/* SPDX-License-Identifier: GPL-2.0-only */
/*
 *  linux/arch/arm/boot/bootp/init.S
 *
 *  Copyright (C) 2000-2003 Russell King.
 *
 *  "Header" file for splitting kernel + initrd.  Note that we pass
 *  r0 through to r3 straight through.
 *
 *  This demonstrates how to append code to the start of the kernel
 *  zImage, and boot the kernel without copying it around.  This
 *  example would be simpler; if we didn't have an object of unknown
 *  size immediately following the kernel, we could build this into
 *  a binary blob, and concatenate the zImage using the cat command.
 */
                .section .start, "ax"
                .type   _start, #function
                .globl  _start

_start:         add     lr, pc, #-0x8           @ lr = current load addr
                adr     r13, data
                ldmia   r13!, {r4-r6}           @ r5 = dest, r6 = length
                add     r4, r4, lr              @ r4 = initrd_start + load addr
                bl      move                    @ move the initrd

/*
 * Setup the initrd parameters to pass to the kernel.  This can only be
 * passed in via the tagged list.
 */
                ldmia   r13, {r5-r9}            @ get size and addr of initrd
                                                @ r5 = ATAG_CORE
                                                @ r6 = ATAG_INITRD2
                                                @ r7 = initrd start
                                                @ r8 = initrd end
                                                @ r9 = param_struct address

                ldr     r10, [r9, #4]           @ get first tag
                teq     r10, r5                 @ is it ATAG_CORE?
/*
 * If we didn't find a valid tag list, create a dummy ATAG_CORE entry.
 */
                movne   r10, #0                 @ terminator
                movne   r4, #2                  @ Size of this entry (2 words)
                stmiane r9, {r4, r5, r10}       @ Size, ATAG_CORE, terminator

/*
 * find the end of the tag list, and then add an INITRD tag on the end.
 * If there is already an INITRD tag, then we ignore it; the last INITRD
 * tag takes precedence.
 */
taglist:        ldr     r10, [r9, #0]           @ tag length
                teq     r10, #0                 @ last tag (zero length)?
                addne   r9, r9, r10, lsl #2
                bne     taglist

                mov     r5, #4                  @ Size of initrd tag (4 words)
                stmia   r9, {r5, r6, r7, r8, r10}
                b       kernel_start            @ call kernel

/*
 * Move the block of memory length r6 from address r4 to address r5
 */
move:           ldmia   r4!, {r7 - r10}         @ move 32-bytes at a time
                stmia   r5!, {r7 - r10}
                ldmia   r4!, {r7 - r10}
                stmia   r5!, {r7 - r10}
                subs    r6, r6, #8 * 4
                bcs     move
                mov     pc, lr

                .size   _start, . - _start

                .align

                .type   data,#object
data:           .word   initrd_start            @ source initrd address
                .word   initrd_phys             @ destination initrd address
                .word   initrd_size             @ initrd size

                .word   0x54410001              @ r5 = ATAG_CORE
                .word   0x54420005              @ r6 = ATAG_INITRD2
                .word   initrd_phys             @ r7
                .word   initrd_size             @ r8
                .word   params_phys             @ r9
                .size   data, . - data