mirror of
https://mirrors.bfsu.edu.cn/git/linux.git
synced 2024-12-29 22:14:41 +08:00
077248fcce
Directives such as .long and .word do not magically cause the
assembler location counter to become aligned in gas. As a result,
using these directives in code sections can result in misaligned
data words when building a Thumb-2 kernel (CONFIG_THUMB2_KERNEL).
This is a Bad Thing, since the ABI permits the compiler to assume
that fundamental types of word size or above are word- aligned when
accessing them from C. If the data is not really word-aligned,
this can cause impaired performance and stray alignment faults in
some circumstances.
In general, the following rules should be applied when using data
word declaration directives inside code sections:
* .quad and .double:
.align 3
* .long, .word, .single, .float:
.align (or .align 2)
* .short:
No explicit alignment required, since Thumb-2
instructions are always 2 or 4 bytes in size.
immediately after an instruction.
Reviewed-by: Will Deacon <will.deacon@arm.com>
Signed-off-by: Dave Martin <dave.martin@linaro.org>
Acked-by: Catalin Marinas <catalin.marinas@arm.com>
Signed-off-by: Russell King <rmk+kernel@arm.linux.org.uk>
89 lines
2.6 KiB
ArmAsm
89 lines
2.6 KiB
ArmAsm
/*
|
|
* linux/arch/arm/boot/bootp/init.S
|
|
*
|
|
* 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
|
|
* 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: 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)
|
|
stmneia 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
|