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What is the purpose of loadable modules?
In computing, a loadable kernel module (LKM) is an object file that contains code to extend the running kernel, or so-called base kernel, of an operating system. LKMs are typically used to add support for new hardware (as device drivers) and/or filesystems, or for adding system calls.
What are kernel modules used for?
A kernel module is an object file that contains code to extend the running kernel of an operating systems. It is a standalone-file, typically used to add support for new hardware.
Why do we need to write kernel module?
Kernel modules may be faster (due to less context switches, less system call overhead, and less interruptions), and certainly do run at very high priority. If you want to export a small amount of fairly simple code into kernel space, this might be OK.
What are the advantages of loadable kernel modules?
Loadable kernel modules have several advantages over monolithic “blobs” of code in the kernel: * Device drivers don’t have to be hard-coded into the kernel. For example, if a new chip-set comes out that powers many webcams, that kernel module can simply be loaded instead of recompiling the kernel with the new module.
What are the advantage and disadvantages of loadable kernel modules and built in modules?
Similarly the advantage of built-in modules is that the base kernel usually does not have any fragmentation and hence utilizes the memory much better. The disadvantage of built-in kernel module is a bug in the module crashes the whole system and the entire kernel needs to be build for just a fix in a module.
How are kernel modules loaded?
Loading a Module By default, modprobe attempts to load the module from /lib/modules/kernel_version/kernel/drivers/ . When you ask modprobe to load a specific kernel module, it first examines the dependencies of that module, if there are any, and loads them if they are not already loaded into the kernel.
What is the difference between kernel module and device driver?
Kernel code can be optimized for a specific processor. Kernel modules can be dynamically loaded. The collection of subroutines and data that constitute a device driver can be compiled into a single loadable module of object code. You can add functionality to the kernel while the system is up and running.
Can a Linux kernel be provided under a dual license?
Aside from that, individual files can be provided under a dual license, e.g. one of the compatible GPL variants and alternatively under a permissive license like BSD, MIT etc. The User-space API (UAPI) header files, which describe the interface of user-space programs to the kernel are a special case.
Do you need license for loadable kernel modules?
Loadable kernel modules also require a MODULE_LICENSE () tag. This tag is neither a replacement for proper source code license information (SPDX-License-Identifier) nor in any way relevant for expressing or determining the exact license under which the source code of the module is provided.
Which is the correct way to express that a module is dual licensed?
The correct way of expressing that the module is dual licensed under a GPL v2 variant or MIT license choice. The module is dual licensed under a GPL v2 variant or BSD license choice. The exact variant of the BSD license can only be determined via the license information in the corresponding source files.
Is the Linux kernel module programming guide free?
The Linux Kernel Module Programming Guide is a free book; you may reproduce and/or modify it under the terms of the Open Software License, version 1.1. You can obtain a copy of this license at http://opensource.org/licenses/osl.php.