Getting context information from the kernel when catching a SIGABRT on iOS.

Until now, the context information was the current one when receiving a
SIGABRT. This is mainly wrong because the signal handler start in a new
context. This instead use the context passed to the signal handler.
Review URL: https://breakpad.appspot.com/435002

git-svn-id: http://google-breakpad.googlecode.com/svn/trunk@1015 4c0a9323-5329-0410-9bdc-e9ce6186880e

src/client/mac/handler/exception_handler.cc

@@ -329,6 +329,7 @@ bool ExceptionHandler::WriteMinidumpForChild(mach_port_t child,
 bool ExceptionHandler::WriteMinidumpWithException(int exception_type,
                                                   int exception_code,
                                                   int exception_subcode,
+                                                  ucontext_t *task_context,
                                                   mach_port_t thread_name,
                                                   bool exit_after_write,
                                                   bool report_current_thread) {
@@ -366,6 +367,7 @@ bool ExceptionHandler::WriteMinidumpWithException(int exception_type,
       MinidumpGenerator md(mach_task_self(),
                            report_current_thread ? MACH_PORT_NULL :
                                                    mach_thread_self());
+      md.SetTaskContext(task_context);
       if (exception_type && exception_code) {
         // If this is a real exception, give the filter (if any) a chance to
         // decide if this should be sent.
@@ -509,7 +511,7 @@ void *ExceptionHandler::WaitForMessage(void *exception_handler_class) {
         // Write out the dump and save the result for later retrieval
         self->last_minidump_write_result_ =
           self->WriteMinidumpWithException(exception_type, exception_code,
-                                           0, thread,
+                                           0, NULL, thread,
                                            false, false);
 
 #if USE_PROTECTED_ALLOCATIONS
@@ -544,8 +546,8 @@ void *ExceptionHandler::WaitForMessage(void *exception_handler_class) {
 
         // Generate the minidump with the exception data.
         self->WriteMinidumpWithException(receive.exception, receive.code[0],
-                                         subcode, receive.thread.name, true,
-                                         false);
+                                         subcode, NULL, receive.thread.name,
+                                         true, false);
 
 #if USE_PROTECTED_ALLOCATIONS
         // This may have become protected again within
@@ -590,6 +592,7 @@ void ExceptionHandler::SignalHandler(int sig, siginfo_t* info, void* uc) {
       EXC_SOFTWARE,
       MD_EXCEPTION_CODE_MAC_ABORT,
       0,
+      static_cast<ucontext_t*>(uc),
       mach_thread_self(),
       true,
       true);

src/client/mac/handler/exception_handler.h

@@ -182,10 +182,13 @@ class ExceptionHandler {
   // success, false otherwise.
   bool SendMessageToHandlerThread(HandlerThreadMessage message_id);
 
-  // All minidump writing goes through this one routine
+  // All minidump writing goes through this one routine.
+  // |task_context| can be NULL. If not, it will be used to retrieve the
+  // context of the current thread, instead of using |thread_get_state|.
   bool WriteMinidumpWithException(int exception_type,
                                   int exception_code,
                                   int exception_subcode,
+                                  ucontext_t *task_context,
                                   mach_port_t thread_name,
                                   bool exit_after_write,
                                   bool report_current_thread);

src/client/mac/handler/minidump_generator.cc

@@ -77,6 +77,7 @@ MinidumpGenerator::MinidumpGenerator()
       crashing_task_(mach_task_self()),
       handler_thread_(mach_thread_self()),
       cpu_type_(DynamicImages::GetNativeCPUType()),
+      task_context_(NULL),
       dynamic_images_(NULL),
       memory_blocks_(&allocator_) {
   GatherSystemInformation();
@@ -94,6 +95,7 @@ MinidumpGenerator::MinidumpGenerator(mach_port_t crashing_task,
       crashing_task_(crashing_task),
       handler_thread_(handler_thread),
       cpu_type_(DynamicImages::GetNativeCPUType()),
+      task_context_(NULL),
       dynamic_images_(NULL),
       memory_blocks_(&allocator_) {
   if (crashing_task != mach_task_self()) {
@@ -168,6 +170,10 @@ void MinidumpGenerator::GatherSystemInformation() {
   os_build_number_ = IntegerValueAtIndex(product_str, 2);
 }
 
+void MinidumpGenerator::SetTaskContext(ucontext_t *task_context) {
+  task_context_ = task_context;
+}
+
 string MinidumpGenerator::UniqueNameInDirectory(const string &dir,
                                                 string *unique_name) {
   CFUUIDRef uuid = CFUUIDCreate(NULL);
@@ -770,6 +776,19 @@ bool MinidumpGenerator::WriteContextX86_64(
 bool MinidumpGenerator::GetThreadState(thread_act_t target_thread,
                                        thread_state_t state,
                                        mach_msg_type_number_t *count) {
+  if (task_context_ && target_thread == mach_thread_self()) {
+    switch (cpu_type_) {
+#ifdef HAS_ARM_SUPPORT
+      case CPU_TYPE_ARM: {
+        size_t final_size =
+            std::min(static_cast<size_t>(*count), sizeof(arm_thread_state_t));
+        memcpy(state, &task_context_->uc_mcontext->__ss, final_size);
+        *count = final_size;
+        return true;
+      }
+#endif
+    }
+  }
   thread_state_flavor_t flavor;
   switch (cpu_type_) {
 #ifdef HAS_ARM_SUPPORT
@@ -878,10 +897,7 @@ bool MinidumpGenerator::WriteMemoryListStream(
     mach_msg_type_number_t stateCount
       = static_cast<mach_msg_type_number_t>(sizeof(state));
 
-    if (thread_get_state(exception_thread_,
-                         BREAKPAD_MACHINE_THREAD_STATE,
-                         state,
-                         &stateCount) == KERN_SUCCESS) {
+    if (GetThreadState(exception_thread_, state, &stateCount)) {
       u_int64_t ip = CurrentPCForStack(state);
       // Bound it to the upper and lower bounds of the region
       // it's contained within. If it's not in a known memory region,

src/client/mac/handler/minidump_generator.h

@@ -102,6 +102,11 @@ class MinidumpGenerator {
     exception_thread_ = thread_name;
   }
 
+  // Specify the task context. If |task_context| is not NULL, it will be used
+  // to retrieve the context of the current thread, instead of using
+  // |thread_get_state|.
+  void SetTaskContext(ucontext_t *task_context);
+
   // Gather system information.  This should be call at least once before using
   // the MinidumpGenerator class.
   static void GatherSystemInformation();
@@ -199,6 +204,9 @@ class MinidumpGenerator {
   static int os_minor_version_;
   static int os_build_number_;
 
+  // Context of the task to dump.
+  ucontext_t *task_context_;
+
   // Information about dynamically loaded code
   DynamicImages *dynamic_images_;
 

src/common/mac/macho_utilities.h

@@ -54,14 +54,6 @@
 # define LC_UUID         0x1b    /* the uuid */
 #endif
 
-#if TARGET_CPU_X86
-# define BREAKPAD_MACHINE_THREAD_STATE i386_THREAD_STATE
-#elif TARGET_CPU_X86_64
-# define BREAKPAD_MACHINE_THREAD_STATE x86_THREAD_STATE64
-#else
-# define BREAKPAD_MACHINE_THREAD_STATE MACHINE_THREAD_STATE
-#endif
-
 // The uuid_command struct/swap routines were added during the 10.4 series.
 // Their presence isn't guaranteed.
 struct breakpad_uuid_command {