How to make glibc support custom syscalls

[Matt McCutchen <hashproduct at gmail dot com>]

Dear glibc people,

I have customized my Linux kernel to support lchmod and lutimes with
syscall numbers 313 and 315 respectively.  I would like to customize
glibc so that it implements lchmod and lutimes via these syscall numbers
and so that, when I compile rsync, it can find the calls at ./configure
time.

I am using Fedora Core 5, and I would prefer to have a set of RPM
packages that correspond one-to-one to the main Fedora ones.  Each
customized package should have a special name so yum won't "upgrade" it
to a newer version of ordinary glibc, breaking programs that use lchmod
and lutimes, yet it should have a provide entry for the ordinary package
name because it serves the purpose of ordinary glibc.

Do I need to add implementations of lchmod and lutimes to the glibc
source?  If so, could someone help me?  The innards of glibc look
terribly complex, and though I bet adding a wrapper for a syscall takes
only a few lines, I don't know what those lines would be.

Thanks.

Matt McCutchen