libbpf: Split BTF presence checks into libbpf- and kernel-specific parts (b35f14f4) · Commits · 戴 / test

Needs for application BTF being present differs between user-space libbpf needs and kernel needs. Currently, BTF is mandatory only in kernel only when BPF application is using STRUCT_OPS. While libbpf itself relies more heavily on presense of BTF: - for BTF-defined maps; - for Kconfig externs; - for STRUCT_OPS as well. Thus, checks for presence and validness of bpf_object's BPF needs to be performed separately, which is patch does. Fixes: ("libbpf: Relax check whether BTF is mandatory") Reported-by:

Michal Rostecki <mrostecki@opensuse.org> Signed-off-by:

Andrii Nakryiko <andriin@fb.com> Signed-off-by:

Daniel Borkmann <daniel@iogearbox.net> Acked-by:

Martin KaFai Lau <kafai@fb.com> Cc: Quentin Monnet <quentin@isovalent.com> Link: https://lore.kernel.org/bpf/20200312185033.736911-1-andriin@fb.com

tools/lib/bpf/libbpf.c

+12 −5

Original line number	Diff line number	Diff line
		@@ -2284,9 +2284,16 @@ static void bpf_object__sanitize_btf_ext(struct bpf_object *obj)
		}
		}

		static bool bpf_object__is_btf_mandatory(const struct bpf_object *obj)
		static bool libbpf_needs_btf(const struct bpf_object *obj)
		{
		return obj->efile.st_ops_shndx >= 0 \|\| obj->nr_extern > 0;
		return obj->efile.btf_maps_shndx >= 0 \|\|
		obj->efile.st_ops_shndx >= 0 \|\|
		obj->nr_extern > 0;
		}

		static bool kernel_needs_btf(const struct bpf_object *obj)
		{
		return obj->efile.st_ops_shndx >= 0;
		}

		static int bpf_object__init_btf(struct bpf_object *obj,
		@@ -2322,7 +2329,7 @@ static int bpf_object__init_btf(struct bpf_object *obj,
		}
		}
		out:
		if (err && bpf_object__is_btf_mandatory(obj)) {
		if (err && libbpf_needs_btf(obj)) {
		pr_warn("BTF is required, but is missing or corrupted.\n");
		return err;
		}
		@@ -2346,7 +2353,7 @@ static int bpf_object__finalize_btf(struct bpf_object *obj)
		btf_ext__free(obj->btf_ext);
		obj->btf_ext = NULL;

		if (bpf_object__is_btf_mandatory(obj)) {
		if (libbpf_needs_btf(obj)) {
		pr_warn("BTF is required, but is missing or corrupted.\n");
		return -ENOENT;
		}
		@@ -2410,7 +2417,7 @@ static int bpf_object__sanitize_and_load_btf(struct bpf_object *obj)
		obj->btf_ext = NULL;
		}

		if (bpf_object__is_btf_mandatory(obj))
		if (kernel_needs_btf(obj))
		return err;
		}
		return 0;

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