Re: [Xen-devel] [PATCH v7 14/36] x86/mm: Insure that boot memory areas are mapped properly

[Borislav Petkov <bp@xxxxxxxxx>]

On Fri, Jun 16, 2017 at 01:52:32PM -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@xxxxxxx>
> ---
>  arch/x86/include/asm/mem_encrypt.h |    6 +++
>  arch/x86/include/asm/pgtable.h     |    3 ++
>  arch/x86/kernel/head64.c           |   30 +++++++++++++--
>  arch/x86/kernel/setup.c            |    9 +++++
>  arch/x86/mm/kasan_init_64.c        |    2 +
>  arch/x86/mm/mem_encrypt.c          |   70 
> ++++++++++++++++++++++++++++++++++++
>  6 files changed, 115 insertions(+), 5 deletions(-)

...

> diff --git a/arch/x86/mm/mem_encrypt.c b/arch/x86/mm/mem_encrypt.c
> index b7671b9..ea5e3a6 100644
> --- a/arch/x86/mm/mem_encrypt.c
> +++ b/arch/x86/mm/mem_encrypt.c
> @@ -19,6 +19,8 @@
>  
>  #include <asm/tlbflush.h>
>  #include <asm/fixmap.h>
> +#include <asm/setup.h>
> +#include <asm/bootparam.h>
>  
>  /*
>   * Since SME related variables are set early in the boot process they must
> @@ -101,6 +103,74 @@ void __init sme_early_decrypt(resource_size_t paddr, 
> unsigned long size)
>       __sme_early_enc_dec(paddr, size, false);
>  }
>  
> +static void __init __sme_early_map_unmap_mem(void *vaddr, unsigned long size,
> +                                          bool map)
> +{
> +     unsigned long paddr = (unsigned long)vaddr - __PAGE_OFFSET;
> +     pmdval_t pmd_flags, pmd;
> +
> +     /* Use early_pmd_flags but remove the encryption mask */
> +     pmd_flags = __sme_clr(early_pmd_flags);
> +
> +     do {
> +             pmd = map ? (paddr & PMD_MASK) + pmd_flags : 0;
> +             __early_make_pgtable((unsigned long)vaddr, pmd);
> +
> +             vaddr += PMD_SIZE;
> +             paddr += PMD_SIZE;
> +             size = (size <= PMD_SIZE) ? 0 : size - PMD_SIZE;
> +     } while (size);
> +
> +     write_cr3(__read_cr3());

local_flush_tlb() or __native_flush_tlb(). Probably the native variant
since this is early fun.

> +}
> +
> +static void __init __sme_map_unmap_bootdata(char *real_mode_data, bool map)
> +{
> +     struct boot_params *boot_data;
> +     unsigned long cmdline_paddr;
> +
> +     /* If SME is not active, the bootdata is in the correct state */
> +     if (!sme_active())
> +             return;
> +
> +     if (!map) {
> +             /*
> +              * If unmapping, get the command line address before
> +              * unmapping the real_mode_data.
> +              */
> +             boot_data = (struct boot_params *)real_mode_data;
> +             cmdline_paddr = boot_data->hdr.cmd_line_ptr |
> +                             ((u64)boot_data->ext_cmd_line_ptr << 32);

Let it stick out:

        cmdline_paddr = bd->hdr.cmd_line_ptr | ((u64)bd->ext_cmd_line_ptr << 
32);

> +     }
> +
> +     __sme_early_map_unmap_mem(real_mode_data, sizeof(boot_params), map);
> +
> +     if (map) {
> +             /*
> +              * If mapping, get the command line address after mapping
> +              * the real_mode_data.
> +              */
> +             boot_data = (struct boot_params *)real_mode_data;
> +             cmdline_paddr = boot_data->hdr.cmd_line_ptr |
> +                             ((u64)boot_data->ext_cmd_line_ptr << 32);
> +     }
> +
> +     if (!cmdline_paddr)
> +             return;
> +
> +     __sme_early_map_unmap_mem(__va(cmdline_paddr), COMMAND_LINE_SIZE, map);

Ok, so from looking at this function now - it does different things
depending on whether we map or not. So it doesn't look like a worker
function anymore and you can move the stuff back to the original callers
below. Should make the whole flow more readable.

> +}
> +
> +void __init sme_unmap_bootdata(char *real_mode_data)
> +{
> +     __sme_map_unmap_bootdata(real_mode_data, false);
> +}
> +
> +void __init sme_map_bootdata(char *real_mode_data)
> +{
> +     __sme_map_unmap_bootdata(real_mode_data, true);
> +}
> +
>  void __init sme_early_init(void)
>  {
>       unsigned int i;
> 

-- 
Regards/Gruss,
    Boris.

Good mailing practices for 400: avoid top-posting and trim the reply.

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