--- a/make/autoconf/basics.m4	Tue Jan 01 20:09:02 2019 -0500
+++ b/make/autoconf/basics.m4	Wed Jan 02 12:59:26 2019 +0100
@@ -223,6 +223,8 @@
       BASIC_FIXUP_PATH_CYGWIN($1)
     elif test "x$OPENJDK_BUILD_OS_ENV" = "xwindows.msys"; then
       BASIC_FIXUP_PATH_MSYS($1)
+    elif test "x$OPENJDK_BUILD_OS_ENV" = "xwindows.wsl"; then
+      BASIC_FIXUP_PATH_WSL($1)
     else
       # We're on a unix platform. Hooray! :)
       path="[$]$1"
@@ -270,6 +272,8 @@
       BASIC_FIXUP_EXECUTABLE_CYGWIN($1)
     elif test "x$OPENJDK_BUILD_OS_ENV" = "xwindows.msys"; then
       BASIC_FIXUP_EXECUTABLE_MSYS($1)
+    elif test "x$OPENJDK_BUILD_OS_ENV" = "xwindows.wsl"; then
+      BASIC_FIXUP_EXECUTABLE_WSL($1)
     else
       # We're on a unix platform. Hooray! :)
       # First separate the path from the arguments. This will split at the first
@@ -607,6 +611,7 @@
 
   # These are not required on all platforms
   BASIC_PATH_PROGS(CYGPATH, cygpath)
+  BASIC_PATH_PROGS(WSLPATH, wslpath)
   BASIC_PATH_PROGS(DF, df)
   BASIC_PATH_PROGS(CPIO, [cpio bsdcpio])
   BASIC_PATH_PROGS(NICE, nice)
@@ -618,6 +623,9 @@
     ENABLE_PANDOC="false"
   fi
   AC_SUBST(ENABLE_PANDOC)
+
+  BASIC_PATH_PROGS(LSB_RELEASE, lsb_release)
+  BASIC_PATH_PROGS(CMD, [cmd.exe /mnt/c/Windows/System32/cmd.exe])
 ])
 
 ###############################################################################
@@ -638,11 +646,14 @@
 
   if test "x$OPENJDK_TARGET_OS" = "xwindows"; then
     PATH_SEP=";"
+    EXE_SUFFIX=".exe"
     BASIC_CHECK_PATHS_WINDOWS
   else
     PATH_SEP=":"
+    EXE_SUFFIX=""
   fi
   AC_SUBST(PATH_SEP)
+  AC_SUBST(EXE_SUFFIX)
 
   # We get the top-level directory from the supporting wrappers.
   AC_MSG_CHECKING([for top-level directory])
@@ -987,6 +998,8 @@
             MAKE_EXPECTED_ENV='cygwin'
           elif test "x$OPENJDK_BUILD_OS_ENV" = "xwindows.msys"; then
             MAKE_EXPECTED_ENV='msys'
+          elif test "x$OPENJDK_BUILD_OS_ENV" = "xwindows.wsl"; then
+            MAKE_EXPECTED_ENV='x86_64-pc-linux-gnu'
           else
             AC_MSG_ERROR([Unknown Windows environment])
           fi
@@ -1274,7 +1287,18 @@
     if $DF $DF_LOCAL_ONLY_OPTION $1 > /dev/null 2>&1; then
       $2
     else
-      $3
+      # In WSL, local Windows drives are considered remote by df, but we are
+      # required to build into a directory accessible from windows, so consider
+      # them local here.
+      if test "x$OPENJDK_BUILD_OS_ENV" = "xwindows.wsl"; then
+        if $DF $1 | $GREP -q "^[[A-Z]]:"; then
+          $2
+        else
+          $3
+        fi
+      else
+        $3
+      fi
     fi
   fi
 ])