99 lines
3.2 KiB
C
99 lines
3.2 KiB
C
//
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// Created by rick on 23-02-21.
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//
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#include <stdbool.h>
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#include <libc/libc.h>
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#include <libk/libk.h>
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#include "pmm.h"
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#define NUM_PAGING_INFOS 16
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#define BLOCK_USED 1
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#define BLOCK_FREE 0
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#define bitmap_block_byte(block) ((block) / 8)
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#define bitmap_block_bit(block) ((block) % 8)
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#define bitmap_set(addr, block) (addr)[bitmap_block_byte(block)] = ((addr)[bitmap_block_byte(block)] | (1 << (bitmap_block_bit(block))))
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#define bitmap_unset(addr, block) (addr)[bitmap_block_byte(block)] = ((addr)[bitmap_block_byte(block)] & ~(1 << (bitmap_block_bit(block))))
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#define bitmap_get(addr, block) ((addr)[bitmap_block_byte(block)] >> bitmap_block_bit(block))
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#define page_to_addr(base_addr, block) ((base_addr) + ((block) * PAGE_SIZE))
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#define addr_to_page(base_addr, addr) (((addr) - (base_addr)) / PAGE_SIZE)
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typedef struct {
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union {
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uint8_t *page_bitmap;
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void *first_page;
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};
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uint32_t num_pages;
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size_t size;
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struct {
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bool present: 1;
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} flags;
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} paging_info;
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uint8_t last_paging_info = 0;
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paging_info paging_infos[NUM_PAGING_INFOS];
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void pmm_init(void *start_addr, size_t size) {
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uint32_t num_pages = size / PAGE_SIZE;
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uint32_t bitmap_size = num_pages / 8;
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uint32_t bitmap_pages = bitmap_size / PAGE_SIZE;
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paging_infos[last_paging_info].page_bitmap = start_addr;
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paging_infos[last_paging_info].num_pages = num_pages;
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paging_infos[last_paging_info].size = size;
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paging_infos[last_paging_info].flags.present = true;
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memset(start_addr, BLOCK_FREE, bitmap_pages);
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for (uint32_t i = 0; i < bitmap_pages; ++i) {
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bitmap_set((uint8_t *) start_addr, i);
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}
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last_paging_info++;
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}
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void *pmm_get_pages(uint32_t num_pages) {
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for (int i = 0; i < last_paging_info; ++i) {
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paging_info *info = &paging_infos[i];
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if (!info->flags.present) continue;
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for (uint32_t j = 0; j < info->num_pages; ++j) {
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if (bitmap_get(info->page_bitmap, j) == BLOCK_FREE) {
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uint32_t k;
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bool usable = true;
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for (k = j + 1; k < j + num_pages; ++k) {
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if (bitmap_get(info->page_bitmap, k) == BLOCK_USED) {
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usable = false;
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j = k; // skip ahead
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break;
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}
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}
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if (!usable) break;
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for (k = j; k < j + num_pages; ++k) {
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bitmap_set(info->page_bitmap, k);
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}
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return page_to_addr(info->first_page, j);
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}
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}
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}
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k_panics("No page found!");
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return NULL;
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}
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void pmm_free_pages(void *page, uint32_t num_pages) {
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for (int i = 0; i < last_paging_info; ++i) {
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paging_info *info = &paging_infos[i];
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if (!info->flags.present) continue;
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// check if page is in memory area
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if (page < info->first_page || page > (info->first_page + info->size)) continue;
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// free page
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uint32_t first_page = addr_to_page(info->first_page, page);
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for (uint32_t current_page = first_page; current_page < first_page + num_pages; ++current_page) {
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bitmap_unset(info->page_bitmap, current_page);
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}
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}
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}
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