fix: Get bpf prog func name from insns

It'll get wrong func name of bpf prog when there are multiple bpf progs
in one BTF.

Instead, get the very first symbol name from bpf prog's instructions as
its entry func name.

Signed-off-by: Leon Hwang <hffilwlqm@gmail.com>

Author: Asphaltt

internal/vista/bpf_prog.go

@@ -9,7 +9,6 @@ import (
 	"fmt"
 
 	"github.com/cilium/ebpf"
-	"github.com/cilium/ebpf/btf"
 	"golang.org/x/sys/unix"
 )
 
@@ -50,26 +49,15 @@ func getEntryFuncName(prog *ebpf.Program) (string, string, error) {
 		return "", "", fmt.Errorf("failed to get program info: %w", err)
 	}
 
-	id, ok := info.BTFID()
-	if !ok {
-		return "", "", errNotFound
-	}
-
-	handle, err := btf.NewHandleFromID(id)
-	if err != nil {
-		return "", "", fmt.Errorf("failed to get BTF handle: %w", err)
-	}
-	defer handle.Close()
-
-	spec, err := handle.Spec(nil)
+	insns, err := info.Instructions()
 	if err != nil {
-		return "", "", fmt.Errorf("failed to get BTF spec: %w", err)
+		return "", "", fmt.Errorf("failed to get program instructions: %w", err)
 	}
 
-	iter := spec.Iterate()
-	for iter.Next() {
-		if fn, ok := iter.Type.(*btf.Func); ok {
-			return fn.Name, info.Name, nil
+	for _, insn := range insns {
+		sym := insn.Symbol()
+		if sym != "" {
+			return sym, info.Name, nil
 		}
 	}