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-rw-r--r--kernel/src/boot.asm28
1 files 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: