xref: /freebsd/sys/conf/kern.mk (revision 2668e76d6e764c5c361156ffa3d39eb02ce8e5d9)
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 -Wswitch \
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
146.if ${LINKER_TYPE} == "lld"
147LDFLAGS += -Wl,-zbti-report=error
148.endif
149# TODO: support outline atomics
150CFLAGS += -mno-outline-atomics
151INLINE_LIMIT?=	8000
152.endif
153
154#
155# For RISC-V we specify the soft-float ABI (lp64) to avoid the use of floating
156# point registers within the kernel. However, we include the F and D extensions
157# in -march so we can have limited floating point support in context switching
158# code. This is different than userland where we use a hard-float ABI (lp64d).
159#
160# We also specify the "medium" code model, which generates code suitable for a
161# 2GiB addressing range located at any offset, allowing modules to be located
162# anywhere in the 64-bit address space.  Note that clang and GCC refer to this
163# code model as "medium" and "medany" respectively.
164#
165.if ${MACHINE_CPUARCH} == "riscv"
166CFLAGS+=	-march=rv64imafdc
167CFLAGS+=	-mabi=lp64
168CFLAGS.clang+=	-mcmodel=medium
169CFLAGS.gcc+=	-mcmodel=medany
170INLINE_LIMIT?=	8000
171
172.if ${LINKER_FEATURES:Mriscv-relaxations} == ""
173CFLAGS+=	-mno-relax
174.endif
175.endif
176
177#
178# For AMD64, we explicitly prohibit the use of FPU, SSE and other SIMD
179# operations inside the kernel itself.  These operations are exclusively
180# reserved for user applications.
181#
182# gcc:
183# Setting -mno-mmx implies -mno-3dnow
184# Setting -mno-sse implies -mno-sse2, -mno-sse3, -mno-ssse3 and -mfpmath=387
185#
186# clang:
187# Setting -mno-mmx implies -mno-3dnow and -mno-3dnowa
188# Setting -mno-sse implies -mno-sse2, -mno-sse3, -mno-ssse3, -mno-sse41 and -mno-sse42
189# (-mfpmath= is not supported)
190#
191.if ${MACHINE_CPUARCH} == "amd64"
192CFLAGS.clang+=	-mno-aes -mno-avx
193CFLAGS+=	-mcmodel=kernel -mno-red-zone -mno-mmx -mno-sse -msoft-float \
194		-fno-asynchronous-unwind-tables
195INLINE_LIMIT?=	8000
196.endif
197
198#
199# For PowerPC we tell gcc to use floating point emulation.  This avoids using
200# floating point registers for integer operations which it has a tendency to do.
201# Also explicitly disable Altivec instructions inside the kernel.
202#
203.if ${MACHINE_CPUARCH} == "powerpc"
204CFLAGS+=	-mno-altivec -msoft-float
205INLINE_LIMIT?=	15000
206.endif
207
208.if ${MACHINE_ARCH} == "powerpcspe"
209CFLAGS.gcc+=	-mno-spe
210.endif
211
212#
213# Use dot symbols (or, better, the V2 ELF ABI) on powerpc64 to make
214# DDB happy. ELFv2, if available, has some other efficiency benefits.
215#
216.if ${MACHINE_ARCH:Mpowerpc64*} != "" && \
217    ${COMPILER_TYPE} == "clang" && ${COMPILER_VERSION} < 160000
218CFLAGS+=	-mabi=elfv2
219.endif
220
221#
222# GCC 3.0 and above like to do certain optimizations based on the
223# assumption that the program is linked against libc.  Stop this.
224#
225CFLAGS+=	-ffreestanding
226
227#
228# The C standard leaves signed integer overflow behavior undefined.
229# gcc and clang opimizers take advantage of this.  The kernel makes
230# use of signed integer wraparound mechanics so we need the compiler
231# to treat it as a wraparound and not take shortcuts.
232#
233CFLAGS+=	-fwrapv
234
235#
236# GCC SSP support
237#
238.if ${MK_SSP} != "no"
239CFLAGS+=	-fstack-protector
240.endif
241
242#
243# Retpoline speculative execution vulnerability mitigation (CVE-2017-5715)
244#
245.if defined(COMPILER_FEATURES) && ${COMPILER_FEATURES:Mretpoline} != "" && \
246    ${MK_KERNEL_RETPOLINE} != "no"
247CFLAGS+=	-mretpoline
248.endif
249
250#
251# Initialize stack variables on function entry
252#
253.if ${OPT_INIT_ALL} != "none"
254.if ${COMPILER_FEATURES:Minit-all}
255CFLAGS+= -ftrivial-auto-var-init=${OPT_INIT_ALL}
256.if ${OPT_INIT_ALL} == "zero" && ${COMPILER_TYPE} == "clang" && ${COMPILER_VERSION} < 160000
257CFLAGS+= -enable-trivial-auto-var-init-zero-knowing-it-will-be-removed-from-clang
258.endif
259.else
260.warning INIT_ALL (${OPT_INIT_ALL}) requested but not supported by compiler
261.endif
262.endif
263
264#
265# Some newer toolchains default to DWARF 5, which isn't supported by some build
266# tools yet.
267#
268.if (${CFLAGS:M-g} != "" || ${CFLAGS:M-g[0-3]} != "") && ${CFLAGS:M-gdwarf*} == ""
269CFLAGS+=	-gdwarf-4
270.endif
271
272CFLAGS+= ${CWARNFLAGS:M*} ${CWARNFLAGS.${.IMPSRC:T}}
273CFLAGS+= ${CWARNFLAGS.${COMPILER_TYPE}}
274CFLAGS+= ${CFLAGS.${COMPILER_TYPE}} ${CFLAGS.${.IMPSRC:T}}
275
276# Tell bmake not to mistake standard targets for things to be searched for
277# or expect to ever be up-to-date.
278PHONY_NOTMAIN = afterdepend afterinstall all beforedepend beforeinstall \
279		beforelinking build build-tools buildfiles buildincludes \
280		checkdpadd clean cleandepend cleandir cleanobj configure \
281		depend distclean distribute exe \
282		html includes install installfiles installincludes \
283		obj objlink objs objwarn \
284		realinstall regress \
285		tags whereobj
286
287.PHONY: ${PHONY_NOTMAIN}
288.NOTMAIN: ${PHONY_NOTMAIN}
289
290CSTD?=		gnu99
291
292# c99/gnu99 is the minimum C standard version supported for kernel build
293.if ${CSTD} == "k&r" || ${CSTD} == "c89" || ${CSTD} == "c90" || \
294    ${CSTD} == "c94" || ${CSTD} == "c95"
295.error "Only c99/gnu99 or later is supported"
296.else # CSTD
297CFLAGS+=        -std=${CSTD}
298.endif # CSTD
299
300NOSAN_CFLAGS= ${CFLAGS:N-fsanitize*:N-fno-sanitize*:N-fasan-shadow-offset*}
301
302# Please keep this if in sync with bsd.sys.mk
303.if ${LD} != "ld" && (${CC:[1]:H} != ${LD:[1]:H} || ${LD:[1]:T} != "ld")
304# Add -fuse-ld=${LD} if $LD is in a different directory or not called "ld".
305.if ${COMPILER_TYPE} == "clang"
306# Note: Clang does not like relative paths for ld so we map ld.lld -> lld.
307.if ${COMPILER_VERSION} >= 120000
308CCLDFLAGS+=	--ld-path=${LD:[1]:S/^ld.//1W}
309.else
310CCLDFLAGS+=	-fuse-ld=${LD:[1]:S/^ld.//1W}
311.endif
312.else
313# GCC does not support an absolute path for -fuse-ld so we just print this
314# warning instead and let the user add the required symlinks.
315# However, we can avoid this warning if -B is set appropriately (e.g. for
316# CROSS_TOOLCHAIN=...-gcc).
317.if !(${LD:[1]:T} == "ld" && ${CC:tw:M-B${LD:[1]:H}/})
318.warning LD (${LD}) is not the default linker for ${CC} but -fuse-ld= is not supported
319.endif
320.endif
321.endif
322
323# Set target-specific linker emulation name.
324LD_EMULATION_aarch64=aarch64elf
325LD_EMULATION_amd64=elf_x86_64_fbsd
326LD_EMULATION_arm=armelf_fbsd
327LD_EMULATION_armv6=armelf_fbsd
328LD_EMULATION_armv7=armelf_fbsd
329LD_EMULATION_i386=elf_i386_fbsd
330LD_EMULATION_powerpc= elf32ppc_fbsd
331LD_EMULATION_powerpcspe= elf32ppc_fbsd
332LD_EMULATION_powerpc64= elf64ppc_fbsd
333LD_EMULATION_powerpc64le= elf64lppc_fbsd
334LD_EMULATION_riscv64= elf64lriscv
335LD_EMULATION=${LD_EMULATION_${MACHINE_ARCH}}
336