xref: /freebsd/sys/conf/kern.mk (revision f1951fd745b894fe6586c298874af98544a5e272)
1# $FreeBSD$
2
3#
4# Warning flags for compiling the kernel and components of the kernel:
5#
6CWARNFLAGS?=	-Wall -Wredundant-decls -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"
20NO_WCONSTANT_CONVERSION=	-Wno-error-constant-conversion
21NO_WSHIFT_COUNT_NEGATIVE=	-Wno-shift-count-negative
22NO_WSHIFT_COUNT_OVERFLOW=	-Wno-shift-count-overflow
23NO_WSELF_ASSIGN=		-Wno-self-assign
24NO_WUNNEEDED_INTERNAL_DECL=	-Wno-error-unneeded-internal-declaration
25NO_WSOMETIMES_UNINITIALIZED=	-Wno-error-sometimes-uninitialized
26NO_WCAST_QUAL=			-Wno-error-cast-qual
27NO_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.
31CWARNEXTRA?=	-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
35CWARNEXTRA+=	-Wno-error-shift-negative-value
36.endif
37.if ${COMPILER_VERSION} >= 40000
38CWARNEXTRA+=	-Wno-address-of-packed-member
39.endif
40
41CLANG_NO_IAS= -no-integrated-as
42.if ${COMPILER_VERSION} < 30500
43# XXX: clang < 3.5 integrated-as doesn't grok .codeNN directives
44CLANG_NO_IAS34= -no-integrated-as
45.endif
46.endif
47
48.if ${COMPILER_TYPE} == "gcc"
49.if ${COMPILER_VERSION} >= 40800
50# Catch-all for all the things that are in our tree, but for which we're
51# not yet ready for this compiler.
52NO_WUNUSED_BUT_SET_VARIABLE = -Wno-unused-but-set-variable
53CWARNEXTRA?=	-Wno-error=address				\
54		-Wno-error=aggressive-loop-optimizations	\
55		-Wno-error=array-bounds				\
56		-Wno-error=attributes				\
57		-Wno-error=cast-qual				\
58		-Wno-error=enum-compare				\
59		-Wno-error=inline				\
60		-Wno-error=maybe-uninitialized			\
61		-Wno-error=overflow				\
62		-Wno-error=sequence-point			\
63		-Wno-error=unused-but-set-variable
64.if ${COMPILER_VERSION} >= 60100
65CWARNEXTRA+=	-Wno-error=misleading-indentation		\
66		-Wno-error=nonnull-compare			\
67		-Wno-error=shift-overflow			\
68		-Wno-error=tautological-compare
69.endif
70.if ${COMPILER_VERSION} >= 70200
71CWARNEXTRA+=	-Wno-error=memset-elt-size
72.endif
73.if ${COMPILER_VERSION} >= 80000
74CWARNEXTRA+=	-Wno-error=packed-not-aligned
75.endif
76.else
77# For gcc 4.2, eliminate the too-often-wrong warnings about uninitialized vars.
78CWARNEXTRA?=	-Wno-uninitialized
79# GCC 4.2 doesn't have -Wno-error=cast-qual, so just disable the warning for
80# the few files that are already known to generate cast-qual warnings.
81NO_WCAST_QUAL= -Wno-cast-qual
82.endif
83.endif
84
85# External compilers may not support our format extensions.  Allow them
86# to be disabled.  WARNING: format checking is disabled in this case.
87.if ${MK_FORMAT_EXTENSIONS} == "no"
88FORMAT_EXTENSIONS=	-Wno-format
89.elif ${COMPILER_TYPE} == "clang" && ${COMPILER_VERSION} >= 30600
90FORMAT_EXTENSIONS=	-D__printf__=__freebsd_kprintf__
91.else
92FORMAT_EXTENSIONS=	-fformat-extensions
93.endif
94
95#
96# On i386, do not align the stack to 16-byte boundaries.  Otherwise GCC 2.95
97# and above adds code to the entry and exit point of every function to align the
98# stack to 16-byte boundaries -- thus wasting approximately 12 bytes of stack
99# per function call.  While the 16-byte alignment may benefit micro benchmarks,
100# it is probably an overall loss as it makes the code bigger (less efficient
101# use of code cache tag lines) and uses more stack (less efficient use of data
102# cache tag lines).  Explicitly prohibit the use of FPU, SSE and other SIMD
103# operations inside the kernel itself.  These operations are exclusively
104# reserved for user applications.
105#
106# gcc:
107# Setting -mno-mmx implies -mno-3dnow
108# Setting -mno-sse implies -mno-sse2, -mno-sse3 and -mno-ssse3
109#
110# clang:
111# Setting -mno-mmx implies -mno-3dnow and -mno-3dnowa
112# Setting -mno-sse implies -mno-sse2, -mno-sse3, -mno-ssse3, -mno-sse41 and -mno-sse42
113#
114.if ${MACHINE_CPUARCH} == "i386"
115CFLAGS.gcc+=	-mno-align-long-strings -mpreferred-stack-boundary=2
116CFLAGS.clang+=	-mno-aes -mno-avx
117CFLAGS+=	-mno-mmx -mno-sse -msoft-float
118INLINE_LIMIT?=	8000
119.endif
120
121.if ${MACHINE_CPUARCH} == "arm"
122INLINE_LIMIT?=	8000
123.endif
124
125.if ${MACHINE_CPUARCH} == "aarch64"
126# We generally don't want fpu instructions in the kernel.
127CFLAGS += -mgeneral-regs-only
128# Reserve x18 for pcpu data
129CFLAGS += -ffixed-x18
130INLINE_LIMIT?=	8000
131.endif
132
133.if ${MACHINE_CPUARCH} == "riscv"
134CFLAGS.gcc+=	-mcmodel=medany -march=rv64imafd -mabi=lp64
135INLINE_LIMIT?=	8000
136.endif
137
138#
139# For sparc64 we want the medany code model so modules may be located
140# anywhere in the 64-bit address space.  We also tell GCC to use floating
141# point emulation.  This avoids using floating point registers for integer
142# operations which it has a tendency to do.
143#
144.if ${MACHINE_CPUARCH} == "sparc64"
145CFLAGS.clang+=	-mcmodel=large -fno-dwarf2-cfi-asm
146CFLAGS.gcc+=	-mcmodel=medany -msoft-float
147INLINE_LIMIT?=	15000
148.endif
149
150#
151# For AMD64, we explicitly prohibit the use of FPU, SSE and other SIMD
152# operations inside the kernel itself.  These operations are exclusively
153# reserved for user applications.
154#
155# gcc:
156# Setting -mno-mmx implies -mno-3dnow
157# Setting -mno-sse implies -mno-sse2, -mno-sse3, -mno-ssse3 and -mfpmath=387
158#
159# clang:
160# Setting -mno-mmx implies -mno-3dnow and -mno-3dnowa
161# Setting -mno-sse implies -mno-sse2, -mno-sse3, -mno-ssse3, -mno-sse41 and -mno-sse42
162# (-mfpmath= is not supported)
163#
164.if ${MACHINE_CPUARCH} == "amd64"
165CFLAGS.clang+=	-mno-aes -mno-avx
166CFLAGS+=	-mcmodel=kernel -mno-red-zone -mno-mmx -mno-sse -msoft-float \
167		-fno-asynchronous-unwind-tables
168INLINE_LIMIT?=	8000
169.endif
170
171#
172# For PowerPC we tell gcc to use floating point emulation.  This avoids using
173# floating point registers for integer operations which it has a tendency to do.
174# Also explicitly disable Altivec instructions inside the kernel.
175#
176.if ${MACHINE_CPUARCH} == "powerpc"
177CFLAGS+=	-mno-altivec -msoft-float
178INLINE_LIMIT?=	15000
179.endif
180
181.if ${MACHINE_ARCH} == "powerpcspe"
182CFLAGS.gcc+=	-mno-spe
183.endif
184
185#
186# Use dot symbols (or, better, the V2 ELF ABI) on powerpc64 to make
187# DDB happy. ELFv2, if available, has some other efficiency benefits.
188#
189.if ${MACHINE_ARCH} == "powerpc64"
190.if ${COMPILER_VERSION} >= 40900
191CFLAGS.gcc+=	-mabi=elfv2
192.else
193CFLAGS.gcc+=	-mcall-aixdesc
194.endif
195CFLAGS.clang+=	-mabi=elfv2
196.endif
197
198#
199# For MIPS we also tell gcc to use floating point emulation
200#
201.if ${MACHINE_CPUARCH} == "mips"
202CFLAGS+=	-msoft-float
203INLINE_LIMIT?=	8000
204.endif
205
206#
207# GCC 3.0 and above like to do certain optimizations based on the
208# assumption that the program is linked against libc.  Stop this.
209#
210CFLAGS+=	-ffreestanding
211
212#
213# The C standard leaves signed integer overflow behavior undefined.
214# gcc and clang opimizers take advantage of this.  The kernel makes
215# use of signed integer wraparound mechanics so we need the compiler
216# to treat it as a wraparound and not take shortcuts.
217#
218CFLAGS+=	-fwrapv
219
220#
221# GCC SSP support
222#
223.if ${MK_SSP} != "no" && \
224    ${MACHINE_CPUARCH} != "arm" && ${MACHINE_CPUARCH} != "mips"
225CFLAGS+=	-fstack-protector
226.endif
227
228#
229# Retpoline speculative execution vulnerability mitigation (CVE-2017-5715)
230#
231.if defined(COMPILER_FEATURES) && ${COMPILER_FEATURES:Mretpoline} != "" && \
232    ${MK_KERNEL_RETPOLINE} != "no"
233CFLAGS+=	-mretpoline
234.endif
235
236#
237# Add -gdwarf-2 when compiling -g. The default starting in clang v3.4
238# and gcc 4.8 is to generate DWARF version 4. However, our tools don't
239# cope well with DWARF 4, so force it to genereate DWARF2, which they
240# understand. Do this unconditionally as it is harmless when not needed,
241# but critical for these newer versions.
242#
243.if ${CFLAGS:M-g} != "" && ${CFLAGS:M-gdwarf*} == ""
244CFLAGS+=	-gdwarf-2
245.endif
246
247CFLAGS+= ${CWARNFLAGS:M*} ${CWARNFLAGS.${.IMPSRC:T}}
248CFLAGS+= ${CFLAGS.${COMPILER_TYPE}} ${CFLAGS.${.IMPSRC:T}}
249
250# Tell bmake not to mistake standard targets for things to be searched for
251# or expect to ever be up-to-date.
252PHONY_NOTMAIN = afterdepend afterinstall all beforedepend beforeinstall \
253		beforelinking build build-tools buildfiles buildincludes \
254		checkdpadd clean cleandepend cleandir cleanobj configure \
255		depend distclean distribute exe \
256		html includes install installfiles installincludes \
257		obj objlink objs objwarn \
258		realinstall regress \
259		tags whereobj
260
261.PHONY: ${PHONY_NOTMAIN}
262.NOTMAIN: ${PHONY_NOTMAIN}
263
264CSTD=		c99
265
266.if ${CSTD} == "k&r"
267CFLAGS+=        -traditional
268.elif ${CSTD} == "c89" || ${CSTD} == "c90"
269CFLAGS+=        -std=iso9899:1990
270.elif ${CSTD} == "c94" || ${CSTD} == "c95"
271CFLAGS+=        -std=iso9899:199409
272.elif ${CSTD} == "c99"
273CFLAGS+=        -std=iso9899:1999
274.else # CSTD
275CFLAGS+=        -std=${CSTD}
276.endif # CSTD
277
278# Set target-specific linker emulation name.
279LD_EMULATION_aarch64=aarch64elf
280LD_EMULATION_amd64=elf_x86_64_fbsd
281LD_EMULATION_arm=armelf_fbsd
282LD_EMULATION_armv6=armelf_fbsd
283LD_EMULATION_armv7=armelf_fbsd
284LD_EMULATION_i386=elf_i386_fbsd
285LD_EMULATION_mips= elf32btsmip_fbsd
286LD_EMULATION_mipshf= elf32btsmip_fbsd
287LD_EMULATION_mips64= elf64btsmip_fbsd
288LD_EMULATION_mips64hf= elf64btsmip_fbsd
289LD_EMULATION_mipsel= elf32ltsmip_fbsd
290LD_EMULATION_mipselhf= elf32ltsmip_fbsd
291LD_EMULATION_mips64el= elf64ltsmip_fbsd
292LD_EMULATION_mips64elhf= elf64ltsmip_fbsd
293LD_EMULATION_mipsn32= elf32btsmipn32_fbsd
294LD_EMULATION_mipsn32el= elf32btsmipn32_fbsd   # I don't think this is a thing that works
295LD_EMULATION_powerpc= elf32ppc_fbsd
296LD_EMULATION_powerpcspe= elf32ppc_fbsd
297LD_EMULATION_powerpc64= elf64ppc_fbsd
298LD_EMULATION_riscv64= elf64lriscv
299LD_EMULATION_sparc64= elf64_sparc_fbsd
300LD_EMULATION=${LD_EMULATION_${MACHINE_ARCH}}
301