diff --git a/sys/amd64/linux/linux_support.s b/sys/amd64/linux/linux_support.S
rename from sys/amd64/linux/linux_support.s
rename to sys/amd64/linux/linux_support.S
diff --git a/sys/amd64/linux32/linux32_support.s b/sys/amd64/linux32/linux32_support.S
rename from sys/amd64/linux32/linux32_support.s
rename to sys/amd64/linux32/linux32_support.S
diff --git a/sys/arm/arm/setstack.s b/sys/arm/arm/setstack.S
rename from sys/arm/arm/setstack.s
rename to sys/arm/arm/setstack.S
diff --git a/sys/arm64/linux/linux_support.s b/sys/arm64/linux/linux_support.S
rename from sys/arm64/linux/linux_support.s
rename to sys/arm64/linux/linux_support.S
diff --git a/sys/conf/files.arm b/sys/conf/files.arm
--- a/sys/conf/files.arm
+++ b/sys/conf/files.arm
@@ -62,7 +62,7 @@
 arm/arm/ptrace_machdep.c	standard
 arm/arm/sc_machdep.c		optional	sc
 arm/arm/setcpsr.S		standard
-arm/arm/setstack.s		standard
+arm/arm/setstack.S		standard
 arm/arm/stack_machdep.c		optional	ddb | stack
 arm/arm/stdatomic.c		standard \
 	compile-with "${NORMAL_C:N-Wmissing-prototypes}"
diff --git a/sys/conf/files.i386 b/sys/conf/files.i386
--- a/sys/conf/files.i386
+++ b/sys/conf/files.i386
@@ -94,9 +94,9 @@
 #
 i386/bios/smapi.c		optional smapi
 i386/bios/smapi_bios.S		optional smapi
-#i386/i386/apic_vector.s		optional apic
+#i386/i386/apic_vector.S		optional apic
 i386/i386/bios.c		standard
-i386/i386/bioscall.s		standard
+i386/i386/bioscall.S		standard
 i386/i386/bpf_jit_machdep.c	optional bpf_jitter
 i386/i386/copyout.c		standard
 i386/i386/db_disasm.c		optional ddb
@@ -105,14 +105,14 @@
 i386/i386/exec_machdep.c	standard
 i386/i386/elan-mmcr.c		optional cpu_elan | cpu_soekris
 i386/i386/elf_machdep.c		standard
-i386/i386/exception.s		standard
+i386/i386/exception.S		standard
 i386/i386/gdb_machdep.c		optional gdb
 i386/i386/geode.c		optional cpu_geode
 i386/i386/in_cksum_machdep.c	optional inet | inet6
 i386/i386/initcpu.c		standard
 i386/i386/io.c			optional io
 i386/i386/k6_mem.c		optional mem
-i386/i386/locore.s		standard	no-obj
+i386/i386/locore.S		standard	no-obj
 i386/i386/longrun.c		optional cpu_enable_longrun
 i386/i386/machdep.c		standard
 i386/i386/mem.c			optional mem
@@ -121,16 +121,16 @@
 i386/i386/minidump_machdep_nopae.c	standard
 i386/i386/mp_clock.c		optional smp
 i386/i386/mp_machdep.c		optional smp
-i386/i386/mpboot.s		optional smp
+i386/i386/mpboot.S		optional smp
 i386/i386/npx.c			standard
 i386/i386/perfmon.c		optional perfmon
 i386/i386/pmap_base.c		standard
 i386/i386/pmap_nopae.c		standard
 i386/i386/pmap_pae.c		standard
 i386/i386/ptrace_machdep.c	standard
-i386/i386/sigtramp.s		standard
-i386/i386/support.s		standard
-i386/i386/swtch.s		standard
+i386/i386/sigtramp.S		standard
+i386/i386/support.S		standard
+i386/i386/swtch.S		standard
 i386/i386/sys_machdep.c		standard
 i386/i386/trap.c		standard
 i386/i386/uio_machdep.c		standard
diff --git a/sys/i386/i386/apic_vector.s b/sys/i386/i386/apic_vector.S
rename from sys/i386/i386/apic_vector.s
rename to sys/i386/i386/apic_vector.S
diff --git a/sys/i386/i386/atpic_vector.s b/sys/i386/i386/atpic_vector.S
rename from sys/i386/i386/atpic_vector.s
rename to sys/i386/i386/atpic_vector.S
diff --git a/sys/i386/i386/bioscall.s b/sys/i386/i386/bioscall.S
rename from sys/i386/i386/bioscall.s
rename to sys/i386/i386/bioscall.S
diff --git a/sys/i386/i386/copyout_fast.s b/sys/i386/i386/copyout_fast.S
rename from sys/i386/i386/copyout_fast.s
rename to sys/i386/i386/copyout_fast.S
diff --git a/sys/i386/i386/exception.s b/sys/i386/i386/exception.S
rename from sys/i386/i386/exception.s
rename to sys/i386/i386/exception.S
--- a/sys/i386/i386/exception.s
+++ b/sys/i386/i386/exception.S
@@ -438,7 +438,7 @@
 	SUPERALIGN_TEXT
 
 #ifdef DEV_ATPIC
-#include <i386/i386/atpic_vector.s>
+#include <i386/i386/atpic_vector.S>
 #endif
 
 #if defined(DEV_APIC) && defined(DEV_ATPIC)
@@ -449,7 +449,7 @@
 #endif
 
 #ifdef DEV_APIC
-#include <i386/i386/apic_vector.s>
+#include <i386/i386/apic_vector.S>
 #endif
 
 #ifdef HYPERV
@@ -464,11 +464,11 @@
 	.p2align 4
 	.text
 	SUPERALIGN_TEXT
-#include <i386/i386/vm86bios.s>
+#include <i386/i386/vm86bios.S>
 
 	.text
 
-#include <i386/i386/copyout_fast.s>
+#include <i386/i386/copyout_fast.S>
 
 /*
  * void doreti(struct trapframe)
diff --git a/sys/i386/i386/locore.s b/sys/i386/i386/locore.S
rename from sys/i386/i386/locore.s
rename to sys/i386/i386/locore.S
diff --git a/sys/i386/i386/mpboot.s b/sys/i386/i386/mpboot.S
rename from sys/i386/i386/mpboot.s
rename to sys/i386/i386/mpboot.S
diff --git a/sys/i386/i386/sigtramp.s b/sys/i386/i386/sigtramp.S
rename from sys/i386/i386/sigtramp.s
rename to sys/i386/i386/sigtramp.S
diff --git a/sys/i386/i386/support.s b/sys/i386/i386/support.S
rename from sys/i386/i386/support.s
rename to sys/i386/i386/support.S
diff --git a/sys/i386/i386/swtch.s b/sys/i386/i386/swtch.S
rename from sys/i386/i386/swtch.s
rename to sys/i386/i386/swtch.S
diff --git a/sys/i386/i386/vm86bios.s b/sys/i386/i386/vm86bios.S
rename from sys/i386/i386/vm86bios.s
rename to sys/i386/i386/vm86bios.S
diff --git a/sys/modules/linux/Makefile b/sys/modules/linux/Makefile
--- a/sys/modules/linux/Makefile
+++ b/sys/modules/linux/Makefile
@@ -46,7 +46,7 @@
 VDSODEPS=linux_vdso_gettc_x86.inc
 .endif
 .if ${MACHINE_CPUARCH} == "amd64"
-SRCS+=	linux${SFX}_support.s
+SRCS+=	linux${SFX}_support.S
 SRCS+=	linux_elf32.c
 .else
 SRCS+=	linux_copyout.c
diff --git a/sys/modules/linux64/Makefile b/sys/modules/linux64/Makefile
--- a/sys/modules/linux64/Makefile
+++ b/sys/modules/linux64/Makefile
@@ -37,7 +37,7 @@
 	bus_if.h \
 	device_if.h \
 	vnode_if.h \
-	linux_support.s
+	linux_support.S
 .if ${MACHINE_CPUARCH} == "amd64"
 SRCS+=	linux_dummy_x86.c
 .endif