Re: [PATCH 16/19] selftests/bpf: Add fentry multi func test

Andrii Nakryiko
2021-06-09T05:40:55Z

On Sat, Jun 5, 2021 at 4:12 AM Jiri Olsa <jolsa@kernel.org> wrote:
>
> Adding selftest for fentry multi func test that attaches
> to bpf_fentry_test* functions and checks argument values
> based on the processed function.
>
> Signed-off-by: Jiri Olsa <jolsa@kernel.org>
> ---
> tools/testing/selftests/bpf/multi_check.h | 52 +++++++++++++++++++
> .../bpf/prog_tests/fentry_multi_test.c | 43 +++++++++++++++
> .../selftests/bpf/progs/fentry_multi_test.c | 18 +++++++
> 3 files changed, 113 insertions(+)
> create mode 100644 tools/testing/selftests/bpf/multi_check.h
> create mode 100644 tools/testing/selftests/bpf/prog_tests/fentry_multi_test.c
> create mode 100644 tools/testing/selftests/bpf/progs/fentry_multi_test.c
>
> diff --git a/tools/testing/selftests/bpf/multi_check.h b/tools/testing/selftests/bpf/multi_check.h
> new file mode 100644
> index 000000000000..36c2a93f9be3
> --- /dev/null
> +++ b/tools/testing/selftests/bpf/multi_check.h

we have a proper static linking now, we don't have to use header
inclusion hacks, let's do this properly?

> @@ -0,0 +1,52 @@
> +/* SPDX-License-Identifier: GPL-2.0 */
> +
> +#ifndef __MULTI_CHECK_H
> +#define __MULTI_CHECK_H
> +
> +extern unsigned long long bpf_fentry_test[8];
> +
> +static __attribute__((unused)) inline
> +void multi_arg_check(unsigned long ip, __u64 a, __u64 b, __u64 c, __u64 d, __u64 e, __u64 f, __u64 *test_result)
> +{
> + if (ip == bpf_fentry_test[0]) {
> + *test_result += (int) a == 1;
> + } else if (ip == bpf_fentry_test[1]) {
> + *test_result += (int) a == 2 && (__u64) b == 3;
> + } else if (ip == bpf_fentry_test[2]) {
> + *test_result += (char) a == 4 && (int) b == 5 && (__u64) c == 6;
> + } else if (ip == bpf_fentry_test[3]) {
> + *test_result += (void *) a == (void *) 7 && (char) b == 8 && (int) c == 9 && (__u64) d == 10;
> + } else if (ip == bpf_fentry_test[4]) {
> + *test_result += (__u64) a == 11 && (void *) b == (void *) 12 && (short) c == 13 && (int) d == 14 && (__u64) e == 15;
> + } else if (ip == bpf_fentry_test[5]) {
> + *test_result += (__u64) a == 16 && (void *) b == (void *) 17 && (short) c == 18 && (int) d == 19 && (void *) e == (void *) 20 && (__u64) f == 21;
> + } else if (ip == bpf_fentry_test[6]) {
> + *test_result += 1;
> + } else if (ip == bpf_fentry_test[7]) {
> + *test_result += 1;
> + }

why not use switch? and why the casting?

> +}
> +

[...]

> diff --git a/tools/testing/selftests/bpf/progs/fentry_multi_test.c b/tools/testing/selftests/bpf/progs/fentry_multi_test.c
> new file mode 100644
> index 000000000000..a443fc958e5a
> --- /dev/null
> +++ b/tools/testing/selftests/bpf/progs/fentry_multi_test.c
> @@ -0,0 +1,18 @@
> +// SPDX-License-Identifier: GPL-2.0
> +#include <linux/bpf.h>
> +#include <bpf/bpf_helpers.h>
> +#include <bpf/bpf_tracing.h>
> +#include "multi_check.h"
> +
> +char _license[] SEC("license") = "GPL";
> +
> +unsigned long long bpf_fentry_test[8];
> +
> +__u64 test_result = 0;
> +
> +SEC("fentry.multi/bpf_fentry_test*")

wait, that's a regexp syntax that libc supports?.. Not .*? We should
definitely not provide btf__find_by_pattern_kind() API, I'd like to
avoid explaining what flavors of regexps libbpf supports.

> +int BPF_PROG(test, unsigned long ip, __u64 a, __u64 b, __u64 c, __u64 d, __u64 e, __u64 f)
> +{
> + multi_arg_check(ip, a, b, c, d, e, f, &test_result);
> + return 0;
> +}
> --
> 2.31.1
>