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

From: Tom Lendacky
Date: Fri May 26 2017 - 12:22:53 EST


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