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xen-devel
Re: [Xen-devel] caml stubdom crashes
Alex Zeffertt wrote:
Hello ocaml minios stubdomain experts (that's narrowed down the list
somewhat!)
I've been playing with the caml version of the "hello world" example
stubdomain that can be found in xen-unstable.hg/stubdom/caml/.
If I make the following trivial modification to stubdom/caml/hello.ml
the stub domain page faults. According to addr2line the page fault is
in ungetc.c:0.
--- a/stubdom/caml/hello.ml Mon Mar 30 11:42:16 2009 +0100
+++ b/stubdom/caml/hello.ml Thu Apr 02 15:15:45 2009 +0100
@@ -1,4 +1,6 @@
+let yr = 2009
+
let main arg =
- Printf.printf "Hello, world!\n%!."
+ Printf.printf "Hello, world %d!\n%!." yr
let _ = Callback.register "main" main
Without the above change the stub domain runs as expected, i.e. it does
not page fault.
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?
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.
Patrick
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