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, 66 insertions, 0 deletions

diff --git a/elf/tst-getauxval-static.c b/elf/tst-getauxval-static.c
new file mode 100644
index 0000000..8bc8707
--- /dev/null
+++ b/elf/tst-getauxval-static.c
@@ -0,0 +1,66 @@
+/* Test getauxval from a dynamic library after static dlopen.
+   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 <dlfcn.h>
+#include <errno.h>
+#include <stdio.h>
+#include <support/check.h>
+#include <support/xdlfcn.h>
+#include <sys/auxv.h>
+
+unsigned long getauxval_wrapper (unsigned long type, int *errnop);
+
+static int
+do_test (void)
+{
+  unsigned long outer_random = getauxval (AT_RANDOM);
+  if (outer_random == 0)
+    FAIL_UNSUPPORTED ("getauxval does not support AT_RANDOM");
+
+  unsigned long missing_auxv_type;
+  for (missing_auxv_type = AT_RANDOM + 1; ; ++missing_auxv_type)
+    {
+      errno = 0;
+      if (getauxval (missing_auxv_type) == 0 && errno != 0)
+        {
+          TEST_COMPARE (errno, ENOENT);
+          break;
+        }
+    }
+  printf ("info: first missing type: %lu\n", missing_auxv_type);
+
+  void *handle = xdlopen ("tst-auxvalmod.so", RTLD_LAZY);
+  void *ptr = xdlsym (handle, "getauxval_wrapper");
+
+  __typeof__ (getauxval_wrapper) *wrapper = ptr;
+  int inner_errno = 0;
+  unsigned long inner_random = wrapper (AT_RANDOM, &inner_errno);
+  TEST_COMPARE (outer_random, inner_random);
+
+  inner_errno = 0;
+  TEST_COMPARE (wrapper (missing_auxv_type, &inner_errno), 0);
+  TEST_COMPARE (inner_errno, ENOENT);
+
+  TEST_COMPARE (getauxval (AT_HWCAP), wrapper (AT_HWCAP, &inner_errno));
+  TEST_COMPARE (getauxval (AT_HWCAP2), wrapper (AT_HWCAP2, &inner_errno));
+
+  xdlclose (handle);
+  return 0;
+}
+
+#include <support/test-driver.c>