Build & Toolchain

Requirements

• NASM — bootloader (-f bin) + entry (-f elf32)
• GCC with -m32 — freestanding kernel
• binutils — ld, objcopy
• QEMU — qemu-system-i386, 256 MiB, rtl8139, vmware VGA

Usage

make              # builds nexos.img
make run          # boots nexos.img in QEMU
make clean        # removes *.bin *.o *.tmp *.img

Build pipeline

boot.bin:        nasm -f bin boot.asm -o boot.bin
kernel_entry.o:  nasm -f elf32 kernel_entry.asm -o kernel_entry.o
ata.o:           gcc -m32 -ffreestanding -nostdlib -fno-pie -O2 -fleading-underscore -c ata.c
fat32.o:         gcc ... -c fat32.c
net.o:           gcc ... -c net.c
kernel.o:        gcc ... -c kernel.c
kernel.tmp:      ld -m elf_i386 -N -e _start -T link.ld -o kernel.tmp \
                    kernel_entry.o ata.o fat32.o net.o kernel.o
kernel.bin:      objcopy -O binary kernel.tmp kernel.bin
nexos.img:       dd zero 64 sectors; dd boot.bin -> sector 0; dd kernel.bin -> sector 1+

Disk image layout

nexos.img — 32,768 bytes (64 sectors x 512)
+---------------------------------------------+
| sector 0 | sectors 1..63 (kernel.bin padded)|
| boot.bin | objcopy'd kernel (ata+fat32+net) |
+---------------------------------------------+
dd if=/dev/zero of=nexos.img bs=512 count=64
dd if=boot.bin    of=nexos.img bs=512 count=1 conv=notrunc
dd if=kernel.bin  of=nexos.img bs=512 seek=1  conv=notrunc

Linker script (link.ld)

SECTIONS
{
    . = 0x8000;
    .text   : { kernel_entry.o(.text) *(.text) *(.text.startup) }
    .rodata : { *(.rodata) *(.rodata.*) }
    .data   : { *(.data) }
    .bss    : { *(.bss) }
}

kernel_entry.o(.text) first so _start lands at 0x8000 (the bootloader’s KERNEL_OFFSET).

Compiler flags

QEMU invocation

qemu-system-i386 -drive format=raw,file=nexos.img \
  -device rtl8139,netdev=n0 -netdev user,id=n0 -vga vmware -m 256

-vga vmware lets high VESA modes probe; rtl8139 provides the NIC the driver expects at 0x300/IRQ11.

• Makefile as in current tree (no start.bat, AL=60, vmware + rtl8139).