linux-kernel - Re: [PATCH] x86/mm: Directly return instead of using local ret variable

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Date:   Sun, 27 Mar 2022 19:49:19 -0700
From:   Dave Hansen <dave.hansen@...el.com>
To:     Haowen Bai <baihaowen@...zu.com>, dave.hansen@...ux.intel.com,
        luto@...nel.org, peterz@...radead.org
Cc:     linux-kernel@...r.kernel.org
Subject: Re: [PATCH] x86/mm: Directly return instead of using local ret
 variable

On 3/27/22 19:12, Haowen Bai wrote:
> 
> diff --git a/arch/x86/mm/pf_in.c b/arch/x86/mm/pf_in.c
> index 3f83e31..4eff3ee 100644
> --- a/arch/x86/mm/pf_in.c
> +++ b/arch/x86/mm/pf_in.c
> @@ -130,7 +130,6 @@ enum reason_type get_ins_type(unsigned long ins_addr)
>  	unsigned char *p;
>  	struct prefix_bits prf;
>  	int i;
> -	enum reason_type rv = OTHERS;
>  
>  	p = (unsigned char *)ins_addr;
>  	p += skip_prefix(p, &prf);
> @@ -141,7 +140,7 @@ enum reason_type get_ins_type(unsigned long ins_addr)
>  	CHECK_OP_TYPE(opcode, imm_wop, IMM_WRITE);
>  
>  exit:
> -	return rv;
> +	return OTHERS;
>  }
>  #undef CHECK_OP_TYPE
>  

Does this even compile?  Take a look at this macro:

> #define CHECK_OP_TYPE(opcode, array, type) \
>         for (i = 0; i < ARRAY_SIZE(array); i++) { \
>                 if (array[i] == opcode) { \
>                         rv = type; \
>                         goto exit; \
>                 } \

It uses 'rv'.