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/Makefile

@@ -11,6 +11,9 @@
 # Copyright (C) 1995-2001 by Russell King
 
 LDFLAGS_vmlinux	:=-p --no-undefined -X
+ifeq ($(CONFIG_CPU_ENDIAN_BE8),y)
+LDFLAGS_vmlinux	+= --be8
+endif
 CPPFLAGS_vmlinux.lds = -DTEXT_OFFSET=$(TEXT_OFFSET)
 OBJCOPYFLAGS	:=-O binary -R .note -R .note.gnu.build-id -R .comment -S
 GZFLAGS		:=-9

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

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) */			\

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__
 
 /*

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

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)
 

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);
 }

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"

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.

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

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