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kernel add
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/*
* linux/arch/arm/boot/bootp/init.S
*
* Copyright (C) 2000-2003 Russell King.
*
* This program is free software; you can redistribute it and/or modify
* it under the terms of the GNU General Public License version 2 as
* published by the Free Software Foundation.
*
* "Header" file for splitting kernel + initrd. Note that we pass
* r0 through to r3 straight through.
*
* This demonstrates how to append code to the start of the kernel
* zImage, and boot the kernel without copying it around. This
* example would be simpler; if we didn't have an object of unknown
* size immediately following the kernel, we could build this into
* a binary blob, and concatenate the zImage using the cat command.
*/
.section .start,#alloc,#execinstr
.type _start, #function
.globl _start
_start: add lr, pc, #-0x8 @ lr = current load addr
adr r13, data
ldmia r13!, {r4-r6} @ r5 = dest, r6 = length
add r4, r4, lr @ r4 = initrd_start + load addr
bl move @ move the initrd
/*
* Setup the initrd parameters to pass to the kernel. This can only be
* passed in via the tagged list.
*/
ldmia r13, {r5-r9} @ get size and addr of initrd
@ r5 = ATAG_CORE
@ r6 = ATAG_INITRD2
@ r7 = initrd start
@ r8 = initrd end
@ r9 = param_struct address
ldr r10, [r9, #4] @ get first tag
teq r10, r5 @ is it ATAG_CORE?
/*
* If we didn't find a valid tag list, create a dummy ATAG_CORE entry.
*/
movne r10, #0 @ terminator
movne r4, #2 @ Size of this entry (2 words)
stmneia r9, {r4, r5, r10} @ Size, ATAG_CORE, terminator
/*
* find the end of the tag list, and then add an INITRD tag on the end.
* If there is already an INITRD tag, then we ignore it; the last INITRD
* tag takes precedence.
*/
taglist: ldr r10, [r9, #0] @ tag length
teq r10, #0 @ last tag (zero length)?
addne r9, r9, r10, lsl #2
bne taglist
mov r5, #4 @ Size of initrd tag (4 words)
stmia r9, {r5, r6, r7, r8, r10}
b kernel_start @ call kernel
/*
* Move the block of memory length r6 from address r4 to address r5
*/
move: ldmia r4!, {r7 - r10} @ move 32-bytes at a time
stmia r5!, {r7 - r10}
ldmia r4!, {r7 - r10}
stmia r5!, {r7 - r10}
subs r6, r6, #8 * 4
bcs move
mov pc, lr
.size _start, . - _start
.align
.type data,#object
data: .word initrd_start @ source initrd address
.word initrd_phys @ destination initrd address
.word initrd_size @ initrd size
.word 0x54410001 @ r5 = ATAG_CORE
.word 0x54420005 @ r6 = ATAG_INITRD2
.word initrd_phys @ r7
.word initrd_size @ r8
.word params_phys @ r9
.size data, . - data
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