tetragon: make GetIndex() consistent

With this change, GetIndex() has the same semantic meaning regardless of
hook type. It returns the index of the Arg within the spec.

This fixes a returnCopy issue where we were overwriting the wrong arg
when we merge the arg value after the retprobe event.

Signed-off-by: Andy Strohman <[email protected]>

Author: andrewstrohman

pkg/sensors/tracing/generickprobe.go

@@ -744,7 +744,8 @@ func addKprobe(funcName string, instance int, f *v1alpha1.KProbeSpec, in *addKpr
 	var argSigPrinters []argPrinter
 	var argReturnPrinters []argPrinter
 	var setRetprobe bool
-	var argRetprobe *v1alpha1.KProbeArg
+	var argRetprobe *v1alpha1.KProbeArg // holds pointer to arg for return handler
+	var argRetprobeIdx int
 	var allBTFArgs [api.EventConfigMaxArgs][api.MaxBTFArgDepth]api.ConfigBTFArg
 
 	errFn := func(err error) (idtable.EntryID, error) {
@@ -790,8 +791,6 @@ func addKprobe(funcName string, instance int, f *v1alpha1.KProbeSpec, in *addKpr
 		return errFn(fmt.Errorf("error: '%w'", err))
 	}
 
-	argRetprobe = nil // holds pointer to arg for return handler
-
 	addArg := func(j int, a *v1alpha1.KProbeArg, data bool) error {
 		// First try userspace types
 		var argType int
@@ -844,6 +843,7 @@ func addKprobe(funcName string, instance int, f *v1alpha1.KProbeSpec, in *addKpr
 		}
 		if argReturnCopy(argMValue) {
 			argRetprobe = &f.Args[j]
+			argRetprobeIdx = j
 		}
 		if a.Index > 4 {
 			return fmt.Errorf("error add arg: ArgType %s Index %d out of bounds",
@@ -855,7 +855,7 @@ func addKprobe(funcName string, instance int, f *v1alpha1.KProbeSpec, in *addKpr
 		eventConfig.RegArg[j] = regArg
 
 		argP := argPrinter{
-			index:    int(a.Index),
+			index:    j,
 			ty:       argType,
 			userType: userArgType,
 			maxData:  a.MaxData,
@@ -934,7 +934,7 @@ func addKprobe(funcName string, instance int, f *v1alpha1.KProbeSpec, in *addKpr
 		argType := gt.GenericTypeFromString(argRetprobe.Type)
 		eventConfig.ArgReturnCopy = int32(argType)
 
-		argP := argPrinter{index: int(argRetprobe.Index), ty: argType, label: argRetprobe.Label}
+		argP := argPrinter{index: argRetprobeIdx, ty: argType, label: argRetprobe.Label}
 		argReturnPrinters = append(argReturnPrinters, argP)
 	} else {
 		eventConfig.ArgReturnCopy = int32(gt.GenericUnsetType)

pkg/sensors/tracing/genericuprobe.go

@@ -470,6 +470,7 @@ func createGenericUprobeSensor(
 
 func addUprobe(spec *v1alpha1.UProbeSpec, ids []idtable.EntryID, in *addUprobeIn) ([]idtable.EntryID, error) {
 	var argRetprobe *v1alpha1.KProbeArg
+	var argRetprobeIdx int
 	var setRetprobe bool
 
 	symbols := len(spec.Symbols)
@@ -584,6 +585,7 @@ func addUprobe(spec *v1alpha1.UProbeSpec, ids []idtable.EntryID, in *addUprobeIn
 		}
 		if argReturnCopy(argMValue) {
 			argRetprobe = &spec.Args[i]
+			argRetprobeIdx = i
 		}
 		if a.Index > 4 {
 			return fmt.Errorf("error add arg: ArgType %s Index %d out of bounds",
@@ -661,7 +663,7 @@ func addUprobe(spec *v1alpha1.UProbeSpec, ids []idtable.EntryID, in *addUprobeIn
 		argType := gt.GenericTypeFromString(argRetprobe.Type)
 		eventConfig.ArgReturnCopy = int32(argType)
 
-		argP := argPrinter{index: int(argRetprobe.Index), ty: argType, label: argRetprobe.Label}
+		argP := argPrinter{index: argRetprobeIdx, ty: argType, label: argRetprobe.Label}
 		argReturnPrinters = append(argReturnPrinters, argP)
 	} else {
 		eventConfig.ArgReturnCopy = int32(gt.GenericUnsetType)

pkg/sensors/tracing/genericusdt.go

@@ -353,7 +353,7 @@ func addUsdt(spec *v1alpha1.UsdtSpec, in *addUsdtIn, ids []idtable.EntryID) ([]i
 			config.ArgType[cfgIdx] = int32(argType)
 
 			argPrinters = append(argPrinters,
-				argPrinter{index: int(arg.Index), ty: argType, label: arg.Label},
+				argPrinter{index: cfgIdx, ty: argType, label: arg.Label},
 			)
 		}
 		config.BTFArg = allBTFArgs