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.if ${COMPILER_VERSION} >= 210000 41NO_WDEFAULT_CONST_INIT_FIELD_UNSAFE= -Wno-default-const-init-field-unsafe 42.endif 43# Several other warnings which might be useful in some cases, but not severe 44# enough to error out the whole kernel build. Display them anyway, so there is 45# some incentive to fix them eventually. 46CWARNEXTRA?= -Wno-error=tautological-compare -Wno-error=empty-body \ 47 -Wno-error=parentheses-equality -Wno-error=unused-function \ 48 -Wno-error=pointer-sign 49CWARNEXTRA+= -Wno-error=shift-negative-value 50CWARNEXTRA+= -Wno-address-of-packed-member 51.if ${COMPILER_VERSION} >= 230000 52CWARNEXTRA+= -Wno-error=unused-but-set-global 53.endif 54.endif # clang 55 56.if ${COMPILER_TYPE} == "gcc" 57# Catch-all for all the things that are in our tree, but for which we're 58# not yet ready for this compiler. 59NO_WUNUSED_BUT_SET_VARIABLE=-Wno-unused-but-set-variable 60CWARNEXTRA?= -Wno-error=address \ 61 -Wno-error=aggressive-loop-optimizations \ 62 -Wno-error=array-bounds \ 63 -Wno-error=attributes \ 64 -Wno-error=cast-qual \ 65 -Wno-error=enum-compare \ 66 -Wno-error=maybe-uninitialized \ 67 -Wno-error=misleading-indentation \ 68 -Wno-error=nonnull-compare \ 69 -Wno-error=overflow \ 70 -Wno-error=sequence-point \ 71 -Wno-error=shift-overflow \ 72 -Wno-error=tautological-compare \ 73 -Wno-error=unused-function 74.if ${COMPILER_VERSION} >= 70100 75CWARNEXTRA+= -Wno-error=stringop-overflow 76.endif 77.if ${COMPILER_VERSION} >= 70200 78CWARNEXTRA+= -Wno-error=memset-elt-size 79.endif 80.if ${COMPILER_VERSION} >= 80000 81CWARNEXTRA+= -Wno-error=packed-not-aligned 82.endif 83.if ${COMPILER_VERSION} >= 90100 84CWARNEXTRA+= -Wno-address-of-packed-member \ 85 -Wno-alloc-size-larger-than \ 86 -Wno-error=alloca-larger-than= 87.if ${COMPILER_VERSION} >= 120100 88CWARNEXTRA+= -Wno-error=nonnull \ 89 -Wno-dangling-pointer \ 90 -Wno-zero-length-bounds 91NO_WINFINITE_RECURSION= -Wno-infinite-recursion 92NO_WSTRINGOP_OVERREAD= -Wno-stringop-overread 93.endif 94.endif 95 96# GCC produces false positives for functions that switch on an 97# enum (GCC bug 87950) 98CWARNFLAGS+= -Wno-return-type 99.endif # gcc 100 101# This warning is utter nonsense 102CWARNFLAGS+= -Wno-format-zero-length 103 104# External compilers may not support our format extensions. Allow them 105# to be disabled. WARNING: format checking is disabled in this case. 106.if ${MK_FORMAT_EXTENSIONS} == "no" 107FORMAT_EXTENSIONS= -Wno-format 108.elif ${COMPILER_TYPE} == "clang" || \ 109 (${COMPILER_TYPE} == "gcc" && ${COMPILER_VERSION} >= 120100) 110FORMAT_EXTENSIONS= -D__printf__=__freebsd_kprintf__ 111.else 112FORMAT_EXTENSIONS= -fformat-extensions 113.endif 114 115# 116# On i386, do not align the stack to 16-byte boundaries. Otherwise GCC 2.95 117# and above adds code to the entry and exit point of every function to align the 118# stack to 16-byte boundaries -- thus wasting approximately 12 bytes of stack 119# per function call. While the 16-byte alignment may benefit micro benchmarks, 120# it is probably an overall loss as it makes the code bigger (less efficient 121# use of code cache tag lines) and uses more stack (less efficient use of data 122# cache tag lines). Explicitly prohibit the use of FPU, SSE and other SIMD 123# operations inside the kernel itself. These operations are exclusively 124# reserved for user applications. 125# 126# gcc: 127# Setting -mno-mmx implies -mno-3dnow 128# Setting -mno-sse implies -mno-sse2, -mno-sse3 and -mno-ssse3 129# 130# clang: 131# Setting -mno-mmx implies -mno-3dnow and -mno-3dnowa 132# Setting -mno-sse implies -mno-sse2, -mno-sse3, -mno-ssse3, -mno-sse41 and -mno-sse42 133# 134.if ${MACHINE_CPUARCH} == "i386" 135CFLAGS.gcc+= -mpreferred-stack-boundary=2 136CFLAGS.clang+= -mno-aes -mno-avx 137CFLAGS+= -mno-mmx -mno-sse -msoft-float 138INLINE_LIMIT?= 8000 139.endif 140 141.if ${MACHINE_CPUARCH} == "arm" 142INLINE_LIMIT?= 8000 143.endif 144 145.if ${MACHINE_CPUARCH} == "aarch64" 146# We generally don't want fpu instructions in the kernel. 147CFLAGS += -mgeneral-regs-only 148# Reserve x18 for pcpu data 149CFLAGS += -ffixed-x18 150# Build with BTI+PAC 151CFLAGS += -mbranch-protection=standard 152.if ${LINKER_FEATURES:Mbti-report} 153LDFLAGS += -Wl,-zbti-report=error 154.endif 155# TODO: support outline atomics 156CFLAGS += -mno-outline-atomics 157INLINE_LIMIT?= 8000 158.endif 159 160# 161# For RISC-V we specify the soft-float ABI (lp64) to avoid the use of floating 162# point registers within the kernel. However, we include the F and D extensions 163# in -march so we can have limited floating point support in context switching 164# code. This is different than userland where we use a hard-float ABI (lp64d). 165# 166# We also specify the "medium" code model, which generates code suitable for a 167# 2GiB addressing range located at any offset, allowing modules to be located 168# anywhere in the 64-bit address space. Note that clang and GCC refer to this 169# code model as "medium" and "medany" respectively. 170# 171.if ${MACHINE_CPUARCH} == "riscv" 172CFLAGS+= -march=rv64imafdch_zifencei_svinval 173CFLAGS+= -mabi=lp64 174CFLAGS.clang+= -mcmodel=medium 175CFLAGS.gcc+= -mcmodel=medany 176INLINE_LIMIT?= 8000 177 178.if ${LINKER_FEATURES:Mriscv-relaxations} == "" 179CFLAGS+= -mno-relax 180.endif 181.endif 182 183# 184# For AMD64, we explicitly prohibit the use of FPU, SSE and other SIMD 185# operations inside the kernel itself. These operations are exclusively 186# reserved for user applications. 187# 188# gcc: 189# Setting -mno-mmx implies -mno-3dnow 190# Setting -mno-sse implies -mno-sse2, -mno-sse3, -mno-ssse3 and -mfpmath=387 191# 192# clang: 193# Setting -mno-mmx implies -mno-3dnow and -mno-3dnowa 194# Setting -mno-sse implies -mno-sse2, -mno-sse3, -mno-ssse3, -mno-sse41 and -mno-sse42 195# (-mfpmath= is not supported) 196# 197.if ${MACHINE_CPUARCH} == "amd64" 198CFLAGS.clang+= -mno-aes -mno-avx 199CFLAGS+= -mcmodel=kernel -mno-red-zone -mno-mmx -mno-sse -msoft-float \ 200 -fno-asynchronous-unwind-tables 201INLINE_LIMIT?= 8000 202.endif 203 204# 205# For PowerPC we tell gcc to use floating point emulation. This avoids using 206# floating point registers for integer operations which it has a tendency to do. 207# Also explicitly disable Altivec instructions inside the kernel. 208# 209.if ${MACHINE_CPUARCH} == "powerpc" 210CFLAGS+= -mno-altivec -msoft-float 211INLINE_LIMIT?= 15000 212.endif 213 214# 215# Use dot symbols (or, better, the V2 ELF ABI) on powerpc64 to make 216# DDB happy. ELFv2, if available, has some other efficiency benefits. 217# 218.if ${MACHINE_ARCH:Mpowerpc64*} != "" && \ 219 ${COMPILER_TYPE} == "clang" && ${COMPILER_VERSION} < 160000 220CFLAGS+= -mabi=elfv2 221.endif 222 223# 224# GCC 3.0 and above like to do certain optimizations based on the 225# assumption that the program is linked against libc. Stop this. 226# 227CFLAGS+= -ffreestanding 228 229# 230# The C standard leaves signed integer overflow behavior undefined. 231# gcc and clang opimizers take advantage of this. The kernel makes 232# use of signed integer wraparound mechanics so we need the compiler 233# to treat it as a wraparound and not take shortcuts. 234# 235CFLAGS+= -fwrapv 236 237# 238# Stack Smashing Protection (SSP) support 239# 240.if ${MK_SSP} != "no" 241CFLAGS+= -fstack-protector-strong 242.endif 243 244# 245# Retpoline speculative execution vulnerability mitigation (CVE-2017-5715) 246# 247.if defined(COMPILER_FEATURES) && ${COMPILER_FEATURES:Mretpoline} != "" && \ 248 ${MK_KERNEL_RETPOLINE} != "no" 249CFLAGS+= -mretpoline 250.endif 251 252# 253# Kernel Address SANitizer support 254# 255.if !empty(KASAN_ENABLED) 256SAN_CFLAGS+= -DSAN_NEEDS_INTERCEPTORS -DSAN_INTERCEPTOR_PREFIX=kasan \ 257 -fsanitize=kernel-address 258.if ${COMPILER_TYPE} == "clang" 259SAN_CFLAGS+= -mllvm -asan-stack=true \ 260 -mllvm -asan-instrument-dynamic-allocas=true \ 261 -mllvm -asan-globals=true \ 262 -mllvm -asan-use-after-scope=true \ 263 -mllvm -asan-instrumentation-with-call-threshold=0 \ 264 -mllvm -asan-instrument-byval=false 265.endif 266 267.if ${MACHINE_CPUARCH} == "aarch64" 268# KASAN/ARM64 TODO: -asan-mapping-offset is calculated from: 269# (VM_KERNEL_MIN_ADDRESS >> KASAN_SHADOW_SCALE_SHIFT) + $offset = KASAN_MIN_ADDRESS 270# 271# This is different than amd64, where we have a different 272# KASAN_MIN_ADDRESS, and this offset value should eventually be 273# upstreamed similar to: https://reviews.llvm.org/D98285 274# 275.if ${COMPILER_TYPE} == "clang" 276SAN_CFLAGS+= -mllvm -asan-mapping-offset=0xdfff208000000000 277.else 278SAN_CFLAGS+= -fasan-shadow-offset=0xdfff208000000000 279.endif 280.elif ${MACHINE_CPUARCH} == "amd64" && \ 281 ${COMPILER_TYPE} == "clang" && ${COMPILER_VERSION} >= 180000 282# Work around https://github.com/llvm/llvm-project/issues/87923, which leads to 283# an assertion failure compiling dtrace.c with asan enabled. 284SAN_CFLAGS+= -mllvm -asan-use-stack-safety=0 285.endif 286.endif # !empty(KASAN_ENABLED) 287 288# 289# Kernel Concurrency SANitizer support 290# 291.if !empty(KCSAN_ENABLED) 292SAN_CFLAGS+= -DSAN_NEEDS_INTERCEPTORS -DSAN_INTERCEPTOR_PREFIX=kcsan \ 293 -fsanitize=thread 294.endif 295 296# 297# Kernel Memory SANitizer support 298# 299.if !empty(KMSAN_ENABLED) 300# Disable -fno-sanitize-memory-param-retval until interceptors have been 301# updated to work properly with it. 302MSAN_CFLAGS+= -DSAN_NEEDS_INTERCEPTORS -DSAN_INTERCEPTOR_PREFIX=kmsan \ 303 -fsanitize=kernel-memory 304.if ${COMPILER_TYPE} == "clang" && ${COMPILER_VERSION} >= 160000 305MSAN_CFLAGS+= -fno-sanitize-memory-param-retval 306.endif 307SAN_CFLAGS+= ${MSAN_CFLAGS} 308.endif # !empty(KMSAN_ENABLED) 309 310# 311# Kernel Undefined Behavior SANitizer support 312# 313.if !empty(KUBSAN_ENABLED) 314SAN_CFLAGS+= -fsanitize=undefined 315.endif 316 317# 318# Generic Kernel Coverage support 319# 320.if !empty(COVERAGE_ENABLED) 321.if ${COMPILER_TYPE} == "clang" || \ 322 (${COMPILER_TYPE} == "gcc" && ${COMPILER_VERSION} >= 80100) 323SAN_CFLAGS+= -fsanitize-coverage=trace-pc,trace-cmp 324.else 325SAN_CFLAGS+= -fsanitize-coverage=trace-pc 326.endif 327.endif # !empty(COVERAGE_ENABLED) 328 329# Add the sanitizer C flags 330CFLAGS+= ${SAN_CFLAGS} 331 332# 333# Initialize stack variables on function entry 334# 335.if ${OPT_INIT_ALL} != "none" 336.if ${COMPILER_FEATURES:Minit-all} 337CFLAGS+= -ftrivial-auto-var-init=${OPT_INIT_ALL} 338.if ${OPT_INIT_ALL} == "zero" && ${COMPILER_TYPE} == "clang" && ${COMPILER_VERSION} < 160000 339CFLAGS+= -enable-trivial-auto-var-init-zero-knowing-it-will-be-removed-from-clang 340.endif 341.else 342.warning INIT_ALL (${OPT_INIT_ALL}) requested but not supported by compiler 343.endif 344.endif 345 346# 347# Some newer toolchains default to DWARF 5, which isn't supported by some build 348# tools yet. 349# 350.if (${CFLAGS:M-g} != "" || ${CFLAGS:M-g[0-3]} != "") && ${CFLAGS:M-gdwarf*} == "" 351CFLAGS+= -gdwarf-4 352.endif 353 354CFLAGS+= ${CWARNFLAGS:M*} ${CWARNFLAGS.${.IMPSRC:T}} 355CFLAGS+= ${CWARNFLAGS.${COMPILER_TYPE}} 356CFLAGS+= ${CFLAGS.${COMPILER_TYPE}} ${CFLAGS.${.IMPSRC:T}} 357 358# Tell bmake not to mistake standard targets for things to be searched for 359# or expect to ever be up-to-date. 360PHONY_NOTMAIN = afterdepend afterinstall all beforedepend beforeinstall \ 361 beforelinking build build-tools buildfiles buildincludes \ 362 checkdpadd clean cleandepend cleandir cleanobj configure \ 363 depend distclean distribute exe \ 364 html includes install installfiles installincludes \ 365 obj objlink objs objwarn \ 366 realinstall regress \ 367 tags whereobj 368 369.PHONY: ${PHONY_NOTMAIN} 370.NOTMAIN: ${PHONY_NOTMAIN} 371 372CSTD?= gnu17 373 374# c99/gnu99 is the minimum C standard version supported for kernel build 375.if ${CSTD} == "k&r" || ${CSTD} == "c89" || ${CSTD} == "c90" || \ 376 ${CSTD} == "c94" || ${CSTD} == "c95" 377.error "Only c99/gnu99 or later is supported" 378.else # CSTD 379CFLAGS+= -std=${CSTD} 380.endif # CSTD 381 382NOSAN_CFLAGS= ${CFLAGS:N-fsanitize*:N-fno-sanitize*:N-fasan-shadow-offset*} 383 384# Please keep this if in sync with bsd.sys.mk 385.if ${LD} != "ld" && (${CC:[1]:H} != ${LD:[1]:H} || ${LD:[1]:T} != "ld") 386# Add -fuse-ld=${LD} if $LD is in a different directory or not called "ld". 387.if ${COMPILER_TYPE} == "clang" 388# Note: Clang does not like relative paths for ld so we map ld.lld -> lld. 389.if ${COMPILER_VERSION} >= 120000 390CCLDFLAGS+= --ld-path=${LD:[1]:S/^ld.//1W} 391.else 392CCLDFLAGS+= -fuse-ld=${LD:[1]:S/^ld.//1W} 393.endif 394.else 395# GCC does not support an absolute path for -fuse-ld so we just print this 396# warning instead and let the user add the required symlinks. 397# However, we can avoid this warning if -B is set appropriately (e.g. for 398# CROSS_TOOLCHAIN=...-gcc). 399.if !(${LD:[1]:T} == "ld" && ${CC:tw:M-B${LD:[1]:H}/}) 400.warning LD (${LD}) is not the default linker for ${CC} but -fuse-ld= is not supported 401.endif 402.endif 403.endif 404 405# Set target-specific linker emulation name. 406LD_EMULATION_aarch64=aarch64elf 407LD_EMULATION_amd64=elf_x86_64_fbsd 408LD_EMULATION_arm=armelf_fbsd 409LD_EMULATION_armv7=armelf_fbsd 410LD_EMULATION_i386=elf_i386_fbsd 411LD_EMULATION_powerpc= elf32ppc_fbsd 412LD_EMULATION_powerpc64= elf64ppc_fbsd 413LD_EMULATION_powerpc64le= elf64lppc_fbsd 414LD_EMULATION_riscv64= elf64lriscv 415LD_EMULATION=${LD_EMULATION_${MACHINE_ARCH}} 416