Re: [PATCH v13 03/10] arm64: add conditional instruction simulation support

[Masami Hiramatsu]

On Thu,  2 Jun 2016 23:26:17 -0400
David Long <dave.long@xxxxxxxxxx> wrote:

> From: "David A. Long" <dave.long@xxxxxxxxxx>
> 
> Cease using the arm32 arm_check_condition() function and replace it with
> a local version for use in deprecated instruction support on arm64. Also
> make the function table used by this available for future use by kprobes
> and/or uprobes.
> 
> This function is dervied from code written by Sandeepa Prabhu.
> 

Basically looks good to me. I have some comments;

> Signed-off-by: Sandeepa Prabhu <sandeepa.s.prabhu@xxxxxxxxx>
> Signed-off-by: David A. Long <dave.long@xxxxxxxxxx>
> ---
>  arch/arm64/include/asm/insn.h        |  3 ++
>  arch/arm64/kernel/Makefile           |  3 +-
>  arch/arm64/kernel/armv8_deprecated.c | 19 ++++++-
>  arch/arm64/kernel/insn.c             | 98 ++++++++++++++++++++++++++++++++++++
>  4 files changed, 119 insertions(+), 4 deletions(-)
> 
> diff --git a/arch/arm64/include/asm/insn.h b/arch/arm64/include/asm/insn.h
> index 9785d10..98e4edd 100644
> --- a/arch/arm64/include/asm/insn.h
> +++ b/arch/arm64/include/asm/insn.h
> @@ -406,6 +406,9 @@ u32 aarch64_extract_system_register(u32 insn);
>  u32 aarch32_insn_extract_reg_num(u32 insn, int offset);
>  u32 aarch32_insn_mcr_extract_opc2(u32 insn);
>  u32 aarch32_insn_mcr_extract_crm(u32 insn);
> +
> +typedef bool (pstate_check_t)(unsigned long);
> +extern pstate_check_t * const opcode_condition_checks[16];

Are those condition checkers only for aarch32 opcode? or
general for aarch64 too? If it is only for aarch32, we'd better
add aarch32 prefix.

>  #endif /* __ASSEMBLY__ */
>  
>  #endif	/* __ASM_INSN_H */
> diff --git a/arch/arm64/kernel/Makefile b/arch/arm64/kernel/Makefile
> index 2173149..4653aca 100644
> --- a/arch/arm64/kernel/Makefile
> +++ b/arch/arm64/kernel/Makefile
> @@ -26,8 +26,7 @@ $(obj)/%.stub.o: $(obj)/%.o FORCE
>  	$(call if_changed,objcopy)
>  
>  arm64-obj-$(CONFIG_COMPAT)		+= sys32.o kuser32.o signal32.o 	\
> -					   sys_compat.o entry32.o		\
> -					   ../../arm/kernel/opcodes.o
> +					   sys_compat.o entry32.o
>  arm64-obj-$(CONFIG_FUNCTION_TRACER)	+= ftrace.o entry-ftrace.o
>  arm64-obj-$(CONFIG_MODULES)		+= arm64ksyms.o module.o
>  arm64-obj-$(CONFIG_ARM64_MODULE_PLTS)	+= module-plts.o
> diff --git a/arch/arm64/kernel/armv8_deprecated.c b/arch/arm64/kernel/armv8_deprecated.c
> index c37202c..88b9165 100644
> --- a/arch/arm64/kernel/armv8_deprecated.c
> +++ b/arch/arm64/kernel/armv8_deprecated.c
> @@ -366,6 +366,21 @@ static int emulate_swpX(unsigned int address, unsigned int *data,
>  	return res;
>  }
>  
> +#define	ARM_OPCODE_CONDITION_UNCOND	0xf
> +
> +static unsigned int __kprobes arm32_check_condition(u32 opcode, u32 psr)

Would you be OK for using arm32 instead of aarch32 prefix?

> +{
> +	u32 cc_bits  = opcode >> 28;
> +
> +	if (cc_bits != ARM_OPCODE_CONDITION_UNCOND) {
> +		if ((*opcode_condition_checks[cc_bits])(psr))
> +			return ARM_OPCODE_CONDTEST_PASS;
> +		else
> +			return ARM_OPCODE_CONDTEST_FAIL;
> +	}
> +	return ARM_OPCODE_CONDTEST_UNCOND;
> +}

Thank you,

-- 
Masami Hiramatsu <mhiramat@xxxxxxxxxx>