linux-kernel - Re: [PATCH v5 12/32] x86/mm: Insure that boot memory areas are mapped properly

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Date:   Thu, 4 May 2017 12:16:09 +0200
From:   Borislav Petkov <bp@...en8.de>
To:     Tom Lendacky <thomas.lendacky@....com>
Cc:     linux-arch@...r.kernel.org, linux-efi@...r.kernel.org,
        kvm@...r.kernel.org, linux-doc@...r.kernel.org, x86@...nel.org,
        kexec@...ts.infradead.org, linux-kernel@...r.kernel.org,
        kasan-dev@...glegroups.com, linux-mm@...ck.org,
        iommu@...ts.linux-foundation.org, Rik van Riel <riel@...hat.com>,
        Radim Krčmář <rkrcmar@...hat.com>,
        Toshimitsu Kani <toshi.kani@....com>,
        Arnd Bergmann <arnd@...db.de>,
        Jonathan Corbet <corbet@....net>,
        Matt Fleming <matt@...eblueprint.co.uk>,
        "Michael S. Tsirkin" <mst@...hat.com>,
        Joerg Roedel <joro@...tes.org>,
        Konrad Rzeszutek Wilk <konrad.wilk@...cle.com>,
        Paolo Bonzini <pbonzini@...hat.com>,
        Larry Woodman <lwoodman@...hat.com>,
        Brijesh Singh <brijesh.singh@....com>,
        Ingo Molnar <mingo@...hat.com>,
        Andy Lutomirski <luto@...nel.org>,
        "H. Peter Anvin" <hpa@...or.com>,
        Andrey Ryabinin <aryabinin@...tuozzo.com>,
        Alexander Potapenko <glider@...gle.com>,
        Dave Young <dyoung@...hat.com>,
        Thomas Gleixner <tglx@...utronix.de>,
        Dmitry Vyukov <dvyukov@...gle.com>
Subject: Re: [PATCH v5 12/32] x86/mm: Insure that boot memory areas are
 mapped properly

On Tue, Apr 18, 2017 at 04:18:22PM -0500, Tom Lendacky wrote:
> The boot data and command line data are present in memory in a decrypted
> state and are copied early in the boot process.  The early page fault
> support will map these areas as encrypted, so before attempting to copy
> them, add decrypted mappings so the data is accessed properly when copied.
> 
> For the initrd, encrypt this data in place. Since the future mapping of the
> initrd area will be mapped as encrypted the data will be accessed properly.
> 
> Signed-off-by: Tom Lendacky <thomas.lendacky@....com>
> ---
>  arch/x86/include/asm/mem_encrypt.h |   11 +++++
>  arch/x86/include/asm/pgtable.h     |    3 +
>  arch/x86/kernel/head64.c           |   30 ++++++++++++--
>  arch/x86/kernel/setup.c            |   10 +++++
>  arch/x86/mm/mem_encrypt.c          |   77 ++++++++++++++++++++++++++++++++++++
>  5 files changed, 127 insertions(+), 4 deletions(-)

...

> diff --git a/arch/x86/kernel/setup.c b/arch/x86/kernel/setup.c
> index 603a166..a95800b 100644
> --- a/arch/x86/kernel/setup.c
> +++ b/arch/x86/kernel/setup.c
> @@ -115,6 +115,7 @@
>  #include <asm/microcode.h>
>  #include <asm/mmu_context.h>
>  #include <asm/kaslr.h>
> +#include <asm/mem_encrypt.h>
>  
>  /*
>   * max_low_pfn_mapped: highest direct mapped pfn under 4GB
> @@ -374,6 +375,15 @@ static void __init reserve_initrd(void)
>  	    !ramdisk_image || !ramdisk_size)
>  		return;		/* No initrd provided by bootloader */
>  
> +	/*
> +	 * If SME is active, this memory will be marked encrypted by the
> +	 * kernel when it is accessed (including relocation). However, the
> +	 * ramdisk image was loaded decrypted by the bootloader, so make
> +	 * sure that it is encrypted before accessing it.
> +	 */
> +	if (sme_active())

That test is not needed here because __sme_early_enc_dec() already tests
sme_me_mask. There you should change that test to sme_active() instead.

> +		sme_early_encrypt(ramdisk_image, ramdisk_end - ramdisk_image);
> +
>  	initrd_start = 0;
>  
>  	mapped_size = memblock_mem_size(max_pfn_mapped);

-- 
Regards/Gruss,
    Boris.

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