bpf/bpftool: Add unprivileged_bpf_disabled check against value of 2

In [1], we added a kconfig knob that can set
/proc/sys/kernel/unprivileged_bpf_disabled to 2

We now check against this value in bpftool feature probe

[1] https://lore.kernel.org/bpf/74ec548079189e4e4dffaeb42b8987bb3c852eee.1620765074.git.daniel@iogearbox.net

Signed-off-by: Milan Landaverde <milan@mdaverde.com>
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
Acked-by: Quentin Monnet <quentin@isovalent.com>
Acked-by: KP Singh <kpsingh@kernel.org>
Link: https://lore.kernel.org/bpf/20220322145012.1315376-1-milan@mdaverde.com

tools/bpf/bpftool/feature.c

@@ -207,7 +207,10 @@ static void probe_unprivileged_disabled(void)
 			printf("bpf() syscall for unprivileged users is enabled\n");
 			break;
 		case 1:
-			printf("bpf() syscall restricted to privileged users\n");
+			printf("bpf() syscall restricted to privileged users (without recovery)\n");
+			break;
+		case 2:
+			printf("bpf() syscall restricted to privileged users (admin can change)\n");
 			break;
 		case -1:
 			printf("Unable to retrieve required privileges for bpf() syscall\n");