debuggerd_handler: actually wait for pseudothread to exit. (f47ca0f2) · Commits · e / os / android_system_core

debuggerd/handler/debuggerd_handler.cpp

+13 −9

Original line number	Diff line number	Diff line
		@@ -31,6 +31,7 @@
		#include <errno.h>
		#include <fcntl.h>
		#include <inttypes.h>
		#include <linux/futex.h>
		#include <pthread.h>
		#include <sched.h>
		#include <signal.h>
		@@ -46,6 +47,7 @@
		#include <sys/wait.h>
		#include <unistd.h>

		#include "private/bionic_futex.h"
		#include "private/libc_logging.h"

		// see man(2) prctl, specifically the section about PR_GET_NAME
		@@ -151,7 +153,6 @@ static bool have_siginfo(int signum) {
		}

		struct debugger_thread_info {
		pthread_mutex_t mutex = PTHREAD_MUTEX_INITIALIZER;
		bool crash_dump_started = false;
		pid_t crashing_tid;
		pid_t pseudothread_tid;
		@@ -228,7 +229,7 @@ static int debuggerd_dispatch_pseudothread(void* arg) {
		}
		}

		pthread_mutex_unlock(&thread_info->mutex);
		syscall(__NR_exit, 0);
		return 0;
		}

		@@ -267,23 +268,26 @@ static void debuggerd_signal_handler(int signal_number, siginfo_t* info, void*)
		}

		debugger_thread_info thread_info = {
		.pseudothread_tid = -1,
		.crashing_tid = gettid(),
		.signal_number = signal_number,
		.info = info
		};
		pthread_mutex_lock(&thread_info.mutex);

		// Essentially pthread_create without CLONE_FILES (see debuggerd_dispatch_pseudothread).
		pid_t child_pid = clone(debuggerd_dispatch_pseudothread, pseudothread_stack,
		CLONE_THREAD \| CLONE_SIGHAND \| CLONE_VM \| CLONE_CHILD_SETTID,
		pid_t child_pid =
		clone(debuggerd_dispatch_pseudothread, pseudothread_stack,
		CLONE_THREAD \| CLONE_SIGHAND \| CLONE_VM \| CLONE_CHILD_SETTID \| CLONE_CHILD_CLEARTID,
		&thread_info, nullptr, nullptr, &thread_info.pseudothread_tid);
		if (child_pid == -1) {
		fatal("failed to spawn debuggerd dispatch thread: %s", strerror(errno));
		}

		// Wait for the child to finish and unlock the mutex.
		// This relies on bionic behavior that isn't guaranteed by the standard.
		pthread_mutex_lock(&thread_info.mutex);
		// Wait for the child to start...
		__futex_wait(&thread_info.pseudothread_tid, -1, nullptr);

		// and then wait for it to finish.
		__futex_wait(&thread_info.pseudothread_tid, child_pid, nullptr);

		// Signals can either be fatal or nonfatal.
		// For fatal signals, crash_dump will PTRACE_CONT us with the signal we