Stanislav Fomichev <sdf@xxxxxxxxxx> writes: > There is an ndo handler per kfunc, the verifier replaces a call to the > generic kfunc with a call to the per-device one. > > For XDP, we define a new kfunc set (xdp_metadata_kfunc_ids) which > implements all possible metatada kfuncs. Not all devices have to > implement them. If kfunc is not supported by the target device, > the default implementation is called instead. BTW, this "the default implementation is called instead" bit is not included in this version... :) [...] > +#ifdef CONFIG_DEBUG_INFO_BTF > +BTF_SET8_START(xdp_metadata_kfunc_ids) > +#define XDP_METADATA_KFUNC(name, str) BTF_ID_FLAGS(func, str, 0) > +XDP_METADATA_KFUNC_xxx > +#undef XDP_METADATA_KFUNC > +BTF_SET8_END(xdp_metadata_kfunc_ids) > + > +static const struct btf_kfunc_id_set xdp_metadata_kfunc_set = { > + .owner = THIS_MODULE, > + .set = &xdp_metadata_kfunc_ids, > +}; > + > +u32 xdp_metadata_kfunc_id(int id) > +{ > + return xdp_metadata_kfunc_ids.pairs[id].id; > +} > +EXPORT_SYMBOL_GPL(xdp_metadata_kfunc_id); So I was getting some really weird values when testing (always getting a timestamp value of '1'), and it turns out to be because this way of looking up the ID doesn't work: The set is always sorted by the BTF ID, not the order it was defined. Which meant that the mapping code got the functions mixed up, and would call a different one instead (so the timestamp value I was getting was really the return value of rx_hash_enabled()). I fixed it by building a secondary lookup table as below; feel free to incorporate that (or if you can come up with a better way, go ahead!). -Toke diff --git a/net/core/xdp.c b/net/core/xdp.c index e43f7d4ef4cf..dc0a9644dacc 100644 --- a/net/core/xdp.c +++ b/net/core/xdp.c @@ -738,6 +738,15 @@ XDP_METADATA_KFUNC_xxx #undef XDP_METADATA_KFUNC BTF_SET8_END(xdp_metadata_kfunc_ids) +static struct xdp_metadata_kfunc_map { + const char *fname; + u32 btf_id; +} xdp_metadata_kfunc_lookup_map[MAX_XDP_METADATA_KFUNC] = { +#define XDP_METADATA_KFUNC(name, str) { .fname = __stringify(str) }, +XDP_METADATA_KFUNC_xxx +#undef XDP_METADATA_KFUNC +}; + static const struct btf_kfunc_id_set xdp_metadata_kfunc_set = { .owner = THIS_MODULE, .set = &xdp_metadata_kfunc_ids, @@ -745,13 +754,41 @@ static const struct btf_kfunc_id_set xdp_metadata_kfunc_set = { u32 xdp_metadata_kfunc_id(int id) { - return xdp_metadata_kfunc_ids.pairs[id].id; + return xdp_metadata_kfunc_lookup_map[id].btf_id; } EXPORT_SYMBOL_GPL(xdp_metadata_kfunc_id); static int __init xdp_metadata_init(void) { - return register_btf_kfunc_id_set(BPF_PROG_TYPE_XDP, &xdp_metadata_kfunc_set); + const struct btf *btf; + int i, j, ret; + + ret = register_btf_kfunc_id_set(BPF_PROG_TYPE_XDP, &xdp_metadata_kfunc_set); + if (ret) + return ret; + + btf = bpf_get_btf_vmlinux(); + + for (i = 0; i < MAX_XDP_METADATA_KFUNC; i++) { + u32 btf_id = xdp_metadata_kfunc_ids.pairs[i].id; + const struct btf_type *t; + const char *name; + + t = btf_type_by_id(btf, btf_id); + if (WARN_ON_ONCE(!t || !t->name_off)) + continue; + + name = btf_name_by_offset(btf, t->name_off); + + for (j = 0; j < MAX_XDP_METADATA_KFUNC; j++) { + if (!strcmp(name, xdp_metadata_kfunc_lookup_map[j].fname)) { + xdp_metadata_kfunc_lookup_map[j].btf_id = btf_id; + break; + } + } + } + + return 0; } late_initcall(xdp_metadata_init); #else /* CONFIG_DEBUG_INFO_BTF */