selftests/bpf: Move test_dev_cgroup to prog_tests

Move test_dev_cgroup.c to prog_tests/dev_cgroup.c to be able to run it
with test_progs. Replace dev_cgroup.bpf.o with skel header file,
dev_cgroup.skel.h and load program from it accourdingly.

  ./test_progs -t dev_cgroup
  mknod: /tmp/test_dev_cgroup_null: Operation not permitted
  64+0 records in
  64+0 records out
  32768 bytes (33 kB, 32 KiB) copied, 0.000856684 s, 38.2 MB/s
  dd: failed to open '/dev/full': Operation not permitted
  dd: failed to open '/dev/random': Operation not permitted
  kernel-patches#72     test_dev_cgroup:OK
  Summary: 1/0 PASSED, 0 SKIPPED, 0 FAILED

Signed-off-by: Muhammad Usama Anjum <usama.anjum@collabora.com>
---
Changes since v2:
- Replace test_dev_cgroup with serial_test_dev_cgroup as there is
  probability that the test is racing against another cgroup test
- Minor changes to the commit message above

I've tested the patch with vmtest.sh on bpf-next/for-next and linux
next. It is passing on both. Not sure why it was failed on BPFCI.
Test run with vmtest.h:
sudo LDLIBS=-static PKG_CONFIG='pkg-config --static' ./vmtest.sh ./test_progs -t dev_cgroup
./test_progs -t dev_cgroup
mknod: /tmp/test_dev_cgroup_null: Operation not permitted
64+0 records in
64+0 records out
32768 bytes (33 kB, 32 KiB) copied, 0.000403432 s, 81.2 MB/s
dd: failed to open '/dev/full': Operation not permitted
dd: failed to open '/dev/random': Operation not permitted
 kernel-patches#69      dev_cgroup:OK
Summary: 1/0 PASSED, 0 SKIPPED, 0 FAILED

Changes since v1:
- Rename file from test_dev_cgroup.c to dev_cgroup.c
- Use ASSERT_* in-place of CHECK

tools/testing/selftests/bpf/prog_tests/dev_cgroup.c

@@ -0,0 +1,58 @@
+// SPDX-License-Identifier: GPL-2.0-only
+/* Copyright (c) 2017 Facebook
+ */
+
+#include <test_progs.h>
+#include <time.h>
+#include "cgroup_helpers.h"
+#include "dev_cgroup.skel.h"
+
+#define TEST_CGROUP "/test-bpf-based-device-cgroup/"
+
+void serial_test_dev_cgroup(void)
+{
+	struct dev_cgroup *skel;
+	int cgroup_fd, err;
+	__u32 prog_cnt;
+
+	skel = dev_cgroup__open_and_load();
+	if (!ASSERT_OK_PTR(skel, "skel_open_and_load"))
+		goto cleanup;
+
+	cgroup_fd = cgroup_setup_and_join(TEST_CGROUP);
+	if (!ASSERT_GT(cgroup_fd, 0, "cgroup_setup_and_join"))
+		goto cleanup;
+
+	err = bpf_prog_attach(bpf_program__fd(skel->progs.bpf_prog1), cgroup_fd,
+			      BPF_CGROUP_DEVICE, 0);
+	if (!ASSERT_EQ(err, 0, "bpf_attach"))
+		goto cleanup;
+
+	err = bpf_prog_query(cgroup_fd, BPF_CGROUP_DEVICE, 0, NULL, NULL, &prog_cnt);
+	if (!ASSERT_EQ(err, 0, "bpf_query") || (!ASSERT_EQ(prog_cnt, 1, "bpf_query")))
+		goto cleanup;
+
+	/* All operations with /dev/zero and /dev/urandom are allowed,
+	 * everything else is forbidden.
+	 */
+	ASSERT_EQ(system("rm -f /tmp/test_dev_cgroup_null"), 0, "rm");
+	ASSERT_NEQ(system("mknod /tmp/test_dev_cgroup_null c 1 3"), 0, "mknod");
+	ASSERT_EQ(system("rm -f /tmp/test_dev_cgroup_null"), 0, "rm");
+
+	/* /dev/zero is whitelisted */
+	ASSERT_EQ(system("rm -f /tmp/test_dev_cgroup_zero"), 0, "rm");
+	ASSERT_EQ(system("mknod /tmp/test_dev_cgroup_zero c 1 5"), 0, "mknod");
+	ASSERT_EQ(system("rm -f /tmp/test_dev_cgroup_zero"), 0, "rm");
+
+	ASSERT_EQ(system("dd if=/dev/urandom of=/dev/zero count=64"), 0, "dd");
+
+	/* src is allowed, target is forbidden */
+	ASSERT_NEQ(system("dd if=/dev/urandom of=/dev/full count=64"), 0, "dd");
+
+	/* src is forbidden, target is allowed */
+	ASSERT_NEQ(system("dd if=/dev/random of=/dev/zero count=64"), 0, "dd");
+
+cleanup:
+	cleanup_cgroup_environment();
+	dev_cgroup__destroy(skel);
+}