init

.gitignore

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+.build

LICENSE

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+MIT License
+
+Copyright (c) 2026 nub31
+
+Permission is hereby granted, free of charge, to any person obtaining a copy of this software and associated documentation files (the "Software"), to deal in the Software without restriction, including without limitation the rights to use, copy, modify, merge, publish, distribute, sublicense, and/or sell copies of the Software, and to permit persons to whom the Software is furnished to do so, subject to the following conditions:
+
+The above copyright notice and this permission notice shall be included in all copies or substantial portions of the Software.
+
+THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.

README.md

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+# Nub OS
+
+## Dependencies
+
+### Building the kernel
+
+- `grub`
+- `mtools`
+- `make`
+- `x86_64-elf-gcc`
+- `x86_64-elf-ld`
+- `nasm`
+
+## Building
+
+### Disk image
+
+```sh
+make iso
+```
+
+## Running
+
+After building the iso, run the following:
+
+```sh
+qemu-system-x86_64 -cdrom .build/nub-os.iso
+```
+
+## Debugging
+
+```sh
+qemu-system-x86_64 -s -S -cdrom .build/nub-os.iso
+gdb -tui .build/kernel/kernel -ex "target remote localhost:1234"
+```

makefile

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+CC = x86_64-elf-gcc
+LD = x86_64-elf-ld
+AS = nasm
+
+# Modify these settings here for defines and debug info
+# CFLAGS 	= -g -D DEBUG
+# LDFLAGS = -g
+# ASFLAGS = -g -F dwarf
+
+# Do not modify
+CFLAGS 	+= -m64 -ffreestanding -nostdinc -nostdlib -Wall -Wextra -Wshadow -std=c23
+LDFLAGS	+=
+ASFLAGS	+= -f elf64
+
+SRC_C	:= $(shell find src -name '*.c')
+SRC_ASM := $(shell find src -name '*.asm')
+
+OBJS := $(patsubst src/%.c, .build/%.o, $(SRC_C)) $(patsubst src/%.asm, .build/%.o, $(SRC_ASM))
+
+iso: .build/nub-os.iso
+	@echo "ISO created at '.build/nub-os.iso'"
+
+run: .build/nub-os.iso
+	qemu-system-x86_64 -cdrom .build/nub-os.iso
+
+clean:
+	@rm -r .build 2>/dev/null || true
+
+.build/nub-os.iso: .build/nub-os src/grub.cfg
+	mkdir -p .build/grub/boot/grub
+	cp src/grub.cfg .build/grub/boot/grub
+	cp .build/nub-os .build/grub/boot/
+	grub-mkrescue -o .build/nub-os.iso .build/grub/
+
+.build/nub-os: $(OBJS)
+	$(LD) $(LDFLAGS) -T src/linker.ld -o $@ $^
+
+.build/%.o: src/%.c
+	@mkdir -p $(dir $@)
+	$(CC) $(CFLAGS) -c -o $@ $<
+
+.build/%.o: src/%.asm
+	@mkdir -p $(dir $@)
+	$(AS) $(ASFLAGS) -o $@ $<

src/boot.asm

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+global entry
+
+%define MAGIC   0xe85250d6
+%define ARCH    0x0
+%define LENGTH  (header.end - header.start)
+
+section .multiboot
+align 8
+header:
+    .start:
+        dd MAGIC
+        dd ARCH
+        dd LENGTH
+        dd -(MAGIC + ARCH + LENGTH)
+        ; end tag
+        dw 0
+        dw 0
+        dd 8
+    .end:
+
+section .text
+bits 32
+entry:
+    jmp $

src/grub.cfg

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+menuentry "nub-os" {
+    multiboot2 /boot/nub-os
+}
+
+set default="nub-os"
+set timeout=0

src/linker.ld

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+ENTRY(entry)
+
+SECTIONS
+{
+	. = 2M;
+
+	.text :
+	{
+		*(.multiboot)
+		*(.text)
+	}
+
+	.rodata :
+	{
+		*(.rodata)
+	}
+
+	.data :
+	{
+		*(.data)
+	}
+
+	.bss :
+	{
+		*(COMMON)
+		*(.bss)
+	}
+
+	kernel_end = .;
+}