kerneldrivers

Kernel drivers are software modules that extend the core functionality of an operating system by implementing interfaces to hardware devices or other kernel subsystems. They run in kernel mode and have direct access to memory, interrupts, and kernel data structures, enabling device I/O, network processing, and file system operations. By isolating hardware-specific operations behind standardized interfaces, drivers allow the rest of the kernel and user-space programs to interact with hardware without needing vendor-specific code.

Most kernels support both built-in and loadable drivers. In Linux, drivers can be compiled into the kernel or deployed as loadable modules (.ko) that are inserted and removed at runtime with modprobe or insmod; in Windows, kernel-mode drivers (.sys) are installed as services and loaded by the system, often subject to digital signatures. Some architectures use microkernel designs in which drivers run in user space and communicate with the kernel via IPC, while others keep drivers largely in kernel space.

Development and maintenance require strict adherence to kernel APIs, careful synchronization, and robust error handling. Drivers must manage concurrency, interrupts, memory allocation, and power management without destabilizing the system. Testing typically involves virtualization or dedicated hardware; secure coding practices and licensing terms (for example, GPL for many Linux drivers) are common considerations.

Security and stability considerations include minimizing privilege, validating all inputs, and supporting mechanisms such as secure boot and driver signing on compatible platforms. The lifecycle of a driver generally includes initialization, resource allocation, operation, and cleanup, with reference counting and safe unloading rules to prevent use-after-free errors.

Common categories encompass storage drivers, network adapters, graphics devices, USB controllers, and bus adapters. Driver availability and licensing vary by platform: open-source ecosystems emphasize community-developed drivers, while proprietary drivers may accompany commercial operating systems.