#
# Copyright (c) 1993 Terrence R. Lambert.
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# $NetBSD: README,v 1.1 2000/12/11 13:48:12 jdolecek Exp $
#
1.0 Overview
This is the README file for the sample loaded system call.
2.0 Directions
To test the module, do the following:
make load
A load message (the copyright) will be printed on the console.
cd test
make load
The system call prints a message on the console when called.
This message will be printed when running "make load" in
the "test" subdirectory.
3.0 Recovering resources
The system call consumes 8 pages of memory when loaded; it
can be freed up by unloading it. To unload it, type the
following from the directory this file is in:
cd module
make unload
The system call will be unloaded by name.
4.0 System call modules
System calls as loadable modules use one of two approaches.
If the system call slot is unspecified (-1), it will attempt
to locate (and allocate) the next free call slot that points
to the address of the "lkmnosys" function (an alias for the
"nosys" function). It replaces this with the user's call;
the user can tell which slot was allocated using the "modstat"
command (the call slot is indicated by the value of "Off").
If the system call slot is specified, it will replace that
specific call (assuming it is in range of the entries in the
sysent[] table). Care should be taken when replacing system
calls. Good candiates are calls which the user is attempting
to repair or make POSIX compliant. It is possible to replace
all calls, although care should be taken with the "ioctl()"
call, as it is the interface for the lkm loader.
When unloaded, the system call module replaces the previous
contents of the call slot it was loaded in. If this was an
allocable slot, it is now reallocable; if it was a particular
call slot, the previous function is restored.
The directory ./sample/syscall contains a sample implementation
of a loadable system call.
5.0 END OF DOCUMENT
