From f3dcfa225a6e3b7e6916e9b5a22db9090275d065 Mon Sep 17 00:00:00 2001
From: Dennis Kobert <dennis@kobert.dev>
Date: Fri, 8 Nov 2019 21:49:25 +0100
Subject: Fix paging

---
 kernel/src/boot.asm | 28 ++++++++++++----------------
 1 file changed, 12 insertions(+), 16 deletions(-)

diff --git a/kernel/src/boot.asm b/kernel/src/boot.asm
index 1c0b3da..96a1fc1 100644
--- a/kernel/src/boot.asm
+++ b/kernel/src/boot.asm
@@ -12,8 +12,8 @@ start:
 
 	call setup_page_tables
 	call enable_paging
-    
-	
+
+   
     ; load the 64-bit GDT
     lgdt [gdt64.pointer]
 	jmp gdt64.code:long_mode_start
@@ -95,29 +95,26 @@ setup_page_tables:
 	; map each P2 entry to a huge 2MiB page
     mov ecx, 0         ; counter variable
     mov eax, 0b10000011 ; present + writable + huge
+    mov edx, stack_bottom
+    shr edx, 18
 
 .map_p2_table:
-    ; map ecx-th P2 entry to a huge page that starts at address 2MiB*ecx
     mov ebx, eax
-    cmp eax, stack_bottom + 0b10000011 - 0x400000 
-    jne .hit_stack 
-    and ebx, ~1
-    mov [p2_table + ecx     ], eax ; map ecx-th entry
-	add ecx, 8
+    ; map ecx-th P2 entry to a huge page that starts at address 2MiB*ecx
+    cmp ecx, edx
+    jne .valid_memory 
+    add ebx, ~1
+    sub eax, 0x200000  ; 2MiB
 
-.hit_stack:
+.valid_memory:
     mov [p2_table + ecx     ], ebx ; map ecx-th entry
     add eax, 0x200000  ; 2MiB
 
 	add ecx, 8
-	;add ecx, 32
     cmp ecx, 4096      ; if counter == 512, the whole P2 table is mapped
     jne .map_p2_table  ; else map the next entry
-
-	ret
-
-    
     
+	ret
 
 enable_paging:
 	mov eax, p4_table
@@ -142,7 +139,6 @@ enable_paging:
     ; move stack pointer to accommodate for the guard page
     add esp, 0x200000
 
-
     ret
 
 section .rodata
@@ -173,5 +169,5 @@ p2_table:
 	resb 4096
 alignb 4096 * 512
 stack_bottom:
-	resb 4096 * 4
+	resb 4096 * 42
 stack_top:
-- 
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