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>

3 files changed, 7 insertions, 1 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
diff --git a/arch/arm/kernel/entry-common.S b/arch/arm/kernel/entry-common.S
index b55cb0331809..366e5097a41a 100644
--- a/arch/arm/kernel/entry-common.S
+++ b/arch/arm/kernel/entry-common.S
@@ -210,6 +210,9 @@ ENTRY(vector_swi)
   A710( teq     ip, #0x0f000000                                         )
   A710( bne     .Larm710bug                                             )
 #endif
+#ifdef CONFIG_CPU_ENDIAN_BE8
+        rev     r10, r10                        @ little endian instruction
+#endif
 
 #elif defined(CONFIG_AEABI)
 
diff --git a/arch/arm/kernel/process.c b/arch/arm/kernel/process.c
index c3265a2e7cd4..1585423699ee 100644
--- a/arch/arm/kernel/process.c
+++ b/arch/arm/kernel/process.c
@@ -365,7 +365,7 @@ pid_t kernel_thread(int (*fn)(void *), void *arg, unsigned long flags)
         regs.ARM_r2 = (unsigned long)fn;
         regs.ARM_r3 = (unsigned long)do_exit;
         regs.ARM_pc = (unsigned long)kernel_thread_helper;
-        regs.ARM_cpsr = SVC_MODE;
+        regs.ARM_cpsr = SVC_MODE | PSR_ENDSTATE;
 
         return do_fork(flags|CLONE_VM|CLONE_UNTRACED, 0, &regs, 0, NULL, NULL);
 }