x86: Add symbolic constant for exceptions with error code

Add a symbolic constant for the bitmask which states which exceptions
carry an error code.
Signed-off-by: H. Peter Anvin <hpa@zytor.com>
Link: http://lkml.kernel.org/r/1334794610-5546-3-git-send-email-hpa@zytor.com

arch/x86/include/asm/segment.h

@@ -205,6 +205,8 @@
 
 #define IDT_ENTRIES 256
 #define NUM_EXCEPTION_VECTORS 32
+/* Bitmask of exception vectors which push an error code on the stack */
+#define EXCEPTION_ERRCODE_MASK  0x00027d00
 #define GDT_SIZE (GDT_ENTRIES * 8)
 #define GDT_ENTRY_TLS_ENTRIES 3
 #define TLS_SIZE (GDT_ENTRY_TLS_ENTRIES * 8)

arch/x86/kernel/head_64.S

@@ -295,7 +295,7 @@ ENTRY(early_idt_handler)
 	ja 0f
 	movl $1,%eax
 	salq %cl,%rax
-	testl $0x27d00,%eax
+	testl $EXCEPTION_ERRCODE_MASK,%eax
 	je 0f
 	popq %r8		# get error code
 0:	movq 0(%rsp),%rcx	# get ip