[PATCH] powerpc/kbuild: set generic machine type for compile with 64-bit toolchain

The 64-bit toolchain uses the wrong ISA variant for compiling 32-bit
kernels, eve with -m32. Set -mcpu=powerpc which is the generic 32-bit
powerpc machine type and scheduling model. 32-bit platforms and CPUs
can override this with -mcpu= options that come later on the command
line.

This fixes a lot of build failures due to incompatible assembly when
compiling 32-bit kernel with 64-bit toolchain.

Signed-off-by: Nicholas Piggin <npiggin@gmail.com>
---
 arch/powerpc/Makefile | 6 ++++++
 1 file changed, 6 insertions(+)

diff --git a/arch/powerpc/Makefile b/arch/powerpc/Makefile
index 95813df90801..aa6464c81a9f 100644
--- a/arch/powerpc/Makefile
+++ b/arch/powerpc/Makefile

@@ -24,6 +24,12 @@ ifeq ($(HAS_BIARCH),y)
 ifeq ($(CROSS32_COMPILE),)
 CROSS32CC	:= $(CC) -m32
 KBUILD_ARFLAGS	+= --target=elf32-powerpc
+
+# These options will be overridden by any -mcpu option that comes
+# later on the command line, but they are needed to set a sane
+# 32-bit cpu target for the 64-bit cross compiler.
+KBUILD_CFLAGS		+= -mcpu=powerpc
+KBUILD_AFLAGS		+= -mcpu=powerpc
 endif
 endif
 

-- 
2.17.0

Bad title, should be set generic machine type for 32-bit compile with
64-bit toolchain

On Thu, 10 May 2018 10:26:37 +1000
Nicholas Piggin [off-list ref] wrote:

On Thu, 10 May 2018 10:26:37 +1000
Nicholas Piggin [off-list ref] wrote:

The 64-bit toolchain uses the wrong ISA variant for compiling 32-bit
kernels, eve with -m32. Set -mcpu=powerpc which is the generic 32-bit
powerpc machine type and scheduling model. 32-bit platforms and CPUs
can override this with -mcpu= options that come later on the command
line.

This fixes a lot of build failures due to incompatible assembly when
compiling 32-bit kernel with 64-bit toolchain.

Actually ignore this patch, it had a few other problems. I'll send a new
version out.

Thanks,
Nick