powerpc/kbuild: Set default generic machine type for 32-bit compile
Some 64-bit toolchains uses the wrong ISA variant for compiling 32-bit
kernels, even with -m32. Debian's powerpc64le is one such case, and
that is because it is built with --with-cpu=power8.
So when cross compiling a 32-bit kernel with a 64-bit toolchain, set
-mcpu=powerpc initially, which is the generic 32-bit powerpc machine
type and scheduling model. CPU and platform code can override this
with subsequent -mcpu flags if necessary.
This is not done for 32-bit toolchains otherwise it would override
their defaults, which are presumably set appropriately for the
environment (moreso than a 64-bit cross compiler).
This fixes a lot of build failures due to incompatible assembly when
compiling 32-bit kernel with the Debian powerpc64le 64-bit toolchain.
Signed-off-by: Nicholas Piggin <npiggin@gmail.com>
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>
diff --git a/arch/powerpc/Makefile b/arch/powerpc/Makefile
index 95813df..d628724 100644
--- a/arch/powerpc/Makefile
+++ b/arch/powerpc/Makefile
@@ -24,6 +24,14 @@
ifeq ($(CROSS32_COMPILE),)
CROSS32CC := $(CC) -m32
KBUILD_ARFLAGS += --target=elf32-powerpc
+ifdef CONFIG_PPC32
+# These options will be overridden by any -mcpu option that the CPU
+# or platform code sets later on the command line, but they are needed
+# to set a sane 32-bit cpu target for the 64-bit cross compiler which
+# may default to the wrong ISA.
+KBUILD_CFLAGS += -mcpu=powerpc
+KBUILD_AFLAGS += -mcpu=powerpc
+endif
endif
endif