From 1500d1a22fe284a0e9352447bf51c58642b45f1b Mon Sep 17 00:00:00 2001
From: Russell King <rmk@flint.arm.linux.org.uk>
Date: Fri, 19 Sep 2003 19:42:24 +0100
Subject: [PATCH] [ARM] Update bootp kernel+initrd loader.

Drop support for old param struct method, and clean up code.
---
 arch/arm/boot/bootp/init.S | 96 ++++++++++++++++----------------------
 1 file changed, 41 insertions(+), 55 deletions(-)

diff --git a/arch/arm/boot/bootp/init.S b/arch/arm/boot/bootp/init.S
index 21c28e25d8f95..192ec8da69446 100644
--- a/arch/arm/boot/bootp/init.S
+++ b/arch/arm/boot/bootp/init.S
@@ -1,86 +1,69 @@
 /*
  *  linux/arch/arm/boot/bootp/init.S
  *
- *  Copyright (C) 2000-2002 Russell King
+ *  Copyright (C) 2000-2003 Russell King.
  *
  * This program is free software; you can redistribute it and/or modify
  * it under the terms of the GNU General Public License version 2 as
  * published by the Free Software Foundation.
  *
- *  Header file for splitting kernel + initrd.  Note that we pass
+ *  "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,#alloc,#execinstr
 		.type	_start, #function
 		.globl	_start
-_start:		adr	r10, initdata
-		ldr	r11, initdata
-		sub	r11, r10, r11		@ work out exec offset
-		b	splitify
-		.size	_entry,. - _entry
-
-		.type	initdata, #object
-initdata:	.word	initdata		@ compiled address of this
-		.size	initdata,. - initdata
 
-splitify:	adr	r13, data
-		ldmia	r13!, {r4-r6}		@ move the initrd
-		add	r4, r4, r11		@ correction
-		bl	move
+_start:		adr	r12, kernel_start	@ offset of kernel zImage
+		ldr	r4, [r12, #0x2c]	@ length of zImage
+		adr	r13, data
+		add	r4, r4, r12		@ end of zImage, start of initrd
+		ldmia	r13!, {r5-r6}		@ r5 = dest, r6 = length
+		bl	move			@ move the initrd
 
 /*
- * Setup the initrd parameters to pass to the kernel.  This can either be
- * passed in via a param_struct or a tag list.  We spot the param_struct
- * method by looking at the first word; this should either indicate a page
- * size of 4K, 16K or 32K.
+ * Setup the initrd parameters to pass to the kernel.  This can only be
+ * passed in via the tagged list.
  */
-		ldmia	r13, {r4-r8}		@ get size and addr of initrd
-						@ r5 = ATAG_INITRD
-						@ r6 = initrd start
-						@ r7 = initrd end
-						@ r8 = param_struct address
-		ldr	r9, [r8, #0]		@ no param struct?
-		teq	r9, #0x1000		@ 4K?
-		teqne	r9, #0x4000		@ 16K?
-		teqne	r9, #0x8000		@ 32K?
-		beq	param_struct
-
-		ldr	r9, [r8, #4]		@ get first tag
-		teq	r9, r4
-		bne	taglist			@ ok, we have a tag 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?
 /*
- * We didn't find a valid tag list - create one.
+ * If we didn't find a valid tag list, create a dummy ATAG_CORE entry.
  */
-		str	r4, [r8, #4]
-		mov	r4, #8
-		str	r4, [r8, #0]
-		mov	r4, #0
-		str	r4, [r8, #8]
+		movne	r10, #0			@ terminator
+		movne	r4, #2			@ Size of this entry (2 words)
+		stmneia	r8, {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 precidence.
  */
-taglist:	ldr	r9, [r8, #0]		@ tag length
-		teq	r9, #0			@ last tag?
-		addne	r8, r8, r9
+taglist:	ldr	r10, [r9, #0]		@ tag length
+		teq	r10, #0			@ last tag (zero length)?
+		addne	r9, r9, r10, lsl #2
 		bne	taglist
 
-		mov	r4, #16			@ length of initrd tag
-		mov	r9, #0			@ end of tag list terminator
-		stmia	r8, {r4, r5, r6, r7, r9}
-		adr	r12, kernel_start
+		mov	r5, #4			@ Size of initrd tag (4 words)
+		stmia	r9, {r5, r6, r7, r8, r10}
 		mov	pc, r12			@ call kernel
 
 /*
- * We found a param struct.  Modify the param struct for the initrd
+ * Move the block of memory length r6 from address r4 to address r5
  */
-param_struct:	add	r8, r8, #16*4
-		stmia	r8, {r6,r7}		@ save in param_struct
-		mov	pc, r12			@ call kernel
-
 move:		ldmia	r4!, {r7 - r10}		@ move 32-bytes at a time
 		stmia	r5!, {r7 - r10}
 		ldmia	r4!, {r7 - r10}
@@ -89,15 +72,18 @@ move:		ldmia	r4!, {r7 - r10}		@ move 32-bytes at a time
 		bcs	move
 		mov	pc, lr
 
-data:		.word	initrd_start
-		.word	initrd_addr
-		.word	initrd_len
+		.size	_start, . - _start
+
+		.type	data,#object
+data:		.word	initrd_addr		@ destination initrd address
+		.word	initrd_len		@ initrd size
 
 		.word	0x54410001		@ r4 = ATAG_CORE
-		.word	0x54420005		@ r5 = ATAG_INITRD
+		.word	0x54420005		@ r5 = ATAG_INITRD2
 		.word	initrd_addr		@ r6
 		.word	initrd_len		@ r7
 		.word	params			@ r8
+		.size	data, . - _data
 
 		.type	initrd_start,#object
 
-- 
2.53.0