Re: [Xen-devel] [PATCH] xenctx: misc adjustments

["Jan Beulich" <JBeulich@xxxxxxxxxx>]

>>> On 11.01.11 at 20:27, Ian Jackson <Ian.Jackson@xxxxxxxxxxxxx> wrote:
> Jan Beulich writes ("[Xen-devel] [PATCH] xenctx: misc adjustments"):
>> - fix off-by-one errors during symbol insertion and lookup
>> - don't store the symbol type, as it wasn't needed at all so far and
>>   is only needed now at parsing time
>> - don't insert certain kinds of symbols
> ...
>> -        insert_symbol(symbol);
>> +        switch (type) {
>> +        case 'A': /* global absolute */
>> +        case 'a': /* local absolute */
>> +            break;
> 
> Is there some reason why these shouldn't included ?  Perhaps I'm
> misunderstanding what their purpose is.

Absolute symbols (with very few exceptions) don't represent
addresses (take the symbol CRC values in older Linux as an
example; current Linux has vDSO relative(!) addresses among
them).

Since some versions have absolute _text etc, they're being
allowed to fall into the code path following the switch
statement (other than undefined symbols), but for the purpose
of annotating stack traces they're useless (and in all reality, for
relocatable kernels, there ought to be a mechanism to add a
fixed offset to all addresses, which immediately disqualifies
all absolute ones except those few special purpose ones).

Jan


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