| 1 | /* SPDX-License-Identifier: GPL-2.0-only */
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| 2 | /*
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| 3 | * linux/arch/arm/boot/bootp/init.S
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| 4 | *
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| 5 | * Copyright (C) 2000-2003 Russell King.
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| 6 | *
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| 7 | * "Header" file for splitting kernel + initrd. Note that we pass
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| 8 | * r0 through to r3 straight through.
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| 9 | *
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| 10 | * This demonstrates how to append code to the start of the kernel
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| 11 | * zImage, and boot the kernel without copying it around. This
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| 12 | * example would be simpler; if we didn't have an object of unknown
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| 13 | * size immediately following the kernel, we could build this into
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| 14 | * a binary blob, and concatenate the zImage using the cat command.
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| 15 | */
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| 16 | .section .start, "ax"
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| 17 | .type _start, #function
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| 18 | .globl _start
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| 19 |
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| 20 | _start: add lr, pc, #-0x8 @ lr = current load addr
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| 21 | adr r13, data
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| 22 | ldmia r13!, {r4-r6} @ r5 = dest, r6 = length
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| 23 | add r4, r4, lr @ r4 = initrd_start + load addr
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| 24 | bl move @ move the initrd
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| 25 |
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| 26 | /*
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| 27 | * Setup the initrd parameters to pass to the kernel. This can only be
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| 28 | * passed in via the tagged list.
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| 29 | */
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| 30 | ldmia r13, {r5-r9} @ get size and addr of initrd
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| 31 | @ r5 = ATAG_CORE
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| 32 | @ r6 = ATAG_INITRD2
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| 33 | @ r7 = initrd start
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| 34 | @ r8 = initrd end
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| 35 | @ r9 = param_struct address
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| 36 |
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| 37 | ldr r10, [r9, #4] @ get first tag
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| 38 | teq r10, r5 @ is it ATAG_CORE?
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| 39 | /*
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| 40 | * If we didn't find a valid tag list, create a dummy ATAG_CORE entry.
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| 41 | */
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| 42 | movne r10, |
| 43 | movne r4, |
| 44 | stmiane r9, {r4, r5, r10} @ Size, ATAG_CORE, terminator
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| 45 |
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| 46 | /*
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| 47 | * find the end of the tag list, and then add an INITRD tag on the end.
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| 48 | * If there is already an INITRD tag, then we ignore it; the last INITRD
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| 49 | * tag takes precedence.
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| 50 | */
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| 51 | taglist: ldr r10, [r9, |
| 52 | teq r10, |
| 53 | addne r9, r9, r10, lsl |
| 54 | bne taglist
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| 55 |
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| 56 | mov r5, |
| 57 | stmia r9, {r5, r6, r7, r8, r10}
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| 58 | b kernel_start @ call kernel
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| 59 |
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| 60 | /*
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| 61 | * Move the block of memory length r6 from address r4 to address r5
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| 62 | */
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| 63 | move: ldmia r4!, {r7 - r10} @ move 32-bytes at a time
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| 64 | stmia r5!, {r7 - r10}
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| 65 | ldmia r4!, {r7 - r10}
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| 66 | stmia r5!, {r7 - r10}
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| 67 | subs r6, r6, |
| 68 | bcs move
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| 69 | mov pc, lr
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| 70 |
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| 71 | .size _start, . - _start
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| 72 |
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| 73 | .align
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| 74 |
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| 75 | .type data, |
| 76 | data: .word initrd_start @ source initrd address
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| 77 | .word initrd_phys @ destination initrd address
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| 78 | .word initrd_size @ initrd size
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| 79 |
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| 80 | .word 0x54410001 @ r5 = ATAG_CORE
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| 81 | .word 0x54420005 @ r6 = ATAG_INITRD2
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| 82 | .word initrd_phys @ r7
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| 83 | .word initrd_size @ r8
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| 84 | .word params_phys @ r9
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| 85 | .size data, . - data
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