function (which has since been replaced by access_ok()).
This function verified that the memory area starting at address
-addr and of size size was accessible for the operation specified
+'addr' and of size 'size' was accessible for the operation specified
in type (read or write). To do this, verify_read had to look up the
virtual memory area (vma) that contained the address addr. In the
normal case (correctly working program), this test was successful.