On Fri, Mar 28, 2025 at 12:16 PM Mykyta Yatsenko
<mykyta.yatsenko5@xxxxxxxxx> wrote:
>
> On 28/03/2025 17:14, Andrii Nakryiko wrote:
> > On Wed, Mar 26, 2025 at 11:07 AM Mykyta Yatsenko
> > <mykyta.yatsenko5@xxxxxxxxx> wrote:
> >> From: Mykyta Yatsenko <yatsenko@xxxxxxxx>
> >>
> >> Introducing new libbpf API getters for BTF.ext func and line info,
> >> namely:
> >> bpf_program__func_info
> >> bpf_program__func_info_cnt
> >> bpf_program__func_info_rec_size
> >> bpf_program__line_info
> >> bpf_program__line_info_cnt
> >> bpf_program__line_info_rec_size
> >>
> >> This change enables scenarios, when user needs to load bpf_program
> >> directly using `bpf_prog_load`, instead of higher-level
> >> `bpf_object__load`. Line and func info are required for checking BTF
> >> info in verifier; verification may fail without these fields if, for
> >> example, program calls `bpf_obj_new`.
> >>
> > Really, bpf_obj_new() needs func_info/line_info? Can you point where
> > in the verifier we check this, curious why we do that.
> Indirectly, yes:
> in verifier.c function check_btf_info_early sets
> `env->prog->aux->btf = btf;`
> only if line_info_cnt or func_info_cnt are non zero.
> and then there is a check that errors out:
> `verbose(env, "bpf_obj_new/bpf_percpu_obj_new requires prog BTF\n");`
> perhaps this can be improved as well, by setting aux->btf even if no
> func info and line info
lol, doesn't seem intentional (just in the early days prog BTF was
only referenced and used with func_info/line_info, which isn't true
anymore), we can probably swap the order and load and remember prog
BTF regardless of func_info/line_info. Feel free to send a patch.
> >
> >> Signed-off-by: Mykyta Yatsenko <yatsenko@xxxxxxxx>
> >> ---
> >> tools/lib/bpf/libbpf.c | 30 ++++++++++++++++++++++++++++++
> >> tools/lib/bpf/libbpf.h | 8 ++++++++
> >> tools/lib/bpf/libbpf.map | 6 ++++++
> >> 3 files changed, 44 insertions(+)
> >>
[...]
> >> diff --git a/tools/lib/bpf/libbpf.map b/tools/lib/bpf/libbpf.map
> >> index d8b71f22f197..a5d83189c084 100644
> >> --- a/tools/lib/bpf/libbpf.map
> >> +++ b/tools/lib/bpf/libbpf.map
> >> @@ -437,6 +437,12 @@ LIBBPF_1.6.0 {
> >> bpf_linker__add_fd;
> >> bpf_linker__new_fd;
> >> bpf_object__prepare;
> >> + bpf_program__func_info;
> >> + bpf_program__func_info_cnt;
> >> + bpf_program__func_info_rec_size;
> >> + bpf_program__line_info;
> >> + bpf_program__line_info_cnt;
> >> + bpf_program__line_info_rec_size;
nit: hm... please check tabs vs spaces, formatting looks off
> >> btf__add_decl_attr;
> >> btf__add_type_attr;
> >> } LIBBPF_1.5.0;
> >> --
> >> 2.48.1
> >>
>
