Disallow '_' in bpf source name

Current design:
1. The bpf compiled object name is derived from the source name
   (e.g. foo.c -> foo.o).
2. Full bpf program/map name are concatenated by object name + '_' +
   program/map name in run-time. (e.g. obj name: x.o; program name: y_z;
   full bpf program name will be x_y_z)

Issue:
x.o with map y_z and x_y.o with map z can cause naming collision in
run-time, since both result in x_y_z. This commit prevents it from
happening with a build-time check.

Bug: 236706995
Test: m
Change-Id: Ic03bfcf07a5748ed63246b71d5ae8de0405e658a

bpf/bpf_test.go

@@ -30,8 +30,9 @@ var prepareForBpfTest = android.GroupFixturePreparers(
 	cc.PrepareForTestWithCcDefaultModules,
 	android.FixtureMergeMockFs(
 		map[string][]byte{
-			"bpf.c":       nil,
-			"BpfTest.cpp": nil,
+			"bpf.c":              nil,
+			"bpf_invalid_name.c": nil,
+			"BpfTest.cpp":        nil,
 		},
 	),
 	PrepareForTestWithBpf,
@@ -58,3 +59,15 @@ func TestBpfDataDependency(t *testing.T) {
 	// value is not available for testing from this package.
 	// TODO(jungjw): Add a check for data or move this test to the cc package.
 }
+
+func TestBpfSourceName(t *testing.T) {
+	bp := `
+		bpf {
+			name: "bpf_invalid_name.o",
+			srcs: ["bpf_invalid_name.c"],
+		}
+	`
+	prepareForBpfTest.ExtendWithErrorHandler(android.FixtureExpectsOneErrorPattern(
+		`\QAndroid.bp:2:3: module "bpf_invalid_name.o" variant "android_common": invalid character '_' in source name\E`)).
+		RunTestWithBp(t, bp)
+}