83 lines
2.4 KiB
C
83 lines
2.4 KiB
C
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#include <string.h>
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#include <stdio.h>
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#include <mm/paging.h>
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#include <mm/pmm.h>
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#define PAGE_DIRECTORY_ENTRIES 1024
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#define PAGE_TABLE_ENTRIES 1024
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#define PAGE_SIZE 4096
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typedef uint32_t page_directory_entry_t;
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typedef uint32_t page_table_entry_t;
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static page_directory_entry_t* page_directory = (page_directory_entry_t*)0x9C000; /* Must be page-aligned */
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static page_table_entry_t* page_tables[PAGE_DIRECTORY_ENTRIES];
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extern void _enable_paging_asm(void);
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void paging_init(void)
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{
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/* Allocate and clear the page directory */
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page_directory = (uint32_t*)alloc_page();
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memset(page_directory, 0, 4096);
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/* Allocate and set up the first identity-mapped page table (0–4MB) */
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uint32_t* first_table = (uint32_t*)alloc_page();
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memset(first_table, 0, 4096);
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for (uint32_t i = 0; i < 1024; i++)
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{
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first_table[i] = (i * 0x1000) | 3; /* Present | RW */
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}
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page_directory[0] = ((uint32_t)first_table) | 3;
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/* --- Map 4MB heap at 0xC0000000 --- */
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uint32_t* heap_table = (uint32_t*)alloc_page();
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memset(heap_table, 0, 4096);
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for (uint32_t i = 0; i < 1024; i++) /* 256 pages = 1MB */
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{
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uint32_t phys = (uint32_t)alloc_page();
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if (phys == 0)
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{
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printf("Out of physical memory during heap mapping!\n");
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while (1);
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}
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heap_table[i] = phys | 3; /* Present | RW */
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}
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/* 0xC0000000 >> 22 == 768 */
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page_directory[768] = ((uint32_t)heap_table) | 3;
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// Load page directory
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asm volatile ("mov %0, %%cr3" : : "r"(page_directory));
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/* Enable paging */
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_enable_paging_asm();
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}
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void map_page(void* phys_addr, void* virt_addr)
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{
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uint32_t pd_index = ((uint32_t)virt_addr >> 22) & 0x3FF;
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uint32_t pt_index = ((uint32_t)virt_addr >> 12) & 0x3FF;
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/* Allocate page table if necessary */
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if (!(page_directory[pd_index] & 1))
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{
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void* pt_phys = alloc_page();
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page_tables[pd_index] = (page_table_entry_t*)((uint32_t)pt_phys + 0xC0000000); /* Map it higher */
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for (int i = 0; i < PAGE_TABLE_ENTRIES; i++)
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{
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page_tables[pd_index][i] = 0x00000002; /* Not present */
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}
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page_directory[pd_index] = ((uint32_t)pt_phys) | 0x3; /* Present, R/W */
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}
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page_table_entry_t* page_table = (page_table_entry_t*)((page_directory[pd_index] & 0xFFFFF000) | 0xC0000000);
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page_table[pt_index] = ((uint32_t)phys_addr & 0xFFFFF000) | 0x3; /* Present, R/W */
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asm volatile ("invlpg (%0)" :: "r" (virt_addr) : "memory");
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}
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