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

Borislav Petkov
2017-05-04T10:16:37Z

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@amd.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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