The prescribed reading is from the commentary section of the book, so
the idea is that you read over Lions' comments whilst referring to the
relevant sections of the v6 source code (sections 1-4 and 6.1-6.2 all
deal with sections of code from Part I of the v6 source).
I know that it's probably pretty intimidating to start with, and if
you've given it your best shot -- say, a couple of hours worth of
reading and trying to figure out the point of / control flow of the
relevant assembly / C source -- then you're good. The most important
thing is that you come to lecture with a rudimentary understanding of
what we're going to cover, and, ideally, a boatload of questions for
me as we do the code review together.
Hope that helps,
- Michael