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"
17 #include "llvm/Support/Mutex.h"
18 #include <mutex>
19 
20 using namespace llvm;
21 using namespace llvm::object;
22 
23 // This must be kept in sync with gdb/gdb/jit.h .
24 extern "C" {
25 
26  typedef enum {
30  } jit_actions_t;
31 
32  struct jit_code_entry {
35  const char *symfile_addr;
37  };
38 
39  struct jit_descriptor {
41  // This should be jit_actions_t, but we want to be specific about the
42  // bit-width.
46  };
47 
48  // We put information about the JITed function in this global, which the
49  // debugger reads. Make sure to specify the version statically, because the
50  // debugger checks the version before we can set it during runtime.
52 
53  // Debuggers puts a breakpoint in this function.
54  extern "C" void __jit_debug_register_code();
55 }
56 
57 namespace {
58 
59 // FIXME: lli aims to provide both, RuntimeDyld and JITLink, as the dynamic
60 // loaders for it's JIT implementations. And they both offer debugging via the
61 // GDB JIT interface, which builds on the two well-known symbol names below.
62 // As these symbols must be unique accross the linked executable, we can only
63 // define them in one of the libraries and make the other depend on it.
64 // OrcTargetProcess is a minimal stub for embedding a JIT client in remote
65 // executors. For the moment it seems reasonable to have the definition there
66 // and let ExecutionEngine depend on it, until we find a better solution.
67 //
68 LLVM_ATTRIBUTE_USED void requiredSymbolDefinitionsFromOrcTargetProcess() {
69  errs() << (void *)&__jit_debug_register_code
70  << (void *)&__jit_debug_descriptor;
71 }
72 
73 struct RegisteredObjectInfo {
74  RegisteredObjectInfo() = default;
75 
76  RegisteredObjectInfo(std::size_t Size, jit_code_entry *Entry,
78  : Size(Size), Entry(Entry), Obj(std::move(Obj)) {}
79 
80  std::size_t Size;
81  jit_code_entry *Entry;
83 };
84 
85 // Buffer for an in-memory object file in executable memory
87  RegisteredObjectBufferMap;
88 
89 /// Global access point for the JIT debugging interface designed for use with a
90 /// singleton toolbox. Handles thread-safe registration and deregistration of
91 /// object files that are in executable memory managed by the client of this
92 /// class.
93 class GDBJITRegistrationListener : public JITEventListener {
94  /// A map of in-memory object files that have been registered with the
95  /// JIT interface.
96  RegisteredObjectBufferMap ObjectBufferMap;
97 
98 public:
99  /// Instantiates the JIT service.
100  GDBJITRegistrationListener() = default;
101 
102  /// Unregisters each object that was previously registered and releases all
103  /// internal resources.
104  ~GDBJITRegistrationListener() override;
105 
106  /// Creates an entry in the JIT registry for the buffer @p Object,
107  /// which must contain an object file in executable memory with any
108  /// debug information for the debugger.
109  void notifyObjectLoaded(ObjectKey K, const ObjectFile &Obj,
110  const RuntimeDyld::LoadedObjectInfo &L) override;
111 
112  /// Removes the internal registration of @p Object, and
113  /// frees associated resources.
114  /// Returns true if @p Object was found in ObjectBufferMap.
115  void notifyFreeingObject(ObjectKey K) override;
116 
117 private:
118  /// Deregister the debug info for the given object file from the debugger
119  /// and delete any temporary copies. This private method does not remove
120  /// the function from Map so that it can be called while iterating over Map.
121  void deregisterObjectInternal(RegisteredObjectBufferMap::iterator I);
122 };
123 
124 /// Lock used to serialize all jit registration events, since they
125 /// modify global variables.
127 
128 /// Do the registration.
129 void NotifyDebugger(jit_code_entry* JITCodeEntry) {
131 
132  // Insert this entry at the head of the list.
133  JITCodeEntry->prev_entry = nullptr;
135  JITCodeEntry->next_entry = NextEntry;
136  if (NextEntry) {
137  NextEntry->prev_entry = JITCodeEntry;
138  }
139  __jit_debug_descriptor.first_entry = JITCodeEntry;
140  __jit_debug_descriptor.relevant_entry = JITCodeEntry;
142 }
143 
144 GDBJITRegistrationListener::~GDBJITRegistrationListener() {
145  // Free all registered object files.
146  std::lock_guard<llvm::sys::Mutex> locked(*JITDebugLock);
147  for (RegisteredObjectBufferMap::iterator I = ObjectBufferMap.begin(),
148  E = ObjectBufferMap.end();
149  I != E; ++I) {
150  // Call the private method that doesn't update the map so our iterator
151  // doesn't break.
152  deregisterObjectInternal(I);
153  }
154  ObjectBufferMap.clear();
155 }
156 
157 void GDBJITRegistrationListener::notifyObjectLoaded(
158  ObjectKey K, const ObjectFile &Obj,
160 
162 
163  // Bail out if debug objects aren't supported.
164  if (!DebugObj.getBinary())
165  return;
166 
167  const char *Buffer = DebugObj.getBinary()->getMemoryBufferRef().getBufferStart();
168  size_t Size = DebugObj.getBinary()->getMemoryBufferRef().getBufferSize();
169 
170  std::lock_guard<llvm::sys::Mutex> locked(*JITDebugLock);
171  assert(ObjectBufferMap.find(K) == ObjectBufferMap.end() &&
172  "Second attempt to perform debug registration.");
173  jit_code_entry* JITCodeEntry = new jit_code_entry();
174 
175  if (!JITCodeEntry) {
177  "Allocation failed when registering a JIT entry!\n");
178  } else {
179  JITCodeEntry->symfile_addr = Buffer;
180  JITCodeEntry->symfile_size = Size;
181 
182  ObjectBufferMap[K] =
183  RegisteredObjectInfo(Size, JITCodeEntry, std::move(DebugObj));
184  NotifyDebugger(JITCodeEntry);
185  }
186 }
187 
188 void GDBJITRegistrationListener::notifyFreeingObject(ObjectKey K) {
189  std::lock_guard<llvm::sys::Mutex> locked(*JITDebugLock);
190  RegisteredObjectBufferMap::iterator I = ObjectBufferMap.find(K);
191 
192  if (I != ObjectBufferMap.end()) {
193  deregisterObjectInternal(I);
194  ObjectBufferMap.erase(I);
195  }
196 }
197 
198 void GDBJITRegistrationListener::deregisterObjectInternal(
199  RegisteredObjectBufferMap::iterator I) {
200 
201  jit_code_entry*& JITCodeEntry = I->second.Entry;
202 
203  // Do the unregistration.
204  {
206 
207  // Remove the jit_code_entry from the linked list.
208  jit_code_entry* PrevEntry = JITCodeEntry->prev_entry;
209  jit_code_entry* NextEntry = JITCodeEntry->next_entry;
210 
211  if (NextEntry) {
212  NextEntry->prev_entry = PrevEntry;
213  }
214  if (PrevEntry) {
215  PrevEntry->next_entry = NextEntry;
216  }
217  else {
218  assert(__jit_debug_descriptor.first_entry == JITCodeEntry);
220  }
221 
222  // Tell the debugger which entry we removed, and unregister the code.
223  __jit_debug_descriptor.relevant_entry = JITCodeEntry;
225  }
226 
227  delete JITCodeEntry;
228  JITCodeEntry = nullptr;
229 }
230 
232 
233 } // end namespace
234 
235 namespace llvm {
236 
238  return &*GDBRegListener;
239 }
240 
241 } // namespace llvm
242 
244 {
246 }
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Definition: FileCheck.h:77
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Definition: GDBRegistrationListener.cpp:44
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Definition: MemoryBufferRef.h:35
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Definition: GDBRegistrationListener.cpp:40
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Definition: MemoryBufferRef.h:37
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Definition: GDBRegistrationListener.cpp:27
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Report a serious error, calling any installed error handler.
Definition: Error.cpp:143
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const char * symfile_addr
Definition: GDBRegistrationListener.cpp:35
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Definition: GDBRegistrationListener.cpp:26
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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
I
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Definition: GDBRegistrationListener.cpp:33
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Definition: Attributes.h:275
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Definition: ObjectFile.h:228
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Definition: RuntimeDyld.h:36
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Information about the loaded object.
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Definition: GDBRegistrationListener.cpp:34
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