1 //===-- GDBRegistrar.cpp - Registers objects with GDB ---------------------===// 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 #include "JITRegistrar.h" 11 #include "llvm/ADT/DenseMap.h" 12 #include "llvm/Support/Compiler.h" 13 #include "llvm/Support/ErrorHandling.h" 14 #include "llvm/Support/Mutex.h" 15 #include "llvm/Support/MutexGuard.h" 16 #include "llvm/Support/ManagedStatic.h" 17 18 using namespace llvm; 19 20 // This must be kept in sync with gdb/gdb/jit.h . 21 extern "C" { 22 23 typedef enum { 24 JIT_NOACTION = 0, 25 JIT_REGISTER_FN, 26 JIT_UNREGISTER_FN 27 } jit_actions_t; 28 29 struct jit_code_entry { 30 struct jit_code_entry *next_entry; 31 struct jit_code_entry *prev_entry; 32 const char *symfile_addr; 33 uint64_t symfile_size; 34 }; 35 36 struct jit_descriptor { 37 uint32_t version; 38 // This should be jit_actions_t, but we want to be specific about the 39 // bit-width. 40 uint32_t action_flag; 41 struct jit_code_entry *relevant_entry; 42 struct jit_code_entry *first_entry; 43 }; 44 45 // We put information about the JITed function in this global, which the 46 // debugger reads. Make sure to specify the version statically, because the 47 // debugger checks the version before we can set it during runtime. 48 struct jit_descriptor __jit_debug_descriptor = { 1, 0, nullptr, nullptr }; 49 50 // Debuggers puts a breakpoint in this function. 51 LLVM_ATTRIBUTE_NOINLINE void __jit_debug_register_code() { 52 // The noinline and the asm prevent calls to this function from being 53 // optimized out. 54 #if !defined(_MSC_VER) 55 asm volatile("":::"memory"); 56 #endif 57 } 58 59 } 60 61 namespace { 62 63 // Buffer for an in-memory object file in executable memory 64 typedef llvm::DenseMap< const char*, 65 std::pair<std::size_t, jit_code_entry*> > 66 RegisteredObjectBufferMap; 67 68 /// Global access point for the JIT debugging interface designed for use with a 69 /// singleton toolbox. Handles thread-safe registration and deregistration of 70 /// object files that are in executable memory managed by the client of this 71 /// class. 72 class GDBJITRegistrar : public JITRegistrar { 73 /// A map of in-memory object files that have been registered with the 74 /// JIT interface. 75 RegisteredObjectBufferMap ObjectBufferMap; 76 77 public: 78 /// Instantiates the JIT service. 79 GDBJITRegistrar() : ObjectBufferMap() {} 80 81 /// Unregisters each object that was previously registered and releases all 82 /// internal resources. 83 virtual ~GDBJITRegistrar(); 84 85 /// Creates an entry in the JIT registry for the buffer @p Object, 86 /// which must contain an object file in executable memory with any 87 /// debug information for the debugger. 88 void registerObject(const ObjectBuffer &Object) override; 89 90 /// Removes the internal registration of @p Object, and 91 /// frees associated resources. 92 /// Returns true if @p Object was found in ObjectBufferMap. 93 bool deregisterObject(const ObjectBuffer &Object) override; 94 95 private: 96 /// Deregister the debug info for the given object file from the debugger 97 /// and delete any temporary copies. This private method does not remove 98 /// the function from Map so that it can be called while iterating over Map. 99 void deregisterObjectInternal(RegisteredObjectBufferMap::iterator I); 100 }; 101 102 /// Lock used to serialize all jit registration events, since they 103 /// modify global variables. 104 llvm::sys::Mutex JITDebugLock; 105 106 /// Do the registration. 107 void NotifyDebugger(jit_code_entry* JITCodeEntry) { 108 __jit_debug_descriptor.action_flag = JIT_REGISTER_FN; 109 110 // Insert this entry at the head of the list. 111 JITCodeEntry->prev_entry = nullptr; 112 jit_code_entry* NextEntry = __jit_debug_descriptor.first_entry; 113 JITCodeEntry->next_entry = NextEntry; 114 if (NextEntry) { 115 NextEntry->prev_entry = JITCodeEntry; 116 } 117 __jit_debug_descriptor.first_entry = JITCodeEntry; 118 __jit_debug_descriptor.relevant_entry = JITCodeEntry; 119 __jit_debug_register_code(); 120 } 121 122 GDBJITRegistrar::~GDBJITRegistrar() { 123 // Free all registered object files. 124 llvm::MutexGuard locked(JITDebugLock); 125 for (RegisteredObjectBufferMap::iterator I = ObjectBufferMap.begin(), E = ObjectBufferMap.end(); 126 I != E; ++I) { 127 // Call the private method that doesn't update the map so our iterator 128 // doesn't break. 129 deregisterObjectInternal(I); 130 } 131 ObjectBufferMap.clear(); 132 } 133 134 void GDBJITRegistrar::registerObject(const ObjectBuffer &Object) { 135 136 const char *Buffer = Object.getBufferStart(); 137 size_t Size = Object.getBufferSize(); 138 139 assert(Buffer && "Attempt to register a null object with a debugger."); 140 llvm::MutexGuard locked(JITDebugLock); 141 assert(ObjectBufferMap.find(Buffer) == ObjectBufferMap.end() && 142 "Second attempt to perform debug registration."); 143 jit_code_entry* JITCodeEntry = new jit_code_entry(); 144 145 if (!JITCodeEntry) { 146 llvm::report_fatal_error( 147 "Allocation failed when registering a JIT entry!\n"); 148 } else { 149 JITCodeEntry->symfile_addr = Buffer; 150 JITCodeEntry->symfile_size = Size; 151 152 ObjectBufferMap[Buffer] = std::make_pair(Size, JITCodeEntry); 153 NotifyDebugger(JITCodeEntry); 154 } 155 } 156 157 bool GDBJITRegistrar::deregisterObject(const ObjectBuffer& Object) { 158 const char *Buffer = Object.getBufferStart(); 159 llvm::MutexGuard locked(JITDebugLock); 160 RegisteredObjectBufferMap::iterator I = ObjectBufferMap.find(Buffer); 161 162 if (I != ObjectBufferMap.end()) { 163 deregisterObjectInternal(I); 164 ObjectBufferMap.erase(I); 165 return true; 166 } 167 return false; 168 } 169 170 void GDBJITRegistrar::deregisterObjectInternal( 171 RegisteredObjectBufferMap::iterator I) { 172 173 jit_code_entry*& JITCodeEntry = I->second.second; 174 175 // Do the unregistration. 176 { 177 __jit_debug_descriptor.action_flag = JIT_UNREGISTER_FN; 178 179 // Remove the jit_code_entry from the linked list. 180 jit_code_entry* PrevEntry = JITCodeEntry->prev_entry; 181 jit_code_entry* NextEntry = JITCodeEntry->next_entry; 182 183 if (NextEntry) { 184 NextEntry->prev_entry = PrevEntry; 185 } 186 if (PrevEntry) { 187 PrevEntry->next_entry = NextEntry; 188 } 189 else { 190 assert(__jit_debug_descriptor.first_entry == JITCodeEntry); 191 __jit_debug_descriptor.first_entry = NextEntry; 192 } 193 194 // Tell the debugger which entry we removed, and unregister the code. 195 __jit_debug_descriptor.relevant_entry = JITCodeEntry; 196 __jit_debug_register_code(); 197 } 198 199 delete JITCodeEntry; 200 JITCodeEntry = nullptr; 201 } 202 203 llvm::ManagedStatic<GDBJITRegistrar> TheRegistrar; 204 205 } // end namespace 206 207 namespace llvm { 208 209 JITRegistrar& JITRegistrar::getGDBRegistrar() { 210 return *TheRegistrar; 211 } 212 213 } // namespace llvm 214
