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Re: Implementing binary compatibility with Linux, *BSD, ...

Farid Hajji wrote:
> [Sorry to mail to both lists, but the topic _is_ relevant in both cases.
>  BTW, could we _please_ reunify both lists?]

Actually, I think this is more appropriate to bug-hurd anyway (which is
actual development list).

> Abstract: The following mail contains a proposal, discussion and technical
>           description on implementing binary compatibility of the Hurd to
>           binaries compiled for Linux-, *BSD- or other OS, without the need
>           to recompile those binaries from scratch. With binary compat.,
>           the Hurd servers can be installed in an existing OS distribution
>           as a simple package and would be ready-to-run.

Wow! You have given this a lot of thought, and this is really a good
However, a smaller problem can be solved a lot easier, and this might be
a good
first step towards your more complete solution.

The Hurd GLibC has a special property: It has almost the same interface
as the Linux GLibC,
because it comes from the same source tree. I say almost, because there
are mainly two things
standing in the way of full compatibility:

1. The Hurd uses stdio, while Linux uses libio.
2. The Hurd does not have pthreads.

Those are the two main items I know. The idea was to implement pthreads
for the Hurd,
and then make both changes in a bunch. This will give us ABI
compatibility with the
Linux glibc. So, Linux binaries which don't use syscalls direclty, but
only exported
interfaces in glibc and other user libraries will work on the Hurd
without any emulation,
because we use the same object format, the same ABIs etc.

Only for direct use of syscalls we would need the syscall trap and
emulation you explain
in your proposal.

Of course, this only is for recent linux binaries, and not for BSD or
older stuff.
But I think it is already tremendous useful, and comparatively easy to
because you don't need to emulate any syscalls.


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