Patch series proposed upstream:

  <https://sourceware.org/pipermail/libc-alpha/2021-June/127473.html>

Author: Florian Weimer <fweimer@redhat.com>

Date:   Wed Jun 9 14:12:46 2021 +0200

    elf: Generalize name-based DSO recognition in ldconfig

    This introduces <dl-is_dso.h> and the _dl_is_dso function.  A

    test ensures that the official names of libc.so, ld.so, and their

    versioned names are recognized.

diff --git a/elf/Makefile b/elf/Makefile

index 38d08e03b8979a81..62f7e8a22544ab9d 100644

--- a/elf/Makefile

+++ b/elf/Makefile

@@ -223,7 +223,8 @@ tests += restest1 preloadtest loadfail multiload origtest resolvfail \

 	 tst-single_threaded tst-single_threaded-pthread \

 	 tst-tls-ie tst-tls-ie-dlmopen argv0test \

 	 tst-glibc-hwcaps tst-glibc-hwcaps-prepend tst-glibc-hwcaps-mask \

-	 tst-tls20 tst-tls21 tst-dlmopen-dlerror tst-dlmopen-gethostbyname

+	 tst-tls20 tst-tls21 tst-dlmopen-dlerror tst-dlmopen-gethostbyname \

+	 tst-dl-is_dso

 #	 reldep9

 tests-internal += loadtest unload unload2 circleload1 \

 	 neededtest neededtest2 neededtest3 neededtest4 \

diff --git a/elf/dl-is_dso.h b/elf/dl-is_dso.h

new file mode 100644

index 0000000000000000..94e00966a16e0df5

--- /dev/null

+++ b/elf/dl-is_dso.h

@@ -0,0 +1,33 @@

+/* Heuristic for recognizing DSO file names.

+   Copyright (C) 2021 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 <stdbool.h>

+#include <string.h>

+

+/* Returns true if the file name looks like a DSO name.  */

+static bool

+_dl_is_dso (const char *name)

+{

+  /* Recognize lib*.so*, ld-*.so*, ld.so.*, ld64.so.*.  ld-*.so*

+     matches both platform dynamic linker names like ld-linux.so.2,

+     and versioned dynamic loader names like ld-2.12.so.  */

+  return (((strncmp (name, "lib", 3) == 0 || strncmp (name, "ld-", 3) == 0)

+           && strstr (name, ".so") != NULL)

+          || strncmp (name, "ld.so.", 6) == 0

+          || strncmp (name, "ld64.so.", 8) == 0);

+}

diff --git a/elf/ldconfig.c b/elf/ldconfig.c

index 96bf7700b2efd37a..1037e8d0cf8d28b6 100644

--- a/elf/ldconfig.c

+++ b/elf/ldconfig.c

@@ -43,6 +43,7 @@

 #include <ldconfig.h>

 #include <dl-cache.h>

 #include <dl-hwcaps.h>

+#include <dl-is_dso.h>

 #include <dl-procinfo.h>

@@ -842,9 +843,7 @@ search_dir (const struct dir_entry *entry)

 	 subdirectory (if not already processing a glibc-hwcaps

 	 subdirectory)?  The dynamic linker is also considered as

 	 shared library.  */

-      if (((strncmp (direntry->d_name, "lib", 3) != 0

-	    && strncmp (direntry->d_name, "ld-", 3) != 0)

-	   || strstr (direntry->d_name, ".so") == NULL)

+      if (!_dl_is_dso (direntry->d_name)

 	  && (direntry->d_type == DT_REG

 	      || (entry->hwcaps == NULL

 		  && !is_hwcap_platform (direntry->d_name))))

diff --git a/elf/tst-dl-is_dso.c b/elf/tst-dl-is_dso.c

new file mode 100644

index 0000000000000000..48d2cc9fbe9edbc6

--- /dev/null

+++ b/elf/tst-dl-is_dso.c

@@ -0,0 +1,35 @@

+/* Test heuristic for recognizing DSO file names.

+   Copyright (C) 2021 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 <dl-is_dso.h>

+#include <gnu/lib-names.h>

+#include <support/check.h>

+

+static int

+do_test (void)

+{

+  /* Official ABI names.  */

+  TEST_VERIFY (_dl_is_dso (LIBC_SO));

+  TEST_VERIFY (_dl_is_dso (LD_SO));

+  /* Version-based names.  The version number does not matter.  */

+  TEST_VERIFY (_dl_is_dso ("libc-2.12.so"));

+  TEST_VERIFY (_dl_is_dso ("ld-2.12.so"));

+  return 0;

+}

+

+#include <support/test-driver.c>