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