linux-kernel - Re: [PATCH v2 17/18] arm64: Kconfig: Add CONFIG_UNMAP_KERNEL_AT

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Date:   Tue, 12 Dec 2017 09:44:09 +0100
From:   Geert Uytterhoeven <geert@...ux-m68k.org>
To:     Will Deacon <will.deacon@....com>
Cc:     "linux-arm-kernel@...ts.infradead.org" 
        <linux-arm-kernel@...ts.infradead.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        Catalin Marinas <catalin.marinas@....com>,
        Mark Rutland <mark.rutland@....com>,
        Ard Biesheuvel <ard.biesheuvel@...aro.org>,
        Stephen Boyd <sboyd@...eaurora.org>,
        Dave Hansen <dave.hansen@...ux.intel.com>,
        Kees Cook <keescook@...omium.org>,
        Mark Salter <msalter@...hat.com>,
        Laura Abbott <labbott@...hat.com>,
        Thomas Gleixner <tglx@...utronix.de>
Subject: Re: [PATCH v2 17/18] arm64: Kconfig: Add CONFIG_UNMAP_KERNEL_AT_EL0

Hi Will,

On Thu, Nov 30, 2017 at 5:39 PM, Will Deacon <will.deacon@....com> wrote:
> Add a Kconfig entry to control use of the entry trampoline, which allows
> us to unmap the kernel whilst running in userspace and improve the
> robustness of KASLR.
>
> Signed-off-by: Will Deacon <will.deacon@....com>

This is now commit 084eb77cd3a81134 in arm64/for-next/core.

> ---
>  arch/arm64/Kconfig | 13 +++++++++++++
>  1 file changed, 13 insertions(+)
>
> diff --git a/arch/arm64/Kconfig b/arch/arm64/Kconfig
> index fdcc7b9bb15d..3af1657fcac3 100644
> --- a/arch/arm64/Kconfig
> +++ b/arch/arm64/Kconfig
> @@ -833,6 +833,19 @@ config FORCE_MAX_ZONEORDER
>           However for 4K, we choose a higher default value, 11 as opposed to 10, giving us
>           4M allocations matching the default size used by generic code.
>
> +config UNMAP_KERNEL_AT_EL0
> +       bool "Unmap kernel when running in userspace (aka \"KAISER\")"

But I believe this is no longer called KAISER?

Gr{oetje,eeting}s,

                        Geert

--
Geert Uytterhoeven -- There's lots of Linux beyond ia32 -- geert@...ux-m68k.org

In personal conversations with technical people, I call myself a hacker. But
when I'm talking to journalists I just say "programmer" or something like that.
                                -- Linus Torvalds