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/MutexGuard.h"
13#include "llvm/Support/Mutex.h"
14#include "llvm/Support/ErrorHandling.h"
15#include "llvm/Support/Compiler.h"
16
17using namespace llvm;
18
19// This must be kept in sync with gdb/gdb/jit.h .
20extern "C" {
21
22  typedef enum {
23    JIT_NOACTION = 0,
24    JIT_REGISTER_FN,
25    JIT_UNREGISTER_FN
26  } jit_actions_t;
27
28  struct jit_code_entry {
29    struct jit_code_entry *next_entry;
30    struct jit_code_entry *prev_entry;
31    const char *symfile_addr;
32    uint64_t symfile_size;
33  };
34
35  struct jit_descriptor {
36    uint32_t version;
37    // This should be jit_actions_t, but we want to be specific about the
38    // bit-width.
39    uint32_t action_flag;
40    struct jit_code_entry *relevant_entry;
41    struct jit_code_entry *first_entry;
42  };
43
44  // We put information about the JITed function in this global, which the
45  // debugger reads.  Make sure to specify the version statically, because the
46  // debugger checks the version before we can set it during runtime.
47  static struct jit_descriptor __jit_debug_descriptor = { 1, 0, 0, 0 };
48
49  // Debuggers puts a breakpoint in this function.
50  LLVM_ATTRIBUTE_NOINLINE void __jit_debug_register_code() { }
51
52}
53
54namespace {
55
56// Buffer for an in-memory object file in executable memory
57typedef llvm::DenseMap< const char*,
58                        std::pair<std::size_t, jit_code_entry*> >
59  RegisteredObjectBufferMap;
60
61/// Global access point for the JIT debugging interface designed for use with a
62/// singleton toolbox. Handles thread-safe registration and deregistration of
63/// object files that are in executable memory managed by the client of this
64/// class.
65class GDBJITRegistrar : public JITRegistrar {
66  /// A map of in-memory object files that have been registered with the
67  /// JIT interface.
68  RegisteredObjectBufferMap ObjectBufferMap;
69
70public:
71  /// Instantiates the JIT service.
72  GDBJITRegistrar() : ObjectBufferMap() {}
73
74  /// Unregisters each object that was previously registered and releases all
75  /// internal resources.
76  virtual ~GDBJITRegistrar();
77
78  /// Creates an entry in the JIT registry for the buffer @p Object,
79  /// which must contain an object file in executable memory with any
80  /// debug information for the debugger.
81  void registerObject(const MemoryBuffer &Object);
82
83  /// Removes the internal registration of @p Object, and
84  /// frees associated resources.
85  /// Returns true if @p Object was found in ObjectBufferMap.
86  bool deregisterObject(const MemoryBuffer &Object);
87
88private:
89  /// Deregister the debug info for the given object file from the debugger
90  /// and delete any temporary copies.  This private method does not remove
91  /// the function from Map so that it can be called while iterating over Map.
92  void deregisterObjectInternal(RegisteredObjectBufferMap::iterator I);
93};
94
95/// Lock used to serialize all jit registration events, since they
96/// modify global variables.
97llvm::sys::Mutex JITDebugLock;
98
99/// Acquire the lock and do the registration.
100void NotifyDebugger(jit_code_entry* JITCodeEntry) {
101  llvm::MutexGuard locked(JITDebugLock);
102  __jit_debug_descriptor.action_flag = JIT_REGISTER_FN;
103
104  // Insert this entry at the head of the list.
105  JITCodeEntry->prev_entry = NULL;
106  jit_code_entry* NextEntry = __jit_debug_descriptor.first_entry;
107  JITCodeEntry->next_entry = NextEntry;
108  if (NextEntry != NULL) {
109    NextEntry->prev_entry = JITCodeEntry;
110  }
111  __jit_debug_descriptor.first_entry = JITCodeEntry;
112  __jit_debug_descriptor.relevant_entry = JITCodeEntry;
113  __jit_debug_register_code();
114}
115
116GDBJITRegistrar::~GDBJITRegistrar() {
117  // Free all registered object files.
118 for (RegisteredObjectBufferMap::iterator I = ObjectBufferMap.begin(), E = ObjectBufferMap.end();
119       I != E; ++I) {
120    // Call the private method that doesn't update the map so our iterator
121    // doesn't break.
122    deregisterObjectInternal(I);
123  }
124  ObjectBufferMap.clear();
125}
126
127void GDBJITRegistrar::registerObject(const MemoryBuffer &Object) {
128
129  const char *Buffer = Object.getBufferStart();
130  size_t      Size = Object.getBufferSize();
131
132  assert(Buffer && "Attempt to register a null object with a debugger.");
133  assert(ObjectBufferMap.find(Buffer) == ObjectBufferMap.end() &&
134         "Second attempt to perform debug registration.");
135  jit_code_entry* JITCodeEntry = new jit_code_entry();
136
137  if (JITCodeEntry == 0) {
138    llvm::report_fatal_error(
139      "Allocation failed when registering a JIT entry!\n");
140  }
141  else {
142    JITCodeEntry->symfile_addr = Buffer;
143    JITCodeEntry->symfile_size = Size;
144
145    ObjectBufferMap[Buffer] = std::make_pair(Size, JITCodeEntry);
146    NotifyDebugger(JITCodeEntry);
147  }
148}
149
150bool GDBJITRegistrar::deregisterObject(const MemoryBuffer& Object) {
151  const char *Buffer = Object.getBufferStart();
152  RegisteredObjectBufferMap::iterator I = ObjectBufferMap.find(Buffer);
153
154  if (I != ObjectBufferMap.end()) {
155    deregisterObjectInternal(I);
156    ObjectBufferMap.erase(I);
157    return true;
158  }
159  return false;
160}
161
162void GDBJITRegistrar::deregisterObjectInternal(
163    RegisteredObjectBufferMap::iterator I) {
164
165  jit_code_entry*& JITCodeEntry = I->second.second;
166
167  // Acquire the lock and do the unregistration.
168  {
169    llvm::MutexGuard locked(JITDebugLock);
170    __jit_debug_descriptor.action_flag = JIT_UNREGISTER_FN;
171
172    // Remove the jit_code_entry from the linked list.
173    jit_code_entry* PrevEntry = JITCodeEntry->prev_entry;
174    jit_code_entry* NextEntry = JITCodeEntry->next_entry;
175
176    if (NextEntry) {
177      NextEntry->prev_entry = PrevEntry;
178    }
179    if (PrevEntry) {
180      PrevEntry->next_entry = NextEntry;
181    }
182    else {
183      assert(__jit_debug_descriptor.first_entry == JITCodeEntry);
184      __jit_debug_descriptor.first_entry = NextEntry;
185    }
186
187    // Tell the debugger which entry we removed, and unregister the code.
188    __jit_debug_descriptor.relevant_entry = JITCodeEntry;
189    __jit_debug_register_code();
190  }
191
192  delete JITCodeEntry;
193  JITCodeEntry = NULL;
194}
195
196} // end namespace
197
198namespace llvm {
199
200JITRegistrar& JITRegistrar::getGDBRegistrar() {
201  static GDBJITRegistrar* sRegistrar = NULL;
202  if (sRegistrar == NULL) {
203    // The mutex is here so that it won't slow down access once the registrar
204    // is instantiated
205    llvm::MutexGuard locked(JITDebugLock);
206    // Check again to be sure another thread didn't create this while we waited
207    if (sRegistrar == NULL) {
208      sRegistrar = new GDBJITRegistrar;
209    }
210  }
211  return *sRegistrar;
212}
213
214} // namespace llvm
215