indigoos/src/kernel/page.c

#include <printf.h>
#include <paging.h>
#include <stdint.h>
#include <libc.h> 

void debug_print_memory() {
  struct memory_table *memtable = (struct memory_table *)&_meminfo_loc; 
  printf(" __________________________________________________________________________\n");
  printf("| type\tstart\t\t\tend\t\t\tsize\t\t   |\n");
  printf("|--------------------------------------------------------------------------|\n");
  for(unsigned int i = 0; memtable[i].length > 0; i++) {
    printf("| %u %u\t0x%p\t0x%p\t0x%p |\n", memtable[i].type, memtable[i].ACPI, memtable[i].base, (memtable[i].base + memtable[i].length), memtable[i].length);
  }
  printf("----------------------------------------------------------------------------\n");
}


//uses buddy system allocation
void init_memory() {
  struct memory_table *memtable = (struct memory_table *)&_meminfo_loc;
  struct phys_map *map = (struct phys_map*)0x200000;
  uintptr_t onpage = 0x200000;
  unsigned int i, x, buddy_size, buddy_bitsize, prev_buddy_bsize;
  uint64_t *buddy_ptr;
  
  map_page((void*)0x200000, (void*)0x200000, PAGE_SIZE_2M);
  void *next_page = (void *)onpage + 0x200000;
  // at this point, we are declaring our header and kernel itself as free (so don't forget to fix that!) 
  
  for(i = 0; memtable[i].length > 0; i++) {
    if((memtable[i].type == MEM_AVAILABLE) && (memtable[i].ACPI & 1)) {
     
      map->chunk_start = (void*)memtable[i].base;
      map->chunk_size = memtable[i].length;
      buddy_ptr = (void*)&map->buddies;


      for(x = 0; x < 8; x++) {

        buddy_bitsize = memtable[i].length / (0x1000 * (1 << x));
        buddy_size = ceil(buddy_bitsize / (float)8);
      
        if((void *)buddy_ptr + buddy_size >= next_page) {
          map_page(next_page, next_page, PAGE_SIZE_2M);
          next_page += 0x200000;
        }

        bzero(buddy_ptr, buddy_size); //meant to be /8?

        if((buddy_bitsize * 2) != prev_buddy_bsize) {
          buddy_ptr[-1] |= (1 << ((prev_buddy_bsize % 8) - 1));
        }

        buddy_ptr += buddy_size;

        prev_buddy_bsize = buddy_bitsize;

      }
      map->map_size = buddy_ptr - (uint64_t*)map;
      map = (struct phys_map *)map + map->map_size;

      if((void *)map + 24 >= next_page) {
        map_page(next_page, next_page, PAGE_SIZE_2M);
        next_page += 0x200000;
      }
    } 
  }
}

//TODO this function was deleted due to it being wrong. 
//I'll create it once I have the physical paging prerequisite set up. 
void create_pagetable_stage2(uint64_t free_mem) {
}


/**
 * BIG TODO:
 * Paging turned out to be simpler then I thought. I've temporarily fixed the code, but needs to be rewritten/simplified.
 * Let's get rid of those nasty GOTOs if we can.
 * Also, once we get physical memory allocator up and running, impliment that in this function.
**/

bool map_page(void *virtual_addr, void *physical_addr, uint8_t size) {
  //printf("map page called\n");
  uintptr_t va_ptr = (uintptr_t)virtual_addr;
  uintptr_t pa_ptr = (uintptr_t)physical_addr;
  if((va_ptr % (1 << size)) || (pa_ptr % (1 << size))) {
    return 0; 
  }
  page_table *table = (page_table *)PAGEMAP_LOCATION;
  int pte_i = (va_ptr >> 12) & 0x1ff;
  int pde_i = (va_ptr >> 21) & 0x1ff;
  int pdpe_i = (va_ptr >> 30) & 0x1ff;
  int pml4e_i = (va_ptr >> 39) & 0x1ff;

  if(table->pml4e[pml4e_i].present) {
    if(table->pml4e[pml4e_i].base_ptr != (uintptr_t)&table->pdpe[pdpe_i] >> 12) goto error;
    if(table->pdpe[pdpe_i].present) {
      if(size == PAGE_SIZE_1G) {
        if(table->pdpe[pdpe_i].base_ptr == (uintptr_t)pa_ptr >> 30 & 0x1ff)
          return true;
        goto error;
      }
      if(table->pdpe[pdpe_i].base_ptr != (uintptr_t)&table->pde[pde_i] >> 12) goto error;

      if(table->pde[pde_i].present) { 
        if(size == PAGE_SIZE_2M) {
          if(table->pde[pde_i].base_ptr == (uintptr_t)pa_ptr >> 21 & 0x1ff)
            return true;
          goto error;
        }
        if(table->pde[pde_i].base_ptr != (uintptr_t)&table->pte[pte_i] >> 12) goto error;
        if(table->pte[pte_i].present) {
          if(table->pte[pte_i].base_ptr != ((pa_ptr >> 12) & 0x1ff)) goto error;
          return true;
        }
        else goto mod_page_pte;
      }
      else goto mod_page_pde;
    }
    else goto mod_page_pdpe;
  }
  else {
    table->pml4e[pml4e_i].base_ptr = (uintptr_t)&table->pdpe[pdpe_i] >> 12;
    table->pdpe[pml4e_i].read_write = 1;
    table->pml4e[pml4e_i].present = 1;
mod_page_pdpe:
    table->pdpe[pdpe_i].read_write = 1;
    //TODO you just found out things are a lot more simple then you thought!
    if(size == PAGE_SIZE_1G) {
      table->pdpe[pdpe_i].size = 1;
      table->pdpe[pdpe_i].base_ptr = pa_ptr >> 12;
      table->pdpe[pdpe_i].present = 1;
      return true;
    }
    table->pdpe[pdpe_i].base_ptr = (uintptr_t)&table->pde[pde_i] >> 12;
    table->pdpe[pdpe_i].present = 1;
mod_page_pde:
    table->pde[pde_i].read_write = 1;
    if(size == PAGE_SIZE_2M) {
      table->pde[pde_i].size = 1;
      table->pde[pde_i].base_ptr = pa_ptr >> 12;
      table->pde[pde_i].present = 1;
      return true;
    }
    table->pde[pde_i].base_ptr = (uintptr_t)&table->pte[pte_i] >> 12;
    table->pde[pde_i].present = 1;
mod_page_pte:
    table->pte[pte_i].base_ptr = pa_ptr >> 12;
    table->pte[pte_i].read_write = 1;
    table->pte[pte_i].present = 1;
    return true;
  }
error:
  printf("Page allocation error!\n");
  return false;
}