diff options
Diffstat (limited to 'kernel/l0/loader.s')
| -rw-r--r-- | kernel/l0/loader.s | 69 |
1 files changed, 69 insertions, 0 deletions
diff --git a/kernel/l0/loader.s b/kernel/l0/loader.s new file mode 100644 index 0000000..a31fcf5 --- /dev/null +++ b/kernel/l0/loader.s @@ -0,0 +1,69 @@ +[EXTERN k_highhalf_addr] + +[GLOBAL loader] ; making entry point visible to linker + +[EXTERN kmain] ; kmain is defined in kmain.c + +; loader stack size +LOADER_STACK_SIZE equ 0x8000 ; 8Kb + +; setting up the Multiboot header - see GRUB docs for details +MODULEALIGN equ 1<<0 ; align loaded modules on page boundaries +MEMINFO equ 1<<1 ; provide memory map +FLAGS equ MODULEALIGN | MEMINFO ; this is the Multiboot 'flag' field +MAGIC equ 0x1BADB002 ; 'magic number' lets bootloader find the header +CHECKSUM equ -(MAGIC + FLAGS) ; checksum required + +section .text +align 4 +MultiBootHeader: + dd MAGIC + dd FLAGS + dd CHECKSUM + +section .setup +loader: ;here, we load our false GDT, used for having the kernel in higher half + lgdt [trickgdt] + mov cx, 0x10; + mov ds, cx; + mov es, cx; + mov fs, cx; + mov gs, cx; + mov ss, cx; + + jmp 0x08:higherhalf + +section .text +higherhalf: ; now we're running in higher half + mov esp, stack_top ; set up the stack + + push eax ; pass Multiboot magic number + add ebx, k_highhalf_addr ; update the MB info structure so that it is in the new seg + push ebx ; pass Multiboot info structure + + call kmain ; call kernel proper + + cli ; disable interupts + +hang: + hlt ; halt machine should kernel return + jmp hang + +[section .setup] ; this is included in the .setup section, so that it thinks it is at 0x00100000 + +trickgdt: ; our false GDT + dw gdt_end - gdt - 1 ; gdt limit + dd gdt ; gdt base + +gdt: + dd 0, 0 ; null GDT entry + db 0xFF, 0xFF, 0, 0, 0, 10011010b, 11001111b, 0x40 ; kernel code segment + db 0xFF, 0xFF, 0, 0, 0, 10010010b, 11001111b, 0x40 ; kernel data segment + +gdt_end: + +[section .bss] +align 4 +stack_bottom: + resb LOADER_STACK_SIZE +stack_top: |