Re: [Qemu-devel] Stuff.

[Fabrice Bellard <fabrice@bellard.org>]

David Woodhouse wrote:
> Has anyone considered the possibility of emulating libc, rather than
> emulating system calls? That's what em86 used to do for emulating i386
> code on Alpha -- rather than letting it run a 'real' non-native libc and
> then emulating only syscalls. 
> 
> I appreciate that syscalls are a far more stable ABI to be emulating,
> and there are far fewer structures to convert -- but wouldn't it be
> faster to emulate the library itself? Especially if we can extend that
> to emulate libX11 too :)

Emulating libc would be _very_ difficult (there are thousands of calls 
to convert). There were provisions in em86 to do that, but it was never 
really used. Moreover, I think the speed up would be small compared to 
the complexity of the task.

> It's cute that I have i386 acroread running in a Mozilla window through
> mozplugger. It'd be cuter if I could get Mozilla plugins running in the
> _same_ process, rather than in a separate process. 
> 
> 
> ----
> 
> Also, why do we do what we do in linux-user/path.c? What does it give us
> that couldn't be achieved by stat("$prefix/$filename") in a trivial
> path() function? Other than taking for ever to start up when
> /usr/gnemul/i386-linux is actually an nfs-mounted root file system from
> elsewhere. (When I say forever I mean that literally. We keep following
> symlinks recursively).

The goal was to avoid making too many syscalls.

Fabrice.