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 */ 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 87