linux-kernel - Re: [PATCH v9 30/44] arm64: kasan: Allow enabling in-kernel MTE

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Message-ID: <20201112094354.GF29613@gaia>
Date:   Thu, 12 Nov 2020 09:43:54 +0000
From:   Catalin Marinas <catalin.marinas@....com>
To:     Andrey Konovalov <andreyknvl@...gle.com>
Cc:     Will Deacon <will.deacon@....com>,
        Vincenzo Frascino <vincenzo.frascino@....com>,
        Dmitry Vyukov <dvyukov@...gle.com>,
        Andrey Ryabinin <aryabinin@...tuozzo.com>,
        Alexander Potapenko <glider@...gle.com>,
        Marco Elver <elver@...gle.com>,
        Evgenii Stepanov <eugenis@...gle.com>,
        Branislav Rankov <Branislav.Rankov@....com>,
        Kevin Brodsky <kevin.brodsky@....com>,
        Andrew Morton <akpm@...ux-foundation.org>,
        kasan-dev@...glegroups.com, linux-arm-kernel@...ts.infradead.org,
        linux-mm@...ck.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH v9 30/44] arm64: kasan: Allow enabling in-kernel MTE

On Tue, Nov 10, 2020 at 11:10:27PM +0100, Andrey Konovalov wrote:
> From: Vincenzo Frascino <vincenzo.frascino@....com>
> 
> Hardware tag-based KASAN relies on Memory Tagging Extension (MTE)
> feature and requires it to be enabled. MTE supports
> 
> This patch adds a new mte_init_tags() helper, that enables MTE in
> Synchronous mode in EL1 and is intended to be called from KASAN runtime
> during initialization.

There's no mte_init_tags() in this function.

> diff --git a/arch/arm64/kernel/mte.c b/arch/arm64/kernel/mte.c
> index 600b26d65b41..7f477991a6cf 100644
> --- a/arch/arm64/kernel/mte.c
> +++ b/arch/arm64/kernel/mte.c
> @@ -129,6 +129,13 @@ void *mte_set_mem_tag_range(void *addr, size_t size, u8 tag)
>  	return ptr;
>  }
>  
> +void mte_enable(void)
> +{
> +	/* Enable MTE Sync Mode for EL1. */
> +	sysreg_clear_set(sctlr_el1, SCTLR_ELx_TCF_MASK, SCTLR_ELx_TCF_SYNC);
> +	isb();
> +}

Nitpick: maybe rename this to mte_enable_kernel() since MTE is already
enabled for user apps.

-- 
Catalin