Re: [PATCH v8 bpf-next 12/13] 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 [off-list ref]
Signed-off-by: Jiri Olsa <jolsa@kernel.org>
---
 .../testing/selftests/bpf/prog_tests/d_path.c | 162 ++++++++++++++++++
 .../testing/selftests/bpf/progs/test_d_path.c |  64 +++++++
 2 files changed, 226 insertions(+)
 create mode 100644 tools/testing/selftests/bpf/prog_tests/d_path.c
 create mode 100644 tools/testing/selftests/bpf/progs/test_d_path.c

diff --git a/tools/testing/selftests/bpf/prog_tests/d_path.c b/tools/testing/selftests/bpf/prog_tests/d_path.c
new file mode 100644
index 000000000000..3b8f87fb17d7
--- /dev/null
+++ b/tools/testing/selftests/bpf/prog_tests/d_path.c

@@ -0,0 +1,162 @@
+// SPDX-License-Identifier: GPL-2.0
+#define _GNU_SOURCE
+#include <test_progs.h>
+#include <sys/stat.h>
+#include <linux/sched.h>
+#include <sys/syscall.h>
+
+#define MAX_PATH_LEN           128
+#define MAX_FILES              7
+#define MAX_EVENT_NUM          16
+
+#include "test_d_path.skel.h"
+
+static struct {
+       __u32 cnt;
+       char paths[MAX_EVENT_NUM][MAX_PATH_LEN];
+} src;
+
+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, src.paths[src.cnt++], MAX_PATH_LEN);
+}
+
+static int trigger_fstat_events(pid_t pid)
+{
+       int sockfd = -1, procfd = -1, devfd = -1;
+       int localfd = -1, indicatorfd = -1;
+       int pipefd[2] = { -1, -1 };
+       struct stat fileStat;
+       int ret = -1;
+
+       /* unmountable pseudo-filesystems */
+       if (CHECK_FAIL(pipe(pipefd) < 0))
+               return ret;
+       /* unmountable pseudo-filesystems */
+       sockfd = socket(AF_INET, SOCK_STREAM, 0);
+       if (CHECK_FAIL(sockfd < 0))
+               goto out_close;
+       /* mountable pseudo-filesystems */
+       procfd = open("/proc/self/comm", O_RDONLY);
+       if (CHECK_FAIL(procfd < 0))
+               goto out_close;
+       devfd = open("/dev/urandom", O_RDONLY);
+       if (CHECK_FAIL(devfd < 0))
+               goto out_close;
+       localfd = open("/tmp/d_path_loadgen.txt", O_CREAT | O_RDONLY);
+       if (CHECK_FAIL(localfd < 0))
+               goto out_close;
+       /* bpf_d_path will return path with (deleted) */
+       remove("/tmp/d_path_loadgen.txt");
+       indicatorfd = open("/tmp/", O_PATH);
+       if (CHECK_FAIL(indicatorfd < 0))
+               goto out_close;
+
+       ret = set_pathname(pipefd[0], pid);
+       if (CHECK_FAIL(ret < 0))
+               goto out_close;
+       ret = set_pathname(pipefd[1], pid);
+       if (CHECK_FAIL(ret < 0))
+               goto out_close;
+       ret = set_pathname(sockfd, pid);
+       if (CHECK_FAIL(ret < 0))
+               goto out_close;
+       ret = set_pathname(procfd, pid);
+       if (CHECK_FAIL(ret < 0))
+               goto out_close;
+       ret = set_pathname(devfd, pid);
+       if (CHECK_FAIL(ret < 0))
+               goto out_close;
+       ret = set_pathname(localfd, pid);
+       if (CHECK_FAIL(ret < 0))
+               goto out_close;
+       ret = set_pathname(indicatorfd, pid);
+       if (CHECK_FAIL(ret < 0))
+               goto out_close;

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..e02dce614256
--- /dev/null
+++ b/tools/testing/selftests/bpf/progs/test_d_path.c

@@ -0,0 +1,64 @@
+// 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_EVENT_NUM          16
+
+pid_t my_pid;
+__u32 cnt_stat;
+__u32 cnt_close;
+char paths_stat[MAX_EVENT_NUM][MAX_PATH_LEN];
+char paths_close[MAX_EVENT_NUM][MAX_PATH_LEN];
+int rets_stat[MAX_EVENT_NUM];
+int rets_close[MAX_EVENT_NUM];
+