how to use bpftrace probe local variable in a function

Question

I want to know how to use bpftrace tool to probe the local variable in a kernel function, like:

int fun1(arg0, arg1, arg2)
{     
    ....  
    ret1 = arg0->param1; 
    var1 = xxxx; 
    .... ;
}

bpftrace can probe the data of arg0, arg1 and arg2

but how to probe the variable data of var1.