Controlling process communications

Linux applications communicate with each other either directly or over a network. But the difference between direct communication and networked communication, from an application programmer's point of view, is not always that big. Let's look at the various communication methods that Linux supports and how SELinux aligns with them.

Using shared memory

The least network-like method is the use of shared memory. Applications can share certain parts of the memory with each other and use those shared segments to communicate between two (or more) processes. To govern access to the shared memory, application programmers can use mutual exclusions (mutexes) or semaphores. A semaphore is an atomically incremented or decremented integer (ensuring that two applications do not overwrite each other's values without knowing about the value change), whereas a mutex can be interpreted as a special semaphore that only takes the values 0 or 1.

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