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