Re: caml stubdom crashes

[Alex Zeffertt <alex.zeffertt@eu.citrix.com>]

Patrick Colp wrote:
> Alex Zeffertt wrote:
>> I suspect the problem is that the caml-stubdom target in 
>> stubdom/caml/Makefile compiles stubdom/caml/hello.ml and links it with 
>> $(CAMLLIB)/libasmrun.a.  But this is a library compiled for the 
>> development machine platform (linux-i386-glibc) not for the stubdomain 
>> platform (minios-i386-newlib).
>>
>> Maybe the original hello.ml only worked through luck, and the fact that 
>> it used so very little of the ocaml language.
> 
> What environment did you use to compile the stubdom? I tried using Ubuntu 
> with George Coker's patch and got the same result as you (page faulting). 
> Interestingly, I could use a %s and a string and that seems to work OK, but 
> not %d with an int.
> 
> When I instead used Debian to compile the stubdom (which requires no 
> patch), then I could compile and run your code just fine (no page faults). 
> Maybe this is the problem you're having?
> 


That's interesting, thanks!  I am using Ubuntu intrepid with ocaml version 
3.10.2-3ubuntu1.

I don't really like the idea of requiring a Debian build environment as a 
solution.  It suggests a dependency on something we really don't understand.
Wouldn't it be better to rebuild ocaml under stubdom/ like we do for newlib and 
lwip, and the be sure we'll get the same results whatever the build machine?

> 
>> In order to run a non trivial ocaml application in a stubdomain (e.g. 
>> ocaml xenstored) do I need to port ocaml to minios-i386-newlib?
> 
> No, it should be possible as is. In fact, I've gotten my OCaml XenStore to 
> run in a caml-stubdom (compiled in a Debian domain).
> 
> I'll soon be releasing a patch against the recently released disaggregated 
> C xenstored stuff that uses my OCaml XenStore in a caml-stubdom instead.
> 
> 

Ah, it looks like we've been duplicating the work.  I've been working on getting
  http://xenbits.xensource.com/ext/xen-ocaml-tools.hg integrated into 
xen-unstable.hg.  The idea is that by default "make dist" builds the in-tree 
xenstored (as both a dom0 daemon and as a stubdom), but by uncommenting a line 
in Config.mk it will download xen-ocaml-tools.hg and build that instead (as both 
a dom0 daemon and as a stubdom).  The choice of whether to run it as a dom0 
daemon or as a stubdom is made post-install.

This system allows you to override the url used to get the "remote" xenstored. 
The build system does something similar for qemu already.

I'll send you my patches offline.

> Patrick
> 

Regards,

Alex