diff --git a/.github/workflows/crossdev.yml b/.github/workflows/crossdev.yml
new file mode 100644
index 0000000..0ef1838
--- /dev/null
+++ b/.github/workflows/crossdev.yml
@@ -0,0 +1,53 @@
+name: CI
+
+on:
+  push:
+    branches:
+      - master
+  pull_request:
+    branches:
+      - master
+  schedule:
+    - cron: 00 4 * * *
+
+jobs:
+  crossdev:
+    strategy:
+      matrix:
+        include:
+          # `target` is the cross target.
+          # `stage3` is the host stage3.
+          - target: aarch64-unknown-linux-musl
+            stage3: musl-llvm
+            args: --llvm
+    name: crossdev target=${{ matrix.target }} stage3=${{ matrix.stage3 }}
+    runs-on: ubuntu-latest
+    container: docker.io/gentoo/stage3:${{ matrix.stage3 }}
+    steps:
+      - uses: actions/checkout@v4
+
+      - name: Install dependencies
+        run: |
+          # FIXME: Uncomment
+          # emerge --sync --quiet
+          emerge \
+            app-eselect/eselect-repository \
+            sys-apps/config-site
+
+      # FIXME: Remove this step once necessary changes are merged.
+      - name: Use patched overlay
+        run: |
+          curl -L \
+            https://github.com/vadorovsky/gentoo/archive/refs/heads/cross-llvm.tar.gz | \
+            tar -xz
+
+      - name: Install crossdev
+        run: make install
+
+      - name: Create cross environment
+        run: crossdev ${{ matrix.args }} --target ${{ matrix.target }}
+
+      # zstd and its dependencies need both C and C++ toolchain. If any of them
+      # is broken, the installation will fail.
+      - name: Sanity check
+        run: ${{ matrix.target }}-emerge app-arch/zstd
diff --git a/crossdev b/crossdev
index 176bb71..2f534e1 100755
--- a/crossdev
+++ b/crossdev
@@ -873,6 +873,9 @@ KCAT="sys-kernel" ; KPKG="linux-headers" ; KVER="" KUSE="" KENV="" KOVL="" KMASK
 LCAT="sys-libs"   ; LPKG="[none]"        ; LVER="" LUSE="" LENV="" LOVL="" LMASK="" LFORCE=""
 DCAT="dev-debug"  ; DPKG="gdb"           ; DVER="" DUSE="" DENV="" DOVL="" DMASK="" DFORCE=""
 RCAT="sys-libs"   ; RPKG="compiler-rt"   ; RVER="" RUSE="" RENV="" ROVL="" RMASK="" RFORCE=""
+UCAT="sys-libs"   ; UPKG="llvm-libunwind" ; UVER="" UUSE="" UENV="" UOVL="" UMASK="" UFORCE=""
+ACAT="sys-libs"   ; APKG="libcxxabi"     ; AVER="" AUSE="" AENV="" AOVL="" AMASK="" AFORCE=""
+CXCAT="sys-libs"  ; CXPKG="libcxx"       ; CXVER="" CXUSE="" CXENV="" CXOVL="" CXMASK="" CXFORCE=""
 CCAT="sys-devel"  ; CPKG="clang-crossdev-wrappers" ; CVER="" CUSE="" CENV="" COVL="" CMASK="" CFORCE=""
 XPKGS=() XVERS=() XUSES=() XENVS=() XOVLS=() XMASKS=() XFORCES=()
 DEFAULT_VER="[latest]"
@@ -915,69 +918,84 @@ LLVM="no"
 
 while [[ $# -gt 0 ]] ; do
 	case $1 in
-	-V|--version)      echo "crossdev-${CROSSDEV_VER}"; exit 0;;
-	-t|--target)       shift; parse_target $1;;
-	--b|--binutils)    shift; BVER=$1;;
-	--benv)            shift; BENV=$1;;
-	-ob|--ov-binutils) shift; BOVL=$1;;
-	--bcat)            shift; BCAT=$1;;
-	--bpkg)            shift; BPKG=$1;;
-	--d|--gdb)         shift; DVER=$1;;
-	--denv)            shift; DENV=$1;;
-	-od|--ov-gdb)      shift; DOVL=$1;;
-	--dcat)            shift; DCAT=$1;;
-	--dpkg)            shift; DPKG=$1;;
-	--g|--gcc)         shift; GVER=$1;;
-	--genv)            shift; GENV=$1;;
-	-og|--ov-gcc)      shift; GOVL=$1;;
-	--gcat)            shift; GCAT=$1;;
-	--gpkg)            shift; GPKG=$1;;
-	--k|--kernel)      shift; KVER=$1;;
-	--kenv)            shift; KENV=$1;;
-	-ok|--ov-kernel)   shift; KOVL=$1;;
-	--kcat)            shift; KCAT=$1;;
-	--kpkg)            shift; KPKG=$1;;
-	--l|--libc)        shift; LVER=$1;;
-	--lenv)            shift; LENV=$1;;
-	-ol|--ov-libc)     shift; LOVL=$1;;
-	--lcat)            shift; LCAT=$1;;
-	--lpkg)            shift; LPKG=$1;;
-	--r|--crt)         shift; RVER=$1;;
-	--renv)            shift; RENV=$1;;
-	-or|--ov-crt)      shift; ROVL=$1;;
-	--rcat)            shift; RCAT=$1;;
-	--rpkg)            shift; RPKG=$1;;
-	--c|--ccw)         shift; CVER=$1;;
-	--cenv)            shift; CENV=$1;;
-	-oc|--ov-ccw)      shift; COVL=$1;;
-	--ccat)            shift; CCAT=$1;;
-	--cpkg)            shift; CPKG=$1;;
-	-ox|--ov-extra)    shift; XOVLS+=( "$1" );;
-	--env)             shift; AENV=$1;;
-	-L|--llvm)         LLVM="yes";;
-	-A|--abis)         shift; MULTILIB_ABIS=$1;;
-	--host-abi)        shift; HOST_ABI=$1;;
-	-S|--stable)       DEFAULT_VER="[stable]";;
-	-C|--clean)        shift; parse_target $1; ACTION="uninstall";;
-	-s?|--stage?)      STAGE=${1:0-1};;
-	-oS|--overlays)    shift; SEARCH_OVERLAYS=$1;;
-	-oO|--ov-output)   shift; CROSSDEV_OVERLAY=$1;;
-	--ex-only)         EX_FAST="yes";;
-	--ex-gcc)          EX_GCC="yes";;
-	--ex-gdb)          EX_GDB="yes";;
-	--ex-pkg)          shift; XPKGS+=( "$1" );;
-	--with-*)          eval $(set_withval $1);;
-	--without-*)       eval $(set_withval $1);;
-	-f|--force)        FORCE="yes";;
-	-x)                SET_X="yes";;
-	--show-target-cfg) SHOW_TARGET_CFG="yes";;
-	--init-target)     INIT_TARGET_ONLY="yes";;
-	--show-fail-log)   SHOW_FAIL_LOG="yes";;
-	--show-repo-cfg)   show_repo_cfg "$2";;
-	-P|--portage)      UOPTS="${UOPTS} $2"; shift;;
-	-h|--help)         usage;;
-	-*)                eerror "UNKNOWN OPTION: '$1'" ; usage 1;;
-	*)                 parse_target $1;;
+	-V|--version)        echo "crossdev-${CROSSDEV_VER}"; exit 0;;
+	-t|--target)         shift; parse_target $1;;
+	--b|--binutils)      shift; BVER=$1;;
+	--benv)              shift; BENV=$1;;
+	-ob|--ov-binutils)   shift; BOVL=$1;;
+	--bcat)              shift; BCAT=$1;;
+	--bpkg)              shift; BPKG=$1;;
+	--d|--gdb)           shift; DVER=$1;;
+	--denv)              shift; DENV=$1;;
+	-od|--ov-gdb)        shift; DOVL=$1;;
+	--dcat)              shift; DCAT=$1;;
+	--dpkg)              shift; DPKG=$1;;
+	--g|--gcc)           shift; GVER=$1;;
+	--genv)              shift; GENV=$1;;
+	-og|--ov-gcc)        shift; GOVL=$1;;
+	--gcat)              shift; GCAT=$1;;
+	--gpkg)              shift; GPKG=$1;;
+	--k|--kernel)        shift; KVER=$1;;
+	--kenv)              shift; KENV=$1;;
+	-ok|--ov-kernel)     shift; KOVL=$1;;
+	--kcat)              shift; KCAT=$1;;
+	--kpkg)              shift; KPKG=$1;;
+	--l|--libc)          shift; LVER=$1;;
+	--lenv)              shift; LENV=$1;;
+	-ol|--ov-libc)       shift; LOVL=$1;;
+	--lcat)              shift; LCAT=$1;;
+	--lpkg)              shift; LPKG=$1;;
+	--r|--crt)           shift; RVER=$1;;
+	--renv)              shift; RENV=$1;;
+	-or|--ov-crt)        shift; ROVL=$1;;
+	--rcat)              shift; RCAT=$1;;
+	--rpkg)              shift; RPKG=$1;;
+	--u|--libunwind)     shift; UVER=$1;;
+	--uenv)              shift; UENV=$1;;
+	-ou|--ov-libuinwind) shift; UOVL=$1;;
+	--ucat)              shift; UCAT=$1;;
+	--upkg)              shift; UPKG=$1;;
+	--a|--libcxxabi)     shift; AVER=$1;;
+	--aenv)              shift; AENV=$1;;
+	-oa|--ov--libcxxabi) shift; AOVL=$1;;
+	--acat)              shift; ACAT=$1;;
+	--apkg)              shift; APKG=$1;;
+	--cx|--libcxx)       shift; CXVER=$1;;
+	--cxenv)             shift; CXENV=$1;;
+	-ocx|--ov-libcxx)    shift; CXOVL=$1;;
+	--cxcat)             shift; CXCAT=$1;;
+	--cxpkg)             shift; CXPKG=$1;;
+	--c|--ccw)           shift; CVER=$1;;
+	--cenv)              shift; CENV=$1;;
+	-oc|--ov-ccw)        shift; COVL=$1;;
+	--ccat)              shift; CCAT=$1;;
+	--cpkg)              shift; CPKG=$1;;
+	-ox|--ov-extra)      shift; XOVLS+=( "$1" );;
+	--env)               shift; AENV=$1;;
+	-L|--llvm)           LLVM="yes";;
+	-A|--abis)           shift; MULTILIB_ABIS=$1;;
+	--host-abi)          shift; HOST_ABI=$1;;
+	-S|--stable)         DEFAULT_VER="[stable]";;
+	-C|--clean)          shift; parse_target $1; ACTION="uninstall";;
+	-s?|--stage?)        STAGE=${1:0-1};;
+	-oS|--overlays)      shift; SEARCH_OVERLAYS=$1;;
+	-oO|--ov-output)     shift; CROSSDEV_OVERLAY=$1;;
+	--ex-only)           EX_FAST="yes";;
+	--ex-gcc)            EX_GCC="yes";;
+	--ex-gdb)            EX_GDB="yes";;
+	--ex-pkg)            shift; XPKGS+=( "$1" );;
+	--with-*)            eval $(set_withval $1);;
+	--without-*)         eval $(set_withval $1);;
+	-f|--force)          FORCE="yes";;
+	-x)                  SET_X="yes";;
+	--show-target-cfg)   SHOW_TARGET_CFG="yes";;
+	--init-target)       INIT_TARGET_ONLY="yes";;
+	--show-fail-log)     SHOW_FAIL_LOG="yes";;
+	--show-repo-cfg)     show_repo_cfg "$2";;
+	-P|--portage)        UOPTS="${UOPTS} $2"; shift;;
+	-h|--help)           usage;;
+	-*)                  eerror "UNKNOWN OPTION: '$1'" ; usage 1;;
+	*)                   parse_target $1;;
 	esac
 	shift
 done
@@ -985,8 +1003,6 @@ done
 if [[ "${LLVM}" == "yes" ]] ; then
 	WITH_HEADERS="yes"
 	CROSSDEV_OVERLAY_CATEGORY_PREFIX="cross_llvm-"
-    # To avoid bug reports
-    [[ "${LPKG}" == "glibc" ]] && die "LLVM/Clang cannot currently compile glibc"
 fi
 
 CROSSDEV_OVERLAY_CATEGORY="${CROSSDEV_OVERLAY_CATEGORY_PREFIX}${CTARGET}"
@@ -1001,6 +1017,10 @@ GVER=${GVER:-${DEFAULT_VER}}
 KVER=${KVER:-${DEFAULT_VER}}
 LVER=${LVER:-${DEFAULT_VER}}
 DVER=${DVER:-${DEFAULT_VER}}
+RVER=${RVER:-${DEFAULT_VER}}
+AVER=${AVER:-${DEFAULT_VER}}
+CXVER=${CXVER:-${DEFAULT_VER}}
+UVER=${UVER:-${DEFAULT_VER}}
 STAGE=${STAGE:-${STAGE_DEFAULT}}
 [[ -z ${CTARGET} ]] && usage 1
 for with in HEADERS ; do
@@ -1017,8 +1037,6 @@ if [[ ${LPKG} == "newlib" && ${LVER} == "[stable]" ]]; then
 	LVER="[latest]"
 fi
 
-RVER="[latest]"
-
 show_target_cfg() {
 	local pkgs crosspkgs=()
 
@@ -1180,6 +1198,9 @@ fi
 info() {
 hr -
 [[ "${LLVM}" == "yes" ]] && einfo "Using LLVM/Clang as cross compiler, experimental!"
+if [[ "${LLVM}" == "yes" && "${CTARGET}" == *-gnu* ]] ; then
+	einfo "Using GCC as a fallback compiler for glibc."
+fi
 einfo "crossdev version:      ${CROSSDEV_VER}"
 einfo "Host Portage ARCH:     ${HARCH}"
 einfo "Host Portage System:   ${HCHOST} (${HCHOSTS[*]})"
@@ -1192,12 +1213,15 @@ einfo "Target ABIs:           ${MULTILIB_ABIS}${def_out}"
 echo
 ex_fast || {
 is_s0 && {
-[[ "${LLVM}" == "yes" ]] || einfo "binutils:              `pretty_atom ${BPKG}- ${BVER}`"
+	if [[ "${LLVM}" != "yes" || "${CTARGET}" == *-gnu* ]] ; then
+		einfo "binutils:              `pretty_atom ${BPKG}- ${BVER}`"
+	fi
 }
 is_s1 && {
 	if [[ "${LLVM}" == "yes" ]] ; then
 		einfo "compiler-rt:           `pretty_atom ${RPKG}- ${RVER}`"
-	else
+	fi
+	if [[ "${LLVM}" != "yes" || "${CTARGET}" == *-gnu* ]] ; then
 		einfo "gcc:                   `pretty_atom ${GPKG}- ${GVER}`"
 	fi
 }
@@ -1208,6 +1232,12 @@ einfo "headers:               `pretty_atom ${KPKG}- ${KVER}`"
 is_s3 && {
 einfo "libc:                  `pretty_atom ${LPKG}- ${LVER}`"
 }
+is_s4 && {
+[[ "${LLVM}" == "yes" ]] && \
+einfo "llvm-libunwind:        `pretty_atom ${UPKG}- ${UVER}`"
+einfo "libcxxabi:             `pretty_atom ${APKG}- ${AVER}`"
+einfo "libcxx:                `pretty_atom ${CXPKG}- ${CXVER}`"
+}
 }
 ex_gcc && {
 einfo "Extra: gcc pass:       DO IT"
@@ -1397,7 +1427,12 @@ set_env() {
 
 	output=$(_set_portage_file ${pkg} package.env)
 	echo "${CROSSDEV_OVERLAY_CATEGORY}/${pkg} ${CROSSDEV_OVERLAY_CATEGORY}/${pkg}.conf" >> ${output}
-    [[ "${LLVM}" == "yes" ]] && echo "${CROSSDEV_OVERLAY_CATEGORY}/${pkg} ${CROSSDEV_OVERLAY_CATEGORY}/llvm.conf" >> ${output}
+
+	# If LLVM is the main toolchain, use the generic LLVM environment for all
+	# packages except gcc and glibc.
+	if [[ "${LLVM}" == "yes" && ! "${pkg}" =~ (binutils|gcc|glibc) ]] ; then
+		echo "${CROSSDEV_OVERLAY_CATEGORY}/${pkg} ${CROSSDEV_OVERLAY_CATEGORY}/llvm.conf" >> ${output}
+	fi
 }
 set_portage() {
 	local l=$1
@@ -1548,7 +1583,11 @@ done
 
 pkglist=( K L )
 if [[ ${LLVM} == "yes" ]] ; then
-	pkglist+=( R C )
+	pkglist+=( R C A CX U )
+	# Install GCC as a fallback compiler for GNU environments.
+	if [[ ${CTARGET} == *-gnu* ]] ; then
+		pkglist+=( B G )
+	fi
 else
 	pkglist+=( B G D )
 fi
@@ -1584,9 +1623,11 @@ LLVM="${LLVM}" emerge-wrapper --target ${CTARGET} --init || exit 1
 ### but gcc relies on their presence by refering to =/lib64 as
 ### =/usr/lib/../lib64 when builds itself (see https://bugs.gentoo.org/652724)
 ###
-### Thus we create non-symlinked layout early.
-xmkdir -p "${EPREFIX}"/usr/${CTARGET}/lib
+### Thus we create the layout early.
 xmkdir -p "${EPREFIX}"/usr/${CTARGET}/usr/lib
+pushd "${EPREFIX}"/usr/${CTARGET} >/dev/null
+ln -s usr/lib lib
+popd >/dev/null
 ###
 ### We need some special riscv sauce here similar as in baselayout. Ugly.
 ### step 1: set up all multilib libdirs
@@ -1736,8 +1777,7 @@ if [[ "${LLVM}" == "yes" ]]; then
 	--rtlib=compiler-rt
 	--sysroot=/usr/${CTARGET}
 	--target=${CTARGET}
-	--unwindlib=libunwind
-	--stdlib=libc++
+	--unwindlib=none
 	-fuse-ld=lld
 	EOF
 	# Workaround until LLVM libc supports dynamic linking and SSP
@@ -1752,7 +1792,7 @@ USE="${USE} -selinux"
 
 if ! ex_fast ; then
 
-	# stage 0: binutils
+	# stage 0: compiler wrappers, binutils
 	if [[ "${LLVM}" == "yes" ]] ; then
 		if ! portageq has_version / "sys-devel/llvm" ; then
 			eerror "LLVM is not installed"
@@ -1785,13 +1825,25 @@ if ! ex_fast ; then
 		[[ ${supported_arch} -eq 0 ]] && die "Target architecture not supported by installed LLVM toolchain"
 
 		USE="${CUSE}" doemerge ${CPKG}
-	else
+	fi
+	if [[ "${LLVM}" != "yes" || "${CTARGET}" == *-gnu* ]]; then
 		USE="${BUSE}" doemerge ${BPKG}
 	fi
 
 	# stage1: bare C compiler
 	if is_s1 ; then
 
+		# Build stage1 GCC if:
+		#
+		# - It's the main compiler.
+		# - LLVM is the main compiler, but in GNU environment, so GCC is needed as a
+		#   fallback compiler for glibc.
+		if [[ "${LLVM}" != "yes" || "${CTARGET}" == *-gnu* ]]; then
+			USE="${GUSE} ${USE} ${GUSE_DISABLE_STAGE_1}" \
+			CROSSCOMPILE_OPTS="" \
+				doemerge ${GPKG} ${GPKG}-stage1
+		fi
+
 		# first install headers if requested
 		if with_headers ; then
 			# install kernel headers (since the C library often uses them)
@@ -1811,16 +1863,11 @@ if ! ex_fast ; then
 			fi
 		fi
 
-		# then finally get around to the C compiler
 		if [[ "${LLVM}" == "yes" ]]; then
 			# Compile compiler-rt
 			USE="${RUSE} ${USE}" \
 			CROSSCOMPILE_OPTS="" \
 				doemerge ${RPKG}
-		else
-			USE="${GUSE} ${USE} ${GUSE_DISABLE_STAGE_1}" \
-			CROSSCOMPILE_OPTS="" \
-				doemerge ${GPKG} ${GPKG}-stage1
 		fi
 
 	fi
@@ -1846,10 +1893,27 @@ if ! ex_fast ; then
 	fi
 
 	# stage4: full compiler (C/C++/etc...)
-	if is_s4 && [[ "${LLVM}" != "yes" ]] ; then
-		EOPTS="${EOPTS_UP} --newuse" \
-		USE="${GUSE} ${USE} ${GUSE_DISABLE_STAGE_2}" \
-			doemerge ${GPKG} ${GPKG}-stage2
+	if is_s4 ; then
+		if [[ "${LLVM}" == "yes" ]]; then
+			USE="${UUSE} ${USE}" \
+				doemerge ${UPKG}
+
+			# Include libunwind in the cross configuration. libc++ depends on it.
+			sed -i "s/--unwindlib=.*$/--unwindlib=libunwind/" "${CLANG_CROSS_CFG}"
+
+			USE="${AUSE} ${USE}" \
+				doemerge ${APKG}
+			USE="${CXUSE} ${USE}" \
+				doemerge ${CXPKG}
+
+			# Finally, include libc++ in the cross configuration.
+			sed -i "/--unwindlib/ a --stdlib=libc++" "${CLANG_CROSS_CFG}"
+		fi
+		if [[ "${LLVM}" != "yes" || "${CTARGET}" == *-gnu* ]]; then
+			EOPTS="${EOPTS_UP} --newuse" \
+			USE="${GUSE} ${USE} ${GUSE_DISABLE_STAGE_2}" \
+				doemerge ${GPKG} ${GPKG}-stage2
+		fi
 	fi
 fi