1//===----- GDBRegistrationListener.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 "llvm/ADT/DenseMap.h"
11#include "llvm/ExecutionEngine/JITEventListener.h"
12#include "llvm/Object/ObjectFile.h"
13#include "llvm/Support/Compiler.h"
14#include "llvm/Support/ErrorHandling.h"
15#include "llvm/Support/ManagedStatic.h"
16#include "llvm/Support/Mutex.h"
17#include "llvm/Support/MutexGuard.h"
18
19using namespace llvm;
20using namespace llvm::object;
21
22// This must be kept in sync with gdb/gdb/jit.h .
23extern "C" {
24
25  typedef enum {
26    JIT_NOACTION = 0,
27    JIT_REGISTER_FN,
28    JIT_UNREGISTER_FN
29  } jit_actions_t;
30
31  struct jit_code_entry {
32    struct jit_code_entry *next_entry;
33    struct jit_code_entry *prev_entry;
34    const char *symfile_addr;
35    uint64_t symfile_size;
36  };
37
38  struct jit_descriptor {
39    uint32_t version;
40    // This should be jit_actions_t, but we want to be specific about the
41    // bit-width.
42    uint32_t action_flag;
43    struct jit_code_entry *relevant_entry;
44    struct jit_code_entry *first_entry;
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.
50  struct jit_descriptor __jit_debug_descriptor = { 1, 0, nullptr, nullptr };
51
52  // Debuggers puts a breakpoint in this function.
53  LLVM_ATTRIBUTE_NOINLINE void __jit_debug_register_code() {
54    // The noinline and the asm prevent calls to this function from being
55    // optimized out.
56#if !defined(_MSC_VER)
57    asm volatile("":::"memory");
58#endif
59  }
60
61}
62
63namespace {
64
65struct RegisteredObjectInfo {
66  RegisteredObjectInfo() {}
67
68  RegisteredObjectInfo(std::size_t Size, jit_code_entry *Entry,
69                       OwningBinary<ObjectFile> Obj)
70    : Size(Size), Entry(Entry), Obj(std::move(Obj)) {}
71
72  RegisteredObjectInfo(RegisteredObjectInfo &&Other)
73    : Size(Other.Size), Entry(Other.Entry), Obj(std::move(Other.Obj)) {}
74
75  RegisteredObjectInfo& operator=(RegisteredObjectInfo &&Other) {
76    Size = Other.Size;
77    Entry = Other.Entry;
78    Obj = std::move(Other.Obj);
79    return *this;
80  }
81
82  std::size_t Size;
83  jit_code_entry *Entry;
84  OwningBinary<ObjectFile> Obj;
85};
86
87// Buffer for an in-memory object file in executable memory
88typedef llvm::DenseMap< const char*, RegisteredObjectInfo>
89  RegisteredObjectBufferMap;
90
91/// Global access point for the JIT debugging interface designed for use with a
92/// singleton toolbox. Handles thread-safe registration and deregistration of
93/// object files that are in executable memory managed by the client of this
94/// class.
95class GDBJITRegistrationListener : public JITEventListener {
96  /// A map of in-memory object files that have been registered with the
97  /// JIT interface.
98  RegisteredObjectBufferMap ObjectBufferMap;
99
100public:
101  /// Instantiates the JIT service.
102  GDBJITRegistrationListener() : ObjectBufferMap() {}
103
104  /// Unregisters each object that was previously registered and releases all
105  /// internal resources.
106  ~GDBJITRegistrationListener() override;
107
108  /// Creates an entry in the JIT registry for the buffer @p Object,
109  /// which must contain an object file in executable memory with any
110  /// debug information for the debugger.
111  void NotifyObjectEmitted(const ObjectFile &Object,
112                           const RuntimeDyld::LoadedObjectInfo &L) override;
113
114  /// Removes the internal registration of @p Object, and
115  /// frees associated resources.
116  /// Returns true if @p Object was found in ObjectBufferMap.
117  void NotifyFreeingObject(const ObjectFile &Object) override;
118
119private:
120  /// Deregister the debug info for the given object file from the debugger
121  /// and delete any temporary copies.  This private method does not remove
122  /// the function from Map so that it can be called while iterating over Map.
123  void deregisterObjectInternal(RegisteredObjectBufferMap::iterator I);
124};
125
126/// Lock used to serialize all jit registration events, since they
127/// modify global variables.
128ManagedStatic<sys::Mutex> JITDebugLock;
129
130/// Do the registration.
131void NotifyDebugger(jit_code_entry* JITCodeEntry) {
132  __jit_debug_descriptor.action_flag = JIT_REGISTER_FN;
133
134  // Insert this entry at the head of the list.
135  JITCodeEntry->prev_entry = nullptr;
136  jit_code_entry* NextEntry = __jit_debug_descriptor.first_entry;
137  JITCodeEntry->next_entry = NextEntry;
138  if (NextEntry) {
139    NextEntry->prev_entry = JITCodeEntry;
140  }
141  __jit_debug_descriptor.first_entry = JITCodeEntry;
142  __jit_debug_descriptor.relevant_entry = JITCodeEntry;
143  __jit_debug_register_code();
144}
145
146GDBJITRegistrationListener::~GDBJITRegistrationListener() {
147  // Free all registered object files.
148  llvm::MutexGuard locked(*JITDebugLock);
149  for (RegisteredObjectBufferMap::iterator I = ObjectBufferMap.begin(),
150                                           E = ObjectBufferMap.end();
151       I != E; ++I) {
152    // Call the private method that doesn't update the map so our iterator
153    // doesn't break.
154    deregisterObjectInternal(I);
155  }
156  ObjectBufferMap.clear();
157}
158
159void GDBJITRegistrationListener::NotifyObjectEmitted(
160                                       const ObjectFile &Object,
161                                       const RuntimeDyld::LoadedObjectInfo &L) {
162
163  OwningBinary<ObjectFile> DebugObj = L.getObjectForDebug(Object);
164
165  // Bail out if debug objects aren't supported.
166  if (!DebugObj.getBinary())
167    return;
168
169  const char *Buffer = DebugObj.getBinary()->getMemoryBufferRef().getBufferStart();
170  size_t      Size = DebugObj.getBinary()->getMemoryBufferRef().getBufferSize();
171
172  const char *Key = Object.getMemoryBufferRef().getBufferStart();
173
174  assert(Key && "Attempt to register a null object with a debugger.");
175  llvm::MutexGuard locked(*JITDebugLock);
176  assert(ObjectBufferMap.find(Key) == ObjectBufferMap.end() &&
177         "Second attempt to perform debug registration.");
178  jit_code_entry* JITCodeEntry = new jit_code_entry();
179
180  if (!JITCodeEntry) {
181    llvm::report_fatal_error(
182      "Allocation failed when registering a JIT entry!\n");
183  } else {
184    JITCodeEntry->symfile_addr = Buffer;
185    JITCodeEntry->symfile_size = Size;
186
187    ObjectBufferMap[Key] = RegisteredObjectInfo(Size, JITCodeEntry,
188                                                std::move(DebugObj));
189    NotifyDebugger(JITCodeEntry);
190  }
191}
192
193void GDBJITRegistrationListener::NotifyFreeingObject(const ObjectFile& Object) {
194  const char *Key = Object.getMemoryBufferRef().getBufferStart();
195  llvm::MutexGuard locked(*JITDebugLock);
196  RegisteredObjectBufferMap::iterator I = ObjectBufferMap.find(Key);
197
198  if (I != ObjectBufferMap.end()) {
199    deregisterObjectInternal(I);
200    ObjectBufferMap.erase(I);
201  }
202}
203
204void GDBJITRegistrationListener::deregisterObjectInternal(
205    RegisteredObjectBufferMap::iterator I) {
206
207  jit_code_entry*& JITCodeEntry = I->second.Entry;
208
209  // Do the unregistration.
210  {
211    __jit_debug_descriptor.action_flag = JIT_UNREGISTER_FN;
212
213    // Remove the jit_code_entry from the linked list.
214    jit_code_entry* PrevEntry = JITCodeEntry->prev_entry;
215    jit_code_entry* NextEntry = JITCodeEntry->next_entry;
216
217    if (NextEntry) {
218      NextEntry->prev_entry = PrevEntry;
219    }
220    if (PrevEntry) {
221      PrevEntry->next_entry = NextEntry;
222    }
223    else {
224      assert(__jit_debug_descriptor.first_entry == JITCodeEntry);
225      __jit_debug_descriptor.first_entry = NextEntry;
226    }
227
228    // Tell the debugger which entry we removed, and unregister the code.
229    __jit_debug_descriptor.relevant_entry = JITCodeEntry;
230    __jit_debug_register_code();
231  }
232
233  delete JITCodeEntry;
234  JITCodeEntry = nullptr;
235}
236
237llvm::ManagedStatic<GDBJITRegistrationListener> GDBRegListener;
238
239} // end namespace
240
241namespace llvm {
242
243JITEventListener* JITEventListener::createGDBRegistrationListener() {
244  return &*GDBRegListener;
245}
246
247} // namespace llvm
248