linux-kernel - Re: [PATCH 6/6] arm64: compat: Check for AArch32 state

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Message-ID: <20160209173606.GX22874@arm.com>
Date:	Tue, 9 Feb 2016 17:36:06 +0000
From:	Will Deacon <will.deacon@....com>
To:	Suzuki K Poulose <suzuki.poulose@....com>
Cc:	linux-arm-kernel@...ts.infradead.org, catalin.marinas@....com,
	mark.rutland@....com, ynorov@...iumnetworks.com,
	linux-kernel@...r.kernel.org
Subject: Re: [PATCH 6/6] arm64: compat: Check for AArch32 state

On Thu, Jan 28, 2016 at 11:32:17AM +0000, Suzuki K Poulose wrote:
> Make sure we have AArch32 state available for running COMPAT binaries.
> 
> Signed-off-by: Yury Norov <ynorov@...iumnetworks.com>
> [ Added checks for ELF HWCAP, Use cap bit in cap_hwcaps ]
> Signed-off-by: Suzuki K Poulose <suzuki.poulose@....com>

[...]

> diff --git a/arch/arm64/kernel/cpuinfo.c b/arch/arm64/kernel/cpuinfo.c
> index 8cc2a86..2890b74 100644
> --- a/arch/arm64/kernel/cpuinfo.c
> +++ b/arch/arm64/kernel/cpuinfo.c
> @@ -124,7 +124,8 @@ static int c_show(struct seq_file *m, void *v)
>  		 * software which does already (at least for 32-bit).
>  		 */
>  		seq_puts(m, "Features\t:");
> -		if (personality(current->personality) == PER_LINUX32) {
> +		if (system_supports_32bit_el0() &&
> +			personality(current->personality) == PER_LINUX32) {

Wouldn't it be better to prevent tasks changing to the PER_LINUX32
personality on systems that don't support AArch32 at EL0?

Will