| Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 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 |
| 52 | * tag takes precidence. |
| 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 | |
| 76 | .type data,#object |
| 77 | data: .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 |