Does /sys/module/foo reflect external module name?

[Andrey Borzenkov <arvidjaar@mail.ru>]

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Is it correct that /sys/module lists module *file* names (sans -_ confusion)? 
Is it possible to find out if module is built in or truly external? The goal 
is to automate initrd build by walking from /dev/root up and pulling in all 
modules. Now missing module may mean that it is built in or that it is really 
missing :) In my case:

{pts/1}% for i in /sys/module/*
for> do
for> grep -q ${i:t} /proc/modules || echo $i
for> done
/sys/module/8250
/sys/module/i8042
/sys/module/md_mod
/sys/module/psmouse
/sys/module/tcp_bic
{pts/1}% for i in $(lsmod | awk '{print $1}')
do
[[ -d /sys/module/$i ]] || echo $i
done
Module

so it looks quite reliable up to built in modules. Is there any information 
that could be exported in sysfs (like "builtin" == 0|1)?

TIA

- -andrey
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