linux-kernel - Re: [PATCH 05/20] arm64: rename COMPAT to AARCH32

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Date:   Thu, 8 Jun 2017 15:09:12 +0100
From:   Catalin Marinas <catalin.marinas@....com>
To:     Yury Norov <ynorov@...iumnetworks.com>
Cc:     linux-arm-kernel@...ts.infradead.org, linux-kernel@...r.kernel.org,
        linux-doc@...r.kernel.org, Arnd Bergmann <arnd@...db.de>,
        Andrew Pinski <Andrew.Pinski@...iumnetworks.com>,
        Heiko Carstens <heiko.carstens@...ibm.com>,
        Chris Metcalf <cmetcalf@...hip.com>,
        philipp.tomsich@...obroma-systems.com,
        Joseph Myers <joseph@...esourcery.com>,
        zhouchengming1@...wei.com,
        Steve Ellcey <sellcey@...iumnetworks.com>,
        Prasun.Kapoor@...iumnetworks.com, Andreas Schwab <schwab@...e.de>,
        agraf@...e.de, szabolcs.nagy@....com, geert@...ux-m68k.org,
        Adam Borowski <kilobyte@...band.pl>,
        manuel.montezelo@...il.com, Chris Metcalf <cmetcalf@...lanox.com>,
        Andrew Pinski <pinskia@...il.com>, linyongting@...wei.com,
        klimov.linux@...il.com, broonie@...nel.org,
        Bamvor Zhangjian <bamvor.zhangjian@...wei.com>,
        Bamvor Jian Zhang <bamvor.zhangjian@...aro.org>,
        Maxim Kuvyrkov <maxim.kuvyrkov@...aro.org>,
        Florian Weimer <fweimer@...hat.com>, Nathan_Lynch@...tor.com,
        Andrew Pinski <apinski@...ium.com>,
        Ramana Radhakrishnan <ramana.gcc@...glemail.com>,
        schwidefsky@...ibm.com, davem@...emloft.net,
        christoph.muellner@...obroma-systems.com
Subject: Re: [PATCH 05/20] arm64: rename COMPAT to AARCH32_EL0 in Kconfig

On Sun, Jun 04, 2017 at 02:59:54PM +0300, Yury Norov wrote:
> --- a/arch/arm64/Kconfig
> +++ b/arch/arm64/Kconfig
> @@ -402,7 +402,7 @@ config ARM64_ERRATUM_834220
>  
>  config ARM64_ERRATUM_845719
>  	bool "Cortex-A53: 845719: a load might read incorrect data"
> -	depends on COMPAT
> +	depends on AARCH32_EL0
>  	default y
>  	help
>  	  This option adds an alternative code sequence to work around ARM
> @@ -784,7 +784,7 @@ config FORCE_MAX_ZONEORDER
>  
>  menuconfig ARMV8_DEPRECATED
>  	bool "Emulate deprecated/obsolete ARMv8 instructions"
> -	depends on COMPAT
> +	depends on AARCH32_EL0
>  	help
>  	  Legacy software support may require certain instructions
>  	  that have been deprecated or obsoleted in the architecture.
> @@ -1062,9 +1062,15 @@ menu "Userspace binary formats"
>  source "fs/Kconfig.binfmt"
>  
>  config COMPAT
> +	bool
> +	depends on AARCH32_EL0

You could just use "def_bool y" here

> +
> +config AARCH32_EL0
>  	bool "Kernel support for 32-bit EL0"
> +	def_bool y
>  	depends on ARM64_4K_PAGES || EXPERT
>  	select COMPAT_BINFMT_ELF if BINFMT_ELF
> +	select COMPAT

and avoid the explicit select.

>  	select HAVE_UID16
>  	select OLD_SIGSUSPEND3
>  	select COMPAT_OLD_SIGACTION
[...]
> --- a/arch/arm64/kernel/cpuinfo.c
> +++ b/arch/arm64/kernel/cpuinfo.c
> @@ -139,15 +139,17 @@ static int c_show(struct seq_file *m, void *v)
>  		 */
>  		seq_puts(m, "Features\t:");
>  		if (compat) {
> -#ifdef CONFIG_COMPAT
> -			for (j = 0; compat_hwcap_str[j]; j++)
> -				if (compat_elf_hwcap & (1 << j))
> -					seq_printf(m, " %s", compat_hwcap_str[j]);
> -
> -			for (j = 0; compat_hwcap2_str[j]; j++)
> -				if (compat_elf_hwcap2 & (1 << j))
> -					seq_printf(m, " %s", compat_hwcap2_str[j]);
> -#endif /* CONFIG_COMPAT */
> +#ifdef CONFIG_AARCH32_EL0
> +			if (personality(current->personality) == PER_LINUX32) {
> +				for (j = 0; compat_hwcap_str[j]; j++)
> +					if (compat_elf_hwcap & (1 << j))
> +						seq_printf(m, " %s", compat_hwcap_str[j]);
> +
> +				for (j = 0; compat_hwcap2_str[j]; j++)
> +					if (compat_elf_hwcap2 & (1 << j))
> +						seq_printf(m, " %s", compat_hwcap2_str[j]);
> +			}
> +#endif /* CONFIG_AARCH32_EL0 */

I don't understand this hunk. Why do you need another check on
personality? "compat" is already true if PER_LINUX32.

-- 
Catalin