diff --git a/sys/conf/kern.mk b/sys/conf/kern.mk
index 6cc22a44f51e..38d0664538ea 100644
--- a/sys/conf/kern.mk
+++ b/sys/conf/kern.mk
@@ -1,328 +1,330 @@
 
 #
 # Warning flags for compiling the kernel and components of the kernel:
 #
 CWARNFLAGS?=	-Wall -Wstrict-prototypes \
 		-Wmissing-prototypes -Wpointer-arith -Wcast-qual \
 		-Wundef -Wno-pointer-sign ${FORMAT_EXTENSIONS} \
 		-Wmissing-include-dirs -fdiagnostics-show-option \
 		-Wno-unknown-pragmas \
 		${CWARNEXTRA}
 #
 # The following flags are next up for working on:
 #	-Wextra
 
 # Disable a few warnings for clang, since there are several places in the
 # kernel where fixing them is more trouble than it is worth, or where there is
 # a false positive.
 .if ${COMPILER_TYPE} == "clang"
 NO_WCONSTANT_CONVERSION=	-Wno-error=constant-conversion
 NO_WSHIFT_COUNT_NEGATIVE=	-Wno-shift-count-negative
 NO_WSHIFT_COUNT_OVERFLOW=	-Wno-shift-count-overflow
 NO_WSELF_ASSIGN=		-Wno-self-assign
 NO_WUNNEEDED_INTERNAL_DECL=	-Wno-error=unneeded-internal-declaration
 NO_WSOMETIMES_UNINITIALIZED=	-Wno-error=sometimes-uninitialized
 NO_WCAST_QUAL=			-Wno-error=cast-qual
 NO_WTAUTOLOGICAL_POINTER_COMPARE= -Wno-tautological-pointer-compare
 .if ${COMPILER_VERSION} >= 100000
 NO_WMISLEADING_INDENTATION=	-Wno-misleading-indentation
 .endif
 .if ${COMPILER_VERSION} >= 130000
 NO_WUNUSED_BUT_SET_VARIABLE=	-Wno-unused-but-set-variable
 .endif
 .if ${COMPILER_VERSION} >= 140000
 NO_WBITWISE_INSTEAD_OF_LOGICAL=	-Wno-bitwise-instead-of-logical
 .endif
 .if ${COMPILER_VERSION} >= 150000
 NO_WSTRICT_PROTOTYPES=		-Wno-strict-prototypes
 NO_WDEPRECATED_NON_PROTOTYPE=	-Wno-deprecated-non-prototype
 .endif
 # Several other warnings which might be useful in some cases, but not severe
 # enough to error out the whole kernel build.  Display them anyway, so there is
 # some incentive to fix them eventually.
 CWARNEXTRA?=	-Wno-error=tautological-compare -Wno-error=empty-body \
 		-Wno-error=parentheses-equality -Wno-error=unused-function \
 		-Wno-error=pointer-sign
 CWARNEXTRA+=	-Wno-error=shift-negative-value
 CWARNEXTRA+=	-Wno-address-of-packed-member
 .endif	# clang
 
 .if ${COMPILER_TYPE} == "gcc"
 # Catch-all for all the things that are in our tree, but for which we're
 # not yet ready for this compiler.
 NO_WUNUSED_BUT_SET_VARIABLE=-Wno-unused-but-set-variable
 CWARNEXTRA?=	-Wno-error=address				\
 		-Wno-error=aggressive-loop-optimizations	\
 		-Wno-error=array-bounds				\
 		-Wno-error=attributes				\
 		-Wno-error=cast-qual				\
 		-Wno-error=enum-compare				\
 		-Wno-error=maybe-uninitialized			\
 		-Wno-error=misleading-indentation		\
 		-Wno-error=nonnull-compare			\
 		-Wno-error=overflow				\
 		-Wno-error=sequence-point			\
 		-Wno-error=shift-overflow			\
 		-Wno-error=tautological-compare			\
 		-Wno-error=unused-function
 .if ${COMPILER_VERSION} >= 70100
 CWARNEXTRA+=	-Wno-error=stringop-overflow
 .endif
 .if ${COMPILER_VERSION} >= 70200
 CWARNEXTRA+=	-Wno-error=memset-elt-size
 .endif
 .if ${COMPILER_VERSION} >= 80000
 CWARNEXTRA+=	-Wno-error=packed-not-aligned
 .endif
 .if ${COMPILER_VERSION} >= 90100
 CWARNEXTRA+=	-Wno-address-of-packed-member			\
 		-Wno-alloc-size-larger-than			\
 		-Wno-error=alloca-larger-than=
 .if ${COMPILER_VERSION} >= 120100
 CWARNEXTRA+=	-Wno-error=nonnull				\
 		-Wno-dangling-pointer				\
 		-Wno-zero-length-bounds
 NO_WINFINITE_RECURSION=	-Wno-infinite-recursion
 NO_WSTRINGOP_OVERREAD=	-Wno-stringop-overread
 .endif
 .endif
 
 # GCC produces false positives for functions that switch on an
 # enum (GCC bug 87950)
 CWARNFLAGS+=	-Wno-return-type
 .endif	# gcc
 
 # This warning is utter nonsense
 CWARNFLAGS+=	-Wno-format-zero-length
 
 # External compilers may not support our format extensions.  Allow them
 # to be disabled.  WARNING: format checking is disabled in this case.
 .if ${MK_FORMAT_EXTENSIONS} == "no"
 FORMAT_EXTENSIONS=	-Wno-format
 .elif ${COMPILER_TYPE} == "clang" || \
     (${COMPILER_TYPE} == "gcc" && ${COMPILER_VERSION} >= 120100)
 FORMAT_EXTENSIONS=	-D__printf__=__freebsd_kprintf__
 .else
 FORMAT_EXTENSIONS=	-fformat-extensions
 .endif
 
 #
 # On i386, do not align the stack to 16-byte boundaries.  Otherwise GCC 2.95
 # and above adds code to the entry and exit point of every function to align the
 # stack to 16-byte boundaries -- thus wasting approximately 12 bytes of stack
 # per function call.  While the 16-byte alignment may benefit micro benchmarks,
 # it is probably an overall loss as it makes the code bigger (less efficient
 # use of code cache tag lines) and uses more stack (less efficient use of data
 # cache tag lines).  Explicitly prohibit the use of FPU, SSE and other SIMD
 # operations inside the kernel itself.  These operations are exclusively
 # reserved for user applications.
 #
 # gcc:
 # Setting -mno-mmx implies -mno-3dnow
 # Setting -mno-sse implies -mno-sse2, -mno-sse3 and -mno-ssse3
 #
 # clang:
 # Setting -mno-mmx implies -mno-3dnow and -mno-3dnowa
 # Setting -mno-sse implies -mno-sse2, -mno-sse3, -mno-ssse3, -mno-sse41 and -mno-sse42
 #
 .if ${MACHINE_CPUARCH} == "i386"
 CFLAGS.gcc+=	-mpreferred-stack-boundary=2
 CFLAGS.clang+=	-mno-aes -mno-avx
 CFLAGS+=	-mno-mmx -mno-sse -msoft-float
 INLINE_LIMIT?=	8000
 .endif
 
 .if ${MACHINE_CPUARCH} == "arm"
 INLINE_LIMIT?=	8000
 .endif
 
 .if ${MACHINE_CPUARCH} == "aarch64"
 # We generally don't want fpu instructions in the kernel.
 CFLAGS += -mgeneral-regs-only
 # Reserve x18 for pcpu data
 CFLAGS += -ffixed-x18
+# TODO: support outline atomics
+CFLAGS += -mno-outline-atomics
 INLINE_LIMIT?=	8000
 .endif
 
 #
 # For RISC-V we specify the soft-float ABI (lp64) to avoid the use of floating
 # point registers within the kernel. However, we include the F and D extensions
 # in -march so we can have limited floating point support in context switching
 # code. This is different than userland where we use a hard-float ABI (lp64d).
 #
 # We also specify the "medium" code model, which generates code suitable for a
 # 2GiB addressing range located at any offset, allowing modules to be located
 # anywhere in the 64-bit address space.  Note that clang and GCC refer to this
 # code model as "medium" and "medany" respectively.
 #
 .if ${MACHINE_CPUARCH} == "riscv"
 CFLAGS+=	-march=rv64imafdc
 CFLAGS+=	-mabi=lp64
 CFLAGS.clang+=	-mcmodel=medium
 CFLAGS.gcc+=	-mcmodel=medany
 INLINE_LIMIT?=	8000
 
 .if ${LINKER_FEATURES:Mriscv-relaxations} == ""
 CFLAGS+=	-mno-relax
 .endif
 .endif
 
 #
 # For AMD64, we explicitly prohibit the use of FPU, SSE and other SIMD
 # operations inside the kernel itself.  These operations are exclusively
 # reserved for user applications.
 #
 # gcc:
 # Setting -mno-mmx implies -mno-3dnow
 # Setting -mno-sse implies -mno-sse2, -mno-sse3, -mno-ssse3 and -mfpmath=387
 #
 # clang:
 # Setting -mno-mmx implies -mno-3dnow and -mno-3dnowa
 # Setting -mno-sse implies -mno-sse2, -mno-sse3, -mno-ssse3, -mno-sse41 and -mno-sse42
 # (-mfpmath= is not supported)
 #
 .if ${MACHINE_CPUARCH} == "amd64"
 CFLAGS.clang+=	-mno-aes -mno-avx
 CFLAGS+=	-mcmodel=kernel -mno-red-zone -mno-mmx -mno-sse -msoft-float \
 		-fno-asynchronous-unwind-tables
 INLINE_LIMIT?=	8000
 .endif
 
 #
 # For PowerPC we tell gcc to use floating point emulation.  This avoids using
 # floating point registers for integer operations which it has a tendency to do.
 # Also explicitly disable Altivec instructions inside the kernel.
 #
 .if ${MACHINE_CPUARCH} == "powerpc"
 CFLAGS+=	-mno-altivec -msoft-float
 INLINE_LIMIT?=	15000
 .endif
 
 .if ${MACHINE_ARCH} == "powerpcspe"
 CFLAGS.gcc+=	-mno-spe
 .endif
 
 #
 # Use dot symbols (or, better, the V2 ELF ABI) on powerpc64 to make
 # DDB happy. ELFv2, if available, has some other efficiency benefits.
 #
 .if ${MACHINE_ARCH:Mpowerpc64*} != "" && \
     ${COMPILER_TYPE} == "clang" && ${COMPILER_VERSION} < 160000
 CFLAGS+=	-mabi=elfv2
 .endif
 
 #
 # GCC 3.0 and above like to do certain optimizations based on the
 # assumption that the program is linked against libc.  Stop this.
 #
 CFLAGS+=	-ffreestanding
 
 #
 # The C standard leaves signed integer overflow behavior undefined.
 # gcc and clang opimizers take advantage of this.  The kernel makes
 # use of signed integer wraparound mechanics so we need the compiler
 # to treat it as a wraparound and not take shortcuts.
 #
 CFLAGS+=	-fwrapv
 
 #
 # GCC SSP support
 #
 .if ${MK_SSP} != "no"
 CFLAGS+=	-fstack-protector
 .endif
 
 #
 # Retpoline speculative execution vulnerability mitigation (CVE-2017-5715)
 #
 .if defined(COMPILER_FEATURES) && ${COMPILER_FEATURES:Mretpoline} != "" && \
     ${MK_KERNEL_RETPOLINE} != "no"
 CFLAGS+=	-mretpoline
 .endif
 
 #
 # Initialize stack variables on function entry
 #
 .if ${MK_INIT_ALL_ZERO} == "yes"
 .if ${COMPILER_FEATURES:Minit-all}
 CFLAGS+= -ftrivial-auto-var-init=zero
 .if ${COMPILER_TYPE} == "clang" && ${COMPILER_VERSION} < 160000
 CFLAGS+= -enable-trivial-auto-var-init-zero-knowing-it-will-be-removed-from-clang
 .endif
 .else
 .warning InitAll (zeros) requested but not supported by compiler
 .endif
 .elif ${MK_INIT_ALL_PATTERN} == "yes"
 .if ${COMPILER_FEATURES:Minit-all}
 CFLAGS+= -ftrivial-auto-var-init=pattern
 .else
 .warning InitAll (pattern) requested but not support by compiler
 .endif
 .endif
 
 CFLAGS+= ${CWARNFLAGS:M*} ${CWARNFLAGS.${.IMPSRC:T}}
 CFLAGS+= ${CWARNFLAGS.${COMPILER_TYPE}}
 CFLAGS+= ${CFLAGS.${COMPILER_TYPE}} ${CFLAGS.${.IMPSRC:T}}
 
 # Tell bmake not to mistake standard targets for things to be searched for
 # or expect to ever be up-to-date.
 PHONY_NOTMAIN = afterdepend afterinstall all beforedepend beforeinstall \
 		beforelinking build build-tools buildfiles buildincludes \
 		checkdpadd clean cleandepend cleandir cleanobj configure \
 		depend distclean distribute exe \
 		html includes install installfiles installincludes \
 		obj objlink objs objwarn \
 		realinstall regress \
 		tags whereobj
 
 .PHONY: ${PHONY_NOTMAIN}
 .NOTMAIN: ${PHONY_NOTMAIN}
 
 CSTD=		gnu99
 
 .if ${CSTD} == "k&r"
 CFLAGS+=        -traditional
 .elif ${CSTD} == "c89" || ${CSTD} == "c90"
 CFLAGS+=        -std=iso9899:1990
 .elif ${CSTD} == "c94" || ${CSTD} == "c95"
 CFLAGS+=        -std=iso9899:199409
 .elif ${CSTD} == "c99"
 CFLAGS+=        -std=iso9899:1999
 .else # CSTD
 CFLAGS+=        -std=${CSTD}
 .endif # CSTD
 
 # Please keep this if in sync with bsd.sys.mk
 .if ${LD} != "ld" && (${CC:[1]:H} != ${LD:[1]:H} || ${LD:[1]:T} != "ld")
 # Add -fuse-ld=${LD} if $LD is in a different directory or not called "ld".
 .if ${COMPILER_TYPE} == "clang"
 # Note: Clang does not like relative paths for ld so we map ld.lld -> lld.
 .if ${COMPILER_VERSION} >= 120000
 CCLDFLAGS+=	--ld-path=${LD:[1]:S/^ld.//1W}
 .else
 CCLDFLAGS+=	-fuse-ld=${LD:[1]:S/^ld.//1W}
 .endif
 .else
 # GCC does not support an absolute path for -fuse-ld so we just print this
 # warning instead and let the user add the required symlinks.
 # However, we can avoid this warning if -B is set appropriately (e.g. for
 # CROSS_TOOLCHAIN=...-gcc).
 .if !(${LD:[1]:T} == "ld" && ${CC:tw:M-B${LD:[1]:H}/})
 .warning LD (${LD}) is not the default linker for ${CC} but -fuse-ld= is not supported
 .endif
 .endif
 .endif
 
 # Set target-specific linker emulation name.
 LD_EMULATION_aarch64=aarch64elf
 LD_EMULATION_amd64=elf_x86_64_fbsd
 LD_EMULATION_arm=armelf_fbsd
 LD_EMULATION_armv6=armelf_fbsd
 LD_EMULATION_armv7=armelf_fbsd
 LD_EMULATION_i386=elf_i386_fbsd
 LD_EMULATION_powerpc= elf32ppc_fbsd
 LD_EMULATION_powerpcspe= elf32ppc_fbsd
 LD_EMULATION_powerpc64= elf64ppc_fbsd
 LD_EMULATION_powerpc64le= elf64lppc_fbsd
 LD_EMULATION_riscv64= elf64lriscv
 LD_EMULATION=${LD_EMULATION_${MACHINE_ARCH}}