2 * linux/arch/arm/boot/bootp/init.S
4 * Copyright (C) 2000-2003 Russell King.
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.
10 * "Header" file for splitting kernel + initrd. Note that we pass
11 * r0 through to r3 straight through.
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.
19 .section .start,#alloc,#execinstr
20 .type _start, #function
24 ldmia r13!, {r4-r6} @ r5 = dest, r6 = length
25 bl move @ move the initrd
28 * Setup the initrd parameters to pass to the kernel. This can only be
29 * passed in via the tagged list.
31 ldmia r13, {r5-r9} @ get size and addr of initrd
36 @ r9 = param_struct address
38 ldr r10, [r9, #4] @ get first tag
39 teq r10, r5 @ is it ATAG_CORE?
41 * If we didn't find a valid tag list, create a dummy ATAG_CORE entry.
43 movne r10, #0 @ terminator
44 movne r4, #2 @ Size of this entry (2 words)
45 stmneia r9, {r4, r5, r10} @ Size, ATAG_CORE, terminator
48 * find the end of the tag list, and then add an INITRD tag on the end.
49 * If there is already an INITRD tag, then we ignore it; the last INITRD
50 * tag takes precidence.
52 taglist: ldr r10, [r9, #0] @ tag length
53 teq r10, #0 @ last tag (zero length)?
54 addne r9, r9, r10, lsl #2
57 mov r5, #4 @ Size of initrd tag (4 words)
58 stmia r9, {r5, r6, r7, r8, r10}
59 b kernel_start @ call kernel
62 * Move the block of memory length r6 from address r4 to address r5
64 move: ldmia r4!, {r7 - r10} @ move 32-bytes at a time
72 .size _start, . - _start
75 data: .word initrd_start @ source initrd address
76 .word initrd_phys @ destination initrd address
77 .word initrd_size @ initrd size
79 .word 0x54410001 @ r5 = ATAG_CORE
80 .word 0x54420005 @ r6 = ATAG_INITRD2
81 .word initrd_phys @ r7
82 .word initrd_size @ r8
83 .word params_phys @ r9