96 lines
3.7 KiB
Plaintext
96 lines
3.7 KiB
Plaintext
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#
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# Copyright (c) 1993 Terrence R. Lambert.
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# All rights reserved.
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#
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# Redistribution and use in source and binary forms, with or without
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# modification, are permitted provided that the following conditions
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# are met:
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# 1. Redistributions of source code must retain the above copyright
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# notice, this list of conditions and the following disclaimer.
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# 2. Redistributions in binary form must reproduce the above copyright
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# notice, this list of conditions and the following disclaimer in the
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# documentation and/or other materials provided with the distribution.
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# 3. All advertising materials mentioning features or use of this software
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# must display the following acknowledgement:
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# This product includes software developed by Terrence R. Lambert.
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# 4. The name Terrence R. Lambert may not be used to endorse or promote
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# products derived from this software without specific prior written
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# permission.
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#
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# THIS SOFTWARE IS PROVIDED BY TERRENCE R. LAMBERT ``AS IS'' AND ANY
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# EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
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# IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
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# ARE DISCLAIMED. IN NO EVENT SHALL THE TERRENCE R. LAMBERT BE LIABLE
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# FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
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# DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
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# OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
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# HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
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# LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
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# OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
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# SUCH DAMAGE.
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#
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# $NetBSD: README,v 1.1 2000/12/11 13:48:12 jdolecek Exp $
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#
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1.0 Overview
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This is the README file for the sample loaded system call.
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2.0 Directions
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To test the module, do the following:
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make load
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A load message (the copyright) will be printed on the console.
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cd test
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make load
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The system call prints a message on the console when called.
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This message will be printed when running "make load" in
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the "test" subdirectory.
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3.0 Recovering resources
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The system call consumes 8 pages of memory when loaded; it
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can be freed up by unloading it. To unload it, type the
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following from the directory this file is in:
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cd module
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make unload
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The system call will be unloaded by name.
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4.0 System call modules
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System calls as loadable modules use one of two approaches.
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If the system call slot is unspecified (-1), it will attempt
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to locate (and allocate) the next free call slot that points
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to the address of the "lkmnosys" function (an alias for the
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"nosys" function). It replaces this with the user's call;
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the user can tell which slot was allocated using the "modstat"
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command (the call slot is indicated by the value of "Off").
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If the system call slot is specified, it will replace that
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specific call (assuming it is in range of the entries in the
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sysent[] table). Care should be taken when replacing system
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calls. Good candiates are calls which the user is attempting
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to repair or make POSIX compliant. It is possible to replace
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all calls, although care should be taken with the "ioctl()"
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call, as it is the interface for the lkm loader.
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When unloaded, the system call module replaces the previous
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contents of the call slot it was loaded in. If this was an
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allocable slot, it is now reallocable; if it was a particular
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call slot, the previous function is restored.
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The directory ./sample/syscall contains a sample implementation
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of a loadable system call.
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5.0 END OF DOCUMENT
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