Fixed #TSB-1234 test

ebpftracer/ebpf/l7/l7.c

@@ -302,8 +302,8 @@ void perf_event_batch_output(void *ctx,  struct l7_event *e) {
 
     __u32 e_length = offsetof(typeof(struct l7_event), payload) + (e->payload_size);
     bpf_printk("IK...perf_event_batch_output...e->payload_size=%d, e_length=%d", e->payload_size, e_length);
-    char *src = (char *)e;
-    char *dst = e_buff->data + e_buff->len;
+    unsigned char *src = (unsigned char *)e;
+    unsigned char *dst = e_buff->data + e_buff->len;
     for (int i = 0; i < e_length; i++) {   //IK:ERROR: IK: BPF stack limit of 512 bytes is exceeded. Please move large on stack variables into BPF per-cpu array map.
         *dst++ = *src++;
     }