QEMU says no multiboot header found, load kernel first.

[varjmes]

Hello, again.

I got as far as linking my boot.asm and multiboot_header.asm scripts. I had errors trying to turn my files into an .iso but I followed the fix here: #35. Now when I try to load my ISO in QEMU I get:

error: no multiboot header found
error: you need to load the kernel first

As far as I can tell, my code is identical to yours in intermezzOS/kernel. You can see my code here: https://github.com/Charlotteis/charlotteOS

Here is the ouput of the os.iso creation, in case that is useful.

charlotte@var-MacBookPro:~/projects/charlotteOS$ grub-mkrescue -o os.iso isofiles
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, 68.4g free
Added to ISO image: directory '/'='/tmp/grub.09DKxz'
xorriso : UPDATE : 548 files added in 1 seconds
Added to ISO image: directory '/'='/home/charlotte/projects/charlotteOS/isofiles'
xorriso : UPDATE : 552 files added in 1 seconds
xorriso : NOTE : Copying to System Area: 512 bytes from file '/usr/lib/grub/i386-pc/boot_hybrid.img'
xorriso : UPDATE :  100.00% done
ISO image produced: 5489 sectors
Written to medium : 5489 sectors at LBA 0
Writing to 'stdio:os.iso' completed successfully.

I am running a fresh install of Ubuntu 14 LTS on a 2012-ish Macbook Pro.

[steveklabnik]

I checked this out locally, and i can reproduce. Something must be off. I looked at everything and it seems accurate.... I have to step out, so I can't look at this more until tonight, but I would try using diff to compare these to the files in https://github.com/intermezzOS/kernel

[sarahhodne]

It looks like the issue is due to a typo in the checksum calculation here: https://github.com/Charlotteis/charlotteOS/blob/db82812d08db0027831311666f4031ecfb485ff4/multiboot_header.asm#L8

The checksum calculation uses 0xe8520d6 as the magic constant instead of 0xe85250d6. I made the exact same typo when I was going through the steps and got the same error, so I was wondering if the constant had been mistyped in the book, but I couldn't find 0xe8520d6 anyware in the code, so it looks like we just made the same typo.

[varjmes]

🙊 my bad! Will test this is the morning, thanks so much @henrikhodne, I can't wait to keep building this.

[varjmes]

That worked perfectly, thank you @henrikhodne and @steveklabnik!