Linker error under Linux

[Mike]

I'm just trying to compile a simple kernel under Linux. I'm getting a linker error:

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[mike@pc-00065 kernel3]$ gcc -c kernel.c -o kernel.o
[mike@pc-00065 kernel3]$ nasm -f aout k_entry.asm -o k_entry.o
[mike@pc-00065 kernel3]$ ld -T kernel.ld  k_entry.o kernel.o
k_entry.o(.text+0x16):k_entry.o: undefined reference to `_k_main'

I'm sure it's something silly. Any help appreciated.

Thanks

Part of the kernel entry asm is:

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[BITS 32]

[global start]
[extern _k_main] ; this is in the c file

start:
  ; stop using bootloader GDT, and load new GDT
  lgdt [gdt_ptr]

  mov ax,LINEAR_DATA_SEL
  mov ds,ax
  mov es,ax
  mov ss,ax
  mov fs,ax
  mov gs,ax

  call _k_main

  jmp $ ; crash

And part of the kernel.c file sis:

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void k_main(void) // like main
{
   k_clear_screen();

   k_printf("Welcome to Simplified OS.", 0);
   update_cursor(1, 0);
   k_printf("Right now the kernel is loaded at 1MB physical,/nbut mapped at FF800000 hex.", 3);
   update_cursor(5, 0);

   k_printf("Remapping the PIC...", 6);
   update_cursor(7,0);
   remap_pics(0x20, 0x28);   // irq 0 20h irq 8 28h

   k_printf("PIC remapped starting at 20 hex.", 7);
   update_cursor(8,0);
};

[Mike]

Argh, solved it. I was compiling a C file, so the C compiler doesn't add an _ to the beginning of exported symbols. D'oh!!! ;D

[Mike]

Ok, another problem. This is my build script:

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#! /bin/bash

gcc -c kernel.c -o kernel.o
nasm -f elf k_entry.asm -o k_entry.o
ld -T kernel.ld k_entry.o kernel.o
mv a.out kernel.bin

The ld command gives the error: File size limit exceeded

I only get this if I use -f elf. -f a,out works fine. However, grub then gives error 13 - unsupported file format, I think.

Thanks

[Solar]

Without seeing your linker script, and the kernel.asm you gave rather obviously being only a quick rip-off what's really in there, it's hard to tell why your file size limit should be exceeded.

I'd point you to "the a.out kludge" in the GRUB documentation which would show you how to make GRUB boot an a.out image, but the ld error message points to an error somewhere in your setup, and the a.out kludge would merely cover that one up...