/*
 * Copyright (c) 2018 William Pitcock <nenolod@dereferenced.org>
 *
 * Permission to use, copy, modify, and/or distribute this software for any
 * purpose with or without fee is hereby granted, provided that the above
 * copyright notice and this permission notice appear in all copies.
 *
 * This software is provided 'as is' and without any warranty, express or
 * implied.  In no event shall the authors be liable for any damages arising
 * from the use of this software.
 */

.globl __start_context;
__start_context:
	/* get the proper context into position and test for NULL */
	movq	%rbx, %rsp
	movq	(%rsp), %rdi
	testq	%rdi, %rdi

	/* if we have no linked context, lets get out of here */
	je	no_linked_context

	/* call setcontext to switch to the linked context */
	call	__setcontext@plt
	movq	%rax, %rdi

no_linked_context:
	/* we are returning into a null context, it seems, so maybe we should exit */
	call	exit@plt

	/* something is really hosed, call hlt to force termination */
	hlt