syscall trace at kernel land

hi , let me explain myself : for example , open syscall calls sys_open then do_sys_open so like: do_sys_open -> do_filp_open -> link_path_walk -> so on. so while the cpu is executing the link_path_walk , is there any procedure in kernel to check for the interrupt vector number which caused it to be invoked? i mean like one of my friends said that when kernel is about to restart a syscall then it raises signal -ERESTARTSYS signal for signal handler. but i think it is for something went wrong and kernel wanna start the syscall again. but in between a syscall routine is it possible to get vector number (i repeat ,sorry) ?? thanks in advance for help -- ........................ *MOHIT VERMA*