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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-c/ExecutionEngine.h"
11 : #include "llvm/ADT/DenseMap.h"
12 : #include "llvm/ExecutionEngine/JITEventListener.h"
13 : #include "llvm/Object/ObjectFile.h"
14 : #include "llvm/Support/Compiler.h"
15 : #include "llvm/Support/ErrorHandling.h"
16 : #include "llvm/Support/ManagedStatic.h"
17 : #include "llvm/Support/Mutex.h"
18 : #include "llvm/Support/MutexGuard.h"
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 {
27 : JIT_NOACTION = 0,
28 : JIT_REGISTER_FN,
29 : JIT_UNREGISTER_FN
30 : } jit_actions_t;
31 :
32 : struct jit_code_entry {
33 : struct jit_code_entry *next_entry;
34 : struct jit_code_entry *prev_entry;
35 : const char *symfile_addr;
36 : uint64_t symfile_size;
37 : };
38 :
39 : struct jit_descriptor {
40 : uint32_t version;
41 : // This should be jit_actions_t, but we want to be specific about the
42 : // bit-width.
43 : uint32_t action_flag;
44 : struct jit_code_entry *relevant_entry;
45 : struct jit_code_entry *first_entry;
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.
51 : struct jit_descriptor __jit_debug_descriptor = { 1, 0, nullptr, nullptr };
52 :
53 : // Debuggers puts a breakpoint in this function.
54 211 : LLVM_ATTRIBUTE_NOINLINE void __jit_debug_register_code() {
55 : // The noinline and the asm prevent calls to this function from being
56 : // optimized out.
57 : #if !defined(_MSC_VER)
58 211 : asm volatile("":::"memory");
59 : #endif
60 211 : }
61 :
62 : }
63 :
64 : namespace {
65 :
66 211 : struct RegisteredObjectInfo {
67 148 : RegisteredObjectInfo() {}
68 :
69 : RegisteredObjectInfo(std::size_t Size, jit_code_entry *Entry,
70 : OwningBinary<ObjectFile> Obj)
71 148 : : Size(Size), Entry(Entry), Obj(std::move(Obj)) {}
72 :
73 : std::size_t Size;
74 : jit_code_entry *Entry;
75 : OwningBinary<ObjectFile> Obj;
76 : };
77 :
78 : // Buffer for an in-memory object file in executable memory
79 : typedef llvm::DenseMap< const char*, RegisteredObjectInfo>
80 : RegisteredObjectBufferMap;
81 :
82 : /// Global access point for the JIT debugging interface designed for use with a
83 : /// singleton toolbox. Handles thread-safe registration and deregistration of
84 : /// object files that are in executable memory managed by the client of this
85 : /// class.
86 : class GDBJITRegistrationListener : public JITEventListener {
87 : /// A map of in-memory object files that have been registered with the
88 : /// JIT interface.
89 : RegisteredObjectBufferMap ObjectBufferMap;
90 :
91 : public:
92 : /// Instantiates the JIT service.
93 119 : GDBJITRegistrationListener() : ObjectBufferMap() {}
94 :
95 : /// Unregisters each object that was previously registered and releases all
96 : /// internal resources.
97 : ~GDBJITRegistrationListener() override;
98 :
99 : /// Creates an entry in the JIT registry for the buffer @p Object,
100 : /// which must contain an object file in executable memory with any
101 : /// debug information for the debugger.
102 : void NotifyObjectEmitted(const ObjectFile &Object,
103 : const RuntimeDyld::LoadedObjectInfo &L) override;
104 :
105 : /// Removes the internal registration of @p Object, and
106 : /// frees associated resources.
107 : /// Returns true if @p Object was found in ObjectBufferMap.
108 : void NotifyFreeingObject(const ObjectFile &Object) override;
109 :
110 : private:
111 : /// Deregister the debug info for the given object file from the debugger
112 : /// and delete any temporary copies. This private method does not remove
113 : /// the function from Map so that it can be called while iterating over Map.
114 : void deregisterObjectInternal(RegisteredObjectBufferMap::iterator I);
115 : };
116 :
117 : /// Lock used to serialize all jit registration events, since they
118 : /// modify global variables.
119 : ManagedStatic<sys::Mutex> JITDebugLock;
120 :
121 : /// Do the registration.
122 : void NotifyDebugger(jit_code_entry* JITCodeEntry) {
123 148 : __jit_debug_descriptor.action_flag = JIT_REGISTER_FN;
124 :
125 : // Insert this entry at the head of the list.
126 148 : JITCodeEntry->prev_entry = nullptr;
127 148 : jit_code_entry* NextEntry = __jit_debug_descriptor.first_entry;
128 148 : JITCodeEntry->next_entry = NextEntry;
129 148 : if (NextEntry) {
130 31 : NextEntry->prev_entry = JITCodeEntry;
131 : }
132 148 : __jit_debug_descriptor.first_entry = JITCodeEntry;
133 148 : __jit_debug_descriptor.relevant_entry = JITCodeEntry;
134 148 : __jit_debug_register_code();
135 : }
136 :
137 26 : GDBJITRegistrationListener::~GDBJITRegistrationListener() {
138 : // Free all registered object files.
139 13 : llvm::MutexGuard locked(*JITDebugLock);
140 13 : for (RegisteredObjectBufferMap::iterator I = ObjectBufferMap.begin(),
141 : E = ObjectBufferMap.end();
142 13 : I != E; ++I) {
143 : // Call the private method that doesn't update the map so our iterator
144 : // doesn't break.
145 0 : deregisterObjectInternal(I);
146 : }
147 13 : ObjectBufferMap.clear();
148 26 : }
149 0 :
150 : void GDBJITRegistrationListener::NotifyObjectEmitted(
151 : const ObjectFile &Object,
152 : const RuntimeDyld::LoadedObjectInfo &L) {
153 :
154 : OwningBinary<ObjectFile> DebugObj = L.getObjectForDebug(Object);
155 :
156 : // Bail out if debug objects aren't supported.
157 : if (!DebugObj.getBinary())
158 : return;
159 :
160 0 : const char *Buffer = DebugObj.getBinary()->getMemoryBufferRef().getBufferStart();
161 26 : size_t Size = DebugObj.getBinary()->getMemoryBufferRef().getBufferSize();
162 :
163 13 : const char *Key = Object.getMemoryBufferRef().getBufferStart();
164 13 :
165 : assert(Key && "Attempt to register a null object with a debugger.");
166 13 : llvm::MutexGuard locked(*JITDebugLock);
167 : assert(ObjectBufferMap.find(Key) == ObjectBufferMap.end() &&
168 : "Second attempt to perform debug registration.");
169 0 : jit_code_entry* JITCodeEntry = new jit_code_entry();
170 :
171 13 : if (!JITCodeEntry) {
172 13 : llvm::report_fatal_error(
173 : "Allocation failed when registering a JIT entry!\n");
174 148 : } else {
175 : JITCodeEntry->symfile_addr = Buffer;
176 : JITCodeEntry->symfile_size = Size;
177 :
178 296 : ObjectBufferMap[Key] = RegisteredObjectInfo(Size, JITCodeEntry,
179 : std::move(DebugObj));
180 : NotifyDebugger(JITCodeEntry);
181 148 : }
182 0 : }
183 :
184 148 : void GDBJITRegistrationListener::NotifyFreeingObject(const ObjectFile& Object) {
185 148 : const char *Key = Object.getMemoryBufferRef().getBufferStart();
186 : llvm::MutexGuard locked(*JITDebugLock);
187 148 : RegisteredObjectBufferMap::iterator I = ObjectBufferMap.find(Key);
188 :
189 : if (I != ObjectBufferMap.end()) {
190 148 : deregisterObjectInternal(I);
191 : ObjectBufferMap.erase(I);
192 : }
193 148 : }
194 :
195 : void GDBJITRegistrationListener::deregisterObjectInternal(
196 : RegisteredObjectBufferMap::iterator I) {
197 :
198 : jit_code_entry*& JITCodeEntry = I->second.Entry;
199 148 :
200 148 : // Do the unregistration.
201 : {
202 296 : __jit_debug_descriptor.action_flag = JIT_UNREGISTER_FN;
203 :
204 : // Remove the jit_code_entry from the linked list.
205 : jit_code_entry* PrevEntry = JITCodeEntry->prev_entry;
206 : jit_code_entry* NextEntry = JITCodeEntry->next_entry;
207 :
208 63 : if (NextEntry) {
209 63 : NextEntry->prev_entry = PrevEntry;
210 63 : }
211 63 : if (PrevEntry) {
212 : PrevEntry->next_entry = NextEntry;
213 63 : }
214 63 : else {
215 : assert(__jit_debug_descriptor.first_entry == JITCodeEntry);
216 : __jit_debug_descriptor.first_entry = NextEntry;
217 63 : }
218 :
219 0 : // Tell the debugger which entry we removed, and unregister the code.
220 : __jit_debug_descriptor.relevant_entry = JITCodeEntry;
221 : __jit_debug_register_code();
222 0 : }
223 :
224 : delete JITCodeEntry;
225 : JITCodeEntry = nullptr;
226 0 : }
227 :
228 : llvm::ManagedStatic<GDBJITRegistrationListener> GDBRegListener;
229 0 :
230 0 : } // end namespace
231 :
232 0 : namespace llvm {
233 0 :
234 : JITEventListener* JITEventListener::createGDBRegistrationListener() {
235 0 : return &*GDBRegListener;
236 0 : }
237 :
238 : } // namespace llvm
239 :
240 0 : LLVMJITEventListenerRef LLVMCreateGDBRegistrationListener(void)
241 : {
242 : return wrap(JITEventListener::createGDBRegistrationListener());
243 : }
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