kernelfacing

Kernelfacing is an informal term used in operating system design to describe the orientation of software components and interfaces toward the kernel boundary. In this view, kernelfacing code comprises APIs, mechanisms, and logic that are intended to operate within or closely with the kernel, as opposed to user-space code that runs outside the kernel.

Scope and orientation

Kernelfacing elements typically include device drivers, kernel subsystems (such as memory management, scheduling, and I/O stacks), and in-kernel libraries or modules. The concept emphasizes designing and maintaining clean, stable interfaces between the kernel and its internal components, as well as between the kernel and any in-kernel extensions. User-facing components—applications and libraries that run in user space—are considered outside the kernelfacing scope.

Design considerations

A kernelfacing approach prioritizes kernel stability, performance, and safety. It encourages minimal and well-documented interfaces, strong dependency management, and rigorous testing, since bugs in kernelfacing code can propagate into the kernel itself. It also motivates clear boundaries between kernel-facing code and user-space code, preserving isolation and reducing surface area exposed to user-space processes.

Relation to broader concepts

The term is not an official architectural category but a useful label in architectural discussions to differentiate kernel-oriented design decisions from user-space design patterns. It aligns with ongoing concerns about kernel ABI stability, modularity, and the balance between a monolithic kernel versus more modular or microkernel-inspired designs.

See also

Kernel-space, User space, Kernel API, Device driver, Kernel module.