selftests/bpf: Add test for d_path helper

Adding test for d_path helper which is pretty much
copied from Wenbo Zhang's test for bpf_get_fd_path,
which never made it in.

The test is doing fstat/close on several fd types,
and verifies we got the d_path helper working on
kernel probes for vfs_getattr/filp_close functions.

Original-patch-by: Wenbo Zhang <ethercflow@gmail.com>

Signed-off-by: Jiri Olsa <jolsa@kernel.org>
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
Acked-by: Andrii Nakryiko <andriin@fb.com>
Link: https://lore.kernel.org/bpf/20200825192124.710397-14-jolsa@kernel.org

1 files changed, 58 insertions, 0 deletions

diff --git a/tools/testing/selftests/bpf/progs/test_d_path.c b/tools/testing/selftests/bpf/progs/test_d_path.c
new file mode 100644
index 000000000000..61f007855649
--- /dev/null
+++ b/tools/testing/selftests/bpf/progs/test_d_path.c
@@ -0,0 +1,58 @@
+// SPDX-License-Identifier: GPL-2.0
+
+#include "vmlinux.h"
+#include <bpf/bpf_helpers.h>
+#include <bpf/bpf_tracing.h>
+
+#define MAX_PATH_LEN		128
+#define MAX_FILES		7
+
+pid_t my_pid = 0;
+__u32 cnt_stat = 0;
+__u32 cnt_close = 0;
+char paths_stat[MAX_FILES][MAX_PATH_LEN] = {};
+char paths_close[MAX_FILES][MAX_PATH_LEN] = {};
+int rets_stat[MAX_FILES] = {};
+int rets_close[MAX_FILES] = {};
+
+SEC("fentry/vfs_getattr")
+int BPF_PROG(prog_stat, struct path *path, struct kstat *stat,
+	     __u32 request_mask, unsigned int query_flags)
+{
+	pid_t pid = bpf_get_current_pid_tgid() >> 32;
+	__u32 cnt = cnt_stat;
+	int ret;
+
+	if (pid != my_pid)
+		return 0;
+
+	if (cnt >= MAX_FILES)
+		return 0;
+	ret = bpf_d_path(path, paths_stat[cnt], MAX_PATH_LEN);
+
+	rets_stat[cnt] = ret;
+	cnt_stat++;
+	return 0;
+}
+
+SEC("fentry/filp_close")
+int BPF_PROG(prog_close, struct file *file, void *id)
+{
+	pid_t pid = bpf_get_current_pid_tgid() >> 32;
+	__u32 cnt = cnt_close;
+	int ret;
+
+	if (pid != my_pid)
+		return 0;
+
+	if (cnt >= MAX_FILES)
+		return 0;
+	ret = bpf_d_path(&file->f_path,
+			 paths_close[cnt], MAX_PATH_LEN);
+
+	rets_close[cnt] = ret;
+	cnt_close++;
+	return 0;
+}
+
+char _license[] SEC("license") = "GPL";