prog: fix Rotator determinism

Currently Rotator.Select produces non-deterministic results
because it relies on map iteration order. Fix that.

2 files changed, 23 insertions, 0 deletions

diff --git a/prog/rotation.go b/prog/rotation.go
index 5651b6e05..8a9e7d2ca 100644
--- a/prog/rotation.go
+++ b/prog/rotation.go
@@ -38,7 +38,14 @@ func MakeRotator(target *Target, calls map[*Syscall]bool, rnd *rand.Rand) *Rotat
 		syscallUses: make(map[*Syscall][]*ResourceDesc),
 		resources:   make(map[*ResourceDesc]rotatorResource),
 	}
+	var sorted []*Syscall
 	for call := range calls {
+		sorted = append(sorted, call)
+	}
+	sort.Slice(sorted, func(i, j int) bool {
+		return sorted[i].Name < sorted[j].Name
+	})
+	for _, call := range sorted {
 		r.syscallUses[call] = append(r.syscallUses[call], call.inputResources...)
 		r.syscallUses[call] = append(r.syscallUses[call], call.outputResources...)
 		var inputs []*ResourceDesc
diff --git a/prog/rotation_test.go b/prog/rotation_test.go
index e218a5eb6..37308f95b 100644
--- a/prog/rotation_test.go
+++ b/prog/rotation_test.go
@@ -133,3 +133,19 @@ retry:
 		}
 	}
 }
+
+func TestRotationDeterminism(t *testing.T) {
+	target, rs, _ := initTest(t)
+	calls := make(map[*Syscall]bool)
+	for _, call := range target.Syscalls {
+		calls[call] = true
+	}
+	seed := rs.Int63()
+	rnd0 := rand.New(rand.NewSource(seed))
+	calls0 := MakeRotator(target, calls, rnd0).Select()
+	rnd1 := rand.New(rand.NewSource(seed))
+	calls1 := MakeRotator(target, calls, rnd1).Select()
+	if diff := cmp.Diff(calls0, calls1); diff != "" {
+		t.Fatal(diff)
+	}
+}