Building goes wrong (sometimes)

[Bleksak]

Hello, I'm having this strange problem, I started with the FAT filesystem and when I try to load a file into memory, I get different results every build.

I posted 2 images so you know, what I'm talking about.

This is my build code, I'm using Windows 10

Code: Select all

DEL /F Build\Image.img
DEL /F Bin\BootLoader.bin
DEL /F Bin\Kernel.bin

imdisk -D -m P:

nasm -f bin -o Bin/BootLoader.bin Dev/BootLoader.asm

nasm -f bin -o Bin/Kernel.bin Dev/Kernel.asm

nasm -f bin -o Bin/TestApp.bin Dev/RandomApp.asm

imdisk -a -f Build/Image.img -s 1440K -m P: -p "/FS:FAT /Y"
imdisk -D -m P:

dd if="Bin/BootLoader.bin" of="Build/Image.img" bs=512 count=1

imdisk -a -f Build/Image.img -m P:

copy Bin\Kernel.bin P:\
copy Bin\TestApp.bin P:\
copy Tische.txt P:\

imdisk -D -m P:

pause

The wrong build

The correct build

This happens randomly, but all the time.. I even tried assembling and copying all my files manually, but got the same result.

[zaval]

i quickly looked at the hexdump, it looks like directory entries. the only difference, i've noticed, is in the fields DIR_CrtTime and DIR_WrtTime. which is probably a normal behaviour.

[Bleksak]

Well then it's even more weird, cause I get random behavior..

Wrong Build
http://prntscr.com/g4h8ra

Correct Build
http://prntscr.com/g4h7hx

[snijj]

It's pretty hard to give advice on what is wrong if you don't provide us all the information. Please provide a link to the source code you are trying to compile.

[Bleksak]

https://bitbucket.org/Bleksak/velekos/

[Octocontrabass]

Why are you writing a real-mode OS?

Are you setting up the stack? You might be overflowing the stack set up by the BIOS.

If your code has hlt with interrupts disabled, some emulators will stop before showing the last thing you displayed on the screen. Replace it with an infinite loop (jmp $) and see if that makes a difference.

[Bleksak]

Why are you writing a real-mode OS?

Are you setting up the stack? You might be overflowing the stack set up by the BIOS.

If your code has hlt with interrupts disabled, some emulators will stop before showing the last thing you displayed on the screen. Replace it with an infinite loop (jmp $) and see if that makes a difference.

For fun, I guess.. I set the stack, changed all hlts to jmp $ but still have the same problem..

[Octocontrabass]

Your strcmp function clobbers several registers that are in use when you call it from disk_load_file.

You should document the calling conventions for all of your functions, so you know exactly which registers will be modified.

[Bleksak]

Your strcmp function clobbers several registers that are in use when you call it from disk_load_file.

You should document the calling conventions for all of your functions, so you know exactly which registers will be modified.

You sir, are a genius, I don't know why I didn't pusha/popa in strcmp when I was writing it though, but you sir fixed my problem! Thank you!