efi: Introduce the EFI_MEM_ATTR bit and set it from the memory attributes table

UEFI v2.6 introduces a configuration table called
EFI_MEMORY_ATTRIBUTES_TABLE which provides additional information about
EFI runtime regions. Currently this table describes memory protections
that may be applied to the EFI Runtime code and data regions by the kernel.

Allocate a EFI_XXX bit to keep track of whether this feature is
published by firmware or not.
Signed-off-by: Sai Praneeth Prakhya <sai.praneeth.prakhya@intel.com>
Signed-off-by: Matt Fleming <matt@codeblueprint.co.uk>
Signed-off-by: Ard Biesheuvel <ard.biesheuvel@linaro.org>
Reviewed-by: Lee, Chun-Yi <jlee@suse.com>
Cc: Borislav Petkov <bp@alien8.de>
Cc: Fenghua Yu <fenghua.yu@intel.com>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
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: linux-efi@vger.kernel.org
Link: http://lkml.kernel.org/r/1485868902-20401-5-git-send-email-ard.biesheuvel@linaro.orgSigned-off-by: Ingo Molnar <mingo@kernel.org>

drivers/firmware/efi/memattr.c

@@ -43,6 +43,7 @@ int __init efi_memattr_init(void)
 
 	tbl_size = sizeof(*tbl) + tbl->num_entries * tbl->desc_size;
 	memblock_reserve(efi.mem_attr_table, tbl_size);
+	set_bit(EFI_MEM_ATTR, &efi.flags);
 
 unmap:
 	early_memunmap(tbl, sizeof(*tbl));

include/linux/efi.h

@@ -1065,6 +1065,7 @@ extern int __init efi_setup_pcdp_console(char *);
 #define EFI_ARCH_1		7	/* First arch-specific bit */
 #define EFI_DBG			8	/* Print additional debug info at runtime */
 #define EFI_NX_PE_DATA		9	/* Can runtime data regions be mapped non-executable? */
+#define EFI_MEM_ATTR		10	/* Did firmware publish an EFI_MEMORY_ATTRIBUTES table? */
 
 #ifdef CONFIG_EFI
 /*