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