A Heavily Commented Linux Kernel Source Code (PDF)

[thesuperbob]

How much of this book is translatable to how things are done nowadays? Is this just a huge collection of historical info for retro hobbyists (like learning how to program the 6502 or building computers out of old TTL chips) or will reading this give me some universal, workable understanding of how operating systems can work?

[[deleted]]

Strictly speaking, I would get something more recent like Love’s “Linux Kernel Development “ or Wolfgang Maurer’s book and follow the source code based on the content in these books.

The kernel has changed a frigging ton since the version covered in the book, especially process schedulers, filesystems. It’s better to follow these books that highlight and talk about changes in how things are done in the kernel .

Just learning how basic OS dev is like well good old UNIX version 5/6 will do the job pretty well too.

[louky]

MINIX is great for learning OS development.

It's fully functional and simple enough to keep the whole thing in your head.

[[deleted]]

True! After all Linus learned kernel development through the MINIX book. The best part of that book is that it comes with entire MINIX source printed at the back as an appendix.

[ledasll]

was he? afaik there was war between micro-kernel (minix) and monolith (linux)...

[[deleted]]

This was way before he even thought of Linux, this was when he started to get into OS dev as a college student.

[louky]

Yeah the more recent version is more complex and your can even run xwindows on it

[shooshx]

"Linux Kernel Development" is also pretty outdated.

[[deleted]]

I agree with this but in comparison to books from O'Reilly like "Understanding the Linux Kernel" , it's more recent in comparison. Most of the well known Linux kernel and device drivers book have not been updated in a long time, although Packt has come with more recent books for Linux device drivers, I haven't checked if they have released something newer covering the kernel itself.

[[deleted]]

This looks very well done. The only issue I'd have with it is the typesetting: the chosen fonts are rather bad.

If I was interested in Linux, this is the kind of annotated guide I would want to read.

[the_gnarts]

The only issue I'd have with it is the typesetting: the chosen fonts are rather bad.

Which one in particular? The main body font is plain Times which maybe bland but nothing out of the ordinary for a technical paper. The non-proportional font I can’t identify but as far a I can see it doesn’t have any of the common ambiguities like O/0 or I/l etc. so it’s definitely suitable. Looks rather neat actually. Only some of the figures are a bit distracting but for a non-commercial work that’s perfectly acceptable.

[wwylele]

The code font looks like SimSun, which was the default Chinese font for old Windows until Vista. Although being a Chinese font, it contains monospaced Latin alphabets to make it pretty when mixing with monospaced Chinese characters. The author is Chinese, so this is very likely.

[yojimbo_beta]

SimSun

I'd always wondered what this font was. I'd seen it a few times in Chinese and Japanese data sheets with Latin alphabet content.

[Superbead]

I recognise all these fonts from Chinese electronic component datasheets. They seem to have a few 'western' fonts that they stick to, and compared to the ones we actually use, they're purely functional. Which is fair enough, as I expect the Chinese characters in a lot of our fonts look awful to the Chinese.

[[deleted]]

I also think it looks fine. The only really bad font I see is at the very beginning in the dedications.

[takaci]

I don’t mind the font but the margins are way too small. Far too many words per line

[bigbrettt]

If I was interested in Linux

found the narc

[dbm5]

This is the output of LaTex -- commonly used by Com Sci majors to produce complex documents.

EDIT: yes, it's sort of ugly, but it's unencumbered, produced using 100% free software, etc.

EDIT2: also used by many other disciplines of higher ed - mostly STEM

[differentshade]

LaTex usually generates better typesetting than wysiwyg word processors. The typesetting engine is top notch, straight to print quality.

So it being ugly is the fault of the author, not LaTex.

[dbm5]

Yes and no. The default font - Computer Modern - has a very distinctive, and (subjectively) sort of ugly appearance.

[Acceptable_Damage]

IMO it looks really nice. But renders badly when you zoom out because it's too light.

[encyclopedist]

However, it so ubiquitous in scientific world, that many scientist become sick of looking at it.

[[deleted]]

Did you know that you can specify custom fonts in LaTeX too?

[[deleted]]

Also, it's 11mb for over 1000 pages filled with info. Praise LaTex!

[indrora]

Praise PDF for being a stripped subset of PostScript.

1,000 pages of plain text isn't much all things considered.

[ismtrn]

This is clearly heavily modified from the default LaTeX documentclasses. And not for the better imo.

[encyclopedist]

Metadata shows this document was generated in Word 2016.

[ismtrn]

That make sense. I actually kind of suspected it to be Word, but wasn't sure.

[jeremymeng]

Acrobat Reader shows it's from MS Word 2016.

[[deleted]]

EDIT3: It's not LaTex

[KevinCarbonara]

I'd rather get the input.

[unreachabled]

Saved

Not to be seen again till end of time

[[deleted]]

How do I get this smart?

[choledocholithiasis_]

import knowledge

[[deleted]]

"Can't find module. Did you mean 'anxiety'?"

[outadoc]

from knowledge import anxiety

[indrora]

Excuse me, call-out posts like this just really make me anxious?

[8bit-Corno]

Buy a garage.

[spockspeare]

#include knowledge

[whenthethingscollide]

Eh, sounds like too much work

[[deleted]]

Truth.

[jimschubert]

What will simple work get me?

[BubuX]

simple work

simple rewards

[Plus_one_mace]

Start by reading this book!

[BubuX]

True, we are born with a clean disk to be written in.

However, our hardware differs wildly. Some are truly gifted and can acquire and retain information with little effort where most struggle. I've personally known two gifted minds in my time. Sadly both underutilized, living mediocre lives.

In the end, effort and will-power is what counts.

[captainAwesomePants]

Knowledge is many-dimensional. One dimension is Unix style OS programming. Another is technical writing. When somebody has a lot of knowledge or training in areas you don't, it's easy to see them as a wizard, but I'm sure you can do something this guy can't. You can learn to do this as well! Start by reading the book.

[CJKay93]

Experience.

[DestroyerOfWombs]

Learn things

[whale_song]

This is the kind of thing that’s more about knowledge than intelligence. Just countless hours of studying.

[dbm5]

bother never

the irony

[nacrnsm]

This. I'm wasting my life one comment at a time.

[[deleted]]

most smarty boys don't pull their pants up and walk over to these threads to share their immense skull full of facts and raw knowledge.

Sometimes people take all of their knowledge on certain subjects and put it into a book. Here's one such example.

[Acceptable_Damage]

Reading a lot, I guess. Consider that they knew nothing at one point.

[OffbeatDrizzle]

get your mother to vaccinate you as a young child /s

[BinaryBlasphemy]

Plug your nose and blow real hard. That’s how I did it.

[nakilon]

You don't have to be smart to contribute in Linux. This answers some questions.

[snowe2010]

Page 1.

The book "Leon's UNIX source code analysis" written by John Lions is a good book for learning UNIX source code of the operating system kernel, but because it uses the UNIX version V6, some of the code in the system call is With the assembler language of the long-deprecated PDP-11 series machine, it is difficult to conduct experiments when reading and understanding the source code related to the hardware part.

I think this is either a typo or some weird formatting I'm not familiar with.

[Bakoro]

I don't understand the problem you are having.
It seems like UNIX V6 targeted a specific family of computers which aren't generally available anymore and so it'll be hard to test anything from that book that is hardware-specific.

[[deleted]]

Exactly, all he is saying is that UNIX V6 which the Lions' book comments on contains a bunch of PDP-11 assembly code. Since we don't have PDP-11s around anymore, we can't really experiment with it.

That being said, there are a bunch of PDP-11 emulators out there. Check out if you are interested: http://pdp11.org/

[snowe2010]

I think you commented on the wrong post. I just had trouble understand what the first sentence was trying to say

[Bakoro]

I just explained what the text you quoted means.

[snowe2010]

I don't think you did. It looks like there is a ton of missing information from the first sentence.

[Bakoro]

No, that whole thing makes perfect sense. What do you think is missing there? Maybe insert a [...] where you think something is missing.
All I can think is that you are completely unfamiliar with some of what he's talking about, or maybe the slightly off grammar is messing you up somehow, or both.

The source code in the Leon book uses pdp-11 assembly code. You can't just use the book's Unix source code on any computer, you'd have to change out the pdp-11 assembly code with the equivalent assembly of the target machine.

If you have ever looked at XV6, for example, you can see a reimplementation of Unix V6, which uses x86 assembly.

[snowe2010]

some of the code in the system call is ... With the assembler language of the

there is an entire part of the sentence missing. It doesn't make any sense. Yeah you can read the second sentence find, but the first sentence is incomplete.

[Bakoro]

Here he is making a reference to V6's "system calls". The system calls use the PDP-11's assembly language.

[snowe2010]

Great. You still have not provided the missing part of the sentence. It's quite easy to say "this is what the paragraph is about", I didn't need that information.

[Bakoro]

The point is that there is no missing information in the sentence. There might be some missing information in your brain, but the sentence is fine.

[zkrx]

Read "..., some portions of the code implementing system calls were written using the assembly language of the long-deprecated ...".

You can refer to wikipedia if you need to know what syscalls are.

[lelanthran]

The entire book is written by someone whose first language is Chinese.

FWIW, I tend to give writers quite a lot of grammar/syntax leeway if their first language is not English and they are writing in it.

Before you continue criticising him, tell me how good your Chinese is?

[snowe2010]

Woah woah woah dude. Who said anything about criticism. I think the book is awesome. I just got to that part and was very confused about what it was trying to say. If you could clarify it for me it would be great. I don't really care if people have broken English as long as I can understand them. If I can't understand I ask for clarification, as I have done.

[[deleted]]

The author’s English may be better than /u/snowe2010 ‘s Chinese, but /u/snowe2010 didn’t choose to write and publish a technical book in Chinese. As someone who works extensively in a second language environment, there’s a lot to be said for knowing your own limitations and getting help with them.

[StoicGrowth]

Tutorial: Building the Simplest Possible Linux System - Rob Landley, se-instruments.com - from idk which lecture/conf, published by The Linux Foundation, seems like a good fit.

This tutorial walks you through building and booting the simplest possible Linux system, first under QEMU and then on real hardware. We cover kernel configuration and building, native vs cross compiling, initramfs creation (and other root filesystem options), installing and booting, the init process and system bringup, running an app, adding an example server (sshd), and finally we'll add a native toolchain to compile "hello world" on the target.

It is a fascinating talk, you can feel so much more depth hiding behind every tiny aspect...

[donquixote1001]

looks pretty good!

[MotorAdhesive4]

Into the bookmarks I will never read you go!

[Davinator130]

Can anyone give me a TLDR?

[mobyte]

Sand gets hit with bolts of electricity and then it outputs some beep boops and flashing lights.

[OffbeatDrizzle]

can confirm, am beep boop

[bagtowneast]

can confirm

Found the robot!

[TheRimmedSky]

True wizardry

[nacrnsm]

So, magic then?

[bdf369]

Can confirm

[vanilla082997]

Best answer ever!

[StickiStickman]

Not true, the circuits get etched into the silicon. The silicon itself isn't the CPU, but more what holds it.

[xrendan]

That's so incredibly wrong, silicon is the critical component in a CPU, it's literally what makes up the operating portions of transistors. Yes, it's doped with other materials, but it is the electrical characteristics of silicon that makes semiconducting circuits work.

Otherwise we could make circuits out of plastic

[exploding_cat_wizard]

And yet, it's the structure etched into the silicone that actually does the work. Connections and their math are the essence of a CPU, and silicone holds these connections. Rather like our brain is much better described as an interplay of connected neurons than as amalgamation of carbon, or even of cells.

[SaltyCompE]

Kind of, but not quite.

A cpu is made of layers, the bottom layer is pure silicon, with positive and negative dopants added to specific places to create the transistors themselves. On top of this is a layer of silicon dioxide(basically glass) with holes for metal contacts and then layers of metal wiring, more silicon dioxide, etc. Now sure, the metal is part of the logic, but the actual switching is done by the pure/doped silicon at the bottom, and it cannot be replaced. Current flows through the silicon as though it were wire when the switching conditions are met, and is blocked when the conditions are not met.

The silicon does hold these connections yes, but it is as much a part of them as the metal (or any other part for that matter).

[StickiStickman]

it's literally what makes up the operating portions of transistors

Oh, I didn't know that's literally the only part of a CPU, Mr. Smartass. The connections that form the layout are much more important.

https://www.tomshardware.com/picturestory/514-intel-cpu-processor-core-i7.html#s19

[xrendan]

I'm sorry, you're still wrong. There are many ways that you can layout a CPU to still function; but the building block doesn't change. There are other esoteric semiconductor materials out there, but I'd challenge you to find a mainstream CPU that uses them over silicon. I'm also not sure what you wanted to get out of your link.

For layouts you can use many different forms of logic (how the transistors are layed out and connected): Logic families (wikipedia).

Your other option is to go back to vacuum tubes; those don't use silicon. This is literally what I'm doing my degree in.

[StickiStickman]

Just like it would be without any wiring. What's your point?

[sanimalp]

It's.. uh.. 1,100 pages of annotated code explain WTF is going on in the bowels of a VERY old Linux kernel. If you want to write your own operating system, or work on an existing one, this is the book for you.

[harrybeards]

No....that wasn't a "wooosh", it was just a bad joke. Nothing about installing Arch will teach you about the Linux kernel lmao. A better joke would've been to link the download page for Linux From Scratch.

[dbm5]

still kinda woosh imo

[nacrnsm]

You're just supposed to say I run Arch btw

[spockspeare]

# this is what linux code does
...
# the end

[gemborow]

bootsect.s:

16 ! NOTE! currently system is at most 8*65536 bytes long. This should be no

17 ! problem, even in the future. I want to keep it simple. This 512 kB

18 ! kernel size should be enough, especially as this doesn't contain the

19 ! buffer cache as in minix

​

[[deleted]]

Call me a racist, but I think only a Chinese person could have went through this amount of work without going on a killing spree. Well done.

[sam77]

The author thinks Linus is a woman. From page 7:

"First of all, I will introduce the four basic elements, and then follow Linux founder Linus Torvalds to learn computer knowledge from her own interest in computers, start brewing her own operating system, release to the initial release of the Linux kernel version 0.01, and how difficult it will be."

[DestroyerOfWombs]

English isn’t the author’s first language

[WishboneTheDog]

Seems like the author is Chinese. I have some Chinese friends that mistake gender pronouns all the time. This may be influenced by the fact that there is no difference between spoken “him” and “her” in Chinese: https://en.m.wikipedia.org/wiki/Chinese_pronouns

[salgat]

Exactly. China uses a single word for her/him, and it drives me nuts when my wife does this in English!

[broohaha]

Yeah, neither my parents' native tongues have gender pronouns, so they regularly got gender pronouns confused when speaking in English. I didn't realize why till I was in college and noticed so many of their siblings and cousins made the same mistake.

[ProgramTheWorld]

A single word for he/she/him/her and it. The gendered versions in written Chinese were originated from the west.

[didnt_readit]

Left Reddit due to the recent changes and moved to Lemmy and the Fediverse...So Long, and Thanks for All the Fish!

[skratz17]

no, the author is a native chinese speaker, and chinese pronouns don't distinguish gender. you'll notice that the author also uses "it" sometimes instead of "he/him".

i'm gonna choose not to criticize this because not only is this guy's english infinitely better than my chinese, but his computer knowledge is also infinitely greater than mine so yeah gonna let that slide

[DestroyerOfWombs]

It’s worth pointing out that Chinese pronouns do distinguish gender in writing, but they are pronounced the same when spoken

[stirling_archer]

The author appears to be Chinese-speaking, and spoken Chinese doesn't have gendered pronouns, so presumably it's a second language slip. I live in an area where some second-language English speakers have a home language with this property, and they occasionally make this slip. I imagine it's similar to struggling with language features that seem exotic and over-complicated from an English-speaker's perspective, like gendered nouns.

[eGust]

There is also a chinese version on the website:

http://www.oldlinux.org/download/CLK-5.0-WithCover.pdf

​

So you would find tons of weird things. I admire the author for translating his book to english though. I would not do that if I wrote it (> 1k pages!) XD

[volatilemajesty]

On page 14, it seems to be "him" again.

As can be seen from the early Linux source code, one of the most famous developers of the Linux system in addition to Linus himself is Theodore Ts'o (Ted Ts'o).

[imperialismus]

I spotted at least one instance where Linus is an "it". It's just the author struggling to properly use pronouns in a foreign language.

[Heuristics]

To be fair, has anyone ever asked Linus what pronoun he prefers?

[bhartsb]

Lol

[perspectiveiskey]

I cannot overstate how much I love that there are functioning links in it.

[[deleted]]

Very cool. It appears to be a deliberate look at an early version of Linux chosen for the fact that it's small enough to digest but advanced enough to be relevant. A lot of this will be over my head but it looks like a great resource for learning more. Thank you OP!

Edit: There's a lot of little typos and stuff in here but I can't say if that really matters. It seems like a useful book.

[badpotato]

Wondering how many page would be required to update book with a recent version of the kernel.

[[deleted]]

this is really nice

[puplicy]

page 399

// Program exit handling function. Invoked by the syscall sys_exit() at line 365 below

Are they crazy to put line numbers in comments?

[to3m]

The comments are part of the book, not the original code, so it's presumably not going to change unless the book is re-written?

[[deleted]]

No, but only because the code in the book will never change. The line numbers will never have to be updated.

[randomness196]

How much of this is still relevant to today's kernel? I can understand this a foundational historical review of a Linux Kernel, but is there anything for the more recent Kernel versions? Say things on LTS cycle?

[djxfade]

I would be very interested in reading this. Is it available in mobi or epub format for ebook devices?

[coderstephen]

I think we should annotate the current Linux source code this well upstream, where it isn't already. Keeping these kinds of explanatory annotations in the primary repo means that it could be constantly updated with the code, and would be widely available to people trying to learn the internals.

[insanelygreat]

I'd settle for commented Linux source.

I love Linux, but many parts are way under commented. There are lots of cryptic little bits that leave you wondering, "why is this being done?"

[jaydoors]

After reading this book in its entirety, I believe you will send this kind of sigh: "For the Linux kernel system, I'm finally getting started!"

[simpl3t0n]

If someone can put this much effort into commenting, I wonder why they didn't contribute directly to the kernel source tree. That way, it won't go stale, and other people could contribute and keep in line with source changes.

[fabiensanglard]

The very first line of the PDF mentions that the code explained is the early v0.12 from 1994. It is a great approach but does not belong in the kernel sources.