tools/libbpf: Add support for BPF_PROG_TYPE_LSM

Since BPF_PROG_TYPE_LSM uses the same attaching mechanism as
BPF_PROG_TYPE_TRACING, the common logic is refactored into a static
function bpf_program__attach_btf_id.

A new API call bpf_program__attach_lsm is still added to avoid userspace
conflicts if this ever changes in the future.
Signed-off-by: KP Singh <kpsingh@google.com>
Signed-off-by: Daniel Borkmann <daniel@iogearbox.net>
Reviewed-by: Brendan Jackman <jackmanb@google.com>
Reviewed-by: Florent Revest <revest@google.com>
Reviewed-by: James Morris <jamorris@linux.microsoft.com>
Acked-by: Yonghong Song <yhs@fb.com>
Acked-by: Andrii Nakryiko <andriin@fb.com>
Link: https://lore.kernel.org/bpf/20200329004356.27286-7-kpsingh@chromium.org

tools/lib/bpf/bpf.c

@@ -235,7 +235,8 @@ int bpf_load_program_xattr(const struct bpf_load_program_attr *load_attr,
 	memset(&attr, 0, sizeof(attr));
 	attr.prog_type = load_attr->prog_type;
 	attr.expected_attach_type = load_attr->expected_attach_type;
-	if (attr.prog_type == BPF_PROG_TYPE_STRUCT_OPS) {
+	if (attr.prog_type == BPF_PROG_TYPE_STRUCT_OPS ||
+	    attr.prog_type == BPF_PROG_TYPE_LSM) {
 		attr.attach_btf_id = load_attr->attach_btf_id;
 	} else if (attr.prog_type == BPF_PROG_TYPE_TRACING ||
 		   attr.prog_type == BPF_PROG_TYPE_EXT) {

tools/lib/bpf/libbpf.c

@@ -2358,7 +2358,8 @@ static int bpf_object__finalize_btf(struct bpf_object *obj)
 
 static inline bool libbpf_prog_needs_vmlinux_btf(struct bpf_program *prog)
 {
-	if (prog->type == BPF_PROG_TYPE_STRUCT_OPS)
+	if (prog->type == BPF_PROG_TYPE_STRUCT_OPS ||
+	    prog->type == BPF_PROG_TYPE_LSM)
 		return true;
 
 	/* BPF_PROG_TYPE_TRACING programs which do not attach to other programs
@@ -4866,7 +4867,8 @@ load_program(struct bpf_program *prog, struct bpf_insn *insns, int insns_cnt,
 	load_attr.insns = insns;
 	load_attr.insns_cnt = insns_cnt;
 	load_attr.license = license;
-	if (prog->type == BPF_PROG_TYPE_STRUCT_OPS) {
+	if (prog->type == BPF_PROG_TYPE_STRUCT_OPS ||
+	    prog->type == BPF_PROG_TYPE_LSM) {
 		load_attr.attach_btf_id = prog->attach_btf_id;
 	} else if (prog->type == BPF_PROG_TYPE_TRACING ||
 		   prog->type == BPF_PROG_TYPE_EXT) {
@@ -4957,6 +4959,7 @@ int bpf_program__load(struct bpf_program *prog, char *license, __u32 kern_ver)
 	int err = 0, fd, i, btf_id;
 
 	if ((prog->type == BPF_PROG_TYPE_TRACING ||
+	     prog->type == BPF_PROG_TYPE_LSM ||
 	     prog->type == BPF_PROG_TYPE_EXT) && !prog->attach_btf_id) {
 		btf_id = libbpf_find_attach_btf_id(prog);
 		if (btf_id <= 0)
@@ -6196,6 +6199,7 @@ bool bpf_program__is_##NAME(const struct bpf_program *prog)	\
 }								\
 
 BPF_PROG_TYPE_FNS(socket_filter, BPF_PROG_TYPE_SOCKET_FILTER);
+BPF_PROG_TYPE_FNS(lsm, BPF_PROG_TYPE_LSM);
 BPF_PROG_TYPE_FNS(kprobe, BPF_PROG_TYPE_KPROBE);
 BPF_PROG_TYPE_FNS(sched_cls, BPF_PROG_TYPE_SCHED_CLS);
 BPF_PROG_TYPE_FNS(sched_act, BPF_PROG_TYPE_SCHED_ACT);
@@ -6262,6 +6266,8 @@ static struct bpf_link *attach_raw_tp(const struct bpf_sec_def *sec,
 				      struct bpf_program *prog);
 static struct bpf_link *attach_trace(const struct bpf_sec_def *sec,
 				     struct bpf_program *prog);
+static struct bpf_link *attach_lsm(const struct bpf_sec_def *sec,
+				   struct bpf_program *prog);
 
 struct bpf_sec_def {
 	const char *sec;
@@ -6312,6 +6318,10 @@ static const struct bpf_sec_def section_defs[] = {
 	SEC_DEF("freplace/", EXT,
 		.is_attach_btf = true,
 		.attach_fn = attach_trace),
+	SEC_DEF("lsm/", LSM,
+		.is_attach_btf = true,
+		.expected_attach_type = BPF_LSM_MAC,
+		.attach_fn = attach_lsm),
 	BPF_PROG_SEC("xdp",			BPF_PROG_TYPE_XDP),
 	BPF_PROG_SEC("perf_event",		BPF_PROG_TYPE_PERF_EVENT),
 	BPF_PROG_SEC("lwt_in",			BPF_PROG_TYPE_LWT_IN),
@@ -6574,6 +6584,7 @@ static int bpf_object__collect_struct_ops_map_reloc(struct bpf_object *obj,
 }
 
 #define BTF_TRACE_PREFIX "btf_trace_"
+#define BTF_LSM_PREFIX "bpf_lsm_"
 #define BTF_MAX_NAME_SIZE 128
 
 static int find_btf_by_prefix_kind(const struct btf *btf, const char *prefix,
@@ -6601,6 +6612,9 @@ static inline int __find_vmlinux_btf_id(struct btf *btf, const char *name,
 	if (attach_type == BPF_TRACE_RAW_TP)
 		err = find_btf_by_prefix_kind(btf, BTF_TRACE_PREFIX, name,
 					      BTF_KIND_TYPEDEF);
+	else if (attach_type == BPF_LSM_MAC)
+		err = find_btf_by_prefix_kind(btf, BTF_LSM_PREFIX, name,
+					      BTF_KIND_FUNC);
 	else
 		err = btf__find_by_name_kind(btf, name, BTF_KIND_FUNC);
 
@@ -7465,7 +7479,8 @@ static struct bpf_link *attach_raw_tp(const struct bpf_sec_def *sec,
 	return bpf_program__attach_raw_tracepoint(prog, tp_name);
 }
 
-struct bpf_link *bpf_program__attach_trace(struct bpf_program *prog)
+/* Common logic for all BPF program types that attach to a btf_id */
+static struct bpf_link *bpf_program__attach_btf_id(struct bpf_program *prog)
 {
 	char errmsg[STRERR_BUFSIZE];
 	struct bpf_link *link;
@@ -7487,7 +7502,7 @@ struct bpf_link *bpf_program__attach_trace(struct bpf_program *prog)
 	if (pfd < 0) {
 		pfd = -errno;
 		free(link);
-		pr_warn("program '%s': failed to attach to trace: %s\n",
+		pr_warn("program '%s': failed to attach: %s\n",
 			bpf_program__title(prog, false),
 			libbpf_strerror_r(pfd, errmsg, sizeof(errmsg)));
 		return ERR_PTR(pfd);
@@ -7496,12 +7511,28 @@ struct bpf_link *bpf_program__attach_trace(struct bpf_program *prog)
 	return (struct bpf_link *)link;
 }
 
+struct bpf_link *bpf_program__attach_trace(struct bpf_program *prog)
+{
+	return bpf_program__attach_btf_id(prog);
+}
+
+struct bpf_link *bpf_program__attach_lsm(struct bpf_program *prog)
+{
+	return bpf_program__attach_btf_id(prog);
+}
+
 static struct bpf_link *attach_trace(const struct bpf_sec_def *sec,
 				     struct bpf_program *prog)
 {
 	return bpf_program__attach_trace(prog);
 }
 
+static struct bpf_link *attach_lsm(const struct bpf_sec_def *sec,
+				   struct bpf_program *prog)
+{
+	return bpf_program__attach_lsm(prog);
+}
+
 struct bpf_link *bpf_program__attach(struct bpf_program *prog)
 {
 	const struct bpf_sec_def *sec_def;

tools/lib/bpf/libbpf.h

@@ -248,6 +248,8 @@ bpf_program__attach_raw_tracepoint(struct bpf_program *prog,
 
 LIBBPF_API struct bpf_link *
 bpf_program__attach_trace(struct bpf_program *prog);
+LIBBPF_API struct bpf_link *
+bpf_program__attach_lsm(struct bpf_program *prog);
 struct bpf_map;
 LIBBPF_API struct bpf_link *bpf_map__attach_struct_ops(struct bpf_map *map);
 struct bpf_insn;
@@ -321,6 +323,7 @@ LIBBPF_API int bpf_program__set_socket_filter(struct bpf_program *prog);
 LIBBPF_API int bpf_program__set_tracepoint(struct bpf_program *prog);
 LIBBPF_API int bpf_program__set_raw_tracepoint(struct bpf_program *prog);
 LIBBPF_API int bpf_program__set_kprobe(struct bpf_program *prog);
+LIBBPF_API int bpf_program__set_lsm(struct bpf_program *prog);
 LIBBPF_API int bpf_program__set_sched_cls(struct bpf_program *prog);
 LIBBPF_API int bpf_program__set_sched_act(struct bpf_program *prog);
 LIBBPF_API int bpf_program__set_xdp(struct bpf_program *prog);
@@ -347,6 +350,7 @@ LIBBPF_API bool bpf_program__is_socket_filter(const struct bpf_program *prog);
 LIBBPF_API bool bpf_program__is_tracepoint(const struct bpf_program *prog);
 LIBBPF_API bool bpf_program__is_raw_tracepoint(const struct bpf_program *prog);
 LIBBPF_API bool bpf_program__is_kprobe(const struct bpf_program *prog);
+LIBBPF_API bool bpf_program__is_lsm(const struct bpf_program *prog);
 LIBBPF_API bool bpf_program__is_sched_cls(const struct bpf_program *prog);
 LIBBPF_API bool bpf_program__is_sched_act(const struct bpf_program *prog);
 LIBBPF_API bool bpf_program__is_xdp(const struct bpf_program *prog);

tools/lib/bpf/libbpf.map

@@ -244,6 +244,9 @@ LIBBPF_0.0.8 {
 		bpf_link__pin_path;
 		bpf_link__unpin;
 		bpf_map__set_initial_value;
+		bpf_program__attach_lsm;
+		bpf_program__is_lsm;
 		bpf_program__set_attach_target;
+		bpf_program__set_lsm;
 		bpf_set_link_xdp_fd_opts;
 } LIBBPF_0.0.7;