Re: [PATCH 09/10] selftest/bpf: Add kprobe_multi attach test

[Andrii Nakryiko <andrii.nakryiko@gmail.com>]

On Tue, Feb 22, 2022 at 9:08 AM Jiri Olsa <jolsa@kernel.org> wrote:
>
> Adding kprobe_multi attach test that uses new fprobe interface to
> attach kprobe program to multiple functions.
>
> The test is attaching programs to bpf_fentry_test* functions and
> uses single trampoline program bpf_prog_test_run to trigger
> bpf_fentry_test* functions.
>
> Signed-off-by: Jiri Olsa <jolsa@kernel.org>
> ---

subj typo: selftest -> selftests

>  .../bpf/prog_tests/kprobe_multi_test.c        | 115 ++++++++++++++++++
>  .../selftests/bpf/progs/kprobe_multi.c        |  58 +++++++++
>  2 files changed, 173 insertions(+)
>  create mode 100644 tools/testing/selftests/bpf/prog_tests/kprobe_multi_test.c
>  create mode 100644 tools/testing/selftests/bpf/progs/kprobe_multi.c
>

[...]

> +
> +static void test_link_api_addrs(void)
> +{
> +       DECLARE_LIBBPF_OPTS(bpf_link_create_opts, opts);
> +       __u64 addrs[8];
> +
> +       kallsyms_find("bpf_fentry_test1", &addrs[0]);
> +       kallsyms_find("bpf_fentry_test2", &addrs[1]);
> +       kallsyms_find("bpf_fentry_test3", &addrs[2]);
> +       kallsyms_find("bpf_fentry_test4", &addrs[3]);
> +       kallsyms_find("bpf_fentry_test5", &addrs[4]);
> +       kallsyms_find("bpf_fentry_test6",  &addrs[5]);
> +       kallsyms_find("bpf_fentry_test7", &addrs[6]);
> +       kallsyms_find("bpf_fentry_test8", &addrs[7]);

ASSERT_OK() that symbols are found? It also sucks that we re-parse
kallsyms so much...

maybe use load_kallsyms() to pre-cache? We should also teach
load_kallsyms() to not reload kallsyms more than once

> +
> +       opts.kprobe_multi.addrs = (__u64) addrs;
> +       opts.kprobe_multi.cnt = 8;

ARRAY_SIZE()?

> +       test_link_api(&opts);
> +}
> +
> +static void test_link_api_syms(void)
> +{
> +       DECLARE_LIBBPF_OPTS(bpf_link_create_opts, opts);

nit: just LIBBPF_OPTS

> +       const char *syms[8] = {
> +               "bpf_fentry_test1",
> +               "bpf_fentry_test2",
> +               "bpf_fentry_test3",
> +               "bpf_fentry_test4",
> +               "bpf_fentry_test5",
> +               "bpf_fentry_test6",
> +               "bpf_fentry_test7",
> +               "bpf_fentry_test8",
> +       };
> +
> +       opts.kprobe_multi.syms = (__u64) syms;
> +       opts.kprobe_multi.cnt = 8;

ARRAY_SIZE() ?

> +       test_link_api(&opts);
> +}
> +
> +void test_kprobe_multi_test(void)
> +{
> +       test_skel_api();
> +       test_link_api_syms();
> +       test_link_api_addrs();

model as subtests?


> +}
> diff --git a/tools/testing/selftests/bpf/progs/kprobe_multi.c b/tools/testing/selftests/bpf/progs/kprobe_multi.c
> new file mode 100644
> index 000000000000..71318c65931c
> --- /dev/null
> +++ b/tools/testing/selftests/bpf/progs/kprobe_multi.c
> @@ -0,0 +1,58 @@
> +// SPDX-License-Identifier: GPL-2.0
> +#include <linux/bpf.h>
> +#include <bpf/bpf_helpers.h>
> +#include <bpf/bpf_tracing.h>
> +
> +char _license[] SEC("license") = "GPL";
> +
> +extern const void bpf_fentry_test1 __ksym;
> +extern const void bpf_fentry_test2 __ksym;
> +extern const void bpf_fentry_test3 __ksym;
> +extern const void bpf_fentry_test4 __ksym;
> +extern const void bpf_fentry_test5 __ksym;
> +extern const void bpf_fentry_test6 __ksym;
> +extern const void bpf_fentry_test7 __ksym;
> +extern const void bpf_fentry_test8 __ksym;
> +
> +/* No tests, just to trigger bpf_fentry_test* through tracing test_run */
> +SEC("fentry/bpf_modify_return_test")
> +int BPF_PROG(test1)
> +{
> +       return 0;
> +}
> +
> +__u64 test2_result = 0;
> +
> +SEC("kprobe.multi/bpf_fentry_test?")
> +int test2(struct pt_regs *ctx)
> +{
> +       __u64 addr = bpf_get_func_ip(ctx);
> +
> +       test2_result += (const void *) addr == &bpf_fentry_test1 ||
> +                       (const void *) addr == &bpf_fentry_test2 ||
> +                       (const void *) addr == &bpf_fentry_test3 ||
> +                       (const void *) addr == &bpf_fentry_test4 ||
> +                       (const void *) addr == &bpf_fentry_test5 ||
> +                       (const void *) addr == &bpf_fentry_test6 ||
> +                       (const void *) addr == &bpf_fentry_test7 ||
> +                       (const void *) addr == &bpf_fentry_test8;
> +       return 0;
> +}
> +
> +__u64 test3_result = 0;
> +
> +SEC("kretprobe.multi/bpf_fentry_test*")
> +int test3(struct pt_regs *ctx)
> +{
> +       __u64 addr = bpf_get_func_ip(ctx);
> +
> +       test3_result += (const void *) addr == &bpf_fentry_test1 ||
> +                       (const void *) addr == &bpf_fentry_test2 ||
> +                       (const void *) addr == &bpf_fentry_test3 ||
> +                       (const void *) addr == &bpf_fentry_test4 ||
> +                       (const void *) addr == &bpf_fentry_test5 ||
> +                       (const void *) addr == &bpf_fentry_test6 ||
> +                       (const void *) addr == &bpf_fentry_test7 ||
> +                       (const void *) addr == &bpf_fentry_test8;
> +       return 0;
> +}
> --
> 2.35.1
>