Xen devel - Jun 2008 - Printing debug message from hypervisor

Hi,
  Iam trying to print some debug messages, from a hypercall function
do_domctl by introducing some printk statemetnts.
But nothing is getting into the log or the terminal. After exploring the
code it seems like we cant directly use printk, because the guest checks the
''console I/O ring buffer after receving an event for the same from
hypervisor '' .  I chekced the functions of drivers/char/console.c and
it has
the funciton printk which is does generate the event for console I/O but the
console.h does''nt include the prototype. So my question is how can i
use it
from domctl.c
  I have been stuck on this for a week now, so please give me some hints on
this.

Thanks,
  Sandesh
  

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>> Which log are you looking at? Does ''xm dmesg'' show
anything more?
> dmesg dose''nt contain any of my messages!!!
I did really mean:
xm dmesg
>
>>
>>> code it seems like we cant directly use printk, because the guest  
>>> checks the
>>> ''console I/O ring buffer after receving an event for the
same from
>>> hypervisor '' .  I chekced the functions of
drivers/char/console.c
>>> and it has
>>> the funciton printk which is does generate the event for console I/
>>> O but the
>>> console.h
>>
>> printk prototype is in lib.h (include/xen/lib.h)
>
>> Are you able to see _any_ output from the hypervisor at all? I
don''t
>> think printk in do_domctl will be any different.
> I get only the messages from xend and from xc_lib but none of the
> hypervisor printks'' are getting printed.
> Atleast i dont know where they are getting printed?? Is it in the
> xenstore..i think not!!!
Xen can be configured to output it''s messages on the serial line, and  
it also puts it in a buffer (console ring) for Dom0''s attention, xm  
dmesg should print all the hypervisors output.

Cheers
Gr(z)egor(z)
>
>
>> Cheers
>> Gr(z)egor(z)
>

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>> I did really mean:
>> xm dmesg
> ok xm dmesg is showing the stuff.
> thanks for the info.
> Does this mean that the printk''s print it to the xenstore??
I don''t think it is stored in xenstore itself, but yes, it is buffered
in Dom0.
>>>
>> Xen can be configured to output it''s messages on the serial
line, and
>> it also puts it in a buffer (console ring) for Dom0''s
attention, xm
>> dmesg should print all the hypervisors output.
> how to enable this???
> by default it does''nt print it on the serial console.
add the following command line options to your xen configuration  
(bootloader config):
com1=115200,8n1 console=com1,tty

Cheers
Gr(z)egor(z)

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>>>>
>> add the following command line options to your xen configuration
>> (bootloader config):
>> com1=115200,8n1 console=com1,tty
> as part of the hypervisor/dom0 boot option right??
As part of the hypervisor boot option. If you are using grub, your  
config is likely to look something like:

title Xen
kernel xen.gz dom0_mem=512M
module vmlinuz ro root=/dev/sda1 console=ttyS0

Change it to:
kernel xen.gz dom0_mem=512M com1=<baud-rate>,8n1 console=com1,vga
module vmlinuz ro root=/dev/sda1 console=ttyS0

(NOTE: I believe ''vga'' is required, instead of
''tty'')
>
>>
>> Cheers
>> Gr(z)egor(z)
>

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> Hi grzegorz,
> I have one more issue. I want to export do_domctl function for
> debugging. I did EXPORT_SYMBOL(do_domctl) its not happening. Any idea
> about this.
Xen doesn''t use modular architecture and consequently EXPORT_SYMBOL  
macro is a no-op (see: include/xen/config.h). You just need to add  
do_domctl definition to a header file. Or define it wherever you need  
with ''extern''.

Cheers
Gr(z)egor(z)
>
>  Sorry to bother you again and again.
>
> Thanks very much.
> Sandesh
>
> On Tue, 2008-06-10 at 14:52 +0100, Grzegorz Miłoś wrote:
>>>> I did really mean:
>>>> xm dmesg
>>> ok xm dmesg is showing the stuff.
>>> thanks for the info.
>>> Does this mean that the printk''s print it to the
xenstore??
>>
>> I don''t think it is stored in xenstore itself, but yes, it is
>> buffered
>> in Dom0.
>>>>>
>>>> Xen can be configured to output it''s messages on the
serial line,
>>>> and
>>>> it also puts it in a buffer (console ring) for Dom0''s
attention, xm
>>>> dmesg should print all the hypervisors output.
>>> how to enable this???
>>> by default it does''nt print it on the serial console.
>>
>> add the following command line options to your xen configuration
>> (bootloader config):
>> com1=115200,8n1 console=com1,tty
>>
>> Cheers
>> Gr(z)egor(z)
>
>
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>>> Hi grzegorz,
>>> I have one more issue. I want to export do_domctl function for
>>> debugging. I did EXPORT_SYMBOL(do_domctl) its not happening. Any  
>>> idea
>>> about this.
>>
>> Xen doesn''t use modular architecture and consequently
EXPORT_SYMBOL
>> macro is a no-op (see: include/xen/config.h).
> But i seen it being used in xen/common/string.c and in other ia-64
> specific src files. And those exported symbols are visible in
> System.map. Is it that during compilation of those files different
> header files are included?
System.map lists symbols for _Linux_ not Xen. So for example
''strlcpy''
is defined in xen/common/strings.c, but also in linux-2.6.18-xen.hg/ 
lib/string.c. It is the second definition that makes it into
System.map.
>
>> You just need to add
>> do_domctl definition to a header file. Or define it wherever you need
>> with ''extern''.
> no acutally i need to debug do_domctl instruction by instruction using
> kdb, and kdb dosent recognize the it, so i thought of exporting it.
I''ve never used kdb to debug Xen. Are you using
http://xenbits.xensource.com/ext/debuggers.hg?

Cheers
Gr(z)egor(z)

BTW: Can you reply to the list, not me personally? It''d make it easier
for me to reply.
>
>>
>> Cheers
>> Gr(z)egor(z)
>>>
>>> Sorry to bother you again and again.
>>>
>>> Thanks very much.
>>> Sandesh
>>>
>>> On Tue, 2008-06-10 at 14:52 +0100, Grzegorz Miłoś wrote:
>>>>>> I did really mean:
>>>>>> xm dmesg
>>>>> ok xm dmesg is showing the stuff.
>>>>> thanks for the info.
>>>>> Does this mean that the printk''s print it to the
xenstore??
>>>>
>>>> I don''t think it is stored in xenstore itself, but
yes, it is
>>>> buffered
>>>> in Dom0.
>>>>>>>
>>>>>> Xen can be configured to output it''s messages
on the serial line,
>>>>>> and
>>>>>> it also puts it in a buffer (console ring) for
Dom0''s
>>>>>> attention, xm
>>>>>> dmesg should print all the hypervisors output.
>>>>> how to enable this???
>>>>> by default it does''nt print it on the serial
console.
>>>>
>>>> add the following command line options to your xen
configuration
>>>> (bootloader config):
>>>> com1=115200,8n1 console=com1,tty
>>>>
>>>> Cheers
>>>> Gr(z)egor(z)
>>>
>>>
>>> Please do not print this email unless it is absolutely necessary.
>>>
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>>> attachments to this message are intended for the exclusive use of
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>>> should not disseminate, distribute or copy this e-mail. Please
>>> notify the sender immediately and destroy all copies of this
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>>>
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>>> recipient should check this email and any attachments for the
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damage
>>> caused by any virus transmitted by this email.
>>>
>>> www.wipro.com
>>
>>
>> _______________________________________________
>> Xen-devel mailing list
>> Xen-devel@lists.xensource.com
>> http://lists.xensource.com/xen-devel
>
>
> Please do not print this email unless it is absolutely necessary.
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>>>>>
>>>> You just need to add
>>>> do_domctl definition to a header file. Or define it wherever
you
>>>> need
>>>> with ''extern''.
>>> no acutally i need to debug do_domctl instruction by instruction  
>>> using
>>> kdb, and kdb dosent recognize the it, so i thought of exporting it.
>>
>> I''ve never used kdb to debug Xen. Are you using
http://xenbits.xensource.com/ext/debuggers.hg?
> no...!! is it the debugger present under tools/debugger/gdb?? but i
> guess its only to debug domU kernels. Will it allow me to break at
> hypercall functions like do_domctl??
No it will not. It''s not for debugging the hypervisor.

Cheers
Gr(z)egor(z)
>
>
>>
>> Cheers
>> Gr(z)egor(z)
>>
>> BTW: Can you reply to the list, not me personally? It''d make
it
>> easier
>> for me to reply.
>>>
>>>>
>>>> Cheers
>>>> Gr(z)egor(z)
>>>>>
>>>>> Sorry to bother you again and again.
>>>>>
>>>>> Thanks very much.
>>>>> Sandesh
>>>>>
>>>>> On Tue, 2008-06-10 at 14:52 +0100, Grzegorz Miłoś wrote:
>>>>>>>> I did really mean:
>>>>>>>> xm dmesg
>>>>>>> ok xm dmesg is showing the stuff.
>>>>>>> thanks for the info.
>>>>>>> Does this mean that the printk''s print it
to the xenstore??
>>>>>>
>>>>>> I don''t think it is stored in xenstore itself,
but yes, it is
>>>>>> buffered
>>>>>> in Dom0.
>>>>>>>>>
>>>>>>>> Xen can be configured to output it''s
messages on the serial
>>>>>>>> line,
>>>>>>>> and
>>>>>>>> it also puts it in a buffer (console ring) for
Dom0''s
>>>>>>>> attention, xm
>>>>>>>> dmesg should print all the hypervisors output.
>>>>>>> how to enable this???
>>>>>>> by default it does''nt print it on the
serial console.
>>>>>>
>>>>>> add the following command line options to your xen
configuration
>>>>>> (bootloader config):
>>>>>> com1=115200,8n1 console=com1,tty
>>>>>>
>>>>>> Cheers
>>>>>> Gr(z)egor(z)
>>>>>
>>>>>
>>>>> Please do not print this email unless it is absolutely
necessary.
>>>>>
>>>>> The information contained in this electronic message and
any
>>>>> attachments to this message are intended for the exclusive
use of
>>>>> the addressee(s) and may contain proprietary, confidential
or
>>>>> privileged information. If you are not the intended
recipient, you
>>>>> should not disseminate, distribute or copy this e-mail.
Please
>>>>> notify the sender immediately and destroy all copies of
this
>>>>> message
>>>>> and any attachments.
>>>>>
>>>>> WARNING: Computer viruses can be transmitted via email. The
>>>>> recipient should check this email and any attachments for
the
>>>>> presence of viruses. The company accepts no liability for
any
>>>>> damage
>>>>> caused by any virus transmitted by this email.
>>>>>
>>>>> www.wipro.com
>>>>
>>>>
>>>> _______________________________________________
>>>> Xen-devel mailing list
>>>> Xen-devel@lists.xensource.com
>>>> http://lists.xensource.com/xen-devel
>>>
>>>
>>> Please do not print this email unless it is absolutely necessary.
>>>
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>>
>
>
> Please do not print this email unless it is absolutely necessary.
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On Wed, 2008-06-11 at 11:24 +0100, Grzegorz Miłoś wrote:
> >>>>>
> >>>> You just need to add
> >>>> do_domctl definition to a header file. Or define it
wherever you
> >>>> need
> >>>> with ''extern''.
> >>> no acutally i need to debug do_domctl instruction by
instruction
> >>> using
> >>> kdb, and kdb dosent recognize the it, so i thought of
exporting it.
> >>
> >> I''ve never used kdb to debug Xen. Are you using
http://xenbits.xensource.com/ext/debuggers.hg?
this is only for 64bit hypervisor!!! its not compiling on 32bit machine.
Is there any way i can get it working for 32bit?
> > no...!! is it the debugger present under tools/debugger/gdb?? but i
> > guess its only to debug domU kernels. Will it allow me to break at
> > hypercall functions like do_domctl??
> 
> No it will not. It''s not for debugging the hypervisor.
> 
> Cheers
> Gr(z)egor(z)
> 
> >
> >
> >>
> >> Cheers
> >> Gr(z)egor(z)
> >>
> >> BTW: Can you reply to the list, not me personally? It''d
make it
> >> easier
> >> for me to reply.
> >>>
> >>>>
> >>>> Cheers
> >>>> Gr(z)egor(z)
> >>>>>
> >>>>> Sorry to bother you again and again.
> >>>>>
> >>>>> Thanks very much.
> >>>>> Sandesh
> >>>>>
> >>>>> On Tue, 2008-06-10 at 14:52 +0100, Grzegorz Miłoś
wrote:
> >>>>>>>> I did really mean:
> >>>>>>>> xm dmesg
> >>>>>>> ok xm dmesg is showing the stuff.
> >>>>>>> thanks for the info.
> >>>>>>> Does this mean that the printk''s
print it to the xenstore??
> >>>>>>
> >>>>>> I don''t think it is stored in xenstore
itself, but yes, it is
> >>>>>> buffered
> >>>>>> in Dom0.
> >>>>>>>>>
> >>>>>>>> Xen can be configured to output
it''s messages on the serial
> >>>>>>>> line,
> >>>>>>>> and
> >>>>>>>> it also puts it in a buffer (console ring)
for Dom0''s
> >>>>>>>> attention, xm
> >>>>>>>> dmesg should print all the hypervisors
output.
> >>>>>>> how to enable this???
> >>>>>>> by default it does''nt print it on the
serial console.
> >>>>>>
> >>>>>> add the following command line options to your xen
configuration
> >>>>>> (bootloader config):
> >>>>>> com1=115200,8n1 console=com1,tty
> >>>>>>
> >>>>>> Cheers
> >>>>>> Gr(z)egor(z)
> >>>>>
> >>>>>
> >>>>> Please do not print this email unless it is absolutely
necessary.
> >>>>>
> >>>>> The information contained in this electronic message
and any
> >>>>> attachments to this message are intended for the
exclusive use of
> >>>>> the addressee(s) and may contain proprietary,
confidential or
> >>>>> privileged information. If you are not the intended
recipient, you
> >>>>> should not disseminate, distribute or copy this
e-mail. Please
> >>>>> notify the sender immediately and destroy all copies
of this
> >>>>> message
> >>>>> and any attachments.
> >>>>>
> >>>>> WARNING: Computer viruses can be transmitted via
email. The
> >>>>> recipient should check this email and any attachments
for the
> >>>>> presence of viruses. The company accepts no liability
for any
> >>>>> damage
> >>>>> caused by any virus transmitted by this email.
> >>>>>
> >>>>> www.wipro.com
> >>>>
> >>>>
> >>>> _______________________________________________
> >>>> Xen-devel mailing list
> >>>> Xen-devel@lists.xensource.com
> >>>> http://lists.xensource.com/xen-devel
> >>>
> >>>
> >>> Please do not print this email unless it is absolutely
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> >>>
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> >>> and any attachments.
> >>>
> >>> WARNING: Computer viruses can be transmitted via email. The
> >>> recipient should check this email and any attachments for the
> >>> presence of viruses. The company accepts no liability for any
damage
> >>> caused by any virus transmitted by this email.
> >>>
> >>> www.wipro.com
> >>
> >
> >
> > Please do not print this email unless it is absolutely necessary.
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> 

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