Revert "Detect ld.so and libc.so version inconsistency during startup"

This reverts commit 6f85dbf102ad7982409ba0fe96886caeb6389fef.

Once this change hits the release branches, it will require relinking
of all statically linked applications before static dlopen works
again, for the majority of updates on release branches: The NEWS file
is regularly updated with bug references, so the __libc_early_init
suffix changes, and static dlopen cannot find the function anymore.

While this ABI check is still technically correct (we do require
rebuilding & relinking after glibc updates to keep static dlopen
working), it is too drastic for stable release branches.

Reviewed-by: Adhemerval Zanella  <adhemerval.zanella@linaro.org>

8 files changed, 44 insertions, 49 deletions

diff --git a/elf/Makefile b/elf/Makefile
index bc68150..3928a08 100644
--- a/elf/Makefile
+++ b/elf/Makefile
@@ -52,6 +52,7 @@ routines = \
 # The core dynamic linking functions are in libc for the static and
 # profiled libraries.
 dl-routines = \
+  dl-call-libc-early-init \
   dl-close \
   dl-debug \
   dl-debug-symbols \
@@ -64,7 +65,6 @@ dl-routines = \
   dl-load \
   dl-lookup \
   dl-lookup-direct \
-  dl-lookup_libc_early_init \
   dl-minimal-malloc \
   dl-misc \
   dl-object \
diff --git a/elf/Versions b/elf/Versions
index 6260c0f..a9ff278 100644
--- a/elf/Versions
+++ b/elf/Versions
@@ -29,8 +29,8 @@ libc {
     __placeholder_only_for_empty_version_map;
   }
   GLIBC_PRIVATE {
-    # A pattern is needed here because the suffix is dynamically generated.
-    __libc_early_init_*;
+    # functions used in other libraries
+    __libc_early_init;
 
     # Internal error handling support.  Interposes the functions in ld.so.
     _dl_signal_exception; _dl_catch_exception;
diff --git a/elf/dl-lookup_libc_early_init.c b/elf/dl-call-libc-early-init.c
index 64bc287..ee9860e 100644
--- a/elf/dl-lookup_libc_early_init.c
+++ b/elf/dl-call-libc-early-init.c
@@ -1,4 +1,4 @@
-/* Find the address of the __libc_early_init function.
+/* Invoke the early initialization function in libc.so.
    Copyright (C) 2020-2022 Free Software Foundation, Inc.
    This file is part of the GNU C Library.
 
@@ -16,21 +16,26 @@
    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>
 
-__typeof (__libc_early_init) *
-_dl_lookup_libc_early_init (struct link_map *libc_map)
+void
+_dl_call_libc_early_init (struct link_map *libc_map, _Bool initial)
 {
+  /* 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_NAME_STRING,
-                         LIBC_EARLY_INIT_GNU_HASH,
+    = _dl_lookup_direct (libc_map, "__libc_early_init",
+                         0x069682ac, /* dl_new_hash output.  */
                          "GLIBC_PRIVATE",
                          0x0963cf85); /* _dl_elf_hash output.  */
-  if (sym == NULL)
-    _dl_signal_error (0, libc_map->l_name, NULL, "\
-ld.so/libc.so mismatch detected (upgrade in progress?)");
-  return DL_SYMBOL_ADDRESS (libc_map, sym);
+  assert (sym != NULL);
+  __typeof (__libc_early_init) *early_init
+    = DL_SYMBOL_ADDRESS (libc_map, sym);
+  early_init (initial);
 }
diff --git a/elf/dl-load.c b/elf/dl-load.c
index 00e08b5..1ad0868 100644
--- a/elf/dl-load.c
+++ b/elf/dl-load.c
@@ -31,6 +31,7 @@
 #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
@@ -1465,6 +1466,14 @@ 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-open.c b/elf/dl-open.c
index dcc2413..a23e659 100644
--- a/elf/dl-open.c
+++ b/elf/dl-open.c
@@ -760,8 +760,8 @@ dl_open_worker_begin (void *a)
   if (!args->libc_already_loaded)
     {
       /* dlopen cannot be used to load an initial libc by design.  */
-      if (GL(dl_ns)[args->nsid].libc_map != NULL)
-	GL(dl_ns)[args->nsid].libc_map_early_init (false);
+      struct link_map *libc_map = GL(dl_ns)[args->nsid].libc_map;
+      _dl_call_libc_early_init (libc_map, false);
     }
 
   args->worker_continue = true;
diff --git a/elf/dl-version.c b/elf/dl-version.c
index d9ec44e..cda0889 100644
--- a/elf/dl-version.c
+++ b/elf/dl-version.c
@@ -23,8 +23,6 @@
 #include <string.h>
 #include <ldsodefs.h>
 #include <_itoa.h>
-#include <gnu/lib-names.h>
-#include <libc-early-init.h>
 
 #include <assert.h>
 
@@ -361,22 +359,6 @@ _dl_check_map_versions (struct link_map *map, int verbose, int trace_mode)
 	}
     }
 
-  /* Detect a libc.so loaded into this namespace.  The
-     __libc_early_init lookup below means that we have to do this
-     after parsing the version data.  */
-  if (GL(dl_ns)[map->l_ns].libc_map == NULL
-      && map->l_info[DT_SONAME] != NULL
-      && strcmp (((const char *) D_PTR (map, l_info[DT_STRTAB])
-		  + map->l_info[DT_SONAME]->d_un.d_val), LIBC_SO) == 0)
-    {
-      /* Look up this symbol early to trigger a mismatch error before
-	 relocation (which may call IFUNC resolvers, and those can
-	 have an internal ABI dependency).  */
-      GL(dl_ns)[map->l_ns].libc_map_early_init
-	= _dl_lookup_libc_early_init (map);
-      GL(dl_ns)[map->l_ns].libc_map = map;
-    }
-
   /* When there is a DT_VERNEED entry with libc.so on DT_NEEDED, issue
      an error if there is a DT_RELR entry without GLIBC_ABI_DT_RELR
      dependency.  */
diff --git a/elf/libc-early-init.h b/elf/libc-early-init.h
index ac8c204..a8edfad 100644
--- a/elf/libc-early-init.h
+++ b/elf/libc-early-init.h
@@ -19,10 +19,13 @@
 #ifndef _LIBC_EARLY_INIT_H
 #define _LIBC_EARLY_INIT_H
 
-#include <libc_early_init_name.h>
-
 struct link_map;
 
+/* If LIBC_MAP is not NULL, look up the __libc_early_init symbol in it
+   and call this function, with INITIAL as the argument.  */
+void _dl_call_libc_early_init (struct link_map *libc_map, _Bool initial)
+  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
@@ -30,18 +33,6 @@ struct link_map;
    startup code.  If INITIAL is true, the libc being initialized is
    the libc for the main program.  INITIAL is false for libcs loaded
    for audit modules, dlmopen, and static dlopen.  */
-void __libc_early_init (_Bool initial)
-#ifdef SHARED
-/* Redirect to the actual implementation name.  */
-  __asm__ (LIBC_EARLY_INIT_NAME_STRING)
-#endif
-  ;
-
-/* Attempts to find the appropriately named __libc_early_init function
-   in LIBC_MAP.  On lookup failure, an exception is signaled,
-   indicating an ld.so/libc.so mismatch.  */
-__typeof (__libc_early_init) *_dl_lookup_libc_early_init (struct link_map *
-                                                          libc_map)
-  attribute_hidden;
+void __libc_early_init (_Bool initial);
 
 #endif /* _LIBC_EARLY_INIT_H */
diff --git a/elf/rtld.c b/elf/rtld.c
index 910075c..cbbaf4a 100644
--- a/elf/rtld.c
+++ b/elf/rtld.c
@@ -1707,6 +1707,15 @@ dl_main (const ElfW(Phdr) *phdr,
       /* Extract the contents of the dynamic section for easy access.  */
       elf_get_dynamic_info (main_map, false, false);
 
+      /* If the main map is libc.so, update the base namespace to
+	 refer to this map.  If libc.so is loaded later, this happens
+	 in _dl_map_object_from_fd.  */
+      if (main_map->l_info[DT_SONAME] != NULL
+	  && (strcmp (((const char *) D_PTR (main_map, l_info[DT_STRTAB])
+		      + main_map->l_info[DT_SONAME]->d_un.d_val), LIBC_SO)
+	      == 0))
+	GL(dl_ns)[LM_ID_BASE].libc_map = main_map;
+
       /* Set up our cache of pointers into the hash table.  */
       _dl_setup_hash (main_map);
     }
@@ -2377,8 +2386,7 @@ dl_main (const ElfW(Phdr) *phdr,
   /* Relocation is complete.  Perform early libc initialization.  This
      is the initial libc, even if audit modules have been loaded with
      other libcs.  */
-  if (GL(dl_ns)[LM_ID_BASE].libc_map != NULL)
-    GL(dl_ns)[LM_ID_BASE].libc_map_early_init (true);
+  _dl_call_libc_early_init (GL(dl_ns)[LM_ID_BASE].libc_map, true);
 
   /* Do any necessary cleanups for the startup OS interface code.
      We do these now so that no calls are made after rtld re-relocation