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1da177e4 LT |
1 | /* |
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 | |
659431fc | 52 | * tag takes precedence. |
1da177e4 LT |
53 | */ |
54 | taglist: 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 | */ | |
66 | move: 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 | ||
077248fc DM |
76 | .align |
77 | ||
1da177e4 LT |
78 | .type data,#object |
79 | data: .word initrd_start @ source initrd address | |
80 | .word initrd_phys @ destination initrd address | |
81 | .word initrd_size @ initrd size | |
82 | ||
83 | .word 0x54410001 @ r5 = ATAG_CORE | |
84 | .word 0x54420005 @ r6 = ATAG_INITRD2 | |
85 | .word initrd_phys @ r7 | |
86 | .word initrd_size @ r8 | |
87 | .word params_phys @ r9 | |
88 | .size data, . - data |