x86, mce: store record length into memory struct mce anchor

This makes it easier for tools who want to extract the mcelog out of
crash images or memory dumps to adapt to changing struct mce size.
The length field replaces padding, so it's fully compatible.
Signed-off-by: NAndi Kleen <ak@linux.intel.com>
Signed-off-by: NHidetoshi Seto <seto.hidetoshi@jp.fujitsu.com>
Signed-off-by: NH. Peter Anvin <hpa@zytor.com>

arch/x86/include/asm/mce.h

@@ -59,7 +59,7 @@ struct mce_log {
 	unsigned len;	    /* = MCE_LOG_LEN */
 	unsigned next;
 	unsigned flags;
-	unsigned pad0;
+	unsigned recordlen;	/* length of struct mce */
 	struct mce entry[MCE_LOG_LEN];
 };
 

arch/x86/kernel/cpu/mcheck/mce.c

@@ -108,8 +108,9 @@ EXPORT_PER_CPU_SYMBOL_GPL(injectm);
  */
 
 static struct mce_log mcelog = {
-	MCE_LOG_SIGNATURE,
-	MCE_LOG_LEN,
+	.signature	= MCE_LOG_SIGNATURE,
+	.len		= MCE_LOG_LEN,
+	.recordlen	= sizeof(struct mce),
 };
 
 void mce_log(struct mce *mce)