xref: /freebsd/sys/conf/kern.mk (revision 06c3fb2749bda94cb5201f81ffdb8fa6c3161b2e)
1
2#
3# Warning flags for compiling the kernel and components of the kernel:
4#
5CWARNFLAGS?=	-Wall -Wstrict-prototypes \
6		-Wmissing-prototypes -Wpointer-arith -Wcast-qual \
7		-Wundef -Wno-pointer-sign ${FORMAT_EXTENSIONS} \
8		-Wmissing-include-dirs -fdiagnostics-show-option \
9		-Wno-unknown-pragmas \
10		${CWARNEXTRA}
11#
12# The following flags are next up for working on:
13#	-Wextra
14
15# Disable a few warnings for clang, since there are several places in the
16# kernel where fixing them is more trouble than it is worth, or where there is
17# a false positive.
18.if ${COMPILER_TYPE} == "clang"
19NO_WCONSTANT_CONVERSION=	-Wno-error=constant-conversion
20NO_WSHIFT_COUNT_NEGATIVE=	-Wno-shift-count-negative
21NO_WSHIFT_COUNT_OVERFLOW=	-Wno-shift-count-overflow
22NO_WSELF_ASSIGN=		-Wno-self-assign
23NO_WUNNEEDED_INTERNAL_DECL=	-Wno-error=unneeded-internal-declaration
24NO_WSOMETIMES_UNINITIALIZED=	-Wno-error=sometimes-uninitialized
25NO_WCAST_QUAL=			-Wno-error=cast-qual
26NO_WTAUTOLOGICAL_POINTER_COMPARE= -Wno-tautological-pointer-compare
27.if ${COMPILER_VERSION} >= 100000
28NO_WMISLEADING_INDENTATION=	-Wno-misleading-indentation
29.endif
30.if ${COMPILER_VERSION} >= 130000
31NO_WUNUSED_BUT_SET_VARIABLE=	-Wno-unused-but-set-variable
32.endif
33.if ${COMPILER_VERSION} >= 140000
34NO_WBITWISE_INSTEAD_OF_LOGICAL=	-Wno-bitwise-instead-of-logical
35.endif
36.if ${COMPILER_VERSION} >= 150000
37NO_WSTRICT_PROTOTYPES=		-Wno-strict-prototypes
38NO_WDEPRECATED_NON_PROTOTYPE=	-Wno-deprecated-non-prototype
39.endif
40# Several other warnings which might be useful in some cases, but not severe
41# enough to error out the whole kernel build.  Display them anyway, so there is
42# some incentive to fix them eventually.
43CWARNEXTRA?=	-Wno-error=tautological-compare -Wno-error=empty-body \
44		-Wno-error=parentheses-equality -Wno-error=unused-function \
45		-Wno-error=pointer-sign
46CWARNEXTRA+=	-Wno-error=shift-negative-value
47CWARNEXTRA+=	-Wno-address-of-packed-member
48.endif	# clang
49
50.if ${COMPILER_TYPE} == "gcc"
51# Catch-all for all the things that are in our tree, but for which we're
52# not yet ready for this compiler.
53NO_WUNUSED_BUT_SET_VARIABLE=-Wno-unused-but-set-variable
54CWARNEXTRA?=	-Wno-error=address				\
55		-Wno-error=aggressive-loop-optimizations	\
56		-Wno-error=array-bounds				\
57		-Wno-error=attributes				\
58		-Wno-error=cast-qual				\
59		-Wno-error=enum-compare				\
60		-Wno-error=maybe-uninitialized			\
61		-Wno-error=misleading-indentation		\
62		-Wno-error=nonnull-compare			\
63		-Wno-error=overflow				\
64		-Wno-error=sequence-point			\
65		-Wno-error=shift-overflow			\
66		-Wno-error=tautological-compare			\
67		-Wno-error=unused-function
68.if ${COMPILER_VERSION} >= 70100
69CWARNEXTRA+=	-Wno-error=stringop-overflow
70.endif
71.if ${COMPILER_VERSION} >= 70200
72CWARNEXTRA+=	-Wno-error=memset-elt-size
73.endif
74.if ${COMPILER_VERSION} >= 80000
75CWARNEXTRA+=	-Wno-error=packed-not-aligned
76.endif
77.if ${COMPILER_VERSION} >= 90100
78CWARNEXTRA+=	-Wno-address-of-packed-member			\
79		-Wno-alloc-size-larger-than			\
80		-Wno-error=alloca-larger-than=
81.if ${COMPILER_VERSION} >= 120100
82CWARNEXTRA+=	-Wno-error=nonnull				\
83		-Wno-dangling-pointer				\
84		-Wno-zero-length-bounds
85NO_WINFINITE_RECURSION=	-Wno-infinite-recursion
86NO_WSTRINGOP_OVERREAD=	-Wno-stringop-overread
87.endif
88.endif
89
90# GCC produces false positives for functions that switch on an
91# enum (GCC bug 87950)
92CWARNFLAGS+=	-Wno-return-type
93.endif	# gcc
94
95# This warning is utter nonsense
96CWARNFLAGS+=	-Wno-format-zero-length
97
98# External compilers may not support our format extensions.  Allow them
99# to be disabled.  WARNING: format checking is disabled in this case.
100.if ${MK_FORMAT_EXTENSIONS} == "no"
101FORMAT_EXTENSIONS=	-Wno-format
102.elif ${COMPILER_TYPE} == "clang" || \
103    (${COMPILER_TYPE} == "gcc" && ${COMPILER_VERSION} >= 120100)
104FORMAT_EXTENSIONS=	-D__printf__=__freebsd_kprintf__
105.else
106FORMAT_EXTENSIONS=	-fformat-extensions
107.endif
108
109#
110# On i386, do not align the stack to 16-byte boundaries.  Otherwise GCC 2.95
111# and above adds code to the entry and exit point of every function to align the
112# stack to 16-byte boundaries -- thus wasting approximately 12 bytes of stack
113# per function call.  While the 16-byte alignment may benefit micro benchmarks,
114# it is probably an overall loss as it makes the code bigger (less efficient
115# use of code cache tag lines) and uses more stack (less efficient use of data
116# cache tag lines).  Explicitly prohibit the use of FPU, SSE and other SIMD
117# operations inside the kernel itself.  These operations are exclusively
118# reserved for user applications.
119#
120# gcc:
121# Setting -mno-mmx implies -mno-3dnow
122# Setting -mno-sse implies -mno-sse2, -mno-sse3 and -mno-ssse3
123#
124# clang:
125# Setting -mno-mmx implies -mno-3dnow and -mno-3dnowa
126# Setting -mno-sse implies -mno-sse2, -mno-sse3, -mno-ssse3, -mno-sse41 and -mno-sse42
127#
128.if ${MACHINE_CPUARCH} == "i386"
129CFLAGS.gcc+=	-mpreferred-stack-boundary=2
130CFLAGS.clang+=	-mno-aes -mno-avx
131CFLAGS+=	-mno-mmx -mno-sse -msoft-float
132INLINE_LIMIT?=	8000
133.endif
134
135.if ${MACHINE_CPUARCH} == "arm"
136INLINE_LIMIT?=	8000
137.endif
138
139.if ${MACHINE_CPUARCH} == "aarch64"
140# We generally don't want fpu instructions in the kernel.
141CFLAGS += -mgeneral-regs-only
142# Reserve x18 for pcpu data
143CFLAGS += -ffixed-x18
144# Build with BTI+PAC
145CFLAGS += -mbranch-protection=standard
146INLINE_LIMIT?=	8000
147.endif
148
149#
150# For RISC-V we specify the soft-float ABI (lp64) to avoid the use of floating
151# point registers within the kernel. However, we include the F and D extensions
152# in -march so we can have limited floating point support in context switching
153# code. This is different than userland where we use a hard-float ABI (lp64d).
154#
155# We also specify the "medium" code model, which generates code suitable for a
156# 2GiB addressing range located at any offset, allowing modules to be located
157# anywhere in the 64-bit address space.  Note that clang and GCC refer to this
158# code model as "medium" and "medany" respectively.
159#
160.if ${MACHINE_CPUARCH} == "riscv"
161CFLAGS+=	-march=rv64imafdc
162CFLAGS+=	-mabi=lp64
163CFLAGS.clang+=	-mcmodel=medium
164CFLAGS.gcc+=	-mcmodel=medany
165INLINE_LIMIT?=	8000
166
167.if ${LINKER_FEATURES:Mriscv-relaxations} == ""
168CFLAGS+=	-mno-relax
169.endif
170.endif
171
172#
173# For AMD64, we explicitly prohibit the use of FPU, SSE and other SIMD
174# operations inside the kernel itself.  These operations are exclusively
175# reserved for user applications.
176#
177# gcc:
178# Setting -mno-mmx implies -mno-3dnow
179# Setting -mno-sse implies -mno-sse2, -mno-sse3, -mno-ssse3 and -mfpmath=387
180#
181# clang:
182# Setting -mno-mmx implies -mno-3dnow and -mno-3dnowa
183# Setting -mno-sse implies -mno-sse2, -mno-sse3, -mno-ssse3, -mno-sse41 and -mno-sse42
184# (-mfpmath= is not supported)
185#
186.if ${MACHINE_CPUARCH} == "amd64"
187CFLAGS.clang+=	-mno-aes -mno-avx
188CFLAGS+=	-mcmodel=kernel -mno-red-zone -mno-mmx -mno-sse -msoft-float \
189		-fno-asynchronous-unwind-tables
190INLINE_LIMIT?=	8000
191.endif
192
193#
194# For PowerPC we tell gcc to use floating point emulation.  This avoids using
195# floating point registers for integer operations which it has a tendency to do.
196# Also explicitly disable Altivec instructions inside the kernel.
197#
198.if ${MACHINE_CPUARCH} == "powerpc"
199CFLAGS+=	-mno-altivec -msoft-float
200INLINE_LIMIT?=	15000
201.endif
202
203.if ${MACHINE_ARCH} == "powerpcspe"
204CFLAGS.gcc+=	-mno-spe
205.endif
206
207#
208# Use dot symbols (or, better, the V2 ELF ABI) on powerpc64 to make
209# DDB happy. ELFv2, if available, has some other efficiency benefits.
210#
211.if ${MACHINE_ARCH:Mpowerpc64*} != "" && \
212    ${COMPILER_TYPE} == "clang" && ${COMPILER_VERSION} < 160000
213CFLAGS+=	-mabi=elfv2
214.endif
215
216#
217# GCC 3.0 and above like to do certain optimizations based on the
218# assumption that the program is linked against libc.  Stop this.
219#
220CFLAGS+=	-ffreestanding
221
222#
223# The C standard leaves signed integer overflow behavior undefined.
224# gcc and clang opimizers take advantage of this.  The kernel makes
225# use of signed integer wraparound mechanics so we need the compiler
226# to treat it as a wraparound and not take shortcuts.
227#
228CFLAGS+=	-fwrapv
229
230#
231# GCC SSP support
232#
233.if ${MK_SSP} != "no"
234CFLAGS+=	-fstack-protector
235.endif
236
237#
238# Retpoline speculative execution vulnerability mitigation (CVE-2017-5715)
239#
240.if defined(COMPILER_FEATURES) && ${COMPILER_FEATURES:Mretpoline} != "" && \
241    ${MK_KERNEL_RETPOLINE} != "no"
242CFLAGS+=	-mretpoline
243.endif
244
245#
246# Initialize stack variables on function entry
247#
248.if ${OPT_INIT_ALL} != "none"
249.if ${COMPILER_FEATURES:Minit-all}
250CFLAGS+= -ftrivial-auto-var-init=${OPT_INIT_ALL}
251.if ${OPT_INIT_ALL} == "zero" && ${COMPILER_TYPE} == "clang" && ${COMPILER_VERSION} < 160000
252CFLAGS+= -enable-trivial-auto-var-init-zero-knowing-it-will-be-removed-from-clang
253.endif
254.else
255.warning INIT_ALL (${OPT_INIT_ALL}) requested but not supported by compiler
256.endif
257.endif
258
259CFLAGS+= ${CWARNFLAGS:M*} ${CWARNFLAGS.${.IMPSRC:T}}
260CFLAGS+= ${CWARNFLAGS.${COMPILER_TYPE}}
261CFLAGS+= ${CFLAGS.${COMPILER_TYPE}} ${CFLAGS.${.IMPSRC:T}}
262
263# Tell bmake not to mistake standard targets for things to be searched for
264# or expect to ever be up-to-date.
265PHONY_NOTMAIN = afterdepend afterinstall all beforedepend beforeinstall \
266		beforelinking build build-tools buildfiles buildincludes \
267		checkdpadd clean cleandepend cleandir cleanobj configure \
268		depend distclean distribute exe \
269		html includes install installfiles installincludes \
270		obj objlink objs objwarn \
271		realinstall regress \
272		tags whereobj
273
274.PHONY: ${PHONY_NOTMAIN}
275.NOTMAIN: ${PHONY_NOTMAIN}
276
277CSTD?=		gnu99
278
279.if ${CSTD} == "k&r"
280CFLAGS+=        -traditional
281.elif ${CSTD} == "c89" || ${CSTD} == "c90"
282CFLAGS+=        -std=iso9899:1990
283.elif ${CSTD} == "c94" || ${CSTD} == "c95"
284CFLAGS+=        -std=iso9899:199409
285.elif ${CSTD} == "c99"
286CFLAGS+=        -std=iso9899:1999
287.else # CSTD
288CFLAGS+=        -std=${CSTD}
289.endif # CSTD
290
291# Please keep this if in sync with bsd.sys.mk
292.if ${LD} != "ld" && (${CC:[1]:H} != ${LD:[1]:H} || ${LD:[1]:T} != "ld")
293# Add -fuse-ld=${LD} if $LD is in a different directory or not called "ld".
294.if ${COMPILER_TYPE} == "clang"
295# Note: Clang does not like relative paths for ld so we map ld.lld -> lld.
296.if ${COMPILER_VERSION} >= 120000
297CCLDFLAGS+=	--ld-path=${LD:[1]:S/^ld.//1W}
298.else
299CCLDFLAGS+=	-fuse-ld=${LD:[1]:S/^ld.//1W}
300.endif
301.else
302# GCC does not support an absolute path for -fuse-ld so we just print this
303# warning instead and let the user add the required symlinks.
304# However, we can avoid this warning if -B is set appropriately (e.g. for
305# CROSS_TOOLCHAIN=...-gcc).
306.if !(${LD:[1]:T} == "ld" && ${CC:tw:M-B${LD:[1]:H}/})
307.warning LD (${LD}) is not the default linker for ${CC} but -fuse-ld= is not supported
308.endif
309.endif
310.endif
311
312# Set target-specific linker emulation name.
313LD_EMULATION_aarch64=aarch64elf
314LD_EMULATION_amd64=elf_x86_64_fbsd
315LD_EMULATION_arm=armelf_fbsd
316LD_EMULATION_armv6=armelf_fbsd
317LD_EMULATION_armv7=armelf_fbsd
318LD_EMULATION_i386=elf_i386_fbsd
319LD_EMULATION_powerpc= elf32ppc_fbsd
320LD_EMULATION_powerpcspe= elf32ppc_fbsd
321LD_EMULATION_powerpc64= elf64ppc_fbsd
322LD_EMULATION_powerpc64le= elf64lppc_fbsd
323LD_EMULATION_riscv64= elf64lriscv
324LD_EMULATION=${LD_EMULATION_${MACHINE_ARCH}}
325