initial commit

.gitignore

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+*.iso
+isodir
+sysroot
+
+.idea
+.vscode

boot.ld

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+ENTRY(_start)
+
+SECTIONS
+{
+  . = 0x7C00;
+
+  .text : {
+    *(.text)
+  }
+
+  .data : { 
+    *(.data)
+  }
+}

boot.s

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+.code16
+.text
+.global _start
+_start:
+	ljmp $0x07C0, $something
+
+something:
+	cli
+	cld
+
+	mov %cs, %ax
+	mov %ax, %ds
+	mov %ax, %es
+
+	# stack stuff
+	mov $0x0000, %ax
+	mov %ax, %ss
+	mov $0xFFF0, %sp
+
+	# copy the first 12 bytes of our MBR table entry
+	mov %dl, (disk_number)
+	mov $mbr_entry, %di
+	mov $12, %cx
+	rep movsb
+
+	mov $0, %ah
+	int $0x13
+	
+	mov $0x08, %ah
+	int $0x13
+	and 0b00111111, %cl
+	mov %cl, (total_sectors)
+	mov %ch, (total_cylinders)
+	mov %dh, (total_heads)
+
+	mov $0x1000, %ax
+	mov %ax, %es
+	mov $0x0000, %bx
+
+	mov (disk_number), %dl
+	mov $0, %ch #cylinder
+	mov $0, %dh #head
+	mov $2, %cl #sector
+
+load_sector:
+	mov $1, %al
+	mov $0x02, %ah
+	int $0x13
+
+	mov (kernel_sectors), %ax
+	cmp $0xffff, %ax
+	jne check_last_sector
+	mov %es:20, %eax
+	shr $9, %eax
+	inc %eax
+
+check_last_sector:
+	dec %ax
+	mov %ax, kernel_sectors
+	cmp $0, %ax
+	je done
+
+move: # inc our offset. If it hits 0, we've moved a segment, inc that too.
+	add $512, %bx
+	cmp $0, %bx
+	jnz read_next_sector
+	mov %es, %ax
+	add $1000, %ax
+	mov %ax, %es
+
+read_next_sector: # find the next valid sector, head, cylinder combo on the disk
+	inc %cl
+	mov (total_sectors), %al
+	cmp %al, %cl
+	jle load_sector
+	mov $1, %cl #go back to sector 1.. of the next head
+
+	inc %dh #next head
+	mov (total_heads), %al
+	cmp %al, %dh
+	jle load_sector
+	mov $0, %dh # go back to head 0.. of the next cylinder
+
+	inc %ch # next cylinder
+	mov (total_cylinders), %al
+	cmp %al, %ch
+	jle load_sector
+	# no more disk... fall through
+done:
+	mov $0, %ah
+	int $0x13
+
+	mov $0x1000, %ax
+	mov %ax, %ds
+	ljmp $0x1000, $0x0000
+
+disk_number:
+	.byte 0
+total_cylinders:
+	.byte 0
+total_heads:
+	.byte 0
+total_sectors:
+	.byte 0
+
+kernel_sectors:
+	.word 0xFFFF
+
+mbr_entry:
+partition_status:
+	.byte 0
+partition_start_chs:
+	.byte 0
+	.byte 0
+	.byte 0
+partition_type:
+	.byte 0
+partition_stop_chs:
+	.byte 0
+	.byte 0
+	.byte 0
+partition_start_lba:
+	.long 0
+partition_start_length:
+	.long 0
+
+.org 510
+magic:
+	.word 0xAA55

compile_commands.json

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+[
+  {
+    "file": "boot.s",
+    "arguments": [
+      "/home/slinky/opt/cross/bin/i686-elf-gcc",
+      "-m32",
+      "-c",
+      "boot.s",
+      "-o",
+      "boot.o"
+    ],
+    "directory": "/home/slinky/source/RockOS",
+    "output": "boot.o"
+  },
+  {
+    "file": "prekernel.s",
+    "arguments": [
+      "/home/slinky/opt/cross/bin/i686-elf-gcc",
+      "-m32",
+      "-c",
+      "prekernel.s",
+      "-o",
+      "prekernel.o"
+    ],
+    "directory": "/home/slinky/source/RockOS",
+    "output": "prekernel.o"
+  },
+  {
+    "file": "kmain.c",
+    "arguments": [
+      "/home/slinky/opt/cross/bin/i686-elf-gcc",
+      "-m32",
+      "-ffreestanding",
+      "-O2",
+      "-Wall",
+      "-Wextra",
+      "-c",
+      "kmain.c",
+      "-o",
+      "kmain.o"
+    ],
+    "directory": "/home/slinky/source/RockOS",
+    "output": "kmain.o"
+  }
+]

kernel.ld

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+ENTRY(_start)
+
+SECTIONS
+{
+    . = 0x10000;
+
+    .text : {
+      *(.text)
+    }
+
+    .rodata : {
+      *(.rodata)
+    }
+
+    .data : {
+      *(.data)
+    }
+
+    .bss : {
+      *(.bss)
+    }
+
+    _end = .;
+}

kmain.c

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+#include <stdint.h>
+
+extern void halt();
+
+typedef struct {
+  uint16_t offset_low;
+  uint16_t selector;
+  uint8_t zero;
+  uint8_t flags;
+  uint16_t offset_high;
+} idt_entry_t __attribute__((packed));
+
+typedef struct {
+  uint16_t limit;
+  uint32_t base;
+} idt_ptr_t;
+
+idt_entry_t idt[256];
+idt_ptr_t idtr;
+
+void load_idt() {}
+
+void kmain() {
+  load_idt();
+  halt();
+}

makefile

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+CC = i686-elf-gcc
+LD = i686-elf-ld
+OBJCOPY = i686-elf-objcopy
+
+CFLAGS = -m32 -ffreestanding -O2 -Wall -Wextra -nostdlib
+ASFLAGS = -m32
+
+.PHONY: all clean run
+
+all: os.img
+
+boot.o: boot.s 
+	$(CC) $(ASFLAGS) -c boot.s -o boot.o
+
+boot.elf: boot.o boot.ld 
+	$(LD) -T boot.ld -o boot.elf boot.o
+
+boot.bin: boot.elf 
+	$(OBJCOPY) -O binary boot.elf boot.bin
+
+prekernel.o: prekernel.s
+	$(CC) $(ASFLAGS) -c prekernel.s -o prekernel.o
+
+kmain.o: kmain.c
+	$(CC) $(CFLAGS) -c kmain.c -o kmain.o
+
+kernel.elf: prekernel.o kmain.o kernel.ld
+	$(LD) -T kernel.ld -o kernel.elf prekernel.o kmain.o
+
+kernel.bin: kernel.elf
+	$(OBJCOPY) -O binary kernel.elf kernel.bin
+
+os.img: boot.bin kernel.bin
+	dd if=boot.bin of=os.img bs=512 count=1
+	dd if=kernel.bin of=os.img bs=512 seek=1
+	truncate -s 1440k os.img
+
+run: os.img
+	qemu-system-i386 -drive format=raw,file=os.img
+
+clean: 
+	rm -f *.o *.elf *.bin os.img

prekernel.s

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+.code16
+.text
+.global _start
+_start:
+	jmp everything
+
+.org 20
+.global kernel_size
+kernel_size:
+	.long _end - _start
+
+everything:
+  mov $0x1000, %ax 
+  mov %ax, %es 
+  mov %ax, %ds
+
+	# reset disk
+	mov $0, %ah
+	int $0x13
+
+	# stop the cursor
+	mov $1, %ah
+  mov $0,%cl
+  mov $0x20,%ch
+  int $0x11
+
+	# get the system memory, if this call fails then halt
+	clc
+	mov $0, %bx
+	mov $0xe801, %ax
+	int $0x15
+	jc halt
+	shr $10, %ax
+	shr $4, %bx
+	add %ax, %bx
+	mov %bx, total_mem_mb-_start
+
+  # vga text mode
+  mov $0x0003, %ax 
+  int $0x10
+	
+enable_a20:
+  #enable the a20 gate
+	inb $0x92, %al
+	orb $2, %al
+	outb %al, $0x92
+prep_protected:
+	cli
+	lgdt (gdt_init-_start)
+	mov %cr0, %eax
+	or $0x01, %eax
+	mov %eax, %cr0 # protected bit set
+  ljmpl $8, $protected
+
+halt16:
+  jmp halt16
+
+.code32
+protected:
+	mov $2*8, %ax
+  mov %ax, %es
+	mov %ax, %ds
+	mov %ax, %ss
+	mov $5*8, %ax
+	ltr %ax
+	mov $0, %ax
+	mov %ax, %fs
+	mov %ax, %gs
+	mov $0xFFF0, %sp
+	mov $0xFFF0, %bp
+	ljmpl $8, $kmain
+
+.align 4
+.global video_info_struct
+video_info_struct:
+	.word	0
+	.byte	0,0
+	.word	0,0,0,0
+	.long	0
+.global video_xbytes
+video_xbytes:
+	.word	0
+.global video_xres
+video_xres:
+	.word	0 
+.global video_yres
+video_yres:
+	.word	0
+	.byte	0,0,0,0,0,0,0,0,0
+	.byte	0,0,0,0,0,0,0,0,0
+.global video_buffer
+video_buffer:
+	.long	0
+	.long	0
+	.word	0
+	.word	0
+	.byte	0,0,0,0,0,0,0,0,0,0
+	.long	0
+.rept 190
+	.byte	0
+.endr
+
+# some assembly stubs we can call from the kernel
+
+.global idt_load
+.extern idtr       
+idt_load:
+	lidt (idtr)     
+	ret            
+
+.global gdt_load
+gdt_load:
+	lgdt (gdt_init)
+	ret
+
+.global reboot
+reboot:
+	cli
+	lidt reboot_struct
+	int $1
+reboot_struct:
+	.word 0
+	.long 0
+
+.global halt
+halt:
+	cli
+	hlt
+	jmp halt
+
+# kernel data structures
+
+.align 16
+.global gdt
+gdt:
+	.word 0,0,0,0
+	.word 0xffff, 0x0000, 0x9a00, 0x00cf
+  .word 0xffff, 0x0000, 0x9200, 0x00cf    
+  .word 0xffff, 0x0000, 0xfa00, 0x00cf   
+  .word 0xffff, 0x0000, 0xf200, 0x00cf  
+  .word 0x0068, (tss-_start), 0x8901, 0x00cf
+gdt_init:
+	.word gdt_init-gdt
+	.long gdt
+
+.align 16
+.global tss
+tss:
+	.long 0
+
+.global total_mem_mb
+total_mem_mb:
+	.word 0