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Modular Kernel: Difference between revisions
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▲!! What is a Modular Kernel ?
A modular kernel is an attempt to merge the good points of kernel-level drivers and third-party drivers. In a modular kernel, some part of the system core will be located in independant files called _modules_ that can be added to the system at run time. Depending on the content of those modules, the goal can vary such as:
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The basic goal remains however the same: keep what is loaded at boot-time minimal while still allowing the kernel to perform more complex functions. The basics of modular kernel are very close to what we find in implementation of _plugins_ in applications or _dynamic libraries_ in general.
There are several components that can be identified in virtually every modular kernel:
;the core
;__the modules loader__: this is a part of the system that will be responsible of preparing a module file so that it can be used as if it was a part of the core itself.▼
;the modules loader
;__the kernel symbols table__: This contains additionnal information about the core and loaded modules that the module loader needs in order to _link_ a new module to the existing kernel.▼
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;__the dependencies tracking__: As soon as you want to _unload_ some module, you'll have to know whether you can do it or not. Especially, if a module _X_ has requested symbols from module _Z_, trying to unload _Z_ while _X_ is present in the system is likely to cause havoc.▼
;the kernel symbols table
;__modules__: Every part of the system you might want (or don't want) to have.▼
▲
;the dependencies tracking
▲
;modules
Modularization must be done within certain limits if you still want your system to be able to boot. Pushing _all_ the filesystems and device drivers (including boot device driver) into module will probably make the boot time a hard time. Following solutions can however be used:
* The kernel is provided with an extremely simple [
* The kernel comes with a built-in
* The bootloader knows it should not only load the _kernel_ but also a collection of pre-configured modules so that the kernel only needs to check those pre-loaded modules and initialize them to access other modules and primary configuration files. This basically means that your bootloader is somehow an OS of its own such as [[GRUB]
Anyway, ramdisk drivers and dedicated boot partitions/reserved sectors will be your friends.
==See Also==
===Threads===
*[Design of a basic module loader|Forum:6962]
*[Calling a function knowing its name|Forum:6768]
*[
*[
*[
*[
*[Design & Implementation of Extensible OS|Forum:5841]▼
▲[Design & Implementation of Extensible OS|Forum:5841]
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