1.\" Copyright (c) 1985, 1991, 1993 2.\" The Regents of the University of California. 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. Neither the name of the University nor the names of its contributors 13.\" may be used to endorse or promote products derived from this software 14.\" without specific prior written permission. 15.\" 16.\" THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND 17.\" ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE 18.\" IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE 19.\" ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE 20.\" FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL 21.\" DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS 22.\" OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) 23.\" HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT 24.\" LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY 25.\" OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF 26.\" SUCH DAMAGE. 27.\" 28.\" @(#)sigreturn.2 8.1 (Berkeley) 6/4/93 29.\" $FreeBSD: src/lib/libc/sys/sigreturn.2,v 1.6.2.6 2002/09/15 00:33:23 archie Exp $ 30.\" 31.Dd June 4, 1993 32.Dt SIGRETURN 2 33.Os 34.Sh NAME 35.Nm sigreturn 36.Nd return from signal 37.Sh LIBRARY 38.Lb libc 39.Sh SYNOPSIS 40.In signal.h 41.Ft int 42.Fn sigreturn "ucontext_t *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 structure pointed to by 49.Fa scp . 50The system call does not return; 51the users stack pointer, frame pointer, argument pointer, 52and processor status longword are restored from the context. 53Execution resumes at the specified pc. 54This system call is used by the trampoline code and 55.Xr longjmp 3 56when returning from a signal to the previously executing program. 57.Sh NOTES 58This system call is not available in 59.Bx 4.2 60hence it should not be used if backward compatibility is needed. 61.Sh RETURN VALUES 62If successful, the system call does not return. 63Otherwise, a value of -1 is returned and 64.Va errno 65is set to indicate the error. 66.Sh ERRORS 67.Fn Sigreturn 68will fail and the process context will remain unchanged 69if one of the following occurs. 70.Bl -tag -width Er 71.It Bq Er EFAULT 72.Fa Scp 73points to memory that is not a valid part of the process 74address space. 75.It Bq Er EINVAL 76The process status longword is invalid or would improperly 77raise the privilege level of the process. 78.El 79.Sh SEE ALSO 80.Xr sigaction 2 , 81.Xr setjmp 3 , 82.Xr ucontext 3 83.Sh HISTORY 84The 85.Fn sigreturn 86function call appeared in 87.Bx 4.3 . 88