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.\" @(#)sigstack.2 6.5 (Berkeley) 3/10/91 33.\" 34.Dd March 10, 1991 35.Dt SIGSTACK 2 36.Os BSD 4.2 37.Sh NAME 38.Nm sigstack 39.Nd set and/or get signal stack context 40.Sh SYNOPSIS 41.Fd #include <sys/signal.h> 42.Bd -literal 43struct sigstack { 44 caddr_t ss_sp; 45 int ss_onstack; 46}; 47.Ed 48.Ft int 49.Fn sigstack "const struct sigstack *ss" "struct sigstack *oss" 50.Sh DESCRIPTION 51.Fn Sigstack 52allows users to define an alternate stack on which signals 53are to be processed. If 54.Fa ss 55is non-zero, 56it specifies a 57.Em "signal stack" 58on which to deliver signals 59and tells the system if the process is currently executing 60on that stack. When a signal's action indicates its handler 61should execute on the signal stack (specified with a 62.Xr sigvec 2 63call), the system checks to see 64if the process is currently executing on that stack. If the 65process is not currently executing on the signal stack, 66the system arranges a switch to the signal stack for the 67duration of the signal handler's execution. 68If 69.Fa oss 70is non-zero, the current signal stack state is returned. 71.Sh NOTES 72Signal stacks are not ``grown'' automatically, as is 73done for the normal stack. If the stack overflows 74unpredictable results may occur. 75.Sh RETURN VALUES 76Upon successful completion, a value of 0 is returned. 77Otherwise, a value of -1 is returned and 78.Va errno 79is set to indicate the error. 80.Sh ERRORS 81.Fn Sigstack 82will fail and the signal stack context will remain unchanged 83if one of the following occurs. 84.Bl -tag -width [EFAULT] 85.It Bq Er EFAULT 86Either 87.Fa ss 88or 89.Fa oss 90points to memory that is not a valid part of the process 91address space. 92.El 93.Sh SEE ALSO 94.Xr sigvec 2 , 95.Xr setjmp 3 96.Sh HISTORY 97The 98.Nm 99function call appeared in 100.Bx 4.2 . 101