How to get filename of an open file descriptor

[Yuri]

I am looking for functionality similar to Linux's /proc/<PID>/fd/<FD>.
I need to know what is the file name of an open file descriptor.

/proc/<PID>/fd is missing on FreeBSD.

There's something called 'fdescfs'. In /dev/fd/ it shows the list of file
descriptors. But they don't seem to be symbolic links to open files. And also it
only shows FDs of the current process.

So why there's no /proc/<PID>/fd in FreeBSD?
And how do I work around this?
Or should I just invest time and write a kernel patch implementing /proc/<PID>/fd/?

Yuri