sys: don't add clock_gettime always

Currently we always enable clock_gettime in config.
This is required since the call is needed for generation of timespec/timeval structs.
The negative side effect is that one gets clock_gettime even
if he wants to fuzz a small set of unrelated syscalls.

Don't enable clock_gettime by default.
Instead handle timeval/timespec as other resources.

2 files changed, 24 insertions, 4 deletions

diff --git a/sys/decl.go b/sys/decl.go
index 322158b92..d09328c91 100644
--- a/sys/decl.go
+++ b/sys/decl.go
@@ -437,10 +437,8 @@ func TransitivelyEnabledCalls(enabled map[*Call]bool) map[*Call]bool {
 	}
 	for {
 		n := len(supported)
-		for c := range enabled {
-			if !supported[c] {
-				continue
-			}
+		haveGettime := supported[CallMap["clock_gettime"]]
+		for c := range supported {
 			canCreate := true
 			for _, res := range c.InputResources() {
 				noctors := true
@@ -455,6 +453,15 @@ func TransitivelyEnabledCalls(enabled map[*Call]bool) map[*Call]bool {
 					break
 				}
 			}
+			// We need to support structs as resources,
+			// but for now we just special-case timespec/timeval.
+			if canCreate && !haveGettime {
+				ForeachType(c, func(typ Type) {
+					if a, ok := typ.(*StructType); ok && a.Dir() != DirOut && (a.Name() == "timespec" || a.Name() == "timeval") {
+						canCreate = false
+					}
+				})
+			}
 			if !canCreate {
 				delete(supported, c)
 			}
diff --git a/sys/decl_test.go b/sys/decl_test.go
index a5c1d7be4..7c64f28fe 100644
--- a/sys/decl_test.go
+++ b/sys/decl_test.go
@@ -33,3 +33,16 @@ func TestTransitivelyEnabledCalls(t *testing.T) {
 		t.Fatalf("epoll fd is not disabled")
 	}
 }
+
+func TestClockGettime(t *testing.T) {
+	calls := make(map[*Call]bool)
+	for _, c := range Calls {
+		calls[c] = true
+	}
+	// Removal of clock_gettime should disable all calls that accept timespec/timeval.
+	delete(calls, CallMap["clock_gettime"])
+	trans := TransitivelyEnabledCalls(calls)
+	if len(trans)+10 > len(calls) {
+		t.Fatalf("clock_gettime did not disable enough calls: before %v, after %v", len(calls), len(trans))
+	}
+}