Commit 786f1b73 authored by Russell King's avatar Russell King
Browse files

ARM: hotplug cpu: ensure that __enable_mmu is identity mapped 



__enable_mmu is required to be executed in an identity mapped region
to ensure that variances in CPUs do not cause a crash.  We currently
achieve this by assuming that it will be co-located with
__create_page_tables.  With hotplug CPU support, this assumption
becomes invalid.  Implement a better solution which ensures that
it will be appropriately mapped no matter where it is placed.

Signed-off-by: default avatarRussell King <rmk+kernel@arm.linux.org.uk>
parent 80924ac5

arch/arm/kernel/head.S

+24 −9
Original line number Diff line number Diff line
@@ -201,6 +201,7 @@ __turn_mmu_on: 
	mov	r3, r3

	mov	r3, r13

	mov	pc, r3

__enable_mmu_end:

ENDPROC(__turn_mmu_on)
@@ -214,7 +215,7 @@ ENDPROC(__turn_mmu_on) 
 * r10 = procinfo

 *

 * Returns:

 *  r0, r3, r6, r7 corrupted

 *  r0, r3, r5-r7 corrupted

 *  r4 = physical page table address

 */

__create_page_tables:
@@ -236,20 +237,30 @@ __create_page_tables: 
	ldr	r7, [r10, #PROCINFO_MM_MMUFLAGS] @ mm_mmuflags



	/*

	 * Create identity mapping for first MB of kernel to

	 * cater for the MMU enable.  This identity mapping

	 * will be removed by paging_init().  We use our current program

	 * counter to determine corresponding section base address.

	 * Create identity mapping to cater for __enable_mmu.

	 * This identity mapping will be removed by paging_init().

	 */

	mov	r6, pc

	mov	r6, r6, lsr #20			@ start of kernel section

	orr	r3, r7, r6, lsl #20		@ flags + kernel base

	str	r3, [r4, r6, lsl #2]		@ identity mapping

	adr	r0, __enable_mmu_loc

	ldmia	r0, {r3, r5, r6}

	sub	r0, r0, r3			@ virt->phys offset

	add	r5, r5, r0			@ phys __enable_mmu

	add	r6, r6, r0			@ phys __enable_mmu_end

	mov	r5, r5, lsr #20

	mov	r6, r6, lsr #20



1:	orr	r3, r7, r5, lsl #20		@ flags + kernel base

	str	r3, [r4, r5, lsl #2]		@ identity mapping

	teq	r5, r6

	addne	r5, r5, #1			@ next section

	bne	1b



	/*

	 * Now setup the pagetables for our kernel direct

	 * mapped region.

	 */

	mov	r3, pc

	mov	r3, r3, lsr #20

	orr	r3, r7, r3, lsl #20

	add	r0, r4,  #(KERNEL_START & 0xff000000) >> 18

	str	r3, [r0, #(KERNEL_START & 0x00f00000) >> 18]!

	ldr	r6, =(KERNEL_END - 1)
@@ -333,5 +344,9 @@ __create_page_tables: 
	mov	pc, lr

ENDPROC(__create_page_tables)

	.ltorg

__enable_mmu_loc:

	.long	.

	.long	__enable_mmu

	.long	__enable_mmu_end



#include "head-common.S"

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