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>

4 files changed, 23 insertions, 0 deletions

diff --git a/arch/arm/mm/Kconfig b/arch/arm/mm/Kconfig
index 76bbcde049b0..a25f34bd99da 100644
--- a/arch/arm/mm/Kconfig
+++ b/arch/arm/mm/Kconfig
@@ -639,6 +639,20 @@ config CPU_BIG_ENDIAN
           port must properly enable any big-endian related features
           of your chipset/board/processor.
 
+config CPU_ENDIAN_BE8
+        bool
+        depends on CPU_BIG_ENDIAN
+        default CPU_V6 || CPU_V7
+        help
+          Support for the BE-8 (big-endian) mode on ARMv6 and ARMv7 processors.
+
+config CPU_ENDIAN_BE32
+        bool
+        depends on CPU_BIG_ENDIAN
+        default !CPU_ENDIAN_BE8
+        help
+          Support for the BE-32 (big-endian) mode on pre-ARMv6 processors.
+
 config CPU_HIGH_VECTOR
         depends on !MMU && CPU_CP15 && !CPU_ARM740T
         bool "Select the High exception vector"
diff --git a/arch/arm/mm/abort-ev6.S b/arch/arm/mm/abort-ev6.S
index 6f7e70907e44..f332df7f0d37 100644
--- a/arch/arm/mm/abort-ev6.S
+++ b/arch/arm/mm/abort-ev6.S
@@ -37,6 +37,9 @@ ENTRY(v6_early_abort)
         movne   pc, lr
         do_thumb_abort
         ldreq   r3, [r2]                        @ read aborted ARM instruction
+#ifdef CONFIG_CPU_ENDIAN_BE8
+        reveq   r3, r3
+#endif
         do_ldrd_abort
         tst     r3, #1 << 20                    @ L = 0 -> write
         orreq   r1, r1, #1 << 11                @ yes.
diff --git a/arch/arm/mm/proc-v6.S b/arch/arm/mm/proc-v6.S
index 087e239704df..524ddae92595 100644
--- a/arch/arm/mm/proc-v6.S
+++ b/arch/arm/mm/proc-v6.S
@@ -170,6 +170,9 @@ __v6_setup:
 #endif /* CONFIG_MMU */
         adr     r5, v6_crval
         ldmia   r5, {r5, r6}
+#ifdef CONFIG_CPU_ENDIAN_BE8
+        orr     r6, r6, #1 << 25                @ big-endian page tables
+#endif
         mrc     p15, 0, r0, c1, c0, 0           @ read control register
         bic     r0, r0, r5                      @ clear bits them
         orr     r0, r0, r6                      @ set them
diff --git a/arch/arm/mm/proc-v7.S b/arch/arm/mm/proc-v7.S
index 0a8ffd3c03fd..4f8486475a79 100644
--- a/arch/arm/mm/proc-v7.S
+++ b/arch/arm/mm/proc-v7.S
@@ -253,6 +253,9 @@ __v7_setup:
         mcr     p15, 0, r6, c10, c2, 1          @ write NMRR
         adr     r5, v7_crval
         ldmia   r5, {r5, r6}
+#ifdef CONFIG_CPU_ENDIAN_BE8
+        orr     r6, r6, #1 << 25                @ big-endian page tables
+#endif
         mrc     p15, 0, r0, c1, c0, 0           @ read control register
         bic     r0, r0, r5                      @ clear bits them
         orr     r0, r0, r6                      @ set them