originalmk/mkos32
1
0
Fork 0
mirror of https://github.com/originalmk/mkos32.git synced 2024-10-03 09:16:10 +00:00
Code Issues Actions Packages Projects Releases Wiki Activity
💾 32-bit operating system displaying current date and time
16 Commits 1 Branch 0 Tags 744 KiB
C 92.2%
Assembly 7.8%
ee8230b8f2
Go to file
Maciej Krzyżanowski ee8230b8f2 Update .gitignore 
Added notes, because they should not be in repository, but it is useful
to have them locally in the same directory. Changed entries for
individual files to directory ignores.
2024-08-19 23:57:32 +02:00
config Repair permissions 2024-08-19 23:57:32 +02:00
scripts Reorganised files into directories 2024-08-19 23:56:10 +02:00
source Repair permissions 2024-08-19 23:57:32 +02:00
.gitignore Update .gitignore 2024-08-19 23:57:32 +02:00
mkos32.png Add README.md 2024-08-19 23:57:32 +02:00
README.md Add README.md 2024-08-19 23:57:32 +02:00

README.md

💾 MKOS32

MKOS32 is very basic operating system, the only thing it can do is printing current date and time twice a second.

mkos running in bochs emulator

Steps

General list of steps which led me to the current state of project:

  1. Cross compilation, preparing gcc and bintuils to compile programs for my OS
  2. Loading operation system, I used GRUB and Multiboot 1 to achieve that
  3. Printing text (useful for debugging), based on VGA, based on osdev wiki code, but extended with ability to:
    • scrolling text when there is no space left
    • ability to use newline character
    • printing numbers in various bases or with '0' padding
    • basic and limited printf
  4. Setting up GDT to a flat memory model (currently only supported model in newer versions of GCC) - for memory protection/isolation paging should be used
    • sources/gdt.h
    • refreshing segment registers (far jump for CS)
    • placing GDT table in memory and loading it using lgdt instruction
  5. Installing and setting up bochs emulator, which made debugging significantly easier
    • memory dumping
    • breakpoints (xchg %bx, %bx)
    • displaying GDT/IDT tables
  6. Interruption handling
    • sources/idt.h
    • set IDT table
    • 8259A PIC initialisation (master and slave, appropriate masks etc)
    • written basic ISRs
    • loaded IDT with lidt
    • one of ISRs is used to handle clock interruptions coming from RTC (real time clock)
    • communication through ports (helper functions outb and inb)
    • RTC configuration

Sources

I used mainly OsDev wiki, Intel x86 ISA and some other related pages as my knowledge source.: