Using PTRACE_POKEDATA to replace data in the heap of a process

问题

I would like to use ptrace in order to attach my tool to a Linux process, read and write to the heap memory of this process and again detach my tool. Actually, it's not working although there is no error. I can not see any modifications in the heap memory of the process after I run the tool. Anyway, I'm quite not sure if that is possible in general. Currently, my C code looks like this:

      int res = 0, i = 0;
      int size = heap_address->end - heap_address->start;

      char tmp_page[size];
      memset(tmp_page, 'x', size); // just a test, I know this makes no sense

      printf(" -> Attaching to process...\n");
      res = ptrace(PTRACE_ATTACH, pid, NULL, NULL);
      if (res == -1) printf(" -> Error: ptrace attach\n");
      res = waitpid(pid, NULL, WUNTRACED);
      if (res != pid) printf(" -> Error: waitpid\n");

      printf(" -> Replacing heap\n");
      for (i=0; i < size; i+=4) {
       res = ptrace(PTRACE_POKEDATA, pid, heap_address->start+i, *(int *)(tmp_page+i));
         if (res == -1) printf(" -> Error: ptrace pokedata\n");
      }

      printf(" -> Detaching from process...\n");
      res = ptrace(PTRACE_DETACH, pid, NULL, NULL);
      if (res == -1) printf(" -> Error: ptrace detach\n");

来源：https://stackoverflow.com/questions/20099916/using-ptrace-pokedata-to-replace-data-in-the-heap-of-a-process