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.\" 30.Dd September 6, 2013 31.Dt SIGRETURN 2 32.Os 33.Sh NAME 34.Nm sigreturn 35.Nd return from signal 36.Sh LIBRARY 37.Lb libc 38.Sh SYNOPSIS 39.In signal.h 40.Ft int 41.Fn sigreturn "const ucontext_t *scp" 42.Sh DESCRIPTION 43The 44.Fn sigreturn 45system call 46allows users to atomically unmask, switch stacks, 47and return from a signal context. 48The thread's signal mask and stack status are 49restored from the context structure pointed to by 50.Fa scp . 51The system call does not return; 52the users stack pointer, frame pointer, argument pointer, 53and processor status longword are restored from the context. 54Execution resumes at the specified pc. 55This system call is used by the trampoline code and 56.Xr longjmp 3 57when returning from a signal to the previously executing program. 58.Sh RETURN VALUES 59If successful, the system call does not return. 60Otherwise, a value of -1 is returned and 61.Va errno 62is set to indicate the error. 63.Sh ERRORS 64The 65.Fn sigreturn 66system call 67will fail and the thread context will remain unchanged 68if one of the following occurs. 69.Bl -tag -width Er 70.It Bq Er EFAULT 71The 72.Fa scp 73argument 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.Xr ucontext 3 84.Sh HISTORY 85The 86.Fn sigreturn 87system call appeared in 88.Bx 4.3 . 89