libbpf: Add btf__set_fd() for more control over loaded BTF FD (81372e12) · Commits · 戴 / test

Add setter for BTF FD to allow application more fine-grained control in more advanced scenarios. Storing BTF FD inside `struct btf` provides little benefit and probably would be better done differently (e.g., btf__load() could just return FD on success), but we are stuck with this due to backwards compatibility. The main problem is that it's impossible to load BTF and than free user-space memory, but keep FD intact, because `struct btf` assumes ownership of that FD upon successful load and will attempt to close it during btf__free(). To allow callers (e.g., libbpf itself for BTF sanitization) to have more control over this, add btf__set_fd() to allow to reset FD arbitrarily, if necessary. Signed-off-by:

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

Daniel Borkmann <daniel@iogearbox.net> Link: https://lore.kernel.org/bpf/20200708015318.3827358-3-andriin@fb.com

tools/lib/bpf/btf.c

+6 −1

Original line number	Diff line number	Diff line
		@@ -389,7 +389,7 @@ void btf__free(struct btf *btf)
		if (!btf)
		return;

		if (btf->fd != -1)
		if (btf->fd >= 0)
		close(btf->fd);

		free(btf->data);
		@@ -700,6 +700,11 @@ int btf__fd(const struct btf *btf)
		return btf->fd;
		}

		void btf__set_fd(struct btf *btf, int fd)
		{
		btf->fd = fd;
		}

		const void btf__get_raw_data(const struct btf btf, __u32 *size)
		{
		*size = btf->data_size;

tools/lib/bpf/btf.h

+1 −0

Original line number	Diff line number	Diff line
		@@ -79,6 +79,7 @@ LIBBPF_API __s64 btf__resolve_size(const struct btf *btf, __u32 type_id);
		LIBBPF_API int btf__resolve_type(const struct btf *btf, __u32 type_id);
		LIBBPF_API int btf__align_of(const struct btf *btf, __u32 id);
		LIBBPF_API int btf__fd(const struct btf *btf);
		LIBBPF_API void btf__set_fd(struct btf *btf, int fd);
		LIBBPF_API const void btf__get_raw_data(const struct btf btf, __u32 *size);
		LIBBPF_API const char btf__name_by_offset(const struct btf btf, __u32 offset);
		LIBBPF_API int btf__get_from_id(__u32 id, struct btf **btf);

tools/lib/bpf/libbpf.map

+1 −0

Original line number	Diff line number	Diff line
		@@ -288,4 +288,5 @@ LIBBPF_0.1.0 {
		bpf_map__value_size;
		bpf_program__autoload;
		bpf_program__set_autoload;
		btf__set_fd;
		} LIBBPF_0.0.9;

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