Hi Namhyung,
Thanks for looking into this!
On 17/09/15 16:26, Namhyung Kim wrote:
> Hi,
>
> On Thu, Sep 17, 2015 at 11:58 PM, Kapileshwar Singh
> <kapileshwar.si...@arm.com> wrote:
>> Hi Steve,
>>
>> Thanks for looking into this!
>>
>> On 17/09/15 14:11, Steven Rostedt wrote:
>>> On Thu, 17 Sep 2015 12:14:36 +0100
>>> Kapileshwar Singh <kapileshwar.si...@arm.com> wrote:
>>>
>>>> When a trace recorded on a 32-bit device is processed with a 64-bit
>>>> binary, the higher 32-bits of the address need to be masked.
>>>>
>>>> The lack of this results in the output of the 64-bit pointer
>>>> value to the trace as the 32-bit address lookup fails in find_printk.
>>>>
>>>> Before:
>>>> burn-1778 [003] 548.600305: bputs: 0xc0046db2s: 2cec5c058d98c
>>>>
>>>> After:
>>>> burn-1778 [003] 548.600305: bputs: 0xc0046db2s: RT throttling
>>>> activated
>>>>
>>>> The problem occurs in PRINT_FEILD when the field is recognized as a pointer
>>>> to a string (of the type const char *)
>>>
>>> Actually, there's two bugs here. You only fixed one of them.
>>>
>>>>
>>>> Cc: Steven Rostedt <rost...@goodmis.org>
>>>> Cc: Arnaldo Carvalho de Melo <a...@redhat.com>
>>>> Cc: Namhyung Kim <namhy...@kernel.org>
>>>> Cc: Javi Merino <javi.mer...@arm.com>
>>>> Cc: David Ahern <dsah...@gmail.com>
>>>> Cc: Jiri Olsa <jo...@kernel.org>
>>>> Reported-by: Juri-Lelli <juri.le...@arm.com>
>>>> Signed-off-by: Kapileshwar Singh <kapileshwar.si...@arm.com>
>>>> ---
>>>> tools/lib/traceevent/event-parse.c | 11 +++++++++++
>>>> 1 file changed, 11 insertions(+)
>>>>
>>>> diff --git a/tools/lib/traceevent/event-parse.c
>>>> b/tools/lib/traceevent/event-parse.c
>>>> index 4d885934b919..39163ea4a048 100644
>>>> --- a/tools/lib/traceevent/event-parse.c
>>>> +++ b/tools/lib/traceevent/event-parse.c
>>>> @@ -3829,6 +3829,17 @@ static void print_str_arg(struct trace_seq *s, void
>>>> *data, int size,
>>>> if (!(field->flags & FIELD_IS_ARRAY) &&
>>>> field->size == pevent->long_size) {
>>>> addr = *(unsigned long *)(data + field->offset);
>>>
>>> addr is of type unsigned long. That means if we read a 64 bit record on
>>> a 32 bit machine (which is supported), this will be truncated.
>>>
>>> Perhaps we need to make addr into a unsigned long long, and then add:
>>>
>>> addr = (pevent->long_size == 8) ?
>>> *(unsigned long long *)(data + field->offset) :
>>> (unsigned long long )*(unsigned int *)(data + field->offset);
>
> What about this? (untested)
>
> addr = *(uint64_t *)(data + field->offset) &
> ((1ULL << pevent->long_size * 8) - 1);
I tested this and it works fine.
>
> Do we also need to consider byte endians? Maybe it'd be better adding
> a helper to dereference pointers then..
In this particular case, since the address is just a key for a lookup into the
printk_map, which seems like a (addr -> const char *) mapping for string
literals in the trace file, the endian-ness should not matter (I could be wrong
though).
Regards,
KP
>
> Thanks,
> Namhyung
>
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