OSDev.org

Hey,

I'm working on porting my operating system to the x64 architecture. I'm following the articles in the wiki for switching to long mode. I use gas for assembly code. The cross compile tool chain is set-up correctly. I compile the 32 bit bootstrap with the following command:

x86_64-elf-as --32 -o CMakeFiles/myOS.elf.dir/src/arch/x64/pc/boot.S.o /home/nils/code/osdev/myOS/src/arch/x64/pc/boot.S

But then the linkage fails with the following error:

/usr/bin/cc -T ../././src//arch/x64/pc/layout.ld -N -ffreestanding -nostdlib CMakeFiles/schlemmiOS.elf.dir/src/arch/x64/pc/boot.S.o -o schlemmiOS.elf
/usr/bin/ld: i386 architecture of input file `CMakeFiles/schlemmiOS.elf.dir/src/arch/x64/pc/boot.S.o' is incompatible with i386:x86-64 output

Obviously the linker complains that it can't build 32bit code into my the binary... How can I fix this? And why is this a problem?

Thanks.

/usr/bin/cc (...)
/usr/bin/ld (...)

You might want to start with making sure you use the cross-compiler all the way

it can't build 32bit code into my the binary

Actually, it can't mix architectures. Instead you should tell the assembler that certain chunks are to be assembled in 32-bits (and some as 64-bits) using .code32 and .code64, instead of passing the 32-bit architecture flag on the command line

Combuster wrote:You might want to start with making sure you use the cross-compiler all the way

Actually these are symlinks to the cross compiler. Ubuntu is doing some magic with the update-alternatives there. Probably not the greatest way for an operating system. But it's working for me and I haven't figured out a better way to say cmake which linker it should use.

Combuster wrote:Actually, it can't mix architectures. Instead you should tell the assembler that certain chunks are to be assembled in 32-bits (and some as 64-bits) using .code32 and .code64, instead of passing the 32-bit architecture flag on the command line

Ah ok. Is working now.Thanks.