Biscuit is a monolithic operating system kernel that is written in Go. This talk introduces the kernel and demonstrate how to build, install, and analyze the code.

1. Biscuit: An Operating
System Written in Go
SeongJae Park <sj38.park@gmail.com>

2. These slides were presented for
1st GDG Golang Korea Meetup
(https://www.meetup.com/GDG-Golang-Korea/events/261344405/)

3. This work by SeongJae Park is licensed under the Creative
Commons Attribution-ShareAlike 3.0 Unported License. To
view a copy of this license, visit
http://creativecommons.org/licenses/by-sa/3.0/.

4. I, SeongJae Park
● SeongJae Park <sj38.park@gmail.com>
● PhD candidate at Seoul National University
● Interested in memory management and parallel programming in OS kernels

5. The kernels are written in the C language
● The C language was designed for the operating system kernel (UNIX)
● Most popular *NIX kernels (C, BSD UNIXs, ...) are written in the C language
https://www.oldcomputerbooks.com/pictures/C810975.jpg?v=1315840637

6. Why not the C++?
> When I first looked at Git source code two things struck me as odd:
> 1. Pure C as opposed to C++. No idea why. Please don't talk about
> portability, it's BS.
*YOU* are full of bullshit.
C++ is a horrible language. It's made more horrible by the fact that a
lot of substandard programmers use it, to the point where it's much much
easier to generate total and utter crap with it. Quite frankly, even if
the choice of C were to do *nothing* but keep the C++ programmers out,
that in itself would be a huge reason to use C.
- Linus Torvalds, 2007-09-06 (https://lwn.net/Articles/249460/)

7. … How about Go?
>I wonder what is your opinion about the Go language. Does
>it look like a move in the right direction?
Hey, I think Go picked a few good and important things to look at, but I
think they called it "experimental" for a reason. I think it looks like
they made a lot of reasonable choices.
But introducing a new language? It's hard. Give it a couple of decades,
and see where it is then.
- Linus Torvalds, 2010-06-08 (https://www.realworldtech.com/forum/?curpostid=104302&threadid=104196)
● Almost one decade has already passed (It’s 2019-05-30, now)...

8. Biscuit: An OS kernel in a high-level language
● Biscuit is a monolithic, POSIX-subset operating system kernel in Go
● A research project of the MIT PDOS lab
● Code is available (https://github.com/mit-pdos/biscuit)
● The paper about the project has published to OSDI’18
https://pdos.csail.mit.edu/projects/

9. Brief review of the paper
● I will reuse the slides from the authors rather than inventing another wheel ;)
https://www.usenix.org/sites/default/files/conference/protected-files/osdi18_slides_cutler.pdf

10. Demonstration: Build & Run
$ git clone https://go.googlesource.com/go go1.4; cd go1.4
$ git checkout release-branch.go1.4; cd src
$ ./make.bash
$ cd ../../
$ git clone https://github.com/mit-pdos/biscuit.git; cd biscuit/src
$ ./make.bash
$ cd ../biscuit/
$ make qemu CPUS=2

11. Build: What the ‘make qemu’ did?
● Build bootloader, kernel (src/kernel/bins.go), and applications
● Create the root file system
● Start qemu with the root file system
220 qemu: gqemu
234 gqemu: go.img
235 $(QEMU) $(QOPTS) -nographic
224 QOPTS += -device ahci,id=ahci0
225 -drive file=go.img,if=none,format=raw,id=drive-sata0-0-0
226 -device
125 go.img: $(K)/boot $(K)/main.gobin $(SKELDEPS) $(FSPROGS) ./mkfs
126 ./mkfs $(K)/boot $(K)/main.gobin $@ $(SKEL)
146 $(K)/main.gobin: chentry $(GOBIN) $(K)/bins.go $(KSRC) $(FSRC) $(PSRC)
biscuit/GNUmakefile

12. Code in detail: Page fault handling of Biscuit
● When a process accesses a memory area that is not mapped in the page
table, page fault occurs
● Kernel allocates a page frame and create a mapping in the page table
main (src/kernel/main.go)
Sched_add (src/proc/proc.go)
run (src/proc/proc.go)
trap_proc (src/proc/proc.go)
Pgfault (src/vm/as.go)
Sys_pgfault (src/vm/as.go)
Ptefor (src/vm/vm.go)
pmap_pgtbl (src/vm/pmap.go)
https://qph.fs.quoracdn.net/main-qimg-a6f4d4dc4b1dc24bdb9366d1d20a9718

13. Conclusion
● Biscuit is an OS kernel written in Go
● Benefits and costs of writing a kernel in Go is clear
● You can use, read, and modify the source :D
https://images.fineartamerica.com/images/artworkimages/mediumlarge/2/funny-himalayan-groundhog-with-biscuit-on-a-green-meadow-oleg-ivanov.jpg

14. Thanks