diff options
| author | Tianhao Wang <shrik3@mailbox.org> | 2024-04-18 03:21:50 +0200 |
|---|---|---|
| committer | Tianhao Wang <shrik3@mailbox.org> | 2024-06-11 15:16:34 +0200 |
| commit | 0614eb0a414311e652391d1eb08b97e1129871c2 (patch) | |
| tree | 5eada2051fb202f6cee453989b7619b00ec636e4 /boot/startup-x86_64.s | |
| parent | 6f236a7dfbbd74284fec216361f30813998397d3 (diff) | |
startup: flatten control flow
Diffstat (limited to 'boot/startup-x86_64.s')
| -rw-r--r-- | boot/startup-x86_64.s | 39 |
1 files changed, 16 insertions, 23 deletions
diff --git a/boot/startup-x86_64.s b/boot/startup-x86_64.s index 5413a80..3a8de41 100644 --- a/boot/startup-x86_64.s +++ b/boot/startup-x86_64.s @@ -95,28 +95,8 @@ init_longmode: or eax, 1 << 5 mov cr4, eax - ; create page table (mandatory) - call setup_paging - - ; activate Long Mode (for now in compatibility mode) - mov ecx, 0x0C0000080 ; select EFER (Extended Feature Enable Register) - rdmsr - or eax, 1 << 8 ; LME (Long Mode Enable) - wrmsr - - ; activate paging - mov eax, cr0 - or eax, 1 << 31 - mov cr0, eax - - ; jump to 64-bit code segment -> full activation of Long Mode - jmp 2 * 0x8 : longmode_start - -; -; Provisional identical page mapping, using 1G huge page (therefore only 2 table -; levels needed) -; - + ; Provisional identical page mapping, using 1G huge page (therefore only 2 table + ; levels needed) setup_paging: ; PML4 (Page Map Level 4 / 1st level) mov eax, pdp @@ -141,7 +121,20 @@ fill_tables2_done: ; set base pointer to PML4 mov eax, pml4 mov cr3, eax - ret +activate_long_mode: + ; activate Long Mode (for now in compatibility mode) + mov ecx, 0x0C0000080 ; select EFER (Extended Feature Enable Register) + rdmsr + or eax, 1 << 8 ; LME (Long Mode Enable) + wrmsr + ; activate paging + mov eax, cr0 + or eax, 1 << 31 + mov cr0, eax + + ; jump to 64-bit code segment -> full activation of Long Mode + jmp 2 * 0x8 : longmode_start + ; ; system start, part 2 (in 64-bit Long Mode) |