Arnd Bergmann ran a quick session on improving the way architectures are
supported in Linux. The usual way to add an architecture is to clone the
x86 tree, then bash away on the code until it works on the new processor.
That means that a lot of code has been duplicated over time, much of it
uselessly. There is still compatibility code to help in the running of
Xenix binaries - on architectures invented long after Xenix faded into
obscurity. The end result is that it's harder than it needs to be to
support new architectures; they all keep making the same mistakes.
So Arnd has been working with the newer architectures over the last year.
He has created a new include/asm-generic hierarchy to contain
headers which should be shared across architectures and has been porting
architecture code to use them. In particular, he has focused on the
relatively new MicroBlaze and S-Core architectures; this work has resulted
in significant reductions in the size of the affected code.
There was lots of talk about grungy details that your editor did not record
very well. One sticking point appears to be the TERMIOS ABI, which
differs significantly between architectures.
What remains to be done? It would be nice to get glibc to use the generic
ABI definitions whenever possible, but nobody seems to know how to get that
support into the library. More architectures can be moved over to the
generic code. Arnd talked about the creation of a skeleton architecture
which can be used by future implementers; he was thinking about making
something which would run under KVM. Other developers recommended using a
real architecture in this role; MIPS was suggested as a good starting
Next: Development process issues
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