diff options
Diffstat (limited to 'kernel/l0')
| -rw-r--r-- | kernel/l0/kmain.c | 126 | ||||
| -rw-r--r-- | kernel/l0/loader.s | 69 |
2 files changed, 195 insertions, 0 deletions
diff --git a/kernel/l0/kmain.c b/kernel/l0/kmain.c new file mode 100644 index 0000000..9139856 --- /dev/null +++ b/kernel/l0/kmain.c @@ -0,0 +1,126 @@ +#if !defined(__cplusplus) +#include <stdbool.h> /* C doesn't have booleans by default. */ +#endif +#include <stddef.h> +#include <stdint.h> + +/* Check if the compiler thinks if we are targeting the wrong operating system. */ +#if defined(__linux__) +#error "You are not using a cross-compiler, you will most certainly run into trouble" +#endif + +/* This tutorial will only work for the 32-bit ix86 targets. */ +#if !defined(__i386__) +#error "This tutorial needs to be compiled with a ix86-elf compiler" +#endif + +#include "multiboot.h" + +extern void k_highhalf_addr; + +/* Hardware text mode color constants. */ +enum vga_color +{ + COLOR_BLACK = 0, + COLOR_BLUE = 1, + COLOR_GREEN = 2, + COLOR_CYAN = 3, + COLOR_RED = 4, + COLOR_MAGENTA = 5, + COLOR_BROWN = 6, + COLOR_LIGHT_GREY = 7, + COLOR_DARK_GREY = 8, + COLOR_LIGHT_BLUE = 9, + COLOR_LIGHT_GREEN = 10, + COLOR_LIGHT_CYAN = 11, + COLOR_LIGHT_RED = 12, + COLOR_LIGHT_MAGENTA = 13, + COLOR_LIGHT_BROWN = 14, + COLOR_WHITE = 15, +}; + +uint8_t make_color(enum vga_color fg, enum vga_color bg) +{ + return fg | bg << 4; +} + +uint16_t make_vgaentry(char c, uint8_t color) +{ + uint16_t c16 = c; + uint16_t color16 = color; + return c16 | color16 << 8; +} + +size_t strlen(const char* str) +{ + size_t ret = 0; + while ( str[ret] != 0 ) + ret++; + return ret; +} + +static const size_t VGA_WIDTH = 80; +static const size_t VGA_HEIGHT = 25; + +size_t terminal_row; +size_t terminal_column; +uint8_t terminal_color; +uint16_t* terminal_buffer; + +void terminal_initialize() +{ + terminal_row = 0; + terminal_column = 0; + terminal_color = make_color(COLOR_LIGHT_GREY, COLOR_BLACK); + terminal_buffer = (uint16_t*) (&k_highhalf_addr + 0xB8000); + for ( size_t y = 0; y < VGA_HEIGHT; y++ ) + { + for ( size_t x = 0; x < VGA_WIDTH; x++ ) + { + const size_t index = y * VGA_WIDTH + x; + terminal_buffer[index] = make_vgaentry(' ', terminal_color); + } + } +} + +void terminal_setcolor(uint8_t color) +{ + terminal_color = color; +} + +void terminal_putentryat(char c, uint8_t color, size_t x, size_t y) +{ + const size_t index = y * VGA_WIDTH + x; + terminal_buffer[index] = make_vgaentry(c, color); +} + +void terminal_putchar(char c) +{ + terminal_putentryat(c, terminal_color, terminal_column, terminal_row); + if ( ++terminal_column == VGA_WIDTH ) + { + terminal_column = 0; + if ( ++terminal_row == VGA_HEIGHT ) + { + terminal_row = 0; + } + } +} + +void terminal_writestring(const char* data) +{ + size_t datalen = strlen(data); + for ( size_t i = 0; i < datalen; i++ ) + terminal_putchar(data[i]); +} + +#if defined(__cplusplus) +extern "C" /* Use C linkage for kernel_main. */ +#endif +void kmain(struct multiboot_info_t *mbd, int32_t mb_magic) +{ + terminal_initialize(); + /* Since there is no support for newlines in terminal_putchar yet, \n will + produce some VGA specific character instead. This is normal. */ + terminal_writestring("Hello, kernel World!\n"); +} diff --git a/kernel/l0/loader.s b/kernel/l0/loader.s new file mode 100644 index 0000000..a31fcf5 --- /dev/null +++ b/kernel/l0/loader.s @@ -0,0 +1,69 @@ +[EXTERN k_highhalf_addr] + +[GLOBAL loader] ; making entry point visible to linker + +[EXTERN kmain] ; kmain is defined in kmain.c + +; loader stack size +LOADER_STACK_SIZE equ 0x8000 ; 8Kb + +; setting up the Multiboot header - see GRUB docs for details +MODULEALIGN equ 1<<0 ; align loaded modules on page boundaries +MEMINFO equ 1<<1 ; provide memory map +FLAGS equ MODULEALIGN | MEMINFO ; this is the Multiboot 'flag' field +MAGIC equ 0x1BADB002 ; 'magic number' lets bootloader find the header +CHECKSUM equ -(MAGIC + FLAGS) ; checksum required + +section .text +align 4 +MultiBootHeader: + dd MAGIC + dd FLAGS + dd CHECKSUM + +section .setup +loader: ;here, we load our false GDT, used for having the kernel in higher half + lgdt [trickgdt] + mov cx, 0x10; + mov ds, cx; + mov es, cx; + mov fs, cx; + mov gs, cx; + mov ss, cx; + + jmp 0x08:higherhalf + +section .text +higherhalf: ; now we're running in higher half + mov esp, stack_top ; set up the stack + + push eax ; pass Multiboot magic number + add ebx, k_highhalf_addr ; update the MB info structure so that it is in the new seg + push ebx ; pass Multiboot info structure + + call kmain ; call kernel proper + + cli ; disable interupts + +hang: + hlt ; halt machine should kernel return + jmp hang + +[section .setup] ; this is included in the .setup section, so that it thinks it is at 0x00100000 + +trickgdt: ; our false GDT + dw gdt_end - gdt - 1 ; gdt limit + dd gdt ; gdt base + +gdt: + dd 0, 0 ; null GDT entry + db 0xFF, 0xFF, 0, 0, 0, 10011010b, 11001111b, 0x40 ; kernel code segment + db 0xFF, 0xFF, 0, 0, 0, 10010010b, 11001111b, 0x40 ; kernel data segment + +gdt_end: + +[section .bss] +align 4 +stack_bottom: + resb LOADER_STACK_SIZE +stack_top: |