From: Yonghong Song <yhs@meta.com>
To: Krister Johansen <kjlx@templeofstupid.com>, bpf@vger.kernel.org
Cc: Alexei Starovoitov <ast@kernel.org>,
Daniel Borkmann <daniel@iogearbox.net>,
Andrii Nakryiko <andrii@kernel.org>,
Martin KaFai Lau <martin.lau@linux.dev>,
Song Liu <song@kernel.org>, Yonghong Song <yhs@fb.com>,
John Fastabend <john.fastabend@gmail.com>,
KP Singh <kpsingh@kernel.org>,
Stanislav Fomichev <sdf@google.com>, Hao Luo <haoluo@google.com>,
Jiri Olsa <jolsa@kernel.org>, Mykola Lysenko <mykolal@fb.com>,
Shuah Khan <shuah@kernel.org>,
linux-kernel@vger.kernel.org, linux-kselftest@vger.kernel.org
Subject: Re: [PATCH bpf v3 2/2] selftests/bpf: add a test for subprogram extables
Date: Thu, 8 Jun 2023 20:52:36 -0700 [thread overview]
Message-ID: <49a8216a-4333-a044-ceea-c59980913966@meta.com> (raw)
In-Reply-To: <9e3041e182a75f558f1132f915ddf2ee7e859c6e.1686268304.git.kjlx@templeofstupid.com>
On 6/8/23 5:11 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.
It would be great if you can add the panic call stack in the commit message.
Please also mention that three identical bpf programs in the test
significantly increased the 'oops' chance. Just one program may
not be able to trigger the issue.
>
> Signed-off-by: Krister Johansen <kjlx@templeofstupid.com>
> ---
> .../bpf/prog_tests/subprogs_extable.c | 31 +++++++++++++
> .../bpf/progs/test_subprogs_extable.c | 46 +++++++++++++++++++
> 2 files changed, 77 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..2201988274a4
> --- /dev/null
> +++ b/tools/testing/selftests/bpf/prog_tests/subprogs_extable.c
> @@ -0,0 +1,31 @@
> +// SPDX-License-Identifier: GPL-2.0
> +
> +#include <test_progs.h>
> +#include "test_subprogs_extable.skel.h"
> +
> +void test_subprogs_extable(void)
> +{
> + const int READ_SZ = 456;
There is no need to use uppercase for READ_SZ.
Just do
const int read_sz = 456;
is sufficient.
> + struct test_subprogs_extable *skel;
> + int err;
> +
> + skel = test_subprogs_extable__open();
> + if (!ASSERT_OK_PTR(skel, "skel_open"))
> + return;
> +
> + err = test_subprogs_extable__load(skel);
> + if (!ASSERT_OK(err, "skel_load"))
> + goto cleanup;
You can combine the above open and load with a single one
test_subprogs_extable__open_and_load().
> +
> + err = test_subprogs_extable__attach(skel);
> + if (!ASSERT_OK(err, "skel_attach"))
> + goto cleanup;
> +
> + /* trigger tracepoint */
> + ASSERT_OK(trigger_module_test_read(READ_SZ), "trigger_read");
I think we should at least ensure that the program is triggered. For
example, add a global variable 'triggered' in the program and
triggered will be set to 1 in the program if the program is running.
Here check
skel->bss->triggered
must be 1.
> +
> + 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..c3ff66bf4cbe
> --- /dev/null
> +++ b/tools/testing/selftests/bpf/progs/test_subprogs_extable.c
> @@ -0,0 +1,46 @@
> +// SPDX-License-Identifier: GPL-2.0
> +
> +#include "vmlinux.h"
> +#include <bpf/bpf_helpers.h>
> +#include <bpf/bpf_tracing.h>
> +
> +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;
> +}
> +
> +SEC("fexit/bpf_testmod_return_ptr")
> +int BPF_PROG(handle_fexit_ret_subprogs, int arg, struct file *ret)
> +{
> + *(volatile long *)ret;
> + *(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)
> +{
> + *(volatile long *)ret;
> + *(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_subprogs3, int arg, struct file *ret)
> +{
> + *(volatile long *)ret;
> + *(volatile int *)&ret->f_mode;
> + bpf_for_each_map_elem(&test_array, test_cb, NULL, 0);
> + return 0;
> +}
> +
> +char _license[] SEC("license") = "GPL";
next prev parent reply other threads:[~2023-06-09 3:53 UTC|newest]
Thread overview: 11+ messages / expand[flat|nested] mbox.gz Atom feed top
2023-06-09 0:10 [PATCH bpf v3 0/2] bpf: fix NULL dereference during extable search Krister Johansen
2023-06-09 0:10 ` [PATCH bpf v3 1/2] bpf: ensure main program has an extable Krister Johansen
2023-06-09 3:33 ` Yonghong Song
2023-06-09 0:11 ` [PATCH bpf v3 2/2] selftests/bpf: add a test for subprogram extables Krister Johansen
2023-06-09 3:52 ` Yonghong Song [this message]
2023-06-09 21:34 ` Krister Johansen
2023-06-09 18:15 ` Alexei Starovoitov
2023-06-09 19:08 ` Krister Johansen
2023-06-12 13:46 ` Ilya Leoshkevich
2023-06-12 22:07 ` Alexei Starovoitov
2023-06-12 22:12 ` Krister Johansen
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