From 9b22a6965579ea1867aea291d910c96f386b518b Mon Sep 17 00:00:00 2001
From: Brett Weiland <brett_weiland@bpcspace.com>
Date: Tue, 24 Aug 2021 14:09:29 -0500
Subject: major backup 8.24.21

---
 src/bootloader/enter_kernel.asm | 72 ++++++++++++++++++++++++-----------------
 1 file changed, 43 insertions(+), 29 deletions(-)

(limited to 'src/bootloader/enter_kernel.asm')

diff --git a/src/bootloader/enter_kernel.asm b/src/bootloader/enter_kernel.asm
index d3933cf..ef2cd71 100644
--- a/src/bootloader/enter_kernel.asm
+++ b/src/bootloader/enter_kernel.asm
@@ -1,14 +1,14 @@
 [extern main]
 [extern _kernel_stack_loc]
-[extern _stage1_pagetable]
+[extern _kernel_page_size]
 enter_longmode:
 cli
 
-; TODO check if a20 is already set
 mov al, 0x92
 or al, 2
 out 0x92, al
 
+;enter 32 bit mode
 lgdt [protected_gdt.descriptor]
 mov eax, cr0
 or eax, 0x1
@@ -30,44 +30,56 @@ mov es, ax
 mov fs, ax
 mov gs, ax
 
-mov edi, _stage1_pagetable ; 0x3000
-mov cr3, edi     
-mov eax, 0      
-mov ecx, 0xc00 ; 0x1000
-rep stosd       
-mov edi, cr3
 
+mov edi, 0x10000
+mov cr3, edi
 
-mov DWORD [edi], _stage1_pagetable + 0x1003 ; pml4e[0] = pdpe
-add edi, 0x1000
-mov DWORD [edi], _stage1_pagetable + 0x2003 ; pdpe[0] = pde
-add edi, 0x1000
-mov DWORD [edi], 0x83 ; pde[0] = pte
+mov eax, 0
+mov ecx, 0x1800     ; bzero 6 pages
+rep stosd
 
-mov eax, cr4         
-or eax, 0x620
-mov cr4, eax         
+mov DWORD [0x10000], 0x11003 ; pml4e[0] = pdpe
+mov DWORD [0x11000], 0x12003 ; pdpe[0] = pde
+mov DWORD [0x12000], 0x83 ; pde[0] = pte
+
+mov DWORD [0x10ff8], 0x13003 
+mov DWORD [0x13ff0], 0x14003
+mov DWORD [0x14000], 0x15003
+
+mov eax, 0x100003
+mov ebx, 0
+mov ecx, _kernel_page_size
+.kernel_load_loop:
+mov DWORD [0x15000 + ebx], eax
+add ebx, 8
+add eax, 0x1000
+loop .kernel_load_loop
 
-;end of setting up pages
 
-mov ecx, 0xc0000080
-rdmsr
-or eax, 1 << 8
-wrmsr
 
-mov eax, cr0
-or eax, 1 << 31 | 1 << 0 ; this is where we set paging and protected mode (respectively)!
-mov cr0, eax
 
+mov eax, cr4         
+; PAE, OSFXSR, OSXMMEXCPT
+or eax, 1 << 5 | 1 << 9 | 1 << 10
+mov cr4, eax         
 
+;end of setting up pages
+;testing to see if NX bit is available. 
+;If it's not and we enable it, it will cause pagefaults on read
+mov eax, 0x80000001
+cpuid
+and edx, 1 << 20
+shr edx, 9
+  
 mov ecx, 0xc0000080
 rdmsr
-or eax, 1 << 8
+or eax, 1 << 8 | 1 << 11
+or eax, edx
 wrmsr
 
 mov eax, cr0
-and ax, 0xfffb
-or eax, 0x80000002
+or eax, 1 << 31 | 1 << 0; 
+and ax, ~(1 << 2)
 mov cr0, eax
 
 
@@ -76,8 +88,10 @@ lgdt [long_gdt.descriptor]
 jmp LONG_CODE_SEGMENT:enter_kernel
 enter_kernel:
 bits 64
-mov rbp, _kernel_stack_loc
+mov rbp, 0
 mov rsp, _kernel_stack_loc
-call main ; where we actually call the kernel
+mov rax, QWORD main
+;push QWORD 0 
+jmp rax
 jmp $
 ret
-- 
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