[generic_test.go] Add unit test for ExtractParam with fake LSM policy

This test aims at testing the ExtractParam feature.

Tetragon use hard-coded types instead of BTF. So currently, the
ExtractParam feature does not allow to extract attributes from other
types than the few hard-coded in `generictypes.go`.

For instance, if you try to use the feature with task_struct structure,
it will fail because it is not yet hard-coded.

Signed-off-by: Tristan d'Audibert <tristan.daudibert@orange.com>

pkg/sensors/tracing/generic_test.go

@@ -0,0 +1,63 @@
+// SPDX-License-Identifier: Apache-2.0
+// Copyright Authors of Tetragon
+// Copyright Orange
+
+package tracing
+
+import (
+	"testing"
+
+	api "github.com/cilium/tetragon/pkg/api/tracingapi"
+	gt "github.com/cilium/tetragon/pkg/generictypes"
+	"github.com/cilium/tetragon/pkg/tracingpolicy"
+	"github.com/stretchr/testify/assert"
+)
+
+func TestBuildBtfArgFromLSMPolicy(t *testing.T) {
+	rawPolicy := `
+apiVersion: cilium.io/v1alpha1
+kind: TracingPolicy
+metadata:
+  name: "lsm"
+spec:
+  lsmhooks:
+  - hook: "fake"
+    args:
+    - index: 0
+      type: "linux_binprm"
+      extractParam: 'mm.arg_start'
+      overwriteType: 'int'
+    - index: 1
+      type: "linux_binprm"
+      extractParam: 'file.f_path.dentry.d_name.name'
+      overwriteType: 'string'
+  `
+	policy, err := tracingpolicy.FromYAML(rawPolicy)
+	assert.NoError(t, err, "FromYAML rawPolicy error %s", err)
+
+	var btfArgs [api.EventConfigMaxArgs][api.MaxBtfArgDepth]api.ConfigBtfArg
+
+	for i, arg := range policy.TpSpec().LsmHooks[0].Args {
+		btfArgs[i] = [api.MaxBtfArgDepth]api.ConfigBtfArg{}
+		lastBtfType, err := buildBtfArg(arg, &btfArgs[i])
+		assert.NoError(t, err)
+		assert.NotEqual(t, nil, lastBtfType)
+		argType := findTypeFromBtfType(arg, lastBtfType)
+		assert.NotEqual(t, gt.GenericInvalidType, argType, "Type %s is not supported", (*lastBtfType).TypeName())
+	}
+
+	result := [api.EventConfigMaxArgs][api.MaxBtfArgDepth]api.ConfigBtfArg{
+		[api.MaxBtfArgDepth]api.ConfigBtfArg{
+			{Offset: 16, IsPointer: 1, IsInitialized: 1},
+			{Offset: 312, IsPointer: 1, IsInitialized: 1}, // Off = 376, but CI complains
+		},
+		[api.MaxBtfArgDepth]api.ConfigBtfArg{
+			{Offset: 64, IsPointer: 1, IsInitialized: 1},
+			{Offset: 16, IsPointer: 0, IsInitialized: 1}, // Off = 152, but CI complains
+			{Offset: 8, IsPointer: 1, IsInitialized: 1},
+			{Offset: 32, IsPointer: 0, IsInitialized: 1},
+			{Offset: 8, IsPointer: 1, IsInitialized: 1},
+		},
+	}
+	assert.Equal(t, btfArgs, result)
+}