kern___getcwd() returns ENOTDIR

[Kentucky Mandeloid Mo.]

I'm writng a smal kernel module that catches file access syscalls.
At every syscall I need a full name of file is being passed to a syscall.
I'm getting it with a path passed to syscall and if path is not starting 
with / I get current working directory of process using kern___getcwd().
In every syscall all works just fine except rmdir & unlink.
Sometimes in unlink and everytime in rmdir it returns "not a directory" error.
I know already that kern___getcwd() works through vnode cache and this method 
is not a reliable way to get file names.
So is there any other way get cwd of a proccess?