start.S revision 256281 
1/*-
2 * Copyright (c) 2008 Semihalf, Rafal Czubak
3 * All rights reserved.
4 *
5 * Redistribution and use in source and binary forms, with or without
6 * modification, are permitted provided that the following conditions
7 * are met:
8 * 1. Redistributions of source code must retain the above copyright
9 *    notice, this list of conditions and the following disclaimer.
10 * 2. Redistributions in binary form must reproduce the above copyright
11 *    notice, this list of conditions and the following disclaimer in the
12 *    documentation and/or other materials provided with the distribution.
13 *
14 * THIS SOFTWARE IS PROVIDED BY THE AUTHOR AND CONTRIBUTORS ``AS IS'' AND
15 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
16 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
17 * ARE DISCLAIMED.  IN NO EVENT SHALL THE AUTHOR OR CONTRIBUTORS BE LIABLE
18 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
19 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
20 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
21 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
22 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
23 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
24 * SUCH DAMAGE.
25 *
26 * $FreeBSD: stable/10/sys/boot/arm/uboot/start.S 248962 2013-03-31 22:43:16Z ian $
27 */
28
29#include <machine/asm.h>
30#include <machine/armreg.h>
31
32/*
33 * Entry point to the loader that U-Boot passes control to.
34 */
35	.text
36	.globl	_start
37_start:
38	/* Hint where to look for the API signature */
39	ldr	ip, =uboot_address
40	str	sp, [ip]
41
42	/* Save U-Boot's r8 */
43	ldr	ip, =saved_regs
44	str	r8, [ip, #0]
45
46#ifdef _ARM_ARCH_6
47	mrc     p15, 0, r2, c1, c0, 0
48	orr	r2, r2, #(CPU_CONTROL_UNAL_ENABLE)
49	orr	r2, r2, #(CPU_CONTROL_AFLT_ENABLE)
50	mcr     p15, 0, r2, c1, c0, 0
51#endif
52
53	/* Start loader */
54	b	main
55
56/*
57 * syscall()
58 */
59ENTRY(syscall)
60	/* Save caller's lr and r8 */
61	ldr	ip, =saved_regs
62	str	lr, [ip, #4]
63	str	r8, [ip, #8]
64	/* Restore U-Boot's r8 */
65	ldr	r8, [ip, #0]
66	/* Call into U-Boot */
67	ldr	lr, =return_from_syscall
68	ldr	ip, =syscall_ptr
69	ldr	pc, [ip]
70return_from_syscall:
71	/* Restore loader's r8 and lr */
72	ldr	ip, =saved_regs
73	ldr	r8, [ip, #8]
74	ldr	lr, [ip, #4]
75	/* Return to caller */
76	mov	pc, lr
77
78/*
79 * Data section
80 */
81	.data
82	.align	4
83	.globl	syscall_ptr
84syscall_ptr:
85	.long	0
86
87	.globl	uboot_address
88uboot_address:
89	.long	0
90
91saved_regs:
92	.long	0	/* U-Boot's r8 */
93	.long	0	/* Loader's r8 */
94	.long	0	/* Loader's lr */
95