140 lines
4.1 KiB
Groff
140 lines
4.1 KiB
Groff
.\" Copyright (c) 2018 Conrad Meyer <cem@FreeBSD.org>
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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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.\"
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.\" THIS SOFTWARE IS PROVIDED BY THE AUTHOR AND CONTRIBUTORS ``AS IS'' AND
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.\" ANY 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 AUTHOR OR CONTRIBUTORS 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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.\" $FreeBSD$
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.\"
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.Dd February 10, 2018
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.Dt SYSCALL_HELPER_REGISTER 9
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.Os
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.Sh NAME
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.Nm syscall_helper_register ,
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.Nm syscall_helper_unregister
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.Nd kernel syscall registration routines
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.\"
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.Sh SYNOPSIS
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.In sys/sysent.h
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.Ft int
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.Fn syscall_helper_register "struct syscall_helper_data *sd" "int flags"
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.Ft int
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.Fn syscall_helper_unregister "struct syscall_helper_data *sd"
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.\"
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.Ss INITIALIZER MACROS
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.Ft struct syscall_helper_data
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.Fn SYSCALL_INIT_HELPER "syscallname"
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.Ft struct syscall_helper_data
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.Fn SYSCALL_INIT_HELPER_F "syscallname" "int flags"
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.\"
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.Ss COMPATIBILITY INITIALIZER MACROS
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.Ft struct syscall_helper_data
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.Fn SYSCALL_INIT_HELPER_COMPAT "syscallname"
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.Ft struct syscall_helper_data
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.Fn SYSCALL_INIT_HELPER_COMPAT_F "syscallname" "int flags"
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.\"
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.Sh DESCRIPTION
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The
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.Fn syscall_helper_register
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registers a system call.
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This function takes the structure
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.Va struct syscall_helper_data sd ,
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which specifies the parameters for syscall registration:
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.Pp
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.Bd -literal -offset indent -compact
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struct syscall_helper_data {
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struct sysent new_sysent;
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struct sysent old_sysent;
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int syscall_no;
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int registered;
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};
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.Ed
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.Pp
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The only valid flag for the
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.Fa flags
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argument to
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.Fn syscall_helper_register
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is
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.Dv SY_THR_STATIC .
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This flag prevents the syscall from being unregistered.
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.\"
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.Pp
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Before use, the structure must be initialized with one of the
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.Fn SYSCALL_INIT_HELPER*
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macros.
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In new code, syscall implementation functions shall be named
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.Fn sys_syscallname
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and the regular macros shall be used.
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.Pp
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For legacy syscall functions named without "sys_" prefixes, the "COMPAT"
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versions of the macros may be used.
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.Pp
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The only valid flag for the
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.Fa flags
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argument to the "F" variants of the initializer macros is
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.Dv SYF_CAPENABLED .
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This flag indicates that the syscall is allowed in capability mode.
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.Pp
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The
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.Fn syscall_helper_unregister
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unregisters a system call.
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This function takes the same structure
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.Va struct syscall_helper_data sd
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that was previously initialized in the manner described above and used in a
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successful invocation of
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.Fn syscall_helper_register .
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.\"
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.Sh RETURN VALUES
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If successful,
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.Fn syscall_helper_register
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and
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.Fn syscall_helper_unregister
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will return 0.
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Otherwise, they will return an error.
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.\"
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.Sh ERRORS
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The
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.Fn syscall_helper_register
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call will fail and the syscall will not be registered if:
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.Bl -tag -width Er
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.It Bq Er EINVAL
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The
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.Fa flags
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argument contained a value other than
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.Dv SY_THR_STATIC .
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.It Bq Er EINVAL
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The specified syscall number,
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.Dv sd.syscall_no
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.Dv ( SYS_syscallname ) ,
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was outside of the valid range of system call numbers (zero through
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.Dv SYS_MAXSYSCALL ) .
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.It Bq Er ENFILE
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The system call table does not have any available slots.
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.It Bq Er EEXIST
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The specified syscall number,
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.Dv sd.syscall_no
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.Dv ( SYS_syscallname ) ,
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was already in use.
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.El
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.\"
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.Sh SEE ALSO
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.Xr SYSCALL_MODULE 9
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