Mastering Linux Kernel Development

Kernel and user space

Modern operating systems not only prevent one process from accessing another but also prevent processes from accidentally accessing or manipulating kernel data and services (as the kernel is shared by all the processes).

Operating systems achieve this protection by segmenting the whole memory into two logical halves, the user and kernel space. This bifurcation ensures that all processes that are assigned address spaces are mapped to the user space section of memory and kernel data and services run in kernel space. The kernel achieves this protection in coordination with the hardware. While an application process is executing instructions from its code segment, the CPU is operating in user mode. When a process intends ...