diff --git a/csu/init-first.c b/csu/init-first.c
index e0f489ee6d..8caec305b7 100644
--- a/csu/init-first.c
+++ b/csu/init-first.c
@@ -16,7 +16,6 @@
    License along with the GNU C Library; if not, see
    <https://www.gnu.org/licenses/>.  */
 
-#include <ctype.h>
 #include <stdio.h>
 #include <stdlib.h>
 #include <fcntl.h>
@@ -80,9 +79,6 @@ _init (int argc, char **argv, char **envp)
 
   __init_misc (argc, argv, envp);
 
-  /* Initialize ctype data.  */
-  __ctype_init ();
-
 #if defined SHARED && !defined NO_CTORS_DTORS_SECTIONS
   __libc_global_ctors ();
 #endif
diff --git a/csu/libc-start.c b/csu/libc-start.c
index 14e2b693f0..6b71a89f1d 100644
--- a/csu/libc-start.c
+++ b/csu/libc-start.c
@@ -22,6 +22,7 @@
 #include <ldsodefs.h>
 #include <exit-thread.h>
 #include <libc-internal.h>
+#include <elf/libc-early-init.h>
 
 #include <elf/dl-tunables.h>
 
@@ -238,6 +239,10 @@ LIBC_START_MAIN (int (*main) (int, char **, char ** MAIN_AUXVEC_DECL),
     __cxa_atexit ((void (*) (void *)) rtld_fini, NULL, NULL);
 
 #ifndef SHARED
+  /* Perform early initialization.  In the shared case, this function
+     is called from the dynamic loader as early as possible.  */
+  __libc_early_init ();
+
   /* Call the initializer of the libc.  This is only needed here if we
      are compiling for the static library in which case we haven't
      run the constructors in `_dl_start_user'.  */
diff --git a/elf/Makefile b/elf/Makefile
index dea51ca182..3e08185654 100644
--- a/elf/Makefile
+++ b/elf/Makefile
@@ -25,7 +25,7 @@ headers		= elf.h bits/elfclass.h link.h bits/link.h
 routines	= $(all-dl-routines) dl-support dl-iteratephdr \
 		  dl-addr dl-addr-obj enbl-secure dl-profstub \
 		  dl-origin dl-libc dl-sym dl-sysdep dl-error \
-		  dl-reloc-static-pie
+		  dl-reloc-static-pie libc_early_init
 
 # The core dynamic linking functions are in libc for the static and
 # profiled libraries.
@@ -33,7 +33,8 @@ dl-routines	= $(addprefix dl-,load lookup object reloc deps hwcaps \
 				  runtime init fini debug misc \
 				  version profile tls origin scope \
 				  execstack open close trampoline \
-				  exception sort-maps)
+				  exception sort-maps lookup-direct \
+				  call-libc-early-init)
 ifeq (yes,$(use-ldconfig))
 dl-routines += dl-cache
 endif
diff --git a/elf/Versions b/elf/Versions
index 3b09901f6c..f26d2817c3 100644
--- a/elf/Versions
+++ b/elf/Versions
@@ -26,6 +26,7 @@ libc {
     _dl_open_hook; _dl_open_hook2;
     _dl_sym; _dl_vsym;
     __libc_dlclose; __libc_dlopen_mode; __libc_dlsym; __libc_dlvsym;
+    __libc_early_init;
 
     # Internal error handling support.  Interposes the functions in ld.so.
     _dl_signal_exception; _dl_catch_exception;
diff --git a/elf/dl-call-libc-early-init.c b/elf/dl-call-libc-early-init.c
new file mode 100644
index 0000000000..6c3ac5bfe7
--- /dev/null
+++ b/elf/dl-call-libc-early-init.c
@@ -0,0 +1,41 @@
+/* Invoke the early initialization function in libc.so.
+   Copyright (C) 2019 Free Software Foundation, Inc.
+   This file is part of the GNU C Library.
+
+   The GNU C Library is free software; you can redistribute it and/or
+   modify it under the terms of the GNU Lesser General Public
+   License as published by the Free Software Foundation; either
+   version 2.1 of the License, or (at your option) any later version.
+
+   The GNU C Library is distributed in the hope that it will be useful,
+   but WITHOUT ANY WARRANTY; without even the implied warranty of
+   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
+   Lesser General Public License for more details.
+
+   You should have received a copy of the GNU Lesser General Public
+   License along with the GNU C Library; if not, see
+   <https://www.gnu.org/licenses/>.  */
+
+#include <assert.h>
+#include <ldsodefs.h>
+#include <libc-early-init.h>
+#include <link.h>
+#include <stddef.h>
+
+void
+_dl_call_libc_early_init (struct link_map *libc_map)
+{
+  /* There is nothing to do if we did not actually load libc.so.  */
+  if (libc_map == NULL)
+    return;
+
+  const ElfW(Sym) *sym
+    = _dl_lookup_direct (libc_map, "__libc_early_init",
+                         0x69682ac, /* dl_new_hash output.  */
+                         "GLIBC_PRIVATE",
+                         0x0963cf85); /* _dl_elf_hash output.  */
+  assert (sym != NULL);
+  __typeof (__libc_early_init) *early_init
+    = DL_SYMBOL_ADDRESS (libc_map, sym);
+  early_init ();
+}
diff --git a/elf/dl-load.c b/elf/dl-load.c
index 24e2819345..704be15d94 100644
--- a/elf/dl-load.c
+++ b/elf/dl-load.c
@@ -30,6 +30,7 @@
 #include <sys/param.h>
 #include <sys/stat.h>
 #include <sys/types.h>
+#include <gnu/lib-names.h>
 
 /* Type for the buffer we put the ELF header and hopefully the program
    header.  This buffer does not really have to be too large.  In most
@@ -1373,6 +1374,14 @@ cannot enable executable stack as shared object requires");
     add_name_to_object (l, ((const char *) D_PTR (l, l_info[DT_STRTAB])
 			    + l->l_info[DT_SONAME]->d_un.d_val));
 
+  /* If we have newly loaded libc.so, update the namespace
+     description.  */
+  if (GL(dl_ns)[nsid].libc_map == NULL
+      && l->l_info[DT_SONAME] != NULL
+      && strcmp (((const char *) D_PTR (l, l_info[DT_STRTAB])
+		  + l->l_info[DT_SONAME]->d_un.d_val), LIBC_SO) == 0)
+    GL(dl_ns)[nsid].libc_map = l;
+
   /* _dl_close can only eventually undo the module ID assignment (via
      remove_slotinfo) if this function returns a pointer to a link
      map.  Therefore, delay this step until all possibilities for
diff --git a/elf/dl-lookup-direct.c b/elf/dl-lookup-direct.c
new file mode 100644
index 0000000000..190b826e1e
--- /dev/null
+++ b/elf/dl-lookup-direct.c
@@ -0,0 +1,116 @@
+/* Look up a symbol in a single specified object.
+   Copyright (C) 1995-2019 Free Software Foundation, Inc.
+   This file is part of the GNU C Library.
+
+   The GNU C Library is free software; you can redistribute it and/or
+   modify it under the terms of the GNU Lesser General Public
+   License as published by the Free Software Foundation; either
+   version 2.1 of the License, or (at your option) any later version.
+
+   The GNU C Library is distributed in the hope that it will be useful,
+   but WITHOUT ANY WARRANTY; without even the implied warranty of
+   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
+   Lesser General Public License for more details.
+
+   You should have received a copy of the GNU Lesser General Public
+   License along with the GNU C Library; if not, see
+   <https://www.gnu.org/licenses/>.  */
+
+#include <ldsodefs.h>
+#include <string.h>
+#include <elf_machine_sym_no_match.h>
+#include <dl-hash.h>
+
+/* This function corresponds to do_lookup_x in elf/dl-lookup.c.  The
+   variant here is simplified because it requires symbol
+   versioning. */
+static const ElfW(Sym) *
+check_match (const struct link_map *const map, const char *const undef_name,
+             const char *version, uint32_t version_hash,
+             const Elf_Symndx symidx)
+{
+  const ElfW(Sym) *symtab = (const void *) D_PTR (map, l_info[DT_SYMTAB]);
+  const ElfW(Sym) *sym = &symtab[symidx];
+
+  unsigned int stt = ELFW(ST_TYPE) (sym->st_info);
+  if (__glibc_unlikely ((sym->st_value == 0 /* No value.  */
+                         && sym->st_shndx != SHN_ABS
+                         && stt != STT_TLS)
+                        || elf_machine_sym_no_match (sym)))
+    return NULL;
+
+  /* Ignore all but STT_NOTYPE, STT_OBJECT, STT_FUNC,
+     STT_COMMON, STT_TLS, and STT_GNU_IFUNC since these are no
+     code/data definitions.  */
+#define ALLOWED_STT \
+  ((1 << STT_NOTYPE) | (1 << STT_OBJECT) | (1 << STT_FUNC) \
+   | (1 << STT_COMMON) | (1 << STT_TLS) | (1 << STT_GNU_IFUNC))
+  if (__glibc_unlikely (((1 << stt) & ALLOWED_STT) == 0))
+    return NULL;
+
+  const char *strtab = (const void *) D_PTR (map, l_info[DT_STRTAB]);
+
+  if (strcmp (strtab + sym->st_name, undef_name) != 0)
+    /* Not the symbol we are looking for.  */
+    return NULL;
+
+  ElfW(Half) ndx = map->l_versyms[symidx] & 0x7fff;
+  if (map->l_versions[ndx].hash != version_hash
+      || strcmp (map->l_versions[ndx].name, version) != 0)
+    /* It's not the version we want.  */
+    return NULL;
+
+  return sym;
+}
+
+
+/* This function corresponds to do_lookup_x in elf/dl-lookup.c.  The
+   variant here is simplified because it does not search object
+   dependencies.  It is optimized for a successful lookup.  */
+const ElfW(Sym) *
+_dl_lookup_direct (struct link_map *map,
+                   const char *undef_name, uint32_t new_hash,
+                   const char *version, uint32_t version_hash)
+{
+  const ElfW(Addr) *bitmask = map->l_gnu_bitmask;
+  if (__glibc_likely (bitmask != NULL))
+    {
+      Elf32_Word bucket = map->l_gnu_buckets[new_hash % map->l_nbuckets];
+      if (bucket != 0)
+        {
+          const Elf32_Word *hasharr = &map->l_gnu_chain_zero[bucket];
+
+          do
+            if (((*hasharr ^ new_hash) >> 1) == 0)
+              {
+                Elf_Symndx symidx = ELF_MACHINE_HASH_SYMIDX (map, hasharr);
+                const ElfW(Sym) *sym = check_match (map, undef_name,
+                                                    version, version_hash,
+                                                    symidx);
+                if (sym != NULL)
+                  return sym;
+              }
+          while ((*hasharr++ & 1u) == 0);
+        }
+    }
+  else
+    {
+      /* Fallback code for lack of GNU_HASH support.  */
+      uint32_t old_hash = _dl_elf_hash (undef_name);
+
+      /* Use the old SysV-style hash table.  Search the appropriate
+         hash bucket in this object's symbol table for a definition
+         for the same symbol name.  */
+      for (Elf_Symndx symidx = map->l_buckets[old_hash % map->l_nbuckets];
+           symidx != STN_UNDEF;
+           symidx = map->l_chain[symidx])
+        {
+          const ElfW(Sym) *sym = check_match (map, undef_name,
+                                              version, version_hash, symidx);
+          if (sym != NULL)
+            return sym;
+        }
+    }
+
+  return NULL;
+}
diff --git a/elf/dl-open.c b/elf/dl-open.c
index a9fd4cbced..98353cdcc3 100644
--- a/elf/dl-open.c
+++ b/elf/dl-open.c
@@ -33,6 +33,7 @@
 #include <stap-probe.h>
 #include <atomic.h>
 #include <libc-internal.h>
+#include <libc-early-init.h>
 
 #include <dl-dst.h>
 #include <dl-prop.h>
@@ -50,6 +51,14 @@ struct dl_open_args
   struct link_map *map;
   /* Namespace ID.  */
   Lmid_t nsid;
+
+  /* Set to to true if libc.so was already loaded into the namespace
+     at the time dl_open_worker was called.  This is used to determine
+     whether libc.so early initialization needs to before, and whether
+     to roll back the cached libc_map value in the namespace in case
+     of a dlopen failure.  */
+  bool libc_already_loaded;
+
   /* Original parameters to the program and the current environment.  */
   int argc;
   char **argv;
@@ -208,6 +217,11 @@ dl_open_worker (void *a)
 	args->nsid = call_map->l_ns;
     }
 
+  /* The namespace ID is now known.  Keep track of whether libc.so was
+     already loaded, to determine whether it is necessary to call the
+     early initialization routine (or clear libc_map on error).  */
+  args->libc_already_loaded = GL(dl_ns)[args->nsid].libc_map != NULL;
+
   /* One might be tempted to assert that we are RT_CONSISTENT at this point, but that
      may not be true if this is a recursive call to dlopen.  */
   _dl_debug_initialize (0, args->nsid);
@@ -502,6 +516,11 @@ TLS generation counter wrapped!  Please report this."));
   if (relocation_in_progress)
     LIBC_PROBE (reloc_complete, 3, args->nsid, r, new);
 
+  /* If libc.so was not there before, attempt to call its early
+     initialization routine.  */
+  if (!args->libc_already_loaded)
+    _dl_call_libc_early_init (GL(dl_ns)[args->nsid].libc_map);
+
 #ifndef SHARED
   DL_STATIC_INIT (new);
 #endif
@@ -584,6 +603,7 @@ no more namespaces available for dlmopen()"));
   args.caller_dlopen = caller_dlopen;
   args.map = NULL;
   args.nsid = nsid;
+  args.libc_already_loaded = true; /* No reset below with early failure.  */
   args.argc = argc;
   args.argv = argv;
   args.env = env;
@@ -599,6 +619,11 @@ no more namespaces available for dlmopen()"));
   /* See if an error occurred during loading.  */
   if (__glibc_unlikely (exception.errstring != NULL))
     {
+      /* Avoid keeping around a dangling reference to the libc.so link
+	 map in case it has been cached in libc_map.  */
+      if (!args.libc_already_loaded)
+	GL(dl_ns)[nsid].libc_map = NULL;
+
       /* Remove the object from memory.  It may be in an inconsistent
 	 state if relocation failed, for example.  */
       if (args.map)
diff --git a/elf/libc-early-init.h b/elf/libc-early-init.h
new file mode 100644
index 0000000000..02b855754e
--- /dev/null
+++ b/elf/libc-early-init.h
@@ -0,0 +1,35 @@
+/* Early initialization of libc.so.
+   Copyright (C) 2019 Free Software Foundation, Inc.
+   This file is part of the GNU C Library.
+
+   The GNU C Library is free software; you can redistribute it and/or
+   modify it under the terms of the GNU Lesser General Public
+   License as published by the Free Software Foundation; either
+   version 2.1 of the License, or (at your option) any later version.
+
+   The GNU C Library is distributed in the hope that it will be useful,
+   but WITHOUT ANY WARRANTY; without even the implied warranty of
+   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
+   Lesser General Public License for more details.
+
+   You should have received a copy of the GNU Lesser General Public
+   License along with the GNU C Library; if not, see
+   <https://www.gnu.org/licenses/>.  */
+
+#ifndef _LIBC_EARLY_INIT_H
+#define _LIBC_EARLY_INIT_H
+
+struct link_map;
+
+/* If LIBC_MAP is not NULL, look up the __libc_early_init symbol in it
+   and call this function.  */
+void _dl_call_libc_early_init (struct link_map *libc_map) attribute_hidden;
+
+/* In the shared case, this function is defined in libc.so and invoked
+   from ld.so (or on the fist static dlopen) after complete relocation
+   of a new loaded libc.so, but before user-defined ELF constructors
+   run.  In the static case, this function is called directly from the
+   startup code.  */
+void __libc_early_init (void);
+
+#endif /* _LIBC_EARLY_INIT_H */
diff --git a/elf/libc_early_init.c b/elf/libc_early_init.c
new file mode 100644
index 0000000000..1ac66d895d
--- /dev/null
+++ b/elf/libc_early_init.c
@@ -0,0 +1,27 @@
+/* Early initialization of libc.so, libc.so side.
+   Copyright (C) 2019 Free Software Foundation, Inc.
+   This file is part of the GNU C Library.
+
+   The GNU C Library is free software; you can redistribute it and/or
+   modify it under the terms of the GNU Lesser General Public
+   License as published by the Free Software Foundation; either
+   version 2.1 of the License, or (at your option) any later version.
+
+   The GNU C Library is distributed in the hope that it will be useful,
+   but WITHOUT ANY WARRANTY; without even the implied warranty of
+   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
+   Lesser General Public License for more details.
+
+   You should have received a copy of the GNU Lesser General Public
+   License along with the GNU C Library; if not, see
+   <https://www.gnu.org/licenses/>.  */
+
+#include <ctype.h>
+#include <libc-early-init.h>
+
+void
+__libc_early_init (void)
+{
+  /* Initialize ctype data.  */
+  __ctype_init ();
+}
diff --git a/elf/rtld.c b/elf/rtld.c
index 8a6e1a11b2..a29e71cfd1 100644
--- a/elf/rtld.c
+++ b/elf/rtld.c
@@ -43,6 +43,7 @@
 #include <stap-probe.h>
 #include <stackinfo.h>
 #include <not-cancel.h>
+#include <libc-early-init.h>
 
 #include <assert.h>
 
@@ -2314,6 +2315,9 @@ ERROR: '%s': cannot process note segment.\n", _dl_argv[0]);
       rtld_timer_accum (&relocate_time, start);
     }
 
+  /* Relocation is complete.  Perform early libc initialization.  */
+  _dl_call_libc_early_init (GL(dl_ns)[LM_ID_BASE].libc_map);
+
   /* Do any necessary cleanups for the startup OS interface code.
      We do these now so that no calls are made after rtld re-relocation
      which might be resolved to different functions than we expect.
diff --git a/sysdeps/generic/ldsodefs.h b/sysdeps/generic/ldsodefs.h
index f3ba13ee68..2c05bff1e9 100644
--- a/sysdeps/generic/ldsodefs.h
+++ b/sysdeps/generic/ldsodefs.h
@@ -329,6 +329,11 @@ struct rtld_global
        allocated by rtld.  Later it keeps the size of the map.  It might be
        reset if in _dl_close if the last global object is removed.  */
     size_t _ns_global_scope_alloc;
+
+    /* Once libc.so has been loaded into the namespace, this points to
+       its link map.  */
+    struct link_map *libc_map;
+
     /* Search table for unique objects.  */
     struct unique_sym_table
     {
@@ -927,6 +932,19 @@ extern lookup_t _dl_lookup_symbol_x (const char *undef,
      attribute_hidden;
 
 
+/* Restricted version of _dl_lookup_symbol_x.  Searches MAP (and only
+   MAP) for the symbol UNDEF_NAME, with GNU hash NEW_HASH (computed
+   with dl_new_hash), symbol version VERSION, and symbol version hash
+   VERSION_HASH (computed with _dl_elf_hash).  Returns a pointer to
+   the symbol table entry in MAP on success, or NULL on failure.  MAP
+   must have symbol versioning information, or otherwise the result is
+   undefined.  */
+const ElfW(Sym) *_dl_lookup_direct (struct link_map *map,
+				    const char *undef_name,
+				    uint32_t new_hash,
+				    const char *version,
+				    uint32_t version_hash) attribute_hidden;
+
 /* Add the new link_map NEW to the end of the namespace list.  */
 extern void _dl_add_to_namespace_list (struct link_map *new, Lmid_t nsid)
      attribute_hidden;
diff --git a/sysdeps/mach/hurd/i386/init-first.c b/sysdeps/mach/hurd/i386/init-first.c
index f1f1c40389..2fb913e922 100644
--- a/sysdeps/mach/hurd/i386/init-first.c
+++ b/sysdeps/mach/hurd/i386/init-first.c
@@ -17,7 +17,6 @@
    <https://www.gnu.org/licenses/>.  */
 
 #include <assert.h>
-#include <ctype.h>
 #include <hurd.h>
 #include <stdio.h>
 #include <unistd.h>
@@ -84,9 +83,6 @@ posixland_init (int argc, char **argv, char **envp)
 #endif
   __init_misc (argc, argv, envp);
 
-  /* Initialize ctype data.  */
-  __ctype_init ();
-
 #if defined SHARED && !defined NO_CTORS_DTORS_SECTIONS
   __libc_global_ctors ();
 #endif
