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Ali Shapal•

great work in explaining how all the different pieces of hardware/software come together

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Philipp Oppermann•

Thank you!

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Nitesh Chauhan•

awesome... :) i am definitely trying this out today...

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Georgiy Slobodenyuk•

On mac OS X, for some reason, 


dd - (0xe85250d6 + 0 + (header_end - header_start))

had no compiler warnings, while


dd 0x100000000 - (0xe85250d6 + 0 + (header_end - header_start))

led to 

multiboot_header.asm:7: warning: numeric constant 0x100000000 does not fit in 32 bits

Mac OS X 10.11.1
NASM version 0.98.40 (Apple Computer, Inc. build 11) compiled on Oct 5 2015

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Philipp Oppermann•

Well, that's unfortunate… Thank you for the hint, I opened an issue: https://github.com/phil-opp...

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Philipp Oppermann•

Did you try `brew install nasm` to upgrade to a 2.11.X version?

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Arnaud Bailly•

I found I had to do

nasm -felf64 boot.S

to generate correct code, after doing `brew install nasm`.

HTH

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Tom Smeding•

If (in my case on Mac OS X) grub-mkrescue (after you've installed it) gives the error "grub-mkrescue: warning: Your xorriso doesn't support `--grub2-boot-info'.", you just need to install xorriso. You probably don't have it at all yet.

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Tom Yandell•

For me (running it in an ubuntu docker container), grub-mkrescue silently fails until you add the -v flag - only with that can you see the error about xorriso (took me a lot of head-scratching to figure it out).

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Philipp Oppermann•

Thanks, I added a note about `--verbose`.

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Reid•

Do you have any instructions on how you got grub built on OS X? Can't get it to build successfully for the x86_64-elf target and the default EFI target won't work with qemu...

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Tom Smeding•

What are your exact problems? IIRC I built it from source as well, but don't remember exactly what I fixed. Stuff did error here and there, I think...

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Reid•

./rs_decoder.h:2:Unknown pseudo-op: .macosx_version_min
./rs_decoder.h:2:Rest of line ignored. 1st junk character valued 49 (1).
clang: error: assembler command failed with exit code 1 (use -v to see invocation)
make[3]: *** [boot/i386/pc/lzma_decompress_image-startup_raw.o] Error 1

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emk1024•

This is an awesome series of blog posts!

If you don't see a green "OK", look for a "GRUB" message. If you don't see "GRUB", then the weak link is probably grub-mkrescue. Two common failure modes:

1. If your grub-mkrescue isn't installed correctly, it may silently do nothing or make bad ISO files. Try mounting your ISO file to make sure that it has your kernel and grub.cfg.

2. If you run Linux on an EFI machine, grub-mkrescue will produce EFI boot images that don't work with BIOS-based systems like QEMU. To fix this, see this article, which recommends installing grub-pc-bin and running:

grub-mkrescue /usr/lib/grub/i386-pc -o myos.iso isodir

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Philipp Oppermann•

Thank you, I didn't know about the EFI issue...

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Jon•

Thanks, that second tip saved me.

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Anonym•

Thank you! This really helped.

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Tom Yandell•

On OSX and found I needed x86_64‑elf‑ld and x86_64‑elf‑objdump. With macports was as simple as:

> sudo port install x86_64-elf-gcc

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Arnaud Bailly•

This is definitely fun! I tried to do this from my Mac OS X (Yosemite) and could not properly boot my fresh ISO disk. Compilation works fine, I have installed a cross-compiler for x86_64-elf architecture, compiled grub following instructions here https://wiki.osdev.org/GRUB_...... I generate a correct ISO file (checked it by mounting using Disk Utility) but it does not boot and I cannot see the GRUB message.

Not sure how to troubleshoot this issue.... I suspect this might be a problem with incorrect format in grub as the last stage of compilation shows this message:

../grub/configure --build=x86_64-elf --target=x86_64-elf --disable-werror TARGET_CC=x86_64-elf-gcc TARGET_OBJCOPY=x86_64-elf-objcopy TARGET_STRIP=x86_64-elf-strip TARGET_NM=x86_64-elf-nm TARGET_RANLIB=x86_64-elf-ranlib LD_FLAGS=/usr/local/opt/flex/ CPP_FLAGS=/usr/local/opt/flex/include/

[..]

config.status: linking ../grub/include/grub/i386 to include/grub/cpu
config.status: linking ../grub/include/grub/i386/pc to include/grub/machine
config.status: executing depfiles commands
config.status: executing po-directories commands
config.status: creating po/POTFILES
config.status: creating po/Makefile
*******************************************************
GRUB2 will be compiled with following components:
Platform: i386-pc
With devmapper support: No (need libdevmapper header)
With memory debugging: No
With disk cache statistics: No
With boot time statistics: No
efiemu runtime: Yes
grub-mkfont: Yes
grub-mount: No (need FUSE headers)
starfield theme: No (No DejaVu found)
With libzfs support: No (need zfs library)
Build-time grub-mkfont: No (no fonts)
Without unifont (no build-time grub-mkfont)
With liblzma from -llzma (support for XZ-compressed mips images)
*******************************************************

I don't know what the i386-pc refer too, but if this is the target platform then it's probably incorrect. Note that I tried to boot using qemu-system-i386 but to no avail.

Regards,

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Arnaud Bailly•

Forget it: grub-mkrescue was not correctly installed so it failed to add needed boot files.

Thanks again for sharing this!

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Chris Cerami•

I'm having an issue where x86_64-elf-gcc isn't found when I try to configure grub, and when I checked I see that it's not included in binutils with the other x86_64-elf tools. How did get x86_64-elf-gcc on OS X?

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Arnaud Bailly•

It should be as simple as `brew install x86_64-elf-gcc x86_64-elf-binutils`

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jcaudle•

It's probably worth noting that you'll need to do `brew tap sevki/gcc_cross_compilers` or `brew tap alexcrichton/formula` to get these formulae. (Sevki's tap has newer cross compilers)

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George•

What would happen if we didn't put hlt? Would the cpu start reading random bytes and execute them as code? I tried without hlt and qemu seems to go into an infinite boot loop, but I'm just wondering what's going on.

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Philipp Oppermann•

Yes, that exactly what happens. The CPU simply tries to read the next instruction, even if it doesn't exist, until it causes some exception. QEMU can print these exceptions, the "Setup Rust" post explains how. I just tried it and it hits an Invalid Opcode exception at some point because some memory is no valid instruction.

Bonus: You can use GDB to disassemble the “code” behind the start label. You need to start `qemu-system-x86_64 -hda build/os-x86_64.iso -s -S` in one console and `gdb build/kernel-x86_64.bin` in another. Then you need the following gdb commands:

- `set architecture i386` because we are still in 32-bit mode
- `target remote :1234` to connect to QEMU
(- `disas /r start,+250` to disassemble the 250 bytes after the `start` label. Everything will be 0 as GRUB did not load our kernel yet)
- `break start` to set a breakpoint at `start`
- `continue` to continue execution until start is reached. Now the kernel is loaded and we can use
- `disas /r start,+250` to disassemble the 250 bytes after the `start` label

Then you can look at the faulting address you got from the QEMU debugging to see your invalid instruction. For me it seems to be an `add (%eax),%al` with the Opcode `02 00`.

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George•

I'm late in replying but just wanted to say thanks so much! It's really neat to learn about something that I used to believe only experts could get into.

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Sanjiv•

oh! What a wonderful article to read!

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Philipp Oppermann•

Thank you :)

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Lifepillar•

Nice post! I am on OS X, but I find it easier to use Linux for this assembly stuff. Using VirtualBox, I have created a minimal Debian machine running an SSH server and with a folder shared between the OS X host and the Debian guest. So, I may install all the needed tools and cross-compile in Debian and have the final .iso accessible in OS X (to use it with QEMU), all of this while working in Terminal.app as usual.

As a side note, I had to set LDEMULATION="elf_x86_64" before linking, because I was getting this error: `ld: i386:x86-64 architecture of input file `multiboot_header.o' is incompatible with i386 output`. This may be because I have used Debian's 32-bit PC netinst iso instead of the 64-bit version.

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Philipp Oppermann•

Thanks for sharing your experiences! There is an issue about Mac OS support, but it seems like using a virtual machine is the easiest way…

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Robert Huang•

Man this is too fucking awesome!

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Dmitry Nikolayev•

On my system and on some others grub-makerescue is actually called grub2-makerescue and should be represented accordingly in the makefile. Perhaps this merits a comment in the text since I was not alone (https://www.reddit.com/r/os... in spending some time trying to figure out what was happening after a rather meaningless error message from make.

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Philipp Oppermann•

Thanks! I opened an issue.

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GW seo•

When I run grub-mkrescue I got no output an just silence

after install xorriso I got error like this
-----
xorriso 1.3.2 : RockRidge filesystem manipulator, libburnia project.

Drive current: -outdev 'stdio:os.iso'

Media current: stdio file, overwriteable

Media status : is blank

Media summary: 0 sessions, 0 data blocks, 0 data, 861g free

Added to ISO image: directory '/'='/tmp/grub.pI5jyq'

xorriso : UPDATE : 276 files added in 1 seconds

Added to ISO image: directory '/'='/path/to/my/work/isofiles'

xorriso : FAILURE : Cannot find path '/efi.img' in loaded ISO image

xorriso : UPDATE : 280 files added in 1 seconds

xorriso : aborting : -abort_on 'FAILURE' encountered 'FAILURE'

-----

and I search for resolve this error, I arrive here[ https://bugs.archlinux.org/42334 ]

after isntall mtools, grub-mkrescue create os.iso

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Phil•

After creating the iso, I can boot to it on QEMU with no problem. Even burning it on to a disk and booting on a different machine works like a charm. However, I am having trouble getting it on to an USB thumb drive. I have tried packing it on to a USB with UNetbootin, but as soon as the UNetbootin screen appears after booting to the USB device, (The OS selection screen, giving you the options [Default] and [my_os]), nothing happens. I can select either of those options, but nothing happens.

EDIT: Got it to work using the command line tool dd!

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Philipp Oppermann•

I just wanted to suggest dd! For the record, the command is sudo dd if=build/os.iso of=/dev/sdX && sync where sdX is the device name of your USB stick. It overwrites everything on that device, so be careful to choose the correct device name.

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Phil•

Yes, I noticed that in the documentation, had me worried for a second ;-)

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liveag•

@phil_opp:disqus i created a GitHub repository where i work through your great guide step-by-step. It is located here: https://github.com/peacememories/rust-kernel-experiments
Please let me know if there are problems with the attribution. =)

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Philipp Oppermann•

Great! Let me know if you find any rough edges :).

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mopp•

Thanks you for your great articles.
I have created my OS in Rust, and these are really useful for me.
I have been revising my OS based on your articles.
Also, I have been writing an article which is similar to your
http://mopp.github.io/articles/os/os00_intro

I added link into my articles to this website.
If you feel unpleasant, please tell me and I will remove it.

Thanks

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Philipp Oppermann•

Thanks! I don't speak Japanese, so I can only read the rough google translation. However, your article seems to be a really good and introduction to OS development!

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mopp•

Many thanks :)
I have been looking forward to your new articles !

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Nick•

I really enjoyed your accessible blog format and your awesome osdev tutorials!
I was inspired by your articles and decided to write my own :)
Let me know what you think.

http://tutorialsbynick.com/...

Thanks,
Nick

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Philipp Oppermann•

It's awesome! I really like that you start without a bootloader and interact with the BIOS directly in real mode. I never programmed at this level, so it was a really great read!

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jpmrno•

If having trouble installing Binutils or GRUB, here are some brew packages:

BINUTILS:
'brew install jpmrno/apps/crossyc --without-gcc'

GRUB (this will install everything needed):
'brew install jpmrno/apps/grub'

Hope it helps!

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Antonio•

Hi guys if you want to boot the kernel in VirtualBox just modify the grub cfg file by setting the following variable properly, check https://www.gnu.org/softwar... for the options.

GRUB_TERMINAL_OUTPUT

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Andrii Zymohliad•

This blog is just a treasure! I'm so happy that I found it. Thank you so much Phil!

By the way, my Arch Linux is booted in legacy BIOS mode (my BIOS doesn't even support EFI), but without '-d /usr/lib/grub/i386-pc/' grub-mkrescue didn't work for me.

P.S. Aside from this project, I think I will refer to your Makefile lot of times in future just to learn techniques that you used. I think it is the shortest example of so many Makefile best practices.

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Philipp Oppermann•

Thanks a lot! :)

Unfortunately I have no idea what's the problem here. I've never had this error.

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Andrii Zymohliad•

Ough.. probably you replied to first edition of my comment, but I didn't reload the page and didn't see your reply. Then I found my mistake (I put grub directory into the root of image, not into boot directory). And while thinking that nobody have seen my comment yet I edited it and removed the question about error. Sorry for my careless.

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Philipp Oppermann•

No worries! Good to hear that you could fix the error.

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Andrey Zloy•

Just perfect. Thnx!

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Кирилл Царёв•

Why for the development of the core operation system, the language Rust? Why not C++? Does Rust have such opportunities as in C++?

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Philipp Oppermann•

Rust aims to be comparable to C++, both it terms of capabilities and in terms of performance. However, it has some great advantages over C++:

The greatest advantage of Rust is its memory safety. It prevents common bugs such as use after free or dangling pointers at compile time. So you get the safety of a garbage collected language, but without garbage collection. In fact, the safety guarantees go even further: The compiler also prevents data races and iterator invalidation bugs. So we should get a much safer kernel compared to C++.

(One caveat: Sometimes we need unsafe blocks for OS development, which weaken some safety guarantees. However, we try to use them only when it's absolutely needed and try to check them thoroughly.)

Another advantage of Rust is the great type system. It allows us to create powerful, generic abstractions, even for low level things such as page tables.

The tooling is great, too. Rust uses a package manager called “cargo”, which makes it easy to add various libraries to our project. Cargo automatically downloads the correct version and compiles/links it. Thus, we can use awesome libraries such as x86 easily.

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Кирилл Царёв•

Interesting... so what Rust is to replace C++, since he has so many advantages over C++?

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Philipp Oppermann•

so what Rust is to replace C++

Sorry, I don't understand this question. Could you rephrase it?

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Andrey Zloy•

Its easy to link kernel on Ubuntu 32-bit. Just need to add -m elf_x86_64 option to linker.
ld --nmagic -m elf_x86_64 -o kernel.bin -T linker.ld multiboot_header.o boot.o

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Lonami•

For anyone else struggling with "Boot failed: Could not read from CDROM (code 0009)", you need to install `grub-pc-bin` and then regenerate the .iso. Solution from here: http://intermezzos.github.io/book/appendix/troubleshooting.html#could-not-read-from-cdrom-code-0009.

By the way, I'm loving the tutorial style. Very clear, thank you!

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Philipp Oppermann•

Thanks so much!

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Philip•

I love you

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skierpage•

This is completely awesome!

YMMV but FWIW in Fedora 25, I needed to install three packages, `sudo dnf install nasm xorriso qemu-system-x86`. The last one installs fewer packages than installing "qemu" which adds two dozen ARM, m68k, S390, sparc, ... emulators as well 8-)

I find the example displays "OK" fine, but it erases the console before this so the boot messages disappear. I'm not sure if the fix lies in grub configuration or the qemu command line.

It is interesting to look at the contents of the CD-ROM image, though it mostly reveals the complexity of the GRUB bootloader. I used `mkdir temp_mount && sudo mount -t iso9660 -o loop os.iso temp_mount` then looked around in temp_mount.

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Harry Rigg•

I had 2 issues with making the iso. First, there was no output file, yet grub-mkrescue didn't complain, I fixed this by running "apt install xorriso" (Ubuntu). The other issue was that qemu couldn't read the cdrom (error 0009), fixed that one by running "apt install grub-pc-bin". Hope this helps some of you... and thanks for the awesome post Phil :)

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Mrvan•

How to shutdown?

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M. Wagner•

The Makefile doesn't work for me. It gives only the error No rule to make target ' build/arch/x86_64/boot.o' needed by 'build/kernel-x86_64.bin'. I don't know what's going wrong....

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Philipp Oppermann•

It seems like there is some problem with this lines:

build/arch/$(arch)/%.o: src/arch/$(arch)/%.asm

Do you have a file named build/arch/x86_64/boot.asm? For debugging, you could use explicit names instead of the wildcards (%):

build/arch/$(arch)/boot.o: src/arch/$(arch)/boot.asm

(Note that you need to copy this rule for every .asm file without wildcards.)

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Anonym•

I'm interested whether it would run on actual hardware, with a real CD. I doubt anyone tried it though...

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Philipp Oppermann•

Yes, it works on real hardware! If not, please file an issue.

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Dendyard•

Lot of tutorials together. Thanks man (y)

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Darryl Rees•

This is incredible, just fantastic..

I did have a couple of hiccups following along using Win10 WSL on a UEFI PC, maybe these details can be folded in to the tutorial?

1) Couldn't boot QEMU with emulated video device

warning: TCG doesn't support requested feature: CPUID.01H:ECX.vmx [bit 5]

  Could not initialize SDL(No available video device) - exiting

Solution: Use -curses option for qemu

qemu-system-x86_64 -curses -cdrom os-x86_64.iso

2) Could not boot from ISO (on a UEFI system)

  Booting from DVD/CD...

   Boot failed: Could not read from CDROM (code 0004)

                         Booting from ROM...

Solution: sudo -S apt-get install grub-pc-bin

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Naad•

I am having the same issue as you have mentioned in number one. It says warning: TCG doesn't support requested feature: CPUID.01H:ECX.vmx [bit 5] And it is not printing out OK, I tried with the -curses option for qemu but not working.

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Myst•

I'm trying to do this, but I can't get the OK to actually display and I've kind of ran out of ideas. Trying to run with QEMU on Arch Linux.

Things I've tried: Adding the multiboot tag that should tell grub I want a text mode, 80x25. Just gives me a black screen, instead of saying "Booting 'my os'"

Switching grub to text mode with every possible switch I can find that looks related, with and without ^. Just gives me a black screen for all of them too. I can confirm my code actually seems to be executed - or, at least, hits the hlt instruction. Just that there's no output, which makes me think VGA problems, hence me trying all of the above. That seems to leave trying to parse the multiboot header or something, and that seems like... something I don't really want to try to do in assembly, including pushing it over assembly? I don't really want to move unless this works, though, because I see you still are using text mode extensively further on. :/

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Myst•

...Never mind. I just figured out, and it was a very tiny mistake. I accidentally typed 0xb800 instead of 0xb8000, so, of course, no output ever because I was copying to the wrong region of memory.

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Person•

RIP windows users

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Anonym•

Hi. Thanks for write, but i have an error when i run it in qemu - "error: no multiboot header found, error: you need to load kernel first". Whats wrong?

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Philipp Oppermann•

It means that GRUB couldn't find a multiboot header at the beginning of your kernel. So either your multiboot header is invalid (maybe a typo somewhere?) or it is not at the beginning of the file (is your linker script correct? did you use the --nmagic flag?).

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Anonym•

I just found this and it is great. Clear, practical explanations without fuss but that don't hide what's going on. That's perfect for how I like my tech explanations

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Philipp Oppermann•

Thanks so much!

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Aswani Kumar•

Thank you so much for the article. It is of great help to understand the basics of developing OS. Especially the in hand experience.

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Philipp Oppermann•

Thanks! Glad that it's useful to you :)

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Fabio•

Thank you for this series, it's exceptional! Clear, deep into details, and fascinating :)

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Philipp Oppermann•

Thank you :)

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Anonym•

For anyone trying to push themselves into using the GNU assembler (i.e. as), if you're getting "no multiboot header" errors with QEMU, put the line:

.align 8

before the end tags.

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windows technical support•

is it possible to manipulate the windows kernel. Which language is used in developing windows kernel?

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