first commit

.gitignore

@@ -0,0 +1 @@
+build

README

@@ -0,0 +1,3 @@
+compilation: (with installed dependencies, see dependencies.txt)
+
+make build

dependencies.txt

@@ -0,0 +1,4 @@
+to compile:
+
+grub-pc-bin, gcc, makefile, grub-mkrescue, tar,
+and lastly: L I N U X

grubtemplate/boot/grub/grub.cfg

@@ -0,0 +1,5 @@
+menuentry "JPOS" {
+	multiboot2 /boot/kernel
+	module2  /boot/JPOS.initrd
+	boot
+}

initrd/vga/main.c

@@ -0,0 +1,9 @@
+void main() {
+	volatile char *video = (volatile char*)0xB8000; // small welcome message
+	char* welcome = "Hello VGA, World!";
+
+    while (*welcome != 0) {
+        *video++ = *welcome++;
+        *video++ = 15;
+    }
+}

linker.ld

@@ -0,0 +1,30 @@
+ENTRY(_start)
+
+SECTIONS {
+	. = ALIGN(8);
+    .boot : {
+        KEEP(*(.multiboot))
+    }
+	. = 1M; /* Load kernel at 1MB */
+
+	.text BLOCK(4K) : ALIGN(4K)
+	{
+		*(.text)
+	}
+
+	.rodata BLOCK(4K) : ALIGN(4K)
+	{
+		*(.rodata)
+	}
+
+	.data BLOCK(4K) : ALIGN(4K)
+	{
+		*(.data)
+	}
+
+	.bss BLOCK(4K) : ALIGN(4K)
+	{
+		*(COMMON)
+		*(.bss)
+	}
+}

makefile

@@ -0,0 +1,27 @@
+build: prepare copygrub
+	nasm -felf32 src/bootload/boot.asm -o build/boot.o	# entrypoint for grub
+
+	gcc -c src/kernel/entry.c -o build/kernel.o -ffreestanding -O2 -Wall -Wextra -m32 # kernel
+	gcc -c src/kernel/registrar.c -o build/registrar.o -ffreestanding -O2 -Wall -Wextra -m32 # registrar
+	
+	gcc -c initrd/vga/main.c -o build/initrddir/vga_graph -ffreestanding -O2 -Wall -Wextra -m32 # initrd/vga driver
+
+	tar -czf build/initrd build/initrddir/* # build initrd
+
+	gcc -m32 -T linker.ld -o build/linked -ffreestanding -O2 -nostdlib build/boot.o build/kernel.o build/registrar.o -fno-pie -fno-pic -no-pie # link
+
+	cp build/linked build/grub/boot/kernel # copy kernel over to grub template
+	cp build/initrd build/grub/boot/JPOS.initrd # copy initrd to grub template
+
+	grub-mkrescue /usr/lib/grub/i386-pc -o build/live.iso build/grub # create final image
+test: build
+	qemu-system-i386 \
+		-boot d \
+		-cdrom build/live.iso	
+copygrub:
+	cp grubtemplate -r build/grub
+prepare: clean
+	mkdir build
+	mkdir build/initrddir
+clean:
+	-rm -rf build

src/bootload/GDT.asm

@@ -0,0 +1,28 @@
+gdt_start:
+    dd 0x0 ; 4 byte
+    dd 0x0 ; 4 byte
+	
+gdt_code: 
+    dw 0xffff    ; segment length, bits 0-15
+    dw 0x0       ; segment base, bits 0-15
+    db 0x0       ; segment base, bits 16-23
+    db 10011010b ; flags (8 bits)
+    db 11001111b ; flags (4 bits) + segment length, bits 16-19
+    db 0x0       ; segment base, bits 24-31
+
+gdt_data:
+    dw 0xffff
+    dw 0x0
+    db 0x0
+    db 10010010b
+    db 11001111b
+    db 0x0
+
+gdt_end:
+
+gdt_descriptor:
+    dw gdt_end - gdt_start - 1
+    dd gdt_start
+
+CODE_SEG equ gdt_code - gdt_start
+DATA_SEG equ gdt_data - gdt_start

src/bootload/boot.asm

@@ -0,0 +1,69 @@
+; constants for multiboot
+MAGIC equ 0xE85250D6
+ARCH equ 0 ; 0 for i386, 4 for MIPS
+HDRLEN equ 24 ; Total length: 4 fields + end tag
+CHECKSUM equ -(MAGIC + ARCH + HDRLEN)
+
+section .multiboot_header
+align 8
+header_start:
+    dd 0xE85250D6                ; Magic
+    dd 0                         ; Architecture (i386)
+    dd header_end - header_start ; Length
+    dd -(0xE85250D6 + 0 + (header_end - header_start)) ; Checksum
+
+    ; End tag
+    dw 0    ; Type
+    dw 0    ; Flags
+    dd 8    ; Size
+header_end:
+
+
+section .bss
+align 16
+stack_bottom:
+resb 16384 ; 16 KiB is reserved for stack
+stack_top:
+
+section .rodata
+%include "src/bootload/GDT.asm"
+
+section .text ; entrypoint for bootloader
+[BITS 32]
+global _start:function (_start.end - _start)
+_start:
+	; To set up a stack, we set the esp register to point to the top of our
+	; stack (as it grows downwards on x86 systems). This is necessarily done
+	; in assembly as languages such as C cannot function without a stack.
+	mov esp, stack_top
+	mov ebp, esp
+	
+	mov ecx, eax ; move multiboot magic number to ecx
+
+	; TODO:
+	; load GDT 		[x]
+	; enter long m. [ ]
+	; init FPU		[ ]
+
+	; load GDT
+	cli
+	lgdt [gdt_descriptor]
+	jmp   CODE_SEG:.final ; if I get problems, check this line here, future me!
+.final:
+	mov   AX, DATA_SEG ; data segment selectors
+	mov   DS, AX
+	mov   ES, AX
+	mov   FS, AX
+	mov   GS, AX
+	mov   SS, AX
+
+	push ecx ; magic number
+	push ebx ; info structure
+	extern kernel_main
+	call kernel_main
+	add esp, 8 ; remove arguments
+	cli ; the infamous infinite loop
+.hang:	hlt
+	jmp .hang
+.end:
+	

src/bootload/longm.asm

@@ -0,0 +1,55 @@
+; DEPRECATED!
+
+CPUID_EXTENSIONS equ 0x80000000
+CPUID_EXT_FEATURES equ 0x80000001
+EFLAGS_ID equ 1 << 21
+CPUID_EDX_EXT_FEAT_LM equ 1 << 29
+
+enterlong:
+	call .queryLongMode
+	
+
+.NoLongMode
+	cli
+	hlt
+	jmp .NoLongMode
+
+.checkCPUID:
+    pushfd
+    pop eax
+
+    ; The original value should be saved for comparison and restoration later
+    mov ecx, eax
+    xor eax, EFLAGS_ID
+
+    ; storing the eflags and then retrieving it again will show whether or not
+    ; the bit could successfully be flipped
+    push eax                    ; save to eflags
+    popfd
+    pushfd                      ; restore from eflags
+    pop eax
+
+    ; Restore EFLAGS to its original value
+    push ecx
+    popfd
+
+    ; if the bit in eax was successfully flipped (eax != ecx), CPUID is supported.
+    xor eax, ecx
+    jnz .NoLongMode
+	ret
+
+.queryLongMode:
+	call .checkCPUID
+
+    mov eax, CPUID_EXTENSIONS
+    cpuid
+    cmp eax, CPUID_FEATURES
+    jb .NoLongMode
+
+	mov eax, CPUID_EXT_FEATURES
+    cpuid
+    test edx, CPUID_EDX_EXT_FEAT_LM
+    jz .NoLongMode
+	
+	ret
+

src/headers/multiboot2.h

@@ -0,0 +1,416 @@
+/*  multiboot2.h - Multiboot 2 header file.  */
+/*  Copyright (C) 1999,2003,2007,2008,2009,2010  Free Software Foundation, Inc.
+ *
+ *  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 ANY
+ *  DEVELOPER OR DISTRIBUTOR 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.
+ */
+
+#ifndef MULTIBOOT_HEADER
+#define MULTIBOOT_HEADER 1
+
+/* How many bytes from the start of the file we search for the header.  */
+#define MULTIBOOT_SEARCH			32768
+#define MULTIBOOT_HEADER_ALIGN			8
+
+/* The magic field should contain this.  */
+#define MULTIBOOT2_HEADER_MAGIC			0xe85250d6
+
+/* This should be in %eax.  */
+#define MULTIBOOT2_BOOTLOADER_MAGIC		0x36d76289
+
+/* Alignment of multiboot modules.  */
+#define MULTIBOOT_MOD_ALIGN			0x00001000
+
+/* Alignment of the multiboot info structure.  */
+#define MULTIBOOT_INFO_ALIGN			0x00000008
+
+/* Flags set in the 'flags' member of the multiboot header.  */
+
+#define MULTIBOOT_TAG_ALIGN                  8
+#define MULTIBOOT_TAG_TYPE_END               0
+#define MULTIBOOT_TAG_TYPE_CMDLINE           1
+#define MULTIBOOT_TAG_TYPE_BOOT_LOADER_NAME  2
+#define MULTIBOOT_TAG_TYPE_MODULE            3
+#define MULTIBOOT_TAG_TYPE_BASIC_MEMINFO     4
+#define MULTIBOOT_TAG_TYPE_BOOTDEV           5
+#define MULTIBOOT_TAG_TYPE_MMAP              6
+#define MULTIBOOT_TAG_TYPE_VBE               7
+#define MULTIBOOT_TAG_TYPE_FRAMEBUFFER       8
+#define MULTIBOOT_TAG_TYPE_ELF_SECTIONS      9
+#define MULTIBOOT_TAG_TYPE_APM               10
+#define MULTIBOOT_TAG_TYPE_EFI32             11
+#define MULTIBOOT_TAG_TYPE_EFI64             12
+#define MULTIBOOT_TAG_TYPE_SMBIOS            13
+#define MULTIBOOT_TAG_TYPE_ACPI_OLD          14
+#define MULTIBOOT_TAG_TYPE_ACPI_NEW          15
+#define MULTIBOOT_TAG_TYPE_NETWORK           16
+#define MULTIBOOT_TAG_TYPE_EFI_MMAP          17
+#define MULTIBOOT_TAG_TYPE_EFI_BS            18
+#define MULTIBOOT_TAG_TYPE_EFI32_IH          19
+#define MULTIBOOT_TAG_TYPE_EFI64_IH          20
+#define MULTIBOOT_TAG_TYPE_LOAD_BASE_ADDR    21
+
+#define MULTIBOOT_HEADER_TAG_END  0
+#define MULTIBOOT_HEADER_TAG_INFORMATION_REQUEST  1
+#define MULTIBOOT_HEADER_TAG_ADDRESS  2
+#define MULTIBOOT_HEADER_TAG_ENTRY_ADDRESS  3
+#define MULTIBOOT_HEADER_TAG_CONSOLE_FLAGS  4
+#define MULTIBOOT_HEADER_TAG_FRAMEBUFFER  5
+#define MULTIBOOT_HEADER_TAG_MODULE_ALIGN  6
+#define MULTIBOOT_HEADER_TAG_EFI_BS        7
+#define MULTIBOOT_HEADER_TAG_ENTRY_ADDRESS_EFI32  8
+#define MULTIBOOT_HEADER_TAG_ENTRY_ADDRESS_EFI64  9
+#define MULTIBOOT_HEADER_TAG_RELOCATABLE  10
+
+#define MULTIBOOT_ARCHITECTURE_I386  0
+#define MULTIBOOT_ARCHITECTURE_MIPS32  4
+#define MULTIBOOT_HEADER_TAG_OPTIONAL 1
+
+#define MULTIBOOT_LOAD_PREFERENCE_NONE 0
+#define MULTIBOOT_LOAD_PREFERENCE_LOW 1
+#define MULTIBOOT_LOAD_PREFERENCE_HIGH 2
+
+#define MULTIBOOT_CONSOLE_FLAGS_CONSOLE_REQUIRED 1
+#define MULTIBOOT_CONSOLE_FLAGS_EGA_TEXT_SUPPORTED 2
+
+#ifndef ASM_FILE
+
+typedef unsigned char		multiboot_uint8_t;
+typedef unsigned short		multiboot_uint16_t;
+typedef unsigned int		multiboot_uint32_t;
+typedef unsigned long long	multiboot_uint64_t;
+
+struct multiboot_header {
+  /* Must be MULTIBOOT_MAGIC - see above.  */
+  multiboot_uint32_t magic;
+
+  /* ISA */
+  multiboot_uint32_t architecture;
+
+  /* Total header length.  */
+  multiboot_uint32_t header_length;
+
+  /* The above fields plus this one must equal 0 mod 2^32. */
+  multiboot_uint32_t checksum;
+};
+
+struct multiboot_header_tag
+{
+  multiboot_uint16_t type;
+  multiboot_uint16_t flags;
+  multiboot_uint32_t size;
+};
+
+struct multiboot_header_tag_information_request
+{
+  multiboot_uint16_t type;
+  multiboot_uint16_t flags;
+  multiboot_uint32_t size;
+  multiboot_uint32_t requests[0];
+};
+
+struct multiboot_header_tag_address
+{
+  multiboot_uint16_t type;
+  multiboot_uint16_t flags;
+  multiboot_uint32_t size;
+  multiboot_uint32_t header_addr;
+  multiboot_uint32_t load_addr;
+  multiboot_uint32_t load_end_addr;
+  multiboot_uint32_t bss_end_addr;
+};
+
+struct multiboot_header_tag_entry_address
+{
+  multiboot_uint16_t type;
+  multiboot_uint16_t flags;
+  multiboot_uint32_t size;
+  multiboot_uint32_t entry_addr;
+};
+
+struct multiboot_header_tag_console_flags
+{
+  multiboot_uint16_t type;
+  multiboot_uint16_t flags;
+  multiboot_uint32_t size;
+  multiboot_uint32_t console_flags;
+};
+
+struct multiboot_header_tag_framebuffer
+{
+  multiboot_uint16_t type;
+  multiboot_uint16_t flags;
+  multiboot_uint32_t size;
+  multiboot_uint32_t width;
+  multiboot_uint32_t height;
+  multiboot_uint32_t depth;
+};
+
+struct multiboot_header_tag_module_align
+{
+  multiboot_uint16_t type;
+  multiboot_uint16_t flags;
+  multiboot_uint32_t size;
+};
+
+struct multiboot_header_tag_relocatable
+{
+  multiboot_uint16_t type;
+  multiboot_uint16_t flags;
+  multiboot_uint32_t size;
+  multiboot_uint32_t min_addr;
+  multiboot_uint32_t max_addr;
+  multiboot_uint32_t align;
+  multiboot_uint32_t preference;
+};
+
+struct multiboot_color
+{
+  multiboot_uint8_t red;
+  multiboot_uint8_t green;
+  multiboot_uint8_t blue;
+};
+
+struct multiboot_mmap_entry
+{
+  multiboot_uint64_t addr;
+  multiboot_uint64_t len;
+#define MULTIBOOT_MEMORY_AVAILABLE		1
+#define MULTIBOOT_MEMORY_RESERVED		2
+#define MULTIBOOT_MEMORY_ACPI_RECLAIMABLE       3
+#define MULTIBOOT_MEMORY_NVS                    4
+#define MULTIBOOT_MEMORY_BADRAM                 5
+  multiboot_uint32_t type;
+  multiboot_uint32_t zero;
+};
+typedef struct multiboot_mmap_entry multiboot_memory_map_t;
+
+struct multiboot_tag
+{
+  multiboot_uint32_t type;
+  multiboot_uint32_t size;
+};
+
+struct multiboot_tag_string
+{
+  multiboot_uint32_t type;
+  multiboot_uint32_t size;
+  char string[0];
+};
+
+struct multiboot_tag_module
+{
+  multiboot_uint32_t type;
+  multiboot_uint32_t size;
+  multiboot_uint32_t mod_start;
+  multiboot_uint32_t mod_end;
+  char cmdline[0];
+};
+
+struct multiboot_tag_basic_meminfo
+{
+  multiboot_uint32_t type;
+  multiboot_uint32_t size;
+  multiboot_uint32_t mem_lower;
+  multiboot_uint32_t mem_upper;
+};
+
+struct multiboot_tag_bootdev
+{
+  multiboot_uint32_t type;
+  multiboot_uint32_t size;
+  multiboot_uint32_t biosdev;
+  multiboot_uint32_t slice;
+  multiboot_uint32_t part;
+};
+
+struct multiboot_tag_mmap
+{
+  multiboot_uint32_t type;
+  multiboot_uint32_t size;
+  multiboot_uint32_t entry_size;
+  multiboot_uint32_t entry_version;
+  struct multiboot_mmap_entry entries[0];  
+};
+
+struct multiboot_vbe_info_block
+{
+  multiboot_uint8_t external_specification[512];
+};
+
+struct multiboot_vbe_mode_info_block
+{
+  multiboot_uint8_t external_specification[256];
+};
+
+struct multiboot_tag_vbe
+{
+  multiboot_uint32_t type;
+  multiboot_uint32_t size;
+
+  multiboot_uint16_t vbe_mode;
+  multiboot_uint16_t vbe_interface_seg;
+  multiboot_uint16_t vbe_interface_off;
+  multiboot_uint16_t vbe_interface_len;
+
+  struct multiboot_vbe_info_block vbe_control_info;
+  struct multiboot_vbe_mode_info_block vbe_mode_info;
+};
+
+struct multiboot_tag_framebuffer_common
+{
+  multiboot_uint32_t type;
+  multiboot_uint32_t size;
+
+  multiboot_uint64_t framebuffer_addr;
+  multiboot_uint32_t framebuffer_pitch;
+  multiboot_uint32_t framebuffer_width;
+  multiboot_uint32_t framebuffer_height;
+  multiboot_uint8_t framebuffer_bpp;
+#define MULTIBOOT_FRAMEBUFFER_TYPE_INDEXED 0
+#define MULTIBOOT_FRAMEBUFFER_TYPE_RGB     1
+#define MULTIBOOT_FRAMEBUFFER_TYPE_EGA_TEXT	2
+  multiboot_uint8_t framebuffer_type;
+  multiboot_uint16_t reserved;
+};
+
+struct multiboot_tag_framebuffer
+{
+  struct multiboot_tag_framebuffer_common common;
+
+  union
+  {
+    struct
+    {
+      multiboot_uint16_t framebuffer_palette_num_colors;
+      struct multiboot_color framebuffer_palette[0];
+    };
+    struct
+    {
+      multiboot_uint8_t framebuffer_red_field_position;
+      multiboot_uint8_t framebuffer_red_mask_size;
+      multiboot_uint8_t framebuffer_green_field_position;
+      multiboot_uint8_t framebuffer_green_mask_size;
+      multiboot_uint8_t framebuffer_blue_field_position;
+      multiboot_uint8_t framebuffer_blue_mask_size;
+    };
+  };
+};
+
+struct multiboot_tag_elf_sections
+{
+  multiboot_uint32_t type;
+  multiboot_uint32_t size;
+  multiboot_uint32_t num;
+  multiboot_uint32_t entsize;
+  multiboot_uint32_t shndx;
+  char sections[0];
+};
+
+struct multiboot_tag_apm
+{
+  multiboot_uint32_t type;
+  multiboot_uint32_t size;
+  multiboot_uint16_t version;
+  multiboot_uint16_t cseg;
+  multiboot_uint32_t offset;
+  multiboot_uint16_t cseg_16;
+  multiboot_uint16_t dseg;
+  multiboot_uint16_t flags;
+  multiboot_uint16_t cseg_len;
+  multiboot_uint16_t cseg_16_len;
+  multiboot_uint16_t dseg_len;
+};
+
+struct multiboot_tag_efi32
+{
+  multiboot_uint32_t type;
+  multiboot_uint32_t size;
+  multiboot_uint32_t pointer;
+};
+
+struct multiboot_tag_efi64
+{
+  multiboot_uint32_t type;
+  multiboot_uint32_t size;
+  multiboot_uint64_t pointer;
+};
+
+struct multiboot_tag_smbios
+{
+  multiboot_uint32_t type;
+  multiboot_uint32_t size;
+  multiboot_uint8_t major;
+  multiboot_uint8_t minor;
+  multiboot_uint8_t reserved[6];
+  multiboot_uint8_t tables[0];
+};
+
+struct multiboot_tag_old_acpi
+{
+  multiboot_uint32_t type;
+  multiboot_uint32_t size;
+  multiboot_uint8_t rsdp[0];
+};
+
+struct multiboot_tag_new_acpi
+{
+  multiboot_uint32_t type;
+  multiboot_uint32_t size;
+  multiboot_uint8_t rsdp[0];
+};
+
+struct multiboot_tag_network
+{
+  multiboot_uint32_t type;
+  multiboot_uint32_t size;
+  multiboot_uint8_t dhcpack[0];
+};
+
+struct multiboot_tag_efi_mmap
+{
+  multiboot_uint32_t type;
+  multiboot_uint32_t size;
+  multiboot_uint32_t descr_size;
+  multiboot_uint32_t descr_vers;
+  multiboot_uint8_t efi_mmap[0];
+}; 
+
+struct multiboot_tag_efi32_ih
+{
+  multiboot_uint32_t type;
+  multiboot_uint32_t size;
+  multiboot_uint32_t pointer;
+};
+
+struct multiboot_tag_efi64_ih
+{
+  multiboot_uint32_t type;
+  multiboot_uint32_t size;
+  multiboot_uint64_t pointer;
+};
+
+struct multiboot_tag_load_base_addr
+{
+  multiboot_uint32_t type;
+  multiboot_uint32_t size;
+  multiboot_uint32_t load_base_addr;
+};
+
+#endif /* ! ASM_FILE */
+
+#endif /* ! MULTIBOOT_HEADER */

src/headers/registrar.h

@@ -0,0 +1,6 @@
+#pragma once
+#include "stddef.h"
+
+typedef void (*FU_kupdbuf_t)(char*, uint16_t);
+extern void* FU_kupdbuf;
+void FUINV_kupdbuf(char* buf, uint16_t count);

src/headers/stddef.h

@@ -0,0 +1,9 @@
+#define uint8_t 	unsigned	char
+#define uint16_t 	unsigned 	short
+#define uint32_t 	unsigned 	int
+
+#define int8_t 		signed		char
+#define int16_t		signed		short
+#define int32_t		signed		int
+
+#define size_t		uint32_t

src/kernel/entry.c

@@ -0,0 +1,81 @@
+#include "../headers/stddef.h"
+#include "../headers/multiboot2.h"
+#include "../headers/registrar.h"
+
+void basevga_writestdout(char* buf, uint16_t count) {
+	volatile char 	*video = (volatile char*)0xB8000;
+	volatile uint8_t VGA_MAX_ROWS = 25;
+	volatile uint8_t VGA_MAX_COLS = 80;
+	uint32_t offset = 0;
+	uint32_t offsets[VGA_MAX_ROWS];
+	for (uint8_t i=0;i<VGA_MAX_ROWS;i++) {
+		offsets[i] = (VGA_MAX_COLS*2)*(i+1);
+	}
+
+	for (uint32_t i=0;i<count;i++) {
+		if (buf[i] == '\n') {
+			for (uint8_t i=0;i<VGA_MAX_ROWS;i++) {
+				if (offsets[i] > count*2%(VGA_MAX_COLS*VGA_MAX_ROWS)) {
+					offset += (count*2%(VGA_MAX_COLS*VGA_MAX_ROWS))-offsets[i];
+					break;
+				}
+			}
+			continue;
+		}
+		video[count*2%(VGA_MAX_COLS*VGA_MAX_ROWS)+offset] = buf[i];
+		video[count*2%(VGA_MAX_COLS*VGA_MAX_ROWS)+1+offset] = 15;
+	}
+}
+struct multiboot_info {
+    uint32_t total_size;
+    uint32_t reserved;
+    struct multiboot_tag tags[0];
+};
+uint32_t findtag(uint32_t type, struct multiboot_info* info) {
+	uint32_t index = 0;
+	while (1) {
+		struct multiboot_tag current = info->tags[index];
+
+		if (current.type == type) {return index;}
+		if (current.type == 0 && current.size == 8) {break;}
+
+		index ++;
+	}
+	return 0; // failsafe
+}
+
+// kernel stdout
+void* FU_kupdbuf = basevga_writestdout; // register basevga_writestdout as kupdbuf function
+char kstdout[8192] = {};
+uint16_t kstdout_count = 0;
+void kputchar(char x) {
+	kstdout[kstdout_count++] = x;
+	FUINV_kupdbuf(kstdout, kstdout_count);
+}
+void kputstr(char* x) {
+	
+	while (*x != 0) {
+		kputchar(*x++);
+	}
+	kputchar('\n');
+}
+
+void kernel_main(struct multiboot_info* header, uint32_t magic) {
+	kputstr("Hello JPOS, World!");
+
+	if (magic != MULTIBOOT2_BOOTLOADER_MAGIC) {
+		kputstr("Invalid magic from bootloader.");
+		return;
+	}
+
+	kputstr("Got past magic check.");
+
+	// load drivers
+	
+	// find boot modules tag
+	struct multiboot_tag_module* bootmodules = (struct multiboot_tag_module*)&header->tags[findtag(3, header)];
+	if (bootmodules->type != 3) {kputstr("Boot module failure.");return;}
+	//memcpy(0x200000, driver_code, size);
+	//((void(*)())0x200000)();
+	
+}

src/kernel/registrar.c

@@ -0,0 +1,7 @@
+#include "../headers/registrar.h"
+
+void FUINV_kupdbuf(char* buf, uint16_t count) {
+	if (FU_kupdbuf != 0x00) {
+		((FU_kupdbuf_t)FU_kupdbuf)(buf, count);
+	}
+}