--- a/doc/building.html	Fri Dec 14 17:12:14 2018 -0800
+++ b/doc/building.html	Mon Dec 17 09:35:15 2018 -0800
@@ -145,7 +145,7 @@
 <li><p>Do not check out the source code in a path which contains spaces. Chances are the build will not work. This is most likely to be an issue on Windows systems.</p></li>
 <li><p>Do not check out the source code in a path which has a very long name or is nested many levels deep. Chances are you will hit an OS limitation during the build.</p></li>
 <li><p>Put the source code on a local disk, not a network share. If possible, use an SSD. The build process is very disk intensive, and having slow disk access will significantly increase build times. If you need to use a network share for the source code, see below for suggestions on how to keep the build artifacts on a local disk.</p></li>
-<li><p>On Windows, extra care must be taken to make sure the <a href="#cygwin">Cygwin</a> environment is consistent. It is recommended that you follow this procedure:</p>
+<li><p>On Windows, if using <a href="#cygwin">Cygwin</a>, extra care must be taken to make sure the environment is consistent. It is recommended that you follow this procedure:</p>
 <ul>
 <li><p>Create the directory that is going to contain the top directory of the JDK clone by using the <code>mkdir</code> command in the Cygwin bash shell. That is, do <em>not</em> create it using Windows Explorer. This will ensure that it will have proper Cygwin attributes, and that it's children will inherit those attributes.</p></li>
 <li><p>Do not put the JDK clone in a path under your Cygwin home directory. This is especially important if your user name contains spaces and/or mixed upper and lower case letters.</p></li>
@@ -201,8 +201,11 @@
 <h3 id="windows">Windows</h3>
 <p>Windows XP is not a supported platform, but all newer Windows should be able to build the JDK.</p>
 <p>On Windows, it is important that you pay attention to the instructions in the <a href="#special-considerations">Special Considerations</a>.</p>
-<p>Windows is the only non-POSIX OS supported by the JDK, and as such, requires some extra care. A POSIX support layer is required to build on Windows. Currently, the only supported such layer is Cygwin. (Msys is no longer supported due to a too old bash; msys2 and the new Windows Subsystem for Linux (WSL) would likely be possible to support in a future version but that would require effort to implement.)</p>
+<p>Windows is the only non-POSIX OS supported by the JDK, and as such, requires some extra care. A POSIX support layer is required to build on Windows. Currently, the only supported such layers are Windows Subsystem for Linux (WSL) and Cygwin. (Msys is no longer supported due to a too old bash; msys2 would likely be possible to support in a future version but that would require effort to implement.)</p>
 <p>Internally in the build system, all paths are represented as Unix-style paths, e.g. <code>/cygdrive/c/hg/jdk9/Makefile</code> rather than <code>C:\hg\jdk9\Makefile</code>. This rule also applies to input to the build system, e.g. in arguments to <code>configure</code>. So, use <code>--with-msvcr-dll=/cygdrive/c/msvcr100.dll</code> rather than <code>--with-msvcr-dll=c:\msvcr100.dll</code>. For details on this conversion, see the section on <a href="#fixpath">Fixpath</a>.</p>
+<h4 id="windows-subsystem-for-linux-wsl">Windows Subsystem for Linux (WSL)</h4>
+<p>Only Windows 10 1803 or newer is supported due to a dependency on the wslpath utility and support for environment variable sharing through WSLENV.</p>
+<p>You may build both Windows and Linux binaries from WSL. To build Windows binaries, you must use a Windows boot JDK (located in a Windows-accessible directory). To build Linux binaries, you must use a Linux boot JDK. The default behavior is to build for Windows. To build for Linux, pass <code>--build=x86_64-unknown-linux-gnu</code> and <code>--host=x86_64-unknown-linux-gnu</code> to <code>configure</code>.</p>
 <h4 id="cygwin">Cygwin</h4>
 <p>A functioning <a href="http://www.cygwin.com/">Cygwin</a> environment is thus required for building the JDK on Windows. If you have a 64-bit OS, we strongly recommend using the 64-bit version of Cygwin.</p>
 <p><strong>Note:</strong> Cygwin has a model of continuously updating all packages without any easy way to install or revert to a specific version of a package. This means that whenever you add or update a package in Cygwin, you might (inadvertently) update tools that are used by the JDK build process, and that can cause unexpected build problems.</p>

--- a/doc/building.md	Fri Dec 14 17:12:14 2018 -0800
+++ b/doc/building.md	Mon Dec 17 09:35:15 2018 -0800
@@ -75,8 +75,8 @@
     network share for the source code, see below for suggestions on how to keep
     the build artifacts on a local disk.
 
-  * On Windows, extra care must be taken to make sure the [Cygwin](#cygwin)
-    environment is consistent. It is recommended that you follow this
+  * On Windows, if using [Cygwin](#cygwin), extra care must be taken to make sure
+    the environment is consistent. It is recommended that you follow this
     procedure:
 
       * Create the directory that is going to contain the top directory of the
@@ -174,10 +174,10 @@
 
 Windows is the only non-POSIX OS supported by the JDK, and as such, requires
 some extra care. A POSIX support layer is required to build on Windows.
-Currently, the only supported such layer is Cygwin. (Msys is no longer
-supported due to a too old bash; msys2 and the new Windows Subsystem for Linux
-(WSL) would likely be possible to support in a future version but that would
-require effort to implement.)
+Currently, the only supported such layers are Windows Subsystem for Linux (WSL)
+and Cygwin. (Msys is no longer supported due to a too old bash; msys2 would 
+likely be possible to support in a future version but that would require effort
+to implement.)
 
 Internally in the build system, all paths are represented as Unix-style paths,
 e.g. `/cygdrive/c/hg/jdk9/Makefile` rather than `C:\hg\jdk9\Makefile`. This
@@ -186,6 +186,17 @@
 `--with-msvcr-dll=c:\msvcr100.dll`. For details on this conversion, see the section
 on [Fixpath](#fixpath).
 
+#### Windows Subsystem for Linux (WSL)
+
+Only Windows 10 1803 or newer is supported due to a dependency on the wslpath utility
+and support for environment variable sharing through WSLENV.
+
+You may build both Windows and Linux binaries from WSL. To build Windows binaries,
+you must use a Windows boot JDK (located in a Windows-accessible directory). To build 
+Linux binaries, you must use a Linux boot JDK. The default behavior is to build for
+Windows. To build for Linux, pass `--build=x86_64-unknown-linux-gnu` and 
+`--host=x86_64-unknown-linux-gnu` to `configure`.
+
 #### Cygwin
 
 A functioning [Cygwin](http://www.cygwin.com/) environment is thus required for

--- a/make/autoconf/basics.m4	Fri Dec 14 17:12:14 2018 -0800
+++ b/make/autoconf/basics.m4	Mon Dec 17 09:35:15 2018 -0800
@@ -616,6 +616,7 @@
   BASIC_PATH_PROGS(CPIO, [cpio bsdcpio])
   BASIC_PATH_PROGS(NICE, nice)
   BASIC_PATH_PROGS(PANDOC, pandoc)
+  BASIC_PATH_PROGS(LSB_RELEASE, lsb_release)
 
   BASIC_PATH_PROGS(CMD, [cmd.exe /mnt/c/Windows/System32/cmd.exe])
 ])
@@ -638,13 +639,14 @@
 
   if test "x$OPENJDK_TARGET_OS" = "xwindows"; then
     PATH_SEP=";"
+    EXE_SUFFIX=".exe"
     BASIC_CHECK_PATHS_WINDOWS
   else
     PATH_SEP=":"
-    EXECUTABLE_SUFFIX=""
+    EXE_SUFFIX=""
   fi
   AC_SUBST(PATH_SEP)
-  AC_SUBST(EXECUTABLE_SUFFIX)
+  AC_SUBST(EXE_SUFFIX)
 
   # We get the top-level directory from the supporting wrappers.
   AC_MSG_CHECKING([for top-level directory])

--- a/make/autoconf/basics_windows.m4	Fri Dec 14 17:12:14 2018 -0800
+++ b/make/autoconf/basics_windows.m4	Mon Dec 17 09:35:15 2018 -0800
@@ -464,7 +464,6 @@
     if test "x$test_cygdrive_prefix" = x; then
       AC_MSG_ERROR([Your cygdrive prefix is not /cygdrive. This is currently not supported. Change with mount -c.])
     fi
-    EXECUTABLE_SUFFIX=""
   elif test "x$OPENJDK_BUILD_OS_ENV" = "xwindows.msys"; then
     AC_MSG_CHECKING([msys release])
     MSYS_VERSION=`$UNAME -r`
@@ -479,9 +478,26 @@
     BASIC_WINDOWS_REWRITE_AS_UNIX_PATH(MSYS_ROOT_PATH)
     AC_MSG_RESULT([$MSYS_ROOT_PATH])
     WINDOWS_ENV_ROOT_PATH="$MSYS_ROOT_PATH"
-    EXECUTABLE_SUFFIX=""
   elif test "x$OPENJDK_BUILD_OS_ENV" = "xwindows.wsl"; then
-    EXECUTABLE_SUFFIX=".exe"
+    AC_MSG_CHECKING([Windows version])
+    # m4 replaces [ and ] so we use @<:@ and @:>@ instead
+    WINDOWS_VERSION=`$CMD /c ver.exe | $EGREP -o '(@<:@0-9@:>@+\.)+@<:@0-9@:>@+'`
+    AC_MSG_RESULT([$WINDOWS_VERSION])
+
+    AC_MSG_CHECKING([WSL kernel version])
+    WSL_KERNEL_VERSION=`$UNAME -v`
+    AC_MSG_RESULT([$WSL_KERNEL_VERSION])
+
+    AC_MSG_CHECKING([WSL kernel release])
+    WSL_KERNEL_RELEASE=`$UNAME -r`
+    AC_MSG_RESULT([$WSL_KERNEL_RELEASE])
+	
+    AC_MSG_CHECKING([WSL distribution])
+    WSL_DISTRIBUTION=`$LSB_RELEASE -d | sed 's/Description:\t//'`
+    AC_MSG_RESULT([$WSL_DISTRIBUTION])
+
+    WINDOWS_ENV_VENDOR='WSL'
+    WINDOWS_ENV_VERSION="$WSL_DISTRIBUTION $WSL_KERNEL_VERSION $WSL_KERNEL_RELEASE (on Windows build $WINDOWS_VERSION)"
   else
     AC_MSG_ERROR([Unknown Windows environment. Neither cygwin, msys, nor wsl was detected.])
   fi

--- a/make/autoconf/boot-jdk.m4	Fri Dec 14 17:12:14 2018 -0800
+++ b/make/autoconf/boot-jdk.m4	Mon Dec 17 09:35:15 2018 -0800
@@ -63,18 +63,18 @@
     # If previous step claimed to have found a JDK, check it to see if it seems to be valid.
     if test "x$BOOT_JDK_FOUND" = xmaybe; then
       # Do we have a bin/java?
-      if test ! -x "$BOOT_JDK/bin/java$EXECUTABLE_SUFFIX"; then
+      if test ! -x "$BOOT_JDK/bin/java$EXE_SUFFIX"; then
         AC_MSG_NOTICE([Potential Boot JDK found at $BOOT_JDK did not contain bin/java; ignoring])
         BOOT_JDK_FOUND=no
       else
         # Do we have a bin/javac?
-        if test ! -x "$BOOT_JDK/bin/javac$EXECUTABLE_SUFFIX"; then
+        if test ! -x "$BOOT_JDK/bin/javac$EXE_SUFFIX"; then
           AC_MSG_NOTICE([Potential Boot JDK found at $BOOT_JDK did not contain bin/javac; ignoring])
           AC_MSG_NOTICE([(This might be an JRE instead of an JDK)])
           BOOT_JDK_FOUND=no
         else
           # Oh, this is looking good! We probably have found a proper JDK. Is it the correct version?
-          BOOT_JDK_VERSION=`"$BOOT_JDK/bin/java$EXECUTABLE_SUFFIX" $USER_BOOT_JDK_OPTIONS -version 2>&1 | $HEAD -n 1`
+          BOOT_JDK_VERSION=`"$BOOT_JDK/bin/java$EXE_SUFFIX" $USER_BOOT_JDK_OPTIONS -version 2>&1 | $HEAD -n 1`
           if [ [[ "$BOOT_JDK_VERSION" =~ "Picked up" ]] ]; then
             AC_MSG_NOTICE([You have _JAVA_OPTIONS or JAVA_TOOL_OPTIONS set. This can mess up the build. Please use --with-boot-jdk-jvmargs instead.])
             AC_MSG_NOTICE([Java reports: "$BOOT_JDK_VERSION".])
@@ -101,7 +101,7 @@
             AC_MSG_CHECKING([for Boot JDK])
             AC_MSG_RESULT([$BOOT_JDK])
             AC_MSG_CHECKING([Boot JDK version])
-            BOOT_JDK_VERSION=`"$BOOT_JDK/bin/java$EXECUTABLE_SUFFIX" $USER_BOOT_JDK_OPTIONS -version 2>&1 | $TR '\n\r' '  '`
+            BOOT_JDK_VERSION=`"$BOOT_JDK/bin/java$EXE_SUFFIX" $USER_BOOT_JDK_OPTIONS -version 2>&1 | $TR '\n\r' '  '`
             AC_MSG_RESULT([$BOOT_JDK_VERSION])
           fi # end check jdk version
         fi # end check javac
@@ -335,11 +335,11 @@
   AC_SUBST(BOOT_JDK)
 
   # Setup tools from the Boot JDK.
-  BOOTJDK_CHECK_TOOL_IN_BOOTJDK(JAVA, java$EXECUTABLE_SUFFIX)
-  BOOTJDK_CHECK_TOOL_IN_BOOTJDK(JAVAC, javac$EXECUTABLE_SUFFIX)
-  BOOTJDK_CHECK_TOOL_IN_BOOTJDK(JAVADOC, javadoc$EXECUTABLE_SUFFIX)
-  BOOTJDK_CHECK_TOOL_IN_BOOTJDK(JAR, jar$EXECUTABLE_SUFFIX)
-  BOOTJDK_CHECK_TOOL_IN_BOOTJDK(JARSIGNER, jarsigner$EXECUTABLE_SUFFIX)
+  BOOTJDK_CHECK_TOOL_IN_BOOTJDK(JAVA, java$EXE_SUFFIX)
+  BOOTJDK_CHECK_TOOL_IN_BOOTJDK(JAVAC, javac$EXE_SUFFIX)
+  BOOTJDK_CHECK_TOOL_IN_BOOTJDK(JAVADOC, javadoc$EXE_SUFFIX)
+  BOOTJDK_CHECK_TOOL_IN_BOOTJDK(JAR, jar$EXE_SUFFIX)
+  BOOTJDK_CHECK_TOOL_IN_BOOTJDK(JARSIGNER, jarsigner$EXE_SUFFIX)
 
   # Finally, set some other options...
 

--- a/make/autoconf/spec.gmk.in	Fri Dec 14 17:12:14 2018 -0800
+++ b/make/autoconf/spec.gmk.in	Mon Dec 17 09:35:15 2018 -0800
@@ -123,8 +123,7 @@
   # On Windows, the Visual Studio toolchain needs the PATH to be adjusted
   # to include Visual Studio tools (this needs to be in cygwin/msys style).
   ifeq ($(OPENJDK_TARGET_OS_ENV), windows.wsl)
-    export FIXPATH_PATH:=@VS_PATH_WINDOWS@
-    export WSLENV:=$(WSLENV):FIXPATH_PATH:DEBUG_FIXPATH
+    export FIXPATH_WSL:=@FIXPATH_WSL@
   else
     export PATH:=@VS_PATH@
   endif

--- a/make/autoconf/toolchain.m4	Fri Dec 14 17:12:14 2018 -0800
+++ b/make/autoconf/toolchain.m4	Mon Dec 17 09:35:15 2018 -0800
@@ -180,7 +180,6 @@
     SHARED_LIBRARY='[$]1.dll'
     STATIC_LIBRARY='[$]1.lib'
     OBJ_SUFFIX='.obj'
-    EXE_SUFFIX='.exe'
   else
     LIBRARY_PREFIX=lib
     SHARED_LIBRARY_SUFFIX='.so'
@@ -188,7 +187,6 @@
     SHARED_LIBRARY='lib[$]1.so'
     STATIC_LIBRARY='lib[$]1.a'
     OBJ_SUFFIX='.o'
-    EXE_SUFFIX=''
     if test "x$OPENJDK_TARGET_OS" = xmacosx; then
       # For full static builds, we're overloading the SHARED_LIBRARY
       # variables in order to limit the amount of changes required.
@@ -212,7 +210,6 @@
   AC_SUBST(SHARED_LIBRARY)
   AC_SUBST(STATIC_LIBRARY)
   AC_SUBST(OBJ_SUFFIX)
-  AC_SUBST(EXE_SUFFIX)
 ])
 
 # Determine which toolchain type to use, and make sure it is valid for this
@@ -281,13 +278,13 @@
 
   TOOLCHAIN_CC_BINARY_clang="clang"
   TOOLCHAIN_CC_BINARY_gcc="gcc"
-  TOOLCHAIN_CC_BINARY_microsoft="cl$EXECUTABLE_SUFFIX"
+  TOOLCHAIN_CC_BINARY_microsoft="cl$EXE_SUFFIX"
   TOOLCHAIN_CC_BINARY_solstudio="cc"
   TOOLCHAIN_CC_BINARY_xlc="xlc_r"
 
   TOOLCHAIN_CXX_BINARY_clang="clang++"
   TOOLCHAIN_CXX_BINARY_gcc="g++"
-  TOOLCHAIN_CXX_BINARY_microsoft="cl$EXECUTABLE_SUFFIX"
+  TOOLCHAIN_CXX_BINARY_microsoft="cl$EXE_SUFFIX"
   TOOLCHAIN_CXX_BINARY_solstudio="CC"
   TOOLCHAIN_CXX_BINARY_xlc="xlC_r"
 
@@ -706,7 +703,7 @@
     # In the Microsoft toolchain we have a separate LD command "link".
     # Make sure we reject /usr/bin/link (as determined in CYGWIN_LINK), which is
     # a cygwin program for something completely different.
-    AC_CHECK_PROG([LD], [link.exe],[link.exe],,, [$CYGWIN_LINK])
+    AC_CHECK_PROG([LD], [link$EXE_SUFFIX],[link$EXE_SUFFIX],,, [$CYGWIN_LINK])
     BASIC_FIXUP_EXECUTABLE(LD)
     # Verify that we indeed succeeded with this trick.
     AC_MSG_CHECKING([if the found link.exe is actually the Visual Studio linker])
@@ -758,7 +755,7 @@
   #
   if test "x$TOOLCHAIN_TYPE" = xmicrosoft; then
     # The corresponding ar tool is lib.exe (used to create static libraries)
-    AC_CHECK_PROG([AR], [lib.exe],[lib.exe],,,)
+    AC_CHECK_PROG([AR], [lib$EXE_SUFFIX],[lib$EXE_SUFFIX],,,)
   elif test "x$TOOLCHAIN_TYPE" = xgcc; then
     BASIC_CHECK_TOOLS(AR, ar gcc-ar)
   else
@@ -782,12 +779,12 @@
   fi
 
   if test "x$TOOLCHAIN_TYPE" = xmicrosoft; then
-    AC_CHECK_PROG([MT], [mt.exe], [mt.exe],,, [/usr/bin/mt])
+    AC_CHECK_PROG([MT], [mt$EXE_SUFFIX], [mt$EXE_SUFFIX],,, [/usr/bin/mt])
     BASIC_FIXUP_EXECUTABLE(MT)
     # Setup the resource compiler (RC)
-    AC_CHECK_PROG([RC], [rc.exe], [rc.exe],,, [/usr/bin/rc])
+    AC_CHECK_PROG([RC], [rc$EXE_SUFFIX], [rc$EXE_SUFFIX],,, [/usr/bin/rc])
     BASIC_FIXUP_EXECUTABLE(RC)
-    AC_CHECK_PROG([DUMPBIN], [dumpbin.exe], [dumpbin.exe],,,)
+    AC_CHECK_PROG([DUMPBIN], [dumpbin$EXE_SUFFIX], [dumpbin$EXE_SUFFIX],,,)
     BASIC_FIXUP_EXECUTABLE(DUMPBIN)
     # We need to check for 'msbuild.exe' because at the place where we expect to
     # find 'msbuild.exe' there's also a directory called 'msbuild' and configure
@@ -796,7 +793,7 @@
     # Notice that we intentionally don't fix up the path to MSBUILD because we
     # will call it in a DOS shell during freetype detection on Windows (see
     # 'LIB_SETUP_FREETYPE' in "libraries.m4"
-    AC_CHECK_PROG([MSBUILD], [msbuild.exe], [msbuild.exe],,,)
+    AC_CHECK_PROG([MSBUILD], [msbuild$EXE_SUFFIX], [msbuild$EXE_SUFFIX],,,)
   fi
 
   if test "x$OPENJDK_TARGET_OS" = xsolaris; then