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.\" -*- nroff -*-
.\"
.\" Copyright (c) 2001 Alexander Langer
.\"
.\" All rights reserved.
.\"
.\" This program is free software.
.\"
.\" Redistribution and use in source and binary forms, with or without
.\" modification, are permitted provided that the following conditions
.\" are met:
.\" 1. Redistributions of source code must retain the above copyright
.\" notice, this list of conditions and the following disclaimer.
.\" 2. Redistributions in binary form must reproduce the above copyright
.\" notice, this list of conditions and the following disclaimer in the
.\" documentation and/or other materials provided with the distribution.
.\"
.\" THIS SOFTWARE IS PROVIDED BY THE DEVELOPERS ``AS IS'' AND ANY EXPRESS OR
.\" IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES
.\" OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED.
.\" IN NO EVENT SHALL THE DEVELOPERS BE LIABLE FOR ANY DIRECT, INDIRECT,
.\" INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT
.\" NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
.\" DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
.\" THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
.\" (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF
.\" THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
.\"
.Dd June 15, 2023
.Dt SYSCALL_MODULE 9
.Os
.Sh NAME
.Nm SYSCALL_MODULE
.Nd syscall kernel module declaration macro
.Sh SYNOPSIS
.In sys/param.h
.In sys/kernel.h
.In sys/proc.h
.In sys/module.h
.In sys/sysent.h
.Fn SYSCALL_MODULE name "int *offset" "struct sysent *new_sysent" "modeventhand_t evh" "void *arg"
.Sh DESCRIPTION
The
.Fn SYSCALL_MODULE
macro declares a new syscall.
.Fn SYSCALL_MODULE
expands into a kernel module declaration with name
.Ql sys/ Ns Fa name .
.Pp
The rest of the arguments expected by this macro are:
.Bl -tag -width ".Fa new_sysent"
.It Fa offset
A pointer to an
.Vt int
which saves the offset in
.Vt "struct sysent"
where the syscall is allocated.
If the location pointed to by
.Fa offset
holds a non 0 number it will be used if possible.
If it holds 0 then one will be assigned.
.It Fa new_sysent
is a pointer to a structure that specifies the function implementing
the syscall and the number of arguments this function needs (see
.In sys/sysent.h ) .
.It Fa evh
A pointer to the kernel module event handler function with the argument
.Fa arg .
Please refer to
.Xr module 9
for more information.
.It Fa arg
The argument passed to the callback functions of the
.Fa evh
event handler when it is called.
.El
.Pp
The syscall number assigned to the module can be retrieved using the
.Xr modstat 2
and
.Xr modfind 2
system calls.
The MACRO
.Fn SYSCALL_MODULE_HELPER
includes
.Fn SYSCALL_MODULE
and much of its boilerplate code.
.Sh EXAMPLES
A minimal example for a syscall module can be found in
.Pa /usr/share/examples/kld/syscall/module/syscall.c .
.Sh SEE ALSO
.Xr module 9
.Pp
.Pa /usr/share/examples/kld/syscall/module/syscall.c
.Sh AUTHORS
This manual page was written by
.An Alexander Langer Aq Mt alex@FreeBSD.org .
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