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>

2 files changed, 11 insertions, 0 deletions

diff --git a/arch/arm/include/asm/processor.h b/arch/arm/include/asm/processor.h
index 1845892260e7..6a89567ffc5b 100644
--- a/arch/arm/include/asm/processor.h
+++ b/arch/arm/include/asm/processor.h
@@ -71,6 +71,7 @@ struct thread_struct {
                 regs->ARM_cpsr = USR26_MODE;                            \
         if (elf_hwcap & HWCAP_THUMB && pc & 1)                          \
                 regs->ARM_cpsr |= PSR_T_BIT;                            \
+        regs->ARM_cpsr |= PSR_ENDSTATE;                                 \
         regs->ARM_pc = pc & ~1;         /* pc */                        \
         regs->ARM_sp = sp;              /* sp */                        \
         regs->ARM_r2 = stack[2];        /* r2 (envp) */                 \
diff --git a/arch/arm/include/asm/ptrace.h b/arch/arm/include/asm/ptrace.h
index 4a4290f7b4a2..67b833c9b6b9 100644
--- a/arch/arm/include/asm/ptrace.h
+++ b/arch/arm/include/asm/ptrace.h
@@ -50,6 +50,7 @@
 #define PSR_F_BIT       0x00000040
 #define PSR_I_BIT       0x00000080
 #define PSR_A_BIT       0x00000100
+#define PSR_E_BIT       0x00000200
 #define PSR_J_BIT       0x01000000
 #define PSR_Q_BIT       0x08000000
 #define PSR_V_BIT       0x10000000
@@ -72,6 +73,15 @@
 #define PSR_IT_MASK     0x0600fc00      /* If-Then execution state mask */
 #define PSR_ENDIAN_MASK 0x00000200      /* Endianness state mask */
 
+/*
+ * Default endianness state
+ */
+#ifdef CONFIG_CPU_ENDIAN_BE8
+#define PSR_ENDSTATE    PSR_E_BIT
+#else
+#define PSR_ENDSTATE    0
+#endif
+
 #ifndef __ASSEMBLY__
 
 /*