On Wed, Feb 28, 2024 at 05:23:57PM -0800, Andrii Nakryiko wrote:
> On Wed, Feb 28, 2024 at 1:03 AM Jiri Olsa <jolsa@xxxxxxxxxx> wrote:
> >
> > Adding support for specify wrapper mode in bpf_kprobe_multi_opts
> > struct object and new bpf program loader section:
> >
> > SEC("kprobe.wrapper/bpf_fentry_test*")
> >
> > to load program as kprobe multi wrapper.
> >
> > Signed-off-by: Jiri Olsa <jolsa@xxxxxxxxxx>
> > ---
> > tools/lib/bpf/libbpf.c | 38 +++++++++++++++++++++++++++++++++++---
> > tools/lib/bpf/libbpf.h | 4 +++-
> > 2 files changed, 38 insertions(+), 4 deletions(-)
> >
> > diff --git a/tools/lib/bpf/libbpf.c b/tools/lib/bpf/libbpf.c
> > index 01f407591a92..5416d784c857 100644
> > --- a/tools/lib/bpf/libbpf.c
> > +++ b/tools/lib/bpf/libbpf.c
> > @@ -8944,6 +8944,7 @@ 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_wrapper(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);
> > @@ -8960,6 +8961,7 @@ 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.wrapper+", KPROBE, BPF_TRACE_KPROBE_MULTI, SEC_NONE, attach_kprobe_wrapper),
> > 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),
> > @@ -11034,7 +11036,7 @@ bpf_program__attach_kprobe_multi_opts(const struct bpf_program *prog,
> > int err, link_fd, prog_fd;
> > const __u64 *cookies;
> > const char **syms;
> > - bool retprobe;
> > + __u32 flags = 0;
> > size_t cnt;
> >
> > if (!OPTS_VALID(opts, bpf_kprobe_multi_opts))
> > @@ -11065,13 +11067,16 @@ bpf_program__attach_kprobe_multi_opts(const struct bpf_program *prog,
> > cnt = res.cnt;
> > }
> >
> > - retprobe = OPTS_GET(opts, retprobe, false);
> > + if (OPTS_GET(opts, retprobe, false))
> > + flags |= BPF_F_KPROBE_MULTI_RETURN;
> > + if (OPTS_GET(opts, wrapper, false))
> > + flags |= BPF_F_KPROBE_MULTI_WRAPPER;
>
> probably error out if both retprobe and wrapper are set?
ok
>
> >
> > lopts.kprobe_multi.syms = syms;
> > lopts.kprobe_multi.addrs = addrs;
> > lopts.kprobe_multi.cookies = cookies;
> > lopts.kprobe_multi.cnt = cnt;
> > - lopts.kprobe_multi.flags = retprobe ? BPF_F_KPROBE_MULTI_RETURN : 0;
> > + lopts.kprobe_multi.flags = flags;
> >
> > link = calloc(1, sizeof(*link));
> > if (!link) {
> > @@ -11187,6 +11192,33 @@ static int attach_kprobe_multi(const struct bpf_program *prog, long cookie, stru
> > return libbpf_get_error(*link);
> > }
> >
> > +static int attach_kprobe_wrapper(const struct bpf_program *prog, long cookie, struct bpf_link **link)
> > +{
> > + LIBBPF_OPTS(bpf_kprobe_multi_opts, opts,
> > + .wrapper = true,
> > + );
>
> nit: keep on a single line?
ok
>
> > + const char *spec;
> > + char *pattern;
> > + int n;
> > +
> > + *link = NULL;
> > +
> > + /* no auto-attach for SEC("kprobe.wrapper") */
> > + if (strcmp(prog->sec_name, "kprobe.wrapper") == 0)
> > + return 0;
> > +
> > + spec = prog->sec_name + sizeof("kprobe.wrapper/") - 1;
> > + n = sscanf(spec, "%m[a-zA-Z0-9_.*?]", &pattern);
> > + if (n < 1) {
> > + pr_warn("kprobe wrapper pattern is invalid: %s\n", pattern);
> > + return -EINVAL;
> > + }
> > +
> > + *link = bpf_program__attach_kprobe_multi_opts(prog, pattern, &opts);
> > + free(pattern);
>
> is it guaranteed that free() won't clobber errno? or should we record
> it right after attach call (and stop using libbpf_get_error())?
hum, I copy&pasted from the attach_kprobe_multi, so did not think of that ;-)
anyway man page says:
The free() function returns no value, and preserves errno.
so we're good
thanks,
jirka
>
>
> > + return libbpf_get_error(*link);
> > +}
> > +
> > static int attach_uprobe_multi(const struct bpf_program *prog, long cookie, struct bpf_link **link)
> > {
> > char *probe_type = NULL, *binary_path = NULL, *func_name = NULL;
> > diff --git a/tools/lib/bpf/libbpf.h b/tools/lib/bpf/libbpf.h
> > index 5723cbbfcc41..72f4e3ad295f 100644
> > --- a/tools/lib/bpf/libbpf.h
> > +++ b/tools/lib/bpf/libbpf.h
> > @@ -539,10 +539,12 @@ struct bpf_kprobe_multi_opts {
> > size_t cnt;
> > /* create return kprobes */
> > bool retprobe;
> > + /* create wrapper kprobes */
> > + bool wrapper;
> > size_t :0;
> > };
> >
> > -#define bpf_kprobe_multi_opts__last_field retprobe
> > +#define bpf_kprobe_multi_opts__last_field wrapper
> >
> > LIBBPF_API struct bpf_link *
> > bpf_program__attach_kprobe_multi_opts(const struct bpf_program *prog,
> > --
> > 2.43.2
> >
