Re: [PATCH v8 bpf-next 12/13] selftests/bpf: Add test for d_path helper

From: Andrii Nakryiko <andrii.nakryiko@gmail.com>
To: Jiri Olsa <jolsa@kernel.org>
Cc: Alexei Starovoitov <ast@kernel.org>,
	Daniel Borkmann <daniel@iogearbox.net>,
	Andrii Nakryiko <andriin@fb.com>,
	Wenbo Zhang <ethercflow@gmail.com>,
	Networking <netdev@vger.kernel.org>, bpf <bpf@vger.kernel.org>,
	Song Liu <songliubraving@fb.com>, Yonghong Song <yhs@fb.com>,
	Martin KaFai Lau <kafai@fb.com>, David Miller <davem@redhat.com>,
	John Fastabend <john.fastabend@gmail.com>,
	KP Singh <kpsingh@chromium.org>,
	Brendan Gregg <bgregg@netflix.com>,
	Florent Revest <revest@chromium.org>,
	Al Viro <viro@zeniv.linux.org.uk>
Subject: Re: [PATCH v8 bpf-next 12/13] selftests/bpf: Add test for d_path helper
Date: Tue, 28 Jul 2020 12:53:00 -0700	[thread overview]
Message-ID: <CAEf4BzYTT23knreKpxPDLeWcLzTVQhtBrRPjrZ+MBpL4ajeavw@mail.gmail.com> (raw)
In-Reply-To: <20200722211223.1055107-13-jolsa@kernel.org>

On Wed, Jul 22, 2020 at 2:14 PM Jiri Olsa <jolsa@kernel.org> wrote:
>
> 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>
> ---
>  .../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;

Please use CHECK instead of CHECK_FAIL. Thanks.

> +
> +       /* triggers vfs_getattr */
> +       fstat(pipefd[0], &fileStat);
> +       fstat(pipefd[1], &fileStat);
> +       fstat(sockfd, &fileStat);
> +       fstat(procfd, &fileStat);
> +       fstat(devfd, &fileStat);
> +       fstat(localfd, &fileStat);
> +       fstat(indicatorfd, &fileStat);
> +
> +out_close:
> +       /* triggers filp_close */
> +       close(pipefd[0]);
> +       close(pipefd[1]);
> +       close(sockfd);
> +       close(procfd);
> +       close(devfd);
> +       close(localfd);
> +       close(indicatorfd);
> +       return ret;
> +}
> +

[...]

> 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];
> +

please zero-initialize all of these, it causes issues on some Clang versions

[...]