Allow for unpriviledged nested containers

If the build itself is run in a container, we may not be able to
fully set up a nested container for test-container testing.
Notably is the mounting of /proc, since it's critical that it
be mounted from within the same PID namespace as its users, and
thus cannot be bind mounted from outside the container like other
mounts.

This patch defaults to using the parent's PID namespace instead of
creating a new one, as this is more likely to be allowed.

If the test needs an isolated PID namespace, it should add the "pidns"
command to its init script.

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

1 files changed, 35 insertions, 0 deletions

diff --git a/support/support_need_proc.c b/support/support_need_proc.c
new file mode 100644
index 0000000000..9b4eab7539
--- /dev/null
+++ b/support/support_need_proc.c
@@ -0,0 +1,35 @@
+/* Indicate that a test requires a working /proc.
+   Copyright (C) 2022 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 <unistd.h>
+#include <support/check.h>
+#include <support/support.h>
+
+/* We test for /proc/self/maps since that's one of the files that one
+   of our tests actually uses, but the general idea is if Linux's
+   /proc/ (procfs) filesystem is mounted.  If not, the process exits
+   with an UNSUPPORTED result code.  */
+
+void
+support_need_proc (const char *why_msg)
+{
+#ifdef __linux__
+  if (access ("/proc/self/maps", R_OK))
+    FAIL_UNSUPPORTED ("/proc is not available, %s", why_msg);
+#endif
+}