Make zygote notifier more reliable

native/jni/core/bootstages.cpp

@@ -583,7 +583,7 @@ static void dump_logs() {
 		sprintf(buf, "/system/bin/%s", app);
 		if (lstat(buf, &st) == 0 && S_ISREG(st.st_mode)) {
 			clone_attr(buf, MAGISKTMP "/app_process");
-			bind_mount(MAGISKTMP "/app_process", buf);
+			bind_mount(MAGISKTMP "/app_process", buf, false);
 		}
 	}
 	unblock_boot_process();

native/jni/core/magisk.cpp

@@ -129,6 +129,7 @@ int app_process_main(int argc, char *argv[]) {
 		int fd = connect_daemon();
 		write_int(fd, ZYGOTE_NOTIFY);
 		write_string(fd, path);
+		read_int(fd);
 		close(fd);
 	} else {
 		// Redirect to system mirror

native/jni/include/daemon.h

@@ -80,7 +80,6 @@ void install_apk(const char *apk);
 
 void magiskhide_handler(int client);
 void zygote_notify(int client, struct ucred *cred);
-void zygote_notify(int pid);
 
 /*************
  * Superuser *

native/jni/magiskhide/hide_utils.cpp

@@ -18,7 +18,7 @@
 
 using namespace std;
 
-static pthread_t proc_monitor_thread;
+pthread_t proc_monitor_thread;
 
 static const char *prop_key[] =
 	{ "ro.boot.vbmeta.device_state", "ro.boot.verifiedbootstate", "ro.boot.flash.locked",
@@ -328,21 +328,3 @@ void auto_start_magiskhide() {
 	}
 }
 
-int next_zygote = -1;
-
-void zygote_notify(int pid) {
-	if (hide_enabled) {
-		MutexGuard lock(monitor_lock);
-		next_zygote = pid;
-		pthread_kill(proc_monitor_thread, SIGZYGOTE);
-	}
-}
-
-void zygote_notify(int client, struct ucred *cred) {
-	char *path = read_string(client);
-	close(client);
-	zygote_notify(cred->pid);
-	usleep(100000);
-	xmount(MAGISKTMP "/app_process", path, nullptr, MS_BIND, nullptr);
-	free(path);
-}

native/jni/magiskhide/magiskhide.h

@@ -1,5 +1,4 @@
-#ifndef MAGISK_HIDE_H
-#define MAGISK_HIDE_H
+#pragma once
 
 #include <pthread.h>
 #include <sys/types.h>
@@ -54,6 +53,7 @@ static inline int parse_int(const char *s) {
 	return val;
 }
 
+extern pthread_t proc_monitor_thread;
 extern bool hide_enabled;
 extern pthread_mutex_t monitor_lock;
 extern std::set<std::pair<std::string, std::string>> hide_set;
@@ -75,5 +75,3 @@ enum {
 	HIDE_ITEM_NOT_EXIST,
 	HIDE_NO_NS
 };
-
-#endif

native/jni/magiskhide/proc_monitor.cpp

@@ -241,6 +241,32 @@ static void term_thread(int) {
 //#define PTRACE_LOG(fmt, args...) LOGD("PID=[%d] " fmt, pid, ##args)
 #define PTRACE_LOG(...)
 
+int next_zygote = -1;
+
+void zygote_notify(int client, struct ucred *cred) {
+	char *path = read_string(client);
+
+	xptrace(PTRACE_ATTACH, cred->pid);
+	// Wait for attach
+	waitpid(cred->pid, nullptr, __WALL | __WNOTHREAD);
+	xptrace(PTRACE_CONT, cred->pid);
+	write_int(client, 0);
+	close(client);
+	// Wait for exec
+	waitpid(cred->pid, nullptr, __WALL | __WNOTHREAD);
+	xptrace(PTRACE_DETACH, cred->pid);
+
+	if (hide_enabled) {
+		MutexGuard lock(monitor_lock);
+		next_zygote = cred->pid;
+		pthread_kill(proc_monitor_thread, SIGZYGOTE);
+	}
+
+	// Remount zygote notifier ASAP
+	xmount(MAGISKTMP "/app_process", path, nullptr, MS_BIND, nullptr);
+	free(path);
+}
+
 static bool check_pid(int pid) {
 	char path[128];
 	char cmdline[1024];