* HW1 development steps, recommendations.

Take it slowly.  Kernel code dev is at least 10x more time consuming than
user-level code.

Don't write too much code all at once.  Code complexity and debugging is
EXPONENTIAL in the size of the code.  Suggest you write just a few LOC first
(5-10 max), test it thoroughly.  If it works, git commit+push, don't forget
to add some comments the code, and move on to the next step.

Generally the assignment is about: a "copy" tool that can also enc/decrypt a
file.

1. Get a decent small size kernel compiler.

2. Ensure you have the syscall (with void*) working.

3. Initially, hard code everything.  Eventually, you'll remove the
hard-coded values and replace them with params passed from userland.  Alt:
just debug the passing of params to syscall, printk the params, but do
nothing yet.

You can decide to hard code the infile and outfile names.

4. Check that you can filp_open(infile) alone, print error if there was an
error, and close the filp if it was opened successfully.

5. Next, see how to read a few bytes from a file you know already how to
open/close.  Just try to read a few bytes from a file you created yourself,
and printk the bytes (use ASCII text in the file), and that's it.

6. Now, see if you can read a larger file, in a loop, until the EOF.  Don't
try and printk a 4KB chunk of data (too much console clutter), but perhaps
only the first few bytes.

Note: you cannot printk a binary buffer as if it were a null-terminated
ASCII string.  Sometimes trying to printk a binary buffer as if it were an
ASCII string, will result in all kind of odd byte codes being displayed,
which could mess up your terminal, console, or ssh session.  If you want to
print binary data, printk it as hex strings ("%x"); to print actual pointer
addresses, you can use "%p".

7. Next, save that code, and try to open a file for writing, then close it.

8. Next, try to write "hello world" to a newly opened file.

9. If you know how to read+write 2 files, you can combine the code to create
a "copy" syscall.

10. If all that works, you can "saved" that code, and now test encryption.
Again, try to hard code everything: see how to get a buffer with "hello
world" in it, encrypt it inside the kernel using some fixed cipher+key,
printk the hex values of the ciphertext (to ensure that encryption actually
took place).

11. If that works, then see how to decrypt the buffer back.

12. Now you can merge the read+write+crypto code.

13. Leave to the end any corner cases, like what happens if the inner
read/write loop fails.