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: Kevin Hao <haokexin@gmail.com>
Signed-off-by: Scott Wood <scottwood@freescale.com>

diff --git a/arch/powerpc/include/asm/ppc_asm.h b/arch/powerpc/include/asm/ppc_asm.h
index f595b98..1279c59 100644 (file)
--- a/arch/powerpc/include/asm/ppc_asm.h
+++ b/arch/powerpc/include/asm/ppc_asm.h
@@ -295,6 +295,11 @@ n:
  *   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 @@ n:
  *      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;             \