[U-Boot] [PATCH 2/4] mpc83xx: Add link vs. load address calculation

[Joakim Tjernlund]

link_off calculates the difference between link address and
actual load address. This is a must for true PIC u-boot.

Signed-off-by: Joakim Tjernlund <Joakim.Tjernlund at transmode.se>
---
 arch/powerpc/cpu/mpc83xx/start.S |   26 ++++++++++++++++++++++++++
 include/common.h                 |    7 +++++++
 2 files changed, 33 insertions(+), 0 deletions(-)

diff --git a/arch/powerpc/cpu/mpc83xx/start.S b/arch/powerpc/cpu/mpc83xx/start.S
index 1ab8c88..16aed0a 100644
--- a/arch/powerpc/cpu/mpc83xx/start.S
+++ b/arch/powerpc/cpu/mpc83xx/start.S
@@ -419,6 +419,32 @@ ProgramCheck:
 _end_of_vectors:
 
 	. = 0x3000
+#ifdef CONFIG_SYS_TRUE_PIC
+	.globl	link_off /* const void * link_off(const void * ptr) */
+	.type	link_off, @function
+	/*
+	 * Calculates the offset between link address and load address
+	 * and subtracs the offset to from its argument(r3)
+	 * This function must be where _GOT2_TABLE_ is defined
+	 */
+link_off:
+	/* GOT hand coded as we cannot clobber r12 */
+	mflr	r4
+	bl	1f
+	.text	2
+0:	.long	.LCTOC1-1f
+	.text
+1:	mflr	r6
+	lwz	r0,0b-1b(r6)
+	add	r6,r0,r6
+	mtlr	r4
+	la	r4,.L__GOT2_TABLE_(r6) /* addi	r4,r6,.L__GOT2_TABLE_ */
+	lwz	r5,.L__GOT2_TABLE_(r6)
+	sub	r4,r5,r4 /* r4 - r5 */
+	sub	r3,r3,r4 /* r4 - r3 */
+	blr
+	.size	link_off, .-link_off
+#endif
 
 /*
  * This code finishes saving the registers to the exception frame
diff --git a/include/common.h b/include/common.h
index 189ad81..a04bd27 100644
--- a/include/common.h
+++ b/include/common.h
@@ -112,6 +112,13 @@ typedef volatile unsigned char	vu_char;
 #include <asm/arch/hardware.h>
 #endif
 
+#ifdef CONFIG_SYS_TRUE_PIC
+const void * link_off(const void *);
+#else
+#define link_off(x) ((const void *)(x))
+#endif
+#define LINK_OFF(x) ((__typeof__(x))link_off(x))
+
 #include <part.h>
 #include <flash.h>
 #include <image.h>
-- 
1.7.2.2