Problem with the gnu linker (ld.exe)

[alphabetagamma]

hi

i found a tutorial to write a bootloader in asm that loads a kernel written in c.

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nasm –f bin –o boot.bin boot.asm

i compiled the bootloader into a binary file and the c source into an obj file.

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

now i want to link the obj and the bin file with the gnu linker. i use the following linker script:

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OUTPUT_FORMAT("binary")
INPUT(kernel.o)
ENTRY(_main)
SECTIONS
{
  .text 0x40000 :
  {
    *(.text)
  }
  .data :
  {
    *(.data)
  }
  .bss :
  {
    *(.bss)
  }
}

i use the following command:

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ld -T link.ld -o kernel.bin

now i get the following error:

ld: PE operations on non PE file.

when i try to link it without the linker script i get the following error:

ld kernel.o -o kernel.bin

kernel.o:kernel.c:(.text+0x12): undefined reference to '__main'

what do i have to do to get this running ? i know i need a binary file of the c-code and then copy boot.bin and kernel.bin together.
the code is in the addition.

system information:
gcc 4.3
nasm-2.05.01
windows vista x64 (yeah i know )

[sdkmvx]

See http://wiki.osdev.org/GCC_Cross-Compiler...

[alphabetagamma]

thanks for the reply.
i understand the problem and the solution but i have never worked with cygwin, gcc and bash commands like that.

it would be nice of someone who knows how to configure this cross compiler under windows could show it to me by doing it over remote access. so that i can watch the steps ? write a pm to me if you have time to do it.

[CodeCat]

I'm not sure the instructions in the wiki could really be any clearer. I followed them and it worked perfectly.

[alphabetagamma]

i dont understand the following step:

binutils

cd /usr/src/build-binutils
../binutils-x.xx/configure --target=$TARGET --prefix=$PREFIX --disable-nls
make all
make install

what is binutils-x.xx ? the cygwin bash says no directory or file found...
is it the gcc directory ? i downloaded the following package:
http://ftp.gnu.org/gnu/gcc/gcc-4.3.2/gc ... 3.2.tar.gz
but there ist no binutils directory in it...

[leledumbo]

It's a separate package containing assembler, linker, and many other utilities, take 'em here. Your ld is compiled ONLY with capability to handle PE files.

[JamesM]

Hi,

As part of my tutorial rewrite (still ongoing before anyone asks) I've created an i686-elf cross compiler for cygwin. You can find it here. Just untar it;

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tar -xvzf i686-xcompiler-cygwin.tar.gz

to a suitable location and add that location to your PATH:

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export PATH=/my/location/where/i/extracted/the/files/bin:$PATH

Note the /bin on the end of the pathname.

Hope this helps,

James

[alphabetagamma]

Hi,

As part of my tutorial rewrite (still ongoing before anyone asks) I've created an i686-elf cross compiler for cygwin. You can find it here. Just untar it;

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tar -xvzf i686-xcompiler-cygwin.tar.gz

to a suitable location and add that location to your PATH:

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export PATH=/my/location/where/i/extracted/the/files/bin:$PATH

Note the /bin on the end of the pathname.

Hope this helps,

James

thanks easier then the other tutorial, but how can i run the gcc.exe in cygwin now ? and where do i have to copy my source files to ?

[JamesM]

Just type "gcc". If you followed my instructions, the cross compiler GCC should be in your path before cygwin's standard one.

[alphabetagamma]

Just type "gcc". If you followed my instructions, the cross compiler GCC should be in your path before cygwin's standard one.

ok, needed to restart cygwin to initialize the path...
but a new problem came up:
i have to compile the assembler file with nasmw the following way

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nasmw -f aout /path/k_entry.asm -o /path/k_entry.o

error:
nasm: fatal: unable to open output file '/path/k_entry.o'
the file exists...so whats the problem here ?

[JamesM]

Hi,

I'm pretty sure the directory "/path" doesn't actually exist. If you're in the directory where your asm files are, you just write:

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nasmw -f aout k_entry.asm -o k_entry.o

By the way, I'd use "-f elf", instead of "-f aout" if you want full compatibility with your GCC toolchain.

[Solar]

nasm: fatal: unable to open output file '/path/k_entry.o'
the file exists...so whats the problem here ?

Think for a minute: "Unable to open output file", and "file exists"... Double-check if the file really exists ("ls -l /path/k_entry.o"), then check the file access permissions on the file. Try "rm /path/k_entry.o" (which should delete the target file). Can you do that? Do you still get the error after deleting the target file?

All in all I'd recommend trying some user-space programming first, to familarize yourself with the tools. Write some simple test programs - asking the user for his name, reading input, and printing a greeting - stuff like that.

Kernel space programming is hard enough when you know your tools. Using unfamiliar tools in an unfamiliar environment for doing unfamiliar kernel-space work is a bit much at once.

[alphabetagamma]

Kernel space programming is hard enough when you know your tools. Using unfamiliar tools in an unfamiliar environment for doing unfamiliar kernel-space work is a bit much at once.

exactly! sag enough that there are no open source ides for that...i just want to go to the step to know how to compile it and then just using c.

back to topic: a new problem. the linker still crashes:

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ld -T link.ld kernel.bin

the linker script is that from above.
error:
ld: cannot perform PE operation on non PE output file 'kernel.bin'


i also tried another source package for a c kernel (addition).
there the linker says:

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ld _t kernel.ld kernel.o k_entry.o

k_entry: file not recognized: File format not recognized

[JamesM]

Hi,

Please can you paste the output of these three commands:

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ld -v
file k_entry.o
file kernel.o

Thanks,

James

[Solar]

sag enough that there are no open source ides for that...

You can use any IDE you like...?!?