Allow dumping live processes on OS X

R=mark at http://breakpad.appspot.com/148001/show

git-svn-id: http://google-breakpad.googlecode.com/svn/trunk@647 4c0a9323-5329-0410-9bdc-e9ce6186880e

src/client/mac/handler/exception_handler.cc

@@ -33,6 +33,7 @@
 #include "client/mac/handler/exception_handler.h"
 #include "client/mac/handler/minidump_generator.h"
 #include "common/mac/macho_utilities.h"
+#include "common/mac/scoped_task_suspend-inl.h"
 
 #ifndef USE_PROTECTED_ALLOCATIONS
 #define USE_PROTECTED_ALLOCATIONS 0
@@ -301,6 +302,37 @@ bool ExceptionHandler::WriteMinidump(const string &dump_path,
   return handler.WriteMinidump();
 }
 
+// static
+bool ExceptionHandler::WriteMinidumpForChild(mach_port_t child,
+					     mach_port_t child_blamed_thread,
+					     const string &dump_path,
+					     MinidumpCallback callback,
+					     void *callback_context) {
+  ScopedTaskSuspend suspend(child);
+
+  MinidumpGenerator generator(child, MACH_PORT_NULL);
+  string dump_id;
+  string dump_filename = generator.UniqueNameInDirectory(dump_path, &dump_id);
+
+  generator.SetExceptionInformation(EXC_BREAKPOINT,
+#if defined (__i386__) || defined(__x86_64__)
+				    EXC_I386_BPT,
+#elif defined (__ppc__) || defined (__ppc64__)
+				    EXC_PPC_BREAKPOINT,
+#else
+  #error architecture not supported
+#endif
+				    0,
+				    child_blamed_thread);
+  bool result = generator.Write(dump_filename.c_str());
+
+  if (callback) {
+    return callback(dump_path.c_str(), dump_id.c_str(),
+		    callback_context, result);
+  }
+  return result;
+}
+
 bool ExceptionHandler::WriteMinidumpWithException(int exception_type,
                                                   int exception_code,
                                                   int exception_subcode,

src/client/mac/handler/exception_handler.h

@@ -121,6 +121,14 @@ class ExceptionHandler {
   static bool WriteMinidump(const string &dump_path, MinidumpCallback callback,
                             void *callback_context);
 
+  // Write a minidump of child immediately. This can be used to capture
+  // the execution state of a child process independently of a crash.
+  static bool WriteMinidumpForChild(mach_port_t child,
+				    mach_port_t child_blamed_thread,
+				    const std::string &dump_path,
+				    MinidumpCallback callback,
+				    void *callback_context);
+
   // Returns whether out-of-process dump generation is used or not.
   bool IsOutOfProcess() const {
     return crash_generation_client_.get() != NULL;

src/client/mac/handler/minidump_generator.cc

@@ -536,7 +536,10 @@ bool MinidumpGenerator::WriteThreadListStream(
     return false;
 
   // Don't include the generator thread
-  non_generator_thread_count = thread_count - 1;
+  if (handler_thread_ != MACH_PORT_NULL)
+    non_generator_thread_count = thread_count - 1;
+  else
+    non_generator_thread_count = thread_count;
   if (!list.AllocateObjectAndArray(non_generator_thread_count,
                                    sizeof(MDRawThread)))
     return false;

src/client/mac/tests/exception_handler_test.cc

@@ -35,6 +35,7 @@
 #include "breakpad_googletest_includes.h"
 #include "client/mac/handler/exception_handler.h"
 #include "client/mac/tests/auto_tempdir.h"
+#include "common/mac/MachIPC.h"
 
 namespace {
 using std::string;
@@ -42,6 +43,12 @@ using google_breakpad::AutoTempDir;
 using google_breakpad::ExceptionHandler;
 using testing::Test;
 
+class ExceptionHandlerTest : public Test {
+ public:
+  AutoTempDir tempDir;
+  string lastDumpName;
+};
+
 static void Crasher() {
   int *a = (int*)0x42;
 
@@ -68,7 +75,7 @@ static bool MDCallback(const char *dump_dir, const char *file_name,
   return true;
 }
 
-TEST(ExceptionHandler, InProcess) {
+TEST_F(ExceptionHandlerTest, InProcess) {
   AutoTempDir tempDir;
   // Give the child process a pipe to report back on.
   int fds[2];
@@ -76,6 +83,7 @@ TEST(ExceptionHandler, InProcess) {
   // Fork off a child process so it can crash.
   pid_t pid = fork();
   if (pid == 0) {
+    // In the child process.
     close(fds[0]);
     ExceptionHandler eh(tempDir.path, NULL, MDCallback, &fds[1], true, NULL);
     // crash
@@ -83,6 +91,7 @@ TEST(ExceptionHandler, InProcess) {
     // not reached
     exit(1);
   }
+  // In the parent process.
   ASSERT_NE(-1, pid);
   // Wait for the background process to return the minidump file.
   close(fds[1]);
@@ -101,4 +110,85 @@ TEST(ExceptionHandler, InProcess) {
   EXPECT_EQ(0, WEXITSTATUS(ret));
 }
 
+static bool ChildMDCallback(const char *dump_dir, const char *file_name,
+			    void *context, bool success) {
+  ExceptionHandlerTest *self = reinterpret_cast<ExceptionHandlerTest*>(context);
+  if (dump_dir && file_name) {
+    self->lastDumpName = dump_dir;
+    self->lastDumpName += "/";
+    self->lastDumpName += file_name;
+    self->lastDumpName += ".dmp";
+  }
+  return true;
+}
+
+TEST_F(ExceptionHandlerTest, DumpChildProcess) {
+  const int kTimeoutMs = 2000;
+  // Create a mach port to receive the child task on.
+  char machPortName[128];
+  sprintf(machPortName, "ExceptionHandlerTest.%d", getpid());
+  ReceivePort parent_recv_port(machPortName);
+
+  // Give the child process a pipe to block on.
+  int fds[2];
+  ASSERT_EQ(0, pipe(fds));
+
+  // Fork off a child process to dump.
+  pid_t pid = fork();
+  if (pid == 0) {
+    // In the child process
+    close(fds[0]);
+
+    // Send parent process the task and thread ports.
+    MachSendMessage child_message(0);
+    child_message.AddDescriptor(mach_task_self());
+    child_message.AddDescriptor(mach_thread_self());
+
+    MachPortSender child_sender(machPortName);
+    if (child_sender.SendMessage(child_message, kTimeoutMs) != KERN_SUCCESS)
+      exit(1);
+
+    // Wait for the parent process.
+    uint8_t data;
+    read(fds[1], &data, 1);
+    exit(0);
+  }
+  // In the parent process.
+  ASSERT_NE(-1, pid);
+  close(fds[1]);
+
+  // Read the child's task and thread ports.
+  MachReceiveMessage child_message;
+  ASSERT_EQ(KERN_SUCCESS,
+	    parent_recv_port.WaitForMessage(&child_message, kTimeoutMs));
+  mach_port_t child_task = child_message.GetTranslatedPort(0);
+  mach_port_t child_thread = child_message.GetTranslatedPort(1);
+  ASSERT_NE(MACH_PORT_NULL, child_task);
+  ASSERT_NE(MACH_PORT_NULL, child_thread);
+
+  // Write a minidump of the child process.
+  bool result = ExceptionHandler::WriteMinidumpForChild(child_task,
+							child_thread,
+							tempDir.path,
+							ChildMDCallback,
+							this);
+  ASSERT_EQ(true, result);
+
+  // Ensure that minidump file exists and is > 0 bytes.
+  ASSERT_FALSE(lastDumpName.empty());
+  struct stat st;
+  ASSERT_EQ(0, stat(lastDumpName.c_str(), &st));
+  ASSERT_LT(0, st.st_size);
+
+  // Unblock child process
+  uint8_t data = 1;
+  (void)write(fds[0], &data, 1);
+
+  // Child process should have exited with a zero status.
+  int ret;
+  ASSERT_EQ(pid, waitpid(pid, &ret, 0));
+  EXPECT_NE(0, WIFEXITED(ret));
+  EXPECT_EQ(0, WEXITSTATUS(ret));
+}
+
 }