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.

Reviewed-by: Carlos O'Donell <carlos@redhat.com>
Tested-by: Carlos O'Donell <carlos@redhat.com>

1 files changed, 33 insertions, 0 deletions

diff --git a/elf/dl-is_dso.h b/elf/dl-is_dso.h
new file mode 100644
index 0000000000..94e00966a1
--- /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);
+}