How to test if an address is readable in linux userspace app

Question

For debugging purposes I need to test a pointer to see if it points to a valid readable page. Currently I am parsing /proc/[pid]/maps to see if the address is mapped ok, but this seems a bit long-winded. Is there a better way? Thanks.

Answer 1

The canonical way is to use the write() system call to read from the page (writing to a dummy pipe() file descriptor). Instead of faulting, it will return -1 with errno == EFAULT if the buffer passed to write() is unreadable.