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.\" Copyright (C) 1995, Thomas K. Dyas <tdyas@eden.rutgers.edu>
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.\" Created   Sat Aug 21 1995     Thomas K. Dyas <tdyas@eden.rutgers.edu>
.\" Modified Tue Oct 22 22:09:03 1996 by Eric S. Raymond <esr@thyrsus.com>
.\" 2008-06-26, mtk, added some more detail on the work done by sigreturn()
.\"
.TH SIGRETURN 2 2013-07-30 "Linux" "Linux Programmer's Manual"
.SH NAME
sigreturn \- return from signal handler and cleanup stack frame
.SH SYNOPSIS
.BI "int sigreturn(unsigned long " __unused );
.SH DESCRIPTION
When the Linux kernel creates the stack frame for a signal handler, a
call to
.BR sigreturn ()
is inserted into the stack frame so that upon
return from the signal handler,
.BR sigreturn ()
will be called.

This
.BR sigreturn ()
call undoes everything that was
done\(emchanging the process's signal mask, switching stacks (see
.BR sigaltstack "(2))\(emin "
order to invoke the signal handler:
it restores the process's signal mask, switches stacks,
and restores the process's context (registers, processor flags),
so that the process directly resumes execution
at the point where it was interrupted by the signal.
.SH RETURN VALUE
.BR sigreturn ()
never returns.
.SH FILES
/usr/src/linux/arch/i386/kernel/signal.c
.br
/usr/src/linux/arch/alpha/kernel/entry.S
.SH CONFORMING TO
.BR sigreturn ()
is specific to Linux and should not be used in programs intended to be
portable.
.SH NOTES
The
.BR sigreturn ()
call is used by the kernel to implement signal handlers.
It should
.B never
be called directly.
Better yet, the specific use of the
.I __unused
argument varies depending on the architecture.
.SH SEE ALSO
.BR kill (2),
.BR restart_syscall (2),
.BR sigaltstack (2),
.BR signal (2),
.BR signal (7)