x86/efi: Correct EFI identity mapping under 'efi=old_map' when KASLR is enabled

For EFI with the 'efi=old_map' kernel option specified, the kernel will panic
when KASLR is enabled:

  BUG: unable to handle kernel paging request at 000000007febd57e
  IP: 0x7febd57e
  PGD 1025a067
  PUD 0

  Oops: 0010 [#1] SMP
  Call Trace:
   efi_enter_virtual_mode()
   start_kernel()
   x86_64_start_reservations()
   x86_64_start_kernel()
   start_cpu()

The root cause is that the identity mapping is not built correctly
in the 'efi=old_map' case.

On 'nokaslr' kernels, PAGE_OFFSET is 0xffff880000000000 which is PGDIR_SIZE
aligned. We can borrow the PUD table from the direct mappings safely. Given a
physical address X, we have pud_index(X) == pud_index(__va(X)).

However, on KASLR kernels, PAGE_OFFSET is PUD_SIZE aligned. For a given physical
address X, pud_index(X) != pud_index(__va(X)). We can't just copy the PGD entry
from direct mapping to build identity mapping, instead we need to copy the
PUD entries one by one from the direct mapping.

Fix it.

Signed-off-by: Baoquan He <[email protected]>
Signed-off-by: Matt Fleming <[email protected]>
Cc: Ard Biesheuvel <[email protected]>
Cc: Bhupesh Sharma <[email protected]>
Cc: Borislav Petkov <[email protected]>
Cc: Dave Young <[email protected]>
Cc: Frank Ramsay <[email protected]>
Cc: Kees Cook <[email protected]>
Cc: Linus Torvalds <[email protected]>
Cc: Peter Zijlstra <[email protected]>
Cc: Russ Anderson <[email protected]>
Cc: Thomas Garnier <[email protected]>
Cc: Thomas Gleixner <[email protected]>
Cc: [email protected]
Link: http://lkml.kernel.org/r/[email protected]
[ Fixed and reworded the changelog and code comments to be more readable. ]
Signed-off-by: Ingo Molnar <[email protected]>

0 files changed, 0 insertions, 0 deletions