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>

4 files changed, 31 insertions, 4 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)
diff --git a/arch/powerpc/boot/Makefile b/arch/powerpc/boot/Makefile
index 15ca2255f438..ca7f08cc4afd 100644
--- a/arch/powerpc/boot/Makefile
+++ b/arch/powerpc/boot/Makefile
@@ -22,7 +22,8 @@ all: $(obj)/zImage
 BOOTCFLAGS    := -Wall -Wundef -Wstrict-prototypes -Wno-trigraphs \
                  -fno-strict-aliasing -Os -msoft-float -pipe \
                  -fomit-frame-pointer -fno-builtin -fPIC -nostdinc \
-                 -isystem $(shell $(CROSS32CC) -print-file-name=include)
+                 -isystem $(shell $(CROSS32CC) -print-file-name=include) \
+                 -mbig-endian
 BOOTAFLAGS      := -D__ASSEMBLY__ $(BOOTCFLAGS) -traditional -nostdinc
 
 ifdef CONFIG_DEBUG_INFO
diff --git a/arch/powerpc/kernel/vdso32/vdso32.lds.S b/arch/powerpc/kernel/vdso32/vdso32.lds.S
index f223409629b9..e58ee10fa5c0 100644
--- a/arch/powerpc/kernel/vdso32/vdso32.lds.S
+++ b/arch/powerpc/kernel/vdso32/vdso32.lds.S
@@ -4,7 +4,11 @@
  */
 #include <asm/vdso.h>
 
+#ifdef __LITTLE_ENDIAN__
+OUTPUT_FORMAT("elf32-powerpcle", "elf32-powerpcle", "elf32-powerpcle")
+#else
 OUTPUT_FORMAT("elf32-powerpc", "elf32-powerpc", "elf32-powerpc")
+#endif
 OUTPUT_ARCH(powerpc:common)
 ENTRY(_start)
 
diff --git a/arch/powerpc/kernel/vdso64/vdso64.lds.S b/arch/powerpc/kernel/vdso64/vdso64.lds.S
index e4863819663b..64fb183a47c2 100644
--- a/arch/powerpc/kernel/vdso64/vdso64.lds.S
+++ b/arch/powerpc/kernel/vdso64/vdso64.lds.S
@@ -4,7 +4,11 @@
  */
 #include <asm/vdso.h>
 
+#ifdef __LITTLE_ENDIAN__
+OUTPUT_FORMAT("elf64-powerpcle", "elf64-powerpcle", "elf64-powerpcle")
+#else
 OUTPUT_FORMAT("elf64-powerpc", "elf64-powerpc", "elf64-powerpc")
+#endif
 OUTPUT_ARCH(powerpc:common64)
 ENTRY(_start)