x86/pti: Unbreak EFI old_memmap

EFI_OLD_MEMMAP's efi_call_phys_prolog() calls set_pgd() with swapper PGD that
has PAGE_USER set, which makes PTI set NX on it, and therefore EFI can't
execute it's code.

Fix that by forcefully clearing _PAGE_NX from the PGD (this can't be done
by the pgprot API).

_PAGE_NX will be automatically reintroduced in efi_call_phys_epilog(), as
_set_pgd() will again notice that this is _PAGE_USER, and set _PAGE_NX on
it.

Tested-by: Dimitri Sivanich <[email protected]>
Signed-off-by: Jiri Kosina <[email protected]>
Signed-off-by: Ingo Molnar <[email protected]>
Signed-off-by: Thomas Gleixner <[email protected]>
Acked-by: Dave Hansen <[email protected]>
Cc: Andrea Arcangeli <[email protected]>
Cc: Ard Biesheuvel <[email protected]>
Cc: Linus Torvalds <[email protected]>
Cc: Matt Fleming <[email protected]>
Cc: Peter Zijlstra <[email protected]>
Cc: Thomas Gleixner <[email protected]>
Cc: [email protected]
Cc: [email protected]
Link: http://lkml.kernel.org/r/[email protected]

diff --git a/arch/x86/platform/efi/efi_64.c b/arch/x86/platform/efi/efi_64.c
index 39c4b35ac7a4a9cc0d2b54cbc7b7ea58997da09f..61975b6bcb1a0a51d88d2f9be779411915cd5e79 100644 (file)
--- a/arch/x86/platform/efi/efi_64.c
+++ b/arch/x86/platform/efi/efi_64.c
@@ -134,7 +134,9 @@ pgd_t * __init efi_call_phys_prolog(void)
                                pud[j] = *pud_offset(p4d_k, vaddr);
                        }
                }
+               pgd_offset_k(pgd * PGDIR_SIZE)->pgd &= ~_PAGE_NX;
        }
+
 out:
        __flush_tlb_all();