Add core support for ARMv6/v7 big-endian

Starting with ARMv6, the CPUs support the BE-8 variant of big-endian
(byte-invariant). This patch adds the core support:

- setting of the BE-8 mode via the CPSR.E register for both kernel and
  user threads
- big-endian page table walking
- REV used to rotate instructions read from memory during fault
  processing as they are still little-endian format
- Kconfig and Makefile support for BE-8. The --be8 option must be passed
  to the final linking stage to convert the instructions to
  little-endian

Signed-off-by: Catalin Marinas <catalin.marinas@arm.com>

arch/arm/boot/compressed/Makefile

@@ -40,7 +40,7 @@ ifeq ($(CONFIG_PXA_SHARPSL),y)
 OBJS		+= head-sharpsl.o
 endif
 
-ifeq ($(CONFIG_CPU_BIG_ENDIAN),y)
+ifeq ($(CONFIG_CPU_ENDIAN_BE32),y)
 ifeq ($(CONFIG_CPU_CP15),y)
 OBJS		+= big-endian.o
 else
@@ -78,6 +78,9 @@ EXTRA_AFLAGS  := -Wa,-march=all
 # linker symbols.  We only define initrd_phys and params_phys if the
 # machine class defined the corresponding makefile variable.
 LDFLAGS_vmlinux := --defsym zreladdr=$(ZRELADDR)
+ifeq ($(CONFIG_CPU_ENDIAN_BE8),y)
+LDFLAGS_vmlinux += --be8
+endif
 ifneq ($(INITRD_PHYS),)
 LDFLAGS_vmlinux += --defsym initrd_phys=$(INITRD_PHYS)
 endif

arch/arm/boot/compressed/head.S

@@ -438,6 +438,9 @@ __armv4_mmu_cache_on:
 		mrc	p15, 0, r0, c1, c0, 0	@ read control reg
 		orr	r0, r0, #0x5000		@ I-cache enable, RR cache replacement
 		orr	r0, r0, #0x0030
+#ifdef CONFIG_CPU_ENDIAN_BE8
+		orr	r0, r0, #1 << 25	@ big-endian page tables
+#endif
 		bl	__common_mmu_cache_on
 		mov	r0, #0
 		mcr	p15, 0, r0, c8, c7, 0	@ flush I,D TLBs
@@ -455,6 +458,9 @@ __armv7_mmu_cache_on:
 		mrc	p15, 0, r0, c1, c0, 0	@ read control reg
 		orr	r0, r0, #0x5000		@ I-cache enable, RR cache replacement
 		orr	r0, r0, #0x003c		@ write buffer
+#ifdef CONFIG_CPU_ENDIAN_BE8
+		orr	r0, r0, #1 << 25	@ big-endian page tables
+#endif
 		orrne	r0, r0, #1		@ MMU enabled
 		movne	r1, #-1
 		mcrne	p15, 0, r3, c2, c0, 0	@ load page table pointer