xref: /freebsd/sys/conf/kern.mk (revision 076b94438c7d42c1b4661ed1e12e3b12ca69361a)
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
28NO_WARRAY_BOUNDS=		-Wno-error-array-bounds
29# Several other warnings which might be useful in some cases, but not severe
30# enough to error out the whole kernel build.  Display them anyway, so there is
31# some incentive to fix them eventually.
32CWARNEXTRA?=	-Wno-error-tautological-compare -Wno-error-empty-body \
33		-Wno-error-parentheses-equality -Wno-error-unused-function \
34		-Wno-error-pointer-sign
35.if ${COMPILER_VERSION} >= 30700
36CWARNEXTRA+=	-Wno-error-shift-negative-value
37.endif
38.if ${COMPILER_VERSION} >= 40000
39CWARNEXTRA+=	-Wno-address-of-packed-member
40.endif
41
42CLANG_NO_IAS= -no-integrated-as
43.endif
44
45.if ${COMPILER_TYPE} == "gcc"
46.if ${COMPILER_VERSION} >= 40800
47# Catch-all for all the things that are in our tree, but for which we're
48# not yet ready for this compiler.
49NO_WUNUSED_BUT_SET_VARIABLE = -Wno-unused-but-set-variable
50CWARNEXTRA?=	-Wno-error=address				\
51		-Wno-error=aggressive-loop-optimizations	\
52		-Wno-error=array-bounds				\
53		-Wno-error=attributes				\
54		-Wno-error=cast-qual				\
55		-Wno-error=enum-compare				\
56		-Wno-error=inline				\
57		-Wno-error=maybe-uninitialized			\
58		-Wno-error=overflow				\
59		-Wno-error=sequence-point			\
60		-Wno-error=unused-but-set-variable
61.if ${COMPILER_VERSION} >= 60100
62CWARNEXTRA+=	-Wno-error=misleading-indentation		\
63		-Wno-error=nonnull-compare			\
64		-Wno-error=shift-overflow			\
65		-Wno-error=tautological-compare
66.endif
67.if ${COMPILER_VERSION} >= 70200
68CWARNEXTRA+=	-Wno-error=memset-elt-size
69.endif
70.if ${COMPILER_VERSION} >= 80000
71CWARNEXTRA+=	-Wno-error=packed-not-aligned
72.endif
73.else
74# For gcc 4.2, eliminate the too-often-wrong warnings about uninitialized vars.
75CWARNEXTRA?=	-Wno-uninitialized
76# GCC 4.2 doesn't have -Wno-error=cast-qual, so just disable the warning for
77# the few files that are already known to generate cast-qual warnings.
78NO_WCAST_QUAL= -Wno-cast-qual
79.endif
80.endif
81
82# External compilers may not support our format extensions.  Allow them
83# to be disabled.  WARNING: format checking is disabled in this case.
84.if ${MK_FORMAT_EXTENSIONS} == "no"
85FORMAT_EXTENSIONS=	-Wno-format
86.elif ${COMPILER_TYPE} == "clang" && ${COMPILER_VERSION} >= 30600
87FORMAT_EXTENSIONS=	-D__printf__=__freebsd_kprintf__
88.else
89FORMAT_EXTENSIONS=	-fformat-extensions
90.endif
91
92#
93# On i386, do not align the stack to 16-byte boundaries.  Otherwise GCC 2.95
94# and above adds code to the entry and exit point of every function to align the
95# stack to 16-byte boundaries -- thus wasting approximately 12 bytes of stack
96# per function call.  While the 16-byte alignment may benefit micro benchmarks,
97# it is probably an overall loss as it makes the code bigger (less efficient
98# use of code cache tag lines) and uses more stack (less efficient use of data
99# cache tag lines).  Explicitly prohibit the use of FPU, SSE and other SIMD
100# operations inside the kernel itself.  These operations are exclusively
101# reserved for user applications.
102#
103# gcc:
104# Setting -mno-mmx implies -mno-3dnow
105# Setting -mno-sse implies -mno-sse2, -mno-sse3 and -mno-ssse3
106#
107# clang:
108# Setting -mno-mmx implies -mno-3dnow and -mno-3dnowa
109# Setting -mno-sse implies -mno-sse2, -mno-sse3, -mno-ssse3, -mno-sse41 and -mno-sse42
110#
111.if ${MACHINE_CPUARCH} == "i386"
112CFLAGS.gcc+=	-mno-align-long-strings -mpreferred-stack-boundary=2
113CFLAGS.clang+=	-mno-aes -mno-avx
114CFLAGS+=	-mno-mmx -mno-sse -msoft-float
115INLINE_LIMIT?=	8000
116.endif
117
118.if ${MACHINE_CPUARCH} == "arm"
119INLINE_LIMIT?=	8000
120.endif
121
122.if ${MACHINE_CPUARCH} == "aarch64"
123# We generally don't want fpu instructions in the kernel.
124CFLAGS += -mgeneral-regs-only
125# Reserve x18 for pcpu data
126CFLAGS += -ffixed-x18
127INLINE_LIMIT?=	8000
128.endif
129
130.if ${MACHINE_CPUARCH} == "riscv"
131CFLAGS.gcc+=	-mcmodel=medany -march=rv64imafdc -mabi=lp64
132INLINE_LIMIT?=	8000
133.endif
134
135#
136# For sparc64 we want the medany code model so modules may be located
137# anywhere in the 64-bit address space.  We also tell GCC to use floating
138# point emulation.  This avoids using floating point registers for integer
139# operations which it has a tendency to do.
140#
141.if ${MACHINE_CPUARCH} == "sparc64"
142CFLAGS.clang+=	-mcmodel=large -fno-dwarf2-cfi-asm
143CFLAGS.gcc+=	-mcmodel=medany -msoft-float
144INLINE_LIMIT?=	15000
145.endif
146
147#
148# For AMD64, we explicitly prohibit the use of FPU, SSE and other SIMD
149# operations inside the kernel itself.  These operations are exclusively
150# reserved for user applications.
151#
152# gcc:
153# Setting -mno-mmx implies -mno-3dnow
154# Setting -mno-sse implies -mno-sse2, -mno-sse3, -mno-ssse3 and -mfpmath=387
155#
156# clang:
157# Setting -mno-mmx implies -mno-3dnow and -mno-3dnowa
158# Setting -mno-sse implies -mno-sse2, -mno-sse3, -mno-ssse3, -mno-sse41 and -mno-sse42
159# (-mfpmath= is not supported)
160#
161.if ${MACHINE_CPUARCH} == "amd64"
162CFLAGS.clang+=	-mno-aes -mno-avx
163CFLAGS+=	-mcmodel=kernel -mno-red-zone -mno-mmx -mno-sse -msoft-float \
164		-fno-asynchronous-unwind-tables
165INLINE_LIMIT?=	8000
166.endif
167
168#
169# For PowerPC we tell gcc to use floating point emulation.  This avoids using
170# floating point registers for integer operations which it has a tendency to do.
171# Also explicitly disable Altivec instructions inside the kernel.
172#
173.if ${MACHINE_CPUARCH} == "powerpc"
174CFLAGS+=	-mno-altivec -msoft-float
175INLINE_LIMIT?=	15000
176.endif
177
178.if ${MACHINE_ARCH} == "powerpcspe"
179CFLAGS.gcc+=	-mno-spe
180.endif
181
182#
183# Use dot symbols (or, better, the V2 ELF ABI) on powerpc64 to make
184# DDB happy. ELFv2, if available, has some other efficiency benefits.
185#
186.if ${MACHINE_ARCH} == "powerpc64"
187.if ${COMPILER_VERSION} >= 40900
188CFLAGS.gcc+=	-mabi=elfv2
189.else
190CFLAGS.gcc+=	-mcall-aixdesc
191.endif
192CFLAGS.clang+=	-mabi=elfv2
193.endif
194
195#
196# For MIPS we also tell gcc to use floating point emulation
197#
198.if ${MACHINE_CPUARCH} == "mips"
199CFLAGS+=	-msoft-float
200INLINE_LIMIT?=	8000
201.endif
202
203#
204# GCC 3.0 and above like to do certain optimizations based on the
205# assumption that the program is linked against libc.  Stop this.
206#
207CFLAGS+=	-ffreestanding
208
209#
210# The C standard leaves signed integer overflow behavior undefined.
211# gcc and clang opimizers take advantage of this.  The kernel makes
212# use of signed integer wraparound mechanics so we need the compiler
213# to treat it as a wraparound and not take shortcuts.
214#
215CFLAGS+=	-fwrapv
216
217#
218# GCC SSP support
219#
220.if ${MK_SSP} != "no" && \
221    ${MACHINE_CPUARCH} != "arm" && ${MACHINE_CPUARCH} != "mips"
222CFLAGS+=	-fstack-protector
223.endif
224
225#
226# Retpoline speculative execution vulnerability mitigation (CVE-2017-5715)
227#
228.if defined(COMPILER_FEATURES) && ${COMPILER_FEATURES:Mretpoline} != "" && \
229    ${MK_KERNEL_RETPOLINE} != "no"
230CFLAGS+=	-mretpoline
231.endif
232
233#
234# Add -gdwarf-2 when compiling -g. The default starting in clang v3.4
235# and gcc 4.8 is to generate DWARF version 4. However, our tools don't
236# cope well with DWARF 4, so force it to genereate DWARF2, which they
237# understand. Do this unconditionally as it is harmless when not needed,
238# but critical for these newer versions.
239#
240.if ${CFLAGS:M-g} != "" && ${CFLAGS:M-gdwarf*} == ""
241CFLAGS+=	-gdwarf-2
242.endif
243
244CFLAGS+= ${CWARNFLAGS:M*} ${CWARNFLAGS.${.IMPSRC:T}}
245CFLAGS+= ${CFLAGS.${COMPILER_TYPE}} ${CFLAGS.${.IMPSRC:T}}
246
247# Tell bmake not to mistake standard targets for things to be searched for
248# or expect to ever be up-to-date.
249PHONY_NOTMAIN = afterdepend afterinstall all beforedepend beforeinstall \
250		beforelinking build build-tools buildfiles buildincludes \
251		checkdpadd clean cleandepend cleandir cleanobj configure \
252		depend distclean distribute exe \
253		html includes install installfiles installincludes \
254		obj objlink objs objwarn \
255		realinstall regress \
256		tags whereobj
257
258.PHONY: ${PHONY_NOTMAIN}
259.NOTMAIN: ${PHONY_NOTMAIN}
260
261CSTD=		c99
262
263.if ${CSTD} == "k&r"
264CFLAGS+=        -traditional
265.elif ${CSTD} == "c89" || ${CSTD} == "c90"
266CFLAGS+=        -std=iso9899:1990
267.elif ${CSTD} == "c94" || ${CSTD} == "c95"
268CFLAGS+=        -std=iso9899:199409
269.elif ${CSTD} == "c99"
270CFLAGS+=        -std=iso9899:1999
271.else # CSTD
272CFLAGS+=        -std=${CSTD}
273.endif # CSTD
274
275# Set target-specific linker emulation name.
276LD_EMULATION_aarch64=aarch64elf
277LD_EMULATION_amd64=elf_x86_64_fbsd
278LD_EMULATION_arm=armelf_fbsd
279LD_EMULATION_armv6=armelf_fbsd
280LD_EMULATION_armv7=armelf_fbsd
281LD_EMULATION_i386=elf_i386_fbsd
282LD_EMULATION_mips= elf32btsmip_fbsd
283LD_EMULATION_mipshf= elf32btsmip_fbsd
284LD_EMULATION_mips64= elf64btsmip_fbsd
285LD_EMULATION_mips64hf= elf64btsmip_fbsd
286LD_EMULATION_mipsel= elf32ltsmip_fbsd
287LD_EMULATION_mipselhf= elf32ltsmip_fbsd
288LD_EMULATION_mips64el= elf64ltsmip_fbsd
289LD_EMULATION_mips64elhf= elf64ltsmip_fbsd
290LD_EMULATION_mipsn32= elf32btsmipn32_fbsd
291LD_EMULATION_mipsn32el= elf32btsmipn32_fbsd   # I don't think this is a thing that works
292LD_EMULATION_powerpc= elf32ppc_fbsd
293LD_EMULATION_powerpcspe= elf32ppc_fbsd
294LD_EMULATION_powerpc64= elf64ppc_fbsd
295LD_EMULATION_riscv64= elf64lriscv
296LD_EMULATION_sparc64= elf64_sparc_fbsd
297LD_EMULATION=${LD_EMULATION_${MACHINE_ARCH}}
298