FreeBSD/Linux Kernel Cross Reference
sys/conf/kern.mk
1 # $FreeBSD$
2
3 #
4 # Warning flags for compiling the kernel and components of the kernel:
5 #
6 CWARNFLAGS?= -Wall -Wnested-externs -Wstrict-prototypes \
7 -Wmissing-prototypes -Wpointer-arith -Wcast-qual \
8 -Wundef -Wno-pointer-sign ${FORMAT_EXTENSIONS} \
9 -Wmissing-include-dirs -fdiagnostics-show-option \
10 -Wno-unknown-pragmas \
11 ${CWARNEXTRA}
12 #
13 # The following flags are next up for working on:
14 # -Wextra
15
16 # Disable a few warnings for clang, since there are several places in the
17 # kernel where fixing them is more trouble than it is worth, or where there is
18 # a false positive.
19 .if ${COMPILER_TYPE} == "clang"
20 NO_WCONSTANT_CONVERSION= -Wno-error=constant-conversion
21 NO_WSHIFT_COUNT_NEGATIVE= -Wno-shift-count-negative
22 NO_WSHIFT_COUNT_OVERFLOW= -Wno-shift-count-overflow
23 NO_WSELF_ASSIGN= -Wno-self-assign
24 NO_WUNNEEDED_INTERNAL_DECL= -Wno-error=unneeded-internal-declaration
25 NO_WSOMETIMES_UNINITIALIZED= -Wno-error=sometimes-uninitialized
26 NO_WCAST_QUAL= -Wno-error=cast-qual
27 NO_WTAUTOLOGICAL_POINTER_COMPARE= -Wno-tautological-pointer-compare
28 .if ${COMPILER_VERSION} >= 100000
29 NO_WMISLEADING_INDENTATION= -Wno-misleading-indentation
30 .endif
31 .if ${COMPILER_VERSION} >= 130000
32 NO_WUNUSED_BUT_SET_VARIABLE= -Wno-unused-but-set-variable
33 .endif
34 .if ${COMPILER_VERSION} >= 140000
35 NO_WBITWISE_INSTEAD_OF_LOGICAL= -Wno-bitwise-instead-of-logical
36 .endif
37 .if ${COMPILER_VERSION} >= 150000
38 NO_WSTRICT_PROTOTYPES= -Wno-strict-prototypes
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.
43 CWARNEXTRA?= -Wno-error=tautological-compare -Wno-error=empty-body \
44 -Wno-error=parentheses-equality -Wno-error=unused-function \
45 -Wno-error=pointer-sign
46 CWARNEXTRA+= -Wno-error=shift-negative-value
47 CWARNEXTRA+= -Wno-address-of-packed-member
48 .if ${COMPILER_VERSION} >= 150000
49 CWARNEXTRA+= -Wno-error=array-parameter
50 CWARNEXTRA+= -Wno-error=deprecated-non-prototype
51 .endif
52 .endif # clang
53
54 .if ${COMPILER_TYPE} == "gcc"
55 # Catch-all for all the things that are in our tree, but for which we're
56 # not yet ready for this compiler.
57 NO_WUNUSED_BUT_SET_VARIABLE=-Wno-unused-but-set-variable
58 CWARNEXTRA?= -Wno-error=address \
59 -Wno-error=aggressive-loop-optimizations \
60 -Wno-error=array-bounds \
61 -Wno-error=attributes \
62 -Wno-error=cast-qual \
63 -Wno-error=enum-compare \
64 -Wno-error=maybe-uninitialized \
65 -Wno-error=misleading-indentation \
66 -Wno-error=nonnull-compare \
67 -Wno-error=overflow \
68 -Wno-error=sequence-point \
69 -Wno-error=shift-overflow \
70 -Wno-error=tautological-compare \
71 -Wno-unused-but-set-variable
72 .if ${COMPILER_VERSION} >= 70100
73 CWARNEXTRA+= -Wno-error=stringop-overflow
74 .endif
75 .if ${COMPILER_VERSION} >= 70200
76 CWARNEXTRA+= -Wno-error=memset-elt-size
77 .endif
78 .if ${COMPILER_VERSION} >= 80000
79 CWARNEXTRA+= -Wno-error=packed-not-aligned
80 .endif
81 .if ${COMPILER_VERSION} >= 90100
82 CWARNEXTRA+= -Wno-address-of-packed-member \
83 -Wno-error=alloca-larger-than=
84 .if ${COMPILER_VERSION} >= 120100
85 CWARNEXTRA+= -Wno-error=nonnull \
86 -Wno-dangling-pointer \
87 -Wno-zero-length-bounds
88 NO_WINFINITE_RECURSION= -Wno-infinite-recursion
89 NO_WSTRINGOP_OVERREAD= -Wno-stringop-overread
90 .endif
91 .endif
92
93 # GCC produces false positives for functions that switch on an
94 # enum (GCC bug 87950)
95 CWARNFLAGS+= -Wno-return-type
96 .endif # gcc
97
98 # This warning is utter nonsense
99 CWARNFLAGS+= -Wno-format-zero-length
100
101 # External compilers may not support our format extensions. Allow them
102 # to be disabled. WARNING: format checking is disabled in this case.
103 .if ${MK_FORMAT_EXTENSIONS} == "no"
104 FORMAT_EXTENSIONS= -Wno-format
105 .elif ${COMPILER_TYPE} == "clang" || \
106 (${COMPILER_TYPE} == "gcc" && ${COMPILER_VERSION} >= 120100)
107 FORMAT_EXTENSIONS= -D__printf__=__freebsd_kprintf__
108 .else
109 FORMAT_EXTENSIONS= -fformat-extensions
110 .endif
111
112 #
113 # On i386, do not align the stack to 16-byte boundaries. Otherwise GCC 2.95
114 # and above adds code to the entry and exit point of every function to align the
115 # stack to 16-byte boundaries -- thus wasting approximately 12 bytes of stack
116 # per function call. While the 16-byte alignment may benefit micro benchmarks,
117 # it is probably an overall loss as it makes the code bigger (less efficient
118 # use of code cache tag lines) and uses more stack (less efficient use of data
119 # cache tag lines). Explicitly prohibit the use of FPU, SSE and other SIMD
120 # operations inside the kernel itself. These operations are exclusively
121 # reserved for user applications.
122 #
123 # gcc:
124 # Setting -mno-mmx implies -mno-3dnow
125 # Setting -mno-sse implies -mno-sse2, -mno-sse3 and -mno-ssse3
126 #
127 # clang:
128 # Setting -mno-mmx implies -mno-3dnow and -mno-3dnowa
129 # Setting -mno-sse implies -mno-sse2, -mno-sse3, -mno-ssse3, -mno-sse41 and -mno-sse42
130 #
131 .if ${MACHINE_CPUARCH} == "i386"
132 CFLAGS.gcc+= -mpreferred-stack-boundary=2
133 CFLAGS.clang+= -mno-aes -mno-avx
134 CFLAGS+= -mno-mmx -mno-sse -msoft-float
135 INLINE_LIMIT?= 8000
136 .endif
137
138 .if ${MACHINE_CPUARCH} == "arm"
139 INLINE_LIMIT?= 8000
140 .endif
141
142 .if ${MACHINE_CPUARCH} == "aarch64"
143 # We generally don't want fpu instructions in the kernel.
144 CFLAGS += -mgeneral-regs-only
145 # Reserve x18 for pcpu data
146 CFLAGS += -ffixed-x18
147 INLINE_LIMIT?= 8000
148 .endif
149
150 #
151 # For RISC-V we specify the soft-float ABI (lp64) to avoid the use of floating
152 # point registers within the kernel. However, for kernels supporting hardware
153 # float (FPE), we have to include that in the march so we can have limited
154 # floating point support in context switching needed for that. This is different
155 # 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"
163 CFLAGS+= -march=rv64imafdc
164 CFLAGS+= -mabi=lp64
165 CFLAGS.clang+= -mcmodel=medium
166 CFLAGS.gcc+= -mcmodel=medany
167 INLINE_LIMIT?= 8000
168
169 .if ${LINKER_FEATURES:Mriscv-relaxations} == ""
170 CFLAGS+= -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"
189 CFLAGS.clang+= -mno-aes -mno-avx
190 CFLAGS+= -mcmodel=kernel -mno-red-zone -mno-mmx -mno-sse -msoft-float \
191 -fno-asynchronous-unwind-tables
192 INLINE_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"
201 CFLAGS+= -mno-altivec -msoft-float
202 INLINE_LIMIT?= 15000
203 .endif
204
205 .if ${MACHINE_ARCH} == "powerpcspe"
206 CFLAGS.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 CFLAGS+= -mabi=elfv2
215 .endif
216
217 #
218 # GCC 3.0 and above like to do certain optimizations based on the
219 # assumption that the program is linked against libc. Stop this.
220 #
221 CFLAGS+= -ffreestanding
222
223 #
224 # The C standard leaves signed integer overflow behavior undefined.
225 # gcc and clang opimizers take advantage of this. The kernel makes
226 # use of signed integer wraparound mechanics so we need the compiler
227 # to treat it as a wraparound and not take shortcuts.
228 #
229 CFLAGS+= -fwrapv
230
231 #
232 # GCC SSP support
233 #
234 .if ${MK_SSP} != "no"
235 CFLAGS+= -fstack-protector
236 .endif
237
238 #
239 # Retpoline speculative execution vulnerability mitigation (CVE-2017-5715)
240 #
241 .if defined(COMPILER_FEATURES) && ${COMPILER_FEATURES:Mretpoline} != "" && \
242 ${MK_KERNEL_RETPOLINE} != "no"
243 CFLAGS+= -mretpoline
244 .endif
245
246 #
247 # Initialize stack variables on function entry
248 #
249 .if ${MK_INIT_ALL_ZERO} == "yes"
250 .if ${COMPILER_FEATURES:Minit-all}
251 CFLAGS+= -ftrivial-auto-var-init=zero \
252 -enable-trivial-auto-var-init-zero-knowing-it-will-be-removed-from-clang
253 .else
254 .warning InitAll (zeros) requested but not support by compiler
255 .endif
256 .elif ${MK_INIT_ALL_PATTERN} == "yes"
257 .if ${COMPILER_FEATURES:Minit-all}
258 CFLAGS+= -ftrivial-auto-var-init=pattern
259 .else
260 .warning InitAll (pattern) requested but not support by compiler
261 .endif
262 .endif
263
264 CFLAGS+= ${CWARNFLAGS:M*} ${CWARNFLAGS.${.IMPSRC:T}}
265 CFLAGS+= ${CWARNFLAGS.${COMPILER_TYPE}}
266 CFLAGS+= ${CFLAGS.${COMPILER_TYPE}} ${CFLAGS.${.IMPSRC:T}}
267
268 # Tell bmake not to mistake standard targets for things to be searched for
269 # or expect to ever be up-to-date.
270 PHONY_NOTMAIN = afterdepend afterinstall all beforedepend beforeinstall \
271 beforelinking build build-tools buildfiles buildincludes \
272 checkdpadd clean cleandepend cleandir cleanobj configure \
273 depend distclean distribute exe \
274 html includes install installfiles installincludes \
275 obj objlink objs objwarn \
276 realinstall regress \
277 tags whereobj
278
279 .PHONY: ${PHONY_NOTMAIN}
280 .NOTMAIN: ${PHONY_NOTMAIN}
281
282 CSTD= c99
283
284 .if ${CSTD} == "k&r"
285 CFLAGS+= -traditional
286 .elif ${CSTD} == "c89" || ${CSTD} == "c90"
287 CFLAGS+= -std=iso9899:1990
288 .elif ${CSTD} == "c94" || ${CSTD} == "c95"
289 CFLAGS+= -std=iso9899:199409
290 .elif ${CSTD} == "c99"
291 CFLAGS+= -std=iso9899:1999
292 .else # CSTD
293 CFLAGS+= -std=${CSTD}
294 .endif # CSTD
295
296 # Please keep this if in sync with bsd.sys.mk
297 .if ${LD} != "ld" && (${CC:[1]:H} != ${LD:[1]:H} || ${LD:[1]:T} != "ld")
298 # Add -fuse-ld=${LD} if $LD is in a different directory or not called "ld".
299 .if ${COMPILER_TYPE} == "clang"
300 # Note: Clang does not like relative paths for ld so we map ld.lld -> lld.
301 .if ${COMPILER_VERSION} >= 120000
302 CCLDFLAGS+= --ld-path=${LD:[1]:S/^ld.//1W}
303 .else
304 CCLDFLAGS+= -fuse-ld=${LD:[1]:S/^ld.//1W}
305 .endif
306 .else
307 # GCC does not support an absolute path for -fuse-ld so we just print this
308 # warning instead and let the user add the required symlinks.
309 # However, we can avoid this warning if -B is set appropriately (e.g. for
310 # CROSS_TOOLCHAIN=...-gcc).
311 .if !(${LD:[1]:T} == "ld" && ${CC:tw:M-B${LD:[1]:H}/})
312 .warning LD (${LD}) is not the default linker for ${CC} but -fuse-ld= is not supported
313 .endif
314 .endif
315 .endif
316
317 # Set target-specific linker emulation name.
318 LD_EMULATION_aarch64=aarch64elf
319 LD_EMULATION_amd64=elf_x86_64_fbsd
320 LD_EMULATION_arm=armelf_fbsd
321 LD_EMULATION_armv6=armelf_fbsd
322 LD_EMULATION_armv7=armelf_fbsd
323 LD_EMULATION_i386=elf_i386_fbsd
324 LD_EMULATION_powerpc= elf32ppc_fbsd
325 LD_EMULATION_powerpcspe= elf32ppc_fbsd
326 LD_EMULATION_powerpc64= elf64ppc_fbsd
327 LD_EMULATION_powerpc64le= elf64lppc_fbsd
328 LD_EMULATION_riscv64= elf64lriscv
329 LD_EMULATION_riscv64sf= elf64lriscv
330 LD_EMULATION=${LD_EMULATION_${MACHINE_ARCH}}
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