On Thu, Jun 8, 2023 at 5:11 PM Krister Johansen <kjlx@xxxxxxxxxxxxxxxxxx> 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@xxxxxxxxxxxxxxxxxx>
> ---
> .../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;
> + 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;
> +
> + 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");
> +
> + 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;
> +}
What is the point of attaching 3 the same progs to the same hook?
One would be enough to test it, no?
In other news...
Looks like this test is triggering a bug on s390.
Ilya,
please take a look:
https://github.com/kernel-patches/bpf/actions/runs/5216942096/jobs/9416404780
bpf_prog_78c0d4c618ed2df7_handle_fexit_ret_subprogs3
is crashing the kernel.
A bug in extable logic on s390?
