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This commit is contained in:
Justus Wolff
2026-02-26 00:06:36 +01:00
commit 115b4c88a1
16 changed files with 750 additions and 0 deletions
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1
.gitignore vendored Normal file
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build

3
README Normal file
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compilation: (with installed dependencies, see dependencies.txt)
make build

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dependencies.txt Normal file
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to compile:
grub-pc-bin, gcc, makefile, grub-mkrescue, tar,
and lastly: L I N U X

5
grubtemplate/boot/grub/grub.cfg Normal file
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menuentry "JPOS" {
multiboot2 /boot/kernel
module2 /boot/JPOS.initrd
boot
}

9
initrd/vga/main.c Normal file
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void main() {
volatile char *video = (volatile char*)0xB8000; // small welcome message
char* welcome = "Hello VGA, World!";
while (*welcome != 0) {
*video++ = *welcome++;
*video++ = 15;
}
}

30
linker.ld Normal file
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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)
}
}

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makefile Normal file
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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

28
src/bootload/GDT.asm Normal file
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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

69
src/bootload/boot.asm Normal file
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; 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:

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src/bootload/longm.asm Normal file
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; 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

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src/headers/multiboot2.h Normal file
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/* 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 */

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src/headers/registrar.h Normal file
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#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);

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src/headers/stddef.h Normal file
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#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

0
src/headers/stdlib.h Normal file
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src/kernel/entry.c Normal file
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#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)();
}

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src/kernel/registrar.c Normal file
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#include "../headers/registrar.h"
void FUINV_kupdbuf(char* buf, uint16_t count) {
if (FU_kupdbuf != 0x00) {
((FU_kupdbuf_t)FU_kupdbuf)(buf, count);
}
}