linux-kernel - Re: arm64: Fix size of __early_cpu_boot

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Message-ID: <20190430110624.GB16204@fuggles.cambridge.arm.com>
Date:   Tue, 30 Apr 2019 12:06:24 +0100
From:   Will Deacon <will.deacon@....com>
To:     Arun KS <arunks@...eaurora.org>
Cc:     Catalin Marinas <catalin.marinas@....com>,
        James Morse <james.morse@....com>,
        Mark Rutland <mark.rutland@....com>,
        Jun Yao <yaojun8558363@...il.com>,
        Steve Capper <steve.capper@....com>,
        Vladimir Murzin <vladimir.murzin@....com>,
        linux-arm-kernel@...ts.infradead.org, linux-kernel@...r.kernel.org
Subject: Re: arm64: Fix size of __early_cpu_boot_status

On Tue, Apr 30, 2019 at 04:05:04PM +0530, Arun KS wrote:
> __early_cpu_boot_status is of type long. Use quad
> assembler directive to allocate proper size.
> 
> Signed-off-by: Arun KS <arunks@...eaurora.org>
> ---
>  arch/arm64/kernel/head.S | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
> 
> diff --git a/arch/arm64/kernel/head.S b/arch/arm64/kernel/head.S
> index eecf792..115f332 100644
> --- a/arch/arm64/kernel/head.S
> +++ b/arch/arm64/kernel/head.S
> @@ -684,7 +684,7 @@ ENTRY(__boot_cpu_mode)
>   * with MMU turned off.
>   */
>  ENTRY(__early_cpu_boot_status)
> -	.long 	0
> +	.quad 	0

Yikes. How did you spot this? Did we end up corrupting an adjacent variable,
or does the alignment in the linker script save us in practice?

Will