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Date: Thu, 8 Jun 2023 10:01:22 -0700
From: Yonghong Song <yhs@...a.com>
To: Krister Johansen <kjlx@...pleofstupid.com>, bpf@...r.kernel.org
Cc: Alexei Starovoitov <ast@...nel.org>,
Daniel Borkmann <daniel@...earbox.net>,
Andrii Nakryiko <andrii@...nel.org>,
Martin KaFai Lau <martin.lau@...ux.dev>,
Song Liu <song@...nel.org>, Yonghong Song <yhs@...com>,
John Fastabend <john.fastabend@...il.com>,
KP Singh <kpsingh@...nel.org>,
Stanislav Fomichev <sdf@...gle.com>,
Hao Luo <haoluo@...gle.com>, Jiri Olsa <jolsa@...nel.org>,
Mykola Lysenko <mykolal@...com>, Shuah Khan <shuah@...nel.org>,
linux-kernel@...r.kernel.org, linux-kselftest@...r.kernel.org,
stable@...r.kernel.org
Subject: Re: [PATCH bpf v2 1/2] selftests/bpf: add a test for subprogram
extables
On 6/7/23 2:04 PM, Krister Johansen wrote:
> In certain situations a program with subprograms may have a NULL
> extable entry. This should not happen, and when it does, it turns a
> single trap into multiple. Add a test case for further debugging and to
> prevent regressions. N.b: without any other patches this can panic or
> oops a kernel.
>
> Signed-off-by: Krister Johansen <kjlx@...pleofstupid.com>
> ---
> .../bpf/prog_tests/subprogs_extable.c | 35 +++++++++
> .../bpf/progs/test_subprogs_extable.c | 71 +++++++++++++++++++
> 2 files changed, 106 insertions(+)
> create mode 100644 tools/testing/selftests/bpf/prog_tests/subprogs_extable.c
> create mode 100644 tools/testing/selftests/bpf/progs/test_subprogs_extable.c
>
> diff --git a/tools/testing/selftests/bpf/prog_tests/subprogs_extable.c b/tools/testing/selftests/bpf/prog_tests/subprogs_extable.c
> new file mode 100644
> index 000000000000..18169b7eedf8
> --- /dev/null
> +++ b/tools/testing/selftests/bpf/prog_tests/subprogs_extable.c
> @@ -0,0 +1,35 @@
> +// SPDX-License-Identifier: GPL-2.0
> +/* Copyright (c) 2020 Facebook */
This copyright is not correct.
> +
> +#include <test_progs.h>
> +#include <stdbool.h>
stdbool.h is not needed.
> +#include "test_subprogs_extable.skel.h"
> +
> +static int duration;
> +
> +void test_subprogs_extable(void)
> +{
> + const int READ_SZ = 456;
> + struct test_subprogs_extable *skel;
> + int err;
> +
> + skel = test_subprogs_extable__open();
> + if (CHECK(!skel, "skel_open", "failed to open skeleton\n"))
> + return;
Please use ASSERT_* macros instead of CHECK macro. The same for below.
See some examples in prog_tests directory.
> +
> + err = test_subprogs_extable__load(skel);
> + if (CHECK(err, "skel_load", "failed to load skeleton\n"))
> + return;
goto cleanup;
> +
> + err = test_subprogs_extable__attach(skel);
> + if (CHECK(err, "skel_attach", "skeleton attach failed: %d\n", err))
> + goto cleanup;
> +
> + /* trigger tracepoint */
> + ASSERT_OK(trigger_module_test_read(READ_SZ), "trigger_read");
> +
> + test_subprogs_extable__detach(skel);
> +
> +cleanup:
> + test_subprogs_extable__destroy(skel);
> +}
> diff --git a/tools/testing/selftests/bpf/progs/test_subprogs_extable.c b/tools/testing/selftests/bpf/progs/test_subprogs_extable.c
> new file mode 100644
> index 000000000000..408137eaaa07
> --- /dev/null
> +++ b/tools/testing/selftests/bpf/progs/test_subprogs_extable.c
> @@ -0,0 +1,71 @@
> +// SPDX-License-Identifier: GPL-2.0
> +/* Copyright (c) 2020 Facebook */
the above copyright is not correct.
> +
> +#include "vmlinux.h"
> +#include <bpf/bpf_helpers.h>
> +#include <bpf/bpf_tracing.h>
> +#include <bpf/bpf_core_read.h>
There is no CORE related operation in the program. The above header is
not needed.
> +#include "../bpf_testmod/bpf_testmod.h"
This one is not needed too.
> +
> +struct {
> + __uint(type, BPF_MAP_TYPE_ARRAY);
> + __uint(max_entries, 8);
> + __type(key, __u32);
> + __type(value, __u64);
> +} test_array SEC(".maps");
> +
> +static __u64 test_cb(struct bpf_map *map, __u32 *key, __u64 *val, void *data)
> +{
> + return 1;
> +}
> +
> +static __u64 test_cb2(struct bpf_map *map, __u32 *key, __u64 *val, void *data)
> +{
> + return 1;
> +}
> +
> +static __u64 test_cb3(struct bpf_map *map, __u32 *key, __u64 *val, void *data)
> +{
> + return 1;
> +}
We can just have one test_cb and used for all programs, right?
Or more subprograms increase the chance of the test failure?
> +
> +SEC("fexit/bpf_testmod_return_ptr")
> +int BPF_PROG(handle_fexit_ret_subprogs, int arg, struct file *ret)
> +{
> + long buf = 0;
> +
> + bpf_probe_read_kernel(&buf, 8, ret);
> + bpf_probe_read_kernel(&buf, 8, (char *)ret + 256);
The above bpf_probe_read_kernel() things are not necessary, right?
> + *(volatile long long *)ret;
just 'volatile long' should be enough.
> + *(volatile int *)&ret->f_mode;
> + bpf_for_each_map_elem(&test_array, test_cb, NULL, 0);
> + return 0;
> +}
> +
> +SEC("fexit/bpf_testmod_return_ptr")
> +int BPF_PROG(handle_fexit_ret_subprogs2, int arg, struct file *ret)
> +{
> + long buf = 0;
> +
> + bpf_probe_read_kernel(&buf, 8, ret);
> + bpf_probe_read_kernel(&buf, 8, (char *)ret + 256);
> + *(volatile long long *)ret;
> + *(volatile int *)&ret->f_mode;
> + bpf_for_each_map_elem(&test_array, test_cb2, NULL, 0);
> + return 0;
> +}
> +
> +SEC("fexit/bpf_testmod_return_ptr")
> +int BPF_PROG(handle_fexit_ret_subprogs3, int arg, struct file *ret)
> +{
> + long buf = 0;
> +
> + bpf_probe_read_kernel(&buf, 8, ret);
> + bpf_probe_read_kernel(&buf, 8, (char *)ret + 256);
> + *(volatile long long *)ret;
> + *(volatile int *)&ret->f_mode;
> + bpf_for_each_map_elem(&test_array, test_cb3, NULL, 0);
> + return 0;
> +}
> +
> +char _license[] SEC("license") = "GPL";
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