mirror of
https://github.com/Plexi09/Nadir-Kernel.git
synced 2026-10-20 15:07:27 +02:00
121 lines
3.5 KiB
C
121 lines
3.5 KiB
C
/* VGA text-mode driver (see console.h). */
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#include <stdint.h>
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#include "console.h"
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#include "io.h"
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#define VGA_WIDTH 80
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#define VGA_HEIGHT 25
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#define VGA_ADDR 0xB8000
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#define COLOR_DEFAULT 0x0FU /* white on black */
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/* VGA CRT controller ports: index selects the register, data reads/writes
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* it. Registers 0x0E/0x0F hold the high/low byte of the cursor offset. */
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#define VGA_CRT_INDEX 0x3D4U
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#define VGA_CRT_DATA 0x3D5U
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#define VGA_CRT_CURSOR_HIGH 0x0EU
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#define VGA_CRT_CURSOR_LOW 0x0FU
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/* Cursor position, lives in BSS. */
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static uint8_t cursor_row;
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static uint8_t cursor_col;
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/* Text buffer, one 16-bit cell per character, low byte is the ASCII code,
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* high byte is the color attribute. `volatile` so the compiler keeps every
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* store in order. */
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static volatile uint16_t *const vga = (uint16_t *)VGA_ADDR;
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/* Sync the blinking hardware cursor to cursor_row/cursor_col.
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* Runs at Ring 0 (CPL 0): `out` traps with #GP(0) if CPL > IOPL, so this
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* must never run in userspace. A wrong port value cannot fault,
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* it would only misplace the visible cursor. */
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static void update_hw_cursor(void)
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{
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uint16_t pos = (uint16_t)(cursor_row * VGA_WIDTH + cursor_col);
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outb(VGA_CRT_INDEX, VGA_CRT_CURSOR_LOW);
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outb(VGA_CRT_DATA, (uint8_t)(pos & 0xFFU));
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outb(VGA_CRT_INDEX, VGA_CRT_CURSOR_HIGH);
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outb(VGA_CRT_DATA, (uint8_t)((pos >> 8) & 0xFFU));
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}
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static void scroll(void)
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{
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for (uint8_t row = 1; row < VGA_HEIGHT; row++) {
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for (uint8_t col = 0; col < VGA_WIDTH; col++) {
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vga[(row - 1) * VGA_WIDTH + col] = vga[row * VGA_WIDTH + col];
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}
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}
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for (uint8_t col = 0; col < VGA_WIDTH; col++) {
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vga[(VGA_HEIGHT - 1) * VGA_WIDTH + col] =
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(uint16_t)((COLOR_DEFAULT << 8) | ' ');
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}
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}
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void console_clear(void)
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{
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for (uint16_t i = 0; i < VGA_WIDTH * VGA_HEIGHT; i++) {
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vga[i] = (uint16_t)((COLOR_DEFAULT << 8) | ' ');
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}
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cursor_row = 0;
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cursor_col = 0;
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update_hw_cursor();
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}
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void console_putchar(char c)
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{
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if (c == '\n') {
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cursor_row++;
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cursor_col = 0;
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} else if (c == '\b') {
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/* kmain echoes keyboard '\b' for editing. Without this the
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* raw 0x08 glyph would print instead of erasing. Move back one
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* cell and blank it (IRQ-safe: mainline only, IF=1 but the
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* IRQ handlers never touch VGA). */
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if (cursor_col > 0) {
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cursor_col--;
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} else if (cursor_row > 0) {
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cursor_row--;
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cursor_col = VGA_WIDTH - 1;
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} else {
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return;
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}
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vga[cursor_row * VGA_WIDTH + cursor_col] =
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(uint16_t)((COLOR_DEFAULT << 8) | ' ');
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} else {
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vga[cursor_row * VGA_WIDTH + cursor_col] =
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(uint16_t)((COLOR_DEFAULT << 8) | c);
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cursor_col++;
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if (cursor_col >= VGA_WIDTH) {
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/* Wrap to the next line. */
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cursor_col = 0;
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cursor_row++;
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}
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}
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/* Past the bottom line scroll and stay on the last line. */
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if (cursor_row >= VGA_HEIGHT) {
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scroll();
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cursor_row = VGA_HEIGHT - 1;
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}
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update_hw_cursor();
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}
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void console_puts(const char *s)
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{
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while (*s != '\0') {
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console_putchar(*s);
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s++;
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}
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}
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void console_puthex64(uint64_t value)
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{
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static const char digits[] = "0123456789ABCDEF";
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console_puts("0x");
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/* Print 16 nibbles, most significant first (shifts 60, 56, …, 0). */
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for (int shift = 60; shift >= 0; shift -= 4) {
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console_putchar(digits[(value >> shift) & 0xFU]);
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}
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}
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