Stalker crashes apparently on pthread_create

[alvarofe]

I have been playing with Stalker however it crashes always on my case on pthread_create. At first, I tried to stalk all threads but that crashes as well though it might reasonable to some extent - not familiar with Stalker API and how it works underneath. Therefore, I intercept a callback generated in the native layer of the application to stalk from there. Basically, the idea is to get all the basic blocks to print them on IDA.

const callback_offset = ;
const callback = Module.findBaseAddress('*****').add(callback_offset);
let thread_followed: number = 0; 

Interceptor.attach(callback, {
  onEnter(args) {
    if (this.threadId != thread_followed) {
      if (thread_followed != 0) {
        Stalker.unfollow(thread_followed);
        Stalker.flush();
      }
      console.log("[+] Following " + this.threadId);
      Stalker.follow(this.threadId, {
        events: {
          compile : true
        },
        onReceive(rawEvents) {
          const events = Stalker.parse(rawEvents, {annotate: false}) as StalkerCompileEventBare[];
          events.forEach(ev => {
            const blockstart = ev[0] as NativePointer;
          });
        }
      });
      thread_followed = this.threadId;
    }
  },
});

This is the backtrace

#00:  0xb7e7db18  (null)
#01:  0x0001f9e0  /system/lib64/libc.so  clone
#02:  0x0001f9e0  /system/lib64/libc.so  clone
#03:  0x0006d3fc  /system/lib64/libc.so  pthread_create
#04:  0x0006d3fc  /system/lib64/libc.so  pthread_create
#05:  0x001c5450  /data/app/com.******

I will spend some time to understand how stalker works. Although this is not my priority number one within the TODO I currently have I would like to fix it. Thus, If you have any idea what would be happening it would help me to fix this sooner.

Btw, running this on Android arm64

[alvarofe]

When stalking one thread that at the same time creates another thread, these two internally share for example the arm64writer failing the process of rewritting leading to a crash. Ideally, it should detect calls to clone to unfollow the child to run freely or stalk this new thread.