diff options
Diffstat (limited to 'kernel/boot.S')
| -rw-r--r-- | kernel/boot.S | 44 |
1 files changed, 36 insertions, 8 deletions
diff --git a/kernel/boot.S b/kernel/boot.S index e870c37..ee35eeb 100644 --- a/kernel/boot.S +++ b/kernel/boot.S @@ -5,6 +5,7 @@ .code32 _start: + cli mov $stack_top, %esp pushl $0 pushl %eax @@ -18,8 +19,8 @@ _start: call setup_page_tables call enable_paging - lgdt gdt64_pointer - ljmp $gdt64_code_segment, $begin_long_mode + lgdt gdt_pointer + ljmp $0x08, $begin_long_mode check_multiboot: @@ -143,11 +144,38 @@ page_table_lvl3: page_table_lvl2: .skip 4096*4 +// Access bits .section .rodata -gdt64: +.set PRESENT, 1 << 7 +.set NOT_SYS, 1 << 4 +.set EXEC, 1 << 3 +.set DC, 1 << 2 +.set RW, 1 << 1 +.set ACCESSED, 1 << 0 + +// Flags bits +.set GRAN_4K, 1 << 7 +.set SZ_32, 1 << 6 +.set LONG_MODE, 1 << 5 + +gdt: +gdt_null = . - gdt .quad 0 -gdt64_code_segment = . - gdt64 - .quad 1<<43 + 1<<44 + 1<<47 + 1<<53 -gdt64_pointer: - .word . - gdt64 - 1 - .quad gdt64 +gdt_code = . - gdt + .long 0xFFFF // Limit & Base (low, bits 0-15) + .byte 0 // Base (mid, bits 16-23) + .byte PRESENT | NOT_SYS | EXEC | RW // Access + .byte GRAN_4K | LONG_MODE | 0xF // Flags & Limit (high, bits 16-19) + .byte 0 // Base (high, bits 24-31) +gdt_data = . - gdt + .long 0xFFFF + .byte 0 + .byte PRESENT | NOT_SYS | RW + .byte GRAN_4K | SZ_32 | 0xF + .byte 0 +gdt_tss = . - gdt + .long 0x00000068 + .long 0x00CF8900 +gdt_pointer: + .word . - gdt - 1 + .quad gdt |