Linker errors with OSDever kernel

maddog39 · Post by **maddog39** » Thu Feb 22, 2007 4:46 pm

Hello all,

I am learning OS development via many tutorials I've found on the internet and now I am trying to build a simple kernel using the osdever.net "Brans Kernel Development" tutorial. Now, all my code is fine except every time I try to link I get hundreds of "undefined references" and this happens every single time I try a kernel tutorial. I cant seem to see what it is that im doing wrong.

Here is the debug output:

Code: Select all

maddog39@maddog39-desktop:~/Projects/freeloader$ make
ld -T link.ld -o kernel.bin boot.o main.o screen.o gdt.o idt.o isrs.o irqs.o  sysclock.o keyboard.o
boot.o:boot.o:(.text+0x2d): undefined reference to `_main'
boot.o:boot.o:(.text+0x36): undefined reference to `_gp'
boot.o:boot.o:(.text+0x53): undefined reference to `_idtp'
boot.o:boot.o:(.text+0x1a3): undefined reference to `_fault_handler'
boot.o:boot.o:(.text+0x26f): undefined reference to `_irq_handler'
gdt.o: In function `gdt_install':gdt.c:(.text+0x109): undefined reference to `gdt_flush'
idt.o: In function `idt_install':idt.c:(.text+0x6d): undefined reference to `idt_load'
isrs.o: In function `isrs_install':isrs.c:(.text+0x17): undefined reference to `isr0'
:isrs.c:(.text+0x3b): undefined reference to `isr1'
:isrs.c:(.text+0x5f): undefined reference to `isr2'
:isrs.c:(.text+0x83): undefined reference to `isr3'
:isrs.c:(.text+0xa7): undefined reference to `isr4'
:isrs.c:(.text+0xcb): undefined reference to `isr5'
:isrs.c:(.text+0xef): undefined reference to `isr6'
:isrs.c:(.text+0x113): undefined reference to `isr7'
:isrs.c:(.text+0x137): undefined reference to `isr8'
:isrs.c:(.text+0x15b): undefined reference to `isr9'
:isrs.c:(.text+0x17f): undefined reference to `isr10'
:isrs.c:(.text+0x1a3): undefined reference to `isr11'
:isrs.c:(.text+0x1c7): undefined reference to `isr12'
:isrs.c:(.text+0x1eb): undefined reference to `isr13'
:isrs.c:(.text+0x20f): undefined reference to `isr14'
:isrs.c:(.text+0x233): undefined reference to `isr15'
:isrs.c:(.text+0x257): undefined reference to `isr16'
:isrs.c:(.text+0x27b): undefined reference to `isr17'
:isrs.c:(.text+0x29f): undefined reference to `isr18'
:isrs.c:(.text+0x2c3): undefined reference to `isr19'
:isrs.c:(.text+0x2e7): undefined reference to `isr20'
:isrs.c:(.text+0x30b): undefined reference to `isr21'
:isrs.c:(.text+0x32f): undefined reference to `isr22'
:isrs.c:(.text+0x353): undefined reference to `isr23'
:isrs.c:(.text+0x377): undefined reference to `isr24'
:isrs.c:(.text+0x39b): undefined reference to `isr25'
:isrs.c:(.text+0x3bf): undefined reference to `isr26'
:isrs.c:(.text+0x3e3): undefined reference to `isr27'
:isrs.c:(.text+0x407): undefined reference to `isr28'
:isrs.c:(.text+0x42b): undefined reference to `isr29'
:isrs.c:(.text+0x44f): undefined reference to `isr30'
:isrs.c:(.text+0x473): undefined reference to `isr31'
irqs.o: In function `irq_install':irqs.c:(.text+0x1ce): undefined reference to `irq0'
:irqs.c:(.text+0x1f2): undefined reference to `irq1'
:irqs.c:(.text+0x216): undefined reference to `irq2'
:irqs.c:(.text+0x23a): undefined reference to `irq3'
:irqs.c:(.text+0x25e): undefined reference to `irq4'
:irqs.c:(.text+0x282): undefined reference to `irq5'
:irqs.c:(.text+0x2a6): undefined reference to `irq6'
:irqs.c:(.text+0x2ca): undefined reference to `irq7'
:irqs.c:(.text+0x2ee): undefined reference to `irq8'
:irqs.c:(.text+0x312): undefined reference to `irq9'
:irqs.c:(.text+0x336): undefined reference to `irq10'
:irqs.c:(.text+0x35a): undefined reference to `irq11'
:irqs.c:(.text+0x37e): undefined reference to `irq12'
:irqs.c:(.text+0x3a2): undefined reference to `irq13'
:irqs.c:(.text+0x3c6): undefined reference to `irq14'
:irqs.c:(.text+0x3ea): undefined reference to `irq15'
make: *** [kernel.bin] Error 1

Linker Script

Code: Select all

OUTPUT_FORMAT("binary")
ENTRY(start)
phys = 0x00100000;
SECTIONS
{
  .text phys : AT(phys) {
    code = .;
    *(.text)
    . = ALIGN(4096);
  }
  .data : AT(phys + (data - code))
  {
    data = .;
    *(.data)
    . = ALIGN(4096);
  }
  .bss : AT(phys + (bss - code))
  {
    bss = .;
    *(.bss)
    . = ALIGN(4096);
  }
  end = .;
}

Assembler File / Loader

Code: Select all

[BITS 32]
global start
start:
    mov esp, _sys_stack     ; This points the stack to our new stack area
    jmp stublet

; This part MUST be 4byte aligned, so we solve that issue using 'ALIGN 4'
ALIGN 4
mboot:
    ; Multiboot macros to make a few lines later more readable
    MULTIBOOT_PAGE_ALIGN	equ 1<<0
    MULTIBOOT_MEMORY_INFO	equ 1<<1
    MULTIBOOT_AOUT_KLUDGE	equ 1<<16
    MULTIBOOT_HEADER_MAGIC	equ 0x1BADB002
    MULTIBOOT_HEADER_FLAGS	equ MULTIBOOT_PAGE_ALIGN | MULTIBOOT_MEMORY_INFO | MULTIBOOT_AOUT_KLUDGE

    MULTIBOOT_CHECKSUM	equ -(MULTIBOOT_HEADER_MAGIC + MULTIBOOT_HEADER_FLAGS)
    EXTERN code, bss, end

    ; This is the GRUB Multiboot header. A boot signature
    dd MULTIBOOT_HEADER_MAGIC
    dd MULTIBOOT_HEADER_FLAGS
    dd MULTIBOOT_CHECKSUM
    
    ; AOUT kludge - must be physical addresses. Make a note of these:
    ; The linker script fills in the data for these ones!
    dd mboot
    dd code
    dd bss
    dd end
    dd start

; This is an endless loop here. Make a note of this: Later on, we
; will insert an 'extern _main', followed by 'call _main', right
; before the 'jmp $'.
stublet:
    extern _main
    call _main
    jmp $

; This will set up our new segment registers. We need to do
; something special in order to set CS. We do what is called a
; far jump. A jump that includes a segment as well as an offset.
; This is declared in C as 'extern void gdt_flush();'
global _gdt_flush
extern _gp
_gdt_flush:
    lgdt [_gp]
    mov ax, 0x10
    mov ds, ax
    mov es, ax
    mov fs, ax
    mov gs, ax
    mov ss, ax
    jmp 0x08:flush2
flush2:
    ret

; Loads the IDT defined in '_idtp' into the processor.
; This is declared in C as 'extern void idt_load();'
global _idt_load
extern _idtp
_idt_load:
    lidt [_idtp]
    ret

; In just a few pages in this tutorial, we will add our Interrupt
; Service Routines (ISRs) right here!
global _isr0
global _isr1
global _isr2
global _isr3
global _isr4
global _isr5
global _isr6
global _isr7
global _isr8
global _isr9
global _isr10
global _isr11
global _isr12
global _isr13
global _isr14
global _isr15
global _isr16
global _isr17
global _isr18
global _isr19
global _isr20
global _isr21
global _isr22
global _isr23
global _isr24
global _isr25
global _isr26
global _isr27
global _isr28
global _isr29
global _isr30
global _isr31

;  0: Divide By Zero Exception
_isr0:
    cli
    push byte 0
    push byte 0
    jmp isr_common_stub

;  1: Debug Exception
_isr1:
    cli
    push byte 0
    push byte 1
    jmp isr_common_stub

;  2: Non Maskable Interrupt Exception
_isr2:
    cli
    push byte 0
    push byte 2
    jmp isr_common_stub

;  3: Int 3 Exception
_isr3:
    cli
    push byte 0
    push byte 3
    jmp isr_common_stub

;  4: INTO Exception
_isr4:
    cli
    push byte 0
    push byte 4
    jmp isr_common_stub

;  5: Out of Bounds Exception
_isr5:
    cli
    push byte 0
    push byte 5
    jmp isr_common_stub

;  6: Invalid Opcode Exception
_isr6:
    cli
    push byte 0
    push byte 6
    jmp isr_common_stub

;  7: Coprocessor Not Available Exception
_isr7:
    cli
    push byte 0
    push byte 7
    jmp isr_common_stub

;  8: Double Fault Exception (With Error Code!)
_isr8:
    cli
    push byte 8
    jmp isr_common_stub

;  9: Coprocessor Segment Overrun Exception
_isr9:
    cli
    push byte 0
    push byte 9
    jmp isr_common_stub

; 10: Bad TSS Exception (With Error Code!)
_isr10:
    cli
    push byte 10
    jmp isr_common_stub

; 11: Segment Not Present Exception (With Error Code!)
_isr11:
    cli
    push byte 11
    jmp isr_common_stub

; 12: Stack Fault Exception (With Error Code!)
_isr12:
    cli
    push byte 12
    jmp isr_common_stub

; 13: General Protection Fault Exception (With Error Code!)
_isr13:
    cli
    push byte 13
    jmp isr_common_stub

; 14: Page Fault Exception (With Error Code!)
_isr14:
    cli
    push byte 14
    jmp isr_common_stub

; 15: Reserved Exception
_isr15:
    cli
    push byte 0
    push byte 15
    jmp isr_common_stub

; 16: Floating Point Exception
_isr16:
    cli
    push byte 0
    push byte 16
    jmp isr_common_stub

; 17: Alignment Check Exception
_isr17:
    cli
    push byte 0
    push byte 17
    jmp isr_common_stub

; 18: Machine Check Exception
_isr18:
    cli
    push byte 0
    push byte 18
    jmp isr_common_stub

; 19: Reserved
_isr19:
    cli
    push byte 0
    push byte 19
    jmp isr_common_stub

; 20: Reserved
_isr20:
    cli
    push byte 0
    push byte 20
    jmp isr_common_stub

; 21: Reserved
_isr21:
    cli
    push byte 0
    push byte 21
    jmp isr_common_stub

; 22: Reserved
_isr22:
    cli
    push byte 0
    push byte 22
    jmp isr_common_stub

; 23: Reserved
_isr23:
    cli
    push byte 0
    push byte 23
    jmp isr_common_stub

; 24: Reserved
_isr24:
    cli
    push byte 0
    push byte 24
    jmp isr_common_stub

; 25: Reserved
_isr25:
    cli
    push byte 0
    push byte 25
    jmp isr_common_stub

; 26: Reserved
_isr26:
    cli
    push byte 0
    push byte 26
    jmp isr_common_stub

; 27: Reserved
_isr27:
    cli
    push byte 0
    push byte 27
    jmp isr_common_stub

; 28: Reserved
_isr28:
    cli
    push byte 0
    push byte 28
    jmp isr_common_stub

; 29: Reserved
_isr29:
    cli
    push byte 0
    push byte 29
    jmp isr_common_stub

; 30: Reserved
_isr30:
    cli
    push byte 0
    push byte 30
    jmp isr_common_stub

; 31: Reserved
_isr31:
    cli
    push byte 0
    push byte 31
    jmp isr_common_stub


; We call a C function in here. We need to let the assembler know
; that '_fault_handler' exists in another file
extern _fault_handler

; This is our common ISR stub. It saves the processor state, sets
; up for kernel mode segments, calls the C-level fault handler,
; and finally restores the stack frame.
isr_common_stub:
    pusha
    push ds
    push es
    push fs
    push gs
    mov ax, 0x10
    mov ds, ax
    mov es, ax
    mov fs, ax
    mov gs, ax
    mov eax, esp
    push eax
    mov eax, _fault_handler
    call eax
    pop eax
    pop gs
    pop fs
    pop es
    pop ds
    popa
    add esp, 8
    iret

global _irq0
global _irq1
global _irq2
global _irq3
global _irq4
global _irq5
global _irq6
global _irq7
global _irq8
global _irq9
global _irq10
global _irq11
global _irq12
global _irq13
global _irq14
global _irq15

; 32: IRQ0
_irq0:
    cli
    push byte 0
    push byte 32
    jmp irq_common_stub

; 33: IRQ1
_irq1:
    cli
    push byte 0
    push byte 33
    jmp irq_common_stub

; 34: IRQ2
_irq2:
    cli
    push byte 0
    push byte 34
    jmp irq_common_stub

; 35: IRQ3
_irq3:
    cli
    push byte 0
    push byte 35
    jmp irq_common_stub

; 36: IRQ4
_irq4:
    cli
    push byte 0
    push byte 36
    jmp irq_common_stub

; 37: IRQ5
_irq5:
    cli
    push byte 0
    push byte 37
    jmp irq_common_stub

; 38: IRQ6
_irq6:
    cli
    push byte 0
    push byte 38
    jmp irq_common_stub

; 39: IRQ7
_irq7:
    cli
    push byte 0
    push byte 39
    jmp irq_common_stub

; 40: IRQ8
_irq8:
    cli
    push byte 0
    push byte 40
    jmp irq_common_stub

; 41: IRQ9
_irq9:
    cli
    push byte 0
    push byte 41
    jmp irq_common_stub

; 42: IRQ10
_irq10:
    cli
    push byte 0
    push byte 42
    jmp irq_common_stub

; 43: IRQ11
_irq11:
    cli
    push byte 0
    push byte 43
    jmp irq_common_stub

; 44: IRQ12
_irq12:
    cli
    push byte 0
    push byte 44
    jmp irq_common_stub

; 45: IRQ13
_irq13:
    cli
    push byte 0
    push byte 45
    jmp irq_common_stub

; 46: IRQ14
_irq14:
    cli
    push byte 0
    push byte 46
    jmp irq_common_stub

; 47: IRQ15
_irq15:
    cli
    push byte 0
    push byte 47
    jmp irq_common_stub

extern _irq_handler

irq_common_stub:
    pusha
    push ds
    push es
    push fs
    push gs

    mov ax, 0x10
    mov ds, ax
    mov es, ax
    mov fs, ax
    mov gs, ax
    mov eax, esp

    push eax
    mov eax, _irq_handler
    call eax
    pop eax

    pop gs
    pop fs
    pop es
    pop ds
    popa
    add esp, 8
    iret

; Here is the definition of our BSS section. Right now, we'll use
; it just to store the stack. Remember that a stack actually grows
; downwards, so we declare the size of the data before declaring
; the identifier '_sys_stack'
SECTION .bss
    resb 8192               ; This reserves 8KBytes of memory here
_sys_stack:

Thanks!
-maddog39

Alboin · Post by **Alboin** » Thu Feb 22, 2007 4:55 pm

Try removing the underscores off the assembly functions.

maddog39 · Post by **maddog39** » Thu Feb 22, 2007 6:00 pm

Okay that worked. Finally! I removed all of the underscores from the functions/variables in the assembler and it worked. Thanks!

Solar · Post by **Solar** » Thu Feb 22, 2007 10:52 pm

Your linker script is missing .rodata. Try this one instead, or you will get confused when you add strings to your kernel:

Code: Select all

OUTPUT_FORMAT("binary") 
ENTRY(start) 
phys = 0x00100000; 
SECTIONS 
{ 
  .text phys : AT(phys) { 
    code = .; 
    *(.text) 
    *(.rodata)
    . = ALIGN(4096); 
  } 
  .data : AT(phys + (data - code)) 
  { 
    data = .; 
    *(.data) 
    . = ALIGN(4096); 
  } 
  .bss : AT(phys + (bss - code)) 
  { 
    bss = .; 
    *(.bss) 
    . = ALIGN(4096); 
  } 
  end = .; 
}

(Could someone get osdever.net to patch this in their tutorial? It's one of the most FAQ's from people using it...)

maddog39 · Post by **maddog39** » Fri Feb 23, 2007 9:33 pm

Alright thanks, will do. I think that the issues I was having with linking have to do with my distrobution, because I noticed that when I ran configure on GRUB it said the default output value of "add underscore infront of functions after compile" was "no". I think its a Ubuntu specific thing but I cant say for sure.

Which leads me to another problem...

I cant get this dang to frickin' boot! I have tried like 3 billion ways to make this dam thing boot and it just wont work... I've used the dd method and the cat boot > /dev/fd0 method, and none of them work. Whats going on this time?

-maddog39

maddog39 · Post by **maddog39** » Sat Feb 24, 2007 12:24 am

Okay well I finally figured it out, and ended up making something better anyway. An ISO image that you can burn to a disk and its essentially a live CD. lol. My only problem now is that I am getting an invalid or unsupported executable format. Its a flat binary although I think I need to convert to ELF, COFF, or AOUT.

[Edit]
I got it to compile as an ELF32 but it still wont work, im really stumped.

Otter · Post by **Otter** » Sat Feb 24, 2007 11:48 am

The easiest way is to use elf, but you can also use flat binary because you have added memory informations to the multiboot header.

If you use elf, you can remove these informations ( it's much easier )

Solar · Post by **Solar** » Mon Feb 26, 2007 2:56 am

Perhaps you would like to use the GCC Cross-Compiler, Bare Bones tutorial and the GRUB how-to from the Wiki as starting points, adding your ASM / C code to that "known good" frame as appropriate.