[v3] elf: Restore ldconfig libc6 implicit soname logic [BZ #30125]

diff --git a/elf/Makefile b/elf/Makefile
index 2fc6391183..476f062dae 100644
--- a/elf/Makefile
+++ b/elf/Makefile
@@ -627,6 +627,7 @@  tests-special += \
   $(objpfx)noload-mem.out \
   $(objpfx)tst-ldconfig-X.out \
   $(objpfx)tst-ldconfig-p.out \
+  $(objpfx)tst-ldconfig-no-soname.out \
   $(objpfx)tst-leaks1-mem.out \
   $(objpfx)tst-rtld-help.out \
   # tests-special
@@ -2402,6 +2403,12 @@  $(objpfx)tst-ldconfig-p.out : tst-ldconfig-p.sh $(objpfx)ldconfig
 		 '$(run-program-env)' > $@; \
 	$(evaluate-test)
 
+$(objpfx)tst-ldconfig-no-soname.out : tst-ldconfig-no-soname.sh \
+	$(objpfx)ldconfig
+	$(SHELL) $< '$(CC)' '$(common-objpfx)' '$(test-wrapper-env)' \
+		 '$(run-program-env)' > $@; \
+	$(evaluate-test)
+
 # Test static linking of all the libraries we can possibly link
 # together.  Note that in some configurations this may be less than the
 # complete list of libraries we build but we try to maxmimize this list.
diff --git a/elf/ldconfig.c b/elf/ldconfig.c
index 3f1b30c570..2fc45ad825 100644
--- a/elf/ldconfig.c
+++ b/elf/ldconfig.c
@@ -616,7 +616,7 @@  manual_link (char *library)
       goto out;
     }
   if (soname == NULL)
-    soname = implicit_soname (libname, flag);
+    soname = xstrdup (libname);
   create_links (real_path, path, libname, soname);
   free (soname);
 out:
@@ -849,7 +849,7 @@  search_dir (const struct dir_entry *entry)
 	}
 
       if (soname == NULL)
-	soname = implicit_soname (direntry->d_name, flag);
+	soname = xstrdup (direntry->d_name);
 
       /* A link may just point to itself.  */
       if (is_link)
diff --git a/elf/readlib.c b/elf/readlib.c
index c5c3591eef..bc13d9acc6 100644
--- a/elf/readlib.c
+++ b/elf/readlib.c
@@ -166,24 +166,5 @@  process_file (const char *real_file_name, const char *file_name,
   return ret;
 }
 
-/* Returns made up soname if lib doesn't have explicit DT_SONAME.  */
-
-char *
-implicit_soname (const char *lib, int flag)
-{
-  char *soname = xstrdup (lib);
-
-  /* Aout files don't have a soname, just return the name
-     including the major number.  */
-  char *major = strstr (soname, ".so.");
-  if (major)
-    {
-      char *dot = strstr (major + 4, ".");
-      if (dot)
-	*dot = '\0';
-    }
-  return soname;
-}
-
 /* Get architecture specific version of process_elf_file.  */
 #include <readelflib.c>
diff --git a/elf/tst-ldconfig-no-soname.sh b/elf/tst-ldconfig-no-soname.sh
new file mode 100644
index 0000000000..a61a8fedba
--- /dev/null
+++ b/elf/tst-ldconfig-no-soname.sh
@@ -0,0 +1,48 @@ 
+#!/bin/sh
+# Test that ldconfig does not create symlinks for libraries without a soname.
+# Copyright (C) 2000-2023 Free Software Foundation, Inc.
+# Copyright The GNU Toolchain Authors.
+# 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/>.
+
+set -ex
+
+CC=$1
+common_objpfx=$2
+test_wrapper_env=$3
+run_program_env=$4
+
+testroot="${common_objpfx}elf/bug30125-test-directory"
+cleanup () {
+    rm -rf "$testroot"
+}
+trap cleanup 0
+
+rm -rf "$testroot"
+mkdir -p $testroot/lib $testroot/etc
+
+$CC /dev/null -o $testroot/lib/libsomething.so.1.2.3 -shared
+
+${test_wrapper_env} \
+${run_program_env} \
+${common_objpfx}elf/ldconfig -f /dev/null \
+  -C $testroot/etc/ld.so.cache \
+  $testroot/lib
+
+if [ -n "$(find $testroot/lib -type l)" ]; then
+    echo "error: $0 - symlink found"
+    exit 1
+fi
diff --git a/sysdeps/generic/ldconfig.h b/sysdeps/generic/ldconfig.h
index 0e1a9a9515..e9e9e19d0f 100644
--- a/sysdeps/generic/ldconfig.h
+++ b/sysdeps/generic/ldconfig.h
@@ -90,8 +90,6 @@  extern int process_file (const char *real_file_name, const char *file_name,
 			 const char *lib, int *flag, unsigned int *isa_level,
 			 char **soname, int is_link, struct stat *stat_buf);
 
-extern char *implicit_soname (const char *lib, int flag);
-
 /* Declared in readelflib.c.  */
 extern int process_elf_file (const char *file_name, const char *lib,
 			     int *flag, unsigned int *isa_level, char **soname,