diff --git a/Makeconfig b/Makeconfig
index 2fa0884b4e..fc6af7a363 100644
--- a/Makeconfig
+++ b/Makeconfig
@@ -398,6 +398,9 @@ LDFLAGS-lib.so += -Wl,-z,now
 # Extra flags for dynamically linked non-test main programs.
 link-extra-flags += -Wl,-z,now
 endif
+ifeq ($(ld_zunique),yes)
+LDFLAGS-lib.so += -Wl,-z,unique
+endif
 
 # Command to run after every final link (executable or shared object).
 # This is invoked with $(call after-link,...), so it should operate on
diff --git a/Makerules b/Makerules
index 596fa68376..830461ae1a 100644
--- a/Makerules
+++ b/Makerules
@@ -581,7 +581,8 @@ $(common-objpfx)shlib.lds: $(common-objpfx)config.make $(..)Makerules
 		 PROVIDE(__start___libc_IO_vtables = .);\
 		 __libc_IO_vtables : { *(__libc_IO_vtables) }\
 		 PROVIDE(__stop___libc_IO_vtables = .);\
-		 /DISCARD/ : { *(.gnu.glibc-stub.*) }@'
+		 /DISCARD/ : { *(.gnu.glibc-stub.*) }@' \
+	      -e 's/^.*\*(\.dynamic).*$$/   .dynamic : { *dynamic-notes.os(.dynamic) *(.dynamic) }/'
 	test -s $@T
 	mv -f $@T $@
 common-generated += shlib.lds
@@ -636,6 +637,16 @@ build-shlib-objlist = $(build-module-helper-objlist) \
 # Also omits crti.o and crtn.o, which we do not want
 # since we define our own `.init' section specially.
 LDFLAGS-c.so = -nostdlib -nostartfiles
+
+# The stub dynamic-notes.os should not have weak/undefined symbol magic in it.
+# It's not really part of the internals, rather it is a vector for linker magic
+# which we need when the linker isn't new enough:
+%/dynamic-notes.os: CPPFLAGS += -UMODULE_NAME
+
+ifeq ($(ld_zunique),yes)
+LDFLAGS-c.so += -Wl,-z,unique
+endif
+
 # But we still want to link libc.so against $(libc.so-gnulib).
 LDLIBS-c.so += $(libc.so-gnulib)
 # Give libc.so an entry point and make it directly runnable itself.
@@ -706,6 +717,11 @@ $(common-objpfx)linkobj/libc.so: $(common-objpfx)linkobj/libc_pic.a \
 	$(build-shlib)
 	$(call after-link,$@)
 
+ifneq ($(ld_zunique),yes)
+$(common-objpfx)libc.so: $(common-objpfx)elf/dynamic-notes.os
+$(common-objpfx)linkobj/libc.so: $(common-objpfx)elf/dynamic-notes.os
+endif
+
 ifeq ($(build-shared),yes)
 $(common-objpfx)libc.so: $(common-objpfx)libc.map
 endif
diff --git a/configure b/configure
index 39d75eb4ed..e191b840dc 100755
--- a/configure
+++ b/configure
@@ -625,6 +625,7 @@ libc_cv_cc_nofma
 libc_cv_mtls_dialect_gnu2
 fno_unit_at_a_time
 libc_cv_has_glob_dat
+libc_cv_ld_zunique
 libc_cv_hashstyle
 libc_cv_fpie
 libc_cv_z_execstack
@@ -6181,9 +6182,46 @@ fi
 $as_echo "$libc_cv_hashstyle" >&6; }
 
 
+old_LDFLAGS="$LDFLAGS"
+LDFLAGS="-Wl,--fatal-warnings -Wl,-z,unique -shared"
+{ $as_echo "$as_me:${as_lineno-$LINENO}: checking for linker DT_GNU_FLAGS_1/ DF_GNU_1_UNIQUE support" >&5
+$as_echo_n "checking for linker DT_GNU_FLAGS_1/ DF_GNU_1_UNIQUE support... " >&6; }
+if { as_var=cat confdefs.h - <<_ACEOF >conftest.$ac_ext
+/* end confdefs.h.  */
+void x (void) { }
+_ACEOF
+if ac_fn_c_try_link "$LINENO"; then :
+  libc_cv_ld_zunique=yes
+else
+  libc_cv_ld_zunique=no
+fi
+rm -f core conftest.err conftest.$ac_objext \
+    conftest$ac_exeext conftest.$ac_ext; eval \${$as_var+:} false; }; then :
+  $as_echo_n "(cached) " >&6
+fi
+eval ac_res=\$cat confdefs.h - <<_ACEOF >conftest.$ac_ext
+/* end confdefs.h.  */
+void x (void) { }
+_ACEOF
+if ac_fn_c_try_link "$LINENO"; then :
+  libc_cv_ld_zunique=yes
+else
+  libc_cv_ld_zunique=no
+fi
+rm -f core conftest.err conftest.$ac_objext \
+    conftest$ac_exeext conftest.$ac_ext
+	       { $as_echo "$as_me:${as_lineno-$LINENO}: result: $ac_res" >&5
+$as_echo "$ac_res" >&6; }
+LDFLAGS="$old_LDFLAGS"
+
+config_vars="$config_vars
+ld_zunique = $libc_cv_ld_zunique"
+
 # The linker's default -shared behavior is good enough if it
 # does these things that our custom linker scripts ensure that
-# all allocated NOTE sections come first.
+# all allocated NOTE sections come first AND it understands
+# -z unique should result in DT_GNU_FLAGS_1/DF_GNU_1_UNIQUE
+# sections in its output.
 if test "$use_default_link" = default; then
   { $as_echo "$as_me:${as_lineno-$LINENO}: checking for sufficient default -shared layout" >&5
 $as_echo_n "checking for sufficient default -shared layout... " >&6; }
@@ -6226,10 +6264,16 @@ EOF
       esac
       shift 2
     done
-    case "$libc_seen_a$libc_seen_b" in
-    yesyes)
+    case "$libc_seen_a$libc_seen_b$libc_cv_ld_zunique" in
+    yesyesyes)
       libc_cv_use_default_link=yes
       ;;
+    yesyesno)
+      echo >&5 "\
+shared layout from:
+$ac_try
+is OK but -Wl,-z,unique is unsupported so linker scripts are required"
+      ;;
     *)
       echo >&5 "\
 $libc_seen_a$libc_seen_b from:
diff --git a/configure.ac b/configure.ac
index 00f49f09f7..928989fac5 100644
--- a/configure.ac
+++ b/configure.ac
@@ -1389,9 +1389,21 @@ fi
 rm -f conftest*])
 AC_SUBST(libc_cv_hashstyle)
 
+old_LDFLAGS="$LDFLAGS"
+LDFLAGS="-Wl,--fatal-warnings -Wl,-z,unique -shared"
+AC_CACHE_CHECK([for linker DT_GNU_FLAGS_1 / DF_GNU_1_UNIQUE support],
+	       AC_LINK_IFELSE([AC_LANG_SOURCE([void foo (void) { }])],
+			      libc_cv_ld_zunique=yes,
+			      libc_cv_ld_zunique=no))
+LDFLAGS="$old_LDFLAGS"
+AC_SUBST(libc_cv_ld_zunique)
+LIBC_CONFIG_VAR([ld_zunique], [$libc_cv_ld_zunique])
+
 # The linker's default -shared behavior is good enough if it
 # does these things that our custom linker scripts ensure that
-# all allocated NOTE sections come first.
+# all allocated NOTE sections come first AND it understands
+# -z unique should result in DT_GNU_FLAGS_1/DF_GNU_1_UNIQUE
+# sections in its output.
 if test "$use_default_link" = default; then
   AC_CACHE_CHECK([for sufficient default -shared layout],
 		  libc_cv_use_default_link, [dnl
@@ -1427,10 +1439,16 @@ EOF
       esac
       shift 2
     done
-    case "$libc_seen_a$libc_seen_b" in
-    yesyes)
+    case "$libc_seen_a$libc_seen_b$libc_cv_ld_zunique" in
+    yesyesyes)
       libc_cv_use_default_link=yes
       ;;
+    yesyesno)
+      echo >&AS_MESSAGE_LOG_FD "\
+shared layout from:
+$ac_try
+is OK but -Wl,-z,unique is unsupported so linker scripts are required"
+      ;;
     *)
       echo >&AS_MESSAGE_LOG_FD "\
 $libc_seen_a$libc_seen_b from:
diff --git a/dlfcn/Makefile b/dlfcn/Makefile
index 6bbfbb8344..13a2684b30 100644
--- a/dlfcn/Makefile
+++ b/dlfcn/Makefile
@@ -35,6 +35,7 @@ routines = \
   libc_dlerror_result \
 
 extra-libs-others := libdl
+not-df-gnu-unique := libdl
 
 libdl-shared-only-routines += libdl-compat
 
diff --git a/elf/Makefile b/elf/Makefile
index 26986c0692..5157469473 100644
--- a/elf/Makefile
+++ b/elf/Makefile
@@ -104,6 +104,9 @@ endif
 
 ifeq (yes,$(build-shared))
 extra-objs	= $(all-rtld-routines:%=%.os) sofini.os interp.os
+ifneq (yes,$(ld_zunique))
+extra-objs      += dynamic-notes.os
+endif
 generated	+= librtld.os dl-allobjs.os ld.so ldd
 install-others	= $(inst_rtlddir)/$(rtld-installed-name)
 install-bin-script = ldd
diff --git a/elf/dynamic-notes.c b/elf/dynamic-notes.c
new file mode 100644
index 0000000000..d0b487e970
--- /dev/null
+++ b/elf/dynamic-notes.c
@@ -0,0 +1,4 @@
+#include <link.h>
+
+const ElfW(Dyn) __dynamic_note __attribute__ ((section (".dynamic"))) =
+  { .d_tag = DT_GNU_FLAGS_1, .d_un.d_val = DF_GNU_1_UNIQUE };
diff --git a/extra-lib.mk b/extra-lib.mk
index 72f8d2e1df..e0165c785d 100644
--- a/extra-lib.mk
+++ b/extra-lib.mk
@@ -101,8 +101,39 @@ $(objpfx)$(lib).so: $(firstword $($(lib)-map) \
 				$(addprefix $(common-objpfx), \
 					    $(filter $(lib).map, \
 						     $(version-maps))))
+
+############################################################################
+# the following have had all functional contents merged back into libc and
+# are no longer considered part of the implicitly DF_GNU_1_UNIQUE cluster:
+#    nptl/libpthread dlfcn/libdl login/libutil resolv/libanl*
+# NOTE: htl/libpthread has NOT been merged
+#    resolv/libanl depends on .../libpthread but it _should_ still be OK
+#    for resolv/libanl not to be tagged in this case
+
+# NOTE: the mechanisms are reversed depending on linker support:
+# If linker support is present, libraries get the unique flag by default and we
+# _suppress_ this with the -z nounique parameter.
+# If linker support is absent then the flag is _added_ via a hacked up extra
+# object from the elf/ subdir to those DSOs that need it.
+
+# The not-df-gnu-unique variable should contain a space separated list of
+# stub library names (eg pthread for libpthread.so) of extra-libs which should
+# NOT have the uniqueness flag.
+# It should be set in the Makefile of the relevant subdir:
+ifneq ($(ld_zunique),yes)
+ifeq (,$(strip $(filter $(not-df-gnu-unique),$(lib))))
+$(objpfx)$(lib).so: $(common-objpfx)/elf/dynamic-notes.os
+else
 endif
+else
+ifneq (,$(strip $(filter $(not-df-gnu-unique),$(lib))))
+LDFLAGS-$(patsubst lib%,%,$(lib)).so += -Wl,-z,nounique
+else
+endif
+endif
+############################################################################
 
+endif
 endif
 
 # This will define `libof-ROUTINE := LIB' for each of the routines.
diff --git a/htl/Makefile b/htl/Makefile
index cf9d12fc12..1a807db6ba 100644
--- a/htl/Makefile
+++ b/htl/Makefile
@@ -169,6 +169,7 @@ shared-only-routines = forward
 
 extra-libs := libpthread
 extra-libs-others := $(extra-libs)
+not-df-gnu-unique :=
 install-lib := libpthread.so
 install-lib-ldscripts := libpthread_syms.a
 
@@ -202,6 +203,7 @@ $(inst_libdir)/libpthread_syms.a: $(srcdir)/libpthread_syms.a $(+force)
 libc-link.so = $(common-objpfx)libc.so
 
 extra-B-pthread.so = -B$(common-objpfx)htl/
+# Turn off DF_GNU_1_UNIQUE for libpthread now that it's a stub.
 LDFLAGS-pthread.so = -Wl,--enable-new-dtags,-z,nodelete,-z,initfirst
 
 include ../Rules
diff --git a/iconvdata/Makefile b/iconvdata/Makefile
index c216f959df..1209239bc1 100644
--- a/iconvdata/Makefile
+++ b/iconvdata/Makefile
@@ -67,6 +67,9 @@ modules	:= ISO8859-1 ISO8859-2 ISO8859-3 ISO8859-4 ISO8859-5		 \
 ifeq ($(bind-now),yes)
 LDFLAGS.so += -Wl,-z,now
 endif
+ifeq ($(ld_zunique),yes)
+LDFLAGS.so += -Wl,-z,unique
+endif
 
 modules.so := $(addsuffix .so, $(modules))
 
diff --git a/iconvdata/extra-module.mk b/iconvdata/extra-module.mk
index ecaf507624..5bdceddd80 100644
--- a/iconvdata/extra-module.mk
+++ b/iconvdata/extra-module.mk
@@ -7,6 +7,10 @@ $(objpfx)$(mod).so: $(addprefix $(objpfx),$(addsuffix .os,$($(mod)-routines)))\
 		    $(shlib-lds) $(link-libc-deps)
 	$(build-module-asneeded)
 
+ifneq ($(ld_zunique),yes)
+$(objpfx)$(mod).so: $(common-objpfx)/elf/dynamic-notes.os
+endif
+
 ifneq (,$(extra-modules-left))
 include extra-module.mk
 endif
diff --git a/login/Makefile b/login/Makefile
index 4e6b97734d..703b3f3bd0 100644
--- a/login/Makefile
+++ b/login/Makefile
@@ -50,6 +50,7 @@ ifeq ($(have-GLIBC_2.33),yes)
 # Empty compatibility library for old binaries.
 extra-libs      := libutil
 extra-libs-others := $(extra-libs)
+not-df-gnu-unique := libutil
 libutil-routines := libutil-compat
 libutil-shared-only-routines := libutil-compat
 
diff --git a/nptl/Makefile b/nptl/Makefile
index ff4d590f11..015cbd0b96 100644
--- a/nptl/Makefile
+++ b/nptl/Makefile
@@ -27,6 +27,7 @@ headers := pthread.h semaphore.h bits/semaphore.h \
 
 extra-libs := libpthread
 extra-libs-others := $(extra-libs)
+not-df-gnu-unique := libpthread
 
 routines = \
   alloca_cutoff \
@@ -375,7 +376,9 @@ CPPFLAGS-tst-pthread-gdb-attach-static.c := \
 # were launched with an explicit ld.so invocation.
 tst-pthread-gdb-attach-no-pie = yes
 
-tests += tst-cancelx7 tst-cancelx17
+LDFLAGS-pthread.so = -Wl,--enable-new-dtags,-z,nodelete,-z,initfirst
+
+tests += tst-cancelx7 tst-cancelx17 tst-cleanupx4
 
 ifeq ($(build-shared),yes)
 tests += tst-compat-forwarder tst-audit-threads
diff --git a/resolv/Makefile b/resolv/Makefile
index 59e599535c..56afc5c279 100644
--- a/resolv/Makefile
+++ b/resolv/Makefile
@@ -77,8 +77,10 @@ tests-internal += tst-inet_aton_exact
 generate := mtrace-tst-leaks.out tst-leaks.mtrace tst-leaks2.mtrace
 
 extra-libs := libresolv libnss_dns
+not-df-gnu-unique :=
 ifeq ($(have-thread-library),yes)
 extra-libs += libanl
+not-df-gnu-unique += libanl
 routines += gai_sigqueue
 
 tests += \
