[1/7] config: Allow memory tagging to be enabled when configuring glibc

diff --git a/config.h.in b/config.h.in
index dea43df438..b7f37e8e2a 100644
--- a/config.h.in
+++ b/config.h.in
@@ -148,6 +148,9 @@ 
 /* Define if __stack_chk_guard canary should be randomized at program startup.  */
 #undef ENABLE_STACKGUARD_RANDOMIZE
 
+/* Define if memory tagging support should be enabled.  */
+#undef _LIBC_MTAG
+
 /* Package description.  */
 #undef PKGVERSION
 
diff --git a/config.make.in b/config.make.in
index 2fed3da773..b3be8e0381 100644
--- a/config.make.in
+++ b/config.make.in
@@ -84,6 +84,8 @@  mach-interface-list = @mach_interface_list@
 
 experimental-malloc = @experimental_malloc@
 
+memory-tagging = @memory_tagging@
+
 nss-crypt = @libc_cv_nss_crypt@
 static-nss-crypt = @libc_cv_static_nss_crypt@
 
diff --git a/configure b/configure
index 8df47d61f8..92854715e0 100755
--- a/configure
+++ b/configure
@@ -678,6 +678,7 @@  link_obsolete_rpc
 libc_cv_static_nss_crypt
 libc_cv_nss_crypt
 build_crypt
+memory_tagging
 experimental_malloc
 enable_werror
 all_warnings
@@ -783,6 +784,7 @@  enable_all_warnings
 enable_werror
 enable_multi_arch
 enable_experimental_malloc
+enable_memory_tagging
 enable_crypt
 enable_nss_crypt
 enable_obsolete_rpc
@@ -1454,6 +1456,8 @@  Optional Features:
                           architectures
   --disable-experimental-malloc
                           disable experimental malloc features
+  --enable-memory-tagging enable memory tagging if supported by the
+                          architecture [default=no]
   --disable-crypt         do not build nor install the passphrase hashing
                           library, libcrypt
   --enable-nss-crypt      enable libcrypt to use nss
@@ -3527,6 +3531,19 @@  fi
 
 
 
+# Check whether --enable-memory-tagging was given.
+if test "${enable_memory_tagging+set}" = set; then :
+  enableval=$enable_memory_tagging; memory_tagging=$enableval
+else
+  memory_tagging=no
+fi
+
+if test "$memory_tagging" = yes; then
+  $as_echo "#define _LIBC_MTAG 1" >>confdefs.h
+
+fi
+
+
 # Check whether --enable-crypt was given.
 if test "${enable_crypt+set}" = set; then :
   enableval=$enable_crypt; build_crypt=$enableval
diff --git a/configure.ac b/configure.ac
index 5f229679a9..307a32d94b 100644
--- a/configure.ac
+++ b/configure.ac
@@ -311,6 +311,16 @@  AC_ARG_ENABLE([experimental-malloc],
 	      [experimental_malloc=yes])
 AC_SUBST(experimental_malloc)
 
+AC_ARG_ENABLE([memory-tagging],
+	      AC_HELP_STRING([--enable-memory-tagging],
+			     [enable memory tagging if supported by the architecture @<:@default=no@:>@]),
+	      [memory_tagging=$enableval],
+	      [memory_tagging=no])
+if test "$memory_tagging" = yes; then
+  AC_DEFINE(_LIBC_MTAG)
+fi
+AC_SUBST(memory_tagging)
+
 AC_ARG_ENABLE([crypt],
               AC_HELP_STRING([--disable-crypt],
                              [do not build nor install the passphrase hashing library, libcrypt]),
diff --git a/manual/install.texi b/manual/install.texi
index 71bf47cac6..abf7197090 100644
--- a/manual/install.texi
+++ b/manual/install.texi
@@ -167,6 +167,19 @@  on non-CET processors.  @option{--enable-cet} has been tested for
 x86_64 and x32 on CET SDVs, but Intel CET support hasn't been validated
 for i686.
 
+@item --enable-memory-tagging
+Enable memory tagging support on architectures that support it.  When
+@theglibc{} is built with this option then the resulting library will
+be able to control the use of tagged memory when hardware support is
+present by use of the tunable @samp{glibc.memtag.enable}.  This includes
+the generation of tagged memory when using the @code{malloc} APIs.
+
+At present only AArch64 platforms with MTE provide this functionality,
+although the library will still operate (without memory tagging) on
+older versions of the architecture.
+
+The default is to disable support for memory tagging.
+
 @item --disable-profile
 Don't build libraries with profiling information.  You may want to use
 this option if you don't plan to do profiling.