Full process name from task_struct

Did you mean exe file name? You can get the exe of current process as follows :

char *pathname,*p;
mm = current->mm;
if (mm) {
    down_read(&mm->mmap_sem);
    if (mm->exe_file) {
                pathname = kmalloc(PATH_MAX, GFP_ATOMIC);
                if (pathname) {
                      p = d_path(&mm->exe_file->f_path, pathname, PATH_MAX);
                    /*Now you have the path name of exe in p*/
                }
            }
    up_read(&mm->mmap_sem);
}