The Place to Start for Operating System Developers
http://f.osdev.org/
Writing to the VGA text mode screen works the same regardless of CPU mode. I suggest you read more about VGA text mode if you don't understand the babystep code.PavelCheckov wrote:Is there a way to write to the screen without BIOS in a 64-bit OS?
It's called "long mode".PavelCheckov wrote:Is there such thing as 64-bit protected mode?
The only reason I ask is because it says that the code is for 32-bit protected mode. I was also hoping to use FHD as the default, which doesn't have text mode, or to my knoweledge, any tutorial.Octocontrabass wrote:Writing to the VGA text mode screen works the same regardless of CPU mode. I suggest you read more about VGA text mode if you don't understand the babystep code.
I was hoping to write my OS independent of a specific BIOS (e.g. UEFI).Octocontrabass wrote:UEFI doesn't have VGA text mode, so if you want to support UEFI in the future you'll have to write new code to support a linear frame buffer. (You can also have a linear frame buffer with BIOS.)
How do I enter long mode?Octocontrabass wrote:It's called "long mode".
So, you want a linear frame buffer. There's quite a bit of information on how to use one of those. Please ignore the page title - it was probably written before long mode existed.PavelCheckov wrote:I was also hoping to use FHD as the default, which doesn't have text mode, or to my knoweledge, any tutorial.
You want a linear frame buffer.PavelCheckov wrote:I was hoping to write my OS independent of a specific BIOS (e.g. UEFI).
Let the bootloader do it for you.PavelCheckov wrote:How do I enter long mode?
To display a character, take a look at the example on PC Screen Font wiki page. You just repeat that code for every character and adjust the cursor position. A very very minimalistic string display example would be:PavelCheckov wrote:How would I write a printf function with this?
Code: Select all
// PSF2 header
typedef struct {
uint32_t magic;
uint32_t version;
uint32_t headersize;
uint32_t flags;
uint32_t numglyph;
uint32_t bytesperglyph;
uint32_t height;
uint32_t width;
uint8_t glyphs;
} __attribute__((packed)) psf2_t;
extern volatile unsigned char _binary_font_psf_start;
void puts(char *s)
{
psf2_t *font = (psf2_t*)&_binary_font_psf_start;
int x,y,kx=0,line,mask,offs;
int bpl=(font->width+7)/8;
while(*s) {
unsigned char *glyph = (unsigned char*)&_binary_font_psf_start + font->headersize +
(*s>0&&*s<font->numglyph?*s:0)*font->bytesperglyph;
offs = (kx * (font->width+1) * 4);
for(y=0;y<font->height;y++) {
line=offs; mask=1<<(font->width-1);
for(x=0;x<font->width;x++) {
*((uint32_t*)(framebuffer_address+line))=((int)*glyph) & (mask)?0xFFFFFF:0;
mask>>=1; line+=4;
}
*((uint32_t*)((uint64_t)&fb+line))=0; glyph+=bpl; offs+=framebuffer_scanline;
}
s++; kx++;
}
}
Basically, you write a routine that renders a font to screen (PC Screen Font is fine, just don't copy n' paste blindly, understand the code first before copying). After that, read up on the ISO C standard or POSIX specification about printf and how it works, and then write it.PavelCheckov wrote:How would I write a printf function with this?
It's very simple — you read the protocol and write the code
Code: Select all
/* example for 320x200 VGA */
void putpixel(int pos_x, int pos_y, unsigned char VGA_COLOR)
{
unsigned char* location = (unsigned char*)0xA0000 + 320 * pos_y + pos_x;
*location = VGA_COLOR;
}Code: Select all
static void putpixel(unsigned char* screen, int x,int y, int color) {
unsigned where = x*pixelwidth + y*pitch;
screen[where] = color & 255; // BLUE
screen[where + 1] = (color >> 8) & 255; // GREEN
screen[where + 2] = (color >> 16) & 255; // RED
}