[Devel] Re: 2.6.20-lxc8: kernel panic with af_unix as module

[Eric W. Biederman]

Pierre Peiffer <pierre.peiffer at bull.net> writes:

> Hi,
>
> I'm trying to test this kernel with network namespace compiled. But I have a
> kernel panic (see below) during the boot when loading the module unix.ko (in
> af_unix_init).
>
> After some search, it seems that specifying a particular section for some
> variables is incompatible with using them in a module.

Bother.   I thought I had that all implemented properly but it looks like
I have missed something.

> In my case, when registering per_net__unix_root_table (in function
> unix_sysctl_register in file net/unix/sysctl_net_unix.c), it tries to access the
> child (which is per_net__unix_net_table) at the address 0x00000080 which is the
> address of this symbol in the section .data.pernet of the module object, but not
> a virtual address.

Hmm.  It should be a global offset in the .data.pernet section.  If it
is just for that module I clearly have a problem.

> When compiling this in the kernel, there is no problem...
> As I'm not familiar with the use of some sections in ELF format, I don't know
> how to correct this....
>
> By the way, just for my knowledge, what is the advantage of specifying a
> particular section (.data.pernet in this case) for some variables ?

So you have one instance for each network namespace.  Currently I think
I'm using the concept a little too much requiring a large page
allocation for all of the network namespace state.  But otherwise it
seems to work fairly well.

Thanks.  I will go back and look but I don't plan on back porting
anything for 2.6.20.  I'm lazy and do not have enough hours in the
day. :)

Eric

_______________________________________________
Containers mailing list
Containers at lists.linux-foundation.org
https://lists.linux-foundation.org/mailman/listinfo/containers