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Linus Torvalds1da177e2005-04-16 15:20:36 -07001/*
2 * linux/arch/arm/boot/bootp/init.S
3 *
4 * Copyright (C) 2000-2003 Russell King.
5 *
6 * This program is free software; you can redistribute it and/or modify
7 * it under the terms of the GNU General Public License version 2 as
8 * published by the Free Software Foundation.
9 *
10 * "Header" file for splitting kernel + initrd. Note that we pass
11 * r0 through to r3 straight through.
12 *
13 * This demonstrates how to append code to the start of the kernel
14 * zImage, and boot the kernel without copying it around. This
15 * example would be simpler; if we didn't have an object of unknown
16 * size immediately following the kernel, we could build this into
17 * a binary blob, and concatenate the zImage using the cat command.
18 */
19 .section .start,#alloc,#execinstr
20 .type _start, #function
21 .globl _start
22
23_start: add lr, pc, #-0x8 @ lr = current load addr
24 adr r13, data
25 ldmia r13!, {r4-r6} @ r5 = dest, r6 = length
26 add r4, r4, lr @ r4 = initrd_start + load addr
27 bl move @ move the initrd
28
29/*
30 * Setup the initrd parameters to pass to the kernel. This can only be
31 * passed in via the tagged list.
32 */
33 ldmia r13, {r5-r9} @ get size and addr of initrd
34 @ r5 = ATAG_CORE
35 @ r6 = ATAG_INITRD2
36 @ r7 = initrd start
37 @ r8 = initrd end
38 @ r9 = param_struct address
39
40 ldr r10, [r9, #4] @ get first tag
41 teq r10, r5 @ is it ATAG_CORE?
42/*
43 * If we didn't find a valid tag list, create a dummy ATAG_CORE entry.
44 */
45 movne r10, #0 @ terminator
46 movne r4, #2 @ Size of this entry (2 words)
47 stmneia r9, {r4, r5, r10} @ Size, ATAG_CORE, terminator
48
49/*
50 * find the end of the tag list, and then add an INITRD tag on the end.
51 * If there is already an INITRD tag, then we ignore it; the last INITRD
52 * tag takes precidence.
53 */
54taglist: ldr r10, [r9, #0] @ tag length
55 teq r10, #0 @ last tag (zero length)?
56 addne r9, r9, r10, lsl #2
57 bne taglist
58
59 mov r5, #4 @ Size of initrd tag (4 words)
60 stmia r9, {r5, r6, r7, r8, r10}
61 b kernel_start @ call kernel
62
63/*
64 * Move the block of memory length r6 from address r4 to address r5
65 */
66move: ldmia r4!, {r7 - r10} @ move 32-bytes at a time
67 stmia r5!, {r7 - r10}
68 ldmia r4!, {r7 - r10}
69 stmia r5!, {r7 - r10}
70 subs r6, r6, #8 * 4
71 bcs move
72 mov pc, lr
73
74 .size _start, . - _start
75
76 .type data,#object
77data: .word initrd_start @ source initrd address
78 .word initrd_phys @ destination initrd address
79 .word initrd_size @ initrd size
80
81 .word 0x54410001 @ r5 = ATAG_CORE
82 .word 0x54420005 @ r6 = ATAG_INITRD2
83 .word initrd_phys @ r7
84 .word initrd_size @ r8
85 .word params_phys @ r9
86 .size data, . - data