1 files changed, 85 insertions, 0 deletions
diff --git a/arch/arm/boot/bootp/init.S b/arch/arm/boot/bootp/init.S
new file mode 100644
index 000000000..b562da2f7
--- /dev/null
+++ b/arch/arm/boot/bootp/init.S
@@ -0,0 +1,85 @@
+/* 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