Re: [PATCH bpf-next 4/7] libbpf: Add support for kprobe multi session attach

[Jiri Olsa <olsajiri@gmail.com>]

On Tue, Apr 23, 2024 at 05:26:59PM -0700, Andrii Nakryiko wrote:

SNIP

> > diff --git a/tools/lib/bpf/libbpf.c b/tools/lib/bpf/libbpf.c
> > index 97eb6e5dd7c8..ca605240205f 100644
> > --- a/tools/lib/bpf/libbpf.c
> > +++ b/tools/lib/bpf/libbpf.c
> > @@ -9272,6 +9272,7 @@ static int attach_tp(const struct bpf_program *prog, long cookie, struct bpf_lin
> >  static int attach_raw_tp(const struct bpf_program *prog, long cookie, struct bpf_link **link);
> >  static int attach_trace(const struct bpf_program *prog, long cookie, struct bpf_link **link);
> >  static int attach_kprobe_multi(const struct bpf_program *prog, long cookie, struct bpf_link **link);
> > +static int attach_kprobe_session(const struct bpf_program *prog, long cookie, struct bpf_link **link);
> >  static int attach_uprobe_multi(const struct bpf_program *prog, long cookie, struct bpf_link **link);
> >  static int attach_lsm(const struct bpf_program *prog, long cookie, struct bpf_link **link);
> >  static int attach_iter(const struct bpf_program *prog, long cookie, struct bpf_link **link);
> > @@ -9288,6 +9289,7 @@ static const struct bpf_sec_def section_defs[] = {
> >         SEC_DEF("uretprobe.s+",         KPROBE, 0, SEC_SLEEPABLE, attach_uprobe),
> >         SEC_DEF("kprobe.multi+",        KPROBE, BPF_TRACE_KPROBE_MULTI, SEC_NONE, attach_kprobe_multi),
> >         SEC_DEF("kretprobe.multi+",     KPROBE, BPF_TRACE_KPROBE_MULTI, SEC_NONE, attach_kprobe_multi),
> > +       SEC_DEF("kprobe.session+",      KPROBE, BPF_TRACE_KPROBE_MULTI_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.multi.s+",      KPROBE, BPF_TRACE_UPROBE_MULTI, SEC_SLEEPABLE, attach_uprobe_multi),
> > @@ -11380,13 +11382,14 @@ bpf_program__attach_kprobe_multi_opts(const struct bpf_program *prog,
> >         struct kprobe_multi_resolve res = {
> >                 .pattern = pattern,
> >         };
> > +       enum bpf_attach_type attach_type;
> >         struct bpf_link *link = NULL;
> >         char errmsg[STRERR_BUFSIZE];
> >         const unsigned long *addrs;
> >         int err, link_fd, prog_fd;
> > +       bool retprobe, session;
> >         const __u64 *cookies;
> >         const char **syms;
> > -       bool retprobe;
> >         size_t cnt;
> >
> >         if (!OPTS_VALID(opts, bpf_kprobe_multi_opts))
> > @@ -11425,6 +11428,13 @@ bpf_program__attach_kprobe_multi_opts(const struct bpf_program *prog,
> >         }
> >
> >         retprobe = OPTS_GET(opts, retprobe, false);
> > +       session  = OPTS_GET(opts, session, false);
> > +
> > +       if (retprobe && session)
> > +               return libbpf_err_ptr(-EINVAL);
> > +
> > +       attach_type = session ? BPF_TRACE_KPROBE_MULTI_SESSION :
> > +                               BPF_TRACE_KPROBE_MULTI;
> 
> doesn't fit under 100?

88 ;-) ok

> 
> >
> >         lopts.kprobe_multi.syms = syms;
> >         lopts.kprobe_multi.addrs = addrs;
> > @@ -11439,7 +11449,7 @@ bpf_program__attach_kprobe_multi_opts(const struct bpf_program *prog,
> >         }
> >         link->detach = &bpf_link__detach_fd;
> >
> > -       link_fd = bpf_link_create(prog_fd, 0, BPF_TRACE_KPROBE_MULTI, &lopts);
> > +       link_fd = bpf_link_create(prog_fd, 0, attach_type, &lopts);
> >         if (link_fd < 0) {
> >                 err = -errno;
> >                 pr_warn("prog '%s': failed to attach: %s\n",
> > @@ -11545,6 +11555,32 @@ static int attach_kprobe_multi(const struct bpf_program *prog, long cookie, stru
> >         return libbpf_get_error(*link);
> >  }
> >
> > +static int attach_kprobe_session(const struct bpf_program *prog, long cookie,
> > +                                struct bpf_link **link)
> > +{
> > +       LIBBPF_OPTS(bpf_kprobe_multi_opts, opts, .session = true);
> > +       const char *spec;
> > +       char *pattern;
> > +       int n;
> > +
> > +       *link = NULL;
> > +
> > +       /* no auto-attach for SEC("kprobe.session") */
> > +       if (strcmp(prog->sec_name, "kprobe.session") == 0)
> > +               return 0;
> > +
> > +       spec = prog->sec_name + sizeof("kprobe.session/") - 1;
> > +       n = sscanf(spec, "%m[a-zA-Z0-9_.*?]", &pattern);
> > +       if (n < 1) {
> > +               pr_warn("kprobe session pattern is invalid: %s\n", pattern);
> > +               return -EINVAL;
> > +       }
> > +
> > +       *link = bpf_program__attach_kprobe_multi_opts(prog, pattern, &opts);
> > +       free(pattern);
> > +       return libbpf_get_error(*link);
> 
> let's try not to add new uses of libbpf_get_error? Would this work:
> 
> return *link ? 0 : -errno;

ok

jirka