[PATCH bpf-next v1 2/3] selftests/bpf:Adding test for bpf_file_d_path helper

[Lin Yikai]

Hi, Adding test for bpf_file_d_path helper.

It passed the test in my environment using QEMU
(./test_progs -t file_d_path)

Below are some partial results:
'''
  + [ -x /etc/rcS.d/S50-startup ]
  + /etc/rcS.d/S50-startup
  ./test_progs -t file_d_path
  Summary: 1/0 PASSED, 0 SKIPPED, 0 FAILED
'''

Signed-off-by: Lin Yikai <yikai.lin@xxxxxxxx>
---
 .../selftests/bpf/prog_tests/file_d_path.c    | 115 ++++++++++++++++++
 .../selftests/bpf/progs/test_file_d_path.c    |  32 +++++
 2 files changed, 147 insertions(+)
 create mode 100644 tools/testing/selftests/bpf/prog_tests/file_d_path.c
 create mode 100644 tools/testing/selftests/bpf/progs/test_file_d_path.c

diff --git a/tools/testing/selftests/bpf/prog_tests/file_d_path.c b/tools/testing/selftests/bpf/prog_tests/file_d_path.c
new file mode 100644
index 000000000000..ba76d9467f3e
--- /dev/null
+++ b/tools/testing/selftests/bpf/prog_tests/file_d_path.c
@@ -0,0 +1,115 @@
+// SPDX-License-Identifier: GPL-2.0
+#include <test_progs.h>
+#include <sys/syscall.h>
+
+#include "test_file_d_path.skel.h"
+
+/* Compatible with older versions of glibc begin */
+#ifndef __NR_close_range
+#ifdef __alpha__
+#define __NR_close_range 546
+#else
+#define __NR_close_range 436
+#endif
+#endif
+
+#define close_fd(fd) syscall(__NR_close_range, fd, fd, 0)
+/* Compatible with older versions of glibc end */
+
+
+#define MAX_PATH_LEN	256
+#define TEST_FILES_NUM		2
+
+static int duration;
+
+static struct {
+	__u32 cnt;
+	char paths[TEST_FILES_NUM][MAX_PATH_LEN];
+} record;
+
+static int set_pathname(int fd, pid_t pid)
+{
+	char buf[MAX_PATH_LEN];
+
+	snprintf(buf, MAX_PATH_LEN, "/proc/%d/fd/%d", pid, fd);
+	return readlink(buf, record.paths[record.cnt++], MAX_PATH_LEN);
+}
+
+static int trigger_filp_close(pid_t pid)
+{
+	int ret = -1;
+	const char *comm_path = "/proc/self/comm";
+	int commfd = -1;
+	const char *tmp_path = "/tmp/test_bpf_file_d_path.txt";
+	int tmpfd = -1;
+
+	/* open file */
+	commfd = open(comm_path, O_RDONLY);
+	if (CHECK(commfd < 0, "test_file_d_path", "open %s failed\n", comm_path))
+		goto fd_close;
+
+	tmpfd = open(tmp_path, O_CREAT | O_RDONLY, 0644);
+	if (CHECK(tmpfd < 0, "test_file_d_path", "open %s failed\n", tmp_path))
+		goto fd_close;
+	remove(tmp_path);
+
+	/* record file */
+	memset(&record, 0, sizeof(record));
+	ret = set_pathname(commfd, pid);
+	if (CHECK(ret < 0, "test_file_d_path", "set_pathname failed for commfd\n"))
+		goto fd_close;
+	ret = set_pathname(tmpfd, pid);
+	if (CHECK(ret < 0, "test_file_d_path", "set_pathname failed for tmpfd\n"))
+		goto fd_close;
+
+	ret = 0;
+	/* close file */
+fd_close:
+	if (commfd != -1)
+		close_fd(commfd);
+	if (tmpfd != -1)
+		close_fd(tmpfd);
+	return ret;
+}
+
+static void test_base(void)
+{
+	int err = -1;
+	struct test_file_d_path__bss *bss;
+	struct test_file_d_path *skel;
+
+	skel = test_file_d_path__open_and_load();
+	if (CHECK(!skel, "open_and_load", "load file_d_path skeleton failed\n"))
+		goto cleanup;
+
+	err = test_file_d_path__attach(skel);
+	if (CHECK(err, "attach", "attach file_d_path failed: %s\n", strerror(errno)))
+		goto cleanup;
+
+	bss = skel->bss;
+	bss->monitor_pid = getpid();
+
+	err = trigger_filp_close(bss->monitor_pid);
+	if (err < 0)
+		goto cleanup;
+
+	if (CHECK(bss->bpf_called_cnt != TEST_FILES_NUM,
+		"bpf_called_cnt",
+		"prog called times diff from with the expectations\n"))
+		goto cleanup;
+
+	for (int i = 0; i < TEST_FILES_NUM; i++) {
+		CHECK(strncmp(record.paths[i], bss->bpf_paths_close[i], MAX_PATH_LEN),
+			"bpf_paths_close",
+			"the paths diff from the expectations: id=[%d], path: %s vs %s\n",
+			i, record.paths[i], bss->bpf_paths_close[i]);
+	}
+
+cleanup:
+	test_file_d_path__destroy(skel);
+}
+
+void test_file_d_path(void)
+{
+	test_base();
+}
diff --git a/tools/testing/selftests/bpf/progs/test_file_d_path.c b/tools/testing/selftests/bpf/progs/test_file_d_path.c
new file mode 100644
index 000000000000..8db2bcd1179f
--- /dev/null
+++ b/tools/testing/selftests/bpf/progs/test_file_d_path.c
@@ -0,0 +1,32 @@
+// SPDX-License-Identifier: GPL-2.0
+#include "vmlinux.h"
+#include <bpf/bpf_helpers.h>
+#include <bpf/bpf_tracing.h>
+
+#define MAX_PATH_LEN	256
+#define TEST_FILES_NUM		2
+
+pid_t monitor_pid = 0;
+
+__u32 bpf_called_cnt = 0;
+char bpf_paths_close[TEST_FILES_NUM][MAX_PATH_LEN] = {0};
+
+SEC("kprobe/filp_close")
+int test_bpf_file_to_path(struct pt_regs *regs)
+{
+	void *file = NULL;
+	pid_t cur_pid = bpf_get_current_pid_tgid() >> 32;
+
+	if (cur_pid != monitor_pid)
+		return 0;
+
+	if (bpf_called_cnt >= TEST_FILES_NUM)
+		return 0;
+
+	file = (void *)PT_REGS_PARM1(regs);
+	bpf_file_d_path(file, bpf_paths_close[bpf_called_cnt++], MAX_PATH_LEN);
+
+	return 0;
+}
+
+char _license[] SEC("license") = "GPL";
-- 
2.34.1