ld: cannot perform PE operations on non PE output file error

Question

I am new to operating system programming and I am reading a book which gives a simple example of kernel as follows:

main() {
   char *video_memory = 0xb8000;
   *video_memory = 'X';
}

To compile this file which is called kernel.c, I use MinGW under Windows 7 as follows:

gcc -ffreestanding -c kernel.c -o kernel.o

This creates the object file kernel.o. However, following command does not work.

ld -o kernel.bin -Ttext 0x1000 kernel.o --oformat binary

I receive the following error:

ld: cannot perform PE operations on non PE output file 'kernel.bin'

I cannot solve the problem. Please help me.

Thank you

After helps of Ross, I succeded to jump to kernel offset. However, I cannot call C function from Kernel_entry.asm. Moreover, when I remove the C function from my kernel.bin and change the code as seen below, Three weird chars are shown on the screen.

Kernel_entry.asm is as follows:

[bits 32]
;[extern _start]
mov ebx, MSG_KERNEL_ENTRY
call print_string_pm
;call _start
jmp $

%include "print_string_pm.asm"

MSG_KERNEL_ENTRY db "Kernel entry is invoked", 0

bootsec.asm is as follows:

[org 0x7c00]

KERNEL_OFFSET equ 0x1000

mov [BOOT_DRIVE], dl
mov bp, 0x9000
mov sp, bp
mov bx, MSG_REAL_MODE
call print_string
call load_kernel
call switch_to_pm

jmp $

%include "print_string.asm"
%include "disk_load.asm"
%include "gdt.asm"
%include "print_string_pm.asm"
%include "switch_to_pm.asm"
%include "clear_screen.asm"
[bits 16]
load_kernel:
mov bx, MSG_LOAD_KERNEL
call print_string

mov bx, KERNEL_OFFSET
mov dh, 15
mov dl, [BOOT_DRIVE]
call disk_load

ret


[bits 32]

BEGIN_PM:
;call clear_screen
mov ebx, MSG_PROT_MODE
call print_string_pm
call KERNEL_OFFSET
jmp $

BOOT_DRIVE  db 0      
MSG_REAL_MODE   db "Started in 16-Bit Real Mode", 0
MSG_PROT_MODE   db "Successfully switched to 32-Bit Protected Mode", 0 
MSG_LOAD_KERNEL db "Loading Kernel into memory", 0  

times 510 - ($ - $$) db 0

dw 0xaa55

All messages are shown correctly but the last one in the Kernel_entry.asm is shown as three weird chars. I don't understand what happens.

Answer 1

The first thing you'll need to is change the name of you function. If you call it main the MinGW version of GCC will insert a call to __main to do initialization. For example:

start() {
   char *video_memory = 0xb8000;
   *video_memory = 'X';
}

This means you'll also have to edit kernel_entry.asm accordingly:

[bits 32]
[extern _start]
call _start
jmp $ 

Next compile and assemble the two files as you did before, and link it with these commands:

ld -T NUL -o kernel.tmp -Ttext 0x1000 kernel_entry.o kernel.o
objcopy -O binary -j .text  kernel.tmp kernel.bin 

The first command links the objects as a PECOFF executable, and then the second command converts it to a binary. Now combine the binary with the boot loader:

copy /b boot_sect.bin+kernel.bin os-image