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ARM: hotplug cpu: ensure that __enable_mmu is identity mapped

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__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: Russell King <rmk+kernel@arm.linux.org.uk>
This commit is contained in:
Russell King 2010-10-04 17:51:54 +01:00
parent 80924ac595
commit 786f1b73f7
1 changed files with 24 additions and 9 deletions
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33
arch/arm/kernel/head.S
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@ -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"