About

JyrOS is a kernel developped to learn the basics about kernel programming. It is written in C and nasm and developped for an i386 architecture.

It follows the 42 school Kernel From Scratch series.

Sneak Preview: Discover the next features on the branch kfs5: process and signal handling, as well as a fully reorganized library.

Features

• boot via Grub
• 8 different terminals
  • 80 x 25 chararcters VGA text mode (code page 437)
  • PS/2 keyboard handling (scan code set 1) (qwerty and azerty layout)
  • scrolling
  • cursor management
• Global Descriptor Table
  • flat segmentation model
• Paging and Virtual Memory
  • page tables (two levels)
  • separated user and kernel space (higher half kernel)
  • virtual and physical allocation
  • buddy allocator
  • malloc and free
• kernel Panic fault handling
• interrupts handling (hardware and software)
• clock handling

Build from sources

Requirements

• Docker
• QEMU
• GDB

Compiling

• Compiling the kernel requires a cross-compiler for the i386 architecture. Our cross-compiler is in a docker that will be downloaded automatically, unless you prefer to build it locally with: make build_docker.
• The kernel is build with the command: make.
• To run the kernel on QEMU:
  • using the iso (start with Grub): make start_iso
  • or the binary (skip Grub): make start_bin

Debug

• For debugging, you can start a gdb session.
• GDB will run in a separate window.
• A default breakpoint is put on kernel_main.
• make debug

terminal

Up to 8 terminals are available.

terminal shortcuts

• C^ left: previous terminal
• C^ right: next terminal
• C^ [: switch foregroud color
• C^ ]: switch background color

terminal builtins

• echo
  • echo <oneword>
  • print the word given as argument
• azerty
  • switch to an AZERTY keyboard
• qwerty
  • switch to a QWERTY keyboard
• interrupt
  • interrupt <number>
  • call the interrupt given as argument
  • see the interrupts section
• bootinfos
  • print infos about boot process
• registers
  • print registers state
• readdump
  • print the stack memory dumped after a Kernel Panic Reboot
• hexdump
  • print the stack
• uptime
  • print time since last boot
• testStackDump
  • test the stack dump mechanism
  • will reboot the computer
• halt
  • turn off the kernel
• reboot
  • reboot the kernel

Interrupts

• Int 0: Divide Error
• Int 1: Debug Exception
• Int 2: Non Maskable Interrupt
• Int 3: Breakpoint
• Int 4: Overflow
• Int 5: Bounds Check
• Int 6: Invalid Opcode
• Int 7: Coprocessor Not Available
• Int 8: Double Fault (error code)
• Int 9: Coprocessor Segment Overrun
• Int 10: Invalid TSS (error code)
• Int 11: Segment Not Present (error code)
• Int 12: Stack Exception (error code)
• Int 13: General Protection Fault (error code)
• Int 14: Page Fault
• Int 15: reserved
• Int 16: Coprocessor Error
• Int 21: marked as NOT PRESENT. Calling it will trigger a Segement Not Present (10) error
• Int 32: Timer
• Int 33: Keyboard

Tests

• test builtins:
  • testStackDump
• test functions:
  • srcs/interrupts/interrupts_test.c:
    • zero_divide_test()
    • debug_exception_test()
    • nmi_test()
    • breakpoint_test()
    • overflow_test()
    • bound_test()
    • invalid_opcode_test()
    • coprocessor_not_available_test()
    • double_fault_test()
    • copro_segment_test()
    • invalid_tss_test()
    • segment_not_present_test()
    • stack_exception_test()
    • general_protection_test()
    • coprocessor_error_test()
  • srcs/memory/mbook.c:
    • mbook_test()
    • memory_test_vmbook()
  • srcs/memory/memory.c:
    • memory_test()
  • srcs/memory/paging.c:
    • page_testing()