Commit d1cf8408 authored by Alan Maguire's avatar Alan Maguire Committed by Andrii Nakryiko
Browse files

libbpf: BTF relocation followup fixing naming, loop logic 



Use less verbose names in BTF relocation code and fix off-by-one error
and typo in btf_relocate.c.  Simplify loop over matching distilled
types, moving from assigning a _next value in loop body to moving
match check conditions into the guard.

Suggested-by: default avatarAndrii Nakryiko <andrii.nakryiko@gmail.com>
Signed-off-by: default avatarAlan Maguire <alan.maguire@oracle.com>
Signed-off-by: default avatarAndrii Nakryiko <andrii@kernel.org>
Acked-by: default avatarEduard Zingerman <eddyz87@gmail.com>
Link: https://lore.kernel.org/bpf/20240620091733.1967885-2-alan.maguire@oracle.com
parent cd387ce5

tools/lib/bpf/btf_relocate.c

+31 −41
Original line number Diff line number Diff line
@@ -160,7 +160,7 @@ static int btf_mark_embedded_composite_type_ids(struct btf_relocate *r, __u32 i) 
 */

static int btf_relocate_map_distilled_base(struct btf_relocate *r)

{

	struct btf_name_info *dist_base_info_sorted, *dist_base_info_sorted_end;

	struct btf_name_info *info, *info_end;

	struct btf_type *base_t, *dist_t;

	__u8 *base_name_cnt = NULL;

	int err = 0;
@@ -169,26 +169,24 @@ static int btf_relocate_map_distilled_base(struct btf_relocate *r) 
	/* generate a sort index array of name/type ids sorted by name for

	 * distilled base BTF to speed name-based lookups.

	 */

	dist_base_info_sorted = calloc(r->nr_dist_base_types, sizeof(*dist_base_info_sorted));

	if (!dist_base_info_sorted) {

	info = calloc(r->nr_dist_base_types, sizeof(*info));

	if (!info) {

		err = -ENOMEM;

		goto done;

	}

	dist_base_info_sorted_end = dist_base_info_sorted + r->nr_dist_base_types;

	info_end = info + r->nr_dist_base_types;

	for (id = 0; id < r->nr_dist_base_types; id++) {

		dist_t = btf_type_by_id(r->dist_base_btf, id);

		dist_base_info_sorted[id].name = btf__name_by_offset(r->dist_base_btf,

								     dist_t->name_off);

		dist_base_info_sorted[id].id = id;

		dist_base_info_sorted[id].size = dist_t->size;

		dist_base_info_sorted[id].needs_size = true;

		info[id].name = btf__name_by_offset(r->dist_base_btf, dist_t->name_off);

		info[id].id = id;

		info[id].size = dist_t->size;

		info[id].needs_size = true;

	}

	qsort(dist_base_info_sorted, r->nr_dist_base_types, sizeof(*dist_base_info_sorted),

	      cmp_btf_name_size);

	qsort(info, r->nr_dist_base_types, sizeof(*info), cmp_btf_name_size);



	/* Mark distilled base struct/union members of split BTF structs/unions

	 * in id_map with BTF_IS_EMBEDDED; this signals that these types

	 * need to match both name and size, otherwise embeddding the base

	 * need to match both name and size, otherwise embedding the base

	 * struct/union in the split type is invalid.

	 */

	for (id = r->nr_dist_base_types; id < r->nr_split_types; id++) {
@@ -216,8 +214,7 @@ static int btf_relocate_map_distilled_base(struct btf_relocate *r) 


	/* Now search base BTF for matching distilled base BTF types. */

	for (id = 1; id < r->nr_base_types; id++) {

		struct btf_name_info *dist_name_info, *dist_name_info_next = NULL;

		struct btf_name_info base_name_info = {};

		struct btf_name_info *dist_info, base_info = {};

		int dist_kind, base_kind;



		base_t = btf_type_by_id(r->base_btf, id);
@@ -225,16 +222,16 @@ static int btf_relocate_map_distilled_base(struct btf_relocate *r) 
		if (!base_t->name_off)

			continue;

		base_kind = btf_kind(base_t);

		base_name_info.id = id;

		base_name_info.name = btf__name_by_offset(r->base_btf, base_t->name_off);

		base_info.id = id;

		base_info.name = btf__name_by_offset(r->base_btf, base_t->name_off);

		switch (base_kind) {

		case BTF_KIND_INT:

		case BTF_KIND_FLOAT:

		case BTF_KIND_ENUM:

		case BTF_KIND_ENUM64:

			/* These types should match both name and size */

			base_name_info.needs_size = true;

			base_name_info.size = base_t->size;

			base_info.needs_size = true;

			base_info.size = base_t->size;

			break;

		case BTF_KIND_FWD:

			/* No size considerations for fwds. */
@@ -248,31 +245,24 @@ static int btf_relocate_map_distilled_base(struct btf_relocate *r) 
			 * unless corresponding _base_ types to match them are

			 * missing.

			 */

			base_name_info.needs_size = base_name_cnt[base_t->name_off] > 1;

			base_name_info.size = base_t->size;

			base_info.needs_size = base_name_cnt[base_t->name_off] > 1;

			base_info.size = base_t->size;

			break;

		default:

			continue;

		}

		/* iterate over all matching distilled base types */

		for (dist_name_info = search_btf_name_size(&base_name_info, dist_base_info_sorted,

							   r->nr_dist_base_types);

		     dist_name_info != NULL; dist_name_info = dist_name_info_next) {

			/* Are there more distilled matches to process after

			 * this one?

			 */

			dist_name_info_next = dist_name_info + 1;

			if (dist_name_info_next >= dist_base_info_sorted_end ||

			    cmp_btf_name_size(&base_name_info, dist_name_info_next))

				dist_name_info_next = NULL;



			if (!dist_name_info->id || dist_name_info->id > r->nr_dist_base_types) {

		for (dist_info = search_btf_name_size(&base_info, info, r->nr_dist_base_types);

		     dist_info != NULL && dist_info < info_end &&

		     cmp_btf_name_size(&base_info, dist_info) == 0;

		     dist_info++) {

			if (!dist_info->id || dist_info->id >= r->nr_dist_base_types) {

				pr_warn("base BTF id [%d] maps to invalid distilled base BTF id [%d]\n",

					id, dist_name_info->id);

					id, dist_info->id);

				err = -EINVAL;

				goto done;

			}

			dist_t = btf_type_by_id(r->dist_base_btf, dist_name_info->id);

			dist_t = btf_type_by_id(r->dist_base_btf, dist_info->id);

			dist_kind = btf_kind(dist_t);



			/* Validate that the found distilled type is compatible.
@@ -319,15 +309,15 @@ static int btf_relocate_map_distilled_base(struct btf_relocate *r) 
				/* size verification is required for embedded

				 * struct/unions.

				 */

				if (r->id_map[dist_name_info->id] == BTF_IS_EMBEDDED &&

				if (r->id_map[dist_info->id] == BTF_IS_EMBEDDED &&

				    base_t->size != dist_t->size)

					continue;

				break;

			default:

				continue;

			}

			if (r->id_map[dist_name_info->id] &&

			    r->id_map[dist_name_info->id] != BTF_IS_EMBEDDED) {

			if (r->id_map[dist_info->id] &&

			    r->id_map[dist_info->id] != BTF_IS_EMBEDDED) {

				/* we already have a match; this tells us that

				 * multiple base types of the same name

				 * have the same size, since for cases where
@@ -337,13 +327,13 @@ static int btf_relocate_map_distilled_base(struct btf_relocate *r) 
				 * to in base BTF, so error out.

				 */

				pr_warn("distilled base BTF type '%s' [%u], size %u has multiple candidates of the same size (ids [%u, %u]) in base BTF\n",

					base_name_info.name, dist_name_info->id,

					base_t->size, id, r->id_map[dist_name_info->id]);

					base_info.name, dist_info->id,

					base_t->size, id, r->id_map[dist_info->id]);

				err = -EINVAL;

				goto done;

			}

			/* map id and name */

			r->id_map[dist_name_info->id] = id;

			r->id_map[dist_info->id] = id;

			r->str_map[dist_t->name_off] = base_t->name_off;

		}

	}
@@ -362,7 +352,7 @@ static int btf_relocate_map_distilled_base(struct btf_relocate *r) 
	}

done:

	free(base_name_cnt);

	free(dist_base_info_sorted);

	free(info);

	return err;

}