Hands-On System Programming with Linux

Memory protection keys – a brief note

Recent Intel 64-bit processors bring to the table a feature called Memory Protection Keys (MPK). Very briefly, MPK (or pkeys, as it's called on Linux) allows userspace to set permissions with page granularity, too. So, if it does the same thing as mprotect or mmap, what benefit does it bring? See the following:

• It's a hardware feature, so setting a huge range of pages (say, gigabytes of memory) to some particular memory permissions will be much faster than mprotect(2) can manage; this is important for some types of applications
• Applications (in-memory databases, perhaps) could benefit by turning off writes on memory regions until absolutely required, reducing spurious write bugs

How do you exploit MPK? ...