Problems building arc-2016.09-eng007 toolchain with 2.6.35 kernel headers

[Alexey.Brodkin@synopsys.com (Alexey Brodkin)]

Hi Waldemar,

On Wed, 2016-08-10@19:03 +0200, Waldemar Brodkorb wrote:
> Hi,
> Vineet Gupta wrote,
> 
> > 
> > On 08/08/2016 02:44 PM, Petri Gynther wrote:
> > > 
> > > uclibc-ng & ARC developers:
> > > 
> > > I'm trying to use buildroot to build the latest ARC toolchain
> > > (arc-2016.09-eng007) against our vendor-provided 2.6.35.12 ARC Linux
> > > kernel. (Yes, it is an ancient kernel, but that's what I have to work
> > > with for now, unfortunately.)
> > > 
> > > ...
> > > 
> > > 
> > > Questions:
> > > 1) Does the latest ARC toolchain use some new ABI for binaries that
> > > makes them incompatible with 2.6.35.12 kernel?
> > 
> > Indeed even if you were to build it successfully - you will run into ABI issues -
> > 2.6.35 is ABI v1 and we are currently at v3 (which is going to change soon even
> > further to v4 - for ARC HS processors)
> > More details at:
> > https://github.com/foss-for-synopsys-dwc-arc-processors/linux/wiki/ARC-Linux-Syscall-ABI-Compatibility
> > 
> > > 
> > > 2) Is uclibc-ng 1.0.17 supposed to be compatible with 2.6.x kernel headers?
> > 
> > No - modern/upstream uClibc-ng is not compatible with 2.6.35
> > You need to use the uClibc of the time - with pairing gcc/binutils - although that
> > will be a can of worms
> 
> This is only the case for ARC, right?
> Other architectures should work fine, like MIPS or ARM.

As Vineet mentioned above that's the case for ARC because of ABI changes, see
Wiki page above.

As for arches that were supported in Linux for much longer time like ARM and MISP most
probably up-to-date uClibc would work with 2.6.x kernels but frankly I haven't tried that
myself.

Still newer arches like Nios and Extensa may have similar issues as we have.
But again I barely have any experience with those arches so asking their maintainers
might be a good idea.

-Alexey