linux-kernel - Re: [PATCH v2 1/6] bus: arm-cci: use asm unreachable

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Date:   Sun, 25 Mar 2018 14:14:26 -0400 (EDT)
From:   Nicolas Pitre <nicolas.pitre@...aro.org>
To:     Stefan Agner <stefan@...er.ch>
cc:     linux@...linux.org.uk, ard.biesheuvel@...aro.org, arnd@...db.de,
        robin.murphy@....com, marc.zyngier@....com,
        behanw@...verseincode.com, keescook@...omium.org,
        Bernhard.Rosenkranzer@...aro.org, mka@...omium.org,
        linux-arm-kernel@...ts.infradead.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH v2 1/6] bus: arm-cci: use asm unreachable

On Sun, 25 Mar 2018, Stefan Agner wrote:

> Mixing asm and C code is not recommended in a naked function by
> gcc and leads to an error when using clang:
>   drivers/bus/arm-cci.c:2107:2: error: non-ASM statement in naked
>   function is not supported
>         unreachable();
>         ^
> 
> While the function is marked __naked it actually properly return
> in asm. There is no need for the unreachable() call.
> 
> Suggested-by: Russell King <linux@....linux.org.uk>
> Signed-off-by: Stefan Agner <stefan@...er.ch>

If that doesn't introduce any warning with gcc then I'm fine with it.

Acked-by: Nicolas Pitre <nico@...aro.org>


> ---
> Changes in v2:
> - Don't add assembly ASM_UNREACHABLE, just drop unreachable()
> 
>  drivers/bus/arm-cci.c | 2 --
>  1 file changed, 2 deletions(-)
> 
> diff --git a/drivers/bus/arm-cci.c b/drivers/bus/arm-cci.c
> index 5426c04fe24b..fc2da3a617ac 100644
> --- a/drivers/bus/arm-cci.c
> +++ b/drivers/bus/arm-cci.c
> @@ -2103,8 +2103,6 @@ asmlinkage void __naked cci_enable_port_for_self(void)
>  	[sizeof_struct_cpu_port] "i" (sizeof(struct cpu_port)),
>  	[sizeof_struct_ace_port] "i" (sizeof(struct cci_ace_port)),
>  	[offsetof_port_phys] "i" (offsetof(struct cci_ace_port, phys)) );
> -
> -	unreachable();
>  }
>  
>  /**
> -- 
> 2.16.2
> 
>