.\"	$OpenBSD: sigreturn.2,v 1.12 2016/05/09 23:57:10 guenther Exp $
.\"	$NetBSD: sigreturn.2,v 1.6 1995/02/27 12:37:40 cgd Exp $
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.\"     @(#)sigreturn.2	8.1 (Berkeley) 6/4/93
.\"
.Dd $Mdocdate: May 9 2016 $
.Dt SIGRETURN 2
.Os
.Sh NAME
.Nm sigreturn
.Nd return from signal
.Sh SYNOPSIS
.Ft int
.Fn sigreturn "struct sigcontext *scp"
.Sh DESCRIPTION
The
.Fn sigreturn
syscall is used by the signal handling facility to
atomically switch stacks, restore registers and the thread's signal mask,
and return from a signal context
to resume the processing that was interrupted by the signal.
.Pp
Note that sigcontext contains machine dependent information.
.Pp
Direct use of
.Nm
is no longer supported and it is not provided as a function.
As used in the signal trampoline provided by the system,
if
.Nm
fails and returns then the process is terminated.
.Sh RETURN VALUES
If successful, the system call does not return.
Otherwise, a value of \-1 is returned and
.Va errno
is set to indicate the error.
.Sh ERRORS
.Fn sigreturn
will fail and the process context will remain unchanged
if one of the following occurs.
.Bl -tag -width Er
.It Bq Er EFAULT
.Fa scp
points to memory that is not a valid part of the process
address space.
.It Bq Er EINVAL
The sigcontext provided is invalid or would improperly
raise the privilege level of the process.
.El
.Sh SEE ALSO
.Xr sigaction 2 ,
.Xr setjmp 3
.Sh HISTORY
The
.Fn sigreturn
function appeared in
.Bx 4.3 .
The function was removed from libc in
.Ox 6.0 .