Index: head/sys/conf/kern.mk
===================================================================
--- head/sys/conf/kern.mk
+++ head/sys/conf/kern.mk
@@ -203,7 +203,7 @@
 # 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
 
 #
@@ -212,6 +212,14 @@
 .if ${MK_SSP} != "no" && \
     ${MACHINE_CPUARCH} != "arm" && ${MACHINE_CPUARCH} != "mips"
 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
 
 #
Index: head/sys/conf/kern.opts.mk
===================================================================
--- head/sys/conf/kern.opts.mk
+++ head/sys/conf/kern.opts.mk
@@ -47,6 +47,7 @@
 
 __DEFAULT_NO_OPTIONS = \
     EXTRA_TCP_STACKS \
+    KERNEL_RETPOLINE \
     NAND \
     OFED \
     RATELIMIT \
@@ -83,6 +84,11 @@
 # for them.
 .if ${MACHINE} != "i386" && ${MACHINE} != "amd64"
 BROKEN_OPTIONS+= OFED
+.endif
+
+# Things that don't work based on toolchain support.
+.if ${MACHINE} != "amd64"
+BROKEN_OPTIONS+= KERNEL_RETPOLINE
 .endif
 
 # expanded inline from bsd.mkopt.mk to avoid share/mk dependency
Index: head/tools/build/options/WITHOUT_KERNEL_RETPOLINE
===================================================================
--- head/tools/build/options/WITHOUT_KERNEL_RETPOLINE
+++ head/tools/build/options/WITHOUT_KERNEL_RETPOLINE
@@ -0,0 +1,3 @@
+.\" $FreeBSD$
+Set to disable the "retpoline" mitigation for CVE-2017-5715 in the kernel
+build.
Index: head/tools/build/options/WITH_KERNEL_RETPOLINE
===================================================================
--- head/tools/build/options/WITH_KERNEL_RETPOLINE
+++ head/tools/build/options/WITH_KERNEL_RETPOLINE
@@ -0,0 +1,3 @@
+.\" $FreeBSD$
+Set to enable the "retpoline" mitigation for CVE-2017-5715 in the kernel
+build.