Index: head/share/mk/bsd.compiler.mk
===================================================================
--- head/share/mk/bsd.compiler.mk
+++ head/share/mk/bsd.compiler.mk
@@ -24,6 +24,7 @@
 # - c++11:     supports full (or nearly full) C++11 programming environment.
 # - retpoline: supports the retpoline speculative execution vulnerability
 #              mitigation.
+# - init-all:  supports stack variable initialization.
 #
 # These variables with an X_ prefix will also be provided if XCC is set.
 #
@@ -214,7 +215,7 @@
 ${X_}COMPILER_FEATURES+=	c++17
 .endif
 .if ${${X_}COMPILER_TYPE} == "clang"
-${X_}COMPILER_FEATURES+=	retpoline
+${X_}COMPILER_FEATURES+=	retpoline init-all
 .endif
 
 .else
Index: head/share/mk/bsd.lib.mk
===================================================================
--- head/share/mk/bsd.lib.mk
+++ head/share/mk/bsd.lib.mk
@@ -85,6 +85,25 @@
 .endif
 .endif
 
+# Initialize stack variables on function entry
+.if ${MK_INIT_ALL_ZERO} == "yes"
+.if ${COMPILER_FEATURES:Minit-all}
+CFLAGS+= -ftrivial-auto-var-init=zero \
+    -enable-trivial-auto-var-init-zero-knowing-it-will-be-removed-from-clang
+CXXFLAGS+= -ftrivial-auto-var-init=zero \
+    -enable-trivial-auto-var-init-zero-knowing-it-will-be-removed-from-clang
+.else
+.warning InitAll (zeros) requested but not support by compiler
+.endif
+.elif ${MK_INIT_ALL_PATTERN} == "yes"
+.if ${COMPILER_FEATURES:Minit-all}
+CFLAGS+= -ftrivial-auto-var-init=pattern
+CXXFLAGS+= -ftrivial-auto-var-init=pattern
+.else
+.warning InitAll (pattern) requested but not support by compiler
+.endif
+.endif
+
 .if ${MK_DEBUG_FILES} != "no" && empty(DEBUG_FLAGS:M-g) && \
     empty(DEBUG_FLAGS:M-gdwarf*)
 CFLAGS+= ${DEBUG_FILES_CFLAGS}
Index: head/share/mk/bsd.opts.mk
===================================================================
--- head/share/mk/bsd.opts.mk
+++ head/share/mk/bsd.opts.mk
@@ -71,6 +71,8 @@
     BIND_NOW \
     CCACHE_BUILD \
     CTF \
+    INIT_ALL_PATTERN \
+    INIT_ALL_ZERO \
     INSTALL_AS_USER \
     PIE \
     RETPOLINE \
@@ -84,6 +86,10 @@
 
 
 .include <bsd.mkopt.mk>
+
+.if ${MK_INIT_ALL_PATTERN} == "yes" && ${MK_INIT_ALL_ZERO} == "yes"
+.error WITH_INIT_ALL_PATTERN and WITH_INIT_ALL_ZERO are mutually exclusive.
+.endif
 
 #
 # Supported NO_* options (if defined, MK_* will be forced to "no",
Index: head/share/mk/bsd.prog.mk
===================================================================
--- head/share/mk/bsd.prog.mk
+++ head/share/mk/bsd.prog.mk
@@ -60,6 +60,25 @@
 .endif
 .endif
 
+# Initialize stack variables on function entry
+.if ${MK_INIT_ALL_ZERO} == "yes"
+.if ${COMPILER_FEATURES:Minit-all}
+CFLAGS+= -ftrivial-auto-var-init=zero \
+    -enable-trivial-auto-var-init-zero-knowing-it-will-be-removed-from-clang
+CXXFLAGS+= -ftrivial-auto-var-init=zero \
+    -enable-trivial-auto-var-init-zero-knowing-it-will-be-removed-from-clang
+.else
+.warning InitAll (zeros) requested but not support by compiler
+.endif
+.elif ${MK_INIT_ALL_PATTERN} == "yes"
+.if ${COMPILER_FEATURES:Minit-all}
+CFLAGS+= -ftrivial-auto-var-init=pattern
+CXXFLAGS+= -ftrivial-auto-var-init=pattern
+.else
+.warning InitAll (pattern) requested but not support by compiler
+.endif
+.endif
+
 .if ${MACHINE_CPUARCH} == "riscv" && ${LINKER_FEATURES:Mriscv-relaxations} == ""
 CFLAGS += -mno-relax
 .endif
Index: head/sys/conf/kern.mk
===================================================================
--- head/sys/conf/kern.mk
+++ head/sys/conf/kern.mk
@@ -228,6 +228,24 @@
 .endif
 
 #
+# Initialize stack variables on function entry
+#
+.if ${MK_INIT_ALL_ZERO} == "yes"
+.if ${COMPILER_FEATURES:Minit-all}
+CFLAGS+= -ftrivial-auto-var-init=zero \
+    -enable-trivial-auto-var-init-zero-knowing-it-will-be-removed-from-clang
+.else
+.warning InitAll (zeros) requested but not support 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
+
+#
 # Add -gdwarf-2 when compiling -g. The default starting in clang v3.4
 # and gcc 4.8 is to generate DWARF version 4. However, our tools don't
 # cope well with DWARF 4, so force it to genereate DWARF2, which they
Index: head/tools/build/options/WITH_INIT_ALL_PATTERN
===================================================================
--- head/tools/build/options/WITH_INIT_ALL_PATTERN
+++ head/tools/build/options/WITH_INIT_ALL_PATTERN
@@ -0,0 +1,5 @@
+.\" $FreeBSD$
+Set to build the base system or kernel with stack variables initialized to
+.Pq compiler defined
+debugging patterns on function entry.
+This option requires the clang compiler.
Index: head/tools/build/options/WITH_INIT_ALL_ZERO
===================================================================
--- head/tools/build/options/WITH_INIT_ALL_ZERO
+++ head/tools/build/options/WITH_INIT_ALL_ZERO
@@ -0,0 +1,4 @@
+.\" $FreeBSD$
+Set to build the base system or kernel with stack variables initialized
+to zero on function entry.
+This option requires that the clang compiler be used.