elf: Partially initialize ld.so after static dlopen (bug 20802)

After static dlopen, a copy of ld.so is loaded into the inner
namespace, but that copy is not initialized at all.  Some
architectures run into serious problems as result, which is why the
_dl_var_init mechanism was invented.  With libpthread moving into
libc and parts into ld.so, more architectures impacted, so it makes
sense to switch to a generic mechanism which performs the partial
initialization.

As a result, getauxval now works after static dlopen (bug 20802).

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

1 files changed, 29 insertions, 0 deletions

diff --git a/elf/tst-auxvalmod.c b/elf/tst-auxvalmod.c
new file mode 100644
index 0000000..f87cf98
--- /dev/null
+++ b/elf/tst-auxvalmod.c
@@ -0,0 +1,29 @@
+/* Wrapper for getauxval testing.
+   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 <errno.h>
+#include <sys/auxv.h>
+
+unsigned long
+getauxval_wrapper (unsigned long type, int *errnop)
+{
+  errno = *errnop;
+  unsigned long result = getauxval (type);
+  *errnop = errno;
+  return result;
+}