simulating wireless device (if_alloc panic, VirtualBox, VIMAGE)

Thu Feb 3 10:51:25 UTC 2011

On Thu, Feb 3, 2011 at 10:55 AM, Bjoern A. Zeeb
<bzeeb-lists at lists.zabbadoz.net> wrote:
> On Thu, 3 Feb 2011, Monthadar Al Jaberi wrote:
>
>> On Wed, Feb 2, 2011 at 8:06 PM, Julian Elischer <julian at freebsd.org>
>> wrote:
>>>
>>> On 2/2/11 10:05 AM, Monthadar Al Jaberi wrote:
>>>>
>>>> I just tried something that seems to work, but please dont hit me ^^;;;
>>>>
>>>> in wtap_ioctl I assigned curthread->td_vnet myself to point to a VNET
>>>> (saved it when the module first loaded) (I have not created any jails
>>>> yet)... and it works... I didnt put any CURVNET macros...
>>>
>>> td->td_vnet is exactly what the CURVNET_SET macro sets.
>>> You should use the Macros because we may change the place where we store
>>> it.
>>>
>>> The vnet for the current thread is picked up from several places
>>> depending
>>> on the context,
>>> and it is cleared again when it is not needed.  the V_xxx usages in the
>>> code
>>> end up being
>>> in effect expanded to curthread->td_vnet.xxx, where each 'xxx' is sort of
>>> like an element in a structure
>>> but not quite.
>>>
>>> Now, theoretically we could just leave it set all the time but then it
>>> would
>>> be nearly impossible
>>> to find places where we should have changed it, but forgot and just got
>>> the
>>> existing one.
>>>
>>> if you want to find the correct place to go, then look at the vnet of the
>>> calling process
>>> which should be in the process cred. or just use vnet0.
>>
>> Can I check it from user space?
>>
>>>
>>> I don't understand why you saw a CRED_TO_VNET of 0
>>> I was under the impression that every process/thread in the system would
>>> be
>>> on vnet0
>>> in a vimage kernel.
>>
>> This is how my printf looks like:
>> struct thread *td = curthread;
>> struct vnet *v = TD_TO_VNET(td);
>> struct ucred *cred = CRED_TO_VNET(td->ucred);
>> struct vnet *td_vnet = td->td_vnet;
>
> here's your problem:
>
> strcut vnet *vnet = cred->cr_prison->pr_vnet;

When I add CURVNET_SET(CRED_TO_VNET(curthread->td_ucred)); I get a panic too...
But your suggestion works if I do like this:
curthread->td_vnet = curthread->td_ucred->cr_prison->pr_vnet;

CRED_TO_VNET(curthread->td_ucred) returns NULL

>
>
>> printf("td=%p, td->td_vnet=%p, td->td_ucred=%p, TD_TO_VNET=%p,
>> CRED_TO_VNET=%p\n", td, td_vnet, td->td_ucred, v, cred);
>>
>> I made a fast search in /usr/src for "td_vnet" and found it was
>> assigned only in
>> int fork1(td, flags, pages, procp):
>> #ifdef VIMAGE
>>        td2->td_vnet = NULL;
>>        td2->td_vnet_lpush = NULL;
>> #endif
>
> Nice try.  Want another search?  Hint: there is this in vnet.h:
>
> #define curvnet curthread->td_vnet
>
> And then you'll, again, find the CURVNET_SET_* macros.

Thank you

>
>
>
>> Maybe something wrong with how I declare my wtap_ioctl:
>>
>> static struct cdevsw wtap_cdevsw = {
>>        .d_version =    D_VERSION,
>>        .d_flags =      0,
>>        .d_ioctl =      wtap_ioctl,
>>        .d_name =       "wtapctl",
>> };
>> ...
>> make_dev(&wtap_cdevsw,0,UID_ROOT,GID_WHEEL,0600,(const char *)"wtapctl");
>>
>>>
>>> your stored vnet idea is ok as well, but may go strange if you load the
>>> driver from a vnet jail
>>> and then remove the jail.
>>
>> Ok, will document it in the code for now
>>
>>>
>>>
>>>
>>>
>>>> my assumption is that if ath drivers dont use VNET I shouldnt :P
>>>>
>>>> What is wrong with this hack?
>>>>
>>>> br,
>>>>
>>>> P.S. I have printed "porting to vnet" text to have it always at hand,
>>>> but its a bit hard for me... doing my best.
>>>>
>>>> On Wed, Feb 2, 2011 at 6:30 PM, Julian Elischer<julian at freebsd.org>
>>>>  wrote:
>>>>>
>>>>> On 2/2/11 9:12 AM, Bjoern A. Zeeb wrote:
>>>>>>
>>>>>> On Wed, 2 Feb 2011, Monthadar Al Jaberi wrote:
>>>>>>
>>>>>> Hi,
>>>>>>
>>>>>>> Thanx makes more sense, but I have noticed something weired if you
>>>>>>> can
>>>>>>> shade some light on.
>>>>>>>
>>>>>>> I added printfs one when the module is first loaded (static int
>>>>>>> event_handler(module_t module, int event, void *arg)):
>>>>>>> curthread=0xc3f95870
>>>>>>> curthread->td_vnet=0xc3170e00
>>>>>>> curthread->td_ucred=0xc3185d00
>>>>>>> TD_TO_VNET=0
>>>>>>> CRED_TO_VNET=0
>>>>>>
>>>>>> Try to load it from laoder on boot; I think that should work as we are
>>>>>> setting the curvent for the kernel startup.
>>>>>>
>>>>>> The problem you are seeing is a bug in the current implementation that
>>>>>> you cannot add any physical network interface after the kernel
>>>>>> started.
>>>>>> This applies to cardbus/usb/... as well as any kind of ethernet
>>>>>> interface, so a kldload igb should yield it as well.
>>>>>>
>>>>>> The fix for that is easy and hard at the same time:
>>>>>> A) either touch all drivers
>>>>>> B) or touch all cloned interfaces and change 3 common lines.
>>>>>>   or try to make cloners aware of vimages.
>>>>>>
>>>>>> Solution B) is sitting in perforce with the entire stuff that it
>>>>>> depends
>>>>>> on and was started with CH=179022,179255 but not limited to that if
>>>>>> you
>>>>>> want to have a peek.
>>>>>>
>>>>>> What you certainly can do locally to your driver for now is to make a
>>>>>> change like this:
>>>>>>
>>>>>> +#ifdef VIMAGE
>>>>>> +       CURVNET_SET(vnet0);
>>>>>> +#endif
>>>>>>        ifp = if_alloc(IFT_ETHER);
>>>>>> +#ifdef VIMAGE
>>>>>> +       CURVNET_RESTORE();
>>>>>> +#endif
>>>>>>
>>>>> you don't really need  the #ifdef except for readability as CURVNET_XXX
>>>>> ar
>>>>> enot defined for !vnet
>>>>>
>>>>>> It's the type A) kind of change from above that will break eventually
>>>>>> in the future.
>>>>>>
>>>>>> /bz
>>>>>>
>>>>>
>>>>
>>>>
>>>
>>>
>>
>>
>>
>>
>
> --
> Bjoern A. Zeeb                                 You have to have visions!
>        <ks> Going to jail sucks -- <bz> All my daemons like it!
>  http://www.freebsd.org/doc/en_US.ISO8859-1/books/handbook/jails.html

-- 
//Monthadar Al Jaberi