Virtual addressing allows the kernel to make a given physical address appear to be another address, the virtual address. Often the first step in doing this is virtual addressing, usually achieved by paging and/or segmentation.
The kernel has full access to the system's memory and must allow processes to safely access this memory as they require it. The kernel is also responsible for context switching between processes or threads.įurther information: Memory management (operating systems) Although the kernel must provide IPC in order to provide access to the facilities provided by each other, kernels must also provide running programs with a method to make requests to access these facilities. These implementations may be located within the kernel itself or the kernel can also rely on other processes it is running. Kernels also provide methods for synchronization and inter-process communication (IPC). Key aspects necessary in resource management are defining the execution domain ( address space) and the protection mechanism used to mediate access to the resources within a domain.
The kernel allocates requests from applications to perform I/O to an appropriate device and provides convenient methods for using the device (typically abstracted to the point where the application does not need to know implementation details of the device). I/O devices include such peripherals as keyboards, mice, disk drives, printers, USB devices, network adapters, and display devices. The kernel is responsible for deciding which memory each process can use, and determining what to do when not enough memory is available. Often multiple programs will want access to memory, frequently demanding more memory than the computer has available. Typically, both need to be present in memory in order for a program to execute. Random-access memory (RAM) is used to store both program instructions and data. 7.1.1 Hardware- or language-based protection.The kernel takes responsibility for deciding at any time which of the many running programs should be allocated to the processor or processors. This central component of a computer system is responsible for executing programs. Instead, the Linux kernel is monolithic, although it is also modular, for it can insert and remove loadable kernel modules at runtime. MINIX 3 is a notable example of microkernel design. Microkernels run most but not all of their services in user space, like user processes do, mainly for resilience and modularity. Monolithic kernels run entirely in a single address space with the CPU executing in supervisor mode, mainly for speed. There are different kernel architecture designs.
When a process requests a service from the kernel, it must invoke a system call, usually through a wrapper function. The kernel's interface is a low-level abstraction layer. Even in systems where the kernel is included in application address spaces, memory protection is used to prevent unauthorized applications from modifying the kernel. This separation prevents user data and kernel data from interfering with each other and causing instability and slowness, as well as preventing malfunctioning applications from affecting other applications or crashing the entire operating system. In contrast, application programs such as browsers, word processors, or audio or video players use a separate area of memory, user space. The kernel performs its tasks, such as running processes, managing hardware devices such as the hard disk, and handling interrupts, in this protected kernel space.
The critical code of the kernel is usually loaded into a separate area of memory, which is protected from access by application software or other less critical parts of the operating system. It handles the rest of startup as well as memory, peripherals, and input/output (I/O) requests from software, translating them into data-processing instructions for the central processing unit.
On most systems, the kernel is one of the first programs loaded on startup (after the bootloader). CPU & cache usage, file systems, and network sockets. I/O, memory, cryptography) via device drivers, arbitrates conflicts between processes concerning such resources, and optimizes the utilization of common resources e.g. A full kernel controls all hardware resources (e.g. It is the portion of the operating system code that is always resident in memory and facilitates interactions between hardware and software components. The kernel is a computer program at the core of a computer's operating system and generally has complete control over everything in the system.
A kernel connects the application software to the hardware of a computer