Building goes wrong (sometimes)

Bleksak · **Joined:** Fri Aug 04, 2017 7:39 am **Posts:** 6

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:

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

Attachment:

File comment: The wrong build

Screenshot_1.png [ 34.47 KiB | Viewed 2603 times ]

Attachment:

File comment: The correct build

Screenshot_2.png [ 33.39 KiB | Viewed 2603 times ]

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

zaval · **Posted:** Fri Aug 04, 2017 2:05 pm

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 · **Joined:** Fri Aug 04, 2017 7:39 am **Posts:** 6

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 · **Posted:** Fri Aug 04, 2017 10:18 pm

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 · **Joined:** Fri Aug 04, 2017 7:39 am **Posts:** 6

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

Octocontrabass · **Joined:** Mon Mar 25, 2013 7:01 pm **Posts:** 5134

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 · **Joined:** Fri Aug 04, 2017 7:39 am **Posts:** 6

Octocontrabass wrote:

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 · **Joined:** Mon Mar 25, 2013 7:01 pm **Posts:** 5134

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 · **Joined:** Fri Aug 04, 2017 7:39 am **Posts:** 6

Octocontrabass wrote:

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!

OSDev.org

Building goes wrong (sometimes)

Who is online