1.\" Copyright (c) 1983, 1991 The Regents of the University of California. 2.\" All rights reserved. 3.\" 4.\" Redistribution and use in source and binary forms, with or without 5.\" modification, are permitted provided that the following conditions 6.\" are met: 7.\" 1. Redistributions of source code must retain the above copyright 8.\" notice, this list of conditions and the following disclaimer. 9.\" 2. Redistributions in binary form must reproduce the above copyright 10.\" notice, this list of conditions and the following disclaimer in the 11.\" documentation and/or other materials provided with the distribution. 12.\" 3. All advertising materials mentioning features or use of this software 13.\" must display the following acknowledgement: 14.\" This product includes software developed by the University of 15.\" California, Berkeley and its contributors. 16.\" 4. Neither the name of the University nor the names of its contributors 17.\" may be used to endorse or promote products derived from this software 18.\" without specific prior written permission. 19.\" 20.\" THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND 21.\" ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE 22.\" IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE 23.\" ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE 24.\" FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL 25.\" DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS 26.\" OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) 27.\" HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT 28.\" LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY 29.\" OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF 30.\" SUCH DAMAGE. 31.\" 32.\" from: @(#)sigstack.2 6.5 (Berkeley) 3/10/91 33.\" $Id: sigstack.2,v 1.4 1993/11/29 21:25:42 jtc Exp $ 34.\" 35.Dd March 10, 1991 36.Dt SIGSTACK 2 37.Os BSD 4.2 38.Sh NAME 39.Nm sigstack 40.Nd set and/or get signal stack context 41.Sh SYNOPSIS 42.Fd #include <sys/signal.h> 43.Bd -literal 44struct sigstack { 45 caddr_t ss_sp; 46 int ss_onstack; 47}; 48.Ed 49.Ft int 50.Fn sigstack "const struct sigstack *ss" "struct sigstack *oss" 51.Sh DESCRIPTION 52.Fn Sigstack 53allows users to define an alternate stack on which signals 54are to be processed. If 55.Fa ss 56is non-zero, 57it specifies a 58.Em "signal stack" 59on which to deliver signals 60and tells the system if the process is currently executing 61on that stack. When a signal's action indicates its handler 62should execute on the signal stack (specified with a 63.Xr sigvec 2 64call), the system checks to see 65if the process is currently executing on that stack. If the 66process is not currently executing on the signal stack, 67the system arranges a switch to the signal stack for the 68duration of the signal handler's execution. 69If 70.Fa oss 71is non-zero, the current signal stack state is returned. 72.Sh NOTES 73Signal stacks are not ``grown'' automatically, as is 74done for the normal stack. If the stack overflows 75unpredictable results may occur. 76.Sh RETURN VALUES 77Upon successful completion, a value of 0 is returned. 78Otherwise, a value of -1 is returned and 79.Va errno 80is set to indicate the error. 81.Sh ERRORS 82.Fn Sigstack 83will fail and the signal stack context will remain unchanged 84if one of the following occurs. 85.Bl -tag -width Er 86.It Bq Er EFAULT 87Either 88.Fa ss 89or 90.Fa oss 91points to memory that is not a valid part of the process 92address space. 93.El 94.Sh SEE ALSO 95.Xr sigvec 2 , 96.Xr setjmp 3 97.Sh HISTORY 98The 99.Fn sigstack 100function call appeared in 101.Bx 4.2 . 102