linux-kernel - Re: [PATCH v8 03/11] arm64: Basic Branch Target Identification support

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]

Message-ID: <20200311163103.GL3216816@arrakis.emea.arm.com>
Date:   Wed, 11 Mar 2020 16:31:03 +0000
From:   Catalin Marinas <catalin.marinas@....com>
To:     Mark Brown <broonie@...nel.org>
Cc:     Will Deacon <will@...nel.org>,
        Alexander Viro <viro@...iv.linux.org.uk>,
        Paul Elliott <paul.elliott@....com>,
        Peter Zijlstra <peterz@...radead.org>,
        Yu-cheng Yu <yu-cheng.yu@...el.com>,
        Amit Kachhap <amit.kachhap@....com>,
        Vincenzo Frascino <vincenzo.frascino@....com>,
        Marc Zyngier <maz@...nel.org>,
        Eugene Syromiatnikov <esyr@...hat.com>,
        Szabolcs Nagy <szabolcs.nagy@....com>,
        "H . J . Lu " <hjl.tools@...il.com>,
        Andrew Jones <drjones@...hat.com>,
        Kees Cook <keescook@...omium.org>,
        Arnd Bergmann <arnd@...db.de>, Jann Horn <jannh@...gle.com>,
        Richard Henderson <richard.henderson@...aro.org>,
        Kristina Martšenko <kristina.martsenko@....com>,
        Thomas Gleixner <tglx@...utronix.de>,
        Florian Weimer <fweimer@...hat.com>,
        Sudakshina Das <sudi.das@....com>,
        linux-arm-kernel@...ts.infradead.org, linux-kernel@...r.kernel.org,
        linux-arch@...r.kernel.org, linux-fsdevel@...r.kernel.org,
        Dave Martin <Dave.Martin@....com>
Subject: Re: [PATCH v8 03/11] arm64: Basic Branch Target Identification
 support

On Thu, Feb 27, 2020 at 05:44:09PM +0000, Mark Brown wrote:
> diff --git a/arch/arm64/Kconfig b/arch/arm64/Kconfig
> index 0b30e884e088..e37f4f07b990 100644
> --- a/arch/arm64/Kconfig
> +++ b/arch/arm64/Kconfig
> @@ -1519,6 +1519,28 @@ endmenu
>  
>  menu "ARMv8.5 architectural features"
>  
> +config ARM64_BTI
> +	bool "Branch Target Identification support"
> +	default y
> +	help
> +	  Branch Target Identification (part of the ARMv8.5 Extensions)
> +	  provides a mechanism to limit the set of locations to which computed
> +	  branch instructions such as BR or BLR can jump.
> +
> +	  To make use of BTI on CPUs that support it, say Y.
> +
> +	  BTI is intended to provide complementary protection to other control
> +	  flow integrity protection mechanisms, such as the Pointer
> +	  authentication mechanism provided as part of the ARMv8.3 Extensions.
> +	  For this reason, it does not make sense to enable this option without
> +	  also enabling support for pointer authentication.  Thus, when
> +	  enabling this option you should also select ARM64_PTR_AUTH=y.
> +
> +	  Userspace binaries must also be specifically compiled to make use of
> +	  this mechanism.  If you say N here or the hardware does not support
> +	  BTI, such binaries can still run, but you get no additional
> +	  enforcement of branch destinations.

To keep the series bisectable, I'd move the Kconfig into a separate
patch towards the end. It looks like the feature is only partially
supported after patch 3, so let's not advertise it here.

-- 
Catalin