[BACK]Return to syscall.2 CVS log [TXT][DIR] Up to [cvs.NetBSD.org] / src / lib / libc / sys

File: [cvs.NetBSD.org] / src / lib / libc / sys / syscall.2 (download)

Revision 1.17, Fri Nov 23 20:29:40 2007 UTC (16 years, 4 months ago) by dsl
Branch: MAIN
CVS Tags: yamt-pf42-baseX, yamt-pf42-base4, yamt-pf42-base3, yamt-pf42-base2, yamt-pf42-base, yamt-pf42, wrstuden-revivesa-base-3, wrstuden-revivesa-base-2, wrstuden-revivesa-base-1, wrstuden-revivesa-base, wrstuden-revivesa, netbsd-5-base, netbsd-5-2-RELEASE, netbsd-5-2-RC1, netbsd-5-2-3-RELEASE, netbsd-5-2-2-RELEASE, netbsd-5-2-1-RELEASE, netbsd-5-2, netbsd-5-1-RELEASE, netbsd-5-1-RC4, netbsd-5-1-RC3, netbsd-5-1-RC2, netbsd-5-1-RC1, netbsd-5-1-5-RELEASE, netbsd-5-1-4-RELEASE, netbsd-5-1-3-RELEASE, netbsd-5-1-2-RELEASE, netbsd-5-1-1-RELEASE, netbsd-5-1, netbsd-5-0-RELEASE, netbsd-5-0-RC4, netbsd-5-0-RC3, netbsd-5-0-RC2, netbsd-5-0-RC1, netbsd-5-0-2-RELEASE, netbsd-5-0-1-RELEASE, netbsd-5-0, netbsd-5, mjf-devfs2-base, mjf-devfs2, matt-nb5-pq3-base, matt-nb5-pq3, matt-nb5-mips64-u2-k2-k4-k7-k8-k9, matt-nb5-mips64-u1-k1-k5, matt-nb5-mips64-premerge-20101231, matt-nb5-mips64-premerge-20091211, matt-nb5-mips64-k15, matt-nb5-mips64, matt-nb4-mips64-k7-u2a-k9b, matt-mips64-base2, matt-armv6-nbase, matt-armv6-base, keiichi-mipv6-base, keiichi-mipv6, jym-xensuspend-nbase, jym-xensuspend-base, jym-xensuspend, hpcarm-cleanup-nbase, hpcarm-cleanup-base, cube-autoconf-base, cube-autoconf, christos-time_t-nbase, christos-time_t-base, christos-time_t
Changes since 1.16: +10 -2 lines

Add a note about the difficulty of actually looking at the return value
of __syscall() caused by ABIs (eg sparc) that don't pass the low bits of
a 64 bit result in the same register as a 32 bit result.

.\"	$NetBSD: syscall.2,v 1.17 2007/11/23 20:29:40 dsl Exp $
.\"
.\" Copyright (c) 1980, 1991, 1993
.\"	The Regents of the University of California.  All rights reserved.
.\"
.\" 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.
.\" 3. Neither the name of the University nor the names of its contributors
.\"    may be used to endorse or promote products derived from this software
.\"    without specific prior written permission.
.\"
.\" THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``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 REGENTS OR CONTRIBUTORS 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.
.\"
.\"     @(#)syscall.2	8.1 (Berkeley) 6/16/93
.\"
.Dd November 23, 2006
.Dt SYSCALL 2
.Os
.Sh NAME
.Nm syscall ,
.Nm __syscall
.Nd indirect system call
.Sh LIBRARY
.Lb libc
.Sh SYNOPSIS
.In sys/syscall.h
.In unistd.h
.Ft int
.Fn syscall "int number" "..."
.Ft quad_t
.Fn __syscall "quad_t number" "..."
.Sh DESCRIPTION
.Fn syscall
performs the system call whose assembly language
interface has the specified
.Fa number
with the specified arguments.
Symbolic constants for system calls can be found in the header file
.Ao Pa sys/syscall.h Ac .
The
.Nm __syscall
form should be used when one or more of the parameters is a
64-bit argument to ensure that argument alignment is correct.
This system call is useful for testing new system calls that
do not have entries in the C library.
.Sh RETURN VALUES
The return values are defined by the system call being invoked.
In general, a 0 return value indicates success.
A \-1 return value indicates an error,
and an error code is stored in
.Va errno .
.Sh HISTORY
The
.Fn syscall
function call appeared in
.Bx 4.0 .
.Sh BUGS
There is no way to simulate system calls that have multiple return values
such as
.Xr pipe 2 .
.Pp
Since architectures return 32 bit and 64 bit results in different registers,
it may be impossible to portably convert the result of
.Fn __syscall
to a 32bit value.
For instance sparc returns 32 bit values in %o0 and 64 bit values in %o0:%o1
(with %o0 containing the most significant part) so a 32 bit right shift
of the result is needed to get a correct 32 bit result.
.Pp
Due to ABI implementation differences in passing struct or union
type arguments to system calls between different processors, all
system calls pass instead pointers to such structs or unions, even
when the documentation of the system call mentions otherwise.
The conversion between passing structs and unions is handled normally
via userland stubs.
The correct arguments for the kernel entry
points for each system call can be found in the header file
.Ao Pa sys/syscallargs.h Ac