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85 lines
2.4 KiB
85 lines
2.4 KiB
/* SPDX-License-Identifier: GPL-2.0-only */ |
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/* |
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* linux/arch/arm/boot/bootp/init.S |
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* |
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* Copyright (C) 2000-2003 Russell King. |
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* |
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* "Header" file for splitting kernel + initrd. Note that we pass |
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* r0 through to r3 straight through. |
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* |
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* This demonstrates how to append code to the start of the kernel |
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* zImage, and boot the kernel without copying it around. This |
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* example would be simpler; if we didn't have an object of unknown |
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* size immediately following the kernel, we could build this into |
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* a binary blob, and concatenate the zImage using the cat command. |
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*/ |
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.section .start, "ax" |
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.type _start, #function |
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.globl _start |
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_start: add lr, pc, #-0x8 @ lr = current load addr |
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adr r13, data |
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ldmia r13!, {r4-r6} @ r5 = dest, r6 = length |
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add r4, r4, lr @ r4 = initrd_start + load addr |
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bl move @ move the initrd |
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/* |
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* Setup the initrd parameters to pass to the kernel. This can only be |
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* passed in via the tagged list. |
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*/ |
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ldmia r13, {r5-r9} @ get size and addr of initrd |
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@ r5 = ATAG_CORE |
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@ r6 = ATAG_INITRD2 |
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@ r7 = initrd start |
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@ r8 = initrd end |
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@ r9 = param_struct address |
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ldr r10, [r9, #4] @ get first tag |
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teq r10, r5 @ is it ATAG_CORE? |
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/* |
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* If we didn't find a valid tag list, create a dummy ATAG_CORE entry. |
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*/ |
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movne r10, #0 @ terminator |
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movne r4, #2 @ Size of this entry (2 words) |
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stmiane r9, {r4, r5, r10} @ Size, ATAG_CORE, terminator |
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/* |
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* find the end of the tag list, and then add an INITRD tag on the end. |
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* If there is already an INITRD tag, then we ignore it; the last INITRD |
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* tag takes precedence. |
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*/ |
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taglist: ldr r10, [r9, #0] @ tag length |
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teq r10, #0 @ last tag (zero length)? |
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addne r9, r9, r10, lsl #2 |
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bne taglist |
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mov r5, #4 @ Size of initrd tag (4 words) |
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stmia r9, {r5, r6, r7, r8, r10} |
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b kernel_start @ call kernel |
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/* |
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* Move the block of memory length r6 from address r4 to address r5 |
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*/ |
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move: ldmia r4!, {r7 - r10} @ move 32-bytes at a time |
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stmia r5!, {r7 - r10} |
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ldmia r4!, {r7 - r10} |
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stmia r5!, {r7 - r10} |
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subs r6, r6, #8 * 4 |
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bcs move |
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mov pc, lr |
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.size _start, . - _start |
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.align |
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.type data,#object |
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data: .word initrd_start @ source initrd address |
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.word initrd_phys @ destination initrd address |
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.word initrd_size @ initrd size |
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.word 0x54410001 @ r5 = ATAG_CORE |
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.word 0x54420005 @ r6 = ATAG_INITRD2 |
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.word initrd_phys @ r7 |
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.word initrd_size @ r8 |
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.word params_phys @ r9 |
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.size data, . - data
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