From f6138df226592bda94117e02e26035f652da1912 Mon Sep 17 00:00:00 2001
From: DualFroz <me@dualfroz.com>
Date: Sun, 23 Aug 2026 09:41:15 +0200
Subject: [PATCH] chore: scaffold build system and linker script

---
 .gitignore |   5 +++
 Makefile   | 111 +++++++++++++++++++++++++++++++++++++++++++++++++++++
 linker.ld  |  62 ++++++++++++++++++++++++++++++
 3 files changed, 178 insertions(+)
 create mode 100644 .gitignore
 create mode 100644 Makefile
 create mode 100644 linker.ld

diff --git a/.gitignore b/.gitignore
new file mode 100644
index 0000000..8651669
--- /dev/null
+++ b/.gitignore
@@ -0,0 +1,5 @@
+build/
+os.iso
+iso/boot/frostbyte.elf
+*.o
+*.elf
diff --git a/Makefile b/Makefile
new file mode 100644
index 0000000..1ea9ba9
--- /dev/null
+++ b/Makefile
@@ -0,0 +1,111 @@
+CC := gcc
+LD := ld
+
+CFLAGS := -std=gnu11 -ffreestanding -nostdlib \
+          -fno-stack-protector -fno-pic -fno-pie \
+          -fno-asynchronous-unwind-tables \
+          -mno-red-zone -mno-mmx -mno-sse -mno-sse2 \
+          -mcmodel=kernel \
+          -Wall -Wextra -Iinclude -g -c
+
+ASFLAGS := -ffreestanding -Iinclude -g -c
+
+LDFLAGS := -nostdlib -z max-page-size=0x1000 --no-warn-rwx-segments -T linker.ld
+
+UCFLAGS := -std=gnu11 -ffreestanding -nostdlib \
+           -fno-stack-protector -fno-pic -fno-pie \
+           -fno-asynchronous-unwind-tables \
+           -mno-red-zone -mno-mmx -mno-sse -mno-sse2 \
+           -Wall -Wextra -Iinclude -Iuser -g -c
+
+UASFLAGS := -ffreestanding -Iinclude -Iuser -g -c
+
+ULDFLAGS := -z max-page-size=0x1000 --no-warn-rwx-segments -e _start -T user/user.ld
+
+BUILD := build
+SRC := src
+USER := user
+UBUILD := $(BUILD)/user
+
+COBJS := $(patsubst $(SRC)/%.c,$(BUILD)/%.o,$(wildcard $(SRC)/*.c))
+SOBJS := $(patsubst $(SRC)/%.S,$(BUILD)/%.o,$(wildcard $(SRC)/*.S))
+OBJS := $(SOBJS) $(COBJS)
+
+USERCOMMON := $(UBUILD)/crt.o $(UBUILD)/ulib.o
+USERPROGRAMS := $(UBUILD)/hello.elf $(UBUILD)/counter.elf \
+                $(UBUILD)/sbrktest.elf $(UBUILD)/fileread.elf
+
+FSFILES := fsroot/etc/motd.txt fsroot/etc/readme.txt fsroot/home/notes.txt
+
+KERNEL := $(BUILD)/frostbyte.elf
+INITRD := $(BUILD)/initrd.img
+MKTAR := $(BUILD)/mktar
+ISO := os.iso
+
+.PHONY: all clean run runserial test
+
+all: $(ISO)
+
+$(BUILD):
+	@mkdir -p $(BUILD)
+
+$(UBUILD):
+	@mkdir -p $(UBUILD)
+
+$(BUILD)/%.o: $(SRC)/%.c | $(BUILD)
+	$(CC) $(CFLAGS) $< -o $@
+
+$(BUILD)/%.o: $(SRC)/%.S | $(BUILD)
+	$(CC) $(ASFLAGS) $< -o $@
+
+$(KERNEL): $(OBJS) linker.ld
+	$(LD) $(LDFLAGS) -o $@ $(OBJS)
+
+$(UBUILD)/%.o: $(USER)/%.c | $(UBUILD)
+	$(CC) $(UCFLAGS) $< -o $@
+
+$(UBUILD)/%.o: $(USER)/%.S | $(UBUILD)
+	$(CC) $(UASFLAGS) $< -o $@
+
+$(UBUILD)/hello.elf: $(UBUILD)/hello.o $(USERCOMMON) user/user.ld
+	$(LD) $(ULDFLAGS) --defsym USER_BASE=0x40000000 -o $@ $(UBUILD)/hello.o $(USERCOMMON)
+
+$(UBUILD)/counter.elf: $(UBUILD)/counter.o $(USERCOMMON) user/user.ld
+	$(LD) $(ULDFLAGS) --defsym USER_BASE=0x50000000 -o $@ $(UBUILD)/counter.o $(USERCOMMON)
+
+$(UBUILD)/sbrktest.elf: $(UBUILD)/sbrktest.o $(USERCOMMON) user/user.ld
+	$(LD) $(ULDFLAGS) --defsym USER_BASE=0x60000000 -o $@ $(UBUILD)/sbrktest.o $(USERCOMMON)
+
+$(UBUILD)/fileread.elf: $(UBUILD)/fileread.o $(USERCOMMON) user/user.ld
+	$(LD) $(ULDFLAGS) --defsym USER_BASE=0x70000000 -o $@ $(UBUILD)/fileread.o $(USERCOMMON)
+
+$(MKTAR): tools/mktar.c | $(BUILD)
+	gcc -O2 -Wall -Wextra -o $@ $<
+
+$(INITRD): $(MKTAR) $(USERPROGRAMS) $(FSFILES)
+	$(MKTAR) $@ \
+	  --dir bin --dir etc --dir home \
+	  --file bin/hello $(UBUILD)/hello.elf \
+	  --file bin/counter $(UBUILD)/counter.elf \
+	  --file bin/sbrktest $(UBUILD)/sbrktest.elf \
+	  --file bin/fileread $(UBUILD)/fileread.elf \
+	  --file etc/motd.txt fsroot/etc/motd.txt \
+	  --file etc/readme.txt fsroot/etc/readme.txt \
+	  --file home/notes.txt fsroot/home/notes.txt
+
+$(ISO): $(KERNEL) $(INITRD) iso/boot/grub/grub.cfg
+	@cp $(KERNEL) iso/boot/frostbyte.elf
+	@cp $(INITRD) iso/boot/initrd.img
+	grub-mkrescue -o $(ISO) iso 2>/dev/null
+
+run: $(ISO)
+	qemu-system-x86_64 -cdrom $(ISO) -serial stdio -m 128M
+
+runserial: $(ISO)
+	qemu-system-x86_64 -cdrom $(ISO) -serial stdio -display none -m 128M -no-reboot
+
+test: $(ISO)
+	sh tools/ci-test.sh
+
+clean:
+	rm -rf $(BUILD) $(ISO) iso/boot/frostbyte.elf iso/boot/initrd.img
diff --git a/linker.ld b/linker.ld
new file mode 100644
index 0000000..a353f4a
--- /dev/null
+++ b/linker.ld
@@ -0,0 +1,62 @@
+ENTRY(_start)
+
+KERNEL_VMA = 0xFFFFFFFF80000000;
+
+PHDRS
+{
+    boot   PT_LOAD FLAGS(7);
+    text   PT_LOAD FLAGS(5);
+    rodata PT_LOAD FLAGS(4);
+    data   PT_LOAD FLAGS(6);
+}
+
+SECTIONS
+{
+    . = 1M;
+    kernelPhysStart = .;
+
+    .boot ALIGN(8) :
+    {
+        *(.multiboot)
+        *(.boot.text)
+        . = ALIGN(4096);
+        *(.boot.pagetables)
+    } :boot
+
+    . += KERNEL_VMA;
+
+    .text ALIGN(4096) : AT(ADDR(.text) - KERNEL_VMA)
+    {
+        *(.text .text.*)
+    } :text
+
+    .rodata ALIGN(4096) : AT(ADDR(.rodata) - KERNEL_VMA)
+    {
+        *(.rodata .rodata.*)
+    } :rodata
+
+    .data ALIGN(4096) : AT(ADDR(.data) - KERNEL_VMA)
+    {
+        *(.data .data.*)
+    } :data
+
+    .bss ALIGN(4096) : AT(ADDR(.bss) - KERNEL_VMA)
+    {
+        bssStart = .;
+        *(COMMON)
+        *(.bss .bss.*)
+        bssEnd = .;
+    } :data
+
+    . = ALIGN(4096);
+    kernelEnd = .;
+    kernelPhysEnd = . - KERNEL_VMA;
+
+    /DISCARD/ :
+    {
+        *(.comment)
+        *(.eh_frame)
+        *(.eh_frame_hdr)
+        *(.note .note.*)
+    }
+}