[PATCH v4] ARM: Implement SLS mitigation

[Russell King - ARM Linux admin]

On Fri, Feb 19, 2021 at 03:08:13PM -0800, Jian Cai wrote:
> diff --git a/security/Kconfig.hardening b/security/Kconfig.hardening
> index 269967c4fc1b..146b75a79d9e 100644
> --- a/security/Kconfig.hardening
> +++ b/security/Kconfig.hardening
> @@ -121,6 +121,16 @@ choice
>  
>  endchoice
>  
> +config HARDEN_SLS_ALL
> +	bool "enable SLS vulnerability hardening"
> +	default n

Please get rid of this useless "default n"

> +	depends on $(cc-option,-mharden-sls=all)
> +	help
> +	  Enables straight-line speculation vulnerability hardening on ARM and ARM64
> +	  architectures. It inserts speculation barrier sequences (SB or DSB+ISB
> +	  depending on the target architecture) after RET and BR, and replacing
> +	  BLR with BL+BR sequence.

Given that this is in an architecture independent Kconfig file, and it
detects support in CC for this feature, why should this help text be
written to be specific to a couple of architectures? Will this feature
only ever be available on these two architectures? What if someone adds
support for another architecture?

-- 
RMK's Patch system: https://www.armlinux.org.uk/developer/patches/
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