LLVM  15.0.0git
GDBRegistrationListener.cpp
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1 //===----- GDBRegistrationListener.cpp - Registers objects with GDB -------===//
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 
10 #include "llvm/ADT/DenseMap.h"
12 #include "llvm/Object/ObjectFile.h"
13 #include "llvm/Support/Compiler.h"
16 #include "llvm/Support/Mutex.h"
17 #include <mutex>
18 
19 using namespace llvm;
20 using namespace llvm::object;
21 
22 // This must be kept in sync with gdb/gdb/jit.h .
23 extern "C" {
24 
25  typedef enum {
29  } jit_actions_t;
30 
31  struct jit_code_entry {
34  const char *symfile_addr;
36  };
37 
38  struct jit_descriptor {
40  // This should be jit_actions_t, but we want to be specific about the
41  // bit-width.
45  };
46 
47  // We put information about the JITed function in this global, which the
48  // debugger reads. Make sure to specify the version statically, because the
49  // debugger checks the version before we can set it during runtime.
51 
52  // Debuggers puts a breakpoint in this function.
53  extern "C" void __jit_debug_register_code();
54 }
55 
56 namespace {
57 
58 // FIXME: lli aims to provide both, RuntimeDyld and JITLink, as the dynamic
59 // loaders for it's JIT implementations. And they both offer debugging via the
60 // GDB JIT interface, which builds on the two well-known symbol names below.
61 // As these symbols must be unique accross the linked executable, we can only
62 // define them in one of the libraries and make the other depend on it.
63 // OrcTargetProcess is a minimal stub for embedding a JIT client in remote
64 // executors. For the moment it seems reasonable to have the definition there
65 // and let ExecutionEngine depend on it, until we find a better solution.
66 //
67 LLVM_ATTRIBUTE_USED void requiredSymbolDefinitionsFromOrcTargetProcess() {
68  errs() << (void *)&__jit_debug_register_code
69  << (void *)&__jit_debug_descriptor;
70 }
71 
72 struct RegisteredObjectInfo {
73  RegisteredObjectInfo() = default;
74 
75  RegisteredObjectInfo(std::size_t Size, jit_code_entry *Entry,
77  : Size(Size), Entry(Entry), Obj(std::move(Obj)) {}
78 
79  std::size_t Size;
80  jit_code_entry *Entry;
82 };
83 
84 // Buffer for an in-memory object file in executable memory
86  RegisteredObjectBufferMap;
87 
88 /// Global access point for the JIT debugging interface designed for use with a
89 /// singleton toolbox. Handles thread-safe registration and deregistration of
90 /// object files that are in executable memory managed by the client of this
91 /// class.
92 class GDBJITRegistrationListener : public JITEventListener {
93  /// Lock used to serialize all jit registration events, since they
94  /// modify global variables.
95  ///
96  /// Only a single instance of GDBJITRegistrationListener is ever created,
97  /// and so the lock can be a member variable of that instance. This ensures
98  /// destructors are run in the correct order.
99  sys::Mutex JITDebugLock;
100 
101  /// A map of in-memory object files that have been registered with the
102  /// JIT interface.
103  RegisteredObjectBufferMap ObjectBufferMap;
104 
105  /// Instantiates the JIT service.
106  GDBJITRegistrationListener() = default;
107 
108  /// Unregisters each object that was previously registered and releases all
109  /// internal resources.
110  ~GDBJITRegistrationListener() override;
111 
112 public:
113  static GDBJITRegistrationListener &instance() {
114  static GDBJITRegistrationListener Instance;
115  return Instance;
116  }
117 
118  /// Creates an entry in the JIT registry for the buffer @p Object,
119  /// which must contain an object file in executable memory with any
120  /// debug information for the debugger.
121  void notifyObjectLoaded(ObjectKey K, const ObjectFile &Obj,
122  const RuntimeDyld::LoadedObjectInfo &L) override;
123 
124  /// Removes the internal registration of @p Object, and
125  /// frees associated resources.
126  /// Returns true if @p Object was found in ObjectBufferMap.
127  void notifyFreeingObject(ObjectKey K) override;
128 
129 private:
130  /// Deregister the debug info for the given object file from the debugger
131  /// and delete any temporary copies. This private method does not remove
132  /// the function from Map so that it can be called while iterating over Map.
133  void deregisterObjectInternal(RegisteredObjectBufferMap::iterator I);
134 };
135 
136 /// Do the registration.
137 void NotifyDebugger(jit_code_entry* JITCodeEntry) {
139 
140  // Insert this entry at the head of the list.
141  JITCodeEntry->prev_entry = nullptr;
143  JITCodeEntry->next_entry = NextEntry;
144  if (NextEntry) {
145  NextEntry->prev_entry = JITCodeEntry;
146  }
147  __jit_debug_descriptor.first_entry = JITCodeEntry;
148  __jit_debug_descriptor.relevant_entry = JITCodeEntry;
150 }
151 
152 GDBJITRegistrationListener::~GDBJITRegistrationListener() {
153  // Free all registered object files.
154  std::lock_guard<llvm::sys::Mutex> locked(JITDebugLock);
155  for (RegisteredObjectBufferMap::iterator I = ObjectBufferMap.begin(),
156  E = ObjectBufferMap.end();
157  I != E; ++I) {
158  // Call the private method that doesn't update the map so our iterator
159  // doesn't break.
160  deregisterObjectInternal(I);
161  }
162  ObjectBufferMap.clear();
163 }
164 
165 void GDBJITRegistrationListener::notifyObjectLoaded(
166  ObjectKey K, const ObjectFile &Obj,
168 
170 
171  // Bail out if debug objects aren't supported.
172  if (!DebugObj.getBinary())
173  return;
174 
175  const char *Buffer = DebugObj.getBinary()->getMemoryBufferRef().getBufferStart();
176  size_t Size = DebugObj.getBinary()->getMemoryBufferRef().getBufferSize();
177 
178  std::lock_guard<llvm::sys::Mutex> locked(JITDebugLock);
179  assert(ObjectBufferMap.find(K) == ObjectBufferMap.end() &&
180  "Second attempt to perform debug registration.");
181  jit_code_entry* JITCodeEntry = new jit_code_entry();
182 
183  if (!JITCodeEntry) {
185  "Allocation failed when registering a JIT entry!\n");
186  } else {
187  JITCodeEntry->symfile_addr = Buffer;
188  JITCodeEntry->symfile_size = Size;
189 
190  ObjectBufferMap[K] =
191  RegisteredObjectInfo(Size, JITCodeEntry, std::move(DebugObj));
192  NotifyDebugger(JITCodeEntry);
193  }
194 }
195 
196 void GDBJITRegistrationListener::notifyFreeingObject(ObjectKey K) {
197  std::lock_guard<llvm::sys::Mutex> locked(JITDebugLock);
198  RegisteredObjectBufferMap::iterator I = ObjectBufferMap.find(K);
199 
200  if (I != ObjectBufferMap.end()) {
201  deregisterObjectInternal(I);
202  ObjectBufferMap.erase(I);
203  }
204 }
205 
206 void GDBJITRegistrationListener::deregisterObjectInternal(
207  RegisteredObjectBufferMap::iterator I) {
208 
209  jit_code_entry*& JITCodeEntry = I->second.Entry;
210 
211  // Do the unregistration.
212  {
214 
215  // Remove the jit_code_entry from the linked list.
216  jit_code_entry* PrevEntry = JITCodeEntry->prev_entry;
217  jit_code_entry* NextEntry = JITCodeEntry->next_entry;
218 
219  if (NextEntry) {
220  NextEntry->prev_entry = PrevEntry;
221  }
222  if (PrevEntry) {
223  PrevEntry->next_entry = NextEntry;
224  }
225  else {
226  assert(__jit_debug_descriptor.first_entry == JITCodeEntry);
228  }
229 
230  // Tell the debugger which entry we removed, and unregister the code.
231  __jit_debug_descriptor.relevant_entry = JITCodeEntry;
233  }
234 
235  delete JITCodeEntry;
236  JITCodeEntry = nullptr;
237 }
238 
239 } // end namespace
240 
241 namespace llvm {
242 
244  return &GDBJITRegistrationListener::instance();
245 }
246 
247 } // namespace llvm
248 
250 {
252 }
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compiles ldr LCPI1_0 ldr ldr mov lsr tst moveq r1 ldr LCPI1_1 and r0 bx lr It would be better to do something like to fold the shift into the conditional move
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Definition: DenseMap.h:716
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Definition: ObjectFile.h:228
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Information about the loaded object.
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