OSDev.org

Code: Select all

[BITS 32]

[global start_kernel]

[extern __CTOR_LIST__]
[extern second_stage]
[extern paging]

%include "multi_boot_header.i"

  section .text
  
  start_kernel:
  
  ; set up stack
  mov esp, 0x7FFFF
  
; set up trick gdt according to tim robinson (segment base at 0x40000000 etc.)
  lgdt [trick_gdt]
  mov ax, 0x10
  mov ds, ax
  mov es, ax
  mov fs, ax
  mov gs, ax
  mov ss, ax
  
; adapt stack pointer
  add esp, 0xC0000000
  
; far jump
  jmp 0x08:flush_trick_gdt  
flush_trick_gdt:

; PLACE A:
; call constructors right after setting up the trick gdt
; doing it that way, it ends up in an endless loop (see call ebx)

    lea eax, [__CTOR_LIST__]
    mov ecx, [eax] ; number of ctor
    add eax, 4
    
call_all_ctor:
    mov ebx, [eax]
    push eax    ; save eax on stack as eax changes during call
    push ecx

; here I call the compiler generated code to create the global objects
; this call does not return and seems to get stucked...
    call ebx

    pop ecx
    ; decrement number of ctor
    dec ecx
    ; get function pointer from stack
    pop eax
    ; increment function pointer of ctor 
    add eax, 4

    cmp ecx, 0

    jnz call_all_ctor
    
  call paging

; set up "normal" gdt (segment base at 0x00000000)  
  lgdt [normal_gdt]
  mov ax, 0x10
  mov ds, ax
  mov es, ax
  mov fs, ax
  mov gs, ax
  mov ss, ax
  
; far jump
  jmp 0x08:flush_normal_gdt
flush_normal_gdt:

  ; PLACE B:
  ; calling constructors here, does not produce any problem...
  ; the kernel will execute just as expected

; rest of kernel...
jmp second_stage



section .setup

trick_gdt:
    dw trick_gdt_end - trick_gdt_start - 1
    dd trick_gdt_start
 
trick_gdt_start:
    dd 0, 0                         ; null gate
    db 0xFF, 0xFF, 0, 0, 0, 10011010b, 11001111b, 0x40  ; code selector 0x08: base 0x40000000, limit 0xFFFFFFFF, type 0x9A, granularity 0xCF
    db 0xFF, 0xFF, 0, 0, 0, 10010010b, 11001111b, 0x40  ; data selector 0x10: base 0x40000000, limit 0xFFFFFFFF, type 0x92, granularity 0xCF
 
trick_gdt_end:


section .data
 
normal_gdt:
    dw normal_gdt_end - normal_gdt_start - 1
    dd normal_gdt_start
 
normal_gdt_start:
    dd 0, 0
    db 0xFF, 0xFF, 0, 0, 0, 10011010b, 11001111b, 0x0  ; code selector 0x08: base 0x0, limit 0xFFFFFFFF, type 0x9A, granularity 0xCF
    db 0xFF, 0xFF, 0, 0, 0, 10010010b, 11001111b, 0x0  ; data selector 0x10: base 0x0, limit 0xFFFFFFFF, type 0x92, granularity 0xCF
 
normal_gdt_end:

Code: Select all

OUTPUT_FORMAT("elf32-i386")
ENTRY(start_kernel)
PAGESIZE = 4096;
GRUB_OFFSET = 0x100000;
SECTIONS
{
  . = GRUB_OFFSET;
  
  /*some add on to recover from GRUB error 13 (complaining about header)*/
  .__mbHeader :
  {
    *(.__mbHeader)
  }
  
  .setup ALIGN (PAGESIZE) :
  {
    *(.setup)
  }
  
  . += 0xC0000000; 
  
  .text ALIGN (PAGESIZE) : AT(ADDR(.text) - 0xC0000000)
  {
    code = .; _code = .; __code = .;
    *(.text)
  }
  
  .data ALIGN (PAGESIZE) : AT(ADDR(.data) - 0xC0000000)
  {
    data_start = .;
    
    __CTOR_LIST__ = .; 
    LONG((__CTOR_END__ - __CTOR_LIST__) / 4-2)
    *(.ctors)
    LONG(0)
    __CTOR_END__ = .;
    
    __DTOR_LIST__ = .;
    LONG((__DTOR_END__ - __DTOR_LIST__) / 4-2)
    *(.dtors) 
    LONG(0)__DTOR_END__ = .;
    
    data = .; _data = .; __data = .;
    *(.data)
  }
  
  .bss ALIGN (PAGESIZE) : AT(ADDR(.bss) - 0xC0000000)
  {
    bss = .; _bss = .; __bss = .;
    *(.bss)
  }
  
  end = .; _end = .; __end = .;
  
  page_dir_sym = ALIGN(PAGESIZE);
  . = . + 4096;
  page_table_sym = ALIGN(PAGESIZE);
  . += 4096;
  
  phys_bitmap_start_sym = ALIGN(PAGESIZE); 
}

Code: Select all

static X &X::Instance()
{
  static X x;
  return x; 
}