ARM: 7311/1: Add generic instruction opcode manipulation helpers

This patch adds some endianness-agnostic helpers to convert machine
instructions between canonical integer form and in-memory
representation.

A canonical integer form for representing instructions is also
formalised here.

Signed-off-by: Dave Martin <dave.martin@linaro.org>
Acked-by: Nicolas Pitre <nico@linaro.org>
Tested-by: Jon Medhurst <tixy@yxit.co.uk>
Signed-off-by: Russell King <rmk+kernel@arm.linux.org.uk>

1 files changed, 59 insertions, 0 deletions

diff --git a/arch/arm/include/asm/opcodes.h b/arch/arm/include/asm/opcodes.h
index c0efdd6..19c48de 100644
--- a/arch/arm/include/asm/opcodes.h
+++ b/arch/arm/include/asm/opcodes.h
@@ -17,4 +17,63 @@ extern asmlinkage unsigned int arm_check_condition(u32 opcode, u32 psr);
 #define ARM_OPCODE_CONDTEST_PASS   1
 #define ARM_OPCODE_CONDTEST_UNCOND 2
 
+
+/*
+ * Opcode byteswap helpers
+ *
+ * These macros help with converting instructions between a canonical integer
+ * format and in-memory representation, in an endianness-agnostic manner.
+ *
+ * __mem_to_opcode_*() convert from in-memory representation to canonical form.
+ * __opcode_to_mem_*() convert from canonical form to in-memory representation.
+ *
+ *
+ * Canonical instruction representation:
+ *
+ *	ARM:		0xKKLLMMNN
+ *	Thumb 16-bit:	0x0000KKLL, where KK < 0xE8
+ *	Thumb 32-bit:	0xKKLLMMNN, where KK >= 0xE8
+ *
+ * There is no way to distinguish an ARM instruction in canonical representation
+ * from a Thumb instruction (just as these cannot be distinguished in memory).
+ * Where this distinction is important, it needs to be tracked separately.
+ *
+ * Note that values in the range 0x0000E800..0xE7FFFFFF intentionally do not
+ * represent any valid Thumb-2 instruction.  For this range,
+ * __opcode_is_thumb32() and __opcode_is_thumb16() will both be false.
+ */
+
+#ifndef __ASSEMBLY__
+
+#include <linux/types.h>
+#include <linux/swab.h>
+
+#ifdef CONFIG_CPU_ENDIAN_BE8
+#define __opcode_to_mem_arm(x) swab32(x)
+#define __opcode_to_mem_thumb16(x) swab16(x)
+#define __opcode_to_mem_thumb32(x) swahb32(x)
+#else
+#define __opcode_to_mem_arm(x) ((u32)(x))
+#define __opcode_to_mem_thumb16(x) ((u16)(x))
+#define __opcode_to_mem_thumb32(x) swahw32(x)
+#endif
+
+#define __mem_to_opcode_arm(x) __opcode_to_mem_arm(x)
+#define __mem_to_opcode_thumb16(x) __opcode_to_mem_thumb16(x)
+#define __mem_to_opcode_thumb32(x) __opcode_to_mem_thumb32(x)
+
+/* Operations specific to Thumb opcodes */
+
+/* Instruction size checks: */
+#define __opcode_is_thumb32(x) ((u32)(x) >= 0xE8000000UL)
+#define __opcode_is_thumb16(x) ((u32)(x) < 0xE800UL)
+
+/* Operations to construct or split 32-bit Thumb instructions: */
+#define __opcode_thumb32_first(x) ((u16)((x) >> 16))
+#define __opcode_thumb32_second(x) ((u16)(x))
+#define __opcode_thumb32_compose(first, second) \
+	(((u32)(u16)(first) << 16) | (u32)(u16)(second))
+
+#endif /* __ASSEMBLY__ */
+
 #endif /* __ASM_ARM_OPCODES_H */