natkernel/memory.c at master · cripto-bot/natkernel · GitHub

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/* NATKERNEL Virtual Memory — N=7 IR kinds */
#include"kernel.h"

#definePAGE_PRESENT 1
#definePAGE_WRITABLE 2
#definePAGE_USER 4
#defineTOTAL_PAGES (256 * 1024 * 1024 / PAGE_SIZE)
#defineBITMAP_SIZE (TOTAL_PAGES / 8)

typedefstruct {
u64entries[512];
} __attribute__((aligned(PAGE_SIZE))) PageTable;

staticu8alloc_bitmap[BITMAP_SIZE];
staticPageTablekernel_pml4 __attribute__((aligned(PAGE_SIZE)));
staticu64total_allocated=0;

staticinlineintbit_test(u8*bitmap, u64idx) {
return (bitmap[idx / 8] >> (idx % 8)) &1;
}
staticinlinevoidbit_set(u8*bitmap, u64idx) {
bitmap[idx / 8] |= (1 << (idx % 8));
}
staticinlinevoidbit_clear(u8*bitmap, u64idx) {
bitmap[idx / 8] &= ~(1 << (idx % 8));
}

u64alloc_page() {
for (u64i=0; i<TOTAL_PAGES; i++) {
if (bit_test(alloc_bitmap, i) ==0) {
bit_set(alloc_bitmap, i);
total_allocated++;
returni*PAGE_SIZE;
 }
 }
return0;
}

voidfree_page(u64addr) {
u64idx=addr / PAGE_SIZE;
if (idx<TOTAL_PAGES) {
if (bit_test(alloc_bitmap, idx)) {
bit_clear(alloc_bitmap, idx);
total_allocated--;
 }
 }
}

voidmap_page(u64vaddr, u64paddr, u64flags) {
u64l4= (vaddr >> 39) &0x1FFULL;
u64l3= (vaddr >> 30) &0x1FFULL;
u64l2= (vaddr >> 21) &0x1FFULL;
u64l1= (vaddr >> 12) &0x1FFULL;

if (kernel_pml4.entries[l4] ==0) {
u64new_pt=alloc_page();
kernel_pml4.entries[l4] =new_pt | PAGE_PRESENT | PAGE_WRITABLE;
 }

PageTable*l3_table= (PageTable*)(kernel_pml4.entries[l4] & ~0xFFF);
if (l3_table->entries[l3] ==0) {
u64new_pt=alloc_page();
l3_table->entries[l3] =new_pt | PAGE_PRESENT | PAGE_WRITABLE;
 }

PageTable*l2_table= (PageTable*)(l3_table->entries[l3] & ~0xFFF);
if (l2_table->entries[l2] ==0) {
u64new_pt=alloc_page();
l2_table->entries[l2] =new_pt | PAGE_PRESENT | PAGE_WRITABLE;
 }

PageTable*l1_table= (PageTable*)(l2_table->entries[l2] & ~0xFFF);
l1_table->entries[l1] =paddr | flags;
}

u64get_allocated() { returntotal_allocated; }