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: head/lib/libc/sys/sigreturn.2 255296 2013-09-06 09:08:40Z jilles $ 30.\" 31.Dd July 20, 2016 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 44The 45.Fn sigreturn 46system call 47allows users to atomically unmask, switch stacks, 48and return from a signal context. 49The thread's signal mask and stack status are 50restored from the context structure pointed to by 51.Fa scp . 52The system call does not return; 53the users stack pointer, frame pointer, argument pointer, 54and processor status longword are restored from the context. 55Execution resumes at the specified pc. 56This system call is used by the trampoline code and 57.Xr longjmp 3 58when returning from a signal to the previously executing program. 59.Sh RETURN VALUES 60If successful, the system call does not return. 61Otherwise, a value of -1 is returned and 62.Va errno 63is set to indicate the error. 64.Sh ERRORS 65The 66.Fn sigreturn 67system call 68will fail and the thread context will remain unchanged 69if one of the following occurs. 70.Bl -tag -width Er 71.It Bq Er EFAULT 72The 73.Fa scp 74argument 75points to memory that is not a valid part of the process 76address space. 77.It Bq Er EINVAL 78The process status longword is invalid or would improperly 79raise the privilege level of the process. 80.El 81.Sh SEE ALSO 82.Xr sigaction 2 , 83.Xr setjmp 3 , 84.Xr ucontext 3 85.Sh HISTORY 86The 87.Fn sigreturn 88system call appeared in 89.Bx 4.3 . 90