
76         : RTDyld(RTDyld), ObjSecToIDMap(std::move(ObjSecToIDMap)) {}
77 
78     virtual object::OwningBinary<object::ObjectFile>
79     getObjectForDebug(const object::ObjectFile &Obj) const = 0;
80 
81     uint64_t
82     getSectionLoadAddress(const object::SectionRef &Sec) const override;
83 
84   protected:
85     virtual void anchor();
86 
87     RuntimeDyldImpl &RTDyld;
88     ObjSectionToIDMap ObjSecToIDMap;
89   };
90 
91   /// Memory Management.
92   class MemoryManager {
93     friend class RuntimeDyld;
94 
95   public:
96     MemoryManager() = default;
97     virtual ~MemoryManager() = default;
98 
99     /// Allocate a memory block of (at least) the given size suitable for
100     /// executable code. The SectionID is a unique identifier assigned by the
101     /// RuntimeDyld instance, and optionally recorded by the memory manager to
102     /// access a loaded section.
103     virtual uint8_t *allocateCodeSection(uintptr_t Size, unsigned Alignment,
104                                          unsigned SectionID,
105                                          StringRef SectionName) = 0;
106 
107     /// Allocate a memory block of (at least) the given size suitable for data.
108     /// The SectionID is a unique identifier assigned by the JIT engine, and
109     /// optionally recorded by the memory manager to access a loaded section.
110     virtual uint8_t *allocateDataSection(uintptr_t Size, unsigned Alignment,
111                                          unsigned SectionID,
112                                          StringRef SectionName,
113                                          bool IsReadOnly) = 0;
114 
115     /// An allocated TLS section
116     struct TLSSection {
117       /// The pointer to the initialization image
118       uint8_t *InitializationImage;
119       /// The TLS offset
120       intptr_t Offset;
121     };
122 
123     /// Allocate a memory block of (at least) the given size to be used for
124     /// thread-local storage (TLS).
125     virtual TLSSection allocateTLSSection(uintptr_t Size, unsigned Alignment,
126                                           unsigned SectionID,
127                                           StringRef SectionName);
128 
129     /// Inform the memory manager about the total amount of memory required to
130     /// allocate all sections to be loaded:
131     /// \p CodeSize - the total size of all code sections
132     /// \p DataSizeRO - the total size of all read-only data sections
133     /// \p DataSizeRW - the total size of all read-write data sections
134     ///
135     /// Note that by default the callback is disabled. To enable it
136     /// redefine the method needsToReserveAllocationSpace to return true.
137     virtual void reserveAllocationSpace(uintptr_t CodeSize, Align CodeAlign,
138                                         uintptr_t RODataSize, Align RODataAlign,
139                                         uintptr_t RWDataSize,
140                                         Align RWDataAlign) {}
141 
142     /// Override to return true to enable the reserveAllocationSpace callback.
143     virtual bool needsToReserveAllocationSpace() { return false; }
144 
145     /// Override to return false to tell LLVM no stub space will be needed.
146     /// This requires some guarantees depending on architecuture, but when
147     /// you know what you are doing it saves allocated space.
148     virtual bool allowStubAllocation() const { return true; }
149 
150     /// Register the EH frames with the runtime so that c++ exceptions work.
151     ///
152     /// \p Addr parameter provides the local address of the EH frame section
153     /// data, while \p LoadAddr provides the address of the data in the target
154     /// address space.  If the section has not been remapped (which will usually
155     /// be the case for local execution) these two values will be the same.
156     virtual void registerEHFrames(uint8_t *Addr, uint64_t LoadAddr,
157                                   size_t Size) = 0;
158     virtual void deregisterEHFrames() = 0;
159 
160     /// This method is called when object loading is complete and section page
161     /// permissions can be applied.  It is up to the memory manager implementation
162     /// to decide whether or not to act on this method.  The memory manager will
163     /// typically allocate all sections as read-write and then apply specific
164     /// permissions when this method is called.  Code sections cannot be executed
165     /// until this function has been called.  In addition, any cache coherency
166     /// operations needed to reliably use the memory are also performed.
167     ///
168     /// Returns true if an error occurred, false otherwise.
169     virtual bool finalizeMemory(std::string *ErrMsg = nullptr) = 0;
170 
171     /// This method is called after an object has been loaded into memory but
172     /// before relocations are applied to the loaded sections.
173     ///
174     /// Memory managers which are preparing code for execution in an external
175     /// address space can use this call to remap the section addresses for the
176     /// newly loaded object.
177     ///
178     /// For clients that do not need access to an ExecutionEngine instance this
179     /// method should be preferred to its cousin
180     /// MCJITMemoryManager::notifyObjectLoaded as this method is compatible with
181     /// ORC JIT stacks.
182     virtual void notifyObjectLoaded(RuntimeDyld &RTDyld,
183                                     const object::ObjectFile &Obj) {}
184 
185   private:
186     virtual void anchor();
187 
188     bool FinalizationLocked = false;
189   };
190 
191   /// Construct a RuntimeDyld instance.
192   RuntimeDyld(MemoryManager &MemMgr, JITSymbolResolver &Resolver);
193   RuntimeDyld(const RuntimeDyld &) = delete;
194   RuntimeDyld &operator=(const RuntimeDyld &) = delete;
195   ~RuntimeDyld();
196 
197   /// Add the referenced object file to the list of objects to be loaded and
198   /// relocated.
199   std::unique_ptr<LoadedObjectInfo> loadObject(const object::ObjectFile &O);
200 
201   /// Get the address of our local copy of the symbol. This may or may not
202   /// be the address used for relocation (clients can copy the data around
203   /// and resolve relocatons based on where they put it).
204   void *getSymbolLocalAddress(StringRef Name) const;
205 
206   /// Get the section ID for the section containing the given symbol.
207   unsigned getSymbolSectionID(StringRef Name) const;
208 
209   /// Get the target address and flags for the named symbol.
210   /// This address is the one used for relocation.
211   JITEvaluatedSymbol getSymbol(StringRef Name) const;
212 
213   /// Returns a copy of the symbol table. This can be used by on-finalized
214   /// callbacks to extract the symbol table before throwing away the
215   /// RuntimeDyld instance. Because the map keys (StringRefs) are backed by
216   /// strings inside the RuntimeDyld instance, the map should be processed
217   /// before the RuntimeDyld instance is discarded.
218   std::map<StringRef, JITEvaluatedSymbol> getSymbolTable() const;
219 
220   /// Resolve the relocations for all symbols we currently know about.
221   void resolveRelocations();
222 
223   /// Map a section to its target address space value.
224   /// Map the address of a JIT section as returned from the memory manager
225   /// to the address in the target process as the running code will see it.
226   /// This is the address which will be used for relocation resolution.
227   void mapSectionAddress(const void *LocalAddress, uint64_t TargetAddress);
228 
229   /// Returns the section's working memory.
230   StringRef getSectionContent(unsigned SectionID) const;
231 
232   /// If the section was loaded, return the section's load address,
233   /// otherwise return std::nullopt.
234   uint64_t getSectionLoadAddress(unsigned SectionID) const;
235 
236   /// Set the NotifyStubEmitted callback. This is used for debugging
237   /// purposes. A callback is made for each stub that is generated.
238   void setNotifyStubEmitted(NotifyStubEmittedFunction NotifyStubEmitted) {
239     this->NotifyStubEmitted = std::move(NotifyStubEmitted);
240   }
241 
242   /// Register any EH frame sections that have been loaded but not previously
243   /// registered with the memory manager.  Note, RuntimeDyld is responsible
244   /// for identifying the EH frame and calling the memory manager with the
245   /// EH frame section data.  However, the memory manager itself will handle
246   /// the actual target-specific EH frame registration.
247   void registerEHFrames();
248 
249   void deregisterEHFrames();
250 
251   bool hasError();
252   StringRef getErrorString();
253 
254   /// By default, only sections that are "required for execution" are passed to
255   /// the RTDyldMemoryManager, and other sections are discarded. Passing 'true'
256   /// to this method will cause RuntimeDyld to pass all sections to its
257   /// memory manager regardless of whether they are "required to execute" in the
258   /// usual sense. This is useful for inspecting metadata sections that may not
259   /// contain relocations, E.g. Debug info, stackmaps.
260   ///
261   /// Must be called before the first object file is loaded.
262   void setProcessAllSections(bool ProcessAllSections) {
263     assert(!Dyld && "setProcessAllSections must be called before loadObject.");
264     this->ProcessAllSections = ProcessAllSections;
265   }
266 
267   /// Perform all actions needed to make the code owned by this RuntimeDyld
268   /// instance executable:
269   ///
270   /// 1) Apply relocations.
271   /// 2) Register EH frames.
272   /// 3) Update memory permissions*.
273   ///
274   /// * Finalization is potentially recursive**, and the 3rd step will only be
275   ///   applied by the outermost call to finalize. This allows different
276   ///   RuntimeDyld instances to share a memory manager without the innermost
277   ///   finalization locking the memory and causing relocation fixup errors in
278   ///   outer instances.
279   ///
280   /// ** Recursive finalization occurs when one RuntimeDyld instances needs the
281   ///   address of a symbol owned by some other instance in order to apply
282   ///   relocations.
283   ///
284   void finalizeWithMemoryManagerLocking();
285 
286 private:
287   friend void jitLinkForORC(
288       object::OwningBinary<object::ObjectFile> O,
289       RuntimeDyld::MemoryManager &MemMgr, JITSymbolResolver &Resolver,
290       bool ProcessAllSections,
291       unique_function<Error(const object::ObjectFile &Obj, LoadedObjectInfo &,
292                             std::map<StringRef, JITEvaluatedSymbol>)>
293           OnLoaded,
294       unique_function<void(object::OwningBinary<object::ObjectFile> O,
295                            std::unique_ptr<LoadedObjectInfo>, Error)>
296           OnEmitted);
297 
298   // RuntimeDyldImpl is the actual class. RuntimeDyld is just the public
299   // interface.
300   std::unique_ptr<RuntimeDyldImpl> Dyld;
301   MemoryManager &MemMgr;
302   JITSymbolResolver &Resolver;
303   bool ProcessAllSections;
304   NotifyStubEmittedFunction NotifyStubEmitted;
305 };
306 
307 // Asynchronous JIT link for ORC.
308 //
309 // Warning: This API is experimental and probably should not be used by anyone
310 // but ORC's RTDyldObjectLinkingLayer2. Internally it constructs a RuntimeDyld
311 // instance and uses continuation passing to perform the fix-up and finalize
312 // steps asynchronously.
313 void jitLinkForORC(
314     object::OwningBinary<object::ObjectFile> O,
315     RuntimeDyld::MemoryManager &MemMgr, JITSymbolResolver &Resolver,
316     bool ProcessAllSections,
317     unique_function<Error(const object::ObjectFile &Obj,
318                           RuntimeDyld::LoadedObjectInfo &,
319                           std::map<StringRef, JITEvaluatedSymbol>)>
320         OnLoaded,
321     unique_function<void(object::OwningBinary<object::ObjectFile>,
322                          std::unique_ptr<RuntimeDyld::LoadedObjectInfo>, Error)>
323         OnEmitted);
324 
325 } // end namespace llvm
326 
327 #endif // LLVM_EXECUTIONENGINE_RUNTIMEDYLD_H
328