diff options
Diffstat (limited to 'head.S')
| -rw-r--r-- | head.S | 51 |
1 files changed, 39 insertions, 12 deletions
@@ -62,26 +62,53 @@ _start: cld cli - /* setup stack, because we are heading off to "C" */ - movl $STACK_OFFSET, %esp - /* after call bootstub, GDT was set (0x10 and 0x18) IDT was clear - * eax will store 32bit entry of bzImage - */ - calll bootstub - /* DS=ES=FS=GS=10 */ + + /* Set our own GDT and IDT, don't derive from IAFW */ + lgdtl %cs:gdtr + lidtl %cs:idtr + + /* Load segment registers per protected mode kernel entry requirement: + * CS=0x10, + * DS=ES=SS=FS=GS=0x18 + */ + ljmp $__BOOT_CS, $1f +1: movl $__BOOT_DS, %ebx movl %ebx, %ds movl %ebx, %es movl %ebx, %fs movl %ebx, %gs movl %ebx, %ss - ljmp $__BOOT_CS,$1f -1: + + /* setup stack, because we are heading off to "C" */ + movl $STACK_OFFSET, %esp + + /* bootstub() returns 32bit entry address of bzImage, stored in eax */ + calll bootstub + /* tell kernel where is boot_param */ movl $(BOOT_PARAMS_OFFSET), %esi xor %ebp, %ebp xor %edi, %edi xor %ebx, %ebx - - jmpl *%eax # Jump to the 32-bit entrypoint - + + /* Jump to the 32-bit entrypoint */ + jmpl *%eax + + .balign 8 +gdt: + .quad 0 + .quad 0 + .quad GDT_ENTRY(0xc09b, 0, 0xfffff) + .quad GDT_ENTRY(0xc093, 0, 0xfffff) +gdtr: + .word 4*8-1 + .long gdt + + .balign 8 +idt: + .quad 0 + .quad 0 +idtr: + .word 2*8-1 + .long idt |