powerpc: introduce macro LOAD_REG_ADDR_PIC

This is used to get the address of a variable when the kernel is not
running at the linked or relocated address.
Signed-off-by: NKevin Hao <haokexin@gmail.com>
Signed-off-by: NScott Wood <scottwood@freescale.com>

arch/powerpc/include/asm/ppc_asm.h

@@ -295,6 +295,11 @@ GLUE(.,name):
  *   you want to access various offsets within it).  On ppc32 this is
  *   identical to LOAD_REG_IMMEDIATE.
  *
+ * LOAD_REG_ADDR_PIC(rn, name)
+ *   Loads the address of label 'name' into register 'run'. Use this when
+ *   the kernel doesn't run at the linked or relocated address. Please
+ *   note that this macro will clobber the lr register.
+ *
  * LOAD_REG_ADDRBASE(rn, name)
  * ADDROFF(name)
  *   LOAD_REG_ADDRBASE loads part of the address of label 'name' into
@@ -305,6 +310,14 @@ GLUE(.,name):
  *      LOAD_REG_ADDRBASE(rX, name)
  *      ld	rY,ADDROFF(name)(rX)
  */
+
+/* Be careful, this will clobber the lr register. */
+#define LOAD_REG_ADDR_PIC(reg, name)		\
+	bl	0f;				\
+0:	mflr	reg;				\
+	addis	reg,reg,(name - 0b)@ha;		\
+	addi	reg,reg,(name - 0b)@l;
+
 #ifdef __powerpc64__
 #define LOAD_REG_IMMEDIATE(reg,expr)		\
 	lis     reg,(expr)@highest;		\