Re: [uml-devel] Current state of UML

[BlaisorBlade <blaisorblade_spam@yahoo.it>]

On Sunday 05 September 2004 22:28, Jeff Garzik wrote:
> Just a FWIW...

Thanks a lot anyway! We need eagerly mainline developer which help us, in any 
way (even comments).

> Using the latest UML code in 2.6.x BitKeeper (2.6.9-rc1-bk), things are
> looking pretty darn good.  I was able to boot a Fedora Core userland
> with "init=/bin/sh", set up networking easily [uml_net helper worked],
> and ssh into my virtual host.

> To problems, one major and two minor:

> (major)
> 1) Using standard Fedora Core SysvInit, rc.sysinit will proceed to
> completion, then the userland boot halts.  ps shows the virtual host's
> /sbin/init process in constant run state, chewing CPU time like mad.
> Didn't investigate further, simply booted with init=/bin/sh and moved on.

> (minor)
> 2) The Makefiles appear to add "-um1" to the kernel version for some
> reason, and IMHO violates the Principle of Least Surprise.  This breaks
> several of my scripts :(

Yes, this should not have gone in mainline (it made sense when releasing 
separate UML patches). I'm queueing the fix to Andrew Morton.

I guess that future separate UML patches (just for updates) will have to 
insert their extraversion to Makefile rather than arch/um/Makefile.

> 3) The arch/um build is verbose, showing each gcc command line as it is
> executed.  This is incorrect when KBUILD_VERBOSE or similar setting are
> not enabled.  As a result, the arch/um is verbose, but the rest is not,
> by default.
There is a ton of problems with kbuild in UML - actually it must build a lot 
of files against userspace headers, and there isn't a kbuild support for 
that. This means for instance that files are not rebuilt when CONFIG_* 
changes, when a header changes and so on.

I've just implemented a patch which simply makes the output nice, but I'm not 
sure whether it should be included.

Some time ago I implemented a rough version of a good patch (which fixed all 
the above problems, but in an unclean way), but nobody liked it, and moreover 
Jeff Dike said that:
1) he did not want to modify kbuild for UML only

2) he was going to build an abstraction layer, which would build with 
userspace includes and would be restricted to arch/um/os-*/, and then the 
Makefile hacks would have been done only for that folder.

> Overall I am really impressed.  Like other arches in the Linux kernel,
> it is IMO very important to be able to work "out of the box", without
> patches.

-- 
Paolo Giarrusso, aka Blaisorblade
Linux registered user n. 292729


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