From 61163efae02040f66a95c8ed17f4407951ba58fa Mon Sep 17 00:00:00 2001 From: Behan Webster Date: Tue, 3 Sep 2013 22:27:23 -0400 Subject: [PATCH] kbuild: LLVMLinux: Add Kbuild support for building kernel with Clang MIME-Version: 1.0 Content-Type: text/plain; charset=utf8 Content-Transfer-Encoding: 8bit Add support to toplevel Makefile for compiling with clang, both for HOSTCC and CC. Use cc-option to prevent gcc option from breaking clang, and from clang options from breaking gcc. Clang 3.4 semantics are the same as gcc semantics for unsupported flags. For unsupported warnings clang 3.4 returns true but shows a warning and gcc shows a warning and returns false. Signed-off-by: Behan Webster Signed-off-by: Jan-Simon Möller Signed-off-by: Mark Charlebois Cc: PaX Team --- Makefile | 30 +++++++++++++++++++++++++++++- 1 file changed, 29 insertions(+), 1 deletion(-) diff --git a/Makefile b/Makefile index cf3e07516a04..10812e495e8d 100644 --- a/Makefile +++ b/Makefile @@ -248,6 +248,11 @@ HOSTCXX = g++ HOSTCFLAGS = -Wall -Wmissing-prototypes -Wstrict-prototypes -O2 -fomit-frame-pointer HOSTCXXFLAGS = -O2 +ifeq ($(shell $(HOSTCC) -v 2>&1 | grep -c "clang version"), 1) +HOSTCFLAGS += -Wno-unused-value -Wno-unused-parameter \ + -Wno-missing-field-initializers -fno-delete-null-pointer-checks +endif + # Decide whether to build built-in, modular, or both. # Normally, just do built-in. @@ -324,6 +329,14 @@ endif export quiet Q KBUILD_VERBOSE +ifneq ($(CC),) +ifeq ($(shell $(CC) -v 2>&1 | grep -c "clang version"), 1) +COMPILER := clang +else +COMPILER := gcc +endif +export COMPILER +endif # Look for make include files relative to root of kernel src MAKEFLAGS += --include-dir=$(srctree) @@ -383,7 +396,7 @@ KBUILD_CFLAGS := -Wall -Wundef -Wstrict-prototypes -Wno-trigraphs \ -fno-strict-aliasing -fno-common \ -Werror-implicit-function-declaration \ -Wno-format-security \ - -fno-delete-null-pointer-checks + $(call cc-option,-fno-delete-null-pointer-checks,) KBUILD_AFLAGS_KERNEL := KBUILD_CFLAGS_KERNEL := KBUILD_AFLAGS := -D__ASSEMBLY__ @@ -623,9 +636,24 @@ endif endif KBUILD_CFLAGS += $(stackp-flag) +ifeq ($(COMPILER),clang) +KBUILD_CPPFLAGS += $(call cc-option,-Qunused-arguments,) +KBUILD_CPPFLAGS += $(call cc-option,-Wno-unknown-warning-option,) +KBUILD_CFLAGS += $(call cc-disable-warning, unused-variable) +KBUILD_CFLAGS += $(call cc-disable-warning, format-invalid-specifier) +KBUILD_CFLAGS += $(call cc-disable-warning, gnu) +# Quiet clang warning: comparison of unsigned expression < 0 is always false +KBUILD_CFLAGS += $(call cc-disable-warning, tautological-compare) +# CLANG uses a _MergedGlobals as optimization, but this breaks modpost, as the +# source of a reference will be _MergedGlobals and not on of the whitelisted names. +# See modpost pattern 2 +KBUILD_CFLAGS += $(call cc-option, -mno-global-merge,) +else + # This warning generated too much noise in a regular build. # Use make W=1 to enable this warning (see scripts/Makefile.build) KBUILD_CFLAGS += $(call cc-disable-warning, unused-but-set-variable) +endif ifdef CONFIG_FRAME_POINTER KBUILD_CFLAGS += -fno-omit-frame-pointer -fno-optimize-sibling-calls -- 2.39.5