diff options
| author | Dennis Kobert <dennis@kobert.dev> | 2019-10-25 03:59:21 +0200 |
|---|---|---|
| committer | Dennis Kobert <dennis@kobert.dev> | 2019-10-25 03:59:21 +0200 |
| commit | 92ad44ce3af9b000146d324e5c0f5dfce16927f9 (patch) | |
| tree | b350c1eda444a67d165882ea42dd41fb3ba9e946 | |
| parent | f45b2e7c13b3c8821832374e3e8860eabaaae5d2 (diff) | |
Start 64bit mode
| -rw-r--r-- | kernel/src/boot.asm | 41 | ||||
| -rw-r--r-- | kernel/src/long_mode_init.asm | 17 |
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 |