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 -Wredundant-decls -Wnested-externs -Wstrict-prototypes \
7 -Wmissing-prototypes -Wpointer-arith -Winline -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 # Several other warnings which might be useful in some cases, but not severe
29 # enough to error out the whole kernel build. Display them anyway, so there is
30 # some incentive to fix them eventually.
31 CWARNEXTRA?= -Wno-error=tautological-compare -Wno-error=empty-body \
32 -Wno-error=parentheses-equality -Wno-error=unused-function \
33 -Wno-error=pointer-sign
34 .if ${COMPILER_VERSION} >= 30700
35 CWARNEXTRA+= -Wno-error=shift-negative-value
36 .endif
37 .if ${COMPILER_VERSION} >= 40000
38 CWARNEXTRA+= -Wno-address-of-packed-member
39 .endif
40 .if ${COMPILER_VERSION} >= 100000
41 NO_WMISLEADING_INDENTATION= -Wno-misleading-indentation
42 .endif
43
44 CLANG_NO_IAS= -no-integrated-as
45 .if ${COMPILER_VERSION} < 30500
46 # XXX: clang < 3.5 integrated-as doesn't grok .codeNN directives
47 CLANG_NO_IAS34= -no-integrated-as
48 .endif
49 .endif
50
51 .if ${COMPILER_TYPE} == "gcc"
52 .if ${COMPILER_VERSION} >= 40800
53 # Catch-all for all the things that are in our tree, but for which we're
54 # not yet ready for this compiler.
55 CWARNEXTRA?= -Wno-error=address \
56 -Wno-error=aggressive-loop-optimizations \
57 -Wno-error=array-bounds \
58 -Wno-error=attributes \
59 -Wno-error=cast-qual \
60 -Wno-error=enum-compare \
61 -Wno-error=inline \
62 -Wno-error=maybe-uninitialized \
63 -Wno-error=overflow \
64 -Wno-error=sequence-point \
65 -Wno-error=unused-but-set-variable
66 .if ${COMPILER_VERSION} >= 60100
67 CWARNEXTRA+= -Wno-error=misleading-indentation \
68 -Wno-error=nonnull-compare \
69 -Wno-error=shift-overflow \
70 -Wno-error=tautological-compare
71 .endif
72 .else
73 # For gcc 4.2, eliminate the too-often-wrong warnings about uninitialized vars.
74 CWARNEXTRA?= -Wno-uninitialized
75 .endif
76 .endif
77
78 # External compilers may not support our format extensions. Allow them
79 # to be disabled. WARNING: format checking is disabled in this case.
80 .if ${MK_FORMAT_EXTENSIONS} == "no"
81 FORMAT_EXTENSIONS= -Wno-format
82 .elif ${COMPILER_TYPE} == "clang" && ${COMPILER_VERSION} >= 30600
83 FORMAT_EXTENSIONS= -D__printf__=__freebsd_kprintf__
84 .else
85 FORMAT_EXTENSIONS= -fformat-extensions
86 .endif
87
88 #
89 # On i386, do not align the stack to 16-byte boundaries. Otherwise GCC 2.95
90 # and above adds code to the entry and exit point of every function to align the
91 # stack to 16-byte boundaries -- thus wasting approximately 12 bytes of stack
92 # per function call. While the 16-byte alignment may benefit micro benchmarks,
93 # it is probably an overall loss as it makes the code bigger (less efficient
94 # use of code cache tag lines) and uses more stack (less efficient use of data
95 # cache tag lines). Explicitly prohibit the use of FPU, SSE and other SIMD
96 # operations inside the kernel itself. These operations are exclusively
97 # reserved for user applications.
98 #
99 # gcc:
100 # Setting -mno-mmx implies -mno-3dnow
101 # Setting -mno-sse implies -mno-sse2, -mno-sse3 and -mno-ssse3
102 #
103 # clang:
104 # Setting -mno-mmx implies -mno-3dnow and -mno-3dnowa
105 # Setting -mno-sse implies -mno-sse2, -mno-sse3, -mno-ssse3, -mno-sse41 and -mno-sse42
106 #
107 .if ${MACHINE_CPUARCH} == "i386"
108 CFLAGS.gcc+= -mno-align-long-strings -mpreferred-stack-boundary=2
109 CFLAGS.clang+= -mno-aes -mno-avx
110 CFLAGS+= -mno-mmx -mno-sse -msoft-float
111 INLINE_LIMIT?= 8000
112 .endif
113
114 .if ${MACHINE_CPUARCH} == "arm"
115 INLINE_LIMIT?= 8000
116 .endif
117
118 .if ${MACHINE_CPUARCH} == "aarch64"
119 # We generally don't want fpu instructions in the kernel.
120 CFLAGS += -mgeneral-regs-only
121 # Reserve x18 for pcpu data
122 CFLAGS += -ffixed-x18
123 .endif
124
125 .if ${MACHINE_CPUARCH} == "riscv"
126 CFLAGS.gcc+= -mcmodel=medany
127 INLINE_LIMIT?= 8000
128 .endif
129
130 #
131 # For sparc64 we want the medany code model so modules may be located
132 # anywhere in the 64-bit address space. We also tell GCC to use floating
133 # point emulation. This avoids using floating point registers for integer
134 # operations which it has a tendency to do.
135 #
136 .if ${MACHINE_CPUARCH} == "sparc64"
137 CFLAGS.clang+= -mcmodel=large -fno-dwarf2-cfi-asm
138 CFLAGS.gcc+= -mcmodel=medany -msoft-float
139 INLINE_LIMIT?= 15000
140 .endif
141
142 #
143 # For AMD64, we explicitly prohibit the use of FPU, SSE and other SIMD
144 # operations inside the kernel itself. These operations are exclusively
145 # reserved for user applications.
146 #
147 # gcc:
148 # Setting -mno-mmx implies -mno-3dnow
149 # Setting -mno-sse implies -mno-sse2, -mno-sse3, -mno-ssse3 and -mfpmath=387
150 #
151 # clang:
152 # Setting -mno-mmx implies -mno-3dnow and -mno-3dnowa
153 # Setting -mno-sse implies -mno-sse2, -mno-sse3, -mno-ssse3, -mno-sse41 and -mno-sse42
154 # (-mfpmath= is not supported)
155 #
156 .if ${MACHINE_CPUARCH} == "amd64"
157 CFLAGS.clang+= -mno-aes -mno-avx
158 CFLAGS+= -mcmodel=kernel -mno-red-zone -mno-mmx -mno-sse -msoft-float \
159 -fno-asynchronous-unwind-tables
160 INLINE_LIMIT?= 8000
161 .endif
162
163 #
164 # For PowerPC we tell gcc to use floating point emulation. This avoids using
165 # floating point registers for integer operations which it has a tendency to do.
166 # Also explicitly disable Altivec instructions inside the kernel.
167 #
168 .if ${MACHINE_CPUARCH} == "powerpc"
169 CFLAGS+= -mno-altivec -msoft-float
170 INLINE_LIMIT?= 15000
171 .endif
172
173 #
174 # Use dot symbols on powerpc64 to make ddb happy
175 #
176 .if ${MACHINE_ARCH} == "powerpc64"
177 CFLAGS.gcc+= -mcall-aixdesc
178 .endif
179
180 #
181 # For MIPS we also tell gcc to use floating point emulation
182 #
183 .if ${MACHINE_CPUARCH} == "mips"
184 CFLAGS+= -msoft-float
185 INLINE_LIMIT?= 8000
186 .endif
187
188 #
189 # GCC 3.0 and above like to do certain optimizations based on the
190 # assumption that the program is linked against libc. Stop this.
191 #
192 CFLAGS+= -ffreestanding
193
194 #
195 # The C standard leaves signed integer overflow behavior undefined.
196 # gcc and clang opimizers take advantage of this. The kernel makes
197 # use of signed integer wraparound mechanics so we need the compiler
198 # to treat it as a wraparound and not take shortcuts.
199 #
200 CFLAGS+= -fwrapv
201
202 #
203 # GCC SSP support
204 #
205 .if ${MK_SSP} != "no" && \
206 ${MACHINE_CPUARCH} != "arm" && ${MACHINE_CPUARCH} != "mips"
207 CFLAGS+= -fstack-protector
208 .endif
209
210 #
211 # Retpoline speculative execution vulnerability mitigation (CVE-2017-5715)
212 #
213 .if defined(COMPILER_FEATURES) && ${COMPILER_FEATURES:Mretpoline} != "" && \
214 ${MK_KERNEL_RETPOLINE} != "no"
215 CFLAGS+= -mretpoline
216 .endif
217
218 #
219 # Add -gdwarf-2 when compiling -g. The default starting in clang v3.4
220 # and gcc 4.8 is to generate DWARF version 4. However, our tools don't
221 # cope well with DWARF 4, so force it to genereate DWARF2, which they
222 # understand. Do this unconditionally as it is harmless when not needed,
223 # but critical for these newer versions.
224 #
225 .if ${CFLAGS:M-g} != "" && ${CFLAGS:M-gdwarf*} == ""
226 CFLAGS+= -gdwarf-2
227 .endif
228
229 CFLAGS+= ${CWARNFLAGS:M*} ${CWARNFLAGS.${.IMPSRC:T}}
230 CFLAGS+= ${CFLAGS.${COMPILER_TYPE}} ${CFLAGS.${.IMPSRC:T}}
231
232 # Tell bmake not to mistake standard targets for things to be searched for
233 # or expect to ever be up-to-date.
234 PHONY_NOTMAIN = afterdepend afterinstall all beforedepend beforeinstall \
235 beforelinking build build-tools buildfiles buildincludes \
236 checkdpadd clean cleandepend cleandir cleanobj configure \
237 depend distclean distribute exe \
238 html includes install installfiles installincludes lint \
239 obj objlink objs objwarn \
240 realinstall regress \
241 tags whereobj
242
243 .PHONY: ${PHONY_NOTMAIN}
244 .NOTMAIN: ${PHONY_NOTMAIN}
245
246 CSTD= c99
247
248 .if ${CSTD} == "k&r"
249 CFLAGS+= -traditional
250 .elif ${CSTD} == "c89" || ${CSTD} == "c90"
251 CFLAGS+= -std=iso9899:1990
252 .elif ${CSTD} == "c94" || ${CSTD} == "c95"
253 CFLAGS+= -std=iso9899:199409
254 .elif ${CSTD} == "c99"
255 CFLAGS+= -std=iso9899:1999
256 .else # CSTD
257 CFLAGS+= -std=${CSTD}
258 .endif # CSTD
259
260 # Set target-specific linker emulation name.
261 LD_EMULATION_aarch64=aarch64elf
262 LD_EMULATION_amd64=elf_x86_64_fbsd
263 LD_EMULATION_arm=armelf_fbsd
264 LD_EMULATION_armeb=armelfb_fbsd
265 LD_EMULATION_armv6=armelf_fbsd
266 LD_EMULATION_i386=elf_i386_fbsd
267 LD_EMULATION_mips= elf32btsmip_fbsd
268 LD_EMULATION_mips64= elf64btsmip_fbsd
269 LD_EMULATION_mipsel= elf32ltsmip_fbsd
270 LD_EMULATION_mips64el= elf64ltsmip_fbsd
271 LD_EMULATION_mipsn32= elf32btsmipn32_fbsd
272 LD_EMULATION_mipsn32el= elf32btsmipn32_fbsd # I don't think this is a thing that works
273 LD_EMULATION_powerpc= elf32ppc_fbsd
274 LD_EMULATION_powerpc64= elf64ppc_fbsd
275 LD_EMULATION_riscv64= elf64lriscv
276 LD_EMULATION_sparc64= elf64_sparc_fbsd
277 LD_EMULATION=${LD_EMULATION_${MACHINE_ARCH}}
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