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