• Home
  • Line#
  • Scopes#
  • Navigate#
  • Raw
  • Download
1 // Copyright (c) 2010 Google Inc.
2 // All rights reserved.
3 //
4 // Redistribution and use in source and binary forms, with or without
5 // modification, are permitted provided that the following conditions are
6 // met:
7 //
8 //     * Redistributions of source code must retain the above copyright
9 // notice, this list of conditions and the following disclaimer.
10 //     * Redistributions in binary form must reproduce the above
11 // copyright notice, this list of conditions and the following disclaimer
12 // in the documentation and/or other materials provided with the
13 // distribution.
14 //     * Neither the name of Google Inc. nor the names of its
15 // contributors may be used to endorse or promote products derived from
16 // this software without specific prior written permission.
17 //
18 // THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
19 // "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
20 // LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
21 // A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
22 // OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
23 // SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
24 // LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
25 // DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
26 // THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
27 // (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
28 // OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
29 
30 #ifndef CLIENT_LINUX_HANDLER_EXCEPTION_HANDLER_H_
31 #define CLIENT_LINUX_HANDLER_EXCEPTION_HANDLER_H_
32 
33 #include <signal.h>
34 #include <stdint.h>
35 #include <stdio.h>
36 #include <sys/ucontext.h>
37 
38 #include <string>
39 
40 #include "client/linux/crash_generation/crash_generation_client.h"
41 #include "client/linux/handler/minidump_descriptor.h"
42 #include "client/linux/minidump_writer/minidump_writer.h"
43 #include "common/scoped_ptr.h"
44 #include "common/using_std_string.h"
45 #include "google_breakpad/common/minidump_format.h"
46 
47 namespace google_breakpad {
48 
49 // ExceptionHandler
50 //
51 // ExceptionHandler can write a minidump file when an exception occurs,
52 // or when WriteMinidump() is called explicitly by your program.
53 //
54 // To have the exception handler write minidumps when an uncaught exception
55 // (crash) occurs, you should create an instance early in the execution
56 // of your program, and keep it around for the entire time you want to
57 // have crash handling active (typically, until shutdown).
58 // (NOTE): There should be only be one this kind of exception handler
59 // object per process.
60 //
61 // If you want to write minidumps without installing the exception handler,
62 // you can create an ExceptionHandler with install_handler set to false,
63 // then call WriteMinidump.  You can also use this technique if you want to
64 // use different minidump callbacks for different call sites.
65 //
66 // In either case, a callback function is called when a minidump is written,
67 // which receives the full path or file descriptor of the minidump.  The
68 // caller can collect and write additional application state to that minidump,
69 // and launch an external crash-reporting application.
70 //
71 // Caller should try to make the callbacks as crash-friendly as possible,
72 // it should avoid use heap memory allocation as much as possible.
73 
74 class ExceptionHandler {
75  public:
76   // A callback function to run before Breakpad performs any substantial
77   // processing of an exception.  A FilterCallback is called before writing
78   // a minidump.  |context| is the parameter supplied by the user as
79   // callback_context when the handler was created.
80   //
81   // If a FilterCallback returns true, Breakpad will continue processing,
82   // attempting to write a minidump.  If a FilterCallback returns false,
83   // Breakpad  will immediately report the exception as unhandled without
84   // writing a minidump, allowing another handler the opportunity to handle it.
85   typedef bool (*FilterCallback)(void *context);
86 
87   // A callback function to run after the minidump has been written.
88   // |descriptor| contains the file descriptor or file path containing the
89   // minidump. |context| is the parameter supplied by the user as
90   // callback_context when the handler was created.  |succeeded| indicates
91   // whether a minidump file was successfully written.
92   //
93   // If an exception occurred and the callback returns true, Breakpad will
94   // treat the exception as fully-handled, suppressing any other handlers from
95   // being notified of the exception.  If the callback returns false, Breakpad
96   // will treat the exception as unhandled, and allow another handler to handle
97   // it. If there are no other handlers, Breakpad will report the exception to
98   // the system as unhandled, allowing a debugger or native crash dialog the
99   // opportunity to handle the exception.  Most callback implementations
100   // should normally return the value of |succeeded|, or when they wish to
101   // not report an exception of handled, false.  Callbacks will rarely want to
102   // return true directly (unless |succeeded| is true).
103   typedef bool (*MinidumpCallback)(const MinidumpDescriptor& descriptor,
104                                    void* context,
105                                    bool succeeded);
106 
107   // In certain cases, a user may wish to handle the generation of the minidump
108   // themselves. In this case, they can install a handler callback which is
109   // called when a crash has occurred. If this function returns true, no other
110   // processing of occurs and the process will shortly be crashed. If this
111   // returns false, the normal processing continues.
112   typedef bool (*HandlerCallback)(const void* crash_context,
113                                   size_t crash_context_size,
114                                   void* context);
115 
116   // Creates a new ExceptionHandler instance to handle writing minidumps.
117   // Before writing a minidump, the optional |filter| callback will be called.
118   // Its return value determines whether or not Breakpad should write a
119   // minidump.  The minidump content will be written to the file path or file
120   // descriptor from |descriptor|, and the optional |callback| is called after
121   // writing the dump file, as described above.
122   // If install_handler is true, then a minidump will be written whenever
123   // an unhandled exception occurs.  If it is false, minidumps will only
124   // be written when WriteMinidump is called.
125   // If |server_fd| is valid, the minidump is generated out-of-process.  If it
126   // is -1, in-process generation will always be used.
127   ExceptionHandler(const MinidumpDescriptor& descriptor,
128                    FilterCallback filter,
129                    MinidumpCallback callback,
130                    void* callback_context,
131                    bool install_handler,
132                    const int server_fd);
133   ~ExceptionHandler();
134 
minidump_descriptor()135   const MinidumpDescriptor& minidump_descriptor() const {
136     return minidump_descriptor_;
137   }
138 
set_minidump_descriptor(const MinidumpDescriptor & descriptor)139   void set_minidump_descriptor(const MinidumpDescriptor& descriptor) {
140     minidump_descriptor_ = descriptor;
141   }
142 
set_crash_handler(HandlerCallback callback)143   void set_crash_handler(HandlerCallback callback) {
144     crash_handler_ = callback;
145   }
146 
set_crash_generation_client(CrashGenerationClient * client)147   void set_crash_generation_client(CrashGenerationClient* client) {
148     crash_generation_client_.reset(client);
149   }
150 
151   // Writes a minidump immediately.  This can be used to capture the execution
152   // state independently of a crash.
153   // Returns true on success.
154   // If the ExceptionHandler has been created with a path, a new file is
155   // generated for each minidump.  The file path can be retrieved in the
156   // MinidumpDescriptor passed to the MinidumpCallback or by accessing the
157   // MinidumpDescriptor directly from the ExceptionHandler (with
158   // minidump_descriptor()).
159   // If the ExceptionHandler has been created with a file descriptor, the file
160   // descriptor is repositioned to its beginning and the previous generated
161   // minidump is overwritten.
162   // Note that this method is not supposed to be called from a compromised
163   // context as it uses the heap.
164   bool WriteMinidump();
165 
166   // Convenience form of WriteMinidump which does not require an
167   // ExceptionHandler instance.
168   static bool WriteMinidump(const string& dump_path,
169                             MinidumpCallback callback,
170                             void* callback_context);
171 
172   // Write a minidump of |child| immediately.  This can be used to
173   // capture the execution state of |child| independently of a crash.
174   // Pass a meaningful |child_blamed_thread| to make that thread in
175   // the child process the one from which a crash signature is
176   // extracted.
177   //
178   // WARNING: the return of this function *must* happen before
179   // the code that will eventually reap |child| executes.
180   // Otherwise there's a pernicious race condition in which |child|
181   // exits, is reaped, another process created with its pid, then that
182   // new process dumped.
183   static bool WriteMinidumpForChild(pid_t child,
184                                     pid_t child_blamed_thread,
185                                     const string& dump_path,
186                                     MinidumpCallback callback,
187                                     void* callback_context);
188 
189   // This structure is passed to minidump_writer.h:WriteMinidump via an opaque
190   // blob. It shouldn't be needed in any user code.
191   struct CrashContext {
192     siginfo_t siginfo;
193     pid_t tid;  // the crashing thread.
194     struct ucontext context;
195 #if !defined(__ARM_EABI__) && !defined(__mips__)
196     // #ifdef this out because FP state is not part of user ABI for Linux ARM.
197     // In case of MIPS Linux FP state is already part of struct
198     // ucontext so 'float_state' is not required.
199     fpstate_t float_state;
200 #endif
201   };
202 
203   // Returns whether out-of-process dump generation is used or not.
IsOutOfProcess()204   bool IsOutOfProcess() const {
205     return crash_generation_client_.get() != NULL;
206   }
207 
208   // Add information about a memory mapping. This can be used if
209   // a custom library loader is used that maps things in a way
210   // that the linux dumper can't handle by reading the maps file.
211   void AddMappingInfo(const string& name,
212                       const uint8_t identifier[sizeof(MDGUID)],
213                       uintptr_t start_address,
214                       size_t mapping_size,
215                       size_t file_offset);
216 
217   // Register a block of memory of length bytes starting at address ptr
218   // to be copied to the minidump when a crash happens.
219   void RegisterAppMemory(void* ptr, size_t length);
220 
221   // Unregister a block of memory that was registered with RegisterAppMemory.
222   void UnregisterAppMemory(void* ptr);
223 
224   // Force signal handling for the specified signal.
225   bool SimulateSignalDelivery(int sig);
226 
227   // Report a crash signal from an SA_SIGINFO signal handler.
228   bool HandleSignal(int sig, siginfo_t* info, void* uc);
229 
230  private:
231   // Save the old signal handlers and install new ones.
232   static bool InstallHandlersLocked();
233   // Restore the old signal handlers.
234   static void RestoreHandlersLocked();
235 
236   void PreresolveSymbols();
237   bool GenerateDump(CrashContext *context);
238   void SendContinueSignalToChild();
239   void WaitForContinueSignal();
240 
241   static void SignalHandler(int sig, siginfo_t* info, void* uc);
242   static int ThreadEntry(void* arg);
243   bool DoDump(pid_t crashing_process, const void* context,
244               size_t context_size);
245 
246   const FilterCallback filter_;
247   const MinidumpCallback callback_;
248   void* const callback_context_;
249 
250   scoped_ptr<CrashGenerationClient> crash_generation_client_;
251 
252   MinidumpDescriptor minidump_descriptor_;
253 
254   // Must be volatile. The compiler is unaware of the code which runs in
255   // the signal handler which reads this variable. Without volatile the
256   // compiler is free to optimise away writes to this variable which it
257   // believes are never read.
258   volatile HandlerCallback crash_handler_;
259 
260   // We need to explicitly enable ptrace of parent processes on some
261   // kernels, but we need to know the PID of the cloned process before we
262   // can do this. We create a pipe which we can use to block the
263   // cloned process after creating it, until we have explicitly enabled
264   // ptrace. This is used to store the file descriptors for the pipe
265   int fdes[2];
266 
267   // Callers can add extra info about mappings for cases where the
268   // dumper code cannot extract enough information from /proc/<pid>/maps.
269   MappingList mapping_list_;
270 
271   // Callers can request additional memory regions to be included in
272   // the dump.
273   AppMemoryList app_memory_list_;
274 };
275 
276 }  // namespace google_breakpad
277 
278 #endif  // CLIENT_LINUX_HANDLER_EXCEPTION_HANDLER_H_
279