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Date: Fri, 28 Jan 2022 17:33:10 -0500
From: Mauricio Vásquez <mauricio@...volk.io>
To: netdev@...r.kernel.org, bpf@...r.kernel.org
Cc: Alexei Starovoitov <ast@...nel.org>,
Daniel Borkmann <daniel@...earbox.net>,
Andrii Nakryiko <andrii@...nel.org>,
Quentin Monnet <quentin@...valent.com>,
Rafael David Tinoco <rafaeldtinoco@...il.com>,
Lorenzo Fontana <lorenzo.fontana@...stic.co>,
Leonardo Di Donato <leonardo.didonato@...stic.co>
Subject: [PATCH bpf-next v5 7/9] bpftool: Implement btfgen_get_btf()
The last part of the BTFGen algorithm is to create a new BTF object with
all the types that were recorded in the previous steps.
This function performs two different steps:
1. Add the types to the new BTF object by using btf__add_type(). Some
special logic around struct and unions is implemented to only add the
members that are really used in the field-based relocations. The type
ID on the new and old BTF objects is stored on a map.
2. Fix all the type IDs on the new BTF object by using the IDs saved in
the previous step.
Signed-off-by: Mauricio Vásquez <mauricio@...volk.io>
Signed-off-by: Rafael David Tinoco <rafael.tinoco@...asec.com>
Signed-off-by: Lorenzo Fontana <lorenzo.fontana@...stic.co>
Signed-off-by: Leonardo Di Donato <leonardo.didonato@...stic.co>
---
tools/bpf/bpftool/gen.c | 158 +++++++++++++++++++++++++++++++++++++++-
1 file changed, 157 insertions(+), 1 deletion(-)
diff --git a/tools/bpf/bpftool/gen.c b/tools/bpf/bpftool/gen.c
index 7413ec808a80..55e6f640cbbb 100644
--- a/tools/bpf/bpftool/gen.c
+++ b/tools/bpf/bpftool/gen.c
@@ -1599,10 +1599,166 @@ static int btfgen_record_obj(struct btfgen_info *info, const char *obj_path)
return err;
}
+static unsigned int btfgen_get_id(struct hashmap *ids, unsigned int old)
+{
+ uintptr_t new = 0;
+
+ /* deal with BTF_KIND_VOID */
+ if (old == 0)
+ return 0;
+
+ if (!hashmap__find(ids, uint_as_hash_key(old), (void **)&new)) {
+ /* return id for void as it's possible that the ID we're looking for is
+ * the type of a pointer that we're not adding.
+ */
+ return 0;
+ }
+
+ return (unsigned int)(uintptr_t)new;
+}
+
+static int btfgen_add_id(struct hashmap *ids, unsigned int old, unsigned int new)
+{
+ return hashmap__add(ids, uint_as_hash_key(old), uint_as_hash_key(new));
+}
+
/* Generate BTF from relocation information previously recorded */
static struct btf *btfgen_get_btf(struct btfgen_info *info)
{
- return ERR_PTR(-EOPNOTSUPP);
+ struct hashmap_entry *entry;
+ struct btf *btf_new = NULL;
+ struct hashmap *ids = NULL;
+ size_t bkt;
+ int err = 0;
+
+ btf_new = btf__new_empty();
+ if (libbpf_get_error(btf_new))
+ goto err_out;
+
+ ids = hashmap__new(btfgen_hash_fn, btfgen_equal_fn, NULL);
+ if (IS_ERR(ids)) {
+ errno = -PTR_ERR(ids);
+ goto err_out;
+ }
+
+ /* first pass: add all types and add their new ids to the ids map */
+ hashmap__for_each_entry(info->types, entry, bkt) {
+ struct btfgen_type *btfgen_type = entry->value;
+ struct btf_type *btf_type = btfgen_type->type;
+ int new_id;
+
+ /* we're adding BTF_KIND_VOID to the list but it can't be added to
+ * the generated BTF object, hence we skip it here.
+ */
+ if (btfgen_type->id == 0)
+ continue;
+
+ /* add members for struct and union */
+ if (btf_is_struct(btf_type) || btf_is_union(btf_type)) {
+ struct hashmap_entry *member_entry;
+ struct btf_type *btf_type_cpy;
+ int nmembers, index;
+ size_t new_size;
+
+ nmembers = btfgen_type->members ? hashmap__size(btfgen_type->members) : 0;
+ new_size = sizeof(struct btf_type) + nmembers * sizeof(struct btf_member);
+
+ btf_type_cpy = malloc(new_size);
+ if (!btf_type_cpy)
+ goto err_out;
+
+ /* copy header */
+ memcpy(btf_type_cpy, btf_type, sizeof(*btf_type_cpy));
+
+ /* copy only members that are needed */
+ index = 0;
+ if (nmembers > 0) {
+ size_t bkt2;
+
+ hashmap__for_each_entry(btfgen_type->members, member_entry, bkt2) {
+ struct btfgen_member *btfgen_member;
+ struct btf_member *btf_member;
+
+ btfgen_member = member_entry->value;
+ btf_member = btf_members(btf_type) + btfgen_member->idx;
+
+ memcpy(btf_members(btf_type_cpy) + index, btf_member,
+ sizeof(struct btf_member));
+
+ index++;
+ }
+ }
+
+ /* set new vlen */
+ btf_type_cpy->info = btf_type_info(btf_kind(btf_type_cpy), nmembers,
+ btf_kflag(btf_type_cpy));
+
+ err = btf__add_type(btf_new, info->src_btf, btf_type_cpy);
+ free(btf_type_cpy);
+ } else {
+ err = btf__add_type(btf_new, info->src_btf, btf_type);
+ }
+
+ if (err < 0)
+ goto err_out;
+
+ new_id = err;
+
+ /* add ID mapping */
+ err = btfgen_add_id(ids, btfgen_type->id, new_id);
+ if (err)
+ goto err_out;
+ }
+
+ /* second pass: fix up type ids */
+ for (unsigned int i = 0; i < btf__type_cnt(btf_new); i++) {
+ struct btf_member *btf_member;
+ struct btf_type *btf_type;
+ struct btf_param *params;
+ struct btf_array *array;
+
+ btf_type = (struct btf_type *) btf__type_by_id(btf_new, i);
+
+ switch (btf_kind(btf_type)) {
+ case BTF_KIND_STRUCT:
+ case BTF_KIND_UNION:
+ for (unsigned short j = 0; j < btf_vlen(btf_type); j++) {
+ btf_member = btf_members(btf_type) + j;
+ btf_member->type = btfgen_get_id(ids, btf_member->type);
+ }
+ break;
+ case BTF_KIND_PTR:
+ case BTF_KIND_TYPEDEF:
+ case BTF_KIND_VOLATILE:
+ case BTF_KIND_CONST:
+ case BTF_KIND_RESTRICT:
+ case BTF_KIND_FUNC:
+ case BTF_KIND_VAR:
+ btf_type->type = btfgen_get_id(ids, btf_type->type);
+ break;
+ case BTF_KIND_ARRAY:
+ array = btf_array(btf_type);
+ array->index_type = btfgen_get_id(ids, array->index_type);
+ array->type = btfgen_get_id(ids, array->type);
+ break;
+ case BTF_KIND_FUNC_PROTO:
+ btf_type->type = btfgen_get_id(ids, btf_type->type);
+ params = btf_params(btf_type);
+ for (unsigned short j = 0; j < btf_vlen(btf_type); j++)
+ params[j].type = btfgen_get_id(ids, params[j].type);
+ break;
+ default:
+ break;
+ }
+ }
+
+ hashmap__free(ids);
+ return btf_new;
+
+err_out:
+ btf__free(btf_new);
+ hashmap__free(ids);
+ return NULL;
}
/* Create BTF file for a set of BPF objects.
--
2.25.1
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