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>

1 files changed, 3 insertions, 0 deletions

diff --git a/arch/arm/kernel/entry-armv.S b/arch/arm/kernel/entry-armv.S
index d662a2f1fd85..9d7ce4377c5e 100644
--- a/arch/arm/kernel/entry-armv.S
+++ b/arch/arm/kernel/entry-armv.S
@@ -482,6 +482,9 @@ __und_usr:
         subeq   r4, r2, #4                      @ ARM instr at LR - 4
         subne   r4, r2, #2                      @ Thumb instr at LR - 2
 1:      ldreqt  r0, [r4]
+#ifdef CONFIG_CPU_ENDIAN_BE8
+        reveq   r0, r0                          @ little endian instruction
+#endif
         beq     call_fpe
         @ Thumb instruction
 #if __LINUX_ARM_ARCH__ >= 7