netdev - Re: [PATCH bpf-next v4 11/11] bpf: selftests: Add selftests for module kfunc support

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]

Date:   Wed, 22 Sep 2021 11:24:15 -0700
From:   Alexei Starovoitov <alexei.starovoitov@...il.com>
To:     Kumar Kartikeya Dwivedi <memxor@...il.com>
Cc:     Andrii Nakryiko <andrii.nakryiko@...il.com>,
        bpf <bpf@...r.kernel.org>, Alexei Starovoitov <ast@...nel.org>,
        Daniel Borkmann <daniel@...earbox.net>,
        Andrii Nakryiko <andrii@...nel.org>,
        Martin KaFai Lau <kafai@...com>,
        Song Liu <songliubraving@...com>, Yonghong Song <yhs@...com>,
        Jesper Dangaard Brouer <brouer@...hat.com>,
        Toke Høiland-Jørgensen <toke@...hat.com>,
        Networking <netdev@...r.kernel.org>
Subject: Re: [PATCH bpf-next v4 11/11] bpf: selftests: Add selftests for
 module kfunc support

On Tue, Sep 21, 2021 at 11:06 PM Kumar Kartikeya Dwivedi
<memxor@...il.com> wrote:
>
> On Wed, Sep 22, 2021 at 05:33:26AM IST, Andrii Nakryiko wrote:
> > > [...]
> > > Hmm, good idea, I'd just need to fill in the BTF id dynamically at runtime,
> > > but that should be possible.
> > >
> > > Though we still need to craft distinct calls (I am trying to test the limit
> > > where insn->off is different for each case). Since we try to reuse index in both
> > > gen_loader and libbpf, just generating same call 256 times would not be enough.
> >
> > You just need to generate one instruction with offset = 257 to test
> > this. And separately one call with fd_array that has module BTF fd at
> > fd_array[256] (to check that 256 is ok). Or am I missing something?
> >
>
> That won't be enough, if I just pass insn->imm = id, insn->off = 257, it becomes
> first descriptor in kfunc_tab and kfunc_btf_tab. The total limit is 256, and
> they are kept in sorted order by based on id and off for the first, off for the
> second. So 256 different offs are needed (imm may be same actually), so that
> both fill up.

Just to test the 256 limit? I don't think it's necessary.
afaik there is no test that exercises the 64 map limit.