diff options
| author | Tianhao Wang <wth@riseup.net> | 2024-02-25 18:19:41 +0100 |
|---|---|---|
| committer | Tianhao Wang <shrik3@mailbox.org> | 2024-06-11 15:13:39 +0200 |
| commit | 798501b4b641e4ee7f329b541ca5a52d1155191f (patch) | |
| tree | 0a03c32a8b3fea06acab95887e6b1d3177d3d7f7 /startup.s | |
| parent | d6695e4c2654877c07b6147bf3867af2b9454694 (diff) | |
paging: switch to 1g huge page for kernel identity mapping
Diffstat (limited to 'startup.s')
| -rw-r--r-- | startup.s | 43 |
1 files changed, 13 insertions, 30 deletions
@@ -23,8 +23,9 @@ STACKSIZE: equ 65536 ; video memory base address CGA: equ 0xB8000 -; 256 GB maximum RAM size for page table -MAX_MEM: equ 254 +; 512 GB maximum RAM size for page table +; DON'T MODIFY THIS UNLESS YOU UPDATE THE setup_paging accordingly +MAX_MEM: equ 512 ; Multiboot constants MULTIBOOT_PAGE_ALIGN equ 1<<0 @@ -165,36 +166,21 @@ setup_paging: or eax, 0xf mov dword [pml4+0], eax mov dword [pml4+4], 0 - - ; PDPE (Page Directory Pointer Entry / 2nd level) for currently 16 GB - mov eax, pd - or eax, 0x7 ; address of the first table (3rd level) with flags + ; PDPE flags + mov eax, 0x0 | 0x87 ; start-address bytes bit [30:31] + flags + mov ebx, 0 ; start-address bytes bit [32:38] mov ecx, 0 fill_tables2: - cmp ecx, MAX_MEM ; reference MAX_MEM tables + ; fill one single PDP table, with 1G pages, 512 PDPE maps to 512 GB + cmp ecx, MAX_MEM je fill_tables2_done - mov dword [pdp + 8*ecx + 0], eax - mov dword [pdp + 8*ecx + 4], 0 - add eax, 0x1000 ; tables are sized 4 kB each + mov dword [pdp + 8*ecx + 0], eax ; low bytes + mov dword [pdp + 8*ecx + 4], ebx ; high bytes + add eax, 0x40000000 ; 1G per page + adc ebx, 0 ; overflow? -> increment higher-order half of the address inc ecx ja fill_tables2 fill_tables2_done: - - ; PDE (Page Directory Entry / 3rd level) - mov eax, 0x0 | 0x87 ; start-address bytes 0..3 (=0) + flags - mov ebx, 0 ; start-address bytes 4..7 (=0) - mov ecx, 0 -fill_tables3: - cmp ecx, 512*MAX_MEM ; fill MAX_MEM tables with 512 entries each - je fill_tables3_done - mov dword [pd + 8*ecx + 0], eax ; low bytes - mov dword [pd + 8*ecx + 4], ebx ; high bytes - add eax, 0x200000 ; 2 MB per page - adc ebx, 0 ; overflow? -> increment higher-order half of the address - inc ecx - ja fill_tables3 -fill_tables3_done: - ; set base pointer to PML4 mov eax, pml4 mov cr3, eax @@ -532,8 +518,5 @@ pml4: alignb 4096 pdp: - resb MAX_MEM*8 + resb 4096 alignb 4096 - -pd: - resb MAX_MEM*4096 |