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authorDennis Kobert <dennis@kobert.dev>2019-10-25 03:59:21 +0200
committerDennis Kobert <dennis@kobert.dev>2019-10-25 03:59:21 +0200
commit92ad44ce3af9b000146d324e5c0f5dfce16927f9 (patch)
treeb350c1eda444a67d165882ea42dd41fb3ba9e946 /kernel
parentf45b2e7c13b3c8821832374e3e8860eabaaae5d2 (diff)
Start 64bit mode
Diffstat (limited to 'kernel')
-rw-r--r--kernel/src/boot.asm41
-rw-r--r--kernel/src/long_mode_init.asm17
2 files changed, 56 insertions, 2 deletions
diff --git a/kernel/src/boot.asm b/kernel/src/boot.asm
index 3d79096..e3484c1 100644
--- a/kernel/src/boot.asm
+++ b/kernel/src/boot.asm
@@ -1,4 +1,5 @@
global start
+extern long_mode_start
section .text
bits 32
@@ -9,8 +10,12 @@ start:
call check_cpuid
call check_long_mode
- ; print 'OK'
- mov dword [0xb8000], 0x2f4b2f4f
+ call setup_page_tables
+ call enable_paging
+ ; load the 64-bit GDT
+ lgdt [gdt64.pointer]
+ jmp gdt64.code:long_mode_start
+
hlt
check_multiboot:
@@ -105,6 +110,38 @@ setup_page_tables:
jne .map_p2_table ; else map the next entry
ret
+
+enable_paging:
+ mov eax, p4_table
+ mov cr3, eax
+
+ ; enable PAE-flag in cr4 (Physical Address Extension)
+ mov eax, cr4
+ or eax, 1 << 5
+ mov cr4, eax
+
+ ; set the long mode bit in the EFER MSR (model specific register)
+ mov ecx, 0xC0000080
+ rdmsr
+ or eax, 1 << 8
+ wrmsr
+
+ ; enable paging in the cr0 register
+ mov eax, cr0
+ or eax, 1 << 31
+ mov cr0, eax
+
+ ret
+
+section .rodata
+gdt64:
+ dq 0 ; zero entry
+.code: equ $ - gdt64
+ dq (1<<43) | (1<<44) | (1<<47) | (1<<53) ; code segment
+.pointer:
+ dw $ - gdt64 - 1
+ dq gdt64
+
; Prints 'ERR: ' and the given error code to the screen and halts
; parameter: error code letter (ascii) in al
error:
diff --git a/kernel/src/long_mode_init.asm b/kernel/src/long_mode_init.asm
new file mode 100644
index 0000000..f105388
--- /dev/null
+++ b/kernel/src/long_mode_init.asm
@@ -0,0 +1,17 @@
+global long_mode_start
+
+section .text
+bits 64
+long_mode_start:
+ ; load 0 into all data segment registers
+ mov ax, 0
+ mov ss, ax
+ mov ds, ax
+ mov es, ax
+ mov fs, ax
+ mov gs, ax
+
+ ; print `Uff!` to screen
+ mov rax, 0x8521846683668255
+ mov qword [0xb8000], rax
+ hlt