debuggerd: fix debug.debuggerd.wait_for_gdb.
Bug: http://b/26513486
Change-Id: I01c28ce810a49f8a4e0e2a86c7d018d95f9617c8
diff --git a/debuggerd/debuggerd.cpp b/debuggerd/debuggerd.cpp
index a8d19fc..8efbacc 100644
--- a/debuggerd/debuggerd.cpp
+++ b/debuggerd/debuggerd.cpp
@@ -59,8 +59,6 @@
#define SOCKET_NAME DEBUGGER_SOCKET_NAME
#endif
-extern "C" int tgkill(int tgid, int tid, int sig);
-
struct debugger_request_t {
debugger_action_t action;
pid_t pid, tid;
@@ -75,7 +73,7 @@
"* Process %d has been suspended while crashing.\n"
"* To attach gdbserver and start gdb, run this on the host:\n"
"*\n"
- "* gdbclient %d\n"
+ "* gdbclient.py -p %d\n"
"*\n"
"* Wait for gdb to start, then press the VOLUME DOWN key\n"
"* to let the process continue crashing.\n"
@@ -83,16 +81,13 @@
request.pid, request.tid);
// Wait for VOLUME DOWN.
- if (init_getevent() == 0) {
- while (true) {
- input_event e;
- if (get_event(&e, -1) == 0) {
- if (e.type == EV_KEY && e.code == KEY_VOLUMEDOWN && e.value == 0) {
- break;
- }
+ while (true) {
+ input_event e;
+ if (get_event(&e, -1) == 0) {
+ if (e.type == EV_KEY && e.code == KEY_VOLUMEDOWN && e.value == 0) {
+ break;
}
}
- uninit_getevent();
}
ALOGI("debuggerd resuming process %d", request.pid);
@@ -454,6 +449,65 @@
return true;
}
+static bool fork_signal_sender(int* in_fd, int* out_fd, pid_t* sender_pid, pid_t target_pid) {
+ int input_pipe[2];
+ int output_pipe[2];
+ if (pipe(input_pipe) != 0) {
+ ALOGE("debuggerd: failed to create input pipe for signal sender: %s", strerror(errno));
+ return false;
+ }
+
+ if (pipe(output_pipe) != 0) {
+ close(input_pipe[0]);
+ close(input_pipe[1]);
+ ALOGE("debuggerd: failed to create output pipe for signal sender: %s", strerror(errno));
+ return false;
+ }
+
+ pid_t fork_pid = fork();
+ if (fork_pid == -1) {
+ ALOGE("debuggerd: failed to initialize signal sender: fork failed: %s", strerror(errno));
+ return false;
+ } else if (fork_pid == 0) {
+ close(input_pipe[1]);
+ close(output_pipe[0]);
+ auto wait = [=]() {
+ char buf[1];
+ if (TEMP_FAILURE_RETRY(read(input_pipe[0], buf, 1)) != 1) {
+ ALOGE("debuggerd: signal sender failed to read from pipe");
+ exit(1);
+ }
+ };
+ auto notify_done = [=]() {
+ if (TEMP_FAILURE_RETRY(write(output_pipe[1], "", 1)) != 1) {
+ ALOGE("debuggerd: signal sender failed to write to pipe");
+ exit(1);
+ }
+ };
+
+ wait();
+ if (kill(target_pid, SIGSTOP) != 0) {
+ ALOGE("debuggerd: failed to stop target '%d': %s", target_pid, strerror(errno));
+ }
+ notify_done();
+
+ wait();
+ if (kill(target_pid, SIGCONT) != 0) {
+ ALOGE("debuggerd: failed to resume target '%d': %s", target_pid, strerror(errno));
+ }
+ notify_done();
+
+ exit(0);
+ } else {
+ close(input_pipe[0]);
+ close(output_pipe[1]);
+ *in_fd = input_pipe[1];
+ *out_fd = output_pipe[0];
+ *sender_pid = fork_pid;
+ return true;
+ }
+}
+
static void handle_request(int fd) {
ALOGV("handle_request(%d)\n", fd);
@@ -534,6 +588,31 @@
// 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);
@@ -556,8 +635,8 @@
}
if (attach_gdb) {
- // Stop the process so we can debug.
- tgkill(request.pid, request.tid, SIGSTOP);
+ // Tell the signal process to send SIGSTOP to the target.
+ notify_signal_sender();
}
}
@@ -569,16 +648,16 @@
ptrace(PTRACE_DETACH, sibling, 0, 0);
}
- if (succeeded && attach_gdb) {
- // if debug.debuggerd.wait_for_gdb is set, its value indicates if we should wait
- // for user action for the crashing process.
- // in this case, we log a message and turn the debug LED on
- // waiting for a gdb connection (for instance)
+ // Wait for gdb, if requested.
+ if (attach_gdb && succeeded) {
wait_for_user_action(request);
- }
- // Resume the stopped process.
- kill(request.pid, SIGCONT);
+ // Tell the signal process to send SIGCONT to the target.
+ notify_signal_sender();
+
+ uninit_getevent();
+ waitpid(signal_pid, nullptr, 0);
+ }
exit(!succeeded);
}