fb3c7e04c4
This includes both separate .md files, and documentation that was on the head of the .S source files. Retest everything as this was done, and fix a few easy things.
114 lines
2.9 KiB
C
114 lines
2.9 KiB
C
#if !defined(__cplusplus)
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#include <stdbool.h> /* C doesn't have booleans by default. */
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#endif
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#include <stddef.h>
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#include <stdint.h>
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/* Check if the compiler thinks we are targeting the wrong operating system. */
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#if defined(__linux__)
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/* TODO how does this check for a cross compiler? It was failing. */
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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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COLOR_BLACK = 0,
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COLOR_BLUE = 1,
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COLOR_GREEN = 2,
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COLOR_CYAN = 3,
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COLOR_RED = 4,
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COLOR_MAGENTA = 5,
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COLOR_BROWN = 6,
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COLOR_LIGHT_GREY = 7,
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COLOR_DARK_GREY = 8,
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COLOR_LIGHT_BLUE = 9,
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COLOR_LIGHT_GREEN = 10,
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COLOR_LIGHT_CYAN = 11,
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COLOR_LIGHT_RED = 12,
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COLOR_LIGHT_MAGENTA = 13,
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COLOR_LIGHT_BROWN = 14,
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COLOR_WHITE = 15,
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};
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uint8_t make_color(enum vga_color fg, enum vga_color bg) {
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return fg | bg << 4;
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}
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uint16_t make_vgaentry(char c, uint8_t color) {
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uint16_t c16 = c;
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uint16_t color16 = color;
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return c16 | color16 << 8;
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}
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size_t strlen(const char* str) {
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size_t ret = 0;
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while ( str[ret] != 0 )
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ret++;
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return ret;
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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() {
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terminal_row = 0;
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terminal_column = 0;
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terminal_color = make_color(COLOR_LIGHT_GREY, 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] = make_vgaentry(' ', 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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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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const size_t index = y * VGA_WIDTH + x;
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terminal_buffer[index] = make_vgaentry(c, color);
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}
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void terminal_putchar(char c) {
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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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}
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void terminal_writestring(const char* data) {
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size_t datalen = strlen(data);
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for (size_t i = 0; i < datalen; i++)
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terminal_putchar(data[i]);
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}
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#if defined(__cplusplus)
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extern "C" /* Use C linkage for kernel_main. */
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#endif
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void kernel_main() {
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/* Initialize terminal interface */
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terminal_initialize();
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/* Since there is no support for newlines in terminal_putchar
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* yet, '\n' would produce some weird VGA specific character instead.
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* This is normal.
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*/
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terminal_writestring("hello world");
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}
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