[PATCH] MIPS: introduce `REL_LA' to get label runtime address

[Du Huanpeng]

replace PTR_LA in the very begining, e.g. in
	arch/mips/cpu/start.S
	arch/mips/lib/cache_init.S
to write position independence code. this is helpfull for make
single binary can be loaded to different ram/rom addresses.

FIXME: only tested on 32 bit system

Signed-off-by: Du Huanpeng <dhu at hodcarrier.cn>
---
 arch/mips/include/asm/asm.h | 21 +++++++++++++++++++++
 1 file changed, 21 insertions(+)

diff --git a/arch/mips/include/asm/asm.h b/arch/mips/include/asm/asm.h
index a6876e1..f93281f 100644
--- a/arch/mips/include/asm/asm.h
+++ b/arch/mips/include/asm/asm.h
@@ -289,6 +289,27 @@ symbol		=	value
 #define PTRLOG		3
 #endif
 
+#ifdef __ASSEMBLER__
+/*
+ * helpers for writing position independence code
+ * FIXME: only tested on 32 bit system
+ */
+	.macro	REL_LA reg lable
+	.set	push
+	.set	noat
+	.set	noreorder
+	move	$at, $ra	/* preserve ra */
+	bal	888f
+	nop
+888:	la	\reg, 888b
+	subu	\reg, $ra, \reg	/* offset store in reg */
+	move	$ra, $at	/* restroe ra */
+	la	$at, \lable
+	addu	\reg, $at, \reg
+	.set	pop
+	.endm
+#endif
+
 /*
  * Some cp0 registers were extended to 64bit for MIPS III.
  */
-- 
2.7.4