NetBSD/lib/libc/sys/sigstack.2

.\" Copyright (c) 1983, 1991 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. All advertising materials mentioning features or use of this software
.\"    must display the following acknowledgement:
.\"	This product includes software developed by the University of
.\"	California, Berkeley and its contributors.
.\" 4. 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.
.\"
.\"     from: @(#)sigstack.2	6.5 (Berkeley) 3/10/91
.\"	$Id: sigstack.2,v 1.4 1993/11/29 21:25:42 jtc Exp $
.\"
.Dd March 10, 1991
.Dt SIGSTACK 2
.Os BSD 4.2
.Sh NAME
.Nm sigstack
.Nd set and/or get signal stack context
.Sh SYNOPSIS
.Fd #include <sys/signal.h>
.Bd -literal
struct sigstack {
	caddr_t ss_sp;
	int     ss_onstack;
};
.Ed
.Ft int
.Fn sigstack "const struct sigstack *ss" "struct sigstack *oss"
.Sh DESCRIPTION
.Fn Sigstack
allows users to define an alternate stack on which signals
are to be processed.  If
.Fa ss
is non-zero,
it specifies a
.Em "signal stack"
on which to deliver signals
and tells the system if the process is currently executing
on that stack.  When a signal's action indicates its handler
should execute on the signal stack (specified with a
.Xr sigvec 2
call), the system checks to see
if the process is currently executing on that stack.  If the
process is not currently executing on the signal stack,
the system arranges a switch to the signal stack for the
duration of the signal handler's execution. 
If
.Fa oss
is non-zero, the current signal stack state is returned.
.Sh NOTES
Signal stacks are not ``grown'' automatically, as is
done for the normal stack.  If the stack overflows
unpredictable results may occur.
.Sh RETURN VALUES
Upon successful completion, a value of 0 is returned.
Otherwise, a value of -1 is returned and 
.Va errno
is set to indicate the error.
.Sh ERRORS
.Fn Sigstack
will fail and the signal stack context will remain unchanged
if one of the following occurs.
.Bl -tag -width Er
.It Bq Er EFAULT
Either
.Fa ss
or
.Fa oss
points to memory that is not a valid part of the process
address space.
.El
.Sh SEE ALSO
.Xr sigvec 2 ,
.Xr setjmp 3
.Sh HISTORY
The
.Fn sigstack
function call appeared in
.Bx 4.2 .