Re: [PATCH v5 17/32] x86/mm: Add support to access boot related data in the clear

Tom Lendacky
2017-05-26T16:22:51Z

On 5/18/2017 2:50 PM, Matt Fleming wrote:
> On Mon, 15 May, at 08:35:17PM, Borislav Petkov wrote:
>> On Tue, Apr 18, 2017 at 04:19:21PM -0500, Tom Lendacky wrote:
>>
>>> + paddr = boot_params.efi_info.efi_memmap_hi;
>>> + paddr <<= 32;
>>> + paddr |= boot_params.efi_info.efi_memmap;
>>> + if (phys_addr == paddr)
>>> + return true;
>>> +
>>> + paddr = boot_params.efi_info.efi_systab_hi;
>>> + paddr <<= 32;
>>> + paddr |= boot_params.efi_info.efi_systab;
>>
>> So those two above look like could be two global vars which are
>> initialized somewhere in the EFI init path:
>>
>> efi_memmap_phys and efi_systab_phys or so.
>>
>> Matt ?
>>
>> And then you won't need to create that paddr each time on the fly. I
>> mean, it's not a lot of instructions but still...
>
> We should already have the physical memmap address available in
> 'efi.memmap.phys_map'.

Unfortunately memremap_is_efi_data() is called before the efi structure
gets initialized, so I can't use that value.

>
> And the physical address of the system table should be in
> 'efi_phys.systab'. See efi_init().

In addition to the same issue as efi.memmap.phys_map, efi_phys has
the __initdata attribute so it will be released/freed which will cause
problems in checks performed afterwards.

Thanks,
Tom

>