elf: Issue audit la_objopen for vDSO

The vDSO is is listed in the link_map chain, but is never the subject of
an la_objopen call.  A new internal flag __RTLD_VDSO is added that
acts as __RTLD_OPENEXEC to allocate the required 'struct auditstate'
extra space for the 'struct link_map'.

The return value from the callback is currently ignored, since there
is no PLT call involved by glibc when using the vDSO, neither the vDSO
are exported directly.

Checked on x86_64-linux-gnu, i686-linux-gnu, and aarch64-linux-gnu.

Reviewed-by: Florian Weimer <fweimer@redhat.com>

1 files changed, 124 insertions, 0 deletions

diff --git a/elf/tst-audit22.c b/elf/tst-audit22.c
new file mode 100644
index 0000000..18fd22a
--- /dev/null
+++ b/elf/tst-audit22.c
@@ -0,0 +1,124 @@
+/* Check DTAUDIT and vDSO interaction.
+   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 <getopt.h>
+#include <limits.h>
+#include <inttypes.h>
+#include <string.h>
+#include <stdlib.h>
+#include <support/capture_subprocess.h>
+#include <support/check.h>
+#include <support/xstdio.h>
+#include <support/support.h>
+#include <sys/auxv.h>
+
+static int restart;
+#define CMDLINE_OPTIONS \
+  { "restart", no_argument, &restart, 1 },
+
+static uintptr_t vdso_addr;
+
+static int
+handle_restart (void)
+{
+  fprintf (stderr, "vdso: %p\n", (void*) vdso_addr);
+  return 0;
+}
+
+static uintptr_t
+parse_address (const char *str)
+{
+  void *r;
+  TEST_COMPARE (sscanf (str, "%p\n", &r), 1);
+  return (uintptr_t) r;
+}
+
+static inline bool
+startswith (const char *str, const char *pre)
+{
+  size_t lenpre = strlen (pre);
+  size_t lenstr = strlen (str);
+  return lenstr >= lenpre && memcmp (pre, str, lenpre) == 0;
+}
+
+static int
+do_test (int argc, char *argv[])
+{
+  vdso_addr = getauxval (AT_SYSINFO_EHDR);
+  if (vdso_addr == 0)
+    FAIL_UNSUPPORTED ("getauxval (AT_SYSINFO_EHDR) returned 0");
+
+  /* We must have either:
+     - One our fource parameters left if called initially:
+       + path to ld.so         optional
+       + "--library-path"      optional
+       + the library path      optional
+       + the application name  */
+  if (restart)
+    return handle_restart ();
+
+  char *spargv[9];
+  int i = 0;
+  for (; i < argc - 1; i++)
+    spargv[i] = argv[i + 1];
+  spargv[i++] = (char *) "--direct";
+  spargv[i++] = (char *) "--restart";
+  spargv[i] = NULL;
+
+  setenv ("LD_AUDIT", "tst-auditmod22.so", 0);
+  struct support_capture_subprocess result
+    = support_capture_subprogram (spargv[0], spargv);
+  support_capture_subprocess_check (&result, "tst-audit22", 0, sc_allow_stderr);
+
+  /* The respawned process should always print the vDSO address (otherwise it
+     will fails as unsupported).  However, on some architectures the audit
+     module might see the vDSO with l_addr being 0, meaning a fixed mapping
+     (linux-gate.so).  In this case we don't check its value against
+     AT_SYSINFO_EHDR one.  */
+  uintptr_t vdso_process = 0;
+  bool vdso_audit_found = false;
+  uintptr_t vdso_audit = 0;
+
+  FILE *out = fmemopen (result.err.buffer, result.err.length, "r");
+  TEST_VERIFY (out != NULL);
+  char *buffer = NULL;
+  size_t buffer_length = 0;
+  while (xgetline (&buffer, &buffer_length, out))
+    {
+      if (startswith (buffer, "vdso: "))
+	vdso_process = parse_address (buffer + strlen ("vdso: "));
+      else if (startswith (buffer, "vdso found: "))
+	{
+	  vdso_audit = parse_address (buffer + strlen ("vdso found: "));
+          vdso_audit_found = true;
+	}
+    }
+
+  TEST_COMPARE (vdso_audit_found, true);
+  if (vdso_audit != 0)
+    TEST_COMPARE (vdso_process, vdso_audit);
+
+  free (buffer);
+  xfclose (out);
+
+  return 0;
+}
+
+#define TEST_FUNCTION_ARGV do_test
+#include <support/test-driver.c>