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Message-ID: <CAErzpmuWAvdbUaVD6-ZnV7aqLpD8yJ+0EVNVzu951VX9bOTb1Q@mail.gmail.com>
Date: Fri, 14 Nov 2025 18:38:08 +0800
From: Donglin Peng <dolinux.peng@...il.com>
To: bot+bpf-ci@...nel.org
Cc: ast@...nel.org, eddyz87@...il.com, andrii.nakryiko@...il.com,
zhangxiaoqin@...omi.com, linux-kernel@...r.kernel.org, bpf@...r.kernel.org,
pengdonglin@...omi.com, alan.maguire@...cle.com, song@...nel.org,
andrii@...nel.org, daniel@...earbox.net, martin.lau@...nel.org,
yonghong.song@...ux.dev, clm@...a.com, ihor.solodrai@...ux.dev
Subject: Re: [RFC PATCH 1/2] libbpf: Add BTF permutation support for type reordering
On Fri, Nov 14, 2025 at 5:47 PM <bot+bpf-ci@...nel.org> wrote:
>
> > diff --git a/tools/lib/bpf/btf.c b/tools/lib/bpf/btf.c
> > index 9f141395c..de3aa62fd 100644
> > --- a/tools/lib/bpf/btf.c
> > +++ b/tools/lib/bpf/btf.c
> > @@ -5829,3 +5829,189 @@ int btf__relocate(struct btf *btf, const struct btf *base_btf)
> > btf->owns_base = false;
> > return libbpf_err(err);
> > }
> > +
> > +struct btf_permute {
> > + struct btf *btf;
> > + __u32 *id_map;
> > + __u32 offs;
> > +};
> > +
> > +/* Callback function to remap individual type ID references */
> > +static int btf_permute_remap_type_id(__u32 *type_id, void *ctx)
> > +{
>
> [ ... ]
>
> > +int btf__permute(struct btf *btf, __u32 *id_map, __u32 id_map_cnt,
> > + const struct btf_permute_opts *opts)
> > +{
> > + struct btf_permute p;
> > + struct btf_ext *btf_ext;
> > + void *next_type, *end_type;
> > + void *nt, *new_types = NULL;
> > + int err = 0, n, i, new_type_len;
> > + __u32 *order_map = NULL;
> > + __u32 offs, id, new_nr_types = 0;
> > +
> > + if (btf__base_btf(btf)) {
> > + /*
> > + * For split BTF, the number of types added on the
> > + * top of base BTF
> > + */
> > + n = btf->nr_types;
> > + offs = btf->start_id;
> > + } else if (id_map[0] != 0) {
> > + /* id_map[0] must be 0 for base BTF */
> > + err = -EINVAL;
> > + goto done;
> > + } else {
> > + /* include VOID type 0 for base BTF */
> > + n = btf__type_cnt(btf);
> > + offs = 0;
> > + }
> > +
> > + if (!OPTS_VALID(opts, btf_permute_opts) || (id_map_cnt != n))
> > + return libbpf_err(-EINVAL);
> > +
> > + /* used to record the storage sequence of types */
> > + order_map = calloc(n, sizeof(*id_map));
> > + if (!order_map) {
> > + err = -ENOMEM;
> > + goto done;
> > + }
> > +
> > + new_types = calloc(btf->hdr->type_len, 1);
> > + if (!new_types) {
> > + err = -ENOMEM;
> > + goto done;
> > + }
> > +
> > + if (btf_ensure_modifiable(btf)) {
> > + err = -ENOMEM;
> > + goto done;
> > + }
> > +
> > + for (i = 0; i < id_map_cnt; i++) {
> > + id = id_map[i];
> > + /*
> > + * 0: Drop the specified type (exclude base BTF type 0).
> > + * For base BTF, type 0 is always preserved.
> > + */
> > + if (id == 0)
> > + continue;
> > + /* Invalid id */
> > + if (id < btf->start_id || id >= btf__type_cnt(btf)) {
> > + err = -EINVAL;
> > + goto done;
> > + }
> > + id -= offs;
> > + /* Multiple types cannot be mapped to the same ID */
> > + if (order_map[id]) {
> > + err = -EINVAL;
> > + goto done;
> > + }
> > + order_map[id] = i + offs;
> > + new_nr_types = max(id + 1, new_nr_types);
> > + }
> > +
> > + /* Check for missing IDs */
> > + for (i = offs ? 0 : 1; i < new_nr_types; i++) {
> > + if (order_map[i] == 0) {
> > + err = -EINVAL;
> > + goto done;
> > + }
> > + }
> > +
> > + p.btf = btf;
> > + p.id_map = id_map;
> > + p.offs = offs;
> > + nt = new_types;
> > + for (i = offs ? 0 : 1; i < new_nr_types; i++) {
> > + struct btf_field_iter it;
> > + const struct btf_type *t;
> > + __u32 *type_id;
> > + int type_size;
> > +
> > + id = order_map[i];
> > + /* must be a valid type ID */
> > + t = btf__type_by_id(btf, id);
> > + if (!t) {
> > + err = -EINVAL;
> > + goto done;
> > + }
> > + type_size = btf_type_size(t);
> > + memcpy(nt, t, type_size);
> > +
> > + /* Fix up referenced IDs for BTF */
> > + err = btf_field_iter_init(&it, nt, BTF_FIELD_ITER_IDS);
> > + if (err)
> > + goto done;
> > + while ((type_id = btf_field_iter_next(&it))) {
> > + err = btf_permute_remap_type_id(type_id, &p);
> > + if (err)
> > + goto done;
> > + }
> > +
> > + nt += type_size;
> > + }
> > +
> > + /* Fix up referenced IDs for btf_ext */
> > + btf_ext = OPTS_GET(opts, btf_ext, NULL);
> > + if (btf_ext) {
> > + err = btf_ext_visit_type_ids(btf_ext, btf_permute_remap_type_id, &p);
> > + if (err)
> > + goto done;
> > + }
> > +
> > + new_type_len = nt - new_types;
> > + next_type = new_types;
> > + end_type = next_type + new_type_len;
> > + i = 0;
> > + while (next_type + sizeof(struct btf_type) <= end_type) {
> > + btf->type_offs[i++] = next_type - new_types;
> > + next_type += btf_type_size(next_type);
> > + }
> > +
> > + /* Resize */
> > + if (new_type_len < btf->hdr->type_len) {
> > + void *tmp_types;
> > +
> > + tmp_types = realloc(new_types, new_type_len);
> > + if (new_type_len && !tmp_types) {
> > + err = -ENOMEM;
> > + goto done;
> > + }
> > + new_types = tmp_types;
> > + btf->nr_types = new_nr_types - (offs ? 0 : 1);
> > + btf->type_offs_cap = btf->nr_types;
> > + btf->types_data_cap = new_type_len;
> > + btf->hdr->type_len = new_type_len;
> > + btf->hdr->str_off = new_type_len;
> > + btf->raw_size = btf->hdr->hdr_len + btf->hdr->type_len + btf->hdr->str_len;
> > + }
> > + free(btf->types_data);
> > + btf->types_data = new_types;
> > + return 0;
>
> Does this leak order_map on the success path? It looks like order_map is
> allocated above and freed only in the error path at the done label, but
> the success path returns here without freeing it.
Thanks, I will fix it.
>
> > +
> > +done:
> > + free(order_map);
> > + free(new_types);
> > + return libbpf_err(err);
> > +}
>
> [ ... ]
>
>
> ---
> AI reviewed your patch. Please fix the bug or email reply why it's not a bug.
> See: https://github.com/kernel-patches/vmtest/blob/master/ci/claude/README.md
>
> CI run summary: https://github.com/kernel-patches/bpf/actions/runs/19359945665
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