Re: [PATCHv5 bpf-next 06/13] libbpf: Add support for uprobe multi session attach

[Andrii Nakryiko]

On Sun, Sep 29, 2024 at 1:58 PM Jiri Olsa <jolsa@xxxxxxxxxx> 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.
>
> Adding sleepable hook (uprobe.session.s) as well.
>
> Signed-off-by: Jiri Olsa <jolsa@xxxxxxxxxx>
> ---
>  tools/lib/bpf/bpf.c    |  1 +
>  tools/lib/bpf/libbpf.c | 21 ++++++++++++++++++---
>  tools/lib/bpf/libbpf.h |  4 +++-
>  3 files changed, 22 insertions(+), 4 deletions(-)
>

LGTM, though see the nit below

Acked-by: Andrii Nakryiko <andrii@xxxxxxxxxx>

> diff --git a/tools/lib/bpf/bpf.c b/tools/lib/bpf/bpf.c
> index 2a4c71501a17..becdfa701c75 100644
> --- a/tools/lib/bpf/bpf.c
> +++ b/tools/lib/bpf/bpf.c
> @@ -776,6 +776,7 @@ int bpf_link_create(int prog_fd, int target_fd,
>                         return libbpf_err(-EINVAL);
>                 break;
>         case BPF_TRACE_UPROBE_MULTI:
> +       case BPF_TRACE_UPROBE_SESSION:
>                 attr.link_create.uprobe_multi.flags = OPTS_GET(opts, uprobe_multi.flags, 0);
>                 attr.link_create.uprobe_multi.cnt = OPTS_GET(opts, uprobe_multi.cnt, 0);
>                 attr.link_create.uprobe_multi.path = ptr_to_u64(OPTS_GET(opts, uprobe_multi.path, 0));
> diff --git a/tools/lib/bpf/libbpf.c b/tools/lib/bpf/libbpf.c
> index 3587ed7ec359..563ff5e64269 100644
> --- a/tools/lib/bpf/libbpf.c
> +++ b/tools/lib/bpf/libbpf.c
> @@ -9410,8 +9410,10 @@ 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_multi),
>         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("uprobe.session.s+",    KPROBE, BPF_TRACE_UPROBE_SESSION, SEC_SLEEPABLE, attach_uprobe_multi),
>         SEC_DEF("ksyscall+",            KPROBE, 0, SEC_NONE, attach_ksyscall),
>         SEC_DEF("kretsyscall+",         KPROBE, 0, SEC_NONE, attach_ksyscall),
>         SEC_DEF("usdt+",                KPROBE, 0, SEC_USDT, attach_usdt),
> @@ -11733,7 +11735,10 @@ static int attach_uprobe_multi(const struct bpf_program *prog, long cookie, stru
>                 ret = 0;
>                 break;
>         case 3:
> -               opts.retprobe = str_has_pfx(probe_type, "uretprobe.multi");
> +               if (str_has_pfx(probe_type, "uprobe.session"))
> +                       opts.session = true;
> +               else
> +                       opts.retprobe = str_has_pfx(probe_type, "uretprobe.multi");

nit: this is very non-uniform, can you please just do:

opts.session = str_has_pfx(probe_type, "uprobe.session");
opts.retprobe = str_has_pfx(probe_type, "uretprobe.multi");

There is no need to micro-optimize str_has_pfx() calls, IMO.

>                 *link = bpf_program__attach_uprobe_multi(prog, -1, binary_path, func_name, &opts);
>                 ret = libbpf_get_error(*link);
>                 break;

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