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Merge pull request #6 from Plexi09/fix/issue-3-cursor-position

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fix: cursor position says fixed in the console (#3)
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Pierre-Emmanuel Gob. 2026-09-19 23:24:27 +02:00 • committed by GitHub
commit 9ad501d068
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2 changed files with 26 additions and 2 deletions
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2
Makefile
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@ -36,7 +36,7 @@ $(BUILD)/isr.o: $(ARCH_DIR)/isr.asm | $(BUILD)
$(BUILD)/kmain.o: kernel/core/kmain.c include/console.h include/idt.h include/pic.h include/pit.h include/serial.h include/keyboard.h | $(BUILD)
$(CC) $(CFLAGS) -c $< -o $@
$(BUILD)/console.o: $(ARCH_DIR)/console.c include/console.h | $(BUILD)
$(BUILD)/console.o: $(ARCH_DIR)/console.c include/console.h include/io.h | $(BUILD)
$(CC) $(CFLAGS) -c $< -o $@
$(BUILD)/idt.o: $(ARCH_DIR)/idt.c include/idt.h include/console.h include/pic.h | $(BUILD)

26
kernel/arch/x86_64/console.c
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@ -3,13 +3,21 @@
#include <stdint.h>
#include "console.h"
#include "io.h"
#define VGA_WIDTH 80
#define VGA_HEIGHT 25
#define VGA_ADDR 0xB8000
#define COLOR_DEFAULT 0x0FU /* white on black */
/* Cursor position. Lives in BSS. */
/* VGA CRT controller ports: index selects the register, data reads/writes
* it. Registers 0x0E/0x0F hold the high/low byte of the cursor offset. */
#define VGA_CRT_INDEX 0x3D4U
#define VGA_CRT_DATA 0x3D5U
#define VGA_CRT_CURSOR_HIGH 0x0EU
#define VGA_CRT_CURSOR_LOW 0x0FU
/* Cursor position, lives in BSS. */
static uint8_t cursor_row;
static uint8_t cursor_col;
@ -18,6 +26,20 @@ static uint8_t cursor_col;
* store in order. */
static volatile uint16_t *const vga = (uint16_t *)VGA_ADDR;
/* Sync the blinking hardware cursor to cursor_row/cursor_col.
* Runs at Ring 0 (CPL 0): `out` traps with #GP(0) if CPL > IOPL, so this
* must never run in userspace. A wrong port value cannot fault,
* it would only misplace the visible cursor. */
static void update_hw_cursor(void)
{
uint16_t pos = (uint16_t)(cursor_row * VGA_WIDTH + cursor_col);
outb(VGA_CRT_INDEX, VGA_CRT_CURSOR_LOW);
outb(VGA_CRT_DATA, (uint8_t)(pos & 0xFFU));
outb(VGA_CRT_INDEX, VGA_CRT_CURSOR_HIGH);
outb(VGA_CRT_DATA, (uint8_t)((pos >> 8) & 0xFFU));
}
static void scroll(void)
{
for (uint8_t row = 1; row < VGA_HEIGHT; row++) {
@ -38,6 +60,7 @@ void console_clear(void)
}
cursor_row = 0;
cursor_col = 0;
update_hw_cursor();
}
void console_putchar(char c)
@ -75,6 +98,7 @@ void console_putchar(char c)
scroll();
cursor_row = VGA_HEIGHT - 1;
}
update_hw_cursor();
}
void console_puts(const char *s)