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awilliam
GitHub Repository: awilliam/linux-vfio
 Path: blob/master/arch/arm/boot/bootp/init.S
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/*

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 *  linux/arch/arm/boot/bootp/init.S

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 *

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 *  Copyright (C) 2000-2003 Russell King.

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 *

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 * This program is free software; you can redistribute it and/or modify

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 * it under the terms of the GNU General Public License version 2 as

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 * published by the Free Software Foundation.

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 *

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 *  "Header" file for splitting kernel + initrd.  Note that we pass

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 *  r0 through to r3 straight through.

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 *

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 *  This demonstrates how to append code to the start of the kernel

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 *  zImage, and boot the kernel without copying it around.  This

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 *  example would be simpler; if we didn't have an object of unknown

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 *  size immediately following the kernel, we could build this into

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 *  a binary blob, and concatenate the zImage using the cat command.

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 */

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		.section .start,#alloc,#execinstr

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		.type	_start, #function

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		.globl	_start

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_start:		add	lr, pc, #-0x8		@ lr = current load addr

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		adr	r13, data

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		ldmia	r13!, {r4-r6}		@ r5 = dest, r6 = length

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		add	r4, r4, lr		@ r4 = initrd_start + load addr

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		bl	move			@ move the initrd

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/*

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 * Setup the initrd parameters to pass to the kernel.  This can only be

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 * passed in via the tagged list.

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 */

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		ldmia	r13, {r5-r9}		@ get size and addr of initrd

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						@ r5 = ATAG_CORE

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						@ r6 = ATAG_INITRD2

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						@ r7 = initrd start

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						@ r8 = initrd end

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						@ r9 = param_struct address

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		ldr	r10, [r9, #4]		@ get first tag

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		teq	r10, r5			@ is it ATAG_CORE?

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/*

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 * If we didn't find a valid tag list, create a dummy ATAG_CORE entry.

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 */

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		movne	r10, #0			@ terminator

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		movne	r4, #2			@ Size of this entry (2 words)

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		stmneia	r9, {r4, r5, r10}	@ Size, ATAG_CORE, terminator

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/*

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 * find the end of the tag list, and then add an INITRD tag on the end.

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 * If there is already an INITRD tag, then we ignore it; the last INITRD

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 * tag takes precedence.

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 */

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taglist:	ldr	r10, [r9, #0]		@ tag length

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		teq	r10, #0			@ last tag (zero length)?

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		addne	r9, r9, r10, lsl #2

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		bne	taglist

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		mov	r5, #4			@ Size of initrd tag (4 words)

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		stmia	r9, {r5, r6, r7, r8, r10}

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		b	kernel_start		@ call kernel

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/*

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 * Move the block of memory length r6 from address r4 to address r5

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 */

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move:		ldmia	r4!, {r7 - r10}		@ move 32-bytes at a time

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		stmia	r5!, {r7 - r10}

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		ldmia	r4!, {r7 - r10}

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		stmia	r5!, {r7 - r10}

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		subs	r6, r6, #8 * 4

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		bcs	move

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		mov	pc, lr

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		.size	_start, . - _start

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		.align

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		.type	data,#object

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data:		.word	initrd_start		@ source initrd address

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		.word	initrd_phys		@ destination initrd address

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		.word	initrd_size		@ initrd size

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		.word	0x54410001		@ r5 = ATAG_CORE

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		.word	0x54420005		@ r6 = ATAG_INITRD2

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		.word	initrd_phys		@ r7

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		.word	initrd_size		@ r8

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		.word	params_phys		@ r9

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		.size	data, . - data

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