linux-kernel - Re: [PATCHv2 bpf-next 4/9] libbpf: Add support for uprobe multi session attach

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Message-ID: <CAEf4BzYP6zW0Mmi_=J5ng+GiUSJpB1JCg-qai0kp_N+_vestxA@mail.gmail.com>
Date: Tue, 2 Jul 2024 14:34:34 -0700
From: Andrii Nakryiko <andrii.nakryiko@...il.com>
To: Jiri Olsa <jolsa@...nel.org>
Cc: Oleg Nesterov <oleg@...hat.com>, Peter Zijlstra <peterz@...radead.org>, 
	Alexei Starovoitov <ast@...nel.org>, Daniel Borkmann <daniel@...earbox.net>, 
	Andrii Nakryiko <andrii@...nel.org>, bpf@...r.kernel.org, Martin KaFai Lau <kafai@...com>, 
	Song Liu <songliubraving@...com>, Yonghong Song <yhs@...com>, 
	John Fastabend <john.fastabend@...il.com>, KP Singh <kpsingh@...omium.org>, 
	Stanislav Fomichev <sdf@...gle.com>, Hao Luo <haoluo@...gle.com>, Steven Rostedt <rostedt@...dmis.org>, 
	Masami Hiramatsu <mhiramat@...nel.org>, linux-kernel@...r.kernel.org, 
	linux-trace-kernel@...r.kernel.org
Subject: Re: [PATCHv2 bpf-next 4/9] libbpf: Add support for uprobe multi
 session attach

On Mon, Jul 1, 2024 at 9:42 AM Jiri Olsa <jolsa@...nel.org> wrote:
>
> Adding support to attach program in uprobe session mode
> with bpf_program__attach_uprobe_multi function.
>
> Adding session bool to bpf_uprobe_multi_opts struct that allows
> to load and attach the bpf program via uprobe session.
> the attachment to create uprobe multi session.
>
> Also adding new program loader section that allows:
>   SEC("uprobe.session/bpf_fentry_test*")
>
> and loads/attaches uprobe program as uprobe session.
>
> Signed-off-by: Jiri Olsa <jolsa@...nel.org>
> ---
>  tools/lib/bpf/bpf.c    |  1 +
>  tools/lib/bpf/libbpf.c | 50 ++++++++++++++++++++++++++++++++++++++++--
>  tools/lib/bpf/libbpf.h |  4 +++-
>  3 files changed, 52 insertions(+), 3 deletions(-)
>

[...]

> @@ -9362,6 +9363,7 @@ static const struct bpf_sec_def section_defs[] = {
>         SEC_DEF("kprobe.session+",      KPROBE, BPF_TRACE_KPROBE_SESSION, SEC_NONE, attach_kprobe_session),
>         SEC_DEF("uprobe.multi+",        KPROBE, BPF_TRACE_UPROBE_MULTI, SEC_NONE, attach_uprobe_multi),
>         SEC_DEF("uretprobe.multi+",     KPROBE, BPF_TRACE_UPROBE_MULTI, SEC_NONE, attach_uprobe_multi),
> +       SEC_DEF("uprobe.session+",      KPROBE, BPF_TRACE_UPROBE_SESSION, SEC_NONE, attach_uprobe_session),

sleepable ones as well?

>         SEC_DEF("uprobe.multi.s+",      KPROBE, BPF_TRACE_UPROBE_MULTI, SEC_SLEEPABLE, attach_uprobe_multi),
>         SEC_DEF("uretprobe.multi.s+",   KPROBE, BPF_TRACE_UPROBE_MULTI, SEC_SLEEPABLE, attach_uprobe_multi),
>         SEC_DEF("ksyscall+",            KPROBE, 0, SEC_NONE, attach_ksyscall),
> @@ -11698,6 +11700,40 @@ static int attach_uprobe_multi(const struct bpf_program *prog, long cookie, stru
>         return ret;
>  }
>
> +static int attach_uprobe_session(const struct bpf_program *prog, long cookie, struct bpf_link **link)
> +{
> +       char *binary_path = NULL, *func_name = NULL;
> +       LIBBPF_OPTS(bpf_uprobe_multi_opts, opts,
> +               .session = true,
> +       );

nit: keep a single line?

> +       int n, ret = -EINVAL;
> +       const char *spec;
> +
> +       *link = NULL;
> +
> +       spec = prog->sec_name + sizeof("uprobe.session/") - 1;
> +       n = sscanf(spec, "%m[^:]:%m[^\n]",
> +                  &binary_path, &func_name);

single line, wrapping lines is a necessary evil, please

[...]