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Commit 61163efa authored by Behan Webster's avatar Behan Webster
Browse files

kbuild: LLVMLinux: Add Kbuild support for building kernel with Clang 



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: default avatarBehan Webster <behanw@converseincode.com>
Signed-off-by: default avatarJan-Simon Möller <dl9pf@gmx.de>
Signed-off-by: default avatarMark Charlebois <charlebm@gmail.com>
Cc: PaX Team <pageexec@freemail.hu>
parent 39de65aa

Makefile

+29 −1
Original line number Diff line number Diff line
@@ -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