Linux 2.6.24 L4FB and VGA_CONSOLE

Ronald Aigner ra3 at
Fri Feb 22 14:33:08 CET 2008

Marc CHALAND wrote on 02/22/2008 02:21 PM this:
>>From Ronald Aigner:
>> The address of the UTCB is taken in the stub from the environment
>> variable. This environment variable (_dice_corba_env->utcb) is set per
>> default with l4sys_utcb_get which in turn does 'asm( "%gs:0" )'. The
>> problem with Linux applications (running on L4Linux) is that they are
>> linked to a glibc that uses %gs for its own purposes. Therefore, the
>> UTCB pointer is probably bogus and thus UTCB IPC fails.
> Wunderbar :). That explains why I encounter problems with L4Linux.
> But this task is abolutely not an L4Linux one. It just uses L4env. The
> values for domain, type and protocol are 2 1 6 on client side and
> 0x221401 0x0 0x7069776c on server side. Return value is absolutely
> anything.
Now that really sounds strange. You say that the task is running as 
L4Env task? No L4Linux involved? Not even on the sender/receiver side of 
the IPC?

>> The quick fix is to go back to a version of Dice that does not use UTCB
>> IPC.
> Could you tell me which version is the last without UTCB feature ? SVN
> is not very explicit about it :).
I'd go with revision 233 from public repository.

Regards, Ron.
Mit freundlichen Gruessen / with regards
ra3 @

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