1.\" $OpenBSD: sigreturn.2,v 1.9 2007/05/31 19:19:34 jmc Exp $ 2.\" $NetBSD: sigreturn.2,v 1.6 1995/02/27 12:37:40 cgd Exp $ 3.\" 4.\" Copyright (c) 1985, 1991, 1993 5.\" The Regents of the University of California. All rights reserved. 6.\" 7.\" Redistribution and use in source and binary forms, with or without 8.\" modification, are permitted provided that the following conditions 9.\" are met: 10.\" 1. Redistributions of source code must retain the above copyright 11.\" notice, this list of conditions and the following disclaimer. 12.\" 2. Redistributions in binary form must reproduce the above copyright 13.\" notice, this list of conditions and the following disclaimer in the 14.\" documentation and/or other materials provided with the distribution. 15.\" 3. Neither the name of the University nor the names of its contributors 16.\" may be used to endorse or promote products derived from this software 17.\" without specific prior written permission. 18.\" 19.\" THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND 20.\" ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE 21.\" IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE 22.\" ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE 23.\" FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL 24.\" DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS 25.\" OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) 26.\" HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT 27.\" LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY 28.\" OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF 29.\" SUCH DAMAGE. 30.\" 31.\" @(#)sigreturn.2 8.1 (Berkeley) 6/4/93 32.\" 33.Dd $Mdocdate: May 31 2007 $ 34.Dt SIGRETURN 2 35.Os 36.Sh NAME 37.Nm sigreturn 38.Nd return from signal 39.Sh SYNOPSIS 40.Fd #include <signal.h> 41.Ft int 42.Fn sigreturn "struct sigcontext *scp" 43.Sh DESCRIPTION 44.Fn sigreturn 45allows users to atomically unmask, switch stacks, 46and return from a signal context. 47The processes signal mask and stack status are 48restored from the context. 49The system call does not return; 50the users stack pointer, frame pointer, argument pointer, 51and processor status longword are restored from the context. 52Execution resumes at the specified pc. 53This system call is used by the trampoline code and 54.Xr longjmp 3 55when returning from a signal to the previously executing program. 56.Pp 57Note that sigcontext contains machine dependent information. 58.Sh NOTES 59This system call is not available in 4.2 60.Tn BSD 61hence it should not be used if backward compatibility is needed. 62.Sh RETURN VALUES 63If successful, the system call does not return. 64Otherwise, a value of \-1 is returned and 65.Va errno 66is set to indicate the error. 67.Sh ERRORS 68.Fn sigreturn 69will fail and the process context will remain unchanged 70if one of the following occurs. 71.Bl -tag -width Er 72.It Bq Er EFAULT 73.Fa scp 74points to memory that is not a valid part of the process 75address space. 76.It Bq Er EINVAL 77The process status longword is invalid or would improperly 78raise the privilege level of the process. 79.El 80.Sh SEE ALSO 81.Xr sigaction 2 , 82.Xr setjmp 3 83.Sh HISTORY 84The 85.Fn sigreturn 86function call appeared in 87.Bx 4.3 . 88