[PATCHv8 bpf-next 19/29] libbpf: Add btf_type_is_traceable_func function
From: Jiri Olsa <jolsa@kernel.org>
Date: 2026-06-06 12:43:12
Also in:
bpf
Subsystem:
bpf [general] (safe dynamic programs and tools), bpf [library] (libbpf), the rest · Maintainers:
Alexei Starovoitov, Daniel Borkmann, Andrii Nakryiko, Eduard Zingerman, Kumar Kartikeya Dwivedi, Linus Torvalds
Adding btf_type_is_traceable_func function to perform same checks as the kernel's btf_distill_func_proto function to prevent attachment on some of the functions. Exporting the function via libbpf_internal.h because it will be used by benchmark test in following changes. Signed-off-by: Jiri Olsa <jolsa@kernel.org> --- tools/lib/bpf/libbpf.c | 79 +++++++++++++++++++++++++++++++++ tools/lib/bpf/libbpf_internal.h | 1 + 2 files changed, 80 insertions(+)
diff --git a/tools/lib/bpf/libbpf.c b/tools/lib/bpf/libbpf.c
index 5bdaa5eb1f50..42f0efd70327 100644
--- a/tools/lib/bpf/libbpf.c
+++ b/tools/lib/bpf/libbpf.c@@ -12450,6 +12450,85 @@ static int attach_uprobe_multi(const struct bpf_program *prog, long cookie, stru return ret; } +#define MAX_BPF_FUNC_ARGS 12 + +static bool btf_type_is_modifier(const struct btf_type *t) +{ + switch (BTF_INFO_KIND(t->info)) { + case BTF_KIND_TYPEDEF: + case BTF_KIND_VOLATILE: + case BTF_KIND_CONST: + case BTF_KIND_RESTRICT: + case BTF_KIND_TYPE_TAG: + return true; + default: + return false; + } +} + +#define MAX_RESOLVE_DEPTH 32 + +static int btf_get_type_size(const struct btf *btf, __u32 type_id, + const struct btf_type **ret_type) +{ + const struct btf_type *t; + int i; + + *ret_type = btf__type_by_id(btf, 0); + if (!type_id) + return 0; + t = btf__type_by_id(btf, type_id); + for (i = 0; i < MAX_RESOLVE_DEPTH && t && btf_type_is_modifier(t); i++) + t = btf__type_by_id(btf, t->type); + if (!t || i == MAX_RESOLVE_DEPTH) + return -EINVAL; + *ret_type = t; + if (btf_is_ptr(t)) + return btf__pointer_size(btf); + if (btf_is_int(t) || btf_is_any_enum(t) || btf_is_struct(t) || btf_is_union(t)) + return t->size; + return -EINVAL; +} + +bool btf_type_is_traceable_func(const struct btf *btf, const struct btf_type *t) +{ + const struct btf_param *args; + const struct btf_type *proto; + __u32 i, nargs; + int ret; + + if (!btf_is_func(t)) + return false; + proto = btf__type_by_id(btf, t->type); + if (!proto || !btf_is_func_proto(proto)) + return false; + + args = (const struct btf_param *)(proto + 1); + nargs = btf_vlen(proto); + if (nargs > MAX_BPF_FUNC_ARGS) + return false; + + /* No support for struct return type. */ + ret = btf_get_type_size(btf, proto->type, &t); + if (ret < 0 || btf_is_struct(t) || btf_is_union(t)) + return false; + + for (i = 0; i < nargs; i++) { + /* No support for variable args. */ + if (i == nargs - 1 && args[i].type == 0) + return false; + ret = btf_get_type_size(btf, args[i].type, &t); + /* No support of struct argument size greater than 16 bytes. */ + if (ret < 0 || ret > 16) + return false; + /* No support for void argument. */ + if (ret == 0) + return false; + } + + return true; +} + static inline int add_uprobe_event_legacy(const char *probe_name, bool retprobe, const char *binary_path, size_t offset) {
diff --git a/tools/lib/bpf/libbpf_internal.h b/tools/lib/bpf/libbpf_internal.h
index 7d93c6c01d60..04cd303fb5a8 100644
--- a/tools/lib/bpf/libbpf_internal.h
+++ b/tools/lib/bpf/libbpf_internal.h@@ -250,6 +250,7 @@ const struct btf_type *skip_mods_and_typedefs(const struct btf *btf, __u32 id, _ const struct btf_header *btf_header(const struct btf *btf); void btf_set_base_btf(struct btf *btf, const struct btf *base_btf); int btf_relocate(struct btf *btf, const struct btf *base_btf, __u32 **id_map); +bool btf_type_is_traceable_func(const struct btf *btf, const struct btf_type *t); static inline enum btf_func_linkage btf_func_linkage(const struct btf_type *t) {
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2.54.0