linux-kernel - Re: [PATCH linux-next] power:pkeys: fix bugon.cocci warnings

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Date:   Mon, 02 May 2022 23:24:07 +1000
From:   Michael Ellerman <mpe@...erman.id.au>
To:     CGEL <cgel.zte@...il.com>,
        Benjamin Herrenschmidt <benh@...nel.crashing.org>,
        Paul Mackerras <paulus@...ba.org>,
        Sandipan Das <sandipan@...ux.ibm.com>,
        linuxppc-dev@...ts.ozlabs.org, linux-kernel@...r.kernel.org
Cc:     Jing Yangyang <jing.yangyang@....com.cn>,
        Zeal Robot <zealci@....com.cn>
Subject: Re: [PATCH linux-next] power:pkeys: fix bugon.cocci warnings

CGEL <cgel.zte@...il.com> writes:
> From: Jing Yangyang <jing.yangyang@....com.cn>
>
> Use BUG_ON instead of a if condition followed by BUG.
>
> ./arch/powerpc/include/asm/book3s/64/pkeys.h:21:2-5:WARNING
> Use BUG_ON instead of if condition followed by BUG.
> ./arch/powerpc/include/asm/book3s/64/pkeys.h:14:2-5:WARNING
> Use BUG_ON instead of if condition followed by BUG.
>
> Generated by: scripts/coccinelle/misc/bugon.cocci
>
> Reported-by: Zeal Robot <zealci@....com.cn>
> Signed-off-by: Jing Yangyang <jing.yangyang@....com.cn>
> ---
>  arch/powerpc/include/asm/book3s/64/pkeys.h | 6 ++----
>  1 file changed, 2 insertions(+), 4 deletions(-)
>
> diff --git a/arch/powerpc/include/asm/book3s/64/pkeys.h b/arch/powerpc/include/asm/book3s/64/pkeys.h
> index 5b17813..5f74f0c 100644
> --- a/arch/powerpc/include/asm/book3s/64/pkeys.h
> +++ b/arch/powerpc/include/asm/book3s/64/pkeys.h
> @@ -10,15 +10,13 @@ static inline u64 vmflag_to_pte_pkey_bits(u64 vm_flags)
>  	if (!mmu_has_feature(MMU_FTR_PKEY))
>  		return 0x0UL;
>  
> -	if (radix_enabled())
> -		BUG();
> +	BUG_ON(radix_enabled());
>  	return hash__vmflag_to_pte_pkey_bits(vm_flags);
>  }
>  
>  static inline u16 pte_to_pkey_bits(u64 pteflags)
>  {
> -	if (radix_enabled())
> -		BUG();
> +	BUG_ON(radix_enabled());
>  	return hash__pte_to_pkey_bits(pteflags);
>  }

Have you checked how this changes the generated code?

radix_enabled() is a jump label, via mmu_feature().

Possibly the compiler just works it all out and generates the same code,
but I'd want some evidence of that before merging this.

cheers