11/7/2023 0 Comments Linux kernel development tutorial![]() This helps in saving memory as we load the LKM only when we need them.ĭifferences Between Kernel Modules and User Programs LKMs are very flexible, in the sense that they can be loaded and unloaded with a single line of command. This saves time and also helps in keeping our base kernel error-free. ![]() One major advantage they have is that we don’t need to keep rebuilding the kernel every time we add a new device or if we upgrade an old device. Or you can decide you don’t like the way Linux does something and override an existing system call with an LKM of your own. Most system calls are integral to the system and very standard, so are always built into the base kernel (no LKM option).īut you can invent a system call of your own and install it as an LKM. For example, there are system calls to read a file, create a new process, and shut down the system. Userspace programs use system calls to get services from the kernel. There is one for the MS-DOS filesystem too, and one for NFS. For example, there’s a filesystem driver for the ext2 filesystem type used almost universally on Linux disk drives. For each way, you need a filesystem driver. There are lots of different ways of storing files and directories and such on disk drives, on network servers, and in other ways. Filesystem DriversĪ filesystem driver interprets the contents of a filesystem (which is typically the contents of a disk drive) as files and directories and such. The kernel uses it to communicate with that piece of hardware without having to know any details of how the hardware works. Loadable kernel modules serve various purposes, but the most common applications are-Ī device driver is designed for a specific piece of hardware. Nonetheless, this LKM is very much part of our kernel, and they communicate with the base kernel to complete their functions. The base kernel is located in the /boot directory and is always loaded when we boot our machine, whereas LKMs are loaded after the base kernel is already loaded. Since we are loading these codes at runtime, and they are not part of the official Linux kernel, these are called loadable kernel modules (LKM), which is different from the “base kernel”. This process is called loading the module, where the module refers to the code that we want to add to the kernel. The basic way is to add the code to the kernel source tree and recompile the kernel.Ī more efficient way to do this is by adding code to the kernel while it is running. They extend the functionality of the kernel without the need to reboot the system.Ĭustom codes can be added to Linux kernels via two methods. Kernel modules are pieces of code that can be loaded and unloaded into the kernel upon demand. User Space is where the user applications are executed. the core of the operating system) executes (i.e. The below image will give you a basic understanding. These two components interact through a System Call Interface – which is a predefined and matured interface to Linux Kernel for Userspace applications. Linux is primarily divided into User Space & Kernel Space. Users can modify and create variations of the source code, known as distributions, for computers and other devices. ![]() Linux is a free open-source operating system (OS) based on UNIX that was created in 1991 by Linus Torvalds. Linux Device Drivers Tutorial – Introduction What is Linux?
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