1 //===- RuntimeDyld.h - Run-time dynamic linker for MC-JIT -------*- C++ -*-===//
2 //
3 //                     The LLVM Compiler Infrastructure
4 //
5 // This file is distributed under the University of Illinois Open Source
6 // License. See LICENSE.TXT for details.
7 //
8 //===----------------------------------------------------------------------===//
9 //
10 // Interface for the runtime dynamic linker facilities of the MC-JIT.
11 //
12 //===----------------------------------------------------------------------===//
13 
14 #ifndef LLVM_EXECUTIONENGINE_RUNTIMEDYLD_H
15 #define LLVM_EXECUTIONENGINE_RUNTIMEDYLD_H
16 
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 
RuntimeDyldError(std::string ErrMsg)46   RuntimeDyldError(std::string ErrMsg) : ErrMsg(std::move(ErrMsg)) {}
47 
48   void log(raw_ostream &OS) const override;
getErrorMessage()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 RuntimeDyldCheckerImpl;
57 class RuntimeDyldImpl;
58 
59 class RuntimeDyld {
60   friend class RuntimeDyldCheckerImpl;
61 
62 protected:
63   // Change the address associated with a section when resolving relocations.
64   // Any relocations already associated with the symbol will be re-resolved.
65   void reassignSectionAddress(unsigned SectionID, uint64_t Addr);
66 
67 public:
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 
LoadedObjectInfo(RuntimeDyldImpl & RTDyld,ObjSectionToIDMap ObjSecToIDMap)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     /// Inform the memory manager about the total amount of memory required to
116     /// allocate all sections to be loaded:
117     /// \p CodeSize - the total size of all code sections
118     /// \p DataSizeRO - the total size of all read-only data sections
119     /// \p DataSizeRW - the total size of all read-write data sections
120     ///
121     /// Note that by default the callback is disabled. To enable it
122     /// redefine the method needsToReserveAllocationSpace to return true.
reserveAllocationSpace(uintptr_t CodeSize,uint32_t CodeAlign,uintptr_t RODataSize,uint32_t RODataAlign,uintptr_t RWDataSize,uint32_t RWDataAlign)123     virtual void reserveAllocationSpace(uintptr_t CodeSize, uint32_t CodeAlign,
124                                         uintptr_t RODataSize,
125                                         uint32_t RODataAlign,
126                                         uintptr_t RWDataSize,
127                                         uint32_t RWDataAlign) {}
128 
129     /// Override to return true to enable the reserveAllocationSpace callback.
needsToReserveAllocationSpace()130     virtual bool needsToReserveAllocationSpace() { return false; }
131 
132     /// Register the EH frames with the runtime so that c++ exceptions work.
133     ///
134     /// \p Addr parameter provides the local address of the EH frame section
135     /// data, while \p LoadAddr provides the address of the data in the target
136     /// address space.  If the section has not been remapped (which will usually
137     /// be the case for local execution) these two values will be the same.
138     virtual void registerEHFrames(uint8_t *Addr, uint64_t LoadAddr,
139                                   size_t Size) = 0;
140     virtual void deregisterEHFrames() = 0;
141 
142     /// This method is called when object loading is complete and section page
143     /// permissions can be applied.  It is up to the memory manager implementation
144     /// to decide whether or not to act on this method.  The memory manager will
145     /// typically allocate all sections as read-write and then apply specific
146     /// permissions when this method is called.  Code sections cannot be executed
147     /// until this function has been called.  In addition, any cache coherency
148     /// operations needed to reliably use the memory are also performed.
149     ///
150     /// Returns true if an error occurred, false otherwise.
151     virtual bool finalizeMemory(std::string *ErrMsg = nullptr) = 0;
152 
153     /// This method is called after an object has been loaded into memory but
154     /// before relocations are applied to the loaded sections.
155     ///
156     /// Memory managers which are preparing code for execution in an external
157     /// address space can use this call to remap the section addresses for the
158     /// newly loaded object.
159     ///
160     /// For clients that do not need access to an ExecutionEngine instance this
161     /// method should be preferred to its cousin
162     /// MCJITMemoryManager::notifyObjectLoaded as this method is compatible with
163     /// ORC JIT stacks.
notifyObjectLoaded(RuntimeDyld & RTDyld,const object::ObjectFile & Obj)164     virtual void notifyObjectLoaded(RuntimeDyld &RTDyld,
165                                     const object::ObjectFile &Obj) {}
166 
167   private:
168     virtual void anchor();
169 
170     bool FinalizationLocked = false;
171   };
172 
173   /// Construct a RuntimeDyld instance.
174   RuntimeDyld(MemoryManager &MemMgr, JITSymbolResolver &Resolver);
175   RuntimeDyld(const RuntimeDyld &) = delete;
176   RuntimeDyld &operator=(const RuntimeDyld &) = delete;
177   ~RuntimeDyld();
178 
179   /// Add the referenced object file to the list of objects to be loaded and
180   /// relocated.
181   std::unique_ptr<LoadedObjectInfo> loadObject(const object::ObjectFile &O);
182 
183   /// Get the address of our local copy of the symbol. This may or may not
184   /// be the address used for relocation (clients can copy the data around
185   /// and resolve relocatons based on where they put it).
186   void *getSymbolLocalAddress(StringRef Name) const;
187 
188   /// Get the target address and flags for the named symbol.
189   /// This address is the one used for relocation.
190   JITEvaluatedSymbol getSymbol(StringRef Name) const;
191 
192   /// Returns a copy of the symbol table. This can be used by on-finalized
193   /// callbacks to extract the symbol table before throwing away the
194   /// RuntimeDyld instance. Because the map keys (StringRefs) are backed by
195   /// strings inside the RuntimeDyld instance, the map should be processed
196   /// before the RuntimeDyld instance is discarded.
197   std::map<StringRef, JITEvaluatedSymbol> getSymbolTable() const;
198 
199   /// Resolve the relocations for all symbols we currently know about.
200   void resolveRelocations();
201 
202   /// Map a section to its target address space value.
203   /// Map the address of a JIT section as returned from the memory manager
204   /// to the address in the target process as the running code will see it.
205   /// This is the address which will be used for relocation resolution.
206   void mapSectionAddress(const void *LocalAddress, uint64_t TargetAddress);
207 
208   /// Register any EH frame sections that have been loaded but not previously
209   /// registered with the memory manager.  Note, RuntimeDyld is responsible
210   /// for identifying the EH frame and calling the memory manager with the
211   /// EH frame section data.  However, the memory manager itself will handle
212   /// the actual target-specific EH frame registration.
213   void registerEHFrames();
214 
215   void deregisterEHFrames();
216 
217   bool hasError();
218   StringRef getErrorString();
219 
220   /// By default, only sections that are "required for execution" are passed to
221   /// the RTDyldMemoryManager, and other sections are discarded. Passing 'true'
222   /// to this method will cause RuntimeDyld to pass all sections to its
223   /// memory manager regardless of whether they are "required to execute" in the
224   /// usual sense. This is useful for inspecting metadata sections that may not
225   /// contain relocations, E.g. Debug info, stackmaps.
226   ///
227   /// Must be called before the first object file is loaded.
setProcessAllSections(bool ProcessAllSections)228   void setProcessAllSections(bool ProcessAllSections) {
229     assert(!Dyld && "setProcessAllSections must be called before loadObject.");
230     this->ProcessAllSections = ProcessAllSections;
231   }
232 
233   /// Perform all actions needed to make the code owned by this RuntimeDyld
234   /// instance executable:
235   ///
236   /// 1) Apply relocations.
237   /// 2) Register EH frames.
238   /// 3) Update memory permissions*.
239   ///
240   /// * Finalization is potentially recursive**, and the 3rd step will only be
241   ///   applied by the outermost call to finalize. This allows different
242   ///   RuntimeDyld instances to share a memory manager without the innermost
243   ///   finalization locking the memory and causing relocation fixup errors in
244   ///   outer instances.
245   ///
246   /// ** Recursive finalization occurs when one RuntimeDyld instances needs the
247   ///   address of a symbol owned by some other instance in order to apply
248   ///   relocations.
249   ///
250   void finalizeWithMemoryManagerLocking();
251 
252 private:
253   friend void
254   jitLinkForORC(object::ObjectFile &Obj,
255                 std::unique_ptr<MemoryBuffer> UnderlyingBuffer,
256                 RuntimeDyld::MemoryManager &MemMgr, JITSymbolResolver &Resolver,
257                 bool ProcessAllSections,
258                 std::function<Error(std::unique_ptr<LoadedObjectInfo>,
259                                     std::map<StringRef, JITEvaluatedSymbol>)>
260                     OnLoaded,
261                 std::function<void(Error)> OnEmitted);
262 
263   // RuntimeDyldImpl is the actual class. RuntimeDyld is just the public
264   // interface.
265   std::unique_ptr<RuntimeDyldImpl> Dyld;
266   MemoryManager &MemMgr;
267   JITSymbolResolver &Resolver;
268   bool ProcessAllSections;
269   RuntimeDyldCheckerImpl *Checker;
270 };
271 
272 // Asynchronous JIT link for ORC.
273 //
274 // Warning: This API is experimental and probably should not be used by anyone
275 // but ORC's RTDyldObjectLinkingLayer2. Internally it constructs a RuntimeDyld
276 // instance and uses continuation passing to perform the fix-up and finalize
277 // steps asynchronously.
278 void jitLinkForORC(object::ObjectFile &Obj,
279                    std::unique_ptr<MemoryBuffer> UnderlyingBuffer,
280                    RuntimeDyld::MemoryManager &MemMgr,
281                    JITSymbolResolver &Resolver, bool ProcessAllSections,
282                    std::function<Error(std::unique_ptr<LoadedObjectInfo>,
283                                        std::map<StringRef, JITEvaluatedSymbol>)>
284                        OnLoaded,
285                    std::function<void(Error)> OnEmitted);
286 
287 } // end namespace llvm
288 
289 #endif // LLVM_EXECUTIONENGINE_RUNTIMEDYLD_H
290