hook the execve system call how to find the file path from the const char __user*

hi i hooked the execve system call with lkm and when i wrote a code that print alert each time process is been execute it work fine but when i tried to print the file name paramter it crashed my computer
Code:asmlinkage long our_execl( const char __user* filename, const char __user* const __user* argv,
const char __user* const __user* envp )
{
printk(filename);
return orignal_execl( filename, argv, envp );
}