From: Alexei Starovoitov <alexei.starovoitov@gmail.com>
To: Andrii Nakryiko <andrii.nakryiko@gmail.com>
Cc: Lorenzo Fontana <fontanalorenz@gmail.com>,
bpf <bpf@vger.kernel.org>, Alexei Starovoitov <ast@kernel.org>,
Daniel Borkmann <daniel@iogearbox.net>
Subject: Re: [PATCH bpf-next 1/2] tools/lib/bpf: bpf_program__insns allow to retrieve insns in libbpf
Date: Thu, 15 Jul 2021 18:51:11 -0700 [thread overview]
Message-ID: <CAADnVQKH2ViNN6QQJR3Fzo2+k+GmVu=nwAREPjuLZ6_HS8-XMg@mail.gmail.com> (raw)
In-Reply-To: <CAEf4BzaMcWGt+eqEqQdpJ_s5Zv80ziCA+vo5fa5HmaZmwBvh6A@mail.gmail.com>
On Thu, Jul 15, 2021 at 2:40 PM Andrii Nakryiko
<andrii.nakryiko@gmail.com> wrote:
>
> On Tue, Jul 13, 2021 at 11:34 AM Lorenzo Fontana
> <fontanalorenz@gmail.com> wrote:
> >
> > This allows consumers of libbpf to iterate trough the insns
> > of a program without loading it first directly after the ELF parsing.
> >
> > Being able to do that is useful to create tooling that can show
> > the structure of a BPF program using libbpf without having to
> > parse the ELF separately.
> >
>
> So I wonder how useful is getting raw BPF instructions before libbpf
> processed them and resolved map references, subprogram calls, etc?
> You'll have lots of zeroes or meaningless constants in ldimm64
> instructions, etc. I always felt that being able to get instructions
> after libbpf processed them is more useful. The problem is that
> currently libbpf frees prog->insns after successful bpf_program__load.
> There is one extra (advanced) scenario where having those instructions
> preserved after load would be really nice -- cloning BPF program (I
> had use case for fentry/fexit). So the question is whether we should
> just leave those prog->insns around until the object is closed or not?
> And if we do, should bpftool dump instructions before or after load?
> Let's see what folks think.
Same here. I understand the desire, but the approach to expose half baked
instructions isn't addressing the need.
next prev parent reply other threads:[~2021-07-16 1:51 UTC|newest]
Thread overview: 12+ messages / expand[flat|nested] mbox.gz Atom feed top
2021-07-13 18:33 [PATCH bpf-next 1/2] tools/lib/bpf: bpf_program__insns allow to retrieve insns in libbpf Lorenzo Fontana
2021-07-13 18:35 ` [PATCH bpf-next 2/2] tools/bpf/bpftool: xlated dump from ELF file directly Lorenzo Fontana
2021-07-14 0:00 ` Lorenzo Fontana
2021-07-15 5:48 ` John Fastabend
2021-07-15 8:10 ` liwei (GF)
2021-07-15 9:55 ` Quentin Monnet
2021-07-14 4:19 ` [PATCH bpf-next 1/2] tools/lib/bpf: bpf_program__insns allow to retrieve insns in libbpf kernel test robot
2021-07-15 5:48 ` John Fastabend
2021-07-15 10:12 ` Quentin Monnet
2021-07-15 21:40 ` Andrii Nakryiko
2021-07-16 1:51 ` Alexei Starovoitov [this message]
2021-07-19 16:42 ` Lorenzo Fontana
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