arch/x86_64/boot/limine/framebuffer.c


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#include "arch/x86_64/hal/paging.h"
#include "jove.h"
#include "config.h"
#include "hal/framebuffer.h"
#include "lib/printf.h"

/*We don't know the size of the framebuffer until runtime, but at the same
 * time we don't want to dynamically allocate from physical memory. In this
 * case we allocate memory for the maximum supported framebuffer at compile
 * time and only use what we need at runtime.*/
#define FRAMEBUFFER_MAX_BYTES (FRAMEBUFFER_MAX_WIDTH * FRAMEBUFFER_MAX_WIDTH * 4)
#define FRAMEBUFFER_MAX_PAGES ((FRAMEBUFFER_MAX_BYTES + 4095) / 0x1000)
#define FRAMEBUFFER_MAX_HUGEPAGES ((FRAMEBUFFER_MAX_PAGES + 511) / 512)
#define FRAMEBUFFER_MAX_GIANTPAGES ((FRAMEBUFFER_MAX_HUGEPAGES + 511) / 512)

PAGEALIGN static page_t fb_pml2[FRAMEBUFFER_MAX_GIANTPAGES][512];

extern page_t _kernel_pml3[512];

void*
fb_remap(uintptr_t fb_address,
         size_t fb_bytes)
{
    fb_address &= ~IDENT_VIRT_BASE;
    size_t fb_pages = (fb_bytes + 4095) >> 12;
    size_t fb_hugepages = (fb_pages + 511) >> 9;
    size_t fb_giantpages = (fb_hugepages + 511) >> 9;

    if(fb_pages > FRAMEBUFFER_MAX_PAGES) {
        kprintf("Framebuffer is too big! Please recompile the kernel with a bigger framebuffer allowance!");
        return NULL;
    }

    for(size_t pml2 = 0; pml2 < fb_giantpages; pml2++) {
        uintptr_t fb_pml2_pptr = KPTR_TOPHYS((uintptr_t)fb_pml2[pml2]);
        _kernel_pml3[pml2].value = fb_pml2_pptr | PAGE_PRESENT | PAGE_GLOBAL | PAGE_WRITEABLE;
    }

    for(size_t pml1 = 0; pml1 < fb_hugepages; pml1++) {
        size_t pml2 = pml1 >> 9;
        size_t pml1_mod = pml1 % 512;
        uintptr_t fb_off = fb_address + (pml1 << 21);
        fb_pml2[pml2][pml1_mod].value = fb_off | PAGE_PRESENT | PAGE_GLOBAL | PAGE_WRITEABLE | PAGE_PS;
    }

    uintptr_t fb_virt = IDENT_VIRT_BASE | (511ULL << PMLI_SHL(3));
    return (void*)fb_virt;
}