One way is to explicitly prompt the permission-requests prior to actual syscall invocation (as against at install time). The user can then choose to approve or

One way is to explicitly prompt the permission-requests prior to actual syscall invocation (as against at install time). The user can then choose to approve or deny. For instance, if a file-manager app is asking to read your SMS, you can opt to deny the permission, unless you're willing to risk the app misusing your data. What they do on the Mac is also acceptable - where they warn you about running apps from unapproved publishers.