Re: [PATCH v3 bpf-next 2/6] libbpf: Adjust btf_vlen() to return a __u32

Mykyta Yatsenko
2026-04-17T18:26:32Z

On 4/17/26 3:30 PM, Alan Maguire wrote:
> Now that vlen is 24 bits, btf_vlen() must return a __u32.
> Adjust use cases in libbpf accordingly. Also add error
> handling to avoid vlen overflow in btf_type_inc_vlen().
>
> Signed-off-by: Alan Maguire <alan.maguire@oracle.com>
> ---

Migrated all vlens in libbpf u16 -> u32, kind does not require widening.
Acked-by: Mykyta Yatsenko <yatsenko@meta.com>

> tools/lib/bpf/btf.c | 50 +++++++++++++++++++++++++--------------
> tools/lib/bpf/btf.h | 2 +-
> tools/lib/bpf/btf_dump.c | 24 +++++++++----------
> tools/lib/bpf/relo_core.c | 16 ++++++-------
> 4 files changed, 53 insertions(+), 39 deletions(-)
>
> diff --git a/tools/lib/bpf/btf.c b/tools/lib/bpf/btf.c
> index ceb57b46a878..267904939098 100644
> --- a/tools/lib/bpf/btf.c
> +++ b/tools/lib/bpf/btf.c
> @@ -421,7 +421,7 @@ static int btf_type_size_unknown(const struct btf *btf, const struct btf_type *t
> {
> __u32 l_cnt = btf->hdr.layout_len / sizeof(struct btf_layout);
> struct btf_layout *l = btf->layout;
> - __u16 vlen = btf_vlen(t);
> + __u32 vlen = btf_vlen(t);
> __u32 kind = btf_kind(t);
>
> /* Fall back to base BTF if needed as they share layout information */
> @@ -454,7 +454,7 @@ static int btf_type_size_unknown(const struct btf *btf, const struct btf_type *t
> static int btf_type_size(const struct btf *btf, const struct btf_type *t)
> {
> const int base_size = sizeof(struct btf_type);
> - __u16 vlen = btf_vlen(t);
> + __u32 vlen = btf_vlen(t);
>
> switch (btf_kind(t)) {
> case BTF_KIND_FWD:
> @@ -506,7 +506,7 @@ static int btf_bswap_type_rest(struct btf_type *t)
> struct btf_array *a;
> struct btf_param *p;
> struct btf_enum *e;
> - __u16 vlen = btf_vlen(t);
> + __u32 vlen = btf_vlen(t);
> int i;
>
> switch (btf_kind(t)) {
> @@ -1007,7 +1007,7 @@ int btf__align_of(const struct btf *btf, __u32 id)
> case BTF_KIND_STRUCT:
> case BTF_KIND_UNION: {
> const struct btf_member *m = btf_members(t);
> - __u16 vlen = btf_vlen(t);
> + __u32 vlen = btf_vlen(t);
> int i, max_align = 1, align;
>
> for (i = 0; i < vlen; i++, m++) {
> @@ -2121,9 +2121,12 @@ static void *btf_add_type_mem(struct btf *btf, size_t add_sz)
> btf->hdr.type_len, UINT_MAX, add_sz);
> }
>
> -static void btf_type_inc_vlen(struct btf_type *t)
> +static int btf_type_inc_vlen(struct btf_type *t)
> {
> + if (btf_vlen(t) == BTF_MAX_VLEN)
> + return -ENOSPC;
> t->info = btf_type_info(btf_kind(t), btf_vlen(t) + 1, btf_kflag(t));
> + return 0;
> }
>
> static void btf_hdr_update_type_len(struct btf *btf, int new_len)
> @@ -2652,6 +2655,8 @@ int btf__add_field(struct btf *btf, const char *name, int type_id,
> t = btf_last_type(btf);
> if (!btf_is_composite(t))
> return libbpf_err(-EINVAL);
> + if (btf_vlen(t) == BTF_MAX_VLEN)
> + return libbpf_err(-ENOSPC);
>
> if (validate_type_id(type_id))
> return libbpf_err(-EINVAL);
> @@ -2686,6 +2691,7 @@ int btf__add_field(struct btf *btf, const char *name, int type_id,
>
> /* btf_add_type_mem can invalidate t pointer */
> t = btf_last_type(btf);
> +
> /* update parent type's vlen and kflag */
> t->info = btf_type_info(btf_kind(t), btf_vlen(t) + 1, is_bitfield || btf_kflag(t));
>
> @@ -2796,7 +2802,9 @@ int btf__add_enum_value(struct btf *btf, const char *name, __s64 value)
>
> /* update parent type's vlen */
> t = btf_last_type(btf);
> - btf_type_inc_vlen(t);
> + err = btf_type_inc_vlen(t);
> + if (err)
> + return libbpf_err(err);
>
> /* if negative value, set signedness to signed */
> if (value < 0)
> @@ -2873,7 +2881,9 @@ int btf__add_enum64_value(struct btf *btf, const char *name, __u64 value)
>
> /* update parent type's vlen */
> t = btf_last_type(btf);
> - btf_type_inc_vlen(t);
> + err = btf_type_inc_vlen(t);
> + if (err)
> + return libbpf_err(err);
>
> btf_hdr_update_type_len(btf, btf->hdr.type_len + sz);
> return 0;
> @@ -3115,7 +3125,9 @@ int btf__add_func_param(struct btf *btf, const char *name, int type_id)
>
> /* update parent type's vlen */
> t = btf_last_type(btf);
> - btf_type_inc_vlen(t);
> + err = btf_type_inc_vlen(t);
> + if (err)
> + return libbpf_err(err);
>
> btf_hdr_update_type_len(btf, btf->hdr.type_len + sz);
> return 0;
> @@ -3257,7 +3269,9 @@ int btf__add_datasec_var_info(struct btf *btf, int var_type_id, __u32 offset, __
>
> /* update parent type's vlen */
> t = btf_last_type(btf);
> - btf_type_inc_vlen(t);
> + err = btf_type_inc_vlen(t);
> + if (err)
> + return libbpf_err(err);
>
> btf_hdr_update_type_len(btf, btf->hdr.type_len + sz);
> return 0;
> @@ -4311,7 +4325,7 @@ static long btf_hash_enum(struct btf_type *t)
> static bool btf_equal_enum_members(struct btf_type *t1, struct btf_type *t2)
> {
> const struct btf_enum *m1, *m2;
> - __u16 vlen;
> + __u32 vlen;
> int i;
>
> vlen = btf_vlen(t1);
> @@ -4329,7 +4343,7 @@ static bool btf_equal_enum_members(struct btf_type *t1, struct btf_type *t2)
> static bool btf_equal_enum64_members(struct btf_type *t1, struct btf_type *t2)
> {
> const struct btf_enum64 *m1, *m2;
> - __u16 vlen;
> + __u32 vlen;
> int i;
>
> vlen = btf_vlen(t1);
> @@ -4406,7 +4420,7 @@ static long btf_hash_struct(struct btf_type *t)
> static bool btf_shallow_equal_struct(struct btf_type *t1, struct btf_type *t2)
> {
> const struct btf_member *m1, *m2;
> - __u16 vlen;
> + __u32 vlen;
> int i;
>
> if (!btf_equal_common(t1, t2))
> @@ -4482,7 +4496,7 @@ static bool btf_compat_array(struct btf_type *t1, struct btf_type *t2)
> static long btf_hash_fnproto(struct btf_type *t)
> {
> const struct btf_param *member = btf_params(t);
> - __u16 vlen = btf_vlen(t);
> + __u32 vlen = btf_vlen(t);
> long h = btf_hash_common(t);
> int i;
>
> @@ -4504,7 +4518,7 @@ static long btf_hash_fnproto(struct btf_type *t)
> static bool btf_equal_fnproto(struct btf_type *t1, struct btf_type *t2)
> {
> const struct btf_param *m1, *m2;
> - __u16 vlen;
> + __u32 vlen;
> int i;
>
> if (!btf_equal_common(t1, t2))
> @@ -4530,7 +4544,7 @@ static bool btf_equal_fnproto(struct btf_type *t1, struct btf_type *t2)
> static bool btf_compat_fnproto(struct btf_type *t1, struct btf_type *t2)
> {
> const struct btf_param *m1, *m2;
> - __u16 vlen;
> + __u32 vlen;
> int i;
>
> /* skip return type ID */
> @@ -5077,7 +5091,7 @@ static int btf_dedup_is_equiv(struct btf_dedup *d, __u32 cand_id,
> case BTF_KIND_STRUCT:
> case BTF_KIND_UNION: {
> const struct btf_member *cand_m, *canon_m;
> - __u16 vlen;
> + __u32 vlen;
>
> if (!btf_shallow_equal_struct(cand_type, canon_type))
> return 0;
> @@ -5105,7 +5119,7 @@ static int btf_dedup_is_equiv(struct btf_dedup *d, __u32 cand_id,
>
> case BTF_KIND_FUNC_PROTO: {
> const struct btf_param *cand_p, *canon_p;
> - __u16 vlen;
> + __u32 vlen;
>
> if (!btf_compat_fnproto(cand_type, canon_type))
> return 0;
> @@ -5439,7 +5453,7 @@ static int btf_dedup_ref_type(struct btf_dedup *d, __u32 type_id)
>
> case BTF_KIND_FUNC_PROTO: {
> struct btf_param *param;
> - __u16 vlen;
> + __u32 vlen;
> int i;
>
> ref_type_id = btf_dedup_ref_type(d, t->type);
> diff --git a/tools/lib/bpf/btf.h b/tools/lib/bpf/btf.h
> index a1f8deca2603..1a31f2da947f 100644
> --- a/tools/lib/bpf/btf.h
> +++ b/tools/lib/bpf/btf.h
> @@ -435,7 +435,7 @@ static inline __u16 btf_kind(const struct btf_type *t)
> return BTF_INFO_KIND(t->info);
> }
>
> -static inline __u16 btf_vlen(const struct btf_type *t)
> +static inline __u32 btf_vlen(const struct btf_type *t)
> {
> return BTF_INFO_VLEN(t->info);
> }
> diff --git a/tools/lib/bpf/btf_dump.c b/tools/lib/bpf/btf_dump.c
> index 53c6624161d7..cc1ba65bb6c5 100644
> --- a/tools/lib/bpf/btf_dump.c
> +++ b/tools/lib/bpf/btf_dump.c
> @@ -316,7 +316,7 @@ static int btf_dump_mark_referenced(struct btf_dump *d)
> {
> int i, j, n = btf__type_cnt(d->btf);
> const struct btf_type *t;
> - __u16 vlen;
> + __u32 vlen;
>
> for (i = d->last_id + 1; i < n; i++) {
> t = btf__type_by_id(d->btf, i);
> @@ -485,7 +485,7 @@ static int btf_dump_order_type(struct btf_dump *d, __u32 id, bool through_ptr)
> */
> struct btf_dump_type_aux_state *tstate = &d->type_states[id];
> const struct btf_type *t;
> - __u16 vlen;
> + __u32 vlen;
> int err, i;
>
> /* return true, letting typedefs know that it's ok to be emitted */
> @@ -798,7 +798,7 @@ static void btf_dump_emit_type(struct btf_dump *d, __u32 id, __u32 cont_id)
> */
> if (top_level_def || t->name_off == 0) {
> const struct btf_member *m = btf_members(t);
> - __u16 vlen = btf_vlen(t);
> + __u32 vlen = btf_vlen(t);
> int i, new_cont_id;
>
> new_cont_id = t->name_off == 0 ? cont_id : id;
> @@ -820,7 +820,7 @@ static void btf_dump_emit_type(struct btf_dump *d, __u32 id, __u32 cont_id)
> break;
> case BTF_KIND_FUNC_PROTO: {
> const struct btf_param *p = btf_params(t);
> - __u16 n = btf_vlen(t);
> + __u32 n = btf_vlen(t);
> int i;
>
> btf_dump_emit_type(d, t->type, cont_id);
> @@ -839,7 +839,7 @@ static bool btf_is_struct_packed(const struct btf *btf, __u32 id,
> {
> const struct btf_member *m;
> int max_align = 1, align, i, bit_sz;
> - __u16 vlen;
> + __u32 vlen;
>
> m = btf_members(t);
> vlen = btf_vlen(t);
> @@ -973,7 +973,7 @@ static void btf_dump_emit_struct_def(struct btf_dump *d,
> bool is_struct = btf_is_struct(t);
> bool packed, prev_bitfield = false;
> int align, i, off = 0;
> - __u16 vlen = btf_vlen(t);
> + __u32 vlen = btf_vlen(t);
>
> align = btf__align_of(d->btf, id);
> packed = is_struct ? btf_is_struct_packed(d->btf, id, t) : 0;
> @@ -1064,7 +1064,7 @@ static void btf_dump_emit_enum_fwd(struct btf_dump *d, __u32 id,
>
> static void btf_dump_emit_enum32_val(struct btf_dump *d,
> const struct btf_type *t,
> - int lvl, __u16 vlen)
> + int lvl, __u32 vlen)
> {
> const struct btf_enum *v = btf_enum(t);
> bool is_signed = btf_kflag(t);
> @@ -1089,7 +1089,7 @@ static void btf_dump_emit_enum32_val(struct btf_dump *d,
>
> static void btf_dump_emit_enum64_val(struct btf_dump *d,
> const struct btf_type *t,
> - int lvl, __u16 vlen)
> + int lvl, __u32 vlen)
> {
> const struct btf_enum64 *v = btf_enum64(t);
> bool is_signed = btf_kflag(t);
> @@ -1122,7 +1122,7 @@ static void btf_dump_emit_enum_def(struct btf_dump *d, __u32 id,
> const struct btf_type *t,
> int lvl)
> {
> - __u16 vlen = btf_vlen(t);
> + __u32 vlen = btf_vlen(t);
>
> btf_dump_printf(d, "enum%s%s",
> t->name_off ? " " : "",
> @@ -1542,7 +1542,7 @@ static void btf_dump_emit_type_chain(struct btf_dump *d,
> }
> case BTF_KIND_FUNC_PROTO: {
> const struct btf_param *p = btf_params(t);
> - __u16 vlen = btf_vlen(t);
> + __u32 vlen = btf_vlen(t);
> int i;
>
> /*
> @@ -2159,7 +2159,7 @@ static int btf_dump_struct_data(struct btf_dump *d,
> const void *data)
> {
> const struct btf_member *m = btf_members(t);
> - __u16 n = btf_vlen(t);
> + __u32 n = btf_vlen(t);
> int i, err = 0;
>
> /* note that we increment depth before calling btf_dump_print() below;
> @@ -2449,7 +2449,7 @@ static int btf_dump_type_data_check_zero(struct btf_dump *d,
> case BTF_KIND_STRUCT:
> case BTF_KIND_UNION: {
> const struct btf_member *m = btf_members(t);
> - __u16 n = btf_vlen(t);
> + __u32 n = btf_vlen(t);
>
> /* if any struct/union member is non-zero, the struct/union
> * is considered non-zero and dumped.
> diff --git a/tools/lib/bpf/relo_core.c b/tools/lib/bpf/relo_core.c
> index 0ccc8f548cba..6ae3f2a15ad0 100644
> --- a/tools/lib/bpf/relo_core.c
> +++ b/tools/lib/bpf/relo_core.c
> @@ -191,8 +191,8 @@ int __bpf_core_types_are_compat(const struct btf *local_btf, __u32 local_id,
> case BTF_KIND_FUNC_PROTO: {
> struct btf_param *local_p = btf_params(local_type);
> struct btf_param *targ_p = btf_params(targ_type);
> - __u16 local_vlen = btf_vlen(local_type);
> - __u16 targ_vlen = btf_vlen(targ_type);
> + __u32 local_vlen = btf_vlen(local_type);
> + __u32 targ_vlen = btf_vlen(targ_type);
> int i, err;
>
> if (local_vlen != targ_vlen)
> @@ -1457,8 +1457,8 @@ static bool bpf_core_names_match(const struct btf *local_btf, size_t local_name_
> static int bpf_core_enums_match(const struct btf *local_btf, const struct btf_type *local_t,
> const struct btf *targ_btf, const struct btf_type *targ_t)
> {
> - __u16 local_vlen = btf_vlen(local_t);
> - __u16 targ_vlen = btf_vlen(targ_t);
> + __u32 local_vlen = btf_vlen(local_t);
> + __u32 targ_vlen = btf_vlen(targ_t);
> int i, j;
>
> if (local_t->size != targ_t->size)
> @@ -1498,8 +1498,8 @@ static int bpf_core_composites_match(const struct btf *local_btf, const struct b
> bool behind_ptr, int level)
> {
> const struct btf_member *local_m = btf_members(local_t);
> - __u16 local_vlen = btf_vlen(local_t);
> - __u16 targ_vlen = btf_vlen(targ_t);
> + __u32 local_vlen = btf_vlen(local_t);
> + __u32 targ_vlen = btf_vlen(targ_t);
> int i, j, err;
>
> if (local_vlen > targ_vlen)
> @@ -1674,8 +1674,8 @@ int __bpf_core_types_match(const struct btf *local_btf, __u32 local_id, const st
> case BTF_KIND_FUNC_PROTO: {
> struct btf_param *local_p = btf_params(local_t);
> struct btf_param *targ_p = btf_params(targ_t);
> - __u16 local_vlen = btf_vlen(local_t);
> - __u16 targ_vlen = btf_vlen(targ_t);
> + __u32 local_vlen = btf_vlen(local_t);
> + __u32 targ_vlen = btf_vlen(targ_t);
> int i, err;
>
> if (local_k != targ_k)