tetragon: Allow override when override helper or fmod_ret is available

Currently we won't validate kprobe with override action when the kernel
is not compiled with CONFIG_BPF_KPROBE_OVERRIDE. But we can still do
override with fmod_ret program if it's available.

Fixes: #4157
Reported-by: Shang-Wen Wang <[email protected]>
Signed-off-by: Jiri Olsa <[email protected]>

Author: olsajiri

pkg/sensors/tracing/generickprobe.go

@@ -454,8 +454,8 @@ func preValidateKprobe(
 	}
 
 	if selectors.HasOverride(f) {
-		if !bpf.HasOverrideHelper() {
-			return nil, errors.New("error override action not supported, bpf_override_return helper not available")
+		if !bpf.HasOverrideHelper() && !bpf.HasModifyReturn() {
+			return nil, errors.New("error override action not supported, bpf_override_return helper and fmodret are not available")
 		}
 		if !f.Syscall {
 			for idx := range calls {