static void worker_process(int fd, debugger_request_t& request) {
// Open the tombstone file if we need it.
std::string tombstone_path;
int tombstone_fd = -1;
switch (request.action) {
case DEBUGGER_ACTION_DUMP_TOMBSTONE:
case DEBUGGER_ACTION_CRASH:
tombstone_fd = open_tombstone(&tombstone_path);
if (tombstone_fd == -1) {
ALOGE("debuggerd: failed to open tombstone file: %s\n", strerror(errno));
exit(1);
}
break;
case DEBUGGER_ACTION_DUMP_BACKTRACE:
break;
default:
ALOGE("debuggerd: unexpected request action: %d", request.action);
exit(1);
}
// At this point, the thread that made the request is blocked in
// a read() call. If the thread has crashed, then this gives us
// time to PTRACE_ATTACH to it before it has a chance to really fault.
//
// The PTRACE_ATTACH sends a SIGSTOP to the target process, but it
// won't necessarily have stopped by the time ptrace() returns. (We
// currently assume it does.) We write to the file descriptor to
// ensure that it can run as soon as we call PTRACE_CONT below.
// See details in bionic/libc/linker/debugger.c, in function
// debugger_signal_handler().
// Attach to the target process.
if (ptrace(PTRACE_ATTACH, request.tid, 0, 0) != 0) {
ALOGE("debuggerd: ptrace attach failed: %s", strerror(errno));
exit(1);
}
// Don't attach to the sibling threads if we want to attach gdb.
// Supposedly, it makes the process less reliable.
bool attach_gdb = should_attach_gdb(request);
if (attach_gdb) {
// Open all of the input devices we need to listen for VOLUMEDOWN before dropping privileges.
if (init_getevent() != 0) {
ALOGE("debuggerd: failed to initialize input device, not waiting for gdb");
attach_gdb = false;
}
}
std::set<pid_t> siblings;
if (!attach_gdb) {
ptrace_siblings(request.pid, request.tid, siblings);
}
// Generate the backtrace map before dropping privileges.
std::unique_ptr<BacktraceMap> backtrace_map(BacktraceMap::Create(request.pid));
bool succeeded = false;
// Now that we've done everything that requires privileges, we can drop them.
if (!drop_privileges()) {
ALOGE("debuggerd: failed to drop privileges, exiting");
_exit(1);
}
int crash_signal = SIGKILL;
succeeded = perform_dump(request, fd, tombstone_fd, backtrace_map.get(), siblings, &crash_signal);
if (succeeded) {
if (request.action == DEBUGGER_ACTION_DUMP_TOMBSTONE) {
if (!tombstone_path.empty()) {
write(fd, tombstone_path.c_str(), tombstone_path.length());
}
}
}
if (attach_gdb) {
// Tell the signal process to send SIGSTOP to the target.
if (!send_signal(request.pid, 0, SIGSTOP)) {
ALOGE("debuggerd: failed to stop process for gdb attach: %s", strerror(errno));
attach_gdb = false;
}
}
if (ptrace(PTRACE_DETACH, request.tid, 0, 0) != 0) {
ALOGE("debuggerd: ptrace detach from %d failed: %s", request.tid, strerror(errno));
}
for (pid_t sibling : siblings) {
ptrace(PTRACE_DETACH, sibling, 0, 0);
}
// Send the signal back to the process if it crashed and we're not waiting for gdb.
if (!attach_gdb && request.action == DEBUGGER_ACTION_CRASH) {
if (!send_signal(request.pid, request.tid, crash_signal)) {
ALOGE("debuggerd: failed to kill process %d: %s", request.pid, strerror(errno));
}
}
// Wait for gdb, if requested.
if (attach_gdb && succeeded) {
wait_for_user_action(request);
// Tell the signal process to send SIGCONT to the target.
if (!send_signal(request.pid, 0, SIGCONT)) {
ALOGE("debuggerd: failed to resume process %d: %s", request.pid, strerror(errno));
}
uninit_getevent();
}
exit(!succeeded);
}
static void handle_request(int fd) {
ALOGV("handle_request(%d)\n", fd);
ScopedFd closer(fd);
debugger_request_t request;
memset(&request, 0, sizeof(request));
int status = read_request(fd, &request);
if (status != 0) {
return;
}
ALOGV("BOOM: pid=%d uid=%d gid=%d tid=%d\n", request.pid, request.uid, request.gid, request.tid);
#if defined(__LP64__)
// On 64 bit systems, requests to dump 32 bit and 64 bit tids come
// to the 64 bit debuggerd. If the process is a 32 bit executable,
// redirect the request to the 32 bit debuggerd.
if (is32bit(request.tid)) {
// Only dump backtrace and dump tombstone requests can be redirected.
if (request.action == DEBUGGER_ACTION_DUMP_BACKTRACE ||
request.action == DEBUGGER_ACTION_DUMP_TOMBSTONE) {
redirect_to_32(fd, &request);
} else {
ALOGE("debuggerd: Not allowed to redirect action %d to 32 bit debuggerd\n", request.action);
}
return;
}
#endif
// Fork a child to handle the rest of the request.
pid_t fork_pid = fork();
if (fork_pid == -1) {
ALOGE("debuggerd: failed to fork: %s\n", strerror(errno));
return;
} else if (fork_pid != 0) {
waitpid(fork_pid, nullptr, 0);
return;
}
// Open the tombstone file if we need it.
std::string tombstone_path;
int tombstone_fd = -1;
switch (request.action) {
case DEBUGGER_ACTION_DUMP_TOMBSTONE:
case DEBUGGER_ACTION_CRASH:
tombstone_fd = open_tombstone(&tombstone_path);
if (tombstone_fd == -1) {
ALOGE("debuggerd: failed to open tombstone file: %s\n", strerror(errno));
exit(1);
}
break;
case DEBUGGER_ACTION_DUMP_BACKTRACE:
break;
default:
ALOGE("debuggerd: unexpected request action: %d", request.action);
exit(1);
}
// At this point, the thread that made the request is blocked in
// a read() call. If the thread has crashed, then this gives us
// time to PTRACE_ATTACH to it before it has a chance to really fault.
//
// The PTRACE_ATTACH sends a SIGSTOP to the target process, but it
// won't necessarily have stopped by the time ptrace() returns. (We
// currently assume it does.) We write to the file descriptor to
// ensure that it can run as soon as we call PTRACE_CONT below.
// See details in bionic/libc/linker/debugger.c, in function
// debugger_signal_handler().
// Attach to the target process.
if (ptrace(PTRACE_ATTACH, request.tid, 0, 0) != 0) {
ALOGE("debuggerd: ptrace attach failed: %s", strerror(errno));
exit(1);
}
// Don't attach to the sibling threads if we want to attach gdb.
// Supposedly, it makes the process less reliable.
bool attach_gdb = should_attach_gdb(&request);
int signal_in_fd = -1;
int signal_out_fd = -1;
pid_t signal_pid = 0;
if (attach_gdb) {
// Open all of the input devices we need to listen for VOLUMEDOWN before dropping privileges.
if (init_getevent() != 0) {
ALOGE("debuggerd: failed to initialize input device, not waiting for gdb");
attach_gdb = false;
}
// Fork a process that stays root, and listens on a pipe to pause and resume the target.
if (!fork_signal_sender(&signal_in_fd, &signal_out_fd, &signal_pid, request.pid)) {
attach_gdb = false;
}
}
auto notify_signal_sender = [=]() {
char buf[1];
if (TEMP_FAILURE_RETRY(write(signal_in_fd, "", 1)) != 1) {
ALOGE("debuggerd: failed to notify signal process: %s", strerror(errno));
} else if (TEMP_FAILURE_RETRY(read(signal_out_fd, buf, 1)) != 1) {
ALOGE("debuggerd: failed to read response from signal process: %s", strerror(errno));
}
};
std::set<pid_t> siblings;
if (!attach_gdb) {
ptrace_siblings(request.pid, request.tid, siblings);
}
// Generate the backtrace map before dropping privileges.
std::unique_ptr<BacktraceMap> backtrace_map(BacktraceMap::Create(request.pid));
bool succeeded = false;
// Now that we've done everything that requires privileges, we can drop them.
if (drop_privileges()) {
succeeded = perform_dump(request, fd, tombstone_fd, backtrace_map.get(), siblings);
if (succeeded) {
if (request.action == DEBUGGER_ACTION_DUMP_TOMBSTONE) {
if (!tombstone_path.empty()) {
write(fd, tombstone_path.c_str(), tombstone_path.length());
}
}
}
if (attach_gdb) {
// Tell the signal process to send SIGSTOP to the target.
notify_signal_sender();
}
}
if (ptrace(PTRACE_DETACH, request.tid, 0, 0) != 0) {
ALOGE("debuggerd: ptrace detach from %d failed: %s", request.tid, strerror(errno));
}
for (pid_t sibling : siblings) {
ptrace(PTRACE_DETACH, sibling, 0, 0);
}
// Wait for gdb, if requested.
if (attach_gdb && succeeded) {
wait_for_user_action(request);
// Tell the signal process to send SIGCONT to the target.
notify_signal_sender();
uninit_getevent();
waitpid(signal_pid, nullptr, 0);
}
exit(!succeeded);
}
