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restructure thread constructor and pagetable

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This commit is contained in:
Eggert Jung
2026-02-25 07:39:32 +01:00
parent 76f782c5ae
commit 22ab2fb2a5
8 changed files with 179 additions and 161 deletions
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148
kernel/memory/pagetable.cc
View File

@@ -104,3 +104,151 @@ void create_basic_page_table(four_lvl_paging_t* table, pagetable_t* kernel_ident
kernel_identity[0].entries[0].present = 0;
}
uintptr_t isMapped(uintptr_t vaddr, four_lvl_paging_t* flpt){
uint16_t l4Index = (vaddr>>39) & 0x1FF;
uint16_t l3Index = (vaddr>>30) & 0x1FF;
uint16_t l2Index = (vaddr>>21) & 0x1FF;
uint16_t l1Index = (vaddr>>12) & 0x1FF;
if(flpt->l4->entries[l4Index].present){
pagetable_t* lvl3 = (pagetable_t*)(flpt->l4->entries[l4Index].address<<12);
if(lvl3->entries[l3Index].present){
pagetable_t* lvl2 = (pagetable_t*)(lvl3->entries[l3Index].address<<12);
if(lvl2->entries[l2Index].present){
pagetable_t* lvl1 = (pagetable_t*)(lvl2->entries[l2Index].address<<12);
if(lvl1->entries[l1Index].present)
return lvl1->entries[l1Index].address<<12;
}
}
}
return 0;
}
void* getFreeVirtSpace(four_lvl_paging_t* search_table, uint8_t num_pages){
uint32_t start_v = 0x4000;
uint32_t stop_v = 0x6000;
static uint32_t next_start_v = 0x4000;
//static uint32_t next_start_v = start_v;
//start from last found address
for (uint32_t v=next_start_v; v<stop_v; v++) {
bool space_is_free = true;
for(uint32_t i=0; i<num_pages; i++){
if(isMapped((uintptr_t)(v+i)<<12, search_table)) {
space_is_free = false;
}
}
if(space_is_free){
//next_start_v = v+num_pages;
return (void*) ((uintptr_t) (v <<12));
}
}
//start again from the real start address
for (uint32_t v=start_v; v<next_start_v; v++) {
bool space_is_free = true;
for(uint32_t i=0; i<num_pages; i++){
if(isMapped((uintptr_t)(v+i)<<12, search_table)) {
space_is_free = false;
}
}
if(space_is_free){
next_start_v = v+num_pages;
return (void*) ((uintptr_t) (v <<12));
}
}
return 0;
}
void setMapping(uintptr_t vaddr, void* frame, four_lvl_paging_t* flpt){
uint16_t l4Index = (vaddr>>39) & 0x1FF;
uint16_t l3Index = (vaddr>>30) & 0x1FF;
uint16_t l2Index = (vaddr>>21) & 0x1FF;
uint16_t l1Index = (vaddr>>12) & 0x1FF;
if(!(flpt->l4->entries[l4Index].present)){
pagetable_t* newl3 = (pagetable_t*)PageFrameAllocator::alloc(true);
memset(newl3, 0, 4096);
flpt->l4->entries[l4Index] = {
.present = 1,
.write = 1,
.user = 1,
.address = (uintptr_t)newl3 >> 12
};
}
pagetable_t* lvl3 = (pagetable_t*)(flpt->l4->entries[l4Index].address<<12);
if(!(lvl3->entries[l3Index].present)){
pagetable_t* newl2 = (pagetable_t*)PageFrameAllocator::alloc(true);
memset(newl2, 0, 4096);
lvl3->entries[l3Index] = {
.present = 1,
.write = 1,
.user = 1,
.address = (uintptr_t)newl2 >> 12
};
}
pagetable_t* lvl2 = (pagetable_t*)(lvl3->entries[l3Index].address<<12);
if(!(lvl2->entries[l2Index].present)){
pagetable_t* newl1 = (pagetable_t*)PageFrameAllocator::alloc(true);
memset(newl1, 0, 4096);
lvl2->entries[l2Index] = {
.present = 1,
.write = 1,
.user = 1,
.address = (uintptr_t)newl1 >> 12
};
}
pagetable_t* lvl1 = (pagetable_t*)(lvl2->entries[l2Index].address<<12);
if(frame){
assert(!(lvl1->entries[l1Index].present)); // should not be present, bc its a new mapping
lvl1->entries[l1Index] = {
.present = 1,
.write = 1,
.user = 1,
.address = (uintptr_t)frame >> 12
};
}
else //unmap if nullptr
lvl1->entries[l1Index].present = 0;
}
void copy_pagetable(four_lvl_paging_t* parent_table, four_lvl_paging_t* child_table){
//can safely assume only one lvl4 entry
pagetable_t* lvl3 = (pagetable_t*)(parent_table->l4->entries[0].address<<12);
for(uint16_t i3=0; i3<512; i3++){
if(lvl3->entries[i3].present){
pagetable_t* lvl2 = (pagetable_t*)(lvl3->entries[i3].address<<12);
for(uint16_t i2=0; i2<512; i2++){
if(lvl2->entries[i2].present){
pagetable_t* lvl1 = (pagetable_t*)(lvl2->entries[i2].address<<12);
for(uint16_t i1=0; i1<512; i1++){
if(lvl1->entries[i1].present){
uintptr_t vaddr =
((uintptr_t)i3<<30) |
((uintptr_t)i2<<21) |
((uintptr_t)i1<<12) ;
if(!isMapped(vaddr, child_table)){
//only copy if not part of basic pagetable
assert( (i3>0) || (i2>=32)); //assert user memory
void* frame = PageFrameAllocator::alloc(false);
setMapping(vaddr, frame, child_table);
//map to local space for copy
void* dest = getFreeVirtSpace(parent_table, 1);
setMapping((uintptr_t)dest, frame, parent_table);
memcpy(dest, (void*)vaddr, 4096);
setMapping((uintptr_t)dest, 0, parent_table);
}
}
}
}
}
}
}
}

5
kernel/memory/pagetable.h
View File

@@ -50,7 +50,10 @@ typedef struct {
void write_identity_map(pagetable_t* identity_table, uint64_t size);
void create_basic_page_table(four_lvl_paging_t* table, pagetable_t* kernel_identity);
void load_cr3(void* cr3_value);
void map_pageframe(four_lvl_paging_t* table, uintptr_t phys, uintptr_t virt);
void setMapping(uintptr_t vaddr, void* frame, four_lvl_paging_t* flpt);
uintptr_t isMapped(uintptr_t vaddr, four_lvl_paging_t* flpt);
void* getFreeVirtSpace(four_lvl_paging_t* search_table, uint8_t num_pages);
void copy_pagetable(four_lvl_paging_t* parent_table, four_lvl_paging_t* child_table);
//typedef struct {
// same