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