where is c code of moderror used in insmod.c?

[fsshl <elins@bresnan.net>]

dear gcc advancer:

  I am trying to find where is the c source code of moderror (a function
used in insmod.c).  In insmod.c, there are manu include files

#include <stdio.h>
#include <string.h>
#include <stdlib.h>
#include <unistd.h>
#include <fcntl.h>
#include <sys/mman.h>
#include <sys/types.h>
#include <sys/stat.h>
#include <unistd.h>
#include <errno.h>
#include <asm/unistd.h>
                         these .h files is stored in my /usr/include
#include "backwards_compat.c"

  I checked all there directory by
root@etutor:/usr/include# find . | xargs grep -n 'moderror' /dev/null

but did not get any message as well as same directory's last one
backwards_compat.c

  please help
eric
(ubuntu linux 5.10-2.6.12-9.386)