Re: [Xen-devel] Re: [PATCH 2 of 4] xentrace: replace ASSERT with printk in __trace_var

[Keir Fraser <keir@xxxxxxx>]

It's not like we have dodgy third-party drivers to worry about. Just fix the
code -- *which is in the tree!* -- that is making the bad calls! It was
correct to make this an assert/bug_on in the first place.

 -- Keir

On 15/07/2011 17:31, "George Dunlap" <george.dunlap@xxxxxxxxxx> wrote:

> This seems likely to spam the console if there is a trace which violates
> this; and this may happen in production environments if the loglevel is
> increased.  I think putting in something to warn just once would be a
> better idea.
> 
>  -George
> 
> On Fri, 2011-07-15 at 16:38 +0100, Olaf Hering wrote:
>> # HG changeset patch
>> # User Olaf Hering <olaf@xxxxxxxxx>
>> # Date 1310741871 -7200
>> # Node ID e0ff4eea0432e0af3210e090a47414a0126e9904
>> # Parent  d0dcdddf5285eba0605a95dfda79b794803fa733
>> xentrace: replace ASSERT with printk in __trace_var
>> 
>> If trace_var gets called with large extra_data, do not crash the hypervisor.
>> Instead print a warning and truncate the buffer.
>> 
>> Signed-off-by: Olaf Hering <olaf@xxxxxxxxx>
>> 
>> diff -r d0dcdddf5285 -r e0ff4eea0432 xen/common/trace.c
>> --- a/xen/common/trace.c
>> +++ b/xen/common/trace.c
>> @@ -683,7 +683,10 @@ void __trace_var(u32 event, bool_t cycle
>>      if ( (extra % sizeof(u32)) != 0 )
>>          extra_word++;
>>      
>> -    ASSERT(extra_word <= TRACE_EXTRA_MAX);
>> +    if ( unlikely(extra_word > TRACE_EXTRA_MAX) )
>> +        printk(XENLOG_WARNING "xentrace: event %x extra_data %u too
>> large.\n",
>> +                event, extra);
>> +
>>      extra_word = min_t(int, extra_word, TRACE_EXTRA_MAX);
>>  
>>      /* Round size up to nearest word */
> 
> 
> 
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