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

[Jiri Olsa <olsajiri@gmail.com>]

On Mon, Sep 30, 2024 at 02:36:35PM -0700, Andrii Nakryiko wrote:
> On Sun, Sep 29, 2024 at 1:58 PM Jiri Olsa <jolsa@kernel.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.
> >
> > Adding sleepable hook (uprobe.session.s) as well.
> >
> > Signed-off-by: Jiri Olsa <jolsa@kernel.org>
> > ---
> >  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@kernel.org>
> 
> > 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.

sure, will change

thanks,
jirka