On Thu, Feb 20, 2025 at 3:34 PM Amery Hung <ameryhung@xxxxxxxxx> wrote:
>
> On Thu, Feb 20, 2025 at 3:10 PM Eduard Zingerman <eddyz87@xxxxxxxxx> wrote:
> >
> > On Thu, 2025-02-20 at 13:25 -0800, Amery Hung wrote:
> >
> > [...]
> >
> > Given that prologue and epilogue generation is already tested,
> > it appears that it would be sufficient to add only two tests:
> > 'test_kfunc_pro_epilogue' / 'syscall_pro_epilogue'.
> > Not sure if testing prologue and epilogue generation separately adds
> > much value in this context, wdyt?
> >
>
> Agree. I will only keep the syscall_pro_epilogue test.
>
> > [...]
> >
> > > diff --git a/kernel/bpf/btf.c b/kernel/bpf/btf.c
> > > index 6c296ff551e0..ddebab05934f 100644
> > > --- a/kernel/bpf/btf.c
> > > +++ b/kernel/bpf/btf.c
> > > @@ -606,6 +606,7 @@ s32 bpf_find_btf_id(const char *name, u32 kind, struct btf **btf_p)
> > > spin_unlock_bh(&btf_idr_lock);
> > > return ret;
> > > }
> > > +EXPORT_SYMBOL_GPL(bpf_find_btf_id);
> >
> > I think this is not necessary, see below.
> >
> > [...]
> >
> > > @@ -1410,6 +1493,13 @@ static void st_ops_unreg(void *kdata, struct bpf_link *link)
> > >
> > > static int st_ops_init(struct btf *btf)
> > > {
> > > + struct btf *kfunc_btf;
> > > +
> > > + bpf_cgroup_from_id_id = bpf_find_btf_id("bpf_cgroup_from_id", BTF_KIND_FUNC, &kfunc_btf);
> > > + bpf_cgroup_release_id = bpf_find_btf_id("bpf_cgroup_release", BTF_KIND_FUNC, &kfunc_btf);
> >
> > Maybe use BTF_ID_LIST for this?
> > E.g. BTF_ID_LIST(bpf_testmod_dtor_ids) in this file, or
> > BTF_ID_LIST(special_kfunc_list) in verifier.c?
> >
> > (Just in case, sorry if you know this already,
> > BTF_ID_LIST declares are set of symbols with special suffix/prefix,
> > at build time tools/bpf/resolve_btfids looks for such symbols and patches
> > their values to correspond to BTF ids of specified functions and structures).
> >
>
> Ah yes. It is an artifact when I was testing a patch for generating
> kfunc in module btf. But since there is no use case, I removed that
> part. I will change it to BTF_ID_LIST. Thanks for catching this.
>
Actually when I use BTF_ID_LIST with a kernel kfunc, I got the warning
below. Since it was not able to resolve the btf id, the test program
failed to load as the generated byte code will contain invalid kfunc
id.
BTF [M] bpf_testmod.ko
WARN: resolve_btfids: unresolved symbol bpf_cgroup_release
WARN: resolve_btfids: unresolved symbol bpf_cgroup_from_id
MOD bpf_testmod.ko
I am not familiar with how resolve_btfids work, specifically when
building a kernel module. Do you have any suggestions?
Thanks,
Amery
> Thanks,
> Amery
>
> > > + if (!bpf_cgroup_from_id_id || !bpf_cgroup_release_id)
> > > + return -EINVAL;
> > > +
> > > return 0;
> > > }
> > >
> >
> >
