Re: [PATCH v4 bpf-next 21/22] selftests/bpf: Convert test printk to use rodata.

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

On Fri, May 7, 2021 at 8:49 PM Alexei Starovoitov
<alexei.starovoitov@gmail.com> wrote:
>
> From: Alexei Starovoitov <ast@kernel.org>
>
> Convert test trace_printk to more aggressively validate and use rodata.
>
> Signed-off-by: Alexei Starovoitov <ast@kernel.org>
> ---
>  tools/testing/selftests/bpf/prog_tests/trace_printk.c | 3 +++
>  tools/testing/selftests/bpf/progs/trace_printk.c      | 4 ++--
>  2 files changed, 5 insertions(+), 2 deletions(-)
>
> diff --git a/tools/testing/selftests/bpf/prog_tests/trace_printk.c b/tools/testing/selftests/bpf/prog_tests/trace_printk.c
> index 39b0decb1bb2..60c2347a3181 100644
> --- a/tools/testing/selftests/bpf/prog_tests/trace_printk.c
> +++ b/tools/testing/selftests/bpf/prog_tests/trace_printk.c
> @@ -21,6 +21,9 @@ void test_trace_printk(void)
>         if (CHECK(!skel, "skel_open", "failed to open skeleton\n"))
>                 return;
>
> +       ASSERT_EQ(skel->rodata->sys_enter_fmt[0], 'T', "invalid printk fmt string");
> +       skel->rodata->sys_enter_fmt[0] = 't';

sys_enter.fmt is no more, need to make it into a global variable.

> +
>         err = trace_printk__load(skel);
>         if (CHECK(err, "skel_load", "failed to load skeleton: %d\n", err))
>                 goto cleanup;
> diff --git a/tools/testing/selftests/bpf/progs/trace_printk.c b/tools/testing/selftests/bpf/progs/trace_printk.c
> index 8ca7f399b670..18c8baaf1143 100644
> --- a/tools/testing/selftests/bpf/progs/trace_printk.c
> +++ b/tools/testing/selftests/bpf/progs/trace_printk.c
> @@ -10,10 +10,10 @@ char _license[] SEC("license") = "GPL";
>  int trace_printk_ret = 0;
>  int trace_printk_ran = 0;
>
> -SEC("tp/raw_syscalls/sys_enter")
> +SEC("fentry/__x64_sys_nanosleep")

this will break on non-x64 systems, can more stable raw_tp be used here?

>  int sys_enter(void *ctx)
>  {
> -       static const char fmt[] = "testing,testing %d\n";
> +       static const char fmt[] = "Testing,testing %d\n";
>
>         trace_printk_ret = bpf_trace_printk(fmt, sizeof(fmt),
>                                             ++trace_printk_ran);
> --
> 2.30.2
>