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The term user space (or userland) refers to all code that runs outside the operating system's kernel. [2] User space usually refers to the various programs and libraries that the operating system uses to interact with the kernel: software that performs input/output, manipulates file system objects, application software, etc.
The unrestricted mode is often called kernel mode, but many other designations exist (master mode, supervisor mode, privileged mode, etc.). Restricted modes are usually referred to as user modes, but are also known by many other names (slave mode, problem state, etc.). [2] Hypervisor
On the other end, the hierarchical protection domains architecture that leads to the design of a monolithic kernel [33] has a significant performance drawback each time there's an interaction between different levels of protection (i.e., when a process has to manipulate a data structure both in "user mode" and "supervisor mode"), since this ...
Linux API, Linux ABI, and in-kernel APIs and ABIs. The Linux kernel provides multiple interfaces to user-space and kernel-mode code that are used for varying purposes and that have varying properties by design. There are two types of application programming interface (API) in the Linux kernel: the "kernel–user space" API; and; the "kernel ...
The Windows NT kernel is a hybrid kernel; the architecture comprises a simple kernel, hardware abstraction layer (HAL), drivers, and a range of services (collectively named Executive), which all exist in kernel mode. [1] User mode in Windows NT is made of subsystems capable of passing I/O requests to the appropriate kernel mode device drivers ...
The Windows NT operating system family's architecture consists of two layers (user mode and kernel mode), with many different modules within both of these layers.One prominent example of a hybrid kernel is the Microsoft Windows NT kernel that powers all operating systems in the Windows NT family, up to and including Windows 11 and Windows Server 2022, and powers Windows Phone 8, Windows Phone ...
The call to the library function itself does not cause a switch to kernel mode and is usually a normal subroutine call (using, for example, a "CALL" assembly instruction in some Instruction set architectures (ISAs)). The actual system call does transfer control to the kernel (and is more implementation-dependent and platform-dependent than the ...
In kernel mode, the processor can execute every instruction in its hardware repertoire, whereas in user mode, it can only execute a subset of the instructions. Instructions that can be executed only in kernel mode are called kernel, privileged, or protected instructions to distinguish them from the user mode instructions. For example, I/O ...