118 lines
No EOL
2.8 KiB
C
118 lines
No EOL
2.8 KiB
C
#include <stdbool.h>
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#include <stddef.h>
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#include <stdint.h>
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/* Check if the compiler thinks you are targeting the wrong operating system. */
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#if defined(__linux__)
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#error "You are not using a cross-compiler, you will most certainly run into trouble"
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#endif
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/* This tutorial will only work for the 32-bit ix86 targets. */
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#if !defined(__i386__)
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#error "This tutorial needs to be compiled with a ix86-elf compiler"
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#endif
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/* Hardware text mode color constants. */
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enum vga_color {
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VGA_COLOR_BLACK = 0,
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VGA_COLOR_BLUE = 1,
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VGA_COLOR_GREEN = 2,
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VGA_COLOR_CYAN = 3,
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VGA_COLOR_RED = 4,
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VGA_COLOR_MAGENTA = 5,
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VGA_COLOR_BROWN = 6,
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VGA_COLOR_LIGHT_GREY = 7,
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VGA_COLOR_DARK_GREY = 8,
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VGA_COLOR_LIGHT_BLUE = 9,
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VGA_COLOR_LIGHT_GREEN = 10,
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VGA_COLOR_LIGHT_CYAN = 11,
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VGA_COLOR_LIGHT_RED = 12,
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VGA_COLOR_LIGHT_MAGENTA = 13,
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VGA_COLOR_LIGHT_BROWN = 14,
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VGA_COLOR_WHITE = 15,
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};
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static inline uint8_t vga_entry_color(enum vga_color fg, enum vga_color bg)
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{
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return fg | bg << 4;
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}
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static inline uint16_t vga_entry(unsigned char uc, uint8_t color)
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{
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return (uint16_t) uc | (uint16_t) color << 8;
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}
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size_t strlen(const char* str)
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{
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size_t len = 0;
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while (str[len])
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len++;
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return len;
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}
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static const size_t VGA_WIDTH = 80;
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static const size_t VGA_HEIGHT = 25;
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size_t terminal_row;
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size_t terminal_column;
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uint8_t terminal_color;
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uint16_t* terminal_buffer;
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void terminal_initialize(void)
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{
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terminal_row = 0;
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terminal_column = 0;
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terminal_color = vga_entry_color(VGA_COLOR_LIGHT_GREY, VGA_COLOR_BLACK);
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terminal_buffer = (uint16_t*) 0xB8000;
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for (size_t y = 0; y < VGA_HEIGHT; y++) {
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for (size_t x = 0; x < VGA_WIDTH; x++) {
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const size_t index = y * VGA_WIDTH + x;
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terminal_buffer[index] = vga_entry(' ', terminal_color);
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}
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}
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}
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void terminal_setcolor(uint8_t color)
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{
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terminal_color = color;
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}
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void terminal_putentryat(char c, uint8_t color, size_t x, size_t y)
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{
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const size_t index = y * VGA_WIDTH + x;
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terminal_buffer[index] = vga_entry(c, color);
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}
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void terminal_putchar(char c)
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{
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terminal_putentryat(c, terminal_color, terminal_column, terminal_row);
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if (++terminal_column == VGA_WIDTH) {
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terminal_column = 0;
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if (++terminal_row == VGA_HEIGHT)
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terminal_row = 0;
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}
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}
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void terminal_write(const char* data, size_t size)
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{
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for (size_t i = 0; i < size; i++)
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terminal_putchar(data[i]);
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}
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void terminal_writestring(const char* data)
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{
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terminal_write(data, strlen(data));
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}
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void kernel_main(void)
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{
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/* Initialize terminal interface */
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terminal_initialize();
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/* Newline support is left as an exercise. */
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terminal_writestring("Hello, ");
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terminal_setcolor(vga_entry_color(VGA_COLOR_GREEN, VGA_COLOR_BLACK));
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terminal_writestring("kernel");
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terminal_setcolor(vga_entry_color(VGA_COLOR_LIGHT_GREY, VGA_COLOR_BLACK));
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terminal_writestring(" World!\n");
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} |