tracer: attach to all kprobes with prefix for off CPU profiling

libpf/symbol.go

@@ -82,15 +82,19 @@ func (symmap *SymbolMap) LookupSymbol(symbolName SymbolName) (*Symbol, error) {
 	return nil, fmt.Errorf("symbol %v not present in map", symbolName)
 }
 
-// LookupSymbolByPrefix loops over all known symbols and returns the first symbol
-// that starts with the given prefix.
-func (symmap *SymbolMap) LookupSymbolByPrefix(prefix string) (*Symbol, error) {
+// LookupSymbolsByPrefix loops over all known symbols and returns all symbols
+// that start with the given prefix.
+func (symmap *SymbolMap) LookupSymbolsByPrefix(prefix string) ([]*Symbol, error) {
+	var symbols []*Symbol
 	for name, sym := range symmap.nameToSymbol {
 		if strings.HasPrefix(string(name), prefix) {
-			return sym, nil
+			symbols = append(symbols, sym)
 		}
 	}
-	return nil, fmt.Errorf("no symbol present that starts with '%s'", prefix)
+	if len(symbols) == 0 {
+		return nil, fmt.Errorf("no symbol present that starts with '%s'", prefix)
+	}
+	return symbols, nil
 }
 
 // LookupSymbolAddress returns the address of a symbol.

tracer/tracer.go

@@ -1297,16 +1297,27 @@ func (t *Tracer) StartOffCPUProfiling() error {
 		return errors.New("off-cpu program finish_task_switch is not available")
 	}
 
-	kprobeSymbol, err := t.kernelSymbols.LookupSymbolByPrefix("finish_task_switch")
+	hookSymbolPrefix := "finish_task_switch"
+	kprobeSymbs, err := t.kernelSymbols.LookupSymbolsByPrefix(hookSymbolPrefix)
 	if err != nil {
-		return errors.New("failed to find kernel symbol for finish_task_switch")
+		return err
 	}
 
-	kprobeLink, err := link.Kprobe(string(kprobeSymbol.Name), kprobeProg, nil)
-	if err != nil {
-		return err
+	attached := false
+	// Attach to all symbols with the prefix finish_task_switch.
+	for _, symb := range kprobeSymbs {
+		kprobeLink, linkErr := link.Kprobe(string(symb.Name), kprobeProg, nil)
+		if linkErr != nil {
+			log.Warnf("Failed to attach to %s: %v", symb.Name, linkErr)
+			continue
+		}
+		attached = true
+		t.hooks[hookPoint{group: "kprobe", name: string(symb.Name)}] = kprobeLink
+	}
+	if !attached {
+		return fmt.Errorf("failed to attach to one of %d symbols with prefix '%s'",
+			len(kprobeSymbs), hookSymbolPrefix)
 	}
-	t.hooks[hookPoint{group: "kprobe", name: "finish_task_switch"}] = kprobeLink
 
 	// Attach the first hook that enables off-cpu profiling.
 	tpProg, ok := t.ebpfProgs["tracepoint__sched_switch"]