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
17 using namespace llvm;
18
19 // This must be kept in sync with gdb/gdb/jit.h .
20 extern "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.
__jit_debug_register_code()50 LLVM_ATTRIBUTE_NOINLINE void __jit_debug_register_code() { }
51
52 }
53
54 namespace {
55
56 // Buffer for an in-memory object file in executable memory
57 typedef 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.
65 class GDBJITRegistrar : public JITRegistrar {
66 /// A map of in-memory object files that have been registered with the
67 /// JIT interface.
68 RegisteredObjectBufferMap ObjectBufferMap;
69
70 public:
71 /// Instantiates the JIT service.
GDBJITRegistrar()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
88 private:
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.
97 llvm::sys::Mutex JITDebugLock;
98
99 /// Acquire the lock and do the registration.
NotifyDebugger(jit_code_entry * JITCodeEntry)100 void 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
~GDBJITRegistrar()116 GDBJITRegistrar::~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
registerObject(const MemoryBuffer & Object)127 void 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
deregisterObject(const MemoryBuffer & Object)150 bool 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
deregisterObjectInternal(RegisteredObjectBufferMap::iterator I)162 void 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
198 namespace llvm {
199
getGDBRegistrar()200 JITRegistrar& 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