diff --git a/ChangeLog b/ChangeLog
index 69e527c3ea..eded27fbe3 100644
--- a/ChangeLog
+++ b/ChangeLog
@@ -1,5 +1,28 @@
 2016-12-31  Siddhesh Poyarekar  <siddhesh@sourceware.org>
 
+	* Makeconfig (have-tunables): Check for non-negative instead
+	of positive.
+	* configure.ac: Add 'valstring' as a valid value for
+	--enable-tunables.
+	* configure: Regenerate.
+	* elf/Makefile (have-tunables): Check for non-negative instead
+	of positive.
+	(CPPFLAGS-dl-tunables.c): Define TUNABLES_FRONTEND for
+	dl-tunables.c.
+	* elf/dl-tunables.c (GLIBC_TUNABLES): Define only when
+	TUNABLES_FRONTEND == TUNABLES_FRONTEND_valstring.
+	(tunables_strdup): Likewise.
+	(disable_tunables): Likewise.
+	(parse_tunables): Likewise.
+	(__tunables_init): Process GLIBC_TUNABLES envvar only when.
+	TUNABLES_FRONTEND == TUNABLES_FRONTEND_valstring.
+	* elf/dl-tunables.h (TUNABLES_FRONTEND_valstring): New macro.
+	(TUNABLES_FRONTEND_yes): New macro, define as
+	TUNABLES_FRONTEND_valstring by default.
+	* manual/install.texi: Document new acceptable values for
+	--enable-tunables.
+	* INSTALL: Regenerate.
+
 	* config.make.in (have-loop-to-function): Define.
 	* elf/Makefile (CFLAGS-dl-tunables.c): Add
 	-fno-tree-loop-distribute-patterns.
diff --git a/INSTALL b/INSTALL
index 25619fc520..55d52c5f15 100644
--- a/INSTALL
+++ b/INSTALL
@@ -172,7 +172,23 @@ will be used, and CFLAGS sets optimization options for the compiler.
 '--enable-tunables'
      Tunables support allows additional library parameters to be
      customized at runtime.  This is an experimental feature and affects
-     startup time and is thus disabled by default.
+     startup time and is thus disabled by default.  This option can take
+     the following values:
+
+     'no'
+          This is the default if the option is not passed to configure.
+          This disables tunables.
+
+     'yes'
+          This is the default if the option is passed to configure.
+          This enables tunables and selects the default frontend
+          (currently 'valstring').
+
+     'valstring'
+          This enables tunables and selects the 'valstring' frontend for
+          tunables.  This frontend allows users to specify tunables as a
+          colon-separated list in a single environment variable
+          'GLIBC_TUNABLES'.
 
 '--build=BUILD-SYSTEM'
 '--host=HOST-SYSTEM'
diff --git a/Makeconfig b/Makeconfig
index b173e4cc08..1a2db6da1d 100644
--- a/Makeconfig
+++ b/Makeconfig
@@ -935,7 +935,7 @@ CPPFLAGS = $(config-extra-cppflags) $(CPPUNDEFS) $(CPPFLAGS-config) \
 			 $(libof-$(<F)) $(libof-$(@F)),$(CPPFLAGS-$(lib))) \
 	   $(CPPFLAGS-$(<F)) $(CPPFLAGS-$(@F)) $(CPPFLAGS-$(basename $(@F)))
 
-ifeq (yes,$(have-tunables))
+ifneq (no,$(have-tunables))
 CPPFLAGS += -DTOP_NAMESPACE=glibc
 endif
 
@@ -1115,7 +1115,7 @@ endif
 
 # Build the tunables list header early since it could be used by any module in
 # glibc.
-ifeq (yes,$(have-tunables))
+ifneq (no,$(have-tunables))
 before-compile += $(common-objpfx)dl-tunable-list.h
 
 $(common-objpfx)dl-tunable-list.h: $(..)scripts/gen-tunables.awk \
diff --git a/configure b/configure
index d80d738fd1..eecd0ace74 100755
--- a/configure
+++ b/configure
@@ -1454,7 +1454,8 @@ Optional Features:
   --disable-build-nscd    disable building and installing the nscd daemon
   --disable-nscd          library functions will not contact the nscd daemon
   --enable-pt_chown       Enable building and installing pt_chown
-  --enable-tunables       Enable tunables support
+  --enable-tunables       Enable tunables support. Known values are 'yes',
+                          'no' and 'valstring'
   --enable-mathvec        Enable building and installing mathvec [default
                           depends on architecture]
 
diff --git a/configure.ac b/configure.ac
index 22f5cab200..4a77411b71 100644
--- a/configure.ac
+++ b/configure.ac
@@ -423,7 +423,7 @@ fi
 
 AC_ARG_ENABLE([tunables],
 	      [AS_HELP_STRING([--enable-tunables],
-	       [Enable tunables support])],
+	       [Enable tunables support. Known values are 'yes', 'no' and 'valstring'])],
 	      [have_tunables=$enableval],
 	      [have_tunables=no])
 AC_SUBST(have_tunables)
diff --git a/elf/Makefile b/elf/Makefile
index 3cda2c9db8..c3636a64d2 100644
--- a/elf/Makefile
+++ b/elf/Makefile
@@ -36,8 +36,10 @@ ifeq (yes,$(use-ldconfig))
 dl-routines += dl-cache
 endif
 
-ifeq (yes,$(have-tunables))
+ifneq (no,$(have-tunables))
 dl-routines += dl-tunables
+tunables-type = $(addprefix TUNABLES_FRONTEND_,$(have-tunables))
+CPPFLAGS-dl-tunables.c = -DTUNABLES_FRONTEND=$(tunables-type)
 
 # Make sure that the compiler does not insert any library calls in tunables
 # code paths.
diff --git a/elf/dl-tunables.c b/elf/dl-tunables.c
index 8d6914020d..39feecde16 100644
--- a/elf/dl-tunables.c
+++ b/elf/dl-tunables.c
@@ -30,7 +30,9 @@
 #define TUNABLES_INTERNAL 1
 #include "dl-tunables.h"
 
-#define GLIBC_TUNABLES "GLIBC_TUNABLES"
+#if TUNABLES_FRONTEND == TUNABLES_FRONTEND_valstring
+# define GLIBC_TUNABLES "GLIBC_TUNABLES"
+#endif
 
 /* Compare environment or tunable names, bounded by the name hardcoded in
    glibc.  */
@@ -48,6 +50,7 @@ is_name (const char *orig, const char *envname)
     return false;
 }
 
+#if TUNABLES_FRONTEND == TUNABLES_FRONTEND_valstring
 static char *
 tunables_strdup (const char *in)
 {
@@ -70,6 +73,7 @@ tunables_strdup (const char *in)
 
   return out;
 }
+#endif
 
 static char **
 get_next_env (char **envp, char **name, size_t *namelen, char **val)
@@ -244,6 +248,7 @@ tunable_initialize (tunable_t *cur, const char *strval)
     }
 }
 
+#if TUNABLES_FRONTEND == TUNABLES_FRONTEND_valstring
 static void
 parse_tunables (char *tunestr)
 {
@@ -309,6 +314,7 @@ parse_tunables (char *tunestr)
 	return;
     }
 }
+#endif
 
 static size_t
 min_strlen (const char *s)
@@ -329,6 +335,7 @@ disable_tunable (tunable_id_t id, char **envp)
   if (env_alias != NULL)
     tunables_unsetenv (envp, tunable_list[id].env_alias);
 
+#if TUNABLES_FRONTEND == TUNABLES_FRONTEND_valstring
   char *tunable = getenv (GLIBC_TUNABLES);
   const char *cmp = tunable_list[id].name;
   const size_t len = min_strlen (cmp);
@@ -345,6 +352,7 @@ disable_tunable (tunable_id_t id, char **envp)
 	}
       tunable++;
     }
+#endif
 }
 
 /* Disable the glibc.malloc.check tunable in SETUID/SETGID programs unless
@@ -375,6 +383,7 @@ __tunables_init (char **envp)
 
   while ((envp = get_next_env (envp, &envname, &len, &envval)) != NULL)
     {
+#if TUNABLES_FRONTEND == TUNABLES_FRONTEND_valstring
       if (is_name (GLIBC_TUNABLES, envname))
 	{
 	  char *val = tunables_strdup (envval);
@@ -382,6 +391,7 @@ __tunables_init (char **envp)
 	    parse_tunables (val);
 	  continue;
 	}
+#endif
 
       for (int i = 0; i < sizeof (tunable_list) / sizeof (tunable_t); i++)
 	{
diff --git a/elf/dl-tunables.h b/elf/dl-tunables.h
index a3f5472b45..033781856a 100644
--- a/elf/dl-tunables.h
+++ b/elf/dl-tunables.h
@@ -84,5 +84,9 @@ extern void __tunable_set_val (tunable_id_t, void *, tunable_callback_t);
 /* Namespace sanity for callback functions.  Use this macro to keep the
    namespace of the modules clean.  */
 # define DL_TUNABLE_CALLBACK(__name) _dl_tunable_ ## __name
+
+# define TUNABLES_FRONTEND_valstring 1
+/* The default value for TUNABLES_FRONTEND.  */
+# define TUNABLES_FRONTEND_yes TUNABLES_FRONTEND_valstring
 #endif
 #endif
diff --git a/manual/install.texi b/manual/install.texi
index d41296294e..2657da108b 100644
--- a/manual/install.texi
+++ b/manual/install.texi
@@ -203,7 +203,22 @@ Use this option to disable the vector math library.
 @item --enable-tunables
 Tunables support allows additional library parameters to be customized at
 runtime.  This is an experimental feature and affects startup time and is thus
-disabled by default.
+disabled by default.  This option can take the following values:
+
+@table @code
+@item no
+This is the default if the option is not passed to configure. This disables
+tunables.
+
+@item yes
+This is the default if the option is passed to configure. This enables tunables
+and selects the default frontend (currently @samp{valstring}).
+
+@item valstring
+This enables tunables and selects the @samp{valstring} frontend for tunables.
+This frontend allows users to specify tunables as a colon-separated list in a
+single environment variable @env{GLIBC_TUNABLES}.
+@end table
 
 @item --build=@var{build-system}
 @itemx --host=@var{host-system}