diff -Nurp a/libphobos/libdruntime/gcc/sections/elf_shared.d b/libphobos/libdruntime/gcc/sections/elf_shared.d
--- a/libphobos/libdruntime/gcc/sections/elf_shared.d	2020-01-01 00:00:00.000000000 +0900
+++ b/libphobos/libdruntime/gcc/sections/elf_shared.d	2020-01-01 00:00:00.000000000 +0900
@@ -1084,7 +1084,9 @@ void[] getTLSRange(size_t mod, size_t sz) nothrow @nogc

         // base offset
         auto ti = tls_index(mod, 0);
-        version (IBMZ_Any)
+        version (CRuntime_Musl)
+            return (__tls_get_addr(&ti)-TLS_DTV_OFFSET)[0 .. sz];
+        else version (IBMZ_Any)
         {
             auto idx = cast(void *)__tls_get_addr_internal(&ti)
                 + cast(ulong)__builtin_thread_pointer();
diff -Nurp a/libphobos/configure.ac b/libphobos/configure.ac
--- a/libphobos/configure.ac	2020-01-01 00:00:00.000000000 +0900
+++ b/libphobos/configure.ac	2020-01-01 00:00:00.000000000 +0900
@@ -140,6 +140,14 @@ case ${host} in
 esac
 AC_MSG_RESULT($LIBPHOBOS_SUPPORTED)

+AC_MSG_CHECKING([if target needs to link in swapcontext])
+AC_MSG_RESULT($LIBDRUNTIME_NEEDS_UCONTEXT)
+AS_IF([test "x$LIBDRUNTIME_NEEDS_UCONTEXT" = xyes], [
+  AC_SEARCH_LIBS([swapcontext], [c ucontext], [], [
+	AC_MSG_ERROR([[can't find library providing swapcontext]])
+  ])
+])
+
 # Decide if it's usable.
 case $LIBPHOBOS_SUPPORTED:$enable_libphobos in
 *:no)  use_libphobos=no  ;;
diff -Nurp a/libphobos/configure.tgt b/libphobos/configure.tgt
--- a/libphobos/configure.tgt	2020-01-01 00:00:00.000000000 +0900
+++ b/libphobos/configure.tgt	2020-01-01 00:00:00.000000000 +0900
@@ -22,6 +22,13 @@
 # Disable the libphobos or libdruntime components on untested or known
 # broken systems.  More targets shall be added after testing.
 LIBPHOBOS_SUPPORTED=no
+
+# Check if we require 'ucontext' or if we have a custom solution.
+# Most platform uses a custom assembly solution for context switches,
+# see `core.thread` and grep for `AsmExternal`.
+# Definitions are in config/ARCH/
+LIBPHOBOS_NEEDS_UCONTEXT=no
+
 case "${target}" in
   aarch64*-*-linux*)
 	LIBPHOBOS_SUPPORTED=yes
@@ -37,6 +44,7 @@ case "${target}" in
 	;;
   s390*-linux*)
 	LIBPHOBOS_SUPPORTED=yes
+	LIBDRUNTIME_NEEDS_UCONTEXT=yes
 	;;
   x86_64-*-kfreebsd*-gnu | i?86-*-kfreebsd*-gnu)
 	LIBPHOBOS_SUPPORTED=yes
diff -Nurp a/libphobos/configure b/libphobos/configure
--- a/libphobos/configure	2020-01-01 00:00:00.000000000 +0900
+++ b/libphobos/configure	2020-01-01 00:00:00.000000000 +0900
@@ -13955,6 +13955,76 @@ esac
 { $as_echo "$as_me:${as_lineno-$LINENO}: result: $LIBPHOBOS_SUPPORTED" >&5
 $as_echo "$LIBPHOBOS_SUPPORTED" >&6; }

+{ $as_echo "$as_me:${as_lineno-$LINENO}: checking if target needs to link in swapcontext" >&5
+$as_echo_n "checking if target needs to link in swapcontext... " >&6; }
+{ $as_echo "$as_me:${as_lineno-$LINENO}: result: $LIBDRUNTIME_NEEDS_UCONTEXT" >&5
+$as_echo "$LIBDRUNTIME_NEEDS_UCONTEXT" >&6; }
+if test "x$LIBDRUNTIME_NEEDS_UCONTEXT" = xyes; then :
+
+  { $as_echo "$as_me:${as_lineno-$LINENO}: checking for library containing swapcontext" >&5
+$as_echo_n "checking for library containing swapcontext... " >&6; }
+if ${ac_cv_search_swapcontext+:} false; then :
+  $as_echo_n "(cached) " >&6
+else
+  ac_func_search_save_LIBS=$LIBS
+cat confdefs.h - <<_ACEOF >conftest.$ac_ext
+/* end confdefs.h.  */
+
+/* Override any GCC internal prototype to avoid an error.
+   Use char because int might match the return type of a GCC
+   builtin and then its argument prototype would still apply.  */
+#ifdef __cplusplus
+extern "C"
+#endif
+char swapcontext ();
+int
+main ()
+{
+return swapcontext ();
+  ;
+  return 0;
+}
+_ACEOF
+for ac_lib in '' c ucontext; do
+  if test -z "$ac_lib"; then
+    ac_res="none required"
+  else
+    ac_res=-l$ac_lib
+    LIBS="-l$ac_lib  $ac_func_search_save_LIBS"
+  fi
+  if ac_fn_c_try_link "$LINENO"; then :
+  ac_cv_search_swapcontext=$ac_res
+fi
+rm -f core conftest.err conftest.$ac_objext \
+    conftest$ac_exeext
+  if ${ac_cv_search_swapcontext+:} false; then :
+  break
+fi
+done
+if ${ac_cv_search_swapcontext+:} false; then :
+
+else
+  ac_cv_search_swapcontext=no
+fi
+rm conftest.$ac_ext
+LIBS=$ac_func_search_save_LIBS
+fi
+{ $as_echo "$as_me:${as_lineno-$LINENO}: result: $ac_cv_search_swapcontext" >&5
+$as_echo "$ac_cv_search_swapcontext" >&6; }
+ac_res=$ac_cv_search_swapcontext
+if test "$ac_res" != no; then :
+  test "$ac_res" = "none required" || LIBS="$ac_res $LIBS"
+
+else
+
+	as_fn_error $? "can't find library providing swapcontext" "$LINENO" 5
+
+fi
+
+
+fi
+
+
 # Decide if it's usable.
 case $LIBPHOBOS_SUPPORTED:$enable_libphobos in
 *:no)  use_libphobos=no  ;;