[PATCH v4 3/9] bpf/btf: Add a function to search a member of a struct/union
From: "Masami Hiramatsu (Google)" <mhiramat@kernel.org>
Date: 2023-07-31 07:32:11
Also in:
bpf, lkml
Subsystem:
bpf [btf], bpf [general] (safe dynamic programs and tools), the rest · Maintainers:
Martin KaFai Lau, Alexei Starovoitov, Daniel Borkmann, Andrii Nakryiko, Eduard Zingerman, Kumar Kartikeya Dwivedi, Linus Torvalds
From: Masami Hiramatsu (Google) <mhiramat@kernel.org> 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 <redacted> --- 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(). Changes in v4: - Use a stack for searching in anonymous members instead of nested call. --- include/linux/btf.h | 3 +++ kernel/bpf/btf.c | 40 ++++++++++++++++++++++++++++++++++++++++ 2 files changed, 43 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..8d81a4ffa67b 100644
--- a/kernel/bpf/btf.c
+++ b/kernel/bpf/btf.c@@ -958,6 +958,46 @@ const struct btf_param *btf_get_func_param(const struct btf_type *func_proto, s3 return NULL; } +#define BTF_ANON_STACK_MAX 16 + +/* + * 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_type *anon_stack[BTF_ANON_STACK_MAX]; + const struct btf_member *member; + const char *name; + int i, top = 0; + +retry: + if (!btf_type_is_struct(type)) + return ERR_PTR(-EINVAL); + + for_each_member(i, type, member) { + if (!member->name_off) { + /* Anonymous union/struct: push it for later use */ + type = btf_type_skip_modifiers(btf, member->type, NULL); + if (type && top < BTF_ANON_STACK_MAX) + anon_stack[top++] = type; + } else { + name = btf_name_by_offset(btf, member->name_off); + if (name && !strcmp(member_name, name)) + return member; + } + } + if (top > 0) { + /* Pop from the anonymous stack and retry */ + type = anon_stack[--top]; + goto retry; + } + + return NULL; +} + #define BTF_SHOW_MAX_ITER 10 #define BTF_KIND_BIT(kind) (1ULL << kind)