[PATCH v3 3/9] bpf/btf: Add a function to search a member of a struct/union

Masami Hiramatsu (Google)
2023-07-26T13:00:39Z

Add btf_find_struct_member() API to search a member of a given data structure
or union from the member's name.

Signed-off-by: Masami Hiramatsu (Google) <mhiramat@kernel.org>
Reviewed-by: Alan Maguire <alan.maguire@oracle.com>
---
Changes in v3:
- Remove simple input check.
- Fix unneeded IS_ERR_OR_NULL() check for btf_type_by_id().
- Move the code next to btf_get_func_param().
- Use for_each_member() macro instead of for-loop.
- Use btf_type_skip_modifiers() instead of btf_type_by_id().
---
include/linux/btf.h | 3 +++
kernel/bpf/btf.c | 35 +++++++++++++++++++++++++++++++++++
2 files changed, 38 insertions(+)

diff --git a/include/linux/btf.h b/include/linux/btf.h
index 20e3a07eef8f..4b10d57ceee0 100644
--- a/include/linux/btf.h
+++ b/include/linux/btf.h
@@ -226,6 +226,9 @@ const struct btf_type *btf_find_func_proto(const char *func_name,
struct btf **btf_p);
const struct btf_param *btf_get_func_param(const struct btf_type *func_proto,
s32 *nr);
+const struct btf_member *btf_find_struct_member(struct btf *btf,
+ const struct btf_type *type,
+ const char *member_name);

#define for_each_member(i, struct_type, member) \
for (i = 0, member = btf_type_member(struct_type); \
diff --git a/kernel/bpf/btf.c b/kernel/bpf/btf.c
index f7b25c615269..5258870030fc 100644
--- a/kernel/bpf/btf.c
+++ b/kernel/bpf/btf.c
@@ -958,6 +958,41 @@ const struct btf_param *btf_get_func_param(const struct btf_type *func_proto, s3
return NULL;
}

+/*
+ * Find a member of data structure/union by name and return it.
+ * Return NULL if not found, or -EINVAL if parameter is invalid.
+ */
+const struct btf_member *btf_find_struct_member(struct btf *btf,
+ const struct btf_type *type,
+ const char *member_name)
+{
+ const struct btf_member *member, *ret;
+ const char *name;
+ int i;
+
+ if (!btf_type_is_struct(type))
+ return ERR_PTR(-EINVAL);
+
+ for_each_member(i, type, member) {
+ if (!member->name_off) {
+ /* unnamed member: dig deeper */
+ type = btf_type_skip_modifiers(btf, member->type, NULL);
+ if (type) {
+ ret = btf_find_struct_member(btf, type,
+ member_name);
+ if (!IS_ERR_OR_NULL(ret))
+ return ret;
+ }
+ } else {
+ name = btf_name_by_offset(btf, member->name_off);
+ if (name && !strcmp(member_name, name))
+ return member;
+ }
+ }
+
+ return NULL;
+}
+
#define BTF_SHOW_MAX_ITER 10

#define BTF_KIND_BIT(kind) (1ULL << kind)