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. 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.\" @(#)sigreturn.2 8.1 (Berkeley) 6/4/93 33.\" $FreeBSD$ 34.\" 35.Dd June 4, 1993 36.Dt SIGRETURN 2 37.Os 38.Sh NAME 39.Nm sigreturn 40.Nd return from signal 41.Sh LIBRARY 42.Lb libc 43.Sh SYNOPSIS 44.Fd #include <signal.h> 45.Pp 46.Bd -literal 47struct sigcontext { 48 int sc_onstack; /* sigstack state to restore */ 49 int sc_mask; /* signal mask to restore */ 50 int sc_esp; /* machine state */ 51 int sc_ebp; 52 int sc_isp; 53 int sc_eip; 54 int sc_efl; 55 int sc_es; 56 int sc_ds; 57 int sc_cs; 58 int sc_ss; 59 int sc_edi; 60 int sc_esi; 61 int sc_ebx; 62 int sc_edx; 63 int sc_ecx; 64 int sc_eax; 65# define sc_sp sc_esp 66# define sc_fp sc_ebp 67# define sc_pc sc_eip 68# define sc_ps sc_efl 69}; 70.Ed 71.Ft int 72.Fn sigreturn "struct sigcontext *scp" 73.Sh DESCRIPTION 74.Fn Sigreturn 75allows users to atomically unmask, switch stacks, 76and return from a signal context. 77The processes signal mask and stack status are 78restored from the context. 79The system call does not return; 80the users stack pointer, frame pointer, argument pointer, 81and processor status longword are restored from the context. 82Execution resumes at the specified pc. 83This system call is used by the trampoline code and 84.Xr longjmp 3 85when returning from a signal to the previously executing program. 86.Sh NOTES 87This system call is not available in 4.2 88.Tn BSD 89hence it should not be used if backward compatibility is needed. 90.Sh RETURN VALUES 91If successful, the system call does not return. 92Otherwise, a value of -1 is returned and 93.Va errno 94is set to indicate the error. 95.Sh ERRORS 96.Fn Sigreturn 97will fail and the process context will remain unchanged 98if one of the following occurs. 99.Bl -tag -width Er 100.It Bq Er EFAULT 101.Fa Scp 102points to memory that is not a valid part of the process 103address space. 104.It Bq Er EINVAL 105The process status longword is invalid or would improperly 106raise the privilege level of the process. 107.El 108.Sh SEE ALSO 109.Xr sigvec 2 , 110.Xr setjmp 3 111.Sh HISTORY 112The 113.Fn sigreturn 114function call appeared in 115.Bx 4.3 . 116