Subject: [PATCH v5] ARM: Add generic instruction opcode manipulation helpers

From: [email-masked] (Tixy)
Date: Tue, 31 Jan 2012 18:22:20 +0000

On Tue, 2012-01-31 at 11:09 +0000, Dave Martin wrote:
> 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 <[email-masked]>
> Acked-by: Nicolas Pitre <[email-masked]>

I can confirm this version applies and builds cleanly against
linux-next. And works with Rabin 's jump label support patches.

-- 
Tixy

> ---
> Changes since v1:
> 
> v5: Avoid inclusion of C headers or definition of the __opcode_*
>     macros when opcodes.h is included in assembler files.  Since
>     the __opcode_* macros rely on C declarations, they are not
>     directly usable in assembler anyway.
> 
> v4: Rebase on top of Leif's patch which created <asm/opcodes.h>
>     ARM: 7206/1: Add generic ARM instruction set condition code checks.
> 
>     No functional changes.
> 
> v3: Fix some stupid errors:
> 
>   * remove bogus extra (x) in __opcode_to_mem_arm
>   * fix use of nonexistent "thumb_opcode" argument in
>         __opcode_thumb32_{first,second} which causes these
>         macros to be broken.
> 
> v2: Remove unnecessary typedef for arm_opcode_t.
> 
>     The general "everything is a word" concept works just fine here --
>     we don't need a typedef, and people will probably not use it
>     anyway.
> 
>  arch/arm/include/asm/opcodes.h |   59 ++++++++++++++++++++++++++++++++++++++++
>  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 */