Hello,
I am trying to convert my x86 kernel into a higher half kernel. I'm using GNU GRUB version 2.06 and without higer half modification my kernel works perfectly.
But when i tried the convert it to higher half i get
Code:
error: entry point isn't a segment
. Here is my updated bootloader code:
loader.asm:
Code:
MBALIGN equ 1<<0
MEMINFO equ 1<<1
FLAGS equ MBALIGN | MEMINFO
MAGIC equ 0x1BADB002
CHECKSUM equ -(MAGIC + FLAGS)
;constants for loading higher half kernel
VM_BASE equ 0xC0000000
PDE_INDEX equ (VM_BASE >> 22)
PSE_BIT equ 0x00000010
PG_BIT equ 0x80000000
section .multiboot
align 4
dd MAGIC
dd FLAGS
dd CHECKSUM
section .data
align 4096
global TEMP_PAGE_DIRECTORY
TEMP_PAGE_DIRECTORY:
dd 0x00000083
times(PDE_INDEX - 1) dd 0
dd 0x00000083
times(1024 - PDE_INDEX - 1) dd 0
section .initial_stack, nobits
align 4
stack_bottom:
; 1mb of uninitialized data(1024*1024=104856)
resb 104856
stack_top:
; Kernel entry
section .text
global kernel_entry
global low_kernel_entry
low_kernel_entry equ (kernel_entry - VM_BASE)
kernel_entry:
mov ecx, (TEMP_PAGE_DIRECTORY - VM_BASE)
mov cr3, ecx
mov ecx, cr4;
or ecx, PSE_BIT
mov cr4, ecx
mov ecx, cr0
or ecx, PG_BIT
mov cr0, ecx
lea ecx, [higher_half]
jmp ecx
higher_half:
mov dword[TEMP_PAGE_DIRECTORY], 0
invlpg[0]
mov esp, stack_top
extern kernel_main
push ebx
call kernel_main
loop:
jmp loop
and here is my linker.ld:
Code:
OUTPUT_FORMAT("elf32-i386")
ENTRY(low_kernel_entry)
SECTIONS
{
. = 0xC0100000;
.text ALIGN(4K) : AT(ADDR(.text)-0xC0000000)
{
*(.multiboot)
*(.text)
}
.rodata ALIGN (4K) : AT(ADDR(.rodata)-0xC0000000)
{
*(.rodata)
}
.bss ALIGN(4K) : AT(ADDR(.bss)-0xC0000000)
{
*(.COMMON)
*(.bss)
*(.initial_stack)
}
.data ALIGN(4K) : AT(ADDR(.data)-0xC0000000)
{
*(.data)
}
end = .;
}
I tried to change manipulate -0xC0000000 parts by assigning them to variables and substracking the variables instead of constants but nothing changed.
I will be thankfull for any help!
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