vga_set_crtc
void vga_set_crtc(int, int, int);
vga_set_crtc(VGA_REG_BASE, VGA_CRTC_CURSOR_LOC_HIGH, addr >> 8);
vga_set_crtc(VGA_REG_BASE, VGA_CRTC_CURSOR_LOC_LOW,
vga_set_crtc(VGA_REG_BASE, VGA_CRTC_CURSOR_START, s);
vga_set_crtc(VGA_REG_BASE, VGA_CRTC_CURSOR_END, e);