From: Nicholas Piggin <npiggin@gmail.com>
To: linux-kbuild@vger.kernel.org
Cc: Nicholas Piggin <npiggin@gmail.com>,
linuxppc-dev@lists.ozlabs.org,
Masahiro Yamada <yamada.masahiro@socionext.com>,
Segher Boessenkool <segher@kernel.crashing.org>
Subject: [PATCH v4 1/4] powerpc/kbuild: set default generic machine type for 32-bit compile
Date: Thu, 17 May 2018 00:14:55 +1000 [thread overview]
Message-ID: <20180516141458.18996-2-npiggin@gmail.com> (raw)
In-Reply-To: <20180516141458.18996-1-npiggin@gmail.com>
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 th Debian powerpc64le 64-bit toolchain.
Cc: Segher Boessenkool <segher@kernel.crashing.org>
Signed-off-by: Nicholas Piggin <npiggin@gmail.com>
---
arch/powerpc/Makefile | 11 +++++++++++
1 file changed, 11 insertions(+)
diff --git a/arch/powerpc/Makefile b/arch/powerpc/Makefile
index 95813df90801..15ca4bafad82 100644
--- a/arch/powerpc/Makefile
+++ b/arch/powerpc/Makefile
@@ -24,9 +24,20 @@ ifeq ($(HAS_BIARCH),y)
ifeq ($(CROSS32_COMPILE),)
CROSS32CC := $(CC) -m32
KBUILD_ARFLAGS += --target=elf32-powerpc
+
+ifdef CONFIG_PPC32
+# These options will be overridden by any -mcpu option that the CPU
+# or platform code sets later on the command line, but they are needed
+# to set a sane 32-bit cpu target for the 64-bit cross compiler which
+# may default to the wrong ISA.
+KBUILD_CFLAGS += -mcpu=powerpc
+KBUILD_AFLAGS += -mcpu=powerpc
+endif
+
endif
endif
+
export CROSS32CC CROSS32AR
ifeq ($(CROSS_COMPILE),)
--
2.17.0
next prev parent reply other threads:[~2018-05-16 14:15 UTC|newest]
Thread overview: 10+ messages / expand[flat|nested] mbox.gz Atom feed top
2018-05-16 14:14 [PATCH v4 0/4] powerpc patches for new Kconfig language Nicholas Piggin
2018-05-16 14:14 ` Nicholas Piggin [this message]
2018-05-29 13:39 ` [PATCH v4 1/4] powerpc/kbuild: set default generic machine type for 32-bit compile Masahiro Yamada
2018-05-30 10:43 ` Nicholas Piggin
2018-05-16 14:14 ` [PATCH v4 2/4] powerpc/kbuild: remove CROSS32 defines from top level powerpc Makefile Nicholas Piggin
2018-05-16 14:14 ` [PATCH v4 3/4] powerpc/kbuild: Use flags variables rather than overriding LD/CC/AS Nicholas Piggin
2018-05-16 14:14 ` [PATCH v4 4/4] powerpc/kbuild: move -mprofile-kernel check to Kconfig Nicholas Piggin
2018-05-17 17:28 ` kbuild test robot
2018-05-20 7:58 ` Nicholas Piggin
2018-05-29 13:48 ` Masahiro Yamada
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