On Sat, 24 Apr 2004, Stanislaw Skowronek wrote: > why do we attempt to compile the kernel with 32-bit GAS abi and 64-bit GCC > abi? Is it because the module loader is broken and supports only 32-bit > ELFs? Then what about machines which load their kernels at weird 64-bit > addresses, like 0xa800000020004000 (Octane)? 1. Backward compatibility. Old versions of gas/ld were buggy or non-functional (depending on the version used) when using the (n)64 ABI. Search the mailing list archives -- I'm pretty sure anything since 2.13.2.1 should be safe, though. 2. Using the o32 ABI makes the binary smaller due to 32-bit pointers. If used without care, it can lead to pointer crops, though. Anyway, some people say it's important for them, despite the associated hassle. > I have changed it to 64-bit abi in my Octane kernel, because it won't even > compile otherwise. I've got gcc 3.3.2, gas 2.14. I know. I build using (n)64 consistently for two years successfully -- it's OK even with gcc 2.95.x. Making a choice between the ABIs for gas user-selectable is on my to-do list for some time. For now I think `make gas-abi=64 ...' is probably the easiest workaround, though you'll need to objcopy the resulting image to a 32-bit ELF file manually if your firmware or loader cannot cope with 64-bit ELF binaries. Well, I don't like the automatic copy anyway -- it wastes too much disk space in the long run; perhaps as a compromise it should be user-selectable, too (ditto about SREC). Maciej -- + Maciej W. Rozycki, Technical University of Gdansk, Poland + +--------------------------------------------------------------+ + e-mail: macro@xxxxxxxxxxxxx, PGP key available +
