User Space and Kernel Space

Kernel space and user space are memory region which differs in the privilege of their components.

Kernel Space:

It is a part of memory where the code of the kernel is located and executed under.
The components used in kernel space are referred to as kernel space components.
Processes running under this space have full access to the kernel and do not require any system calls to avail of service provided by the kernel.
They can access any machine instruction of the underlying architecture
They can access h/w controllers and register as per to rules.
Example: getpid, socket, read, write, open, process management subsystem, memory management subsystem are system space or kernel space components.

User Space:

It is a set of locations where normal user’s processes run that is space other than kernel space.
This area is often referred to as userland and components are referred to as user space components, the code that runs outside the operating system’s kernel.
Userland usually refers to the various programs and libraries that the operating system uses to interact with the kernel.
Processes running under this pace do not have the full privilege and do not have access to kernel space.
They can access a small part of the kernel by using system calls.
They cannot access all the machine instructions and can access h/w controllers and register with the help of system calls.
Examples: Any C program or top, ps, ls, malloc, fopen are common user space program which evokes system calls to get the job done.

Diag-1: User space and Kernel Space

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‹ System calls and its working

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