bpf: Introduce BPF_PROG_TYPE_LSM

Introduce types and configs for bpf programs that can be attached to
LSM hooks. The programs can be enabled by the config option
CONFIG_BPF_LSM.

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: Thomas Garnier <thgarnie@google.com>
Acked-by: Yonghong Song <yhs@fb.com>
Acked-by: Andrii Nakryiko <andriin@fb.com>
Acked-by: James Morris <jamorris@linux.microsoft.com>
Link: https://lore.kernel.org/bpf/20200329004356.27286-2-kpsingh@chromium.org

tools/include/uapi/linux/bpf.h

@@ -181,6 +181,7 @@ enum bpf_prog_type {
 	BPF_PROG_TYPE_TRACING,
 	BPF_PROG_TYPE_STRUCT_OPS,
 	BPF_PROG_TYPE_EXT,
+	BPF_PROG_TYPE_LSM,
 };
 
 enum bpf_attach_type {
@@ -211,6 +212,7 @@ enum bpf_attach_type {
 	BPF_TRACE_FENTRY,
 	BPF_TRACE_FEXIT,
 	BPF_MODIFY_RETURN,
+	BPF_LSM_MAC,
 	__MAX_BPF_ATTACH_TYPE
 };