diff options
Diffstat (limited to 'src/stem/loader_.asm')
| -rw-r--r-- | src/stem/loader_.asm | 63 |
1 files changed, 63 insertions, 0 deletions
diff --git a/src/stem/loader_.asm b/src/stem/loader_.asm new file mode 100644 index 0000000..e1031b4 --- /dev/null +++ b/src/stem/loader_.asm @@ -0,0 +1,63 @@ +[GLOBAL loader] ; making entry point visible to linker +[EXTERN kmain] ; kmain is defined in kmain.c + +STACKSIZE equ 0x4000 ; that's 16k. + +; 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+STACKSIZE ; set up the stack + push eax ; pass Multiboot magic number + add ebx, 0xE0000000 ; 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, 0x20 ; kernel code segment + db 0xFF, 0xFF, 0, 0, 0, 10010010b, 11001111b, 0x20 ; kernel data segment + +gdt_end: + +[section .bss] +align 32 +stack: + resb STACKSIZE ; reserve 16k stack on a quadword boundary |