x86/boot/e820: Use 'enum e820_type' in 'struct e820_entry'

Use a stricter type for struct e820_entry. Add a build-time check to make
sure the compiler won't ever pack the enum into a field smaller than
'int'.

No change in functionality.

Cc: Alex Thorlton <athorlton@sgi.com>
Cc: Andy Lutomirski <luto@kernel.org>
Cc: Borislav Petkov <bp@alien8.de>
Cc: Brian Gerst <brgerst@gmail.com>
Cc: Dan Williams <dan.j.williams@intel.com>
Cc: Denys Vlasenko <dvlasenk@redhat.com>
Cc: H. Peter Anvin <hpa@zytor.com>
Cc: Huang, Ying <ying.huang@intel.com>
Cc: Josh Poimboeuf <jpoimboe@redhat.com>
Cc: Juergen Gross <jgross@suse.com>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Paul Jackson <pj@sgi.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Rafael J. Wysocki <rjw@sisk.pl>
Cc: Tejun Heo <tj@kernel.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: Wei Yang <richard.weiyang@gmail.com>
Cc: Yinghai Lu <yinghai@kernel.org>
Cc: linux-kernel@vger.kernel.org
Signed-off-by: Ingo Molnar <mingo@kernel.org>

arch/x86/include/asm/e820/types.h

 #ifndef _ASM_E820_TYPES_H
 #define _ASM_E820_TYPES_H
 
-enum e820_type {
-	E820_RAM		= 1,
-	E820_RESERVED		= 2,
-	E820_ACPI		= 3,
-	E820_NVS		= 4,
-	E820_UNUSABLE		= 5,
-	E820_PMEM		= 7,
-
-	/*
-	 * This is a non-standardized way to represent ADR or
-	 * NVDIMM regions that persist over a reboot.
-	 *
-	 * The kernel will ignore their special capabilities
-	 * unless the CONFIG_X86_PMEM_LEGACY=y option is set.
-	 *
-	 * ( Note that older platforms also used 6 for the same
-	 *   type of memory, but newer versions switched to 12 as
-	 *   6 was assigned differently. Some time they will learn... )
-	 */
-	E820_PRAM		= 12,
-
-	/*
-	 * Reserved RAM used by the kernel itself if
-	 * CONFIG_INTEL_TXT=y is enabled, memory of this type
-	 * will be included in the S3 integrity calculation
-	 * and so should not include any memory that the BIOS
-	 * might alter over the S3 transition:
-	 */
-	E820_RESERVED_KERN	= 128,
-};
-
 #include <uapi/asm/e820/types.h>
 
 /*

arch/x86/include/uapi/asm/e820/types.h

@@ -6,14 +6,45 @@
 
 #ifndef __ASSEMBLY__
 
+enum e820_type {
+	E820_RAM		= 1,
+	E820_RESERVED		= 2,
+	E820_ACPI		= 3,
+	E820_NVS		= 4,
+	E820_UNUSABLE		= 5,
+	E820_PMEM		= 7,
+
+	/*
+	 * This is a non-standardized way to represent ADR or
+	 * NVDIMM regions that persist over a reboot.
+	 *
+	 * The kernel will ignore their special capabilities
+	 * unless the CONFIG_X86_PMEM_LEGACY=y option is set.
+	 *
+	 * ( Note that older platforms also used 6 for the same
+	 *   type of memory, but newer versions switched to 12 as
+	 *   6 was assigned differently. Some time they will learn... )
+	 */
+	E820_PRAM		= 12,
+
+	/*
+	 * Reserved RAM used by the kernel itself if
+	 * CONFIG_INTEL_TXT=y is enabled, memory of this type
+	 * will be included in the S3 integrity calculation
+	 * and so should not include any memory that the BIOS
+	 * might alter over the S3 transition:
+	 */
+	E820_RESERVED_KERN	= 128,
+};
+
 /*
  * A single E820 map entry, describing a memory range of [addr...addr+size-1],
  * of 'type' memory type:
  */
 struct e820_entry {
-	__u64 addr;
-	__u64 size;
-	__u32 type;
+	__u64			addr;
+	__u64			size;
+	enum e820_type		type;
 } __attribute__((packed));
 
 #endif /* __ASSEMBLY__ */

arch/x86/kernel/e820.c

@@ -1164,6 +1164,9 @@ void __init e820__memory_setup(void)
 {
 	char *who;
 
+	/* This is a firmware interface ABI - make sure we don't break it: */
+	BUILD_BUG_ON(sizeof(struct e820_entry) != 20);
+
 	who = x86_init.resources.memory_setup();
 
 	memcpy(e820_table_firmware, e820_table, sizeof(struct e820_table));