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[20080118] Another stab at kernel modules
Currently, NetBSD supports loadable kernel modules via the LKM interface. The interface supports a few types of kernel modules, e.g. for file systems, system calls and executable file formats. Support for loadable device drivers is currently limited, and source code for LKMs needs to be adjusted to the interface, so the same code cannot be used inside the kernel and as module. Andrew Doran has done some work on improved support for kernel modules. His improvements include
  • an in-kernel loader/linker so there's no need to rely on running the ld(1), and rely on have a working userland, thus
  • module dependencies so that one module can request to load other modules automatically
  • support to load modules from the boot loader and provide them to the kernel
  • use the same code for kernel modules and in-kernel use, so things that are currently used inside the kernel can be moved to a module easily, without changes in code.
The current state of the work is that this is a first version of the code that needs quite some more work. For more information, see Andrew's posting, which also includes examples for testing, and future directions that need to be done to replace LKMs. More thoughts on what else needs to do are outlines in Andrew's second mail on the subject.

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