freebsd-skq/sys/boot/arm/uboot/start.S
raj 745c5c702f Initial support of loader(8) for ARM machines running U-Boot.
This uses the common U-Boot support lib (sys/boot/uboot, already used on
FreeBSD/powerpc), and assumes the underlying firmware has the modern API for
stand-alone apps enabled in the config (CONFIG_API).

Only netbooting is supported at the moment.

Obtained from:	Marvell, Semihalf
2008-10-14 10:11:14 +00:00

94 lines
2.4 KiB
ArmAsm

/*-
* Copyright (c) 2008 Semihalf, Rafal Czubak
* All rights reserved.
*
* Redistribution and use in source and binary forms, with or without
* modification, are permitted provided that the following conditions
* are met:
* 1. Redistributions of source code must retain the above copyright
* notice, this list of conditions and the following disclaimer.
* 2. Redistributions in binary form must reproduce the above copyright
* notice, this list of conditions and the following disclaimer in the
* documentation and/or other materials provided with the distribution.
*
* THIS SOFTWARE IS PROVIDED BY THE AUTHOR AND CONTRIBUTORS ``AS IS'' AND
* ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
* IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
* ARE DISCLAIMED. IN NO EVENT SHALL THE AUTHOR OR CONTRIBUTORS BE LIABLE
* FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
* DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
* OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
* HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
* LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
* OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
* SUCH DAMAGE.
*
* $FreeBSD$
*/
#include <machine/asm.h>
/*
* Entry point to the loader that U-Boot passes control to.
*/
.text
.globl _start
_start:
/* Hint where to look for the API signature */
ldr ip, =uboot_address
str sp, [ip]
/* Save U-Boot's r8 */
ldr ip, =saved_regs
str r8, [ip, #0]
/* Start loader */
b main
/*
* syscall()
*/
ENTRY(syscall)
/* Save caller's lr */
ldr ip, =saved_regs
str lr, [ip, #4]
/* Save loader's r8 */
ldr ip, =saved_regs
str r8, [ip, #8]
/* Restore U-Boot's r8 */
ldr ip, =saved_regs
ldr r8, [ip, #0]
/* Call into U-Boot */
ldr lr, =return_from_syscall
ldr ip, =syscall_ptr
ldr pc, [ip]
return_from_syscall:
/* Restore loader's r8 */
ldr ip, =saved_regs
ldr r8, [ip, #8]
/* Restore caller's lr */
ldr ip, =saved_regs
ldr lr, [ip, #4]
/* Return to caller */
mov pc, lr
/*
* Data section
*/
.data
.align 4
.globl syscall_ptr
syscall_ptr:
.long 0
.globl uboot_address
uboot_address:
.long 0
saved_regs:
.long 0 /* U-Boot's r8 */
.long 0 /* Loader's r8 */
.long 0 /* Loader's lr */