sys/conf/kern.mk

# $FreeBSD: stable/11/sys/conf/kern.mk 316423 2017-04-02 17:24:58Z dim $

#
# Warning flags for compiling the kernel and components of the kernel:
#
CWARNFLAGS?=	-Wall -Wredundant-decls -Wnested-externs -Wstrict-prototypes \
		-Wmissing-prototypes -Wpointer-arith -Winline -Wcast-qual \
		-Wundef -Wno-pointer-sign ${FORMAT_EXTENSIONS} \
		-Wmissing-include-dirs -fdiagnostics-show-option \
		-Wno-unknown-pragmas \
		${CWARNEXTRA}
#
# The following flags are next up for working on:
#	-Wextra

# Disable a few warnings for clang, since there are several places in the
# kernel where fixing them is more trouble than it is worth, or where there is
# a false positive.
.if ${COMPILER_TYPE} == "clang"
NO_WCONSTANT_CONVERSION=	-Wno-constant-conversion
NO_WSHIFT_COUNT_NEGATIVE=	-Wno-shift-count-negative
NO_WSHIFT_COUNT_OVERFLOW=	-Wno-shift-count-overflow
NO_WSELF_ASSIGN=		-Wno-self-assign
NO_WUNNEEDED_INTERNAL_DECL=	-Wno-unneeded-internal-declaration
NO_WSOMETIMES_UNINITIALIZED=	-Wno-error-sometimes-uninitialized
NO_WCAST_QUAL=			-Wno-cast-qual
# Several other warnings which might be useful in some cases, but not severe
# enough to error out the whole kernel build.  Display them anyway, so there is
# some incentive to fix them eventually.
CWARNEXTRA?=	-Wno-error-tautological-compare -Wno-error-empty-body \
		-Wno-error-parentheses-equality -Wno-error-unused-function \
		-Wno-error-pointer-sign
.if ${COMPILER_VERSION} >= 30700
CWARNEXTRA+=	-Wno-error-shift-negative-value
.endif
.if ${COMPILER_VERSION} >= 40000
CWARNEXTRA+=	-Wno-error-address-of-packed-member
.endif

CLANG_NO_IAS= -no-integrated-as
.if ${COMPILER_VERSION} < 30500
# XXX: clang < 3.5 integrated-as doesn't grok .codeNN directives
CLANG_NO_IAS34= -no-integrated-as
.endif
.endif

.if ${COMPILER_TYPE} == "gcc"
.if ${COMPILER_VERSION} >= 40800
# Catch-all for all the things that are in our tree, but for which we're
# not yet ready for this compiler.
CWARNEXTRA?=	-Wno-error=inline -Wno-error=enum-compare -Wno-error=unused-but-set-variable \
		-Wno-error=aggressive-loop-optimizations -Wno-error=maybe-uninitialized \
		-Wno-error=array-bounds -Wno-error=address \
		-Wno-error=cast-qual -Wno-error=sequence-point -Wno-error=attributes \
		-Wno-error=strict-overflow -Wno-error=overflow
.else
# For gcc 4.2, eliminate the too-often-wrong warnings about uninitialized vars.
CWARNEXTRA?=	-Wno-uninitialized
.endif
.endif

# External compilers may not support our format extensions.  Allow them
# to be disabled.  WARNING: format checking is disabled in this case.
.if ${MK_FORMAT_EXTENSIONS} == "no"
FORMAT_EXTENSIONS=	-Wno-format
.elif ${COMPILER_TYPE} == "clang" && ${COMPILER_VERSION} >= 30600
FORMAT_EXTENSIONS=	-D__printf__=__freebsd_kprintf__
.else
FORMAT_EXTENSIONS=	-fformat-extensions
.endif

#
# On i386, do not align the stack to 16-byte boundaries.  Otherwise GCC 2.95
# and above adds code to the entry and exit point of every function to align the
# stack to 16-byte boundaries -- thus wasting approximately 12 bytes of stack
# per function call.  While the 16-byte alignment may benefit micro benchmarks,
# it is probably an overall loss as it makes the code bigger (less efficient
# use of code cache tag lines) and uses more stack (less efficient use of data
# cache tag lines).  Explicitly prohibit the use of FPU, SSE and other SIMD
# operations inside the kernel itself.  These operations are exclusively
# reserved for user applications.
#
# gcc:
# Setting -mno-mmx implies -mno-3dnow
# Setting -mno-sse implies -mno-sse2, -mno-sse3 and -mno-ssse3
#
# clang:
# Setting -mno-mmx implies -mno-3dnow and -mno-3dnowa
# Setting -mno-sse implies -mno-sse2, -mno-sse3, -mno-ssse3, -mno-sse41 and -mno-sse42
#
.if ${MACHINE_CPUARCH} == "i386"
CFLAGS.gcc+=	-mno-align-long-strings -mpreferred-stack-boundary=2
CFLAGS.clang+=	-mno-aes -mno-avx
CFLAGS+=	-mno-mmx -mno-sse -msoft-float
INLINE_LIMIT?=	8000
.endif

.if ${MACHINE_CPUARCH} == "arm"
INLINE_LIMIT?=	8000
.endif

.if ${MACHINE_CPUARCH} == "aarch64"
# We generally don't want fpu instructions in the kernel.
CFLAGS += -mgeneral-regs-only
# Reserve x18 for pcpu data
CFLAGS += -ffixed-x18
.endif

.if ${MACHINE_CPUARCH} == "riscv"
CFLAGS.gcc+=	-mcmodel=medany
INLINE_LIMIT?=	8000
.endif

#
# For sparc64 we want the medany code model so modules may be located
# anywhere in the 64-bit address space.  We also tell GCC to use floating
# point emulation.  This avoids using floating point registers for integer
# operations which it has a tendency to do.
#
.if ${MACHINE_CPUARCH} == "sparc64"
CFLAGS.clang+=	-mcmodel=large -fno-dwarf2-cfi-asm
CFLAGS.gcc+=	-mcmodel=medany -msoft-float
INLINE_LIMIT?=	15000
.endif

#
# For AMD64, we explicitly prohibit the use of FPU, SSE and other SIMD
# operations inside the kernel itself.  These operations are exclusively
# reserved for user applications.
#
# gcc:
# Setting -mno-mmx implies -mno-3dnow
# Setting -mno-sse implies -mno-sse2, -mno-sse3, -mno-ssse3 and -mfpmath=387
#
# clang:
# Setting -mno-mmx implies -mno-3dnow and -mno-3dnowa
# Setting -mno-sse implies -mno-sse2, -mno-sse3, -mno-ssse3, -mno-sse41 and -mno-sse42
# (-mfpmath= is not supported)
#
.if ${MACHINE_CPUARCH} == "amd64"
CFLAGS.clang+=	-mno-aes -mno-avx
CFLAGS+=	-mcmodel=kernel -mno-red-zone -mno-mmx -mno-sse -msoft-float \
		-fno-asynchronous-unwind-tables
INLINE_LIMIT?=	8000
.endif

#
# For PowerPC we tell gcc to use floating point emulation.  This avoids using
# floating point registers for integer operations which it has a tendency to do.
# Also explicitly disable Altivec instructions inside the kernel.
#
.if ${MACHINE_CPUARCH} == "powerpc"
CFLAGS+=	-mno-altivec -msoft-float
INLINE_LIMIT?=	15000
.endif

#
# Use dot symbols on powerpc64 to make ddb happy
#
.if ${MACHINE_ARCH} == "powerpc64"
CFLAGS.gcc+=	-mcall-aixdesc
.endif

#
# For MIPS we also tell gcc to use floating point emulation
#
.if ${MACHINE_CPUARCH} == "mips"
CFLAGS+=	-msoft-float
INLINE_LIMIT?=	8000
.endif

#
# GCC 3.0 and above like to do certain optimizations based on the
# assumption that the program is linked against libc.  Stop this.
#
CFLAGS+=	-ffreestanding

#
# The C standard leaves signed integer overflow behavior undefined.
# gcc and clang opimizers take advantage of this.  The kernel makes
# use of signed integer wraparound mechanics so we need the compiler
# to treat it as a wraparound and not take shortcuts.
#
CFLAGS+=	-fwrapv

#
# GCC SSP support
#
.if ${MK_SSP} != "no" && \
    ${MACHINE_CPUARCH} != "arm" && ${MACHINE_CPUARCH} != "mips"
CFLAGS+=	-fstack-protector
.endif

#
# Add -gdwarf-2 when compiling -g. The default starting in clang v3.4
# and gcc 4.8 is to generate DWARF version 4. However, our tools don't
# cope well with DWARF 4, so force it to genereate DWARF2, which they
# understand. Do this unconditionally as it is harmless when not needed,
# but critical for these newer versions.
#
.if ${CFLAGS:M-g} != "" && ${CFLAGS:M-gdwarf*} == ""
CFLAGS+=	-gdwarf-2
.endif

CFLAGS+= ${CWARNFLAGS} ${CWARNFLAGS.${.IMPSRC:T}}
CFLAGS+= ${CFLAGS.${COMPILER_TYPE}} ${CFLAGS.${.IMPSRC:T}}

# Tell bmake not to mistake standard targets for things to be searched for
# or expect to ever be up-to-date.
PHONY_NOTMAIN = afterdepend afterinstall all beforedepend beforeinstall \
		beforelinking build build-tools buildfiles buildincludes \
		checkdpadd clean cleandepend cleandir cleanobj configure \
		depend distclean distribute exe \
		html includes install installfiles installincludes lint \
		obj objlink objs objwarn \
		realinstall regress \
		tags whereobj

.PHONY: ${PHONY_NOTMAIN}
.NOTMAIN: ${PHONY_NOTMAIN}

CSTD=		c99

.if ${CSTD} == "k&r"
CFLAGS+=        -traditional
.elif ${CSTD} == "c89" || ${CSTD} == "c90"
CFLAGS+=        -std=iso9899:1990
.elif ${CSTD} == "c94" || ${CSTD} == "c95"
CFLAGS+=        -std=iso9899:199409
.elif ${CSTD} == "c99"
CFLAGS+=        -std=iso9899:1999
.else # CSTD
CFLAGS+=        -std=${CSTD}
.endif # CSTD