trap (GPF) when starting l4linux -- resolved!

Adam Lackorzynski adam at
Thu Sep 25 19:45:21 CEST 2008


On Wed Sep 24, 2008 at 14:09:10 +1300, valerius wrote:
> I spent a night reconfiguring Fiasco and L4Linux and reading the Mailing list 
> archive. And it appears that l4linux itself was configured correctly. But I 
> encountered a troubles with 'Mysterious double fault' when using QEMU that 
> could be overcome if disable 'Assembler IPC shortcut' option in Fiasco 
> configuration. Also I found that options in loader config file have 
> significant order of precedence. They should appear in the following order:
> allow_cli
> allow_vga
> all_sects_writable
> If all_sects_writable appears before allow_cli then loader says that l4linux 
> task is not allowed to do any I/O. It is really strange and non-obvious.
> Also, some diversity in options order may lead to unresolved page faults and 
> GPFs like the GPF which I was asking for.
> Someone can say it is very trivial but I spent a night to figure out the way
> it works. 
> I just wanted to point these non-obvious moments to novices. (and, maybe, 
> developers of loader server -- what if to make these options order to be 
> non-significant? It could make loader behaviour more predictable.) 

Thanks for describing your findings!
I don't understand why the order plays a role, looking at the code.
Those options are just task flags which are parsed and toggle some bits
in a flag word. I don't see how order could be important.
And yes, GPFs should not happen, I second.

Adam                 adam at

More information about the l4-hackers mailing list