powerpc: Add ability to build little endian kernels

This patch allows the kbuild system to successfully compile a kernel
for the little endian PowerPC64 architecture. A subsequent patch
will add the CONFIG_CPU_LITTLE_ENDIAN kernel config option which
must be set to build such a kernel.

If cross compiling, CROSS_COMPILE must point to a suitable toolchain
(compiled for the powerpc64le-linux and powerpcle-linux targets).

Signed-off-by: Ian Munsie <imunsie@au1.ibm.com>
Signed-off-by: Anton Blanchard <anton@samba.org>
Signed-off-by: Benjamin Herrenschmidt <benh@kernel.crashing.org>

1 files changed, 21 insertions, 3 deletions

diff --git a/arch/powerpc/Makefile b/arch/powerpc/Makefile
index debfa2b1c1de..d3c91bf923b7 100644
--- a/arch/powerpc/Makefile
+++ b/arch/powerpc/Makefile
@@ -65,11 +65,29 @@ endif
 
 UTS_MACHINE := $(OLDARCH)
 
+ifeq ($(CONFIG_CPU_LITTLE_ENDIAN),y)
+override CC     += -mlittle-endian
+override AS     += -mlittle-endian
+override LD     += -EL
+override CROSS32CC += -mlittle-endian
+override CROSS32AS += -mlittle-endian
+LDEMULATION     := lppc
+GNUTARGET       := powerpcle
+MULTIPLEWORD    := -mno-multiple
+else
+override CC     += -mbig-endian
+override AS     += -mbig-endian
+override LD     += -EB
+LDEMULATION     := ppc
+GNUTARGET       := powerpc
+MULTIPLEWORD    := -mmultiple
+endif
+
 ifeq ($(HAS_BIARCH),y)
 override AS     += -a$(CONFIG_WORD_SIZE)
-override LD     += -m elf$(CONFIG_WORD_SIZE)ppc
+override LD     += -m elf$(CONFIG_WORD_SIZE)$(LDEMULATION)
 override CC     += -m$(CONFIG_WORD_SIZE)
-override AR     := GNUTARGET=elf$(CONFIG_WORD_SIZE)-powerpc $(AR)
+override AR     := GNUTARGET=elf$(CONFIG_WORD_SIZE)-$(GNUTARGET) $(AR)
 endif
 
 LDFLAGS_vmlinux-y := -Bstatic
@@ -95,7 +113,7 @@ endif
 CFLAGS-$(CONFIG_PPC64)  := -mtraceback=no -mcall-aixdesc
 CFLAGS-$(CONFIG_PPC64)  += $(call cc-option,-mcmodel=medium,-mminimal-toc)
 CFLAGS-$(CONFIG_PPC64)  += $(call cc-option,-mno-pointers-to-nested-functions)
-CFLAGS-$(CONFIG_PPC32)  := -ffixed-r2 -mmultiple
+CFLAGS-$(CONFIG_PPC32)  := -ffixed-r2 $(MULTIPLEWORD)
 
 ifeq ($(CONFIG_PPC_BOOK3S_64),y)
 CFLAGS-$(CONFIG_GENERIC_CPU) += $(call cc-option,-mtune=power7,-mtune=power4)