freebsd-dev/sys/boot/arm/uboot/start.S
Ian Lepore 31825f28cf Create a relocatable instance of ubldr for ARM. The original ubldr,
static-linked to run at a fixed position, is still installed to maintain
compatibility with existing configurations.  The makefile now also creates
and installs ubldr.bin, a stripped binary (no elf headers) with an entry
point offset of 0 that can be loaded by u-boot at any address and launched
with "go ${loadaddr}".

To use ubldr.bin, U-Boot must still be built with the CONFIG_API option,
but no longer needs the CONFIG_ELF option.
2015-05-10 19:14:28 +00:00

131 lines
3.7 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>
#include <machine/armreg.h>
.text
.extern _C_LABEL(self_reloc), _C_LABEL(main)
.weak _DYNAMIC
/*
* Entry point to the loader that U-Boot passes control to.
*/
.globl _start
_start:
#ifdef _ARM_ARCH_6
mrc p15, 0, ip, c1, c0, 0
orr ip, ip, #(CPU_CONTROL_UNAL_ENABLE)
orr ip, ip, #(CPU_CONTROL_AFLT_ENABLE)
mcr p15, 0, ip, c1, c0, 0
#endif
/*
* Do self-relocation when the weak external symbol _DYNAMIC is non-NULL.
* When linked as a dynamic relocatable file, the linker automatically
* defines _DYNAMIC with a value that is the offset of the dynamic
* relocation info section.
* Note that we're still on u-boot's stack here, but the self_reloc
* code uses only a couple dozen bytes of stack space.
*/
adr ip, .here_off /* .here_off is a symbol whose value */
ldr r0, [ip] /* is its own offset in the text seg. */
sub r0, ip, r0 /* Get its pc-relative address and */
ldr r1, .dynamic_off /* subtract its value and we get */
teq r1, #0 /* r0 = physaddr we were loaded at. */
addne r1, r1, r0 /* r1 = dynamic section physaddr. */
blne _C_LABEL(self_reloc) /* Do reloc if _DYNAMIC is non-NULL. */
/* Hint where to look for the API signature */
ldr ip, =uboot_address
str sp, [ip]
/* Save U-Boot's r8 and r9 */
ldr ip, =saved_regs
str r8, [ip, #0]
str r9, [ip, #4]
/*
* Start loader. This is basically a tail-recursion call; if main()
* returns, it returns to u-boot (which reports the value returned r0).
*/
b main
/*
* Data for self-relocation, in the text segment for pc-rel access.
*/
.here_off:
.word .
.dynamic_off:
.word _DYNAMIC
/*
* syscall()
*/
ENTRY(syscall)
/* Save caller's lr, r8 and r9 */
ldr ip, =saved_regs
str r8, [ip, #8]
str r9, [ip, #12]
str lr, [ip, #16]
/* Restore U-Boot's r8 and r9 */
ldr r8, [ip, #0]
ldr r9, [ip, #4]
/* Call into U-Boot */
ldr lr, =return_from_syscall
ldr ip, =syscall_ptr
ldr pc, [ip]
return_from_syscall:
/* Restore loader's r8, r9 and lr */
ldr ip, =saved_regs
ldr lr, [ip, #16]
ldr r9, [ip, #12]
ldr r8, [ip, #8]
/* 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 /* U-Boot's r9 */
.long 0 /* Loader's r8 */
.long 0 /* Loader's r9 */
.long 0 /* Loader's lr */