xnoe-os/src/kernel/memory.cpp

#include "memory.h"

void memset(uint8_t* address, uint32_t count, uint8_t value) {
  for (int i=0; i<count; i++)
    address[i] = value;
}

void memcpy(uint8_t* src, uint8_t* dst, uint32_t count) {
  for (int i = 0; i<count; i++)
    dst[i] = src[i];
}

void PageMap::set_bit(uint32_t index) {
  uint32_t offset = index % 8;
  uint32_t i = index / 8;
  
  pagemap[i] |= 1<<(7-offset);
}

void PageMap::unset_bit(uint32_t index) {
  uint32_t offset = index % 8;
  uint32_t i = index / 8;
  
  pagemap[i] &= 255 - (1<<(7-offset));
}

bool PageMap::bit_set(uint32_t index) {
  uint32_t offset = index % 8;
  uint32_t i = index / 8;

  return pagemap[i] & 1<<(7-offset);
}

void PageMap::mark_unavailable(uint32_t address) {
  unset_bit(address >> 12);
}

void PageMap::mark_unavailable(uint32_t address, uint32_t count) {
  for (int i=0; i<count; i++)
    unset_bit((address >> 12) + i);
}

void PageMap::mark_available(uint32_t address) {
  set_bit(address >> 12);
}

void PageMap::mark_available(uint32_t address, uint32_t count) {
  for (int i=0; i<count; i++)
    set_bit((address >> 12) + i);
}

bool PageMap::available(uint32_t address) {
  return bit_set(address >> 4096);
}

uint32_t PageMap::find_next_available_from(uint32_t address) {
  while (!available(address)) address += 4096;

  return address;
}

uint32_t PageMap::find_next_available_from(uint32_t address, uint32_t count) {
  while (1) {
    while (!available(address)) address += 4096;

    for (int a=address, i=0; i<count; i++, a+=4096)
      if (!available(address))
        continue;
    
    return address;
  }
}

PageTable::PageTable(uint32_t phys, uint32_t virt) {
  phys_addr = phys;
  virt_addr = virt;

  page_table = (PTE*)virt;
}

PageTable::PageTable(){}

void PageTable::map_table(uint32_t index, uint32_t addr) {
  page_table[index] = (PTE){
    .present = 1,
    .read_write = 1,
    .privilege = 0,
    .write_through_cache = 0,
    .disable_cache = 0,
    .accessed = 0,
    .dirty = 0,
    .ignored = 0,
    .global = 0,
    .available = 0,
    .address = addr
  };
}

void PageTable::unmap_table(uint32_t index) {
  page_table[index] = (PTE){
    .present = 0,
    .read_write = 0,
    .privilege = 0,
    .write_through_cache = 0,
    .disable_cache = 0,
    .accessed = 0,
    .dirty = 0,
    .ignored = 0,
    .global = 0,
    .available = 0,
    .address = 0
  };
}

uint32_t PageTable::get_physical_address(uint32_t index) {
  return page_table[index].address << 12;
}

PageDirectory::PageDirectory(PDE* page_directory, uint32_t phys_addr, uint32_t offset) {
  this->page_directory = page_directory;
  this->phys_addr = phys_addr;

  for (int i=0; i<1024; i++) {
    uint32_t table_phys_addr = page_directory[i].getPhysicalPTAddress();
    page_tables[i] = PageTable(table_phys_addr >> 12, table_phys_addr + offset);
  }
}

void PageDirectory::map(uint32_t phys, uint32_t virt) {
  split_addr* split = (split_addr*)&virt;

  page_directory[split->pd_index] = (PDE){
    .present = 1,
    .read_write = 1,
    .privilege = 0,
    .write_through_cache = 0,
    .disable_cache = 0,
    .accessed = 0,
    .ignored2 = 0,
    .page_4mb = 0,
    .ignored = 0,
    .available = 0,
    .address = page_tables[split->pd_index].phys_addr
  };

  page_tables[split->pd_index].map_table(split->pt_index, phys >> 12);
}

void PageDirectory::unmap(uint32_t virt) {
  split_addr* split = (split_addr*)&virt;
  page_tables[split->pd_index].unmap_table(split->pt_index);
}

uint32_t PageDirectory::virtual_to_physical(uint32_t virt) {
  split_addr* split = (split_addr*)&virt;
  return page_tables[split->pd_index].get_physical_address(split->pt_index);
}

void PageDirectory::select() {
  asm volatile("mov %0, %%eax; mov %%eax, %%cr3" : : "m" (phys_addr));
}

PageMap* Allocator::phys;

Allocator::Allocator(PageDirectory* page_directory, PageMap* phys, PageMap* virt) {
  PD = page_directory;
  phys = phys;
  virt = virt;

  remaining = 0;
}

void* Allocator::allocate() {
  uint32_t phys_addr = phys->find_next_available_from(0);
  uint32_t virt_addr = virt->find_next_available_from(virt_alloc_base);

  phys->mark_unavailable(phys_addr);
  virt->mark_unavailable(virt_addr);

  PD->map(phys, virt);
}

void Allocator::deallocate(uint32_t virt_addr) {
  uint32_t phys_addr = PD->virtual_to_physical(virt_addr);

  PD->unmap(virt_addr);

  phys->mark_available(phys_addr);
  virt->mark_unavailable(virt_addr);
}