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: Russell King <rmk+kernel@arm.linux.org.uk>

1 files changed, 24 insertions, 9 deletions

diff --git a/arch/arm/kernel/head.S b/arch/arm/kernel/head.S
index aa6ab9d86461..17414e299482 100644
--- a/arch/arm/kernel/head.S
+++ b/arch/arm/kernel/head.S
@@ -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"