Commit c9284882 authored by Ard Biesheuvel's avatar Ard Biesheuvel Committed by Zheng Zengkai
Browse files

ARM: kernel: use PC-relative symbol references in MMU switch code 

maillist inclusion
commit 7e279c05992a88d0517df371a48e72d060b2ca21
category: feature
feature: ARM kaslr support
bugzilla: 47952
CVE: NA

Reference: https://git.kernel.org/pub/scm/linux/kernel/git/ardb/linux.git/commit/?h=arm-kaslr-latest&id=7e279c05992a88d0517df371a48e72d060b2ca21



-------------------------------------------------

To prepare for adding support for KASLR, which relocates all absolute
symbol references at runtime after the caches have been enabled,
update the MMU switch code to avoid using absolute symbol references
where possible. This ensures these quantities are invariant under
runtime relocation.

Cc: Russell King <linux@armlinux.org.uk>
Signed-off-by: default avatarArd Biesheuvel <ard.biesheuvel@linaro.org>
Signed-off-by: default avatarCui GaoSheng <cuigaosheng1@huawei.com>
Reviewed-by: default avatarXiu Jianfeng <xiujianfeng@huawei.com>
Signed-off-by: default avatarZheng Zengkai <zhengzengkai@huawei.com>
parent 88072baa

arch/arm/kernel/head-common.S

+18 −43
Original line number Diff line number Diff line
@@ -80,70 +80,45 @@ __mmap_switched: 
	mov	r8, r2

	mov	r10, r0



	adr	r4, __mmap_switched_data

	mov	fp, #0



#if defined(CONFIG_XIP_DEFLATED_DATA)

   ARM(	ldr	sp, [r4], #4 )

 THUMB(	ldr	sp, [r4] )

 THUMB(	add	r4, #4 )

	adr_l	r4, __bss_stop

	mov	sp, r4				@ sp (temporary stack in .bss)

	bl	__inflate_kernel_data		@ decompress .data to RAM

	teq	r0, #0

	bne	__error

#elif defined(CONFIG_XIP_KERNEL)

   ARM(	ldmia	r4!, {r0, r1, r2, sp} )

 THUMB(	ldmia	r4!, {r0, r1, r2, r3} )

 THUMB(	mov	sp, r3 )

	adr_l	r0, _sdata

	adr_l	r1, __data_loc

	adr_l	r2, _edata_loc

	adr_l	r3, __bss_stop

	mov	sp, r3				@ sp (temporary stack in .bss)

	sub	r2, r2, r1

	bl	__memcpy			@ copy .data to RAM

#endif



   ARM(	ldmia	r4!, {r0, r1, sp} )

 THUMB(	ldmia	r4!, {r0, r1, r3} )

 THUMB(	mov	sp, r3 )

	adr_l	r0, __bss_start

	adr_l	r1, __bss_stop

	adr_l	r3, init_thread_union + THREAD_START_SP

	mov	sp, r3

	sub	r2, r1, r0

	mov	r1, #0

	bl	__memset			@ clear .bss



	ldmia	r4, {r0, r1, r2, r3}

	str	r9, [r0]			@ Save processor ID

	str	r7, [r1]			@ Save machine type

	str	r8, [r2]			@ Save atags pointer

	cmp	r3, #0

	strne	r10, [r3]			@ Save control register values

#ifdef CONFIG_KASAN

	bl	kasan_early_init

#endif

	mov	lr, #0

	b	start_kernel

ENDPROC(__mmap_switched)



	.align	2

	.type	__mmap_switched_data, %object

__mmap_switched_data:

#ifdef CONFIG_XIP_KERNEL

#ifndef CONFIG_XIP_DEFLATED_DATA

	.long	_sdata				@ r0

	.long	__data_loc			@ r1

	.long	_edata_loc			@ r2

#endif

	.long	__bss_stop			@ sp (temporary stack in .bss)

#endif



	.long	__bss_start			@ r0

	.long	__bss_stop			@ r1

	.long	init_thread_union + THREAD_START_SP @ sp



	.long	processor_id			@ r0

	.long	__machine_arch_type		@ r1

	.long	__atags_pointer			@ r2

	str_l	r9, processor_id, r4		@ Save processor ID

	str_l	r7, __machine_arch_type, r4	@ Save machine type

	str_l	r8, __atags_pointer, r4		@ Save atags pointer

#ifdef CONFIG_CPU_CP15

	.long	cr_alignment			@ r3

#else

M_CLASS(.long	exc_ret)			@ r3

AR_CLASS(.long	0)				@ r3

	str_l	r10, cr_alignment, r4		@ Save control register values

#endif

	.size	__mmap_switched_data, . - __mmap_switched_data

	mov	lr, #0

	b	start_kernel

ENDPROC(__mmap_switched)



	__FINIT

	.text