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(upbeat music)

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- [Instructor] Now you get to write kernel code.

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Don't do anything crazy, right?

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This is running in your kernel.

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Bad things could happen.

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You could wipe out your file system.

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Unlikely, but almost any bad thing could happen.

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Might even be possible

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to set your computer on fire. (chuckles)

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So of course, be careful.

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Do this, you know, like on a VM

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that you can easily restart, or something.

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So we're asking you to write a kernel module file.

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Call it lab.c.

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You got to include the init and cleanup functions.

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Got to include the header files,

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got to have prototypes for your functions.

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Do a GPL license.

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Do the register macros for your init and cleanup functions.

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Put a printk in the init and cleanup function.

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Pretty much just like we did in the example.

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You can pretty much type in the example,

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but call it lab.c instead of simple module.

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Then create a Makefile, one line in there, for your lab.o.

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Do the make command to build your module,

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get your ko, insert it, remove it,

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and then check the output showed up with dmesg.

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Cool.

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Now, edit your module,

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and instead of returning 0 return -1,

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rebuild it, insmod it,

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check the dmesg output and stuff.

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What happens when you return -1

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is what we're wanting you to look at.

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All right, be careful. Good luck.