Re: [Xen-devel] [PATCH v9 16/27] x86, xsplice: Print payload's symbol name and payload name in backtraces

["Jan Beulich" <JBeulich@xxxxxxxx>]

>>> On 26.04.16 at 13:06, <ross.lagerwall@xxxxxxxxxx> wrote:
> On 04/25/2016 04:35 PM, Konrad Rzeszutek Wilk wrote:
>> @@ -142,6 +145,55 @@ void *xsplice_symbols_lookup_by_name(const char 
>> *symname)
>>       return 0;
>>   }
>>
>> +static const char *xsplice_symbols_lookup(unsigned long addr,
>> +                                          unsigned long *symbolsize,
>> +                                          unsigned long *offset,
>> +                                          char *namebuf)
>> +{
>> +    const struct payload *data;
>> +    unsigned int i, best;
>> +    const void *va = (const void *)addr;
>> +    const char *n = NULL;
>> +
>> +    /*
>> +     * Only RCU locking since this list is only ever changed during apply
>> +     * or revert context. And in case it dies there we need an safe list.
>> +     */
>> +    rcu_read_lock(&rcu_applied_lock);
>> +    list_for_each_entry_rcu ( data, &applied_list, applied_list )
>> +    {
>> +        if ( va < data->text_addr &&
>> +             va >= (data->text_addr + data->pages * PAGE_SIZE) )
> 
> This calculation is wrong due to the use of void * and results in 
> incorrect backtrace results.

When text_addr is void *, how is this calculation wrong then?

>> @@ -422,6 +475,13 @@ static int prepare_payload(struct payload *payload,
>>           }
>>       }
>>
>> +    /* Setup the virtual region with proper data. */
>> +    region = &payload->region;
>> +
>> +    region->symbols_lookup = xsplice_symbols_lookup;
>> +    region->start = payload->text_addr;
>> +    region->end = payload->text_addr + payload->text_size;
> 
> This calculation is wrong due to the use of void *.

And again - why?

Jan


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