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@templeofstupid.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";