x86, extable: Add _ASM_EXTABLE_EX() macro

Add _ASM_EXTABLE_EX() to generate the special extable entries that are
associated with uaccess_err.  This allows us to change the protocol
associated with these special entries.
Signed-off-by: H. Peter Anvin <hpa@zytor.com>
Cc: David Daney <david.daney@cavium.com>
Link: http://lkml.kernel.org/r/CA%2B55aFyijf43qSu3N9nWHEBwaGbb7T2Oq9A=9EyR=Jtyqfq_cQ@mail.gmail.com

arch/x86/include/asm/asm.h

@@ -40,16 +40,28 @@
 
 /* Exception table entry */
 #ifdef __ASSEMBLY__
-# define _ASM_EXTABLE(from,to)			\
-	.pushsection "__ex_table","a" ;		\
-	_ASM_ALIGN ;				\
-	_ASM_PTR from , to ;			\
+# define _ASM_EXTABLE(from,to)					\
+	.pushsection "__ex_table","a" ;				\
+	_ASM_ALIGN ;						\
+	_ASM_PTR from , to ;					\
+	.popsection
+
+# define _ASM_EXTABLE_EX(from,to)				\
+	.pushsection "__ex_table","a" ;				\
+	_ASM_ALIGN ;						\
+	_ASM_PTR from , (to) - (from) ;				\
 	.popsection
 #else
-# define _ASM_EXTABLE(from,to)			\
-	" .pushsection \"__ex_table\",\"a\"\n"	\
-	_ASM_ALIGN "\n" 			\
-	_ASM_PTR #from "," #to "\n" 		\
+# define _ASM_EXTABLE(from,to)					\
+	" .pushsection \"__ex_table\",\"a\"\n"			\
+	_ASM_ALIGN "\n" 					\
+	_ASM_PTR #from "," #to "\n" 				\
+	" .popsection\n"
+
+# define _ASM_EXTABLE_EX(from,to)				\
+	" .pushsection \"__ex_table\",\"a\"\n"			\
+	_ASM_ALIGN "\n" 					\
+	_ASM_PTR #from ",(" #to ")-(" #from ")\n" 		\
 	" .popsection\n"
 #endif
 

arch/x86/include/asm/uaccess.h

@@ -202,8 +202,8 @@ extern int __get_user_bad(void);
 	asm volatile("1:	movl %%eax,0(%1)\n"			\
 		     "2:	movl %%edx,4(%1)\n"			\
 		     "3:\n"						\
-		     _ASM_EXTABLE(1b, 2b - 1b)				\
-		     _ASM_EXTABLE(2b, 3b - 2b)				\
+		     _ASM_EXTABLE_EX(1b, 2b)				\
+		     _ASM_EXTABLE_EX(2b, 3b)				\
 		     : : "A" (x), "r" (addr))
 
 #define __put_user_x8(x, ptr, __ret_pu)				\
@@ -408,7 +408,7 @@ do {									\
 #define __get_user_asm_ex(x, addr, itype, rtype, ltype)			\
 	asm volatile("1:	mov"itype" %1,%"rtype"0\n"		\
 		     "2:\n"						\
-		     _ASM_EXTABLE(1b, 2b - 1b)				\
+		     _ASM_EXTABLE_EX(1b, 2b)				\
 		     : ltype(x) : "m" (__m(addr)))
 
 #define __put_user_nocheck(x, ptr, size)			\
@@ -450,7 +450,7 @@ struct __large_struct { unsigned long buf[100]; };
 #define __put_user_asm_ex(x, addr, itype, rtype, ltype)			\
 	asm volatile("1:	mov"itype" %"rtype"0,%1\n"		\
 		     "2:\n"						\
-		     _ASM_EXTABLE(1b, 2b - 1b)				\
+		     _ASM_EXTABLE_EX(1b, 2b)				\
 		     : : ltype(x), "m" (__m(addr)))
 
 /*