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#include "paging.hpp"
#include "core/types.hpp"
#include "libs/stdio.hpp"
#include "libs/string.hpp"
char paging_status[PAGING_MAX_PAGE / 8];
u64 kernel_vma,stack_pma,userspace_pma;
u64 kpages[MAX_TABLES][512] __attribute__((aligned(4096)));
int kpages_next=1; // First page is for the pml4
u64* paging_allocate_table(){
u64 addr=(u64)kpages[kpages_next];
u64* allocated=(u64*)(addr-kernel_vma);
kpages_next++;
return allocated;
}
void paging_enable() {
// Init linker variables
asm("movq $__kernel_vma, %0":"=r"(kernel_vma));
asm("movq $__userspace_pma, %0":"=r"(userspace_pma));
asm("movq $__stack_pma, %0":"=r"(stack_pma));
// Init status
for (int i = 0; i < PAGING_MAX_PAGE / 8; i++) {
paging_status[i] = 0;
}
// Init tables
for(int i=0;i<MAX_TABLES;i++){
memset(kpages[i], 0, 512*64);
}
// Allocate paging for the kernel (to not override the source
// code during the next paging_allocate_table() calls)
paging_allocate_contiguous(userspace_pma/4096);
// Setting up new kernel address space
for(u64 i=0;i<=0x10000000;i+=4096){
paging_allocate_addr(kpages[0],kernel_vma+i,i, 0x3,0); // Identity map
}
// 4096 bytes stack
paging_allocate_addr(kpages[0],kernel_vma-4096,stack_pma,0x3,0);
// Load new pml4
u64 kpage_phy=((u64)kpages[0]-kernel_vma);
asm volatile(
"mov %0, %%rax \n\t"
"mov %%rax, %%cr3 \n\t"
:: "r" (kpage_phy));
}
u64 paging_as_phy(u64* pml4_table, u64 virt){
u16 pml4=virt>>39&0x1FF;
u16 pdp=virt>>30&0x1FF;
u16 pd=virt>>21&0x1FF;
u16 pt=(virt>>12)&0x1FF;
u64* pdp_table=(u64*)PAGE(pml4_table[pml4]);
u64* pd_table=(u64*)PAGE(pdp_table[pdp]);
u64* pt_table=(u64*)PAGE(pd_table[pd]);
return((PAGE(pt_table[pt]))|(virt&0xFFF));
}
u64* paging_allocate_contiguous(int npages){
int n_contiguous=0;
for (int i = 0; i < PAGING_MAX_PAGE / 8; i++) {
for (int j = 0; j < 8; j++) {
char bit=(paging_status[i]&(0x1<<j))>>j;
if(bit!=1){
n_contiguous++;
}
else {
n_contiguous=0;
}
if(n_contiguous==npages){
n_contiguous--; // Since we use it now as index, not a counter
int start_page=(i*8+j)-n_contiguous;
while(n_contiguous>=0){
int cur_page=(i*8+j)-n_contiguous;
paging_status[cur_page/8]|=(0x1<<(cur_page%8)); // Allocate
n_contiguous--;
}
u64 phy_addr=(4096*start_page);
return (u64*) phy_addr;
}
}
}
printk("Could not allocate %d contigous pages. Kernel panic!",npages);
while(1);
return 0;
}
void paging_deallocate(u64 addr){
u64 page_number=PAGE(addr)/4096;
char byte=paging_status[page_number/8];
paging_status[page_number/8]=byte&(~(1<<(page_number%8)));
}
void paging_deallocate_pml4(u64* pml4){
for(int i=0;i<512;i++){
u64* pdp=(u64*)PAGE(pml4[i]);
if(pml4[i]==0)
continue;
for(int j=0;j<512;j++){
u64* pd=(u64*)PAGE(pdp[j]);
if(pdp[j]==0)
continue;
for(int k=0;k<512;k++){
u64* pt=(u64*)PAGE(pd[k]);
if(pd[k]==0)
continue;
for(int l=0;l<512;l++){
if(pt[l]==0)
continue;
paging_deallocate_table((u64*)PAGE(pt[l]));
}
paging_deallocate_table((u64*)PAGE(pd[k]));
}
paging_deallocate_table((u64*)PAGE(pdp[j]));
}
paging_deallocate_table((u64*)PAGE(pml4[i]));
}
paging_deallocate_table((u64*)PAGE((u64)pml4));
}
void paging_dump(int min, int max) {
for (int i = 0; i < PAGING_MAX_PAGE / 8; i++) {
if(i>=min && i<=max){
printk("Byte %d ", i);
for (int j = 0; j < 8; j++) {
char bit = (paging_status[i] & (0x1 << j)) >> j;
printk("%d", bit);
}
print("\n");
}
}
}
void paging_deallocate_table(u64* table){
char *c_table=(char*)PAGE((u64)table);
for(u8 i=0;i<8;i++){
paging_deallocate((u64)c_table);
c_table+=4096;
}
}
void paging_allocate_addr(u64* pml4_table, u64 virt, u64 phy, u16 options, u64 offset){
u16 pml4=virt>>39&0x1FF;
u16 pdp=virt>>30&0x1FF;
u16 pd=virt>>21&0x1FF;
u16 pt=virt>>12&0x1FF;
options&=0xFFF; // Ensure options are on 12bits
// Solve pdp
if(pml4_table[pml4] == 0){
pml4_table[pml4]=(u64)paging_allocate_table();
pml4_table[pml4]|=options;
paging_allocate_addr(pml4_table,virt,phy,options,offset);
return;
}
// Solve pd
u64* pdp_table=(u64*)(PAGE(pml4_table[pml4])+offset);
if(pdp_table[pdp] == 0){
pdp_table[pdp]=(u64)paging_allocate_table();
pdp_table[pdp]|=options;
paging_allocate_addr(pml4_table,virt,phy,options,offset);
return;
}
// Solve pt
u64* pd_table=(u64*)(PAGE(pdp_table[pdp])+offset);
if(pd_table[pd] == 0){
pd_table[pd]=(u64)paging_allocate_table();
pd_table[pd]|=options;
paging_allocate_addr(pml4_table,virt,phy,options,offset);
return;
}
// Solve address
u64* pt_table=(u64*)(PAGE(pd_table[pd])+offset);
if(pt_table[pt] == 0){
pt_table[pt]=PAGE(phy);
pt_table[pt]|=options;
return;
}
}
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