From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752505AbdDJVJy (ORCPT ); Mon, 10 Apr 2017 17:09:54 -0400 Received: from mail-pf0-f171.google.com ([209.85.192.171]:33142 "EHLO mail-pf0-f171.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751140AbdDJVJw (ORCPT ); Mon, 10 Apr 2017 17:09:52 -0400 From: Matthias Kaehlcke To: Michal Marek Cc: linux-kbuild@vger.kernel.org, linux-kernel@vger.kernel.org, Behan Webster , Grant Grundler , Greg Hackmann , Michael Davidson , Peter Foley , Matthias Kaehlcke Subject: [PATCH v2] kbuild: Add better clang cross build support Date: Mon, 10 Apr 2017 14:09:04 -0700 Message-Id: <20170410210904.68211-1-mka@chromium.org> X-Mailer: git-send-email 2.12.2.715.g7642488e1d-goog MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Add cross target to CC if using clang. Also add custom gcc toolchain path for fallback gcc tools. COMPILER is previously set to "clang" if CC=clang was set from the make command line. So -target and -gcc-toolchain can be added to CC, since we already know that it is set. Clang will fallback to using things like ld, as, and libgcc if (respectively) one of the llvm linkers isn't available, the integrated assembler is turned off, or an appropriately cross-compiled version of compiler-rt isn't available. To this end, you can specify the path to this fallback gcc toolchain with GCC_TOOLCHAIN. From: Behan Webster Signed-off-by: Behan Webster Reviewed-by: Jan-Simon Möller Reviewed-by: Mark Charlebois Signed-off-by: Greg Hackmann Signed-off-by: Matthias Kaehlcke --- Changes in v2: - Fix GCC_TOOLCHAIN definition. $(LD) is needed to link the kernel, use its path to determine the installation prefix of the toolchain. (From: Greg Hackmann ) Makefile | 18 ++++++++++++++---- 1 file changed, 14 insertions(+), 4 deletions(-) diff --git a/Makefile b/Makefile index e11989d36c87..d3a02786bb53 100644 --- a/Makefile +++ b/Makefile @@ -375,6 +375,16 @@ LDFLAGS_vmlinux = CFLAGS_GCOV = -fprofile-arcs -ftest-coverage -fno-tree-loop-im -Wno-maybe-uninitialized CFLAGS_KCOV := $(call cc-option,-fsanitize-coverage=trace-pc,) +ifeq ($(cc-name),clang) +ifneq ($(CROSS_COMPILE),) +CLANG_TARGET := -target $(notdir $(CROSS_COMPILE:%-=%)) +GCC_TOOLCHAIN := $(realpath $(dir $(shell which $(LD)))/..) +endif +ifneq ($(GCC_TOOLCHAIN),) +CLANG_GCC_TC := -gcc-toolchain $(GCC_TOOLCHAIN) +endif +CLANG_FLAGS := $(CLANG_TARGET) $(CLANG_GCC_TC) +endif # Use USERINCLUDE when you must reference the UAPI directories only. USERINCLUDE := \ @@ -395,18 +405,18 @@ LINUXINCLUDE := \ LINUXINCLUDE += $(filter-out $(LINUXINCLUDE),$(USERINCLUDE)) -KBUILD_CPPFLAGS := -D__KERNEL__ +KBUILD_CPPFLAGS := -D__KERNEL__ $(CLANG_FLAGS) KBUILD_CFLAGS := -Wall -Wundef -Wstrict-prototypes -Wno-trigraphs \ -fno-strict-aliasing -fno-common \ -Werror-implicit-function-declaration \ -Wno-format-security \ - -std=gnu89 $(call cc-option,-fno-PIE) - + -std=gnu89 $(call cc-option,-fno-PIE) \ + $(CLANG_FLAGS) KBUILD_AFLAGS_KERNEL := KBUILD_CFLAGS_KERNEL := -KBUILD_AFLAGS := -D__ASSEMBLY__ $(call cc-option,-fno-PIE) +KBUILD_AFLAGS := -D__ASSEMBLY__ $(call cc-option,-fno-PIE) $(CLANG_FLAGS) KBUILD_AFLAGS_MODULE := -DMODULE KBUILD_CFLAGS_MODULE := -DMODULE KBUILD_LDFLAGS_MODULE := -T $(srctree)/scripts/module-common.lds -- 2.12.2.715.g7642488e1d-goog