x86/efi: Map EFI_MEMORY_{XP,RO} memory region bits to EFI page tables

Now that we have EFI memory region bits that indicate which regions do
not need execute permission or read/write permission in the page tables,
let's use them.

We also check for EFI_NX_PE_DATA and only enforce the restrictive
mappings if it's present (to allow us to ignore buggy firmware that sets
bits it didn't mean to and to preserve backwards compatibility).

Instead of assuming that firmware would set appropriate attributes in
memory descriptor like EFI_MEMORY_RO for code and EFI_MEMORY_XP for
data, we can expect some firmware out there which might only set *type*
in memory descriptor to be EFI_RUNTIME_SERVICES_CODE or
EFI_RUNTIME_SERVICES_DATA leaving away attribute. This will lead to
improper mappings of EFI runtime regions. In order to avoid it, we check
attribute and type of memory descriptor to update mappings and moreover
Windows works this way.

Signed-off-by: Sai Praneeth Prakhya <sai.praneeth.prakhya@intel.com>
Signed-off-by: Matt Fleming <matt@codeblueprint.co.uk>
Cc: Andrew Morton <akpm@linux-foundation.org>
Cc: Andy Lutomirski <luto@amacapital.net>
Cc: Ard Biesheuvel <ard.biesheuvel@linaro.org>
Cc: Borislav Petkov <bp@alien8.de>
Cc: Brian Gerst <brgerst@gmail.com>
Cc: Denys Vlasenko <dvlasenk@redhat.com>
Cc: H. Peter Anvin <hpa@zytor.com>
Cc: Kees Cook <keescook@chromium.org>
Cc: Lee, Chun-Yi <jlee@suse.com>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Luis R. Rodriguez <mcgrof@suse.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Ravi Shankar <ravi.v.shankar@intel.com>
Cc: Ricardo Neri <ricardo.neri@intel.com>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: Toshi Kani <toshi.kani@hp.com>
Cc: linux-efi@vger.kernel.org
Link: http://lkml.kernel.org/r/1455712566-16727-13-git-send-email-matt@codeblueprint.co.uk
Signed-off-by: Ingo Molnar <mingo@kernel.org>

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